JP3671189B2 - Power supply control device, DC-DC conversion circuit, and electronic equipment - Google Patents

Description

  The present invention relates to a power supply control device that adjusts an output voltage of a power supply circuit to a voltage corresponding to a reference voltage. The present invention also relates to a load test method for testing the operation of a load connected to a power supply circuit using a power supply control device.

  In general, a power supply circuit that is incorporated in an electronic device such as a laptop computer and supplies an operating voltage to each part (hereinafter referred to as “load”) of the electronic device is a control unit (power control) that controls the output voltage to be constant. Device).

For example, a DC-DC converter, which is one of power supply circuits, is generally configured as shown in FIG. This DC-DC converter includes a transistor Tr1, a choke coil L1, a flywheel diode D2, a diode D1, a smoothing capacitor C1, a resistor R1, a resistor R2, and a control unit 60a.

An input voltage Vi is applied to the input terminal of the transistor Tr1. The control terminal of the transistor Tr1 is connected to the output terminal of the control unit 60a, and is turned ON / OFF by the control unit 60a. The output terminal of the transistor Tr1 is connected to one end of the choke coil L1.

  A flywheel diode D2 is provided between one end of the choke coil L1 and the ground. Further, the anode of the diode D1 is connected to the other end of the choke coil L1. On the other hand, the cathode of the diode D1 is connected to the output terminal of the DC-DC converter.

A smoothing capacitor C1 is provided between the cathode of the diode D1 and the ground. Further, a series circuit of a resistor R1 and a resistor R2 is provided between the output terminal of the DC-DC converter and the ground. This series circuit is a detection circuit for the output voltage Vo.

The controller 60a has an input terminal for the input voltage Vi of the DC-DC converter in addition to the output terminal described above. As a result, the input voltage Vi is applied as an operating voltage to the controller 60a. The control unit 60a also has an input terminal (hereinafter referred to as “terminal SC”) for inputting an ON / OFF signal, which is a control command for the output voltage Vo, from the outside. Furthermore, the control unit 60a has an input terminal for the output voltage Vo (hereinafter referred to as “terminal FB”). The terminal FB is connected to a contact point between the resistor R1 and the resistor R2. As a result, the detected value of the output voltage Vo appearing at both ends of the resistor R2 is input to the control unit 60a as the control voltage ERR.

The operation of such a DC-DC converter is roughly as follows. That is, when the transistor Tr1 is turned on, power is accumulated in the choke coil L1. When the transistor Tr1 is turned off, the power stored in the choke coil L1 is released by the flywheel diode D2. A predetermined output voltage Vo is transformed and output to the output terminal of the DC-DC converter.

The resistors R1 and R2 detect the output voltage Vo as needed, and input the detected voltage to the control unit 60a as the control voltage ERR. The controller 60a controls the control voltage ERR
Based on the above, ON / OFF of the transistor Tr1 is controlled so as to keep the output voltage Vo constant at a predetermined value.

For this reason, the controller 60a is configured as shown in FIG. The control unit 60a is configured by a single LSI (Large Scale Integration circuit), and includes a built-in reference voltage source 66, an error amplifier (error amplifier) 61, a PWM (Pulse-Width Modulation) comparator 62, a power supply 63, and a triangular wave oscillator 64. And a drive circuit 65.

The power source 63 is connected to the input terminal of the input voltage Vi and the terminal SC, and forms the operating power of each part of the control unit 60a from the input voltage Vi. The power source 63 is turned on / off from the outside.
When the FF signal is “ON”, operating power is supplied to each unit of the control unit 60a. The error amplifier 61 is supplied with a control voltage ERR from its negative phase input terminal and a reference voltage e1 from its positive phase input terminal. The error amplifier 61 detects and amplifies the difference between the control voltage ERR and the reference voltage e1, and outputs the result.

  The output terminal of the error amplifier 61 is connected to the positive phase input terminal of the PWM comparator 62. On the other hand, a triangular wave oscillator 64 is connected to the negative phase input terminal of the PWM comparator 62. Here, the triangular wave oscillator 64 generates a conversion triangular wave signal for converting a voltage into a pulse width at a constant frequency. The PWM comparator 62 receives the differential amplification result of the error amplifier 61 from the positive phase input terminal as an output signal, and when a triangular wave signal is input from the negative phase input terminal, the pulse corresponding to these differences. A PWM signal having a width and a pulse interval is generated.

One end of the drive circuit 65 is connected to the PWM comparator 62, and the other end is connected to a control terminal connected to the control end of the transistor Tr1. As a result, the drive circuit 65
Is ON / OFF of the transistor Tr1 based on the PWM signal input from the PWM comparator 62.
Controls OFF.

Such a control unit 60a operates as follows on the assumption that an input voltage Vi is applied as an operating voltage and an “ON” signal that is a control command for the output voltage Vo is input to the terminal SC. .

  That is, when the control voltage ERR is input from the terminal FB into the control unit 60a, the control voltage ERR is input to the error amplifier 61. On the other hand, the error amplifier 61 receives the reference voltage e1 from the built-in reference voltage source 66. Then, the error amplifier 61 detects and amplifies an error between the control voltage ERR and the reference voltage e1, and inputs the result to the PWM comparator 62 as an output signal. On the other hand, the triangular wave oscillator 64 inputs a triangular wave signal to the PWM comparator 62.

The PWM comparator 62 compares the output signal of the error amplifier 61 with the triangular wave signal. At this time, when the output signal of the error amplifier 61 is larger than the output signal of the triangular wave transmitter 64, the PWM comparator 62 generates a PWM signal for turning on the transistor Tr1 and drives this PWM signal. Input to the circuit 65. Then, the drive circuit 65 gives the PWM signal input from the PWM comparator 62 to the transistor Tr1.

Thereby, the transistor Tr1 is turned on, and a voltage for holding the output voltage Vo constant at a predetermined value is applied to the output terminal side of the transistor Tr1. By repeating such an operation, a predetermined value of the output voltage Vo is constantly output to the output terminal of the DC-DC converter.

By the way, when the power supply circuit such as the DC-DC converter described above is actually mounted and used in an electronic device, the characteristics of the components of the power supply circuit change due to a temperature change around the electronic device. As a result, the output voltage of the power supply circuit may change. For this reason, when an electronic device is manufactured, a voltage range (hereinafter referred to as “margin”) in which the load can operate normally even when the output voltage of the power supply circuit changes from a predetermined value is secured. It is common to manufacture. Before shipping an electronic device to the market, if the output voltage of the power supply circuit incorporated in the electronic device changes, a load test (hereinafter referred to as “load test”) is performed to check whether the load operates normally within the margin. "Margin test").

When this margin test is performed on an electronic device incorporating the DC-DC converter shown in FIGS. 12 and 13, the configuration of the DC-DC converter shown in FIG. 12 is as shown in FIG. Be changed. That is, the resistor R2 shown in FIG. 12 is replaced with a variable resistor R3 as shown in FIG. 14, and the output voltage Vo detected by the resistors R1 and R3, that is, the control voltage ERR is changed. Made variable. And the control voltage ER
By changing the value of R accordingly, the operating condition of the load is tested. Electronic devices that have passed this margin test are shipped to the market after the variable resistor R3 of the DC-DC converter is replaced with the resistor R2 again.

  However, since this margin test is performed for each electronic device, replacement of the resistor R2 and the resistor R3 in the DC-DC converter of the electronic device has to be performed for each electronic device. This has a problem that a huge number of man-hours are required in combination with the adjustment work of the variable resistor R3.

In recent years, the load of an electronic device is often configured by an IC (Integrated Circuit) or LSI (for example, a CPU (Central Processing Unit)), and the operation voltage of the load has been lowered. Yes. For this reason, the load margin decreases and the load yield deteriorates.

  On the other hand, a power supply circuit of an electronic device is required to supply a highly accurate output voltage to the load as the load margin decreases. In order to meet this demand, the power supply circuit is incorporated with the power circuit components as much as possible to improve the output accuracy and the power circuit reliability. For example, the resistors R1 and R2 of the DC-DC converter shown in FIG. 12 and FIG. 13 are built in the control unit 60b as shown in FIG. 15 and FIG. .

However, in the DC-DC converter in which the resistor R1 and the resistor R2 are built in the control unit 60b, the resistor R2 cannot be detached. Therefore, in order to make the control voltage ERR variable for the margin test, for example, the transistor Tr1 shown in FIG. 15 is removed, and a variable voltage source is newly connected to one end of the choke coil L1, or the choke coil L1. And a variable voltage source had to be installed. For this reason, there is a problem that the margin test is very troublesome.

  Therefore, the margin test actually performed is performed on several electronic devices selected from a large number of electronic devices to be shipped manufactured at one time. If all of the selected electronic devices pass the margin test, all of the electronic devices scheduled to be shipped are considered to have passed the margin test and are shipped to the market.

As described above, since no margin test is performed on all electronic devices to be shipped, some electronic devices shipped without undergoing the margin test may not operate normally within the margin. There was a fear. However, since the margin test is very troublesome as described above, there is a problem that it is extremely difficult to perform the margin test on the total number of electronic devices.

  The present invention has been made in view of the above-described problems, and a power supply control device that can easily vary the output voltage of the power supply circuit without detaching the components of the power supply circuit, and a DC power supply including such a power supply control device. It is an object of the present invention to provide a DC conversion circuit and an electronic device including such a DC-DC conversion circuit.

  The power supply control device according to the present invention employs the following configuration in order to solve the above-described problems. That is, the power supply control device according to the present invention includes output voltage detection means for detecting the output voltage of the power supply circuit and a built-in reference voltage source for supplying a reference voltage, and the output voltage detected by the output voltage detection means and the built-in reference voltage source. A power supply control device for comparing a reference voltage supplied from a reference voltage source and outputting a control signal for controlling a constant output voltage of the power supply circuit based on a result of the comparison, wherein the output voltage detection A selector for selecting one of the reference voltage supplied from the built-in reference voltage source and the external reference voltage applied from the outside to the power supply control device as a voltage to be compared with the output voltage detected by the means; Features.

  Here, the selection operation of the selector may be performed manually, for example, or may be performed automatically. The power supply control device according to the present invention further includes an external input detection unit that detects whether or not the external reference voltage is applied, and the selector includes the reference voltage and the external reference voltage based on a detection result of the external input detection unit. Or one of them may be selected.

  A power supply control device according to the present invention includes an output voltage detection means for detecting an output voltage of a power supply circuit and a built-in reference voltage source for supplying a reference voltage, and the output voltage detected by the output voltage detection means and the built-in reference voltage. A power supply control device that compares a reference voltage supplied from a source and outputs a control signal for controlling the output voltage of the power supply circuit to be constant based on a result of the comparison, and the power supply control device from the outside A digital-to-analog converter for converting digital data of the external reference voltage input to the analog external reference voltage and a voltage to be compared with the output voltage detected by the output voltage detection means from the built-in reference voltage source And a selector for selecting one of the reference voltage converted by the digital / analog converter and the external reference voltage And it features.

  The power supply control device according to the present invention further includes an external input detection unit that detects whether or not the external reference voltage is applied, and the selector includes the reference voltage and the external reference voltage based on a detection result of the external input detection unit. Or one of them may be selected.

  The external input detecting means detects the analog external reference voltage converted by the digital / analog converter, and the selector is configured to detect the reference voltage and the external reference based on a detection result of the external input detecting means. One of the voltage and the voltage may be selected.

  The external input detection means detects digital data of the external reference voltage input to the digital-analog converter, and the selector is configured to detect the reference voltage and the reference voltage based on a detection result of the external input detection means. One of the external reference voltages may be selected.

Here, the digital data detected by the external input means may be serial data or parallel data. Further, the digital data of the external reference voltage includes data for selecting operation of the selector, and the selector detects data for selecting operation of the selector, and based on the data for selecting operation of the selector, the built-in data One of a reference voltage from a reference voltage source and the external reference voltage converted by the digital / analog converter may be selected. The selector in this case has a function equivalent to that in the case where the external input detection means is incorporated.

  A power supply control device according to the present invention includes an output voltage detection unit that detects an output voltage of a power supply circuit as a control voltage, a built-in reference voltage source that supplies an internal reference voltage, and the control voltage detected by the output voltage detection unit. A selector for selecting one of the internal reference voltage supplied from the built-in reference voltage source and an external reference voltage source applied from the outside as a selection reference voltage to be compared, and the control voltage detected by the output voltage detection means Control signal generating means for generating a control signal for adjusting the output voltage of the power supply circuit to a voltage corresponding to the selected reference voltage based on a comparison result between the selector and the selection reference voltage selected by the selector. One integrated circuit may be provided.

  The power supply control device according to the present invention includes an output voltage detection means for detecting the output voltage of the power supply circuit as a control voltage, a built-in reference voltage source for supplying an internal reference voltage, and digital data of an external reference voltage input from the outside. A digital-to-analog converter for converting the signal into an analog external reference voltage, the internal reference voltage supplied from the built-in reference voltage source as a selected reference voltage to be compared with the control voltage detected by the output voltage detection means, and the A comparison result between the selector that selects one of the external reference voltages converted by the digital / analog converter, and the control voltage detected by the output voltage detection means and the selected reference voltage selected by the selector. Based on this, a control signal for adjusting the output voltage of the power supply circuit to a voltage corresponding to the selected reference voltage is generated And that the control signal generating unit may be provided inside a single integrated circuit.

  Here, the integrated circuit may be an IC or an LSI as long as it is made into one chip. Further, the voltage corresponding to the selection reference voltage may be a voltage having the same value as the selection reference voltage, or may be a voltage obtained by amplifying the selection reference voltage.

  The load test method according to the present invention is configured as follows to solve the above-described problems. That is, output voltage detection means for detecting the output voltage of the power supply circuit as a control voltage, a built-in reference voltage source for supplying an internal reference voltage, and a selection reference voltage for comparison with the control voltage detected by the output voltage detection means A selector that selects one of the internal reference voltage supplied from a built-in reference voltage source and an external reference voltage applied from the outside, the control voltage detected by the output voltage detection means, and the selector selected by the selector Using a power supply control device comprising control signal generation means for generating a control signal for adjusting an output voltage of the power supply circuit to a voltage corresponding to the selection reference voltage based on a comparison result with a selection reference voltage; A load test method for testing an operation of a load connected to a circuit, wherein the load control method is external to the power supply control device when testing the operation of the load. And applying the external reference voltage and causing the selector to select the external reference voltage as the selected reference voltage, thereby allowing the output voltage of the power supply circuit adjusted to a voltage according to the external reference voltage to the load. It is characterized by supplying.

The load test method according to the present invention includes an output voltage detection means for detecting an output voltage of a power supply circuit as a control voltage, a built-in reference voltage source for supplying an internal reference voltage, and digital data of an external reference voltage inputted from outside. A digital / analog converter for converting the external reference voltage to the external reference voltage, and the internal reference voltage supplied from the built-in reference voltage source as the selected reference voltage to be compared with the control voltage detected by the output voltage detecting means, and the digital / analog A selector that selects one of the external reference voltages converted by the converter, and the control voltage detected by the output voltage detecting means and the selection reference voltage selected by the selector based on the comparison result A control signal for adjusting the output voltage of the power supply circuit to a voltage corresponding to the selected reference voltage is generated A load test method for testing the operation of a load connected to the power supply circuit using a power supply control device comprising a control signal generating means, wherein when testing the operation of the load, the power supply control device is externally The digital data of the external reference voltage is input, and by causing the selector to select the external reference voltage as the selection reference voltage, the output voltage of the power supply circuit adjusted to a voltage according to the external reference voltage is selected. It is characterized by supplying a load.

  In the load test of the present invention, the power supply control device is provided with external input detection means for detecting whether or not the external reference voltage is applied, and the selector determines the external reference voltage based on the detection result of the external input detection means. It may be selected as a selection reference voltage.

  The detection target of the external input detection means may be the external reference voltage converted by the digital / analog converter, or digital data of the external reference voltage input to the digital / analog converter. There may be.

  The digital data of the external reference voltage includes data for selecting operation of the selector. The selector detects data for selecting operation of the selector, and the digital data based on the data for selecting operation of the selector is used. The external reference voltage converted by the analog converter may be selected as the selection reference voltage.

  The load test method of the present invention changes the value of the output voltage of the power supply circuit supplied to the load by changing the value of the external reference voltage input to the power supply control device or the digital data of the external reference voltage. You may do it.

  As described above, according to the present invention, the output voltage of the power supply circuit can be easily varied without detaching the components of the power supply circuit. For this reason, it is possible to save labor in the margin test (load test), and it is also possible to perform the margin test on all electronic devices equipped with the power supply circuit. Further, the margin test can be further saved by automatically performing the selector selecting operation.

<Outline of Embodiment>
First, an outline of an embodiment according to the power supply control device of the present invention will be described with reference to FIGS. A power supply control device 1a shown in FIG. 1 is constituted by a single integrated circuit, and includes an output voltage detection means 8, a built-in reference voltage source 2, a comparison and comparison means 3, a selector 4, and a control signal generation means 9. Yes.

  An output voltage of a power supply circuit (not shown) is input to the output voltage detection means 8. The output voltage detection means 8 detects the output voltage input to itself, and inputs it to the comparison means 3 as the control voltage b. The selector 4 selects one of an internal reference voltage a supplied from the built-in reference voltage source 2 and an external reference voltage d applied from the outside to the power supply control device 1a as a reference voltage (selection reference voltage) to be compared with the control voltage b. And the selected reference voltage is input to the comparison means 3.

When the selector 4 selects the internal reference voltage a, the comparison unit 3 compares the internal reference voltage a and the control voltage b, and inputs the comparison result to the control signal generation unit 9. Based on the comparison result of the comparison means 3, the control signal generation means 9 controls the control signal c (for adjusting the output voltage of the power supply circuit to a voltage corresponding to the selected reference voltage) for controlling the output voltage of the power supply circuit constant. Control signal) is generated and output. By this control signal c, the output voltage of the power supply circuit is controlled to be constant with a voltage value that substantially matches the internal reference voltage a, for example.

  On the other hand, when the selector 4 selects the external reference voltage d, the comparison unit 3 compares the external reference voltage d with the control voltage b, and inputs the comparison result to the control signal generation unit 9. Based on the comparison result of the comparison means 3, the control signal generation means 9 generates and outputs a control signal c for controlling the output voltage of the power supply circuit to be constant. By this control signal c, the output voltage of the power supply circuit is controlled to be constant with a voltage value that substantially matches the external reference voltage d, for example.

  A power supply control device 1b shown in FIG. 2 is obtained by adding an external input detection means 5 for detecting whether or not an external reference voltage d is applied to the power supply control device 1a of FIG. According to the power supply control device 1 b, when the external reference voltage d is applied to the external input detection unit 5, the external input detection unit 5 inputs the switching signal f of the selector 4 to the selector 4. The selector 4 performs a selection operation and inputs the external reference voltage d to the comparison unit 3.

  The power supply control device 1c shown in FIG. 3 is based on the premise that the external reference voltage digital data e is input from the outside, and the external reference voltage digital data e is supplied to the analog external reference voltage to the power supply control device 1a of FIG. A digital / analog converter 6 for converting to d and an external input detecting means 5 for detecting the external reference voltage d converted by the digital / analog converter 6 are added.

  According to the power supply control device 1c, when the external input detection means 5 does not detect an analog external reference voltage, the selector 4 selects the reference voltage a of the built-in reference voltage source 2. On the other hand, when an analog external reference voltage d is output from the digital / analog converter 6, the external reference voltage d is applied to the external input detecting means 5. Thereby, the external input detecting means 5 gives the selector 4 the switching signal f of the selector 4. Then, the selector 4 performs a selection operation to select the external reference voltage d, and this external reference voltage d is input to the comparison means 3.

  The power supply control device 1d shown in FIG. 4 assumes that the digital data e of the external reference voltage input to the power supply control device 1d includes data for the selection operation of the selector 4, and the digital data e of the external reference voltage. Based on the above, the selector 4 is switched.

  According to this power supply control device 1d, when digital data e of the external reference voltage source is input from the outside to the power supply control device 1d, this digital data e is input to the digital / analog converter 6 and the selector 4 Also given to. Then, the selector 4 performs a selection operation, selects the analog external reference voltage d converted by the digital / analog converter 6, and the external reference voltage d is input to the comparison means 3.

<First Embodiment>
Next, a first embodiment of the present invention will be described. FIG. 5 shows a DC-DC converter 10 that uses the power supply control device according to the first embodiment as the control unit 21a. This DC-DC converter 10 corresponds to the power supply circuit of the present invention. The DC-DC converter 10 includes a transistor Tr1, a choke coil L1, a flywheel diode D2, and a diode D1.
, A capacitor C1 and a control unit 21a.

The transistor Tr1 is configured by using a field effect transistor (FET), and an input end thereof is connected to an input end of the DC-DC converter 10. Thereby, the input voltage Vi is applied to the input terminal of the transistor Tr1. The control terminal of the transistor Tr1 is connected to the output terminal of the control unit 21a. Thereby, the transistor Tr1 is
The controller 21a is turned on / off by the operation. The output terminal of the transistor Tr1 is connected to one end of the choke coil L1.

The choke coil L1 accumulates power supplied when the transistor Tr1 is ON. A flywheel diode D2 is provided between one end of the choke coil L1 and the ground. This flywheel diode D2 releases the electric power stored in the choke coil L1 when the transistor Tr1 is OFF.

  The other end of the choke coil L1 is connected to the anode of the diode D1. On the other hand, the cathode of the diode D <b> 1 is connected to the output terminal of the DC-DC converter 10. The diode D1 shields a backflow current from a load (not shown) connected to the output terminal of the DC-DC converter 10.

A capacitor C1 is provided between the cathode of the diode D1 and the ground. The capacitor C1 removes a pulsating component from the output voltage Vo. This capacitor C1
Thus, the smoothed voltage is output from the output terminal of the DC-DC converter 10 as the output voltage Vo.

In addition to the above-described output terminal, the control unit 21a inputs the input voltage Vi of the DC-DC converter 10.
Input terminal. As a result, the input voltage Vi is applied as an operating voltage to the controller 21a. In addition, the control unit 21a is an ON / OF that is a control command for stabilizing the output voltage Vo.
An input terminal (hereinafter referred to as “terminal SC”) for inputting the F signal from the outside is provided.

The control unit 21a has an input terminal for the output voltage Vo (hereinafter referred to as “terminal FB”). This terminal FB is connected between the diode D1 and the output terminal of the DC-DC converter 10. Thereby, the output voltage Vo of the DC-DC converter 10 is input to the control unit 21a. Further, the control unit 21a has a terminal (hereinafter referred to as “terminal OSV”) for inputting an external reference voltage Vref applied from an external reference voltage source (not shown).

  Next, the internal configuration of the control unit 21a will be described with reference to FIG. The control unit 21a is configured by a single LSI, and includes a built-in reference voltage source 66, an error amplifier (error amplifier) 61, a PWM comparator 62, a power source 63, a triangular wave oscillator 64, a drive circuit 65, a resistor R1, and a resistor R2. , Resistor R4, switch (selector) 22, comparator 23, and comparison voltage source 30.

The power supply 63 is connected to the input terminal of the input voltage Vi and the terminal SC. This power supply 63 generates the operating power of each part of the control part 21a from the input voltage Vi. The power supply 63 supplies operating power to each unit of the control unit 21a when the ON / OFF signal input from the outside is “ON”. On the other hand, when the ON / OFF signal input from the outside is “OFF”, the power source 63 stops supplying the operating power. Therefore, the ON / OFF control of the transistor Tr1 by the control unit 21a is performed when the ON / OFF signal input to the power supply 63 is “ON”.

The triangular wave oscillator 64 outputs a triangular wave signal for conversion for converting a voltage into a pulse width at a constant frequency. One end of the resistor R1 is connected to the terminal FB, and the other end of the resistor R1 is connected to one end of the resistor R2. The other end of the resistor R2 is grounded. As a result, the output voltage Vo becomes the control voltage E at the contact point between the resistors R1 and R2.
It is detected as RR. These resistors R1 and R2 are the output voltage detection means of the present invention.

  The error amplifier 61 is composed of an operational amplifier. The reverse phase input terminal of the error amplifier 61 is connected to a contact point between the resistor R1 and the resistor R2. On the other hand, the positive phase input terminal of the error amplifier 61 is connected to the output terminal α of the switch 22. The switch 22 has a switching input terminal β and a switching input terminal γ in addition to the output terminal α described above. The switching input terminal β is connected to the built-in reference voltage source 66. On the other hand, the switching input terminal γ is connected to the terminal OSV via a signal line.

Thereby, the switch 22 selects one of the internal reference voltage e1 supplied from the built-in reference voltage source 66 and the external reference voltage Vref supplied from the external reference voltage source (not shown) via the terminal OSV as the selection reference voltage. At the same time, it is input to the error amplifier 61. Accordingly, the error amplifier 61 is supplied with the internal reference voltage e1 or the external reference voltage Vref from the negative phase input terminal and the control voltage ERR from the positive phase input terminal. The error amplifier 61 detects and amplifies an error between the internal reference voltage e1 or the external reference voltage Vref and the control voltage ERR. This error amplifier 61 corresponds to the comparison means.

  The PWM comparator 62 has a positive-phase input terminal and a negative-phase input terminal, and compares a signal input from the positive-phase input terminal with a signal input from the negative-phase input terminal, and these two inputs. It is a voltage pulse width converter that determines the ON time of the output pulse according to the signal difference. That is, the PWM comparator 62 generates a signal (PWM signal) having a pulse width and a pulse interval corresponding to the magnitude of the output signal of the error amplifier 61. This PWM comparator 62 corresponds to the control signal generating means.

  The output terminal of the error amplifier 61 is connected to the positive phase input terminal of the PWM comparator 62. On the other hand, a triangular wave oscillator 64 is connected to the negative phase input terminal of the PWM comparator 62. Therefore, the PWM comparator 62 receives the detection amplification result of the error amplifier 61 from its positive phase input terminal as an output signal, and also receives a triangular wave signal from its negative phase input terminal.

  Here, the PWM comparator 62 outputs a high-level PWM signal while the triangular wave signal input from the triangular wave oscillator 64 is higher than the output signal of the error amplifier 61. In contrast, the PWM comparator 62 outputs a LOW level PWM signal while the triangular wave signal input from the triangular wave oscillator 64 is lower than the output signal of the error amplifier 61.

One end of the drive circuit 65 is connected to the PWM comparator 62, and the other end is connected to a control terminal connected to the control end of the transistor Tr1. As a result, the drive circuit 65
Is ON / OFF of the transistor Tr1 based on the PWM signal input from the PWM comparator 62.
Controls OFF. That is, when a HIGH level PWM signal is input to the drive circuit 65, the drive circuit 65 turns on the transistor Tr1. In contrast,
When a LOW level PWM signal is input, the drive circuit 65 stops its operation.

  The selection operation of the switch 22 is performed in response to the output signal of the comparator 23. The positive phase input terminal of the comparator 23 is connected to a signal line connecting the switching input terminal γ and the terminal OSV. On the other hand, the negative phase input terminal of the comparator 23 is connected to the comparison voltage source 30.

The comparator 23 compares the external reference voltage Vref with the comparison voltage e2, and when the external reference voltage Vref is larger than the comparison voltage e2, the HIGH signal is input to the switch 22, and the external reference voltage Vref is compared with the comparison voltage. When it is smaller than e2, a LOW signal is inputted to the switch 22.

The value of the comparison voltage e2 is set to a value smaller than the value of the external reference voltage Vref to be applied. For this reason, when the external reference voltage Vref is applied to the control unit 21a, the comparator 23 outputs a HIGH signal. The switch 22 selects the switching input terminal γ when a HIGH signal is given, and selects the switching input terminal β when a LOW signal is given. This comparator 23 corresponds to the external input detecting means of the present invention.

One end of the resistor R4 is connected to the signal line connecting the terminal OSV and the switching input terminal γ of the switch 22, and the other end is grounded. Thereby, when the external reference voltage Vref is not supplied from an external reference voltage source (not shown), the switching input terminal γ of the terminal OSV and the switch 22
The potential of the signal line connecting the two becomes the ground potential.

  Such a DC-DC converter 10 is mounted on an electronic device such as a notebook personal computer (not shown), and is used as a power supply circuit for a load (not shown) of the electronic device. Hereinafter, examples of use of the DC-DC converter 10 mounted on the electronic device will be described for a case where the electronic device is normally used and a case where the above-described margin test (the load test method of the present invention) is performed.

(1) When an electronic device is normally used As a premise, an operator applies an input voltage Vi to the input terminal of the DC-DC converter 10 shown in FIG. 5 and inputs an ON signal from the terminal SC to the controller 21a. . In this case, the operator does not apply the external reference voltage Vref to the control unit 21a.

Power is supplied to the power source 63 of the control unit 21a and an ON signal is input. The power supply 63 supplies power to each unit of the control unit 21a according to the ON signal. Then, the triangular wave transmitter 64 outputs a triangular wave signal. Further, the comparison voltage source 30 inputs the comparison voltage e2 to the comparator 23. On the other hand, as described above, since the external reference voltage Vref is not applied, the ground voltage is input to the comparator 23. The comparator 23 compares the comparison voltage e2 with the ground voltage, and gives the LOW signal to the switch 22 because the comparison voltage e2 is higher than the ground voltage.

When the switch 22 receives the LOW signal from the comparator 23, the switch 22 selects the switching input terminal β. As a result, the internal reference voltage e1 is input from the built-in reference voltage source 66 to the error amplifier 61. On the other hand, the control voltage ERR detected by the resistor R1 and the resistor R2 is input to the error amplifier 61. However, at this time, since the transistor Tr1 has never been turned on after the input voltage Vi is applied, the output voltage Vo is not output. In this case, the voltage zero is input to the error amplifier 61 as the control voltage ERR.

  The error amplifier 61 compares the internal reference voltage e1 and the control voltage ERR, detects and amplifies these errors, and inputs the result as an output signal to the PWM comparator 62. On the other hand, the triangular wave signal is input from the triangular wave transmitter 64 to the PWM comparator 62.

The PWM comparator 62 compares the output signal of the error amplifier 61 with the triangular wave signal. When the value of the control voltage ERR is zero, the triangular wave signal becomes higher than the output signal of the error amplifier 61, so that a HIGH level PWM signal is input to the drive circuit 65. The drive circuit 65 inputs a high-level PWM signal to the control terminal of the transistor Tr1 shown in FIG. As a result, the transistor Tr1 is turned on.

Then, a voltage is applied to the output terminal side of the transistor Tr1, and electric power is accumulated in the choke coil L1. When the transistor Tr1 is turned off, the power stored in the choke coil L1 is discharged by the flywheel diode D2. As a result, an output voltage Vo having a magnitude determined by the internal reference voltage e1 (voltage adjusted to correspond to the selected reference voltage) is output to the output terminal of the DC-DC converter 10.

The output voltage Vo is input to the control unit 21a as needed from the terminal FB, and is detected as the control voltage ERR by the resistors R1 and R2 shown in FIG. This control voltage ERR is input to the error amplifier 61 via the switch 22. The error amplifier 61 inputs the result of detecting and amplifying the error between the control voltage ERR and the internal reference voltage e1 to the PWM comparator 62.

The PWM comparator 62 compares the output signal of the error amplifier 61 with the triangular wave signal, generates a HIGH level or LOW level PWM signal, and inputs the PWM signal to the drive circuit 65. The drive circuit 65 receives the transistor Tr every time a HIGH level PWM signal is input.
Set 1 to ON. Such an operation is repeated.

In this way, the control unit 21a monitors the output voltage Vo, and turns on the transistor Tr1 when the output voltage Vo decreases from a voltage value determined by the internal reference voltage e1. As a result, the output voltage Vo having a value determined by the internal reference voltage e1 is constantly output to the output terminal of the DC-DC converter 10. That is, the output voltage Vo adjusted to a voltage corresponding to the internal reference voltage e1 is supplied as an operating voltage to the load, and the load operates normally.

(2) When performing a margin test When performing a margin test, an operator applies an input voltage Vi to the input terminal of the DC-DC converter 10 shown in FIG. Input an ON signal from. Further, from the terminal OSV, an external reference voltage Vref for margin testing is used.
Apply.

Then, as described above, the power supply 63 supplies power to each part of the control unit 21 a according to the ON signal, and the triangular wave transmitter 64 inputs the triangular wave signal to the PWM comparator 62. The comparison voltage source 30 inputs the comparison voltage e2 to the comparator 23. On the other hand, the external reference voltage Vref input from the terminal OSV is input to the comparator 23. Then, the comparator 23 compares the comparison voltage e2 with the external reference voltage Vref, and gives the HIGH signal to the switch 22 because the external reference voltage Vref is higher than the comparison voltage e2.

When the switch 22 receives the HIGH signal from the comparator 23, the switch 22 selects the switching input terminal γ. As a result, the external reference voltage Vref is input to the error amplifier 61. Subsequent operations are the same as those in the case where the electronic device is normally used, and thus description thereof is omitted. Finally, the output voltage Vo adjusted to a value based on the external reference voltage Vref is constantly output to the output terminal of the DC-DC converter 10 and supplied to the load.

Thereby, the operator can confirm whether or not the load operates normally at the output voltage Vo. Further, the operator operates an external reference voltage source (not shown), appropriately changes the value of the external reference voltage Vref for margin test, and applies it to the control unit 21a, thereby supplying a plurality of values of the output voltage Vo to the load. It becomes possible to do. Thus, for example, by changing the operating voltage from the lower limit to the upper limit of the margin, it can be confirmed whether or not the load operates normally within the margin.

When the operator stops applying the external reference voltage Vref, the ground voltage is input to the comparator 23 instead of the external reference voltage Vref. As a result, the comparator 23 becomes L
An OW signal is generated and this LOW signal is supplied to the switch 22. Then, the switch 22 performs a selection operation, and selects the switching input terminal β instead of the switching input terminal γ. Thereby, the selection reference voltage is switched from the external reference voltage Vref to the internal reference voltage e1. That is, the electronic device can be shipped.

According to the power supply control device (control unit 21a) according to the first embodiment, the switch 22 can select one of the internal reference voltage e1 and the external reference voltage Vref. For this reason, the value of the output voltage Vo supplied to the load can be changed by switching the switch 22. Therefore, when the operating voltage is supplied to the load by the DC-DC converter 10, if the switch 22 selects the internal reference voltage e1 supplied from the built-in reference voltage source 66, the operating voltage Vo with high accuracy can be obtained. Is supplied to the load.

On the other hand, when the margin test is performed, if the external reference voltage Vref for margin test is input to the control unit 21a, the switch 22 selects the switching input terminal γ, so that the output voltage Vo for margin test is applied to the load. Supplied. Thereby, the margin test can be performed without replacing the components of the DC-DC converter 10.

  As a result, it is possible to save labor, improve efficiency, and reduce the cost of the margin test, and the margin test can be performed for all electronic devices in which the DC-DC converter 10 is mounted. Therefore, it can be confirmed that the loads of all electronic devices shipped to the market operate normally within the margin. For this reason, it is possible to eliminate the failure of the electronic device that occurs because the load does not operate normally within the margin.

Further, the selection operation of the switch 22 is performed using the comparator 22 depending on whether or not the external reference voltage Vref is applied. Therefore, the selection operation of the switch 22 can be automatically performed, and the margin test can be performed more easily. Furthermore, since the configuration for automating the selection operation of the switch 22 can be realized with a simple configuration such as the comparator 23, the controller 21a is not increased in size and complexity.

  Note that the comparator 23, the comparison voltage source 30, and the resistor R4 may be removed from the control unit 21a shown in FIG. 1, and the selection operation of the switch 22 may be performed manually.

<Second Embodiment>
Next, a second embodiment of the present invention will be described. FIG. 7 shows a DC-DC converter 10 using the power supply control device according to the second embodiment as the control unit 21b. This DC-DC converter 10 corresponds to the power supply circuit of the present invention. The DC-DC converter 10 has the same configuration as the DC-DC converter 10 according to the first embodiment except for the control unit 21b. For this reason, description of common points is omitted, and differences are described.

  Instead of the terminal OSV described in the first embodiment, the control unit 21b has an external reference voltage value digital data input terminal (hereinafter referred to as "terminal DI") and a clock input terminal (hereinafter referred to as "terminal T"). ") Is provided. As shown in FIG. 8, in addition to the configuration of the control unit 21a shown in FIG. 6, a shift register 24 and a digital / analog converter (hereinafter referred to as “DAC”) 25 are provided inside the control unit 21b. ing.

  The terminal DI and the terminal T are connected to the shift register 24 so that digital data and a clock are input. The shift register 24 is connected to the DAC 25. As a result, the shift register 24 captures the digital data of the external reference voltage value input in bit serial according to the clock input from the terminal T, converts the digital data into parallel data, and inputs the parallel data to the DAC 25. It has become.

  The shift register 24 is connected to a signal line connecting the terminal SC and the power source 63, and an ON / OFF signal input from the terminal SC of the control unit 21b is input. As a result, the shift register 24 resets its own contents when an OFF signal is input.

The DAC 25 analogizes the parallel data of the external reference voltage value output from the shift register 24 to obtain an external reference voltage Vref (analog external reference voltage), and outputs the external reference voltage Vref. The DAC 25 can obtain a predetermined resolution such as 8 bits. The DAC 25 is connected to the switching input terminal γ of the switch 22 via a signal line.

On the other hand, the switching input terminal β of the switch 22 is connected to the built-in reference voltage source 66 as in the first embodiment. As a result, the switch 22 selects one of the reference voltage e1 from the internal reference voltage 66 and the external reference voltage Vref from the DAC 25, and inputs it to the error amplifier 61.

Similarly to the first embodiment, the switch 22 receives the output signal from the comparator 23 (corresponding to the external input detection means) and performs a selection operation. The positive phase input terminal of the comparator 23 is connected to a signal line that connects the DAC 25 and the switching input terminal γ of the switch 22. On the other hand, the negative phase input terminal of the comparator 23 is connected to the comparison voltage source 30. Thus, the external reference voltage Vref and the comparison voltage e2 are input to the comparator 23. The comparator 23 compares the magnitude relation between the external reference voltage Vref and the comparison voltage e2, and outputs the result as a HIGH signal or a LOW signal.

Here, when the external reference voltage Vref is higher than the comparison voltage e2, the comparator 23 gives a HIGH signal to the switch 22 assuming that the external reference voltage Vref is applied. In contrast,
When the external reference voltage Vref is lower than the comparison voltage e2, a LOW signal is given to the switch 22.

Note that the value of the comparison voltage e2 is set to a value smaller than the external reference voltage Vref. When the external reference voltage Vref is input to the comparator 23, a HIGH signal is supplied to the switch 22. ing. The switch 22 selects the switching input terminal γ when it receives a HIGH signal, and selects the switching input terminal β when it receives a LOW signal.

  Similar to the first embodiment, the DC-DC converter 10 including such a control unit 21b is mounted on an electronic device (not shown) and supplies an operating voltage to a load (not shown) of the electronic device. Below, the usage example of the DC-DC converter 10 mounted in the electronic device will be described for a case where the electronic device is normally used and a case where a margin test is performed.

(1) When an electronic device is normally used As a premise, an operator applies an input voltage Vi to the DC-DC converter 10 and inputs an ON signal to the control unit 21b. However, it is assumed that the operator does not input the digital data and clock of the external reference voltage value.

For this reason, the external reference voltage Vref is not input to the comparator 23. Therefore, the comparator 23
Gives a LOW signal to the switch 22. Then, the switch 22 selects the switching input terminal β. As a result, the internal reference voltage e 1 of the built-in reference voltage source 66 is input to the error amplifier 61. In addition, the control voltage ERR is input to the error amplifier 61. From this point on,
Since the operation is the same as that described in the first embodiment, the description thereof is omitted. Finally, the output voltage Vo having a value corresponding to the internal reference voltage e1 is constantly output to the output terminal of the DC-DC converter 10, and the load operates normally.

(2) When performing a margin test In this case, the operator presupposes that the input voltage Vi is applied to the DC-DC converter 10.
And an ON signal is input to the control unit 21b, and digital data and a clock having a predetermined external reference voltage value are input from the outside to the control unit 21b. At this time, the operator inputs the digital data of the external reference voltage value for the margin test in bit serial.

  This digital data is input to the shift register 24 of the control unit 21b. The shift register 24 converts this digital data into parallel data and inputs it to the DAC 25. The DAC 25 converts the parallel data into analog to generate an external reference voltage Vref.

The external reference voltage Vref is input to the comparator 23. On the other hand, the comparison voltage e <b> 2 is input to the comparator 23 from the comparison voltage source 30. The comparator 23 compares the external reference voltage Vref with the comparison voltage e2 of the comparison voltage source 30. Since the external reference voltage Vref is larger than the comparison voltage e2, the comparator 23 gives a HIGH signal to the switch 22.

Then, the switch 22 selects the switching input terminal γ. As a result, the external reference voltage Vref is input to the error amplifier 61. In addition, the control voltage ERR is input to the error amplifier 61. Subsequent operations are substantially the same as those described in the first embodiment, and thus description thereof is omitted. The output voltage Vo having a value based on the external reference voltage Vref is output to the output terminal of the DC-DC converter 10 in a constant manner.

When the digital data input to the control unit 21b is stopped, the external reference voltage Vref is not input to the comparator 23. For this reason, the comparator 23 changes the LOW signal to the switch 22.
To give. Then, the switch 22 selects the switching input terminal β. That is, the selection operation from the switching input terminal γ to the switching input terminal β is performed. Then, the reference voltage is changed from the external reference voltage Vref to the internal reference voltage e1, and the output voltage Vo based on the internal reference voltage e1 is output to the output terminal of the DC-DC converter 10. As a result, the electronic device can be shipped.

The effect of the power supply control device (control unit 21b) according to the second embodiment is almost the same as that of the first embodiment, but the external reference voltage Vref can be generated from digital data. Therefore, the external reference voltage Vref can be set by software processing by a computer. Therefore, for example, if the start-up control of the control unit 21b is performed by a monitoring program for monitoring the charging state and discharging state of the battery power source, the battery can be automatically charged.

  Note that the control unit 21b according to the second embodiment is configured to input digital data in bit serial in order to minimize the number of input / output terminals. Therefore, when it is not necessary to limit the number of input / output terminals, digital data may be input in bit parallel. In this case, the shift register 24 of the control unit 21b can be omitted.

<Third Embodiment>
Next, a third embodiment of the present invention will be described. FIG. 9 shows a power supply control device (control unit 21c) according to the third embodiment of the present invention. The control unit 21c is premised on that the digital data of the external reference voltage value is composed of a bit string representing the external reference voltage Vref and one bit for selection operation (selection operation data) of the switch 22. The parallel data output from is input to the switch 22.

  The switch 22 detects one bit for selection operation from parallel data. In other words, the switch 22 has a function equivalent to that of incorporating the external input detecting means of the present invention. Then, the switch 22 selects the switching input terminal β when the 1 bit for selection operation is not detected, or when the 1 bit for selection operation is 0, and when the 1 bit for selection operation is 1, the switch input terminal γ is selected. Since other configurations are the same as those of the second embodiment, description thereof is omitted.

  According to the control unit 21c according to the third embodiment, when digital data of an external reference voltage value is input, the digital data is converted into parallel data by the shift register 24. The parallel data is input to the DAC 25 and the switch 22 and converted to an analog external reference voltage Vref by the DAC 25.

On the other hand, the switch 22 detects one bit for selection operation from the parallel data, and selects the switching input terminal γ when determining that the one bit is “1”. As a result, the external reference voltage Vref converted by the DAC 25 is input to the error amplifier 61. Subsequent operations are the same as those in the second embodiment, and a description thereof will be omitted.

  The effect of the third embodiment is almost the same as the effect of the second embodiment, but the comparator 23 and the comparison power supply 30 may be omitted instead of adding a 1-bit detection function for selection operation to the switch 22. it can.

  The digital data input to the switch 22 may be serial data input from the terminal DI. Further, when the switch 22 detects one bit for selection operation, the switching input terminal γ may be selected regardless of whether the one bit for selection is 0 or 1. Furthermore, when the digital data of the external reference voltage value does not include one bit for the selection operation and the digital data of the external reference voltage value is input to the switch 22, the switch 22 detects this digital data and the switching input terminal γ may be selected.

  Further, the first to third embodiments described above show the configuration in the case where the output voltage is changed from the original value in the + direction. However, in order to change in the − direction in practice, a plurality of comparators 23 or a logic circuit may be provided to change both in the + direction and the − direction.

<Fourth embodiment>
Next, a fourth embodiment of the present invention will be described. FIG. 10 shows a synchronous rectification DC-DC converter 10 (corresponding to a power supply circuit) using the power supply control circuit according to the fourth embodiment as a control unit 21d. The DC-DC converter 10 has substantially the same configuration as the DC-DC converter 10 (see FIG. 5) according to the first embodiment. For this reason, description of common points is omitted, and differences are described.

The control unit 21d is provided with an output terminal DH and an output terminal DL, and the output terminal DH is connected to the control terminal of the transistor Tr1 as in the first embodiment. On the other hand, the output terminal DL is connected to the control terminal of the transistor Tr2. The input terminal of the transistor Tr2 is connected between the output terminal of the transistor Tr1 and the choke coil L1, and the output terminal of the transistor Tr2 is grounded.

The transistor Tr2 is a so-called synchronous rectification transistor, and is a flywheel switch circuit that discharges the electric power stored in the choke coil L1 while the transistor Tr1 is OFF. The transistor Tr2 is ON / OFF controlled by the controller 21d.

That is, the transistor Tr2 is turned on when the voltage applied to the flywheel diode D2 is in the forward direction, and turned off when the voltage applied to the flywheel diode D2 is in the reverse direction. Thereby, the voltage drop of the flywheel diode D2 is reduced. The transistor Tr2 is configured using an FET. Further, the diode D1 provided between the choke coil L1 and the output terminal of the DC-DC converter 10 is removed.

  Next, the internal configuration of the control unit 21d will be described with reference to FIG. The control unit 21d has substantially the same configuration as the control unit 21a (see FIG. 6) according to the first embodiment. For this reason, description of common points is omitted, and differences are described.

  The control unit 21d is obtained by removing the comparator 23, the comparison voltage source 30, and the resistor R4 from the control unit 21a shown in FIG. 6, and newly adds a charge pump circuit 67, a synchronous rectification control circuit 68, and a second drive. A circuit 69 is added. The output terminal of the PWM comparator (corresponding to the control signal generating means) 62 is connected to the drive circuit 65 and the synchronous rectification control circuit 68. As a result, the PWM signal is input from the PWM comparator 62 to the synchronous rectification control circuit 68.

The synchronous rectification control circuit 68 turns on / off the transistor Tr2 so that synchronous rectification is performed.
This circuit controls OFF. That is, when the PWM signal input from the PWM comparator 62 is at the LOW level so that the transistor Tr2 is turned on / off at the same time as the transistor Tr1 is turned on / off, the HIGH level PWM signal is changed to the high level PWM signal. In the case of the level, the LOW level PWM signal is inputted to the second drive circuit 69 while adjusting the input timing.

  The charge pump circuit 67 is connected to the drive circuit 65 and the second drive circuit 69. The charge pump circuit 67 is a power supply circuit that supplies the operating voltages of the transistors Tr1 and Tr2 to the drive circuit 65 and the second drive circuit 69.

The drive circuit 65 is connected to the control terminal of the transistor Tr1 via the terminal DH. When the drive circuit 65 receives a high-level PWM signal from the PWM comparator 62, the drive circuit 65 applies the voltage supplied from the charge pump circuit 67 to the control terminal of the transistor Tr1, and turns on the transistor Tr1 for a predetermined time. Yes.

The second drive circuit 69 is connected to the output terminal of the synchronous rectification control circuit 68. The second drive circuit 69 is connected to the control terminal of the transistor Tr2 via the terminal DL. When the second drive circuit 69 receives a HIGH level PWM signal from the synchronous rectification control circuit 68, the second drive circuit 69 applies the voltage supplied from the charge pump circuit 67 to the control terminal of the transistor Tr2. As a result, the transistor Tr2 is turned on for a predetermined time based on the PWM signal. Note that the switch 22 performs the selection operation by manual operation.

  Similarly to the first embodiment, the DC-DC converter 10 including such a control unit 21d is mounted on an electronic device (not shown) and supplies an operating voltage to a load (not shown) of the electronic device. Below, the usage example of the DC-DC converter 10 mounted in the electronic device will be described for a case where the electronic device is normally used and a case where a margin test is performed.

(1) When electronic equipment is normally used As a premise, the operator tilts the switch 22 shown in FIG. 11 to the switching input terminal β side, and applies the input voltage Vi to the input terminal of the DC-DC converter 10 shown in FIG. In addition, an ON signal is input to the control unit 21d.

  Then, power is supplied to the power source 63 of the control unit 21d and an ON signal is input. The power supply 63 supplies power to each part of the control unit 21d according to the ON signal. Then, the triangular wave transmitter 64 outputs a triangular wave signal. The charge pump circuit 67 supplies a voltage to the drive circuit 65 and the second drive circuit 69. Further, the comparison voltage source 30 inputs the comparison voltage e2 to the comparator 23.

On the other hand, as described above, since the switch 22 is in the state of selecting the switching input terminal β, the internal reference voltage e1 is input from the built-in reference voltage source 66 to the error amplifier 61. However, since the output voltage Vo is not detected at this time, the voltage zero is input to the error amplifier 61 as the control voltage ERR.

  The error amplifier 61 compares the internal reference voltage e1 and the control voltage ERR, detects and amplifies these errors, and inputs the result as an output signal to the PWM comparator 62. On the other hand, the triangular wave signal is input from the triangular wave transmitter 64 to the PWM comparator 62. The PWM comparator 62 compares the output signal of the error amplifier 61 with the triangular wave signal, and since the value of the control voltage ERR is zero, the triangular wave signal is higher than the output signal of the error amplifier 61. The signal is input to the drive circuit 65 and the synchronous rectification control circuit 68.

When receiving the HIGH level PWM signal, the drive circuit 65 uses the voltage supplied from the charge pump circuit 67 to turn on the transistor Tr1 shown in FIG. 10 based on the PWM signal. On the other hand, when the synchronous rectification control circuit 68 receives the HIGH level PWM signal, the synchronous rectification control circuit 68 generates a LOW signal and takes the second time into consideration when the transistor Tr1 is turned on.
Input to the drive circuit 69.

When receiving the LOW level signal, the second drive circuit 69 uses the voltage supplied from the charge pump circuit 67 to turn off the transistor Tr2 shown in FIG. 10 based on the PWM signal. As a result, the transistor Tr1 is turned on and the transistor Tr2 is turned off simultaneously. The transistor Tr1 is turned off and the transistor Tr2 is turned on simultaneously.

While the transistor Tr1 is ON, a voltage is applied to the output terminal side of the transistor Tr1, and electric power is accumulated in the choke coil L1. When the transistor Tr1 is turned off, the transistor Tr2 is turned on at the same time. Then, the electric power accumulated in the choke coil L1 is released by the flywheel diode D2. As a result, the output voltage Vo having a value based on the internal reference voltage e1 is output to the output terminal of the DC-DC converter 10.

The output voltage Vo is input to the control unit 21d as needed from the terminal FB, and is detected as the control voltage ERR by the resistors R1 and R2 shown in FIG. This control voltage ERR is input to the error amplifier 61. Then, the error amplifier 61 inputs the result of detecting and amplifying the difference between the control voltage ERR and the internal reference voltage e1 to the PWM comparator 62.

  The PWM comparator 62 compares the output signal of the error amplifier 61 with the triangular wave signal, generates a HIGH level or LOW level PWM signal, and inputs the PWM signal to the drive circuit 65 and the synchronous rectification control circuit 68. Then, the drive circuit 65 and the second drive circuit turn on / off the transistor Tr1 and the transistor Tr2 based on the PWM signal. Such an operation is repeated.

As described above, the control unit 21d monitors the output voltage Vo, and when the value of the output voltage Vo decreases, the control unit 21d sets the transistors Tr1 and Tr2 so that the output voltage Vo becomes a voltage value that substantially matches the internal reference voltage e1. Controls ON / OFF. As a result, the output voltage Vo having a value based on the internal reference voltage e1 is constantly output to the output terminal of the DC-DC converter 10, supplied to the load as an operating voltage, and the load operates normally.

(2) When performing a margin test When performing a margin test, the operator, as a premise, tilts the switch 22 shown in FIG. 11 to the switching input terminal γ side and inputs the DC-DC converter 10 shown in FIG. An input voltage Vi is applied to the end, and an ON signal is input to the control unit 21d. In addition, terminal OS
From V, an external reference voltage Vref for a margin test is applied.

  Then, the power supply 63 supplies power to each part of the control unit 21d according to the ON signal, and the triangular wave transmitter 64 inputs the triangular wave signal to the PWM comparator 62. The charge pump circuit 67 supplies a voltage to the drive circuit 65 and the second drive circuit.

Since the switch 22 is in a state in which the switching input terminal γ is selected, the external reference voltage Vref is thereby input to the error amplifier 61. On the other hand, since the control voltage ERR cannot detect the output voltage Vo at this time, the voltage zero is input to the differential voltage device 61 as the control voltage ERR. Subsequent operations are the same as those when the electronic device is normally used, and thus the description thereof is omitted. Finally, the output voltage Vo based on the external reference voltage Vref is output to the output terminal of the DC-DC converter 10 in a constant manner. If the operator tilts the switch 22 toward the switching input end β after the margin test, the electronic device is ready for shipment.

  The effect of the power supply control device according to the fourth embodiment is substantially the same as the effect of the first embodiment. However, since the selection operation of the switch 22 according to the present embodiment is performed by a manual operation, the number of man-hours in the margin test increases as compared with the first embodiment.

In the first to fourth embodiments, the input voltage Vi may be used as it is as the drive voltage of the control unit, or the input voltage Vi may be measured and used. Further, although the DC-DC converter 10 is shown as the power supply circuit, the power supply circuit to which the power supply control device of the present invention is applied is not limited to this and can be similarly applied to a series regulator or the like.

It is a block diagram which shows the outline | summary of embodiment of this invention. It is a block diagram which shows the outline | summary of embodiment of this invention. It is a block diagram which shows the outline | summary of embodiment of this invention. It is a block diagram which shows the outline | summary of embodiment of this invention. 1 is an overall configuration diagram of a DC-DC converter using a power supply control device according to a first embodiment of the present invention. It is an internal block diagram of the power supply control apparatus (control part) shown by FIG. It is a whole block diagram of the DC-DC converter using the power supply control device by 2nd Embodiment of this invention. It is an internal block diagram of the power supply control apparatus (control part) shown in FIG. It is an internal block diagram of the power supply control device (control part) by 3rd Embodiment of this invention. It is a whole block diagram of the DC-DC converter using the power supply control device by 4th Embodiment of this invention. It is an internal block diagram of the power supply control apparatus (control part) shown in FIG. It is a whole block diagram of the DC-DC converter using the conventional power supply control apparatus. It is an internal block diagram of the power supply control apparatus (control part) shown in FIG. It is a whole block diagram at the time of the margin test of the DC-DC converter shown in FIG. It is a whole block diagram of the DC-DC converter using the conventional power supply control apparatus. It is an internal block diagram of the power supply control apparatus (control part) shown in FIG.

Explanation of symbols

R1, R2 resistors (output voltage detection means)
Vo output voltage e1 Internal reference voltage (reference voltage)
Vref External reference voltage 10 DC-DC converter (power supply circuit)
21a, 21b, 21c, 21d Control unit (power control device)
22 switch 23 comparator (external input detection means)
24 DAC (digital / analog converter)
30 Comparison voltage source 61 Error amplifier (contrast (comparison) means)
62 PWM comparator (control signal generating means)
66 Built-in reference voltage source

Claims (11)

Output voltage detection means for detecting the output voltage of the power supply circuit and outputting a control voltage;
A built-in reference voltage source for supplying an internal reference voltage;
A selector for selecting one of the internal reference voltage supplied from the built-in reference voltage source and the external reference voltage applied from the outside as a selection reference voltage to be compared with the control voltage;
Control signal generating means for generating a control signal for adjusting the output voltage of the power supply circuit to a voltage corresponding to the selected reference voltage based on a comparison result between the control voltage and the selected reference voltage selected by the selector When,
An input terminal for inputting the external reference voltage from the outside;
The external reference voltage input from the input terminal is input, the external reference voltage is compared with a comparison voltage different from the internal reference voltage from a comparison voltage source, and the external reference voltage is higher than the comparison voltage. If the external reference voltage is lower than the comparison voltage, the selector outputs the output for the selector to select the external reference voltage and input it to the control signal generating means. A power supply control device comprising: a comparator for providing an output for selecting a reference voltage to the selector. A DC-DC conversion circuit that controls DC-DC conversion by a pulse width modulation control method using an output of an error amplifier,
Output voltage detection means for detecting an output voltage of the DC-DC conversion circuit and outputting a control voltage;
A built-in reference voltage source for supplying an internal reference voltage;
A selector for selecting one of the internal reference voltage supplied from the built-in reference voltage source and the external reference voltage source applied from the outside as a selection reference voltage to be compared with the control voltage;
An error amplifier to which the control voltage and the selection reference voltage selected by the selector are input;
A PWM comparator that generates a control signal for adjusting the output voltage of the DC-DC converter circuit to a voltage according to the selected reference voltage using the output of the error amplifier;
An input terminal for inputting the external reference voltage from the outside;
The external reference voltage input from the input terminal is input, the external reference voltage is compared with a comparison voltage different from the internal reference voltage from a comparison voltage source, and the external reference voltage is higher than the comparison voltage. In this case, the selector selects the external reference voltage and gives an output for inputting to the error amplifier. When the external reference voltage is lower than the comparison voltage, the selector selects the internal reference voltage. And a comparator for supplying an output for selecting the selector to the selector. In an electronic device equipped with a load and a power supply control device,
The power supply control device is provided inside a single integrated circuit.
Output voltage detection means for detecting the output voltage of the power supply circuit and outputting a control voltage;
A built-in reference voltage source for supplying an internal reference voltage;
A selector for selecting one of the internal reference voltage supplied from the built-in reference voltage source and the external reference voltage applied from the outside as a selection reference voltage to be compared with the control voltage;
Control signal generating means for generating a control signal for adjusting the output voltage of the power supply circuit to a voltage corresponding to the selected reference voltage based on a comparison result between the control voltage and the selected reference voltage selected by the selector When,
An input terminal for inputting the external reference voltage from the outside;
The external reference voltage input from the input terminal is input, the external reference voltage is compared with a comparison voltage different from the internal reference voltage from a comparison voltage source, and the external reference voltage is higher than the comparison voltage. In this case, the selector provides an output for selecting the external reference voltage and inputting it to the control signal generating means. When the external reference voltage is lower than the comparison voltage, the selector An electronic device comprising: a comparator for providing an output for selecting a reference voltage to the selector. In an electronic device including a load and a DC-DC conversion circuit that controls DC-DC conversion by a pulse width modulation control method using an output of an error amplifier,
The DC-DC conversion circuit is:
Output voltage detection means for detecting an output voltage of the DC-DC conversion circuit and outputting a control voltage;
A built-in reference voltage source for supplying an internal reference voltage;
A selector for selecting one of the external reference voltage applied from the internal reference voltage and an external supplied from the internal voltage reference as a selection reference voltage to be compared with the control voltage,
An error amplifier to which the control voltage and the selection reference voltage selected by the selector are input;
A PWM comparator that generates a control signal for adjusting the output voltage of the DC-DC converter using the output of the error amplifier to a voltage corresponding to the selected reference voltage;
An input terminal for inputting the external reference voltage from the outside;
The external reference voltage input from the input terminal is input, the external reference voltage is compared with a comparison voltage different from the internal reference voltage from a comparison voltage source, and the external reference voltage is higher than the comparison voltage. In this case, the selector selects the external reference voltage and gives an output for inputting to the error amplifier. When the external reference voltage is lower than the comparison voltage, the selector selects the internal reference voltage. An electronic device comprising: a comparator for providing an output for selecting the selector to the selector. Output voltage detection means for detecting the output voltage of the power supply circuit and outputting a control voltage;
A built-in reference voltage source for supplying an internal reference voltage;
External input detection means for detecting whether or not an external analog reference voltage applied from outside is applied by comparing the external reference voltage with a comparison voltage different from the internal reference voltage ;
A selector that selects one of the internal reference voltage and the external reference voltage as a selection reference voltage to be compared with the control voltage based on the detection result of the external input detection means;
Control signal generating means for generating a control signal for adjusting the output voltage of the power supply circuit to a voltage corresponding to the selected reference voltage based on a comparison result between the control voltage and the selected reference voltage selected by the selector And a power supply control device. A DC-DC conversion circuit that controls DC-DC conversion by a pulse width modulation control method using an output of an error amplifier,
Output voltage detection means for detecting an output voltage of the DC-DC conversion circuit and outputting a control voltage;
A built-in reference voltage source for supplying an internal reference voltage;
External input detection means for detecting whether or not an external analog reference voltage applied from outside is applied by comparing the external reference voltage with a comparison voltage different from the internal reference voltage ;
A selector that selects one of the internal reference voltage and the external reference voltage source as a selection reference voltage to be compared with the control voltage based on a detection result of the external input detection unit;
An error amplifier to which the control voltage and the selection reference voltage selected by the selector are input;
And a PWM comparator that generates a control signal for adjusting an output voltage of the DC-DC converter circuit to a voltage corresponding to the selected reference voltage using an output of the error amplifier. DC conversion circuit. In an electronic device equipped with a load and a power supply control device,
The power supply control device is provided inside a single integrated circuit.
Output voltage detection means for detecting the output voltage of the power supply circuit and outputting a control voltage;
A built-in reference voltage source for supplying an internal reference voltage;
An external input detecting means for detecting whether or not an analog external reference voltage applied from outside is applied by comparing the external reference voltage with a comparison voltage different from the internal reference voltage ;
A selector that selects one of the internal reference voltage and the external reference voltage as a selection reference voltage to be compared with the control voltage based on the detection result of the external input detection means;
Control signal generating means for generating a control signal for adjusting the output voltage of the power supply circuit to a voltage corresponding to the selected reference voltage based on a comparison result between the control voltage and the selected reference voltage selected by the selector An electronic device characterized by comprising: In an electronic device including a load and a DC-DC conversion circuit that performs DC-DC conversion control by a pulse width modulation control method using an output of an error amplifier,
The DC-DC conversion circuit is:
Output voltage detection means for detecting an output voltage of the DC-DC conversion circuit and outputting a control voltage;
A built-in reference voltage source for supplying an internal reference voltage;
An external input detecting means for detecting whether or not an analog external reference voltage applied from outside is applied by comparing the external reference voltage with a comparison voltage different from the internal reference voltage ;
A selector that selects one of the internal reference voltage and the external reference voltage as a selection reference voltage to be compared with the control voltage, based on a detection result of the external input detection unit;
An error amplifier to which the control voltage and the selection reference voltage selected by the selector are input;
An electronic apparatus comprising: a PWM comparator that generates a control signal for adjusting an output voltage of the DC-DC converter using the output of the error amplifier to a voltage corresponding to the selected reference voltage. . The external input detection means detects application of the external reference voltage when the external reference voltage is higher than the comparison voltage,
  The selector selects the external reference voltage when application of the external reference voltage is detected by the external input detection means.
The power supply control device according to claim 5. The external input detection means detects application of the external reference voltage when the external reference voltage is higher than the comparison voltage,
  The selector selects the external reference voltage when application of the external reference voltage is detected by the external input detection means.
The DC-DC converter circuit according to claim 6. The external input detection means detects application of the external reference voltage when the external reference voltage is higher than the comparison voltage,
  The selector selects the external reference voltage when application of the external reference voltage is detected by the external input detection means.
The electronic device according to claim 7 or 8, characterized in that.

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