TWI429181B - Apparatus and method for switching converter - Google Patents

Description

Switching converter device and method

The present invention is generally related to power supplies, and more particularly to switching converters.

Most electronic products, such as notebook computers, desktop computers, PDAs, etc., require a direct current (DC) power supply to provide regulated power to each functional module. The DC-DC synchronous buck converter has the advantages of high efficiency and small size, and has been widely used. Low voltage ripple and fast transient response are the most basic requirements for DC-DC synchronous buck converters.

The hysteresis control circuit has the advantages of fast transient response speed and simple structure, and can be used as a control circuit of a DC-DC synchronous buck converter. As shown in FIG. 1, the input voltage is modulated by the transistors 101 and 102. coupled to an output filter inductor 103 and a capacitor 104 composed of voltage after filtering is output to a load resistor 105, output voltage V _out through the voltage sampling circuit by the resistors 106 and 107 constitute a voltage sampling while the signal FB Feedback to the input of the hysteresis comparator 108, compared to the upper threshold voltage V _H and the lower threshold voltage V _L , the output signal of the hysteresis comparator 108 is coupled to the drive circuit 109, and the drive circuit 109 generates a corresponding The signals are driven to control the turn-on and turn-off of transistors 101 and 102, and the gate drive signals of transistors 101 and 102 are complementary. The example of FIG. 1 shows that the transistors 101 and 102 are metal oxide semiconductor field effect transistors (MOSFETs), and in other examples, such as bipolar junction transistors (BJT) or insulated gate bipolar transistors ( Other suitable electronic devices such as IGBTs are implemented. 2 shows the gate drive signal waveforms of the voltage sampling signal FB, the transistors 101 and 102 of FIG. When the feedback signal FB reaches the upper limit threshold V _H , the transistor 101 is turned off, the transistor 102 is turned on, and when the feedback signal FB reaches the lower limit threshold V _L , the transistor 102 is turned off, and the transistor 101 is turned on. However, the hysteresis control circuit relies excessively on the output voltage harmonics. By comparing the voltage harmonics with the upper and lower threshold voltages to generate the control signals of the upper and lower transistors, the output voltage harmonics of the converter cannot be controlled within the ideal range. Within this, the switching frequency of the converter also changes due to changes in peripheral components and operating conditions.

Figure 3 shows a DC-DC synchronous buck converter circuit employing a constant on-time (COT) control circuit. Output voltage V _out through the voltage sampling circuit and the voltage sampling signal FB back to the input terminal of the comparator 308, compared with the reference voltage signal V _REF, the output signal of the comparator 308 is coupled to a driving circuit 109, while the on-time clocking circuit 310 is also coupled to the driving circuit 109, and generates a conduction signal of the transistor 101 by comparing the voltage sampling signal FB with the reference voltage signal V _REF . The on-time of the transistor 101 is fixed, and is turned on by the conduction timing circuit 310. control. This method reduces the harmonics of the output voltage, but the turn-off time of the transistor 101 is variable and the switching frequency of the converter changes accordingly. Since the constant on-time control is used, the upper threshold voltage is omitted. If the load jump occurs when the transistor 101 is turned on, the circuit cannot make a rapid transient response, and the transistor 101 must be turned off after the on-time is over. This causes a large change in the output voltage. Fig. 4 shows waveforms of the voltage sampling signal FB and the transistor 101 gate driving signal of Fig. 3. When the feedback signal FB signal reaches the reference voltage V _REF, the transistor 101 is turned on, the on-time T _on is controlled by a system timing circuit 310 is turned on. The DC-DC synchronous buck converter circuit with constant on-time (COT) control circuit has improved the output voltage harmonics, but the switching frequency will still change due to changes in peripheral components and operating conditions, and under severe conditions The transient response speed is limited.

It is an object of the present invention to provide a device for a switching converter that has its output voltage ripple controlled within a small range, has a fast transient response speed, and has a stable switching frequency of the transistor.

It is an object of the present invention to provide a method of switching a converter that controls the output voltage ripple of the switching converter to a small range to have a fast transient response speed to ensure stable switching frequency of the transistor.

In order to achieve the above object, a switching converter circuit includes: an input terminal for receiving an input voltage; an output terminal coupled to the load circuit to provide an output voltage for the load circuit; and a feedback circuit coupled to the output voltage To provide a feedback signal to the driving circuit; the driving circuit is coupled to the feedback circuit to output the driving signal; and the switching circuit switches the transistor to be turned on or off based on the driving signal output by the driving circuit.

In one embodiment, the feedback circuit includes a voltage sampling circuit that samples the output voltage to generate a voltage sampling signal.

In one embodiment, the feedback circuit further includes a turn-on timing The turn-on timing circuit outputs a turn-on timing signal.

In one embodiment, the feedback circuit further includes an adaptive module that receives the drive signal and the turn-on timing signal to output an upper threshold voltage and a lower threshold voltage.

In one embodiment, the feedback circuit further includes a comparator circuit that compares the voltage sampling signal with the upper threshold voltage and the lower threshold voltage to generate the feedback signal .

In one embodiment, the on-time circuit is coupled to the input voltage, including a charging circuit coupled by at least one mirror current source and a first capacitor, and a comparison circuit; One end of the capacitor is coupled to the comparison circuit and compared to a reference voltage to generate the turn-on timing signal.

In one embodiment, the adaptive module includes a discharge circuit coupled by at least one first transistor and a first current source, and a second transistor and a second current A charging circuit coupled to the source.

In one embodiment, the gate of the first transistor is coupled to a driving signal output by the driving circuit, and the gate of the second transistor is coupled to the conduction timing signal.

In one embodiment, the adaptive module further includes a second capacitor coupled to the discharge circuit and the charging circuit. When the first transistor is turned on, the first current source discharges the second capacitor. The second current source charges the second capacitor when the second transistor is turned on.

In one embodiment, the adaptive module further includes a reference voltage a source, outputting the lower threshold voltage; the reference voltage source coupled to a hysteresis voltage source and coupled to the second capacitor; the reference voltage source, a hysteresis voltage source, and a second capacitor After the voltages of the three are added, the upper threshold voltage is output.

In one embodiment, the adaptive module further includes a reference voltage source that outputs the upper threshold voltage; the reference voltage source is coupled to a negative hysteresis voltage source, and the second capacitor The phase voltage is coupled to the reference voltage source voltage, and after the hysteresis voltage source voltage and the second capacitor voltage are subtracted, the lower threshold voltage is output.

In one embodiment, the switching circuit includes a first transistor and a second transistor, wherein a source of the first transistor is coupled to a drain of the second transistor as an output, and then a filter circuit It is coupled to the output terminal.

In one embodiment, the driving signals are two complementary pulse signals coupled to the gates of the first transistor and the second transistor, respectively.

The present invention adopts the above-mentioned structure device and/or method, and samples the output voltage signal of the switching converter via the voltage sampling circuit, and is supplied to the driving circuit via the feedback circuit to control the turning on and off of the transistor, and the output voltage can be adjusted. The adaptive control circuit provides upper and lower threshold voltages, so that the switching converter has a fast transient response speed, which can respond quickly even in the worst case. In addition, the adaptive control circuit can be based on the actual operation of the switching converter. The upper threshold voltage and/or the lower threshold voltage are adjusted to stabilize the switching frequency of the transistor.

A method and apparatus for a switching converter is disclosed. In the following description, numerous specific details are set forth in order to provide a However, it will be apparent to those skilled in the art that the invention In other instances, well-known materials or methods have not been specifically described in order to avoid obscuring the invention.

Reference throughout the specification to "one embodiment", "an embodiment", "an" or "an" or "an" In at least one embodiment. The appearances of the phrase "in one embodiment", "in the embodiment", "the" Furthermore, the particular features, structures, or characteristics may be combined in one or more embodiments or examples in any suitable combination and/or sub-combination. In addition, those skilled in the art should understand that the drawings are provided for the purpose of illustration, and the drawings are not necessarily drawn to scale.

5 is an input voltage coupled to an input capacitor and a switching circuit, the switching circuit is composed of transistors 101 and 102, and a common point of the transistors 101 and 102 is coupled to the inductor 103, in accordance with an embodiment of the present invention. And a filter formed by capacitor 104, and the output of the filter is coupled to the load circuit. One input of the adaptive hysteresis control circuit 511 is coupled to the gate of the transistor 101 to receive its drive control signal HS, and the other input of the adaptive hysteresis control circuit 511 is coupled to the turn-on timing circuit 510. To receive its turn-on timing signal. The output signals of the adaptive hysteresis control circuit 511 are coupled to the two inputs of the hysteresis comparator 508, respectively, to which an upper threshold voltage V _H and a lower threshold voltage V _{L are provided} . , The output voltage V _out is sampled by resistors 106 and 107 constitute a voltage sampling circuit, the feedback signal FB takes the voltage to the other input terminal of the hysteresis comparator 508. The hysteresis comparator 508 compares the voltage sampling signal FB with the upper and lower threshold voltages, couples the comparison result to the driving circuit 109, and the driving circuit 109 outputs a complementary driving signal according to the comparison result to control the transistors 101 and 102. Turn on and off.

Figure 6 is an embodiment of a turn-on timing circuit 510 of the present invention. The turn-on timing circuit 510 is coupled to the input voltage V _in , the mirror current source 601 charges the capacitor 602 with a current I, and the voltage across the capacitor 602 is coupled to the input of the comparator 603 by setting the mirror current source 601 and the capacitor. 602 can determine the turn-on timing signal. The reference voltage signal V _REF is coupled to the other input of the comparator 603. Compared with the voltage on the capacitor 602, the comparator 603 outputs a turn-on timing signal according to the comparison result, and the turn-on timing signal is coupled to the adaptive hysteresis control. An input of circuit 511.

Figure 7 is an embodiment of an adaptive control circuit 511 in the present invention. The gate of the transistor 701 is coupled to the gate drive signal HS of the transistor 101, and the gate of the transistor 702 is coupled to the turn-on timing signal. When the HS signal is high, the transistor 701 is turned on, the current source 704 discharges the capacitor 703 via the transistor 701 with the current I1; when the turn-on timing signal is high, the transistor 702 is turned on, and the current source 705 is passed through the transistor 702. The capacitor 703 is charged with a current I2. The reference voltage signal V _L is a lower threshold voltage and is added to a hysteresis voltage, such as 15 mV as shown in FIG. 7, but in a specific application, it can be adjusted according to actual conditions, and the summed voltage and the capacitor 703 are The voltage V _{C is} added and the obtained voltage is the upper threshold voltage V _H , V _H = V _L +15 mV + V _C (which can be implemented via an adder circuit). 8 is a schematic diagram showing the relationship between the upper limit threshold voltage and the lower limit threshold voltage in FIG. 7. The lower limit threshold voltage V _L is fixed, and the hysteresis voltage provides the upper limit threshold voltage V _H and the lower limit threshold voltage V _L during stable operation. The difference between this difference and the voltage V _C on the capacitor 703 is superimposed, so that the upper threshold voltage V _H is adjusted according to the actual operating conditions to achieve adaptive control. For example, in the case of I1=I2, the _on- time of the transistor 701 is _Ton-HS , the _on- time of the transistor 702 is _Ton-COT , and if _Ton-HS =T _on-COT , the voltage on the capacitor 703 is V _C = 0, V _H = V _L + 15 mV; if T _{on - HS} < T _{on - COT} , the voltage V _{C of the} capacitor 703 is > 0, V _H > V _L + 15 mV, and the _on- time of the transistor 101 T _on-HS It becomes larger to reach a higher upper limit threshold V _H ; if _Ton-HS >T _on-COT , the voltage V _C <0, V _H <V _L +15 mV on the capacitor 703, the _on- time T of the transistor 101 _{The on-HS} will become smaller because the upper threshold voltage V _H becomes smaller. The adaptive control circuit adjusts the upper threshold voltage according to the actual operation of the switching converter to ensure that the switching frequency varies within a small range. And the adaptive control circuit outputs the upper threshold voltage and the lower threshold voltage to ensure the transient response speed of the switching converter under the worst conditions.

Figure 9 is a waveform diagram obtained by simulation in accordance with the present invention. The lower limit threshold voltage V _L is a fixed value of 800 mV, the input voltage V _in is varied between 5 V and 16 V, and the upper limit threshold V _H is also varied between 810 mV and 815 mV, and the upper limit threshold is self-operating according to actual operation conditions. Adapt to adjustment.

Figure 10 is another embodiment of an adaptive control circuit 511 in accordance with the present invention. The reference voltage signal V _H is the upper limit threshold voltage, and V _H is a fixed voltage, which is subtracted from a hysteresis voltage, such as 15 mV as shown in FIG. 10, but can be adjusted according to actual conditions in a specific application, and the difference will be The post voltage is subtracted from the voltage V _C across capacitor 703, and the resulting voltage is the lower threshold voltage V _L , V _L = V _H -15 mV - V _C (which can be implemented via a subtractor circuit).

The above description of the illustrated examples of the invention, including the description of the present invention, is not intended to be exhaustive or limited to the precise forms disclosed. While the invention has been described with respect to the specific embodiments and examples of the present invention, various equivalent modifications are possible without departing from the spirit and scope of the invention. In fact, it should be understood that particular voltages, currents, frequencies, power range values, times, etc. are provided for illustrative purposes, and other values may be used in other embodiments and examples in accordance with the teachings of the present invention.

These modifications can be made to the examples of the invention in light of the above detailed description. The terms used in the following claims should not be construed as limiting the invention to the specific embodiments disclosed in the specification and claims. Rather, the scope is fully determined by the scope of the following patent application, and the scope of the patent application is to be understood in accordance with the principles of interpretation of the scope of the patent application that has been established. Accordingly, the specification and drawings are to be regarded as

101‧‧‧Optoelectronics

102‧‧‧Optoelectronics

103‧‧‧Inductors

104‧‧‧ capacitor

105‧‧‧Load resistors

106‧‧‧Resistors

107‧‧‧Resistors

108‧‧‧ Hysteresis comparator

109‧‧‧Drive circuit

308‧‧‧ comparator

310‧‧‧ Turn-on timing circuit

508‧‧‧ Hysteresis comparator

510‧‧‧ Turn-on timing circuit

511‧‧‧Adaptive hysteresis control circuit

601‧‧‧Mirror current source

602‧‧‧ capacitor

603‧‧‧ comparator

701‧‧‧Optoelectronics

702‧‧‧Optoelectronics

703‧‧‧ capacitor

704‧‧‧current source

705‧‧‧current source

FB‧‧‧ voltage sampling signal

HS‧‧‧ drive control signal

1 is a schematic diagram of controlling a DC-DC synchronous buck converter via a hysteresis control circuit.

2 is a waveform diagram of a transistor gate drive signal and a voltage sample signal of FIG. 1.

3 is a schematic diagram of controlling a DC-DC synchronous buck converter via a constant on-time control circuit.

4 is a waveform diagram of a transistor gate drive signal and a voltage sample signal of FIG.

5 is a schematic diagram of one embodiment of the present invention for controlling a DC-DC synchronous buck converter via an adaptive control circuit.

Figure 6 is a schematic illustration of one embodiment of the turn-on timing circuit of Figure 5.

Figure 7 is a schematic illustration of one embodiment of the adaptive control circuit of Figure 5.

Figure 8 is a schematic illustration of the upper and lower voltage thresholds of Figure 7.

Figure 9 is a schematic illustration of the circuit simulation results of Figure 5.

Figure 10 is a schematic illustration of another embodiment of the adaptive control circuit of Figure 5.

101‧‧‧Optoelectronics

102‧‧‧Optoelectronics

103‧‧‧Inductors

104‧‧‧ capacitor

105‧‧‧Load resistors

106‧‧‧Resistors

107‧‧‧Resistors

109‧‧‧Drive circuit

508‧‧‧ Hysteresis comparator

510‧‧‧ Turn-on timing circuit

511‧‧‧Adaptive hysteresis control circuit

Claims (23)

A switching converter circuit includes: an input terminal for receiving an input voltage; an output terminal coupled to the load circuit to provide an output voltage for the load circuit; and a feedback circuit coupled to the output voltage to provide feedback a signal is applied to the driving circuit; the driving circuit is coupled to the feedback circuit to output a driving signal; and the switching circuit switches the transistor to be turned on or off based on the driving signal output by the driving circuit, wherein the reverse The circuit includes a voltage sampling circuit, a turn-on timing circuit and an adaptive module. The voltage sampling circuit samples the output voltage to generate a voltage sampling signal, and the conduction timing circuit outputs a conduction timing signal, and the adaptive module receives the driving signal. And the turn-on timing signal to output an upper threshold voltage and a lower threshold voltage. The switching converter circuit of claim 1, wherein the feedback circuit further comprises a comparator circuit, the comparator circuit comparing the voltage sampling signal with the upper threshold voltage and the lower threshold voltage, To generate the feedback signal. The switching converter circuit of claim 1, wherein the on-time circuit is coupled to the input voltage, and includes a charging circuit coupled by at least one mirror current source and a first capacitor. And a comparison circuit; one end of the first capacitor is coupled to the ratio The comparator circuit is compared to a reference voltage to generate the turn-on timing signal. The switching converter circuit of claim 3, wherein the adaptive module comprises a discharge circuit coupled by at least one first transistor and a first current source, and a A charging circuit coupled by a second transistor and a second current source. The switching converter circuit of claim 4, wherein a gate of the first transistor is coupled to a driving signal output by the driving circuit, and a gate of the second transistor is coupled to the gate Turn on the timing signal. The switching converter circuit of claim 5, wherein the adaptive module further includes a second capacitor coupled to the discharge circuit and the charging circuit, when the first transistor is turned on, A first current source discharges the second capacitor; and when the second transistor is turned on, the second current source charges the second capacitor. The switching converter circuit of claim 6, wherein the adaptive module further includes a reference voltage source to output the lower threshold voltage; the reference voltage source is coupled to a hysteresis voltage source And coupling with the second capacitor; after the voltages of the reference voltage source, the hysteresis voltage source and the second capacitor are added, the upper threshold voltage is output. The switching converter circuit of claim 6, wherein the adaptive module further includes a reference voltage source to output the upper threshold voltage; the reference voltage source is coupled to a negative hysteresis voltage source After being connected, coupled to the second capacitor; after the reference voltage source voltage subtracts the hysteresis voltage source voltage and the second capacitor voltage, the lower threshold voltage is output. The switching converter circuit of claim 1, wherein the switching circuit comprises a first transistor and a second transistor, wherein a source of the first transistor and a drain of the second transistor The phase is coupled to serve as an output terminal, and is coupled to the output terminal via a filter circuit. The switching converter circuit of claim 9, wherein the driving signal is two complementary pulse signals coupled to the first transistor and the gate of the second transistor, respectively. A voltage conversion method, comprising: controlling a transistor to be turned on or off by using a driving signal to control an output voltage; adaptively outputting an upper threshold voltage or based on a turn-on timing signal and a driving signal for controlling the transistor a lower threshold voltage; a comparison of the sampling signal based on the output voltage with the upper threshold voltage and the lower threshold voltage to output a comparison signal; and based on the comparison signal to output a driving signal. The method of claim 11, wherein the sampling signal of the output voltage is implemented via a voltage sampling circuit coupled to the output voltage. The method of claim 11, wherein the turn-on timing signal is implemented by a turn-on timing circuit comprising: a charging circuit coupled by at least one mirror current source and a first capacitor And a comparison circuit; one end of the first capacitor is coupled to the comparison circuit and compared with a reference voltage to generate the on-time signal. The method of claim 11, wherein the adaptively outputting the upper threshold voltage is implemented by: a second capacitor coupled to the discharge circuit and the charging circuit, the discharge circuit borrowing The on/off is controlled by a driving signal, and the charging circuit controls on-off by turning on a timing signal, and the voltage terminal of the second capacitor superimposes the reference voltage source and the hysteresis voltage source, and outputs the upper threshold voltage, wherein the reference The voltage of the voltage source is used as the lower threshold voltage. The method of claim 14, wherein the discharge circuit is coupled by the first current source and the first transistor, and the gate of the first transistor receives the drive signal. The method of claim 14 or 15, wherein the charging circuit is coupled by the second current source and the second transistor, and the gate of the second transistor receives the conduction timing signal. The method of claim 16, wherein the first transistor is turned on when the driving signal is at a high level, and the first current source discharges the second capacitor via the first transistor. The method of claim 16, wherein the second transistor is turned on when the turn-on timing signal is at a high level, and the second current source charges the second capacitor via the second transistor. The method of claim 11, wherein the adaptively outputting the lower threshold voltage is implemented by: a second capacitor coupled to the discharge circuit and the charging circuit, the discharge circuit borrowing The on/off is controlled by a driving signal that is controlled to be turned on and off by turning on the timing signal, and the reference voltage source is subtracted from the voltage of the second capacitor, The lower threshold voltage is output after the voltage of the hysteresis voltage source, and the voltage of the reference voltage source is used as the upper threshold voltage. The method of claim 19, wherein the discharge circuit is coupled by the first current source and the first transistor, and the gate of the first transistor receives the driving signal. The method of claim 19 or 20, wherein the charging circuit is coupled by the second current source and the second transistor, and the gate of the second transistor receives the conduction timing signal. The method of claim 21, wherein the first transistor is turned on when the driving signal is at a high level, and the first current source discharges the second capacitor via the first transistor. The method of claim 21, wherein the second transistor is turned on when the turn-on timing signal is at a high level, and the second current source charges the second capacitor via the second transistor.