JP5169031B2 - Power supply - Google Patents

Description

  The present invention relates to a power supply device, and more particularly, to a stabilized power supply circuit suitable for improving transient characteristics and ensuring a phase margin.

  FIG. 4 is a diagram showing a typical configuration of the stabilized power supply circuit. Referring to FIG. 4, this stabilized power supply circuit includes a voltage conversion circuit 11, a reference voltage source 12, and a low-pass filter (low voltage) that amplifies an error between the voltage signal of the reference voltage source 12 and the output voltage of the voltage conversion circuit 11. A pass-pass filter / error amplifier 19 and a control circuit 16. The control circuit 16 receives the output signal of the low-pass filter / error amplifier 19 and controls the voltage conversion ratio of the voltage conversion circuit 11. The low-pass filter / error amplifier 19 includes a resistor 17 having one end connected to the output of the voltage conversion circuit 11, a resistor 18 having one end connected to the output of the reference voltage source 12, and an inverting input terminal and a non-inverting input terminal serving as resistors. The differential amplifier 13 is connected to the other end of 17 and 18, and a resistor 15 and a capacitor (capacitance) 14 connected in parallel with each other are provided between the output terminal and the inverting input terminal of the differential amplifier 13.

In order to set the ramp rate of the output voltage at power-on to an appropriate value,
(A) Only when the power supply is activated, the control circuit 16 ignores the signal of the low-pass filter and error amplifier 19 and forcibly outputs a preset control signal to control the voltage conversion circuit 11;
(B) A method of setting the output voltage ramp rate by changing the output voltage of the reference voltage source 12 only when the power source is started.

  In the AC output stabilization power supply circuit, the reference voltage source 12 generates a reference waveform having a necessary frequency and sets the output voltage of the voltage conversion circuit 11.

  As a configuration for changing the cutoff frequency of the low-pass filter provided in the feedback path, for example, in Patent Document 1, when there is a load fluctuation, the response characteristic is lowered, and when there is no load fluctuation, the response characteristic is changed. A configuration to raise is disclosed.

Japanese Patent Laid-Open No. 2005-20886

  In the circuit system in which the output voltage of the reference voltage source 12 is changed in either the DC output stabilized power supply or the AC output stabilized power supply, when the ratio between the input voltage and the output voltage of the voltage conversion circuit 11 is large, for example, DC In the stabilized output power supply, the gain of the voltage conversion circuit 11 increases during the period when the AC output stabilized power supply is set to a low output voltage in the vicinity of 0 degrees and 180 degrees when the power supply is activated.

  The gain of the low-pass filter / error amplifier 19 is increased in order to improve the frequency response characteristics at the rated voltage output of the DC output stabilizing power supply and at the high voltage output of the phase output 90 degrees and 270 degrees in the AC output power supply. When set or when the cut-off frequency is increased, the gain (voltage conversion ratio) of the voltage conversion circuit 11 is large during the period when the stabilized power supply circuit outputs a low output voltage. There is a limit to speeding up response characteristics.

Accordingly, an object of the present invention is to provide a power supply apparatus that can suppress a gain increase and prevent a decrease in phase margin even when a difference between an input voltage and an output voltage of a voltage conversion circuit is large, thereby enabling a high-speed response characteristic. There is to do.

  The invention disclosed in the present application has the following configuration in order to solve the above-described problems.

An apparatus according to one aspect of the present invention includes a feedback control system that performs error amplification between an output voltage of a voltage conversion circuit and a reference voltage and controls the output voltage based on an error amplification result.
A low-pass filter whose cutoff frequency is variable according to the output voltage or the reference voltage is provided.

  In the present invention, the low-pass filter may receive an output voltage of an error amplifier that performs the error amplification. The present invention includes a control circuit that controls a voltage conversion ratio of the voltage conversion circuit based on an output voltage of the low-pass filter.

  In the present invention, the low-pass filter has one capacitor whose capacitance is variable according to an applied DC voltage, and when the output voltage of the error amplifier is relatively low, the capacitor The capacitance of the capacitor decreases, and when the output voltage of the error amplifier is relatively high, the capacitance of the capacitor decreases. The cutoff frequency and gain of the pass filter are increased.

  In the present invention, the low-pass filter is inserted in a feedback path between an output terminal and an input terminal of an error amplifier that performs error amplification, and a cutoff frequency of the low-pass filter is set according to the reference voltage. It is good also as a variable structure.

  In the present invention, the low-pass filter includes a feedback resistor connected between the output terminal and the input terminal of the error amplifier, and a series circuit of a capacitor and a variable resistor connected in parallel with the feedback resistor. The resistance value of the variable resistor is variable according to the reference voltage, and when the reference voltage is relatively low, the resistance value of the variable resistor increases, and the cutoff frequency of the low-pass filter When the gain is reduced and the reference voltage is relatively high, the resistance value of the variable resistor may be reduced, and the cutoff frequency and gain of the low-pass filter may be increased.

  An apparatus according to another aspect of the present invention includes an A / D conversion circuit that converts an analog output voltage of a voltage conversion circuit into a digital signal, and a voltage conversion ratio of the voltage conversion circuit that receives an output signal of the A / D conversion circuit. A digital control circuit for controlling the voltage conversion circuit, wherein when the output voltage of the voltage conversion circuit is relatively low, the digital control circuit is set so as to reduce the gain and the cut-off frequency. When the output voltage is high, the gain and cut-off frequency are set to increase.

A method according to one aspect of the present invention relates to a low-pass filter of a feedback control system that performs error amplification between an output voltage of a voltage conversion circuit and a reference voltage.
When the output voltage of the voltage conversion circuit or the reference voltage is relatively low, the cutoff frequency and gain of the low-pass filter are reduced,
When the output voltage of the voltage conversion circuit or the reference voltage is relatively high, control is performed to increase the cutoff frequency and gain of the low-pass filter.

  According to another aspect of the present invention, there is provided a method for converting the output voltage of a voltage conversion circuit into a digital signal and controlling the voltage conversion ratio of the voltage conversion circuit based on the digital signal with respect to the gain and cutoff frequency of the control circuit. When the output voltage of the conversion circuit is relatively low, the gain and the cut-off frequency are set to be lowered. When the output voltage of the voltage conversion circuit is relatively high, the gain and the cut-off frequency are raised. Set to

  According to the present invention, it is possible to suppress an increase in gain during a time during which the output voltage of the voltage conversion circuit is set low, prevent a decrease in phase margin, and obtain a high-speed response characteristic.

  The present invention will be described with reference to the drawings in order to explain it in more detail. First, the principle of the present invention will be described. In order to increase the voltage stability of the stabilized power supply circuit, it is necessary to respond to fluctuations in negative overcurrent and input voltage at high speed. If the gain of the feedback control system is simply increased or the gain at high frequencies is increased, the phase margin will decrease and oscillation may occur if the input / output voltage difference of the voltage converter circuit is large. There is a limit to setting the system gain and high gain at high frequencies.

  According to the present invention, when the difference between the input voltage and the output voltage of the voltage conversion circuit is large, the gain of the feedback control system is lowered, and a stable output voltage can be obtained even in various fluctuations and transient states. . The present invention provides a stabilized power supply circuit having a phase margin and a high-speed response characteristic. In both the DC output stabilized power supply and the AC output stabilized power supply, the voltage signal and voltage conversion of the reference voltage source are provided. A feedback circuit that amplifies an error in the output voltage of the circuit with an error amplifier is provided with a low-pass filter (low-pass filter) that varies the cutoff frequency in accordance with the voltage signal of the reference voltage source and the output voltage of the power supply circuit. For example, the gain increase during the time when the output voltage of the voltage conversion circuit is set low can be suppressed, the phase margin can be prevented from decreasing, and high-speed response characteristics can be realized even during the period when the output voltage of the voltage conversion circuit is set high. It is said.

  In Patent Document 1, the response characteristic is lowered when there is a load fluctuation, and the response characteristic is raised when there is no load fluctuation, whereas the transient characteristic is improved in the present invention. The cut-off frequency is changed to follow the condition that the phase margin is eliminated (when the difference between the input voltage and the output voltage of the voltage conversion circuit is large). According to the present invention, in the case of a DC stabilized power supply, for example, the cut-off frequency is lowered at startup. In the case of an AC stabilized power supply, the cutoff frequency near the zero crossing is lowered, and the cutoff frequency is controlled according to the change of the output voltage (reference voltage), so that the AC stabilized power supply can also be supported. . In the following, description will be made in accordance with examples.

  FIG. 1 is a diagram showing the configuration of an embodiment of the present invention. Referring to FIG. 1, a low-pass filter (comprising a resistor 20 and a capacitor 21) is added to the configuration of FIG. That is, the differential amplifier 13, the capacitor 14 inserted in parallel between the output terminal and the inverting input terminal of the differential amplifier 13, the resistor 15, the inverting input terminal of the differential amplifier 13, and the output of the voltage conversion circuit 11. The resistor 20 connected between the resistor 20 and the output of the low-pass filter / error amplifier 19 including the resistor 18 connected between the non-inverting input terminal of the differential amplifier 13 and the output of the reference voltage source 12 are connected to the resistor 20 A low-pass filter composed of a capacitor 21 is added. As the capacitor 21, a ceramic capacitor or the like having voltage dependency (DC voltage characteristics) whose capacitance decreases when a voltage is applied is used.

  When the output signal voltage of the low-pass filter and error amplifier 19 is low, the capacitance (C) of the capacitor 21 increases, and the cutoff frequency (1 / (2πRC)) of the low-pass filter (20, 21) decreases. The gain is reduced, and the phase margin (the difference between the phase lag and the 180 degree frequency at a frequency of 1 in the frequency characteristic) is increased. As a result, the phase margin of the stabilized power supply circuit is increased, and the operation is stabilized.

  When the output signal voltage of the low-pass filter and error amplifier 19 is high, the capacitance (C) of the capacitor 21 decreases, the cutoff frequency (1 / (2πRC)) of the low-pass filter (20, 21) increases, The gain can be increased and high-speed response characteristics can be obtained.

  Next, a second embodiment of the present invention will be described. FIG. 2 is a diagram showing the configuration of the second exemplary embodiment of the present invention. In this embodiment, a variable resistor 22 whose resistance is variable according to the output voltage of the reference voltage source 12 is provided in series with the capacitor 14 inserted in the feedback path of the low-pass filter / error amplifier 19 of FIG. is there. That is, the low-pass filter / error amplifier 19 ′ includes the differential amplifier 13, the resistor 15 inserted between the output terminal and the inverting input terminal of the differential amplifier 13, and the variable resistor 22 connected in parallel to the resistor 15. And a capacitor 14, a resistor 17 connected between the inverting input terminal of the differential amplifier 13 and the output of the voltage conversion circuit 11, and between the non-inverting input terminal of the differential amplifier 13 and the output of the reference voltage source 12. A connected resistor 18 is provided. For example, the variable resistor 22 may be formed of a MOS transistor that receives an output reference voltage from the reference voltage source 12 at the gate and varies the on-resistance. Alternatively, any circuit configuration can be used as long as the resistance value can be varied within a desired range according to the output reference voltage.

  By changing the resistance value of the variable resistor 22 according to the output (output reference voltage) of the reference voltage source 12, the cutoff frequency of the low-pass filter / error amplifier 19 'is changed.

  When the output reference voltage of the reference voltage source 12 is low, the cutoff frequency of the low-pass filter / error amplifier 19 'is lowered, the gain is lowered, and the phase margin is increased.

  When the output reference voltage of the reference voltage source 12 is high, the cutoff frequency of the low-pass filter / error amplifier 19 'is increased, the gain is increased, and high-speed response characteristics are obtained.

  FIG. 3 is a diagram showing the configuration of the third exemplary embodiment of the present invention. Referring to FIG. 3, in this stabilized power supply circuit, the A / D conversion circuit 32 converts the output voltage of the voltage conversion circuit 31 into a digital signal, and the digital control circuit 33 controls the voltage conversion ratio of the voltage conversion circuit 31. To do. Regarding the gain and cut-off frequency characteristics of the digital control circuit 33, when the output voltage of the voltage conversion circuit 31 is low, the gain and cut-off frequency are set so as to decrease, thereby increasing the phase margin. Further, regarding the gain and cut-off frequency characteristics of the digital control circuit 33, when the output voltage of the voltage conversion circuit 31 is high, the gain and cut-off frequency are set so as to increase, thereby obtaining a high-speed response characteristic. The digital control circuit 33 may be configured by hard wired logic or may be realized by program control using a processor.

  The above-described embodiment can be applied to any DC stabilized power supply circuit provided in a feedback control system that performs error comparison, such as a series regulation system or a switching regulation system (chopper system, inverter system). A frequency conversion method (linear amplifier method, inverter) as well as a slidac method in which a slidac is inserted between the input and output to make a direct current and then compared with a direct current voltage, and a voltage comparison method in which a sine wave reference voltage is applied to compare the voltage This method can also be applied to an AC stabilized power source.

  It should be noted that the disclosures of the above patent documents are incorporated herein by reference. Within the scope of the entire disclosure (including claims) of the present invention, the embodiments and examples can be changed and adjusted based on the basic technical concept. Various combinations and selections of various disclosed elements are possible within the scope of the claims of the present invention. That is, the present invention of course includes various variations and modifications that could be made by those skilled in the art according to the entire disclosure including the claims and the technical idea.

It is a figure which shows the structure of the 1st Example of this invention. It is a figure which shows the structure of the 2nd Example of this invention. It is a figure which shows the structure of the 3rd Example of this invention. It is a figure which shows the typical structure of a stabilized power supply circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Voltage conversion circuit 12 Reference voltage source 13 Differential amplifier 14, 21 Capacitor 15, 17, 18, 20 Resistance 16 Control circuit 19, 19 'Low-pass filter and error amplifier 22 Variable resistance 31 Voltage conversion circuit 32 A / D conversion circuit
33 Digital control circuit

Claims (7)

In the feedback control system that performs error amplification between the output voltage of the voltage conversion circuit and the reference voltage and controls the output voltage based on the error amplification result,
A power supply apparatus comprising: a low-pass filter that receives an output voltage of an error amplifier that performs error amplification and whose cutoff frequency is variable according to the output voltage of the error amplifier or the reference voltage. The low-pass filter has one capacitor whose capacitance is variable according to the applied DC voltage,
When the output voltage of the error amplifier is relatively low, the capacitance of the capacitor increases, the cutoff frequency and gain of the low-pass filter decrease,
Wherein when the output voltage of the error amplifier is relatively high, the capacitance of the capacitor is reduced, the cutoff frequency and the gain of the low-pass filter is increased, the power supply according to claim 1, wherein the apparatus. Based on said low-pass output voltage of the filter, and a control circuit for controlling the voltage conversion ratio of the voltage conversion circuit, the power supply device according to claim 1 or 2 wherein. The low-pass filter is inserted in a feedback path between an output terminal and an input terminal of an error amplifier that performs the error amplification,
The power supply device according to claim 1, wherein a cutoff frequency of the low-pass filter is varied according to the reference voltage. The low-pass filter includes a feedback resistor connected between the output terminal and the input terminal of the error amplifier, and a series circuit of a capacitor and a variable resistor connected in parallel with the feedback resistor.
The variable resistor has a resistance value varied according to the reference voltage,
When the reference voltage is relatively low, the resistance value of the variable resistor increases, the cutoff frequency and gain of the low-pass filter decreases,
5. The power supply device according to claim 4 , wherein when the reference voltage is relatively high, a resistance value of the variable resistor is decreased, and a cutoff frequency and a gain of the low-pass filter are increased. The power supply apparatus according to any one of claims 1 to 5 , wherein a DC stabilized power supply is configured and the cut-off frequency is lowered at startup. AC stabilized power constitute, in the vicinity of zero cross, lowering the cutoff frequency, the power supply device according to any one of claims 1 to 5, characterized in that.

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