Power supply control device and power supply control method

Abstract

In recent years, it is desired to further improve the responsiveness in the case of preventing the output voltage from decreasing. The present invention provides a power supply control device, comprising: a switch control unit for controlling the on and off of a switch element of a step-up chopper using an oscillation wave; a voltage acquisition unit for acquiring a DC output voltage corresponding to the output of the step-up chopper; and an oscillation control unit for reducing the change speed of the oscillation wave during at least a part of the period during which the switch element is turned on, in response to the decrease in the DC output voltage.

Description

Technical Field

[0001] The invention relates to a power supply control device and a power supply control method. Background Art

[0002] Conventionally, various techniques have been proposed to prevent a drop in output voltage in a power supply device using a step-up chopper when a load suddenly increases or the like (see, for example, Patent Documents 1 and 2 and Non-Patent Document 1).

[0003] Patent Document 1: Japanese Patent Application Publication No. 2010-279190

[0004] Patent Document 2: Japanese Patent Application Publication No. 2000-116134

[0005] Non-patent document 1: "Current Continuous Mode Control Power Factor Improvement IC", page 15 / 30, [Online], [Retrieved on February 13, 2011], URL <URL:https: / / felib.fujielectric.co.jp / download / details.htm?dataid=1734586&site=japan&lang=ja>

[0006] Technical Problems to be Solved by the Invention

[0007] In recent years, there has been a demand for further improvement in responsiveness in preventing a decrease in output voltage. Summary of the invention

[0008] In order to solve the above problems, a first embodiment of the present invention provides a power supply control device. The power supply control device may include a switch control unit, which uses an oscillation wave to control the on and off of a switch element of a boost chopper. The power supply control device may include a voltage acquisition unit, which acquires a DC output voltage corresponding to the output of the boost chopper. The power supply control device may include an oscillation control unit, which reduces the change speed of the oscillation wave during at least a part of the conduction period of the switch element according to the fact that the DC output voltage drops.

[0009] The oscillation control unit may gradually reduce a change speed of the oscillation wave in at least a portion of a period during which the switching element is turned on, as the DC output voltage decreases.

[0010] The switch control unit may control the on and off of the switch element using the ramp wave as the oscillation wave. The oscillation control unit may reduce the efficiency of the ramp wave in at least a portion of the on period of the switch element according to the drop in the DC output voltage.

[0011] The power supply control device may further include an operation control unit configured to maintain the oscillation control unit in an enabled state in response to the DC output voltage exceeding a threshold voltage.

[0012] The power supply control device may further include an oscillator that generates an oscillation wave. The oscillator unit may include a capacitor. The oscillator may include a charge-discharge circuit that charges and discharges the capacitor. The oscillation control unit may reduce the charging current provided to the capacitor by the charge-discharge circuit according to the decrease in the DC output voltage.

[0013] The oscillation control unit may include a current output amplifier that subtracts a current corresponding to a difference between a reference voltage and a detection voltage obtained by detecting the DC output voltage from the charging current.

[0014] The current output amplifier can subtract the current that changes according to the magnitude of the difference between the reference voltage and the detection voltage from the charging current.

[0015] The current output amplifier can keep the charging current unchanged when the detection voltage is greater than the reference voltage, and can subtract a current that changes according to the difference between the reference voltage and the detection voltage from the charging current when the detection voltage is less than the reference voltage.

[0016] The current output amplifier may provide hysteresis between a reference voltage used when the detection voltage is equal to or higher than the reference voltage and a reference voltage used when the detection voltage is lower than the reference voltage.

[0017] The power supply control device may further include a trigger unit configured to switch the switching element to conduction in response to the current flowing through the step-up chopper being smaller than a reference current.

[0018] A second embodiment of the present invention provides a power supply control method. The power supply control method may include a switch control stage, in which an oscillation wave is used to control the on and off of a switch element of a boost chopper. The power supply control method may include a voltage acquisition stage, in which a DC output voltage corresponding to the output of the boost chopper is acquired. The power supply control method may include an oscillation control stage, in which, according to the decrease in the DC output voltage, a change speed of the oscillation wave during at least a portion of the period during which the switch element is turned on is reduced.

[0019] The above summary does not list all the necessary features of the present invention. In addition, sub-combinations of these feature groups may also constitute inventions. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A power supply device 1 according to this embodiment is shown.

[0021] Figure 2 The power supply control device 5 is shown.

[0022] Figure 3 The oscillator 52 and the oscillation control unit 59 are shown.

[0023] Figure 4 Indicates the feedback voltage V FB Changes in the ramp when the voltage drops.

[0024] Figure 5 Indicates the operating waveforms before and after a load surge.

[0025] Figure 6 Indicates the operating waveforms before and after a load surge.

[0026] Figure 7 The operation of the power supply control device 5 is shown. DETAILED DESCRIPTION

[0027] The present invention will be described below by way of embodiments of the invention, but the following embodiments do not limit the invention involved in the claims. In addition, the combination of features described in the embodiments is not necessarily required to be a technical means for solving the technical problem of the present invention.

[0028] [1. Power supply device]

[0029] Figure 1 1 shows a power supply device 1 according to the present embodiment. The power supply device 1 includes an AC power supply 2, a full-wave rectifier circuit 3 for full-wave rectifying an AC input voltage of the AC power supply 2, and a boost chopper 4 for boosting a DC output voltage of the full-wave rectifier circuit 3. A filtering capacitor (not shown) may be connected between the positive output side and the negative output side of the full-wave rectifier circuit 3.

[0030] [1-1. Step-up chopper 4]

[0031] The boost chopper 4 is connected between the positive output side and the negative output side of the full-wave rectifier circuit 3, and in this embodiment, for example, functions as a power factor improvement circuit. The boost chopper 4 includes: an inductor L1 and a diode D1 connected in series on the positive output side of the full-wave rectifier circuit 3, a boost switch element Q1, an output capacitor C1 connected between the cathode side of the diode D1 and the negative output side of the full-wave rectifier circuit 3, voltage dividing resistors R1 and R2 connected in parallel with the output capacitor C1 for detecting the output voltage, a power supply control device 5, and a voltage error detection compensation circuit 7.

[0032] The inductor L1 rectifies the current and uses the induced voltage to boost the DC output voltage of the full-wave rectifier circuit 3 along with the action inside the boost chopper 4. The inductor current IL1 can be a pulsating current of a high-order harmonic of, for example, 10kHz to 1000kHz. The diode D1 serves as a reverse current prevention diode. The switching element Q1 is, for example, an N-channel MOS transistor. The switching element Q1 can also be replaced by other MOS transistors or IGBTs. The drain and source of the switching element Q1 are electrically connected between the connection point of the inductor L1 and the anode side of the diode D1 and the negative output side of the full-wave rectifier circuit 3, and the gate is driven by a drive signal from the power supply control device 5. For example, the switching element Q1 is driven by PWM. The output capacitor C1 filters the voltage output by the power supply device 1. The output voltage V out For example, it may be about 400 V. The voltage dividing resistors R1 and R2 are connected in series with each other.

[0033] The power supply control device 5 may be, for example, an IC, and has a feedback terminal FB as an output voltage detection terminal, an output terminal OUT, a ground terminal GND, and a voltage error detection and compensation terminal COMP. The feedback terminal FB is connected to the connection point of the voltage dividing resistors R1 and R2, and the output voltage V out The divided voltage is used as the detection voltage (also called feedback voltage V FB The output terminal OUT outputs a drive signal S that has been pulse-width modulated to drive the boost switching element Q1. DV A voltage error detection and compensation circuit 7 is connected between the voltage error detection and compensation terminal COMP and the ground.

[0034] The voltage error detection compensation circuit 7 is used to remove the error signal V COMP The ripple component has a capacitor C71 and an RC phase compensation circuit 70 connected in parallel. The RC phase compensation circuit 70 has a resistor R700 and a capacitor C700 connected in series.

[0035] [2. Power supply control device 5]

[0036] Figure 2 5 represents a power supply control device 5. The power supply control device 5 includes a low voltage malfunction prevention unit 51, an oscillator 52, a voltage acquisition unit 53, an error amplifier 54, a level shift unit 55, an overcurrent detection unit 56, a trigger unit 57, a switch control unit 58, an oscillation control unit 59, a pull-up control unit 60, an overvoltage detection unit 61, a light load state detection unit 62, and a pull-down control unit 63. In addition, in the present embodiment, for example, the power supply control device 5 includes a resistor connection terminal RT for connecting a resistor, a control voltage supply terminal V in addition to the feedback terminal FB, the output terminal OUT, the ground terminal GND, and the voltage error detection compensation terminal COMP.CC The input control power supply terminal VCC and the current detection terminal CS for detecting the inductor current IL1. CC For example, it is a voltage generated by a voltage induced in an auxiliary winding of a transformer provided on the output side of the power supply device 1. The current detection terminal CS can input a detection voltage of a current detection resistor (not shown), which is connected between the DC negative output side of the full-wave rectifier circuit 3 and the ground, and is used to detect the inductor current IL1.

[0037] [2-1. Low voltage malfunction prevention unit 51]

[0038] The low voltage malfunction prevention unit 51 includes a comparator 51a. The inverting input terminal of the comparator 51a is connected to the control power supply terminal VCC, and the reference voltage V ref51 Therefore, the comparator output signal (also called low voltage detection signal) UVLO is at the control voltage V CC Higher than the reference voltage V ref51 In the case of a low level indicating a normal state, the control voltage V CC Lower than the reference voltage V ref51 In the case of , it becomes a high level indicating a low voltage abnormality. The comparator 51a may have a hysteresis characteristic, such as the reference voltage V ref51 It can be 12.5V and 7.5V.

[0039] [2-2. Oscillator 52]

[0040] The oscillator 52 generates an oscillation wave. For example, the oscillator 52 generates a ramp wave Ramp as the oscillation wave. The ramp wave Ramp may be in the shape of a triangular wave (e.g., a sawtooth wave). The oscillator 52 may be connected to a resistor (not shown) for determining an oscillation reference frequency via the resistor connection terminal RT of the power supply control device 5. The oscillator 52 may have a single-shot pulse P OS The input signal is input to terminal S, according to the single trigger pulse P OS The timing of the voltage waveform Ramp is generated by a sharp drop followed by a gradual increase. In addition, the oscillator 52 can use a single trigger pulse P OS The oscillator 52 may provide the ramp wave Ramp and the pulse signal Tonmax to the switch control section 58 .

[0041] [2-3. Voltage Acquisition Unit 53]

[0042] The voltage acquisition unit 53 acquires the DC output voltage V corresponding to the output of the step-up chopper 4. outIn this embodiment, for example, the voltage acquisition unit 53 is a feedback terminal FB of the power supply control device 5, and uses the voltage dividing resistors R1 and R2 (see Figure 1 ) for output voltage V out The feedback voltage after voltage division is V FB As the DC output voltage V out Thus, the DC output voltage V out Small feedback voltage V FB The feedback voltage V acquired by the voltage acquisition unit 53 is FB It can be provided to the error amplifier 54, the oscillation control section 59, the pull-up control section 60, the overvoltage detection section 61, and the like.

[0043] [2-4. Error amplifier 54]

[0044] The error amplifier 54 responds to the feedback voltage V FB With reference voltage V ref54 For example, a feedback voltage V is provided to the inverting input side of the error amplifier 54. FB , providing a reference voltage V corresponding to the target output voltage to the non-inverting input side ref54 For example, the reference voltage V ref54 The maximum feedback voltage can be V fb The error amplifier 42 may be a transconductance amplifier. The error amplifier 54 may generate a current corresponding to the differential voltage and charge the capacitor C71 of the voltage error detection and compensation circuit 7 connected to the voltage error detection and compensation terminal COMP, thereby generating an error signal V COMP By using the voltage error detection compensation circuit 7 to generate an error signal V COMP , so that the ripple component contained in the output current of the error amplifier 54 becomes smooth, and the error signal V COMP In a stable state, it becomes a DC voltage. The error signal V COMP It can be provided to the switch control section 58, the pull-up control section 60, the light load state detection section 62, the pull-down control section 63, and the like.

[0045] [2-5. Level shift unit 55]

[0046] The level shifter 55 pulls up the negative voltage input to the current detection terminal CS according to the inductor current IL1 and converts it into a positive voltage. The smaller the current flowing through the current detection resistor connected between the DC negative output side of the full-wave rectifier circuit 3 and the ground, the smaller the converted voltage V LS The higher the voltage V after being pulled up by the level shifter 55 LS The current is supplied to the overcurrent detection unit 56 and the trigger unit 57 .

[0047] [2-6. Overcurrent detection unit 56]

[0048] The overcurrent detection unit 56 detects an overcurrent of the inductor current IL1. For example, the overcurrent detection unit 56 detects an overcurrent of the inductor current IL1 when the voltage V LS Lower than the reference voltage V ref56 In the case of a high current (for example, in the present embodiment, when the current flowing through the current detection resistor is large), the overcurrent detection signal OCP at a high level is provided to the switch control unit 58. For example, the reference voltage V ref56 It can be -0.6V.

[0049] [2-7. Trigger unit 57]

[0050] The trigger unit 57 switches the switch element Q1 to conduction when the current flowing through the step-up chopper 4 is lower than the reference current. The trigger unit 57 includes a filter 57a, a comparator 57b, a masking circuit 57c, and a delay circuit 57d. The filter 57a removes the voltage V LS The noise is input to the comparator 57b. The voltage V from the filter 57a is input to the non-inverting input terminal of the comparator 57b. LS , the reference voltage V is input to the inverting input terminal ref57 . Reference voltage V ref57 It may be a voltage (e.g. -4 mV) when the current flowing through the step-up chopper 4 is a reference current (e.g., a current slightly larger than zero current). Thus, when the switch element Q1 is turned off and the inductor current IL1 is reduced to zero current, a determination signal of a high level is output from the comparator 57b. The comparator 57b provides the output signal to the masking circuit 57c. The masking circuit 57c transmits the output of the comparator 57b to the delay circuit 57b to prevent malfunction caused by noise just after the switch element Q1 is turned off, and can transmit the output before the change even when the output of the comparator 57b changes within a preset period. For example, the masking circuit 57c maintains the output of the comparator 57b just before the negative output QB rises until a predetermined time (e.g., 700 ns) has passed, based on the fact that the negative output signal QB from the RS-type flip-flop 58c described later in the switch control unit 58 rises to a high level (in this embodiment, for example, the switch element Q1 is turned off). Here, when the AC input voltage from the AC power source 2 is cut off, no current will flow through the inductor L1, so the outputs of the comparator 57b and the masking circuit 57c maintain a high level, so that the output signal from the masking circuit 57c (also called the zero current detection signal ZCD) indicates whether the pulsating current flowing through the inductor L1 is zero (or close to zero). The zero current detection signal ZCD can be provided to the switch control unit 58 via the delay circuit 57d.

[0051] [2-8. Switch control unit 58]

[0052] The switch control unit 58 controls the on and off of the switch element Q1 using an oscillation wave (for example, a ramp wave Ramp in this embodiment). The switch control unit 58 includes a pulse width modulation comparator 58a, an OR gate 58b, an RS type flip-flop 58c, an AND gate 58d, a driver 58e, a restart timer 58f, an OR gate 58g, and a one-shot circuit 58h.

[0053] The pulse width modulation comparator 58a outputs a pulse width modulation signal for modulating the pulse width of the drive signal of the switching element Q1. The oscillation wave (in this embodiment, for example, a ramp wave Ramp) from the oscillator 52 is input to the non-inverting input terminal of the pulse width modulation comparator 58a, and the error signal V generated by the error amplifier 54 and the voltage error detection compensation circuit 7 is input to the inverting input terminal. COMP . Error signal V COMP is an example of a threshold voltage for turning off the switching element Q1. The pulse width modulation comparator 58a outputs an output signal to the OR gate 58b. The OR gate 58b obtains the logical OR of the pulse width modulation signal from the pulse width modulation comparator 58a, the pulse signal Tonmax from the oscillator 52, and the overcurrent detection signal OCP from the overcurrent detection unit 56, and provides the logical OR signal to the RS type flip-flop 58c. The set terminal S of the RS type flip-flop 58c is input with the one-shot pulse P from the one-shot circuit 58h. OS , the reset terminal R is input with the output signal of the OR gate 58b. The RS-type flip-flop 58c provides the affirmative output signal QQ from the affirmative output terminal Q to the AND gate 58d and the restart timer 58f. The RS-type flip-flop 58c also provides the negative output signal QB from the negative output terminal QB to the masking circuit 57c. The AND gate 58d obtains the logical AND of the affirmative output signal QQ of the RS-type flip-flop 58c and the inverted signal of the low voltage malfunction prevention signal UVLO from the low voltage malfunction prevention unit 51, and provides the logical AND signal to the driver 58e. The driver 58e outputs the drive signal S to the gate of the switching element Q1 via the output terminal OUT. DV The restart timer 58f generates a start signal in response to the input of the high-level affirmative output signal QQ from the RS-type flip-flop 58c, and supplies the start signal to the one-shot circuit 58h via the OR gate 58g. The OR gate 58g calculates the logical OR of the zero current detection signal ZCD from the trigger unit 57 and the start signal from the restart timer 58f, and supplies the logical OR signal to the one-shot circuit 58h. The one-shot circuit 58h generates a one-shot pulse P which rises in response to the input of the high-level signal. OSThe RS flip-flop 58c is provided to the set terminal S. Thus, when the current flowing through the step-up chopper 4 is smaller than the reference current (for example, zero current), the RS flip-flop 58c is set.

[0054] [2-9. Oscillation control unit 59]

[0055] The oscillation control unit 59 generates a DC output voltage V corresponding to the output of the step-up chopper 4. OUT The oscillation control unit 59 reduces the change speed of the oscillation wave (in this embodiment, for example, the ramp wave Ramp) from the oscillator 52 during at least a portion of the on-time of the switching element Q1. For example, the oscillation control unit 59 reduces the change speed of the oscillation wave (in this embodiment, for example, the slope of the ramp wave Ramp) during at least a portion of the on-time of the switching element Q1 as the feedback voltage V FB For example, the oscillation control unit 59 has a current output amplifier 59a. The current output amplifier 59a may be a transconductance amplifier. The inverting output terminal of the current output amplifier 59a is input with the detected DC output voltage V from the voltage acquisition unit 53. OUT The feedback voltage V FB The non-inverting output terminal is input with a reference voltage V as a threshold value of the power factor improvement operation of the step-up chopper 4. ref59 The current output amplifier 59a outputs a current corresponding to the differential voltage and supplies it to the oscillator 52. The change speed of the ramp wave Ramp output from the oscillator 52 is reduced by the current from the current output amplifier 59a, and the details will be described later.

[0056] The current output amplifier 59a can make the detection voltage equal to the reference voltage V ref59 The reference voltage V used in the above cases ref59 and the detection voltage is less than the reference voltage V ref59 The reference voltage used in the case of V ref59 For example, it is used to determine whether the detection voltage is less than the reference voltage V ref59 In the case of reference voltage V ref59 Can be lower than the reference voltage V used to determine whether the detection voltage reaches the reference voltage ref59 In the case of reference voltage V ref59 For example, the reference voltage V ref59 The maximum feedback voltage can be V fb , and 0.72×maximum feedback voltage V fb .

[0057] [2-10. Pull-up control unit 60]

[0058] The pull-up control unit 60 pulls up the output of the error amplifier 54. In this embodiment, if the output of the error amplifier 54 is pulled up, the error signal V COMP The value of will become larger, and as a result, the conduction width of the switch element Q1 becomes larger, thereby transferring more energy to the output side, and the output voltage V OUT and feedback voltage V FB The pull-up control unit 60 includes a comparator 60a, an RS-type flip-flop 60b, an OR gate 60c, a P-channel MOSFET 60d, and a pull-up resistor 60e.

[0059] The feedback voltage V is input to the non-inverting input terminal of the comparator 60a. FB , the reference voltage V is input to the inverting input terminal ref60 For example, the reference voltage V ref60 Can be 0.86×maximum feedback voltage V fb The comparator 60a supplies the output signal UVP to the RS flip-flop 60b. The reset terminal R of the RS flip-flop 60b is input with the low voltage malfunction prevention signal UVLO from the low voltage malfunction prevention unit 51. The RS flip-flop 60b may be reset-first. The RS flip-flop 60b supplies the inverted signal of the output signal from the affirmative output terminal Q to the OR gate 60c. The RS flip-flop 60b may also be an example of an action control unit, which may be configured to control the output voltage V out When the threshold voltage is exceeded (in this embodiment, for example, according to the feedback voltage V FB Exceeds the reference voltage V ref60 In this case, the current output amplifier 59a of the oscillation control unit 59 is maintained in an enabled state. The RS type flip-flop 60b can also be controlled by the control voltage V CC Less than the reference voltage V ref51 In the case where the low voltage malfunction prevention signal UVLO is at a high level (in the present embodiment, for example), the current output amplifier 59a is disabled. For example, the output signal from the affirmative output terminal Q of the RS-type flip-flop 60b can be provided to the current output amplifier 59a of the oscillation control unit 59 to switch the on and off of the current output amplifier 59a. The OR gate 60c calculates the logical OR of the output signal UVP from the comparator 60a and the inverted signal of the output signal from the affirmative output terminal Q of the RS-type flip-flop 60b, and provides the logical OR signal to the gate of the P-channel MOSFET 60d. The P-channel MOSFET 60d is connected in series with the pull-up resistor 60e between the internal bias power supply terminal and the output of the error amplifier 54, and pulls up the output voltage of the error amplifier 54 when in the on state. In the above pull-up control unit 60, when the feedback voltage V FB Exceeds the reference voltage V ref60 Then it returns to the reference voltage V ref60During the following period, and the control power supply V CC is the reference voltage V ref51 The pull-up operation is stopped during the period from 0 to 1000 V and the UVLO signal is at a high level. Therefore, the overvoltage state can be suppressed during startup or in the low voltage malfunction prevention state.

[0060] [2-11. Overvoltage detection unit 61]

[0061] The overvoltage detection unit 61 detects the output voltage V out For example, the overvoltage detection unit 61 is fed back to the voltage V FB Higher than the reference voltage V ref61 In the case of a high voltage, the overvoltage detection signal OVP is provided to the pull-down control unit 63. For example, the reference voltage V ref61 Can be 0.98×maximum feedback voltage V fb .

[0062] [2-12. Light load state detection unit 62]

[0063] The light load state detection unit 62 detects that the power supply device 1 is in a light load state. In this embodiment, when the power supply device 1 is in a light load state, the error signal V COMP The light load state detection unit 62 includes a comparator 62a with hysteresis characteristics. The error signal V is provided to the inverting input terminal of the comparator 62a. COMP , the non-inverting input terminal is input with a reference voltage V of, for example, 0.6V or 0.75V. ref62 Therefore, the output signal of the comparator 62a (also called the light load detection signal) LLD is COMP When it is below 0.60V, it becomes high level, and then the error signal V COMP When it becomes equal to or higher than 0.7 V, it becomes a low level. The comparator 62 a supplies the light load detection signal LLD to the pull-down control unit 63 .

[0064] [2-13. Pull-down control unit 63]

[0065] The pull-down control section 63 pulls down the output of the error amplifier 54. The pull-down control section 63 includes an OR gate 63a, an RS-type flip-flop 63b, an AND gate 63c, an OR gate 63d, an N-channel MOSFET 63e, a pull-down resistor 63f, and a timer 63g. The OR gate 63a obtains a logical OR of the light load detection signal LLD from the light load state detection section 62 and the output signal of the timer 63g, and supplies the logical OR signal to the reset terminal of the RS-type flip-flop 63b. The set terminal of the RS-type flip-flop 63b is input with the low voltage malfunction prevention signal UVLO from the low voltage malfunction prevention section 51. The RS-type flip-flop 63b may be reset-first. The RS-type flip-flop 63b supplies the output signal from the affirmative output terminal Q to the AND gate 63c. The AND gate 63c obtains a logical AND of the output signal of the affirmative output terminal Q of the RS-type flip-flop 63b and the overvoltage detection signal OVP from the overvoltage detection section 61, and supplies the logical AND signal to the OR gate 63d and the timer 63g. The OR gate 63d obtains the logical OR of the output signal from the AND gate 63c and the low voltage malfunction prevention signal UVLO from the low voltage malfunction prevention unit 51, and inputs the logical OR signal to the gate of the N-channel MOSFET 63e. The N-channel MOSFET 63e is connected in series with the pull-down resistor 63f between the output terminal of the error amplifier 54 and the ground, and pulls down the output voltage of the error amplifier 54 when it is on. When the output signal of the AND gate 63c is at a high level for a predetermined period of time, the timer 63g outputs a high-level pulse signal to the AND gate 63c, thereby resetting the RS flip-flop 63b. Thus, the output of the AND gate 63c becomes a high level and the period during which the N-channel MOSFET 63e is turned on is limited. When the low voltage malfunction prevention signal UVLO is at a high level, or when the low voltage malfunction prevention signal UVLO becomes a high level, thereby setting the RS flip-flop 63b and the overvoltage detection signal OVP is at a high level, the output voltage of the error amplifier 54 is pulled down by the above pull-down control unit 63, and the error signal V COMP is fixed at a voltage lower than a predetermined reference voltage (e.g., a reference voltage V ref524 (Refer to Figure 3 )) voltage.

[0066] [2-14. Internal Structure of Oscillator 52 and Oscillation Control Unit 59]

[0067] Figure 3 The oscillator 52 and the oscillation control unit 59 are shown.

[0068] [2-14-1. Oscillator 52]

[0069] The oscillator 52 includes a capacitor C52 and a charge-discharge circuit 520 that charges and discharges the capacitor C52.

[0070] One side of the capacitor C52 is grounded, and the other side is connected to the charge-discharge circuit 520. The charge amount of the capacitor C52 is increased or decreased by the charge-discharge circuit 520 and output as a Ramp signal.

[0071] The charge and discharge circuit 520 includes a current source 521 , a P-channel MOSFET 522 , an N-channel MOSFET 523 , and a comparator 524 .

[0072] The current source 521 is a current source that outputs a constant current. CC A P-channel MOSFET 522 is connected in series with capacitor C52.

[0073] The gate of the P-channel MOSFET 522 is connected to the one-shot circuit 58h of the switch control unit 58. OS In this embodiment, when the P-channel MOSFET 522 is turned off, the charging of the capacitor C52 stops. When the P-channel MOSFET 522 is turned on, the current from the current source 521 charges the capacitor C52.

[0074] The N-channel MOSFET 523 is connected in parallel with the charging and discharging capacitor C52 between the P-channel MOSFET 522 and the ground. The gate of the N-channel MOSFET 523 is connected to the one-shot circuit 58h of the switch control unit 58. OS The capacitor C52 is turned on at the rising edge and turned off at the falling edge. In this embodiment, when the N-channel MOSFET 523 is turned on, the capacitor C52 is discharged, and when the N-channel MOSFET 523 is turned off, the discharge of the capacitor C52 stops.

[0075] The charging voltage of the charging and discharging capacitor C52 is input to the non-inverting input terminal of the comparator 524, and the reference voltage V ref524 Therefore, when the discharge voltage from capacitor C52 is greater than the reference voltage V ref524 In the case of , the comparator 524 outputs a pulse signal Tonmax of a high level.

[0076] [2-14-2. Oscillation control unit 59]

[0077] The oscillation control unit 59 generates a DC output voltage V OUT The decrease in the charging current provided to the capacitor C52 by the charge-discharge circuit 520 reduces the charging current. ref59 With the feedback voltage V FBThe current corresponding to the differential voltage is subtracted from the charging current of capacitor C52. For example, the current output amplifier 59a of the oscillation control unit 59 can be connected between the connection point of the current source 521 and the P-channel MOSFET522 and the ground, thereby playing the role of an injection (sucking) current source. Alternatively, the current output amplifier 59a of the oscillation control unit 59 can also be connected between the connection point of the P-channel MOSFET522 and the capacitor C52 and the ground. The current sucked in by the current output amplifier 59a can increase with the differential voltage, for example, it can increase continuously with the differential voltage, or it can increase in stages. Thus, the current that changes according to the size of the differential voltage will be subtracted from the charging current of capacitor C52.

[0078] The current output amplifier 59a can be used when the feedback voltage VFB is the reference voltage V ref59 In the above case, the charging current is kept constant and the feedback voltage V FB Less than the reference voltage V ref59 In this case, the reference voltage V ref59 and feedback voltage V FB The size of the difference is the changing current subtracted from the charging current.

[0079] According to the above oscillation control unit 59, the feedback voltage V FB Less than the reference voltage V ref59 In this case, the charging current is based on the reference voltage V ref59 and feedback voltage V FB The difference between the feedback voltage V FB is the reference voltage V ref59 In the above case, the charging current does not change, so the output voltage V out Changes occur.

[0080] The sink current is at the feedback voltage V FB Less than the reference voltage V ref59 It can also not increase with the difference voltage, but be greater than the feedback voltage V FB is the reference voltage V ref59 For example, the feedback voltage V FB is the reference voltage V ref59 When the absorption current is above zero, the feedback voltage V FB Less than the reference voltage V ref59 The absorption current when V can be a preset positive current. In this case, the oscillation control unit 59 can have: FB Less than the reference voltage V ref59A comparator that outputs a high-level output signal when the comparator is on, and a current source that draws a constant current from the charging current in response to the high-level output signal being provided from the comparator.

[0081] According to the above power supply control device 5, the DC output voltage V corresponding to the output of the step-up chopper 4 is OUT To reduce this situation, the change speed of the ramp wave Ramp is reduced during at least a part of the period during which the switch element Q1 is turned on. Therefore, the ramp wave Ramp exceeds the threshold voltage (in this embodiment, for example, the error voltage V COMP ) will be delayed, and the timing of the switch element turning off will be delayed, resulting in a wider on-time of the switch element and an increase in the output of the step-up chopper 4. Therefore, by reducing the change speed of the oscillation wave, it is possible to prevent the output voltage V out is reduced, thus preventing the output voltage V out Reduced responsiveness in case of

[0082] In addition, since the change speed of the ramp wave Ramp gradually decreases, the element current of the switching element Q1 can be prevented from changing suddenly, compared with the case where the change speed is switched in steps. Therefore, the element current of the inductor L1 can be prevented from changing suddenly, and audible sound can be prevented.

[0083] In addition, according to the feedback voltage V FB Exceeds the reference voltage V ref60 In this case, the current output amplifier 59a of the oscillation control unit 59 is maintained in the enabled state, thereby preventing the oscillation control unit 59 from operating at startup and causing an overvoltage state. In addition, when the low voltage malfunction prevention signal UVLO is at a high level, the current output amplifier 59a is disabled, thereby preventing the oscillation control unit 59 from operating in the low voltage malfunction prevention state and causing an overvoltage state.

[0084] In addition, the current output amplifier 59a has a hysteresis characteristic, so when the detection voltage is lower than the reference voltage V ref59 When a slight change occurs in the vicinity, the operation of the power supply control device 4 can be stabilized.

[0085] Furthermore, since the switching element Q1 is switched on in response to the fact that the current flowing through the step-up chopper 4 is smaller than the reference current, it is possible to prevent the output current from decreasing.

[0086] [3. Action waveform]

[0087] Figure 4 Indicates the feedback voltage V FB Changes in the ramp wave Ramp when the voltage is falling. In the figure, the vertical axis represents voltage and the horizontal axis represents time.

[0088] The ramp on the upper side of the figure is based on the feedback voltage V FB Less than the reference voltage V ref59 In this case, the current sucked by the oscillation control unit 59 changes from zero to a predetermined positive current. In this ramp Ramp, the feedback voltage V FB is the reference voltage V ref59 When the change speed is higher, the feedback voltage V FB Less than the reference voltage V ref59 In addition, the feedback voltage V FB Less than the reference voltage V ref59 The changing speed of the ramp Ramp is fixed and has nothing to do with the differential voltage.

[0089] In addition, the ramp Ramp on the lower side of the figure is based on the feedback voltage V FB With reference voltage V ref59 The waveform of the case where the current sucked by the oscillation control unit 59 continuously increases due to the magnitude of the differential voltage. FB is the reference voltage V ref59 When the change speed is higher, the feedback voltage V FB Less than the reference voltage V ref59 In addition, the feedback voltage V FB Less than the reference voltage V ref59 The changing speed of ramp Ramp gradually decreases with the difference voltage.

[0090] Figure 5 Indicates the feedback voltage V FB <Reference voltage V ref59 When the ramp rate is constant and has nothing to do with the voltage difference between the two (refer to Figure 4 The waveform at the top of the figure shows the output voltage V OUT , the waveform in the middle represents the error voltage V COMP The waveform at the bottom represents the element current I of the switching element Q1. DS The horizontal axis represents time, and the load surges at time t in the figure.

[0091] As shown in the figure, according to the feedback voltage V FB When the ramp rate decreases, the output voltage V out The figure shows that the waveform of the element current IDS is disturbed and an audible sound is emitted.

[0092] Figure 6 Indicates the feedback voltage VFB <Reference voltage V ref59 When the ramp rate of change increases with the magnitude of the difference voltage between the two (refer to Figure 4 The action waveform before and after the load surge is shown in the ramp wave Ramp on the lower side of the figure. Figure 5 same.

[0093] As shown in the figure, the feedback voltage V FB Less than the reference voltage V ref59 When the ramp Ramp changes gradually with the differential voltage, it can prevent the device current I DS The waveform is disrupted, resulting in audible sound.

[0094] [4.Action]

[0095] Figure 7 2 shows the operation of the power supply control device 5. The figure shows the operation of the oscillator 52, the switch control unit 58, and the oscillation control unit 59 in the operation of the power supply control device 5.

[0096] In step S11, the switch control unit 59 controls the on / off of the switch element Q1 of the step-up chopper 4 using the ramp wave Ramp from the oscillator 52. For example, the pulse width modulation comparator 58a inputs the error signal V to the reset terminal R of the RS type flip-flop 58c via the OR gate 58b. COMP The following is a low level, when the ramp Ramp is greater than the error signal V COMP Therefore, when the ramp wave Ramp is the error signal V COMP In the following case, the RS flip-flop 58 is set by the one-shot pulse from the one-shot circuit 58h. According to this case, the high-level positive output signal QQ is provided to the driver 58, and the switch element Q1 is turned on. On the other hand, when the ramp wave Ramp is greater than the error signal V COMP In this case, the RS flip-flop 58 is reset, and the low-level affirmative output signal QQ is provided to the driver 58e, setting the switch element Q1 to the off state.

[0097] In step S13, the voltage acquisition unit 53 acquires the DC output voltage V corresponding to the output of the step-up chopper 4. OUT For example, the voltage acquisition unit 53 outputs the voltage V out The feedback voltage V after voltage division by the voltage divider resistors R1 and R2 FB Obtained as a DC output voltage.

[0098] In step S15, the oscillation control unit 59 controls the DC output voltage V OUTTo reduce this, the change speed of the ramp wave Ramp during at least a portion of the on-time of the switch element Q1 is reduced. For example, the current output amplifier 59a converts the reference voltage V ref59 The feedback voltage V FB The current corresponding to the difference in the detection voltage is subtracted from the charging current of capacitor C52, thereby reducing the changing speed of ramp Ramp.

[0099] Thereafter, the power supply control device 5 repeats the processing of steps S11 to S15.

[0100] Through the above actions, according to the DC output voltage V OUT To reduce this, the change speed of the oscillation wave during at least a portion of the period during which the switch element Q1 is turned on is reduced, so that the ramp wave Ramp exceeds the threshold voltage (in this embodiment, for example, the error voltage V COMP ) will be delayed, and the timing of the switch element Q1 turning off will be delayed, resulting in a wider on-time of the switch element Q1 and an increase in the output of the step-up chopper 4. Therefore, by reducing the change speed of the oscillation wave, it is possible to prevent the output voltage V out is reduced, thus preventing the output voltage V out Reduced responsiveness in case of

[0101] [5. Modifications]

[0102] In the above embodiment, the power supply device 1 is described as including the AC power supply 2 and the full-wave rectifier circuit 3 , but one of the two may not be provided in the power supply device 1 but may be connected to the power supply device 1 from the outside.

[0103] In addition, it is described that the power supply control device 5 has a low voltage malfunction prevention unit 51, an oscillator 52, an error amplifier 54, a level shifter unit 55, a trigger unit 57, a pull-up control unit 60, an overvoltage detection unit 61, a light load state detection unit 62 and a pull-down control unit 63, but at least one of these components may not be provided.

[0104] The present invention has been described above using the embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments. It is obvious to those skilled in the art that various changes or improvements can be made on the basis of the above embodiments. According to the description of the patent claims, the above-mentioned various changes or improvements are also included in the technical scope of the present invention.

[0105] Please note that the execution order of the actions, processes, steps, and stages of the devices, systems, programs, and methods shown in the claims, specifications, and drawings can be implemented in any order unless "before", "previously", etc. are specifically stated, and the output of the previous processing is not used in the subsequent processing. In the action flow in the claims, specifications, and drawings, "first", "then", etc. are used for convenience of explanation, but it does not mean that it must be implemented in this order.

[0106] Description of symbols

[0107] 1 power supply device; 2 AC power supply; 3 full-wave rectifier circuit; 4 step-up chopper; 5 power supply control device; 7 voltage error detection compensation circuit; 51 low voltage malfunction prevention unit; 51a comparator; 52 oscillator; 53 voltage acquisition unit; 54 error amplifier; 55 level shift unit; 56 overcurrent detection unit; 57 trigger unit; 57a filter; 57b comparator; 57c masking circuit; 57d delay circuit; 58 switch control unit; 58a comparator for pulse width modulation; 58b OR gate; 58c RS type flip-flop; 58d AND gate; 58e driver; 58f restart timer; 58g OR gate; 58h one-shot circuit; 59 oscillation control unit; 59a current output amplifier; 60 pull-up control unit; 60a comparator; 60b RS type flip-flop; 60c OR gate; 60d P-channel MOSFET 60d; 61 overvoltage detection unit; 62 light load state detection unit; 62a comparator; 63 pull-down control unit; 63a OR gate; 63b RS type flip-flop; 63c AND gate; 63d OR gate; 63e N-channel MOSFET; 63f pull-down resistor; 63g timer; 70 RC phase compensation circuit; 520 charging and discharging circuit; 521 current source; 522 P-channel MOSFET; 523 N-channel MOSFET; 524 comparator; C1 capacitor; C71 capacitor; C700 capacitor; D1 diode; Q1 switch element; R1 voltage divider resistor; R2 voltage divider resistor; R700 resistor.

Claims

1. A power supply control device, characterized in that: include: a switch control unit that uses the oscillation wave to control the on and off of a switch element of the step-up chopper; a voltage acquisition unit configured to acquire a DC output voltage corresponding to an output of the boost chopper; an oscillation control unit that reduces a change speed of the oscillation wave during at least a portion of a period during which the switching element is turned on, in response to a decrease in the DC output voltage; When it is detected that the feedback voltage corresponding to the DC output voltage is greater than a first threshold, the oscillation control unit keeps the change speed constant; When it is detected that the feedback voltage is less than the first threshold, the oscillation control unit gradually reduces the change speed according to the difference between the DC output voltage and a preset voltage.

2. The power control device according to claim 1, characterized in that: The oscillation control unit gradually reduces a change speed of the oscillation wave during at least a portion of a period in which the switching element is turned on as the DC output voltage decreases.

3. The power control device according to claim 2, characterized in that: The switch control unit uses a ramp wave as the oscillation wave to control the on and off of the switch element. The oscillation control unit reduces the slope of the ramp wave during at least a portion of a period in which the switching element is on, in response to a decrease in the DC output voltage.

4. The power supply control device according to any one of claims 1 to 3, characterized in that: An oscillator is also provided, the oscillator generates the oscillation wave, The oscillator comprises: Capacitors; and a charging and discharging circuit for charging and discharging the capacitor, The oscillation control unit reduces the charging current supplied by the charging and discharging circuit to the capacitor in response to the decrease in the DC output voltage.

5. The power control device according to claim 4, characterized in that: The oscillation control unit includes a current output amplifier that subtracts a current corresponding to a difference between a reference voltage and a detection voltage obtained by detecting the DC output voltage from the charging current.

6. The power control device according to claim 5, characterized in that: The current output amplifier subtracts a current that changes according to a magnitude of a difference between the reference voltage and the detection voltage from the charging current.

7. The power control device according to claim 6, characterized in that: The current output amplifier keeps the charging current unchanged when the detection voltage is greater than the reference voltage, and subtracts a current that changes according to the difference between the reference voltage and the detection voltage from the charging current when the detection voltage is less than the reference voltage.

8. The power supply control device according to any one of claims 5 to 7, characterized in that: The current output amplifier provides hysteresis between the reference voltage used when the detection voltage is equal to or higher than the reference voltage and the reference voltage used when the detection voltage is lower than the reference voltage.

9. The power supply control device according to any one of claims 1 to 3, characterized in that: A trigger unit is further provided for switching the switching element on in response to the current flowing through the step-up chopper being smaller than a reference current.

10. A power supply control device, characterized in that: include: a switch control unit that uses the oscillation wave to control the on and off of a switch element of the step-up chopper; a voltage acquisition unit configured to acquire a DC output voltage corresponding to an output of the boost chopper; an oscillation control unit that reduces a change speed of the oscillation wave during at least a portion of a period during which the switching element is turned on, in response to a decrease in the DC output voltage; as well as an operation control unit that provides the oscillation control unit with an output signal for maintaining the oscillation control unit in an enabled state in response to the DC output voltage exceeding a threshold voltage.

11. A power supply control method, characterized in that: The following phases are included: A switch control stage, in which the oscillation wave is used to control the on and off of the switch element of the boost chopper; A voltage acquisition stage, in which a DC output voltage corresponding to the output of the boost chopper is acquired; an oscillation control stage, in which, in response to a decrease in the DC output voltage, a change rate of the oscillation wave during at least a portion of a period during which the switching element is turned on is reduced; The oscillating wave is generated by an oscillator, wherein the oscillator comprises a capacitor and a charging and discharging circuit for charging and discharging the capacitor; The stage of charging and discharging the capacitor; A stage in which the charging current supplied to the capacitor by the charging and discharging circuit is reduced according to the decrease of the DC output voltage; A stage in which a current corresponding to a difference between a reference voltage and a detection voltage obtained by detecting the DC output voltage is subtracted from the charging current.

Images