WO2020066111A1 - Switching power supply device - Google Patents

Switching power supply device Download PDF

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Publication number
WO2020066111A1
WO2020066111A1 PCT/JP2019/019040 JP2019019040W WO2020066111A1 WO 2020066111 A1 WO2020066111 A1 WO 2020066111A1 JP 2019019040 W JP2019019040 W JP 2019019040W WO 2020066111 A1 WO2020066111 A1 WO 2020066111A1
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WO
WIPO (PCT)
Prior art keywords
output
voltage
power supply
pulse
switching power
Prior art date
Application number
PCT/JP2019/019040
Other languages
French (fr)
Japanese (ja)
Inventor
健志 ▲濱▼田
秀明 渡邊
アナンダ ビターナゲ
チェンギャム タン
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Fdk株式会社
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Publication of WO2020066111A1 publication Critical patent/WO2020066111A1/en

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    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02MAPPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00Conversion of dc power input into dc power output
    • H02M3/02Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02MAPPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00Conversion of dc power input into dc power output
    • H02M3/22Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02MAPPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode

Definitions

  • the present invention relates to a switching power supply device.
  • Switching power supplies are widely used as one type of power converter that converts an input voltage into a desired voltage and outputs the converted voltage.
  • switching power supply apparatuses have been increased by full digital control in which a feedback signal such as an output voltage, an output current, or temperature is A / D converted and taken into a microcomputer control circuit, and power conversion is performed based on the feedback signal.
  • a switching power supply device based on full digital control can accurately control the timing of the switching operation in response to changes in load conditions and input conditions, so that noise and power loss can be reduced.
  • various sequence operations can be set by firmware, so that parts can be reduced and the system can be downsized.
  • the switching power supply device is often provided with a protection function for stopping the operation when the output voltage or the output current rises abnormally.
  • a protection function for stopping the operation when the output voltage or the output current rises abnormally.
  • an overvoltage protection function OVP: Over Voltage Protection
  • OCP Over Current Protection
  • Patent Document 1 More specifically, the conventional technology described in Patent Document 1 is a switching power supply device that sets a latch-off state when an overcurrent is detected and releases the latch-off at a predetermined timing.
  • the switching power supply device based on digital control performs control in discrete time according to the clock frequency, the output voltage fluctuates greatly due to a sudden load fluctuation or input fluctuation, and the output is stopped due to latch-off. Therefore, an external load device to which power is supplied from the switching power supply device is protected from a failure due to overvoltage or overcurrent, but power supply is cut off.
  • the switching power supply device is designed to quickly lower the output voltage by extracting the charge stored in the capacitor on the output side in a latch-off state in order to avoid a further increase in the output voltage. May be. In such a switching power supply device, once in the latch-off state, there is a possibility that the output voltage supplied to the load device becomes unstable even if the latch-off is released thereafter.
  • the present invention has been made in view of such a situation, and an object of the present invention is to stably supply power by suppressing output stop caused by a protection function even for sharp input / output fluctuations. It is an object of the present invention to provide a switching power supply device that can perform the switching.
  • the switching power supply of the present invention includes a switching circuit that converts an input voltage into a target voltage by using a switching element and outputs the target voltage, and a PWM control unit that performs PWM control on the switching element based on an output voltage of the switching circuit, A control circuit that shuts down when the output voltage is equal to or greater than a predetermined latch-off threshold, wherein the control circuit includes a feedback signal including at least one of the output current and the output voltage of the switching circuit and a predetermined limit value.
  • An analog comparator, and a PWM skip setting unit configured to skip a pulse output from the PWM control unit to the switching element when the feedback signal is equal to or greater than the limit value, wherein the PWM The control unit, after skipping the output pulse, Before the force voltage drops below the target voltage, it restarts the output of the pulse with a small return duty ratio than immediately before the duty ratio immediately before skipping the pulses.
  • 1 is a circuit diagram illustrating a configuration of a switching power supply device according to the present invention.
  • 5 is a flowchart illustrating output continuation control based on the output voltage of the switching power supply according to the present invention.
  • 6 is a timing chart illustrating an example of changes in an input voltage, an output voltage, and a PWM pulse of a switching power supply device in output continuation control based on an output voltage.
  • 9 is a timing chart illustrating an example of changes in an input voltage, an output voltage, and a PWM pulse when the output voltage after pulse skipping is slowly reduced.
  • 6 is a timing chart showing an example of changes in an input voltage, an output voltage, and a PWM pulse when the input voltage increases stepwise.
  • 4 is a flowchart illustrating output continuation control based on the output current of the switching power supply according to the present invention.
  • 5 is a timing chart illustrating an example of changes in an input voltage, an output voltage, an output current, and a PWM pulse of a switching power supply device in output continuation control based on an output current.
  • FIG. 1 is a circuit diagram showing a configuration of a switching power supply device 1 according to the present invention.
  • Switching power supply device 1 in this embodiment, is connected to an external power source 2 to the two input terminals T IN, by the external load 3 is connected to two output terminals T OUT, is input from the external power supply 2
  • This is a so-called DC-DC converter that converts the DC input voltage VIN to a desired target voltage V TARGET and outputs a stable DC output voltage V OUT to the external load 3.
  • the switching power supply device 1 includes a switching circuit 10 that performs power conversion, and a control circuit 20 that controls the switching circuit 10 while acquiring various signals from the switching circuit 10.
  • the switching circuit 10 includes an input capacitor C IN , an input current detection resistor R IN , a switching element SW, a choke coil L, a commutation diode D, an output capacitor C OUT , and an output current detection resistor R OUT .
  • the input current detection resistor R IN is provided to detect a current input from the external power supply 2 and is a resistor having a small resistance value.
  • the switching element SW is in the present embodiment, MOSFET: consist (Metal Oxide Semiconductor Field Effect Transistor metal oxide semiconductor field effect transistor), a drain connected to the input terminal T IN on the high potential side, the source is a choke coil L Is connected to the output terminal TOUT on the high potential side via the.
  • the switching element SW is PWM-controlled by a pulse signal from the control circuit 20 being input to the gate, as described later.
  • the switching element SW may be another element such as a known bipolar transistor or an IGBT (Insulated Gate Bipolar Transistor).
  • Choke coil L the state of the switching element SW is ON, stores energy by a current flowing from the switching element SW to the output terminal T OUT of the high potential side.
  • the commutation diode D is composed of, for example, a Schottky barrier diode, the anode is connected to a connection point between the input capacitor C IN and the input current detection resistor R IN, and the cathode is connected to a connection point between the switching element SW and the choke coil L. ing.
  • the commutation diode D releases energy stored in the choke coil L when a forward current flows in a state where the switching element SW is OFF.
  • One end of the output capacitor C OUT is connected to a connection point between the choke coil L and the output terminal T OUT on the high potential side, and the other end is connected to the anode of the commutation diode D.
  • Output current detection resistor R OUT has one end connected to the anode of the commutation diode D, other end is connected to the output terminal T OUT of the low potential side.
  • the output current detection resistor R OUT is a resistor provided for detecting a current output to the external load 3 and having a small resistance value.
  • the switching circuit 10 can output the output voltage V OUT by reducing the input voltage VIN by performing PWM control on the switching element SW.
  • the switching circuit 10 according to the present invention is not limited to the above configuration, and various changes can be made.
  • the switching circuit 10 may be configured as an AC-DC converter when AC power is input from the external power supply 2, or may be configured to increase the input voltage VIN to form the output voltage VOUT. Good.
  • the switching circuit 10 is not limited to the diode rectification, and may be a synchronous rectification employing a switching element instead of the commutation diode D.
  • the switching circuit 10 may be an isolated DC-DC converter via an insulating transformer, and may be of various types such as a so-called flyback type, forward type, push-pull type, half-bridge type, and full-bridge type. Circuit configuration can be adopted.
  • the control circuit 20 includes a microcomputer control circuit including, for example, an internal timer, and includes a PWM control unit 21, a PWM skip setting unit 22, an output voltage detection unit 23, a voltage limit comparator 24, an output current detection unit 25, and a current limit comparator 26. , An input current detecting unit 27, and an input voltage detecting unit 28.
  • the PWM control unit 21 adjusts the duty ratio based on the output voltage V OUT of the switching circuit 10 and outputs a pulse voltage to the gate of the switching element SW, so that the output voltage V OUT of the switching circuit 10 becomes the target voltage V TARGET. PWM control is performed so that Further, PWM control unit 21, the overvoltage protection function (Over Voltage Protection) is actuated, the latch off condition to shut down the control circuit 20 when the output voltage V OUT exceeds the latch off threshold V OVP abnormally elevated .
  • Overvoltage protection function Over Voltage Protection
  • the PWM skip setting unit 22 temporarily skips the pulse output of the PWM control unit 21 according to a procedure described later when the output voltage V OUT sharply rises with respect to the regulation operation of the switching power supply device 1. While protecting the load 3 from overvoltage, the operation of the overvoltage protection function is suppressed as much as possible, and power supply to the external load 3 is continued.
  • the output voltage detection unit 23 includes, for example, a voltage dividing circuit, and detects the output voltage VOUT of the switching circuit 10. Further, the voltage limit comparator 24 includes an analog comparator, and compares the output voltage V OUT detected by the output voltage detection unit 23 with a predetermined voltage limit value V TH to prevent the output voltage V OUT from rising. It is determined whether the pulse skip of the PWM control unit 21 is necessary. That is, the PWM skip setting unit 22 instructs the PWM control unit 21 to perform pulse skip based on the output signal from the voltage limit comparator 24.
  • the output current detection unit 25 includes, for example, an operational amplifier, and amplifies and detects the output current I OUT of the switching circuit 10 in the output current detection resistor R OUT .
  • the current limit comparator 26 includes an analog comparator, and compares the output current I OUT detected by the output current detection unit 25 with a predetermined current limit value I TH so that the output current I OUT can be increased. It is determined whether the pulse skip of the PWM control unit 21 is necessary. That is, the PWM skip setting unit 22 instructs the PWM control unit 21 to skip pulses based on the output signal from the current limit comparator 26.
  • the control circuit 20 includes both the voltage limit comparator 24 and the current limit comparator 26 so that when any of the output signals is output to the PWM skip setting unit 22, the PWM control unit 21 pulse skips are performed.
  • the control circuit 20 compares the output voltage V OUT as the “feedback signal” with the voltage limit value V TH as the “limit value” and the output current I OUT as the “feedback signal”. It can be configured by including at least one of the current limit comparators 26 that compare the current limit value I TH as the “limit value”.
  • the input current detection unit 27 includes, for example, an operational amplifier.
  • the input current detection resistor R IN amplifies and detects the input current I IN of the switching circuit 10 and outputs the amplified current to the PWM control unit 21.
  • the input voltage detection unit 28 includes, for example, a voltage dividing circuit, detects the input voltage VIN of the switching circuit 10, and outputs the input voltage VIN to the PWM control unit 21.
  • the input current detection unit 27 and the input voltage detection unit 28 are not essential components of the present invention, but are used when the PWM control unit 21 calculates the power conversion efficiency ⁇ or adjusts the duty ratio of the PWM control. can do.
  • FIG. 2 is a flowchart illustrating output continuation control based on the output voltage VOUT of the switching power supply device 1 according to the present invention.
  • FIG. 3 the output continues control based on the output voltage V OUT, is a timing chart showing the input voltage V IN of the switching power supply device 1, the output voltage V OUT, and an example of a change in the PWM pulse.
  • the switching power supply device 1 When the input voltage VIN is stable within a standard range, the switching power supply device 1 forms the target voltage V TARGET by PWM control based on the duty ratio calculated based on the output voltage V OUT and outputs the target voltage V TARGET. Output from terminal TOUT .
  • the switching power supply device 1 controls the output voltage V OUT while suppressing the increase in the output voltage V OUT by performing output continuation control according to the flowchart of FIG. The shutdown of the control circuit 20 by the operation of the overvoltage protection function is suppressed as much as possible.
  • the control circuit 20 starts the output continuation control together with the start of the PWM control in the PWM control unit 21. Then, the voltage limit comparator 24 determines whether or not the output voltage V OUT, which is detected through the output voltage detection unit 23 becomes the voltage limit value V TH or more (step S1).
  • the predetermined voltage limit value V TH is a threshold value for detecting the output voltage V OUT that rises sharply with respect to the PWM control clock, and is set in advance as a voltage value lower than the latch-off threshold value VOVP .
  • Step S1 the control circuit 20 continues the normal PWM control based on the output voltage V OUT as shown in the state up to the timing T2 in FIG. 3 (Step S1). No).
  • the control circuit 20 stores capture last duty ratio D L is the duty ratio of the PWM control unit 21 at that time (step S2).
  • control circuit 20 skips the output of the pulse from the PWM control unit 21 to the switching element SW in order to prevent the output voltage VOUT from further increasing (Step S3). Thereby, the control circuit 20 cuts off the current from the input terminal T IN to the output terminal T OUT, and reduces the output voltage V OUT to the voltage limit value V as shown as a period from timing T2 to timing T3 in FIG. TH can be lowered.
  • the control circuit 20 starts the internal timer at the timing T2 at which the pulse skip is started, and measures the duration of the pulse skip (step S4).
  • the control circuit 20 sets the release time T CANCEL in advance as the upper limit of the pulse skip duration, and when the duration of the pulse skip measured by the internal timer reaches the release time T CANCEL , the PWM control unit 21 restarts the PWM control. It is preferable that the release time T CANCEL is set as short as possible within a range where the output voltage V OUT does not immediately exceed the voltage limit value V TH even when the PWM control is restarted.
  • control circuit 20 controls the pulse skipping so that the pulse output can be restarted immediately when the output voltage V OUT becomes equal to or lower than the predetermined release voltage V CANCEL before the duration of the pulse skip reaches the release time T CANCEL. setting the return duty ratio D R at the time of starting (step S5).
  • the release voltage V CANCEL is a threshold value of the output voltage V OUT for restarting the PWM control after the pulse skip, and is set in advance in a range not less than the target voltage V TARGET and less than the voltage limit value V TH .
  • the release voltage V CANCEL is set to be equal to the target voltage V TARGET .
  • the control circuit 20 determines whether the state higher than the output voltage V OUT is the release voltage V CANCEL (step S6). That is, the control circuit 20 determines whether the output voltage V OUT that has exceeded the voltage limit value V TH has dropped to or below the release voltage V CANCEL due to pulse skipping.
  • step S6 when the output voltage V OUT decreases to the release voltage V CANCEL or less (No in step S6), the control circuit 20 controls the PWM control unit 21 for the switching element SW as shown by the timing T3 in FIG.
  • the PWM control is restarted (step S7).
  • the PWM control unit 21 performs the PWM control while adjusting the duty ratio to reflect the rise of the input voltage VIN , thereby returning the output voltage V OUT to the target voltage V TARGET again.
  • FIG. 4 is a timing chart illustrating an example of changes in the input voltage V IN , the output voltage V OUT , and the PWM pulse when the output voltage V OUT after pulse skipping is slowly reduced.
  • the duration of the pulse skip reaches the release time T CANCEL before the output voltage V OUT drops to the release voltage V CANCEL .
  • step S6 of FIG. 2 the control circuit 20 determines that the duration of the pulse skip measured by the internal timer has reached the release time T CANCEL in a state where the output voltage V OUT has not decreased to the release voltage V CANCEL or less. It is determined whether or not it has been performed (step S8). That is, the control circuit 20 determines whether the duration of the pulse skip has reached the release time T CANCEL and whether the output voltage V OUT has dropped to the release voltage V CANCEL or less. (No in step S8).
  • the control circuit 20 captures the input voltage VIN via the input voltage detection unit 28 (Step S9). ), it is reconfigured to overwrite the return duty ratio D R which is set in step S5 (step S10). That is, when resuming the PWM control based on the release time T CANCEL , the control circuit 20 has a predetermined time from the start of the pulse skip to the resumption of the PWM control, and prepares for the resumption of the PWM control. because there is a time margin, by previously reconfigure the return duty ratio D R based on the input voltage V iN just before restart PWM control by a suitable duty ratio than corresponding to increased input voltage V iN PWM control can be resumed.
  • the control circuit 20 temporarily increases the voltage limit value V TH by a predetermined potential difference ⁇ , as shown at timing T4 in FIG. 4 (step S11).
  • the predetermined potential difference ⁇ is arbitrarily set so that the increased voltage limit value V TH does not exceed the latch-off threshold value VOVP .
  • control circuit 20 resumes the PWM control using as shown in the timing T5 in Fig. 4, a return duty ratio D R which is reset in step S10 (step S12). Thereby, the control circuit 20 can return the output voltage V OUT to the target voltage V TARGET again by performing the PWM control while adjusting the duty ratio to reflect the rise of the input voltage VIN .
  • the control circuit 20 determines whether the output voltage V OUT is higher than the target voltage V TARGET (step S13). Then, when the output voltage V OUT has decreased to the target voltage V TARGET (No in step S13), the control circuit 20 increases the potential difference ⁇ in step S11 as shown at timing T6 in FIG.
  • the voltage limit value V TH is initialized and returned to the voltage limit value V TH before the rise (step S14).
  • the control circuit 20 whether the output voltage V OUT becomes equal to the target when it is higher than the voltage V TARGET (at step S13 Yes), the output voltage V OUT is the voltage limit value V TH or more after rising Is determined (step S15). That is, after increasing the voltage limit value V TH in step S11 and restarting the PWM control in step S12, the control circuit 20 reduces the output voltage V OUT to the target voltage V TARGET or less, or The voltage limit value V TH increased by the potential difference ⁇ is maintained until it rises to V TH or more (No in step S15).
  • FIG. 5 is a timing chart showing an example of the input voltage V IN, the output voltage V OUT, and the PWM pulse change in the case where the input voltage V IN increases rapidly stepwise. More specifically, FIG. 5 illustrates each voltage change when the output voltage V OUT again becomes equal to or higher than the voltage limit value V TH before the voltage limit value V TH is initialized after the restart of the PWM control. I have.
  • step S15 After restarting the PWM control at the timing T5, for example, when the output voltage V OUT rises to the voltage limit value V TH or more due to the sudden increase in the input voltage VIN (Yes in step S15), the output voltage It is determined whether V OUT has become equal to or higher than the latch-off threshold value VOVP (step S16). Then, the control circuit 20, as the timing T7 of FIG. 5, if the output voltage V OUT does not exceed the latch off threshold V OVP, suppressing an increase in the output voltage V OUT by performing again pulse skipping back to the step S2 I do.
  • the control circuit 20 increases the voltage limit value V TH again by the potential difference ⁇ at timing T8. That is, at the timing T8, the control circuit 20 raises the voltage limit value V TH to a voltage higher than the initial value by the potential difference 2 ⁇ . That is, the control circuit 20, as long as the output voltage V OUT does not become more latch off threshold V OVP, by repeating the increase and the pulse skipping voltage limit value V TH stepwise, the output voltage with respect to the proliferation of the input voltage V IN The rise of V OUT is suppressed, and the transition to the latch-off state is avoided as much as possible.
  • the switching power supply device 1 protects the external load 3 from the excessively high output voltage VOUT by preventing the output voltage VOUT equal to or higher than the latch-off threshold VOVP from being output to the external load 3.
  • FIG. 6 is a flowchart showing an output continuation control based on the output current I OUT of the switching power supply 1 according to the present invention.
  • FIG. 7 the output continues control based on the output current I OUT, is a timing chart showing the input voltage V IN of the switching power supply device 1, the output voltage V OUT, an output current I OUT, and an example of a change in the PWM pulse .
  • the output current I OUT is an overcurrent protection function to migrate if equal to or greater than a predetermined over-current threshold I OCP, latched off by shut down control circuit 20 (Over Current Protection) It has. Then, even if the output voltage V OUT does not exceed the voltage limit value V TH , if the output current I OUT satisfies the condition described later, the switching power supply 1 continues to output according to the flowchart of FIG. the control, while suppressing the increase of the output current I OUT, as much as possible shutdown of the control circuit 20 by the overcurrent protection function to suppress.
  • the current limit value I TH is set in advance as a current value larger than the overcurrent threshold value IOCP .
  • the current limit comparator 26 determines whether or not the output current IOUT detected via the output current detection unit 25 has become equal to or larger than the overcurrent threshold IOCP. (Step S21).
  • the control circuit 20 continues the normal PWM control based on the output voltage V OUT as shown as a period up to timing T12 in FIG. (No in S21).
  • the output current I OUT increases with the surge of the input voltage V IN at the timing T1 in FIG. 7, if the output current I OUT at the timing T12 becomes an overcurrent threshold I OCP or more (Yes at step S21), and The control circuit 20 suspends the shutdown by the overcurrent protection function that normally operates (step S22), and starts an internal timer to measure the time when the output current IOUT is equal to or greater than the overcurrent threshold IOCP. (Step S23).
  • the control circuit 20 determines whether or not the time measured by the internal timer is equal to or longer than a predetermined first period Td1 (Step S24).
  • a predetermined first period Td1 is set in advance to a length that can prevent the damage.
  • Step S24 if the state where the output current I OUT is an overcurrent threshold I OCP or is less than the first period Td1 (No in step S24), and the control circuit 20, the output current I OUT is a current limit value I TH or It is determined whether or not it has been (Step S25).
  • the control circuit 20 continues the measurement by the internal timer by repeating steps S24 and S25.
  • the control circuit 20 for example, when the output current I OUT with that input voltage V IN rises rapidly rises at a timing T1, the output current I OUT at the timing T13 becomes the current limit value I TH above (step S25 Yes), that takes in storing last duty ratio D L is the duty ratio of the PWM control unit 21 at that time (step S2).
  • control circuit 20 skips the output of the pulse from the PWM control unit 21 to the switching element SW in order to prevent the output current IOUT from further increasing (Step S27). Thereby, the control circuit 20 cuts off the current from the input terminal T IN to the output terminal T OUT, and stops the output current I OUT as shown at the timing T13 in FIG.
  • the control circuit 20 After returning the duty ratio D R is set, the control circuit 20, as shown in the timing T14 in FIG. 7, when the period of the pulse skip reaches a predetermined time [Delta] T, PWM control unit 21 to the switching element SW Is restarted (step S29).
  • the predetermined time ⁇ T can be arbitrarily set as one or more times of the pulse of the PWM control.
  • the PWM control unit 21 When the PWM control is restarted, the PWM control unit 21 performs the PWM control while adjusting the duty ratio to reflect the rise of the input voltage VIN , thereby returning the output voltage V OUT to the target voltage V TARGET again. As a result, the output current IOUT is also stabilized in a state below the overcurrent threshold value IOCP .
  • the switching power supply device 1 prevents the output current I OUT equal to or greater than the current limit value I TH from being output to the external load 3 and sets the state where the output current I OUT is equal to or greater than the overcurrent threshold I OCP in the first period Td1.
  • the external load 3 is protected so as not to continue.
  • the switching power supply device 1 suppresses the occurrence of latch-off due to the overvoltage protection function by performing pulse skipping even when input fluctuations and load fluctuations occur. Further increase of I OUT and output voltage V OUT can be avoided.
  • the switching power supply device 1 can suppress the output voltage V OUT from greatly dropping from the target voltage V TARGET when the PWM control is restored. Therefore, according to the switching power supply device 1 of the present invention, it is possible to suppress the output stop caused by the protection function and to stably supply the power even for a sudden input / output change.
  • the present invention is not limited to the above-described embodiment.
  • the manner of calculating the return duty ratio D R are multiplied by a coefficient ⁇ just before the duty ratio D L, based on the input voltage V IN which is detected by the input voltage detection unit 28 return to calculate the duty ratio D R, since it is possible to directly reflect the input voltage after variation in the time of the PWM control resume returning the duty ratio D R, PWM with the appropriate duty ratio to the target voltage V tARGET Control can be resumed.
  • the hold of the overcurrent protection function when a state where the output current I OUT is an overcurrent threshold I OCP or continued first period Td1 or more It has been exemplified embodiment for releasing, when the output current I OUT is an overcurrent threshold I OCP or may remove the hold of the overcurrent protection function when a predetermined number of times has occurred in a predetermined second period Td2.
  • a first aspect of the present invention includes a switching circuit that converts an input voltage into a target voltage by a switching element and outputs the target voltage, and a PWM control unit that performs PWM control on the switching element based on an output voltage of the switching circuit.
  • a control circuit that shuts down when the output voltage is equal to or higher than a predetermined latch-off threshold, wherein the control circuit includes a feedback signal including at least one of an output current and the output voltage of the switching circuit and a predetermined limit value.
  • a PWM skip setting unit that skips a pulse output from the PWM control unit to the switching element when the feedback signal is equal to or greater than the limit value, After skipping the output pulse, the PWM control unit sets the output voltage to a previous level. Before it drops below the target voltage, and resumes the output of the pulse with a small return duty ratio than immediately before the duty ratio immediately before skipping the pulses, a switching power supply.
  • the switching power supply converts the input voltage so that the output voltage becomes a predetermined target voltage by performing PWM control on the switching element, and outputs the converted voltage.
  • the control circuit shuts down. Has a protection function.
  • the switching power supply device skips the pulse output of the PWM control when at least one of the output current and the output voltage of the switching circuit is equal to or more than a predetermined limit value, so that the output without shifting to the latch-off state. Suppress the rapid rise. Then, the switching power supply device restarts the PWM control with the return duty ratio smaller than the immediately preceding duty ratio immediately before the pulse skip, thereby controlling the output voltage again to the predetermined target voltage.
  • the switching power supply device performs pulse skipping by providing a predetermined limit value different from the latch-off threshold value, so that, for example, even when input fluctuation or load fluctuation occurs, The output current and the output voltage can be prevented from further increasing while suppressing the occurrence of latch-off due to the overvoltage protection function. Therefore, according to the switching power supply according to the first aspect of the present invention, it is possible to suppress the output stop caused by the protection function and to stably supply the power even for a sharp input / output fluctuation.
  • control circuit restarts the output of the pulse on condition that a predetermined release time has elapsed since the skip of the pulse.
  • a switching power supply device
  • the output voltage is not excessively reduced during the pulse skip period by limiting the period during which the pulse is skipped by the predetermined release time. Can be.
  • the control circuit is set to be equal to or higher than the target voltage and lower than the limit value when the feedback signal includes the output voltage.
  • a switching power supply that restarts outputting the pulse on condition that the output voltage decreases to a predetermined release voltage.
  • the switching power supply device even when the output voltage drops relatively quickly during the pulse skip period, the output voltage drops to the release voltage set to the target voltage or higher.
  • the PWM control is restarted, so that the output voltage can be prevented from dropping too much.
  • the control circuit increases the limit value within a range not exceeding the latch-off threshold before restarting the output of the pulse.
  • a switching power supply device that initializes the limit value on condition that the output voltage decreases to the target voltage.
  • the limit value for the output is temporarily increased during the period from the start of the pulse skip to the restart of the PWM control, so that the pulse power during the pulse skip period is reduced. Even when the output voltage decreases relatively slowly, it is possible to reduce the possibility that the output voltage will become equal to or higher than the limit value again when the PWM control is restarted.
  • control circuit is configured such that, each time the output voltage becomes equal to or more than the limit value before initializing the limit value, A switching power supply device that repeats a skip and an increase in the limit value stepwise.
  • the switching power supply device even when the output voltage increases stepwise due to, for example, an input change or a load change, the pulse skip and the increase in the limit value are correspondingly performed.
  • the pulse skip and the increase in the limit value are correspondingly performed.
  • a sixth aspect of the present invention is the switching power supply device according to any one of the first to fifth aspects of the present invention, wherein the return duty ratio is calculated by multiplying the immediately preceding duty ratio by a coefficient less than 1. It is.
  • the output voltage can be reliably increased immediately after the return of the PWM control simply by multiplying the preset coefficient while taking in the duty ratio of the PWM control immediately before the pulse skip. Therefore, safety against overvoltage can be easily increased.
  • the control circuit includes an input voltage detecting unit for detecting an input voltage of the switching circuit, Is a switching power supply device calculated based on the input voltage immediately before restarting the output of the pulse.
  • the input voltage after the fluctuation at the time of resumption of the PWM control can be directly reflected on the return duty ratio. PWM control can be resumed.
  • the control circuit when the feedback signal includes the output current, causes the output current to exceed the limit value. Also has an overcurrent protection function that shuts down when the output current is equal to or higher than a predetermined overcurrent threshold set low, and suspends shutdown until the state where the output current is equal to or higher than the overcurrent threshold continues for a predetermined first period. , A switching power supply device.
  • the switching power supply according to the eighth aspect of the present invention has an overcurrent protection function in which the control circuit shuts down when the output current is equal to or greater than the overcurrent threshold. Then, even in the case where the output current is in the state of being equal to or more than the overcurrent threshold, the switching power supply holds the shutdown by latch-off until the state continues for the first predetermined period.
  • the switching power supply device when the output current is equal to or larger than the limit value, the output current is stopped by the pulse skip of the PWM control, and the output current is equal to or larger than the overcurrent threshold.
  • the control circuit when the feedback signal includes the output current, sets the output current to be less than the limit value.
  • the switching power supply according to the ninth aspect of the present invention has an overcurrent protection function in which the control circuit shuts down when the output current is equal to or higher than the overcurrent threshold. Then, even in the case where the output current is equal to or higher than the overcurrent threshold, the switching power supply device suspends the shutdown by latch-off until the state occurs a predetermined number of times during the predetermined second period.
  • the switching power supply according to the ninth aspect of the present invention when the output current is equal to or larger than the limit value, the output current is stopped by the pulse skip of the PWM control, and the output current is equal to or larger than the overcurrent threshold.

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Abstract

A switching power supply device 1 is provided with a switching circuit 10 and a control circuit 20 that includes a PWM control unit 21 for performing PWM control on the basis of an output voltage VOUT and performs a shutdown when the output voltage VOUT exceeds a latch-off threshold value VOVP. The control circuit 20 includes: a voltage limit comparator 24 for comparing the output voltage VOUT of the switching circuit 10 with a voltage limit value VTH; and a PWM skip setting unit 22 for skipping a pulse when the output voltage VOUT becomes greater than or equal to the voltage limit value VTH. The PWM control unit 21 restarts pulse output with a return duty ratio DR smaller than the last duty ratio DL after the pulse skip and before the output voltage VOUT drops to less than a target voltage VTARGET.

Description

スイッチング電源装置Switching power supply
 本発明は、スイッチング電源装置に関する。 << The present invention relates to a switching power supply device.
 入力された電圧を所望の電圧に変換して出力する電力変換装置の1つとして、スイッチング電源装置が広く利用されている。近年、スイッチング電源装置は、出力電圧や出力電流、温度などの帰還信号をA/D変換してマイコン制御回路に取り込み、当該帰還信号に基づいて電力変換を行うフルデジタル制御によるものが増加している。このようなフルデジタル制御によるスイッチング電源装置は、負荷条件や入力条件の変化に対して、スイッチング動作のタイミングを正確に制御することができるため、ノイズや電力損失を低減することができる。また、フルデジタル制御によるスイッチング電源装置は、様々なシーケンス動作をファームウェアで設定できるため、部品の削減が可能となり、システムを小型化することができる。 Switching power supplies are widely used as one type of power converter that converts an input voltage into a desired voltage and outputs the converted voltage. In recent years, switching power supply apparatuses have been increased by full digital control in which a feedback signal such as an output voltage, an output current, or temperature is A / D converted and taken into a microcomputer control circuit, and power conversion is performed based on the feedback signal. I have. Such a switching power supply device based on full digital control can accurately control the timing of the switching operation in response to changes in load conditions and input conditions, so that noise and power loss can be reduced. Further, in a switching power supply device under full digital control, various sequence operations can be set by firmware, so that parts can be reduced and the system can be downsized.
 ところで、スイッチング電源装置は、出力電圧や出力電流が異常に上昇した場合に動作を停止する保護機能が搭載されていることが多い。例えば、スイッチング電源装置の出力電圧が所定の閾値以上となる場合にラッチオフ状態となる過電圧保護機能(OVP:Over Voltage Protection)や、スイッチング電源装置の出力電流が所定の閾値以上となる場合にラッチオフ状態となる過電流保護機能(OCP:Over Current Protection)が知られており、後者の機能を搭載したスイッチング電源装置が特許文献1に開示されている。より具体的には、特許文献1に記載された従来技術は、過電流を検出した場合にラッチオフ状態とし、所定のタイミングでラッチオフを解除するスイッチング電源装置である。 ス イ ッ チ ン グ By the way, the switching power supply device is often provided with a protection function for stopping the operation when the output voltage or the output current rises abnormally. For example, an overvoltage protection function (OVP: Over Voltage Protection) that enters a latch-off state when the output voltage of the switching power supply is equal to or higher than a predetermined threshold, or a latch-off state when the output current of the switching power supply is equal to or higher than a predetermined threshold. An overcurrent protection function (OCP: Over Current Protection) is known, and a switching power supply device equipped with the latter function is disclosed in Patent Document 1. More specifically, the conventional technology described in Patent Document 1 is a switching power supply device that sets a latch-off state when an overcurrent is detected and releases the latch-off at a predetermined timing.
特開平11-18418号公報JP-A-11-18418
 しかしながら、デジタル制御によるスイッチング電源装置は、クロック周波数に伴う離散時間で制御を行うため、急激な負荷変動や入力変動に対して出力電圧の変動が大きくなり、ラッチオフにより出力が停止されてしまう。そのため、スイッチング電源装置から電力が供給される外部の負荷装置は、過電圧や過電流による障害から保護されるものの、電力供給が遮断されてしまう。また、スイッチング電源装置は、更なる出力電圧の上昇を回避するため、ラッチオフ状態になった場合に、出力側のコンデンサに蓄えられた電荷を引き抜くことで出力電圧を速やかに低下させるように設計されている場合がある。このようなスイッチング電源装置は、一旦ラッチオフ状態となると、その後ラッチオフを解除したとしても、負荷装置へ供給される出力電圧が不安定化する虞が生じる。 However, since the switching power supply device based on digital control performs control in discrete time according to the clock frequency, the output voltage fluctuates greatly due to a sudden load fluctuation or input fluctuation, and the output is stopped due to latch-off. Therefore, an external load device to which power is supplied from the switching power supply device is protected from a failure due to overvoltage or overcurrent, but power supply is cut off. In addition, the switching power supply device is designed to quickly lower the output voltage by extracting the charge stored in the capacitor on the output side in a latch-off state in order to avoid a further increase in the output voltage. May be. In such a switching power supply device, once in the latch-off state, there is a possibility that the output voltage supplied to the load device becomes unstable even if the latch-off is released thereafter.
 本発明は、このような状況に鑑みてなされたものであり、その目的とするところは、急峻な入出力変動に対しても保護機能に伴う出力停止を抑制して電力を安定供給することができるスイッチング電源装置を提供することにある。 The present invention has been made in view of such a situation, and an object of the present invention is to stably supply power by suppressing output stop caused by a protection function even for sharp input / output fluctuations. It is an object of the present invention to provide a switching power supply device that can perform the switching.
 本発明のスイッチング電源装置は、入力された電圧をスイッチング素子により目標電圧に変換して出力するスイッチング回路と、前記スイッチング回路の出力電圧に基づいて前記スイッチング素子をPWM制御するPWM制御部を含み、前記出力電圧が所定のラッチオフ閾値以上である場合にシャットダウンする制御回路と、を備え、前記制御回路は、前記スイッチング回路の出力電流及び前記出力電圧の少なくとも一方からなる帰還信号と所定の制限値とをアナログコンパレータで比較する制限比較器と、前記帰還信号が前記制限値以上となる場合に前記PWM制御部から前記スイッチング素子へ出力されるパルスをスキップさせるPWMスキップ設定部と、を含み、前記PWM制御部は、出力される前記パルスをスキップした後、前記出力電圧が前記目標電圧未満に低下する前に、前記パルスをスキップする直前の直前デューティ比よりも小さい復帰デューティ比で前記パルスの出力を再開する。 The switching power supply of the present invention includes a switching circuit that converts an input voltage into a target voltage by using a switching element and outputs the target voltage, and a PWM control unit that performs PWM control on the switching element based on an output voltage of the switching circuit, A control circuit that shuts down when the output voltage is equal to or greater than a predetermined latch-off threshold, wherein the control circuit includes a feedback signal including at least one of the output current and the output voltage of the switching circuit and a predetermined limit value. An analog comparator, and a PWM skip setting unit configured to skip a pulse output from the PWM control unit to the switching element when the feedback signal is equal to or greater than the limit value, wherein the PWM The control unit, after skipping the output pulse, Before the force voltage drops below the target voltage, it restarts the output of the pulse with a small return duty ratio than immediately before the duty ratio immediately before skipping the pulses.
 本発明によれば、保護機能に伴う出力変動を安定化するスイッチング電源装置を提供することができる。 According to the present invention, it is possible to provide a switching power supply that stabilizes output fluctuations caused by a protection function.
本発明に係るスイッチング電源装置の構成を示す回路図である。1 is a circuit diagram illustrating a configuration of a switching power supply device according to the present invention. 本発明に係るスイッチング電源装置の出力電圧に基づく出力継続制御を示すフローチャートである。5 is a flowchart illustrating output continuation control based on the output voltage of the switching power supply according to the present invention. 出力電圧に基づく出力継続制御において、スイッチング電源装置の入力電圧、出力電圧、及びPWMパルスの変化の一例を示すタイミングチャートである。6 is a timing chart illustrating an example of changes in an input voltage, an output voltage, and a PWM pulse of a switching power supply device in output continuation control based on an output voltage. パルススキップ後の出力電圧の低下が遅い場合における入力電圧、出力電圧、及びPWMパルスの変化の一例を示すタイミングチャートである。9 is a timing chart illustrating an example of changes in an input voltage, an output voltage, and a PWM pulse when the output voltage after pulse skipping is slowly reduced. 入力電圧が段階的に急増する場合における入力電圧、出力電圧、及びPWMパルスの変化の一例を示すタイミングチャートである。6 is a timing chart showing an example of changes in an input voltage, an output voltage, and a PWM pulse when the input voltage increases stepwise. 本発明に係るスイッチング電源装置の出力電流に基づく出力継続制御を示すフローチャートである。4 is a flowchart illustrating output continuation control based on the output current of the switching power supply according to the present invention. 出力電流に基づく出力継続制御において、スイッチング電源装置の入力電圧、出力電圧、出力電流、及びPWMパルスの変化の一例を示すタイミングチャートである。5 is a timing chart illustrating an example of changes in an input voltage, an output voltage, an output current, and a PWM pulse of a switching power supply device in output continuation control based on an output current.
 以下、図面を参照し、本発明の実施の形態について詳細に説明する。なお、本発明は以下に説明する内容に限定されるものではなく、その要旨を変更しない範囲において任意に変更して実施することが可能である。また、実施の形態の説明に用いる図面は、いずれも構成部材を模式的に示すものであって、理解を深めるべく部分的な強調、拡大、縮小、または省略などを行っており、構成部材の縮尺や形状等を正確に表すものとはなっていない場合がある。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described below, and can be arbitrarily changed and implemented without changing the gist. In addition, the drawings used in the description of the embodiments each schematically show constituent members, and partial emphasis, enlargement, reduction, or omission is performed for better understanding. In some cases, the scale or shape is not accurately represented.
 図1は、本発明に係るスイッチング電源装置1の構成を示す回路図である。スイッチング電源装置1は、本実施形態においては、2つの入力端子TINに外部電源2が接続され、2つの出力端子TOUTに外部負荷3が接続されることにより、外部電源2から入力される直流の入力電圧VINを所望の目標電圧VTARGETに変換して外部負荷3へ安定した直流の出力電圧VOUTを出力する所謂DC-DCコンバータである。スイッチング電源装置1は、電力の変換を行うスイッチング回路10、及びスイッチング回路10から各種信号を取得しつつスイッチング回路10を制御する制御回路20を備える。 FIG. 1 is a circuit diagram showing a configuration of a switching power supply device 1 according to the present invention. Switching power supply device 1, in this embodiment, is connected to an external power source 2 to the two input terminals T IN, by the external load 3 is connected to two output terminals T OUT, is input from the external power supply 2 This is a so-called DC-DC converter that converts the DC input voltage VIN to a desired target voltage V TARGET and outputs a stable DC output voltage V OUT to the external load 3. The switching power supply device 1 includes a switching circuit 10 that performs power conversion, and a control circuit 20 that controls the switching circuit 10 while acquiring various signals from the switching circuit 10.
 スイッチング回路10は、入力コンデンサCIN、入力電流検出抵抗RIN、スイッチング素子SW、チョークコイルL、転流ダイオードD、出力コンデンサCOUT、及び出力電流検出抵抗ROUTを含む。 The switching circuit 10 includes an input capacitor C IN , an input current detection resistor R IN , a switching element SW, a choke coil L, a commutation diode D, an output capacitor C OUT , and an output current detection resistor R OUT .
 入力コンデンサCINは、一端が高電位側の入力端子TINに接続され、他端が入力電流検出抵抗RINを介して低電位側の入力端子TINに接続されることにより、入力端子に入力された入力電圧VINの変動を抑制する。入力電流検出抵抗RINは、外部電源2から入力される電流を検出するために設けられ、微小な抵抗値を有する抵抗器である。 One end of the input capacitor C IN is connected to the input terminal T IN on the high potential side, and the other end is connected to the input terminal T IN on the low potential side via the input current detection resistor R IN. The fluctuation of the input voltage VIN that has been input is suppressed. The input current detection resistor R IN is provided to detect a current input from the external power supply 2 and is a resistor having a small resistance value.
 スイッチング素子SWは、本実施形態においては、MOSFET(Metal Oxide Semiconductor Field Effect Transistor:金属酸化膜半導体電界効果トランジスタ)からなり、ドレインが高電位側の入力端子TINに接続され、ソースがチョークコイルLを介して高電位側の出力端子TOUTに接続されている。そして、スイッチング素子SWは、後述するように、制御回路20からのパルス信号がゲートに入力されることによりPWM制御される。尚、スイッチング素子SWは、公知のバイポーラトランジスタやIGBT(Insulated Gate Bipolar Transistor:絶縁ゲート型バイポーラトランジスタ)などの他の素子であってもよい。 The switching element SW is in the present embodiment, MOSFET: consist (Metal Oxide Semiconductor Field Effect Transistor metal oxide semiconductor field effect transistor), a drain connected to the input terminal T IN on the high potential side, the source is a choke coil L Is connected to the output terminal TOUT on the high potential side via the. The switching element SW is PWM-controlled by a pulse signal from the control circuit 20 being input to the gate, as described later. Note that the switching element SW may be another element such as a known bipolar transistor or an IGBT (Insulated Gate Bipolar Transistor).
 チョークコイルLは、スイッチング素子SWがONの状態において、スイッチング素子SWから高電位側の出力端子TOUTへ流れる電流によりエネルギーを蓄える。転流ダイオードDは、例えばショットキバリアダイオードからなり、アノードが入力コンデンサCINと入力電流検出抵抗RINとの接続点に接続され、カソードがスイッチング素子SWとチョークコイルLとの接続点に接続されている。転流ダイオードDは、スイッチング素子SWがOFFの状態において順方向電流が流れることにより、チョークコイルLに蓄えられたエネルギーを開放する。 Choke coil L, the state of the switching element SW is ON, stores energy by a current flowing from the switching element SW to the output terminal T OUT of the high potential side. The commutation diode D is composed of, for example, a Schottky barrier diode, the anode is connected to a connection point between the input capacitor C IN and the input current detection resistor R IN, and the cathode is connected to a connection point between the switching element SW and the choke coil L. ing. The commutation diode D releases energy stored in the choke coil L when a forward current flows in a state where the switching element SW is OFF.
 出力コンデンサCOUTは、一端がチョークコイルLと高電位側の出力端子TOUTとの接続点に接続され、他端が転流ダイオードDのアノードに接続されている。出力電流検出抵抗ROUTは、一端が転流ダイオードDのアノードに接続され、多端が低電位側の出力端子TOUTに接続されている。出力電流検出抵抗ROUTは、外部負荷3へ出力される電流を検出するために設けられ、微小な抵抗値を有する抵抗器である。 One end of the output capacitor C OUT is connected to a connection point between the choke coil L and the output terminal T OUT on the high potential side, and the other end is connected to the anode of the commutation diode D. Output current detection resistor R OUT has one end connected to the anode of the commutation diode D, other end is connected to the output terminal T OUT of the low potential side. The output current detection resistor R OUT is a resistor provided for detecting a current output to the external load 3 and having a small resistance value.
 本実施形態におけるスイッチング回路10は、スイッチング素子SWに対するPWM制御により、入力電圧VINを降圧して出力電圧VOUTを出力することができる。ただし、本発明に係るスイッチング回路10は、上記の構成に限定されるものではなく、種々の変更が可能である。例えば、スイッチング回路10は、外部電源2から交流電力が入力される場合にはAC-DCコンバータとして構成してもよく、また、入力電圧VINを昇圧して出力電圧VOUTを形成してもよい。さらに、スイッチング回路10は、ダイオード整流に限られず、転流ダイオードDに替えてスイッチング素子を採用した同期整流であってもよい。また、スイッチング回路10は、絶縁トランスを介した絶縁型のDC-DCコンバータであってもよく、所謂フライバック方式、フォーワード方式、プッシュプル方式、ハーフブリッジ方式、及びフルブリッジ方式などの様々な形態の回路構成を採用することができる。 The switching circuit 10 according to the present embodiment can output the output voltage V OUT by reducing the input voltage VIN by performing PWM control on the switching element SW. However, the switching circuit 10 according to the present invention is not limited to the above configuration, and various changes can be made. For example, the switching circuit 10 may be configured as an AC-DC converter when AC power is input from the external power supply 2, or may be configured to increase the input voltage VIN to form the output voltage VOUT. Good. Further, the switching circuit 10 is not limited to the diode rectification, and may be a synchronous rectification employing a switching element instead of the commutation diode D. Further, the switching circuit 10 may be an isolated DC-DC converter via an insulating transformer, and may be of various types such as a so-called flyback type, forward type, push-pull type, half-bridge type, and full-bridge type. Circuit configuration can be adopted.
 制御回路20は、例えば内部タイマを含むマイコン制御回路を備え、PWM制御部21、PWMスキップ設定部22、出力電圧検出部23、電圧制限比較器24、出力電流検出部25、電流制限比較器26、入力電流検出部27、及び入力電圧検出部28を含む。 The control circuit 20 includes a microcomputer control circuit including, for example, an internal timer, and includes a PWM control unit 21, a PWM skip setting unit 22, an output voltage detection unit 23, a voltage limit comparator 24, an output current detection unit 25, and a current limit comparator 26. , An input current detecting unit 27, and an input voltage detecting unit 28.
 PWM制御部21は、スイッチング回路10の出力電圧VOUTに基づいてデューティ比を調整し、スイッチング素子SWのゲートにパルス電圧を出力することにより、スイッチング回路10の出力電圧VOUTが目標電圧VTARGETとなるようにPWM制御する。また、PWM制御部21は、出力電圧VOUTが異常に上昇してラッチオフ閾値VOVPを超えた場合には過電圧保護機能(Over Voltage Protection)が作動し、制御回路20をシャットダウンさせるラッチオフ状態となる。 The PWM control unit 21 adjusts the duty ratio based on the output voltage V OUT of the switching circuit 10 and outputs a pulse voltage to the gate of the switching element SW, so that the output voltage V OUT of the switching circuit 10 becomes the target voltage V TARGET. PWM control is performed so that Further, PWM control unit 21, the overvoltage protection function (Over Voltage Protection) is actuated, the latch off condition to shut down the control circuit 20 when the output voltage V OUT exceeds the latch off threshold V OVP abnormally elevated .
 PWMスキップ設定部22は、スイッチング電源装置1のレギュレーション動作に対して出力電圧VOUTが急激に上昇した場合に、後述する手順によりPWM制御部21のパルス出力を一時的にスキップさせることで、外部負荷3を過電圧から保護しつつも過電圧保護機能の作動を可能な限り抑制して外部負荷3への電力供給を継続する。 The PWM skip setting unit 22 temporarily skips the pulse output of the PWM control unit 21 according to a procedure described later when the output voltage V OUT sharply rises with respect to the regulation operation of the switching power supply device 1. While protecting the load 3 from overvoltage, the operation of the overvoltage protection function is suppressed as much as possible, and power supply to the external load 3 is continued.
 出力電圧検出部23は、例えば分圧回路からなり、スイッチング回路10の出力電圧VOUTを検出する。また、電圧制限比較器24は、アナログコンパレータを含み、出力電圧検出部23により検出された出力電圧VOUTを所定の電圧制限値VTHと比較することにより、出力電圧VOUTの上昇に対してPWM制御部21のパルススキップが必要か否かを判定する。すなわち、PWMスキップ設定部22は、電圧制限比較器24からの出力信号に基づいて、PWM制御部21に対してパルススキップを指示する。 The output voltage detection unit 23 includes, for example, a voltage dividing circuit, and detects the output voltage VOUT of the switching circuit 10. Further, the voltage limit comparator 24 includes an analog comparator, and compares the output voltage V OUT detected by the output voltage detection unit 23 with a predetermined voltage limit value V TH to prevent the output voltage V OUT from rising. It is determined whether the pulse skip of the PWM control unit 21 is necessary. That is, the PWM skip setting unit 22 instructs the PWM control unit 21 to perform pulse skip based on the output signal from the voltage limit comparator 24.
 出力電流検出部25は、例えばオペアンプからなり、出力電流検出抵抗ROUTにおけるスイッチング回路10の出力電流IOUTを増幅して検出する。また、電流制限比較器26は、アナログコンパレータを含み、出力電流検出部25により検出された出力電流IOUTを所定の電流制限値ITHと比較することにより、出力電流IOUTの上昇に対してPWM制御部21のパルススキップが必要か否かを判定する。すなわち、PWMスキップ設定部22は、電流制限比較器26からの出力信号に基づいて、PWM制御部21に対してパルススキップを指示する。 The output current detection unit 25 includes, for example, an operational amplifier, and amplifies and detects the output current I OUT of the switching circuit 10 in the output current detection resistor R OUT . In addition, the current limit comparator 26 includes an analog comparator, and compares the output current I OUT detected by the output current detection unit 25 with a predetermined current limit value I TH so that the output current I OUT can be increased. It is determined whether the pulse skip of the PWM control unit 21 is necessary. That is, the PWM skip setting unit 22 instructs the PWM control unit 21 to skip pulses based on the output signal from the current limit comparator 26.
 ここで、制御回路20は、本実施形態においては電圧制限比較器24及び電流制限比較器26を共に備えることにより、いずれかの出力信号がPWMスキップ設定部22に出力されたときにPWM制御部21のパルススキップが実行される。ただし、制御回路20は、「帰還信号」としての出力電圧VOUTを「制限値」としての電圧制限値VTHと比較する電圧制限比較器24、及び「帰還信号」としての出力電流IOUTを「制限値」としての電流制限値ITHと比較する電流制限比較器26のうち、少なくとも一方を備えることにより構成することができる。 Here, in the present embodiment, the control circuit 20 includes both the voltage limit comparator 24 and the current limit comparator 26 so that when any of the output signals is output to the PWM skip setting unit 22, the PWM control unit 21 pulse skips are performed. However, the control circuit 20 compares the output voltage V OUT as the “feedback signal” with the voltage limit value V TH as the “limit value” and the output current I OUT as the “feedback signal”. It can be configured by including at least one of the current limit comparators 26 that compare the current limit value I TH as the “limit value”.
 入力電流検出部27は、例えばオペアンプからなり、入力電流検出抵抗RINにおいてスイッチング回路10の入力電流IINを増幅して検出し、PWM制御部21に出力する。入力電圧検出部28は、例えば分圧回路からなり、スイッチング回路10の入力電圧VINを検出し、PWM制御部21に出力する。入力電流検出部27及び入力電圧検出部28は、本発明に必須の構成要素ではないが、PWM制御部21が電力変換効率ηを算出する場合やPWM制御のデューティ比を調整する場合などに使用することができる。 The input current detection unit 27 includes, for example, an operational amplifier. The input current detection resistor R IN amplifies and detects the input current I IN of the switching circuit 10 and outputs the amplified current to the PWM control unit 21. The input voltage detection unit 28 includes, for example, a voltage dividing circuit, detects the input voltage VIN of the switching circuit 10, and outputs the input voltage VIN to the PWM control unit 21. The input current detection unit 27 and the input voltage detection unit 28 are not essential components of the present invention, but are used when the PWM control unit 21 calculates the power conversion efficiency η or adjusts the duty ratio of the PWM control. can do.
 次に、スイッチング電源装置1の出力電圧検出部23及び電圧制限比較器24による出力継続制御について説明する。図2は、本発明に係るスイッチング電源装置1の出力電圧VOUTに基づく出力継続制御を示すフローチャートである。また、図3は、出力電圧VOUTに基づく出力継続制御において、スイッチング電源装置1の入力電圧VIN、出力電圧VOUT、及びPWMパルスの変化の一例を示すタイミングチャートである。 Next, output continuation control by the output voltage detection unit 23 and the voltage limit comparator 24 of the switching power supply 1 will be described. FIG. 2 is a flowchart illustrating output continuation control based on the output voltage VOUT of the switching power supply device 1 according to the present invention. Further, FIG. 3, the output continues control based on the output voltage V OUT, is a timing chart showing the input voltage V IN of the switching power supply device 1, the output voltage V OUT, and an example of a change in the PWM pulse.
 スイッチング電源装置1は、入力電圧VINが標準的な範囲内で安定している状態においては、出力電圧VOUTに基づいて算出されたデューティ比によるPWM制御で目標電圧VTARGETを形成して出力端子TOUTから出力する。そして、PWM制御の実行中に出力電圧VOUTが急激に上昇した場合には、スイッチング電源装置1は、図2のフローチャートに沿った出力継続制御により、出力電圧VOUTの上昇を抑制しながら、過電圧保護機能の作動により制御回路20がシャットダウンすることを可能な限り抑制する。 When the input voltage VIN is stable within a standard range, the switching power supply device 1 forms the target voltage V TARGET by PWM control based on the duty ratio calculated based on the output voltage V OUT and outputs the target voltage V TARGET. Output from terminal TOUT . When the output voltage V OUT sharply increases during execution of the PWM control, the switching power supply device 1 controls the output voltage V OUT while suppressing the increase in the output voltage V OUT by performing output continuation control according to the flowchart of FIG. The shutdown of the control circuit 20 by the operation of the overvoltage protection function is suppressed as much as possible.
 制御回路20は、PWM制御部21におけるPWM制御の開始と共に出力継続制御を開始する。そして、電圧制限比較器24は、出力電圧検出部23を介して検出された出力電圧VOUTが電圧制限値VTH以上となったか否かを判定する(ステップS1)。ここで、所定の電圧制限値VTHは、PWM制御のクロックに対して急上昇する出力電圧VOUTを検出するための閾値であり、ラッチオフ閾値VOVPよりも低い電圧値として事前に設定される。 The control circuit 20 starts the output continuation control together with the start of the PWM control in the PWM control unit 21. Then, the voltage limit comparator 24 determines whether or not the output voltage V OUT, which is detected through the output voltage detection unit 23 becomes the voltage limit value V TH or more (step S1). Here, the predetermined voltage limit value V TH is a threshold value for detecting the output voltage V OUT that rises sharply with respect to the PWM control clock, and is set in advance as a voltage value lower than the latch-off threshold value VOVP .
 制御回路20は、出力電圧VOUTが電圧制限値VTHを超えるまでは、図3におけるタイミングT2までの状態で示されるように、出力電圧VOUTに基づく通常のPWM制御を継続する(ステップS1でNo)。 Until the output voltage V OUT exceeds the voltage limit value V TH , the control circuit 20 continues the normal PWM control based on the output voltage V OUT as shown in the state up to the timing T2 in FIG. 3 (Step S1). No).
 一方、例えばタイミングT1において入力電圧VINが急上昇することに伴って出力電圧VOUTが上昇し、タイミングT2において出力電圧VOUTが電圧制限値VTH以上となった場合には(ステップS1でYes)、制御回路20は、その時点におけるPWM制御部21のデューティ比である直前デューティ比Dを取り込んで記憶する(ステップS2)。 On the other hand, for example, when the output voltage V OUT rises due to the sudden rise of the input voltage VIN at the timing T1, and the output voltage V OUT exceeds the voltage limit value V TH at the timing T2 (Yes in step S1) ), the control circuit 20 stores capture last duty ratio D L is the duty ratio of the PWM control unit 21 at that time (step S2).
 また、制御回路20は、出力電圧VOUTの更なる上昇を防止するため、PWM制御部21からスイッチング素子SWへのパルスの出力をスキップする(ステップS3)。これにより、制御回路20は、入力端子TINから出力端子TOUTへの電流を遮断し、図3のタイミングT2からタイミングT3までの期間として示されるように、出力電圧VOUTを電圧制限値VTHから低下させることができる。 In addition, the control circuit 20 skips the output of the pulse from the PWM control unit 21 to the switching element SW in order to prevent the output voltage VOUT from further increasing (Step S3). Thereby, the control circuit 20 cuts off the current from the input terminal T IN to the output terminal T OUT, and reduces the output voltage V OUT to the voltage limit value V as shown as a period from timing T2 to timing T3 in FIG. TH can be lowered.
 このとき、制御回路20は、パルススキップを開始するタイミングT2において内部タイマをスタートさせ、パルススキップの継続時間を計測する(ステップS4)。ここで、制御回路20は、パルススキップの継続時間の上限として解除時間TCANCELが予め設定され、内部タイマが計測したパルススキップの継続時間が解除時間TCANCELに達した場合には、PWM制御部21によるPWM制御を再開する。解除時間TCANCELは、PWM制御を再開しても出力電圧VOUTがすぐには電圧制限値VTHを超えない範囲において、出来るだけ短く設定されることが好ましい。 At this time, the control circuit 20 starts the internal timer at the timing T2 at which the pulse skip is started, and measures the duration of the pulse skip (step S4). Here, the control circuit 20 sets the release time T CANCEL in advance as the upper limit of the pulse skip duration, and when the duration of the pulse skip measured by the internal timer reaches the release time T CANCEL , the PWM control unit 21 restarts the PWM control. It is preferable that the release time T CANCEL is set as short as possible within a range where the output voltage V OUT does not immediately exceed the voltage limit value V TH even when the PWM control is restarted.
 また、制御回路20は、パルススキップの継続時間が解除時間TCANCELに達する前に、出力電圧VOUTが所定の解除電圧VCANCEL以下となった場合に、直ちにパルス出力を再開できるよう、パルススキップを開始した時点で復帰デューティ比Dを設定しておく(ステップS5)。 Further, the control circuit 20 controls the pulse skipping so that the pulse output can be restarted immediately when the output voltage V OUT becomes equal to or lower than the predetermined release voltage V CANCEL before the duration of the pulse skip reaches the release time T CANCEL. setting the return duty ratio D R at the time of starting (step S5).
 ここで、解除電圧VCANCELとは、パルススキップ後にPWM制御を再開するための出力電圧VOUTの閾値であり、目標電圧VTARGET以上で且つ電圧制限値VTH未満の範囲で予め設定される。解除電圧VCANCELは、本実施形態においては、目標電圧VTARGETと一致するように設定されているものとする。 Here, the release voltage V CANCEL is a threshold value of the output voltage V OUT for restarting the PWM control after the pulse skip, and is set in advance in a range not less than the target voltage V TARGET and less than the voltage limit value V TH . In the present embodiment, the release voltage V CANCEL is set to be equal to the target voltage V TARGET .
 また、復帰デューティ比Dは、本実施形態においては、上記のステップS2で取り込まれた直前デューティ比Dに1未満の係数αをかけて算出される。例えば、係数α=0.9とすれば、制御回路20は、復帰デューティ比D=直前デューティ比D×0.9として設定することにより、パルススキップの直前の出力電圧VOUTに対応する直前デューティ比Dよりも小さいデューティ比でPWM制御を再開することができ、出力電圧VOUTの更なる上昇を容易に抑制することができる。 Also, return the duty ratio D R, in this embodiment, it is calculated by multiplying the coefficient α of less than 1 to just before the duty ratio D L taken in the above step S2. For example, if the coefficient α is 0.9, the control circuit 20 corresponds to the output voltage V OUT immediately before the pulse skip by setting the return duty ratio D R = the immediately preceding duty ratio D L × 0.9. just before the duty ratio D L can restart the PWM control with a small duty ratio than, a further increase of the output voltage V OUT can be easily suppressed.
 復帰デューティ比Dが設定されると、制御回路20は、出力電圧VOUTが解除電圧VCANCELよりも高い状態であるか否かを判定する(ステップS6)。すなわち、制御回路20は、電圧制限値VTHを超えた出力電圧VOUTがパルススキップにより解除電圧VCANCEL以下まで低下したかを判定する。 When returning the duty ratio D R is set, the control circuit 20 determines whether the state higher than the output voltage V OUT is the release voltage V CANCEL (step S6). That is, the control circuit 20 determines whether the output voltage V OUT that has exceeded the voltage limit value V TH has dropped to or below the release voltage V CANCEL due to pulse skipping.
 そして、制御回路20は、出力電圧VOUTが解除電圧VCANCEL以下まで低下した場合には(ステップS6でNo)、図3のタイミングT3で示されるように、スイッチング素子SWに対するPWM制御部21のPWM制御を再開する(ステップS7)。これにより、PWM制御部21は、入力電圧VINの上昇を反映させたデューティ比に調整しながらPWM制御を行うことにより、出力電圧VOUTをあらためて目標電圧VTARGETに復帰させることができる。 Then, when the output voltage V OUT decreases to the release voltage V CANCEL or less (No in step S6), the control circuit 20 controls the PWM control unit 21 for the switching element SW as shown by the timing T3 in FIG. The PWM control is restarted (step S7). As a result, the PWM control unit 21 performs the PWM control while adjusting the duty ratio to reflect the rise of the input voltage VIN , thereby returning the output voltage V OUT to the target voltage V TARGET again.
 ところで、パルススキップ後の出力電圧VOUTは、出力コンデンサCOUTや外部負荷3に含まれる図示しないコンデンサの容量の大きさによって、解除電圧VCANCELまで低下するのに要する時間が長くなる場合がある。図4は、パルススキップ後の出力電圧VOUTの低下が遅い場合における入力電圧VIN、出力電圧VOUT、及びPWMパルスの変化の一例を示すタイミングチャートである。このような場合には、図4に見られるように、出力電圧VOUTが解除電圧VCANCELまで低下する前に、パルススキップの継続時間が解除時間TCANCELに達することになる。 By the way, the output voltage V OUT after the pulse skip may take a long time to decrease to the release voltage V CANCEL depending on the capacitance of the output capacitor C OUT and a capacitor (not shown) included in the external load 3. . FIG. 4 is a timing chart illustrating an example of changes in the input voltage V IN , the output voltage V OUT , and the PWM pulse when the output voltage V OUT after pulse skipping is slowly reduced. In such a case, as shown in FIG. 4, the duration of the pulse skip reaches the release time T CANCEL before the output voltage V OUT drops to the release voltage V CANCEL .
 このため、制御回路20は、図2のステップS6において、出力電圧VOUTが解除電圧VCANCEL以下まで低下していない状態において、内部タイマが計測したパルススキップの継続時間が解除時間TCANCELに達したか否かを判定する(ステップS8)。すなわち、制御回路20は、パルススキップの継続時間が解除時間TCANCELに達したか、及び出力電圧VOUTが解除電圧VCANCEL以下まで低下したかを判定し、いずれかの条件を満たすまでパルススキップを継続する(ステップS8でNo)。 For this reason, in step S6 of FIG. 2, the control circuit 20 determines that the duration of the pulse skip measured by the internal timer has reached the release time T CANCEL in a state where the output voltage V OUT has not decreased to the release voltage V CANCEL or less. It is determined whether or not it has been performed (step S8). That is, the control circuit 20 determines whether the duration of the pulse skip has reached the release time T CANCEL and whether the output voltage V OUT has dropped to the release voltage V CANCEL or less. (No in step S8).
 図4のタイミングT5において、パルススキップの継続時間が解除時間TCANCELに達すると(ステップS8でYes)、制御回路20は、入力電圧検出部28を介して入力電圧VINを取り込むと共に(ステップS9)、ステップS5で設定された復帰デューティ比Dを上書きするように再設定する(ステップS10)。すなわち、制御回路20は、解除時間TCANCELに基づいてPWM制御を再開する場合には、パルススキップの開始からPWM制御を再開するまでの時間が事前に決まっており、PWM制御の再開に備えるための時間的余裕があるため、PWM制御の再開直前の入力電圧VINに基づいて復帰デューティ比Dを再設定しておくことにより、上昇した入力電圧VINに対応したより適切なデューティ比によりPWM制御を再開することができる。 At the timing T5 in FIG. 4, when the duration of the pulse skip reaches the release time T CANCEL (Yes in Step S8), the control circuit 20 captures the input voltage VIN via the input voltage detection unit 28 (Step S9). ), it is reconfigured to overwrite the return duty ratio D R which is set in step S5 (step S10). That is, when resuming the PWM control based on the release time T CANCEL , the control circuit 20 has a predetermined time from the start of the pulse skip to the resumption of the PWM control, and prepares for the resumption of the PWM control. because there is a time margin, by previously reconfigure the return duty ratio D R based on the input voltage V iN just before restart PWM control by a suitable duty ratio than corresponding to increased input voltage V iN PWM control can be resumed.
 ただし、出力電圧VOUTは、電圧制限値VTHからの低下が遅い場合には、例えばノイズ等の影響によりPWM制御を再開するタイミングで再び電圧制限値VTHを超過することも起こり得る。そのため、制御回路20は、図4のタイミングT4に示されるように、一時的に電圧制限値VTHを所定の電位差βだけ上昇させる(ステップS11)。ここで、所定の電位差βは、上昇させた電圧制限値VTHがラッチオフ閾値VOVPを超えないように任意に設定される。 However, if the output voltage V OUT slowly decreases from the voltage limit value V TH , the output voltage V OUT may exceed the voltage limit value V TH again at the timing of restarting the PWM control due to, for example, noise. Therefore, the control circuit 20 temporarily increases the voltage limit value V TH by a predetermined potential difference β, as shown at timing T4 in FIG. 4 (step S11). Here, the predetermined potential difference β is arbitrarily set so that the increased voltage limit value V TH does not exceed the latch-off threshold value VOVP .
 そして、制御回路20は、図4のタイミングT5に示されるように、ステップS10において再設定された復帰デューティ比Dを用いてPWM制御を再開する(ステップS12)。これにより、制御回路20は、入力電圧VINの上昇を反映させたデューティ比に調整しながらPWM制御を行うことにより、出力電圧VOUTをあらためて目標電圧VTARGETに復帰させることができる。 Then, the control circuit 20 resumes the PWM control using as shown in the timing T5 in Fig. 4, a return duty ratio D R which is reset in step S10 (step S12). Thereby, the control circuit 20 can return the output voltage V OUT to the target voltage V TARGET again by performing the PWM control while adjusting the duty ratio to reflect the rise of the input voltage VIN .
 PWM制御が再開すると、制御回路20は、出力電圧VOUTが目標電圧VTARGETよりも高い状態であるかを判定する(ステップS13)。そして、制御回路20は、図4のタイミングT6に示されるように、出力電圧VOUTが目標電圧VTARGETまで低下した場合には(ステップS13でNo)、ステップS11にて電位差βだけ上昇させた電圧制限値VTHを初期化して上昇前の電圧制限値VTHに復帰させる(ステップS14)。 When the PWM control is restarted, the control circuit 20 determines whether the output voltage V OUT is higher than the target voltage V TARGET (step S13). Then, when the output voltage V OUT has decreased to the target voltage V TARGET (No in step S13), the control circuit 20 increases the potential difference β in step S11 as shown at timing T6 in FIG. The voltage limit value V TH is initialized and returned to the voltage limit value V TH before the rise (step S14).
 また、制御回路20は、出力電圧VOUTが目標電圧VTARGETよりも高い状態である場合には(ステップS13でYes)、出力電圧VOUTが上昇後の電圧制限値VTH以上となるか否かを判定する(ステップS15)。すなわち、制御回路20は、ステップS11にて電圧制限値VTHを上昇させてステップS12にてPWM制御を再開した後、出力電圧VOUTが目標電圧VTARGET以下に低下するか、又は電圧制限値VTH以上に上昇するまで、電位差βだけ上昇させた電圧制限値VTHを維持する(ステップS15でNo)。 Further, the control circuit 20, whether the output voltage V OUT becomes equal to the target when it is higher than the voltage V TARGET (at step S13 Yes), the output voltage V OUT is the voltage limit value V TH or more after rising Is determined (step S15). That is, after increasing the voltage limit value V TH in step S11 and restarting the PWM control in step S12, the control circuit 20 reduces the output voltage V OUT to the target voltage V TARGET or less, or The voltage limit value V TH increased by the potential difference β is maintained until it rises to V TH or more (No in step S15).
 図5は、入力電圧VINが段階的に急増する場合における入力電圧VIN、出力電圧VOUT、及びPWMパルスの変化の一例を示すタイミングチャートである。より具体的には、図5は、PWM制御の再開後において電圧制限値VTHを初期化する前に、出力電圧VOUTが再び電圧制限値VTH以上となる場合の各電圧変化を表している。 Figure 5 is a timing chart showing an example of the input voltage V IN, the output voltage V OUT, and the PWM pulse change in the case where the input voltage V IN increases rapidly stepwise. More specifically, FIG. 5 illustrates each voltage change when the output voltage V OUT again becomes equal to or higher than the voltage limit value V TH before the voltage limit value V TH is initialized after the restart of the PWM control. I have.
 制御回路20は、タイミングT5においてPWM制御を再開した後、例えば入力電圧VINが再び急増することにより出力電圧VOUTが電圧制限値VTH以上に上昇した場合(ステップS15でYes)、出力電圧VOUTがラッチオフ閾値VOVP以上となったか否かを判定する(ステップS16)。そして、制御回路20は、図5のタイミングT7のように、出力電圧VOUTがラッチオフ閾値VOVPを超えていなければ、ステップS2に戻り再びパルススキップを行うことによって出力電圧VOUTの上昇を抑制する。 After restarting the PWM control at the timing T5, for example, when the output voltage V OUT rises to the voltage limit value V TH or more due to the sudden increase in the input voltage VIN (Yes in step S15), the output voltage It is determined whether V OUT has become equal to or higher than the latch-off threshold value VOVP (step S16). Then, the control circuit 20, as the timing T7 of FIG. 5, if the output voltage V OUT does not exceed the latch off threshold V OVP, suppressing an increase in the output voltage V OUT by performing again pulse skipping back to the step S2 I do.
 また、制御回路20は、2回目のパルススキップの継続時間が解除時間TCANCELに達する場合には、タイミングT8において再び電圧制限値VTHを電位差βだけ上昇させる。すなわち、制御回路20は、タイミングT8において、電圧制限値VTHを初期値よりも電位差2βだけ高い電圧まで上昇させることになる。つまり、制御回路20は、出力電圧VOUTがラッチオフ閾値VOVP以上とならない限りにおいて、電圧制限値VTHの上昇とパルススキップとを段階的に繰り返すことにより、入力電圧VINの急増に対する出力電圧VOUTの上昇を抑制し、ラッチオフ状態への移行を出来る限り回避している。 When the duration of the second pulse skip reaches the release time T CANCEL , the control circuit 20 increases the voltage limit value V TH again by the potential difference β at timing T8. That is, at the timing T8, the control circuit 20 raises the voltage limit value V TH to a voltage higher than the initial value by the potential difference 2β. That is, the control circuit 20, as long as the output voltage V OUT does not become more latch off threshold V OVP, by repeating the increase and the pulse skipping voltage limit value V TH stepwise, the output voltage with respect to the proliferation of the input voltage V IN The rise of V OUT is suppressed, and the transition to the latch-off state is avoided as much as possible.
 一方、タイミングT10において、出力電圧VOUTがラッチオフ閾値VOVPに達した場合には(ステップS16でYes)、制御回路20は、電圧制限値VTHを更に上昇させることができないため、ラッチオフ状態となりシャットダウンにより動作を停止する。これにより、スイッチング電源装置1は、ラッチオフ閾値VOVP以上の出力電圧VOUTを外部負荷3に出力させないようにすることで、外部負荷3を過剰に高い出力電圧VOUTから保護する。 On the other hand, at the timing T10, if the output voltage V OUT reaches a latched-off threshold V OVP (Yes in step S16), and the control circuit 20, it is not possible to further increase the voltage limit value V TH, become latched off Stop operation by shutdown. Accordingly, the switching power supply device 1 protects the external load 3 from the excessively high output voltage VOUT by preventing the output voltage VOUT equal to or higher than the latch-off threshold VOVP from being output to the external load 3.
 続いて、スイッチング電源装置1の出力電流検出部25及び電流制限比較器26による出力継続制御について説明する。図6は、本発明に係るスイッチング電源装置1の出力電流IOUTに基づく出力継続制御を示すフローチャートである。また、図7は、出力電流IOUTに基づく出力継続制御において、スイッチング電源装置1の入力電圧VIN、出力電圧VOUT、出力電流IOUT、及びPWMパルスの変化の一例を示すタイミングチャートである。 Subsequently, output continuation control by the output current detection unit 25 and the current limit comparator 26 of the switching power supply 1 will be described. Figure 6 is a flowchart showing an output continuation control based on the output current I OUT of the switching power supply 1 according to the present invention. Further, FIG. 7, the output continues control based on the output current I OUT, is a timing chart showing the input voltage V IN of the switching power supply device 1, the output voltage V OUT, an output current I OUT, and an example of a change in the PWM pulse .
 本実施形態に係るスイッチング電源装置1は、出力電流IOUTが所定の過電流閾値IOCP以上となる場合に、制御回路20をシャットダウンさせてラッチオフ状態に移行する過電流保護機能(Over Current Protection)を備えている。そして、スイッチング電源装置1は、出力電圧VOUTが電圧制限値VTHを超えない場合であっても、出力電流IOUTが後述する条件を満たす場合には、図6のフローチャートに沿った出力継続制御により、出力電流IOUTの上昇を抑制しながら、過電流保護機能による制御回路20のシャットダウンを可能な限り抑制する。ここで、本実施形態においては、電流制限値ITHは、過電流閾値IOCPよりも大きい電流値として事前に設定されている。 Switching power supply apparatus 1 according to this embodiment, the output current I OUT is an overcurrent protection function to migrate if equal to or greater than a predetermined over-current threshold I OCP, latched off by shut down control circuit 20 (Over Current Protection) It has. Then, even if the output voltage V OUT does not exceed the voltage limit value V TH , if the output current I OUT satisfies the condition described later, the switching power supply 1 continues to output according to the flowchart of FIG. the control, while suppressing the increase of the output current I OUT, as much as possible shutdown of the control circuit 20 by the overcurrent protection function to suppress. Here, in the present embodiment, the current limit value I TH is set in advance as a current value larger than the overcurrent threshold value IOCP .
 出力電流IOUTに基づく出力継続制御が開始すると、電流制限比較器26は、出力電流検出部25を介して検出された出力電流IOUTが過電流閾値IOCP以上となったか否かを判定する(ステップS21)。 When the output continuation control based on the output current IOUT starts, the current limit comparator 26 determines whether or not the output current IOUT detected via the output current detection unit 25 has become equal to or larger than the overcurrent threshold IOCP. (Step S21).
 制御回路20は、出力電流IOUTが過電流閾値IOCP以上となるまでは、図7のタイミングT12までの期間として示されるように、出力電圧VOUTに基づく通常のPWM制御を継続する(ステップS21でNo)。 Until the output current I OUT becomes equal to or more than the overcurrent threshold I OCP , the control circuit 20 continues the normal PWM control based on the output voltage V OUT as shown as a period up to timing T12 in FIG. (No in S21).
 一方、図7のタイミングT1における入力電圧VINの急上昇に伴って出力電流IOUTが上昇し、タイミングT12において出力電流IOUTが過電流閾値IOCP以上となった場合(ステップS21でYes)、制御回路20は、本来であれば作動する過電流保護機能によるシャットダウンを保留すると共に(ステップS22)、出力電流IOUTが過電流閾値IOCP以上である時間を測定するために内部タイマを開始する(ステップS23)。 On the other hand, the output current I OUT increases with the surge of the input voltage V IN at the timing T1 in FIG. 7, if the output current I OUT at the timing T12 becomes an overcurrent threshold I OCP or more (Yes at step S21), and The control circuit 20 suspends the shutdown by the overcurrent protection function that normally operates (step S22), and starts an internal timer to measure the time when the output current IOUT is equal to or greater than the overcurrent threshold IOCP. (Step S23).
 そして、制御回路20は、内部タイマで計測される時間が所定の第1期間Td1以上であるか否かを判定する(ステップS24)。ここで、出力電流IOUTが過電流閾値IOCP以上の状態が長期間継続すると、スイッチング電源装置1の構成部品及び外部負荷3の温度が過度に上昇して破損する虞が生じる。そのため、第1期間Td1は、当該破損を防止することができる長さに事前に設定される。 Then, the control circuit 20 determines whether or not the time measured by the internal timer is equal to or longer than a predetermined first period Td1 (Step S24). Here, if the state where the output current I OUT is equal to or higher than the overcurrent threshold I OCP continues for a long time, the temperature of the components of the switching power supply device 1 and the external load 3 may rise excessively and cause damage. Therefore, the first period Td1 is set in advance to a length that can prevent the damage.
 一方、出力電流IOUTが過電流閾値IOCP以上となる状態が第1期間Td1未満である場合(ステップS24でNo)、制御回路20は、出力電流IOUTが電流制限値ITH以上となったか否かを判定する(ステップS25)。ここで、出力電流IOUTが電流制限値ITH未満である状態においては、制御回路20は、ステップS24及びステップS25を繰り返すことにより、内部タイマによる測定を継続する。 On the other hand, if the state where the output current I OUT is an overcurrent threshold I OCP or is less than the first period Td1 (No in step S24), and the control circuit 20, the output current I OUT is a current limit value I TH or It is determined whether or not it has been (Step S25). Here, in a state where the output current I OUT is less than the current limit value I TH , the control circuit 20 continues the measurement by the internal timer by repeating steps S24 and S25.
 そして、制御回路20は、例えばタイミングT1において入力電圧VINが急上昇することに伴って出力電流IOUTが上昇し、タイミングT13において出力電流IOUTが電流制限値ITH以上となった場合には(ステップS25でYes)、その時点におけるPWM制御部21のデューティ比である直前デューティ比Dを取り込んで記憶する(ステップS2)。 Then, the control circuit 20, for example, when the output current I OUT with that input voltage V IN rises rapidly rises at a timing T1, the output current I OUT at the timing T13 becomes the current limit value I TH above (step S25 Yes), that takes in storing last duty ratio D L is the duty ratio of the PWM control unit 21 at that time (step S2).
 また、制御回路20は、出力電流IOUTの更なる上昇を防止するため、PWM制御部21からスイッチング素子SWへのパルスの出力をスキップする(ステップS27)。これにより、制御回路20は、入力端子TINから出力端子TOUTへの電流が遮断され、図7のタイミングT13に示されるように、出力電流IOUTが停止することになる。 Further, the control circuit 20 skips the output of the pulse from the PWM control unit 21 to the switching element SW in order to prevent the output current IOUT from further increasing (Step S27). Thereby, the control circuit 20 cuts off the current from the input terminal T IN to the output terminal T OUT, and stops the output current I OUT as shown at the timing T13 in FIG.
 また、復帰デューティ比Dは、本実施形態においては、上記した出力電圧VOUTに基づく出力継続制御と同様に、ステップS26で取り込まれた直前デューティ比Dに1未満の係数αをかけて算出される(ステップS28)。例えば、係数α=0.9とすれば、制御回路20は、復帰デューティ比D=直前デューティ比D×0.9として設定することにより、パルススキップの直前の出力電流IOUTに対応する直前デューティ比Dよりも小さいデューティ比でPWM制御を再開することができ、出力電流IOUTの更なる上昇を容易に抑制することができる。 Also, return the duty ratio D R, in the present embodiment, similarly to the output continues control based on the output voltage V OUT as described above, by applying a coefficient less than 1 alpha just before the duty ratio D L taken in step S26 It is calculated (step S28). For example, if the coefficient α is 0.9, the control circuit 20 corresponds to the output current I OUT immediately before the pulse skip by setting the return duty ratio D R = the immediately preceding duty ratio D L × 0.9. just before the duty ratio D L can restart the PWM control with a small duty ratio than, a further increase of the output current I OUT can be easily suppressed.
 復帰デューティ比Dが設定された後、制御回路20は、図7のタイミングT14で示されるように、パルススキップの期間が所定の時間ΔTとなった場合に、スイッチング素子SWに対するPWM制御部21のPWM制御を再開する(ステップS29)。ここで、所定の時間ΔTは、PWM制御のパルスの1回分以上の時間として任意に設定することができる。 After returning the duty ratio D R is set, the control circuit 20, as shown in the timing T14 in FIG. 7, when the period of the pulse skip reaches a predetermined time [Delta] T, PWM control unit 21 to the switching element SW Is restarted (step S29). Here, the predetermined time ΔT can be arbitrarily set as one or more times of the pulse of the PWM control.
 PWM制御が再開すると、PWM制御部21は、入力電圧VINの上昇を反映させたデューティ比に調整しながらPWM制御を行うことにより、出力電圧VOUTをあらためて目標電圧VTARGETに復帰させることができ、これに伴い出力電流IOUTについても過電流閾値IOCP未満の状態で安定することになる。 When the PWM control is restarted, the PWM control unit 21 performs the PWM control while adjusting the duty ratio to reflect the rise of the input voltage VIN , thereby returning the output voltage V OUT to the target voltage V TARGET again. As a result, the output current IOUT is also stabilized in a state below the overcurrent threshold value IOCP .
 これに対し、図7のタイミングT15からタイミングT16までの期間で示されるように、出力電流IOUTが過電流閾値IOCP以上となる状態が第1期間Td1以上となった場合(ステップS24でYes)、制御回路20は、出力電流IOUTが電流制限値ITH未満であったとしても、ステップS22における過電流保護機能の保留を解除してシャットダウンする(ステップS30)。 On the other hand, as shown in a period from timing T15 to timing T16 in FIG. 7, the state in which the output current I OUT is equal to or higher than the overcurrent threshold I OCP is equal to or longer than the first period Td1 (Yes in step S24). ), Even if the output current I OUT is less than the current limit value I TH , the control circuit 20 releases the suspension of the overcurrent protection function in step S22 and shuts down (step S30).
 これにより、スイッチング電源装置1は、電流制限値ITH以上の出力電流IOUTを外部負荷3に出力させないようにしつつ、出力電流IOUTが過電流閾値IOCP以上となる状態が第1期間Td1以上継続しないようにして外部負荷3を保護する。 As a result, the switching power supply device 1 prevents the output current I OUT equal to or greater than the current limit value I TH from being output to the external load 3 and sets the state where the output current I OUT is equal to or greater than the overcurrent threshold I OCP in the first period Td1. The external load 3 is protected so as not to continue.
 以上のように、本発明に係るスイッチング電源装置1は、入力変動や負荷変動が生じた場合であっても、パルススキップを行うことにより過電圧保護機能に伴うラッチオフの発生を抑制しつつ、出力電流IOUT及び出力電圧VOUTの更なる上昇を回避することができる。また、スイッチング電源装置1は、PWM制御の復帰時において、出力電圧VOUTが目標電圧VTARGETから大きく低下することを抑制することができる。従って、本発明に係るスイッチング電源装置1によれば、急峻な入出力変動に対しても保護機能に伴う出力停止を抑制して電力を安定供給することができる。 As described above, the switching power supply device 1 according to the present invention suppresses the occurrence of latch-off due to the overvoltage protection function by performing pulse skipping even when input fluctuations and load fluctuations occur. Further increase of I OUT and output voltage V OUT can be avoided. In addition, the switching power supply device 1 can suppress the output voltage V OUT from greatly dropping from the target voltage V TARGET when the PWM control is restored. Therefore, according to the switching power supply device 1 of the present invention, it is possible to suppress the output stop caused by the protection function and to stably supply the power even for a sudden input / output change.
 以上で実施形態の説明を終えるが、本発明は上記した実施形態に限定されるものではない。例えば、上記の実施形態では、直前デューティ比Dに係数αをかけて復帰デューティ比Dを算出する態様を例示したが、入力電圧検出部28で検出された入力電圧VINに基づいて復帰デューティ比Dを算出する場合には、PWM制御の再開時における変動後の入力電圧を復帰デューティ比Dに直接反映させることができるため、目標電圧VTARGETに対して適切なデューティ比でPWM制御を再開することができる。 The description of the embodiment is finished above, but the present invention is not limited to the above-described embodiment. For example, in the above embodiment has illustrated the manner of calculating the return duty ratio D R are multiplied by a coefficient α just before the duty ratio D L, based on the input voltage V IN which is detected by the input voltage detection unit 28 return to calculate the duty ratio D R, since it is possible to directly reflect the input voltage after variation in the time of the PWM control resume returning the duty ratio D R, PWM with the appropriate duty ratio to the target voltage V tARGET Control can be resumed.
 また、上記の実施形態では、出力電流IOUTに基づく出力継続制御として、出力電流IOUTが過電流閾値IOCP以上となる状態が第1期間Td1以上継続する場合に過電流保護機能の保留を解除する態様を例示したが、出力電流IOUTが過電流閾値IOCP以上となる状態が所定の第2期間Td2に所定回数発生した場合に過電流保護機能の保留を解除してもよい。 In the above embodiment, as the output continues control based on the output current I OUT, the hold of the overcurrent protection function when a state where the output current I OUT is an overcurrent threshold I OCP or continued first period Td1 or more It has been exemplified embodiment for releasing, when the output current I OUT is an overcurrent threshold I OCP or may remove the hold of the overcurrent protection function when a predetermined number of times has occurred in a predetermined second period Td2.
<本発明の実施態様>
 本発明の第1の態様は、入力された電圧をスイッチング素子により目標電圧に変換して出力するスイッチング回路と、前記スイッチング回路の出力電圧に基づいて前記スイッチング素子をPWM制御するPWM制御部を含み、前記出力電圧が所定のラッチオフ閾値以上である場合にシャットダウンする制御回路と、を備え、前記制御回路は、前記スイッチング回路の出力電流及び前記出力電圧の少なくとも一方からなる帰還信号と所定の制限値とをアナログコンパレータで比較する制限比較器と、前記帰還信号が前記制限値以上となる場合に前記PWM制御部から前記スイッチング素子へ出力されるパルスをスキップさせるPWMスキップ設定部と、を含み、前記PWM制御部は、出力される前記パルスをスキップした後、前記出力電圧が前記目標電圧未満に低下する前に、前記パルスをスキップする直前の直前デューティ比よりも小さい復帰デューティ比で前記パルスの出力を再開する、スイッチング電源装置である。
<Embodiments of the present invention>
A first aspect of the present invention includes a switching circuit that converts an input voltage into a target voltage by a switching element and outputs the target voltage, and a PWM control unit that performs PWM control on the switching element based on an output voltage of the switching circuit. A control circuit that shuts down when the output voltage is equal to or higher than a predetermined latch-off threshold, wherein the control circuit includes a feedback signal including at least one of an output current and the output voltage of the switching circuit and a predetermined limit value. And a PWM skip setting unit that skips a pulse output from the PWM control unit to the switching element when the feedback signal is equal to or greater than the limit value, After skipping the output pulse, the PWM control unit sets the output voltage to a previous level. Before it drops below the target voltage, and resumes the output of the pulse with a small return duty ratio than immediately before the duty ratio immediately before skipping the pulses, a switching power supply.
 スイッチング電源装置は、スイッチング素子をPWM制御することにより出力電圧が所定の目標電圧となるように入力電圧を変換して出力すると共に、出力電圧がラッチオフ閾値以上である場合に制御回路がシャットダウンする過電圧保護機能を有している。また、スイッチング電源装置は、スイッチング回路の出力電流及び出力電圧のうち、少なくとも一方が所定の制限値以上となる場合に、PWM制御のパルス出力をスキップすることで、ラッチオフ状態に移行することなく出力の急上昇を抑制する。そして、スイッチング電源装置は、パルススキップの直前における直前デューティ比よりも小さい復帰デューティ比でPWM制御を再開することにより、出力電圧をあらためて所定の目標電圧となるように制御する。 The switching power supply converts the input voltage so that the output voltage becomes a predetermined target voltage by performing PWM control on the switching element, and outputs the converted voltage. In addition, when the output voltage is equal to or higher than the latch-off threshold, the control circuit shuts down. Has a protection function. Further, the switching power supply device skips the pulse output of the PWM control when at least one of the output current and the output voltage of the switching circuit is equal to or more than a predetermined limit value, so that the output without shifting to the latch-off state. Suppress the rapid rise. Then, the switching power supply device restarts the PWM control with the return duty ratio smaller than the immediately preceding duty ratio immediately before the pulse skip, thereby controlling the output voltage again to the predetermined target voltage.
 これにより本発明の第1の態様に係るスイッチング電源装置は、ラッチオフ閾値とは異なる所定の制限値を設けてパルススキップを行うことにより、例えば入力変動や負荷変動が生じた場合であっても、過電圧保護機能に伴うラッチオフの発生を抑制しつつ、出力電流及び出力電圧の更なる上昇を回避することができる。従って、本発明の第1の態様に係るスイッチング電源装置によれば、急峻な入出力変動に対しても保護機能に伴う出力停止を抑制して電力を安定供給することができる。 Accordingly, the switching power supply device according to the first aspect of the present invention performs pulse skipping by providing a predetermined limit value different from the latch-off threshold value, so that, for example, even when input fluctuation or load fluctuation occurs, The output current and the output voltage can be prevented from further increasing while suppressing the occurrence of latch-off due to the overvoltage protection function. Therefore, according to the switching power supply according to the first aspect of the present invention, it is possible to suppress the output stop caused by the protection function and to stably supply the power even for a sharp input / output fluctuation.
 本発明の第2の態様は、上記した本発明の第1の態様において、前記制御回路は、前記パルスをスキップしてから所定の解除時間が経過したことを条件として、前記パルスの出力を再開する、スイッチング電源装置である。 In a second aspect of the present invention based on the first aspect of the present invention, the control circuit restarts the output of the pulse on condition that a predetermined release time has elapsed since the skip of the pulse. A switching power supply device.
 本発明の第2の態様に係るスイッチング電源装置によれば、パルスがスキップされる期間を所定の解除時間で制限することにより、パルススキップの期間中に出力電圧が低下し過ぎないようにすることができる。 According to the switching power supply device according to the second aspect of the present invention, the output voltage is not excessively reduced during the pulse skip period by limiting the period during which the pulse is skipped by the predetermined release time. Can be.
 本発明の第3の態様は、上記した本発明の第1の態様において、前記制御回路は、前記帰還信号が前記出力電圧を含む場合に、前記目標電圧以上で且つ前記制限値未満に設定された所定の解除電圧まで前記出力電圧が低下したことを条件として、前記パルスの出力を再開する、スイッチング電源装置である。 According to a third aspect of the present invention, in the first aspect of the present invention, the control circuit is set to be equal to or higher than the target voltage and lower than the limit value when the feedback signal includes the output voltage. A switching power supply that restarts outputting the pulse on condition that the output voltage decreases to a predetermined release voltage.
 本発明の第3の態様に係るスイッチング電源装置によれば、パルススキップの期間中における出力電圧の低下が比較的早い場合であっても、出力電圧が目標電圧以上に設定された解除電圧まで低下したときにPWM制御を再開するため、出力電圧が低下し過ぎないようにすることができる。 According to the switching power supply device according to the third aspect of the present invention, even when the output voltage drops relatively quickly during the pulse skip period, the output voltage drops to the release voltage set to the target voltage or higher. When this is done, the PWM control is restarted, so that the output voltage can be prevented from dropping too much.
 本発明の第4の態様は、上記した本発明の第2又は3の態様において、前記制御回路は、前記パルスの出力を再開する前に、前記ラッチオフ閾値を超えない範囲で前記制限値を上昇させ、前記出力電圧が前記目標電圧まで低下したことを条件として、前記制限値を初期化する、スイッチング電源装置である。 According to a fourth aspect of the present invention, in the second or third aspect of the present invention, the control circuit increases the limit value within a range not exceeding the latch-off threshold before restarting the output of the pulse. A switching power supply device that initializes the limit value on condition that the output voltage decreases to the target voltage.
 本発明の第4の態様に係るスイッチング電源装置によれば、パルススキップの開始からPWM制御を再開するまでの間に、出力に対する制限値を一時的に上昇させることよって、パルススキップの期間中における出力電圧の低下が比較的遅い場合であっても、PWM制御の再開時に出力電圧が再び制限値以上となる虞を低減することができる。 According to the switching power supply device according to the fourth aspect of the present invention, the limit value for the output is temporarily increased during the period from the start of the pulse skip to the restart of the PWM control, so that the pulse power during the pulse skip period is reduced. Even when the output voltage decreases relatively slowly, it is possible to reduce the possibility that the output voltage will become equal to or higher than the limit value again when the PWM control is restarted.
 本発明の第5の態様は、上記した本発明の第4の態様において、前記制御回路は、前記制限値を初期化する前に前記出力電圧が前記制限値以上となる度に、前記パルスのスキップと前記制限値の上昇とを段階的に繰り返す、スイッチング電源装置である。 According to a fifth aspect of the present invention, in the above-mentioned fourth aspect of the present invention, the control circuit is configured such that, each time the output voltage becomes equal to or more than the limit value before initializing the limit value, A switching power supply device that repeats a skip and an increase in the limit value stepwise.
 本発明の第5の態様に係るスイッチング電源装置によれば、例えば入力変動や負荷変動に伴い出力電圧が段階的に上昇する場合であっても、これに対応してパルススキップと制限値の上昇とを段階的に繰り返すことにより、保護機能に伴う出力停止を抑制して電力を安定供給することができる。 According to the switching power supply device according to the fifth aspect of the present invention, even when the output voltage increases stepwise due to, for example, an input change or a load change, the pulse skip and the increase in the limit value are correspondingly performed. By repeating the steps in a stepwise manner, it is possible to suppress the output stop caused by the protection function and to stably supply power.
 本発明の第6の態様は、上記した本発明の第1乃至5のいずれかの態様において、前記復帰デューティ比は、前記直前デューティ比に1未満の係数をかけて算出される、スイッチング電源装置である。 A sixth aspect of the present invention is the switching power supply device according to any one of the first to fifth aspects of the present invention, wherein the return duty ratio is calculated by multiplying the immediately preceding duty ratio by a coefficient less than 1. It is.
 本発明の第6の態様に係るスイッチング電源装置によれば、パルススキップの直前におけるPWM制御のデューティ比を取り込みつつ予め設定された係数をかけるだけで、PWM制御の復帰直後に出力電圧を確実に低下させることができ、過電圧に対する安全性を容易に高めることができる。 According to the switching power supply device according to the sixth aspect of the present invention, the output voltage can be reliably increased immediately after the return of the PWM control simply by multiplying the preset coefficient while taking in the duty ratio of the PWM control immediately before the pulse skip. Therefore, safety against overvoltage can be easily increased.
 本発明の第7の態様は、上記した本発明の第1乃至5のいずれかの態様において、前記制御回路は、前記スイッチング回路の入力電圧を検出する入力電圧検出部を備え、前記復帰デューティ比は、前記パルスの出力を再開する直前の前記入力電圧に基づいて算出される、スイッチング電源装置である。 According to a seventh aspect of the present invention, in any one of the first to fifth aspects of the present invention, the control circuit includes an input voltage detecting unit for detecting an input voltage of the switching circuit, Is a switching power supply device calculated based on the input voltage immediately before restarting the output of the pulse.
 本発明の第7の態様に係るスイッチング電源装置によれば、PWM制御の再開時における変動後の入力電圧を復帰デューティ比に直接反映させることができるため、目標電圧に対して適切なデューティ比でPWM制御を再開することができる。 According to the switching power supply device according to the seventh aspect of the present invention, the input voltage after the fluctuation at the time of resumption of the PWM control can be directly reflected on the return duty ratio. PWM control can be resumed.
 本発明の第8の態様は、上記した本発明の第1乃至7のいずれかの態様において、前記制御回路は、前記帰還信号が前記出力電流を含む場合に、前記出力電流が前記制限値よりも低く設定された所定の過電流閾値以上となる場合にシャットダウンする過電流保護機能を有し、前記出力電流が前記過電流閾値以上である状態が所定の第1期間継続するまでシャットダウンを保留する、スイッチング電源装置である。 According to an eighth aspect of the present invention, in any one of the first to seventh aspects of the present invention, when the feedback signal includes the output current, the control circuit causes the output current to exceed the limit value. Also has an overcurrent protection function that shuts down when the output current is equal to or higher than a predetermined overcurrent threshold set low, and suspends shutdown until the state where the output current is equal to or higher than the overcurrent threshold continues for a predetermined first period. , A switching power supply device.
 本発明の第8の態様に係るスイッチング電源装置は、出力電流が過電流閾値以上である場合に制御回路がシャットダウンする過電流保護機能を有している。そして、スイッチング電源装置は、出力電流が過電流閾値以上である状態となった場合であっても、当該状態が所定の第1期間継続するまでラッチオフによるシャットダウンを保留する。これにより本発明の第8の態様に係るスイッチング電源装置によれば、出力電流が制限値以上となる場合にはPWM制御のパルススキップにより出力電流を停止し、出力電流が過電流閾値以上である状態を一定期間許容することにより、急峻な入出力変動に対しても保護機能に伴う出力停止を抑制して電力を安定供給することができる。 The switching power supply according to the eighth aspect of the present invention has an overcurrent protection function in which the control circuit shuts down when the output current is equal to or greater than the overcurrent threshold. Then, even in the case where the output current is in the state of being equal to or more than the overcurrent threshold, the switching power supply holds the shutdown by latch-off until the state continues for the first predetermined period. Thus, according to the switching power supply device according to the eighth aspect of the present invention, when the output current is equal to or larger than the limit value, the output current is stopped by the pulse skip of the PWM control, and the output current is equal to or larger than the overcurrent threshold. By allowing the state for a certain period of time, it is possible to suppress the output stop caused by the protection function even for a sudden input / output fluctuation and supply power stably.
 本発明の第9の態様は、上記した本発明の第1乃至7のいずれかの態様において、前記制御回路は、前記帰還信号が前記出力電流を含む場合に、前記出力電流が前記制限値よりも低く設定された所定の過電流閾値以上となる場合にシャットダウンする過電流保護機能を有し、前記出力電流が前記過電流閾値以上である状態が所定の第2期間に所定回数発生するまでシャットダウンを保留する、スイッチング電源装置である。 According to a ninth aspect of the present invention, in any one of the first to seventh aspects of the present invention described above, when the feedback signal includes the output current, the control circuit sets the output current to be less than the limit value. Has an overcurrent protection function that shuts down when the output current is equal to or higher than a predetermined overcurrent threshold set low, and shuts down until a state in which the output current is equal to or higher than the overcurrent threshold occurs a predetermined number of times in a predetermined second period. Is a switching power supply.
 本発明の第9の態様に係るスイッチング電源装置は、出力電流が過電流閾値以上である場合に制御回路がシャットダウンする過電流保護機能を有している。そして、スイッチング電源装置は、出力電流が過電流閾値以上である状態となった場合であっても、当該状態が所定の第2期間の間に所定回数発生するまでラッチオフによるシャットダウンを保留する。これにより本発明の第9の態様に係るスイッチング電源装置によれば、出力電流が制限値以上となる場合にはPWM制御のパルススキップにより出力電流を停止し、出力電流が過電流閾値以上である状態を一定回数許容することにより、急峻な入出力変動に対しても保護機能に伴う出力停止を抑制して電力を安定供給することができる。 The switching power supply according to the ninth aspect of the present invention has an overcurrent protection function in which the control circuit shuts down when the output current is equal to or higher than the overcurrent threshold. Then, even in the case where the output current is equal to or higher than the overcurrent threshold, the switching power supply device suspends the shutdown by latch-off until the state occurs a predetermined number of times during the predetermined second period. Thus, according to the switching power supply according to the ninth aspect of the present invention, when the output current is equal to or larger than the limit value, the output current is stopped by the pulse skip of the PWM control, and the output current is equal to or larger than the overcurrent threshold. By allowing the state to be performed a certain number of times, it is possible to suppress the output stop caused by the protection function and to stably supply the power even for a sudden input / output fluctuation.
  1 スイッチング電源装置
  2 外部電源
  3 外部負荷
 10 スイッチング回路
 20 制御回路
 21 PWM制御部
 22 PWMスキップ設定部
 23 出力電圧検出部
 24 電圧制限比較器
 25 出力電流検出部
 26 電流制限比較器
 SW スイッチング素子
 
Reference Signs List 1 switching power supply device 2 external power supply 3 external load 10 switching circuit 20 control circuit 21 PWM control unit 22 PWM skip setting unit 23 output voltage detection unit 24 voltage limit comparator 25 output current detection unit 26 current limit comparator SW switching element

Claims (9)

  1.  入力された電圧をスイッチング素子により目標電圧に変換して出力するスイッチング回路と、
     前記スイッチング回路の出力電圧に基づいて前記スイッチング素子をPWM制御するPWM制御部を含み、前記出力電圧が所定のラッチオフ閾値以上である場合にシャットダウンする制御回路と、を備え、
     前記制御回路は、前記スイッチング回路の出力電流及び前記出力電圧の少なくとも一方からなる帰還信号と所定の制限値とをアナログコンパレータで比較する制限比較器と、前記帰還信号が前記制限値以上となる場合に前記PWM制御部から前記スイッチング素子へ出力されるパルスをスキップさせるPWMスキップ設定部と、を含み、
     前記PWM制御部は、出力される前記パルスをスキップした後、前記出力電圧が前記目標電圧未満に低下する前に、前記パルスをスキップする直前の直前デューティ比よりも小さい復帰デューティ比で前記パルスの出力を再開する、スイッチング電源装置。
    A switching circuit that converts the input voltage to a target voltage by a switching element and outputs the target voltage;
    A control circuit that includes a PWM control unit that performs PWM control on the switching element based on an output voltage of the switching circuit, and that shuts down when the output voltage is equal to or higher than a predetermined latch-off threshold.
    A control circuit configured to compare a feedback signal including at least one of the output current and the output voltage of the switching circuit with a predetermined limit value by an analog comparator; and a case where the feedback signal is equal to or more than the limit value. And a PWM skip setting unit that skips a pulse output from the PWM control unit to the switching element.
    The PWM control unit, after skipping the output pulse, before the output voltage drops below the target voltage, sets the pulse with a return duty ratio smaller than the immediately preceding duty ratio immediately before skipping the pulse. Switching power supply that restarts output.
  2.  前記制御回路は、前記パルスをスキップしてから所定の解除時間が経過したことを条件として、前記パルスの出力を再開する、請求項1に記載のスイッチング電源装置。 The switching power supply device according to claim 1, wherein the control circuit restarts outputting the pulse on condition that a predetermined release time has elapsed since the skip of the pulse.
  3.  前記制御回路は、前記帰還信号が前記出力電圧を含む場合に、前記目標電圧以上で且つ前記制限値未満に設定された所定の解除電圧まで前記出力電圧が低下したことを条件として、前記パルスの出力を再開する、請求項1に記載のスイッチング電源装置。 The control circuit, when the feedback signal includes the output voltage, on the condition that the output voltage has decreased to a predetermined release voltage set to be equal to or higher than the target voltage and less than the limit value, The switching power supply according to claim 1, wherein output is restarted.
  4.  前記制御回路は、前記パルスの出力を再開する前に、前記ラッチオフ閾値を超えない範囲で前記制限値を上昇させ、前記出力電圧が前記目標電圧まで低下したことを条件として、前記制限値を初期化する、請求項2又は3に記載のスイッチング電源装置。 Before restarting the output of the pulse, the control circuit raises the limit value within a range not exceeding the latch-off threshold, and initializes the limit value on condition that the output voltage drops to the target voltage. The switching power supply device according to claim 2, wherein the switching power supply device comprises:
  5.  前記制御回路は、前記制限値を初期化する前に前記出力電圧が前記制限値以上となる度に、前記パルスのスキップと前記制限値の上昇とを段階的に繰り返す、請求項4に記載のスイッチング電源装置。 5. The control circuit according to claim 4, wherein the control circuit repeats stepwise skipping of the pulse and increase of the limit value each time the output voltage becomes equal to or higher than the limit value before initializing the limit value. Switching power supply.
  6.  前記復帰デューティ比は、前記直前デューティ比に1未満の係数をかけて算出される、請求項1乃至5のいずれかに記載のスイッチング電源装置。 The switching power supply device according to any one of claims 1 to 5, wherein the return duty ratio is calculated by multiplying the last duty ratio by a coefficient less than one.
  7.  前記制御回路は、前記スイッチング回路の入力電圧を検出する入力電圧検出部を備え、
     前記復帰デューティ比は、前記パルスの出力を再開する直前の前記入力電圧に基づいて算出される、請求項1乃至5のいずれかに記載のスイッチング電源装置。
    The control circuit includes an input voltage detection unit that detects an input voltage of the switching circuit,
    The switching power supply device according to claim 1, wherein the return duty ratio is calculated based on the input voltage immediately before restarting the output of the pulse.
  8.  前記制御回路は、前記帰還信号が前記出力電流を含む場合に、前記出力電流が前記制限値よりも低く設定された所定の過電流閾値以上となる場合にシャットダウンする過電流保護機能を有し、前記出力電流が前記過電流閾値以上である状態が所定の第1期間継続するまでシャットダウンを保留する、請求項1乃至7のいずれかに記載のスイッチング電源装置。 The control circuit has an overcurrent protection function of shutting down when the feedback signal includes the output current and when the output current is equal to or higher than a predetermined overcurrent threshold set lower than the limit value, The switching power supply according to any one of claims 1 to 7, wherein shutdown is suspended until a state in which the output current is equal to or larger than the overcurrent threshold continues for a predetermined first period.
  9.  前記制御回路は、前記帰還信号が前記出力電流を含む場合に、前記出力電流が前記制限値よりも低く設定された所定の過電流閾値以上となる場合にシャットダウンする過電流保護機能を有し、前記出力電流が前記過電流閾値以上である状態が所定の第2期間に所定回数発生するまでシャットダウンを保留する、請求項1乃至7のいずれかに記載のスイッチング電源装置。
     
    The control circuit has an overcurrent protection function of shutting down when the feedback signal includes the output current and when the output current is equal to or higher than a predetermined overcurrent threshold set lower than the limit value, The switching power supply device according to claim 1, wherein shutdown is suspended until a state in which the output current is equal to or larger than the overcurrent threshold occurs a predetermined number of times in a predetermined second period.
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