JP2006158073A - Charging/discharging method for capacitor and power conversion equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charging/discharging method for capacitors wherein capacitors can be charged with less energy loss, and to provide power conversion equipment. <P>SOLUTION: A power source 1 of direct-current voltage E is connected to a capacitor 2 with a capacitance of C through a DC/DC converter 31 whose output voltage is continuously varied. Electrical energy outputted from the power source 1 is stored through a current detection resistor R1 having a very small resistance value, inserted in series with the capacitor 2. The DC/DC converter 41 is so constructed that it switches its inductor L1, thereby steps the output voltage of the power source 1 up to a predetermined voltage. Computation is carried out based on the time in which it is required to charge the capacitor 2 and the value of the parasitic resistance of a path. The output voltage of the DC/DC converter 41 is stepped up while voltage increase is controlled to a minimum required degree according to the result of computation. Thus, the capacitor 2 can be charged with low energy loss. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a capacitor charging / discharging method for charging a capacitor through a power converter having a variable output voltage, and more particularly to a power converter that charges a capacitor with low power loss.

In the conventional strobe lighting circuit as shown in FIG. 11, the first switch sw1 is turned on to charge the capacitor 2 having the capacity C connected to the power source 1 of the DC voltage E, and then the first switch sw1 is turned on. By turning off and turning on the second switch sw2, energy is supplied to the load 3 such as a strobe lighting circuit. In that case, a loss due to the wiring resistance r or the like occurs in the process of charging the energy of the power source 1 to the capacitor 2. That is, electric power W that can be supplied from the power supply 1 to the load 3 becomes Equation (1) below, on the other hand, finally stored in the capacitor 2, since the discharge can become energy is CE ^2/2, energy of the difference CE ^2/2 is dissipated in the wiring resistance r or the like.

W = E × CE = CE ² (1)
And in the thing like the strobe lighting circuit for the purpose of charging / discharging the capacitor 2, the majority of the energy loss is occupied.

  Patent Document 1 discloses an invention of an electrical energy storage method that charges and discharges a capacitor connected to a power source having power generation means with high efficiency. Here, a solar cell is assumed as a power source, and the existence of a method using a DC / DC converter and its problems are pointed out as conventional techniques when charging a capacitor.

  However, when the power converter is used as a pulse power source for a strobe lighting circuit or the like, unlike the case where a solar cell is used as the power source, the conditions for charging the capacitor are always almost the same. Such low efficiency at low power is not a problem. Ordinarily, in order to charge the capacitor to a voltage different from the power supply voltage, some power conversion device is already mounted, and only an improvement may be added thereto.

On the other hand, Patent Document 2 describes an invention of a capacitor charging circuit for charging a discharging capacitor. Here, the value of constant current charging is reduced over time, or the power at the start of constant current charging is limited to a constant value, and the maximum charging power is averaged to reduce the maximum input power. As a result, the power conversion efficiency is improved, and the apparatus is downsized and inexpensive.
JP 2001-309569 A JP 2004-129345 A

  However, in the invention of Patent Document 2, energy loss in the parasitic resistance of the path for charging the capacitor is not considered, and thus there is a problem that the capacitor cannot be charged with high conversion efficiency.

  This invention is made | formed in view of such a point, and it aims at providing the charging / discharging method and power converter device of a capacitor which can charge a capacitor | condenser with little energy loss.

  In order to solve the above problem, the present invention provides a capacitor charging / discharging method for charging a capacitor via a power converter having a variable output voltage, wherein the power converter is connected to a given power source. There is provided a method for charging and discharging a capacitor, wherein the capacitor is charged with electric charges while increasing the output voltage continuously or stepwise.

  Further, in the present invention, in a power converter that extracts an output voltage that continuously changes from a voltage applied by a DC power supply, a capacitor that accumulates electrical energy output from the DC power supply, and the DC power supply and the capacitor A DC / DC converter that boosts the output voltage to a predetermined voltage by an inductor and a switching transistor connected therebetween, and a current value supplied to the capacitor is maintained at a constant magnitude based on the voltage of the capacitor Thus, a power conversion device comprising a control circuit for controlling the conduction time of the switching transistor can be provided.

  Further, in the present invention, in a power converter that extracts an output voltage that changes stepwise from a voltage applied by a DC power supply, a capacitor that accumulates electrical energy output from the DC power supply, and the DC power supply and the capacitor By switching a plurality of capacitors connected between them by a plurality of switches, a DC / DC converter that outputs different voltages, and turning on and off the plurality of switches so that the output voltage to the capacitors is gradually switched to a large value. It is possible to provide a power conversion device including a control circuit for controlling.

  Furthermore, in the present invention, in a power converter that extracts an output voltage that changes stepwise from a voltage supplied by a DC power supply, a capacitor that stores electrical energy output from the DC power supply, a primary side of the transformer, or a secondary side By switching the tap switch provided on the side winding, the DC / DC converter whose winding ratio can be changed, and the plurality of switches so that the output voltage to the capacitor is gradually switched to a large value. It is possible to provide a power conversion device including a control circuit that performs on / off control.

According to the present invention, a voltage (V) for charging a capacitor having a capacity (C) is continuously converted by using a high-efficiency power conversion device based on a given power supply voltage (E). Or step by step. At this time, if the power efficiency of the power converter is 100%, the output voltage continuously changes, and the parasitic resistance of the path for charging the capacitor can be ignored, the energy supplied from the power supply is theoretically in the above, it becomes a ^{∫V · Cdv = CE 2/2} , does not result in energy loss. Actually, it is impossible to reduce the loss to 0 as in this equation, but when the conversion efficiency of the power converter is 80% and the voltage drop due to parasitic resistance is suppressed to 0.1E, for example. The energy supplied from the power source is 0.75CE ^2, and the energy loss can be reduced to half of that in the prior art.

Embodiments of the present invention will be described below with reference to the drawings.
(First embodiment)
FIG. 1 is a circuit diagram illustrating a power conversion device according to the first embodiment.

  In the figure, a power source 1 having a DC voltage E is connected to a capacitor 2 having a capacitance C via a DC / DC converter 41 whose output voltage is continuously variable. The electric energy output from the power supply 1 is accumulated through a current detection resistor R1 having a minute resistance value inserted in series with the capacitor 2. The DC / DC converter 41 is configured to boost the output voltage of the power source 1 to a predetermined voltage by switching the current of the inductor L1.

  Here, the DC voltage E of the power source 1 is not set as a target value from the beginning, but is calculated from the time required for charging the capacitor 2 and the parasitic resistance value of the path, and is minimum required by the DC / DC converter 41. Charging the capacitor 2 with low energy loss can be realized by raising it while controlling it to a certain extent.

  As a specific control method of the DC / DC converter 41, for example, a minute current detection resistor R1 is inserted in series with the capacitor 2, and the voltage drop is controlled to be constant. That is, the current value for charging the capacitor 2 is controlled to be kept constant. The magnitude of the charging current of the capacitor 2 can be determined in consideration of the capacitance value C of the capacitor 2 and the charging time required for the power converter.

FIG. 2 is a diagram illustrating a specific configuration of the power conversion device in FIG. 1.
The specific configuration of the DC / DC converter 41 and its control circuit 5 will be described with reference to FIG. The DC / DC converter 41 includes a switching transistor Q1 whose source is connected to the + electrode of the power supply 1, an inductor L1 whose one end is connected to the drain of the switching transistor Q1, and a connection point between the inductor L1 and the drain of the switching transistor Q1. And a flywheel diode D1 having a cathode connected to the negative electrode of the power source 1 and an anode connected thereto.

  The control circuit 5 includes an operational amplifier 6 to which both ends of the current detection resistor R1 and positive and negative input terminals are connected via resistors R2 and R3, and a constant current source 7 connected to a terminal on the operational amplifier 6 side of the resistor R2, respectively. The capacitor C1 connected between the negative input terminal and the output terminal of the operational amplifier 6 and the comparator 8 connected to the output terminal of the operational amplifier 6 for comparing with the reference triangular wave signal. The output terminal is connected to the gate of the switching transistor Q1.

  In the control circuit 5, the phase is compensated by the resistor R3 and the capacitor C1 connected to the operational amplifier 6, and the ON / OFF interval with respect to the switching transistor Q1 can be controlled. The magnitude of the charging current I flowing from the inductor L1 into the capacitor 2 is determined by the ratio of the resistance values of the current detection resistor R1 and the resistor R2. That is, when the current value in the constant current source 7 is I1, the charging current I can be controlled by the following equation (2).

I = I1 × (R2 / R1) (2)
As described above, in the first embodiment, the output voltage is set by the capacitor 2 that stores the electric energy output from the power source 1 of the DC voltage E, and the inductor L1 and the switching transistor Q1 that are connected between the power source 1 and the capacitor 2. A DC / DC converter 41 that boosts the voltage to a predetermined voltage, and a control circuit that controls the conduction time of the switching transistor Q1 based on the voltage of the capacitor 2 so that the current value supplied to the capacitor 2 is maintained at a constant magnitude. Therefore, the capacitor 2 can be charged with low energy loss.

(Second Embodiment)
FIG. 3 is a circuit diagram showing a power conversion device according to the second embodiment of the present invention.
In this power converter, a power source 1 having a DC voltage E is connected to a capacitor 2 having a capacity C via a DC / DC converter 42 whose output voltage varies stepwise. This DC / DC converter 42 detects the voltage value according to the electric charge stored in the capacitor 2 having the capacity C, and controls so that the output voltage to the capacitor 2 is gradually switched to a larger value. Is used. In a switched capacitor type power conversion device, in order to make the output voltage ratio variable, a plurality of capacitors and a plurality of switches for switching their connection are used, and the output voltage ratio is determined by the circuit structure of the switched capacitor.

FIG. 4 is a diagram illustrating a specific configuration of the power conversion device in FIG. 3.
A specific configuration of the DC / DC converter 42 will be described with reference to FIG. The DC / DC converter 42 includes three capacitors C11 to C13, switches Si1 to Si3 for connecting one end of these capacitors C11 to C13 to the power supply 1, switches So1 to So3 for connecting to the capacitor 2, Switches Sg1 to Sg3 for grounding the other ends of the capacitors C11 to C13 and switches S12, S13, and S23 for connecting any two of the capacitors C11 to C13 in series.

  In a simple example, two capacitors can be connected to a power supply in parallel and charged, and then they can be disconnected, connected in series and discharged, thereby doubling the output voltage to the capacitor 2. Here, the output voltage to the capacitor 2 is configured to be tripled by the three capacitors C11 to C13.

Next, switching operations of the switches Si1 to Si3, So1 to So3, Sg1 to Sg3, and S12, S13, and S23 for switching the output voltage ratio will be described.
FIG. 5 is an equivalent circuit diagram showing a first-stage switching operation in the power conversion apparatus according to the second embodiment.

  In this first stage, only 1/3 of the DC power supply voltage E is charged to the capacitor 2 from the power supply 1. First, at timing T1, the switch Si1, the switches S12 and S23, and the switch Sg3 are turned on, and the remaining switches are turned off. As a result, the three capacitors C11 to C13 are charged in a state of being connected in series to the power source 1. At the next timing T2, the switches So1 to So3 and the switches Sg1 to Sg3 are turned on and the remaining switches are turned off, so that the capacitor 2 is discharged to the capacitor 2 in a state where the capacitors C11 to C13 are connected in parallel. The The operation at the timings T1 and T2 is repeated as necessary, and the capacitor 2 is finally charged to a voltage value of E / 3 by the switch control in the first stage.

  Table 1 below summarizes the ON / OFF control state of each switch in the first stage shown in FIG.

At the time of charging at the timing T1, the power W1 supplied from the power source 1 to the capacitors C11 to C13 is expressed by the following equation (3).
W1 = (E / 3) × C (E / 3) = CE 2/9 ... (3)
On the other hand, the energy stored in the capacitor 2 during the discharge of the timing T2 becomes CE ^2/18. Therefore, the energy loss in the first stage, it can be seen that a CE ^2/18.

FIG. 6 is an equivalent circuit diagram showing the switching operation of the second stage.
In this second stage, the capacitor 2 is charged from the power source 1 to 2/3 of the DC power source voltage E. First, at timing T3, the switches Si1 and Si2, the switches S13 and S23, and the switch Sg3 are turned on, and the remaining switches are turned off. Thus, the three capacitors C11 to C13 are charged in a state where the parallel circuit of the capacitors C11 and C12 and the capacitor C13 are connected in series to the power source 1. At the next timing T4, the switches So1, So3, the switch S12, and the switches Sg2, Sg3 are turned on, and the remaining switches are turned off, so that the series circuit of the capacitors C11, C12 and the capacitor C13 are connected to the power source 1. In a state of being connected in parallel, the capacitor 2 is discharged from the three capacitors C11 to C13. The operation at timings T3 and T4 is repeated as necessary, and the capacitor 2 is finally charged to a voltage value of 2E / 3 by the switch control in the second stage.

  Table 2 below summarizes the ON / OFF control state of each switch in the second stage shown in FIG.

At the time of charging at the timing T3, the power W2 supplied from the power source 1 to the capacitors C11 to C13 is expressed by the following equation (4).
^{W2 = 2CE 2/9 ... (} 4)
On the other hand, energy is newly stored in the capacitor 2 during the discharge of the timing T4 becomes CE ^2/6. Thus, energy loss in the second stage also, like the CE ^2/18 and the first stage.

FIG. 7 is an equivalent circuit diagram showing the switching operation in the third stage.
In this third stage, the capacitor 2 is charged directly by the power supply 1 and charged to the DC power supply voltage E. That is, at timing T5, the switches Si1 to Si3 and the switches Sg1 to Sg3 are turned on and the remaining switches are turned off. Thereby, the capacitors C11 to C13 are charged in a state of being connected in parallel to the power source 1, respectively. At the next timing T6, the switches So1 to So3 and the switches Sg1 to Sg3 are turned on and the remaining switches are turned off, so that three capacitors C11 to C13 are connected in parallel to the power source 1 to the capacitor 2. Is discharged. The operations at timings T5 and T6 are repeated as necessary, and the capacitor 2 is finally charged to the voltage value E by the switch control in the third stage.

  Table 3 below summarizes the ON / OFF control state of each switch in the third stage shown in FIG.

At the time of charging at timing T5, the power W3 supplied from the power source 1 to the capacitors C11 to C13 is expressed by the following equation (5).
^{W3 = CE 2/3 ... (} 5)
On the other hand, the energy stored in the capacitor 2 during the discharge of the timing T6 becomes 5CE ^2/18. Thus, energy loss in the third stage, the first stage, like the CE ^2/18 and the second stage.

Thus, the total energy loss when charging by classifying into three levels can be reduced becomes CE ^2/6, to 1/3 when compared to the loss CE ^2/2 in the case of charging from the beginning in the power supply voltage E.

  In this way, if the circuit structure is switched in order from the lowest output voltage ratio so that the output voltage of the power converter is slightly higher than the voltage of the capacitor 2, energy loss during charging is reduced. Thus, a highly efficient power conversion device can be realized. Further, the efficiency can be increased by changing the output voltage ratio in small increments, but in that case, a circuit structure with many capacitors and switches must be provided.

  Further, in this switched capacitor type power converter, if the circuit structure of the DC / DC converter 42 and the capacities of the capacitors C11 to C13 are given, the charging characteristics of the capacitor 2 are determined by the number of times of switching. For this reason, not only the circuit structure is switched by detecting the voltage of the capacitor 2, but the switching operation may be programmed in advance.

  As described above, in the second embodiment, the capacitor 2 that stores electrical energy output from the power source 1 of the DC voltage E, and the plurality of capacitors C11 to C13 connected between the power source 1 and the capacitor 2 are connected to the plurality of switches. A DC / DC converter 42 that outputs different voltages by switching between Si1 to Si3, So1 to So3, Sg1 to Sg3, and S12, S13, and S23. Since the plurality of switches Si1 to Si3, So1 to So3, Sg1 to Sg3, and S12, S13, and S23 are controlled to be switched on and off, the capacitor 2 can be charged with low energy loss.

(Third embodiment)
FIG. 8 is a circuit diagram showing a power conversion device according to the third embodiment of the present invention.
This power conversion device extracts an output voltage that changes stepwise from a voltage applied by a DC power supply 1. Here, a DC / DC converter is constituted by an oscillation circuit 11, a transformer 12, and a rectification circuit 13. Has been. Then, by switching the tap switches sw11, sw12, sw13 provided in the windings L21, L22, L23 on the secondary side of the transformer 12, the winding ratio of the transformer 12 can be changed. The detection / control circuit 14 controls the on / off of these switches sw11, sw12, and sw13 so that the output voltage to the capacitor 2 is gradually switched to a large value. Note that these switches sw11, sw12, and sw13 are assumed to be semiconductor switches having a high operating speed, but are not limited thereto.

FIG. 9 is a diagram illustrating a specific configuration of the power conversion device in FIG. 8.
The specific configuration of the oscillation circuit 11, the transformer 12, and the rectifier circuit 13 that constitute the DC / DC converter will be described with reference to FIG. The oscillation circuit 11 includes an AC power supply 10 and a resistor R11, and supplies predetermined energy to the primary winding L11 of the transformer 12. The secondary side winding of the transformer 12 includes three windings L21 to L23, and one end of the winding L21 is connected to the diode D11 via the switch sw11. The connection point between the windings L21 and L22 is connected to the diode D11 via the switch sw12, and the connection point between the windings L22 and L23 is connected to the diode D11 via the switch sw13.

  The diode D11 constitutes the rectifier circuit 13, and the capacitor 2 is connected to the cathode side. The capacitor 2 is connected in parallel with a circuit composed of two capacitors C21 and C22 connected in series. Further, the switches sw21 and sw22 constituting the initial charge discharging switch circuit 15 are connected to the capacitors C21 and C22. Are connected in parallel.

  The control circuit 16 compares the connection point potentials of the switches sw21 and sw22 with the reference voltages Vref1 and Vref2, respectively, the inverter 19 that inverts the output signal of the comparator 18, the output signal of the comparator 17, and the inverter 19 The AND circuit 20 to which each of the signals is input and the inverter 21 for inverting the output signal of the comparator 17 are configured. Therefore, after the switches sw21 and sw22 of the initial charge discharge switch circuit 15 are on / off controlled, the voltage levels at the connection points of the switches sw21 and sw22 are compared with the reference voltages Vref1 and Vref2 of the control circuit 16, thereby the capacitors C21 and C22. The capacitor with low energy loss is controlled by switching the switches sw11, sw12, and sw13 in order from the low output voltage so that the output voltage of the transformer 12 slightly exceeds the voltage of the capacitor 2. 2 can be charged.

  As described above, in the third embodiment, the capacitor 2 that stores electrical energy output from the power source 1 of the DC voltage E and the tap switches sw11 and sw12 provided in the primary or secondary winding of the transformer 12 are used. , Sw13, and a DC / DC converter whose winding ratio can be changed, and a control for turning on and off the plurality of switches sw11, sw12, sw13 so that the output voltage to the capacitor 2 is gradually switched to a large value. Since the circuit 16 is provided, the capacitor 2 can be charged with low energy loss.

  In the circuit of FIG. 9, the tap on the secondary winding side of the transformer 12 is switched, but depending on the application, a tap may be provided on the primary winding side, or on both the primary side and the secondary side, Tap switching may be performed. Further, instead of switching taps, it is possible to convert the voltage on the primary side of the transformer using a DC / DC converter.

(Fourth embodiment)
FIG. 10 is a circuit diagram showing a power conversion apparatus according to the fourth embodiment of the present invention.
In this power conversion device, power with variable output voltage can be taken out via a flyback transformer T formed of at least two windings L31 and L32. Here, the switching element Q2 that controls on / off of the power supplied to the primary winding L31 of the flyback transformer T, and the secondary winding L32 of the flyback transformer T when the switching element Q2 changes from on to off. A rectifier diode D21 for rectifying the flyback pulse, a capacitor 2 for accumulating the current rectified by the rectifier diode D21, and a resistor for detecting a flyback pulse provided in series with the primary winding L31. R12 and the control circuit 30 are comprised.

  The control circuit 30 generates a control signal for controlling the on-time of the switching element Q2 in accordance with the flyback pulse current detected by the flyback pulse detection resistor R12 so that the off-time is constant and performs switching. A reference power supply 31, a first comparator 32 to which the reference power supply 31 is connected to a negative input terminal, a flip-flop circuit 33, a constant current source 34, The capacitor C23 charged via the constant current source 34, the second comparator 35 to which the connection point between the constant current source 34 and the capacitor C23 and the + input terminal are connected, and the reference power source for the second comparator 35 36, and a switching element Q3 having a source and a drain connected to both ends of the capacitor C23, respectively. The output signal of the first comparator 32 is supplied to the set input terminal S of the flip-flop circuit 33, the output signal of the second comparator 35 is supplied to the reset input terminal R of the flip-flop circuit 33, and the flip-flop circuit 33. Are supplied to the gate of the switching element Q2 and the gate of the switching element Q3, respectively.

  Here, a control signal is generated with a constant duty and frequency according to the period during which the flyback pulse is generated by the current flowing through the flyback pulse detection resistor R12, and the duty is kept at an appropriate value while maintaining a high value. Can be charged with conversion efficiency.

  In the first to fourth embodiments described above, the power conversion device intended for the pulse power supply having the strobe lighting circuit as a load has been described, but the present invention is not limited to these. For example, the power conversion device of the present invention can be used as a device for connecting and charging a large-capacity capacitor used for memory backup or the like as a load.

It is a circuit diagram showing the power converter concerning a 1st embodiment. It is a figure which shows the specific structure of the power converter device of FIG. It is a circuit diagram which shows the power converter device which concerns on 2nd Embodiment. It is a figure which shows the specific structure of the power converter device of FIG. It is an equivalent circuit diagram which shows the switching operation of the 1st step in the power converter device which concerns on 2nd Embodiment. Similarly, it is an equivalent circuit diagram showing the switching operation of the second stage. Similarly, it is an equivalent circuit diagram showing the switching operation of the third stage. It is a circuit diagram which shows the power converter device which concerns on 3rd Embodiment. It is a figure which shows the specific structure of the power converter device of FIG. It is a circuit diagram which shows the power converter device which concerns on 4th Embodiment. It is a circuit diagram which shows an example of the conventional strobe lighting circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Power supply 2 Capacitor 3 Load 5 Control circuit 6 Operational amplifier 7 Constant current source 8 Comparator 10 AC power supply 11 Oscillation circuit 12 Transformer 13 Rectifier circuit 14 Detection / control circuit 41, 42 DC / DC converter C11-C13 Capacitor C21, C22 Capacitor D1 Fly Wheel diode D11 Diode L1 Inductor L11 Primary winding L21 to L23 Winding R1 Current detection resistance Si1 to Si3, So1 to So3, Sg1 to Sg3, S12, S13, S23, sw11, sw12, sw13, sw21, sw22 Switch Q1 Switching transistor

Claims (8)

In a capacitor charging / discharging method of charging a capacitor via a power converter having a variable output voltage,
A method for charging and discharging a capacitor, comprising: connecting the power conversion device to a given power source, and charging the capacitor while increasing the output voltage continuously or stepwise.   2. The capacitor charging / discharging method according to claim 1, wherein a strobe lighting circuit is connected to the capacitor as a load to discharge the electric charge. In a power converter that extracts an output voltage that continuously changes from a voltage given by a DC power supply,
A capacitor for accumulating electrical energy output from the DC power source;
A DC / DC converter that boosts the output voltage to a predetermined voltage by an inductor and a switching transistor connected between the DC power supply and the capacitor;
A control circuit for controlling the conduction time of the switching transistor based on the voltage of the capacitor so that a current value supplied to the capacitor is maintained at a constant magnitude;
A power conversion device comprising:   The power conversion device according to claim 3, wherein the conduction time of the switching transistor is determined from a capacitance value of the capacitor and a charging time set in the capacitor. In a power converter that extracts an output voltage that changes stepwise from a voltage given by a DC power supply,
A capacitor for accumulating electrical energy output from the DC power source;
A DC / DC converter that outputs different voltages by switching a plurality of capacitors connected between the DC power source and the capacitor by a plurality of switches;
A control circuit that performs on / off control of the plurality of switches so that an output voltage to the capacitor is gradually switched to a large value;
A power conversion device comprising: In a power converter that extracts an output voltage that changes stepwise from a voltage given by a DC power supply,
A capacitor for accumulating electrical energy output from the DC power source;
A DC / DC converter whose winding ratio can be changed by switching a tap switch provided on the transformer primary side or secondary side winding;
A control circuit that performs on / off control of the plurality of switches so that an output voltage to the capacitor is gradually switched to a large value;
A power conversion device comprising: In a power conversion apparatus that extracts power with variable output voltage via a flyback transformer configured with at least two coils,
A switching element that controls on / off of the power supplied to the primary coil of the flyback transformer;
A rectifier diode that rectifies a flyback pulse generated in a secondary coil of the flyback transformer when the switching element changes from on to off;
A capacitor for accumulating current rectified by the rectifier diode;
A flyback pulse detection resistor for detecting the flyback pulse, provided in series with either the primary side coil or the secondary side coil,
A control signal for controlling the on-time of the switching element in accordance with the flyback pulse current detected by the flyback pulse detection resistor is generated so that the off-time is constant, and is applied to the control terminal of the switching element. A control circuit to supply;
A power conversion device comprising: The power converter according to any one of claims 3 to 7, wherein a load circuit for discharging the stored electric energy is connected to the capacitor.

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