JP7167870B2 - power converter - Google Patents

Description

The present invention relates to a power converter that converts AC power into DC power.

Conventionally, as seen in Patent Document 1, a diode bridge composed of a plurality of rectifier diodes, a current detection resistor connected in series to the output side of the diode bridge, and a current detection unit that detects the current flowing through the current detection resistor. is known. In this power converter, an AC input voltage input from an AC power supply is converted into a DC voltage by a diode bridge, and this DC voltage is input from a DC terminal to a DCDC converter.

A capacitor is connected between the DC terminals of the power converter. By performing pre-charging to charge the capacitor at the start of power supply from the power converter, it is possible to suppress the inrush current from flowing from the AC power supply. A switch is connected in series with the capacitor between the DC terminals of the power converter. The switch switches between a power supply state and a power cutoff state from the AC power source to the capacitor. In this power converter, the switch is controlled based on the current detected by the current detector. As a result, it is possible to prevent excessive current from flowing through the power converter when precharging the capacitor.

JP 2017-221033 A

The following problems arise when the current detector is used to control the switch. For example, when a shunt resistor is used as the current detection unit, the heat generated by the shunt resistor causes a problem that the power conversion efficiency of the power converter is lowered. Further, when a clamp-type current detection unit is used as the current detection unit, the cost of the clamp-type current detection unit is high, so there is a problem that the product cost of the power converter increases. Furthermore, the current detection unit needs to convert the detected current value into a voltage value and output it, and there is concern that this conversion will delay control of the switch. Therefore, there is a demand for a technique capable of controlling the switch without using the current detection section.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a power converter capable of suppressing an excessive current in precharging without using a current detection unit.

A first means for solving the above problems is a power conversion unit that has a rectifying element, converts an AC input current input from an AC power supply into a DC current by the rectifying element, and outputs the DC current from a pair of DC terminals. a capacitor connected between the pair of DC terminals; a switch for switching between a power supply state and a power cut-off state from the AC power source to the capacitor; a voltage detection unit, a second voltage detection unit that detects a capacitor voltage that is the inter-electrode voltage of the capacitor, and either a voltage difference between the detected absolute value of the input voltage and the capacitor voltage or a correlation value thereof a controller for controlling the switch based on a voltage difference parameter.

In the above means, the AC input current input from the AC power supply by the power conversion unit is converted into a DC current by the rectifying element and output from the DC terminal, and at the start of power supply from the AC power supply, between the DC terminals By precharging the connected capacitor, the inrush current from the AC power supply is suppressed. In this precharging, in order to suppress an excessive current from flowing through the power conversion unit, the power supply state and the power cutoff state from the AC power source to the capacitor are switched based on the capacitor voltage and the input voltage. A switching switch is controlled. Specifically, the switches are controlled based on a voltage difference parameter, which is either the voltage difference between the absolute value of the input voltage and the capacitor voltage or the correlation value thereof. Since the current during precharging is generated based on the voltage difference between the absolute value of the input voltage and the capacitor voltage, controlling the switch based on this voltage difference parameter suppresses excessive current without using a current detector. can.

In the second means, the control unit switches the switch to the power supply state on condition that the absolute value is smaller than a threshold voltage that is larger than the capacitor voltage by a predetermined value.

A capacitor is precharged when the absolute value of the input voltage is greater than the capacitor voltage. In the above means, the voltage range of the absolute value of the input voltage in which the capacitor is precharged is limited to the voltage range from the capacitor voltage to the threshold voltage. Therefore, excessive current in precharging can be suitably suppressed.

In the third means, the controller switches the switch to the power supply state on condition that the absolute value is greater than the capacitor voltage.

In the above means, the capacitor can be properly precharged because the switch is switched to the power supply state only when the capacitor is precharged.

In the fourth means, the absolute value of the input voltage repeats an increasing period during which the voltage value increases and a decreasing period during which the voltage value decreases, and the control section controls the increasing period and the decreasing period. only during the decreasing period of time, the switch is switched to the powered state.

If the switch is switched to the power supply state during the period in which the absolute value of the input voltage is increasing, and the timing of switching to the power cutoff state is delayed after that, it is not possible to suppress an excessive current from flowing through the power conversion unit during precharging. In the above means, the switch is switched to the power supply state only during the decrease period of the absolute value increase period and decrease period, so even if the timing of switching to the power cutoff state is delayed, an excessive current flows through the power conversion unit. can be reliably suppressed.

In the fifth means, the control unit outputs a pulse signal that is switched on and off at a predetermined cycle to the switch, and the switch is in the power supply state during an on period in which the pulse signal is on. The power cutoff state occurs in the OFF period in which the pulse signal is OFF, and the controller sets the ON period occupying the predetermined period to be shorter as the absolute value of the capacitor voltage is larger.

The speed of current increase in precharging increases as the absolute value of the input voltage increases with respect to the capacitor voltage. In the above means, the control unit outputs a pulse signal that switches on and off at a predetermined cycle to the switch to control the switch. Shorten the ON period for the supply state. Therefore, in precharging, it is possible to suppress the flow of excessive current.

In the sixth means, the DC terminals include a high voltage side DC terminal and a low voltage side DC terminal, the switch is connected between the capacitor and the low voltage side DC terminal, and the low voltage side DC terminal connected directly to

According to the above configuration, the potential of the low voltage side DC terminal of the power conversion section and the potential of the portion of the switch connected to this low voltage side DC terminal can be made equal. Thereby, the configuration of the power converter can be simplified compared to the case where these potentials are different.

In the seventh means, a voltage adjusting section including an input side capacitor and connected in parallel with the capacitor is provided, and the switch is connected between the voltage adjusting section and the low voltage side DC terminal.

According to the above configuration, the precharge of the input-side capacitor can also be controlled using the switch. Also, since the capacitor and the voltage adjustment section are connected in parallel, the capacitor voltage can be detected by detecting the voltage of the voltage adjustment section.

The eighth means comprises a voltage adjustment unit connected to the DC terminals, the DC terminals including a high-voltage side DC terminal and a low-voltage side DC terminal, and the high-voltage side DC terminals are connected via high-voltage side wiring. The low-voltage side DC terminal is connected to the low-voltage input side of the voltage adjustment section via a low-voltage side wiring, and the capacitor is connected to the high-voltage side wiring and the low-voltage side. The switch is provided in a connection wiring that connects to the side wiring, and the switch is connected between the high-voltage side wiring and the capacitor in the connection wiring.

According to the above configuration, it is possible to shorten the wiring length between the high-voltage side wiring and the switch among the connection wirings. As a result, the surge voltage generated by the reactance component of the wiring can be suppressed when the switch is switched.

In the ninth means, a filter circuit is provided between the AC power supply and the power conversion unit and has a filter capacitor for removing noise contained in the input voltage, and the switch is connected to the AC power supply. It is connected between said filter circuit.

According to the above configuration, the precharge of the filter capacitor can also be controlled using the switch. In addition, since the switch is provided closer to the AC power supply than the power conversion unit, a surge voltage generated by switching of the switch can be suppressed using the rectifier included in the power conversion unit.

The block diagram of the power converter device which concerns on 1st Embodiment. 4 is a flowchart of control processing according to the first embodiment; 4 is a time chart showing changes in capacitor voltage in control processing; 4 is a time chart showing the transition of switch states in the control process of the first embodiment; 9 is a flowchart of control processing according to the second embodiment; FIG. 10 is a time chart showing changes in switch states in the control process of the second embodiment; FIG. 9 is a flowchart of control processing according to the third embodiment; FIG. 11 is a time chart showing the transition of switch states in the control process of the third embodiment; FIG. 10 is a flowchart of control processing according to the fourth embodiment; FIG. 11 is a time chart showing the transition of switch states in the control process of the fourth embodiment; FIG. The block diagram of the power converter device which concerns on 5th Embodiment. The block diagram of the power converter device which concerns on 6th Embodiment. The block diagram of the power converter device which concerns on 7th Embodiment. The block diagram of the power converter device which concerns on other embodiment. The block diagram of the power converter device which concerns on other embodiment. The block diagram of the power converter device which concerns on other embodiment. The block diagram of the power converter device which concerns on other embodiment. The block diagram of the power converter device which concerns on other embodiment. The block diagram of the power converter device which concerns on other embodiment. The block diagram of the power converter device which concerns on other embodiment. The block diagram of the power converter device which concerns on other embodiment.

<First Embodiment>
A first embodiment in which a power conversion device according to the present invention is applied to a power conversion device 100 mounted on a vehicle will be described below with reference to the drawings. The power converter 100 according to the present embodiment converts an AC input voltage Vin input from an AC power supply 200 into a DC output voltage Vout.

As shown in FIG. 1, the power conversion device 100 includes a power conversion section 10, a smoothing capacitor 20, a switch 30, a control section 40, and a DCDC converter (hereinafter referred to as DDC) 50 as a voltage adjustment section. there is The power converter 10 is connected to an AC power supply 200 via a first AC terminal TA1 and a second AC terminal TA2, and is connected to an electric load 300 via a first DC terminal TD1 and a second DC terminal TD2. The AC power supply 200 is, for example, a commercial power supply, and the electric load 300 is, for example, a vehicle-mounted battery. In this embodiment, the first DC terminal TD1 corresponds to "a DC terminal, a high voltage side DC terminal", and the second DC terminal TD2 corresponds to a "DC terminal, a low voltage side DC terminal".

The power converter 10 includes a rectifier circuit 11 and a PFC (Power Factor Correction) circuit 12 . The rectifier circuit 11 is a diode bridge circuit as a full-wave rectifier circuit including first to fourth diodes D1 to D4 as rectifying elements, and the anode of the first diode D1 and the cathode of the second diode D2 are connected. , constitute a first series connection. Also, the anode of the third diode D3 and the cathode of the fourth diode D4 are connected to form a second series connection. The first series connection body and the second series connection body are connected in parallel.

A first intermediate point PA1 between the first diode D1 and the second diode D2 in the first series connection body is connected to the first AC terminal TA1 via the first wiring LP1. A second intermediate point PA2 between the third diode D3 and the fourth diode D4 in the second series connection body is connected to the second AC terminal TA2 via the second wiring LP2. Each cathode of the first and third diodes D1 and D3 is connected to one end of a third wiring LP3 as a high-voltage side wiring, and each anode of the second and fourth diodes D2 and D4 is connected as a low-voltage side wiring. It is connected to one end of the fourth wiring LP4. The third wiring LP3 is connected to the high voltage input side of the switching circuit 52 via the first DC terminal TD1, and the fourth wiring LP4 is connected to the low voltage input side of the switching circuit 52 via the second DC terminal TD2. there is The switching circuit 52 is connected to the electrical load 300 through output terminals TO1 and TO2.

The PFC circuit 12 is a circuit that improves the power factor by adjusting the phase and frequency of the input voltage Vin and the input current Iin input from the AC power supply 200. The rectifier circuit 11 and a pair of DC terminals TD1, TD2 is provided between The PFC circuit 12 includes a reactor 13, a PFC switch 14, and a fifth diode D5. The reactor 13 and the fifth diode D5 are provided on the third wiring LP3, the cathode of the fifth diode D5 is connected to the first DC terminal TD1, and the anode of the fifth diode D5 is connected to the reactor 13. there is

The PFC switch 14 is a voltage-driven switch, and is an N-channel MOSFET in this embodiment. The PFC switch 14 is provided between the third wiring LP3 and the fourth wiring LP4. Specifically, the drain of the PFC switch 14 is connected to the first connection point PB1 between the reactor 13 and the fifth diode D5, and the source of the PFC switch 14 is connected to the second connection on the fourth wiring LP4. It is connected to point PB2. The PFC switch 14 has a parasitic diode 16 connected in parallel.

The smoothing capacitor 20 is connected between the first DC terminal TD1 and the second DC terminal TD2. Specifically, the smoothing capacitor 20 is provided on the fifth wiring LP5 as a connection wiring that connects the third wiring LP3 and the fourth wiring LP4. The fifth wiring LP5 is connected to the third wiring LP3 at the third connection point PB3 between the first DC terminal TD1 and the DDC50, and is connected to the fourth connection point PB4 between the second DC terminal TD2 and the DDC50. , is connected to the fourth wiring LP4. Smoothing capacitor 20 is, for example, an electrolytic capacitor.

The switch 30 is a voltage-driven switch, and is an N-channel MOSFET in this embodiment. The switch 30 is connected in series with the smoothing capacitor 20 on the fifth line LP5. Specifically, the drain of the switch 30 is connected to the electrode of the smoothing capacitor 20 on the second DC terminal TD2 side, and the source of the switch 30 is connected to the fourth wiring LP4. That is, the switch 30 is connected between the smoothing capacitor 20 and the second DC terminal TD2, and directly connected to the second DC terminal TD2 via the fourth wiring LP4. The switch 30 has a parasitic diode 31 connected in parallel.

The switch 30 is driven by a control signal SC output from the control section 40 and switches between an ON state and an OFF state. By turning on the switch 30 , power is supplied from the AC power supply 200 to the smoothing capacitor 20 , and electric charge is stored in the smoothing capacitor 20 . Also, by switching the switch 30 to the OFF state, power supply from the AC power supply 200 to the smoothing capacitor 20 is cut off, and power supply to the smoothing capacitor 20 is cut off. In other words, the switch 30 switches between a power supply state and a power cutoff state from the AC power supply 200 to the smoothing capacitor 20 . In this embodiment, the ON state of the switch 30 corresponds to the "power supply state", and the OFF state of the switch 30 corresponds to the "power cutoff state".

DDC 50 is connected to a series connection of smoothing capacitor 20 and switch 30 . The DDC 50 includes a DDC input capacitor 51 as an input side capacitor and a switching circuit 52, which are connected to the third wiring LP3 and the fourth wiring LP4. The DDC input capacitor 51 suppresses oscillation of the DDC input voltage Vddc output from the first and second DC terminals TD1 and TD2 of the power converter 10 due to the operation of the switching circuit 52 . The switching circuit 52 converts the voltage value of the DDC input voltage Vddc into a voltage value suitable for the electric load 300 . The DDC 50 outputs the output voltage Vout having the voltage value converted by the switching circuit 52 to the electric load 300 from the output terminals TO1 and TO2.

The power conversion device 100 includes a first voltage sensor 41 that detects the input voltage Vin of the AC power supply 200, a second voltage sensor 42 that detects the DDC input voltage Vddc input to the DDC 50, and the drain-source voltage of the switch 30. A third voltage sensor 43 that detects the switch voltage Vsw and a fourth voltage sensor 44 that detects the output voltage Vout output from the DDC 50 are provided. A detection value of each sensor is input to the control unit 40 . In this embodiment, the first voltage sensor 41 corresponds to the "first voltage detection section", and the second voltage sensor 42 and the third voltage sensor 43 correspond to the "second voltage detection section".

The control unit 40 is a control device equipped with a well-known microcomputer composed of CPU, ROM, RAM, flash memory, and the like. The control unit 40 acquires various signals and performs various controls based on the acquired information. Specifically, based on the input voltage Vin detected by the first voltage sensor 41 and the DDC input voltage Vddc detected by the second voltage sensor 42, the control unit 40 generates a PFC signal SP for switching the PFC switch 14. to the PFC switch 14 . Further, the control unit 40 switches the drive signal SD for driving the switching circuit 52 based on the DDC input voltage Vddc detected by the second voltage sensor 42 and the output voltage Vout detected by the fourth voltage sensor 44. Output to circuit 52 . Thereby, the voltage value of the output voltage Vout is converted into a voltage value suitable for the electric load 300 .

Also, the control unit 40 outputs the control signal SC to the switch 30 as described above. The control unit 40 controls pre-charging of the smoothing capacitor 20 from the AC power supply 200 when power supply to the electric load 300 is started, using the control signal SC. By precharging the smoothing capacitor 20, it is possible to suppress the inrush current from flowing from the AC power supply 200 when power supply to the electric load 300 is started.

By the way, when precharging the smoothing capacitor 20, if the input current Iin flowing through the first to fourth wirings LP1 to LP4 increases, the reactor 13 and the first to fifth diodes provided on these wirings LP1 to LP4 It is necessary to increase the rated current of elements such as D1 to D5. Since an element with a large rated current is expensive, the product cost of the power conversion device 100 increases. Therefore, a technique for suppressing the input current Iin is desired.

In order to suppress the input current Iin, it is conceivable to detect the input current Iin using, for example, a current sensor and control precharging of the smoothing capacitor 20 based on the detected current value of the input current Iin.

However, using a current sensor to suppress the input current Iin causes the following problems. For example, when a shunt resistor is used as a current sensor, the problem arises that the power conversion efficiency of the power conversion device 100 is lowered due to the heat generated by the shunt resistor. Moreover, when a clamp-type current sensor is used as the current sensor, the product cost of the power conversion device 100 increases because the clamp-type current sensor is expensive. Furthermore, the current sensor needs to convert the current value of the detected input current Iin into a voltage value and output it. Therefore, a technique that can control the switch 30 without using a current sensor is desired.

Therefore, in this embodiment, the switch 30 is controlled using the voltages Vin, Vddc, and Vsw detected by the first to third voltage sensors 41-43. Specifically, the switch 30 is controlled based on the voltage difference between the absolute value of the input voltage Vin and the capacitor voltage Vcn obtained by subtracting the switch voltage Vsw from the DDC input voltage Vddc. As a result, it is possible to suppress an increase in the input current Iin without using a current sensor. In this embodiment, the voltage difference between the absolute value of the input voltage Vin and the capacitor voltage Vcn corresponds to the "voltage difference parameter".

FIG. 2 shows a flowchart of the control processing of this embodiment. The control unit 40 repeats the control process every predetermined period when power supply to the electric load 300 is started.

When the control process is started, the control unit 40 detects the respective voltages Vin, Vddc and Vsw using the first to third voltage sensors 41 to 43 in step S10. In subsequent step S12, the capacitor voltage Vcn is calculated using the output voltage Vout and switch voltage Vsw detected in step S10. The capacitor voltage Vcn is the inter-electrode voltage of the smoothing capacitor 20, and is represented by (Equation 1) using the DDC input voltage Vddc and the switch voltage Vsw.

Vcn=Vddc−Vsw (Formula 1)
Therefore, detecting the DDC input voltage Vddc and the switch voltage Vsw corresponds to detecting the capacitor voltage Vcn calculated using these voltages.

In subsequent step S14, it is determined whether or not the capacitor voltage Vcn calculated in step S12 has reached or exceeded a predetermined target voltage Vtg. In this embodiment, the target voltage Vtg is the capacitor voltage Vcn at which precharging of the smoothing capacitor 20 is completed, and is set to a voltage value equal to or lower than the maximum voltage value Vmax of the input voltage Vin.

If a negative determination is made in step S14, an absolute value voltage Vab indicating the absolute value of the input voltage Vin is calculated in step S15. As shown in FIG. 1 , the absolute value voltage Vab is the voltage output from the rectifier circuit 11 to the PFC circuit 12 . In subsequent step S16, it is determined whether the absolute value voltage Vab calculated in step S15 is in the decreasing period DH.

In this embodiment, the input voltage Vin has a sinusoidal voltage waveform, and the absolute value voltage Vab indicating its absolute value has an increasing period IH during which the voltage value increases and a decreasing period DH during which the voltage value decreases. are repeated (see FIG. 4). If the absolute value voltage Vab is in the increasing period IH, a negative determination is made in step S16. In this case, the control process ends without precharging the smoothing capacitor 20 .

On the other hand, when the absolute value voltage Vab is in the decreasing period DH, an affirmative determination is made in step S16. In this case, in step S18, whether the absolute value voltage Vab calculated in step S15 is larger than the capacitor voltage Vcn calculated in step S12 and smaller than a threshold voltage Vth which is larger than the capacitor voltage Vcn by a predetermined value. judge. In this embodiment, the predetermined value is set to a voltage value equal to or less than the voltage difference between the maximum voltage value Vmax and the capacitor voltage Vcn, for example, set to the voltage difference between the maximum voltage value Vmax and the target voltage Vtg.

If a negative determination is made in step S18, the control process is terminated without precharging the smoothing capacitor 20. FIG. On the other hand, if an affirmative determination is made in step S18, the switch 30 is turned on using the control signal SC in order to precharge the smoothing capacitor 20 in step S20. That is, the switch 30 is turned on on condition that the absolute voltage Vab is lower than the threshold voltage Vth and higher than the capacitor voltage Vcn in the decreasing period DH of the absolute voltage Vab.

In subsequent step S22, it is determined whether or not a predetermined ON period TN has elapsed after the switch 30 was turned on in step S20. In the present embodiment, during the decrease period DH, the absolute value voltage Vab is set to decrease from the threshold voltage Vth to the capacitor voltage Vcn. Therefore, in step S22, it may be determined whether the absolute value voltage Vab calculated in step S15 is lower than the capacitor voltage Vcn calculated in step S12.

If a negative determination is made in step S22, the process of step S22 is repeated. On the other hand, if an affirmative determination is made in step S22, in step S24 the switch 30 is turned off using the control signal SC in order to finish precharging the smoothing capacitor 20, and the control process ends.

On the other hand, if an affirmative determination is made in step S14, completion of precharging is determined in step S26. In the subsequent step S28, the control signal SC is used to turn on the switch 30 in order to supply power to the electric load 300, and the control process ends.

3 and 4 show an example of control processing. FIG. 3 shows transition of the capacitor voltage Vcn from the start of precharging of the smoothing capacitor 20 to the end thereof. In FIG. 3, (A) shows the transition of the input voltage Vin, (B) shows the transition of the capacitor voltage Vcn, (C) shows the transition of the DDC input voltage Vddc, and (D) shows the transition of the input It shows the transition of the current Iin.

FIG. 4 shows transition of the state of the switch 30 during a partial period from the precharge start timing t1 to the precharge end timing t2 in FIG. Therefore, in FIG. 4, the capacitor voltage Vcn is shown as a constant value. In FIG. 4, (A) shows the transition of the input voltage Vin, (B) shows the transition of the absolute value voltage Vab, (C) shows the transition of the state of the switch 30, and (D) 4 shows the transition of the DDC input voltage Vddc.

As shown in FIG. 4, in the control process, the absolute value voltage Vab repeats an increase period IH and a decrease period DH. , the switch 30 is switched from the off state to the on state. Thereby, the smoothing capacitor 20 is charged with power from the AC power supply 200 via the switch 30 . At this time, the electric charge of the DDC input capacitor 51 also moves to the smoothing capacitor 20 , and the voltage of the smoothing capacitor 20 becomes equal to the voltage of the DDC input capacitor 51 .

The switch 30 is kept on for the on period TN. Then, when the absolute value voltage Vab becomes smaller than the capacitor voltage Vcn at time t12 after the ON period TN has passed from time t11, the switch 30 is switched from the ON state to the OFF state. As a result, the DDC input voltage Vddc has a voltage value corresponding to the voltage division ratio between the smoothing capacitor 20 and the parasitic capacitance of the switch 30 .

After that, the absolute value voltage Vab switches from the decreasing period DH to the increasing period IH. Then, at time t13, when the absolute value voltage Vab becomes larger than the above voltage value, charge is accumulated in the DDC input capacitor 51, so that the DDC input voltage Vddc rises.

Thereafter, at time t14, the absolute value voltage Vab reaches the maximum voltage value Vmax, and when the absolute value voltage Vab switches from the increasing period IH to the decreasing period DH, the absolute value voltage Vab decreases. On the other hand, the DDC input voltage Vddc is maintained at the maximum voltage value Vmax by the charges stored in the DDC input capacitor 51 .

Thereafter, when the absolute value voltage Vab becomes smaller than the threshold voltage Vth at time t15 in the decreasing period DH, the switch 30 is switched from the off state to the on state again. In the control process, the process from time t11 to time t15 is repeatedly performed every predetermined period. As a result, during the ON period TN of the switch 30 from time t11 to time t12, electric charge is accumulated in the smoothing capacitor 20, and the capacitor voltage Vcn rises.

As a result, as shown in FIG. 3, the capacitor voltage Vcn, which was zero at time t1, rises. The rate of increase of the capacitor voltage Vcn increases as the voltage difference between the maximum voltage value Vmax and the capacitor voltage Vcn increases, and decreases as this voltage difference decreases. Therefore, as the capacitor voltage Vcn increases, the rate of increase of the capacitor voltage Vcn decreases.

As the capacitor voltage Vcn rises, the fluctuation lower limit of the DDC input voltage Vddc rises, and the fluctuation width of the DDC input voltage Vddc shrinks. Also, the maximum value of the input current Iin is reduced, and the range of fluctuation of the input current Iin is reduced. Then, at time t2, when the capacitor voltage Vcn reaches the threshold voltage Vth, it is determined that precharging is completed, and the control process ends.

According to this embodiment detailed above, the following effects can be obtained.

In the present embodiment, the AC input current Iin input from the AC power supply 200 by the power conversion unit 10 is converted into a full-wave rectified current by the rectifier circuit 11 and output from the first and second DC terminals TD1 and TD2. be done. In addition, when the power supply to the electric load 300 is started, a rush current may flow from the AC power supply 200 by precharging the smoothing capacitor 20 connected between the first DC terminal TD1 and the second DC terminal TD2. Suppressed.

In this embodiment, in this precharge, in order to suppress an excessive input current Iin from flowing to the power conversion unit 10, based on the capacitor voltage Vcn and the input voltage Vin, the flow from the AC power supply 200 to the smoothing capacitor 20 is controlled. The switch 30 that switches between the power supply state and the power cutoff state is controlled. Specifically, the switch 30 is controlled based on the voltage difference between the absolute value voltage Vab indicating the absolute value of the input voltage Vin and the capacitor voltage Vcn. Since the input current Iin during precharging is generated based on the voltage difference between the absolute value voltage Vab and the capacitor voltage Vcn, by controlling the switch 30 based on this voltage difference, an excessive current Iin during precharging can be prevented without using a current sensor. input current Iin can be suppressed.

Specifically, the smoothing capacitor 20 is precharged when the absolute value voltage Vab is greater than the capacitor voltage Vcn. In this embodiment, the voltage range of the absolute value voltage Vab with which the smoothing capacitor 20 is precharged is limited to the voltage range from the capacitor voltage Vcn to the target voltage Vtg. Therefore, the excessive input current Iin in precharging can be suitably suppressed.

- In this embodiment, the switch 30 is turned on on condition that the absolute value voltage Vab is higher than the capacitor voltage Vcn. That is, since the switch 30 is turned on only when the smoothing capacitor 20 is precharged, the smoothing capacitor 20 can be appropriately precharged.

- The absolute value voltage Vab repeats an increase period IH and a decrease period DH. Of these, if the switch 30 is switched to the ON state during the increase period IH, and the timing of switching to the OFF state is delayed after that, it is not possible to prevent an excessive input current Iin from flowing through the power conversion unit 10 during precharging. In the present embodiment, the switch 30 is switched to the ON state only during the decrease period DH of the increase period IH and the decrease period DH of the absolute value voltage Vab. The input current Iin can be reliably suppressed.

- In this embodiment, the source of the switch 30 is directly connected to the second DC terminal TD2 via the fourth wiring LP4. Therefore, the low-side potential of the DDC input voltage Vddc and the source potential of the switch 30 can be made equal, and the capacitor voltage Vcn can be easily calculated by subtracting the switch voltage Vsw from the DDC input voltage Vddc. Also, the source potential of the switch 30 can be shared with the potentials of other elements, such as the anode potentials of the second diode D2 and the fourth diode D4 and the source potential of the PFC switch 14 . Thereby, the configuration of the power conversion device 100 can be simplified compared to the case where these potentials are different.

(Second embodiment)
The second embodiment will be described below with reference to FIGS. 5 and 6, focusing on differences from the first embodiment. In FIG. 5, the same step numbers are assigned to the same processes as those shown in FIG. 2, and description thereof will be omitted.

This embodiment differs from the first embodiment in that the switch 30 is turned on not only during the decreasing period DH of the absolute value voltage Vab but also during the increasing period IH. FIG. 5 shows a flowchart of control processing according to the present embodiment. In the control process of this embodiment, when the absolute value voltage Vab is calculated in step S15, the process proceeds to step S18 without determining whether the absolute value voltage Vab is in the decreasing period DH. That is, the switch 30 is turned on on condition that the absolute value voltage Vab is smaller than the threshold voltage Vth and larger than the capacitor voltage Vcn.

FIG. 6 shows an example of control processing in this embodiment. FIG. 6 corresponds to FIG. 4 of the first embodiment, and the description of the DDC input voltage Vddc is omitted.

As shown in FIG. 6, in this embodiment, when the absolute value voltage Vab becomes smaller than the threshold voltage Vth at time t21 of the decrease period DH, the switch 30 is switched from the off state to the on state. Then, when the absolute value voltage Vab becomes smaller than the capacitor voltage Vcn at time t22 after the ON period TN has passed from time t21, the switch 30 is switched from the ON state to the OFF state.

After that, the absolute value voltage Vab switches from the decreasing period DH to the increasing period IH, and when the absolute value voltage Vab becomes larger than the capacitor voltage Vcn at time t23 in this increasing period IH, the switch 30 is switched from the OFF state to the ON state. . Then, when the absolute value voltage Vab becomes larger than the threshold voltage Vth at time t24 when the ON period TN has passed from time t23, the switch 30 is switched from the ON state to the OFF state.

After that, the absolute value voltage Vab switches from the increasing period IH to the decreasing period DH again, and at time t25 in the decreasing period DH, when the absolute value voltage Vab becomes smaller than the threshold voltage Vth, the switch 30 is turned on again from the off state. can be switched. In the control process of this embodiment, the process from time t21 to time t25 is repeatedly performed every predetermined period.

According to the present embodiment described above, the switch 30 is turned on not only during the decreasing period DH of the absolute value voltage Vab but also during the increasing period IH of the absolute value voltage Vab. Therefore, the period required for precharging the smoothing capacitor 20 can be shortened as compared with the case where the switch 30 is turned on only during the decreasing period DH of the absolute value voltage Vab.

(Third embodiment)
The third embodiment will be described below with reference to FIGS. 7 and 8, focusing on differences from the second embodiment. In FIG. 7, the same step numbers are assigned to the same processes as those shown in FIG. 5, and description thereof will be omitted.

This embodiment maintains the switch 30 in the on state not only when the absolute value voltage Vab is higher than the capacitor voltage Vcn, but also when the absolute value voltage Vab is lower than the capacitor voltage Vcn. different from FIG. 7 shows a flowchart of control processing according to this embodiment. In the control process of the present embodiment, when the absolute value voltage Vab is calculated in step S15, it is determined in step S30 whether the absolute value voltage Vab calculated in step S15 is smaller than the threshold voltage Vth.

If a negative determination is made in step S30, the control process ends. On the other hand, if an affirmative determination is made in step S30, the process proceeds to step S20. That is, the switch 30 is turned on on condition that the absolute value voltage Vab is smaller than the threshold voltage Vth.

FIG. 8 shows an example of control processing in this embodiment. FIG. 8 corresponds to FIG. 6 of the second embodiment. As shown in FIG. 8, in the present embodiment, when the absolute value voltage Vab becomes smaller than the threshold voltage Vth at time t31 of the decrease period DH, the switch 30 is switched from the off state to the on state. After that, the absolute value voltage Vab switches from the decreasing period DH to the increasing period IH, and when the absolute value voltage Vab becomes larger than the threshold voltage Vth at time t32 in the increasing period IH, the switch 30 is switched from the ON state to the OFF state. .

After that, the absolute value voltage Vab switches from the increasing period IH to the decreasing period DH again, and at time t33 in the decreasing period DH, when the absolute value voltage Vab becomes smaller than the threshold voltage Vth, the switch 30 is turned on again from the off state. can be switched. In the control process of this embodiment, the process from time t31 to time t33 is repeatedly performed for each predetermined period.

According to the present embodiment described above, the switch 30 is kept on not only when the absolute value voltage Vab is higher than the capacitor voltage Vcn, but also when the absolute value voltage Vab is lower than the capacitor voltage Vcn. Therefore, when the absolute value voltage Vab is smaller than the capacitor voltage Vcn, the process of switching the switch 30 to the off state becomes unnecessary, and the processing load of the control section 40 in the control process can be reduced.

(Fourth embodiment)
The fourth embodiment will be described below with reference to FIGS. 9 and 10, focusing on differences from the first embodiment. In FIG. 9, for the sake of convenience, the same step numbers are assigned to the same processes as those shown in FIG. 2, and the description thereof is omitted.

This embodiment differs from the first embodiment in that the switch 30 is turned on not only when the absolute value voltage Vab is lower than the threshold voltage Vth, but also when the absolute value voltage Vab is higher than the threshold voltage Vth. different. Specifically, the control signal SC is a pulse signal that switches between ON and OFF at a predetermined cycle TZ. The predetermined period TZ includes an ON period TN during which the control signal SC is ON and an OFF period TF during which the control signal SC is OFF. The predetermined period TZ is represented by (Equation 2) using the ON period TN and the OFF period TF.

TZ=TN+TF (Formula 2)
In the present embodiment, the ratio between the ON period TN and the OFF period TF can be variably set. Specifically, the ON period TN is set shorter as the absolute value voltage Vab increases with respect to the capacitor voltage Vcn.

FIG. 9 shows a flowchart of control processing according to this embodiment. In the control process of the present embodiment, when the absolute value voltage Vab is calculated in step S15, it is determined in step S40 whether the absolute value voltage Vab calculated in step S15 is greater than the capacitor voltage Vcn calculated in step S12. do.

If a negative determination is made in step S40, the control process ends. On the other hand, when an affirmative determination is made in step S40, in step S42, the ON period TN is set based on the voltage difference between the absolute value voltage Vab and the capacitor voltage Vcn, and the process proceeds to step S20. Then, in step S22, using the ON period TN set in step S42, it is determined whether the ON period TN has elapsed.

FIG. 10 shows an example of control processing in this embodiment. FIG. 10 corresponds to FIG. 4 of the first embodiment, and the description of the DDC input voltage Vddc is omitted. As shown in FIG. 10, in this embodiment, the absolute value voltage Vab switches from the decreasing period DH to the increasing period IH at time t41. At time t42 of this increasing period IH, when the absolute value voltage Vab becomes larger than the capacitor voltage Vcn, the switch 30 is switched from the OFF state to the ON state.

At time t42, the absolute value voltage Vab is approximately equal to the capacitor voltage Vcn. Therefore, in the predetermined period TZ starting at time t42, the ON period TN is set to the relatively long first ON period TN1. In the predetermined cycle TZ starting at time t42, the switch 30 is switched from the ON state to the OFF state at time t43 when the first ON period TN1 has passed from time t42, and the switch 30 is switched from the ON state to the OFF state at time t44 when the predetermined cycle TZ has passed since time t42. 30 is again switched from off to on.

In the control process of the present embodiment, the process from time t42 to time t44 is repeatedly performed at predetermined intervals TZ during the period in which the absolute value voltage Vab is greater than the capacitor voltage Vcn. set. Specifically, in a predetermined cycle TZ from time t44 to time t46, the second on-period TN2 is set from time t44 to time t45. A third ON period TN3 up to is set. Further, in a predetermined period TZ from time t48 to time t50, a third ON period TN3 from time t48 to time t49 is set. 5 ON period TN5 is set.

Among the first to fifth ON periods TN1 to TN5, in the first to third ON periods TN1 to TN3 included in the increasing period IH, the ON period TN is shortened as the absolute value voltage Vab increases. . Further, in the fourth and fifth on-periods TN4 and TN5 included in the decreasing period DH, the on-period TN is extended as the absolute value voltage Vab decreases.

Thereafter, when the absolute value voltage Vab drops to zero at time t53, the absolute value voltage Vab switches from the decreasing period DH to the increasing period IH again. In the control process of this embodiment, the process from time t41 to time t52 is repeatedly performed at predetermined intervals.

According to the present embodiment described above, the switch 30 is turned on not only when the absolute value voltage Vab is lower than the threshold voltage Vth, but also when the absolute value voltage Vab is higher than the threshold voltage Vth. Therefore, the number of times the switch 30 is turned on can be increased, and the period required for precharging the smoothing capacitor 20 can be shortened.

*Here, the rate of increase dIin/dt of the input current Iin during precharging increases as the absolute value voltage Vab increases with respect to the capacitor voltage Vcn. Therefore, in the present embodiment, the larger the absolute value voltage Vab with respect to the capacitor voltage Vcn, the shorter the ON period TN that occupies the predetermined period TZ is set. Therefore, while shortening the period required for precharging the smoothing capacitor 20, it is possible to suppress the flow of an excessive input current Iin during precharging.

(Fifth embodiment)
The fifth embodiment will be described below with reference to FIG. 11, focusing on differences from the first embodiment. In FIG. 11, for the sake of convenience, the same step numbers are assigned to the same configurations as those shown in FIG. 1, and the description thereof is omitted.

This embodiment differs from the first embodiment in that the switch 30 is connected between the first DC terminal TD1 and the smoothing capacitor 20 on the fifth wiring LP5. Specifically, the drain of the switch 30 is connected to the third wiring LP3, and the source of the switch 30 is connected to the electrode of the smoothing capacitor 20 on the first DC terminal TD1 side.

- According to this embodiment described above, since the switch 30 is provided on the first DC terminal TD1 side of the smoothing capacitor 20, the switch 30 is provided on the second DC terminal TD2 side of the smoothing capacitor 20 in the first embodiment. Compared to , the wiring length between the third connection point PB3 and the switch 30 in the fifth wiring LP5 can be shortened. Thereby, when the switch 30 is switched, the surge voltage generated by the reactance component of the fifth wiring LP5 between the third connection point PB3 and the switch 30 can be suppressed.

(Sixth embodiment)
The sixth embodiment will be described below with reference to FIG. 12, focusing on differences from the first embodiment. In FIG. 12, for the sake of convenience, the same step numbers are assigned to the same configurations as those shown in FIG. 1, and the description thereof is omitted.

The present embodiment differs from the first embodiment in that the switch 30 is provided not on the fifth wiring LP5 but on the fourth wiring LP4. Specifically, the switch 30 is provided closer to the second DC terminal TD2 than the fourth connection point PB4 where the fifth wiring LP5 connects to the fourth wiring LP4. Therefore, in this embodiment, the switch 30 is connected in series with the smoothing capacitor 20 and is also connected in series with the DDC input capacitor 51 included in the DDC 50 .

- According to this embodiment described above, the switch 30 is connected in series with the DDC input capacitor 51 . Therefore, the switch 30 can be used to control not only the precharging of the smoothing capacitor 20 but also the precharging of the DDC input capacitor 51 .

- According to the present embodiment, the smoothing capacitor 20 is connected in parallel to the DDC 50 . Therefore, the capacitor voltage Vcn is equal to the DDC input voltage Vddc, and there is no need to detect the switch voltage Vsw to calculate the capacitor voltage Vcn. Therefore, the power conversion device 100 does not need the third voltage sensor 43, and the configuration of the power conversion device 100 can be simplified.

(Seventh embodiment)
The seventh embodiment will be described below with reference to FIG. 13, focusing on differences from the first embodiment. In FIG. 13, for the sake of convenience, the same step numbers are assigned to the same configurations as those shown in FIG. 1, and the description thereof is omitted.

This embodiment differs from the first embodiment in that a filter circuit 70 is provided between the power converter 10 and the AC power supply 200 . In this embodiment, the first and second wirings LP1 and LP2 extend to the AC power supply 200 via the first and second AC terminals TA1 and TA2, and the filter circuit 70 includes the first wiring LP1 and the second wiring. It has a filter capacitor 71 provided between it and LP2. The filter capacitor 71 removes noise contained in the input voltage Vin.

Further, the present embodiment differs from the first embodiment in that the switch 30 is provided not on the fifth wiring LP5 but on the second wiring LP2. Specifically, switch 30 is provided between filter circuit 70 and AC power supply 200 . In this embodiment, a switch without a parasitic diode 31, such as an IGBT, is used as the switch 30 in order to cut off the AC input voltage Vin.

- According to this embodiment described above, the switch 30 is connected in series with the filter capacitor 71 included in the filter circuit 70 . Therefore, the switch 30 can be used to control not only the precharging of the smoothing capacitor 20 but also the precharging of the filter capacitor 71 .

Further, according to the present embodiment, since the switch 30 is provided closer to the AC power supply 200 than the power conversion unit 10, the reactor 13 and the first to fifth diodes D1 to D5 of the power conversion unit 10 are can be used to suppress the surge voltage caused by the switching of the switch 30 .

(Other embodiments)
It should be noted that each of the above-described embodiments may be modified as follows.

- Although the example with which the power conversion part 10 was equipped with the PFC circuit 12 was shown in the said embodiment, it is not restricted to this. A smoothing circuit including, for example, a capacitor and a reactor may be provided instead of the PFC circuit 12 .

- In the above embodiment, the ON period TN may be set based on the allowable current of the reactor 13 .

- The rectifier circuit 11 in the power converter 10 is not limited to a full-wave rectifier circuit, and may be a half-wave rectifier circuit. By using a full-wave rectifier circuit as the rectifier circuit 11, the period required for precharging the smoothing capacitor 20 can be shortened.

- The configuration of the PFC circuit 12 in the power converter 10 is not limited to the above embodiment. For example, in the embodiment shown in FIG. 14A, the rectifier circuit 11 and the PFC circuit 12 are integrated. Specifically, the power converter 10 includes sixth and seventh diodes D6 and D7, first and second reactors 13A and 13B, and first and second PFC switches 14A and 14B. A third series connection is configured by connecting the anode of the sixth diode D6 and the drain of the first PFC switch 14A. Also, the anode of the seventh diode D7 and the drain of the second PFC switch 14B are connected to form a fourth series connection. The third series connection body and the fourth series connection body are connected in parallel.

A third intermediate point PA3 between the sixth diode D6 and the first PFC switch 14A in the third series connection body is connected to the first AC terminal TA1 via the first wiring LP1. 1 reactor 13A is provided. A fourth intermediate point PA4 between the seventh diode D7 and the second PFC switch 14B in the fourth series connection body is connected to the second AC terminal TA2 via the second wiring LP2. Two reactors 13B are provided. Each cathode of the sixth and seventh diodes D6 and D7 is connected to one end of the third wiring LP3. Each source of the first and second PFC switches 14A, 14B is connected to one end of the fourth wiring LP4. The first and second PFC switches 14A, 14B have parasitic diodes 16 connected in parallel. Note that the description of the control unit 40 is omitted in FIG. The same applies to FIG. 14B and FIGS. 16-21.

In the embodiment shown in FIG. 14A, the PFC signal SP from the control unit 40 switches the first and second PFC switches 14A and 14B between the ON state and the OFF state. As a result, the AC input voltage Vin is converted to the DC DDC input voltage Vddc, and the power factor is improved.

Moreover, in the embodiment shown in FIG. 14B, the PFC circuit 12 is provided between the rectifier circuit 11 and the first and second AC terminals TA1 and TA2. The PFC circuit 12 includes third and fourth reactors 13C and 13D and third and fourth PFC switches 14C and 14D. The third reactor 13C is provided on the first wiring LP1, and the fourth reactor 13D is provided on the second wiring LP2.

A source of the third PFC switch 14C and a source of the fourth PFC switch 14D are connected to form a fifth series connection. A drain of the third PFC switch 14C is connected to a first wiring LP1 between the first intermediate point PA1 and the third reactor 13C. Also, the drain of the fourth PFC switch 14C is connected to the second wiring LP2 between the second intermediate point PA2 and the fourth reactor 13D. The third and fourth PFC switches 14C, 14D have parasitic diodes 16 connected in parallel.

In the embodiment shown in FIG. 14B, the PFC signal SP from the control unit 40 switches the third and fourth PFC switches 14C and 14D between the ON state and the OFF state. As a result, the PFC circuit 12 first improves the power factor, and then the rectifier circuit 11 converts the AC input voltage Vin into a DC DDC input voltage Vddc.

- Arrangement|positioning of the switch 30 in the power converter device 100 is not restricted to the said embodiment. For example, switches 30 may be provided at first to sixth positions PL1 to PL6 shown in FIG. A first position PL1 is a position between the rectifier circuit 11 and the PFC circuit 12 on the third wiring LP3 in the power conversion unit 10 . A second position PL2 is a position between the reactor 13 on the third wiring LP3 in the PFC circuit 12 and the first connection point PB1. A third position PL3 is a position between the first connection point PB1 on the third wiring LP3 in the PFC circuit 12 and the fifth diode D5. A fourth position PL4 is a position between the first DC terminal TD1 on the third wiring LP3 in the power converter 100 and the third connection point PB3. A fifth position PL5 is a position between the power converter 10 and the filter circuit 70 on the second wiring LP2 in the power converter 100 . A sixth position PL<b>6 is a position between the rectifier circuit 11 and the PFC circuit 12 on the fourth wiring LP<b>4 in the power converter 10 .

- Although the switch 30 is controlled based on the voltage difference between the maximum voltage value Vmax and the capacitor voltage Vcn in the above embodiment, the present invention is not limited to this. The switch 30 may be controlled based on the voltage difference correlation value instead of the voltage difference. For example, instead of the capacitor voltage Vcn, a switch voltage Vsw correlated with the capacitor voltage Vcn may be used, and the switch 30 may be controlled based on the maximum voltage value Vmax and the switch voltage Vsw.

- Although the said embodiment showed the example provided with the one power converter device 100 with respect to the one AC power supply 200, it is not restricted to this. For example, as shown in FIG. 16 , first and second power converters 100A and 100B may be provided in parallel with respect to one AC power supply 200 . In this case, since the input voltage Vin is the same between the power converters 100A and 100B, the first voltage sensor 41 can be omitted in one of the power converters (the second power converter 100B in FIG. 16).

Further, as shown in FIGS. 17 and 18, the first to third power converters 100A to 100C may be provided in parallel with the AC power supply 200 of three-phase AC. In this case, as shown in FIG. 17, the smoothing capacitor 20 and the switch 30 may be shared in each of the power converters 100A to 100C. Thereby, the second and third voltage sensors 42 and 43 can also be shared. Furthermore, as shown in FIG. 18, an electric load 300 may be shared for each of the power converters 100A to 100C. Thereby, the fourth voltage sensor 44 can also be shared. Alternatively, only the electrical load 300 may be shared, and the smoothing capacitor 20 and the switch 30 may be provided separately.

Furthermore, when the AC power supply 200 is a three-phase AC power supply, one power converter 100 may convert the three-phase input voltage Vin into the DC output voltage Vout. For example, in the embodiment shown in FIG. 19, the rectifier circuit 11 is a diode bridge circuit including first to fourth, eighth, and ninth diodes D1 to D4, D8, and D9. 9 is connected to the cathode of diode D9 to form a sixth series connection. The first series connection body, the second series connection body, and the sixth series connection body are connected in parallel.

A first intermediate point PA1 in the first series connection is connected to one voltage DC terminal of the AC power supply 200 via a first wiring LP1. A second intermediate point PA2 in the second series connection is connected to another voltage DC terminal of the AC power supply 200 via a second wiring LP2. A sixth intermediate point PA6 between the eighth diode D8 and the ninth diode D9 in the sixth series connection is connected to the remaining one voltage DC terminal of the AC power supply 200 via a sixth wiring LP6.

In the configuration shown in FIG. 19, as shown in FIG. 20, the fifth to seventh reactors 13E to 13G forming the PFC circuit 12 are provided on the first, second and sixth wirings LP1, LP2 and LP6, respectively. may be

Moreover, as shown in FIG. 21, the rectifier circuit 11 and the PFC circuit 12 may be integrated. Specifically, the power converter 10 includes a tenth diode D10, an eighth reactor 13H, and a fifth PFC switch 14E in addition to the configuration in FIG. 14(A). A seventh series connection is configured by connecting the anode of the tenth diode D10 and the drain of the fifth PFC switch 14E. The third series connection body, the fourth series connection body and the seventh series connection body are connected in parallel. The fifth PFC switch 14E has a parasitic diode 16 connected in parallel.

A third intermediate point PA3 in the third series connection body is connected to one voltage DC terminal of the AC power supply 200 via the first wiring LP1, and the first reactor 13A is provided on the first wiring LP1. there is A fourth intermediate point PA4 in the fourth series connection body is connected to another DC voltage terminal of the AC power supply 200 via a second wiring LP2, and the second reactor 13B is provided on the second wiring LP2. It is A seventh intermediate point PA7 between the tenth diode D10 and the fifth PFC switch 14E in the seventh series connection is connected to the remaining one voltage DC terminal of the AC power supply 200 via a seventh wiring LP7, An eighth reactor 13H is provided on the seventh wiring LP7.

- Although the above-mentioned embodiment showed the example which detects input current Iin in the exchange power supply 200 side rather than the rectifier circuit 11, it is not restricted to this. For example, as shown in FIGS. 19 to 21, the input current Iin may be detected on the electrical load 300 side of the rectifier circuit 11. FIG.

In addition, in the above-described embodiment, the DDC input voltage Vddc and the switch voltage Vsw are detected in order to calculate the capacitor voltage Vcn, but the capacitor voltage Vcn may be directly detected.

DESCRIPTION OF SYMBOLS 10... Power conversion part 20... Smoothing capacitor 30... Switch 40... Control part 41... First voltage sensor 42... Second voltage sensor 43... Third voltage sensor 200... AC power supply D1 to D10... 1st to 10th diodes, TD1...first DC terminal, TD2...second DC terminal.

Claims (5)

It has rectifying elements (D1 to D10), and converts an AC input current (Iin) input from an AC power supply (200) into a DC current by the rectifying element and outputs it from a pair of DC terminals (TD1, TD2). a power converter (10);
a capacitor (20) connected between the pair of DC terminals;
a switch (30) for switching between a power supply state and a power cutoff state from the AC power source to the capacitor;
a first voltage detection unit (41) for detecting an input voltage (Vin) input from the AC power supply;
a second voltage detection unit (42, 43) for detecting a capacitor voltage (Vcn), which is the voltage between the electrodes of the capacitor;
a control unit (40) that controls the switch based on a voltage difference parameter that is either a voltage difference between the detected absolute value (Vab) of the input voltage and the capacitor voltage or a correlation value thereof ,
The control unit outputs a pulse signal (SC) that switches on and off at a predetermined cycle to the switch,
The switch is in the power supply state during an on period (TN, TN1 to TN5) during which the pulse signal is turned on, and is in the power cutoff state during an off period (TF) during which the pulse signal is turned off,
The power conversion device , wherein the control unit sets the ON period occupying the predetermined period to be shorter as the absolute value of the capacitor voltage is larger . The DC terminals include a high voltage side DC terminal (TD1) and a low voltage side DC terminal (TD2),
2. The power converter according to claim 1 , wherein said switch is connected between said capacitor and said low-voltage side DC terminal, and is directly connected to said low-voltage side DC terminal. A voltage adjustment unit (50) including an input side capacitor (51) and connected in parallel with the capacitor,
3. The power converter according to claim 2 , wherein said switch is connected between said voltage regulator and said low-voltage side DC terminal. A voltage adjustment unit (50) connected to the DC terminal,
The DC terminals include a high-voltage side DC terminal (TD1) and a low-voltage side DC terminal (TD2), and the high-voltage side DC terminal is connected to the high-voltage input side of the voltage regulator via a high-voltage side wiring (LP3). and the low-voltage side DC terminal is connected to the low-voltage input side of the voltage regulator via a low-voltage side wiring (LP4),
The capacitor is provided in a connection wiring (LP5) that connects the high voltage side wiring and the low voltage side wiring,
2. The power converter according to claim 1 , wherein said switch is connected between said high-voltage side wiring and said capacitor in said connection wiring. A filter circuit (70) provided between the AC power supply and the power conversion unit and having a filter capacitor (71) for removing noise contained in the input voltage,
2. The power converter according to claim 1 , wherein said switch is connected between said AC power supply and said filter circuit.

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