Patent ID: 12191695

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a charging system10according to the embodiment of the present invention will be described with reference to the accompanying drawings.

FIG.1is a diagram which shows a configuration of the charging system10in the embodiment.

The charging system10according to the present embodiment is mounted in, for example, a vehicle such as an electric vehicle. The charging system10is connected to a power storage device mounted in the vehicle. The electric vehicle is an electric vehicle, a hybrid vehicle, a fuel cell vehicle, or the like. An electric vehicle is driven by a battery as a power source. A hybrid vehicle is driven by a battery and an internal combustion engine as power sources. A fuel cell vehicle is driven by a fuel cell as a power source.

As shown inFIG.1, the power storage device connected to the charging system10is, for example, a high-voltage battery1which is a power source of the vehicle. The battery1includes, for example, a string3formed of a plurality of cells2connected in series, and positive electrode terminals and negative electrode terminals at both ends of the string3. The battery1includes a plurality of battery modules4formed by dividing the string3into a plurality of sub-strings in series. The plurality of battery modules4are, for example, a first battery module4a,a second battery module4b,a third battery module4c,and a fourth battery module4dformed by dividing the string3into four parts. For example, the first battery module4a,the second battery module4b,the third battery module4c,and the fourth battery module4dare sequentially connected in series.

The charging system10includes an AC power source11, a plurality of circuit modules13, and a control device15.

FIG.2is a diagram which shows a configuration of an AC power source11of the charging system10in the embodiment.

As shown inFIG.2, the AC power source11includes a DC power supply21, a first power conversion unit22, and a second power conversion unit23.

The DC power supply21is, for example, a solar cell or the like.

The first power conversion unit22includes, for example, a DC-DC converter that performs two types of power conversion of step-up and step-down. The first power conversion unit22includes a first positive electrode terminal P1, a first negative electrode terminal N1, a second positive electrode terminal P2, and a second negative electrode terminal N2.

The first positive electrode terminal P1and the first negative electrode terminal N1of the first power conversion unit22are connected to a positive electrode terminal DP and a negative electrode terminal DN of the DC power supply21. The second positive electrode terminal P2and the second negative electrode terminal N2of the first power conversion unit22are connected to a positive electrode terminal PT and a negative electrode terminal NT of the second power conversion unit23.

The first power conversion unit22includes, for example, a switching element of a low-side arm and a high-side arm paired using two phases, and a reactor. The switching element is a transistor such as a metal oxide semiconductor field effect transistor (MOSFET) or an insulated gate bipolar transistor (IGBT), and is, for example, an N channel type MOSFET. The reactor is a choke coil L.

Each transistor may include a rectifying element. The rectifying element is a diode connected in parallel to each transistor. The rectifying element is, for example, a freewheel diode that is connected between a drain and a source of the MOSFET from the source to the drain in a forward direction.

The first power conversion unit22includes high-side arm and low-side arm first-phase transistors S1H and S1L paired using a first phase, and high-side arm and low-side arm second-phase transistors S2H and S2L paired using a second phase.

A drain of the high-side arm first phase transistor S1H is connected to the first positive electrode terminal P1. A drain of the high-side arm second phase transistor S2H is connected to the second positive electrode terminal P2. A source of the low-side arm first phase transistor S1L is connected to the first negative electrode terminal N1. A source of the low-side arm second phase transistor S2L is connected to the second negative electrode terminal N2. A source of the high-side arm first phase transistor S1H and a drain of the low-side arm first phase transistor S1L are connected to first ends at both ends of the choke coil L. A source of the high-side arm second phase transistor S2H and a drain of the low-side arm second phase transistor S2L are connected to second ends at both ends of the choke coil L.

The first power conversion unit22includes a first smoothing capacitor SC1connected between the first positive electrode terminal P1and the first negative electrode terminal N1and a second smoothing capacitor SC2connected between the second positive electrode terminal P2and the second negative electrode terminal N2. The first smoothing capacitor SC1and the second smoothing capacitor SC2smooth voltage fluctuations generated by an on or off switching operation of each of the transistors S1H, S1L, S2H, and S2L.

The first power conversion unit22switches between on (conduction) and off (cut off) of each of the transistors S1H, S1L, S2H, and S2L based on a gate signal which is a switching command input to a gate of each of the transistors S1H, S1L, S2H, and S2L.

The first power conversion unit22steps up power input from a DC power supply21to the first positive electrode terminal P1and the first negative electrode terminal N1at the time of stepping up a voltage, and outputs the stepped-up power from the second positive electrode terminal P2and the second negative electrode terminal N2. The first power conversion unit22maintains an on state (conduction) of the high-side arm first phase transistor S1H and an off state (cut off) of the low-side arm first phase transistor S1L at the time of stepping up a voltage.

The first power conversion unit22accumulates magnetic energy by direct current excitation of the reactor (choke coil L) when the high-side arm second phase transistor S2H is turned off (cut off) and the low-side arm second phase transistor S2L is turned on (conduction). The first power conversion unit22causes a voltage higher than those of the first positive electrode terminal P1and the first negative electrode terminal N1to be generated in the second positive electrode terminal P2and the second negative electrode terminal N2by superimposing an induced voltage generated by the magnetic energy of the reactor (choke coil L) when the high-side arm second phase transistor S2H is turned on (conduction) and the low-side arm second phase transistor S2L is turned off (cut off) and the voltage applied to the first positive electrode terminal P1and the first negative electrode terminal N1.

The first power conversion unit22steps down a voltage of the power input from the first positive electrode terminal P1and the first negative electrode terminal N1at the time of stepping down a voltage, and outputs the power whose voltage is stepped down from the second positive electrode terminal P2and the second negative electrode terminal N2. The first power conversion unit22maintains an on state (conduction) of the high-side arm second phase transistor S2H and an off state (cut off) of the low-side arm second phase transistor S2L at the time of stepping down a voltage.

The first power conversion unit22accumulates magnetic energy by direct current excitation of the reactor (choke coil L) when the high-side arm first phase transistor S1H is turned on (conduction) and the low-side arm first phase transistor S1L is turned off (cut off). The first power conversion unit22causes a voltage lower than that of the first positive electrode terminal P1and the first negative electrode terminal N1to be generated in the second positive electrode terminal P2and the second negative electrode terminal N2by stepping down an induced voltage generated by the magnetic energy of the reactor (choke coil L) when the high-side arm first phase transistor S1H is turned off (cut off) and the low-side arm first phase transistor S1L is turned on (conduction).

The second power conversion unit23includes, for example, an inverter that converts DC power input from the first power conversion unit22into AC power and outputs it to an AC electric circuit12.

The second power conversion unit23includes, for example, a bridge circuit formed of a plurality of switching elements that are bridge-connected by two phases, an A phase and a B phase. The switching element is a transistor such as a MOSFET or an IGBT, and is, for example, an N channel-type MOSFET. Each transistor may include a rectifying element. The rectifying element is a diode connected in parallel to each transistor. The rectifying element is, for example, a freewheel diode that is connected between the drain and the source of the MOSFET in a forward direction from a source to a drain.

The second power conversion unit23includes high-side arm and low-side arm A-phase transistors SaH and SaL that form a pair using the A phase, and high-side arm and low-side arm B-phase transistors SbH and SbL that form a pair using the B phase.

Each drain of the high-side arm A-phase transistor SaH and the high-side arm B-phase transistor SbH is connected to the positive electrode terminal PT. Each source of the low-side arm A-phase transistor SaL and the low-side arm B-phase transistor SbL is connected to the negative electrode terminal NT. The source of the high-side arm A-phase transistor SaH and the drain of the low-side arm A-phase transistor SaL are connected to an A-phase terminal AT. The source of the high-side arm B-phase transistor SbH and the drain of the low-side arm B-phase transistor SbL are connected to a B-phase terminal BT.

The second power conversion unit23switches between on (conduction) and off (cut off) of a transistor pair of each phase based on a gate signal which is a switching command input to a gate of each transistor SaH, SaL, SbH, or SbL. The second power conversion unit23converts DC power input from the positive electrode terminal PT and the negative electrode terminal NT into single-phase AC power and outputs it from the A-phase terminal AT and the B-phase terminal BT. The A-phase terminal AT of the second power conversion unit23is connected to an A-phase terminal11A of the AC power source11, and the B-phase terminal BT of the second power conversion unit23is connected to a B-phase terminal11B of the AC power source11.

The AC power source11supplies the same current (power) to each battery module4of the battery1, for example, when an alternating current having a frequency close to a resonance frequency of an AC electric circuit31(a resonance electric circuit) to be described below is generated.

As shown inFIG.1, the plurality of circuit modules13are connected between the AC power source11and each of the plurality of battery modules4. The number of the plurality of circuit modules13is the same as the number of the plurality of battery modules4. The plurality of circuit modules13are, for example, a first circuit module13a,a second circuit module13b,a third circuit module13c,and a fourth circuit module13d.

For example, the first battery module4aand the first circuit module13aare integrally connected, the second battery module4band the second circuit module13bare integrally connected, the third battery module4cand the third circuit module13care integrally connected, and the fourth battery module4dand the fourth circuit module13dare integrally connected. Each battery module4and each circuit module13are connected by, for example, a bus bar (not shown) having an insulating coating. The plurality of circuit modules13are sequentially connected from the AC power source11by wiring (not shown). For example, the second circuit module13band the first circuit module13aare sequentially connected from the AC power source11, and the third circuit module13cand the fourth circuit module13dare sequentially connected from the AC power source11.

As shown inFIG.1, each of the plurality of circuit modules13includes an AC electric circuit31, a rectifier circuit33, and a positive electrode side current cutoff circuit35. For example, the first circuit module13aincludes a first AC electric circuit31a,a first rectifier circuit33a,and a first positive electrode side current cutoff circuit35a.The second circuit module13bincludes a second AC electric circuit31b,a second rectifier circuit33b,and a second positive electrode side current cutoff circuit35b.The third circuit module13cincludes a third AC electric circuit31c,a third rectifier circuit33c,and a third positive electrode side current cutoff circuit35c.The fourth circuit module13dincludes a fourth AC electric circuit31d,a fourth rectifier circuit33d,and a fourth positive electrode side current cutoff circuit35d.

Each AC electric circuit31includes an A-phase electric circuit41directly or indirectly connected to the A-phase terminal11A of the AC power source11and a B-phase electric circuit43directly or indirectly connected to the B-phase terminal11B of the AC power source11. Each of the A-phase electric circuit41and the B-phase electric circuit43includes an LC row45of a first capacitor C1and a first reactor L1connected in series on an input side of AC power, and a second reactor L2.

The second reactor L2is connected between a first connection point47provided from the input side of AC power via the LC row45in the AC electric circuit31and a second connection point49on the rectifier circuit33side. The second connection point49is connected to the second reactor L2, the rectifier circuit33, and the positive electrode side current cutoff circuit35.

A combination of a combined capacitance of capacitors and a combined inductance of inductors of the AC electric circuit31in each of the plurality of circuit modules13(for example, a product of the combined capacitance and the combined inductance) may be an appropriate combination. For example, when the product (LC product) of the combined capacitance and the combined inductance of resonance electric circuits of each stage corresponding to each battery module4of the battery1is the same, a current gain for each battery module4is the same, and the same current (power) is uniformly supplied to each battery module4.

For example, when a first LC product for the first battery module4a,a second LC product for the second battery module4b,a third LC product for the third battery module4c,and a fourth LC product for the fourth battery module4dare all the same, the same current (power) is uniformly supplied to each of the battery modules4a,4b,4c,and4d.For example, each LC product is a product of the combined capacitance and the combined inductance of capacitors and reactors other than the second reactor L2in each electric circuit from the AC power source11to each rectifier circuit33.

The first LC product is a product of the combined capacitance and the combined inductance of a first capacitor C1and a first reactor L1of the first circuit module13aindirectly connected to the AC power source11via the second circuit module13b,and a first capacitor C1and a first reactor L1of the second circuit module13b.

The second LC product is a product of the combined capacitance and the combined inductance of the first capacitor C1and the first reactor L1of the second circuit module13bdirectly connected to the AC power source11.

The third LC product is a product of the combined capacitance and the combined inductance of a first capacitor C1and a first reactor L1of the third circuit module13cdirectly connected to the AC power source11.

The fourth LC product is a product of the combined capacitance and the combined inductance of a first capacitor C1and a first reactor L1of a fourth circuit module13dindirectly connected to the AC power source11via the third circuit module13c,and the first capacitor C1and the first reactor L1of the third circuit module13c.

Each rectifier circuit33of the plurality of circuit modules13is connected between the AC electric circuit31and a corresponding battery module4in the battery1. In each of the plurality of circuit modules13, a second connection point49of the A-phase electric circuit41of the AC electric circuit31is connected to an A-phase terminal AS of the rectifier circuit33. A second connection point49of the B-phase electric circuit43of the AC electric circuit31is connected to a B-phase terminal BS of the rectifier circuit33.

FIG.3is a diagram which shows a configuration of the rectifier circuit33of the charging system10in the embodiment.

As shown inFIG.3, the rectifier circuit33includes, for example, a bridge circuit formed of a plurality of diodes that are bridge-connected in two rows of a first row and a second row.

The rectifier circuit33is, for example, a full-wave rectifier circuit. The rectifier circuit33includes a first diode51aand a second diode51bconnected in the forward direction in the first row, and a third diode51cand a fourth diode51dconnected in the forward direction in the second row.

A connection point33A of an anode of the first diode51aand a cathode of the second diode51bis connected to the A-phase terminal AS. A connection point33B of an anode of the third diode51cand a cathode of the fourth diode51dis connected to the B-phase terminal BS.

Each cathode of the first diode51aand the third diode51cis connected to a positive electrode terminal PR. Each anode of the second diode51band the fourth diode51dis connected to the negative electrode terminal NR. The positive electrode terminal PR and the negative electrode terminal NR of the rectifier circuit42are connected to a positive electrode end and a negative electrode end of a corresponding battery module4in the battery1.

The rectifier circuit33full-wave rectifies AC power input from the A-phase terminal AS and the B-phase terminal BS, and outputs the rectified DC power from the positive electrode terminal PR and negative electrode terminal NR.

FIG.4is a diagram which shows a configuration of the positive electrode side current cutoff circuit35of the charging system10in the embodiment.

As shown inFIG.4, each positive electrode side current cutoff circuit35of the plurality of circuit modules13is connected between the rectifier circuit33and the positive electrode end of a corresponding battery module4in the battery1. The positive electrode side current cutoff circuit35includes a positive electrode side switch unit61and a positive electrode side switch drive unit63.

The positive electrode side switch unit61is connected between a positive electrode terminal PR of the rectifier circuit33and the positive electrode end of a corresponding battery module4in the battery1. The positive electrode side switch unit61is, for example, a bidirectional switch formed of two switching elements. The switching element is a transistor such as a MOSFET or an IGBT, and is, for example, an N channel type MOSFET. Each transistor may have a rectifying element. The rectifying element is a diode connected in parallel to each transistor. The rectifying element is, for example, a freewheel diode that is connected between the drain and source of the MOSFET in the forward direction from a source to a drain.

The positive electrode side switch unit61includes a positive electrode side first transistor61aand a positive electrode side second transistor61bconnected in anti-series.

Gates G of the positive electrode side first transistor61aand the positive electrode side second transistor61bare connected to the positive electrode end of the positive electrode side switch drive unit63(for example, the connection point65P of a positive electrode side rectifier circuit65to be described below). Sources of the positive electrode side first transistor61aand the positive electrode side second transistor61bare connected to the negative electrode end of the positive electrode side switch drive unit63(for example, a connection point65N of the positive electrode side rectifier circuit65to be described below). A drain of the positive electrode side first transistor61ais connected to the positive electrode end of a corresponding battery module4in the battery1. A drain of the positive electrode side second transistor61bis connected to the positive electrode terminal PR of the rectifier circuit33.

The positive electrode side switch unit61switches between on (conduction) and off (cut off) of the positive electrode side first transistor61aand the positive electrode side second transistor61bbased on a gate signal, which is a switching command based on a voltage applied from the positive electrode side switch drive unit63between the gate and the source of each of the positive electrode side first transistor61aand the positive electrode side second transistor61b.The positive electrode side switch unit61switches between conduction and cutoff of a current between each battery module4and the rectifier circuit33according to on (conduction) or off (cut off) of the positive electrode side first transistor61aand the positive electrode side second transistor61b.

The positive electrode side switch drive unit63includes two positive electrode side capacitors CPs for DC insulation, a positive electrode side rectifier circuit65, and a positive electrode side resistor RP for discharge.

The two positive electrode side capacitors CPs are connected to the second connection point49of each of the A-phase electric circuit41and the B-phase electric circuit43of the AC electric circuit31.

The positive electrode side rectifier circuit65includes, for example, a bridge circuit formed of a plurality of diodes that are bridge-connected in two rows of the first row and the second row.

The positive electrode side rectifier circuit65is, for example, a full-wave rectifier circuit. The positive electrode side rectifier circuit65includes a positive electrode side first diode65aand a positive electrode side second diode65bconnected in the forward direction in the first row, and a positive electrode side third diode65cand a positive electrode side fourth diode65dconnected in the forward direction in the second row.

A connection point (an A-phase connection point)65A between an anode of the positive electrode side first diode65aand a cathode of the positive electrode side second diode65bis connected to a second connection point49of the A-phase electric circuit41via the positive electrode side capacitor CP. A connection point (a B-phase connection point)65B between an anode of the positive electrode side third diode65cand a cathode of the positive electrode side fourth diode65dis connected to a second connection point49of the B-phase electric circuit43via the positive electrode side capacitor CP.

A connection point65P between cathodes of the positive electrode side first diode65aand the positive electrode side third diode65cis connected to gates G of the transistors61aand61bof the positive electrode side switch unit61. A connection point65N between anodes of the positive electrode side second diode65band the positive electrode side fourth diode65dis connected to sources of the transistors61aand61bof the positive electrode side switch unit61.

The positive electrode side rectifier circuit65full-wave rectifies AC power input from the A-phase electric circuit41and the B-phase electric circuit43to the A-phase connection point65A and the B phase connection point65B, and outputs the rectified DC power from the connection point65P and the connection point65N.

The positive electrode side resistor RP is connected between the connection point65P and the connection point65N of the positive electrode side rectifier circuit65.

The positive electrode side switch drive unit63automatically switches between conduction and cutoff of a current of the positive electrode side switch unit61according to AC power input from the A-phase electric circuit41and the B-phase electric circuit43to the rectifier circuit33.

First, in the positive electrode side switch drive unit63, when the AC power is not applied to the AC electric circuit31, the positive electrode side resistor RP for discharge discharges charges between the gates and the sources of the transistors61aand61bof the positive electrode side switch unit61, and thereby each of the transistors61aand61bis put into a cut-off state, and a leakage current of the battery module4via the rectifier circuit33becomes extremely small.

When the AC power source11is activated and AC power is applied from the AC electric circuit31to the positive electrode side switch drive unit63, only an AC component is input to the positive electrode side rectifier circuit65via the positive electrode side capacitor CP. When capacitance between the gates and the sources of the transistors61aand61bof the positive electrode side switch unit61is charged with the DC power rectified by the positive electrode side rectifier circuit65, and a gate-source potential becomes sufficiently high, each of the transistors61aand61bis conduced, and the DC power generated by the rectifier circuit33is used to charge the battery module4.

When the AC power source11is stopped and AC power of the AC electric circuit31is cut off, the transistors61aand61bof the positive electrode side switch unit61are put into the cut-off state again, and a leakage current of the battery module4through the rectifier circuit33becomes extremely small.

FIG.5is a diagram which shows an example of changes in each of a charging current, a source-gate potential, and an AC voltage amplitude in the charging system10of the embodiment.

As shown inFIG.5, as an amplitude of an AC voltage increases, for example, after a time t1, a potential between the source and the gate of each of the transistors61aand61bof the positive electrode side switch unit61changes in an increasing tendency.

Then, as shown after a time t2, after the amplitude of the AC voltage reaches a predetermined amplitude Vb and the potential between the source and the gate of each of the transistors61aand61breaches a predetermined potential Va, each of the transistors61aand61bof the positive electrode side switch unit61is turned into a conduction state, and a predetermined charging current Ia flows through the battery module4.

Then, as shown after a time t3, the amplitude of the AC voltage decreases from the predetermined amplitude Vb, such that the charging current of the battery module4decreases from the predetermined charging current Ia. Along with this, as shown after a time t4, the potential between the source and the gate of each of the transistors61aand61bdrops from the predetermined potential Va.

Then, as shown at a time t5, the amplitude of the AC voltage and the charging current of the battery module4reach zero, the potential between the source and the gate of each of the transistors61aand61bfalls, and each of the transistors61aand61bof the positive electrode side switch unit61is put into the cut-off state.

As described above, by applying the AC power, each of the transistors61aand61bis automatically conduced, and each of the transistors61aand61bis automatically put into the cut-off state by stopping the AC power.

As shown inFIG.1, the control device15controls an operation of the charging system10. For example, the control device15is a software functional unit that functions by a processor such as a central processing unit (CPU) executing a predetermined program. The software functional unit is an electronic control unit (ECU) that includes a processor such as a CPU, a read only memory (ROM) for storing a program, a random access memory (RAM) for temporarily storing data, and an electronic circuit such as a timer. At least a part of the control device15may also be an integrated circuit such as a large scale integration (LSI).

For example, the control device15sets a timing to drive each switching element of the AC power source11to be turned on (conduction) or off (cut oft), and generates a gate signal for actually driving each switching element to be turned on (conduction) or off (cut off).

As described above, the charging system10of the embodiment includes the positive electrode side current cutoff circuit35that automatically switches between the conduction and the cut off of a current between the battery module4and the rectifier circuit33according to the AC power input to the rectifier circuit33, and thereby it is possible to suppress an increase in leakage current of the battery module4via the rectifier circuit33while suppressing an increase in cost required for the configuration.

The positive electrode side current cutoff circuit35includes the positive electrode side switch drive unit63that automatically switches between on (conduction) and off (cut off) of each of the transistors61aand61bof the positive electrode side switch unit61, and thereby, for example, it is possible to suppress an increase in cost required for the configuration as compared with a case of adding a photo coupler, an isolated DC-DC converter, or the like.

The positive electrode side switch drive unit63can automatically switch between the conduction and the cut off of the current of the positive electrode side switch unit61according to the presence or absence of application of AC power. When the AC power is not applied, each of the transistors61aand61bis cut off by discharge of the positive electrode side resistor RP, and, when the AC power is applied, the gate-source potential of each of the transistors61aand61bincreases and each of the transistors61aand61bis conduced.

MODIFIED EXAMPLE

In the following description, modified examples of the embodiment will be described. The same parts as those in the embodiment described above will be denoted by the same reference numerals, and the description thereof will be omitted or simplified.

FIRST MODIFIED EXAMPLE

In the embodiment described above, each of the plurality of circuit modules13includes a positive electrode side current cutoff circuit35between the rectifier circuit33and the positive electrode end of the battery module4, but the present invention is not limited to this.

FIG.6is a diagram which shows a configuration of a charging system10A in a first modified example of the embodiment.FIG.7is a diagram which shows a configuration of a negative electrode side current cutoff circuit37of the charging system10A in the first modified example of the embodiment.

As shown inFIG.6, the charging system10A in the first modified example includes an AC power source11, a plurality of circuit modules13A, and a control device15. The plurality of circuit modules13A are connected between the AC power source11and each of the plurality of battery modules4. The number of the plurality of circuit modules13A is the same as the number of the plurality of battery modules4. The plurality of circuit modules13A are, for example, a first circuit module13Aa, a second circuit module13Ab, a third circuit module13Ac, and a fourth circuit module13Ad.

Each of the plurality of circuit modules13A includes an AC electric circuit31, a rectifier circuit33, and a negative electrode side current cutoff circuit37. For example, the first circuit module13Aa includes a first AC electric circuit31a,a first rectifier circuit33a,and a first negative electrode side current cutoff circuit37a.The second circuit module13Ab includes a second AC electric circuit31b,a second rectifier circuit33b,and a second negative electrode side current cutoff circuit37b.The third circuit module13Ac includes a third AC electric circuit31c,a third rectifier circuit33c,and a third negative electrode side current cutoff circuit37c.The fourth circuit module13Ad includes a fourth AC electric circuit31d,a fourth rectifier circuit33d,and a fourth negative electrode side current cutoff circuit37d.

As shown inFIG.7, each negative electrode side current cutoff circuit37of the plurality of circuit modules13A is connected between the rectifier circuit33and the negative electrode end of a corresponding battery module4in the battery1. The negative electrode side current cutoff circuit37includes a negative electrode side switch unit71and a negative electrode side switch drive unit73.

The negative electrode side switch unit71is connected between the negative electrode terminal NR of the rectifier circuit33and the negative electrode end of a corresponding battery module4in the battery1. The negative electrode side switch unit71is, for example, a bidirectional switch formed of two switching elements. The switching element is a transistor such as a MOSFET or an IGBT, and is, for example, an N channel-type MOSFET. Each transistor may include a rectifying element. The rectifying element is a diode connected in parallel to each transistor. The rectifying element is, for example, a freewheel diode that is connected between the drain and the source of the MOSFET in the forward direction from a source to a drain.

The negative electrode side switch unit71includes a negative electrode side first transistor71aand a negative electrode side second transistor71bconnected in anti-series.

The gates G of the negative electrode side first transistor71aand the negative electrode side second transistor71bare connected to a positive electrode end of the negative electrode side switch drive unit73(for example, a connection point75P of a negative electrode side rectifier circuit75to be described below). The sources of the negative electrode side first transistor71aand the negative electrode side second transistor71bare connected to a negative electrode end of the negative electrode side switch drive unit73(for example, a connection point75N of the negative electrode side rectifier circuit75to be described below). A drain of the negative electrode side first transistor71ais connected to the negative electrode terminal NR of the rectifier circuit33. A drain of the negative electrode side second transistor71bis connected to the negative electrode end of a corresponding battery module4in the battery1.

The negative electrode side switch unit71switches between on (conduction) and off (cut off) of the negative electrode side first transistor71aand negative electrode side second transistor71bbased on a gate signal, which is a switching command based on a voltage applied from the negative electrode side switch drive unit73between each gate and each source of the negative electrode side first transistor71aand the negative electrode side second transistor71b.The negative electrode side switch unit71switches between the conduction and the cut-off of a current between each battery module4and the rectifier circuit33according to on (conduction) or off (cut off) of the negative electrode side first transistor71aand the negative electrode side second transistor71b.

The negative electrode side switch drive unit73includes two negative electrode side capacitors CNs for DC insulation, a negative electrode side rectifier circuit75, and a negative electrode side resistance RN for discharge.

The two negative electrode side capacitors CNs are connected to the second connection point49of each of the A-phase electric circuit41and the B-phase electric circuit43of the AC electric circuit31.

The negative electrode side rectifier circuit75includes, for example, a bridge circuit formed of a plurality of diodes that are bridge-connected in two rows of the first row and the second row.

The negative electrode side rectifier circuit75is, for example, a full-wave rectifier circuit. The negative electrode side rectifier circuit75includes a negative electrode side first diode75aand a negative electrode side second diode75bconnected in the forward direction in the first row, and a negative electrode side third diode75cand a negative electrode side fourth diode75dconnected in the forward direction in the second row.

A connection point (an A-phase connection point)75A between an anode of the negative electrode side first diode75aand a cathode of the negative electrode side second diode75bis connected to the second connection point49of the A-phase electric circuit41via the negative electrode side capacitor CN. A connection point (a B-phase connection point)75B between an anode of the negative electrode side third diode75cand a cathode of the negative electrode side fourth diode75dis connected to the second connection point49of the B-phase electric circuit43via the negative electrode side capacitor CN.

A connection point75P between cathodes of the negative electrode side first diode75aand the negative electrode side third diode75cis connected to the gate G of each of the transistors71aand71bof the negative electrode side switch unit71. A connection point75N between anodes of each of the negative electrode side second diode75band the negative electrode side fourth diode75dis connected to the source of each of the transistors71aand71bof the negative electrode side switch unit71.

The negative electrode side rectifier circuit75full-wave rectifies AC power input from the A-phase electric circuit41and the B-phase electric circuit43to the A-phase connection point75A and the B-phase connection point75B, and outputs the rectified DC power from the connection point75P and the connection point75N.

The negative electrode side resistance RN is connected between the connection point75P and the connection point75N of the negative electrode side rectifier circuit75.

The negative electrode side switch drive unit73automatically switches between the conduction and cut-off of a current of the negative electrode side switch unit71according to AC power input from the A-phase electric circuit41and the B-phase electric circuit43to the rectifier circuit33.

SECOND MODIFIED EXAMPLE

In the embodiment or the first modified example described above, each of the plurality of circuit modules13includes a positive electrode side current cutoff circuit35or a negative electrode side current cutoff circuit37between the rectifier circuit33and the positive electrode end or the negative electrode end of the battery module4, but the present invention is not limited to this.

FIG.8is a diagram which shows a configuration of a charging system10B in a second modified example of the embodiment.FIG.9is a diagram which shows a configurations of the positive electrode side current cutoff circuit35and the negative electrode side current cutoff circuit37of the charging system10B in the second modified example of the embodiment.

As shown inFIGS.8and9, the charging system10B in the second modified example includes an AC power source11, a plurality of circuit modules13B, and a control device15. The plurality of circuit modules13B are connected between the AC power source11and each of the plurality of battery modules4. The number of the plurality of circuit modules13B is the same as the number of the plurality of battery modules4. The plurality of circuit modules13B are, for example, a first circuit module13Ba, a second circuit module13Bb, a third circuit module13Bc, and a fourth circuit module13Bd. Each of the plurality of circuit modules13B includes an AC electric circuit31, a rectifier circuit33, a positive electrode side current cutoff circuit35, and a negative electrode side current cutoff circuit37. For example, the first circuit module13Ba includes a first AC electric circuit31a,a first rectifier circuit33a,a first positive electrode side current cutoff circuit35a,and a first negative electrode side current cutoff circuit37a.The second circuit module13Bb includes a second AC electric circuit31b,a second rectifier circuit33b,a second positive electrode side current cutoff circuit35b,and a second negative electrode side current cutoff circuit37b.The third circuit module13Bc includes a third AC electric circuit31c,a third rectifier circuit33c,a third positive electrode side current cutoff circuit35c,and a third negative electrode side current cutoff circuit37c.The fourth circuit module13Bd includes a fourth AC electric circuit31d,a fourth rectifier circuit33d,a fourth positive electrode side current cutoff circuit35d,and a fourth negative electrode side current cutoff circuit37d.

THIRD MODIFIED EXAMPLE

In the embodiment described above, each positive electrode side current cutoff circuit35of the plurality of circuit modules13includes a bridge circuit formed of a plurality of diodes, but the present invention is not limited to this, and may include other rectifier circuits.

FIG.10is a diagram which shows a configuration of a positive electrode side current cutoff circuit35A of a charging system10C in a third modified example of the embodiment.

As shown inFIG.10, the positive electrode side current cutoff circuit35A of the charging system10C in the third modified example includes a positive electrode side switch unit61and a positive electrode side switch drive unit63A. The positive electrode side switch drive unit63A includes two negative electrode side capacitors CNs for DC insulation, a positive electrode side rectifier circuit81, and a positive electrode side resistor RP for discharge.

The positive electrode side rectifier circuit81includes, for example, a first diode81a,a second diode81b,and a third diode81c.

A cathode of the first diode81ais connected to the positive electrode side capacitor CP on an A-phase side, and an anode of the first diode81ais connected to the positive electrode side capacitor CP on a B-phase side.

A cathode of the second diode81bis connected to the gate G of each of the transistors61aand61bof the positive electrode side switch unit61, and an anode of the second diode81bis connected to the cathode of the first diode81a.

A cathode of the third diode81cis connected to the anode of the first diode81a,and an anode of the third diode81cis connected to the source of each of the transistors61aand61bof the positive electrode side switch unit61.

In the embodiment described above, it is described that the first power conversion unit22performs two types of power conversion of step-up and step-down, but the present invention is not limited to this, and may include a step-up circuit or a step-down circuit.

In the embodiment described above, the charging system10is mounted in a vehicle, but the present invention is not limited to this, and the charging system10may be mounted in other devices.

In the embodiment described above, the charging system10is connected to a power storage device, but the present invention is not limited to this, and the charging system10may be connected to another load to supply power.

The embodiment of the present invention is presented as an example, and is not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made within a range not departing from the gist of the invention. These embodiments and modified examples thereof are included in the scope and gist of the invention, as well as in the invention described in the scope of the claims and the equivalent scope thereof.