charger

Abstract

To control a battery charger in high efficiency.SOLUTION: A battery charger comprises: a rectifier having input terminals connected to an AC power supply, a cathode terminal and an anode terminal; a DC / DC converter having a first terminal connected to the cathode terminal of the rectifier, a second terminal connected to the anode terminal of the rectifier and an output terminal connected to a battery; a power ripple absorber circuit having a first diode, a second diode, a third diode, an inductor, a capacitor, a first switch and a second switch; and a control part controlling a switch of the DC / DC converter, the first switch and the second switch. The control part changes switching frequencies of the switch of DC / DC converter and the first switch during one period of AC voltage input from the AC power supply.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a charger. [Background technology]

[0002] Various isolated single-phase AC / DC converters are being considered for use as chargers for electric vehicles. A typical circuit configuration for electric vehicle chargers is one that consists of a diode rectifier with a power factor correction (PFC) circuit, a large-capacity capacitor in the DC link, and a high-frequency isolated DC / DC converter. The large-capacity capacitor in the DC link must have enough capacity to absorb the power pulsation of the single-phase AC power supply, making it difficult to miniaturize such a circuit configuration.

[0003] As a compact charger capable of absorbing power pulsation, Non-Patent Document 1 discloses a charging circuit in which an active buffer for absorbing power pulsation is added to a Dual-Active-Bridge (DAB) converter, and its control. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Shohei Yoneda, Yoshiya Onuma, "Study on Dual Active Bridge AC-DC Converter with Active Buffer", Semiconductor Power Conversion Study Group Materials, 2021, SPC-21-003, pp. 13-18 Summary of the Invention [Problem to be solved by the invention]

[0005] In the control disclosed in Non-Patent Document 1, there is a period (zero current period) when all switches of the DAB converter are off. This results in a large number of switching operations and large switching losses. Furthermore, during this zero current period, all switches are off, so the current flowing through the inductor L of the DAB converter should be zero. However, in reality, there is a lag in the timing at which the switches are turned off. This lag causes current to remain, resulting in resonance between the inductor L of the DC / DC converter 120 and the parasitic capacitance of the switches S21 to S28. As a result, the switching after the zero current period becomes hard switching, resulting in switching losses.

[0006] Therefore, an object of the present invention is to control a charger with high efficiency. [Means for solving the problem]

[0007] In order to solve the above problems, a charger of the present invention includes a rectifier having two input terminals for connection to an AC power supply, a cathode terminal, and an anode terminal, a DC / DC converter having a first terminal connected to the cathode terminal of the rectifier via a first line, a second terminal connected to the anode terminal of the rectifier via a second line, and two output terminals for connection to a battery, a power pulsation absorbing circuit having a first diode, a second diode, a third diode, an inductor, a capacitor, a first switch, and a second switch, and a control unit that controls switching of the switches of the DC / DC converter, the first switch, and the second switch, wherein the first diode is connected to the inductor of the power pulsation absorbing circuit and the anode terminal of the rectifier. the second diode is connected between the inductor and one of the two input terminals of the rectifier, the capacitor and the first switch are connected in series between the first line and the second line, the capacitor is disposed on the second line side, the third diode is connected between a line connecting the capacitor and the first switch and an inductor of the power pulsation absorption circuit, the second switch is connected between a line connecting the inductor of the power pulsation absorption circuit and the third diode and the second line, and a control unit changes the switching frequencies of the switch of the DC / DC converter and the first switch during one period of the AC voltage input from the AC power supply. [Effects of the Invention]

[0008] According to the present invention, it is possible to control the charger with high efficiency. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram showing a charger 100 according to an embodiment of the present invention. [Figure 2] 10 is a diagram showing the relationship between the instantaneous power pS output from the AC power supply and the instantaneous power pC output from the buffer capacitor Cbuf. [Figure 3]3A and 3B are diagrams illustrating the states of each switch in each mode. [Figure 4] 10 is a diagram showing an operating waveform iL of an inductor L of a DC / DC converter 120 according to the present embodiment and its equivalent square wave iL'. FIG. [Figure 5] FIG. 10 is a diagram showing the duty ratio in each period when the switching frequency fSW is kept constant. [Figure 6] 4 is a diagram showing an example of values ​​of various parameters of the charger 100. FIG. [Figure 7] 2 is a diagram illustrating changes over time in current iL and voltage VL of inductor L of DC / DC converter 120. FIG. [Figure 8] FIG. 10 is a diagram showing the duty ratio of each period when the switching frequency fSW is changed so that the zero current period T0 becomes zero. [Figure 9] 10 is a diagram showing the operating waveform of the inductor L of the DC / DC converter 120 when the phase of the AC power supply is zero. FIG. [Figure 10] FIG. 10 is a diagram showing a switching frequency fSW when the value of the current command value IL′ is not optimized. [Figure 11] FIG. 10 is a diagram showing the switching frequency fSW when the value of the current command value IL′ is changed so that the minimum value of the switching frequency fSW is constant. DETAILED DESCRIPTION OF THE INVENTION

[0010] <Charger 100> FIG. 1 is a diagram showing a charger 100 according to an embodiment of the present invention. The charger 100 includes a rectifier 110, a DC / DC converter 120, a power pulsation absorbing circuit 130, and a control unit 140. The charger 100 converts a single-phase AC voltage v input from a single-phase AC power source 200 into a voltage v . S DC voltage V dc and outputs it to the battery 300.

[0011] The rectifier 110 has a cathode terminal 111 and an anode terminal 112 connected to the DC / DC converter 120, and two input terminals 113 for connection to the AC power supply 200. The rectifier 110 is, for example, a bridge diode rectifier made up of four diodes as shown in Fig. 1, and converts AC current input between the two input terminals 111 connected to the AC power supply into DC current and outputs it from the cathode terminal 111. As shown in Fig. 1, the rectifier 110 may be connected to the AC power supply 200 via a filter F having an inductor Lac and a capacitor Cac.

[0012] The DC / DC converter 120 is, for example, a DAB (Dual Active Bridge) converter. The DC / DC converter 120 has a first terminal 121 connected to the cathode terminal 111 of the rectifier 110, a second terminal 122 connected to the anode terminal 112 of the rectifier 110, a third terminal 123 for connection to the positive electrode of the battery 300, and a fourth terminal 124 for connection to the negative electrode of the battery 300. The DC / DC converter 120 has a transformer Tr and four switches, a first switch S21, a second switch S22, a third switch S23, and a fourth switch S24, on the input end side (primary side) across the transformer Tr, and four switches, a fifth switch S25, a sixth switch S26, a seventh switch S27, and an eighth switch S28, on the output end side (secondary side). Each of the eight switches S21 to S28 is, for example, an N-channel power MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) equipped with a reverse polarity diode (body diode). In this case, the N-channel power MOSFET may have a snubber capacitor as shown in FIG.

[0013] The DC / DC converter 120 has an inductor L on the primary side of a transformer Tr. This inductor L is, for example, a leakage inductor of the transformer Tr.

[0014] In addition, a DC capacitor Cdc is connected between the third terminal 123 and the fourth terminal 124 of the DC / DC converter 120. An inductor Ldc may be connected between the third terminal 123 of the DC / DC converter 120 and the positive electrode of the battery 300.

[0015] The power pulsation absorbing circuit 130 includes a first diode D31, a second diode D32, a third diode D33, an inductor Lb, a buffer capacitor Cbuf, a first switch S31, and a second switch S32.

[0016] The first diode D31 of the power pulsation absorption circuit 130 is connected between the inductor Lb of the power pulsation absorption circuit 130 and one of the two input terminals 113 of the rectifier 110, and the second diode D32 of the power pulsation absorption circuit 130 is connected between the inductor Lb of the power pulsation absorption circuit 130 and the other of the two input terminals 113 of the rectifier 110. In this case, each of the first diode D31 and the second diode D32 of the power pulsation absorption circuit 130 is connected between the inductor Lb of the power pulsation absorption circuit 130 and the input terminal 113 of the rectifier 110 so that the forward direction is from the input terminal 113 of the rectifier 110 to the inductor Lb. For this reason, even if an AC power supply 200 is connected to the input terminal 113 of the rectifier 110, a DC current is input to the inductor Lb of the power pulsation absorption circuit 130.

[0017] The buffer capacitor Cbuf and the first switch S31 of the power pulsation absorbing circuit 130 are connected in series between a first line LH connecting the cathode terminal 111 of the rectifier 110 and the first terminal 121 of the DC / DC converter 120 and a second line LL connecting the anode terminal 112 of the rectifier 110 and the second terminal 122 of the DC / DC converter 120. The buffer capacitor Cbuf is disposed on the second line LL side, and the first switch S31 is disposed on the first line LH side. The first switch S31 is, for example, an N-channel power MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) equipped with a reverse-polarity diode (body diode). In this case, it is preferable that the source of the N-channel power MOSFET is connected to the first line LH, and the drain of the N-channel power MOSFET is connected to the buffer capacitor.

[0018] The third diode D33 of the power pulsation absorption circuit 130 is connected between the line connecting the buffer capacitor Cbuf of the power pulsation absorption circuit 130 and the first switch S31 and the inductor Lb of the power pulsation absorption circuit 130, so that the direction from the inductor Lb to this line is the forward direction.

[0019] The second switch S32 of the power pulsation absorber circuit 130 is connected between the second line LL and a line connecting the inductor Lb and the third diode D33 of the power pulsation absorber circuit 130. The second switch S32 is, for example, an N-channel power MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) equipped with a reverse-polarity diode (body diode). In this case, it is preferable that the drain of the N-channel power MOSFET is connected to the line connecting the inductor Lb and the third diode D33 of the power pulsation absorber circuit 130, and the source of the N-channel power MOSFET is connected to the second line LL.

[0020] The control unit 140 controls the switching of the switches S21 to S28 of the DC / DC converter 120 and the switches S31 and S32 of the power pulsation absorbing circuit .

[0021] The power pulsation absorbing circuit 130 includes a first diode D31, a second diode D32, a third diode D33, an inductor Lb, a buffer capacitor Cbuf, and a second switch S32, and therefore can function as a power factor correction (PFC) circuit. S , sinusoidal current i S However, it is possible to control the charger 100 so that the power is input from the AC power supply 200 to the charger 100.

number

[0022] At this time, the instantaneous power p output from the AC power supply 200 S is calculated as follows: S I S ) and the pulsating part p rip (t)(=-V S I S cos2ω S t), and as shown by the solid line in Figure 2, the average power P (dashed line in Figure 2) is sandwiched between the AC angular frequency ω S It pulsates at twice the angular frequency.

number

[0023] Therefore, the control unit 140 controls the switching of the switches S21 to S28 of the DC / DC converter 120 and the switches S31 and S32 of the power pulsation absorbing circuit 130, thereby absorbing the power pulsation of the AC power supply in the power pulsation absorbing circuit 130 and keeping the power input to the DC / DC converter 120 constant.

[0024] At this time, in the charger 100 according to the present embodiment, the instantaneous power p output from the AC power supply 200 S is higher than the average power P (p S >P), and when the instantaneous power p output from the AC power supply 200 S is lower than the average power P (p S <P), the control is changed

[0025] When the instantaneous power p output from the AC power supply S is higher than the average power P (p S >P), by controlling the switching of the eight switches S21 to S28 of the DC / DC converter 120 and the two switches S31 and S32 of the power pulsation absorption circuit 130, the pulsation part p S of the instantaneous power p rip is charged to the buffer capacitor Cbuf through the inductor Lb of the power pulsation absorption circuit 130, so that only the average power P of the power output from the AC power supply is input to the DC / DC converter 120. That is, in the present embodiment, during the period when the instantaneous power p output from the AC power supply S is higher than the average power P, it is the period (charging period) during which the buffer capacitor Cbuf is charged, and the instantaneous power p C output from the buffer capacitor Cbuf becomes negative as shown by the dashed line in FIG. 2

[0026] On the other hand, when the instantaneous power p output from the AC power supply 200 S is lower than the average power P (p S <P), while the second switch S32 of the power pulsation absorption circuit 130 is kept off, by controlling the switching of the eight switches S21 to S28 of the DC / DC converter 120 and the first switch S31 of the power pulsation absorption circuit 130, the buffer capacitor Cbuf is actively discharged through the first switch S31, and the pulsation part p S which is the difference between the instantaneous power p output from the AC power supply 200 rip [[]]By compensating for this, the average power P is input to the DC / DC converter 120. That is, in this embodiment, the instantaneous power p S The period when the average power P is lower than the average power P is the period when the buffer capacitor Cbuf discharges (discharge period), and the instantaneous power p C becomes positive as shown by the dashed line in Figure 2.

[0027] That is, in this embodiment, the control unit 140 calculates the instantaneous power p output from the AC power supply 200. S and the instantaneous power p output from the buffer capacitor Cbuf C The switching of the switches S21 to S28 of the DC / DC converter 120 and the switches S31 to S32 of the power pulsation absorbing circuit 130 is controlled so that the sum of these is constant.

[0028] In this manner, in this embodiment, the buffer capacitor Cbuf is actively discharged during the discharge period, which makes it possible to reduce the amount of power stored in the buffer capacitor Cbuf (i.e., the capacitance of the buffer capacitor Cbuf) and thereby reduce the size of the buffer capacitor Cbuf.

[0029] In this embodiment, the second switch S32 operates only during the charging period, which makes it possible to reduce the amount of power stored in the inductor Lb (i.e., the inductance of the inductor Lb), thereby enabling the inductor Lb to be made smaller.

[0030] Furthermore, in this embodiment, there is no pulsation in the power input to the DC / DC converter 120. Therefore, in this embodiment, the transformer Tr and DC capacitor Cdc of the DC / DC converter 120 can be made smaller.

[0031] As described above, in this embodiment, it is possible to reduce the size of passive elements such as capacitors, inductors, and transformers, and therefore it is possible to provide a compact charger that can absorb power pulsation.

[0032] <Switching mode and operating waveforms> The control unit 140 calculates the operating waveform i of the inductor L of the DC / DC converter 120. L The switching of the switches S21 to S28 of the DC / DC converter 120 and the first switch S31 of the power pulsation absorber circuit 130 is controlled in seven modes so that the operating waveform can be approximated by a square waveform. Figure 3 is a diagram showing the state of each switch in each of the seven modes. The seven modes include a mode (mode 5) in which all of the switches S21 to S28 of the DC / DC converter 120 and the first switch S31 of the power pulsation absorber circuit 130 are turned off.

[0033] FIG. 4 shows the operating waveform i of the inductor L of the DC / DC converter 120 according to this embodiment. L and its equivalent square wave i L This is a diagram showing the operation waveform i L is obtained by switching the seven modes shown in Figure 3 in the order of mode 1, mode 2, mode 3, mode 4, mode 5, mode 4, mode 6, mode 7, mode 1, and mode 5. At this time, the current i L is as follows (see Non-Patent Document 1):

number

[0034] In this embodiment, in order to more actively discharge the buffer capacitor Cbuf when the first switch S31 of the power pulsation absorbing circuit 130 is on, the control unit 140 controls the voltage v C is the instantaneous voltage v output from the rectifier 110. rec Therefore, in this embodiment, the voltage v associated with the buffer capacitor Cbuf is controlled to be always greater than C is the instantaneous voltage v of the rectifier 110. recThe operating waveforms in Mode 2 and Mode 3 have different values. L Similarly, the operating waveforms in modes 6 and 7 are L Therefore, in this embodiment, as shown in FIG. 4, the waveform in the positive direction and the waveform in the negative direction are different. L It is possible to generate operating waveforms that are asymmetric with respect to .DELTA..times ...

[0035] The operating waveforms shown in Figure 4 L In |t0-t1|=|t6-t7|, |t1-t2|=|t8-t9|, |t2-t3|=|t7-t8|, |t3-t5|=|t9-t 11 t0~t3, t5~t9, t 11 , t 12 Set |t0-t1|=|t4-t5|=|t 10 -t 11 So that t4 is placed between t3 and t5, and t9 and t 11 Between 10 When you set the operating waveform i L is the equivalent square waveform i L It can be approximated by

number

[0036] equivalent square waveform i L ′t0~t1, t4~t5, t6~t7, t 10 ~t 11 The period is the reactive current period T q The periods t1 to t2 and t8 to t9 are defined as the buffer capacitor discharge current periods T C The periods t2 to t3 and t7 to t8 are defined as the power supply current periods T rec and t3~t4, t9~t 10 The period is called the current balancing period T b t5~t6, t 11 ~t 12 If the period is defined as the zero current period T0, the switching period T SW The duty ratio of each period is as follows:

number

number

[0037] <switching frequency f SW Control of > Figure 5 shows the switching frequency f SW (=1 / T SW 5 is a diagram showing the duty ratio of each period when f SW = 50 kHz, P = 7 kW, and other parameters of the charger 100 are determined as shown in FIG. 6. In FIG. 5, the horizontal axis represents the AC voltage v input from the AC power source 200. S Phase ω S t, and the vertical axis represents the duty ratio. As shown in Figure 5, the AC voltage v S Phase ω S Except when t is 45 degrees, the duty ratio D0 of the zero current period T0 is not zero, that is, the zero current period T0 is not zero.

[0038] This zero current period T0 is mode 5, and is a period in which all switches S21 to S28 of the DC / DC converter 120 are turned off. However, in reality, there is a difference in the timing at which the switches are turned off, and this difference causes current to remain, resulting in resonance between the inductor L of the DC / DC converter 120 and the parasitic capacitance of the switches S21 to S28. Figure 7 shows the current i L and voltage V L 7A is a diagram illustrating the time change of the AC power supply voltage v S When the phase of inductor L is 0 degrees, the current i L and voltage V L Fig. 7(B) shows the time change of AC power supply voltage v S When the phase of inductor L is 30 degrees, the current i L and voltage V L As can be seen from Figure 7, during the zero current period T0, the current i L and voltage V L As a result, the switching after the zero current period T0 (switching when switching from mode 5 to mode 4, and switching when switching from mode 5 to mode 1) becomes hard switching, resulting in switching loss.

[0039] Therefore, in this embodiment, the control unit 140 controls the AC voltage v input from the AC power supply 200. S During one period, the switching frequency f SW The control unit 140 changes the switching frequency f of the switches S21 to S28 of the DC / DC converter 120 and the switch S31 of the power pulsation absorbing circuit 130 so that the zero current period T0 becomes zero, for example. SW As can be seen from the above equation (1), the reactive current period T q D q and only D0 in the zero current period T0 is SW (=1 / f SW ) is a function of the switching frequency fSW Even if the period during which power is transmitted (reactive current period T q , periods other than the zero current period T0) does not change, and the transmitted power is not affected. By solving the above equation (1) with D0 = 0, the switching frequency f SW is found as follows:

number

[0040] Figure 8 shows the switching frequency f SW 8 is a diagram showing the duty ratio for each period when P is set to 7 kW and the other parameters of the charger 100 are set to the values ​​shown in FIG. 6, and the switching frequency f SW is calculated by changing the above equation (2), and in FIG. 8, the horizontal axis represents the AC voltage v input from the AC power supply 200. S Phase ω S t, and the vertical axis represents the duty ratio. As shown in FIG. 8, the reactive current period T q , the duty ratio D of the zero current period T0 q , duty ratio D other than D0 C , D rec , D d is unchanged from Figure 5.

[0041] In this way, in this embodiment, the switching frequency f is set so that the zero current period T0 is zero. SW By changing the current i of the inductor L, L and voltage V L This eliminates the oscillation and makes it possible to avoid hard switching after the zero current period T0, thereby enabling the charger 100 to be controlled with high efficiency.

[0042] Furthermore, in this embodiment, there is no zero current period T0 in which all switches are off, so it is possible to reduce the number of switching operations compared to control in which there is a zero current period T0, and as a result, it is possible to reduce switching losses.

[0043] Figure 9 shows the AC power supply voltage v S When the phase of inductor L is 0 degrees, the current i L 9. In FIG. 9, the horizontal axis represents the current i flowing through the inductor L. L The vertical axis represents the phase of the current i flowing through the inductor L. L 9 is the value obtained when P=7 kW and other parameters of the charger 100 are the values ​​shown in FIG. 6. The thin line indicates the switching frequency f SW When is kept constant (f SW = 50 kHz) current i of inductor L L The thick line shows the time change of the switching frequency f SW When the current i of the inductor L is changed as shown in the above equation (2), L The graph shows the change over time.

[0044] As can be seen from Figure 9, the switching frequency f SW When the current i of the inductor L is changed as shown in the above equation (2), L The peak value of the switching frequency f SW When is kept constant, the current i of inductor L L Therefore, in this embodiment, the peak value of the current i flowing through the inductor L is L It is possible to reduce the peak value of , and as a result, it is possible to reduce the loss in the inductor L.

[0045] <equivalent square wave i L ′ wave height I L ' command value> Figure 10 shows the equivalent square waveform i L ′ wave height I L When the command value of f′ is not optimized, SW That is, the switching frequency f SW Instead of using the above equation (2), the equivalent square waveform i obtained so that the duty ratio of each period is valid when a constant value is given L ′ wave height I L′ is the equivalent square waveform i L ′ wave height I L The switching frequency f SW When is kept constant, the AC power supply voltage v S Phase ω S When t is 0 degrees, the duty ratio Dq of the reactive current period Tq becomes 0. From this condition, the switching frequency f SW The peak value I of the equivalent square waveform iL' when L ′ command value I L ' * becomes:

number

[0046] As can be seen in Figure 10, as the average power (effective value of AC power) P decreases, the switching frequency f SW Therefore, as the average power P decreases, the switching loss increases and the efficiency decreases.

[0047] Therefore, the control unit 140 sets the switching frequency f SW The minimum value of f base The equivalent square waveform i L ′ wave height I L As shown in Figure 10, the switching frequency f SW Regardless of the average power P, the AC power supply voltage v S Phase ω SThe voltage is smallest when t is 45 degrees. S Phase ω S Switching frequency f when t is 45 degrees SW is a given value f base The equivalent square waveform i L ′ wave height I L ' command value. At this time, the equivalent square waveform i L ′ wave height I L ′ command value I L ' * becomes:

number

[0048] Figure 11 shows the equivalent square waveform i as shown in equation (4) above. L ′ wave height I L The switching frequency f when the command value of SW As can be seen from Figures 10 and 11, the equivalent square waveform i L ′ wave height I L The switching frequency f when the command value of SW The average of the equivalent square waveform i shown in Figure 10 L ′ wave height I L When the command value of f′ is not optimized, SW In other words, the switching frequency f SW The equivalent square waveform i is calculated so that the minimum value of is constant. L ′ wave height I L When the command value of ' is controlled, the switching loss decreases and the efficiency increases.

[0049] Also, as shown in Figure 9, the equivalent square waveform i L ′ wave height I L The peak value i of the current flowing through the inductor L when the command value of L(bold dashed line) is the equivalent square waveform i L ′ wave height I L The peak value i of the current flowing through the inductor L when the command value of ′ is not optimized L (thick solid line). In other words, the switching frequency f SW The equivalent square waveform i is calculated so that the minimum value of is constant. L ′ wave height I L When the command value of ′ is controlled, the peak value i of the current flowing through the inductor L is L can be further reduced, and as a result, the loss in the inductor L can be further reduced.

[0050] The present invention has been described above in terms of preferred embodiments thereof. While the present invention has been described herein with reference to specific examples, various modifications and variations can be made to these examples without departing from the spirit and scope of the present invention as set forth in the claims. [Explanation of symbols]

[0051] 100 charger 110 Rectifier 120 DC / DC converter S21~S28 DC / DC converter switches 130 Power pulsation absorption circuit D31 First diode D32 Second diode D33 Third diode Lb inductor Cbuf Buffer capacitor S31 First Switch S32 Second Switch

Claims

1. a rectifier having two input terminals for connection to an AC power source, a cathode terminal, and an anode terminal; a DC / DC converter having a first terminal connected to a cathode terminal of the rectifier via a first line, a second terminal connected to an anode terminal of the rectifier via a second line, and two output terminals for connection to a battery; a power pulsation absorbing circuit including a first diode, a second diode, a third diode, an inductor, a capacitor, a first switch, and a second switch; a control unit that controls switching of the switch of the DC / DC converter, the first switch, and the second switch; the first diode is connected between an inductor of the power pulsation absorbing circuit and one of two input terminals of the rectifier, and the second diode is connected between the inductor and the other of the two input terminals of the rectifier; the capacitor and the first switch are connected in series between the first line and the second line, and the capacitor is disposed on the second line side; the third diode is connected between a line connecting the capacitor and the first switch and an inductor of the power pulsation absorbing circuit; the second switch is connected between the second line and a line connecting the inductor of the power pulsation absorbing circuit and the third diode; the DC / DC converter is a DAB (Dual Active Bridge) converter, The control unit controlling a switch of the DC / DC converter, the first switch, and the second switch so that a sum of the power output from the AC power supply and the power output from the capacitor becomes constant; A charger that controls values ​​of switching frequencies of the switches of the DC / DC converter and the first switch so that a period during which all of the switches of the DC / DC converter and the first switch are turned off is zero.

2. The control unit controlling switching of the switch of the DC / DC converter and the first switch so that the operating waveform of an inductor of the DC / DC converter becomes an operating waveform that can be approximated by a square waveform; 2. The charger according to claim 1, wherein a command value of a peak value of the square waveform is controlled so that the minimum value of the switching frequency becomes a predetermined value.

Images