Power source device and control method

Abstract

To suppress efficiency deterioration and discharge power stored in a capacitor without adding any element for power discharge.SOLUTION: A power source device includes a bidirectional step-up / step-down chopper including a first capacitor, a first switching element, a second switching element, an inductor, a third switching element, a fourth switching element, and a second capacitor, and a control unit that controls the bidirectional step-up / step-down chopper. To discharge power stored in the first capacitor, the control unit controls the third switching element to be turned off, controls the fourth switching element to be turned on, and controls the first switching element and the second switching element to be alternately turned on and off.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a power supply device and a control method. [Background technology]

[0002] Patent Documents 1 and 2 describe inverters that discharge power stored in a smoothing capacitor on the DC voltage side when operation is stopped. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-2943 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-123202 Summary of the Invention [Problem to be solved by the invention]

[0004] In a bidirectional buck-boost chopper, it is conceivable to use a discharge resistor to consume the power stored in the smoothing capacitor when the chopper is not in operation. However, if the discharge resistor is always connected in parallel to the smoothing capacitor, the efficiency of the bidirectional buck-boost chopper will decrease during normal operation. If the resistance value of the discharge resistor is reduced to suppress the decrease in efficiency, the discharge time will become longer. On the other hand, if one tries to shorten the discharge time, the allowable power of the discharge resistor must be increased, which requires a large discharge resistor.

[0005] In order to prevent the efficiency of the bidirectional buck-boost chopper from decreasing during normal operation, it is possible to provide a switch element that connects the discharge resistor to the smoothing capacitor only during discharge. However, this requires the addition of a switch element and a gate circuit to control the switch element.

[0006] The present disclosure aims to suppress a decrease in efficiency and discharge power stored in a capacitor without adding a discharge element. [Means for solving the problem]

[0007] A power supply device according to an embodiment of the present disclosure includes: a bidirectional buck-boost chopper including: a first capacitor having one end electrically connected to a first terminal and the other end electrically connected to a second terminal; a first switching element having a drain electrically connected to the first terminal and a source electrically connected to a first node; a second switching element having a drain electrically connected to the first node and a source electrically connected to the second terminal; an inductor having one end electrically connected to the first node and the other end electrically connected to a second node; a third switching element having a drain electrically connected to a third terminal and a source electrically connected to the second node; a fourth switching element having a drain electrically connected to the second node and a source electrically connected to a fourth terminal and a source of the second switching element; and a second capacitor having one end electrically connected to the third terminal and the other end electrically connected to the fourth terminal; a control unit for controlling the bidirectional buck-boost chopper; Including, The control unit When discharging the power stored in the first capacitor, the third switching element is controlled to be turned off, the fourth switching element is controlled to be turned on, and the first switching element and the second switching element are alternately turned on and off. It is characterized by:

[0008] In the power supply device, The control unit a period for alternately controlling the first switching element and the second switching element to be turned on and off is constant, and in a first period within the period, the first switching element is controlled to be on and the second switching element is controlled to be off, and in a second period within the period, the first switching element is controlled to be off and the second switching element is controlled to be on, and lengths of the first period and the second period are determined so that the current flowing through the inductor becomes zero during the second period. It is characterized by:

[0009] In the power supply device, The control unit using the voltage of the first capacitor, referencing a table in which the voltage of the first capacitor and the length of the first period are associated with each other to determine the first period; It is characterized by:

[0010] In the power supply device, The control unit When discharging the power stored in the second capacitor, the first switching element is controlled to be turned off, the second switching element is controlled to be turned on, and the third switching element and the fourth switching element are controlled to be alternately turned on and off. It is characterized by:

[0011] In the power supply device, the bidirectional buck-boost choppers are included in a plurality, the first terminals and the second terminals of the plurality of bidirectional buck-boost choppers are electrically connected to a plurality of power supplies, respectively, and the third terminals and the fourth terminals of the plurality of bidirectional buck-boost choppers are electrically connected to one load; The control unit when discharging power stored in the first capacitor of one bidirectional buck-boost chopper among the plurality of bidirectional buck-boost choppers, the third switching element of one of the plurality of bidirectional buck-boost choppers is controlled to be off, the fourth switching element of one of the plurality of bidirectional buck-boost choppers is controlled to be on, and the first switching element and the second switching element of one of the plurality of bidirectional buck-boost choppers are alternately controlled to be on and off; It is characterized by:

[0012] A control method according to one aspect of the present disclosure includes: a first capacitor having one end electrically connected to a first terminal and the other end electrically connected to a second terminal; a first switching element having a drain electrically connected to the first terminal and a source electrically connected to a first node; a second switching element having a drain electrically connected to the first node and a source electrically connected to the second terminal; an inductor having one end electrically connected to the first node and the other end electrically connected to a second node; a third switching element having a drain electrically connected to a third terminal and a source electrically connected to the second node; a fourth switching element having a drain electrically connected to the second node and a source electrically connected to a fourth terminal and a source of the second switching element; and a second capacitor having one end electrically connected to the third terminal and the other end electrically connected to the fourth terminal, When discharging the power stored in the first capacitor, the third switching element is controlled to be turned off, the fourth switching element is controlled to be turned on, and the first switching element and the second switching element are alternately turned on and off. It is characterized by: [Effects of the Invention]

[0013] According to the present disclosure, it is possible to suppress a decrease in efficiency and discharge power stored in a capacitor without adding a discharge element. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram illustrating a configuration of a power supply device according to a first embodiment. [Figure 2] FIG. 2 is a timing diagram of the discharge operation of the power supply device according to the first embodiment. [Figure 3] FIG. 3 illustrates an example of a table stored in the control of the power supply device according to the first embodiment. [Figure 4] FIG. 4 is a timing diagram of the discharge operation of the power supply device according to the first embodiment. [Figure 5]FIG. 5 is a diagram illustrating a configuration of a power supply device according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Note that the present disclosure is not limited to these embodiments, and in the following embodiments, the same components are designated by the same reference numerals, and redundant description will be omitted.

[0016] First Embodiment (composition) FIG. 1 is a diagram illustrating a configuration of a power supply device according to a first embodiment.

[0017] The power supply device 1 steps up or steps down the voltage output from the power supply 2 and outputs it to the power supply 3. The power supply device 1 also steps up or steps down the voltage output from the power supply 3 and outputs it to the power supply 2.

[0018] In other words, the power supply device 1 is a bidirectional step-up / step-down type power supply device.

[0019] The power supply device 1 includes a bidirectional buck-boost chopper 11 and a control unit 12.

[0020] A terminal 11a of the bidirectional buck-boost chopper 11 is electrically connected to a high-potential terminal of a power source 2 (e.g., a battery). A terminal 11b of the bidirectional buck-boost chopper 11 is electrically connected to a low-potential terminal of the power source 2. A terminal 11c of the bidirectional buck-boost chopper 11 is electrically connected to a high-potential terminal of a power source 3 (e.g., a battery). A terminal 11d of the bidirectional buck-boost chopper 11 is electrically connected to a low-potential terminal of the power source 3.

[0021] Terminal 11a corresponds to an example of a "first terminal" in the present disclosure. Terminal 11b corresponds to an example of a "second terminal" in the present disclosure. Terminal 11c corresponds to an example of a "third terminal" in the present disclosure. Terminal 11d corresponds to an example of a "fourth terminal" in the present disclosure.

[0022] The bidirectional buck-boost chopper 11 includes a capacitor C1 and a capacitor C2, switching elements SW1 to SW4, and an inductor L1.

[0023] In the embodiment, each switching element is a transistor, but the present disclosure is not limited to this. Also, each transistor is a MOSFET, but the present disclosure is not limited to this. Each transistor may be a silicon power device, a GaN power device, a SiC power device (e.g., an IGBT (Insulated Gate Bipolar Transistor)), etc.

[0024] Each transistor has a parasitic diode (body diode) that can actively conduct current, or has a diode connected in anti-parallel: the pn junction between the back gate and the source and drain of the MOSFET.

[0025] One end of the capacitor C1 is electrically connected to the terminal 11a, and the other end of the capacitor C1 is electrically connected to the terminal 11b. The capacitor C1 is a smoothing capacitor that smoothes the voltage V1 input / output between the terminals 11a and 11b.

[0026] The drain of the switching element SW1 is electrically connected to the terminal 11a. The source of the switching element SW1 is electrically connected to the node N1. The control signal S1 is input from the control unit 12 to the gate of the switching element SW1.

[0027] The node N1 corresponds to an example of a "first node" in the present disclosure.

[0028] The drain of the switching element SW2 is electrically connected to the node N1. The source of the switching element SW2 is electrically connected to the terminal 11b. The control signal S2 is input from the control unit 12 to the gate of the switching element SW2.

[0029] One end of the inductor L1 is electrically connected to the node N1, and the other end of the inductor L1 is electrically connected to the node N2.

[0030] The node N2 corresponds to an example of a "second node" in the present disclosure.

[0031] The source of the switching element SW3 is electrically connected to the node N2. The drain of the switching element SW3 is electrically connected to the terminal 11c. The control signal S3 is input from the control unit 12 to the gate of the switching element SW3.

[0032] The drain of the switching element SW4 is electrically connected to the node N2. The source of the switching element SW4 is electrically connected to the terminal 11b and the source of the switching element SW2. A control signal S4 is input from the control unit 12 to the gate of the switching element SW4.

[0033] One end of capacitor C2 is electrically connected to terminal 11c, and the other end of capacitor C2 is electrically connected to terminal 11d. Capacitor C2 is a smoothing capacitor that smoothes voltage V2 input / output between terminal 11c and terminal 11d.

[0034] The control unit 12 outputs control signals S1 to S4 to the gates of the switching elements SW1 to SW4, respectively, to control the switching elements SW1 to SW4.

[0035] The control unit 12 stores a table 13. The table 13 will be explained later.

[0036] (Power output operation of power supply unit 1 (normal operation)) The power output operation (normal operation) of the power supply device 1 will now be described.

[0037] The circuit configuration of the bidirectional buck-boost chopper 11 is symmetrical with respect to the inductor L1. Therefore, the operation of the power supply device 1, which boosts or bucks the voltage output from the power supply 2 and outputs it to the power supply 3, is in contrast to the operation of the power supply device 1, which boosts or bucks the voltage output from the power supply 3 and outputs it to the power supply 2.

[0038] Therefore, in the embodiment, only the operation of the power supply device 1 that boosts or lowers the voltage output from the power supply 2 and outputs it to the power supply 3 will be described, and the operation of the power supply device 1 that boosts or lowers the voltage output from the power supply 3 and outputs it to the power supply 2 will not be described.

[0039] [Boost operation] The control unit 12 maintains the switching element SW1 in the ON state and the switching element SW2 in the OFF state.

[0040] The control unit 12 controls the on / off of the switching elements SW3 and SW4.

[0041] When switching element SW3 is in the OFF state and switching element SW4 is in the ON state, current flows from one end of capacitor C1 to switching element SW1 to inductor L1 to switching element SW4 to the other end of capacitor C1, and electromagnetic energy is stored in inductor L1. At this time, the voltage across inductor L1 is voltage V1.

[0042] When switching element SW3 is on and switching element SW4 is off, current flows through the path of one end of capacitor C1 → switching element SW1 → inductor L1 → switching element SW3 → capacitor C2 → the other end of capacitor C1. At this time, the sum of voltage V1 and the voltage of inductor L1 is applied to capacitor C2.

[0043] This allows the power supply device 1 to achieve a boost operation.

[0044] [Step-down operation] The control unit 12 maintains the switching element SW3 in the ON state and the switching element SW4 in the OFF state.

[0045] The control unit 12 controls the on / off of the switching elements SW1 and SW2.

[0046] When switching element SW1 is on and switching element SW2 is off, current flows from one end of capacitor C1 to switching element SW1 to inductor L1 to switching element SW3 to capacitor C2 to the other end of capacitor C1, and electromagnetic energy is stored in inductor L1. At this time, the voltage across inductor L1 is (V1-V2).

[0047] When switching element SW1 is in the off state and switching element SW2 is in the on state, current flows through the other end of inductor L1, switching element SW3, capacitor C2, switching element SW2, and one end of inductor L1. At this time, the voltage of inductor L1 is applied to capacitor C2.

[0048] This allows the power supply device 1 to perform a step-down operation.

[0049] (Power supply unit 1 capacitor discharge operation) It is desirable for the power supply device 1 to discharge the power from the capacitor C1 and the power from the capacitor C2.

[0050] For example, if the power source 2 is a battery and this battery is replaced with another battery, it is desirable for the power supply device 1 to discharge the power of the capacitor C1.

[0051] Similarly, for example, if the power supply 3 is a battery and this battery is replaced with another battery, it is desirable for the power supply device 1 to discharge the power of the capacitor C2.

[0052] The power supply device 1 is able to meet such demands.

[0053] [Capacitor C1 power discharge operation] The operation of discharging power from the capacitor C1 of the power supply device 1 will now be described.

[0054] When the control signal S11 is input, the control unit 12 discharges the power of the capacitor C1. The control signal S11 may be input from an external circuit or may be input from a power source 2 (for example, a battery). For example, when replacing the battery, the power source 2 cuts off the power supply to the bidirectional buck-boost chopper 11 and then outputs the control signal S11 to the control unit 12.

[0055] When the control signal S11 is input, the control unit 12 starts discharging the power from the capacitor C1.

[0056] 2 is a timing diagram of the discharge operation of the power supply device according to the first embodiment. In the embodiment, the description of dead time is omitted.

[0057] 2, line 101 represents the control signal S1. Line 102 represents the control signal S2. Line 103 represents the control signal S3. Line 104 represents the control signal S4. Line 105 represents the current IL in inductor L1.

[0058] The control unit 12 maintains the control signal S3 at a low level, thereby maintaining the switching element SW3 in an off state. The control unit 12 also maintains the control signal S4 at a high level, thereby maintaining the switching element SW4 in an on state.

[0059] Then, the control unit 12 alternately sets the control signal S1 and the control signal S2 to a high level.

[0060] In the embodiment, the length of one cycle T1 is fixed. One cycle T1 includes periods T2 and T3. The control unit 12 refers to the table 13 using the voltage V1 to determine the length of the period T2. The control unit 12 sets the length of the period T3 as T3 = T1 - T2.

[0061] The period T2 corresponds to an example of a "first period" in the present disclosure, and the period T3 corresponds to an example of a "second period" in the present disclosure.

[0062] During the period T2, the control unit 12 controls the switching element SW1 to be in the ON state and the switching element SW2 to be in the OFF state.

[0063] During period T2, current IL of inductor L1 flows through a path of one end of capacitor C1→switching element SW1→inductor L1→switching element SW4→other end of capacitor C1 (see line 105 during period T2).

[0064] In the period T2, the current IL of the inductor L1 increases with time.

[0065] At this time, the capacitor C2 is not included in the path through which the current IL flows, and therefore the power of the capacitor C2 is maintained.

[0066] During the period T3, the control unit 12 controls the switching element SW1 to be in the OFF state and the switching element SW2 to be in the ON state.

[0067] During period T3, current IL of inductor L1 flows through the path of the other end of inductor L1 → switching element SW4 → switching element SW2 → one end of inductor L1 (see line 105 during period T3).

[0068] In the period T3, the current IL of the inductor L1 decreases over time.

[0069] At this time, the capacitor C2 is not included in the path through which the current IL flows, and therefore the power of the capacitor C2 is maintained.

[0070] In the power supply device 1, the flow of the current IL causes switching loss in the switching elements SW1, SW2, and SW4, copper loss in the wiring, iron loss in the inductor L1, etc., and allows the power of the capacitor C1 to be discharged.

[0071] FIG. 2 shows three cycles, and as the cycles progress, the voltage V1 gradually decreases, and the peak value of the current IL gradually decreases, until the voltage V1 reaches 0 V and the peak value of the current IL reaches 0 A.

[0072] This allows the power supply device 1 to discharge the power from the capacitor C1.

[0073] FIG. 3 illustrates an example of a table stored in the control of the power supply device according to the first embodiment.

[0074] The voltage V1 (voltage V2) and the period T2 (period T5) are associated with each other in the table 13. The period T2 is determined in advance so that the current IL reaches 0 A within the period T3.

[0075] The longer the period T2, the larger the current IL and the shorter the discharge time. However, if the period T2 is too long, the current IL will not reach 0 A within the period T3, and will instead increase cumulatively as shown by line 106.

[0076] Therefore, it is preferable to make the period T2 as long as possible within a range in which the current IL becomes 0 A within the period T3.

[0077] For example, when the voltage V1 is 50V or more, the period T2 is set to A1 μs. When the voltage V1 is 40V or more and less than 50V, the period T2 is set to A2 μs. When the voltage V1 is 30V or more and less than 40V, the period T2 is set to A3 μs. When the voltage V1 is 20V or more and less than 30V, the period T2 is set to A4 μs. When the voltage V1 is 10V or more and less than 20V, the period T2 is set to A5 μs. When the voltage V1 is less than 10V, the period T2 is set to A6 μs. Here, it is exemplified that A1 < A2 < A3 < A4 < A5 < A6.

[0078] [Discharge operation of the charge of capacitor C2] The discharge operation of the charge of the capacitor C2 in the power supply device 1 will be described.

[0079] When the control signal S12 is input, the control unit 12 discharges the charge of the capacitor C2. The control signal S12 may be input from an external circuit or may be input from the power supply 3 (for example, a battery). For example, in the case of battery replacement, the power supply 3 cuts off the power supply to the bidirectional buck-boost chopper 11 and then outputs the control signal S12 to the control unit 12.

[0080] When the control signal S12 is input, the control unit 12 starts the discharge operation of the power of the capacitor C2.

[0081] FIG.  4 is a timing diagram of the discharge operation of the power supply device according to the first embodiment. In the embodiment, the description of the dead time is omitted.

[0082] In FIG. 4, line 111 represents the control signal S1. Line 112 represents the control signal S2. Line 113 represents the control signal S3. Line 114 represents the control signal S4. Line 115 represents the current IL of the inductor L1.

[0083] The control unit 12 maintains the control signal S1 at a low level, thereby maintaining the switching element SW1 in an off state. The control unit 12 also maintains the control signal S2 at a high level, thereby maintaining the switching element SW2 in an on state.

[0084] Then, the control unit 12 alternately sets the control signal S3 and the control signal S4 to a high level.

[0085] In this embodiment, the length of one cycle T4 is fixed. One cycle T4 includes periods T5 and T6. The control unit 12 refers to the table 13 using the voltage V2 to determine the length of the period T5. The control unit 12 sets the length of the period T6 as T6 = T4 - T5.

[0086] The period T5 corresponds to an example of the "first period" in the present disclosure, and the period T6 corresponds to an example of the "second period" in the present disclosure.

[0087] During the period T5, the control unit 12 controls the switching element SW3 to be in the ON state and the switching element SW4 to be in the OFF state.

[0088] During period T5, current IL of inductor L1 flows through a path of one end of capacitor C2, switching element SW3, inductor L1, switching element SW2, and the other end of capacitor C2 (see line 115 during period T5).

[0089] In the period T5, the absolute value of the current IL of the inductor L1 increases with time.

[0090] At this time, the capacitor C1 is not included in the path through which the current IL flows, so the power of the capacitor C1 is maintained.

[0091] During the period T6, the control unit 12 controls the switching element SW3 to be in the OFF state and the switching element SW4 to be in the ON state.

[0092] During a period T6, the current IL of the inductor L1 flows through a path of one end of the inductor L1 → switching element SW2 → switching element SW4 → other end of the inductor L1 (see line 115 during the period T6).

[0093] In the period T6, the absolute value of the current IL of the inductor L1 decreases with time.

[0094] At this time, the capacitor C1 is not included in the path through which the current IL flows, so the power of the capacitor C1 is maintained.

[0095] In the power supply device 1, the flow of the current IL causes switching loss in the switching elements SW2, SW3, and SW4, copper loss in the wiring, iron loss in the inductor L1, etc., and allows the power of the capacitor C2 to be discharged.

[0096] Figure 4 shows three cycles, and as the cycles progress, the voltage V2 gradually decreases, and the peak absolute value of the current IL gradually decreases, until the voltage V2 reaches 0 V and the peak absolute value of the current IL reaches 0 A.

[0097] This allows the power supply device 1 to discharge the power from the capacitor C2.

[0098] (effect) In this way, the power supply device 1 can discharge the power stored in the capacitors C1 and C2 without adding any discharge elements.

[0099] Furthermore, the power supply device 1 does not use a discharge resistor, so that a decrease in efficiency can be suppressed.

[0100] Furthermore, the power supply device 1 can discharge the power stored in the capacitor C1 without affecting the power and voltage V2 of the capacitor C2 (that is, without affecting the power supply 3).

[0101] Similarly, power supply 1 can discharge the power stored in capacitor C2 without affecting the power and voltage V1 of capacitor C1 (ie, without affecting power supply 2).

[0102] <Second embodiment> (composition) FIG. 5 is a diagram illustrating a configuration of a power supply device according to the second embodiment.

[0103] The power supply device 1A includes a plurality of (four in the example of FIG. 5) bidirectional buck-boost choppers 11-1 to 11-4. One control unit 12 controls the four bidirectional buck-boost choppers 11-1 to 11-4.

[0104] A terminal 11-1a of the bidirectional buck-boost chopper 11-1 is electrically connected to a high-potential terminal of a power source 2-1 (e.g., a battery). A terminal 11-1b of the bidirectional buck-boost chopper 11-1 is electrically connected to a low-potential terminal of the power source 2-1. A terminal 11-1c of the bidirectional buck-boost chopper 11-1 is electrically connected to a high-potential terminal of a power source 3 (e.g., a battery). A terminal 11-1d of the bidirectional buck-boost chopper 11-1 is electrically connected to a low-potential terminal of the power source 3.

[0105] A terminal 11-2a of the bidirectional buck-boost chopper 11-2 is electrically connected to a high-potential terminal of a power source 2-2 (e.g., a battery). A terminal 11-2b of the bidirectional buck-boost chopper 11-2 is electrically connected to a low-potential terminal of the power source 2-2. A terminal 11-2c of the bidirectional buck-boost chopper 11-2 is electrically connected to a high-potential terminal of the power source 3. A terminal 11-2d of the bidirectional buck-boost chopper 11-2 is electrically connected to a low-potential terminal of the power source 3.

[0106] A terminal 11-3a of the bidirectional buck-boost chopper 11-3 is electrically connected to a high-potential terminal of a power source 2-3 (e.g., a battery). A terminal 11-3b of the bidirectional buck-boost chopper 11-3 is electrically connected to a low-potential terminal of the power source 2-3. A terminal 11-3c of the bidirectional buck-boost chopper 11-3 is electrically connected to a high-potential terminal of the power source 3. A terminal 11-3d of the bidirectional buck-boost chopper 11-3 is electrically connected to a low-potential terminal of the power source 3.

[0107] A terminal 11-4a of the bidirectional buck-boost chopper 11-4 is electrically connected to a high-potential terminal of a power source 2-4 (e.g., a battery). A terminal 11-4b of the bidirectional buck-boost chopper 11-4 is electrically connected to a low-potential terminal of the power source 2-4. A terminal 11-4c of the bidirectional buck-boost chopper 11-4 is electrically connected to a high-potential terminal of the power source 3. A terminal 11-4d of the bidirectional buck-boost chopper 11-4 is electrically connected to a low-potential terminal of the power source 3.

[0108] The circuit configurations of the bidirectional buck-boost chopper 11-1 to bidirectional buck-boost chopper 11-4 are similar to the circuit configuration of the bidirectional buck-boost chopper 11, and therefore will not be described.

[0109] (effect) For example, when the power supply 2-1 connected to the bidirectional buck-boost chopper 11-1 is replaced, the control unit 12 discharges the power stored in the capacitor C1 of the bidirectional buck-boost chopper 11-1.

[0110] At this time, the bidirectional buck-boost chopper 11-1 can discharge the power stored in the capacitor C1 without affecting the power and voltage V2 of the capacitor C2 (i.e., without affecting the bidirectional buck-boost chopper 11-2 to the bidirectional buck-boost chopper 11-4 and the power supply 3).

[0111] Therefore, in the power supply device 1A, the power supply 2-1 can be replaced while the bidirectional buck-boost chopper 11-2 to the bidirectional buck-boost chopper 11-4 continue to supply power to the power supply 3.

[0112] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the contents of these embodiments. Furthermore, the above-described components include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the above-described components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the above-described embodiments. [Explanation of symbols]

[0113] 1, 1A power supply 2, 2-1, 2-2, 2-3, 2-4, 3 power supply 11, 11-1, 11-2, 11-3, 11-4 Bidirectional buck-boost chopper 12 Control Unit 13 Tables C1 and C2 capacitors L1 inductor SW1, SW2, SW3, SW4 switching elements

Claims

1. a bidirectional buck-boost chopper including: a first capacitor having one end electrically connected to a first terminal and the other end electrically connected to a second terminal; a first switching element having a drain electrically connected to the first terminal and a source electrically connected to a first node; a second switching element having a drain electrically connected to the first node and a source electrically connected to the second terminal; an inductor having one end electrically connected to the first node and the other end electrically connected to a second node; a third switching element having a drain electrically connected to a third terminal and a source electrically connected to the second node; a fourth switching element having a drain electrically connected to the second node and a source electrically connected to a fourth terminal and a source of the second switching element; and a second capacitor having one end electrically connected to the third terminal and the other end electrically connected to the fourth terminal; a control unit for controlling the bidirectional buck-boost chopper; Including, The control unit When discharging the power stored in the first capacitor, the third switching element is controlled to be turned off, the fourth switching element is controlled to be turned on, and the first switching element and the second switching element are alternately turned on and off. A power supply device comprising:

2. The control unit a period for alternately controlling the first switching element and the second switching element to be turned on and off is kept constant, the first switching element is controlled to be on and the second switching element is controlled to be off in a first period of the period, and the first switching element is controlled to be off and the second switching element is controlled to be on in a second period of the period, and lengths of the first period and the second period are determined so that the current flowing through the inductor becomes zero in the second period.

2. The power supply device according to claim 1 .

3. The control unit using the voltage of the first capacitor, referencing a table in which the voltage of the first capacitor and the length of the first period are associated with each other to determine the first period; 3. The power supply device according to claim 2, wherein:

4. The control unit When discharging the power stored in the second capacitor, the first switching element is controlled to be turned off, the second switching element is controlled to be turned on, and the third switching element and the fourth switching element are controlled to be alternately turned on and off.

2. The power supply device according to claim 1 .

5. the bidirectional buck-boost choppers are included in a plurality, the first terminals and the second terminals of the plurality of bidirectional buck-boost choppers are electrically connected to a plurality of power supplies, respectively, and the third terminals and the fourth terminals of the plurality of bidirectional buck-boost choppers are electrically connected to a single load; The control unit when discharging power stored in the first capacitor of one bidirectional buck-boost chopper among the plurality of bidirectional buck-boost choppers, the third switching element of one of the plurality of bidirectional buck-boost choppers is controlled to be off, the fourth switching element of one of the plurality of bidirectional buck-boost choppers is controlled to be on, and the first switching element and the second switching element of one of the plurality of bidirectional buck-boost choppers are alternately controlled to be on and off.

2. The power supply device according to claim 1 .

6. a first capacitor having one end electrically connected to a first terminal and the other end electrically connected to a second terminal; a first switching element having a drain electrically connected to the first terminal and a source electrically connected to a first node; a second switching element having a drain electrically connected to the first node and a source electrically connected to the second terminal; an inductor having one end electrically connected to the first node and the other end electrically connected to a second node; a third switching element having a drain electrically connected to a third terminal and a source electrically connected to the second node; a fourth switching element having a drain electrically connected to the second node and a source electrically connected to a fourth terminal and a source of the second switching element; and a second capacitor having one end electrically connected to the third terminal and the other end electrically connected to the fourth terminal, When discharging the power stored in the first capacitor, the third switching element is controlled to be turned off, the fourth switching element is controlled to be turned on, and the first switching element and the second switching element are alternately turned on and off. A control method comprising:

Images