Power converter

Abstract

To provide a power converter capable of stably outputting a predetermined voltage even when a change in input voltage is large.SOLUTION: The transformer circuitry 10 of the power converter 1 includes a transformer T, a switch Q1, a switch Q2, a capacitor C1, a switch Q3, and a switch Q4. The control device 40 alternately and repeatedly performs first control of turning on the switch Q1 and the switch Q4 and turning off the switch Q2 and the switch Q3 and second control of turning on the switch Q2 and the switch Q3 and turning off the switch Q1 and the switch Q4. Q2 Q1, in addition, third control of turning off the switch Q3 and the switch Q4 and fourth control of turning on the switch Q2 and the switch Q3 and turning off the switch Q1 and the switch Q4 are alternately and repeatedly executed.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Conventionally, power converters that convert power between a battery and a load are well known. For example, Japanese Patent Application Laid-Open Publication No. 2020-202679 (Patent Document 1) discloses a power converter (DC-DC converter) that converts a voltage input from a battery to a predetermined voltage and outputs the voltage to a load or the like. The power converter disclosed in Patent Document 1 includes, on the primary side, a transformer, a cutoff switch connected between one terminal of a primary coil of the transformer and one terminal of a battery, and a drive switch connected between the other terminal of the primary coil and the other terminal of the battery. The power converter includes, on the secondary side, a rectifier circuit and a smoothing circuit. The power converter configured in this manner is configured to convert the voltage input from the battery and output a predetermined target voltage from the secondary side by alternately and repeatedly executing control to turn on the cutoff switch and the drive switch and control to turn off the cutoff switch and the drive switch based on a duty ratio. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-202679 Summary of the Invention [Problem to be solved by the invention]

[0004] According to the power converter disclosed in Patent Document 1, an input voltage can be converted to a predetermined voltage by controlling each switch based on the duty ratio, but as the input voltage increases, the voltage applied to each component such as the rectifier circuit on the secondary side of the power converter also increases, so in order to output the predetermined voltage, it is necessary to construct a power converter with higher voltage tolerance.In recent years, power converters are sometimes used in systems that handle voltages with large fluctuations, and there is a demand for power converters that can output a target predetermined voltage even when such input voltage changes greatly.

[0005] The present disclosure has been made to solve the above-mentioned problems, and its purpose is to provide a power converter that can output a predetermined voltage even when the input voltage changes significantly. [Means for solving the problem]

[0006] According to an aspect of the present disclosure, there is provided a power converter including a transformer circuit that transforms an input voltage and outputs the transformed voltage as an output voltage, a rectifier circuit including a pair of output power lines and rectifying the output voltage, and a control device that controls the transformer circuit. The pair of output power lines includes a first output power line and a second output power line to which a voltage higher than that of the first output power line is applied. The transformer circuit includes: a first input power line; a second input power line to which a higher voltage than the first input power line is applied; a transformer including a primary coil connected between the first input power line and the second input power line; and a secondary coil provided between the first output power line and the second output power line; a first switch provided on one of the first input power line and the second input power line; a second switch provided on the other of the first input power line and the second input power line; a capacitor provided on the other input power line and connected to one of the terminals on both sides of the second switch opposite to the terminal connected to the primary coil; a third switch provided between the first input power line and the second input power line and connected in parallel to a first series connection consisting of the primary coil, the second switch, and the capacitor; and a fourth switch provided between a point between the primary coil and the second switch and the other of the terminals on both sides of the capacitor opposite to the terminal connected to the second switch. When the input voltage is equal to or lower than a threshold voltage, the control device alternately and repeatedly executes a first control in which the first switch and the fourth switch are turned on and the second switch and the third switch are turned off, and a second control in which the second switch and the third switch are turned on and the first switch and the fourth switch are turned off, and when the input voltage exceeds the threshold voltage, the control device alternately and repeatedly executes a third control in which the first switch and the second switch are turned on and the third switch and the fourth switch are turned off, and a fourth control in which the second switch and the third switch are turned on and the first switch and the fourth switch are turned off. [Effects of the Invention]

[0007] According to the present disclosure, the power converter controls each switch differently depending on the input voltage, thereby being able to output a predetermined voltage even when the input voltage changes greatly. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing a configuration of a vehicle according to a first embodiment. [Figure 2] 1 is a diagram showing a circuit configuration of a power converter according to a first embodiment. [Figure 3] 4 is a timing chart of a first control and a second control performed by the power converter on each switch when the input voltage is equal to or lower than a threshold voltage. [Figure 4] FIG. 4 is a diagram for explaining a current flow in the power converter when first control is executed. [Figure 5] FIG. 4 is a diagram for explaining a current flow in the power converter when second control is executed. [Figure 6] 10 is a timing chart of a third control and a fourth control performed by the power converter on each switch when the input voltage exceeds a threshold voltage. [Figure 7] FIG. 10 is a diagram for explaining the flow of current in the power converter when the third control is executed. [Figure 8] FIG. 10 is a diagram for explaining the flow of current in the power converter when fourth control is executed. [Figure 9] FIG. 10 is a diagram illustrating a circuit configuration of a power converter according to a second embodiment. [Figure 10] 4 is a timing chart of a first control and a second control performed by the power converter on each switch when the input voltage is equal to or lower than a threshold voltage. [Figure 11] FIG. 4 is a diagram for explaining a current flow in the power converter when first control is executed. [Figure 12] FIG. 4 is a diagram for explaining a current flow in the power converter when second control is executed. [Figure 13] 10 is a timing chart of a third control and a fourth control performed by the power converter on each switch when the input voltage exceeds a threshold voltage. [Figure 14] FIG. 10 is a diagram for explaining the flow of current in the power converter when the third control is executed. [Figure 15] FIG. 10 is a diagram for explaining the flow of current in the power converter when fourth control is executed. DETAILED DESCRIPTION OF THE INVENTION

[0009] <First Embodiment> A power converter 1 according to a first embodiment will be described with reference to Figures 1 to 8. In the drawings, the same or corresponding parts are given the same reference numerals, and description thereof will not be repeated. [Vehicle configuration] Fig. 1 is a diagram showing the configuration of a vehicle 300 according to embodiment 1. As shown in Fig. 1, the vehicle 300 includes a power converter 1, a battery 50, a connector 60, loads 70 and 80, a pair of relays 91, a pair of relays 92, a pair of external input power lines 150, a pair of external output power lines 250, and an ECU (Electronic Control Unit) 400.

[0010] The pair of external input power lines 150 includes an external input power line 151 and an external input power line 152 to which a higher voltage than that of the external input power line 151 is applied. The potential of the external input power line 151 is maintained at a reference potential (for example, 0 V). The pair of relays 91 includes a relay 91A connected to the external input power line 151 and a relay 91B connected to the external input power line 152. The pair of relays 92 includes a relay 92A provided on the external input power line 151 and a relay 92B provided on the external input power line 152.

[0011] One terminal of the pair of external input power lines 150 is connected to the load 70. The other terminal of the pair of external input power lines 150 is connected inside the power converter 1. A relay 92A is arranged on the path of the external input power line 151 between the load 70 and the power converter 1. A relay 92B is arranged on the path of the external input power line 152 between the load 70 and the power converter 1. The connector 60 is connected to the pair of external input power lines 150 via the pair of relays 91. The connection point between the connector 60 and the pair of external input power lines 150 is located on the power converter 1 side of the pair of relays 92.

[0012] A battery 50 is provided between an external input power line 151 and an external input power line 152. The negative electrode of the battery 50 is connected to the external input power line 151. The positive electrode of the battery 50 is connected to the external input power line 152. A node 103, to which the negative electrode of the battery 50 and the external input power line 151 are connected, is disposed on the path of the external input power line 151 between the relay 92A and the power converter 1. A node 104, to which the positive electrode of the battery 50 and the external input power line 152 are connected, is disposed on the path of the external input power line 152 between the relay 92B and the power converter 1.

[0013] The pair of external output power lines 250 includes an external output power line 251 and an external output power line 252 to which a higher voltage than that of the external output power line 251 is applied. The external output power line 251 is maintained at a reference potential (for example, 0 V). The reference potential of the external output power line 251 may be the same as or different from the reference potential of the external input power line 151, but they are insulated from each other. One terminal of the pair of external output power lines 250 is connected to the inside of the power converter 1. The other terminal of the pair of external output power lines 250 is connected to the load 80.

[0014] Power converter 1 is a DC-DC converter that, when a DC voltage is input, converts the input DC voltage to a predetermined DC voltage and outputs the converted DC voltage. Specifically, power converter 1 performs power conversion on the input voltage from battery 50 or charger 500 and outputs the predetermined DC voltage to load 80.

[0015] Battery 50 is a DC power supply configured by a chargeable and dischargeable secondary battery such as a lithium ion secondary battery, a nickel-metal hydride battery, or a lead-acid battery, and capable of outputting a DC voltage to a pair of external input power lines 150. The voltage output from battery 50 can be changed under the control of ECU 400.

[0016] Connector 60 can be connected to a connector (not shown) of a charging cable 550 extending from a charger 500 installed outside vehicle 300. When vehicle 300 is connected to charger 500 via connector 60, it can charge battery 50 using power supplied from charger 500.

[0017] The load 70 includes, for example, a traction inverter that supplies power to a motor that generates driving force for the vehicle 300. The load 80 is, for example, a group of auxiliaries, and includes an air conditioning system for the vehicle, a temperature control system for the battery 50, an auxiliary battery, or other auxiliaries, all of which are not shown.

[0018] The pair of relays 91 connect or disconnect the path between the connector 60 and the pair of external input power lines 150 under the control of the ECU 400. For example, when the pair of relays 91 are turned on, the path between the connector 60 and the pair of external input power lines 150 is connected. On the other hand, when the pair of relays 91 are turned off, the path between the connector 60 and the pair of external input power lines 150 is disconnected.

[0019] The pair of relays 92 connect or disconnect paths between the load 70 and the battery 50 and the power converter 1 under the control of the ECU 400. For example, when the pair of relays 92 are turned on, the paths between the load 70 and the battery 50 and the power converter 1 are connected. On the other hand, when the pair of relays 92 are turned off, the paths between the load 70 and the battery 50 and the power converter 1 are disconnected.

[0020] ECU 400 is a computing entity (computer) that executes predetermined processing. ECU 400 includes a processor such as a central processing unit (CPU), a micro-processing unit (MPU), a tensor processing unit (TPU), or a graphics processing unit (GPU), and a memory such as a random access memory (RAM) or a read-only memory (ROM). ECU 400 is configured so that the processor controls each component of vehicle 300 based on data such as programs and parameters stored in the memory. The processor included in ECU 400 may be interpreted as a processing circuitry. The memory included in ECU 400 may be interpreted as one or more non-transitory computer-readable media.

[0021] The ECU 400 controls the pair of relays 91, 92 and the battery 50 in the following manner according to the state of the vehicle 300.

[0022] When ECU 400 controls vehicle 300 to the running mode, it turns off a pair of relays 91 and turns on a pair of relays 92. As a result, the power output from battery 50 is input to load 70. Load 70 becomes operable using the power from battery 50. Furthermore, the power output from battery 50 is input to power converter 1. Power converter 1 converts the voltage from battery 50 to a predetermined voltage and outputs it to load 80. Load 80 becomes operable using the predetermined voltage from power converter 1. As vehicle 300 runs, the voltage of battery 50 also changes.

[0023] When controlling vehicle 300 to the charging mode, ECU 400 turns on a pair of relays 91 and turns off a pair of relays 92. Here, the voltage that can be supplied to battery 50 may vary depending on the specifications of charger 500. For example, if charger 500 can output a voltage that can charge battery 50, battery 50 can remain as is. However, if charger 500 can only output a voltage lower than the voltage of battery 50, ECU 400 charges battery 50 by, for example, switching the connection of cells in battery 50 from a series connection to a parallel connection. This makes it possible to charge battery 50 using power supplied from charger 500 via connector 60. Furthermore, even when battery 50 is being charged, if the vehicle's air conditioning system, battery temperature control system, or vehicle accessories are used, power converter 1 converts the input voltage from battery 50 or charger 500 to a predetermined voltage and outputs it to load 80.

[0024] In this way, the input voltage from battery 50 or charger 500 to power converter 1 may vary greatly. Even when the input voltage varies greatly, power converter 1 is configured to convert the input voltage to a predetermined DC voltage and output it to load 80. Note that the voltage input to power converter 1 is not limited to a fixed value, and may include values ​​that vary over time.

[0025] [Power converter configuration] Fig. 2 is a diagram showing the circuit configuration of the power converter 1 according to the first embodiment. As shown in Fig. 2, the power converter 1 includes a transformer circuit 10, a rectifier circuit 20, a smoothing circuit 30, and a control device 40. The transformer circuit 10 includes a pair of input power lines 100. The rectifier circuit 20 includes a pair of output power lines 200.

[0026] The pair of input power lines 100 includes input power line 101 and input power line 102 to which a higher voltage than that of input power line 101 is applied, and are connected to a pair of external input power lines 150. An input voltage from battery 50 or charger 500 is input to transformer circuit 10 via the pair of external input power lines 150. Input power line 101 is an example of a "first input power line" in the present disclosure. Input power line 102 is an example of a "second input power line" in the present disclosure.

[0027] The transformer circuit 10 transforms an input voltage supplied via a pair of input power lines 100 and outputs the resulting output voltage to a pair of output power lines 200. The transformer circuit 10 includes a transformer T, a switch Q1, a switch Q2, a switch Q3, a switch Q4, a capacitor C1, and a capacitor C2. The switches Q1, Q2, Q3, and Q4 are examples of the "first switch," "second switch," "third switch," and "fourth switch" of the present disclosure, respectively.

[0028] The switches Q1, Q2, Q3, and Q4 are semiconductor switches such as N-channel metal oxide semiconductor field effect transistors (MOSFETs) or insulated gate bipolar transistors (IGBTs). In the following, an example will be described in which N-channel MOSFETs are used for the switches Q1, Q2, Q3, and Q4. The switches Q1, Q2, Q3, and Q4 will also be collectively referred to simply as "switches."

[0029] Transformer T includes a primary coil L1 provided between input power line 101 and input power line 102, and a secondary coil L2 connected between output power line 201 and output power line 202.

[0030] The switch Q1 is provided on the input power line 102. Specifically, the input power line 102 connects the positive electrode of the battery 50 and one terminal of the primary coil L1 of the transformer T. The switch Q1 is provided on the path of the input power line 102 between the positive electrode of the battery 50 and one terminal of the primary coil L1 of the transformer T, and is connected in series with the primary coil L1. In this case, the input power line 102 is an example of the "one input power line" of the present disclosure. The source of the switch Q1 is connected to one terminal of the primary coil L1 and the drain of the switch Q3 via a node 112. The drain of the switch Q1 is connected to the positive electrode of the battery 50 and one terminal of the capacitor C2 via a node 115. The gate of the switch Q1 is connected to the control device 40.

[0031] Switch Q1 connects or disconnects the path between node 112 and node 115 on input power line 102 under the control of control device 40. For example, when switch Q1 is turned on, the path between node 112 and node 115 on input power line 102 is connected. On the other hand, when switch Q1 is turned off, the path between node 112 and node 115 on input power line 102 is disconnected.

[0032] The switch Q2 is provided on the input power line 101. Specifically, the input power line 101 connects the negative electrode of the battery 50 and the other terminal of the primary coil L1 of the transformer T. The switch Q2 is provided on the path of the input power line 101 between the negative electrode of the battery 50 and the other terminal of the primary coil L1 of the transformer T, and is connected in series with the primary coil L1. In this case, the input power line 101 is an example of the "other input power line" of the present disclosure. The source of the switch Q2 is connected to the other terminal of the primary coil L1 and the drain of the switch Q4 via a node 113. The drain of the switch Q2 is connected to one terminal of the capacitor C1. The gate of the switch Q2 is connected to the control device 40.

[0033] Switch Q2 connects or disconnects the path between node 113 in input power line 101 and one terminal of capacitor C1 under the control of control device 40. For example, when switch Q2 is turned on, the path between node 113 in input power line 101 and one terminal of capacitor C1 is connected. On the other hand, when switch Q2 is turned off, the path between node 113 in input power line 101 and one terminal of capacitor C1 is disconnected.

[0034] Capacitor C1 is provided on input power line 101 and connected in series with switch Q2. Specifically, one terminal of capacitor C1 is connected to the terminal (drain of switch Q2) opposite to the terminal connected to primary coil L1 of both sides of switch Q2. The other terminal of capacitor C1 is connected to the source of switch Q3 and the negative electrode of battery 50 via node 111.

[0035] The switch Q3 is provided between the input power line 101 and the input power line 102, and is connected in parallel with a series-connected structure formed by the primary coil L1, the switch Q2, and the capacitor C1. The source of the switch Q3 is connected to the other terminal of the capacitor C1 and the negative electrode of the battery 50 via a node 111. The drain of the switch Q3 is connected to the source of the switch Q1 and one terminal of the primary coil L1 via a node 112. The gate of the switch Q3 is connected to the control device 40. In this way, between the nodes 111 and 112, the switch Q3 is connected in parallel with the series-connected structure formed by the primary coil L1, the switch Q2, and the capacitor C1. The series-connected structure formed by the primary coil L1, the switch Q2, and the capacitor C1 is an example of a "first series-connected structure" in the present disclosure.

[0036] Switch Q3 connects or disconnects the path between node 111 on input power line 101 and node 112 on input power line 102 under the control of control device 40. For example, when switch Q3 is turned on, the path between node 111 on input power line 101 and node 112 on input power line 102 is connected. On the other hand, when switch Q3 is turned off, the path between node 111 on input power line 101 and node 112 on input power line 102 is disconnected.

[0037] The switch Q4 is provided between a node 113, which is a point between the other terminal of the primary coil L1 and the source of the switch Q2, and the other terminal of the capacitor C1 (the negative terminal located on the battery 50) opposite to the one terminal connected to the drain of the switch Q2. The source of the switch Q4 is connected to the other terminal of the capacitor C1 and the negative electrode of the battery 50 via a node 111. The drain of the switch Q4 is connected to the other terminal of the primary coil L1 and the drain of the switch Q2 via a node 113. The gate of the switch Q4 is connected to the control device 40. In this way, the switch Q4 is connected in parallel with the series connection formed by the switch Q2 and the capacitor C1 between the node 111 and the node 113.

[0038] The switch Q4 connects or disconnects a path between the node 111 and the node 113 that is different from the path through which the switch Q2 is provided, under the control of the control device 40. For example, when the switch Q4 is turned on, the path between the node 111 and the node 113 that is different from the path through which the switch Q2 is provided is connected. On the other hand, when the switch Q4 is turned off, the path between the node 111 and the node 113 that is different from the path through which the switch Q2 is provided is disconnected.

[0039] Capacitor C2 is provided between input power line 101 and input power line 102. Specifically, one terminal of capacitor C2 is connected to the drain of switch Q1 and the positive terminal of battery 50 via node 115. The other terminal of capacitor C2 is connected to node 111 and the negative terminal of battery 50 via node 114.

[0040] The pair of output power lines 200 includes output power line 201 and output power line 202 to which a higher voltage than that of output power line 201 is applied. Output power line 201 is an example of a "first output power line" in the present disclosure. Output power line 202 is an example of a "second output power line" in the present disclosure. One terminal of the secondary coil of transformer T is connected to load 80 via output power line 202. The other terminal of the secondary coil of transformer T is connected to load 80 via output power line 201. The output voltage from transformer circuit 10 is rectified by rectifier circuit 20, smoothed by smoothing circuit 30, and then input to load 80.

[0041] The rectifier circuit 20 rectifies the output voltage from the transformer circuit 10. The rectifier circuit 20 includes a diode D1 and a diode D2. The diode D1 is an example of a "first diode" in the present disclosure. The diode D2 is an example of a "second diode" in the present disclosure.

[0042] Diode D1 is provided on output power line 201. The anode of diode D1 is connected to the anode of diode D2 and load 80 via node 211. The cathode of diode D1 is connected to the other terminal of secondary coil L2.

[0043] The diode D1 may be provided on the output power line 202. In this case, the anode of the diode D1 is connected to one terminal of the secondary coil L2. The cathode of the diode D1 is connected to the cathode of the diode D2 and the coil L3 of the smoothing circuit 30 via the node 212.

[0044] Diode D2 is provided between output power line 201 and output power line 202, and is connected in parallel with a series connection formed by secondary coil L2 and diode D1. The anode of diode D2 is connected to the anode of diode D1 in output power line 201 and load 80 via node 211. The cathode of diode D2 is connected to one terminal of secondary coil L2 and smoothing circuit 30 via node 212. In this way, between node 211 and node 212, diode D2 is connected in parallel with the series connection formed by secondary coil L2 and diode D1. The series connection formed by secondary coil L2 and diode D1 is an example of a "second series connection" in the present disclosure.

[0045] The smoothing circuit 30 smoothes the output voltage rectified by the rectifier circuit 20. The smoothing circuit 30 includes a capacitor C3 and a coil L3.

[0046] Capacitor C3 is connected in parallel with the series connection formed by secondary coil L2 and diode D1, and with diode D2, via coil L3. One terminal of capacitor C3 is connected to load 80 via node 311. The other terminal of capacitor C3 is connected to coil L3 and load 80 via node 312. In this way, between nodes 311 and 312, capacitor C3 is connected in parallel with the series connection formed by secondary coil L2 and diode D1, and with diode D2.

[0047] One terminal of the coil L3 is connected to one terminal of the secondary coil L2 and the cathode of the diode D2 via a node 212. The other terminal of the coil L3 is connected to the other terminal of the capacitor C3 and the load 80 via a node 312. The coil L3 may be provided on the output power line 201 side. In this case, one terminal of the coil L3 is connected to the anode of the diode D1 and the anode of the diode D2 via a node 211. The other terminal of the coil L3 is connected to one terminal of the capacitor C3 and the load 80 via a node 311.

[0048] The control device 40 is a computing entity (computer) that executes predetermined processing. The control device 40 includes, for example, a processor such as a CPU, an MPU, a TPU, or a GPU, and a memory such as a RAM or a ROM. The control device 40 is configured so that the processor controls each component of the power converter 1 based on data such as programs and parameters stored in the memory. The processor included in the control device 40 may be interpreted as a processing circuitry. The memory included in the control device 40 may be interpreted as one or more non-transitory computer-readable media.

[0049] [Switching control by control device] In the power converter 1 configured as described above, the control device 40 controls each switch based on the duty ratio to transform the input voltage applied to the pair of input power lines 100 and supply a predetermined DC voltage to the load 80. The duty ratio indicates the proportion of the period during which a switch is on in one cycle when the switch is periodically turned on and off. Specifically, the duty ratio used in the power converter 1 indicates the proportion of the period during which the switch Q1 is on in one cycle.

[0050] 3 is a timing chart of the first control and the second control for each switch executed by the power converter 1 when the input voltage is equal to or lower than the threshold voltage. In FIG. 3, the period of one cycle of the switching control is indicated by "T", and the duty ratio is indicated by "D".

[0051] As shown in Fig. 3, the control device 40 alternately executes the first control and the second control based on the duty ratio. In one cycle, the first control and the second control are each executed once. The period during which the first control is executed and the period during which the second control is executed within one cycle are determined based on the duty ratio. For example, the period during which the first control is executed within one cycle is calculated by multiplying the period (T) of one cycle by the duty ratio (D).

[0052] The first control is a control to turn on the switches Q1 and Q4 and turn off the switches Q2 and Q3, and is a control to excite the transformer T. The second control is a control to turn on the switches Q2 and Q3 and turn off the switches Q1 and Q4, and is a control to reset the energy stored in the transformer T.

[0053] For example, in the example shown in FIG. 3, the period from timing t1 to timing t5 is defined as one cycle. At timing t1, the control device 40 switches the switches Q1 and Q4 from off to on. Thereafter, at timing t2, the control device 40 switches the switches Q1 and Q4 from on to off. As a result, during the period from timing t1 to timing t2, the switches Q1 and Q4 are in the on state, and the switches Q2 and Q3 are in the off state. In this way, the control device 40 executes the first control of turning on the switches Q1 and Q4 and turning off the switches Q2 and Q3 during the period from timing t1 to timing t2.

[0054] At timing t3, the control device 40 switches the switches Q2 and Q3 from off to on. Thereafter, at timing t4, the control device 40 switches the switches Q2 and Q3 from on to off. As a result, during the period from timing t3 to timing t4, the switches Q2 and Q3 are in the on state, and the switches Q1 and Q4 are in the off state. In this way, the control device 40 executes the second control of turning on the switches Q2 and Q3 and turning off the switches Q1 and Q4 during the period from timing t3 to timing t4.

[0055] At timing t5, the control device 40 switches the switches Q1 and Q4 from off to on again.

[0056] In this way, the control device 40 performs the first control once and the second control once in one cycle spanning timing t1 to timing t5. Furthermore, as described above, the control device 40 determines the period during which the first control is performed in one cycle and the period during which the second control is performed in one cycle based on the duty ratio. By repeatedly performing such cycles, the control device 40 can transform the input voltage into a predetermined DC voltage using the power converter 1.

[0057] Fig. 4 is a diagram for explaining the flow of current in the power converter 1 when the first control is executed. As shown in Fig. 4, when the first control is executed by the control device 40, the switches Q1 and Q4 are turned on, and the switches Q2 and Q3 are turned off.

[0058] On the primary side of the power converter 1, current flows from the battery 50 through the switch Q1, the primary coil L1 of the transformer T, and the switch Q4, and then returns to the battery 50.

[0059] On the secondary side of the power converter 1, electromagnetic induction caused by current flowing through the primary coil L1 of the transformer T causes current to flow in the secondary coil L2 of the transformer T. The current from the secondary coil L2 of the transformer T flows through the coil L3, capacitor C3, and diode D1, and then returns to the secondary coil L2.

[0060] Fig. 5 is a diagram for explaining the flow of current in the power converter 1 when the second control is executed. As shown in Fig. 5, when the second control is executed by the control device 40, the switches Q2 and Q3 are turned on, and the switches Q1 and Q4 are turned off.

[0061] On the primary side of the power converter 1, current flows from capacitor C1 through switch Q2, primary coil L1 of transformer T, and switch Q3, before returning to capacitor C1. In this way, the current from capacitor C1 flows through primary coil L1 of transformer T from the input power line 101 side toward the input power line 102 side, thereby resetting the energy stored in primary coil L1 by the first control. This process of resetting the energy stored in primary coil L1 of transformer T is also called "transformer reset."

[0062] On the secondary side of the power converter 1, the energy stored in the coil L3 causes a current to flow from the coil L3 through the capacitor C3 and the diode D2, and back to the coil L3.

[0063] The control device 40 can use the power converter 1 to transform the input voltage into a predetermined DC voltage and output it to the load 80 by alternately and periodically repeating the first control and the second control as shown in Figures 3 to 5 based on the duty ratio.

[0064] Here, during execution of the first control shown in FIG. 4, the voltage V1 (voltage across the primary coil L1) on the input power line 102 side of the primary coil L1 of the transformer T is expressed by the following equation (1).

number

[0065] In equation (1), “Vin” is the input voltage input to the power converter 1 from the battery 50 or the charger 500.

[0066] Therefore, during execution of the first control, the voltage V2 (voltage across the secondary coil L2) on the output power line 202 side of the secondary coil L2 of the transformer T is expressed by the following equation (2).

number

[0067] In equation (2), "N" is the turn ratio between the primary coil L1 and the secondary coil L2 in the transformer T. The DC voltage Vout output from the power converter 1 to the load 80 is expressed by the following equation (3).

number

[0068] In this way, on the secondary side of power converter 1, during execution of the first control, voltage V2 obtained by dividing input voltage Vin by number of turns N is applied to output power line 202. Meanwhile, diode D2 is provided in the path between output power line 201 and output power line 202, and the forward characteristics of diode D2 prevent current from flowing in the path between output power line 201 and output power line 202.

[0069] Here, when the input voltage from battery 50 or charger 500 increases, voltage V2 on the cathode side of diode D2 also increases. For example, when vehicle 300 on which power converter 1 is mounted is in charging mode and the cells in battery 50 are connected in parallel, the input voltage from battery 50 or charger 500 may change to twice the input voltage from battery 50 or charger 500 when vehicle 300 is in driving mode or when the cells in battery 50 are connected in series even when vehicle 300 is in charging mode. According to equation (2) above, when input voltage Vin from battery 50 doubles, voltage V2 on the cathode side of diode D2 also doubles.

[0070] If the voltage on the cathode side of the diode D2 rises and exceeds the breakdown voltage of the diode D2, the diode D2 will be damaged and it will not be possible to obtain a DC voltage of the specified voltage.

[0071] Considering the possibility of a large input voltage, diode D2 with high voltage resistance is required, but there are limitations on the selection of elements and costs increase.

[0072] Therefore, the power converter 1 of the present disclosure performs switching control as shown in Figures 3 to 5 when the input voltage is equal to or lower than a predetermined threshold voltage, and performs switching control as shown in Figures 6 to 8 described below when the input voltage exceeds the predetermined threshold voltage. Note that the threshold voltage is a voltage value according to the breakdown voltage of the diode D2.

[0073] 6 is a timing chart of the third control and the fourth control for each switch executed by the power converter 1 when the input voltage exceeds the threshold voltage. In FIG. 6, the period of one cycle of the switching control is indicated by "T", and the duty ratio is indicated by "D".

[0074] As shown in Fig. 6, the control device 40 alternately executes the third control and the fourth control based on the duty ratio. In one cycle, the third control and the fourth control are each executed once. The period during one cycle during which the third control is executed and the period during which the fourth control is executed are determined based on the duty ratio. For example, the period during which the third control is executed in one cycle is calculated by multiplying the period (T) of one cycle by the duty ratio (D).

[0075] The third control is a control for turning on the switches Q1 and Q2 and turning off the switches Q3 and Q4, and is a control for exciting the transformer T. The fourth control is a control for turning on the switches Q2 and Q3 and turning off the switches Q1 and Q4, and is a control for resetting the energy stored in the transformer T.

[0076] For example, in the example shown in FIG. 6, the period from timing t11 to timing t15 is defined as one cycle. The control device 40 keeps the switch Q2 always on and keeps the switch Q4 always off. At timing t11, the control device 40 switches the switch Q1 from off to on. Thereafter, at timing t12, the control device 40 switches the switch Q1 from on to off. As a result, during the period from timing t11 to timing t12, the switches Q1 and Q2 are in the on state, and the switches Q3 and Q4 are in the off state. In this way, the control device 40 executes the third control of keeping the switches Q1 and Q2 on and the switches Q3 and Q4 off during the period from timing t1 to timing t2.

[0077] At timing t13, the control device 40 switches the switch Q3 from off to on. Thereafter, at timing t14, the control device 40 switches the switch Q3 from on to off. As a result, during the period from timing t13 to timing t14, the switches Q2 and Q3 are in the on state, and the switches Q1 and Q4 are in the off state. In this way, the control device 40 executes the fourth control of turning on the switches Q2 and Q3 and turning off the switches Q1 and Q4 during the period from timing t13 to timing t14.

[0078] Thereafter, at timing t15, the control device 40 switches the switch Q1 from OFF to ON again.

[0079] In this way, the control device 40 performs the third control once and the fourth control once in one cycle spanning from timing t11 to timing t15. Furthermore, as described above, the control device 40 determines the period during which the third control is performed in one cycle and the period during which the fourth control is performed in one cycle based on the duty ratio. By repeatedly performing such cycles, the control device 40 can transform the input voltage to a predetermined voltage using the power converter 1.

[0080] 7 is a diagram for explaining the flow of current in the power converter 1 when the third control is executed. As shown in FIG. 7, when the third control is executed by the control device 40, the switches Q1 and Q2 are turned on, and the switches Q3 and Q4 are turned off.

[0081] On the primary side of the power converter 1, current flows from the battery 50 through the switch Q1, the primary coil L1 of the transformer T, the switch Q2, and the capacitor C1, and then returns to the battery 50.

[0082] On the secondary side of the power converter 1, electromagnetic induction caused by current flowing through the primary coil L1 of the transformer T causes current to flow in the secondary coil L2 of the transformer T. The current from the secondary coil L2 of the transformer T flows through the coil L3, capacitor C3, and diode D1, and then returns to the secondary coil L2.

[0083] Fig. 8 is a diagram for explaining the flow of current in the power converter 1 when the fourth control is executed. As shown in Fig. 8, when the fourth control is executed by the control device 40, the switches Q2 and Q3 are turned on, and the switches Q1 and Q4 are turned off.

[0084] On the primary side of power converter 1, current flows from capacitor C1 through switch Q2, primary coil L1 of transformer T, and switch Q3, before returning to capacitor C1. In this way, the current from capacitor C1 flows through primary coil L1 of transformer T from the input power line 101 side toward the input power line 102 side, thereby resetting the energy stored in primary coil L1 by the first control.

[0085] On the secondary side of the power converter 1, the energy stored in the coil L3 causes a current to flow from the coil L3 through the capacitor C3 and the diode D2, and back to the coil L3.

[0086] The control device 40 can use the power converter 1 to transform the input voltage to a predetermined voltage and output it to the load 80 by alternately and periodically repeating the third control and the fourth control as shown in Figures 6 to 8 based on the duty ratio.

[0087] Here, during execution of the third control shown in FIG. 7, the voltage Vc across the capacitor C1 is expressed by the following equation (4).

number

[0088] In equation (4), "D" is the duty ratio.

[0089] Therefore, during execution of the third control, the voltage V1' (voltage across the primary coil L1) on the input power line 102 side of the primary coil L1 of the transformer T is expressed by the following equation (5).

number

[0090] Therefore, during execution of the third control, the voltage V2' (voltage across the secondary coil L2) on the output power line 202 side of the secondary coil L2 of the transformer T is expressed by the following equation (6).

number

[0091] The DC voltage Vout output from the power converter 1 to the load 80 is expressed by the following equation (7).

number

[0092] Thus, on the secondary side of the power converter 1, during execution of the third control, a voltage V2' obtained by dividing the voltage V1' by the number of turns N is applied to the cathode side of the diode D2 in the output power line 202. Here, as shown in equation (5), voltage V1' is a value obtained by multiplying the input voltage Vin by a value (1-D) that is less than 1. That is, as can be seen from a comparison of equations (2) and (6), voltage V2' on the cathode side of diode D2 when the third control is executed can be less affected by input voltage Vin than voltage V2 on the cathode side of diode D2 when the first control is executed.

[0093] For example, when the input voltage Vin from the battery 50 doubles, the voltage V2 on the cathode side of the diode D2 doubles when the first control is executed, but the voltage V2' on the cathode side of the diode D2 does not double when the third control is executed because it is multiplied by a value less than 1 (1-D).

[0094] The control device 40 is configured to determine the magnitude or range of the input voltage using information from a monitoring unit that monitors the input voltage from the battery 50 or the charger 500, information about the series / parallel connection of the cells in the battery 50, information from a voltage sensor (not shown) provided on the input power line 101, or connection information of the connector 60 (information about the charger 500) obtained from the ECU 400, and to alternately and repeatedly execute first control and second control based on the duty ratio if the input voltage is equal to or less than a threshold voltage, and to alternately and repeatedly execute third control and fourth control based on the duty ratio if the input voltage exceeds the threshold voltage. In other words, the control device 40 may determine whether the input voltage is equal to or less than the threshold voltage or exceeds the threshold voltage based on an expected voltage range rather than a specific voltage value.

[0095] In this way, when the input voltage exceeds a predetermined threshold voltage, the control device 40 alternately executes the third control and the fourth control based on the duty ratio, thereby reducing the voltage on the cathode side of the diode D2 relative to the input voltage. This allows the power converter 1 to suppress the application of a voltage that exceeds the breakdown voltage of the diode D2 even if the input voltage changes significantly, and to output a predetermined voltage.

[0096] <Embodiment 2> A power converter 1A according to the second embodiment will be described with reference to Figures 9 to 15. Note that in the power converter 1A according to the second embodiment, only the parts that are different from the power converter 1 according to the first embodiment will be described, and the description of the parts that are the same as those of the power converter 1 may be omitted.

[0097] [Power converter configuration] Fig. 9 is a diagram showing a circuit configuration of a power converter 1A according to embodiment 2. As shown in Fig. 9, the power converter 1A includes a transformer circuit 10A instead of the transformer circuit 10 in the power converter 1. Furthermore, the power converter 1A includes a rectifier circuit 20A instead of the rectifier circuit 20 in the power converter 1.

[0098] Transformer circuit 10A includes a switch Q11 provided on input power line 101, instead of switch Q1 provided on input power line 102 in transformer circuit 10. Furthermore, transformer circuit 10A includes switches Q12 and Q14 connected to input power line 102, instead of switches Q2 and Q4 connected to input power line 101 in transformer circuit 10. Note that switch Q13 of transformer circuit 10A is provided between input power line 101 and input power line 102, similar to switch Q3 of transformer circuit 10. Below, an example will be described in which N-channel MOSFETs are used for switches Q11, Q12, Q13, and Q14.

[0099] The switch Q11 is provided on the path of the input power line 101. Specifically, the input power line 101 connects the negative electrode of the battery 50 to a node 119, which is the other terminal of the primary coil L1 of the transformer T. The switch Q11 is provided on the path of the input power line 101 between the negative electrode of the battery 50 and the other terminal of the primary coil L1 of the transformer T, and is connected in series with the primary coil L1. In this case, the input power line 101 is an example of the “one input power line” of the present disclosure. The drain of the switch Q11 is connected to the other terminal of the primary coil L1 and the source of the switch Q13 via a node 116. The source of the switch Q11 is connected to the negative electrode of the battery 50 and the other terminal of the capacitor C2 via a node 114. The gate of the switch Q11 is connected to the control device 40.

[0100] Switch Q11 connects or disconnects the path between node 114 and node 116 on input power line 101 under the control of control device 40. For example, when switch Q11 is turned on, the path between node 114 and node 116 on input power line 101 is connected. On the other hand, when switch Q11 is turned off, the path between node 114 and node 116 on input power line 101 is disconnected.

[0101] The switch Q12 is provided on the input power line 102. Specifically, the input power line 102 connects the positive electrode of the battery 50 and one terminal of the primary coil L1 of the transformer T. The switch Q12 is provided on the path of the input power line 102 between the positive electrode of the battery 50 and one terminal of the primary coil L1 of the transformer T, and is connected in series with the primary coil L1. In this case, the input power line 102 is an example of the "other input power line" of the present disclosure. The drain of the switch Q12 is connected to one terminal of the primary coil L1 and the source of the switch Q14 via a node 120. The source of the switch Q12 is connected to one terminal of the capacitor C11. The gate of the switch Q12 is connected to the control device 40.

[0102] Switch Q12 connects or disconnects a path between node 120 in input power line 102 and one terminal of capacitor C11 under the control of control device 40. For example, when switch Q12 is turned on, the path between node 120 in input power line 102 and one terminal of capacitor C11 is connected. On the other hand, when switch Q12 is turned off, the path between node 120 in input power line 102 and one terminal of capacitor C1 is disconnected.

[0103] Capacitor C11 is provided on input power line 102 and connected in series with switch Q12. Specifically, one terminal of capacitor C11 is connected to the terminal (the source of switch Q2) opposite to the terminal connected to primary coil L1 of switch Q12. The other terminal of capacitor C11 is connected to the drain of switch Q13 and the positive electrode of battery 50 via nodes 117 and 118.

[0104] Switch Q13 is provided between input power line 101 and input power line 102, and is connected in parallel with a series connection formed by primary coil L1, switch Q12, and capacitor C11. The drain of switch Q13 is connected to input power line 102 via node 117. The source of switch Q13 is connected to the drain of switch Q11 and the other terminal of primary coil L1 via node 116. The gate of switch Q13 is connected to control device 40. In this way, between nodes 116 and 117, switch Q13 is connected in parallel with the series connection formed by primary coil L1, switch Q12, and capacitor C11. The series connection formed by primary coil L1, switch Q12, and capacitor C11 is an example of a "first series connection" in the present disclosure.

[0105] Switch Q13 connects or disconnects the path between node 116 on input power line 101 and node 117 on input power line 102 under the control of control device 40. For example, when switch Q13 is turned on, the path between node 116 on input power line 101 and node 117 on input power line 102 is connected. On the other hand, when switch Q13 is turned off, the path between node 116 on input power line 101 and node 117 on input power line 102 is disconnected.

[0106] The switch Q14 is provided between a node 120, which is a point between the primary coil L1 and the switch Q12, and the other terminal of the capacitor C11 opposite to the terminal connected to the switch Q12 (the positive terminal of the battery 50). The drain of the switch Q14 is connected to the other terminal of the capacitor C11 and the positive electrode of the battery 50 via a node 118. The source of the switch Q14 is connected to one terminal of the primary coil L1 and the drain of the switch Q12 via a node 120. The gate of the switch Q14 is connected to the control device 40. In this way, the switch Q14 is connected in parallel with the series connection formed by the switch Q12 and the capacitor C11 between the node 118 and the node 120.

[0107] Switch Q14 connects or disconnects a path between node 118 and node 120 that is different from the path through which switch Q12 is provided, under the control of control device 40. For example, when switch Q14 is turned on, a path between node 118 and node 120 that is different from the path through which switch Q12 is provided is connected. On the other hand, when switch Q14 is turned off, a path between node 118 and node 120 that is different from the path through which switch Q12 is provided is disconnected.

[0108] The rectifier circuit 20A includes a switch Q15 and a switch Q16. The switch Q15 is an example of a "fifth switch" in the present disclosure. The switch Q16 is an example of a "sixth switch" in the present disclosure.

[0109] The switch Q15 is provided on the output power line 201. The source of the switch Q15 is connected to the source of the switch Q16 and the load 80 via a node 211. The drain of the switch Q15 is connected to the other terminal of the secondary coil L2. The gate of the switch Q15 is connected to the control device 40.

[0110] Switch Q15 may be provided on output power line 202. In this case, the source of switch Q15 is connected to one terminal of secondary coil L2. The drain of switch Q15 is connected to the drain of switch Q16 and coil L3 of smoothing circuit 30 via node 212.

[0111] Switch Q16 is provided between output power line 201 and output power line 202, and is connected in parallel with a series connection formed by secondary coil L2 and switch Q15. The source of switch Q16 is connected to the source of switch Q15 on output power line 201 and load 80 via node 211. The drain of switch Q16 is connected to one terminal of secondary coil L2 and smoothing circuit 30 via node 212. In this way, between nodes 211 and 212, switch Q16 is connected in parallel with the series connection formed by secondary coil L2 and switch Q15. The series connection formed by secondary coil L2 and switch Q15 is an example of a "third series connection" in the present disclosure.

[0112] [Switching control by control device] In the power converter 1A configured as described above, the control device 40 controls each switch based on the duty ratio, thereby transforming the input voltage applied to the pair of input power lines 100 and supplying a DC voltage to the load 80.

[0113] FIG. 10 is a timing chart of the first control and the second control for each switch executed by the power converter 1A when the input voltage is equal to or lower than the threshold voltage. As shown in FIG. 10, when the input voltage is equal to or lower than the threshold voltage, the control device 40 alternately executes the first control and the second control based on the duty ratio. In one cycle, the first control and the second control are each executed once. The period during which the first control is executed and the period during which the second control is executed within one cycle are determined based on the duty ratio. The duty ratio used in the power converter 1A indicates the proportion of the period during which the switch Q11 is on within one cycle.

[0114] The first control is a control that turns on switches Q11, Q14, and Q15 and turns off switches Q12, Q13, and Q16, and is a control that excites the transformer T. The second control is a control that turns on switches Q12, Q13, and Q16 and turns off switches Q11, Q14, and Q15, and is a control that resets the energy stored in the transformer T.

[0115] For example, in the example shown in FIG. 10, the period from timing t21 to timing t25 is defined as one cycle. At timing t21, the control device 40 switches the switches Q11, Q14, and Q15 from off to on. Thereafter, at timing t22, the control device 40 switches the switches Q11, Q14, and Q15 from on to off. As a result, during the period from timing t21 to timing t22, the switches Q11, Q14, and Q15 are in the on state, and the switches Q12, Q13, and Q16 are in the off state. In this way, during the period from timing t21 to timing t22, the control device 40 executes the first control of turning on the switches Q11, Q14, and Q15 and turning off the switches Q12, Q13, and Q16.

[0116] At timing t23, the control device 40 switches the switches Q12, Q13, and Q16 from off to on. Thereafter, at timing t24, the control device 40 switches the switches Q12, Q13, and Q16 from on to off. As a result, during the period from timing t23 to timing t24, the switches Q12, Q13, and Q16 are in the on state, and the switches Q11, Q14, and Q15 are in the off state. In this way, during the period from timing t23 to timing t24, the control device 40 executes second control to turn on the switches Q12, Q13, and Q16 and turn off the switches Q11, Q14, and Q15.

[0117] At timing t25, the control device 40 switches the switches Q11, Q4, and Q15 from OFF to ON again.

[0118] In this way, the control device 40 performs the first control once and the second control once in one cycle spanning from timing t21 to timing t25. Furthermore, the control device 40 determines the period during which the first control is performed in one cycle and the period during which the second control is performed in one cycle based on the duty ratio. By repeatedly performing such cycles, the control device 40 can transform the input voltage to a predetermined voltage using the power converter 1A.

[0119] Fig. 11 is a diagram for explaining the flow of current in the power converter 1A when the first control is executed. As shown in Fig. 11, when the first control is executed by the control device 40, the switches Q11, Q14, and Q15 are turned on, and the switches Q12, Q13, and Q16 are turned off.

[0120] On the primary side of the power converter 1A, current flows from the battery 50 through the switch Q14, the primary coil L1 of the transformer T, and the switch Q11, and returns to the battery 50 again.

[0121] On the secondary side of the power converter 1A, current flows in the secondary coil L2 of the transformer T due to electromagnetic induction caused by current flowing through the primary coil L1 of the transformer T. The current from the secondary coil L2 of the transformer T flows through the coil L3, capacitor C3, and switch Q15, and then returns to the secondary coil L2.

[0122] Fig. 12 is a diagram for explaining the flow of current in the power converter 1A when the second control is executed. As shown in Fig. 12, when the second control is executed by the control device 40, the switches Q12, Q13, and Q16 are turned on, and the switches Q11, Q14, and Q15 are turned off.

[0123] On the primary side of power converter 1A, current flows from capacitor C11 through switch Q13, primary coil L1 of transformer T, and switch Q12, before returning to capacitor C11. In this way, current from capacitor C11 flows through primary coil L1 of transformer T from the input power line 102 side toward the input power line 101 side, thereby resetting the energy stored in primary coil L1 by the first control.

[0124] On the secondary side of the power converter 1A, the energy stored in the coil L3 causes a current to flow from the coil L3 through the capacitor C3 and the switch Q16, and back to the coil L3.

[0125] The control device 40 can use the power converter 1A to transform the input voltage to a predetermined voltage and output it to the load 80 by alternately and periodically repeating the first control and the second control as shown in Figures 10 to 12 based on the duty ratio.

[0126] Here, during execution of the first control shown in FIG. 11, switch Q16 is controlled to the off state, so that no current flows in the path between node 211 of output power line 201 and node 212 of output power line 202.

[0127] However, when the input voltage Vin from battery 50 changes and increases, the voltage on the drain side of switch Q16 also increases. For this reason, switch Q16 needs to have a voltage tolerance that prevents current from flowing from node 212 of output power line 202 to node 211 of output power line 201 even when the input voltage changes significantly.

[0128] Therefore, the power converter 1A of the present disclosure performs switching control as shown in Figures 10 to 12 when the input voltage is equal to or lower than a predetermined threshold voltage, and performs switching control as shown in Figures 13 to 15 when the input voltage exceeds the predetermined threshold voltage. Note that the threshold voltage is a voltage value within a range in which no current flows through the switch Q16 that is controlled to the off state.

[0129] 13 is a timing chart of the third control and the fourth control for each switch executed by the power converter 1A when the input voltage exceeds the threshold voltage. As shown in FIG. 13, when the input voltage exceeds the threshold voltage, the control device 40 alternately executes the third control and the fourth control based on the duty ratio. In one cycle, the third control and the fourth control are each executed once. The period during which the third control is executed and the period during which the fourth control is executed within one cycle are determined based on the duty ratio.

[0130] The third control is a control for turning on switches Q11, Q12, and Q15 and turning off switches Q13, Q14, and Q16, and is a control for exciting the transformer T. The fourth control is a control for turning on switches Q12, Q13, and Q16 and turning off switches Q11, Q14, and Q15, and is a control for resetting the energy stored in the transformer T.

[0131] For example, in the example shown in FIG. 13, the period from timing t31 to timing t35 is defined as one cycle. The control device 40 keeps the switch Q12 always on and keeps the switch Q14 always off. At timing t31, the control device 40 switches the switches Q11 and Q15 from off to on. Thereafter, at timing t32, the control device 40 switches the switches Q11 and Q15 from on to off. As a result, during the period from timing t31 to timing t32, the switches Q11, Q12, and Q15 are in the on state, and the switches Q13, Q14, and Q16 are in the off state. In this way, during the period from timing t31 to timing t32, the control device 40 executes the third control of keeping the switches Q11, Q12, and Q15 on and keeping the switches Q13, Q14, and Q16 off.

[0132] At timing t33, the control device 40 switches the switches Q13 and Q16 from off to on. Thereafter, at timing t34, the control device 40 switches the switches Q13 and Q16 from on to off. As a result, during the period from timing t33 ​​to timing t34, the switches Q12, Q13, and Q16 are in the on state, and the switches Q11, Q14, and Q15 are in the off state. In this way, during the period from timing t33 ​​to timing t34, the control device 40 executes the fourth control of turning on the switches Q12, Q13, and Q16 and turning off the switches Q11, Q14, and Q15.

[0133] Thereafter, at timing t35, the control device 40 switches the switches Q11 and Q15 from OFF to ON again.

[0134] In this way, the control device 40 performs the third control once and the fourth control once in one cycle spanning from timing t31 to timing t35. Furthermore, as described above, the control device 40 determines the period during which the third control is performed in one cycle and the period during which the fourth control is performed in one cycle based on the duty ratio. By repeatedly performing such cycles, the control device 40 can transform the input voltage to a predetermined voltage using the power converter 1A.

[0135] Fig. 14 is a diagram for explaining the flow of current in the power converter 1A when the third control is executed. As shown in Fig. 14, when the third control is executed by the control device 40, the switches Q11, Q12, and Q15 are turned on, and the switches Q13, Q14, and Q16 are turned off.

[0136] On the primary side of the power converter 1A, current flows from the battery 50 through the capacitor C11, the switch Q12, the primary coil L1 of the transformer T, and the switch Q11, and then returns to the battery 50.

[0137] On the secondary side of the power converter 1A, current flows in the secondary coil L2 of the transformer T due to electromagnetic induction caused by current flowing through the primary coil L1 of the transformer T. The current from the secondary coil L2 of the transformer T flows through the coil L3, capacitor C3, and switch Q15, and then returns to the secondary coil L2.

[0138] Fig. 15 is a diagram for explaining the current flow in the power converter 1A when the fourth control is executed. As shown in Fig. 15, when the fourth control is executed by the control device 40, the switches Q12, Q13, and Q16 are turned on, and the switches Q11, Q14, and Q15 are turned off.

[0139] On the primary side of power converter 1A, current from capacitor C11 flows through switch Q13, primary coil L1 of transformer T, and switch Q12, before returning to capacitor C11. In this way, the current from capacitor C11 flows through primary coil L1 of transformer T from the input power line 101 side toward the input power line 102 side, thereby resetting the energy stored in primary coil L1 by the first control.

[0140] On the secondary side of the power converter 1A, the energy stored in the coil L3 causes a current to flow from the coil L3 through the capacitor C3 and the switch Q16, and back to the coil L3.

[0141] When the input voltage exceeds the threshold voltage, the control device 40 can transform the input voltage to a predetermined voltage using the power converter 1A and output it to the load 80 by alternately and periodically repeating the third control and the fourth control as shown in Figures 13 to 15 based on the duty ratio.

[0142] Here, similarly to the power converter 1 according to the first embodiment, when the power converter 1A executes the third control, during execution of the third control, the voltage V1' across the primary coil L1 is obtained by multiplying the input voltage Vin by a value (1-D) that is less than 1. Therefore, the voltage V2' on the drain side of the switch Q16 when the third control is executed can be less affected by the input voltage Vin than the voltage V2 on the drain side of the switch Q16 when the first control is executed.

[0143] In this way, when the input voltage exceeds a predetermined threshold voltage, control device 40 alternately executes the third control and the fourth control based on the duty ratio, thereby reducing the voltage on the drain side of switch Q16 relative to the input voltage. This prevents application of a voltage exceeding the withstand voltage of switch Q16 to power converter 1A, even if the input voltage changes significantly, and allows power converter 1A to output a predetermined voltage.

[0144] Note that even if the secondary-side circuit of the power converter 1 according to the first embodiment shown in Figures 2 to 8 is replaced with the secondary-side circuit of the power converter 1A according to the second embodiment shown in Figures 9 to 15, the power converter 1 will still produce the same effects. Also, even if the secondary-side circuit of the power converter 1A according to the second embodiment shown in Figures 9 to 15 is replaced with the secondary-side circuit of the power converter 1 according to the first embodiment shown in Figures 2 to 8, the power converter 1A will still produce the same effects.

[0145] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0146] 1,1A power converter, 10,10A transformer circuit, 20,20A rectifier circuit, 30 smoothing circuit, 40 control device, 50 battery, 60 connector, 70,80 load, 91,91A,91B,92,92A,92B relay, 100,101,102 input power line, 150,151,152 external input power line, 103,104,111,112,113,114,115,116,117,118,119,120,211,212,311,312 node, 200,201,202 output power line, 250,251,252 external output power line, 300 vehicle, 500 charger, 550 Charging cable, C1, C2, C3, C11, C21 capacitors, D1, D2 diodes, L1 primary coil, L2 secondary coil, L3 coil, Q1, Q2, Q3, Q4, Q11, Q12, Q13, Q14, Q15, Q16 switches, T transformer.

Claims

1. a transformer circuit that transforms an input voltage and outputs it as an output voltage; a rectifier circuit including a pair of output power lines and configured to rectify the output voltage; a control device for controlling the transformer circuit, the pair of output power lines includes a first output power line and a second output power line to which a voltage higher than that of the first output power line is applied, The transformer circuit includes: a pair of input power lines including a first input power line and a second input power line to which a voltage higher than that of the first input power line is applied, the input voltage being applied; a transformer including a primary coil provided between the first input power line and the second input power line, and a secondary coil connected between the first output power line and the second output power line; a first switch provided on one of the first input power line and the second input power line; a second switch provided on the other of the first input power line and the second input power line; a capacitor provided on the other input power line and connected to one of the terminals on both sides of the second switch opposite to the terminal connected to the primary coil; a third switch provided between the first input power line and the second input power line and connected in parallel with a first series connection constituted by the primary coil, the second switch, and the capacitor; a fourth switch provided between a point between the primary coil and the second switch and one of the terminals on both sides of the capacitor opposite to the terminal connected to the second switch, The control device when the input voltage is equal to or lower than a threshold voltage, alternately and repeatedly executing a first control of turning on the first switch and the fourth switch and turning off the second switch and the third switch, and a second control of turning on the second switch and the third switch and turning off the first switch and the fourth switch; a third control for turning on the first switch and the second switch and turning off the third switch and the fourth switch, and a fourth control for turning on the second switch and the third switch and turning off the first switch and the fourth switch, when the input voltage exceeds the threshold voltage, are alternately and repeatedly executed.

2. the one input power line is the second input power line, The power converter of claim 1 , wherein the other input power line is the first input power line.

3. the one input power line is the first input power line, The power converter of claim 1 , wherein the other input power line is the second input power line.

4. The rectifier circuit includes: a first diode provided on the first output power line or the second output power line; a second diode provided between the first output power line and the second output power line and connected in parallel with a second series connection constituted by the secondary coil and the first diode, When the first diode is provided on the first output power line, a cathode of the first diode is connected to the secondary coil, When the first diode is provided on the second output power line, an anode of the first diode is connected to the secondary coil; the anode of the second diode is connected to the first output power line; 4. The power converter according to claim 1, wherein the cathode of the second diode is connected to the second output power line.

5. The rectifier circuit includes: a fifth switch provided on the first output power line or the second output power line; a sixth switch that is provided between the first output power line and the second output power line and is connected in parallel with a third series connection that is configured of the secondary coil and the fifth switch, The control device when the input voltage is equal to or lower than the threshold voltage, the first control further executes a control of turning on the fifth switch and turning off the sixth switch, and the second control further executes a control of turning off the fifth switch and turning on the sixth switch; 4. The power converter according to claim 1, wherein, when the input voltage exceeds the threshold voltage, the third control further executes control to turn on the fifth switch and turn off the sixth switch, and the fourth control further executes control to turn off the fifth switch and turn on the sixth switch.

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