Power conversion device

Abstract

To disclose a power conversion device that can prevent oscillation of a current at a switching point when performing switching of switching patterns between a step-up operation and a step-down operation.SOLUTION: A power conversion device comprises: a DC / DC converter having a first full-bridge circuit including a first switching leg and a second switching leg connected in parallel with a first input / output terminal pair, a second full-bridge circuit including a third switching leg and a fourth switching leg connected in parallel with a second input / output terminal pair, and a transformer including one winding connected with the first full-bridge circuit and the other winding connected with the second full-bridge circuit; and a control unit controlling the DC / DC converter. The control unit has at least two types, for step-up and step-down, of switching patterns of a switching element included in each switching leg, and performs switching of the switching patterns between a step-up operation and a step-down operation so that the switching patterns at a switching point match each other.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] As a power conversion device, for example, an isolated DC / DC converter having full-bridge circuits on both sides of a transformer has been proposed (see, for example, Patent Documents 1 to 4). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-48700 [Patent Document 2] Patent Publication No. 2021-48699 [Patent Document 3] JP 2021-121139 A [Patent Document 4] JP 2023-84037 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a non-insulated full-bridge type or an isolated type DC / DC converter circuit in which leakage inductance is extremely small relative to the excitation inductance, consideration of the load current is sufficient, and the excitation current does not pose a problem. However, in a DC / DC converter circuit in which the excitation current cannot be ignored, when switching between step-up and step-down switching patterns, the current oscillation at the switching point may become large enough to be ignored. Therefore, this application discloses a power conversion device capable of preventing the current oscillation at the switching point when switching between step-up and step-down switching patterns. [Means for solving the problem]

[0005] In order to solve the above problem, in the present invention, when switching between the step-up operation and the step-down operation, the switching patterns are switched so that the switching patterns at the switching points match.

[0006] In detail, the present invention is a power conversion device comprising: a DC / DC converter having a first full bridge circuit including a first switching leg and a second switching leg connected in parallel to a first input / output terminal pair, a second full bridge circuit including a third switching leg and a fourth switching leg connected in parallel to a second input / output terminal pair, and a transformer including one winding connected to the first full bridge circuit and the other winding connected to the second full bridge circuit, and a control unit for controlling the DC / DC converter, wherein the control unit has at least two types of switching patterns, for step-down and step-up, for the switching elements of each switching leg, and when switching between step-up operation and step-down operation, the switching patterns are switched so that the switching patterns at the switching point match.

[0007] In the above power conversion device, when switching between the step-up operation and the step-down operation, the switching patterns match at the switching point, so that it is possible to prevent current oscillations caused by a mismatch in the switching patterns at the switching point.

[0008] In addition, when switching from the boost operation to the step-down operation, the control unit may switch so that the boost switching pattern before the switching and the step-down switching pattern after the switching match at the switching point. According to this, when switching the switching pattern when switching from the boost operation to the step-down operation, the boost switching pattern before the switching and the step-down switching pattern after the switching match at the switching point. Therefore, it is possible to prevent current oscillations caused by a mismatch in the switching patterns at the switching points.

[0009] Furthermore, when switching from the step-down operation to the step-up operation, the control unit may switch so that the step-down switching pattern before the switching and the step-up switching pattern after the switching match at the switching point. In this way, when switching the switching pattern when switching from the step-down operation to the step-up operation, the step-down switching pattern before the switching and the step-up switching pattern after the switching match. This makes it possible to prevent current oscillations caused by a mismatch in the switching patterns at the switching point.

[0010] Moreover, the first switching leg has a first switching element and a third switching element, a source terminal of the first switching element and a drain terminal of the third switching element are connected in series at a first connection point, and a drain terminal of the first switching element and a source terminal of the third switching element are connected to the first input / output terminal pair; the second switching leg has a second switching element and a fourth switching element, a source terminal of the second switching element and a drain terminal of the fourth switching element are connected in series at a second connection point, and a drain terminal of the second switching element and a source terminal of the fourth switching element are connected to the first input / output terminal pair; the third switching leg has a fifth switching element and a seventh switching element, a source terminal of the fifth switching element and a drain terminal of the seventh switching element are connected in series at a third connection point, and The drain terminal of the seventh switching element and the source terminal of the seventh switching element are connected to the second input / output terminal pair, the fourth switching leg has a sixth switching element and an eighth switching element, the source terminal of the sixth switching element and the drain terminal of the eighth switching element are connected in series at the fourth connection point, and the drain terminal of the sixth switching element and the source terminal of the eighth switching element are connected to the second input / output terminal pair, one winding of the transformer is connected to the first connection point and the second connection point, and the other winding of the transformer is connected to the third connection point and the fourth connection point, and the control unit has at least two types of switching patterns for step-down and step-up for each of the first to eighth switching elements, and may switch the switching patterns between step-up and step-down operations so that the switching patterns at the switching points match. According to this, the switching patterns at the switching points match when switching between step-up and step-down operations. Therefore, it is possible to prevent current oscillation caused by a mismatch in the switching patterns at the switching points. Effect of the Invention

[0011] The above power conversion device can prevent current oscillation at the switching point when switching between voltage step-up and voltage step-down switching patterns. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic configuration diagram of a power conversion device according to an embodiment. [Diagram 2] FIG. 2 is a control block diagram realized by the control device. [Diagram 3] FIG. 3 shows a timing chart according to a first example of signals used when the DC / DC converter according to the embodiment is operated as a step-down converter. [Figure 4] FIG. 4 shows a timing chart according to a second example of signals used when the DC / DC converter according to the embodiment is operated as a boost converter. [Diagram 5] FIG. 5 is a schematic diagram showing a switching pattern at a switching point from the step-down operation to the step-up operation. [Figure 6] FIG. 6 is a diagram showing waveforms of a load current flowing through a DC / DC converter in the application example and the comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] <Application Examples> BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing an example of an application of the present invention; FIG.

[0014] The power conversion device 1 includes a DC / DC converter 10, a control device 20, and two pairs of input / output terminals 13 (13p, 13m) and 14 (14p, 14m). Capacitors C1 and C2 for smoothing the input voltages are connected between the input / output terminals 13m and 13p, and between the input / output terminals 14m and 14p, respectively.

[0015] The DC / DC converter 10 is an isolated bidirectional DC / DC converter whose main components are a transformer TR, two reactors Lr1 and Lr2, and two full bridge circuits 11 and 12. The reactors Lr1 and Lr2 generate AC power under the control of the full bridge circuits 11 and 12, and the capacitors C1 and C2 smooth out pulsations in the DC voltage caused by the transmission of power. An isolated transformer can be used as the transformer TR, but a non-isolated transformer may also be used.

[0016] The full bridge circuit 11 of the DC / DC converter 10 includes a leg L1 having switching elements Q1 and Q3 connected in series, and a leg L2 having switching elements Q2 and Q4 connected in series. The full bridge circuit 12 of the DC / DC converter 10 includes a leg L3 having switching elements Q5 and Q7 connected in series, and a leg L4 having switching elements Q6 and Q8 connected in series.

[0017] FIG. 5 is a schematic diagram showing a switching pattern at a switching point from step-down operation to step-up operation. FIG. 6 shows a diagram showing the waveform of the load current flowing through the DC / DC converter 10 in the application example and the comparative example. As can be seen from FIG. 5(B), in this application example, the switching patterns at the switching point are made to match. Therefore, as shown in the application example in FIG. 6, almost no current amplitude occurs. Therefore, with this application example, it is possible to prevent the occurrence of current oscillation at the switching point between step-down operation and step-up operation.

[0018] <Embodiment> Hereinafter, the power conversion device according to the embodiment of the present invention will be described in more detail with reference to the drawings.

[0019] <Configuration of power conversion device> FIG. 1 is a schematic diagram of a power conversion device according to an embodiment. The power conversion device 1 according to this embodiment is a device capable of bidirectional power conversion. As shown in the figure, the power conversion device 1 includes a DC / DC converter 10, a control device 20, and two pairs of input / output terminals 13 (13p, 13m) and an input / output terminal pair 14 (14p, 14m). In the input / output terminal pairs 13 and 14, the input / output terminals 13p and 14p are high-potential input / output terminals, and the input / output terminals 13m and 14m are low-potential input / output terminals. A capacitor C1 for smoothing the input / output voltage is connected between the input / output terminals 13m and 13p. Similarly, a capacitor C2 for smoothing the input / output voltage is connected between the input / output terminals 14m and 14p. Electrolytic capacitors can be used as the capacitors C1 and C2.

[0020] The DC / DC converter 10 is an insulated bidirectional DC / DC converter whose main components are a transformer TR, two reactors Lr1 and Lr2, and two full-bridge circuits 11 and 12. The reactors Lr1 and Lr2 may utilize leakage inductances of the windings Wn1 and Wn2 of the transformer TR. The transformer TR does not have to have a turns ratio of 1:1. However, in the following, the configuration and operation of the power conversion device 1 will be described assuming that the turns ratio of the transformer TR is 1:1.

[0021] The full-bridge circuit 11 of the DC / DC converter 10 includes a leg L1 having a switching element Q1 and a switching element Q3 connected in series, and a leg L2 having a switching element Q2 and a switching element Q4 connected in series. As shown in the figure, a diode Dn (n=1 to 4) is connected in parallel between the terminals of the switching element Qn (n=1 to 4) of each leg. Each leg is connected to an input / output terminal pair 13, and a connection point p1 between the switching element Q1 and the switching element Q3 of the leg L1 is connected to one end of the winding Wn1 of the transformer TR via a reactor Lr1. A connection point p2 between the switching element Q2 and the switching element Q4 of the leg L2 is connected to the other end of the winding Wn1 of the transformer TR.

[0022] The full bridge circuit 12 of the DC / DC converter 10 includes a leg L3 having a switching element Q5 and a switching element Q7 connected in series, and a leg L4 having a switching element Q6 and a switching element Q8 connected in series. As shown in the figure, a diode Dn (n=5 to 8) is connected in parallel between the terminals of the switching element Qn (n=5 to 8) of each leg. In addition, both the leg L3 and the leg L4 are connected to an input / output terminal pair 14. In addition, a connection point p3 between the switching element Q5 and the switching element Q7 of the leg L3 is connected to one end of the winding Wn2 of the transformer TR via a reactor Lr2, and a connection point p4 between the switching element Q6 and the switching element Q8 of the leg L4 is connected to the other end of the winding Wn2 of the transformer TR.

[0023] The semiconductor material of the switching elements Q1 to Q8 may be, but is not limited to, gallium nitride (GaN), silicon (Si), silicon carbide (SiC), etc. The semiconductor switching elements may be, for example, a metal oxide semiconductor field effect transistor (MOSFET), an insulated gate bipolar transistor (IGBT), etc. The diodes D1 to D8 are connected in antiparallel to these semiconductor switching elements used as the switching elements Q1 to Q8.

[0024] The DC / DC converter 10 is also equipped with various sensors (not shown) for measuring the magnitude of input / output voltages and input / output currents.

[0025] Control device 20 is a unit that controls DC / DC converter 10 (ON / OFF of each switching element in DC / DC converter 10) by changing the level of a control signal to each switching element in DC / DC converter 10.

[0026] The control device 20 is composed of a processor (in this embodiment, a microcontroller), a gate driver, etc., and receives outputs from the various sensors described above.

[0027] The control device 20 is configured (programmed) to determine whether the DC / DC converter 10 should operate as one of the following four types of converters based on the input data (current value, voltage value), and to control the DC / DC converter 10 so that it operates as the determined converter. Input / output terminal pair 13 is the primary side boost converter Input / output terminal pair 13 is the primary side of the step-down converter Input / output terminal pair 14 is the primary side boost converter Input / output terminal pair 14 is the primary side of the step-down converter

[0028] In addition, the control device 20 is configured (programmed) to instantly change the control content for the DC / DC converter 10 (such as changing from control that causes the DC / DC converter 10 to operate as a step-up converter with the input / output terminal pair 13 side as the primary side to control that causes the DC / DC converter 10 to operate as a step-down converter with the input / output terminal pair 14 side as the primary side).

[0029] Fig. 2 is a control block diagram realized by the control device 20. As shown in Fig. 2, in this embodiment, the DC / DC converter 10 is connected to an EV2 (electrically-driven automobile) and an inverter 30. The inverter 30 is a device that performs AC / DC conversion, and electrically connects the DC / DC converter 10 (direct current) to an AC power system 3. Examples of the EV2 include a BEV (Battery Electric Vehicle) that runs only on battery power, a PHV (Plug-in Hybrid Vehicle) that uses both a battery and an internal combustion engine, an FCV (Fuel Cell Vehicle) that runs on fuel cell power, and various other types of electrically-driven automobiles. However, the DC / DC converter The DC / DC converter 10 is not limited to being used with such an EV 2, and may be connected to, for example, a residential storage battery. The DC / DC converter 10 may also be used for controlling the running of an electric vehicle that runs on DC power, or for controlling various other electric devices.

[0030] The control device 20 controls the DC / DC converter 10 according to command values ​​sent from a higher-level device. The command values ​​sent from the higher-level device to the control device 20 are values ​​determined based on the remaining charge of the EV 2 and the power consumption of the load 4. The control device 20 includes a central processing unit (CPU), and storage devices such as a read only memory (ROM) and a random access memory (RAM). The control device 20 is equipped with an input / output interface, and the CPU executes a computer program stored in the storage device to realize each of the functional blocks shown below. The control device 20 uses each of the functional blocks shown below to generate a PWM signal according to a command value sent from a higher-level device, and sends the PWM signal to the DC / DC converter 10.

[0031] The control device 20 executes a computer program to implement a control unit 21, a PWM generating unit 24, and a step-up / step-down switching control unit 25, as shown in Fig. 2. Each functional block in the control device 20 will be described below.

[0032] The control unit 21 generates a phase shift amount. The PWM generation unit 24 generates a PWM signal based on the phase shift amount generated by the control unit 21. When generating the PWM signal, the PWM generation unit 24 uses a step-up / step-down signal output from the step-up / step-down switching control unit 25. By using the signal output from the step-up / step-down switching control unit 25, the PWM generation unit 24 generates a PWM signal of a switching pattern for causing the DC / DC converter 10 to perform a step-up operation or a step-down operation. The PWM signal generated by the PWM generation unit 24 is sent to the DC / DC converter 10 and operates each of the switching elements Q1 to Q8.

[0033] The step-up / step-down switching control unit 25 generates a step-up / step-down signal based on the amount of phase shift output from the control unit 21 and the outputs of the voltage sensors 22, 23 that measure the input / output voltages of the DC / DC converter 10. That is, the step-up / step-down switching control unit 25 selects whether the DC / DC converter 10 should perform step-up operation or step-down operation based on the amount of phase shift output from the control unit 21. Then, the step-up / step-down switching control unit 25 outputs a signal according to the selection result.

[0034] <Operation of the power conversion device> The operation of the power conversion device 1 according to this embodiment will be described below.

[0035] The DC / DC converter 10 basically performs step-up operation and step-down operation by relatively changing the amount of phase shift related to ON / OFF of each switching element included in legs L1 to L4. That is, in the power conversion device 1 according to this embodiment, the control device 20 changes the amount of phase shift as follows, thereby making it possible to switch between the step-up operation and the step-down operation of the DC / DC converter 10.

[0036] For example, when the operation of the DC / DC converter 10 is switched from the step-down operation to the step-up operation with the input / output terminal pair 13 side as the primary side and the input / output terminal pair 14 side as the secondary side, the phase shift amount of the switching element Q4 relative to the switching element Q1 or the phase shift amount of the switching element Q2 relative to the switching element Q3 is transitioned to a predetermined value. Then, the phase shift amount of the switching element Q7 relative to the switching elements Q1 and Q4 or the phase shift amount of the switching element Q8 relative to the switching elements Q3 and Q2 is adjusted to a desired phase value. Here, the phase shift amount of the step-down operation can be expressed as the time (TΦ) when the ON of the switching element Q1 and the switching element Q4 overlaps, or the time (TΦ) when the ON of the switching element Q3 and the switching element Q2 overlaps. In addition, the phase shift amount of the boost operation can be expressed as the time (TΦ) when the ON state of switching element Q1 and switching element Q7 overlaps with the ON state of switching element Q4, or the time (TΦ) when the ON state of switching element Q3 and switching element Q8 overlaps with the ON state of switching element Q2.

[0037] Furthermore, for example, when the operation of DC / DC converter 10 is switched from step-up operation to step-down operation with input / output terminal pair 13 as the primary side and input / output terminal pair 14 as the secondary side, the phase shift amount of switching element Q7 relative to switching element Q1 and switching element Q4, or the phase shift amount of switching element Q8 relative to switching element Q3 and switching element Q2, is transitioned to a predetermined value. Then, the phase shift amount of switching element Q4 relative to switching element Q1, or the phase shift amount of switching element Q2 relative to switching element Q3, is adjusted to a desired phase value.

[0038] In the following description, the terms "step-up operation" and "step-down operation" in DC / DC converter 10 refer to operations based on switching patterns relating to the ON / OFF of each switching element included in legs L1 to L4, and do not refer to the relationship between the input voltage and the output voltage relating to voltage conversion. That is, in this embodiment, DC / DC converter 10 may operate with "input voltage > output voltage" in "step-up operation", and may also operate with "input voltage < output voltage" in "step-down operation". The step-up operation of DC / DC converter 10 is also referred to as the "step-up mode", and the step-down operation is also referred to as the "step-down mode".

[0039] In the power conversion device 1 of this embodiment, the control device 20 acquires information such as the input / output conditions of the DC / DC converter 10, and determines in which mode the DC / DC converter 10 will operate using information previously set in a table or the like, and outputs a switching pattern signal according to the determination result.

[0040] 3 shows a timing chart according to a first example of signals used when the DC / DC converter 10 according to this embodiment is operated as a step-down converter. The timing chart according to the first example is an example of a switching pattern used when the DC / DC converter 10 is operated in a step-down manner. In the state of #11, only the switching elements Q1, Q4, and Q8 are ON, and the other switching elements are OFF. This causes the switching elements Q1 and Q4 to start transmitting power. In the state of #12, only the switching elements Q1, Q4, Q5, and Q8 are ON, and the other switching elements are OFF. This starts synchronous rectification by the switching element Q5. In the state of #13, only the switching elements Q4, Q5, and Q8 are ON, and the other The switching element Q1 is turned off. When the switching element Q1 is turned off, the excitation current starts to return on the primary side. In the state of #14, only switching elements Q3, Q4, Q5, and Q8 are ON, and the other switching elements are OFF. As a result, the ON state of switching element Q3 continues the return flow of excitation current on the primary side. In the state of #15, only switching elements Q3, Q4, and Q8 are ON, and the other switching elements are OFF. As a result, the load current continues even after switching element Q5 is turned OFF, and the excitation current circulates on the primary side. In state #16, only switching elements Q3 and Q8 are ON, and the other switching elements are OFF. When switching element Q4 is turned OFF, both the load current and the excitation current are regenerated and disappear.

[0041] By performing the above operation, the load current increases in the switching pattern between #11 and #12. Also, the load current decreases in the switching pattern between #13 and #16. In the power conversion device 1 according to this embodiment, for example, the step-down operation is realized by performing the operation according to such a switching pattern according to the first example.

[0042] 4 shows a timing chart according to a second example of signals used when the DC / DC converter 10 according to this embodiment is operated as a boost converter. The timing chart according to the second example is an example of a switching pattern used when the DC / DC converter 10 is operated as a boost converter. In the state of #31, only the switching elements Q1, Q4, Q7, and Q8 are ON, and the other switching elements are OFF. This starts preparation for power transmission by the switching elements Q1 and Q4. In the state of #32, only switching elements Q1, Q4, and Q8 are ON, and the other switching elements are OFF. As a result, power transmission begins when switching element Q7 is turned OFF. In the state of #33, only switching elements Q1, Q4, Q5, and Q8 are ON, and the other switching elements are OFF. Synchronous rectification begins when switching element Q5 is turned ON. In the state of #34, only switching elements Q4 and Q8 are ON, and the other switching elements are OFF. With switching element Q1 OFF, the excitation current circulates on the primary side. This allows the load current to continue. In the state of #35, only switching elements Q3 and Q8 are ON, and the other switching elements are OFF. When switching element Q4 is turned OFF, both the load current and the excitation current are regenerated and disappear.

[0043] By performing the above operation, the load current increases in the switching pattern #31. Also, the load current decreases in the switching patterns between #32 and #35. In the power conversion device 1 according to this embodiment, for example, the boost operation is realized by performing the operation according to such a switching pattern according to the second example.

[0044] In the power conversion device 1 according to this embodiment, for example, the two switching patterns as described above or various other switching patterns are appropriately selected, and each switching element is operated according to the selected switching pattern. For this reason, when switching the operation of the DC / DC converter 10 from boost operation to buck operation or from buck operation to boost operation, the control device 20 switches the switching pattern. However, when the switching pattern is switched, a current amplitude due to the excitation current before the switching may occur. Therefore, the control device 20 uses a voltage regulator to adjust the voltage when switching the switching pattern between boost operation and buck operation. In this case, by switching so that the switching patterns at the switching points match, operation of the switching elements that generates a current amplitude due to the excitation current at the switching points is prevented.

[0045] Fig. 5 is a schematic diagram showing switching patterns at a switching point from a step-down operation to a step-up operation, Fig. 5(A) shows a switching pattern according to a comparative example, and Fig. 5(B) shows a switching pattern according to an application example.

[0046] For example, in switching from step-down operation to step-up operation, if attention is paid only to the load current and not to the excitation current, there is no problem with the ON or OFF timing of the switching element Q7 at the switching point as long as a certain condition is satisfied. Therefore, as shown in FIG. 5(A), even if the switching patterns do not match at the switching point, it is possible to ignore the influence of the excitation current generated by this. However, in an isolated DC / DC converter 10, if an attempt is made to ensure the DC superposition characteristics of the transformer Tr in consideration of the variation in the characteristics of each component of the gate circuit and the semiconductor switch, the self-inductance of the circuit decreases, and the excitation current cannot be ignored due to the decrease in excitation inductance. Therefore, in the power conversion device 1 according to this embodiment, in order to prevent the influence of such excitation current, the switching patterns are switched so that the switching patterns at the switching point match when switching between the step-up operation and the step-down operation. That is, in the power conversion device 1 according to this embodiment, the switching patterns at the switching point are matched as shown in FIG. 5(B). By matching the switching patterns at the switching points, the difference in the commutation of the excitation current that differed before and after the switching points in the comparative example is eliminated in this embodiment, so the influence of the excitation current caused by a mismatch in the switching patterns at the switching points is eliminated, making it possible to prevent current oscillations.

[0047] FIG. 6 is a diagram showing the waveform of the load current flowing through the DC / DC converter 10 in the application example and the comparative example. When switching from the step-down operation to the step-up operation, if the switching elements of the DC / DC converter 10 are operated according to the switching pattern shown in the comparative example of FIG. 5, current amplitude occurs as shown in the area surrounded by the dashed line in the comparative example of FIG. 6. On the other hand, if the switching elements of the DC / DC converter 10 are operated according to the switching pattern shown in the application example of FIG. 5, almost no current amplitude occurs as shown in the application example of FIG. 6. Therefore, with the power conversion device 1 according to this embodiment, it is possible to prevent the occurrence of current oscillation at the switching point between the step-down operation and the step-up operation.

[0048] In this embodiment, the switching from the step-down operation to the step-up operation is illustrated, but the same applies to the switching from the step-up operation to the step-down operation.

[0049] <Other> The above embodiment is merely an example, and the disclosure of the present embodiment may be modified as appropriate without departing from the spirit of the present disclosure. The processes and means described in the present disclosure may be freely combined and implemented as long as no technical contradiction occurs.

[0050] Furthermore, a process described as being performed by one circuit or device may be shared and executed by multiple circuits or devices, or a process described as being performed by different circuits or devices may be executed by a single circuit or device.

[0051] In addition, this application includes the following additional matters. <Appendix 1> A first full-bridge circuit (11) including a first switching leg (L1) and a second switching leg (L2) connected in parallel to a first input / output terminal pair (13p, 13m); a DC / DC converter (10) including: a second full-bridge circuit (12) including a third switching leg (L3) and a fourth switching leg (L4) connected in parallel to a terminal pair; and a transformer (TR) including one winding connected to the first full-bridge circuit and the other winding connected to the second full-bridge circuit; A control unit (20) that controls the DC / DC converter, The control unit is Each switching leg has a switching element with at least two types of switching patterns, one for step-down and one for step-up, and when switching between the step-up operation and the step-down operation, the switching patterns are switched so that the switching patterns at the switching points match. Power conversion device (1). <Appendix 2> the control unit, when switching from the step-up operation to the step-down operation, performs switching such that a step-up switching pattern before the switching and a step-down switching pattern after the switching match at a switching point. 2. A power conversion device as described in claim 1. <Appendix 3> the control unit, when switching from the step-down operation to the step-up operation, performs switching such that a step-down switching pattern before the switching and a step-up switching pattern after the switching match at a switching point. 3. The power conversion device according to claim 1 or 2. <Appendix 4> the first switching leg has a first switching element and a third switching element, a source terminal of the first switching element and a drain terminal of the third switching element are connected in series at a first connection point, and a drain terminal of the first switching element and a source terminal of the third switching element are connected to the first input / output terminal pair; the second switching leg has a second switching element and a fourth switching element, a source terminal of the second switching element and a drain terminal of the fourth switching element are connected in series at a second connection point, and a drain terminal of the second switching element and a source terminal of the fourth switching element are connected to the first input / output terminal pair, the third switching leg has a fifth switching element and a seventh switching element, a source terminal of the fifth switching element and a drain terminal of the seventh switching element are connected in series at a third connection point, and a drain terminal of the fifth switching element and a source terminal of the seventh switching element are connected to the second input / output terminal pair; the fourth switching leg has a sixth switching element and an eighth switching element, a source terminal of the sixth switching element and a drain terminal of the eighth switching element are connected in series at a fourth connection point, and a drain terminal of the sixth switching element and a source terminal of the eighth switching element are connected to the second input / output terminal pair; one winding of the transformer is connected to the first connection point and the second connection point, and the other winding of the transformer is connected to the third connection point and the fourth connection point; The control unit is The switching patterns of each of the first switching element to the eighth switching element are at least two types, one for step-down and one for step-up, and when switching between the step-up operation and the step-down operation, the switching patterns are switched so that the switching patterns at the switching points match. 4. A power conversion device according to any one of claims 1 to 3. [Explanation of symbols]

[0052] 1. Power conversion device 2··EV 10. DC / DC converter 20. Control device 30. Inverter 21 Control section 22,23 Voltage sensor 24...PWM generation section 25··Step-up / step-down switching control section Q1~Q8 Switching elements

Claims

1. a DC / DC converter including: a first full bridge circuit including a first switching leg and a second switching leg connected in parallel to a first input / output terminal pair; a second full bridge circuit including a third switching leg and a fourth switching leg connected in parallel to a second input / output terminal pair; and a transformer including one winding connected to the first full bridge circuit and the other winding connected to the second full bridge circuit; A control unit that controls the DC / DC converter, The control unit is Each switching leg has a switching element with at least two types of switching patterns, one for step-down and one for step-up, and when switching between the step-up operation and the step-down operation, the switching patterns are switched so that the switching patterns at the switching points match. Power conversion equipment.

2. the control unit, when switching from the step-up operation to the step-down operation, performs switching such that a step-up switching pattern before the switching and a step-down switching pattern after the switching match at a switching point. The power conversion device according to claim 1 .

3. the control unit, when switching from the step-down operation to the step-up operation, performs switching such that a step-down switching pattern before the switching and a step-up switching pattern after the switching match at a switching point. The power conversion device according to claim 1 .

4. the first switching leg has a first switching element and a third switching element, a source terminal of the first switching element and a drain terminal of the third switching element are connected in series at a first connection point, and a drain terminal of the first switching element and a source terminal of the third switching element are connected to the first input / output terminal pair; the second switching leg has a second switching element and a fourth switching element, a source terminal of the second switching element and a drain terminal of the fourth switching element are connected in series at a second connection point, and a drain terminal of the second switching element and a source terminal of the fourth switching element are connected to the first input / output terminal pair, the third switching leg has a fifth switching element and a seventh switching element, a source terminal of the fifth switching element and a drain terminal of the seventh switching element are connected in series at a third connection point, and a drain terminal of the fifth switching element and a source terminal of the seventh switching element are connected to the second input / output terminal pair, the fourth switching leg has a sixth switching element and an eighth switching element, a source terminal of the sixth switching element and a drain terminal of the eighth switching element are connected in series at a fourth connection point, and a drain terminal of the sixth switching element and a source terminal of the eighth switching element are connected to the second input / output terminal pair, one winding of the transformer is connected to the first connection point and the second connection point, and the other winding of the transformer is connected to the third connection point and the fourth connection point; The control unit is The switching patterns of each of the first switching element to the eighth switching element are at least two types, a step-down pattern and a step-up pattern, and when switching between the step-up operation and the step-down operation, the switching patterns are switched so that the switching patterns at the switching points match. The power conversion device according to claim 1 .

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