Power conversion device

Abstract

To provide a power conversion device that can transmit a current near 0 A by adjusting the magnitude of an exciting current.SOLUTION: A power conversion device comprises: an input terminal pair; an output terminal pair; a first capacitor; a second capacitor; a first switching unit; a second switching unit; a transformer; and a control unit that controls switching of the first switching unit and the second switching unit according to a command value input from a host device, to switch between a step-up mode and a step-down mode. When switching from the step-down mode to the step-up mode when the input voltage is equal to or less than the output voltage, or when changing the output current to be output from the output terminal pair from a current within a predetermined range including 0 A to a current outside the predetermined range in the step-up mode, the control unit switches to an in-step-up step-down mode for performing switching control in the step-down mode in a predetermined section present before a starting point on a phase shift amount axis in the step-up mode.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Conventionally, in a bidirectional DC / DC converter, which is a power conversion device, a technique has been proposed for adjusting the amount of phase delay of a control signal when switching control between step-up operation and step-down operation, as described in Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-121139 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a DC / DC converter, when the input voltage on the input side is equal to or lower than the output voltage on the output side, if power is sent to the output side by boosting, it may not be possible to output a current of around 0 A due to the influence of the excitation current, etc.

[0005] An object of one aspect of the disclosed technique is to provide a power conversion device capable of transmitting a current close to 0 A by adjusting the magnitude of an excitation current. [Means for solving the problem]

[0006] One aspect of the disclosed technology is exemplified by a power conversion device as follows: The power conversion device includes an input terminal pair, an output terminal pair, a first capacitor connected in parallel to the input terminal pair, a second capacitor connected in parallel to the output terminal pair, a first switching unit connected to the first capacitor, a second switching unit connected to the second capacitor, a transformer disposed between the first switching unit and the second switching unit, and a control unit that switches between a step-up mode in which switching of the first switching unit and the second switching unit is controlled so that an output voltage higher than an input voltage input to the input terminal pair is output from the output terminal pair, and a step-down mode in which switching of the first switching unit and the second switching unit is controlled so that an output voltage lower than the input voltage is output from the output terminal pair, according to a command value input from a higher-level device. When switching from the buck mode to the boost mode when the input voltage is equal to or lower than the output voltage, or when changing the output current to be output from the output terminal pair from a current within a predetermined range of 0 A in the boost mode to a current outside the predetermined range, the control unit uses a buck-in-boost mode that performs switching control of the buck mode in a predetermined section that exists before a starting point on the phase shift amount axis of the boost mode.

[0007] Here, a current within a predetermined range from 0 A means, for example, a current near 0 A. According to this power conversion device, a step-down mode (step-down mode within step-up) is executed in a predetermined section existing before the start point on the phase shift amount axis of the step-up mode when the input voltage is equal to or lower than the output voltage, or in the step-up mode, when the output current output from the output terminal pair is changed from a current within a predetermined range from 0 A to a current outside the predetermined range. According to this power conversion device, the step-down mode within step-up is executed, and the conduction time of each switch is adjusted to suppress the excitation current flowing through the transformer, and thus the power conversion device can output a current near 0 A.

[0008] The power conversion device may further include the following features: When the control unit detects that the output voltage becomes less than the input voltage during the in-boost buck-step-down mode, the control unit switches from the in-boost buck-step-down mode to the buck mode. When the control unit detects that the input voltage becomes equal to or less than the output voltage during the in-boost mode, the control unit maintains the boost mode or switches from the boost mode to the in-boost buck-step-down mode. By including such features, the power conversion device can switch between the boost mode, the buck mode, and the in-boost buck-step-down mode according to the relationship between the input voltage and the output voltage.

[0009] The power conversion device may further include the following features. The section in which the step-down mode is executed is a first section, the section in which the step-up mode is executed is a third section, and the predetermined section in which the step-up-intra-step-down mode is executed is a section shorter than the first section and the third section. The control unit executes switching control in each of the step-up mode, the step-down mode, and the step-up-intra-step-down mode by supplying a PWM signal to each of the first switching unit and the second switching unit, and the PWM signal in the step-up-intra-step-down mode is a signal obtained by compressing a waveform output in the first section in the step-down mode in the phase shift amount axis direction so as to fit within the predetermined section. By defining the PWM signal in the step-up-intra-step-down mode in this way, a connection of PWM waveforms becomes smooth when transitioning from the step-down mode to the step-up mode, and switching between modes becomes seamless. Effect of the Invention

[0010] According to the disclosed technology, a current close to 0 A can be transmitted by adjusting the magnitude of the excitation current. [Brief description of the drawings]

[0011] [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 unit. [Diagram 3] FIG. 3 is a diagram illustrating an example of a waveform of a PWM signal in the step-down mode of the DC / DC converter according to the embodiment. [Figure 4] FIG. 4 is a diagram illustrating an example of a waveform of a PWM signal in the boost mode of the DC / DC converter according to the embodiment. [Diagram 5] FIG. 5 is a first diagram illustrating a current path of the power conversion device. [Figure 6] FIG. 6 is a second diagram illustrating a current path in the power conversion device. [Figure 7] FIG. 7 is a diagram illustrating an excitation current generated in the boost mode of the DC / DC converter according to the embodiment. [Figure 8] FIG. 8 is a diagram showing a schematic diagram of the operation of the internal boost step-down mode in this embodiment. [Figure 9] FIG. 9 is a first diagram showing mode switching. [Figure 10] FIG. 10 is a second diagram showing mode switching. [Figure 11] FIG. 11 is a third diagram showing mode switching. [Figure 12] FIG. 12 is a fourth diagram showing mode switching. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] <Application Examples> An application example of the present invention will be described below with reference to the drawings. The present invention is applied to a power conversion device 1 including an isolated bidirectional DC / DC converter 10 shown in FIG. 1. The power conversion device 1 comprises the DC / DC converter 10, a control unit 20, and two pairs of input / output terminals 13 (13p, 13m) and an input / output terminal pair 14 (14p, 14m). Capacitors C1 and C2 for smoothing the input voltage are connected between the input / output terminals 13m, 13p and between the input / output terminals 14m, 14p, respectively. Here, capacitor C1 is a capacitor according to the present invention. In addition, the capacitor C2 corresponds to the second capacitor of the present invention. However, the correspondence between the capacitors C1 and C2 and the first and second capacitors of the present invention is interchangeable depending on the input / output direction.

[0013] 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 generate AC power under the control of the full-bridge circuits 11 and 12, and the capacitors C1 and C2 smooth the AC power into DC power. An insulating transformer can be used as the transformer TR, but a non-insulated reactor may also be used.

[0014] 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. In addition, both the leg L1 and the leg L2 are connected to an input / output terminal pair 13. 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, and a connection point p2 between the switching element Q2 and the switching element Q3 of the leg L2 is connected to the other end of the winding Wn1 of the transformer TR.

[0015] 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.

[0016] 2 shows an example of a control block diagram realized by the control unit 20. The control unit 20 includes a control unit 21, a PWM generating unit 22, and a step-up / step-down switching control unit .

[0017] In DC / DC converter 10, the step-up mode and the step-down mode are switched by relatively changing the phase shift amount related to ON / OFF of each switching element included in legs L1 to L4. Here, when DC / DC converter 10 is in the step-up mode with the input voltage being equal to or lower than the output voltage, DC / DC converter 10 may not be able to output a current of around 0 A due to the influence of the excitation current, etc.

[0018] Therefore, in this application example, a buck mode (step-down mode within a boost mode) is executed in a predetermined section that exists before the start point on the phase shift amount axis of the boost mode. According to this application example, the step-down mode within a boost mode is executed, and the conduction time of each switch is adjusted to suppress the excitation current flowing through the transformer, and thus the power conversion device can output a current of about 0 A.

[0019] [Embodiment] Hereinafter, the power conversion device 1 according to the embodiment of the present invention will be described in more detail with reference to the drawings.

[0020] <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 unit 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, 14p are high-potential input / output terminals, and the input / output terminals 13m, 14m are low-potential input / output terminals. A capacitor C1 for smoothing input / output voltages is connected between the input / output terminals 13m, 13p. Similarly, a capacitor C2 for smoothing input / output voltages is connected between the input / output terminals 14m, 14p. Electrolytic capacitors can be used as the capacitors C1 and C2.

[0021] 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. Hereinafter, the full bridge circuit 11 on the left side and the full bridge circuit 12 on the right side in FIG. 1 will be referred to as the full bridge circuit 11 and the full bridge circuit 12, respectively. Similarly, the reactors Lr1 and Lr2 on the left side and the right side in FIG. 1 will be referred to as the reactor Lr1 and the reactor Lr2, respectively, and the winding Wn1 on the left side and the winding Wn2 on the right side in FIG. 1 of the transformer TR will be referred to as the winding Wn1 and the winding Wn2, respectively. In addition, the input / output terminal pair 13 (13p, 13m) and the input / output terminal pair 14 (14p, 14m) on the left side and the right side in FIG. 1 will be referred to as the input / output terminal pair 13 and the input / output terminal pair 14, respectively. The reactors Lr1 and Lr2 may utilize leakage inductance of the windings Wn1 and Wn2 of the transformer TR. The transformer TR of the DC / DC converter 10 does not need 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.

[0022] 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.

[0023] 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.

[0024] The semiconductor materials for the switching elements Q1 to Q8 may be, but are not limited to, gallium nitride (GaN), silicon (Si), silicon carbide (SiC), etc. The semiconductor switching elements may be, for example, MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), IGBTs (Insulated Gate Bipolar Transistors), etc. These semiconductors used as the switching elements Q1 to Q8 The diodes D1 to D8 are connected in anti-parallel to the switching elements.

[0025] The DC / DC converter 10 is equipped with sensors (eg, voltage sensors 15p, 15s, etc.) for measuring the magnitude of input / output voltages and input / output currents.

[0026] The control unit 20 is a unit that controls the DC / DC converter 10 (ON / OFF of each switching element in the DC / DC converter 10) by changing the level of a control signal to each switching element in the DC / DC converter 10. Hereinafter, the control signal for the switching element Qn (n=1 to 8) will be referred to as a control signal Gn.

[0027] The control unit 20 is composed of a processor (in this embodiment, a microcontroller), a gate driver, and the like, and outputs of the above-mentioned various sensors (voltage sensors 15p, 15s, etc.) are input to the control unit 20.

[0028] The control unit 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 to operate 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

[0029] In addition, control unit 20 is configured (programmed) to instantly change the control content for DC / DC converter 10 (such as changing from control that causes DC / DC converter 10 to operate as a step-up converter on the input / output terminal pair 13 side as the primary side to control that causes DC / DC converter 10 to operate as a step-down converter on the input / output terminal pair 14 side as the primary side).

[0030] Fig. 2 is a control block diagram realized by the control unit 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 10 is not necessarily connected to an EV2. The DC / DC converter 10 is not limited to being used in such an EV 2, and may be connected to, for example, a home storage battery, etc. The DC / DC converter 10 may also be used for, for example, driving control of an electric vehicle that runs on DC power, or for control of various other electric devices.

[0031] The control unit 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 unit 20 are values ​​determined based on the remaining charge of the EV 2 and the power consumption of the load 4. The control unit 20 includes a CPU (Central Processing Unit), a ROM (read only memory), and a RAM (Random Access Memory ) and 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. Using each of the functional blocks shown below, the control unit 20 generates a PWM signal according to a command value sent from a higher-level device and sends it to the DC / DC converter 10.

[0032] The control unit 20 executes a computer program to implement a control unit 21, a PWM generating unit 22, and a step-up / step-down switching control unit 23, as shown in Fig. 2. Each functional block in the control unit 20 will be described below.

[0033] The control unit 21 generates a phase shift amount. The PWM generation unit 22 generates a PWM signal based on the phase shift amount generated by the control unit 21. The PWM generation unit 22 uses a step-up / step-down signal output from the step-up / step-down switching control unit 23 when generating the PWM signal. By using the signal output from the step-up / step-down switching control unit 23, the PWM generation unit 22 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 22 is sent to the DC / DC converter 10 and operates each of the switching elements Q1 to Q8.

[0034] The step-up / step-down switching control unit 23 generates a step-up / step-down signal based on the amount of phase shift output from the control unit 21. That is, the step-up / step-down switching control unit 23 selects whether the DC / DC converter 10 performs 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 23 outputs a signal according to the selection result.

[0035] <Operation of the power conversion device> The operation of the power conversion device 1 according to this embodiment will be described below.

[0036] Basically, the DC / DC converter 10 can switch between the step-up operation and the step-down operation by relatively changing the phase shift amount 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 unit 20 can switch between the step-up operation and the step-down operation of the DC / DC converter 10 by changing the phase shift amount as follows.

[0037] 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 leg L2 relative to the leg L1 is transitioned to a predetermined value. Then, while maintaining the phase shift amount of the leg L2 relative to the leg L1 at the predetermined value, the phase shift amount of the leg L4 relative to the leg L2 is adjusted from the predetermined value to a desired phase value. Here, the phase shift amount of the leg L2 relative to the leg L1 can be expressed as a delay amount (TΦ) between the falling timing when the switching element Q1 changes from ON to OFF and the falling timing when the switching element Q2 changes from ON to OFF, or a delay amount (TΦ) between the falling timing when the switching element Q3 changes from ON to OFF and the falling timing when the switching element Q4 changes from ON to OFF. The phase shift amount of leg L4 relative to leg L2 can be expressed as the delay amount (TΦ) between the falling edge timing when switching element Q3 changes from ON to OFF and the falling edge timing when switching element Q7 changes from ON to OFF, or the delay amount (TΦ) between the falling edge timing when switching element Q4 changes from ON to OFF and the falling edge timing when switching element Q7 changes from ON to OFF. Note that since the ON and OFF of switching elements Qn (n=1 to 8) changes at a predetermined period (T), the delay amount (TΦ) can also be expressed as a phase lead amount (TΦ).

[0038] Also, 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 side as the primary side and input / output terminal pair 14 side as the secondary side, the phase shift amount of leg L4 relative to leg L2 is reduced to 0. Then, the phase shift amount of leg L1 relative to leg L2 is adjusted from 0 to a desired phase value while keeping the phase shift amount of leg L4 relative to leg L2 at 0. In this way, in power conversion device 1, the step-up and step-down operations are continuously switched by relatively changing the phase shift amounts related to the ON / OFF of each switching element included in legs L1 to L4.

[0039] 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".

[0040] The relationship between the input voltage and the output voltage in the voltage conversion can be expressed as a "step-up state" and a "step-down state." The "step-up state" refers to a state in which the input voltage is equal to or lower than the output voltage. The "step-down state" refers to a state in which the input voltage is greater than the output voltage.

[0041] Fig. 3 is a diagram illustrating waveforms of PWM signals in the step-down mode of the DC / DC converter 10 according to the embodiment. Fig. 3 illustrates waveforms of PWM signals supplied to each of the switching elements Q1 to Q8. Fig. 3 also illustrates dead times provided to prevent short circuits between the switching elements Qn (n=1 to 8). In the step-down mode, the step-down mode is realized by switching between a state in which the switching elements Q1, Q2, and Q7 are turned ON and the switching elements Q3, Q4, Q5, Q6, and Q8 are turned OFF, and a state in which the switching elements Q3, Q4, and Q8 are turned ON and the switching elements Q1, Q2, Q5, Q6, and Q7 are turned OFF.

[0042] When the amount of phase shift increases, the phase of the waveform of the PWM signal supplied to the switching elements Q2, Q3, Q7, and Q8 changes. The change in the phase of the waveform of the PWM signal supplied to the switching elements Q2, Q3, Q7, and Q8 creates a conduction angle for the switching elements Q1, Q4, and the switching elements Q2, Q3, and changes the excitation current.

[0043] Fig. 4 is a diagram illustrating waveforms of PWM signals in the boost mode of the DC / DC converter 10 according to the embodiment. Fig. 4 illustrates waveforms of PWM signals supplied to each of the switching elements Q1 to Q8. Fig. 4 also illustrates dead times provided to prevent short circuits between the switching elements Qn (n=1 to 8). In the boost mode, the boost mode is realized by switching between a state in which the switching elements Q1, Q4, and Q8 are turned ON and the switching elements Q2, Q3, Q5, Q6, and Q7 are turned OFF, and a state in which the switching elements Q2, Q3, and Q7 are turned ON and the switching elements Q1, Q4, Q5, and Q6 are turned OFF.

[0044] 5 and 6 are diagrams showing current paths in the boost mode of the DC / DC converter 10 according to the embodiment. FIG. 5 illustrates a current path in a state where switching elements Q1, Q4, and Q8 are turned ON and switching elements Q2, Q3, Q5, Q6, and Q7 are turned OFF. FIG. 6 illustrates a current path in a state where switching elements Q2, Q3, and Q7 are turned ON and switching elements Q1, Q4, Q5, and Q6 are turned OFF. The current path in FIG. 5 is, for example, a current path in a period B2 in FIG. 4. The current path in FIG. 6 is, for example, a current path in a period B1 and B3 in FIG. 4.

[0045] 7 is a diagram illustrating an excitation current flowing through Lr2 when the current flowing from node p4 to node p3, which occurs in the boost mode of the DC / DC converter 10 according to the embodiment, is taken as positive. FIG. 7 illustrates a case in which the input voltage is equal to or lower than the output voltage. In the boost mode of the DC / DC converter 10, excitation currents are generated in periods B1, B2, and B3, as illustrated by current waveforms F1, F2, and F3. That is, in the DC / DC converter 10 performing boost operation in a state in which the input voltage is equal to or lower than the output voltage, the operating point at which the amount of phase shift is minimum is During the dead time (see Figs. 3 and 4), an excitation current flows through the transformer TR. Therefore, the DC / DC converter 10 may not be able to output a current close to 0 A due to the influence of such an excitation current. Therefore, in the power conversion device 1 according to this embodiment, the step-up / step-down switching control unit 23 performs the following control, so that a current close to 0 A can be output even when the step-up operation is performed in a state where the input voltage is equal to or lower than the output voltage.

[0046] When the step-up / step-down switching control unit 23 transitions to step-up operation when the input voltage is equal to or lower than the output voltage, the step-up / step-down switching control unit 23 causes the DC / DC converter 10 to perform step-down operation in a predetermined leading section of the section in which the step-up operation is performed on the phase shift amount axis. By performing step-down operation in a predetermined leading section of the section in which the step-up operation is performed, the conduction time of the switch that causes the excitation current to flow is adjusted. Therefore, the excitation current is suppressed, and the DC / DC converter 10 is able to output a current of about 0 A.

[0047] Hereinafter, in this specification, performing a step-down operation in a predetermined section at the beginning of a section on the phase shift amount axis in which a step-up operation is performed will also be referred to as a "step-down mode within step-up".

[0048] Fig. 8 is a diagram showing a schematic diagram of the operation of the in-boost buck mode in this embodiment. In Fig. 8, P11, P12, P13, P21, P22, and P23 exemplify the phase shift amount. The buck-boost switching control unit 23 operates the DC / DC converter 10 in the in-boost buck mode in the leading section T2 of the section T1 in which the boost operation is performed on the phase shift amount axis. The buck-boost switching control unit 23 also operates the DC / DC converter 10 in the boost mode in section T3, which is section T1 minus the leading section T2. ​​The leading section T2 is set to be shorter than sections T1 and T3.

[0049] Here, the leading section T2 is, for example, between the minimum value of the phase shift amount and the phase shift amount taking into account the dead time. The minimum value of the phase shift amount may be, for example, 0. The minimum value of the phase shift amount may also be a value equal to or greater than 0 taking into account the transmission delay of the PWM pulse.

[0050] The waveform of the PWM signal in the buck-in-boost mode is obtained by compressing the waveform of the PWM signal supplied to each switching element in the buck mode to the leading section T2 on the phase shift amount axis. Therefore, the leading P11 of the PWM signal in the buck-in-boost mode and the leading P21 of the PWM signal in the buck mode, the center P12 of the PWM signal in the buck-in-boost mode and the center P22 of the PWM signal in the buck mode, and the end P13 of the PWM signal in the buck-in-boost mode and the end P23 of the PWM signal in the buck mode have the same waveform.

[0051] <Handling fluctuations in input and output voltage> The step-up / step-down switching control unit 23 switches between the step-up mode, the step-down mode, and the step-down mode within the step-up mode based on the magnitude relationship between the input voltage and the output voltage. FIG. 9 is a diagram showing the mode switching when the DC / DC converter 10 according to the embodiment transitions from the step-down state to the step-up state in the step-down mode. In FIG. 9, P31, P32, P33, P41, P42, and P43 exemplify phase shift amounts. In the example of FIG. 9, it is assumed that the step-up state is reached when the phase shift amount is P31. When the step-up / step-down switching control unit 23 detects that the step-up state is reached in the step-down mode, it transitions the DC / DC converter 10 to the step-down mode within the step-up mode. At this time, the step-up / step-down switching control unit 23 transitions to a phase shift amount that results in the same PWM waveform as the PWM waveform in the step-down operation when the phase shift amount is P31. At this time, the phase shift amount of the transition destination is, for example, "(phase shift amount P31 when transitioning to the boost state in the buck mode-minimum phase shift amount P32) / (maximum phase shift amount P33 in the buck mode-minimum phase shift amount P32)=(phase shift amount P41 of the transition destination in the buck mode within the boost mode-minimum phase shift amount P42) / (maximum phase shift amount P33 in the buck mode-minimum phase shift amount P32) / (maximum phase shift amount P41 in the buck mode within the boost mode-minimum phase shift amount P4 ... The phase shift amount P32) / (maximum phase shift amount P43 in step-down mode within step-up mode-minimum phase shift amount P42) can be determined using the relational expression.

[0052] FIG. 10 is a diagram showing a mode switching when the DC / DC converter 10 according to the embodiment changes from a boost state to a buck state in the boost-in buck mode. In the example of FIG. 10, the buck state is assumed to be entered when the phase shift amount is P51. In FIG. 10, P51, P52, P53, P61, P62, and P63 are examples of phase shift amounts. When the boost-in buck switching control unit 23 detects that the buck state is entered in the boost-in buck mode, it transitions the DC / DC converter 10 to the buck mode. At this time, the boost-in buck switching control unit 23 transitions to a phase shift amount that results in the same PWM waveform as the PWM waveform in the boost-in buck mode when the phase shift amount is P51. The phase shift amount of the transition destination can be determined, for example, by using the above-mentioned relational expression.

[0053] Fig. 11 is a diagram showing mode switching when the DC / DC converter 10 according to the embodiment transitions from the buck state to the boost state in the boost mode executed following the buck-in-boost mode. In the example of Fig. 11, the transition from the buck state to the boost state occurs when the phase shift amount is P71. In Fig. 11, P71, P72, P73, P74, P81, P82, P83, and P84 exemplify the phase shift amount. When the buck-in-boost switching control unit 23 detects the transition from the buck state to the boost state in the boost mode, the region of the buck-in-boost mode becomes available while maintaining the phase shift amount.

[0054] Fig. 12 is a diagram showing mode switching when the DC / DC converter 10 according to the embodiment transitions from the buck state to the boost state in the boost mode. In the example of Fig. 12, the transition from the buck state to the boost state occurs when the phase shift amount is P91. In Fig. 12, P91, P92, P93, P94, P01, P02, P03, and P04 exemplify the phase shift amount. When the boost / buck switching control unit 23 detects the transition from the boost state to the buck state in the boost mode, the boost / buck switching control unit 23 becomes unable to use the region of the boost-in-buck mode while maintaining the phase shift amount within the region of the boost mode.

[0055] <Effects of the embodiment> In this embodiment, the buck mode (step-down mode within the boost mode) is executed in a predetermined section that exists before the start point on the phase shift amount axis of the boost mode in the boost state. According to this embodiment, the step-down mode within the boost mode is executed, and the excitation current is suppressed by adjusting the conduction time of each switch that causes the excitation current to flow, and thus the DC / DC converter 10 can output a current of about 0 A.

[0056] In this embodiment, when the step-up state is transitioned from the step-down state during the step-down mode within the step-up, the step-down mode is switched to the step-down mode. Also, when the step-down state is transitioned from the step-down state to the step-up state during the step-down mode, the step-down mode is switched to the step-down mode within the step-up. Also, when the step-down state is transitioned from the step-down state to the step-up state during the step-up mode, the region of the step-up mode within the step-up can be used while maintaining the phase shift amount. At this time, the magnitude of the phase shift amount may be changed to enter the region of the step-up mode within the step-up. Also, when the step-up state is transitioned from the step-down state during the step-up mode, the region of the step-up mode within the step-up cannot be used while maintaining the phase shift amount. Therefore, according to this embodiment, the power conversion device 1 can be transitioned to a mode suitable for the step-up state and the step-down state.

[0057] In this embodiment, the step-down mode in the boost mode is obtained by compressing the waveform of the PWM signal supplied in section T1 (see FIG. 8) in the step-down mode in the phase shift amount axis direction so that it fits into the first section T2 (see FIG. 8). Therefore, when transitioning from the step-down mode to the step-up mode, the connection of the PWM waveform becomes smooth, and the switching between the modes becomes seamless.

[0058] <Modification> In the embodiment described above, the power conversion device 1 includes the insulating DC / DC converter 10. However, the power conversion device 1 may include a non-insulated DC / DC converter 10.

[0059] Furthermore, the step-up / step-down switching control unit 23 of the power conversion device 1 may use the internal step-up / step-down mode when changing the output current in the step-up mode from a current near 0 A (current within a predetermined range from 0 A) to a desired current greater than 0 A (current outside the predetermined range). The internal step-up / step-down mode adjusts the magnitude of the excitation current, thereby enabling the output of a current near 0 A to be suitably performed.

[0060] The embodiments and modifications disclosed above can be combined with each other.

[0061] <Appendix 1> An input terminal pair (13); An output terminal pair (14); a first capacitor (C1) connected in parallel to the input terminal pair (13); a second capacitor (C2) connected in parallel to the output terminal pair (14); a first switching unit (11) connected to the first capacitor (C1); a second switching unit (12) connected to the second capacitor (C2); a transformer (TR) disposed between the first switching unit (11) and the second switching unit (12); a control unit (20) that switches between a step-up mode that controls switching of the first switching unit (11) and the second switching unit (12) so that an output voltage higher than an input voltage input to the input terminal pair (13) is output from the output terminal pair (14) in response to a command value input from a higher-level device, and a step-down mode that controls switching of the first switching unit (11) and the second switching unit (12) so that an output voltage lower than the input voltage is output from the output terminal pair (14), When switching from the buck mode to the boost mode when the input voltage is equal to or lower than the output voltage, or when changing the output current to be output from the output terminal pair in the boost mode from a current within a predetermined range from 0 A to a current outside the predetermined range, the control unit (20) uses a buck-in-boost mode that performs switching control of the buck mode in a predetermined section (T2) that exists before a start point on an axis of a phase shift amount of the boost mode. Power conversion device (1). <Appendix 2> When the control unit (20) detects that the output voltage becomes less than the input voltage during the step-down mode, the control unit (20) switches from the step-down mode to the step-down mode. The power conversion device (1) as described in appendix 1. <Appendix 3> When the control unit (20) detects that the input voltage becomes equal to or lower than the output voltage during the voltage boost mode, the control unit (20) maintains the voltage boost mode or switches from the voltage boost mode to the voltage buck mode within the voltage boost mode. The power conversion device (1) according to appendix 1 or 2. <Appendix 4> A section on the phase shift amount axis in which the step-down mode is executed is a first section (T1), and a section in which the step-up mode is executed is a third section (T3), the predetermined period (T2) during which the in-boost step-down mode is executed is shorter than the first period (T1) and the third period (T3); The control unit (20) A PWM signal is supplied to each of the first switching unit and the second switching unit. by supplying the power supply voltage to the power supply terminals, the power supply voltage in the step-up mode, the step-down mode, and the step-down mode within the step-up mode, The PWM signal in the step-up step-down mode is a signal obtained by compressing a waveform output in the first section (T1) in the step-down mode in a phase shift amount axis direction so as to fit within the predetermined section (T2). 4. A power conversion device according to any one of claims 1 to 3. [Explanation of symbols]

[0062] 1. Power conversion device 2··EV 3...Power system 4. Load 10. DC / DC converter 11. Full bridge circuit 12. Full bridge circuit 20. Control unit 21 Control section 22...PWM generation section 23. Buck-boost switching control section 30. Inverter 13 Input / Output Terminal Pair 14 Input / Output Terminal Pair 13p Input / output terminal 13m...Input / output terminal 14p Input / output terminal 14m...Input / output terminal 15p Voltage sensor 15s··Voltage Sensor C1 Capacitor C2 Capacitor TR··Transformer Lr1 Reactor Lr2 Reactor Q1 Switching element Q2 Switching element Q3 Switching element Q4 Switching element Q5 Switching element Q6 Switching element Q7 Switching element Q8 Switching element

Claims

1. An input terminal pair; an output terminal pair; a first capacitor connected in parallel to the pair of input terminals; a second capacitor connected in parallel to the pair of output terminals; a first switching unit connected to the first capacitor; a second switching unit connected to the second capacitor; A transformer disposed between the first switching unit and the second switching unit; a control unit that switches between a step-up mode that controls switching of the first switching unit and the second switching unit so that an output voltage higher than an input voltage input to the input terminal pair is output from the output terminal pair in response to a command value input from a higher-level device, and a step-down mode that controls switching of the first switching unit and the second switching unit so that the output voltage lower than the input voltage is output from the output terminal pair, the control unit uses a step-down mode within a step-up converter for controlling switching of the step-down mode in a predetermined section that exists before a start point on a phase shift amount axis of the step-up mode when switching from the step-down mode to the step-up mode when the input voltage is equal to or lower than the output voltage, or when changing an output current to be output from the output terminal pair in the step-up mode from a current within a predetermined range from 0 A to a current outside the predetermined range. Power conversion equipment.

2. when the control unit detects that the output voltage becomes less than the input voltage during the step-down-boost mode, the control unit switches from the step-down-boost mode to the step-down mode. The power conversion device according to claim 1 .

3. When the control unit detects that the input voltage becomes equal to or lower than the output voltage during the voltage-boost mode, the control unit maintains the voltage-boost mode or switches from the voltage-boost mode to the voltage-in-boost step-down mode. The power conversion device according to claim 1 .

4. a section in which the step-down mode is executed is a first section, and a section in which the step-up mode is executed is a third section, the predetermined period during which the in-boost step-down mode is executed is a period shorter than the first period and the third period, The control unit is supplying a PWM signal to each of the first switching unit and the second switching unit, thereby performing switching control in each of the step-up mode, the step-down mode, and the step-down-in-step-up mode; the PWM signal in the step-down mode within the step-up mode is a signal obtained by compressing a waveform output in the first section in the step-down mode in a phase shift amount axis direction so as to fit within the predetermined section. The power conversion device according to claim 1 .

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