Power conversion device and power conversion system

Abstract

To obtain a power conversion device capable of setting charging characteristics in a precharge operation by a simple configuration.SOLUTION: A power conversion device has a first power terminal, a switching circuit having a plurality of first switching elements which can be turned on and off based on a first driving signal, a transformer, a rectification circuit having a plurality of second switching elements which can be turned on and off based on a second driving signal, a smoothing circuit, a second power terminal, and a control circuit. The control circuit, in a first period before supplying power from the first power terminal to the second power terminal, generates a first threshold value increasing as time elapses, and when a voltage value of voltage in the first power terminal reaches the first threshold value, performs switching from an output state of outputting the second driving signal to an output stop state of stopping the output of the second driving signal, or switching from the output stop state to the output state.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a power conversion device and a power conversion system for converting electric power. [Background technology]

[0002] Some power conversion devices that convert the power of a primary battery and supply it to a secondary battery perform a so-called precharge operation, in which the power of the secondary battery is supplied to a primary capacitor via the power conversion device before the power conversion operation is performed. For example, Patent Document 1 discloses a technique for controlling the current during the precharge operation. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-205293 Summary of the Invention [Problem to be solved by the invention]

[0004] In a power conversion device that performs such a precharge operation, for example, the voltage of the primary-side capacitor changes less as charging progresses, so it takes time to charge. Furthermore, the charging time required for the precharge operation and the voltage gradient during the precharge operation may vary depending on, for example, the capacitance value of the primary-side capacitor. It is desirable that the charging characteristics of such a precharge operation can be set to, for example, predetermined characteristics. It is desirable that a power conversion device be able to set such charging characteristics using a simple configuration.

[0005] It is desirable to provide a power conversion device and a power conversion system that can set the charging characteristics in the precharge operation with a simple configuration. [Means for solving the problem]

[0006] A power conversion device according to an embodiment of the present invention includes a first power terminal, a switching circuit, a transformer, a rectifier circuit, a smoothing circuit, a second power terminal, and a control circuit. The first power terminal is connected to the capacitor. The switching circuit is connected to the first power terminal and has a first plurality of switching elements that can be turned on and off based on a first drive signal. The transformer has a first winding connected to the switching circuit and a second winding. The rectifier circuit is connected to the second winding and has a second plurality of switching elements that can be turned on and off based on a second drive signal. The smoothing circuit is connected to the rectifier circuit. The second power terminal is connected to the smoothing circuit. The control circuit is capable of controlling the operation of the first plurality of switching elements and the second plurality of switching elements. The control circuit is capable of generating a first threshold that increases over time during a first period before supplying power from the first power terminal to the second power terminal, and is capable of switching from an output state in which the second drive signal is output to an output stopped state in which output of the second drive signal is stopped, or from the output stopped state to an output state, when the voltage value of the voltage at the first power terminal reaches the first threshold.

[0007] A power conversion system according to one embodiment of the present invention includes a first battery, a capacitor, a first switch, a second switch, a power conversion device, and a second battery. The first battery has a first terminal and a second terminal. The capacitor has a first terminal and a second terminal. The first switch is provided in a path connecting the first terminal of the first battery and the first terminal of the capacitor. The second switch is provided in a path connecting the second terminal of the first battery and the second terminal of the capacitor. The power conversion device includes a first power terminal, a switching circuit, a transformer, a rectifier circuit, a smoothing circuit, a second power terminal, and a control circuit. The first power terminal has a first connection terminal connected to the first terminal of the capacitor and a second connection terminal connected to the second terminal of the capacitor. The switching circuit is connected to the first power terminal and includes a first plurality of switching elements that can be turned on and off based on a first drive signal. The transformer has a first winding connected to a switching circuit and a second winding. The rectifier circuit is connected to the second winding and has a second plurality of switching elements that can be turned on and off based on a second drive signal. The smoothing circuit is connected to the rectifier circuit. The second power terminal is connected to the smoothing circuit. The control circuit is capable of controlling the operation of the first plurality of switching elements and the second plurality of switching elements. The control circuit is capable of generating a first threshold value that increases over time during a first period before power is supplied from the first power terminal to the second power terminal, and is capable of switching from an output state in which the second drive signal is output to an output stop state in which output of the second drive signal is stopped, or from the output stop state to an output state, when the voltage value of the voltage at the first power terminal reaches the first threshold value. [Effects of the Invention]

[0008] According to the power conversion device and power conversion system according to an embodiment of the present invention, the charging characteristics in the precharge operation can be set with a simple configuration. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a circuit diagram illustrating an example of a configuration of a power conversion system according to an embodiment of the present invention. [Figure 2] 2 is a block diagram illustrating an example of the configuration of a control circuit illustrated in FIG. 1. FIG. [Figure 3] 3 is an explanatory diagram illustrating an example of an operation of the threshold value generating unit illustrated in FIG. 2. FIG. [Figure 4] 3 is an explanatory diagram illustrating an example of a characteristic of a comparison operation in the comparison section shown in FIG. 2. [Figure 5] 3 is a timing chart illustrating an example of the operation of the comparison unit illustrated in FIG. 2. [Figure 6] 2 is a timing chart illustrating an example of a precharge operation in the power conversion system shown in FIG. 1. [Figure 7] 7 is a timing waveform diagram showing the relationship between the enable signal and the gate signal shown in FIG. 6. [Figure 8] 2 is a timing waveform diagram illustrating an example of a precharge operation in the power conversion system shown in FIG. 1. [Figure 9] FIG. 10 is an explanatory diagram illustrating an example of an operation of a threshold value generating unit according to a modified example. [Figure 10] FIG. 10 is an explanatory diagram illustrating an example of an operation of a threshold value generating unit according to another modified example. [Figure 11] FIG. 10 is a block diagram illustrating an example of the configuration of a control circuit according to another modified example. [Figure 12] 12 is a timing chart illustrating an example of the operation of the comparison unit illustrated in FIG. 11. [Figure 13] FIG. 10 is a block diagram illustrating an example of the configuration of a control circuit according to another modified example. [Figure 14] 14 is a timing chart illustrating an example of the operation of the comparison unit illustrated in FIG. 13. [Figure 15] FIG. 10 is a timing chart illustrating an example of a precharge operation in a power conversion system according to another modified example. [Figure 16] FIG. 10 is a timing chart illustrating an example of a precharge operation in a power conversion system according to another modified example. [Figure 17] FIG. 10 is a block diagram illustrating an example of the configuration of a control circuit according to another modified example. [Figure 18] 8 is a timing chart illustrating an example of a precharge operation in the power conversion system including the control circuit shown in FIG. 7. [Figure 19] FIG. 10 is a block diagram illustrating an example of the configuration of a control circuit according to another modified example. [Figure 20] FIG. 10 is a circuit diagram illustrating a configuration example of a power conversion system according to another modified example. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0011] <Embodiment> [Configuration example] 1 shows an example of the configuration of a power conversion system 1 including a power conversion device according to an embodiment of the present invention. The power conversion system 1 includes a high-voltage battery BH, switches SW1 and SW2, a capacitor 9, a power conversion device 10, and a low-voltage battery BL. The power conversion system 1 is configured to convert power supplied from the high-voltage battery BH and supply the converted power to the low-voltage battery BL.

[0012] The high-voltage battery BH is configured to store electric power and supplies the electric power to the power conversion device 10 via the switches SW1 and SW2.

[0013] The switches SW1 and SW2 are configured to supply power stored in the high-voltage battery BH to the power conversion device 10 when they are turned on. The switches SW1 and SW2 are configured using, for example, relays. When the switch SW1 is turned on, it connects the positive terminal of the high-voltage battery BH to the terminal T11 of the power conversion device 10. When the switch SW2 is turned on, it connects the negative terminal of the high-voltage battery BH to the terminal T12 of the power conversion device 10. The switches SW1 and SW2 are turned on and off based on instructions from a system control unit (not shown).

[0014] One end of the capacitor 9 is connected to the terminal T11 of the power conversion device 10 and the switch SW1, and the other end is connected to the terminal T12 of the power conversion device 10 and the switch SW2.

[0015] The power conversion device 10 is configured to convert power by stepping down the voltage supplied from the high-voltage battery BH and supply the converted power to the low-voltage battery BL. The power conversion device 10 has terminals T11 and T12, a voltage sensor 11, a switching circuit 12, a transformer 13, a rectifier circuit 14, a smoothing circuit 15, a voltage sensor 18, a control circuit 19, and terminals T21 and T22. The high-voltage battery BH, switches SW1 and SW2, capacitor 9, voltage sensor 11, and switching circuit 12 constitute a primary circuit of the power conversion system 1, and the rectifier circuit 14, smoothing circuit 15, voltage sensor 18, and low-voltage battery BL constitute a secondary circuit of the power conversion system 1.

[0016] When the switches SW1 and SW2 are turned on, the terminals T11 and T12 are supplied with a voltage from the high-voltage battery BH. Within the power conversion device 10, the terminal T11 is connected to the voltage line L11, and the terminal T12 is connected to the reference voltage line L12.

[0017] The voltage sensor 11 is configured to detect the voltage on the voltage line L11. One end of the voltage sensor 11 is connected to the voltage line L11, and the other end is connected to a reference voltage line L12. The voltage sensor 11 detects the voltage on the voltage line L11 relative to the voltage on the reference voltage line L12 as a voltage VH. The voltage sensor 11 then supplies the detection result of the voltage VH to the control circuit 19.

[0018] The switching circuit 12 is configured to convert a DC voltage supplied from the high-voltage battery BH into an AC voltage. The switching circuit 12 is a full-bridge circuit and includes transistors S1 to S4. The transistors S1 to S4 are switching elements that perform switching operations based on gate signals GA to GD, respectively. The transistors S1 to S4 are configured using, for example, N-type field effect transistors (FETs). The transistors S1 to S4 each include body diodes D1 to D4. For example, the anode of the body diode D1 is connected to the source of the transistor S1, and the cathode is connected to the drain of the transistor S1. The same applies to the body diodes D2 to D4. Note that this configuration is not limited to this, and for example, a diode element may be externally connected between the drain and source of each of the transistors S1 to S4. Although N-type field effect transistors are used in this example, any switching element may be used.

[0019] The transistor S1 is provided in a path connecting the voltage line L11 and the node N1, and is configured to connect the node N1 to the voltage line L11 when turned on. The drain of the transistor S1 is connected to the voltage line L11, the gate is supplied with a gate signal GA, and the source is connected to the node N1. The transistor S2 is provided in a path connecting the node N1 and the reference voltage line L12, and is configured to connect the node N1 to the reference voltage line L12 when turned on. The drain of the transistor S2 is connected to the node N1, the gate is supplied with a gate signal GB, and the source is connected to the reference voltage line L12. The node N1 is the connection point between the source of the transistor S1 and the drain of the transistor S2.

[0020] The transistor S3 is provided in a path connecting the voltage line L11 and the node N2, and is configured to connect the node N2 to the voltage line L11 when turned on. The drain of the transistor S3 is connected to the voltage line L11, the gate is supplied with a gate signal GC, and the source is connected to the node N2. The transistor S4 is provided in a path connecting the node N2 and the reference voltage line L12, and is configured to connect the node N2 to the reference voltage line L12 when turned on. The drain of the transistor S4 is connected to the node N2, the gate is supplied with a gate signal GD, and the source is connected to the reference voltage line L12. The node N2 is the connection point between the source of the transistor S3 and the drain of the transistor S4.

[0021] Transformer 13 is configured to insulate the primary side circuit from the secondary side circuit in terms of DC current and connect them in terms of AC current, convert the AC voltage supplied from the primary side circuit at a transformation ratio N of transformer 13, and supply the converted AC voltage to the secondary side circuit. Transformer 13 has windings 13A and 13B. One end of winding 13A is connected to node N1 in switching circuit 12, and the other end is connected to node N2 in switching circuit 12. One end of winding 13B is connected to node N4 (described later) in rectifier circuit 14, and the other end is connected to node N5 (described later) in rectifier circuit 14.

[0022] The rectifier circuit 14 is configured to generate an output voltage by rectifying the AC voltage output from the winding 13B of the transformer 13. The rectifier circuit 14 is a full-bridge circuit and includes transistors S5 to S8. The transistors S5 to S8 are configured to perform switching operations based on gate signals GE and GF. Like the transistors S1 to S4 of the switching circuit 12, the transistors S5 to S8 are configured using, for example, N-type field effect transistors. Like the transistors S1 to S4, the transistors S5 to S8 include body diodes D5 to D8, respectively.

[0023] The transistor S5 is provided in a path connecting the voltage line L21A and the node N4, and is configured to connect the node N4 to the voltage line L21A when turned on. The drain of the transistor S5 is connected to the voltage line L21A, the gate is supplied with a gate signal GF, and the source is connected to the node N4. The transistor S6 is provided in a path connecting the node N4 and the reference voltage line L22, and is configured to connect the node N4 to the reference voltage line L22 when turned on. The drain of the transistor S6 is connected to the node N4, the gate is supplied with a gate signal GE, and the source is connected to the reference voltage line L22. The node N4 is the connection point between the source of the transistor S5 and the drain of the transistor S6.

[0024] Transistor S7 is provided in a path connecting voltage line L21A and node N5, and is configured to connect node N5 to voltage line L21A when turned on. The drain of transistor S7 is connected to voltage line L21A, a gate signal GE is supplied to its gate, and a source is connected to node N5. Transistor S8 is provided in a path connecting node N5 and reference voltage line L22, and is configured to connect node N5 to reference voltage line L22 when turned on. The drain of transistor S8 is connected to node N5, a gate signal GF is supplied to its gate, and a source is connected to reference voltage line L22. Node N5 is the connection point between the source of transistor S7 and the drain of transistor S8.

[0025] The smoothing circuit 15 is configured to smooth the output voltage of the rectifier circuit 14. The smoothing circuit 15 has a choke inductor 16 and a capacitor 17. One end of the choke inductor 16 is connected to the voltage line L21A, and the other end is connected to the voltage line L21B. One end of the capacitor 17 is connected to the voltage line L21B, and the other end is connected to the reference voltage line L22. In this example, the choke inductor 16 is provided on the voltage lines L21A and L21B, but this is not limiting and the choke inductor 16 may instead be provided on the reference voltage line L22, for example.

[0026] The voltage sensor 18 is configured to detect the voltage on the voltage line L21B. One end of the voltage sensor 18 is connected to the voltage line L21B, and the other end is connected to the reference voltage line L22. The voltage sensor 18 detects the voltage on the voltage line L21B relative to the voltage on the reference voltage line L22 as the voltage VL. The voltage sensor 18 then supplies the detection result of the voltage VL to the control circuit 19.

[0027] The control circuit 19 is configured to control the operation of the power conversion device 10 by controlling the operation of the switching circuit 12 and the rectifier circuit 14 based on the voltage VH detected by the voltage sensor 11, the voltage VL detected by the voltage sensor 18, and control information CTL supplied from a system control unit (not shown). Specifically, the control circuit 19 generates gate signals GA to GF based on the voltages VH and VL, and controls the operation of the power conversion device 10 by performing PWM (Pulse Width Modulation) control using the gate signals GA to GF. The control circuit 19 is configured using, for example, a microcontroller. The control circuit 19 performs AD conversion on the supplied voltages VH and VL, and performs processing based on the AD-converted digital values. Hereinafter, the voltages VH and VL will be appropriately used to represent the AD-converted digital values.

[0028] The terminals T21 and T22 are configured to supply the voltage generated by the power conversion device 10 to the low-voltage battery BL. Within the power conversion device 10, the terminal T21 is connected to the voltage line L21B, and the terminal T22 is connected to the reference voltage line L22. Furthermore, the terminal T21 is connected to the positive terminal of the low-voltage battery BL, and the terminal T22 is connected to the negative terminal of the low-voltage battery BL.

[0029] The low-voltage battery BL is configured to store the power supplied from the power conversion device 10.

[0030] With this configuration, the power conversion system 1 performs a power conversion operation of converting the power supplied from the high-voltage battery BH and supplying the converted power to the low-voltage battery BL.

[0031] The power conversion system 1 also has a function of performing a so-called precharge operation, which charges the capacitor 9 during a preparation period (precharge period P1) before starting such a power conversion operation. During this precharge operation, the switches SW1 and SW2 are in the off state, and the control circuit 19 controls the operation of the switching circuit 12 and the rectifier circuit 14, so that the power conversion system 1 supplies power from the low-voltage battery BL to the capacitor 9. This allows the power conversion device 10 to suppress inrush current flowing from the high-voltage battery BH to the capacitor 9 when the switches SW1 and SW2 are turned on to perform the power conversion operation.

[0032] 2 shows an example of the configuration of the control circuit 19. The control circuit 19 has a precharge control unit 21, a power conversion control unit 27, and gate signal generation units 28 and 29.

[0033] The precharge control unit 21 is configured to generate, based on the voltage VL, a duty ratio DP for the switching operation in the switching circuit 12 and a duty ratio DS for the switching operation in the rectifier circuit 14 during a precharge period P1 and a period following the precharge period P1 (a voltage maintenance period P2). The precharge control unit 21 also has a function of generating, based on the voltage VH, an enable signal EN that indicates whether the control circuit 19 should output gate signals GA to GF. The precharge control unit 21 has duty ratio generation units 23 and 24, a threshold generation unit 25, and a comparison unit 26.

[0034] The duty ratio generation unit 23 is configured to generate a duty ratio DP for the switching circuit 12 based on the voltage VL during the precharge period P1 and the voltage maintenance period P2. Specifically, the duty ratio generation unit 23 generates the duty ratio DP in the precharge period P1 such that the duty ratio DP decreases as the voltage VL increases. The duty ratio generation unit 23 can generate the duty ratio DP based on the voltage VL using a function such as "DP = X1 / VL," where "X1" is a constant having a voltage dimension and is an arbitrary constant smaller than the value of the voltage VL. The duty ratio generation unit 23 may also generate the duty ratio DP based on the voltage VL using table data indicating the relationship between the duty ratio DP and the voltage VL, for example. The duty ratio generation unit 23 generates the duty ratio DP in the precharge period P1 such that the duty ratio DP gradually increases. This allows the power conversion system 1 to reduce current stress within the circuit. Furthermore, the duty ratio generation unit 23 generates a duty ratio DP of a predetermined value corresponding to, for example, the voltage VL during the voltage maintenance period P2. However, without being limited to this, the duty ratio generation unit 23 may generate the duty ratio DP by performing feedback control based on the voltage VL during the voltage maintenance period P2.

[0035] The duty ratio generation unit 24 is configured to generate a duty ratio DS for the rectifier circuit 14 based on the voltage VL during the precharge period P1 and the voltage maintenance period P2. Specifically, the duty ratio generation unit 24 generates the duty ratio DS during the precharge period P1 such that the duty ratio DS decreases as the voltage VL increases. The duty ratio generation unit 24 can generate the duty ratio DS based on the voltage VL using a function such as "DS=X2 / VL," where "X2" is a constant having a voltage dimension and is an arbitrary constant smaller than the value of the voltage VL. Alternatively, the duty ratio generation unit 24 may generate the duty ratio DS based on the voltage VL using table data indicating the relationship between the duty ratio DS and the voltage VL. The duty ratio generation unit 24 generates the duty ratio DS during the precharge period P1 such that the duty ratio DS gradually increases. This allows the power conversion system 1 to reduce current stress within the circuit. Furthermore, the duty ratio generation unit 24 generates a duty ratio DS of a predetermined value corresponding to, for example, the voltage VL during the voltage maintenance period P2. However, without being limited to this, the duty ratio generation unit 24 may generate the duty ratio DS by performing feedback control based on the voltage VL during the voltage maintenance period P2.

[0036] The threshold generator 25 is configured to generate thresholds THtop and THbot based on a target voltage command value VHtarget for the voltage VH included in the control information CTL during the precharge period P1 and the voltage maintenance period P2. The threshold THtop is a value corresponding to the upper limit voltage of the voltage VH, and the threshold THbot is a value corresponding to the lower limit voltage of the voltage VH.

[0037] FIG. 3 shows an example of the thresholds THtop and THbot. In this example, the threshold generator 25 linearly increases the threshold THtop as time passes from timing t1 onward when the precharge period P1 starts, and stops changing the threshold THtop from timing t3 onward. The value of the threshold THtop from timing t3 onward is the target voltage command value VHtarget. In this example, the value of the threshold THtop is set to the same value as the target voltage command value VHtarget from timing t3 onward. However, this is not limited to this. For example, the threshold THtop may be a value (VHtarget+ΔV) obtained by adding a value ΔV to the target voltage command value VHtarget. Here, ΔV is an arbitrary value corresponding to the target voltage command value VHtarget. Furthermore, the threshold generator 25 linearly increases the threshold THbot as time passes from timing t2 onward, which is after timing t1, and stops changing the threshold THbot from timing t4 onward, which is after timing t3. The threshold THtop is a value greater than the threshold THbot. In this example, the slope ktop of the threshold value THtop in the period from timing t1 to t3 is equal to the slope kbot of the threshold value THbot in the period from timing t2 to t4.

[0038] As will be described later, voltage VH is controlled to be within a voltage range equal to or greater than threshold value THbot and equal to or less than threshold value THtop. When voltage VH reaches target voltage command value VHtarget (timing t5 in this example), precharge period P1 ends and voltage maintenance period P2 begins. After that, voltage maintenance period P2 ends, and a period during which power conversion is performed (power conversion period P3) begins.

[0039] The threshold value generating unit 25 generates such threshold values ​​THtop and THbot using, for example, a function or table data, and supplies these threshold values ​​THtop and THbot to the comparing unit 26.

[0040] The comparison unit 26 (FIG. 2) is configured to generate the enable signal EN by comparing the voltage VH with the thresholds THtop and THbot during the precharge period P1 and the voltage maintenance period P2.

[0041] 4 shows an example of the characteristics of the comparison operation of the comparator 26. When the voltage VH is lower than the threshold value THbot, the comparator 26 sets the enable signal EN to a high level. When the voltage VH gradually increases and reaches the threshold value THtop, the comparator 26 changes the enable signal EN from a high level to a low level. On the other hand, when the voltage VH is higher than the threshold value THtop, the comparator 26 sets the enable signal EN to a low level. When the voltage VH gradually decreases and reaches the threshold value THbot, the comparator 26 changes the enable signal EN from a low level to a high level. In this way, the comparison characteristics of the comparator 26 exhibit hysteresis characteristics in which the difference between the threshold value THtop and the threshold value THbot is the hysteresis amount HYS.

[0042] 3, the slope ktop of the threshold value THtop during the period from timing t1 to t3 is equal to the slope kbot of the threshold value THbot during the period from timing t2 to t4. Therefore, the hysteresis amount HYS is constant during the period from timing t2 to t3. Also, in this example, the hysteresis amount HYS during the period when the threshold values ​​THtop and THbot increase is greater than the hysteresis amount HYS during the voltage maintenance period P2. However, this is not limiting, and for example, the hysteresis amount HYS during the period when the threshold values ​​THtop and THbot increase may be the same as the hysteresis amount HYS during the voltage maintenance period P2.

[0043] FIG. 5 shows an example of the operation of the comparator 26. For example, at timing t11, the enable signal EN changes from low to high. As will be described later, when the enable signal EN changes to high, the control circuit 19 outputs gate signals GA to GF. The power converter 10 performs switching operations based on these gate signals GA to GF, supplies power from the low-voltage battery BL to the capacitor 9, and increases the voltage VH. Then, at timing t12, when the voltage VH reaches a threshold value THtop, the comparator 26 changes the enable signal EN from high to low. As will be described later, when the enable signal EN changes to low, the control circuit 19 maintains the gate signals GA to GF at low. As a result, the power converter 10 stops switching operations, and the voltage VH decreases. Then, at timing t13, when the voltage VH reaches a threshold value THbot, the comparator 26 changes the enable signal EN from low to high. Subsequent operations are similar.

[0044] In this way, the comparator 26 generates the enable signal EN by comparing the voltage VH with the thresholds THtop and THbot during the precharge period P1 and the voltage maintenance period P2. The comparator 26 also maintains the enable signal EN at a high level during the power conversion period P3.

[0045] The power conversion control unit 27 (FIG. 2) is configured to generate a duty ratio DP of the switching operation in the switching circuit 12 and a duty ratio DS of the switching operation in the rectifier circuit 14 based on the voltages VH, VL and control information CTL supplied from a system control unit (not shown) during the power conversion period P3.

[0046] The gate signal generation unit 28 is configured to generate the gate signals GA to GD based on the duty ratio DP generated by the duty ratio generation unit 23 and the power conversion control unit 27, and the enable signal EN. Specifically, during the precharge period P1 and the voltage maintenance period P2, when the enable signal EN is at a high level, the gate signal generation unit 28 generates the gate signals GC and GD based on the duty ratio DP generated by the duty ratio generation unit 23 and maintains the gate signals GA and GB at a low level, and when the enable signal EN is at a low level, maintains the gate signals GA to GD at a low level. Furthermore, during the power conversion period P3, the gate signal generation unit 28 generates the gate signals GA to GD based on the duty ratio DP generated by the power conversion control unit 27.

[0047] The gate signal generation unit 29 is configured to generate the gate signals GE and GF based on the duty ratio DS generated by the duty ratio generation unit 24 and the power conversion control unit 27, and the enable signal EN. Specifically, in the precharge period P1 and the voltage maintenance period P2, when the enable signal EN is at a high level, the gate signal generation unit 29 generates the gate signals GE and GF based on the duty ratio DS generated by the duty ratio generation unit 24, and when the enable signal EN is at a low level, the gate signal generation unit 29 maintains the gate signals GE and GF at a low level. Furthermore, in the power conversion period P3, the gate signal generation unit 29 generates the gate signals GE and GF based on the duty ratio DS generated by the power conversion control unit 27.

[0048] Here, terminals T11 and T12 correspond to a specific example of a "first power terminal" in the present disclosure. Terminal T11 corresponds to a specific example of a "first connection terminal" in the present disclosure. Terminal T12 corresponds to a specific example of a "second connection terminal" in the present disclosure. Switching circuit 12 corresponds to a specific example of a "switching circuit" in the present disclosure. Transformer 13 corresponds to a specific example of a "transformer" in the present disclosure. Winding 13A corresponds to a specific example of a "first winding" in the present disclosure. Winding 13B corresponds to a specific example of a "second winding" in the present disclosure. Rectifier circuit 14 corresponds to a specific example of a "rectifier circuit" in the present disclosure. Smoothing circuit 15 corresponds to a specific example of a "smoothing circuit" in the present disclosure. Control circuit 19 corresponds to a specific example of a "control circuit" in the present disclosure. Threshold value THbot corresponds to a specific example of a "first threshold value" in the present disclosure. Threshold value THtop corresponds to a specific example of a "second threshold value" in the present disclosure. The comparison unit 26 corresponds to a specific example of a "comparison unit" in the present disclosure. The duty ratio generation unit 24 corresponds to a specific example of a "duty ratio generation unit" in the present disclosure. The gate signal generation unit 29 corresponds to a specific example of a "drive unit" in the present disclosure.

[0049] [Actions and Actions] Next, the operation and function of the power conversion system 1 of this embodiment will be described.

[0050] (Overview of overall operation) First, an overview of the overall operation of the power conversion system 1 will be described with reference to FIGS. 1 and 2. When the power conversion system 1 starts, the switches SW1 and SW2 are in the off state. First, during a precharge period P1 and a voltage maintenance period P2, the control circuit 19 generates gate signals GC to GF based on the voltages VH and VL and the control information CTL, and maintains the gate signals GA and GB at a low level. This activates the switching circuit 12 and the rectifier circuit 14, and the power conversion device 10 supplies power from the low-voltage battery BL to the capacitor 9. As a result, the capacitor 9 is charged, and the voltage VH increases and is maintained near the voltage indicated by the target voltage command value VHtarget. Then, during a power conversion period P3, the switches SW1 and SW2 are turned on, and the control circuit 19 generates the gate signals GA to GF based on the voltages VH and VL. This allows the power conversion device 10 to convert power supplied from the high-voltage battery BH and supply the converted power to the low-voltage battery BL.

[0051] (Detailed operation) 6 shows an example of the precharge operation in the power conversion system 1, where (A) shows the waveform of the enable signal EN, (B) shows the duty ratio DS of the switching operation in the rectifier circuit 14, (C) shows the duty ratio DP of the switching operation in the switching circuit 12, and (D) shows the waveform of the voltage VH and the thresholds THtop and THbot. FIG. 7 shows an example of the operation of the gate signal generation units 28 and 29.

[0052] In this example, the precharge period P1 starts at timing t21. The precharge control unit 21 generates duty ratios DP and DS so that the duty ratios DP and DS gradually increase during this precharge period P1 (FIGS. 6B and 6C). In this example, the precharge control unit 21 generates duty ratios DP and DS so that the duty ratio DS is 0.5 or less and the duty ratio DP is equal to or less than the duty ratio DS. The threshold generation unit 25 also generates thresholds THtop and THbot so that the thresholds THtop and THbot gradually increase during the precharge period P1 (FIG. 6D). The comparison unit 26 generates an enable signal EN by comparing the voltage VH with the thresholds THtop and THbot (FIG. 6A). As shown in FIG. 7, the gate signal generation unit 28 generates gate signals GC and GD based on the duty ratio DP and maintains the gate signals GA and GB at a low level when the enable signal EN is at a high level, and maintains the gate signals GA to GD at a low level when the enable signal EN is at a low level. The gate signal generating unit 29 generates the gate signals GE and GF based on the duty ratio DS when the enable signal EN is at a high level, and maintains the gate signals GE and GF at a low level when the enable signal EN is at a low level.

[0053] At timing t21, the power conversion system 1 starts a precharge operation. At this timing t21, the comparator 26 changes the enable signal EN from low level to high level (FIG. 6(A)). The gate signal generator 28 generates gate signals GC and GD based on the duty ratio DP (FIG. 6(C)), and the gate signal generator 29 generates gate signals GE and GF based on the duty ratio DS (FIG. 6(B)) (FIG. 7). The power conversion device 10 performs a switching operation based on these gate signals GA to GF, supplies power from the low-voltage battery BL to the capacitor 9, and increases the voltage VH (FIG. 6(D)).

[0054] When the voltage VH reaches the threshold value THtop at timing t22 (FIG. 6(D)), the comparator 26 changes the enable signal EN from high to low (FIG. 6(A)). The gate signal generator 28 maintains the gate signals GC and GD at low levels, and the gate signal generator 29 maintains the gate signals GE and GF at low levels. This causes the power converter 10 to stop switching, and the voltage VH drops (FIG. 6(D)).

[0055] When the voltage VH reaches the threshold value THbot at timing t23 (FIG. 6(D)), the comparator 26 changes the enable signal EN from low level to high level (FIG. 6(A)). The gate signal generator 28 generates gate signals GC and GD based on the duty ratio DP (FIG. 6(C)), and the gate signal generator 29 generates gate signals GE and GF based on the duty ratio DS (FIG. 6(B)). The power converter 10 performs switching operations based on these gate signals GA to GF, supplies power from the low-voltage battery BL to the capacitor 9, and increases the voltage VH (FIG. 6(D)).

[0056] When the voltage VH reaches the threshold value THtop at timing t24 (FIG. 6(D)), the comparator 26 changes the enable signal EN from high level to low level (FIG. 6(A)).

[0057] The power conversion system 1 repeats this operation from timing t22 to t24. The gate signal generators 28 and 29 output the gate signals GC to GF while the enable signal EN is at a high level, and stop outputting the gate signals GC to GF while the enable signal EN is at a low level. In this manner, the power conversion system 1 operates intermittently during the precharge period P1. As a result, the voltage VH fluctuates between the threshold value THtop and the threshold value THbot. The voltage VH is controlled to be within a voltage range that is equal to or less than the threshold value THtop and equal to or greater than the threshold value THbot. The threshold values ​​THtop and THbot are set so as to gradually increase over time during the precharge period P1, and therefore the voltage VH rises toward the threshold values ​​THtop and THbot.

[0058] 8 shows an example of simulated waveforms of the precharge operation during the period P1 when the enable signal EN is at a high level, where (A) shows the waveform of gate signals GE and GF, (B) shows the waveform of gate signals GC and GD, (C) shows the waveform of the current (charge current ICHG) flowing into capacitor 9, (D) shows the waveform of the excitation current IM of transformer 13, (E) shows the waveform of the current (inductor current IL) flowing from voltage line L21B to voltage line L21A in choke inductor 16, (F) shows the waveform of the voltage (transformer voltage VTR2) at node N4 in winding 13B of transformer 13 relative to node N5, and (G) shows the waveform of voltage VH. In FIG. 8, T indicates the period of the switching operation.

[0059] In the precharge operation, the control circuit 19 generates gate signals GC and GD based on a duty ratio DP and generates gate signals GE and GF based on a duty ratio DS. The duty ratio DP indicates the pulse width of each of the gate signals GC and GD when the period T (the time length from timings t41 to t43) is set to "1," and the duty ratio DS indicates the pulse width of each of the gate signals GE and GF when the period T is set to "1." As shown in FIGS. 8A and 8B, the control circuit 19 changes the gate signals GC and GF from low to high at timing t41. Then, the control circuit 19 changes the gate signal GC from high to low when a time corresponding to the duty ratio DP (duty ratio DP × period T) has elapsed since timing t41, and changes the gate signal GF from high to low when a time corresponding to the duty ratio DS (duty ratio DS × period T) has elapsed since timing t41. Next, at timing t42, the control circuit 19 changes the gate signals GD and GE from low to high. Then, the control circuit 19 changes the gate signal GD from high to low when a time corresponding to the duty ratio DP (duty ratio DP × period T) has elapsed since timing t42, and changes the gate signal GE from high to low when a time corresponding to the duty ratio DS (duty ratio DS × period T) has elapsed since timing t42. Although not shown, the control circuit 19 maintains the gate signals GA and GB at low levels. As a result, a charge current ICHG flows into the capacitor 9 as shown in FIG. 8(C), and the voltage VH gradually increases (FIG. 8(G)).

[0060] Thus, while the enable signal EN is at a high level, the voltage VH rises. The voltage gradient of this voltage VH, shown in Figure 6, is set by the duty ratios DP and DS. The larger the voltage gradient of this voltage VH is compared to the gradients of the thresholds THtop and THbot, the shorter the time it takes for the voltage VH to change from the threshold THbot to the threshold THtop, and therefore the more frequently the enable signal EN (Figure 6(A)) transitions.

[0061] In the example of FIG. 6, after timing t25, the threshold value generating unit 25 sets the threshold value THtop to a value indicated by the target voltage command value VHtarget, and sets the threshold value THbot to a value corresponding to the target voltage command value VHtarget (FIG. 6(D)). Note that this is not limited to this, and the threshold value generating unit 25 may set the threshold value THbot to a value indicated by the target voltage command value VHtarget, and set the threshold value THtop to a value corresponding to the target voltage command value VHtarget. Furthermore, the threshold value generating unit 25 may set the threshold value THtop to a value corresponding to the target voltage command value VHtarget (for example, VHtarget+ΔV1), and set the threshold value THbot to a value corresponding to the target voltage command value VHtarget (for example, VHtarget-ΔV2). Here, ΔV1 and ΔV2 are arbitrary values ​​corresponding to the target voltage command value VHtarget.

[0062] Then, at timing t26, the voltage VH reaches the threshold value THtop, which is the target voltage command value VHtarget (FIG. 6(D)). This ends the precharge period P1 and starts the voltage maintenance period P2. During the voltage maintenance period P2, the precharge control unit 21 sets the duty ratios DP and DS to predetermined values ​​(FIGS. 6(B) and 6(C)). In this example, the precharge control unit 21 sets the duty ratio DP to a value slightly lower than the value immediately before timing t26, and sets the duty ratio DS to a value slightly lower than the value immediately before timing t26. During the voltage maintenance period P2, the duty ratio generation units 23 and 24 generate the duty ratios DP and DS of predetermined values ​​according to the voltage VL. Note that this is not a limitation, and the duty ratio generation units 23 and 24 may generate the duty ratios DP and DS by performing feedback control based on the voltage VL.

[0063] When the voltage VH reaches the threshold value THtop at timing t26 (FIG. 6(D)), the comparator 26 changes the enable signal EN from high to low (FIG. 6(A)). The gate signal generator 28 maintains the gate signals GC and GD at low levels, and the gate signal generator 29 maintains the gate signals GE and GF at low levels. This causes the power converter 10 to stop switching, and the voltage VH drops (FIG. 6(D)).

[0064] When the voltage VH reaches the threshold value THbot at timing t27 (FIG. 6(D)), the comparator 26 changes the enable signal EN from low level to high level (FIG. 6(A)). The gate signal generator 28 generates gate signals GC and GD based on the duty ratio DP (FIG. 6(C)), and the gate signal generator 29 generates gate signals GE and GF based on the duty ratio DS (FIG. 6(B)). As a result, the power converter 10 performs switching operation based on these gate signals GA to GF, supplies power from the low-voltage battery BL to the capacitor 9, and increases the voltage VH (FIG. 6(D)).

[0065] When the voltage VH reaches the threshold value THtop at timing t28 (FIG. 6(D)), the comparator 26 changes the enable signal EN from high level to low level (FIG. 6(A)).

[0066] The power conversion system 1 repeats this operation from timing t26 to t28. The gate signal generators 28 and 29 output the gate signals GC to GF while the enable signal EN is at a high level, and stop outputting the gate signals GC to GF while the enable signal EN is at a low level. In this manner, the power conversion system 1 operates intermittently during the voltage maintenance period P2. As a result, the voltage VH fluctuates between the threshold value THtop and the threshold value THbot. The voltage VH is controlled to a voltage within a voltage range that is equal to or less than the threshold value THtop and equal to or greater than the threshold value THbot. The threshold values ​​THtop and THbot are set to values ​​corresponding to the target voltage command value VHtarget during the voltage maintenance period P2, so the voltage VH is maintained near the voltage indicated by the target voltage command value VHtarget.

[0067] In this manner, in the power conversion system 1, the control circuit 19 generates a first threshold (threshold THbot) that increases over time during a first period before power is supplied from the first power terminals (terminals T11 and T12) to the second power terminals (terminals T21 and T22), and when the voltage value of the voltage VH at the first power terminals (terminals T11 and T12) reaches the first threshold (threshold THbot), the control circuit 19 switches from an output stop state in which output of the gate signals GE and GF is stopped to an output state in which output of the gate signals GE and GF is stopped. Furthermore, during this first period, the control circuit 19 generates a second threshold (threshold THtop) that increases over time and has a value greater than the first threshold (threshold THbot), and when the voltage value of the voltage VH at the first power terminals (terminals T11 and T12) reaches the second threshold (threshold THtop), the control circuit 19 switches from the output state in which output of the gate signals GE and GF to an output stop state in which output of the gate signals GE and GF is stopped. As a result, the power conversion system 1 can control the voltage change of the voltage VH based on the thresholds THtop and THbot during the precharge period P1. Therefore, the power conversion system 1 can control various characteristics, such as the charging time required for the precharge operation and the voltage gradient of the voltage VH during the precharge operation. Furthermore, for example, when the capacitance value of the capacitor 9 is changed depending on the application, the power conversion system 1 can set the charging characteristics of the precharge operation to predetermined characteristics regardless of the capacitance value of the capacitor 9. In this way, the power conversion system 1 can set the charging characteristics during the precharge operation.

[0068] In addition, in the power conversion system 1, the outputs of the gate signals GE and GF are controlled based on the comparison result between the voltage VH and the threshold values ​​THtop and THbot in this way. This eliminates the need for a current sensor used in the technology described in Patent Document 1, for example, and thus allows for a simple configuration.

[0069] In addition, in the power conversion system 1, the outputs of the gate signals GE and GF are controlled based on the comparison result between the voltage VH and the thresholds THtop and THbot in this way, so that the enable signal EN transitions and performs intermittent operation as shown in Fig. 6. This makes it possible to suppress temperature increases in the switching circuit 12 and the rectifier circuit 14, for example.

[0070] [effect] As described above, in this embodiment, during a first period before power is supplied from the first power terminal to the second power terminal, a first threshold value that increases over time is generated, and when the voltage value at the first power terminal reaches the first threshold value, the state switches from an output stop state in which output of the gate signal is stopped to an output state in which output of the gate signal is output. Furthermore, during this first period, a second threshold value that increases over time and has a value greater than the first threshold value is generated, and when the voltage value at the first power terminal reaches the second threshold value, the state switches from an output state in which output of the gate signal to an output stop state in which output of the gate signal is stopped. This allows the charging characteristics of the precharge operation to be set with a simple configuration.

[0071] [Variation 1] In the above embodiment, as shown in FIG. 3, the slope ktop of the threshold value THtop and the slope kbot of the threshold value THbot are set equal to each other during the precharge period P1. However, this is not limitative and they may be set differently as shown in FIG. 9. In this case, the hysteresis amount HYS changes over time. In this example, the slope ktop of the threshold value THtop is set smaller than the slope kbot of the threshold value THbot. Therefore, the hysteresis amount HYS gradually decreases over time.

[0072] [Variation 2] In the above embodiment, as shown in Fig. 3, the threshold value THtop is increased linearly and the threshold value THbot is increased linearly over time during the precharge period P1, but this is not limited to this. Instead, for example, as shown in Fig. 10, the threshold value THtop may be changed linearly, and the threshold value THbot may be changed linearly. Note that this is not limited to this, and for example, the threshold value THtop may be changed in a curved line, and the threshold value THbot may be changed in a curved line.

[0073] [Variation 3] In the above embodiment, the threshold generator 25 generates two thresholds THtop and THbot, and the comparator 26 generates the enable signal EN by comparing the voltage VH with the thresholds THtop and THbot, but this is not limiting. Alternatively, for example, the comparator 26 may operate based on only one of the two thresholds THtop and THbot. Some examples will be described below.

[0074] 11 shows an example of the configuration of a control circuit 19A according to this modification. The control circuit 19A has a precharge control unit 21A. The precharge control unit 21A has a threshold value generation unit 25A and a comparison unit 26A. The threshold value generation unit 25A controls the voltage during the precharge period P1 and the voltage maintenance period P2. information The comparator 26A is configured to generate the threshold value THbot based on the target voltage command value VHtarget of the voltage VH included in the CTL. The comparator 26A is configured to generate the enable signal EN by comparing the voltage VH with the threshold value THbot during the precharge period P1 and the voltage maintenance period P2.

[0075] FIG. 12 shows an example of the operation of the comparator 26A. For example, at timing t51, the enable signal EN changes from low to high. When the enable signal EN becomes high, the control circuit 19A outputs gate signals GA to GF. The power converter 10 performs switching operations based on these gate signals GA to GF, supplies power from the low-voltage battery BL to the capacitor 9, and increases the voltage VH. Then, at timing t52, a predetermined time T1 has elapsed since timing t51, the comparator 26A changes the enable signal EN from high to low. When the enable signal EN becomes low, the control circuit 19A maintains the gate signals GA to GF at low. As a result, the power converter 10 stops switching operations, and the voltage VH decreases. Then, at timing t53, when the voltage VH reaches the threshold value THbot, the comparator 26A changes the enable signal EN from low to high. Subsequent operations are similar.

[0076] 13 shows an example of the configuration of another control circuit 19B according to this modification. The control circuit 19B has a precharge control unit 21B. The precharge control unit 21B has a threshold value generation unit 25B and a comparison unit 26B. The threshold value generation unit 25B controls the voltage during the precharge period P1 and the voltage maintenance period P2. information The comparator 26B is configured to generate the threshold value THtop based on the target voltage command value VHtarget of the voltage VH included in the CTL. The comparator 26B is configured to generate the enable signal EN by comparing the voltage VH with the threshold value THtop during the precharge period P1 and the voltage maintenance period P2.

[0077] FIG. 14 shows an example of the operation of the comparator 26B. For example, at timing t61, the enable signal EN changes from low level to high level. When the enable signal EN becomes high level, the control circuit 19B outputs gate signals GA to GF. The power conversion device 10 performs switching operations based on these gate signals GA to GF, supplies power from the low-voltage battery BL to the capacitor 9, and increases the voltage VH. Then, at timing t62, when this voltage VH reaches the threshold value THtop, the comparator 26B changes the enable signal EN from high level to low level. When the enable signal EN becomes low level, the control circuit 19B maintains the gate signals GA to GF at a low level. As a result, the power conversion device 10 stops switching operations, and the voltage VH drops. Then, at a timing t63, which is a predetermined time T2 after the timing t62, the comparator 26B changes the enable signal EN from a low level to a high level. Subsequent operations are similar.

[0078] [Variation 4] In the above embodiment, the threshold generator 25 controls informationThe thresholds THtop and THbot are generated based on the target voltage command value VHtarget included in the CTL. For example, as shown in FIG. 15 , when the target voltage command value VHtarget is changed, the threshold generation unit 25 may update the thresholds THtop and THbot based on the changed target voltage command value VHtarget. In this example, the threshold generation unit 25 generates the thresholds THtop and THbot based on the target voltage command value VHtarget so that the thresholds THtop and THbot gradually increase during the period up to timing t72. Then, at timing t72, the threshold generation unit 25 sets the thresholds THtop and THbot to values ​​corresponding to the target voltage command value VHtarget. Thereafter, when the target voltage command value VHtarget is changed, the threshold generation unit 25 sets the thresholds THtop and THbot to values ​​corresponding to the changed target voltage command value VHtarget at timing t74. In this example, the thresholds THtop and THbot change stepwise at timing t74. Thereafter, the threshold value generating unit 25 similarly sets the threshold values ​​THtop and THbot to values ​​according to the changed target voltage command value VHtarget at timings t75 and t76, respectively.

[0079] [Variation 5] In the above embodiment, the control circuit 19 generates both the duty ratio DP and the duty ratio DS during the precharge period P1 and the voltage maintenance period P2, but this is not limited to this. Alternatively, for example, as shown in FIG. 16, the control circuit 19 may generate only the duty ratio DS and maintain the duty ratio DP at "0." In this case, the switching circuit 12 does not perform a switching operation, and the rectifier circuit 14 performs a switching operation. Even in this case, the precharge operation can be performed in the same way as in the above embodiment by setting the duty ratio DS to 0.5 or more, for example.

[0080] [Variation 6] In the above embodiment, the gate signal generating units 28 and 29 operate based on the enable signal EN to output and stop the output of the gate signals GA to GF, but this is not limited to this, and for example, the duty ratio generating unit may operate based on the enable signal EN to output and stop the output of the gate signals GA to GF. This modification will be described in detail below.

[0081] 17 shows an example of the configuration of a control circuit 19C according to this modification. The control circuit 19C includes a precharge control unit 21C and gate signal generation units 28C and 29C.

[0082] The precharge control unit 21C has duty ratio generation units 23C and 24C. The duty ratio generation unit 23C is configured to generate a duty ratio DP based on the voltage VL when the enable signal EN is at a high level during the precharge period P1 and the voltage maintenance period P2. The duty ratio generation unit 24C is configured to generate a duty ratio DS based on the voltage VL when the enable signal EN is at a high level during the precharge period P1 and the voltage maintenance period P2.

[0083] The gate signal generation unit 28C is configured to generate gate signals GA to GD based on the duty ratio DP generated by the duty ratio generation unit 23C and the power conversion control unit 27. Specifically, during the precharge period P1 and the voltage maintenance period P2, the gate signal generation unit 28C generates gate signals GC and GD based on the duty ratio DP generated by the duty ratio generation unit 23C, and maintains the gate signals GA and GB at a low level. Furthermore, during the power conversion period P3, the gate signal generation unit 28C generates gate signals GA to GD based on the duty ratio DP generated by the power conversion control unit 27.

[0084] The gate signal generation unit 29C is configured to generate the gate signals GE and GF based on the duty ratio DS generated by the duty ratio generation unit 24C and the power conversion control unit 27. Specifically, the gate signal generation unit 29C generates the gate signals GE and GF based on the duty ratio DS generated by the duty ratio generation unit 24C during the precharge period P1 and the voltage maintenance period P2. Furthermore, the gate signal generation unit 29C generates the gate signals GE and GF based on the duty ratio DS generated by the power conversion control unit 27 during the power conversion period P3.

[0085] Figure 18 shows an example of precharge operation in a power conversion system 1 equipped with a control circuit 19C, where (A) shows the waveform of the enable signal EN, (B) shows the duty ratio DS of the switching operation in the rectifier circuit 14, (C) shows the duty ratio DP of the switching operation in the switching circuit 12, and (D) shows the waveform of the voltage VH and the thresholds THtop and THbot.

[0086] At timing t81, the power conversion system 1 starts a precharge operation. At this timing t81, the comparator 26 changes the enable signal EN from low level to high level (FIG. 18(A)). Based on this enable signal EN, the duty ratio generator 24C starts generating a duty ratio DS at this timing t81 (FIG. 18(B)), and the duty ratio generator 23C starts generating a duty ratio DP at a timing after this timing t81 (FIG. 18(C)). The gate signal generator 28C generates gate signals GC and GD based on the duty ratio DP, and the gate signal generator 29C generates gate signals GE and GF based on the duty ratio DS. The power conversion device 10 performs a switching operation based on these gate signals GA to GF, supplies power from the low-voltage battery BL to the capacitor 9, and increases the voltage VH (FIG. 18(D)).

[0087] When the voltage VH reaches the threshold value THtop at timing t82 (FIG. 18(D)), the comparator 26 changes the enable signal EN from high to low (FIG. 18(A)). Based on this enable signal EN, the duty ratio generator 23C sets the duty ratio DS to "0" (FIG. 18(B)), and the duty ratio generator 24C sets the duty ratio DP to "0" (FIG. 18(C)). The gate signal generator 28C maintains the gate signals GC and GD at low levels based on this duty ratio DP, and the gate signal generator 29C maintains the gate signals GE and GF at low levels based on this duty ratio DS. This causes the power converter 10 to stop switching, and the voltage VH drops (FIG. 18(D)).

[0088] When the voltage VH reaches the threshold value THbot at timing t83 (FIG. 18(D)), the comparator 26 changes the enable signal EN from low level to high level (FIG. 18(A)). Based on this enable signal EN, the duty ratio generator 23C starts to generate the duty ratio DS (FIG. 18(B)), and the duty ratio generator 24C starts to generate the duty ratio DP (FIG. 18(C)). At this time, the duty ratio generator 23C gradually increases the duty ratio DS, and the duty ratio generator 24C gradually increases the duty ratio DP. The gate signal generator 28C generates gate signals GC and GD based on this duty ratio DP, and the gate signal generator 29C generates gate signals GE and GF based on this duty ratio DS. The power converter 10 performs switching operations based on these gate signals GA to GF, supplies power from the low-voltage battery BL to the capacitor 9, and increases the voltage VH (FIG. 18(D)).

[0089] When the voltage VH reaches the threshold value THtop at timing t84 (FIG. 18(D)), the comparing section 26 changes the enable signal EN from high level to low level (FIG. 18(A)).

[0090] The power conversion system 1 repeats this operation from timing t82 to t84. In this way, in the power conversion system 1 according to this modification, the duty ratios DP and DS are set to "0" while the enable signal EN is at a low level, and the duty ratios DP and DS are gradually increased when the enable signal EN changes from a low level to a high level. This makes it possible for the power conversion system 1 to reduce the inrush current when the enable signal EN changes from a low level to a high level.

[0091] [Variation 7] In the above embodiment, the control circuit 19 generates the duty ratios DP and DS based on the voltage VL during the precharge period P1 and the voltage maintenance period P2. However, this is not limiting. Instead, for example, the duty ratios DP and DS may be generated based on the voltage VH, as in the control circuit 19D shown in FIG. 19 . The control circuit 19D includes a precharge control unit 21D. The precharge control unit 21D includes duty ratio generation units 23D and 24D. The duty ratio generation unit 23D is configured to generate the duty ratio DP based on the voltage VH during the precharge period P1 and the voltage maintenance period P2. The duty ratio generation unit 24D is configured to generate the duty ratio DS based on the voltage VH during the precharge period P1 and the voltage maintenance period P2. The duty ratio generation units 23D and 24D may generate the duty ratios DP and DS of predetermined values ​​corresponding to, for example, the voltage VH, or may generate the duty ratios DP and DS by performing feedback control based on the voltage VH.

[0092] [Variation 8] In the above embodiment, the rectifier circuit 14 is configured using a full-bridge circuit as shown in Fig. 1, but the present invention is not limited to this and various circuits can be applied. For example, a so-called center-tap type power conversion system may also be used. This modification will be described in detail below.

[0093] 20 shows an example of a power conversion system 2 according to this modification. The power conversion system 2 includes a transformer 33, a rectifier circuit 34, and a control circuit 39.

[0094] The transformer 33 has windings 33A, 33B, and 33C. One end of the winding 33A is connected to a node N1 in the switching circuit 12, and the other end is connected to a node N2 in the switching circuit 12. One end of the winding 33B is connected to a node N6, and the other end is connected to one end of the winding 33C and the voltage line L21A. One end of the winding 33C is connected to the other end of the winding 33B and the voltage line L21A, and the other end is connected to a node N7.

[0095] The rectifier circuit 34 has transistors S9 and S10. The transistors S9 and S10 are configured using, for example, N-type field effect transistors. The transistors S9 and S10 have body diodes D9 and D10, respectively. The transistor S9 is provided in a path connecting the node N6 and the reference voltage line L22, and is configured to connect the node N6 to the reference voltage line L22 when turned on. The drain of the transistor S9 is connected to the node N6, the gate is supplied with a gate signal GF, and the source is connected to the reference voltage line L22. The transistor S10 is provided in a path connecting the node N7 and the reference voltage line L22, and is configured to connect the node N7 to the reference voltage line L22 when turned on. Transistor S10 The drain of this transistor is connected to the node N7, the gate of which is supplied with a gate signal GE, and the source of which is connected to the reference voltage line L22.

[0096] The control circuit 39 controls the operations of the switching circuit 12 and the rectifier circuit 14 based on the voltage VH detected by the voltage sensor 11, the voltage VL detected by the voltage sensor 18, and control information CTL supplied from a system control unit (not shown). 30 Specifically, the control circuit is configured to control the operation of 39generates gate signals GA to GF based on the voltages VH and VL, and controls the operation of the power conversion device 30 by performing PWM control using these gate signals GA to GF.

[0097] Similarly, in the above embodiment, as shown in FIG. 1, the switching circuit 12 is configured using a full-bridge type circuit, but this is not limitative and various circuits can be applied.

[0098] [Other variations] Two or more of these variations may also be combined.

[0099] Although the present invention has been described above by way of embodiments and modifications, the present invention is not limited to these embodiments and can be modified in various ways.

[0100] For example, in the above embodiment, the voltage step-down operation is performed in the power conversion operation, but this is not limitative, and the voltage step-up operation may also be performed. [Explanation of symbols]

[0101] 1...power conversion system, 9...capacitor, 10, 30...power conversion device, 11...voltage sensor, 12...switching circuit, 13, 33...transformer, 13A, 13B, 33A to 33C...winding, 14, 34...rectifier circuit, 15...smoothing circuit, 16...choke inductor, 17...capacitor, 18...voltage sensor, 19, 19A, 19B, 19C, 19D, 39...control circuit, 21, 21A, 21C, 21D...precharge control unit, 23, 23C, 23D, 24, 24C, 24D...duty ratio generation unit, 25, 25A, 25B...threshold generation unit, 26, 26A, 26B...comparison unit, 27...power conversion control unit, 28, 28C, 29 ,29C...gate signal generation unit, 34...rectifier circuit, BH...high voltage battery, BL...low voltage battery, CTL...control information, DP, DS...duty ratio, D1 to D10...body diode, EN...enable signal, GA to GF...gate signal, L11, L21A, L21B...voltage line, L12, L22...reference voltage line, N1 to N4, N6, N7...node, P1...precharge period, P2...voltage maintenance period, P3...power conversion period, SW1, SW2...switch, S1 to S10...transistor, THtop, THbot...threshold, T11, T12, T21, T22...terminal, VH, VL...voltage, VHtarget...target voltage command value.

Claims

1. A first power terminal connected to a capacitor; a switching circuit connected to the first power terminal and having a first plurality of switching elements that can be turned on and off based on a first drive signal; a transformer having a first winding and a second winding connected to the switching circuit; a rectifier circuit connected to the second winding and having a second plurality of switching elements that can be turned on and off based on a second drive signal; a smoothing circuit connected to the rectifier circuit; a second power terminal connected to the smoothing circuit; a control circuit capable of controlling operations of the first plurality of switching elements and the second plurality of switching elements; Equipped with During a first period before supplying power from the first power terminal to the second power terminal, the control circuit: A first threshold value can be generated that increases over time; When the voltage value of the voltage at the first power terminal reaches the first threshold value, it is possible to switch from an output state in which the second drive signal is output to an output stop state in which output of the second drive signal is stopped, or to switch from the output stop state to the output state. Power conversion device.

2. the output state is a state in which the first drive signal and the second drive signal are output; The output stop state is a state in which the output of the first drive signal and the second drive signal is stopped. The power conversion device according to claim 1 .

3. The control circuit During the first period, a second threshold value can be generated that increases over time and has a value greater than the first threshold value; When the voltage value reaches the first threshold value, the output stop state can be switched to the output state, When the voltage value reaches the second threshold value, the output state can be switched to the output stop state. The power conversion device according to claim 1 or 2.

4. The control circuit is capable of setting the first threshold to a first predetermined value and the second threshold to a second predetermined value during a second period after the first period. The power conversion device according to claim 3 .

5. The control circuit is capable of changing the first threshold value and the second threshold value based on a control signal supplied from an external device during a second period after the first period. The power conversion device according to claim 3 .

6. The control circuit When the voltage value reaches the first threshold value, the output stop state can be switched to the output state, The output state can be switched to the output stop state at a timing when a predetermined length of time has elapsed since the timing when the voltage value reaches the first threshold value. The power conversion device according to claim 1 or 2.

7. The control circuit When the voltage value reaches the first threshold value, the output state can be switched to the output stop state, The output stop state can be switched to the output state at a timing when a predetermined length of time has elapsed since the timing when the voltage value reaches the first threshold value. The power conversion device according to claim 1 or 2.

8. The control circuit is capable of setting the first threshold to a predetermined value during a second period after the first period. The power conversion device according to claim 6 or 7.

9. The control circuit is capable of changing the first threshold value based on a control signal supplied from an external device during a second period after the first period. The power conversion device according to claim 6 or 7.

10. The control circuit a comparison unit that determines whether the voltage value reaches the first threshold value; a duty ratio generating unit capable of generating a duty ratio during the first period; a drive unit capable of generating the second drive signal based on the duty ratio and capable of switching from the output stop state to the output state or from the output state to the output stop state based on a determination result of the comparison unit; have The power conversion device according to any one of claims 1 to 9.

11. The control circuit a comparison unit that determines whether the voltage value reaches the first threshold value; a duty ratio generating unit capable of generating a duty ratio based on a determination result of the comparing unit during the first period; a drive unit capable of generating the second drive signal based on the duty ratio; have The power conversion device according to any one of claims 1 to 9.

12. The duty ratio generating unit is capable of generating the duty ratio by performing feedback control based on the voltage at the first power terminal or the voltage at the second power terminal during a second period after the first period. The power conversion device according to claim 10 or 11.

13. a first battery having a first terminal and a second terminal; a capacitor having a first terminal and a second terminal; a first switch provided in a path connecting the first terminal of the first battery and the first terminal of the capacitor; a second switch provided in a path connecting the second terminal of the first battery and the second terminal of the capacitor; a power conversion device; a second battery; Equipped with The power conversion device is a first power terminal having a first connection terminal connected to the first terminal of the capacitor and a second connection terminal connected to the second terminal of the capacitor; a switching circuit connected to the first power terminal and having a first plurality of switching elements that can be turned on and off based on a first drive signal; a transformer having a first winding and a second winding connected to the switching circuit; a rectifier circuit connected to the second winding and having a second plurality of switching elements that can be turned on and off based on a second drive signal; a smoothing circuit connected to the rectifier circuit; a second power terminal connected to the smoothing circuit; a control circuit capable of controlling operations of the first plurality of switching elements and the second plurality of switching elements; and During a first period before supplying power from the first power terminal to the second power terminal, the control circuit: A first threshold value can be generated that increases over time; When the voltage value of the voltage at the first power terminal reaches the first threshold value, it is possible to switch from an output state in which the second drive signal is output to an output stop state in which output of the second drive signal is stopped, or to switch from the output stop state to the output state. Power conversion systems.

Images