DC power converter

Abstract

This DC electric power conversion device comprises a chopper circuit having a first switch that is connected in series to a first connection point and a second connection point, a first diode that is connected in antiparallel to the first switch, a second switch that is connected in series to the first connection point and a third connection point, a second diode that is connected in antiparallel to the second switch, a first capacitor that is connected in series to the second contact point and the third contact point, a second capacitor that is connected in series to the third contact point and a fourth contact point, and a DC power supply and a first reactor that are connected in series to the fourth connection point and the first connection point in the stated order. In the chopper circuit, when a step-up mode is in effect, an electric current path returning to the DC power supply from the DC power supply via the first reactor, the first connection point, the second switch, the third connection point, the second capacitor, and the fourth connection point in the stated order is formed while the first switch is off and the second switch is on, and an electric current path returning to the DC power supply from the DC power supply via the first reactor, the first connection point, the first diode, the second connection point, the first capacitor, the third connection point, the second capacitor, and the fourth connection point in the stated order is formed while the first switch and the second switch are both off. Additionally, in the chopper circuit, when a step-down mode is in effect, an electric current path returning to the second capacitor via the second capacitor, the third connection point, the first capacitor, the second connection point, the first switch, the first connection point, the first reactor, the DC power supply, and the fourth connection point in the stated order is formed while the first switch is on and the second switch is off, and an electric current path returning on the second capacitor via the second capacitor, the third connection point, the second diode, the first connection point, the first reactor, the DC power supply, and the fourth connection point in the stated order is formed while the first switch and the second switch are both off.

Description

[Technical Field]

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

[0002] Conventionally, DC power converters have been known that have chopper circuits that change DC voltage. In DC power converters, the chopper circuits change DC voltage by repeatedly turning on and off semiconductor switching elements (hereinafter also referred to as "semiconductor switches").

[0003] In a DC power converter (chopper circuit), for example, in a boost mode, energy from a battery such as a storage battery or a solar cell connected to one end is stored in a reactor, and the energy stored in the reactor is used to boost the voltage of a capacitor connected to the other end. For this reason, a reactor is required for a DC power converter (chopper circuit) (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent No. 5070937 [Patent Document 2] Japanese Patent No. 6771700 Summary of the Invention [Problem to be solved by the invention]

[0005] Fig. 14 is a diagram showing an example of the configuration of a conventional chopper circuit 100 capable of bidirectional operation. In Fig. 14, the chopper circuit 100 includes a reactor 129 and semiconductor switches 130A and 131A configured with IGBTs (Insulated Gate Bipolar Transistors) or the like. The chopper circuit 100 also includes diodes (freewheeling diodes) 130D and 131D connected in antiparallel to the semiconductor switches 130A and 131A, respectively, a smoothing capacitor 132, circuit terminals 133A and 133B, and circuit terminals 135A and 135B. The chopper circuit 100 can operate bidirectionally, i.e., in a step-up mode and a step-down mode.

[0006] When the chopper circuit 100 is in the step-up mode, for example, a DC power supply (not shown) is connected between the circuit terminals 133A and 133B, and a load (not shown) is connected between the circuit terminals 135A and 135B. On the other hand, when the chopper circuit 100 is in the step-down mode, for example, a load (not shown) is connected between the circuit terminals 133A and 133B, and a DC power supply (not shown) is connected between the circuit terminals 135A and 135B. When the chopper circuit 100 is in the step-up mode and the step-down mode, a current flows in the directions of the arrows shown in FIG. 14 .

[0007] When chopper circuit 100 is in the boost mode, semiconductor switch 130A is turned on and off based on a duty ratio determined by the voltage V of a DC power supply (not shown) between circuit terminals 133A and 133B and the voltage E between circuit terminals 135A and 135B. That is, semiconductor switch 130A is controlled to be turned on and off so that the voltage E between circuit terminals 135A and 135B is constant. Note that semiconductor switch 131A is fixed in the off state so that it operates as a freewheeling diode.

[0008] 14, when semiconductor switch 130A is turned on, the full voltage V of a DC power supply (not shown) is applied to reactor 129, increasing the ripple current of reactor 129, increasing the loss of reactor 129, and increasing the size of reactor 129. That is, when semiconductor switch 130A switches on, energy that has passed through diode 131D charges smoothing capacitor 132. In this case, because the full voltage V is applied to reactor 129, there is a problem that reactor 129 becomes larger. In addition, because semiconductor switch 130A switches on at a voltage E, there is a problem that the loss of the semiconductor switch increases.

[0009] Fig. 15 is a diagram showing an example of the configuration of another conventional chopper circuit 200 capable of bidirectional operation. In Fig. 15, chopper circuit 200 includes reactor 201 and semiconductor switches 202A, 202B, 203A, and 203B configured with IGBTs or the like. Chopper circuit 200 also includes diodes 202AD, 202BD, 203AD, and 203BD connected in antiparallel to semiconductor switches 202A, 202B, 203A, and 203B, respectively. Chopper circuit 200 also includes smoothing capacitors 204A and 204B having a DC voltage of E / 2.

[0010] 15, smoothing capacitors 204A and 204B are connected in series. A circuit in which semiconductor switches 202A and 203A are connected in series is connected to both ends of smoothing capacitor 204A, and the connection point between semiconductor switches 202A and 203A is connected to terminal 201a of reactor 201. A circuit in which semiconductor switches 202B and 203B are connected in series is connected to both ends of smoothing capacitor 204B, and the connection point between semiconductor switches 202B and 203B is connected to terminal 201b of reactor 201. Reference numeral 205 denotes a neutral point. Circuit terminals 206A and 206B are connected to terminals 201c and 201d of reactor 201, and circuit terminals 207A and 207B are connected to terminals on both sides of smoothing capacitors 204A and 204B connected in series.

[0011] 15, the voltage difference between the power supply voltage V and the capacitor voltage E / 2 is applied to reactor 201 by the semiconductor switches, which allows reactor 201 to be made smaller. Furthermore, because the switching of the semiconductor switches is performed at a voltage of E / 2, loss in the semiconductor switches can be reduced. However, there was a problem in that current always passes through two semiconductor switches, which increases conduction loss in the semiconductor switches.

[0012] 15, for example, in the step-up mode, semiconductor switch 202A and semiconductor switch 202B are alternately switched, and in the step-down mode, semiconductor switches 203A and 203B are alternately switched. This reduces the ripple current in reactor 201, allowing reactor 201 to be made smaller. However, since there are semiconductor switches on the upper and lower sides, the potential of power supply V fluctuates (potential swings) with respect to the potential of neutral point 205 of the capacitor voltage (virtual earth potential), which poses a problem of increased noise.

[0013] Fig. 16 is a diagram showing an example of the configuration of a DC power conversion device 210 having the conventional chopper circuit 200 shown in Fig. 15. In Fig. 16, the DC power conversion device 210 has the chopper circuit 200, smoothing capacitors 204A and 204B, a neutral point (virtual earth) 205, a battery 211, stray capacitances 214A and 214B, and an intermediate potential 215 of the battery 211.

[0014] For example, battery 211, such as a storage battery or solar cell, has stray capacitances 214A and 214B between it and ground. In the configuration shown in FIG. 16, switching of chopper circuit 200 causes a difference between the potential of virtual ground 205 of smoothing capacitors 204A and 204B and intermediate potential 215 of battery 211, causing leakage current to flow through stray capacitances 214A and 214B and ground. For this reason, the configuration shown in FIG. 16 may cause noise interference. Note that battery 211, such as a solar cell, generally has a high rating and large stray capacitances 214A and 214B, which increases the impact of noise interference.

[0015] 15 (FIG. 16), for example, in order to suppress an increase in noise, it is conceivable to fix the potential of the power supply V by simultaneously switching on and off semiconductor switch 202A and semiconductor switch 202B or 203B. However, in this case, reactor 201 becomes large in size, as in the configuration shown in FIG.

[0016] Fig. 17 is a diagram showing an example of the configuration of a DC power converter 300 having another conventional chopper circuit 301 capable of bidirectional operation. In Fig. 17, the DC power converter 300 includes the chopper circuit 301, four power semiconductor elements 303Q, 304Q, 305Q, and 306Q, a capacitor 313, a capacitor 316, and a reactor 321. In the chopper circuit 301, the source of the power semiconductor element 303Q and the drain of the power semiconductor element 304Q are connected at a connection point 300b. In the chopper circuit 301, the source of the power semiconductor element 305Q and the drain of the power semiconductor element 306Q are connected at a connection point 300c. The chopper circuit 301 also includes a capacitor 323, which functions as a flyback capacitor, between the connection points 300b and 300c.

[0017] According to the chopper circuit 301 shown in FIG. 17, the high-frequency ripple current flowing through the reactor 321 is significantly suppressed at a boost ratio of, for example, about 2, allowing the reactor 321 to be miniaturized. Therefore, the chopper circuit 301 is an effective circuit scheme for boosting the voltage by approximately 2 at a conduction ratio of 50%, for example. That is, as shown in FIG. 17, the chopper circuit 301 is provided with a capacitor 323, and the voltage difference between the capacitor 316 and the capacitor 323 is applied to the reactor 321, thereby allowing the reactor 321 to be miniaturized. However, the configuration shown in FIG. 17 requires a dedicated capacitor 323, which increases the size of the capacitor 323. Furthermore, the configuration shown in FIG. 17 requires a current to always pass through two power semiconductor elements (semiconductor switches), which increases the loss in the semiconductor switches.

[0018] Therefore, an object of the present disclosure is to provide a DC power conversion device that can reduce the ripple current of a reactor, downsize the reactor, reduce the loss of a semiconductor switch, reduce costs, and achieve low noise compared to conventional devices. [Means for solving the problem]

[0019] A DC power conversion device according to one aspect includes a chopper circuit having a first switch connected in series between a first connection point and a second connection point, a first diode connected in anti-parallel to the first switch, a second switch connected in series between the first connection point and a third connection point, a second diode connected in anti-parallel to the second switch, a first capacitor connected in series between the second connection point and the third connection point, a second capacitor connected in series between the third connection point and a fourth connection point, and a DC power source and a first reactor connected in series in this order between the fourth connection point and the first connection point, wherein in a boost mode, when the first switch is in an off state and the second switch is in an on state, a current path is formed in the chopper circuit that runs from the DC power source via the first reactor, the first connection point, the second switch, the third connection point, the second capacitor, and the fourth connection point in this order, and returns to the DC power source. When the first switch is in an off state and the second switch is in an off state, a current path is formed from the DC power supply, passing through the first reactor, the first connection point, the first diode, the second connection point, the first capacitor, the third connection point, the second capacitor, and the fourth connection point in that order, and returning to the DC power supply; and in the step-down mode, when the first switch is in an on state and the second switch is in an off state, a current path is formed from the DC power supply, passing through the second capacitor, the third connection point, the first capacitor, the second connection point, the first switch, the first connection point, the first reactor, the DC power supply, and the fourth connection point in that order, and returning to the second capacitor; and when the first switch is in an off state and the second switch is in an off state, a current path is formed from the DC power supply, passing through the second capacitor, the third connection point, the second diode, the first connection point, the first reactor, the DC power supply, and the fourth connection point in that order, and returning to the second capacitor.

[0020] A DC power conversion device according to another aspect includes a chopper circuit having a first diode connected in series between a first connection point and a second connection point, a second switch connected in series between the first connection point and a third connection point, a second diode connected in anti-parallel to the second switch, a first capacitor connected in series between the second connection point and the third connection point, a second capacitor connected in series between the third connection point and a fourth connection point, and a DC power source and a first reactor connected in series in this order between the fourth connection point and the first connection point. In the step-up mode, when the second switch is on, the chopper circuit forms a current path that returns from the DC power supply to the DC power supply, passing sequentially through the first reactor, the first connection point, the second switch, the third connection point, the second capacitor, and the fourth connection point; and when the second switch is off, forms a current path that returns from the DC power supply to the DC power supply, passing sequentially through the first reactor, the first connection point, the first diode, the second connection point, the first capacitor, the third connection point, the second capacitor, and the fourth connection point.

[0021] A DC power conversion device according to another aspect includes a chopper circuit having: a first switch connected in series between a first connection point and a second connection point; a first diode connected in anti-parallel to the first switch; a second diode connected in series between the first connection point and a third connection point; a first capacitor connected in series between the second connection point and the third connection point; a second capacitor connected in series between the third connection point and a fourth connection point; and a DC power supply and a first reactor connected in series in this order between the fourth connection point and the first connection point. In the chopper circuit, in a step-down mode, when the first switch is in an on state, a current path is formed that returns to the second capacitor by passing through the second capacitor, the third connection point, the first capacitor, the second connection point, the first switch, the first connection point, the first reactor, the DC power supply, and the fourth connection point in that order; and when the first switch is in an off state, a current path is formed that returns to the second capacitor by passing through the second capacitor, the third connection point, the second diode, the first connection point, the first reactor, the DC power supply, and the fourth connection point in that order. [Effects of the Invention]

[0022] According to the present disclosure, it is possible to provide a DC power conversion device that can reduce the ripple current of a reactor and the size of the reactor compared to conventional devices, as well as reduce the loss of a semiconductor switch and reduce costs, and that is low noise. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a diagram illustrating an example of the configuration of a DC power conversion device according to a first embodiment. [Figure 2] 2 is a diagram showing a current flow in the chopper circuit shown in FIG. 1 in the step-up mode. [Figure 3] 2 is a diagram showing a current flow in the chopper circuit shown in FIG. 1 in the step-down mode. [Figure 4] 4 is a diagram showing an example of the configuration of a control device in the DC power conversion device shown in FIGS. 1 to 3 and a control method in a boost mode.

[0021] FIG. [Figure 5] 4 is a diagram showing an example of the configuration of a control device in the DC power conversion device shown in FIGS. 1 to 3 and a control method in a step-down mode.

[0021] FIG. [Figure 6] FIG. 10 is a diagram illustrating an example of the configuration of a DC power conversion device according to a second embodiment. [Figure 7] 7 is a diagram showing a current flow when energy of a second capacitor is transferred to a first capacitor in the chopper circuit shown in FIG. 6. FIG. [Figure 8] 7 is a diagram showing a current flow when energy of a first capacitor is transferred to a second capacitor in the chopper circuit shown in FIG. 6. FIG. [Figure 9] 9 is a diagram showing an example of the configuration of a control device in the DC power converter shown in FIGS. 6 to 8 and a control method for controlling the voltage balance between a first capacitor and a second capacitor. FIG. [Figure 10] FIG. 10 is a diagram illustrating an example of the configuration of a chopper circuit in a DC power conversion device according to a third embodiment. [Figure 11] FIG. 10 is a diagram illustrating an example of the configuration of a chopper circuit in a DC power conversion device according to a fourth embodiment. [Figure 12] FIG. 10 is a diagram illustrating an example of the configuration of a chopper circuit in a DC power conversion device according to a fifth embodiment. [Figure 13] 13 is a conceptual diagram showing an example of the hardware configuration of a processing circuit included in the control device in the embodiment shown in FIGS. 1 to 12. FIG. [Figure 14] FIG. 1 is a diagram illustrating an example of the configuration of a conventional chopper circuit capable of bidirectional operation. [Figure 15] FIG. 10 is a diagram showing an example of the configuration of another conventional chopper circuit capable of bidirectional operation. [Figure 16] 16 is a diagram showing an example of the configuration of a DC power conversion device having the conventional chopper circuit shown in FIG. 15. FIG. [Figure 17] FIG. 10 is a diagram showing an example of the configuration of a DC power conversion device having another conventional chopper circuit capable of bidirectional operation. DETAILED DESCRIPTION OF THE INVENTION

[0024] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a DC power conversion device according to the present disclosure will be described with reference to the drawings.

[0025] First Embodiment FIG. 1 is a diagram showing an example of the configuration of a DC power conversion device 1 according to the first embodiment.

[0026] 1, the DC power conversion device 1 includes a chopper circuit 10 and a control device 30. The DC power conversion device 1 is also called a "DC (Direct Current) / DC converter" and is, for example, a power supply device that generates a DC voltage of a different voltage from a DC power supply that outputs a predetermined voltage.

[0027] The chopper circuit 10 is also called a DC chopper, and changes the DC voltage by, for example, repeatedly turning on and off a semiconductor switching element. The chopper circuit 10 of this embodiment is a buck-boost chopper that can both boost the output DC voltage higher than the input DC voltage, and buck the output DC voltage lower than the input DC voltage.

[0028] The chopper circuit 10 includes a DC power supply Vb, a first reactor L1, a first semiconductor switch Q1, a second semiconductor switch Q2, a first diode D1, a second diode D2, a first capacitor C1, and a second capacitor C2. These components of the chopper circuit 10 are interconnected via a first connection point 11, a second connection point 12, a third connection point 13, and a fourth connection point 14.

[0029] That is, the first capacitor C1 and the second capacitor C2 are connected in series via a third node 13, and the first semiconductor switch Q1 and the second semiconductor switch Q2 are connected in series via a first node 11. The series-connected first semiconductor switch Q1 and second semiconductor switch Q2 are connected to both ends of the first capacitor C1 via a second node 12 at both ends of the first capacitor C1 and a third node 13. The first node 11, which is the node between the first semiconductor switch Q1 and the second semiconductor switch Q2, is connected to one end of a first reactor L1, and the other end of the first reactor L1 is connected to one end of a DC power source Vb. The other end of the DC power source Vb is connected to the second capacitor C2 via a fourth node 14. The first diode D1 is connected in anti-parallel to the first semiconductor switch Q1, and the second diode D2 is connected in anti-parallel to the second semiconductor switch Q2.

[0030] The DC power supply Vb is, for example, a storage battery or the like, and is connected in series between the fourth connection point 14 and the first reactor L1. When the chopper circuit 10 (DC power conversion device 1) is in the step-up mode, the DC power supply Vb discharges power to the first capacitor C1 and the second capacitor C2. When the chopper circuit 10 (DC power conversion device 1) is in the step-down mode, the DC power supply Vb is charged with power received from the first capacitor C1 and the second capacitor C2.

[0031] The first reactor L1 is connected in series between the DC power supply Vb and the first connection point 11. For example, when the chopper circuit 10 (DC power conversion device 1) is in a boost mode, the first reactor L1 stores energy from the power supplied from the DC power supply Vb and uses the stored energy to boost the voltages of the first capacitor C1 and the second capacitor C2.

[0032] The first semiconductor switch Q1 is connected between the first node 11 and the second node 12, and the second semiconductor switch Q2 is connected between the first node 11 and the third node 13. The first semiconductor switch Q1 and the second semiconductor switch Q2 are semiconductor switching elements formed, for example, of IGBTs. The first semiconductor switch Q1 and the second semiconductor switch Q2 perform switching based on, for example, a chopper duty corresponding to the output voltage, output current, etc. The on / off operations of the first semiconductor switch Q1 and the second semiconductor switch Q2 are controlled, for example, by a gate drive signal (gate signal) output from the control device 30. The chopper duty is, for example, the on / off time ratio of the semiconductor switching element, and is also referred to as the "on duty" or "duty ratio." The first semiconductor switch Q1 is an example of a "first switch," and the second semiconductor switch Q2 is an example of a "second switch."

[0033] The first diode D1 is connected in anti-parallel to the first semiconductor switch Q1, and the second diode D2 is connected in anti-parallel to the second semiconductor switch Q2. The first diode D1 and the second diode D2 are, for example, freewheeling diodes that return energy to the DC power supply Vb when the IGBT is turned off.

[0034] The first capacitor C1 is connected in series between the second node 12 and the third node 13, and the second capacitor C2are connected in series between the third connection point 13 and the fourth connection point 14. The first capacitor C1 and the second capacitor C2 are DC smoothing capacitors that smooth out voltage fluctuations (ripples). When the chopper circuit 10 (DC power conversion device 1) is in the step-up mode, the first capacitor C1 and the second capacitor C2 are charged with power received from the DC power source Vb. When the chopper circuit 10 (DC power conversion device 1) is in the step-down mode, the first capacitor C1 and the second capacitor C2 discharge power toward the DC power source Vb.

[0035] The DC power conversion device 1 also includes a first voltage sensor 21, a first current sensor 22, a second voltage sensor 23, and a third voltage sensor 24. The locations at which the first voltage sensor 21, the first current sensor 22, the second voltage sensor 23, and the third voltage sensor 24 are arranged are not limited to those shown in Fig. 1, and these sensors may be arranged anywhere as long as they can acquire the current or voltage values ​​they are intended to acquire. In Fig. 2 and subsequent figures, the illustration of these sensors will be omitted as appropriate.

[0036] The first voltage sensor 21 is disposed, for example, at a position where it can detect the voltage across the DC power supply Vb, and constantly detects the value of the voltage VVb of the DC power supply Vb. The value of the voltage VVb of the DC power supply Vb detected by the first voltage sensor 21 is acquired (monitored) by the control device 30.

[0037] The first current sensor 22 is disposed, for example, at a position where it can detect the current flowing through the first reactor L1, and constantly detects the value of the current ID flowing through the first reactor L1. The value of the current ID flowing through the first reactor L1 detected by the first current sensor 22 is acquired (monitored) by the control device 30.

[0038] The second voltage sensor 23 is disposed, for example, at a position where it can detect the voltage of the first capacitor C1, and constantly detects the value of the voltage VC1 of the first capacitor C1. The value of the voltage VC1 of the first capacitor C1 detected by the second voltage sensor 23 is acquired (monitored) by the control device 30.

[0039] The third voltage sensor 24 is disposed, for example, at a position where it can detect the voltage of the second capacitor C2, and constantly detects the value of the voltage VC2 of the second capacitor C2. The value of the voltage VC2 of the second capacitor C2 detected by the third voltage sensor 24 is acquired (monitored) by the control device 30.

[0040] The control device 30 includes a processor 91 (see FIG. 13 ), such as a CPU (Central Processing Unit), which operates by executing a program. The control device 30 includes a memory 92 (see FIG. 13 ), which will be described later. For example, the control device 30 executes a predetermined program stored in the memory 92 to operate the processor 91, thereby controlling the overall operation of the DC power conversion device 1 (chopper circuit 10). The control device 30 may operate according to instructions received from an operator or the like via a higher-level device (not shown) or an operation unit (not shown). The control device 30 is connected to each component of the DC power conversion device 1 via signal lines (not shown). The control device 30 controls the operation of the first semiconductor switch Q1 and the second semiconductor switch Q2 based on current and voltage values ​​acquired from the first voltage sensor 21, the first current sensor 22, the second voltage sensor 23, and the third voltage sensor 24. The detailed configuration and control method (operation) of the control device 30 will be described later (see FIGS. 4 and 5 ).

[0041] Fig. 2 is a diagram showing the current flow in the chopper circuit 10 shown in Fig. 1 in the boost mode. Fig. 2(a) is a diagram showing the current flow in the chopper circuit 10 shown in Fig. 1 when the second semiconductor switch Q2 is in the on state in the boost mode. Fig. 2(b) is a diagram showing the current flow in the chopper circuit 10 shown in Fig. 1 when the second semiconductor switch Q2 is in the off state in the boost mode.

[0042] 2(a), when the chopper circuit 10 (DC power conversion device 1) is in the boost mode, if the first semiconductor switch Q1 is in the off state and the second semiconductor switch Q2 is in the on state, the following current path is formed in the chopper circuit 10. That is, a current path is formed that runs from the DC power supply Vb, sequentially through the first reactor L1, the first node 11, the second semiconductor switch Q2, the third node 13, the second capacitor C2, and the fourth node 14, and returns to the DC power supply Vb.

[0043] 2(b), when the chopper circuit 10 (DC power conversion device 1) is in the boost mode, if the first semiconductor switch Q1 is in the off state and the second semiconductor switch Q2 is in the off state, the following current path is formed in the chopper circuit 10. That is, a current path is formed that runs from the DC power supply Vb, sequentially through the first reactor L1, the first node 11, the first diode D1, the second node 12, the first capacitor C1, the third node 13, the second capacitor C2, and the fourth node 14, and returns to the DC power supply Vb.

[0044] Fig. 3 is a diagram showing the current flow in the chopper circuit 10 shown in Fig. 1 in the step-down mode. Fig. 3(a) is a diagram showing the current flow in the chopper circuit 10 shown in Fig. 1 when the first semiconductor switch Q1 is in the on state in the step-down mode. Fig. 3(b) is a diagram showing the current flow in the chopper circuit 10 shown in Fig. 1 when the first semiconductor switch Q1 is in the off state in the step-down mode.

[0045] 3(a), when the chopper circuit 10 (DC power conversion device 1) is in the step-down mode, if the first semiconductor switch Q1 is in the on state and the second semiconductor switch Q2 is in the off state, the following current path is formed in the chopper circuit 10. That is, a current path is formed that passes through the second capacitor C2, the third node 13, the first capacitor C1, the second node 12, the first semiconductor switch Q1, the first node 11, the first reactor L1, the DC power supply Vb, and the fourth node 14 in this order, and then returns to the second capacitor C2.

[0046] 3(b), when the chopper circuit 10 (DC power conversion device 1) is in the step-down mode, if the first semiconductor switch Q1 is in the off state and the second semiconductor switch Q2 is in the off state, the following current path is formed in the chopper circuit 10. That is, a current path is formed that passes through the second capacitor C2, the third node 13, the second diode D2, the first node 11, the first reactor L1, the DC power supply Vb, and the fourth node 14 in this order, and then returns to the second capacitor C2.

[0047] <Control method of the first embodiment> FIG. 4 is a diagram showing an example of the configuration of the control device 30 in the DC power conversion device 1 shown in FIGS. 1 to 3 and a control method in the boost mode.

[0048] The control device 30 has a memory 92 (see FIG. 13 ), which will be described later, and functions as the following units by executing, for example, a predetermined program stored in the memory 92, which will be described later. That is, by executing the predetermined program, the control device 30 functions as a first subtractor 31, a voltage controller 32, a second subtractor 33, a current controller 34, and a PWM (Pulse Width Modulation) control unit 35. Note that each of the above functions may be realized by a program executed by a processor 91 (see FIG. 13 ) included in the control device 30, or may be realized by hardware 93 (see FIG. 13 ). In the boost mode, each of the above units executes a predetermined program to perform the following processes.

[0049] The first subtractor 31 acquires the VC reference from, for example, a memory 92 (see FIG. 13 ), which will be described later. Here, the VC reference is a predetermined voltage reference value (voltage command value) for controlling the value of the voltage VC, which is the sum of the value of the voltage VC1 of the first capacitor C1 and the value of the voltage VC2 of the second capacitor C2, to a predetermined value or a constant value. Note that the first subtractor 31 may calculate the VC reference based on, for example, a predetermined calculation, or may acquire the VC reference by receiving an instruction from a higher-level device (not shown) or an operator (not shown).

[0050] Furthermore, the first subtractor 31 acquires (as a feedback) the value of the voltage VC1 across the first capacitor C1 from the second voltage sensor 23 (see FIG. 1), and acquires (as a feedback) the value of the voltage VC2 across the second capacitor C2 from the third voltage sensor 24 (see FIG. 1). Alternatively, the first subtractor 31 acquires (as a feedback) the value of the voltage VC, which is the value of the voltage VC1 across the first capacitor C1 plus the value of the voltage VC2 across the second capacitor C2, from the second voltage sensor 23 and the third voltage sensor 24. Then, the first subtractor 31 subtracts the acquired value of the voltage VC (or the value of voltages VC1+VC2) from the acquired (or calculated) VC reference, and outputs the subtracted value to the voltage controller 32.

[0051] The voltage controller 32 performs, for example, PI (Proportional-Integral) control on the value acquired from the first subtractor 31 to obtain an ID reference. Here, the ID reference is a reference value (current command value) of the current to be flowed through the first reactor L1 in order to control the value of the voltage VC, which is the sum of the value of the voltage VC1 of the first capacitor C1 and the value of the voltage VC2 of the second capacitor C2, to a predetermined value or a constant value. The voltage controller 32 outputs the obtained ID reference to the second subtractor 33. Note that the first subtractor 31 and the voltage controller 32 are examples of a "voltage control unit," the VC reference is an example of a "first voltage command value," and the ID reference is an example of a "first current command value."

[0052] The second subtractor 33 acquires the ID reference from the voltage controller 32. The second subtractor 33 also acquires (feeds back) the value of the current ID flowing through the first reactor L1 from the first current sensor 22 (see FIG. 1). The second subtractor 33 then subtracts the acquired value of the current ID from the acquired ID reference and outputs the subtracted value to the current controller 34.

[0053] The current controller 34 performs, for example, PI control on the value acquired from the second subtractor 33, and calculates a voltage command value V1 * The current controller 34 calculates the voltage command value V1 *to the PWM control unit 35. The second subtractor 33 and the current controller 34 are an example of a "current control unit", and the voltage command value V1 * is an example of a "second voltage command value."

[0054] The PWM control unit 35 calculates the voltage command value V1 obtained from the current controller 34. * and a predetermined triangular-wave carrier signal, for example, to generate a gate signal, which is a pulse-width modulation (PWM) signal for controlling the operation of the second semiconductor switch Q2. The PWM control unit 35 outputs the generated gate signal (Q2 pulse) to the second semiconductor switch Q2 to control the on / off operation of the second semiconductor switch Q2. The Q2 pulse is an example of a "first pulse."

[0055] When the DC power conversion device 1 (chopper circuit 10) is in the boost mode, by controlling the on / off operation of the second semiconductor switch Q2 using the above control method, the first capacitor C1 and the second capacitor C2 can be charged from the DC power supply Vb, thereby boosting the voltage.

[0056] FIG. 5 is a diagram showing an example of the configuration of the control device 30 in the DC power conversion device 1 shown in FIGS. 1 to 3 and a control method in the step-down mode.

[0057] As described above, the control device 30 executes a predetermined program to function as the first subtractor 31, the voltage controller 32, the second subtractor 33, the current controller 34, and the PWM control unit 35. In the step-down mode, each of the above units executes a predetermined program to perform the following processes.

[0058] The first subtractor 31 acquires the Vb reference from, for example, a memory 92 (see FIG. 13 ), which will be described later. Here, the Vb reference is a predetermined voltage reference value (voltage command value) for controlling the value of the voltage VVb of the DC power supply Vb to a predetermined value or a constant value. For example, the Vb reference is a voltage reference value (voltage command value) indicating how many volts, such as 500 volts, the value of the voltage VVb of the DC power supply (battery) Vb should be. Note that the first subtractor 31 may calculate the Vb reference based on, for example, a predetermined calculation, or may acquire the Vb reference by receiving an instruction from a higher-level device (not shown) or an operator (not shown).

[0059] The first subtractor 31 also acquires (feeds back) the value of the voltage VVb of the DC power supply Vb from the first voltage sensor 21 (see FIG. 1). The first subtractor 31 then subtracts the acquired value of the voltage VVb from the acquired (or calculated) Vb reference, and outputs the subtracted value to the voltage controller 32.

[0060] The voltage controller 32 performs, for example, PI control on the value acquired from the first subtractor 31 to obtain an ID reference. The ID reference here is a reference value (current command value) of a current to be flowed through the first reactor L1 in order to control the value of the voltage VVb of the DC power supply Vb to a predetermined value or a constant value. The voltage controller 32 outputs the obtained ID reference to the second subtractor 33. The Vb reference is an example of a "third voltage command value," and the ID reference here is an example of a "second current command value."

[0061] The second subtractor 33 acquires the ID reference from the voltage controller 32. The second subtractor 33 also acquires (feeds back) a value obtained by multiplying the value of the current ID flowing through the first reactor L1 by −1 from the first current sensor 22 (see FIG. 1 ). The reason the value of the current ID is multiplied by −1 is because, in the step-down mode, the current direction is opposite to that in the step-up mode. That is, since the current direction is opposite to the charge direction and the discharge direction, the value of the current ID is multiplied by −1 to make the control consistent. The second subtractor 33 then subtracts the value obtained by multiplying the acquired value of the current ID by −1 from the acquired ID reference, and outputs the subtracted value to the current controller 34.

[0062] The current controller 34 performs, for example, PI control on the value acquired from the second subtractor 33, and calculates a voltage command value V2 which is a duty command (chopper duty) in the step-down mode. * The current controller 34 calculates the voltage command value V2 * is output to the PWM control unit 35. Note that the voltage command value V2 * is an example of a "fourth voltage command value."

[0063] The PWM control unit 35 calculates the voltage command value V2 obtained from the current controller 34. * and a predetermined triangular-wave carrier signal, for example, to generate a gate signal, which is a pulse-width modulation (PWM) signal for controlling the operation of the first semiconductor switch Q1. The PWM control unit 35 outputs the generated gate signal (Q1 pulse) to the first semiconductor switch Q1 to control the on / off operation of the first semiconductor switch Q1. The Q1 pulse is an example of a "second pulse."

[0064] When the DC power conversion device 1 (chopper circuit 10) is in the step-down mode, by controlling the on / off operation of the first semiconductor switch Q1 using the above control method, the DC power supply Vb can be charged from the first capacitor C1 and the second capacitor C2, thereby stepping down the voltage.

[0065] <Effects of the First Embodiment> As described above, according to the first embodiment shown in FIGS. 1 to 5, in the chopper circuit 10, the voltage applied to the first reactor L1 is the difference between the voltage VVb of the DC power supply Vb and the voltage VC2 of the second capacitor C2, so it is possible to reduce the ripple current of the first reactor L1. This makes it possible to reduce the loss and size of the first reactor L1. In other words, according to the first embodiment shown in FIGS. 1 to 5, it is possible to reduce the ripple current of the first reactor L1 and to reduce the size of the first reactor L1 more than in the past.

[0066] According to the first embodiment shown in FIGS. 1 to 5, a current path is formed in the chopper circuit 10 that passes through only one of the first semiconductor switch Q1 and the second semiconductor switch Q2. The first semiconductor switch Q1 and the second semiconductor switch Q2 are switched within the voltage range of the voltage VC1 of the first capacitor C1. This reduces the switching loss of the first semiconductor switch Q1 and the second semiconductor switch Q2. This allows inexpensive semiconductor switches with low rated voltages to be used for the first semiconductor switch Q1 and the second semiconductor switch Q2. That is, according to the first embodiment shown in FIGS. 1 to 5, it is possible to reduce the loss and cost of the first semiconductor switch Q1 and the second semiconductor switch Q2 compared to conventional methods.

[0067] According to the first embodiment shown in FIGS. 1 to 5, the negative electrode of the capacitor in the chopper circuit 10 is connected to the negative electrode of the DC power supply Vb. Therefore, the negative electrode of the DC power conversion device 1 (chopper circuit 10) and the negative electrode of the DC power supply Vb are common to each other, reducing the potential difference and the leakage current. This fixes the potential to ground, reducing noise interference due to leakage current (see FIG. 16), thereby achieving low noise. That is, according to the first embodiment shown in FIGS. 1 to 5, it is possible to provide a DC power conversion device 1 (chopper circuit 10) that generates less noise than conventional devices.

[0068] Second Embodiment Fig. 6 is a diagram showing an example of the configuration of a DC power converter 1A according to a second embodiment. In the second embodiment, components that are the same as or similar to those of the first embodiment shown in Figs. 1 to 5 are denoted by the same reference numerals, and duplicated or detailed descriptions will be omitted or simplified. The DC power converter 1A according to the second embodiment is obtained by adding a configuration for uniformly controlling the voltage balance between the first capacitor C1 and the second capacitor C2 to the DC power converter 1 shown in Figs. 1 to 5.

[0069] As shown in Fig. 6, the DC power converter 1A has a chopper circuit 10A and a control device 30A. The DC power converter 1A (chopper circuit 10A) has the following configuration in addition to the configuration of the DC power converter 1 (chopper circuit 10) shown in Fig. 1. That is, the DC power converter 1A (chopper circuit 10A) has a third semiconductor switch Q3, a fourth semiconductor switch Q4, a third diode D3, a fourth diode D4, and a second reactor L2 in addition to the configuration shown in Fig. 1. Then, in the chopper circuit 10A, these components are connected to each other via a second connection point 12, a third connection point 13, a fourth connection point 14, a fifth connection point 15, a sixth connection point 16, and a seventh connection point 17.

[0070] That is, two sets of semiconductor switches are added by connecting a third semiconductor switch Q3 and a fourth semiconductor switch Q4 to both ends of the first capacitor C1 and the second capacitor C2. A second reactor L2 is connected between a sixth node 16, which is the node between the third semiconductor switch Q3 and the fourth semiconductor switch Q4, and a third node 13, which is the node between the first capacitor C1 and the second capacitor C2.

[0071] The third diode D3 is connected in anti-parallel to the third semiconductor switch Q3, and the fourth diode D4 is connected in anti-parallel to the fourth semiconductor switch Q4. The fifth connection point is connected to the first terminal 18 on the right side in Fig. 6, and the seventh connection point is connected to the second terminal 19 on the right side in Fig. 6, and a load (not shown) is connected between the first terminal 18 and the second terminal 19, for example.

[0072] The third semiconductor switch Q3 is connected in series between a fifth node 15 between the second node 12 and the first terminal 18 and a sixth node 16, and the fourth semiconductor switch Q4 is connected in series between the sixth node 16 and a seventh node 17 between the fourth node 14 and the second terminal 19. The third semiconductor switch Q3 and the fourth semiconductor switch Q4 are semiconductor switching elements formed, for example, by IGBTs. The third semiconductor switch Q3 and the fourth semiconductor switch Q4 perform switching based on, for example, the voltage difference between the voltage VC1 of the first capacitor C1 and the voltage VC2 of the second capacitor C2. The on / off operations of the third semiconductor switch Q3 and the fourth semiconductor switch Q4 are controlled, for example, by a gate drive signal (gate signal) output from the control device 30A. The third semiconductor switch Q3 is an example of a "third switch," and the fourth semiconductor switch Q4 is an example of a "fourth switch."

[0073] The third diode D3 is connected in anti-parallel to the third semiconductor switch Q3, and the fourth diode D4 is connected in anti-parallel to the fourth semiconductor switch Q4. The third diode D3 and the fourth diode D4 are, for example, freewheeling diodes that return energy to the first capacitor C1 or the second capacitor C2 when the IGBT is turned off.

[0074] The second reactor L2 is connected in series between the third node 13 and the sixth node 16. As will be described later (see FIGS. 7 and 8, etc.), the second reactor L2 functions as a balancer for controlling the voltage balance between the voltage VC1 of the first capacitor C1 and the voltage VC2 of the second capacitor C2 to a constant or arbitrary value.

[0075] For example, in the configuration of the first embodiment shown in FIGS. 1 to 5, the charge / discharge energies of the first capacitor C1 and the second capacitor C2 are different, which can cause a voltage difference between the voltage VC1 of the first capacitor C1 and the voltage VC2 of the second capacitor C2. For example, in the configuration of the first embodiment shown in FIGS. 1 to 5, in the step-up mode, when the first semiconductor switch Q1 and the second semiconductor switch Q2 are alternately switched, the voltage of the second capacitor C2 can become higher than the voltage of the first capacitor C1. In this case, for example, if the discharged energy is the same, a voltage difference can occur between the voltage VC1 of the first capacitor C1 and the voltage VC2 of the second capacitor C2.

[0076] 6, in the second embodiment, a second reactor L2 is connected in series between the sixth node 16 and the third node 13. As a result, by switching the third semiconductor switch Q3 and the fourth semiconductor switch Q4, it is possible to arbitrarily control the voltage balance between the voltage VC1 of the first capacitor C1 and the voltage VC2 of the second capacitor C2.

[0077] Further, a second current sensor 25 is disposed in the DC power conversion apparatus 1A. The position where the second current sensor 25 is disposed is not limited to the position shown in Fig. 6, and the second current sensor 25 may be disposed anywhere as long as the sensor can acquire the value of the current to be acquired. In Fig. 7 and subsequent drawings, the second current sensor 25 is omitted as appropriate.

[0078] The second current sensor 25 is disposed, for example, at a position where it can detect the current flowing through the second reactor L2, and constantly detects the value of the current IB flowing through the second reactor L2. The value of the current IB flowing through the second reactor L2 detected by the second current sensor 25 is acquired (monitored) by the control device 30A.

[0079] The control device 30A is connected to each component of the DC power conversion device 1A via signal lines and the like (not shown), and has the same functions as the control device 30 in the first embodiment shown in FIGS. 1 to 5. That is, the control device 30A controls the operation of the first semiconductor switch Q1 and the second semiconductor switch Q2 based on the current and voltage values ​​and the like acquired from the various sensors and the like. The control device 30A also controls the operation of the third semiconductor switch Q3 and the fourth semiconductor switch Q4 based on the current and voltage values ​​and the like acquired from the various sensors and the like. The detailed configuration and control method (operation) of the control device 30A will be described later (see FIG. 9 and the like).

[0080] Fig. 7 is a diagram showing the current flow when the energy of the second capacitor C2 is transferred to the first capacitor C1 in the chopper circuit 10A shown in Fig. 6. Fig. 7(a) is a diagram showing the current flow when the fourth semiconductor switch Q4 is turned on in a case where the energy stored in the second capacitor C2 is greater than the energy stored in the first capacitor C1. Fig. 7(b) is a diagram showing the current flow when the fourth semiconductor switch Q4 is turned off in a case where the energy stored in the second capacitor C2 is greater than the energy stored in the first capacitor C1.

[0081] 7(a), when the energy stored in the second capacitor C2 is greater than the energy stored in the first capacitor C1, the following current path is formed when the third semiconductor switch Q3 is turned off and the fourth semiconductor switch Q4 is turned on: That is, a current path is formed that sequentially passes through the second capacitor C2, the third node 13, the second reactor L2, the sixth node 16, the fourth semiconductor switch Q4, the seventh node 17, and the fourth node 14, and then returns to the second capacitor C2. As a result, the energy stored in the second capacitor C2 is stored in the second reactor L2.

[0082] 7(b), in this case, when the third semiconductor switch Q3 is turned off and the fourth semiconductor switch Q4 is turned off, the following current path is formed: the current path passes through the second reactor L2, the sixth node 16, the third diode D3, the fifth node 15, the second node 12, the first capacitor C1, and the third node 13 in this order, and then returns to the second reactor L2. As a result, the energy stored in the second reactor L2 is stored in the first capacitor C1, and the first capacitor C1 is charged. As a result, the voltage VC1 of the first capacitor C1 and the voltage VC2 of the second capacitor C2 are balanced (equal).

[0083] Fig. 8 is a diagram showing the current flow when the energy of the first capacitor C1 is transferred to the second capacitor C2 in the chopper circuit 10A shown in Fig. 6. Fig. 8(a) is a diagram showing the current flow when the third semiconductor switch Q3 is turned on in a case where the energy stored in the first capacitor C1 is greater than the energy stored in the second capacitor C2. Fig. 8(b) is a diagram showing the current flow when the third semiconductor switch Q3 is turned off in a case where the energy stored in the first capacitor C1 is greater than the energy stored in the second capacitor C2.

[0084] 8(a), when the energy stored in the first capacitor C1 is greater than the energy stored in the second capacitor C2, the following current path is formed when the third semiconductor switch Q3 is turned on and the fourth semiconductor switch Q4 is turned off: That is, a current path is formed that sequentially passes through the first capacitor C1, the second node 12, the fifth node 15, the third semiconductor switch Q3, the sixth node 16, the second reactor L2, and the third node 13, and then returns to the first capacitor C1. As a result, the energy stored in the first capacitor C1 is stored in the second reactor L2.

[0085] 8(b), in this case, when the third semiconductor switch Q3 is turned off and the fourth semiconductor switch Q4 is turned off, the following current path is formed: the current path passes through the second reactor L2, the third node 13, the second capacitor C2, the fourth node 14, the seventh node 17, the fourth diode D4, and the sixth node 16 in this order, before returning to the second reactor L2. As a result, the energy stored in the second reactor L2 is stored in the second capacitor C2, and the second capacitor C2 is charged. As a result, the voltage VC1 of the first capacitor C1 and the voltage VC2 of the second capacitor C2 are balanced (equal).

[0086] When the chopper duty is 100%, equal energy flows through the first capacitor C1 and the second capacitor C2, so the voltage VC1 of the first capacitor C1 and the voltage VC2 of the second capacitor C2 are balanced (equal). In this case, switching of the third semiconductor switch Q3 and the fourth semiconductor switch Q4 is unnecessary. Therefore, although the chopper circuit 10A includes a circuit having the third semiconductor switch Q3, the fourth semiconductor switch Q4, and the second reactor L2, no current flows through these. In other words, when the chopper duty is 100%, the current in the chopper circuit 10A passes through only one semiconductor switch, and does not necessarily pass through two semiconductor switches.

[0087] <Control method of the second embodiment> FIG. 9 is a diagram showing an example of the configuration of the control device 30A in the DC power conversion device 1A shown in FIGS. 6 to 8 and a control method for controlling the voltage balance between the first capacitor C1 and the second capacitor C2.

[0088] As described above, the control device 30A has the same functions as the control device 30 in the first embodiment shown in Figures 1 to 5. Therefore, the control device 30A controls the operations of the first semiconductor switch Q1 and the second semiconductor switch Q2 using the control method described in Figures 4 and 5. Furthermore, the control device 30A controls the operations of the third semiconductor switch Q3 and the fourth semiconductor switch Q4 as follows.

[0089] The control device 30A controls the operations of the third semiconductor switch Q3 and the fourth semiconductor switch Q4 so that both the third semiconductor switch Q3 and the fourth semiconductor switch Q4 are in the off state when the chopper duty of the chopper circuit 10A is 100%. As described above, when the chopper duty is 100%, equal energy flows through the first capacitor C1 and the second capacitor C2, so that the voltage VC1 of the first capacitor C1 and the voltage VC2 of the second capacitor C2 are balanced (uniform).

[0090] As described above, the control device 30A executes a predetermined program to function as a first subtractor 31A, a voltage controller 32A, a second subtractor 33A, a current controller 34A, and a PWM control unit 35A. Each of the above units executes a predetermined program to perform the following processes.

[0091] The first subtractor 31A performs the same processing as the first subtractor 31 in the first embodiment shown in FIGS. 1 to 5. Furthermore, the first subtractor 31A acquires a VC2 reference, for example, from a memory 92 (see FIG. 13), which will be described later. Here, the VC2 reference is a predetermined voltage reference value (voltage command value) for controlling the voltage VC2 of the second capacitor C2 so that it is equal to the voltage VC1 of the first capacitor C1. The VC2 reference is also a predetermined voltage reference value (voltage command value) for controlling the voltage VC2 of the second capacitor C2 so that it is equal to or less than the voltage VVb of the DC power supply Vb. Note that the first subtractor 31A may calculate the VC2 reference based on a predetermined calculation or the like, or may acquire the VC2 reference by receiving an instruction from a higher-level device (not shown) or an operator (not shown).

[0092] The first subtractor 31A also acquires (feeds back) the value of the voltage VC2 of the second capacitor C2 from the third voltage sensor 24 (see FIG. 6).Then, the first subtractor 31A subtracts the acquired (or calculated) VC2 reference from the acquired value of the voltage VC2, and outputs the subtracted value to the voltage controller 32A.

[0093] The voltage controller 32A performs the same processing as the voltage controller 32 in the first embodiment shown in FIGS. 1 to 5. Furthermore, the voltage controller 32A performs, for example, PI control or the like on the value acquired from the first subtractor 31A to obtain an IB reference. Here, the IB reference is a reference value (current command value) of the current to be flowed through the second reactor L2 in order to control the value of the voltage VC2 of the second capacitor C2 so that it is equal to the value of the voltage VC1 of the first capacitor C1. The voltage controller 32A outputs the obtained IB reference to the second subtractor 33A. Note that the first subtractor 31A and the voltage controller 32A are examples of a "voltage control unit," the VC2 reference is an example of a "fifth voltage command value," and the IB reference is an example of a "third current command value."

[0094] The second subtractor 33A performs the same processing as the second subtractor 33 in the first embodiment shown in Figures 1 to 5. Furthermore, the second subtractor 33A acquires an IB reference from the voltage controller 32A. The second subtractor 33A also acquires (feeds back) the value of the current IB flowing through the second reactor L2 from the second current sensor 25 (see Figure 6). Then, the second subtractor 33A subtracts the acquired value of the current IB from the acquired IB reference and outputs the subtracted value to the current controller 34A.

[0095] The current controller 34A performs the same processing as the current controller 34 in the first embodiment shown in Figures 1 to 5. Furthermore, the current controller 34A performs, for example, PI control on the value acquired from the second subtractor 33A, and outputs a voltage command value V3, which is a command for controlling the value of the voltage VC2 of the second capacitor C2 to be equal to the value of the voltage VC1 of the first capacitor C1. * The current controller 34A calculates the voltage command value V3 * The second subtractor 33A and the current controller 34A are an example of a "current controller" and output the voltage command value V3 * is an example of the "sixth voltage command value."

[0096] The PWM control unit 35A performs the same processing as the PWM control unit 35 in the first embodiment shown in Figures 1 to 5. Furthermore, the ... * and a carrier signal having, for example, a predetermined triangular waveform. The PWM control unit 35A generates a gate signal, which is a pulse-width modulation (PWM) signal for controlling the operation of at least one of the third semiconductor switch Q3 and the fourth semiconductor switch Q4. The PWM control unit 35A outputs the generated gate signal (Q3, Q4 pulse) to at least one of the third semiconductor switch Q3 and the fourth semiconductor switch Q4. The PWM control unit 35A controls the on / off operation of at least one of the third semiconductor switch Q3 and the fourth semiconductor switch Q4. The Q3, Q4 pulses are an example of a "third pulse."

[0097] When the chopper duty of the chopper circuit 10A is 100%, the PWM control unit 35A controls the operations of the third semiconductor switch Q3 and the fourth semiconductor switch Q4 so that both the third semiconductor switch Q3 and the fourth semiconductor switch Q4 are in the off state.

[0098] In the DC power conversion device 1A (chopper circuit 10A), the on / off operation of at least one of the third semiconductor switch Q3 and the fourth semiconductor switch Q4 is controlled by the above control method, thereby making it possible to control the voltage VC1 of the first capacitor C1 and the voltage VC2 of the second capacitor C2 to be uniform or to be arbitrarily balanced.

[0099] In the above description, a control method for controlling the voltage VC2 of the second capacitor C2 to be equal to the voltage VC1 of the first capacitor C1 has been described. However, the control device 30A may also control the voltage VC1 of the first capacitor C1 to be equal to the voltage VC2 of the second capacitor C2.

[0100] In this case, the first subtractor 31A acquires (calculates) the VC1 reference, and acquires (feeds back) the value of the voltage VC1 of the first capacitor C1. The first subtractor 31A then subtracts the acquired (calculated) VC1 reference from the acquired value of the voltage VC1 and outputs the subtracted value to the voltage controller 32A. Thereafter, the same control as described above is performed. In this case, the gate signals (Q3, Q4 pulses) generated and output by the PWM control unit 35A have pulses opposite to those of the gate signals (Q3, Q4 pulses) generated and output in the above description. However, even with this control method, the control device 30A can control the voltage VC1 of the first capacitor C1 and the voltage VC2 of the second capacitor C2 to be uniform or arbitrarily balanced, as in the above control method.

[0101] <Effects of the Second Embodiment> As described above, according to the second embodiment shown in FIGS. 6 to 9, the same effects as those of the first embodiment shown in FIGS. 1 to 5 are achieved.

[0102] 6 to 9, in the chopper circuit 10A, the charging energy of the second capacitor C2 can be transferred to the first capacitor C1 via the second reactor L2. Also, in the chopper circuit 10A, the charging energy of the first capacitor C1 can be transferred to the second capacitor C2 via the second reactor L2. As a result, by controlling the switching of the third semiconductor switch Q3 and the fourth semiconductor switch Q4, the voltage balance between the voltage VC1 of the first capacitor C1 and the voltage VC2 of the second capacitor C2 can be controlled uniformly or arbitrarily.

[0103] Furthermore, according to the second embodiment shown in FIGS. 6 to 9, by controlling the switching of the third semiconductor switch Q3 and the fourth semiconductor switch Q4, it is possible to optimize the voltage VC2 of the second capacitor C2 so as to reduce the ripple current in the first reactor L1.

[0104] 6 to 9, when the chopper duty is 100%, the voltage VC1 of the first capacitor C1 and the voltage VC2 of the second capacitor C2 are balanced (equal). This eliminates the need to switch the third semiconductor switch Q3 and the fourth semiconductor switch Q4, and in this case, no current flows through the third semiconductor switch Q3 or the fourth semiconductor switch Q4. In this case, the current passes through only one semiconductor switch (not necessarily two semiconductor switches), which reduces the total loss of the semiconductor switches and improves efficiency compared to the conventional method in which the current always passes through two semiconductor switches.

[0105] 6 to 9, by controlling the switching of the third semiconductor switch Q3 and the fourth semiconductor switch Q4, the voltage VC2 of the second capacitor C2 can be controlled to be equal to or lower than the voltage VVb of the DC power supply Vb. This allows the voltage VC2 of the second capacitor C2 to be controlled and optimized so as to approach the voltage VVb of the DC power supply Vb, thereby reducing the ripple of the first reactor L1.

[0106] <Third embodiment> FIG. 10 is a diagram showing an example of the configuration of a chopper circuit 10B in a DC power conversion device 1B according to the third embodiment.

[0107] In the third embodiment, components that are the same as or similar to those of the first and second embodiments shown in Figures 1 to 9 are denoted by the same reference numerals, and duplicated or detailed descriptions will be omitted or simplified. A chopper circuit 10B according to the third embodiment does not include the first semiconductor switch Q1 in the chopper circuit 10 of the first embodiment shown in Figures 1 to 5, and only a first diode D1 is connected in that position. Other aspects of the configuration and the control method are the same as those of the boost mode of the first embodiment shown in Figures 1 to 5.

[0108] In the DC power conversion device 1B (chopper circuit 10B) according to the third embodiment, only the boost mode is performed. That is, for example, if the DC power conversion device 1 (chopper circuit 10) performs only the boost mode, the first semiconductor switch Q1 can be omitted, and the corresponding position can be configured with only the first diode D1. The third embodiment shown in FIG. 10 can also achieve the same effects as the boost mode of the first embodiment shown in FIGS. 1 to 5.

[0109] Although not shown, if the DC power conversion device 1A (chopper circuit 10A) of the second embodiment shown in Figures 6 to 9 performs only the boost mode, the first semiconductor switch Q1 can be omitted and the corresponding part can be configured with only the first diode D1. Even with such a configuration, it is possible to achieve the same effects as those of the boost mode of the second embodiment shown in Figures 6 to 9.

[0110] <Fourth embodiment> FIG. 11 is a diagram showing an example of the configuration of a chopper circuit 10C in a DC power conversion device 1C according to the fourth embodiment.

[0111] In the fourth embodiment, components that are the same as or similar to those of the first and second embodiments shown in Figures 1 to 9 are denoted by the same reference numerals, and duplicated or detailed descriptions will be omitted or simplified. A chopper circuit 10C according to the fourth embodiment does not include the second semiconductor switch Q2 in the chopper circuit 10 of the first embodiment shown in Figures 1 to 5, and only a second diode D2 is connected in its place. Other aspects of the configuration and the control method are the same as those of the step-down mode of the first embodiment shown in Figures 1 to 5.

[0112] In the DC power conversion device 1C (chopper circuit 10C) according to the fourth embodiment, only the step-down mode is performed. That is, for example, if the DC power conversion device 1 (chopper circuit 10) performs only the step-down mode, the second semiconductor switch Q2 can be omitted, and the corresponding position can be configured with only the second diode D2. The fourth embodiment shown in FIG. 11 can also achieve the same effects as the step-down mode of the first embodiment shown in FIGS. 1 to 5.

[0113] Although not shown, the DC power conversion device 1A (chopper circuit 10A) of the second embodiment shown in Figures 6 to 9 can also omit the second semiconductor switch Q2 if it operates in only the step-down mode, and the corresponding part can be configured with only the second diode D2. Even with such a configuration, it is possible to achieve the same effects as those of the step-down mode of the second embodiment shown in Figures 6 to 9.

[0114] Fifth Embodiment FIG. 12 is a diagram showing an example of the configuration of a chopper circuit 10D in a DC power converter 1D according to the fifth embodiment.

[0115] In the fifth embodiment, the same or similar components as those in the first to fourth embodiments shown in Figures 1 to 11 are denoted by the same reference numerals, and duplicated or detailed descriptions will be omitted or simplified. A chopper circuit 10D in a DC power converter 1D according to the fifth embodiment has a configuration in which the positive and negative sides of the chopper circuit 10A in the DC power converter 1A according to the second embodiment shown in Figures 6 to 9 are interchanged. Other configurations and concepts of the control method are the same as those of the second embodiment shown in Figures 6 to 9.

[0116] That is, in the chopper circuit 10A of the second embodiment shown in Figures 6 to 9, the negative electrode side of the DC power supply Vb is connected to the second capacitor C2, but in the chopper circuit 10D of the fifth embodiment shown in Figure 12, the positive electrode side of the DC power supply Vb is connected to the first capacitor C1. With such a configuration of the fifth embodiment shown in Figure 12, it is possible to achieve the same effects as those of the second embodiment shown in Figures 6 to 9.

[0117] Although not shown, the chopper circuit 10 in the DC power conversion device 1 according to the first embodiment shown in Figures 1 to 5 may also have a configuration in which the positive and negative sides are interchanged. That is, in the chopper circuit 10 according to the first embodiment shown in Figures 1 to 5, the negative side of the DC power supply Vb is connected to the second capacitor C2, but the positive side of the DC power supply Vb may be connected to the first capacitor C1. Even with such a configuration, it is possible to achieve the same effects as those of the first embodiment shown in Figures 1 to 5.

[0118] Furthermore, the third embodiment shown in FIG. 10 and the fourth embodiment shown in FIG. 11 can also be configured similarly to the fifth embodiment shown in FIG. 12, and in this case too, the same effects as those of the third embodiment shown in FIG. 10 and the fourth embodiment shown in FIG. 11 can be achieved.

[0119] <Hardware configuration example> 13 is a conceptual diagram showing an example of the hardware configuration of the processing circuitry 90 included in the control device 30, 30A in the embodiment shown in FIGS. 1 to 12. The functions described above are realized by the processing circuitry 90. In one aspect, the processing circuitry 90 includes at least one processor 91 and at least one memory 92. In another aspect, the processing circuitry 90 includes at least one dedicated hardware 93.

[0120] When the processing circuit 90 includes a processor 91 and a memory 92, each function is realized by software, firmware, or a combination of software and firmware. At least one of the software and firmware is written as a program. At least one of the software and firmware is stored in the memory 92. The processor 91 realizes each function by reading and executing the program stored in the memory 92.

[0121] When the processing circuitry 90 comprises dedicated hardware 93, the processing circuitry 90 may be, for example, a single circuit, multiple circuits, a programmed processor, or a combination thereof. Each function is implemented by the processing circuitry 90.

[0122] Each function of the control devices 30 and 30A may be partially or entirely configured by hardware, or may be configured as a program executed by a processor. That is, the control devices 30 and 30A can also be realized by a computer and a program, and the program can be stored in a storage medium or provided over a network.

[0123] <Supplementary information on the implementation form> As described above, the embodiments shown in Figures 1 to 12 are divided into a first embodiment shown in Figures 1 to 5, a second embodiment shown in Figures 6 to 9, a third embodiment shown in Figure 10, a fourth embodiment shown in Figure 11, and a fifth embodiment shown in Figure 12. However, these embodiments may be combined in series or in parallel. The combined embodiments can also achieve the same effects as the respective effects achieved by the respective embodiments before being combined.

[0124] Although illustration is omitted, in the DC power conversion device 1A (chopper circuit 10A) according to the second embodiment shown in FIGS. 6 to 9, when the voltage of the capacitor always satisfies VC1 < VC2, the position of the third semiconductor switch Q3 can be constituted only by the third diode D3. On the other hand, although illustration is omitted, in the DC power conversion device 1A (chopper circuit 10A) of the second embodiment shown in FIGS. 6 to 9, when the voltage of the capacitor always satisfies VC2 < VC1, the position of the fourth semiconductor switch Q4 can be constituted only by the fourth diode D4. Also with these configurations, the same operational effects as those of the second embodiment shown in FIGS. 6 to 9 can be achieved.

[0125] Further, according to the embodiments shown in FIGS. 1 to 12, as one aspect of the present disclosure, the DC power conversion devices 1 to 1D and the control devices 30, 30A they have are described as examples, but it is not limited thereto. The present disclosure can also be realized as a control method in which processing steps in each part of the control devices 30, 30A are performed.

[0126] Also, the present disclosure can be realized as a control program that causes a computer to execute the processing steps in each part of the control devices 30, 30A.

[0127] Also, the present disclosure can be realized as a storage medium (non-temporary computer-readable storage medium) in which the control program is stored. The control program can be stored and distributed, for example, in removable media such as a CD (Compact Disc), a DVD (Digital Versatile Disc), a USB (Universal Serial Bus) memory, etc. Note that the control program may be uploaded onto a network via a network interface (not shown) that the control devices 30, 30A have, and may be downloaded from the network and stored in the memory 92 or the like.

[0128] The features and advantages of the embodiments will be apparent from the above detailed description. It is intended that the claims encompass the features and advantages of the above-described embodiments without departing from the spirit and scope of the claims. Furthermore, any improvements and modifications will be readily apparent to those skilled in the art. Therefore, it is not intended that the scope of the inventive embodiments be limited to the above-described embodiments, and appropriate improvements and equivalents within the scope of the disclosed embodiments may be utilized. [Explanation of symbols]

[0129] 1, 1A, 1B, 1C, 1D... DC power converter; 10, 10A, 10B, 10C, 10D... chopper circuit; 11... first connection point; 12... second connection point; 13... third connection point; 14... fourth connection point; 15... fifth connection point; 16... sixth connection point; 17... seventh connection point; 18... first terminal; 19... second terminal; 21... first voltage sensor; 22... first current sensor; 23... second voltage sensor; 24... third voltage sensor; 25... second current sensor; 30, 30A... control device; 31, 31A... first subtractor; 32, 32A ...Voltage controller; 33, 33A...Second subtractor; 34, 34A...Current controller; 35, 35A...PWM control unit; 90...Processing circuit; 91...Processor; 92...Memory; 93...Hardware; 100...Chopper circuit; 129...Reactor; 130A, 131A...Semiconductor switch; 130D, 131D...Diode; 132...Smoothing capacitor; 133A, 133B, 135A, 135B...Circuit terminal; 200...Chopper circuit; 201...Reactor; 201a, 201b, 201c...Terminal; 20 2A, 202B, 203A, 203B...semiconductor switches; 202AD, 202BD, 203AD, 203BD...diodes; 204A, 204B...smoothing capacitors; 205...neutral point (virtual earth); 206A, 207A...circuit terminals; 210...DC power converter; 211...battery; 214A, 214B...stray capacitance; 215...intermediate potential; 300...DC power converter; 300a, 300b, 300c...connection points; 301...chopper circuit; 303Q, 304Q, 305Q, 306Q...power Semiconductor element; 313...capacitor; 316...capacitor; 321...reactor; 323...capacitor; C1...first capacitor; C2...second capacitor; D1...first diode; D2...second diode; D3...third diode; D4...fourth diode; E...voltage; IB...current; ID...current; L1...first reactor; L2...second reactor; Q1...first semiconductor switch; Q2...second semiconductor switch; Q3...third semiconductor switch; Q4...fourth semiconductor switch; V...voltage; V...power supply; V1 * ,V2 * ,V3 * …Voltage command value; Vb…DC power supply (battery); VC, VC1, VC2…Voltage; VVb…Voltage

Claims

1. a first switch connected in series between the first connection point and the second connection point; a first diode connected in antiparallel to the first switch; a second switch connected in series between the first connection point and a third connection point; a second diode connected in antiparallel to the second switch; a first capacitor connected in series between the second connection point and the third connection point; a second capacitor connected in series between the third connection point and the fourth connection point; a DC power supply and a first reactor connected in series in this order between the fourth connection point and the first connection point; a chopper circuit having In the boost mode, the chopper circuit: when the first switch is in an off state and the second switch is in an on state, a current path is formed that runs from the DC power supply, sequentially through the first reactor, the first connection point, the second switch, the third connection point, the second capacitor, and the fourth connection point, and returns to the DC power supply; when the first switch is in an off state and the second switch is in an off state, a current path is formed that runs from the DC power supply, sequentially through the first reactor, the first connection point, the first diode, the second connection point, the first capacitor, the third connection point, the second capacitor, and the fourth connection point, and returns to the DC power supply; In the step-down mode, the chopper circuit when the first switch is in an on state and the second switch is in an off state, a current path is formed that passes through the second capacitor, the third connection point, the first capacitor, the second connection point, the first switch, the first connection point, the first reactor, the DC power supply, and the fourth connection point in this order, and returns to the second capacitor; When the first switch is in an off state and the second switch is in an off state, a current path is formed that passes through the second capacitor, the third connection point, the second diode, the first connection point, the first reactor, the DC power supply, and the fourth connection point in this order and returns to the second capacitor. A DC power conversion device characterized by:

2. 2. The DC power converter according to claim 1, a control device having a voltage control unit, a current control unit, and a PWM control unit, and controlling the chopper circuit; In the voltage step-up mode, the control device the voltage control unit calculates a first current command value for controlling a value of a current to be flowed through the first reactor, based on a voltage value of the first capacitor, a voltage value of the second capacitor, and a predetermined first voltage command value for controlling the voltage values ​​of the first capacitor and the second capacitor to constant values; the current control unit calculates a second voltage command value that is a duty command in the voltage step-up mode, based on the first current command value calculated by the voltage control unit and a value of a current flowing through the first reactor; The PWM control unit outputs a first pulse for controlling the operation of the second switch based on the second voltage command value calculated by the current control unit and a predetermined carrier signal. A DC power conversion device characterized by:

3. 2. The DC power converter according to claim 1, a control device having a voltage control unit, a current control unit, and a PWM control unit, and controlling the chopper circuit; In the step-down mode, the control device the voltage control unit calculates a second current command value for controlling a value of a current to be flowed through the first reactor, based on a predetermined third voltage command value for controlling a value of a voltage of the DC power supply to a constant value and the value of the voltage of the DC power supply; the current control unit calculates a fourth voltage command value that is a duty command in the voltage step-down mode, based on the second current command value calculated by the voltage control unit and a value obtained by multiplying a value of the current flowing through the first reactor by −1; The PWM control unit outputs a second pulse for controlling the operation of the first switch based on the fourth voltage command value calculated by the current control unit and a predetermined carrier signal. A DC power conversion device characterized by:

4. 2. The DC power converter according to claim 1, The chopper circuit is a third switch connected in series between a fifth connection point between the second connection point and the first terminal and a sixth connection point; a third diode connected in antiparallel to the third switch; a fourth switch connected in series between the sixth connection point and a seventh connection point between the fourth connection point and a second terminal; a fourth diode connected in antiparallel to the fourth switch; a second reactor connected in series between the third connection point and the sixth connection point; and When the energy stored in the second capacitor is greater than the energy stored in the first capacitor, when the third switch is in an off state and the fourth switch is in an on state, a current path is formed that passes through the second capacitor, the third connection point, the second reactor, the sixth connection point, the fourth switch, the seventh connection point, and the fourth connection point in this order, and returns to the second capacitor, so that the energy stored in the second capacitor is stored in the second reactor; when the third switch is in an off state and the fourth switch is in an off state, a current path is formed that passes through the second reactor, the sixth connection point, the third diode, the fifth connection point, the second connection point, the first capacitor, and the third connection point in this order, and returns to the second reactor, whereby the energy stored in the second reactor is stored in the first capacitor; When the energy stored in the first capacitor is greater than the energy stored in the second capacitor, when the third switch is in an on state and the fourth switch is in an off state, a current path is formed that passes through the first capacitor, the second connection point, the fifth connection point, the third switch, the sixth connection point, the second reactor, and the third connection point in this order, and returns to the first capacitor, so that the energy stored in the first capacitor is stored in the second reactor; When the third switch is in an off state and the fourth switch is in an off state, a current path is formed that passes through the second reactor, the third connection point, the second capacitor, the fourth connection point, the seventh connection point, the fourth diode, and the sixth connection point in this order, and returns to the second reactor, so that the energy stored in the second reactor is stored in the second capacitor. A DC power conversion device characterized by:

5. 5. The DC power converter according to claim 4, a control device having a voltage control unit, a current control unit, and a PWM control unit, and controlling the chopper circuit; When the chopper duty of the chopper circuit is not 100%, the control device the voltage control unit calculates a third current command value for controlling a value of a current to be passed through the second reactor, based on a predetermined fifth voltage command value for controlling a voltage value of the second capacitor so that the voltage value of the second capacitor is equal to a voltage value of the first capacitor, and the voltage value of the second capacitor; the current control unit calculates a sixth voltage command value, which is a command for controlling a voltage value of the second capacitor to be equal to a voltage value of the first capacitor, based on the third current command value calculated by the voltage control unit and a value of the current flowing through the second reactor; The PWM control unit outputs a third pulse for controlling the operation of at least one of the third switch and the fourth switch, based on the sixth voltage command value calculated by the current control unit and a predetermined carrier signal. A DC power conversion device characterized by:

6. 6. The DC power converter according to claim 5, The fifth voltage command value is a command value for controlling the voltage value of the second capacitor to be equal to or less than the voltage value of the DC power supply. A DC power conversion device characterized by:

7. 6. The DC power converter according to claim 5, When the chopper duty of the chopper circuit is 100%, The control device controls both the third switch and the fourth switch to be in an off state. A DC power conversion device characterized by:

8. a first diode connected in series between the first connection point and the second connection point; a second switch connected in series between the first connection point and a third connection point; a second diode connected in antiparallel to the second switch; a first capacitor connected in series between the second connection point and the third connection point; a second capacitor connected in series between the third connection point and the fourth connection point; a DC power supply and a first reactor connected in series in this order between the fourth connection point and the first connection point; a chopper circuit having In the boost mode, the chopper circuit: when the second switch is in an on state, a current path is formed that runs from the DC power supply, sequentially through the first reactor, the first connection point, the second switch, the third connection point, the second capacitor, and the fourth connection point, and returns to the DC power supply; When the second switch is in an off state, a current path is formed that runs from the DC power supply back to the DC power supply, sequentially passing through the first reactor, the first connection point, the first diode, the second connection point, the first capacitor, the third connection point, the second capacitor, and the fourth connection point. A DC power conversion device characterized by:

9. a first switch connected in series between the first connection point and the second connection point; a first diode connected in antiparallel to the first switch; a second diode connected in series between the first node and the third node; a first capacitor connected in series between the second connection point and the third connection point; a second capacitor connected in series between the third connection point and the fourth connection point; a DC power supply and a first reactor connected in series in this order between the fourth connection point and the first connection point; a chopper circuit having In the step-down mode, the chopper circuit when the first switch is in an on state, a current path is formed that passes through the second capacitor, the third connection point, the first capacitor, the second connection point, the first switch, the first connection point, the first reactor, the DC power supply, and the fourth connection point in this order, and returns to the second capacitor; When the first switch is in an off state, a current path is formed that passes through the second capacitor, the third connection point, the second diode, the first connection point, the first reactor, the DC power supply, and the fourth connection point in this order, and returns to the second capacitor. A DC power conversion device characterized by:

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