Power supply device

Abstract

The present invention comprises: a multi-parallel chopper circuit having a plurality of unit chopper circuits; and a control device having a plurality of control units provided so as to correspond to each of the plurality of unit chopper circuits. The plurality of control units control the operation of the plurality of unit chopper circuits so that a normal mode current component flowing through the unit chopper circuits approaches a normal mode current reference and a common mode current component flowing through the unit chopper circuits approaches a common mode current reference. As a result, the current shares of each of the unit choppers can be equalized even when two serial choppers are used as unit choppers and a plurality of unit choppers are connected in multi-parallel.

Description

power supply

[0001] FIELD An embodiment of the present invention relates to a power supply device.

[0002] Chopper circuits are used in power supplies to obtain an appropriate voltage value for a load from a DC power source. Chopper circuits regulate voltage by switching semiconductor switching elements, and have the ability to regulate voltage at high speeds. However, there is a problem in that the capacity of the power supply is limited by the current capacity of the semiconductor switching elements.

[0003] Therefore, for example, Patent Document 1 proposes a method of expanding the device capacity by configuring a power supply device by connecting multiple chopper circuits in parallel. Patent Document 1 shows a configuration in which a reactor is provided in the chopper output section and the outputs are connected in parallel via the reactor. The current of each reactor is detected and controlled on a chopper-by-chopper basis, thereby equalizing the current sharing of each chopper. This makes it possible to cover the required power with the minimum number of choppers connected in parallel and to equalize the load of each chopper.

[0004] On the other hand, the size of the reactor connected to the output of each chopper is limited by the switching frequency of each chopper. Therefore, in order to reduce the size of the reactor, it is necessary to reduce the voltage harmonics applied to the reactor, for example, without increasing the switching frequency. For example, Patent Document 2 proposes a chopper circuit in which chopper circuits each consisting of two semiconductor switching elements are connected in two stages in series. Furthermore, Patent Document 3 proposes a method for reducing harmonic voltages generated by providing a switching phase difference between multiple series-connected chopper circuits. It is believed that by combining the circuit proposed in Patent Document 2 with the method of Patent Document 3, it is possible to reduce the output voltage harmonics of the unit chopper and reduce the reactor size.

[0005] It is believed that the capacity of a power supply unit can be increased by miniaturizing the reactor of the unit chopper using the techniques of Patent Documents 2 and 3, and configuring a power supply unit by connecting the unit choppers in multiple parallel connections using the control method of Patent Document 1. Sharing the load current of a power supply unit configured by connecting multiple unit choppers in parallel among the unit choppers is rational from the viewpoint of minimizing the number of choppers connected in parallel and the unit chopper capacity.

[0006] Patent Document 1 proposes a control method in which the current of a reactor connected to the positive side of each chopper is detected and the current of each chopper is equally shared. Also, Patent Document 2 proposes a method in which the current of a reactor connected to the positive side of a two-series chopper is detected and controlled in the same way as Patent Document 1. However, when the outputs of two series-connected choppers are connected in parallel, it is difficult to equalize the current of each chopper using these methods.

[0007] As shown in Patent Document 2, a two-series chopper has two choppers connected in series, with the terminal between the two switching elements constituting each chopper serving as an output terminal. The output terminals are an upper chopper and a lower chopper. When a multi-parallel chopper circuit is configured using two series choppers as unit choppers, the respective terminals are connected in parallel to the load. Furthermore, assuming that each chopper receives power from a common DC power source, the input sides of each chopper are also connected in parallel. When the output and input sections are interconnected, the upper chopper and the lower chopper are connected between the parallel choppers, forming a cross-current path between the upper and lower choppers. Therefore, when the control methods shown in Patent Documents 1 and 2 are applied, the positive pole current of the upper chopper can be controlled, but the current of the lower chopper cannot, potentially resulting in a current imbalance.

[0008] For this reason, in a power supply device, it is desirable to use two series choppers as unit chopper circuits and to be able to more appropriately control the current flowing through each unit chopper circuit even when multiple unit chopper circuits are connected in parallel.

[0009] Japanese Patent Laid-Open No. 9-215322 Japanese Patent Laid-Open No. 2011-188655 Japanese Patent Laid-Open No. 2014-96969

[0010] An embodiment of the present invention provides a power supply device that can more appropriately control the current flowing through each unit chopper circuit even when two series choppers are used as unit chopper circuits and a plurality of unit chopper circuits are connected in parallel.

[0011] According to an embodiment of the present invention, there is provided a multi-parallel chopper circuit having a plurality of unit chopper circuits connected in parallel to a first DC circuit and connected in parallel to a second DC circuit, and performing at least one of converting DC power according to the first DC circuit to DC power according to the second DC circuit and converting DC power according to the second DC circuit to DC power according to the first DC circuit by operation of the plurality of unit chopper circuits; and a control device having a plurality of control sections provided corresponding to each of the plurality of unit chopper circuits, and controlling operation of each of the plurality of unit chopper circuits by the plurality of control sections, wherein each of the plurality of unit chopper circuits has a first positive terminal and a first negative terminal connected to the first DC circuit, a second positive terminal and a second negative terminal connected to the second DC circuit, two charge storage elements connected in series between the first positive terminal and the first negative terminal, two upper stage elements connected in series between the first positive terminal and a neutral point which is a connection point of the two charge storage elements, and a connection point between the neutral point and the first a first inductor provided between a junction of the two upper elements and the second positive terminal; a second inductor provided between the junction of the two lower elements and the second negative terminal; a first current sensor that detects a magnitude of a current flowing to the second positive terminal; and a second current sensor that detects a magnitude of a current flowing to the second negative terminal, wherein at least one of the two upper elements and at least one of the two lower elements are switching elements that can switch between an ON state in which a current flows and an OFF state in which a current is blocked, and the control device defines a direction of a current flowing from the junction of the two upper elements toward the second positive terminal as positive, and defines a direction of a current flowing from the second negative terminal toward the junction of the two lower elements as positive, and the plurality of control units calculate a normal mode current component based on a sum of a current detection value of the first current sensor and a current detection value of the second current sensor, and calculates a normal mode current component based on the normal mode current component and a normal mode current reference.a first calculation unit that calculates a normal mode duty ratio that indicates a ratio of a period of the on state to a switching frequency of the switching element so as to bring the normal mode current component closer to the normal mode current reference; a second calculation unit that calculates a common mode current component based on a difference between a current detection value of the first current sensor and a current detection value of the second current sensor, and calculates a common mode duty ratio that indicates a ratio of a period of the on state to a switching frequency of the switching element so as to bring the common mode current component closer to the common mode current reference, based on the common mode current component and the common mode current reference; a first control signal generating unit that determines the duty ratio of the switching element of at least one of the two upper stage elements by adding the common mode duty ratio to the normal mode duty ratio and generates a control signal for switching the switching element of at least one of the two upper stage elements at the determined duty ratio, and a second control signal generating unit that determines the duty ratio of the switching element of at least one of the two lower stage elements by subtracting the common mode duty ratio from the normal mode duty ratio and generates a control signal for switching the switching element of at least one of the two lower stage elements at the determined duty ratio.

[0012] According to an embodiment of the present invention, a power supply device is provided that can more appropriately control the current flowing through each unit chopper circuit even when two series choppers are used as unit chopper circuits and a plurality of unit chopper circuits are connected in parallel.

[0013] FIG. 11 is a block diagram schematically showing a power supply device according to an embodiment. FIG. 11 is a simplified block diagram for explaining an example of the operation of the power supply device. FIG. 11 is a block diagram schematically showing a reference control unit. FIG. 11 is a graph schematically showing an example of the reference operation of the power supply device. FIG. 11 is a block diagram schematically showing a control unit according to an embodiment. FIG. 11 is a graph schematically showing an example of the operation of the power supply device according to an embodiment. FIG. 11 is a block diagram schematically showing a modified example of the power supply device according to an embodiment. FIG. 11 is a simplified block diagram for explaining a modified example of the power supply device. FIG. 11 is a block diagram schematically showing a modified example of the power supply device according to an embodiment. FIGS. 11(a) and 11(b) are block diagrams schematically showing modified examples of unit chopper circuits according to an embodiment.

[0014] Each embodiment will be described below with reference to the drawings. The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc., are not necessarily the same as those in reality. Even when the same part is shown, the dimensions and ratios may be different depending on the drawing. In this specification and each drawing, elements similar to those previously described with reference to the previous drawings are designated by the same reference numerals, and detailed descriptions thereof will be omitted as appropriate.

[0015] 1 is a block diagram illustrating a power supply device according to an embodiment. As shown in FIG. 1, the power supply device 10 includes a multi-parallel chopper circuit 12 and a control device 14.

[0016] The multi-parallel chopper circuit 12 has a plurality of unit chopper circuits 16 connected in parallel to the first DC circuit DC1 and connected in parallel to the second DC circuit DC2, and by operation of the plurality of unit chopper circuits 16, performs at least one of conversion from DC power corresponding to the first DC circuit DC1 to DC power corresponding to the second DC circuit DC2, and conversion from DC power corresponding to the second DC circuit DC2 to DC power corresponding to the first DC circuit DC1.

[0017] The control device 14 has a plurality of control sections 18 provided corresponding to the plurality of unit chopper circuits 16 , respectively, and the plurality of control sections 18 control the operation of each of the plurality of unit chopper circuits 16 .

[0018] Each of the plurality of unit chopper circuits 16 includes a first positive terminal 21p and a first negative terminal 21n connected to the first DC circuit DC1, a second positive terminal 22p and a second negative terminal 22n connected to the second DC circuit DC2, two charge storage elements 23a and 23b connected in series between the first positive terminal 21p and the first negative terminal 21n, two upper stage elements 24a and 24b connected in series between the first positive terminal 21p and a neutral point 21c which is a connection point between the first positive terminal 21p and the two charge storage elements 23a and 23b, and a neutral point 21c. The power supply circuit has two lower elements 25a, 25b connected in series between the first positive terminal 21c and the first negative terminal 21n, a first inductor 26a provided between the connection point of the two upper elements 24a, 24b and the second positive terminal 22p, a second inductor 26b provided between the connection point of the two lower elements 25a, 25b and the second negative terminal 22n, a first current sensor 27a that detects the magnitude of the current flowing through the second positive terminal 22p, and a second current sensor 27b that detects the magnitude of the current flowing through the second negative terminal 22n.

[0019] In this way, a plurality of unit chopper circuits 16 (two or more) are connected in parallel to form a multi-parallel chopper circuit 12, thereby forming a power supply device 10 that can handle large load capacities. The unit chopper circuit 16 is configured such that a DC circuit consisting of two charge storage elements 23a, 23b is connected in parallel with two upper stage elements 24a, 24b connected in series and two lower stage elements 25a, 25b connected in series to each of the charge storage elements 23a, 23b. The two upper stage elements 24a, 24b and the two lower stage elements 25a, 25b are, for example, switching elements. Since this configuration results in two chopper circuits, each consisting of two switching elements, having their outputs connected in series, this unit chopper circuit 16 is called a two-series chopper.

[0020] The two-series chopper has two charge storage elements 23a, 23b. The terminal with the highest potential of the two charge storage elements 23a, 23b is defined as a first positive terminal 21p (P in the figure), the interconnection point of the two charge storage elements 23a, 23b is defined as a neutral point 21c (O in the figure), and the terminal with the lowest potential is defined as a first negative terminal 21n (N in the figure). The two charge storage elements 23a, 23b are, for example, capacitors. The two charge storage elements 23a, 23b may also be, for example, other energy storage elements such as storage batteries.

[0021] The chopper circuit connected between the first positive terminal 21p and the neutral point 21c is defined as an upper chopper, and the chopper circuit connected between the neutral point 21c and the first negative terminal 21n is defined as a lower chopper. Of the two upper elements 24a, 24b that make up the upper chopper, the element connected to the first positive terminal 21p side is defined as an upper outer element, and the element connected to the neutral point 21c side is defined as an upper inner element.

[0022] Of the two lower stage elements 25a, 25b that make up the lower stage chopper, the element connected to the neutral point 21c side is defined as the lower stage inner element, and the element connected to the first negative terminal 21n side is defined as the lower stage outer element.

[0023] The upper elements 24a, 24b and the lower elements 25a, 25b are self-extinguishing elements such as IGBTs or MOSFETs, or are configured with diodes connected in anti-parallel to the elements. The upper elements 24a, 24b and the lower elements 25a, 25b are, for example, semiconductor switching elements. The upper elements 24a, 24b and the lower elements 25a, 25b each have, for example, a pair of main terminals and a control terminal. The upper elements 24a, 24b and the lower elements 25a, 25b each have an ON state in which current flows between the pair of main terminals and an OFF state in which current is blocked between the pair of main terminals. The upper elements 24a, 24b and the lower elements 25a, 25b switch between the ON state and the OFF state depending on, for example, the voltage between the pair of main terminals and the voltage at the control terminal. However, the upper stage elements 24 a, 24 b and the two lower stage elements 25 a, 25 b are not limited to these, and may be any switching elements that can switch between an ON state in which a current flows and an OFF state in which a current flow is blocked. The OFF state does not have to be a state in which no current flows at all, but may be a state in which a weak current flows within a range that does not affect the operation of the unit chopper circuit 16.

[0024] Furthermore, the upper elements 24a, 24b and the lower elements 25a, 25b can be configured, for example, such that the inner elements of the upper and lower stages are diodes and the outer elements of the upper and lower stages are self-extinguishing elements, or such that the inner elements of the upper and lower stages are self-extinguishing elements and the outer elements of the upper and lower stages are diodes.

[0025] The interconnection point between the outer element and the inner element of the upper chopper is defined as the upper chopper output terminal, to which the first inductor 26a is connected. A first current sensor 27a is provided to detect the current flowing through the first inductor 26a, and the other terminal of the first inductor 26a that is not connected to the upper chopper is defined as the second positive terminal 22p of the unit chopper circuit 16.

[0026] The interconnection point between the inner and outer elements of the lower chopper is defined as the lower chopper output terminal, and similar to the upper chopper, a second inductor 26b and a second current sensor 27b for detecting its current are provided, and the other terminal of the second inductor 26b that is not connected to the lower chopper is defined as the second negative terminal 22n of the unit chopper circuit 16.

[0027] The first inductor 26 a and the second inductor 26 b are inductance elements such as reactors. The first inductor 26 a and the second inductor 26 b suppress abrupt changes in the current flowing between the upper chopper and the second positive terminal 22 p and between the lower chopper and the second negative terminal 22 n. The first inductor 26 a and the second inductor 26 b suppress ripples caused by switching of the upper elements 24 a, 24 b and the lower elements 25 a, 25 b.

[0028] The multi-parallel chopper circuit 12 is configured by interconnecting the first positive terminal 21p, the first negative terminal 21n, and the neutral point 21c of each of the unit chopper circuits 16, and by interconnecting the second positive terminal 22p and the second negative terminal 22n. The interconnection point of the first positive terminal 21p and the interconnection point of the first negative terminal 21n form a high-voltage side DC circuit of the multi-parallel chopper circuit 12, and is connected to a first DC circuit DC1 such as a DC power supply. The second positive terminal 22p and the second negative terminal 22n form a low-voltage side DC circuit and are connected to a second DC circuit DC2 such as a load. Alternatively, the high-voltage side DC circuit may be connected to a load, and the low-voltage side DC circuit may be connected to a power supply. Alternatively, power supplies may be connected to both the high-voltage and low-voltage sides to form a power supply interface circuit. In this manner, the first DC circuit DC1 and the second DC circuit DC2 may be DC power supplies, DC loads, or the like.

[0029] The plurality of control units 18 of the control device 14 have a calculation unit that calculates duty, which is the conduction rate of the unit chopper circuit 16, from the current at the second positive electrode terminal 22p and the second negative electrode terminal 22n of each unit chopper circuit 16, and a control signal generation unit that generates a control signal from the duty. The configuration of the plurality of control units 18 is the same for all the unit chopper circuits 16 that make up the multi-parallel chopper circuit 12, for example.

[0030] Each unit chopper circuit 16 detects the current at the second positive terminal 22p and the second negative terminal 22n, and controls the unit chopper circuit 16 using the detected value, thereby making it possible to arbitrarily control the current at each unit chopper circuit 16 and appropriately control the load current at each unit chopper circuit 16 constituting the multi-parallel chopper circuit 12. For example, if the magnitude of the current flowing through the second positive terminal 22p and the second negative terminal 22n is set to be the same in each unit chopper circuit 16, it becomes possible for each unit chopper circuit 16 to equally share the load current.

[0031] Next, the reason why the configuration of this embodiment makes it possible to control the currents at the second positive terminal 22p and the second negative terminal 22n of each unit chopper circuit 16 of the multi-parallel chopper circuit 12, in which each unit chopper circuit 16 is a two-series chopper, will be explained.

[0032] FIG. 2 is a simplified block diagram illustrating an example of the operation of a power supply device. FIG. 2 shows a configuration diagram of a multi-parallel chopper circuit composed of two two-series choppers, unit chopper circuit A and unit chopper circuit B. Unit chopper circuit A and unit chopper circuit B are interconnected by a high-voltage side DC circuit and a low-voltage side DC circuit. Therefore, a cross-current path is formed between each unit chopper circuit for each of the upper and lower choppers. For example, a circuit loop is formed by the interconnection point of the first positive terminal 21p and the second positive terminal 22p of unit chopper circuit A and the second positive terminal 22p of unit chopper circuit B, and a circuit loop is formed by the interconnection point of the first negative terminal 21n and the second negative terminal 22n of unit chopper circuit A and the second negative terminal 22n of unit chopper circuit B.

[0033] The current of the second positive terminal 22p of the unit chopper circuit A is expressed as i ａＡ , the current of the second negative electrode terminal 22n is i ａＢ and the current of the second positive terminal 22p of the unit chopper circuit B is i ｂＡ , the current of the second negative electrode terminal 22n is i ｂＢ Then, the load current i ｌｏａｄ (The current flowing through the second DC circuit DC2) can be expressed by the following equation (1) from Kirchhoff's law.

[0034] The direction of the current flow is defined as positive in the direction of the arrow of each current in Fig. 2. The control device 14 defines the direction of the current flowing from the connection point of the two upper elements 24a, 24b toward the second positive electrode terminal 22p as positive, and defines the direction of the current flowing from the second negative electrode terminal 22n toward the connection point of the two lower elements 25a, 25b as positive.

[0035] Here, the normal mode current is defined as the average value of the current at the second positive terminal 22p and the current at the second negative terminal 22n, and is a current component that is common to the positive and negative poles. The normal mode current of the unit chopper circuit A is defined as i ｎａ , the normal mode current of the unit chopper circuit B is i ｎｂ The common mode current i of the unit chopper circuit A is defined as a value obtained by dividing the difference between the current at the second positive terminal 22p and the current at the second negative terminal 22n by 2, and the current component that differs between the positive and negative terminals is defined as a common mode current. ｃａ , the common mode current of the unit chopper circuit B is i ｃｂ Using these normal mode current and common mode current, the currents at the second positive terminal 22p and second negative terminal 22n of each unit chopper circuit A, B can be expressed by the following equation (2).

[0036] Substituting equation (2) into equation (1) gives the following equation (3), where i ｃａ +i ｃｂ Unless is zero, equation (1) does not hold.

[0037] This is because the load (second DC circuit DC2) is a two-terminal circuit and cannot pass a common-mode current component. Therefore, it is assumed that the common-mode currents of unit chopper circuit A and unit chopper circuit B cancel each other out, and each common-mode current is defined as in the following equation (4).

[0038] Substituting equation (4) into equation (3) gives the following equation (5).

[0039] The above results show that there is a possibility that a common mode current component will flow through each of the unit chopper circuits A and B under the condition that the sum of the common mode current components of the unit chopper circuits A and B is zero.

[0040] Here, consider a case where the current of each unit chopper circuit is controlled using only the current at the second positive terminal 22p of each unit chopper circuit of a multi-parallel chopper circuit in which two series choppers are unit chopper circuits. Then, assume that the same current command value is given to control each unit chopper circuit so that the current is the same in order to distribute the load current equally among the unit chopper circuits. In this case, it is considered that the current at the second positive terminal 22p of each unit chopper circuit used for control is equal between the unit chopper circuits and coincides with the current command value. Here, the current command of each unit chopper circuit is i ｒｅｆ and assuming that the current at the second positive electrode terminal 22p of each unit chopper circuit matches the current command value, the current at the second positive electrode terminal 22p of each unit chopper circuit can be expressed by the following equations (6) and (7).

[0041] When the normal mode currents are calculated from the equations (6) and (7), the following equations (8) and (9) are obtained.

[0042] By substituting the obtained normal mode currents into equation (2) to find the current at the second negative terminal 22n, the following equations (10) and (11) are obtained.

[0043] When the current of each unit chopper circuit is controlled using only the current of the second positive electrode terminal 22p, the output terminal current of each unit chopper circuit can be summarized as follows:

[0044] It can be seen that the current at the second positive terminal 22p used for current control is balanced between each unit chopper circuit, but the current at the second negative terminal 22n not used for current control is unbalanced between each unit chopper circuit. In other words, this means that the current on the second negative terminal 22n side cannot be controlled to an arbitrary value. There is no problem with the second positive terminal 22p side because it is balanced, but this indicates that the current at the second negative terminal 22n becomes unbalanced, which may result in current concentrating at the second negative terminal 22n of a specific unit chopper circuit.

[0045] The current at the second negative terminal 22n passes through the switching elements that make up the unit chopper circuits. This limits the allowable current, and the output of the multi-parallel chopper circuits cannot be maximized. To maximize the output of the multi-parallel chopper circuits, it is necessary to balance not only the current at the second positive terminal 22p of each unit chopper circuit but also the current at the second negative terminal 22n between the unit chopper circuits.

[0046] Therefore, by detecting the current on the second positive terminal 22p side and the second negative terminal 22n side in each unit chopper circuit, and using the respective current detection values ​​to determine the conduction rate of each unit chopper circuit and controlling the current, it becomes possible to control the current on the second positive terminal 22p and the second negative terminal 22n to any value.

[0047] Next, a configuration for determining the duty ratio of a unit chopper circuit using the currents at the second positive terminal 22p and the second negative terminal 22n will be described in detail. The description will be given taking as an example a two-parallel configuration consisting of unit chopper circuits A and B shown in FIG.

[0048] Fig. 3 is a block diagram schematically illustrating a reference control unit. The control block diagram shown in Fig. 3 illustrates an example of a reference control unit 18ref provided corresponding to each unit chopper circuit 16. The reference control unit 18ref includes a calculation unit 100 and a control signal generation unit 110.

[0049] The calculation unit 100 includes an adder 101, a calculator 102, a subtractor 103, and a current controller 104. The calculation unit 100 adds the current detection value at the second positive terminal 22p and the current detection value at the second negative terminal 22n of the unit chopper circuit 16 using the adder 101, multiplies the result of addition by 1 / 2 using the calculator 102, and calculates the average value of the current detection value at the second positive terminal 22p and the current detection value at the second negative terminal 22n, thereby determining the normal mode current component from each current detection value. Note that the calculation unit 100 may omit the calculator 102 and calculate the sum of the current detection value at the second positive terminal 22p and the current detection value at the second negative terminal 22n as the normal mode current component.

[0050] The calculation unit 100 calculates the difference between the determined normal mode current component and a current reference that serves as a current command value using a subtractor 103. The calculation unit 100 inputs the difference calculated by the subtractor 103 to a current controller 104 that is configured with a PI compensator and the like. The current controller 104 performs proportional calculations, proportional integral calculations, and the like on the input difference to calculate the duty ratio (duty) of the unit chopper circuit 16 for bringing the normal mode current component closer to the current reference. The calculation unit 100 inputs the calculated duty ratio to a control signal generation unit 110.

[0051] The control signal generating unit 110 sets the duty ratio of the unit chopper circuit 16 to be equal between the upper chopper and the lower chopper. The control signal generating unit 110 has comparators 111 and 112. The comparator 111 compares the duty ratio with a triangular wave carrier to generate control signals S1 and S2 for switching the upper stage elements 24a and 24b of the upper chopper at the determined duty ratio. The comparator 112 compares the duty ratio with a triangular wave carrier to generate control signals S3 and S4 for switching the lower stage elements 25a and 25b of the lower chopper at the determined duty ratio. In this case, the comparator 112 uses a triangular wave carrier that is 180° out of phase with the triangular wave carrier of the upper chopper.

[0052] The duty ratio is a DC signal that is set to a magnitude between the minimum and maximum amplitude values ​​of a carrier signal, such as a triangular wave carrier. In other words, the duty ratio is a signal that determines the duty ratio of the control signals S1 to S4. The carrier signal is not limited to a triangular wave, and may be a sawtooth wave or the like.

[0053] The control signals S1 to S4 are, for example, pulsed signals that have a high state (high voltage state) corresponding to the on state of the switching element and a low state (low voltage state) corresponding to the off state of the switching element. The control signals S1 to S4 are, for example, PWM signals. The control signals S1 to S4 are also sometimes called gate signals. The comparators 111 and 112, for example, set the control signals S1 to S4 to a high state when the duty ratio signal is equal to or greater than the carrier signal, and set the control signals S1 to S4 to a low state when the duty ratio signal is less than the carrier signal.

[0054] In this example, each unit chopper circuit 16 has two upper stage elements 24a, 24b and two lower stage elements 25a, 25b as switching elements. In this case, the control signal generating unit 110 switches the two upper stage elements 24a, 24b at a determined duty ratio so that when the upper stage element 24a is turned on, the upper stage element 24b is turned off, and when the upper stage element 24b is turned on, the upper stage element 24a is turned off. The control signal generating unit 110 then switches the two lower stage elements 25a, 25b at a determined duty ratio so that when the lower stage element 25a is turned on, the lower stage element 25b is turned off, and when the lower stage element 25b is turned on, the lower stage element 25a is turned off.

[0055] The control signal generating unit 110 includes, for example, NOT gates 113 and 114. For example, when performing a step-down operation to convert DC power from the first DC circuit DC1 to DC power corresponding to the second DC circuit DC2, the control signal generating unit 110 controls the switching of the upper and lower elements 24a and 25b, which are outer elements. In this case, the control signal generating unit 110 generates, for example, a control signal S1 for the upper element 24a and a control signal S4 for the lower element 25b, and generates a control signal S2 for the upper element 24b and a control signal S3 for the lower element 25a, which are inner elements, by inverting the control signal S1 for the upper element 24a and the control signal S4 for the lower element 25b using the NOT gates 113 and 114.

[0056] Here, when the upper and lower elements 24b and 25a of the inner elements are diodes and the upper and lower elements 24a and 25b of the outer elements are switching elements (self-extinguishing elements), only the control signals S1 and S4 of the upper and lower elements 24a and 25b are used. When the upper and lower elements 24a and 25b are diodes and the upper and lower elements 24b and 25a are switching elements, only the control signals S2 and S3 of the upper and lower elements 24b and 25a are used. In either configuration, the relationship between the chopper output voltage and the conduction ratio is the same, and therefore the operation described below is the same.

[0057] Fig. 4 is a graph showing a schematic example of a reference operation of the power supply device. Fig. 4 shows an example of the operation of each of the unit chopper circuits A and B shown in Fig. 2 when the two unit chopper circuits A and B shown in Fig. 2 are controlled by the reference control section 18ref shown in Fig. 3 which gives the same conduction rate to the upper and lower choppers constituting the unit chopper circuit 16. Fig. 4 shows the control signals S1 and S4 of the unit chopper circuits A and B, and the current (i ａＡ ) and the current (i ａＢ ), and the average value of the current at the second positive electrode terminal 22p and the current at the second negative electrode terminal 22n (i ａＡ / 2+i ａＢ / 2), and the difference between the current at the second positive terminal 22p and the current at the second negative terminal 22n divided by 2 (i ａＡ / 2-i ａＢ / 2).

[0058] 4 shows an example of the output voltage Vap of the upper chopper of unit chopper circuit A, the output voltage Van of the lower chopper of unit chopper circuit A, the output voltage Vbp of the upper chopper of unit chopper circuit B, the output voltage Vbn of the lower chopper of unit chopper circuit B, the carrier signal CSp of the upper chopper, the carrier signal CSn of the lower chopper, the conduction ratio Da of unit chopper circuit A, and the conduction ratio Db of unit chopper circuit B, all relative to the neutral point 21c. Fig. 4 shows an example in which the conduction ratios Da and Db are changed at the timing of the peak of the carrier signal CSn of the lower chopper (the valley of the carrier signal CSp of the upper chopper).

[0059] It can be seen that the value of the normal mode current changes before and after the carrier cycle in accordance with changes in the duty ratios Da and Db. On the other hand, it can be seen that the change in the common mode current returns to its original value over the half carrier cycle, and the value does not change before and after the carrier cycle. This is because, when the same duty ratios Da and Db are applied to the upper and lower choppers, the period in which the switching patterns differ between unit chopper circuits A and B occurs twice in each half carrier cycle, but since each period has the same time width, the common mode current that flows due to the difference in switching patterns between unit chopper circuits A and B is reset over the half carrier cycle and returns to the amplitude before the change.

[0060] Therefore, when the same duty ratios Da, Db are applied to the upper and lower choppers of each unit chopper circuit A, B, it is impossible to intentionally adjust the common-mode current. Even when the same duty ratios Da, Db are applied to the upper and lower choppers of each unit chopper circuit A, B, it is thought that, due to switching timing delays caused by variations in transmission delay time of the control signal in each switching element, jitter, and individual differences in the drive circuits that drive each switching element in response to the control signal, an unintentional difference occurs in the duration of the periods in which the switching patterns differ between the unit chopper circuits A, B, which occur twice per half carrier cycle, and that this causes a common-mode current. Once a common-mode current is generated due to the above factors, it cannot be intentionally controlled and so remains in the chopper current, which can become a cause of current imbalance between the unit chopper circuits A, B.

[0061] The configuration of a control unit 18 proposed to address these problems is shown in Fig. 5. Fig. 5 is a block diagram schematically illustrating a control unit according to an embodiment. As shown in Fig. 5, each control unit 18 includes a first calculation unit 31, a second calculation unit 32, a first control signal generation unit 41, and a second control signal generation unit 42.

[0062] The first calculation unit 31 calculates a normal mode current component based on the sum of the current detection value of the first current sensor 27a and the current detection value of the second current sensor 27b, and also calculates a normal mode conduction ratio, based on the normal mode current component and a normal mode current reference, which represents the ratio of the on-state period to the switching frequency of the switching element, in order to bring the normal mode current component closer to the normal mode current reference.

[0063] The first calculation unit 31 includes, for example, an adder 50, a calculator 51, a subtractor 52, and a current controller 53. The first calculation unit 31 calculates the sum of the current detection value of the first current sensor 27a and the current detection value of the second current sensor 27b using the adder 50, multiplies the calculated sum by 1 / 2 using the calculator 51, and calculates the average value of the current detection value of the first current sensor 27a and the current detection value of the second current sensor 27b, thereby calculating the normal mode current component from each of the current detection values. Note that, as described above, the first calculation unit 31 may omit the calculator 51 and calculate the sum of the current detection value of the first current sensor 27a and the current detection value of the second current sensor 27b as the normal mode current component.

[0064] First calculation unit 31 calculates the difference between the calculated normal mode current component and a normal mode current reference, which serves as a current command value, using subtractor 52. First calculation unit 31 inputs the difference calculated by subtractor 52 to current controller 53, which is composed of a PI compensator and the like. Current controller 53 performs proportional calculations, proportional-integral calculations and the like on the input difference to calculate a normal mode conduction ratio for bringing the normal mode current component closer to the normal mode current reference. First calculation unit 31 inputs the calculated normal mode conduction ratio to first control signal generator 41 and second control signal generator 42.

[0065] The control device 14 sets, for example, a plurality of normal mode current references that are individually given to the plurality of unit chopper circuits 16, respectively, to the plurality of control units 18 (see FIG. 1). As a result, in the power supply device 10, by setting the same normal mode current reference to each control unit 18, it is possible to cause each unit chopper circuit 16 to share the load current equally, and by setting different normal mode current references to each control unit 18, it is also possible to adjust the magnitude of the current shared by each unit chopper circuit 16.

[0066] The second calculation unit 32 calculates a common mode current component based on the difference between the current detection value of the first current sensor 27a and the current detection value of the second current sensor 27b, and also calculates a common mode conduction ratio, which represents the ratio of the on-state period to the switching frequency of the switching element, based on the common mode current component and a common mode current reference, in order to bring the common mode current component closer to the common mode current reference.

[0067] The second calculation unit 32 includes, for example, a subtractor 54, a calculator 55, a subtractor 56, and a current controller 57. The second calculation unit 32 calculates the difference between the current detection value of the first current sensor 27a and the current detection value of the second current sensor 27b using the subtractor 54, and multiplies the calculated difference by 1 / 2 using the calculator 55 to calculate the common mode current component from each current detection value. Note that the second calculation unit 32 may omit the calculator 55 and calculate the difference between the current detection value of the first current sensor 27a and the current detection value of the second current sensor 27b as the common mode current component.

[0068] The second calculation unit 32 uses a subtractor 56 to calculate the difference between the calculated common mode current component and a common mode current reference, which serves as a current command value. The second calculation unit 32 inputs the difference calculated by the subtractor 56 to a current controller 57, which is composed of a PI compensator and the like. The current controller 57 performs proportional calculations, proportional integral calculations, and the like on the input difference to calculate a common mode duty ratio for bringing the common mode current component closer to the common mode current reference. The second calculation unit 32 inputs the calculated common mode duty ratio to the first control signal generation unit 41 and the second control signal generation unit 42.

[0069] For example, the control units 18 set the common mode current reference to zero. In this case, the operation of each unit chopper circuit 16 can be controlled so as to make the common mode current component zero.

[0070] The first control signal generating unit 41 determines the conduction rate of at least one of the two upper stage elements 24a, 24b by adding the common mode conduction rate to the normal mode conduction rate, and generates a control signal for switching at least one of the two upper stage elements 24a, 24b at the determined conduction rate.

[0071] The first control signal generator 41 includes, for example, an adder 60, a comparator 61, and a NOT gate 62. The first control signal generator 41 determines the duty ratios of the upper-stage elements 24a and 24b by adding the normal-mode duty ratio and the common-mode duty ratio using the adder 60. The comparator 61 compares the determined duty ratios of the upper-stage elements 24a and 24b with a triangular wave carrier (carrier signal) to generate a control signal S1 for switching the upper-stage element 24a at the determined duty ratio. The first control signal generator 41 then inverts the logic (high state or low state) of the control signal S1 using the NOT gate 62 to generate a control signal S2 for switching the upper-stage element 24b at the determined duty ratio.

[0072] As described above, the normal-mode duty ratio and the common-mode duty ratio are DC signals whose amplitudes are set between the minimum and maximum amplitudes of the carrier signal. In other words, the common-mode duty ratio is a correction value for the normal-mode duty ratio required to adjust the common-mode current component.

[0073] The second control signal generating unit 42 determines the conduction rate of at least one of the two lower stage elements 25a, 25b by subtracting the common mode conduction rate from the normal mode conduction rate, and generates a control signal for switching at least one of the two lower stage elements 25a, 25b at the determined conduction rate.

[0074] The second control signal generator 42 includes, for example, a subtractor 63, a comparator 64, and a NOT gate 65. The second control signal generator 42 determines the duty ratios of the lower-stage elements 25a and 25b by subtracting the common-mode duty ratio from the normal-mode duty ratio using the subtractor 63. The comparator 64 compares the determined duty ratios of the lower-stage elements 25a and 25b with a triangular wave carrier (carrier signal) to generate a control signal S4 for switching the lower-stage element 25b at the determined duty ratio. In this case, as described above, the comparator 64 uses a triangular wave carrier that is 180° out of phase with the triangular wave carrier of the upper-stage chopper. The second control signal generator 42 then inverts the logic (high state or low state) of the control signal S4 using the NOT gate 65 to generate a control signal S3 for switching the lower-stage element 25a at the determined duty ratio.

[0075] In this example, each unit chopper circuit 16 has two upper stage elements 24a, 24b and two lower stage elements 25a, 25b as switching elements. In this case, the first control signal generator 41 switches the two upper stage elements 24a, 24b at a determined duty ratio so that when the upper stage element 24a is turned on, the upper stage element 24b is turned off, and when the upper stage element 24b is turned on, the upper stage element 24a is turned off. The second control signal generator 42 switches the two lower stage elements 25a, 25b at a determined duty ratio so that when the lower stage element 25a is turned on, the lower stage element 25b is turned off, and when the lower stage element 25b is turned on, the lower stage element 25a is turned off.

[0076] As described above, the control unit 18 according to the embodiment is similar in configuration to the reference control unit 18ref shown in FIG. 3 , in that the difference between the normal mode current reference and the normal mode current component is input to the current controller 53 formed of a PI compensator or the like, and the normal mode conduction factor component common to the upper and lower stages is calculated; however, a second calculation unit 32 using a common mode current is added.

[0077] The second calculation unit 32 calculates a common-mode current component from the difference between the current detection value at the second positive terminal 22p and the current detection value at the second negative terminal 22n, calculates the difference from a common-mode current reference, and calculates a common-mode duty factor using a current controller 57 including a PI compensator, etc. Note that the common-mode current component is a current that circulates between the choppers and does not contribute to the load power, so the common-mode current reference is set to, for example, zero.

[0078] The upper chopper duty ratio is the sum of the normal mode duty ratio calculated from the normal mode current component and the common mode duty ratio calculated from the common mode current component, and this sum is compared with the carrier to generate the upper chopper control signals S1 and S2. The lower chopper duty ratio is calculated from the difference between the normal mode duty ratio and the common mode duty ratio, and this sum is compared with the carrier to generate the lower chopper control signals S4 and S3. With this configuration, it is possible to set a difference between the duty ratios of the upper and lower choppers depending on the common mode current component.

[0079] Fig. 6 is a graph schematically showing an example of the operation of the power supply device according to the embodiment. Fig. 6 shows an example of the operation when a difference is made in the conduction rate between the upper and lower choppers. As in Fig. 4, Fig. 6 shows an example of the operation of each of the unit chopper circuits A and B when the two unit chopper circuits A and B shown in Fig. 2 are controlled by the control unit 18 that makes a difference in the conduction rate between the upper and lower choppers that make up the unit chopper circuit 16. Fig. 6 shows the control signals S1 and S4 of each of the unit chopper circuits A and B, and the current (i ａＡ ) and the current (i ａＢ ), and the average value of the current at the second positive electrode terminal 22p and the current at the second negative electrode terminal 22n (i ａＡ / 2+i ａＢ / 2), and the difference between the current at the second positive terminal 22p and the current at the second negative terminal 22n divided by 2 (i ａＡ / 2-i ａＢ / 2).

[0080] 6 shows an example of the output voltage Vap of the upper chopper of unit chopper circuit A, the output voltage Van of the lower chopper of unit chopper circuit A, the output voltage Vbp of the upper chopper of unit chopper circuit B, the output voltage Vbn of the lower chopper of unit chopper circuit B, the carrier signal CSp of the upper chopper, the carrier signal CSn of the lower chopper, the duty ratio Dap of the upper chopper of unit chopper circuit A, the duty ratio Dan of the lower chopper of unit chopper circuit A, the duty ratio Dbp of the upper chopper of unit chopper circuit B, and the duty ratio Dbn of the lower chopper of unit chopper circuit B. As with FIG. 4, FIG. 6 shows an example in which the duty ratios Dap, Dan, Dbp, and Dbn are changed at the timing of the peak of the carrier signal CSn of the lower chopper (the valley of the carrier signal CSp of the upper chopper).

[0081] As shown in Figure 6, when different duty ratios are applied to the upper and lower choppers, the periods in which the switching patterns differ between the choppers, which occur twice per half carrier cycle, have different durations (t2 and t3 in the figure). As a result, the common-mode current component can be changed without being reset per half carrier cycle. As described above, by providing a difference in the duty ratios of the upper and lower choppers, it is possible to intentionally control the common-mode current and suppress current imbalances between the unit chopper circuits.

[0082] As described above, it has been described that controlling the normal mode and common mode current components for each unit chopper circuit 16 makes it possible to balance the current between the unit chopper circuits 16. As described above, according to the power supply device 10 of this embodiment, even when two series-connected choppers are used as the unit chopper circuits 16 and a plurality of unit chopper circuits 16 are connected in parallel, the current flowing through each unit chopper circuit 16 can be more appropriately controlled.

[0083] Next, consider a case where an offset error exists in the current sensor of a specific unit chopper circuit 16, but there is no error in the current sensors of the other unit chopper circuits 16 connected in parallel. Also, assume that the common-mode current component of each unit chopper circuit 16 is zero in the initial state.

[0084] In the control unit 18 shown in Figure 5, the common-mode current reference is zero, and each unit chopper circuit 16 controls to zero the common-mode current component. In a unit chopper circuit 16 with an offset error in the current sensor, even if the common-mode current component is actually zero, the control unit 18 will recognize that a common-mode current component is flowing due to the offset error. In this case, a deviation occurs from the common-mode current reference, which is zero, and the manipulated variable for the common-mode current component (common-mode duty factor) increases accordingly, causing the unit chopper circuit 16 to operate to suppress the mistakenly recognized common-mode current component even though it is not actually flowing. Since no common-mode current component actually flows, instead of suppressing it, the unit chopper circuit 16 will flow a current of an amount that offsets the mistakenly recognized current.

[0085] As shown in the above equation (4), according to Kirchhoff's law, the sum of the common mode current components of all the parallel-connected unit chopper circuits 16 is always zero. For this reason, the common mode current component that a unit chopper circuit 16 having a current sensor with an error attempts to pass will flow to the other unit chopper circuits 16.

[0086] The other unit chopper circuits 16 having current sensors with no error operate to suppress the common mode current components flowing in by the unit chopper circuits 16 having current sensors with errors. As a result, the control operation amounts are cancelled out by the unit chopper circuits 16 that try to pass the common mode current components and the unit chopper circuits 16 that try to prevent current from flowing in. As a result, even if a unit chopper circuit 16 having an offset error in its current sensor operates to suppress a current that has been erroneously detected due to the error, the intended current cannot be passed due to interference from the other unit chopper circuits 16.

[0087] This means that the deviation between the common-mode current reference and the common-mode current component does not always converge to zero in each unit chopper circuit 16. As a result, for example, the integrator of the PI controller constituting the current controller 57 for the common-mode current component in each unit chopper circuit 16 may continue to perform integral operation, potentially resulting in saturation. As a result, the common-mode current control function may be lost, raising concerns that it may become difficult to continue operating as a multi-parallel chopper circuit 12.

[0088] In order to avoid this state, it is believed that mutual interference and saturation of the integrator can be avoided by configuring the control so that the sum of the control operation amounts (common-mode conduction rates) of the common-mode current components of each unit chopper circuit 16 connected in parallel is always zero.

[0089] Fig. 7 is a block diagram schematically showing a modified example of the power supply device according to the embodiment. Fig. 8 is a block diagram schematically showing a modified example of the control unit according to the embodiment. As shown in Figs. 7 and 8, in the power supply device 10a, the control device 14a further includes an average value calculation unit 70. Note that components that are substantially the same in function and configuration as those in the above embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

[0090] The multiple control units 18a of the control device 14a output the calculation results of the common mode current components to the average value calculation unit 70. The average value calculation unit 70 calculates an average value of the common mode current components based on the calculation results of the common mode current components input from the multiple control units 18a, and inputs the calculated average value of the common mode current components to each of the multiple control units 18a. The multiple control units 18a set the average value of the common mode current components of the multiple unit chopper circuits 16 input from the average value calculation unit 70 as a common mode current reference.

[0091] In this way, to address the above problem, the power supply device 10a uses the average value of the common mode current components of all the unit chopper circuits 16 connected in parallel as the common mode current reference. This average value of the common mode current component is a value found from the results of calculation of the common mode current component found from the current detection value, which includes error, in each unit chopper circuit 16. This ensures that the sum of the common mode current control operations (common mode duty factors) of each unit chopper circuit 16 is always zero, suppressing mutual interference and divergence of the common mode current control integrator, thereby improving operational continuity.

[0092] The principle by which mutual interference in common mode current control can be suppressed by using the common mode current average value as the common mode current reference will be described below.

[0093] First, in the multi-parallel chopper circuit 12 in which n unit chopper circuits 16 are connected in parallel, the current of the second positive terminal 22p of each unit chopper circuit 16 is expressed as i Ｐ（ｋ） , the current of the second negative electrode terminal 22n is i Ｎ（ｋ） The offset error of the first current sensor 27a is set to i ｏｆｓｅｔＰ（ｋ） , the offset error of the second current sensor 27b is i ｏｆｓｅｔＮ（ｋ） Then, the average value of the common mode current component i ０ａｖｅ is expressed by the following equation (13): where k=1, 2, 3, . . . n, and is an integer value that is the upper limit of the number of unit chopper circuits 16 connected in parallel.

[0094] The deviation i between the common mode current reference and the common mode current component in each unit chopper circuit 16 when the average value of the common mode current component is the common mode current reference. ０ｅｒｒ（ｋ） can be expressed by the following equation (14).

[0095] Here, if each common mode current control is a PI control, the operation amount ν ０ｃａｃｒ（ｋ） The common mode conduction ratio is given by the following equation (15).

[0096] The operation amount ν of the common mode current control of each unit chopper circuit 16 connected in parallel ０ｃａｃｒ（ｋ） Sum of ν０ｃａｃｒ＿ｔｏｔ is expressed as the following equation (16), which is zero.

[0097] As described above, it can be seen that by setting the common mode current reference for each unit chopper circuit 16 to the average value of the common mode current components determined from the current sensor detection values ​​including errors, the sum of the operation amounts for common mode current control is always zero, and common mode current control can be decoupled between each of the parallel-connected unit chopper circuits 16. Due to the decoupling, even if there is an offset error, divergence of the integrator constituting the current controller 57 for each common mode current control can be suppressed, thereby improving operational continuity.

[0098] Fig. 9 is a simplified block diagram for explaining a modified example of the power supply device. In Fig. 9, the configuration of a modified example of the multi-parallel chopper circuit 12 is explained using as an example a multi-parallel chopper circuit configured of two two-series choppers, unit chopper circuit A and unit chopper circuit B, as in Fig. 2.

[0099] In the above embodiment, a configuration has been described in which the first positive terminals 21 p, the first negative terminals 21 n, and the neutral points 21 c of the plurality of unit chopper circuits 16 are interconnected. As shown in Fig. 9 , in this example, the neutral points 21 c are not interconnected.

[0100] 9 , even in a configuration in which the neutral points 21c are not interconnected, a cross-current path is formed between the unit chopper circuits A and B, and a common-mode current component may flow through each of the unit chopper circuits A and B. Therefore, even in a configuration in which the neutral points 21c are not interconnected, similarly to the above embodiment, the output current of each of the unit chopper circuits A and B can be appropriately controlled by detecting the current at the second positive terminal 22p and the current at the second negative terminal 22n and using the respective current detection values ​​to determine the duty ratio of each of the unit chopper circuits A and B. In this way, the configuration of the multi-parallel chopper circuit 12 does not necessarily have to be a configuration in which the neutral points 21c are interconnected.

[0101] 10 is a block diagram schematically illustrating a modification of the power supply device according to the embodiment. As shown in FIG. 10, in a power supply device 10b, a control device 14b sets the same normal mode current reference for each of a plurality of control units 18b.

[0102] The control device 14b provides a common normal mode current reference to each control unit 18b of all unit chopper circuits 16 that make up the multi-parallel chopper circuit 12. Each control unit 18b determines the normal mode duty ratio of each unit chopper circuit 16 using the normal mode current reference and each current detection value, and switches the upper stage elements 24a, 24b and the lower stage elements 25a, 25b based on the determined normal mode duty ratio. In this way, each control unit 18b balances the current at the second positive terminal 22p and the current at the second negative terminal 22n between each unit chopper circuit 16. By controlling the current using the same normal mode current reference, the current in each unit chopper circuit 16 roughly coincides with the normal mode current reference, thereby achieving balancing.

[0103] In this way, the control device may set a plurality of normal mode current references that are individually given to the plurality of unit chopper circuits for each of the plurality of control units, or may set the same normal mode current reference for each of the plurality of control units.

[0104] 11(a) and 11(b) are block diagrams schematically showing modified examples of the unit chopper circuit according to the embodiment. As shown in FIG. 11(a), in the unit chopper circuit 16a, the upper and lower elements 24a and 25b, which are outer elements, are used as switching elements, and the upper and lower elements 24b and 25a, which are inner elements, are used as rectifying elements. In this case, the unit chopper circuit 16a only converts DC power corresponding to the first DC circuit DC1 to DC power corresponding to the second DC circuit DC2. The unit chopper circuit 16a functions, for example, as a step-down chopper.

[0105] 11(b), in the unit chopper circuit 16b, the upper and lower elements 24a and 25b, which are outer elements, are used as rectifying elements, and the upper and lower elements 24b and 25a, which are inner elements, are used as switching elements. In this case, the unit chopper circuit 16b only converts DC power corresponding to the second DC circuit DC2 to DC power corresponding to the first DC circuit DC1. The unit chopper circuit 16b functions as, for example, a step-up chopper.

[0106] In this way, the configuration of each unit chopper circuit may be any configuration in which at least one of the two upper stage elements 24a, 24b and at least one of the two lower stage elements 25a, 25b are used as switching elements, and which is capable of performing at least one of the power conversions of converting DC power corresponding to the first DC circuit DC1 to DC power corresponding to the second DC circuit DC2, and converting DC power corresponding to the second DC circuit DC2 to DC power corresponding to the first DC circuit DC1.

[0107] This embodiment includes the following aspects: (Supplementary Note 1) A multi-parallel chopper circuit has a plurality of unit chopper circuits connected in parallel to a first DC circuit and connected in parallel to a second DC circuit, and performs at least one of converting DC power according to the first DC circuit to DC power according to the second DC circuit and converting DC power according to the second DC circuit to DC power according to the first DC circuit by operation of the plurality of unit chopper circuits, and a control device has a plurality of control sections provided corresponding to each of the plurality of unit chopper circuits, and controls operation of each of the plurality of unit chopper circuits by the plurality of control sections, wherein each of the plurality of unit chopper circuits has: a first positive terminal and a first negative terminal connected to the first DC circuit, a second positive terminal and a second negative terminal connected to the second DC circuit, two charge storage elements connected in series between the first positive terminal and the first negative terminal, and two upper stage elements connected in series between the first positive terminal and a neutral point which is a connection point of the two charge storage elements, a first inductor provided between a connection point of the two upper elements and the second positive terminal; a second inductor provided between the connection point of the two lower elements and the second negative terminal; a first current sensor that detects the magnitude of a current flowing to the second positive terminal; and a second current sensor that detects the magnitude of a current flowing to the second negative terminal, wherein at least one of the two upper elements and at least one of the two lower elements are switching elements that can switch between an ON state in which a current flows and an OFF state in which a current is blocked, and wherein the control device defines the direction of a current flowing from the connection point of the two upper elements toward the second positive terminal as positive, and defines the direction of a current flowing from the second negative terminal toward the connection point of the two lower elements as positive, and wherein the plurality of control unitsa first calculation unit that calculates a normal mode current component based on the sum of the current detection value of the first current sensor and the current detection value of the second current sensor, and calculates a normal mode duty ratio that indicates a ratio of a period of the on state to a switching frequency of the switching element so that the normal mode current component approaches the normal mode current reference, based on the normal mode current component and a normal mode current reference; a second calculation unit that calculates a common mode current component based on a difference between the current detection value of the first current sensor and the current detection value of the second current sensor, and calculates a common mode duty ratio that indicates a ratio of a period of the on state to a switching frequency of the switching element so that the common mode current component approaches the common mode current reference, based on the common mode current component and the common mode current reference; a first control signal generation unit that determines a duty ratio of the switching element of at least one of the two upper stage elements by adding the common mode duty ratio to the normal mode duty ratio, and generates a control signal for switching the switching element of at least one of the two upper stage elements at the determined duty ratio; and a second control signal generation unit that determines a duty ratio of the switching element of at least one of the two lower stage elements by subtracting the common mode duty ratio from the normal mode duty ratio, and generates a control signal for switching the switching element of at least one of the two lower stage elements at the determined duty ratio.

[0108] (Supplementary Note 2) The power supply device according to Supplementary Note 1, wherein the plurality of control units set the common mode current reference to zero.

[0109] (Supplementary Note 3) The power supply device according to Supplementary Note 1, wherein the plurality of control units set an average value of the common mode current components of the plurality of unit chopper circuits as the common mode current reference.

[0110] (Supplementary Note 4) The power supply device according to any one of Supplementary Notes 1 to 3, wherein the control device sets a plurality of the normal mode current references individually given to the plurality of unit chopper circuits, respectively, for the plurality of control units.

[0111] (Supplementary Note 5) The power supply device according to any one of Supplementary Notes 1 to 3, wherein the control device sets the normal mode current reference to be equal for each of the plurality of control units.

[0112] (Supplementary Note 6) The power supply device according to any one of Supplementary Notes 1 to 5, wherein the multi-parallel chopper circuit electrically connects the neutral points of the plurality of unit chopper circuits.

[0113] (Supplementary Note 7) The power supply device according to any one of Supplementary Notes 1 to 6, wherein the plurality of unit chopper circuits each use the two upper stage elements and the two lower stage elements as the switching elements, the first control signal generation unit switches the switching element of one of the two upper stage elements at a determined duty ratio such that when one of the two upper stage elements is set to the on state, the other of the two upper stage elements is set to the off state, and when the other of the two upper stage elements is set to the on state, the one of the two upper stage elements is set to the off state, and the second control signal generation unit switches the switching element of one of the two lower stage elements at a determined duty ratio such that when one of the two lower stage elements is set to the on state, the other of the two lower stage elements is set to the off state, and when the other of the two lower stage elements is set to the on state, the one of the two lower stage elements is set to the off state.

[0114] (Supplementary Note 8) The power supply device according to any one of Supplementary Notes 1 to 6, wherein, of the two upper stage elements, the upper stage element on the first positive terminal side is the switching element, the upper stage element on the neutral point side is the rectifying element, and, of the two lower stage elements, the lower stage element on the neutral point side is the rectifying element, and the lower stage element on the first negative terminal side is the switching element.

[0115] (Supplementary Note 9) The power supply device according to any one of Supplementary Notes 1 to 6, wherein, of the two upper stage elements, the upper stage element on the first positive terminal side is a rectifying element, the upper stage element on the neutral point side is the switching element, and, of the two lower stage elements, the lower stage element on the neutral point side is the switching element, and the lower stage element on the first negative terminal side is the rectifying element.

[0116] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims.

[0117] REFERENCE SIGNS LIST 10, 10a, 10b... power supply device, 12... multi-parallel chopper circuit, 14, 14a, 14b... control device, 16, 16a, 16b... unit chopper circuit, 18, 18a, 18b, 18ref... control unit, 21p... first positive terminal, 21n... first negative terminal, 21c... neutral point, 22p... second positive terminal, 22n... second negative terminal, 23a, 23b... charge storage element, 24a, 24b... upper element, 25a, 25b... lower element, 26a... first inductor, 26b... second inductor, 27a... first current sensor, 27b... second current sensor, 31... first calculation unit, 32... second calculation unit, 41... first control signal generation unit, 42... second control signal generation unit 50...adder, 51...operator, 52...subtractor, 53...current controller, 54...subtractor, 55...operator, 56...subtractor, 57...current controller, 60...adder, 61...comparator, 62...NOT gate, 63...subtractor, 64...comparator, 65...NOT gate, 70...average value calculator, 100...operator, 101...adder, 102...operator, 103...subtractor, 104...current controller, 110...control signal generator, 111, 112...comparator, 113, 114...NOT gate, DC1...first DC circuit, DC2...second DC circuit

Claims

a multi-parallel chopper circuit having a plurality of unit chopper circuits connected in parallel to a first DC circuit and connected in parallel to a second DC circuit, and performing at least one of conversion from DC power corresponding to the first DC circuit to DC power corresponding to the second DC circuit and conversion from DC power corresponding to the second DC circuit to DC power corresponding to the first DC circuit by operation of the plurality of unit chopper circuits; a control device having a plurality of control sections provided corresponding to the plurality of unit chopper circuits, respectively, and controlling the operation of each of the plurality of unit chopper circuits by the plurality of control sections; Equipped with Each of the plurality of unit chopper circuits comprises: a first positive terminal and a first negative terminal connected to the first DC circuit; a second positive terminal and a second negative terminal connected to the second DC circuit; two charge storage elements connected in series between the first positive terminal and the first negative terminal; two upper stage elements connected in series between the first positive terminal and a neutral point which is a connection point of the two charge storage elements; two lower stage elements connected in series between the neutral point and the first negative terminal; a first inductor provided between the connection point of the two upper stage elements and the second positive terminal; a second inductor provided between the connection point of the two lower elements and the second negative terminal; a first current sensor that detects the magnitude of a current flowing through the second positive terminal; a second current sensor that detects the magnitude of a current flowing through the second negative terminal; and at least one of the two upper elements and at least one of the two lower elements is a switching element that can switch between an ON state in which a current flows and an OFF state in which a current flow is interrupted, the control device defines a direction of current flowing from the connection point of the two upper elements toward the second positive terminal as positive, and defines a direction of current flowing from the second negative terminal toward the connection point of the two lower elements as positive; The plurality of control units include: a first calculation unit that calculates a normal mode current component based on the sum of the current detection value of the first current sensor and the current detection value of the second current sensor, and that calculates a normal mode duty ratio that indicates a ratio of a period of the on state to a switching frequency of the switching element, based on the normal mode current component and a normal mode current reference, so as to bring the normal mode current component closer to the normal mode current reference; a second calculation unit that calculates a common-mode current component based on a difference between the current detection value of the first current sensor and the current detection value of the second current sensor, and calculates a common-mode duty factor that represents a ratio of a period of the on-state to a switching frequency of the switching element, based on the common-mode current component and a common-mode current reference, so as to bring the common-mode current component closer to the common-mode current reference; a first control signal generating unit that determines a duty ratio of at least one of the switching elements of the two upper elements by adding the common mode duty ratio to the normal mode duty ratio, and generates a control signal for switching the at least one of the switching elements of the two upper elements at the determined duty ratio; a second control signal generating unit that determines a duty ratio of at least one of the switching elements of the two lower elements by subtracting the common mode duty ratio from the normal mode duty ratio, and generates a control signal for switching the at least one of the switching elements of the two lower elements at the determined duty ratio; A power supply device having 　 The power supply device according to claim 1 , wherein the plurality of controllers set the common mode current reference to zero.

2. The power supply device according to claim 1, wherein the plurality of control sections set an average value of the common-mode current components of the plurality of unit chopper circuits as the common-mode current reference.

2. The power supply device according to claim 1, wherein the control device sets a plurality of normal mode current references, which are individually given to the plurality of unit chopper circuits, for the plurality of control sections, respectively.

2. The power supply device according to claim 1, wherein the control device sets the normal mode current reference equal to each of the plurality of control sections.

2. The power supply device according to claim 1, wherein the multiple parallel chopper circuit electrically connects the neutral points of the plurality of unit chopper circuits. 　 the plurality of unit chopper circuits each have the two upper stage elements and the two lower stage elements as the switching elements, the first control signal generation unit switches the switching element of one of the two upper stage elements at a determined conduction rate so that, when one of the two upper stage elements is set to the on state, the other of the two upper stage elements is set to the off state, and, when the other of the two upper stage elements is set to the on state, the one of the two upper stage elements is set to the off state; 2. The power supply device according to claim 1, wherein the second control signal generation unit switches the switching element of one of the two lower elements at a determined conduction rate so that when one of the two lower elements is set to the on state, the other of the two lower elements is set to the off state, and when the other of the two lower elements is set to the on state, the one of the two lower elements is set to the off state.

2. The power supply device according to claim 1, wherein, of the two upper stage elements, the upper stage element on the first positive terminal side serves as the switching element, the upper stage element on the neutral point side serves as a rectifying element, and, of the two lower stage elements, the lower stage element on the neutral point side serves as a rectifying element, and the lower stage element on the first negative terminal side serves as the switching element.

2. The power supply device according to claim 1, wherein, of the two upper stage elements, the upper stage element on the first positive terminal side is a rectifying element, the upper stage element on the neutral point side is the switching element, and, of the two lower stage elements, the lower stage element on the neutral point side is the switching element, and the lower stage element on the first negative terminal side is the rectifying element.

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