Power conversion device and power conversion system

Abstract

This power conversion device comprises a first capacitor, a second capacitor, at least one first DC / DC converter, at least one second DC / DC converter, and a control circuit. The first DC / DC converter comprises a first switching circuit and a first inductor. The second DC / DC converter comprises a second switching circuit and a second inductor. The inductance of the first inductor is smaller than the inductance of the second inductor. The control circuit controls at least one first DC / DC converter and at least one second DC / DC converter so that at least one first DC / DC converter and at least one second DC / DC converter operate.

Description

Power conversion device and power conversion system

[0001] The present disclosure relates generally to power conversion devices and power conversion systems, and more particularly to power conversion devices including DC / DC converters and power conversion systems including power conversion devices.

[0002] Patent Document 1 discloses a power supply circuit (power conversion device) as an example. The power supply circuit includes a DC / DC converter and a control unit. The DC / DC converter includes a DC / DC controller, an input capacitor, an output capacitor, an upper FET, a lower FET, an inductor, an input current monitoring circuit, and an output current monitoring circuit. The DC / DC controller is electrically connected to a variable load. The DC / DC controller measures the input current, output current, etc. while varying the size of the variable load, the switching frequency of each FET, and the inductance of the inductor, and calculates the conversion efficiency based on the measurement results.

[0003] Japanese Patent Application Laid-Open No. 2005-137172

[0004] The power supply circuit described in Patent Document 1 calculates (measures) the conversion efficiency for a combination of the magnitude of the variable load, the switching frequency of each FET, and the inductance of the inductor. Therefore, the power supply circuit described in Patent Document 1 can set the switching frequency of each FET and the inductor inductance during load fluctuations, thereby improving the conversion efficiency during load fluctuations. However, in a power conversion device such as the power supply circuit described in Patent Document 1, it is desirable to not only improve the conversion efficiency during load fluctuations, but also to improve the responsiveness to the load (load responsiveness).

[0005] A power conversion device according to one aspect of the present disclosure includes a first capacitor, a second capacitor, at least one first DC / DC converter, at least one second DC / DC converter, and a control circuit. The first capacitor is electrically connected across a DC power source. The second capacitor is electrically connected across a load. The at least one first DC / DC converter is connected in parallel to the first capacitor. The at least one second DC / DC converter is connected in parallel to the first capacitor. The control circuit controls the at least one first DC / DC converter and the at least one second DC / DC converter. The at least one first DC / DC converter includes a first switching circuit and a first inductor. The first switching circuit includes a first switching element and a second switching element connected in series to each other. A first end of the first inductor is connected to a connection point between the first switching element and the second switching element. The first switching circuit is connected in parallel to the first capacitor. The second end of the first inductor is electrically connected to the second switching element via the second capacitor. The at least one second DC / DC converter includes a second switching circuit and a second inductor. The second switching circuit includes a third switching element and a fourth switching element connected in series to each other. A first end of the second inductor is connected to a connection point between the third switching element and the fourth switching element. The second switching circuit is connected in parallel to the first capacitor. The second end of the second inductor is electrically connected to the fourth switching element via the second capacitor. The inductance of the first inductor is smaller than the inductance of the second inductor. The control circuit controls the at least one first DC / DC converter and the at least one second DC / DC converter to operate at least one of the at least one first DC / DC converter and the at least one second DC / DC converter.

[0006] A power conversion system according to one aspect of the present disclosure includes the power conversion device and the load.

[0007] According to one aspect of the present disclosure, it is possible to improve load responsiveness and reduce loss.

[0008] FIG. 1 is a block diagram of a power conversion system including a power conversion apparatus according to a first embodiment. FIG. 2 is a circuit diagram of a power conversion system including the power conversion apparatus according to the same. FIG. 3 is a diagram schematically illustrating a change in output current of the power conversion apparatus according to the same. FIG. 4 is a diagram schematically illustrating an output current waveform of the power conversion apparatus according to the same. FIG. 5 is a block diagram of a DC / DC converter system of a power conversion apparatus according to a modification of the first embodiment. FIG. 6 is a diagram illustrating an arrangement of a first DC / DC converter and a second DC / DC converter of the power conversion apparatus according to the same. FIG. 7 is a block diagram of a DC / DC converter system of a power conversion apparatus according to another modification of the first embodiment. FIG. 8 is a diagram illustrating an arrangement of a first DC / DC converter and a second DC / DC converter of the power conversion apparatus according to the same. FIG. 9 is a block diagram of a DC / DC converter system of a power conversion apparatus according to a second and third embodiments. FIG. 10 is a diagram schematically illustrating a change in output current of the power conversion apparatus according to the same. FIG. 11 is a diagram schematically illustrating a change in output current of each DC / DC converter of the power conversion apparatus according to the same. FIG. 12 is a block diagram of a power conversion device according to a fourth embodiment. FIG. 13 is a diagram schematically showing changes in output current and output voltage for the power conversion device according to the fourth embodiment. FIG. 14 is a block diagram of a power conversion device according to a fifth embodiment. FIG. 15 is a diagram schematically showing changes in output current and output voltage for the power conversion device according to the fifth embodiment. FIG. 16 is a block diagram of a power conversion device according to a sixth embodiment. FIG. 17 is a diagram schematically showing changes in output current and output voltage for the power conversion device according to the fifth embodiment. FIG. 18 is a diagram schematically showing changes in output current for the power conversion device according to a seventh embodiment. FIG. 19 is a diagram schematically showing changes in output current of each DC / DC converter for the power conversion device according to the seventh embodiment. FIG. 20 is a diagram schematically showing changes in output current for the power conversion device according to the eighth embodiment. FIG. 21 is a diagram schematically showing changes in output current of each DC / DC converter for the power conversion device according to the nineth embodiment. FIG. 22 is a block diagram of a power conversion system including a power conversion device according to a ninth embodiment.

[0009] Hereinafter, a power conversion system including a power conversion device according to Embodiments 1 to 9 will be described with reference to the drawings. The configurations described in the following embodiments are merely examples of the present disclosure. The present disclosure is not limited to the following embodiments, and various modifications are possible depending on the design, etc., as long as the effects of the present disclosure can be achieved.

[0010] First Embodiment A power conversion system according to a first embodiment will be described below with reference to FIGS.

[0011] (1) Power Conversion System As shown in Fig. 1, the power conversion system B1 includes a power conversion device A1 and a load 50. The load 50 is, for example, a microprocessor such as a CPU or a GPU.

[0012] (2) Power Conversion Device As shown in Fig. 2, the power conversion device A1 includes a pair of input terminals 1a and 1b, a pair of output terminals 2a and 2b, a DC / DC converter system 10, and a control circuit 40. The power conversion device A1 converts a DC voltage Vi to a DC voltage Vo. For example, the power conversion device A1 steps down the DC voltage Vi to the DC voltage Vo.

[0013] (2.1) Pair of Input Terminals The pair of input terminals 1a, 1b are electrically and mechanically connected to the DC power supply V1 via, for example, a pair of electrical paths. That is, in the power conversion device A1, the DC power supply V1 is electrically connected between the pair of input terminals 1a, 1b. The voltage between the pair of input terminals 1a, 1b is the voltage (input voltage) Vi from the DC power supply V1. The input voltage Vi is, for example, 12 V.

[0014] (2.2) Pair of Output Terminals The pair of output terminals 2a, 2b are electrically and mechanically connected to the load 50, for example, via a pair of electrical paths. That is, in the power conversion device A1, the load 50 is electrically connected between the pair of output terminals 2a, 2b. The voltage between the pair of output terminals 2a, 2b is the voltage (output voltage) Vo across the second capacitor C2. The output voltage Vo is, for example, 1 V.

[0015] 2, the DC / DC converter system 10 has a first capacitor C1, a plurality of (three in the illustrated example) first DC / DC converters 21 to 23, one second DC / DC converter 31, and a second capacitor C2. Note that, hereinafter, to facilitate understanding of the description of the embodiment, the "three first DC / DC converters 21 to 23" may be referred to as "first converters 20," and the "one second DC / DC converter 31" may be referred to as "second converter 30."

[0016] (2.3.1) First Capacitor The first capacitor C1 is electrically connected between a pair of input terminals 1a and 1b. The high-potential side terminal of the first capacitor C1 is electrically connected to the input terminal 1a. The low-potential side terminal of the first capacitor C1 is electrically connected to the input terminal 1b. In short, the first capacitor C1 is electrically connected across the DC power supply V1. The low-potential side terminal of the first capacitor C1 is electrically connected to, for example, the ground of the power conversion device A1 (for example, the ground of a circuit board including the power conversion device A1).

[0017] (2.3.2) First DC / DC Converter The first DC / DC converter 21 is connected in parallel to the first capacitor C1. The first DC / DC converter 21 includes a switching circuit 71 and an inductor L1. The switching circuit 71 includes a switching element Q1 and a switching element Q2 connected in series. Each of the switching elements Q1 and Q2 is, for example, a metal-oxide-semiconductor field effect transistor (MOSFET). Each of the switching elements Q1 and Q2 includes a first main terminal, a second main terminal, and a control terminal. In the following description, to facilitate understanding of the embodiments, the first main terminal will be referred to as a drain terminal, the second main terminal will be referred to as a source terminal, and the control terminal will be referred to as a gate terminal.

[0018] The switching circuit 71 is connected in parallel to the first capacitor C1. The drain terminal of the switching element Q1 is electrically connected to the high-potential terminal of the first capacitor C1. The gate terminal of the switching element Q1 is electrically connected to the control circuit 40. The source terminal of the switching element Q1 is electrically connected to the inductor L1. The source terminal of the switching element Q1 is electrically connected to the drain terminal of the switching element Q2. The gate terminal of the switching element Q2 is electrically connected to the control circuit 40. The source terminal of the switching element Q2 is electrically connected to the low-potential terminal of the first capacitor C1. The switching elements Q1 and Q2 are connected in series to each other at a connection point 3. A first end of the inductor L1 is electrically connected to the connection point 3 between the switching elements Q1 and Q2. A second end of the inductor L1 is electrically connected to the high-potential terminal of the second capacitor C2.

[0019] The first DC / DC converter 22 is connected in parallel to the first capacitor C1. In other words, the first DC / DC converter 22 is connected in parallel to the first DC / DC converter 21. The first DC / DC converter 22 includes a switching circuit 72 and an inductor L2. The switching circuit 72 includes a switching element Q3 and a switching element Q4 connected in series. Each of the switching elements Q3 and Q4 is, for example, a MOSFET. Each of the switching elements Q3 and Q4 includes a first main terminal, a second main terminal, and a control terminal. In the following description of the embodiment, to facilitate understanding, the first main terminal will be referred to as a drain terminal, the second main terminal will be referred to as a source terminal, and the control terminal will be referred to as a gate terminal.

[0020] The switching circuit 72 is connected in parallel to the first capacitor C1. In other words, the switching circuit 72 is connected in parallel to the switching circuit 71. The drain terminal of the switching element Q3 is electrically connected to the drain terminal of the switching element Q1. The gate terminal of the switching element Q3 is electrically connected to the control circuit 40. The source terminal of the switching element Q3 is electrically connected to the inductor L2. The source terminal of the switching element Q3 is electrically connected to the drain terminal of the switching element Q4. The gate terminal of the switching element Q4 is electrically connected to the control circuit 40. The source terminal of the switching element Q4 is electrically connected to the source terminal of the switching element Q2. The switching elements Q3 and Q4 are connected in series to each other at a connection point 4. A first end of the inductor L2 is electrically connected to the connection point 4 of the switching elements Q3 and Q4. A second end of the inductor L2 is electrically connected to the high-potential terminal of the second capacitor C2.

[0021] The first DC / DC converter 23 is connected in parallel to the first capacitor C1. In other words, the first DC / DC converter 23 is connected in parallel to the first DC / DC converter 22. The first DC / DC converter 23 includes a switching circuit 73 and an inductor L3. The switching circuit 73 includes a switching element Q5 and a switching element Q6 connected in series. Each of the switching elements Q5 and Q6 is, for example, a MOSFET. Each of the switching elements Q5 and Q6 includes a first main terminal, a second main terminal, and a control terminal. In the following description, to facilitate understanding of the embodiments, the first main terminal will be referred to as a drain terminal, the second main terminal will be referred to as a source terminal, and the control terminal will be referred to as a gate terminal.

[0022] The switching circuit 73 is connected in parallel to the first capacitor C1. In other words, the switching circuit 73 is connected in parallel to the switching circuit 72. The drain terminal of the switching element Q5 is electrically connected to the drain terminal of the switching element Q3. The gate terminal of the switching element Q5 is electrically connected to the control circuit 40. The source terminal of the switching element Q5 is electrically connected to the inductor L3. The source terminal of the switching element Q5 is electrically connected to the drain terminal of the switching element Q6. The gate terminal of the switching element Q6 is electrically connected to the control circuit 40. The source terminal of the switching element Q6 is electrically connected to the source terminal of the switching element Q4. The switching elements Q5 and Q6 are connected in series to each other at the connection point 5. The first end of the inductor L3 is electrically connected to the connection point 5 between the switching elements Q5 and Q6. The second end of the inductor L3 is electrically connected to the high-potential terminal of the second capacitor C2.

[0023] (2.3.3) Second DC / DC Converter The second DC / DC converter 31 is connected in parallel to the first capacitor C1. The second DC / DC converter 31 includes a switching circuit 74 and an inductor L4. The switching circuit 74 includes a switching element Q7 and a switching element Q8 connected in series. Each of the switching elements Q7 and Q8 is, for example, a MOSFET. Each of the switching elements Q7 and Q8 includes a first main terminal, a second main terminal, and a control terminal. In the following description, to facilitate understanding of the embodiments, the first main terminal will be referred to as the drain terminal, the second main terminal will be referred to as the source terminal, and the control terminal will be referred to as the gate terminal.

[0024] The switching circuit 74 is connected in parallel to the first capacitor C1. In other words, the switching circuit 74 is connected in parallel to the switching circuit 73. The drain terminal of the switching element Q7 is electrically connected to the drain terminal of the switching element Q5. The gate terminal of the switching element Q7 is electrically connected to the control circuit 40. The source terminal of the switching element Q7 is electrically connected to the inductor L4. The source terminal of the switching element Q7 is electrically connected to the drain terminal of the switching element Q8. The gate terminal of the switching element Q8 is electrically connected to the control circuit 40. The source terminal of the switching element Q8 is electrically connected to the source terminal of the switching element Q6. The switching elements Q7 and Q8 are connected in series to each other at the connection point 6. The first end of the inductor L4 is electrically connected to the connection point 6 between the switching elements Q7 and Q8. The second end of the inductor L4 is electrically connected to the high-potential terminal of the second capacitor C2.

[0025] Inductors L1, L2, and L3 have the same inductance. The inductance of inductor L1 of the first DC / DC converter 21 is smaller than the inductance of inductor L4 of the second DC / DC converter 31. That is, the inductance of inductor L2 of the first DC / DC converter 22 is also smaller than the inductance of inductor L4 of the second DC / DC converter 31. The inductance of inductor L3 of the first DC / DC converter 23 is also smaller than the inductance of inductor L4 of the second DC / DC converter 31. Note that "same" does not necessarily mean a perfect match, but also includes a deviation of about ±20% (e.g., the tolerance of the inductor), for example.

[0026] (2.3.4) Second Capacitor The second capacitor C2 is electrically connected between the pair of output terminals 2a and 2b. The high-potential side terminal of the second capacitor C2 is electrically connected to the output terminal 2a. The low-potential side terminal of the second capacitor C2 is electrically connected to the output terminal 2b. In other words, the second capacitor C2 is electrically connected across the load 50. The high-potential side terminal of the second capacitor C2 is electrically connected to the second ends of the inductors L1, L2, L3, and L4. The low-potential side terminal of the second capacitor C2 is electrically connected to the source terminal of the switching element Q8. In other words, the low-potential side terminal of the second capacitor C2 is electrically connected to the switching elements Q2, Q4, Q6, and Q8.

[0027] (2.4) Control Circuit The control circuit 40 is realized, for example, by a computer system having one or more processors and one or more memories. In other words, the functions of the control circuit 40 are realized by the one or more processors executing a program recorded in the memory. The program may be pre-recorded in the memory, or may be provided via a telecommunications line such as the Internet, or may be recorded on a non-transitory recording medium such as a memory card and provided.

[0028] The control circuit 40 controls the first converter 20. Specifically, the control circuit 40 controls the first DC / DC converter 21. More specifically, the control circuit 40 controls the switching element Q1 and the switching element Q2. The control circuit 40 switches the switching element Q1 between an on state and an off state. The control circuit 40 also switches the switching element Q2 between an on state and an off state. The control circuit 40 also controls the switching elements Q1 and Q2 so that a trade-off relationship exists between the switching elements Q1 and Q2. For example, when the control circuit 40 turns the switching element Q1 on, the control circuit 40 turns the switching element Q2 off. On the other hand, when the control circuit 40 turns the switching element Q1 off, the control circuit 40 turns the switching element Q2 on.

[0029] The control circuit 40 also controls the first DC / DC converter 22. More specifically, the control circuit 40 controls the switching elements Q3 and Q4. The control circuit 40 also controls the first DC / DC converter 23. More specifically, the control circuit 40 controls the switching elements Q5 and Q6. The switching frequencies of the switching elements Q1 to Q8 are, for example, the same frequency. Note that the operation of the control circuit 40 to control the switching elements Q3 and Q4 is similar to the operation of the control circuit 40 to control the switching elements Q1 and Q2, except for the target switching elements, and therefore a description thereof will be omitted. Note that the operation of the control circuit 40 to control the switching elements Q5 and Q6 is similar to the operation of the control circuit 40 to control the switching elements Q1 and Q2, except for the target switching elements, and therefore a description thereof will be omitted.

[0030] The control circuit 40 also controls the second DC / DC converter 31. More specifically, the control circuit 40 controls the switching element Q7 and the switching element Q8. The control circuit 40 switches the switching element Q7 between an ON state and an OFF state. The control circuit 40 also switches the switching element Q8 between an ON state and an OFF state. The control circuit 40 also controls the switching elements Q7 and Q8 so that a trade-off relationship exists between the switching elements Q7 and Q8. For example, when the control circuit 40 switches the switching element Q7 to an ON state, the control circuit 40 switches the switching element Q8 to an OFF state. On the other hand, when the control circuit 40 switches the switching element Q7 to an OFF state, the control circuit 40 switches the switching element Q8 to an ON state.

[0031] The control circuit 40 controls the first converter 20 and the second converter 30 so as to operate either the first converter 20 or the second converter 30. For example, the control circuit 40 controls the first converter 20 and the second converter 30 so as to operate the first converter 20 and not operate the second converter 30. Alternatively, the control circuit 40 controls the first converter 20 and the second converter 30 so as to not operate the first converter 20 and to operate the second converter 30.

[0032] The control circuit 40 has a detector 41. The detector 41 detects the output current Io of the DC / DC converter system 10. In other words, the detector 41 detects the output current Io of the multiple DC / DC converters (first converter 20 and second converter 30). The "output current Io of the multiple DC / DC converters" is the sum of the output currents of the multiple DC / DC converters, for example, the combined current of the output current of the first converter 20 and the output current of the second converter 30.

[0033] (3) Operation of the Power Conversion Device The power conversion device A1 steps down the DC voltage Vi to the DC voltage Vo by the control circuit 40 controlling the DC / DC converter system 10. In other words, the power conversion device A1 steps down the DC voltage Vi to the DC voltage Vo by the control circuit 40 performing synchronous rectification.

[0034] The control circuit 40 controls the first converter 20 and the second converter 30 so as to operate either one of the first converter 20 or the second converter 30, for example, based on the output current Io detected by the detector 41. For example, the control circuit 40 controls the first converter 20 and the second converter 30 so as to operate either one of the first converter 20 or the second converter 30, based on the presence or absence of a change in the output current Io detected by the detector 41.

[0035] Specifically, when the output current Io detected by the detector 41 does not change (when the operation of the load 50 is stable), the control circuit 40 does not operate the first converter 20 but operates the second converter 30. Furthermore, when the output current Io detected by the detector 41 changes (when the operation of the load 50 changes), the control circuit 40 operates the first converter 20 but does not operate the second converter 30. More specifically, when the output current Io increases due to, for example, an increase in the calculation processing of the load 50 (when the load 50 changes from a low load state to a high load state), the control circuit 40 operates the first converter 20 but does not operate the second converter 30. Furthermore, when the output current Io decreases due to, for example, a decrease in the calculation processing of the load 50 (when the load 50 changes from a high load state to a low load state), the control circuit 40 operates the first converter 20 but does not operate the second converter 30.

[0036] The control circuit 40 has, for example, one threshold value, and determines that the output current Io changes when the current value of the output current Io detected by the detector 41 crosses the threshold value. More specifically, the control circuit 40 determines that the output current Io changes (the output current Io increases) when the current value of the output current Io detected by the detector 41 is greater than the threshold value. Furthermore, the control circuit 40 determines that the output current Io changes (the output current Io decreases) when the current value of the output current Io detected by the detector 41 is less than the threshold value. On the other hand, the control circuit 40 determines that the output current Io does not change when the current value of the output current Io detected by the detector 41 does not cross the threshold value. The threshold value is, for example, pre-stored in the memory of the control circuit 40. Note that the control circuit 40 compares the current value of the output current Io detected by the detector 41 with one threshold value to determine whether the output current Io changes. However, for example, the control circuit 40 may compare the current value of the output current Io detected by the detector 41 with multiple threshold values ​​to determine whether the output current Io changes.

[0037] In the power conversion device A1, the inductance of each of the inductors L1, L2, and L3 of the first converter 20 is smaller than the inductance of the inductor L4 of the second converter 30. Furthermore, the control circuit 40 operates either the first converter 20 or the second converter 30 based on the output current Io detected by the detector 41. As a result, in the power conversion device A1, for example, when the operation of the load 50 changes (e.g., when the output current Io increases), only the first converter 20 is operated. This results in a faster change in the output current Io (the rise of the output current Io) than when only the second converter 30 is operated (see FIG. 3 ). Therefore, the power conversion device A1 can improve load responsiveness. In FIG. 3 , Io1 represents the output current when only the second converter 30 is operated. In FIG. 3 , Io2 represents the output current when only the first converter 20 is operated. In FIG. 3 , t1 represents the time when the load 50 changes from a low-load state to a high-load state.

[0038] Furthermore, in the power conversion device A1, for example, only the second converter 30 is operated when the operation of the load 50 is stable (the output current Io does not change), and therefore the ripple of the output current Io is smaller than when only the first converter 20 is operated (see FIG. 4). Therefore, the power conversion device A1 can achieve low loss. Note that Io in FIG. 4 represents the output current of the DC / DC converter system 10. The solid line waveform in FIG. 4 represents the waveform of the output current Io when only the second converter 30 is operated. The dashed-dotted line waveform in FIG. 4 represents the waveform of the output current Io when only the first converter 20 is operated.

[0039] Therefore, the power conversion device A1 can improve load responsiveness and reduce loss compared to, for example, a power conversion device equipped with a DC / DC converter system including only the first converter 20 or the second converter 30. Therefore, the power conversion system B1 can also improve load responsiveness and reduce loss.

[0040] (4) Modification The switching frequencies of the switching elements Q1 to Q8 are the same, but may be different frequencies. For example, it is preferable that the switching frequencies of the switching elements Q1 to Q6 of the first converter 20 are higher than the switching frequencies of the switching elements Q7 and Q8 of the second converter 30. Specifically, the switching frequencies of the switching elements Q1 to Q6 of the first converter 20 are the same. The switching frequencies of the switching elements Q7 and Q8 of the second converter 30 are the same. The switching frequency of the switching element Q1 of the first converter 20 is higher than the switching frequency of the switching element Q7 of the second converter 30. In other words, the switching frequencies of the switching elements Q1 to Q6 of the first converter 20 are higher than the switching frequencies of the switching elements Q7 and Q8 of the second converter 30.

[0041] In the power conversion device A1 in which the switching frequencies of the switching elements Q1 to Q8 are the same, for example, when the operation of the load 50 changes, only the first converter 20 is operated, so that the output current Io changes quickly (see FIG. 3), but the ripple of the output current Io becomes large (see FIG. 4). On the other hand, in the power conversion device A1 in which the switching frequencies of the switching elements Q1 to Q6 are higher than the switching frequencies of the switching elements Q7 and Q8, the switching of the switching elements Q1 to Q6 can be made faster while only the first converter 20 is operated. As a result, in the power conversion device A1 in which the switching frequencies of the switching elements Q1 to Q6 are higher than the switching frequencies of the switching elements Q7 and Q8, the ripple of the output current Io can be made smaller than when the switching frequencies of the switching elements Q1 to Q8 are the same. Therefore, in the power conversion device A1, when the switching frequency of each of the switching elements Q1 to Q6 is higher than the switching frequency of each of the switching elements Q7 and Q8, it is possible to achieve lower loss than when the switching frequencies of each of the switching elements Q1 to Q8 are the same. In other words, in the power conversion device A1, when the switching frequency of each of the switching elements Q1 to Q6 is higher than the switching frequency of each of the switching elements Q7 and Q8, it is possible to improve load responsiveness and further reduce loss.

[0042] The first converter 20 is not limited to the three first DC / DC converters 21 to 23, and may be, for example, one or two first DC / DC converters, or four or more first DC / DC converters. In short, it is sufficient that the first converter 20 is at least one first DC / DC converter. The second converter 30 is not limited to the one second DC / DC converter 31, and may be, for example, two or more second DC / DC converters. In short, it is sufficient that the second converter 30 is at least one second DC / DC converter.

[0043] For example, the number of first converters 20 is not limited to three first DC / DC converters 21 to 23, but may be six first DC / DC converters 21 to 26 as shown in FIG. 5 . The number of second converters 30 is not limited to one second DC / DC converter 31, but may be two second DC / DC converters 31 and 32 as shown in FIG. 5 . In this case, the six first DC / DC converters 21 to 26 are preferably disposed closer to the load 50 than the two second DC / DC converters 31 and 32, as shown in FIG. 6 . For example, the distance (first distance) between the six first DC / DC converters 21 to 26 and the load 50 is preferably shorter than the distance (second distance) between the two second DC / DC converters 31 and 32 and the load 50. The first distance is, for example, the shortest length of the electrical path (e.g., wiring length) between each of the first DC / DC converters 21 to 26 and the load 50. The second distance is, for example, the shortest distance of the length of the electrical path (e.g., the wiring length) between each of the second DC / DC converters 31, 32 and the load 50. As a result, in the power conversion device A1, the parasitic component between the first converter 20 and the load 50 is smaller than the parasitic component between the second converter 30 and the load 50, thereby making it possible to further improve the load responsiveness. Note that the first distance is not limited to the electrical path between each of the first DC / DC converters 21 to 26 and the load 50, but may be, for example, the shortest distance across space between each of the first DC / DC converters 21 to 26 and the load 50. Furthermore, the second distance is not limited to the electrical path between each of the second DC / DC converters 31, 32 and the load 50, but may be, for example, the shortest distance across space between each of the second DC / DC converters 31, 32 and the load 50.

[0044] Furthermore, the first converter 20 is not limited to six first DC / DC converters 21 to 26, and may be configured, for example, as shown in Fig. 7, with five first DC / DC converters 21 to 25 and one second DC / DC converter 31. The second converter 30 is not limited to two second DC / DC converters 31, 32, and may be configured, for example, as shown in Fig. 7, with one first DC / DC converter 26 and one second DC / DC converter 32. In this case, the positions of the first DC / DC converter 26 and the second DC / DC converter 32 may be interchanged, for example, as shown in Fig. 8.

[0045] The control circuit 40 operates either the first converter 20 or the second converter 30 based on the output current Io detected by the detector 41, but may operate at least one of the first converter 20 and the second converter 30. For example, when the current value of the output current Io detected by the detector 41 is less than a threshold, the control circuit 40 controls the first converter 20 and the second converter 30 to not operate the first converter 20 and to operate the second converter 30. Furthermore, when the current value of the output current Io detected by the detector 41 is equal to or greater than the threshold, the control circuit 40 controls the first converter 20 and the second converter 30 to operate the first converter 20 and the second converter 30. In this case as well, the power conversion device A1 can improve load responsiveness and reduce loss.

[0046] Furthermore, although the control circuit 40 controls the first converter 20 and the second converter 30, for example, the power conversion device A1 may include a plurality of control circuits (for example, a first control circuit and a second control circuit), with the first control circuit controlling the first converter 20 and the second control circuit controlling the second converter 30. In other words, the first control circuit may control the first DC / DC converter 21, the first DC / DC converter 22, and the first DC / DC converter 23, and the second control circuit may control the second DC / DC converter 31.

[0047] Each of the switching elements Q1 to Q8 is not limited to a MOSFET, but may be, for example, an IGBT (Insulated Gate Bipolar Transistor), etc. In this case, the first main terminal, the second main terminal, and the control terminal of each of the switching elements Q1 to Q8 become a collector terminal, an emitter terminal, and a gate terminal.

[0048] The power conversion device A1 has a pair of input terminals 1a and 1b, but does not necessarily have to have the pair of input terminals 1a and 1b.Furthermore, the power conversion device A1 has a pair of output terminals 2a and 2b, but does not necessarily have to have the pair of output terminals 2a and 2b.

[0049] The detector 41 is located inside the control circuit 40, but may be located outside the control circuit 40. In short, the control circuit 40 does not have the detector 41, and the power conversion device A1 or the DC / DC converter system 10 may have the detector 41, for example.

[0050] The control circuit 40 is not limited to a computer system having one or more processors and one or more memories, but may be, for example, a microcomputer.

[0051] Although the power conversion device A1 steps down the DC voltage Vi to the DC voltage Vo, the power conversion device A1 may step up the DC voltage Vi to the DC voltage Vo.

[0052] The load 50 is not limited to a microprocessor, but may be, for example, a control IC, another power conversion device (DC / DC converter), or the like.

[0053] The first embodiment and the modifications described above are merely a part of the various embodiments and modifications of the present disclosure.

[0054] Second Embodiment Hereinafter, a power conversion system including a power conversion device according to a second embodiment will be described with reference to FIGS.

[0055] As shown in Fig. 9 , the power conversion device A1 according to the second embodiment differs from the power conversion device A1 according to the first embodiment in that the configuration of the DC / DC converter system 10 is different. Note that, with respect to the power conversion device A1 according to the second embodiment, the same components as those of the power conversion device A1 according to the first embodiment (see Figs. 1 and 2 ) are denoted by the same reference numerals and description thereof will be omitted. Furthermore, since the power conversion device A1 according to the second embodiment has the same configuration as the power conversion device A1 according to the first embodiment except for the configuration of the DC / DC converter system 10, the power conversion device A1 according to the second embodiment will be described with reference to the drawings (Figs. 1 and 2 ) of the power conversion device A1 according to the first embodiment.

[0056] (1) DC / DC Converter System As shown in Fig. 9, the DC / DC converter system 10 has a first capacitor C1 (see Fig. 2), a plurality of (three in the example of Fig. 9) first DC / DC converters 21-23, and one second DC / DC converter 31. The DC / DC converter system 10 also has a plurality of (three in the example of Fig. 9) third DC / DC converters 61-63, and a second capacitor C2 (see Fig. 2). Note that, hereinafter, to facilitate understanding of the description of the embodiment, the "three third DC / DC converters 61-63" may also be referred to as a "third converter 60."

[0057] Each of the third DC / DC converters 61 to 63 has the same configuration as each of the first DC / DC converters 21 to 23. The inductors of each of the third DC / DC converters 61 to 63 have the same inductance. The inductance of each of the inductors of each of the third DC / DC converters 61 to 63 is greater than the inductance of each of the inductors L1 to L3 of each of the first DC / DC converters 21 to 23. Furthermore, the inductance of each of the inductors of each of the third DC / DC converters 61 to 63 is smaller than the inductance of the inductor L4 of the second DC / DC converter 31.

[0058] (2) Control Circuit The control circuit 40 controls the third converter 60. In short, the control circuit 40 controls a plurality of DC / DC converters (the first converter 20, the second converter 30, and the third converter 60). Note that the operation of the control circuit 40 to control the third converter 60 is the same as the operation to control the first converter 20, except for the target switching element, and therefore a description thereof will be omitted.

[0059] The detector 41 detects the output current Io of the plurality of DC / DC converters (the first converter 20, the second converter 30, and the third converter 60).

[0060] The control circuit 40 controls the multiple DC / DC converters to operate at least one of the first converter 20, the second converter 30, and the third converter 60, based on the current value of the output current Io detected by the detector 41, for example. Specifically, when the current value of the output current Io detected by the detector 41 is less than a first reference value It1 (see FIGS. 10 and 11 ), the control circuit 40 controls the multiple DC / DC converters to operate the second converter 30. More specifically, when the current value of the output current Io detected by the detector 41 is less than the first reference value It1, the control circuit 40 controls the multiple DC / DC converters to operate the second converter 30 and not operate the first converter 20 and the third converter 60. The black arrow in FIG. 10 indicates the operating state of the second converter 30. The shaded arrow in FIG. 10 indicates the operating state of the third converter 60. The white arrow in FIG. 10 indicates the operating state of the first converter 20. In addition, Io in Fig. 11 represents the output current of the multiple DC / DC converters. IL1 in Fig. 11 represents the output current of the first converter 20. IL2 in Fig. 11 represents the output current of the second converter 30. IL3 in Fig. 11 represents the output current of the third converter 60.

[0061] Furthermore, when the current value of the output current Io detected by the detector 41 is equal to or greater than the first reference value It1 and less than the second reference value It2 (see FIGS. 10 and 11 ), the control circuit 40 controls the multiple DC / DC converters to operate the second converter 30 and the third converter 60. More specifically, when the current value of the output current Io detected by the detector 41 is equal to or greater than the first reference value It1 and less than the second reference value It2, the control circuit 40 controls the multiple DC / DC converters to operate the second converter 30 and the third converter 60 and not operate the first converter 20. The second reference value It2 is greater than the first reference value It1. Furthermore, when the current value of the output current Io detected by the detector 41 is equal to or greater than the second reference value It2, the control circuit 40 controls the multiple DC / DC converters to operate the first converter 20, the second converter 30, and the third converter 60.

[0062] (3) Operation of the Power Conversion Device In the power conversion device A1 of the second embodiment, similarly to the power conversion device A1 of the first embodiment, the control circuit 40 controls the DC / DC converter system 10 to step down the DC voltage Vi to the DC voltage Vo.

[0063] In the power conversion device A1 of the second embodiment, the inductance of each inductor of the third converter 60 is larger than the inductance of each of the inductors L1, L2, and L3 of the first converter 20. Furthermore, the inductance of each inductor of the third converter 60 is smaller than the inductance of the inductor L4 of the second converter 30. Furthermore, as described above, the control circuit 40 operates at least one of the first converter 20, the second converter 30, and the third converter 60 based on the current value of the output current Io detected by the detector 41. In other words, the control circuit 40 increases the number of groups of converters to operate as the output current Io detected by the detector 41 increases (see FIGS. 10 and 11 ).

[0064] For example, the control circuit 40 operates only the second converter 30 when the current value of the output current Io detected by the detector 41 is less than the first reference value It1. Furthermore, the control circuit 40 operates the second converter 30 and the third converter 60 when the current value of the output current Io detected by the detector 41 is equal to or greater than the first reference value It1 and less than the second reference value It2. Furthermore, the control circuit 40 operates the first converter 20, the second converter 30, and the third converter 60 when the current value of the output current Io detected by the detector 41 is equal to or greater than the second reference value It2. As a result, in the power conversion device A1 of the second embodiment, when the operation of the load 50 changes (for example, when the output current Io increases), the change in the output current Io (the rise of the output current Io) becomes faster than when all converters are always operating. Therefore, the power conversion device A1 of the second embodiment also enables improved load responsiveness. Furthermore, in the power conversion device A1 of the second embodiment, for example, when the load 50 is in a low-load state, the first converter 20 is not operated, thereby enabling lower loss than when all converters are operated at all times. Furthermore, in the power conversion device A1 of the second embodiment, the inductance of each inductor of the first converter 20 is smaller than the inductance of each inductor of the second converter 30 and the third converter 60. That is, the power conversion device A1 of the second embodiment includes the first converter 20 in which the inductance of each inductor is small, thereby enabling improved load responsiveness than when, for example, all converters are the second converter 30 or the third converter 60. Furthermore, in the power conversion device A1 of the second embodiment, the inductance of each inductor of the second converter 30 is larger than the inductance of each inductor of the first converter 20 and the third converter 60. That is, the power conversion device A1 of the second embodiment includes the second converter 30 in which the inductance of each inductor is large, thereby enabling smaller ripple in the output current Io than when, for example, all converters are the first converter 20 or the third converter 60.

[0065] Furthermore, in the power conversion device A1 of the second embodiment, when the current value of the output current Io detected by the detector 41 is less than the first reference value It1, only the second converter 30 is operated, so that the ripple of the output current Io is smaller than when all the converters are operated all the time. Therefore, the power conversion device A1 of the second embodiment can also achieve low loss.

[0066] Therefore, the power conversion device A1 of the second embodiment can improve the load response and reduce the loss. Therefore, the power conversion system B1 of the second embodiment can also improve the load response and reduce the loss.

[0067] (4) Modifications As a modification of the second embodiment, modifications similar to those of the power conversion device A1 according to the modification of the first embodiment are possible. Therefore, the power conversion device A1 according to the modification of the second embodiment also achieves the same effects as the power conversion device A1 according to the second embodiment.

[0068] The second embodiment and the modified examples described above are merely a part of the various embodiments and modified examples of the present disclosure.

[0069] (Embodiment 3) Hereinafter, a power conversion system including a power conversion device according to embodiment 3 will be described with reference to Fig. 9. The power conversion device A1 according to embodiment 3 differs from the power conversion device A1 according to embodiment 2 in that the control by the control circuit 40 is different.

[0070] The control circuit 40 determines the number of DC / DC converters to operate among the plurality of DC / DC converters according to the current value of the output current Io detected by the detector 41. The plurality of DC / DC converters may be, for example, three first DC / DC converters 21-23, one second DC / DC converter 31, and three third DC / DC converters 61-63.

[0071] When the current value of the output current Io detected by the detector 41 is less than a first current value, the control circuit 40 operates only the second DC / DC converter 31 (operates one DC / DC converter). Furthermore, when the current value of the output current Io detected by the detector 41 is equal to or greater than the first current value and less than a second current value, the control circuit 40 operates only the second DC / DC converter 31 and the third DC / DC converter 61 (operates two DC / DC converters). Furthermore, when the current value of the output current Io detected by the detector 41 is equal to or greater than the second current value and less than a third current value, the control circuit 40 operates only the second DC / DC converter 31 and the two third DC / DC converters 61 and 62 (operates three DC / DC converters). Furthermore, when the current value of the output current Io detected by the detector 41 is equal to or greater than the third current value and less than a fourth current value, the control circuit 40 operates only the second DC / DC converter 31 and the three third DC / DC converters 61 to 63 (operates four DC / DC converters). In addition, when the current value of the output current Io detected by the detector 41 is equal to or greater than the fourth current value and less than the fifth current value, the control circuit 40 operates only the second DC / DC converter 31, the three third DC / DC converters 61 to 63, and the first DC / DC converter 21 (operating five DC / DC converters).

[0072] Furthermore, when the current value of the output current Io detected by the detector 41 is equal to or greater than a fifth current value and less than a sixth current value, the control circuit 40 operates the second DC / DC converter 31, the three third DC / DC converters 61-63, and the two first DC / DC converters 21 and 22 (operating six DC / DC converters). Furthermore, when the current value of the output current Io detected by the detector 41 is equal to or greater than a sixth current value and less than a seventh current value, the control circuit 40 operates the second DC / DC converter 31, the three third DC / DC converters 61-63, and the three first DC / DC converters 21-23 (operating seven DC / DC converters). The second current value is greater than the first current value. The third current value is greater than the second current value. The fourth current value is greater than the third current value. The fifth current value is greater than the fourth current value. The sixth current value is greater than the fifth current value. The seventh current value is greater than the sixth current value. The first current value, the second current value, the third current value, the fourth current value, the fifth current value, the sixth current value, and the seventh current value are stored in advance in the memory of the control circuit 40, for example.

[0073] In the power conversion device A1 of embodiment 3, the control circuit 40 operates the second converter 30, the third converter 60, and the first converter 20 in this order according to the current value of the output current Io detected by the detector 41. Therefore, the power conversion device A1 of embodiment 3 can improve load responsiveness and reduce loss, similar to the power conversion device A1 of embodiment 2. Furthermore, as described above, the power conversion device A1 of embodiment 3 determines (changes) the number of DC / DC converters to be operated according to the current value of the output current Io, and therefore can achieve higher efficiency than the power conversion device A1 of embodiment 2.

[0074] (Modification) As a modification of the third embodiment, modifications similar to those of the power conversion device A1 according to the modification of the first embodiment are possible. Therefore, the power conversion device A1 according to the modification of the third embodiment also achieves the same effects as the power conversion device A1 according to the third embodiment.

[0075] The third embodiment and the modifications described above are merely a part of the various embodiments and modifications of the present disclosure.

[0076] (Fourth embodiment) Hereinafter, a power conversion system including a power conversion device according to a fourth embodiment will be described with reference to Fig. 12 and Fig. 13. The power conversion device A1 according to the fourth embodiment differs from the power conversion device A1 according to the second embodiment in that the configuration of the control circuit 40 is different.

[0077] The control circuit 40 includes a detector 41 , a pulse generator 42 , a PWM output circuit 43 , a comparator 44 , and a setting unit 46 .

[0078] The detector 41 detects the output voltage Vo of the DC / DC converter system 10, i.e., the multiple DC / DC converters (the first converter 20, the second converter 30, and the third converter 60). The detector 41 is, for example, a voltage divider circuit having a first resistor R1 and a second resistor R2 connected in series, as shown in FIG. 12 . A first end of the first resistor R1 is electrically connected to the high-potential terminal of a second capacitor C2 (see FIG. 2 ). A second end of the first resistor R1 is electrically connected to the inverting input terminal of a comparator 44 (described later). The second end of the first resistor R1 is electrically connected to the second resistor R2. A first end of the second resistor R2 is electrically connected to the second end of the first resistor R1. The second end of the second resistor R2 is electrically connected to the low-potential terminal of the first capacitor C1 (see FIG. 2 ).

[0079] The pulse generator 42 outputs a pulse signal in response to the output of the comparator 44. The PWM output circuit 43 converts the pulse signal from the pulse generator 42 into a PWM signal and outputs the PWM signal to the DC / DC converter system 10. The comparator 44 has an inverting input terminal, a non-inverting input terminal, and an output terminal. The first resistor R1 and the second resistor R2 of the detector 41 are connected in series to each other at a connection point 41N. The inverting input terminal of the comparator 44 is electrically connected to the connection point 41N of the first resistor R1 and the second resistor R2 of the detector 41. The non-inverting input terminal of the comparator 44 is electrically connected to a setting unit 46. The output terminal of the comparator 44 is electrically connected to the pulse generator 42. The setting unit 46 sets a first threshold Vt1 (see FIG. 13 ) and a second threshold Vt2, which will be described later.

[0080] The comparator 44 outputs an output signal Vd (see FIGS. 12 and 13 ) based on the voltage value of the output voltage Vo detected by the detector 41. The output signal Vd is, for example, a pulse signal. As shown in FIG. 13 , the comparator 44 does not output the output signal Vd when the voltage value of the output voltage Vo detected by the detector 41 is equal to or greater than the first threshold Vt1 and equal to or less than the second threshold Vt2. Furthermore, the comparator 44 outputs a positive output signal Vd when the voltage value of the output voltage Vo detected by the detector 41 is less than the first threshold Vt1. Furthermore, the comparator 44 outputs a negative output signal Vd when the voltage value of the output voltage Vo detected by the detector 41 is greater than the second threshold Vt2. The positive output signal Vd is a signal (pulse signal) whose signal level is positive. The negative output signal Vd is a signal (pulse signal) whose signal level is negative. In this embodiment, the comparator 44 outputs either a positive output signal Vd or a negative output signal Vd, but any output signal may be used as long as the pulse generator 42 can determine the signal level of the output signal Vd.

[0081] When the comparator 44 does not output an output signal Vd, the control circuit 40 controls the multiple DC / DC converters to operate the second converter 30. In this embodiment, when the comparator 44 does not output an output signal Vd, the control circuit 40 controls the multiple DC / DC converters so that converters other than the second converter 30, such as the third converter 60 and the first converter 20, do not operate. Furthermore, when the comparator 44 outputs a positive output signal Vd, the control circuit 40 controls the multiple DC / DC converters to operate the second converter 30, the third converter 60, and the first converter 20 in that order as the current value of the output current Io increases. Furthermore, when the comparator 44 outputs a negative output signal Vd, the control circuit 40 controls the multiple DC / DC converters so that the first converter 20, the second converter 30, and the third converter 60 do not operate.

[0082] In the power conversion device A1 of the fourth embodiment, the control circuit 40 operates at least one of the first converter 20, the second converter 30, and the third converter 60 based on the output signal Vd from the comparator 44, while not operating the other converters. In other words, in the power conversion device A1 of the fourth embodiment, at least one of the first converter 20, the second converter 30, and the third converter 60 is operated in response to a change in the output voltage Vo (a change in the output current Io) detected by the detector 41. Therefore, in the power conversion device A1 of the fourth embodiment, by detecting the threshold voltages (the first threshold Vt1 and the second threshold Vt2), the PWM signal from the PWM output circuit 43 can be controlled, thereby minimizing voltage drops and voltage increases in the output voltage Vo and improving load responsiveness. Furthermore, in the power conversion device A1 of the fourth embodiment, the second converter 30 is operated when the operation of the load 50 is stable (the output current Io does not change), thereby reducing ripple in the output current Io and achieving low loss. That is, the power conversion device A1 of embodiment 4 can also improve load responsiveness and reduce loss. Therefore, the power conversion system B1 of embodiment 4 can also improve load responsiveness and reduce loss.

[0083] (Modification) As a modification of the fourth embodiment, modifications similar to those of the power conversion device A1 according to the modification of the first embodiment are possible. Therefore, the power conversion device A1 according to the modification of the fourth embodiment also achieves the same effects as the power conversion device A1 according to the fourth embodiment.

[0084] When the comparator 44 does not output an output signal Vd, the control circuit 40 operates the second converter 30, but may also operate the third converter 60 in addition to the second converter 30, without operating the first converter 20. Furthermore, when the comparator 44 outputs a positive output signal Vd, the control circuit 40 operates the first converter 20 and the second converter 30, but may also operate the third converter 60.

[0085] The control circuit 40 determines the threshold voltages (first threshold Vt1 and second threshold Vt2) to control the multiple DC / DC converters. Alternatively, the control circuit 40 may control the multiple DC / DC converters by feedback control, such as constant on time control. In this case, the control circuit 40 may include, for example, an output unit that outputs a feedback reference voltage instead of the setting unit 46. The control circuit 40 may also control the multiple DC / DC converters by feedback control, such as PWM control. In this case, the control circuit 40 may include, for example, an error amplifier and the output unit instead of the setting unit 46.

[0086] Furthermore, the control circuit 40 operates at least one of the first converter 20, the second converter 30, and the third converter 60 and does not operate the other converters based on the output signal Vd from the comparator 44, but may stop the operation of the first converter 20, the second converter 30, and the third converter 60 when, for example, a negative output signal Vd is output from the comparator 44. In other words, the control circuit 40 may stop the operation of the first converter 20, the second converter 30, and the third converter 60 when the voltage value of the output voltage Vo detected by the detector 41 is greater than the second threshold value Vt2.

[0087] The fourth embodiment and the modifications described above are merely a part of the various embodiments and modifications of the present disclosure.

[0088] Fifth Embodiment Hereinafter, a power conversion system including a power conversion device according to a fifth embodiment will be described with reference to Fig. 14 and Fig. 15. The power conversion device A1 according to the fifth embodiment differs from the power conversion device A1 according to the fourth embodiment in that the configuration of the control circuit 40 is different.

[0089] As shown in FIG. 14 , the detector 41 is configured to detect a notification signal S1 from the load 50. The notification signal S1 is, for example, a signal that notifies in advance of the state of the load 50 (e.g., when the load 50 changes from a low-load state to a high-load state). In other words, the notification signal S1 is a signal related to either an increase or a decrease in the output current Io of the multiple DC / DC converters (the first converter 20, the second converter 30, and the third converter 60). The notification signal S1 is a signal that includes either an instruction value instructing an increase in the output current Io or an instruction value instructing a decrease in the output current Io. When the instruction value instructs an increase in the output current Io, the notification signal S1 is, for example, a positive pulse signal (see FIG. 15 ). When the instruction value instructs a decrease in the output current Io, the notification signal S1 is, for example, a negative pulse signal (see FIG. 15 ). A positive pulse signal is a signal whose signal level is positive. Moreover, a negative pulse signal is a signal whose signal level has a negative polarity.

[0090] When the detector 41 does not detect the notification signal S1, the control circuit 40 controls the multiple DC / DC converters to operate the second converter 30. When the detector 41 detects the notification signal S1 and the instruction value included in the notification signal S1 is an instruction value to increase the output current Io, the control circuit 40 controls the multiple DC / DC converters to operate the second converter 30, the third converter 60, and the first converter 20 in that order as the current value of the output current Io increases. When the detector 41 detects the notification signal S1 and the instruction value included in the notification signal S1 is an instruction value to decrease the output current Io, the control circuit 40 controls the multiple DC / DC converters not to operate the first converter 20, the second converter 30, and the third converter 60.

[0091] In the power conversion device A1 of the fifth embodiment, the control circuit 40 operates at least one of the first converter 20, the second converter 30, and the third converter 60 in response to a notification signal S1 from the load 50. Therefore, the power conversion device A1 of the fifth embodiment can also improve load responsiveness and reduce loss. Therefore, the power conversion system B1 of the fifth embodiment can also improve load responsiveness and reduce loss.

[0092] (Modification) As a modification of the fifth embodiment, modifications similar to those of the power conversion device A1 according to the modification of the first embodiment are possible. Therefore, the power conversion device A1 according to the modification of the fifth embodiment also achieves the same effects as the power conversion device A1 according to the fifth embodiment.

[0093] When the detector 41 does not detect the notification signal S1, the control circuit 40 operates the second converter 30, but may also operate the third converter 60 in addition to the second converter 30. Furthermore, when the detector 41 detects the notification signal S1 and the instruction value included in the notification signal S1 is an instruction value for increasing the output current Io, the control circuit 40 operates the first converter 20 and the second converter 30, but may also operate the third converter 60.

[0094] The notification signal S1 is not limited to notifying the state of the load 50 in advance, but may also notify the state of the load 50 simultaneously with the timing when the state of the load 50 changes, for example.

[0095] The control circuit 40 operates at least one of the first converter 20, the second converter 30, and the third converter 60 in response to the notification signal S1 from the load 50, but may stop the operation of the first converter 20, the second converter 30, and the third converter 60, for example, when the notification signal S1 is detected by the detector 41 and the instruction value included in the notification signal S1 is an instruction value that instructs a decrease in the output current Io.

[0096] The fifth embodiment and the modifications described above are merely a part of the various embodiments and modifications of the present disclosure.

[0097] Sixth Embodiment A power conversion system including a power conversion device according to a sixth embodiment will be described below with reference to FIGS. 16 and 17. FIG.

[0098] The power conversion device A1 according to the sixth embodiment differs from the power conversion device A1 according to the fifth embodiment in that it further includes a processing circuit 45. Note that, with respect to the power conversion device A1 according to the sixth embodiment, the same components as those of the power conversion device A1 according to the fifth embodiment (see FIG. 14) are denoted by the same reference numerals and description thereof will be omitted.

[0099] 16, the control circuit 40 further includes a processing circuit 45. The processing circuit 45 has data that associates the indication value included in the notification signal S1 detected by the detector 41 with the operations of the multiple DC / DC converters (the first converter 20, the second converter 30, and the third converter 60). The data is stored in advance in the memory of the control circuit 40, for example.

[0100] The processing circuit 45 generates a signal (corresponding signal) S2 (see FIGS. 16 and 17) including operation instructions for the multiple DC / DC converters based on the above data, and outputs the signal to the pulse generator 42. The corresponding signal S2 is, for example, a signal including instructions (operation instructions) for operating at least one of the first converter 20, the second converter 30, and the third converter 60. The corresponding signal S2 is, for example, a pulse-like signal.

[0101] In the power conversion device A1 of embodiment 6, the control circuit 40 determines the operation of the multiple DC / DC converters based on the above data. In other words, the control circuit 40 operates at least one of the first converter 20, the second converter 30, and the third converter 60 based on the above data. Therefore, the power conversion device A1 of embodiment 6 can also improve load responsiveness and reduce loss. Therefore, the power conversion system B1 of embodiment 6 can also improve load responsiveness and reduce loss.

[0102] (Modification) As a modification of the sixth embodiment, modifications similar to those of the power conversion device A1 according to the modification of the first embodiment are possible. Therefore, the power conversion device A1 according to the modification of the sixth embodiment also achieves the same effects as the power conversion device A1 according to the sixth embodiment. The detector 41 is located outside the processing circuit 45, but may be located inside the processing circuit 45.

[0103] The control circuit 40 operates at least one of the first converter 20, the second converter 30, and the third converter 60 based on the above data, but may also stop the operation of the first converter 20, the second converter 30, and the third converter 60 based on the above data, for example.

[0104] The sixth embodiment and the modifications described above are merely a part of the various embodiments and modifications of the present disclosure.

[0105] (Seventh embodiment) A power conversion system including a power conversion device according to a seventh embodiment will be described below with reference to Fig. 18 and Fig. 19. The power conversion device A1 according to the seventh embodiment differs from the power conversion device A1 according to the fifth embodiment in that the control by the control circuit 40 is different. Note that the power conversion device A1 according to the seventh embodiment has the same configuration as the power conversion device A1 according to the fifth embodiment except for the control by the control circuit 40, and therefore will be described with reference to the drawing of the power conversion device A1 according to the fifth embodiment (Fig. 14).

[0106] The detector 41 detects whether or not there is an increase in the output current Io of the multiple DC / DC converters (the first converter 20, the second converter 30, and the third converter 60). The detector 41 is configured to be able to detect, for example, a notification signal S1 from the load 50.

[0107] When the detector 41 does not detect the notification signal S1, the control circuit 40 controls the multiple DC / DC converters so that the second converter 30 operates more frequently than the first converter 20. In other words, when there is no increase in the output current Io (when the output current Io is stable), the control circuit 40 controls the multiple DC / DC converters so that the second converter 30 operates more frequently than the first converter 20, as shown in FIG. 18 . Furthermore, when the detector 41 does not detect the notification signal S1 (when there is no increase in the output current Io), the control circuit 40 controls the multiple DC / DC converters so that the second converter 30 operates more frequently than the third converter 60. In other words, when there is no increase in the output current Io, the control circuit 40 controls the multiple DC / DC converters so that the operation of the second converter 30 is dominant. Note that the black arrow in FIG. 18 represents the operating state of the second converter 30. The shaded arrow in FIG. 18 represents the operating state of the third converter 60. The white arrow in FIG. 18 represents the operating state of the first converter 20. The phrase "operating the second converter 30 more frequently than the first converter 20 or the third converter 60" includes, for example, a case where only the second converter 30 is operated without operating the first converter 20 or the third converter 60. Furthermore, the phrase "operating the second converter 30 more frequently than the first converter 20 or the third converter 60" also includes, for example, a case where the amount of output current IL2 of the second converter 30 is greater than the amount of output current IL1 of the first converter 20 or the amount of output current IL3 of the third converter 60.

[0108] Furthermore, when the detector 41 detects the notification signal S1 and the instruction value included in the notification signal S1 indicates an instruction to increase the output current Io, the control circuit 40 controls the multiple DC / DC converters to operate the first converter 20 more than the second converter 30. In other words, when the output current Io increases, the control circuit 40 controls the multiple DC / DC converters to operate the first converter 20 more than the second converter 30, as shown in FIG. 19 . When the output current Io increases, the control circuit 40 controls the multiple DC / DC converters to operate the first converter 20 more than the third converter 60. In other words, when the output current Io increases, the control circuit 40 controls the multiple DC / DC converters so that the operation of the first converter 20 becomes dominant. Note that Io in FIG. 19 represents the output current of the DC / DC converter system 10. IL1 in FIG. 19 represents the output current of the first converter 20. IL2 in FIG. 19 represents the output current of the second converter 30. 19, IL3 represents the output current of the third converter 60.

[0109] In the power conversion device A1 of embodiment 7, the control circuit 40 controls the multiple DC / DC converters so that the operation of the second converter 30 becomes dominant when the output current Io does not increase. Furthermore, the control circuit 40 controls the multiple DC / DC converters so that the operation of the first converter 20 becomes dominant when the output current Io increases. This makes it possible to improve load responsiveness and reduce loss in the power conversion device A1 of embodiment 7 as well. Therefore, it is possible to improve load responsiveness and reduce loss in the power conversion system B1 of embodiment 7 as well.

[0110] (Modification) As a modification of the seventh embodiment, modifications similar to those of the power conversion device A1 according to the modification of the first embodiment are possible. Therefore, the power conversion device A1 according to the modification of the seventh embodiment also achieves the same effects as the power conversion device A1 according to the seventh embodiment.

[0111] The detector 41 is configured to be able to detect the notification signal S1 from the load 50 in order to detect whether the output current Io has increased, but may also detect whether the output current Io has increased based on, for example, the output voltage Vo of the DC / DC converter system 10. The detector 41 may also detect whether the output current Io has increased based on, for example, the output current Io of the DC / DC converter system 10.

[0112] The seventh embodiment and the modifications described above are merely a part of the various embodiments and modifications of the present disclosure.

[0113] (Embodiment 8) Hereinafter, a power conversion system including a power conversion device according to embodiment 8 will be described with reference to Fig. 20 and Fig. 21. The power conversion device A1 according to embodiment 8 differs from the power conversion device A1 according to embodiment 5 in that the control by the control circuit 40 is different. Note that the power conversion device A1 according to embodiment 8 has the same configuration as the power conversion device A1 according to embodiment 5 except for the control by the control circuit 40, and therefore will be described with reference to the drawing of the power conversion device A1 according to embodiment 5 (Fig. 14).

[0114] The detector 41 detects whether or not there is a decrease in the output current Io of the multiple DC / DC converters (the first converter 20, the second converter 30, and the third converter 60). The detector 41 is configured to be able to detect, for example, a notification signal S1 from the load 50.

[0115] When the detector 41 does not detect the notification signal S1, the control circuit 40 controls the multiple DC / DC converters so that the second converter 30 operates more frequently than the first converter 20. In other words, when there is no decrease in the output current Io (when the output current Io is stable), the control circuit 40 controls the multiple DC / DC converters so that the second converter 30 operates more frequently than the first converter 20, as shown in FIG. 20 . Furthermore, when the detector 41 does not detect the notification signal S1 (when there is no decrease in the output current Io), the control circuit 40 controls the multiple DC / DC converters so that the second converter 30 operates more frequently than the third converter 60. In other words, when there is no decrease in the output current Io, the control circuit 40 controls the multiple DC / DC converters so that the operation of the second converter 30 is dominant. Note that the black arrow in FIG. 20 represents the operating state of the second converter 30. The shaded arrow in FIG. 20 represents the operating state of the third converter 60. The white arrow in FIG. 20 represents the operating state of the first converter 20.

[0116] Furthermore, when the detector 41 detects the notification signal S1 and the instruction value included in the notification signal S1 indicates a decrease in the output current Io, the control circuit 40 controls the multiple DC / DC converters to operate the first converter 20 more than the second converter 30. In other words, when the output current Io decreases, the control circuit 40 controls the multiple DC / DC converters to operate the first converter 20 more than the second converter 30, as shown in FIG. 21 . When the output current Io decreases, the control circuit 40 controls the multiple DC / DC converters to operate the first converter 20 more than the third converter 60. In other words, when the output current Io decreases, the control circuit 40 controls the multiple DC / DC converters so that the operation of the first converter 20 becomes dominant. Note that Io in FIG. 21 represents the output current of the DC / DC converter system 10. IL1 in FIG. 21 represents the output current of the first converter 20. IL2 in FIG. 21 represents the output current of the second converter 30. 21 indicates the output current of the third converter 60.

[0117] In the power conversion device A1 of embodiment 8, the control circuit 40 controls the multiple DC / DC converters so that the operation of the second converter 30 is dominant when there is no decrease in the output current Io. Furthermore, the control circuit 40 controls the multiple DC / DC converters so that the operation of the first converter 20 is dominant when there is a decrease in the output current Io. As a result, in the power conversion device A1 of embodiment 8, for example, when there is a decrease in the output current Io, the operation of the first converter 20 is dominant, thereby making it possible to hasten the decrease in the output current Io (the current flowing through the load 50). Therefore, the power conversion device A1 of embodiment 8 can also improve load responsiveness and reduce loss. Furthermore, the power conversion system B1 of embodiment 8 can also improve load responsiveness and reduce loss.

[0118] (Modification) As a modification of the eighth embodiment, modifications similar to those of the power conversion device A1 according to the modification of the first embodiment are possible. Therefore, the power conversion device A1 according to the modification of the eighth embodiment also achieves the same effects as the power conversion device A1 according to the eighth embodiment.

[0119] The detector 41 is configured to be able to detect the notification signal S1 from the load 50 in order to detect whether or not the output current Io has decreased, but may also detect whether or not the output current Io has decreased based on, for example, the output voltage Vo of the DC / DC converter system 10. The detector 41 may also detect whether or not the output current Io has decreased based on, for example, the output current Io of the DC / DC converter system 10.

[0120] Furthermore, as a modified example of embodiment 8, the power conversion device A1 according to embodiment 8 may be appropriately combined with a portion of the configuration of the power conversion device A1 according to embodiment 7 (for example, a configuration in which the detector 41 detects whether or not the output current Io has increased).

[0121] The eighth embodiment and the modifications described above are merely a part of the various embodiments and modifications of the present disclosure.

[0122] Ninth Embodiment Hereinafter, a power conversion system including a power conversion device according to a ninth embodiment will be described with reference to FIG.

[0123] 22, the power conversion device A2 according to the ninth embodiment differs from the power conversion device A1 according to the first embodiment in that two types of voltages Vi1 and Vi2 are applied to the DC / DC converter system 10. Note that, with respect to the power conversion device A2 according to the ninth embodiment, the same components as those of the power conversion device A1 according to the first embodiment (see FIG. 1) are denoted by the same reference numerals and description thereof will be omitted.

[0124] The first converter 20 is connected in parallel to a DC power supply (first DC power supply) V1. That is, in the power conversion device A2, a voltage (first voltage) Vi1 from the first DC power supply V1 is applied to the first converter 20. The second converter 30 is connected in parallel to a DC power supply (second DC power supply) V2. That is, in the power conversion device A2, a voltage (second voltage) Vi2 from the second DC power supply V2 is applied to the second converter 30. The voltage value of the first voltage Vi1 is greater than the voltage value of the second voltage Vi2. The second converter 30 includes a second DC / DC converter 31 and a second DC / DC converter 32. In short, the second converter 30 of the power conversion device A2 is made up of two second DC / DC converters 31 and 32. The second DC / DC converter 32 has the same configuration as the second DC / DC converter 31. The inductance of the inductor of the second DC / DC converter 32 is the same as the inductance of the inductor L4 of the second DC / DC converter 31 (see FIG. 2).

[0125] For example, when the operation of the load 50 changes, the control circuit 40 operates only the first converter 20, which makes it possible to quickly change the output current Io (rise of the output current Io) and improve load responsiveness. Also, for example, when the operation of the load 50 is stable, the control circuit 40 operates only the second converter 30, which makes it possible to reduce ripples in the output current Io and reduce loss.

[0126] The amount of change in the output current of the first converter 20 is expressed by the equation dI / dt = Vi1 / La1, where dI / dt is the amount of change in the output current of the first converter 20, Vi1 is the input voltage of the first converter 20, and La1 is the inductance of the combined inductor of the first converter 20. In other words, the amount of change in the output current of the first converter 20 is proportional to the magnitude of the input voltage Vi1 of the first converter 20. Therefore, in the power conversion device A2, the first DC power source V1 is electrically connected to the first converter 20, and the second DC power source V2 is electrically connected to the second converter 30. Since the voltage value of the first voltage Vi1 is greater than the voltage value of the second voltage Vi2, the load response can be further improved. Therefore, the power conversion device A2 can further improve the load response and reduce loss. Therefore, the power conversion system B1 including the power conversion device A2 can also further improve the load response and reduce loss.

[0127] (Modification) As a modification of the ninth embodiment, modifications similar to those of the power conversion device A1 according to the modification of the first embodiment are possible. Therefore, the power conversion device A1 according to the modification of the ninth embodiment also achieves the same effects as the power conversion device A1 according to the ninth embodiment.

[0128] The switching frequency of each of the switching elements Q1 to Q6 of the first converter 20 is preferably higher than the switching frequency of each of the switching elements Q7, Q8 of the second converter 30. This makes it possible for the power conversion device A1 according to the modification of the ninth embodiment to further improve load responsiveness and achieve further reduction in loss.

[0129] The ninth embodiment and the modifications described above are merely a part of the various embodiments and modifications of the present disclosure.

[0130] The present disclosure is not limited to the above-described embodiments, and at least some of the configurations of the embodiments and modified examples can be combined as appropriate and applied.

[0131] (Aspects) The present specification discloses the following aspects.

[0132] A power conversion device (A1) according to a first aspect includes a first capacitor (C1), a second capacitor (C2), at least one first DC / DC converter (21), at least one second DC / DC converter (31), and a control circuit (40). The first capacitor (C1) is electrically connected across a DC power source (V1). The second capacitor (C2) is electrically connected across a load (50). The at least one first DC / DC converter (21) is connected in parallel with the first capacitor (C1). The at least one second DC / DC converter (31) is connected in parallel with the first capacitor (C1). The control circuit (40) controls the at least one first DC / DC converter (21) and the at least one second DC / DC converter (31). The at least one first DC / DC converter (21) includes a first switching circuit (71) and a first inductor (L1). The first switching circuit (71) has a first switching element (Q1) and a second switching element (Q2) connected in series. A first end of a first inductor (L1) is connected to a connection point (3) between the first switching element (Q1) and the second switching element (Q2). The first switching circuit (71) is connected in parallel to a first capacitor (C1). A second end of the first inductor (L1) is electrically connected to the second switching element (Q2) via a second capacitor (C2). At least one second DC / DC converter (31) has a second switching circuit (74) and a second inductor (L4). The second switching circuit (74) has a third switching element (Q7) and a fourth switching element (Q8) connected in series. A first end of the second inductor (L4) is connected to a connection point (6) between the third switching element (Q7) and the fourth switching element (Q8). The second switching circuit (74) is connected in parallel to the first capacitor (C1). A second end of the second inductor (L4) is electrically connected to the fourth switching element (Q8) via the second capacitor (C2). The inductance of the first inductor (L1) is smaller than the inductance of the second inductor (L4).The control circuit (40) controls at least one first DC / DC converter (21) and at least one second DC / DC converter (31) so as to operate at least one of the at least one first DC / DC converter (21) and the at least one second DC / DC converter (31).

[0133] According to this aspect, it is possible to improve load response and reduce loss.

[0134] In a power conversion device (A1) according to a second aspect, in the first aspect, a control circuit (40) has a detector (41) that detects output currents (Io) of a plurality of DC / DC converters (21, 31) including at least one first DC / DC converter (21) and at least one second DC / DC converter (31). When the current value of the output current (Io) detected by the detector (41) is less than a threshold, the control circuit (40) operates at least one second DC / DC converter (31). When the current value of the output current (Io) detected by the detector (41) is equal to or greater than the threshold, the control circuit (40) operates at least one first DC / DC converter (21) and at least one second DC / DC converter (31).

[0135] According to this aspect, it is possible to improve load response and reduce loss.

[0136] A power conversion device (A1) according to a third aspect is the first aspect, wherein the control circuit (40) has a detector (41) that detects output currents (Io) of a plurality of DC / DC converters (21, 31) including at least one first DC / DC converter (21) and at least one second DC / DC converter (31). The control circuit (40) determines the number of DC / DC converters (21, 31) to operate, according to the current value of the output current (Io) detected by the detector (41).

[0137] According to this aspect, it is possible to achieve high efficiency.

[0138] A power conversion device (A1) according to a fourth aspect is the first aspect, wherein the control circuit (40) has a detector (41) that detects output voltages (Vo) of a plurality of DC / DC converters (21, 31) including at least one first DC / DC converter (21) and at least one second DC / DC converter (31). The control circuit (40) operates at least one second DC / DC converter (31) when the voltage value of the output voltage (Vo) detected by the detector (41) is equal to or greater than a first threshold (Vt1) and equal to or less than a second threshold (Vt2). The control circuit (40) operates at least one first DC / DC converter (21) and at least one second DC / DC converter (31) when the voltage value of the output voltage (Vo) detected by the detector (41) is less than the first threshold (Vt1). The control circuit (40) does not operate at least one first DC / DC converter (21) and at least one second DC / DC converter (31) when the voltage value of the output voltage (Vo) detected by the detector (41) is greater than a second threshold (Vt2).

[0139] According to this aspect, it is possible to improve load response and reduce loss.

[0140] A power conversion device (A1) according to a fifth aspect is the first aspect, wherein the control circuit (40) has a detector (41) capable of detecting an external notification signal (S1). The notification signal (S1) is a signal related to either an increase or a decrease in the output current (Io) of a plurality of DC / DC converters (21, 31) including at least one first DC / DC converter (21) and at least one second DC / DC converter (31). The notification signal (S1) includes either an instruction value instructing an increase in the output current (Io) or an instruction value instructing a decrease in the output current (Io). When the detector (41) does not detect the notification signal (S1), the control circuit (40) operates at least one second DC / DC converter (31). The control circuit (40) operates at least one first DC / DC converter (21) and at least one second DC / DC converter (31) when the detector (41) detects the notification signal (S1) and the instruction value included in the notification signal (S1) is an instruction value for increasing the output current (Io). The control circuit (40) does not operate at least one first DC / DC converter (21) and at least one second DC / DC converter (31) when the detector (41) detects the notification signal (S1) and the instruction value included in the notification signal (S1) is an instruction value for decreasing the output current (Io).

[0141] According to this aspect, it is possible to improve load response and reduce loss.

[0142] A power conversion device (A1) according to a sixth aspect is the fifth aspect, wherein the control circuit (40) has data in which an instruction value included in the notification signal (S1) is associated with operations of at least one first DC / DC converter (21) and at least one second DC / DC converter (31). The control circuit (40) determines operations of the at least one first DC / DC converter (21) and at least one second DC / DC converter (31) based on the data.

[0143] According to this aspect, it is possible to improve load response and reduce loss.

[0144] A power conversion device (A1) according to a seventh aspect is the first aspect, wherein the control circuit (40) has a detector (41) that detects whether or not there is an increase in output current (Io) of a plurality of DC / DC converters (21, 31) including at least one first DC / DC converter (21) and at least one second DC / DC converter (31). When there is no increase in the output current (Io), the control circuit (40) operates the at least one second DC / DC converter (31) more than the at least one first DC / DC converter (21). When there is an increase in the output current (Io), the control circuit (40) operates the at least one first DC / DC converter (21) more than the at least one second DC / DC converter (31).

[0145] According to this aspect, it is possible to improve load response and reduce loss.

[0146] In a power conversion device (A1) according to an eighth aspect, in the first aspect, a control circuit (40) has a detector (41) that detects whether or not there is a decrease in output current (Io) of a plurality of DC / DC converters (21, 31) including at least one first DC / DC converter (21) and at least one second DC / DC converter (31). When there is no decrease in output current (Io), the control circuit (40) operates the at least one second DC / DC converter (31) more than the at least one first DC / DC converter (21). When there is a decrease in output current (Io), the control circuit (40) operates the at least one first DC / DC converter (21) more than the at least one second DC / DC converter (31).

[0147] According to this aspect, it is possible to improve load response and reduce loss.

[0148] The power conversion device (A2) according to the ninth aspect is any one of the first to eighth aspects, in which the voltage value of the first voltage (Vi1) applied to at least one first DC / DC converter (21) is greater than the voltage value of the second voltage (Vi2) applied to at least one second DC / DC converter (31).

[0149] According to this aspect, it is possible to further improve the load response and reduce loss.

[0150] The power conversion device (A1) according to the tenth aspect is any one of the first to ninth aspects, in which the switching frequency of the first switching element (Q1) and the second switching element (Q2) in the first switching circuit (71) is higher than the switching frequency of the third switching element (Q7) and the fourth switching element (Q8) in the second switching circuit (74).

[0151] According to this aspect, it is possible to improve the load response and further reduce loss.

[0152] A power conversion system (B1) according to an eleventh aspect includes a power conversion device (A1; A2) and a load (50).

[0153] According to this aspect, it is possible to improve load response and reduce loss.

[0154] A power conversion system (B1) according to a twelfth aspect is the eleventh aspect, in which at least one first DC / DC converter (21) of the power conversion device (A1; A2) is arranged closer to the load (50) than at least one second DC / DC converter (31) of the power conversion device (A1; A2).

[0155] According to this aspect, it is possible to further improve the load responsiveness.

[0156] 3 Connection point 6 Connection point 21 First DC / DC converter 31 Second DC / DC converter 40 Control circuit 41 Detector 50 Load 71 Switching circuit (first switching circuit) 74 Switching circuit (second switching circuit) A1 Power conversion device A2 Power conversion device B1 Power conversion system C1 First capacitor C2 Second capacitor Io Output current L1 Inductor (first inductor) L4 Inductor (second inductor) Q1 Switching element (first switching element) Q2 Switching element (second switching element) Q7 Switching element (third switching element) Q8 Switching element (fourth switching element) S1 Notification signal Vi1 First voltage Vi2 Second voltage Vo Output voltage Vt1 First threshold Vt2 Second threshold

Claims

1. A power supply comprising: a first capacitor electrically connected across a DC power source; a second capacitor electrically connected across a load; at least one first DC / DC converter connected in parallel to the first capacitor; at least one second DC / DC converter connected in parallel to the first capacitor; and a control circuit that controls the at least one first DC / DC converter and the at least one second DC / DC converter, wherein the at least one first DC / DC converter comprises a first switching circuit having a first switching element and a second switching element connected in series to each other, and a first inductor having a first end connected to a connection point between the first switching element and the second switching element, the first switching circuit being connected in parallel to the first capacitor; and a second end of the first inductor being electrically connected to the second switching element via the second capacitor, a second inductor having a first end connected to a connection point between the third switching element and the fourth switching element; the second switching circuit being connected in parallel to the first capacitor; a second end of the second inductor being electrically connected to the fourth switching element via the second capacitor; the inductance of the first inductor being smaller than the inductance of the second inductor; and the control circuit controlling the at least one first DC / DC converter and the at least one second DC / DC converter to operate at least one of the at least one first DC / DC converter and the at least one second DC / DC converter.

2. The power conversion device according to claim 1, wherein the control circuit has a detector that detects output currents of a plurality of DC / DC converters including the at least one first DC / DC converter and the at least one second DC / DC converter, and when the current value of the output current detected by the detector is less than a threshold, operates the at least one second DC / DC converter, and when the current value of the output current detected by the detector is equal to or greater than the threshold, operates the at least one first DC / DC converter and the at least one second DC / DC converter.

3. The power conversion device according to claim 1, wherein the control circuit has a detector that detects output currents of a plurality of DC / DC converters including the at least one first DC / DC converter and the at least one second DC / DC converter, and determines the number of DC / DC converters to operate from among the plurality of DC / DC converters according to the current value of the output current detected by the detector.

4. The power conversion device according to claim 1, wherein the control circuit has a detector that detects output voltages of a plurality of DC / DC converters including the at least one first DC / DC converter and the at least one second DC / DC converter, and operates the at least one second DC / DC converter when a voltage value of the output voltage detected by the detector is equal to or greater than a first threshold value and equal to or less than a second threshold value, operates the at least one first DC / DC converter and the at least one second DC / DC converter when the voltage value of the output voltage detected by the detector is less than the first threshold value, and does not operate the at least one first DC / DC converter and the at least one second DC / DC converter when the voltage value of the output voltage detected by the detector is greater than the second threshold value.

5. The power conversion device according to claim 1, wherein the control circuit has a detector capable of detecting a notification signal from outside, the notification signal being a signal related to either an increase or a decrease in output current of a plurality of DC / DC converters including the at least one first DC / DC converter and the at least one second DC / DC converter, and including one of an instruction value instructing to increase the output current and an instruction value instructing to decrease the output current, the control circuit: when the notification signal is not detected by the detector, operates the at least one second DC / DC converter; when the notification signal is detected by the detector and the instruction value included in the notification signal is an instruction value instructing to increase the output current, operates the at least one first DC / DC converter and the at least one second DC / DC converter; and when the notification signal is detected by the detector and the instruction value included in the notification signal is an instruction value instructing to decrease the output current, does not operate the at least one first DC / DC converter and the at least one second DC / DC converter.

6. The power conversion device according to claim 5, wherein the control circuit has data in which the instruction value included in the notification signal is associated with the operation of the at least one first DC / DC converter and the at least one second DC / DC converter, and determines the operation of the at least one first DC / DC converter and the at least one second DC / DC converter based on the data.

7. The power conversion device according to claim 1, wherein the control circuit has a detector that detects whether or not there is an increase in output current of a plurality of DC / DC converters including the at least one first DC / DC converter and the at least one second DC / DC converter, and when there is no increase in the output current, operates the at least one second DC / DC converter more than the at least one first DC / DC converter, and when there is an increase in the output current, operates the at least one first DC / DC converter more than the at least one second DC / DC converter.

8. The power conversion device according to claim 1, wherein the control circuit has a detector that detects whether or not there is a decrease in output current of a plurality of DC / DC converters including the at least one first DC / DC converter and the at least one second DC / DC converter, and when there is no decrease in output current, operates the at least one second DC / DC converter more than the at least one first DC / DC converter, and when there is a decrease in output current, operates the at least one first DC / DC converter more than the at least one second DC / DC converter.

9. The power conversion device according to claim 1, wherein a voltage value of the first voltage applied to the at least one first DC / DC converter is greater than a voltage value of the second voltage applied to the at least one second DC / DC converter.

10. The power conversion device according to claim 1, wherein the switching frequency of the first switching element and the second switching element in the first switching circuit is higher than the switching frequency of the third switching element and the fourth switching element in the second switching circuit.

11. A power conversion system comprising: the power conversion device according to any one of claims 1 to 10; and the load.

12. The power conversion system of claim 11, wherein the at least one first DC / DC converter of the power conversion device is located closer to the load than the at least one second DC / DC converter of the power conversion device.

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