DC / DC Converter

Abstract

To reduce heat evolution within a DC / DC converter.SOLUTION: A DC / DC converter (1) has an inductor (L1), a converter of one phase composed of an upper side switching element (Fu1) and a lower side switching element (Fd1), and a control section (10) switching the upper side switching element (Fu1) between ON / OFF, and switching the lower side switching element (Fd1) between ON / OFF. The control section (10) turns the upper side switching element (Fu1) on when a predetermined determination condition is satisfied.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] There is known a power supply system that supplies power to a motor drive device via a DC / DC converter that steps up or steps down the voltage supplied from a power source such as a battery. This power supply system is provided with a large-capacity power supply stabilization capacitor to absorb the ripple current flowing through the motor and stabilize the power supply voltage.

[0003] The power supply stabilizing capacitor is connected in parallel to a motor drive device, which is a load on the battery. Patent Document 1 discloses a precharge circuit that precharges the power supply stabilizing capacitor when the power supply is turned on. The precharge circuit prevents an excessive inrush current from flowing from the power supply to the power supply stabilizing capacitor when the power supply is turned on. This prevents the semiconductor elements arranged in the DC / DC converter in the power supply system from breaking down. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-336609 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-mentioned power supply system, if the motor drive device suddenly stops while supplying power to the motor drive device after the precharge circuit has performed preliminary charging, current will flow from the power supply to the power supply stabilization capacitor if the voltage of the power supply stabilization capacitor is lower than the power supply voltage.

[0006] At this time, the switching element in the DC / DC converter is turned off. Therefore, the current flowing from the power supply to the power supply stabilization capacitor passes through the body diode that is parasitic to the switching element. This current passage causes the body diode to heat up.

[0007] One embodiment of the present invention has been made in view of the above-described problems, and has an object to provide a DC / DC converter capable of reducing heat generation therein. [Means for solving the problem]

[0008] In order to solve the above problems, a DC / DC converter according to one embodiment of the present invention includes a one-phase converter composed of an inductor, an upper switching element, and a lower switching element, and a control unit that switches the upper switching element between ON and OFF and switches the lower switching element between ON and OFF, and the control unit turns the upper switching element ON when a predetermined judgment condition is satisfied.

[0009] In the above configuration, if an abnormality occurs in an electric vehicle equipped with a DC / DC converter and the electric vehicle stops boost control, a direct current will flow from the input side to the output side of the DC / DC converter if the output voltage of the DC / DC converter is lower than the input voltage.

[0010] According to the above configuration, when a predetermined judgment condition is satisfied, the control unit turns on the upper switching element. As a result, the direct current flowing from the input side to the output side of the DC / DC converter does not flow through the body diode, which is a parasitic diode of the upper switching element, but flows through the channel portion of the upper switching element, which has a smaller resistance than the body diode. Therefore, the DC / DC converter can reduce heat generation within the DC / DC converter.

[0011] It is preferable that the control unit turns on the upper switching element when the DC current flowing through the inductor becomes equal to or greater than a current threshold.

[0012] According to the above configuration, the control unit can determine whether or not a predetermined determination condition is satisfied by measuring the direct current flowing through the inductor of the DC / DC converter.

[0013] It is preferable that the control unit turns on the upper switching element when the output voltage of the DC / DC converter becomes lower than the input voltage of the DC / DC converter by a voltage threshold value or more.

[0014] According to the above configuration, the control unit can determine whether or not a predetermined determination condition is satisfied by measuring the output voltage and the input voltage of the DC / DC converter.

[0015] The control unit may turn on the upper switching element when the output voltage of the DC / DC converter becomes lower than the input voltage of the DC / DC converter by a voltage threshold or more and when the DC current flowing through the inductor becomes equal to or greater than a current threshold.

[0016] It is preferable that a plurality of the single-phase converters are provided, and that the DC / DC converter is a multi-phase DC / DC converter.

[0017] According to the above configuration, even if the DC / DC converter is a multi-phase DC / DC converter, heat generation within the DC / DC converter can be reduced. Effect of the Invention

[0018] According to one aspect of the present invention, heat generation in a DC / DC converter can be reduced. [Brief description of the drawings]

[0019] [Figure 1] 1 is a schematic configuration diagram of an electric vehicle equipped with a DC / DC converter according to a first embodiment of the present invention. [Diagram 2] 4 shows a flowchart of a control process of the DC / DC converter. [Diagram 3] 4 is a diagram for explaining a current path when the electric vehicle performs precharging. FIG. [Figure 4] 4 is a diagram for explaining a current path when the electric vehicle starts boost control. FIG. [Diagram 5] 10A and 10B are diagrams illustrating the operation of the upper switching element and the lower switching element when the electric vehicle starts boost control. [Figure 6] 10A and 10B are diagrams illustrating other operations of the upper and lower switching elements when the electric vehicle starts boost control. [Figure 7] 4 is a diagram for explaining a current path when the electric vehicle stops boost control. FIG. [Figure 8] FIG. 11 is a schematic configuration diagram of an electric vehicle equipped with a DC / DC converter according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] [Embodiment 1] Hereinafter, the first embodiment of the present invention will be described in detail.

[0021] <Electric vehicle configuration> 1 is a schematic configuration diagram of an electric vehicle equipped with a DC / DC converter 1 according to embodiment 1. In embodiment 1, an embodiment in which the DC / DC converter 1 is a DC / DC converter equipped in an electric vehicle will be described as an example.

[0022] As shown in FIG. 1, the electric vehicle includes a DC / DC converter 1, a high-voltage power supply 2, a power supply control unit 3, a contactor 4, a pre-charge circuit 5, a storage capacitor 7, an inverter 8, and a motor 9.

[0023] The high-voltage power supply 2 supplies a DC voltage to the DC / DC converter 1 via a contactor 4 or a precharge circuit 5. For example, the high-voltage power supply 2 supplies a DC voltage of 200 V to the DC / DC converter 1.

[0024] The power supply control unit 3 turns on or off the contactor 4. The power supply control unit 3 also turns on or off a contactor 51 included in a pre-charge circuit 5. The pre-charge circuit 5 will be described in detail later.

[0025] When the power supply control unit 3 turns the contactor 4 ON and the contactor 51 OFF, a current flows from the high voltage power supply 2 through the contactor 4 to the DC / DC converter 1. When the power supply control unit 3 turns the contactor 4 OFF and the contactor 51 ON, a current flows from the high voltage power supply 2 through the pre-charge circuit 5 to the DC / DC converter 1. When the power supply control unit 3 turns the contactor 4 OFF and the contactor 51 OFF, no current flows from the high voltage power supply 2 to the DC / DC converter 1.

[0026] The contactor 4 is, for example, a relay-type electromagnetic switch.

[0027] The pre-charge circuit 5 is a circuit for preventing an inrush current from flowing from the high-voltage power supply 2 to the DC / DC converter 1 when the high-voltage power supply 2 is started up. The pre-charge circuit 5 includes the above-mentioned contactor 51 and a resistor 52 connected in series to the contactor 51. The contactor 51 is, for example, a relay-type electromagnetic switch.

[0028] When an inrush current flows into the DC / DC converter 1, there is a risk that the semiconductor elements inside the DC / DC converter 1 will malfunction. Therefore, when the high-voltage power supply 2 is started, the power supply control unit 3 turns off the contactor 4 and turns on the contactor 51, so that the direct current flowing from the high-voltage power supply 2 to the DC / DC converter 1 passes through the pre-charge circuit 5. The direct current will flow through the resistor 52 of the pre-charge circuit 5, and the current value of the direct current will decrease by the value of the resistance of the resistor 52. Therefore, according to the pre-charge circuit 5, it is possible to prevent an inrush current from flowing into the DC / DC converter 1.

[0029] The DC / DC converter 1 charges the storage capacitor 7. The storage capacitor 7 discharges to supply a direct current to the inverter 8.

[0030] The inverter 8 converts the direct current supplied from the storage capacitor 7 into an alternating current.

[0031] The motor 9 is driven when an alternating current is supplied from the inverter 8. In the example of FIG. 1, there is one motor 9, but there may be a plurality of motors.

[0032] <Functional configuration of the DC / DC converter> The DC / DC converter 1 is a circuit that converts the direct current voltage supplied from the high-voltage power supply 2. For example, when the direct current voltage of the high-voltage power supply 2 is 200V, the DC / DC converter 1 converts the 200V direct current voltage into a 450V direct current voltage. Also, the DC / DC converter can step down the direct current voltage supplied from the high-voltage power supply 2.

[0033] The DC / DC converter 1 includes a first input terminal T1, a second input terminal T2, an inductor L1, an upper switching element Fu1, a lower switching element Fd1, a smoothing capacitor C, a first output terminal T3, a second output terminal T4, and a control unit 10. Note that the DC / DC converter 1 may further include a first voltmeter D1, a second voltmeter D2, and an ammeter E1.

[0034] The first input terminal T1 is connected to the positive terminal of the high voltage power supply 2 via a contactor 4 or a precharge circuit 5. The second input terminal T2 is connected to the negative terminal of the high voltage power supply 2.

[0035] The inductor L1, the upper switching element Fu1, and the lower switching element Fd1 constitute a one-phase converter. The upper switching element Fu1 is, for example, a metal oxide semiconductor-field effect transistor (MOS-FET). The lower switching element Fd1 is, for example, a MOS-FET.

[0036] One terminal of the inductor L1 is connected to the first input terminal, and the other terminal is connected to the source of the upper switching element Fu1. The inductor L1 stores or discharges a direct current supplied from the high-voltage power supply 2.

[0037] The gate of the upper switching element Fu1 is connected to the control unit 10, and the drain is connected to the first output terminal T3.

[0038] The gate of the lower switching element Fd1 is connected to the control unit 10, the drain is connected to the other terminal of the inductor L1 and the source of the upper switching element, and the source is connected to the second input terminal T2 and the second output terminal T4.

[0039] A body diode Bu1 is formed between the source and drain of the upper switching element Fu1. The body diode Bu1 is a parasitic diode of the upper switching element Fu1. When the upper switching element Fu1 is ON, the current flowing through the upper switching element Fu1 does not flow through the body diode Bu1, but through a channel portion having a smaller resistance than the body diode Bu1. When the upper switching element Fu1 is OFF, the current flowing through the body diode Bu1.

[0040] A body diode Bd1 is formed between the source and drain of the low-side switching element Fd1. The body diode Bd1 is a parasitic diode of the low-side switching element Fd1. When the low-side switching element Fd1 is ON, the current flowing through the low-side switching element Fd1 does not flow through the body diode Bd1, but through a channel portion having a smaller resistance than the body diode Bd1. When the low-side switching element Fd1 is OFF, the current flowing through the body diode Bd1.

[0041] The upper switching element Fu1 is turned ON when an H-level gate signal Gu1 is input to its gate from the control unit 10. On the other hand, the upper switching element Fu1 is turned OFF when an L-level gate signal Gu1 is input to its gate from the control unit 10.

[0042] The low-side switching element Fd1 is turned ON when an H-level gate signal Gd1 is input to its gate from the control unit 10. On the other hand, the low-side switching element Fd1 is turned OFF when an L-level gate signal Gd1 is input to its gate from the control unit 10.

[0043] The smoothing capacitor C is connected between the first output terminal T3 and the second output terminal T4. The smoothing capacitor C smoothes the output voltage Vout that is output between the first output terminal T3 and the second output terminal T4.

[0044] The first voltmeter D1 is connected between the first input terminal T1 and the second input terminal T2. The first voltmeter D1 measures the input voltage Vin between the first input terminal T1 and the second input terminal T2. The first voltmeter D1 outputs a measurement result H1 to the control unit 10.

[0045] The second voltmeter D2 is connected between the first output terminal T3 and the second output terminal T4. The second voltmeter D2 measures the output voltage Vout between the first output terminal T3 and the second output terminal T4. The second voltmeter D2 outputs a measurement result H2 to the control unit 10.

[0046] The ammeter E1 is connected between the inductor L1 and the first input terminal T1. The ammeter E1 measures the direct current I1 flowing through the inductor L1. The ammeter E1 outputs the measurement result J1 to the control unit 10.

[0047] <Control Processing of DC / DC Converter> Figure 2 shows a flowchart of the control processing of the DC / DC converter 1. When the high-voltage power supply 2 of the electric vehicle shown in Figure 1 is activated, the control of the DC / DC converter 1 is started.

[0048] Step S101: The electric vehicle performs pre-charging to store the storage capacitor 7. More specifically, the power supply control unit 3 turns off the contactor 4 and turns on the contactor 51. The control unit 10 turns off the upper switching element Fu1 and turns off the lower switching element Fd1. If a large current is required for pre-charging, the control unit 10 may turn on the upper switching element Fu1. Next, it proceeds to step S102.

[0049] Here, the current path when the electric vehicle performs pre-charging will be described.

[0050] Figure 3 is a diagram for explaining the current path when the electric vehicle performs pre-charging.

[0051] When the electric vehicle performs pre-charging, the DC / DC converter 1 stores the direct current I1 in the storage capacitor 7.

[0052] As shown in Figure 3, the direct current I1 flows from the high-voltage power supply 2 through the DC / DC converter 1 to the storage capacitor 7. There are a current path R1 and a current path R2 in the path of the direct current I1.

[0053] The current path R1 is a path through which the DC current I1 flows through the body diode Bu1 of the upper switching element Fu1. The current path R1 is a path that corresponds to when the upper switching element Fu1 is OFF. The current path R2 is a path through which the DC current I1 flows through the channel portion of the upper switching element Fu1. The current path R2 is a path that corresponds to when the upper switching element Fu1 is ON.

[0054] Step S102: The electric vehicle starts boost control. The boost control is a control for supplying power to the inverter 8 for rotating the motor 9. More specifically, the power supply control unit 3 turns on the contactor 4 and turns off the contactor 51. The control unit 10 turns off the upper switching element Fu1 and controls the lower switching element Fd1 with PWM (Pulse Width Modulation). When the load applied to the motor 9 is high, the control unit 10 may also PWM control the upper switching element Fu1. However, the control unit 10 PWM controls the upper switching element Fu1 so that the ON period of the upper switching element Fu1 and the OFF period of the lower switching element Fd1 coincide with each other, and the OFF period of the upper switching element Fu1 and the ON period of the lower switching element Fd1 coincide with each other. Next, the process proceeds to step S103.

[0055] Here, the current path when the electric vehicle starts boost control will be described.

[0056] FIG. 4 is a diagram for explaining a current path when the electric vehicle starts boost control.

[0057] The electric vehicle starts boost control when power is stored in the storage capacitor 7 by precharging. The boost control causes the output voltage Vout of the DC / DC converter 1 to be stored in the storage capacitor 7. At this time, the control unit 10 PWM controls the lower switching element Fd1. When the motor 9 is under a low load, the control unit 10 turns off the upper switching element Fu1. When the motor 9 is under a high load, the control unit 10 also PWM controls the upper switching element Fu1.

[0058] As shown in FIG. 4, the paths of the DC current I1 include a current path R3, a current path R4, and a current path R5.

[0059] Current path R3 is a path through which DC current I1 flows through the channel portion of the low-side switching element Fd1. Current path R3 is a path that corresponds to when the low-side switching element Fd1 is ON. Current path R4 is a path through which DC current I1 flows through the body diode Bu1 of the high-side switching element Fu1. Current path R4 is a path that corresponds to when the low-side switching element Fd1 is OFF and the high-side switching element Fu1 is OFF. Current path R5 is a path through which DC current I1 flows through the channel portion of the high-side switching element Fu1. Current path R5 is a path that corresponds to when the high-side switching element Fu1 is ON.

[0060] Fig. 5 is a diagram illustrating the operation of the upper switching element Fu1 and the lower switching element Fd1 when the electric vehicle starts boost control. Fig. 5 corresponds to the case where the load applied to the motor 9 is low.

[0061] As shown in FIG. 5, the upper switching element Fu1 is OFF during the period from time t10 to time t14. On the other hand, the lower switching element Fd1 is ON during the period from time t10 to time t11, OFF during the period from time t11 to time t12, ON during the period from time t12 to time t13, and OFF during the period from time t13 to time t14. The period from time t10 to time t11 is the same as the period from time t12 to time t13. The period from time t11 to time t12 is the same as the period from time t13 to time t14. That is, the control unit 10 PWM controls the lower switching element Fd1 based on the following duty ratio.

[0062] Duty ratio: (period from time t10 to time t11) / (period from time t10 to time t12).

[0063] Fig. 6 is a diagram for explaining another operation of the upper switching element Fu1 and the lower switching element Fd1 when the electric vehicle starts boost control. Fig. 6 corresponds to the case where the load applied to the motor 9 is high.

[0064] 6, the upper switching element Fu1 is OFF during the period from time t20 to time t21, ON during the period from time t21 to time t22, OFF during the period from time t22 to time t23, and ON during the period from time t23 to time t24. The period from time t20 to time t21 is the same as the period from time t22 to time t23. The period from time t21 to time t22 is the same as the period from time t23 to time t24. That is, the control unit 10 PWM controls the upper switching element Fu1 based on the following duty ratio.

[0065] Duty ratio: (period from time t21 to time t22) / (period from time t21 to time t23).

[0066] On the other hand, the lower switching element Fd1 is ON during the period from time t20 to time t21, OFF during the period from time t21 to time t22, ON during the period from time t22 to time t23, and OFF during the period from time t23 to time t24. The period from time t20 to time t21 is the same as the period from time t22 to time t23. The period from time t21 to time t22 is the same as the period from time t23 to time t24. That is, the control unit 10 PWM controls the lower switching element Fd1 based on the following duty ratio.

[0067] Duty ratio: (period from time t20 to time t21) / (period from time t20 to time t22).

[0068] Step S103: The electric vehicle stops the boost control. More specifically, the control unit 10 turns off the upper switching element Fu1 and turns off the lower switching element Fd1. The boost control stop in step S103 means a stop caused by an abnormality occurring in the electric vehicle. An abnormality in the electric vehicle refers to, for example, a state in which the inverter 8 or the motor 9 breaks down and stops their operation. Specific examples of abnormalities occurring in the electric vehicle include (1) a situation in which the inverter 8 has a short circuit failure at a timing when the inverter 8 should not operate, causing a current to flow into the inverter 8 side, and (2) a situation in which the contactor 4, which should normally be turned off, does not turn off when the boost control is stopped. When an abnormality occurs in the electric vehicle, the electric vehicle stops the boost control and also stops the control of the DC / DC converter 1. Next, the process proceeds to step S104.

[0069] Here, the current path when the boost control of the electric vehicle is stopped will be described.

[0070] FIG. 7 is a diagram for explaining a current path when the electric vehicle stops boost control.

[0071] As shown in Fig. 7, a DC current I1 flows from a high voltage power supply 2 through a DC / DC converter 1 to a storage capacitor 7. The path of the DC current I1 is a current path R5. The current path R5 is a path through which the DC current I1 flows through a channel portion of the upper switching element Fu1. This path corresponds to when the upper switching element Fu1 is ON.

[0072] Step S104: The control unit 10 receives the measurement result H1 from the first voltmeter D1 and the measurement result H2 from the second voltmeter D2. The control unit 10 acquires the input voltage Vin from the measurement result H1 and the output voltage Vout from the measurement result H2. If the input voltage Vin and the output voltage Vout satisfy the determination condition (YES in step S104), the process proceeds to step S105. On the other hand, if the input voltage Vin and the output voltage Vout do not satisfy the determination condition (NO in step S104), the process proceeds to step S106.

[0073] Here, the above-mentioned judgment condition is a condition that the output voltage Vout is lower than the input voltage Vin by at least a voltage threshold Th1. The voltage threshold Th1 is, for example, 10 V. However, the voltage threshold Th1 depends on the design value of the maximum current of the DC / DC converter 1, the rating of the body diode of the switching element mounted in the DC / DC converter 1, etc.

[0074] Step S105: The control unit 10 turns on the high-side switching element Fu1. The control unit 10 keeps the low-side switching element Fd1 OFF. Next, the process proceeds to step S106.

[0075] Here, a current path when the control unit 10 turns on the upper switching element Fu1 will be described.

[0076] FIG. 7 is a diagram for explaining a current path when the control unit 10 turns on the upper switching element Fu1.

[0077] 7, the path of the DC current I1 is the current path R5. The current path R5 is a path through which the DC current I1 flows through the channel portion of the upper switching element Fu1. The current path R5 is a path that corresponds to when the upper switching element Fu1 is ON.

[0078] Step S106: If there is a request to start boost control (YES in step S106), the process returns to step S102. Otherwise (NO in step S106), this control process ends.

[0079] <Effects of the First Embodiment> When an abnormality occurs in the electric vehicle and the electric vehicle stops the boost control, if the output voltage Vout is lower than the input voltage Vin, a direct current flows from the high voltage power supply 2 to the DC / DC converter 1. At this time, since the upper switching element Fu1 is OFF, the direct current flows through the body diode Bu1 of the upper switching element Fu1. According to the DC / DC converter 1, when the above-mentioned judgment condition is satisfied, that is, when the output voltage Vout is lower than the input voltage Vin by the voltage threshold value Th1 or more, the control unit 10 turns on the upper switching element Fu1. As a result, the direct current flowing from the high voltage power supply 2 to the DC / DC converter 1 flows through a channel portion having a smaller resistance than the body diode Bu1. The heat generated when the direct current flows through the body diode Bu1 is greater than the heat generated when the direct current flows through the channel portion of the upper switching element Fu1. Therefore, according to the DC / DC converter 1, the heat generation in the DC / DC converter 1 can be reduced.

[0080] <Variation 1> The only difference between this modified example 1 and the above-described embodiment 1 is the determination condition used in step S104 in FIG.

[0081] In this first modification, the condition that the DC current I1 flowing through the inductor L1 is equal to or greater than a current threshold value Th2 is used as the determination condition used in step S104 in Fig. 2. The current threshold value Th2 is, for example, 10 A. However, the current threshold value Th2 depends on the design value of the maximum current of the DC / DC converter 1, the rating of the body diode of the switching element mounted in the DC / DC converter 1, and the like.

[0082] <Variation 2> The only difference between this modified example 2 and the above-described embodiment 1 is the determination condition used in step S104 in FIG.

[0083] In the present modified example 2, the condition used in step S104 in FIG. 2 is that both the judgment condition in the above-mentioned first embodiment and the judgment condition in the above-mentioned modified example 1 are satisfied.

[0084] 2 can be more accurately performed than when the determination is made using only one of the determination conditions of the above-mentioned embodiment 1 or the determination conditions of the above-mentioned modification 1. Also, according to the present modification 2, it is possible to prevent overlooking of the direct current flowing from the high-voltage power supply 2 to the DC / DC converter 1, compared to when the determination is made using only one of the determination conditions of the above-mentioned embodiment 1 or the determination conditions of the above-mentioned modification 1.

[0085] [Embodiment 2] Other embodiments of the present invention will be described below. For ease of explanation, the same reference numerals are given to members having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0086] 8 is a schematic configuration diagram of an electric vehicle equipped with a DC / DC converter 1N according to embodiment 2. DC / DC converter 1N differs from DC / DC converter 1 in that DC / DC converter 1 includes a single-phase converter, whereas DC / DC converter 1N includes a multi-phase converter.

[0087] 8, the DC / DC converter 1N includes a first-phase converter including an inductor L1, an upper switching element Fu1, and a lower switching element Fd1, a second-phase converter including an inductor L2, an upper switching element Fu2, and a lower switching element Fd2, a third-phase converter including an inductor L3, an upper switching element Fu3, and a lower switching element Fd3, and an n-th phase converter including an inductor Ln, an upper switching element Fun, and a lower switching element Fdn, where "n" in the n-th phase is an integer equal to or greater than 2.

[0088] The functions and operations of the inductor, upper switching element, and lower switching element constituting the converter of each phase are similar to those of the inductor L1, upper switching element Fu1, and lower switching element Fd1 of the DC / DC converter 1, and therefore the description thereof will not be repeated. However, with regard to the PWM control shown in Figures 5 and 6 above, the phases of pulses are shifted from each other between the phases.

[0089] [Additional Notes] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0090] 1,1N DC / DC Converter 2 High voltage power supply 3 Power supply control section 4, 51 Contactor 5 Precharge Circuit 7. Storage Capacitor 8. Inverter 9. Motor 10 Control section 52 Resistance Bu1, Bd1 body diodes D1 First voltmeter D2 Second voltmeter E1 ammeter Fu1, Fu2, Fu3, Fun Upper switching element Fd1, Fd2, Fd3, Fdn Lower switching elements L1, L2, L3, Ln Inductors T1 First input terminal T2 Second input terminal T3 1st output terminal T4 2nd output terminal Th1 voltage threshold Th2 current threshold Vin Input voltage Vout Output voltage

Claims

1. a one-phase converter including an inductor, an upper switching element, and a lower switching element; a control unit that switches the upper switching element between ON and OFF and switches the lower switching element between ON and OFF; A DC / DC converter comprising: The control unit turns on the upper switching element when an output voltage of the DC / DC converter becomes lower than an input voltage of the DC / DC converter by a voltage threshold value or more.

2. A one-phase converter including an inductor, an upper switching element, and a lower switching element; a control unit that switches the upper switching element between ON and OFF and switches the lower switching element between ON and OFF; A DC / DC converter comprising: The control unit is The output voltage of the DC / DC converter is lower than the input voltage of the DC / DC converter by a voltage threshold or more, and When the DC current flowing through the inductor exceeds the current threshold, a second switching element connected to the first switching element;

3. A plurality of the one-phase converters are provided, 3. The DC / DC converter according to claim 1, wherein the DC / DC converter is a multi-phase DC / DC converter.

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