Dc-dc converter

Abstract

A DCDC converter that suppresses an inrush current flowing to a capacitor is provided. A DCDC converter (1) includes: first and second capacitors (C1, C2) provided between a reference conductive path (93) and one of first and second conductive paths (91, 92); first and second cut-off switches (71, 72) interposed between a first external power supply (61) and the first capacitor (C1) and between a second external power supply (62) and the second capacitor (C2); and a control unit (12) that switches the first and second cut-off switches (71, 72) between an on state and an off state, wherein, in a case where a switch from cut-off control that maintains the first and second cut-off switches (71, 72) in the off state to energization control that maintains the first and second cut-off switches (71, 72) in the on state is performed, the control unit (12) performs intermittent control that intermittently places the first and second cut-off switches (71, 72) in the on state before the energization control.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a DCDC converter. BACKGROUND

[0002] In the past, a structure in which a capacitor is provided to an input side or an output side of a conductive path in a DCDC converter has been known. For example, a DCDC converter disclosed in Patent Literature 1 electrically connects an input side capacitor to an input side conductive path and electrically connects an output side capacitor to an output side conductive path.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Publication No. 2018-61438 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] In a DCDC converter, a structure in which a switch is interposed between an external power supply and a capacitor is easily adopted.

[0008] For example, in the past, a DCDC converter in which a cut-off switch is provided to an input side conductive path or an output side conductive path has been proposed in anticipation of a short circuit failure or the like of a circuit. Such a DCDC converter can adopt a structure in which a cut-off switch is interposed between an external power supply provided to an input side or an output side and a capacitor electrically connected to a conductive path. In a DCDC converter adopting such a structure, if the cut-off switch is switched from an open state to a closed state in a state in which the capacitor is not sufficiently charged, a large rush current is easily caused to flow to the capacitor according to the switching of the switch to the closed state. In addition, a DCDC converter in which a switch is interposed between an external power supply and a capacitor is not limited to the above example, and the same problem can occur in any example.

[0009] Therefore, in the present disclosure, a technology capable of suppressing a rush current flowing to a capacitor in a DCDC converter is provided.

[0010] TECHNICAL SOLUTION FOR SOLVING THE PROBLEMS

[0011] The DCDC converter of one embodiment of the present disclosure includes a voltage conversion portion provided between a first conductive path and a second conductive path, a capacitor provided between a conductive path of one of the first conductive path and the second conductive path and a reference conductive path, a switch between an external power supply and the capacitor, and a control portion that switches the switch between an on state and an off state, cuts off inflow of current from the external power supply to the capacitor when the switch is in the off state, and allows inflow of current from the external power supply to the capacitor via the conductive path of one of the first conductive path and the second conductive path at least when the switch is in the on state. The control portion performs intermittent control that makes the switch intermittently in the on state before switching from off control that maintains the switch in the off state to on control that maintains the switch in the on state.

[0012] Effect of Invention

[0013] The DCDC converter of one embodiment of the present disclosure can suppress rush current flowing into a capacitor. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 FIG. 1 is a circuit diagram illustrating a DCDC converter of Embodiment 1.

[0015] Figure 2 FIG. 2 is a timing chart illustrating one example of waveforms of drive signals output from a control portion in first intermittent control and second intermittent control to first cut-off switches and second cut-off switches in the DCDC converter of Embodiment 1.

[0016] Figure 3 FIG. 3 is a circuit diagram illustrating a path of current flowing from a second external power supply to a second capacitor when the second cut-off switch is in the on state at the time of performing the second intermittent control and a path of current flowing from a first external power supply to a first capacitor when the first cut-off switch is in the on state at the time of performing the first intermittent control in the DCDC converter of Embodiment 1.

[0017] Figure 4 FIG. 4 is a circuit diagram illustrating a DCDC converter of Embodiment 2.

[0018] Figure 5 FIG. 5 is one example of waveforms of drive signals output from a control portion in intermittent control to first cut-off switches, second cut-off switches, and a semiconductor switch in the DCDC converter of another embodiment. DETAILED DESCRIPTION

[0019] [Explanation of Embodiment of the Present Disclosure]

[0020] First, an embodiment of the present disclosure is described.

[0021] (1) A DCDC converter of one embodiment of the present disclosure includes a voltage conversion unit, a capacitor, a switch, and a control unit. The voltage conversion unit is provided between a first conductive path and a second conductive path. The capacitor is provided between the conductive path of one of the first conductive path and the second conductive path and a reference conductive path. The switch is interposed between an external power supply and the capacitor. The control unit switches the switch between an on state and an off state. When the switch is in the off state, inflow of current from the external power supply to the capacitor is cut off. At least when the switch is in the on state, inflow of current from the external power supply to the capacitor through the conductive path of one of the first conductive path and the second conductive path is permitted. The control unit performs intermittent control that makes the switch intermittently in the on state before switching from off control that maintains the switch in the off state to on control that maintains the switch in the on state.

[0022] The DCDC converter of the above structure (1) can more suppress the rush current flowing into the capacitor when the switch is switched from the off control to the on control because of the intermittent control, compared with the case where the on control is started at the end timing of the off control. Thus, the DCDC converter can be less likely to cause a problem due to too much rush current flowing into the capacitor when the off control is released.

[0023] (2) The DCDC converter of the above structure (1) can be a DCDC converter further including the following feature. The switch can include a cutoff switch provided between the external power supply and the voltage conversion unit in the conductive path of one of the first conductive path and the second conductive path. The cutoff switch can be configured to permit conduction from the external power supply side to the voltage conversion unit side when the cutoff switch is in the on state and cut off the conduction from the external power supply side to the voltage conversion unit side when the cutoff switch is in the off state.

[0024] The DCDC converter of the above structure (2) can suppress too much current at the time of release of the off control using the cutoff switch needed for the protection function while suppressing an increase in a special dedicated component or the like. Thus, the DCDC converter can suppress the rush current to the capacitor with a simpler structure.

[0025] (3) The DCDC converter described in the above (1) can be a DCDC converter further having the following feature. The switch can include a first cut-off switch provided in the first conductive path between the first external power supply and the voltage conversion section and a second cut-off switch provided in the second conductive path between the second external power supply and the voltage conversion section. The first cut-off switch can allow electric conduction from the first external power supply side to the voltage conversion section side when the first cut-off switch is in an on state, and cut off the electric conduction from the first external power supply side to the voltage conversion section side when the first cut-off switch is in an off state. The second cut-off switch can allow electric conduction from the second external power supply side to the voltage conversion section side when the second cut-off switch is in an on state, and cut off the electric conduction from the second external power supply side to the voltage conversion section side when the second cut-off switch is in an off state. The control section can, in a case where the control is switched from the first cut-off control that maintains the first cut-off switch in the off state to the first electric conduction control that maintains the first cut-off switch in the on state, perform the first intermittent control that intermittently brings the first cut-off switch in the on state before the first electric conduction control. The control section can, in a case where the control is switched from the second cut-off control that maintains the second cut-off switch in the off state to the second electric conduction control that maintains the second cut-off switch in the on state, perform the second intermittent control that intermittently brings the second cut-off switch in the on state before the second electric conduction control.

[0026] The DCDC converter described in the above (3) is provided with a cut-off switch in either of the first conductive path and the second conductive path, and can each achieve protection. Further, the DCDC converter achieves such a protection function while suppressing a rush current flowing from the external power supply to the capacitor in a case where the cut-off control is released by the cut-off switch of either of the first conductive path and the second conductive path.

[0027] (4) The DCDC converter described in any one of the above (1) to (3) can be a DCDC converter in which the switch includes a semiconductor switch formed as part of the voltage conversion section.

[0028] The DCDC converter described in the above (4) can suppress excessive current at the time of release of the cut-off control using the semiconductor switch required for achieving the function of the voltage conversion section while suppressing an increase in a special dedicated component or the like. Therefore, the DCDC converter can suppress the rush current to the capacitor with a simpler structure.

[0029] (5) The DCDC converter described in any one of the above (1) to (4) can be a DCDC converter further having the following feature. The control section can make the on time of the switch longer in a part of the entire period during which the intermittent control is performed than the on time of the switch in a period before the part.

[0030] When the time of each on state (hereinafter also referred to as on time) is constant in the intermittent control, the more the on states are repeated, the smaller the current flowing into the capacitor in each on time becomes. This phenomenon is one of the reasons that the charging time of the capacitor becomes longer. In contrast, the DCDC converter described in the above (5) relatively lengthens the on time during a relatively late period, so it is possible to suppress the reduction in current due to the repetition of the on states. Therefore, this DCDC converter can complete the charging of the capacitor more promptly while achieving the function of suppressing the inrush current to the capacitor.

[0031] (6) The DCDC converter described in any one of the above (1) to (5) can also be a DCDC converter further having the following feature. The voltage conversion section has a driving switching element, and is able to apply an output voltage to one of the first conductive path and the second conductive path by boosting or reducing the voltage applied to the one of the first conductive path and the second conductive path according to the on-off operation of the driving switching element. The control section performs voltage conversion control of turning the driving switching element on and off, and is able to make the frequency of the on-off operation of the switch in the intermittent control higher than the frequency of the on-off operation of the driving switching element in the voltage conversion control.

[0032] The DCDC converter described in the above (6) is able to make the frequency of the on-off operation of the switch in the intermittent control higher than the frequency of the on-off operation of the driving switching element in the voltage conversion control. That is, this DCDC converter is able to further shorten each on time in the intermittent control, and is able to further reduce the current flowing into the capacitor in each on time in the intermittent control. Therefore, this DCDC converter is able to more reliably suppress the inrush current to the capacitor.

[0033] (7) The DCDC converter described in any one of the above (1) to (6) can also be a DCDC converter in which the capacitor is a ceramic capacitor.

[0034] A ceramic capacitor is able to be downsized compared to an electrolytic capacitor having the same electrical characteristics. On the other hand, a ceramic capacitor has a smaller internal resistance compared to an electrolytic capacitor. Therefore, because the internal resistance is smaller, a ceramic capacitor has a tendency that the inrush current easily becomes larger compared to an electrolytic capacitor. The DCDC converter described in the above (7) is able to well suppress the magnitude of the inrush current to the capacitor in one on state even when a ceramic capacitor is used by performing the intermittent control.

[0035] (8) In the DCDC converter described in any one of the above (1) to (7), it is also desirable that the reference conductive path is a conductive path held at a reference potential lower than the potential of the above one of the conductive paths.

[0036] (9) In the DCDC converter described in the above (2), the control section switches the cut-off switch to the open state in a case where a current of the threshold value or more flows in the one of the conductive paths, or in a case where the voltage becomes the threshold value or less.

[0037] [Details of Embodiments of the Present Disclosure]

[0038] Embodiment 1

[0039] [Outline of DCDC Converter 1]

[0040] Figure 1 The DCDC converter 1 illustrated is configured as, for example, a step-up / down DCDC converter for a vehicle, and is structured to step up or step down a direct current voltage applied to one of the first conductive path 91 and the second conductive path 92 and output to the other conductive path.

[0041] The DCDC converter 1 has a first conductive path 91 and a second conductive path 92 as power lines. The first conductive path 91 is a wiring electrically connected to and in conduction with a terminal on a high potential side of a first external power supply 61. The first conductive path 91 is structured to be applied with a predetermined direct current voltage from the first external power supply 61. The second conductive path 92 is a wiring electrically connected to and in conduction with a terminal on a high potential side of a second external power supply 62. The second conductive path 92 is structured to be applied with a predetermined direct current voltage from the second external power supply 62.

[0042] In the present disclosure, "electrically connected" is intended to be a structure connected in a state (a state of making a current flow) in which both of the connection objects are in conduction with each other in a manner that the potentials of both of the connection objects are equal. However, it is not limited to this structure. For example, "electrically connected" can also be a structure in which two connection objects are connected in a state of being able to be in conduction while an electrical component is interposed between the two connection objects.

[0043] The first external power supply 61 and the second external power supply 62 are configured by, for example, a known power storage unit such as a lead storage battery, a lithium ion battery, an electric double layer capacitor device, a lithium ion capacitor device, or another power storage section. The specific values of the output voltage of the first external power supply 61 and the output voltage of the second external power supply 62 are not particularly limited. The terminals on the low potential side of the first external power supply 61 and the second external power supply 62 are electrically connected to a ground portion not illustrated and maintained at a predetermined ground potential (0 V).

[0044] The DCDC converter 1 has a voltage conversion section 6, a first capacitor C1, a second capacitor C2, a cut-off switch 70, a first current detection section 81, a second current detection section 82, a third current detection section 83, a first voltage detection section, a second voltage detection section, and a control section 12.

[0045] The voltage conversion section 6 has a function of boosting or reducing the voltage applied to one of the first conductive path 91 and the second conductive path 92 to apply an output voltage to the other, in accordance with the on-off operation of the semiconductor switches T1, T2, T3, T4. The voltage conversion section 6 is provided between the first conductive path 91 and the second conductive path 92. The voltage conversion section 6 can perform a first conversion operation and a second conversion operation. The first conversion operation is at least one of an operation of reducing the voltage applied to the first conductive path 91 to apply the voltage to the second conductive path 92 and an operation of boosting the voltage applied to the second conductive path 92 to apply the voltage to the first conductive path 91. The second conversion operation is at least one of an operation of boosting the voltage applied to the first conductive path 91 to apply the voltage to the second conductive path 92 and an operation of reducing the voltage applied to the second conductive path 92 to apply the voltage to the first conductive path 91.

[0046] The voltage conversion section 6 has the semiconductor switches T1, T2, T3, T4 and the inductor L arranged in an H-bridge configuration, and functions as a DCDC converter that performs so-called bidirectional step-up and step-down. The semiconductor switches T1, T2, T3, T4 are each configured as an N-channel MOSFET. The semiconductor switch T1 is a first high-voltage-side element. The semiconductor switch T2 is a first low-voltage-side element. The semiconductor switch T3 is a second high-voltage-side element. The semiconductor switch T4 is a second low-voltage-side element. The semiconductor switches T1, T2 constitute a first switching section S1. The semiconductor switches T3, T4 constitute a second switching section S2.

[0047] Each of the semiconductor switches T1, T2, T3, T4 is configured to have a parasitic diode T11, T12, T13, T14 as a parasitic component. Specifically, each of the semiconductor switches T1, T2, T3, T4 is configured such that the cathode of each parasitic diode T11, T12, T13, T14 is electrically connected to the drain side and the anode is electrically connected to the source side of each semiconductor switch. The inductor L is configured as a known coil having a predetermined inductance.

[0048] In the voltage conversion section 6, the first conductive path 91 is electrically connected to the drain of the semiconductor switch Tl, and the drain of the semiconductor switch T2 and one end of the inductor L are electrically connected to the source of the semiconductor switch Tl. The second conductive path 92 is electrically connected to the drain of the semiconductor switch T3, and the drain of the semiconductor switch T4 and the other end of the inductor L are electrically connected to the source of the semiconductor switch T3. The sources of the semiconductor switches T2 and T4 are electrically connected to the ground G via a reference conductive path 93. A drive signal such as a PWM signal is input to the gates of the semiconductor switches Tl, T2, T3, and T4 from the control section 12. The reference conductive path 93 is a conductive path that is maintained at a reference potential (the potential of the ground G) that is lower than the potentials of the first conductive path 91 and the second conductive path 92.

[0049] The first capacitor Cl is provided between the first conductive path 91 and the reference conductive path 93. Specifically, one terminal of the first capacitor Cl is electrically connected to the first conductive path 91, and the other terminal is electrically connected to the reference conductive path 93.

[0050] The second capacitor C2 is provided between the second conductive path 92 and the reference conductive path 93. Specifically, one terminal of the second capacitor C2 is electrically connected to the second conductive path 92, and the other terminal is electrically connected to the reference conductive path 93. As the first capacitor Cl and the second capacitor C2, for example, a ceramic capacitor, a film capacitor, or the like is used. A ceramic capacitor and a film capacitor have a tendency to have a smaller internal resistance than an electrolytic capacitor. As the first capacitor Cl and the second capacitor C2, an electrolytic capacitor can also be used.

[0051] The cut-off switch 70 has a first cut-off switch 71 and a second cut-off switch 72. The first cut-off switch 71 is configured as, for example, an N-channel MOSFET. Specifically, the first cut-off switch 71 is formed in a structure that switches between an on state that allows bidirectional conduction of the first conductive path 91 and an off state that cuts off conduction of the first conductive path 91 in a direction from the first external power supply 61 to the voltage conversion section 6 side. The first cut-off switch 71 is interposed in the first conductive path 91, and one end side (source) is electrically connected to the voltage conversion section 6 and one terminal of the first capacitor Cl. The other end side (drain) of the first cut-off switch 71 is electrically connected to the first conductive path 91 on the first external power supply 61 side, and is formed in a structure that is switched between the on state and the off state by the control section 12. That is, the first cut-off switch 71 is provided between the first external power supply 61 and the voltage conversion section 6 in the first conductive path 91.

[0052] The first cut-off switch 71 is a switch S interposed between the first external power supply 61 and the first capacitor Cl. The first cut-off switch 71, when in an on state, allows at least energization from the first external power supply 61 to the voltage conversion section 6 side, and allows current to flow to the first capacitor Cl. The first cut-off switch 71, when in an off state, cuts off energization from the first external power supply 61 to the voltage conversion section 6 side, and cuts off current flow to the first capacitor Cl. A parasitic diode 71A is electrically connected to the first cut-off switch 71. The anode of the parasitic diode 71A is electrically connected to the voltage conversion section 6, and the cathode is electrically connected to the first conductive path 91 on the first external power supply 61 side.

[0053] The second cut-off switch 72 is configured as, for example, an N-channel MOSFET. Specifically, the second cut-off switch 72 is configured to switch between an on state that allows bidirectional energization of the second conductive path 92, and an off state that cuts off energization in the direction from the second external power supply 62 to the voltage conversion section 6 in the second conductive path 92. The second cut-off switch 72 is interposed in the second conductive path 92, and one end side (source) is electrically connected to a terminal of one of the voltage conversion section 6 and the second capacitor C2. The other end side (drain) of the second cut-off switch 72 is electrically connected to the second conductive path 92 on the second external power supply 62 side, and is configured to be switched between the on state and the off state by the control section 12. That is, the second cut-off switch 72 is provided between the second external power supply 62 and the voltage conversion section 6 in the second conductive path 92.

[0054] The second cut-off switch 72 is a switch S interposed between the second external power supply 62 and the second capacitor C2. The second cut-off switch 72, when in an on state, allows at least energization from the second external power supply 62 to the voltage conversion section 6 side, and allows current to flow to the second capacitor C2. The second cut-off switch 72, when in an off state, cuts off energization from the second external power supply 62 to the voltage conversion section 6 side, and cuts off current flow to the second capacitor C2. A parasitic diode 72A is electrically connected to the second cut-off switch 72. The anode of the parasitic diode 72A is electrically connected to the voltage conversion section 6, and the cathode is electrically connected to the second conductive path 92 on the second external power supply 62 side.

[0055] The first current detection section 81 is provided in the first conductive path 91 between the voltage conversion section 6 and the first cut-off switch 71. The second current detection section 82 is provided in the second conductive path 92 between the voltage conversion section 6 and the second cut-off switch 72. The third current detection section 83 is provided in the reference conductive path 93 between the voltage conversion section 6 and the ground G. The first current detection section 81, the second current detection section 82, and the third current detection section 83 are configured, for example, using a known current detection circuit such as a current transformer, a shunt resistor, or the like.

[0056] A first voltage detecting section (not shown) outputs a value indicative of the first voltage at the first conductive path 91 to the control section 12. A second voltage detecting section (not shown) outputs a value indicative of the second voltage at the second conductive path 92 to the control section 12.

[0057] The control section 12 is configured as, for example, a microcomputer. The control section 12 performs feedback control based on the value indicative of the first voltage at the first conductive path 91 and the value indicative of the second voltage at the second conductive path 92 from the first voltage detecting section and the second voltage detecting section and a target voltage value by a known method. Thereby, the control section 12 sets a duty ratio of the PWM signal supplied to the voltage conversion section 6. Also, the control section 12 outputs the set signal to the gates of the semiconductor switches T1, T2, T3, T4 of the voltage conversion section 6. The control section 12 performs voltage conversion control to turn the semiconductor switches T1, T2, T3, T4 on and off. The target voltage value can be a value set by the control section 12 or a value instructed from an external device such as an external ECU.

[0058] For example, in the case of performing the first conversion operation of stepping down from the first external power supply 61 to the second external power supply 62 or stepping up from the second external power supply 62 to the first external power supply 61, the control section 12 performs voltage conversion control of the first switching section S1. At this time, the control section 12 maintains the semiconductor switch T3 in the on state and maintains the semiconductor switch T4 in the off state. The semiconductor switches T1, T2 of the first switching section S1 are subjected to voltage conversion control, thereby performing on and off operations, and function as driving switching elements D1, D2 that step up or step down the voltage applied to one of the first conductive path 91 and the second conductive path 92 and apply the output voltage to the other.

[0059] In the case of performing the second conversion operation of stepping down from the second external power supply 62 to the first external power supply 61 or stepping up from the first external power supply 61 to the second external power supply 62, the control section 12 performs voltage conversion control of the second switching section S2. At this time, the control section 12 maintains the semiconductor switch T1 in the on state and maintains the semiconductor switch T2 in the off state. The semiconductor switches T3, T4 of the second switching section S2 are subjected to voltage conversion control, thereby performing on and off operations, and function as driving switching elements D3, D4 that step up or step down the voltage applied to one of the first conductive path 91 and the second conductive path 92 and apply the output voltage to the other.

[0060] 〔Operation in DCDC converter〕

[0061] Next, the operation of the DCDC converter 1 of the present disclosure will be described.

[0062] The control section 12 performs the cut-off control in a case where the ignition switch, not shown, provided in the vehicle is in the off state, and an ignition off signal indicating that the ignition switch is in the off state is input from a device (an external ECU or the like) provided outside the DCDC converter 1. Specifically, at this time, the control section 12 outputs a signal set to the L level to the gates of the semiconductor switches Tl, T2, T3, T4, the first cut-off switch 71, and the second cut-off switch 72, respectively. Thus, the semiconductor switches Tl, T2, T3, T4, the first cut-off switch 71, and the second cut-off switch 72 each become in the off state. In this way, the control section 12 causes the semiconductor switches Tl, T2, T3, T4, the first cut-off switch 71 (switch S), and the second cut-off switch 72 (switch S) to be maintained in the off state by performing the cut-off control. The cut-off control performed by the control section 12 on the first cut-off switch 71 is first cut-off control, and the cut-off control performed by the control section 12 on the second cut-off switch 72 is second cut-off control. At this time, the first capacitor Cl and the second capacitor C2 are in the uncharged state.

[0063] 〔Intermittent Control〕

[0064] If the ignition switch, not shown, provided in the vehicle is switched from the off state to the on state, an ignition on signal indicating that the ignition switch is in the on state is input to the control section 12 from the external ECU or the like. Then, the control section 12 performs intermittent control of intermittently bringing the first cut-off switch 71 and the second cut-off switch 72 into the on state before switching to the power-on control of maintaining the first cut-off switch 71 and the second cut-off switch 72 in the on state. Specifically, the control section 12 performs first intermittent control of intermittently bringing the first cut-off switch 71 into the on state before switching from the first cut-off control of maintaining the first cut-off switch 71 in the off state to the first power-on control of maintaining the first cut-off switch 71 in the on state. Also, the control section 12 performs second intermittent control of intermittently bringing the second cut-off switch 72 into the on state before switching from the second cut-off control of maintaining the second cut-off switch 72 in the off state to the second power-on control of maintaining the second cut-off switch 72 in the on state.

[0065] Specifically, as Figure 2As shown, the signal at the H level is repeated for a predetermined period P2, and then the signal at the L level is repeated for a predetermined period P3. The control section 12 alternately repeats outputting the H level signal and the L level signal to the gate of each of the first cut-off switch 71 and the second cut-off switch 72 during the period PI in which the first intermittent control and the second intermittent control (intermittent control) are performed. Thus, the first cut-off switch 71 and the second cut-off switch 72 become the on state in which the drain and the source are made conductive when the H level signal is input to the gate. The time P2 of the H level signal is shorter than the time of the H level signal of the PWM signal at the time of the voltage conversion control (not shown). That is, the frequency of the on-off operation of the first cut-off switch 71 (switch S) and the second cut-off switch 72 (switch S) in the first intermittent control and the second intermittent control (intermittent control) is greater than the frequency of the on-off operation of the drive switching elements D1, D2, D3, D4 (semiconductor switches T1, T2, T3, T4) in the voltage conversion control. In the second intermittent control, as shown, the current flows from the second external power supply 62 to the second capacitor C2 in the path shown by the arrow A2. In the first intermittent control, as shown, the current flows from the first external power supply 61 to the first capacitor C1 in the path shown by the arrow Al when the first cut-off switch 71 is in the on state. Figure 3

[0066] The first cut-off switch 71 and the second cut-off switch 72 become the off state in which the drain and the source are not made conductive when the L level signal is input to the gate. That is, the control section 12 intermittently causes the current to flow from the first external power supply 61 to the first capacitor C1 by performing the first intermittent control on the first cut-off switch 71. Also, the control section 12 intermittently causes the current to flow from the second external power supply 62 to the second capacitor C2 by performing the second intermittent control on the second cut-off switch 72. Thus, it is possible to suppress the current (surge current) flowing to the first capacitor C1 and the second capacitor C2 from becoming excessively large.

[0067] The DCDC converter 1 is configured such that the first current detection section 81 can detect the current flowing to the first conductive path 91. The DCDC converter 1 is configured such that the second current detection section 82 can detect the current flowing to the second conductive path 92. The DCDC converter 1 is configured such that the third current detection section 83 can detect the current flowing to the ground G via the first capacitor C1, the second capacitor C2, and the voltage conversion section 6. Thus, the DCDC converter 1 suppresses the current flowing to the first capacitor C1 and the second capacitor C2 from becoming excessively large, and thereby suppresses the excessively large current value from being detected in the first current detection section 81, the second current detection section 82, and the third current detection section 83.

[0068] ​Also, the charging of the first capacitor CI and the second capacitor C2 is promoted, and a condition for ending the first intermittent control and the second intermittent control is satisfied. Then, the control section 12 starts the first conversion operation or the second conversion operation after ending the first intermittent control and the second intermittent control in the first cut-off switch 71 and the second cut-off switch 72, respectively. The condition for ending the first intermittent control and the second intermittent control is, for example, a case where the current flowing to the first capacitor CI and the second capacitor C2 is less than a predetermined value, a case where a predetermined time has elapsed from the start of the first intermittent control and the second intermittent control, or the like. The case where the current flowing to the first capacitor CI and the second capacitor C2 is less than a predetermined value means a case where the current value detected in the first current detection section 81, the second current detection section 82, and the third current detection section 83 is less than a predetermined threshold value. Also, the control section 12 switches to the first conduction control that maintains the first cut-off switch 71 in the on state and switches to the second conduction control that maintains the second cut-off switch 72 in the on state.

[0069] [First conversion operation]

[0070] The first conversion operation (an operation of boosting the voltage applied to the second conductive path 92 to apply the voltage to the first conductive path 91 and an operation of stepping down the voltage applied to the first conductive path 91 to apply the voltage to the second conductive path 92) will be described. The control section 12 outputs a drive signal to the voltage conversion section 6. The drive signal in the first conversion operation is a signal that complementarily outputs, to each gate of the first switch section SI (semiconductor switches T1, T2 (driving switching elements D1, D2)) of the voltage conversion section 6, a PWM signal of a form in which a dead time is set. The first switch section SI (semiconductor switches T1, T2 (driving switching elements D1, D2)) is subjected to voltage conversion control by the drive signal. Specifically, during the period in which an on signal (for example, an H-level signal) is output to the semiconductor switch T1 (driving switching element D1), an off signal (for example, an L-level signal) is output to the semiconductor switch T2 (driving switching element D2). Also, during the period in which an on signal (for example, an H-level signal) is output to the semiconductor switch T2 (driving switching element D2), an off signal (for example, an L-level signal) is output to the semiconductor switch T1 (driving switching element D1), and voltage conversion control is performed in this manner.

[0071] The control section 12 continuously outputs an on signal (for example, an H-level signal) to the semiconductor switch T3 of the second switching section S2 while performing voltage conversion control of the first switching section S1, and maintains the semiconductor switch T3 in an on state. At the same time, the control section 12 continuously outputs an off signal (for example, an L-level signal) to the semiconductor switch T4 and maintains the semiconductor switch T4 in an off state. In the case where the voltage applied to the second conductive path 92 is boosted by the second voltage (input voltage) of the direct current and the voltage is applied to the first conductive path 91, the output voltage higher than the second voltage applied to the second conductive path 92 is applied to the first conductive path 91. Also, in the case where the voltage applied to the first conductive path 91 is stepped down by the first voltage (input voltage) of the direct current and the voltage is applied to the second conductive path 92, the output voltage lower than the first voltage applied to the first conductive path 91 is applied to the second conductive path 92.

[0072] 〔Second conversion operation〕

[0073] The second conversion operation (operation of stepping down the voltage applied to the second conductive path 92 and applying the voltage to the first conductive path 91 and operation of boosting the voltage applied to the first conductive path 91 and applying the voltage to the second conductive path 92) will be described. The control section 12 outputs a drive signal to the voltage conversion section 6. The drive signal in the second conversion operation is a signal in which a PWM signal in which a dead time is set is complementarily output to each gate of the second switching section S2 (semiconductor switches T3, T4 (driving switching elements D3, D4)) of the voltage conversion section 6. The second switching section S2 (semiconductor switches T3, T4 (driving switching elements D3, D4)) performs voltage conversion control by the drive signal. Specifically, in the process of outputting an on signal (for example, an H-level signal) to the semiconductor switch T3 (driving switching element D3), an off signal (for example, an L-level signal) is output to the semiconductor switch T4 (driving switching element D4). Also, in the process of outputting an on signal (for example, an H-level signal) to the semiconductor switch T4 (driving switching element D4), an off signal (for example, an L-level signal) is output to the semiconductor switch T3 (driving switching element D3), and voltage conversion control is performed in the above manner.

[0074] The control section 12 continues to output an ON signal (for example, an H-level signal) to the semiconductor switch T1 of the first switching section S1 so as to maintain the semiconductor switch T1 in the ON state, when performing voltage conversion control at the second switching section S2. At the same time, the control section 12 continues to output an OFF signal (for example, an L-level signal) to the semiconductor switch T2 so as to maintain the semiconductor switch T2 in the OFF state. In the case where the voltage is applied to the first conductive path 91 by stepping down the second voltage (input voltage) of the direct current applied to the second conductive path 92 through this control, an output voltage lower than the second voltage applied to the second conductive path 92 is applied to the first conductive path 91. Also, in the case where the voltage is applied to the second conductive path 92 by stepping up the first voltage (input voltage) of the direct current applied to the first conductive path 91, an output voltage higher than the first voltage applied to the first conductive path 91 is applied to the second conductive path 92.

[0075] The control section 12 switches the first cut-off switch 71 or the second cut-off switch 72 to the OFF state when a current of a predetermined threshold value or more flows in the conductive path of either one of the first conductive path 91 and the second conductive path 92 during a period in which the first intermittent control and the second intermittent control are not performed. Specifically, the control section 12 switches the first cut-off switch 71 or the second cut-off switch 72 to the OFF state when the current values detected by the first current detection section 81, the second current detection section 82, and the third current detection section 83 are a predetermined threshold value or more.

[0076] The control section 12 switches the first cut-off switch 71 or the second cut-off switch 72 to the OFF state when a voltage of a predetermined threshold value or less is generated in the conductive path of either one of the first conductive path 91 and the second conductive path 92 during a period in which the first intermittent control and the second intermittent control are not performed. Specifically, the control section 12 switches the first cut-off switch 71 or the second cut-off switch 72 to the OFF state when the voltage values detected by the first voltage detection section and the second voltage detection section are a predetermined threshold value or less.

[0077] Next, the effect of the present configuration will be illustrated.

[0078] The DCDC converter 1 of the present disclosure includes a voltage conversion section 6, a first capacitor C1, a second capacitor C2, a first cut-off switch 71, a second cut-off switch 72, and a control section 12. The voltage conversion section 6 is provided between the first conductive path 91 and the second conductive path 92. The first capacitor C1 is provided between the first conductive path 91 and a reference conductive path 93. The second capacitor C2 is provided between the second conductive path 92 and the reference conductive path 93. The control section 12 switches the first cut-off switch 71 and the second cut-off switch 72 between the ON state and the OFF state.

[0079] When the first cutoff switch 71 is in the off state, the inflow of the cutoff current from the first external power supply 61 to the first capacitor C1 is cut off. At least when the first cutoff switch 71 is in the on state, the inflow of the current from the first external power supply 61 to the first capacitor C1 via the first conductive path 91 is allowed. When the second cutoff switch 72 is in the off state, the inflow of the cutoff current from the second external power supply 62 to the second capacitor C2 is cut off. At least when the second cutoff switch 72 is in the on state, the inflow of the current from the second external power supply 62 to the second capacitor C2 via the second conductive path 92 is allowed. The control section 12, in a case where the control is switched from the cutoff control to the power-on control, performs intermittent control that intermittently makes the first cutoff switch 71 and the second cutoff switch 72 in the on state before the power-on control. The cutoff control maintains the first cutoff switch 71 and the second cutoff switch 72 in the off state. The power-on control maintains the first cutoff switch 71 and the second cutoff switch 72 in the on state.

[0080] The DCDC converter 1 of the present disclosure performs the intermittent control when switching the first cutoff switch 71 and the second cutoff switch 72 from the cutoff control to the power-on control. Therefore, the DCDC converter 1 can more suppress the rush current flowing to the first capacitor C1 and the second capacitor C2 than in a case where the power-on control is started at the end timing of the cutoff control. Therefore, the DCDC converter 1 can not easily cause a problem due to too much rush current flowing to the first capacitor C1 and the second capacitor C2 when the cutoff control is released.

[0081] The switch of the DCDC converter 1 of the present disclosure includes the first cutoff switch 71 provided between the first external power supply 61 and the voltage conversion section 6 in the first conductive path 91 and the second cutoff switch 72 provided between the second external power supply 62 and the voltage conversion section 6 in the second conductive path 92. The first cutoff switch 71 allows the power-on from the first external power supply 61 side to the voltage conversion section 6 side when the first cutoff switch 71 is in the on state, and cuts off the power-on from the first external power supply 61 side to the voltage conversion section 6 side when the first cutoff switch 71 is in the off state. The second cutoff switch 72 allows the power-on from the second external power supply 62 side to the voltage conversion section 6 side when the second cutoff switch 72 is in the on state, and cuts off the power-on from the second external power supply 62 side to the voltage conversion section 6 side when the second cutoff switch 72 is in the off state.

[0082] The control section 12, in a case where the control is switched from the first cutoff control that maintains the first cutoff switch 71 in the off state to the first power-on control that maintains the first cutoff switch 71 in the on state, performs the first intermittent control that intermittently makes the first cutoff switch 71 in the on state before the first power-on control. The control section 12, in a case where the control is switched from the second cutoff control that maintains the second cutoff switch 72 in the off state to the second power-on control that maintains the second cutoff switch 72 in the on state, performs the second intermittent control that intermittently makes the second cutoff switch 72 in the on state before the second power-on control.

[0083] According to this structure, the DCDC converter 1 is provided with the cut-off switch (first cut-off switch 71, second cut-off switch 72) in either one of the first conductive path 91 and the second conductive path 92, and protection can be individually sought. Further, the DCDC converter 1, while realizing such a protection function, can suppress the rush current flowing from each external power supply (first external power supply 61, second external power supply 62) to the first capacitor C1 and the second capacitor C2, regardless of which of the cut-off switches of the first conductive path 91 and the second conductive path 92 is in the cut-off control.

[0084] The voltage conversion section 6 of the DCDC converter 1 of the present disclosure is provided with the drive switching elements D1, D2, D3, D4. The DCDC converter 1 boosts or steps down the voltage applied to one of the first conductive path 91 and the second conductive path 92 according to the on-off operation of the drive switching elements D1, D2, D3, D4, and applies the output voltage to the other. The control section 12 performs voltage conversion control that turns the drive switching elements D1, D2, D3, D4 on and off. The control section 12 makes the frequency of the on-off operation of the switch S in the intermittent control greater than the frequency of the on-off operation of the drive switching elements D1, D2, D3, D4 in the voltage conversion control.

[0085] According to this structure, the DCDC converter 1 can make the frequency of the on-off operation of the switch S in the intermittent control greater than the frequency of the on-off operation of the drive switching elements D1, D2, D3, D4 in the voltage conversion control. That is, the DCDC converter 1 can further shorten each on-time in the intermittent control, and can further reduce the current flowing to the first capacitor C1 and the second capacitor C2 in each on-time in the intermittent control. Therefore, the DCDC converter 1 can more reliably suppress the rush current to the first capacitor C1 and the second capacitor C2.

[0086] The first capacitor C1 and the second capacitor C2 of the DCDC converter 1 of the present disclosure are ceramic capacitors.

[0087] The ceramic capacitor has a smaller internal resistance than the electrolytic capacitor, and thus has a tendency to have a larger rush current than the electrolytic capacitor. Therefore, the DCDC converter 1, even if a ceramic capacitor is used, can suppress the magnitude of the rush current to the first capacitor C1 and the second capacitor C2 in one on-state by performing the intermittent control.

[0088] The reference conductive path 93 of the DCDC converter 1 of the present disclosure is a conductive path that is maintained at a reference potential lower than the potential of one of the conductive paths (the first conductive path 91 or the second conductive path 92).

[0089] The control section of the DCDC converter of the present disclosure switches at least one of the first cut-off switch 71 and the second cut-off switch 72 to the open state in a case where a current of a threshold value or more flows in one of the conductive paths (the first conductive path 91 or the second conductive path 92), or in a case where the voltage becomes below a threshold value.

[0090] <Embodiment 2>

[0091] Next, the DCDC converter 2 of Embodiment 2 will be described with reference to Figure 4 and the like. The DCDC converter 2 differs from Embodiment 1 in that the first external power supply and the first cut-off switch are not provided, and that the semiconductor switch T3 of the voltage conversion section 6 is intermittently controlled before the first conversion operation is performed. As for the same structures, the same reference numerals are added, and the description of the configuration, the action, and the effect will be omitted.

[0092] [Outline of DCDC converter 2]

[0093] The first conductive path 91 of the DCDC converter 2 is not connected to the first external power supply. The load 7 is connected to the first conductive path 91. The load 7 is formed in a structure that receives the power supply from the second external power supply 62, for example. The load 7 is a publicly known electrical component for a vehicle, and the kind is not particularly limited.

[0094] [Action in DCDC converter]

[0095] The action of the DCDC converter 2 will be described.

[0096] The control section 12 intermittently controls the second cut-off switch 72 if the ignition-on signal indicating that the ignition switch is in the on state is input from the external ECU or the like.

[0097] [Intermittent control of second cut-off switch]

[0098] The control section 12 intermittently controls the second cut-off switch 72 (switch S). Specifically, the same as the second intermittent control (intermittent control) of the second cut-off switch 72 in Embodiment 1. Also, the charging of the second capacitor C2 is promoted, and if a condition for ending the intermittent control is satisfied, the control section 12 ends the intermittent control of the second cut-off switch 72, and maintains the second cut-off switch 72 in the on state. The condition for ending the intermittent control is, for example, a case where the current flowing to the second capacitor C2 is less than a predetermined value, a case where a predetermined time has elapsed from the start of the intermittent control, and the like. The case where the current flowing to the second capacitor C2 is less than the predetermined value means a case where the current value detected in the second current detection section 82 and the third current detection section 83 is less than a predetermined threshold value.

[0099] [Intermittent control of semiconductor switch element]

[0100] In a state where the second cut-off switch 72 is maintained in the on state, the semiconductor switch T3 is in a state of being interposed between the second external power supply 62 and the first capacitor Cl. The control section 12 intermittently controls the semiconductor switch T3 before performing the first conversion operation (an operation of boosting the voltage applied to the second conductive path 92 to apply the voltage to the first conductive path 91). The semiconductor switch T3 is maintained in the on state without being subjected to voltage conversion control at the time of the first conversion operation. In the first conversion operation, the semiconductor switch T3 is a switch S that forms part of the voltage conversion section 6.

[0101] First, the control section 12 alternately repeats outputting an H-level signal and an L-level signal to the gate of the semiconductor switch T3 (the switch S). Due to this, the semiconductor switch T3 becomes in the on state where the drain and the source are conductive when the H-level signal is input to the gate, and becomes in the off state where the drain and the source are not conductive when the L-level signal is input to the gate. At this time, the control section 12 continuously outputs the L-level signal to the semiconductor switches T1, T2, and T4. Due to this, the semiconductor switches T1, T2, and T4 become in the off state where the drain and the source are not conductive.

[0102] In the intermittent control, when the semiconductor switch T3 is in the on state, the current flows from the second external power supply 62 to the first capacitor Cl along the path indicated by an arrow A3 in FIG. 8. At this time, although the semiconductor switch T1 is in the off state, the current flows to the first conductive path 91 via the parasitic diode T11. Also, the semiconductor switch T3 becomes in the off state where the drain and the source are not conductive when the L-level signal is input to the gate. Due to this, the current does not flow from the second external power supply 62 to the first capacitor Cl. That is, by the intermittent control of the semiconductor switch T3 by the control section 12, the current intermittently flows from the second external power supply 62 to the first capacitor Cl. Due to this, it is possible to suppress the current flowing to the first capacitor Cl from becoming excessively large. The signal output to the semiconductor switch T3 at the time of the intermittent control is the same signal as the signal output to the semiconductor switch T3 at the time of the voltage conversion control. Figure 4 In the intermittent control, when the semiconductor switch T3 is in the on state, the current flows from the second external power supply 62 to the first capacitor Cl along the path indicated by an arrow A3 in FIG. 8. At this time, although the semiconductor switch T1 is in the off state, the current flows to the first conductive path 91 via the parasitic diode T11. Also, the semiconductor switch T3 becomes in the off state where the drain and the source are not conductive when the L-level signal is input to the gate. Due to this, the current does not flow from the second external power supply 62 to the first capacitor Cl. That is, by the intermittent control of the semiconductor switch T3 by the control section 12, the current intermittently flows from the second external power supply 62 to the first capacitor Cl. Due to this, it is possible to suppress the current flowing to the first capacitor Cl from becoming excessively large. The signal output to the semiconductor switch T3 at the time of the intermittent control is the same signal as the signal output to the semiconductor switch T3 at the time of the voltage conversion control. Figure 2 The frequency of the on-off operation of the second cut-off switch 72 (the switch S) and the semiconductor switch T3 (the switch S) in the intermittent control is higher than the frequency of the on-off operation of the drive switching elements D1, D2, D3, and D4 (the semiconductor switches T1, T2, T3, and T4) in the voltage conversion control.

[0103] The DC-DC converter 2 has a first current detection unit 81 capable of detecting current flowing through the first conductive path 91. The second current detection unit 82 is capable of detecting current flowing through the second conductive path 92. The third current detection unit 83 is capable of detecting current flowing through the first capacitor C1, the second capacitor C2, and the voltage conversion unit 6 to ground G. Therefore, the DC-DC converter 2 prevents the current flowing through the first and second capacitors C1 and C2 from becoming excessive, thereby preventing the first, second, and third current detection units 81, 82, and 83 from detecting excessive current values. Furthermore, as charging of the first capacitor C1 progresses, the control unit 12 terminates the intermittent control of the semiconductor switch T3 if the conditions for terminating the intermittent control are met. These conditions for terminating the intermittent control include, for example, when the current flowing through the first capacitor C1 falls below a predetermined value or when a predetermined time has passed since the start of the intermittent control. The current flowing into the first capacitor C1 is less than the predetermined value when the current values ​​detected by the first current detection unit 81, the second current detection unit 82, and the third current detection unit 83 are less than a predetermined threshold value. The control unit 12 continuously outputs an on signal (e.g., an H-level signal) to the semiconductor switch T3, thereby maintaining the semiconductor switch T3 in the on state and terminating the intermittent control of the semiconductor switch T3 (switch S).

[0104] [First conversion action]

[0105] The control unit 12 continuously outputs an on signal (e.g., an H-level signal) to the semiconductor switch T3, maintaining the semiconductor switch T3 in the on state, and continuously outputs an off signal (e.g., an L-level signal) to the semiconductor switch T4, maintaining the semiconductor switch T4 in the off state. Furthermore, the control unit 12 outputs a drive signal to the first switch unit S1 (driving switching elements D1 and D2), controlling the voltage conversion of the first switch unit S1. This causes the DC-DC converter 2 to initiate the first conversion operation. This control boosts the DC second voltage (input voltage) applied to the second conductive path 92, applying an output voltage to the first conductive path 91 that is higher than the second voltage applied to the second conductive path 92.

[0106] [Second conversion action]

[0107] The control section 12 performs voltage conversion control on the second switching section S2 in the case of performing the second conversion operation (operation of stepping down the voltage applied to the second conductive path 92 and applying the voltage to the first conductive path 91). In the voltage conversion control in the second conversion operation, the semiconductor switches T3, T4 (driving switching elements D3, D4) perform on-off operation. At this time, the semiconductor switch T3 can make the current flow intermittently from the second external power supply 62 to the first capacitor C1 as in the case of the intermittent control. Thus, the current flowing to the first capacitor C1 can be suppressed from becoming excessively large. That is, in the case where the DCDC converter 2 performs the second conversion operation, the voltage conversion operation is performed by the second switching section S2 (semiconductor switches T3, T4 (driving switching elements D3, D4)), so that the semiconductor switch T3 does not perform the intermittent control and the current flows intermittently from the second external power supply 62 to the first capacitor C1. Also, after the charging of the first capacitor C1 is advanced, the voltage conversion operation is continuously performed, so that the second voltage (input voltage) of the direct current applied to the second conductive path 92 is stepped down and the output voltage lower than the second voltage applied to the second conductive path 92 is applied to the first conductive path 91.

[0108] Next, the effect of the present configuration will be illustrated.

[0109] The switch S of the DCDC converter 2 of the present disclosure includes the second cut-off switch 72 provided between the second external power supply 62 and the voltage conversion section 6 in the second conductive path 92. The second cut-off switch 72 allows the current to flow from the second external power supply 62 side to the voltage conversion section 6 side when it is in the on state, and cuts off the current from the second external power supply 62 side to the voltage conversion section 6 side when it is in the off state.

[0110] According to this configuration, the DCDC converter 2 can suppress the excessive current at the time of canceling the cut-off control using the second cut-off switch 72 required for the protection function while suppressing the increase of a special dedicated component or the like. Thus, the DCDC converter 2 can suppress the rush current to the second capacitor C2 by a simpler configuration.

[0111] The switch S of the DCDC converter 2 of the present disclosure includes the semiconductor switch T3 formed as a part of the voltage conversion section 6.

[0112] According to this configuration, the DCDC converter 2 can suppress the excessive current at the time of canceling the cut-off control using the semiconductor switch T3 required for the function of the voltage conversion section 6 while suppressing the increase of a special dedicated component or the like. Thus, the DCDC converter 2 can suppress the rush current to the first capacitor C1 by a simpler configuration.

[0113] <Other Embodiments>

[0114] The present structure is not limited to the embodiments described above and illustrated in the drawings, and for example, the following embodiments are also included within the technical scope of the present application.

[0115] In Embodiment 2, the charging of the second capacitor C2 and the first capacitor Cl from the second external power supply 62 by the intermittent control is disclosed, but a structure in which the second external power supply and the second cut-off switch are not provided and the first external power supply and the first cut-off switch are provided can also be included. In this case, the control section performs intermittent control on the first cut-off switch, thereby charging the first capacitor in a manner that avoids excessive current from flowing to the first capacitor. Also, after the charging of the first capacitor is advanced, the first high-voltage side element of the first switch section is intermittently controlled before the second conversion operation (an operation of boosting the voltage applied to the first conductive path and applying the voltage to the second conductive path) is performed.

[0116] At this time, the control section continuously outputs an L-level signal to the other semiconductor switch. In this case, the first high-voltage side element of the first switch section is a switch formed as part of the voltage conversion section. The control section performs intermittent control on the first high-voltage side element of the first switch section, thereby charging the second capacitor in a manner that avoids excessive current from flowing to the second capacitor. At this time, the second high-voltage side element of the second switch section is in an open state, but current flows to the second conductive path via a parasitic diode. Also, after the charging of the second capacitor is advanced, if a condition for ending the intermittent control of the first high-voltage side element of the first switch section is satisfied, the control section continuously outputs an on signal (for example, an H-level signal) to the first high-voltage side element of the first switch section. Thereby, the first high-voltage side element of the first switch section is maintained in an on state, the intermittent control of the first high-voltage side element (switch) of the first switch section is ended, and the second conversion operation is performed.

[0117] The control section performs voltage conversion control on the first switch section in the case where the first conversion operation (an operation of stepping down the voltage applied to the first conductive path and applying the voltage to the second conductive path) is performed. At this time, the first high-voltage side element of the first switch section, like when it performs intermittent control itself, can cause current to intermittently flow from the first external power supply to the second capacitor. Thereby, it is possible to suppress the current flowing to the second capacitor from becoming excessive. In this case, when the first conversion operation is performed, the voltage conversion operation is performed by the first switch section, and thereby the first high-voltage side element of the first switch section does not perform intermittent control and causes current to intermittently flow from the first external power supply to the second capacitor.

[0118] In the first and second embodiments, the time P2 of the H-level signal outputted from the control unit 12 to the first disconnect switch 71, the second disconnect switch 72, and the semiconductor switch T3 during intermittent control is disclosed to be constant. However, this is not limiting, and the switch-on time during a portion of the entire period during which intermittent control is performed may be longer than the switch-on time during the period preceding the portion. Specifically, Figure 5 As shown, the on-time of the switch in a portion P8 of the entire period P4 during intermittent control can be made longer than the on-time of the switch in the periods P5, P6, and P7 preceding the portion P8. When the time of each on-state (hereinafter also referred to as on-time) is constant in intermittent control, the more the on-state is repeated, the smaller the current flowing into the capacitor during each on-time. This phenomenon becomes a reason for the longer charging time of the capacitor. In contrast, the DCDC converter makes the on-time relatively longer in a relatively later portion of the period, so that the reduction in current caused by the repetition of the on-state can be suppressed. Therefore, the DCDC converter can complete the charging of the capacitor earlier while achieving the function of suppressing the inrush current to the capacitor.

[0119] In Embodiments 1 and 2, a bidirectional buck-boost DCDC converter is illustrated as an example of a DCDC converter. However, the DCDC converter may be a buck DCDC converter, a boost DCDC converter, or a buck-boost DCDC converter. Furthermore, the DCDC converter may be a bidirectional DCDC converter with variable input and output sides, as in Embodiment 1, or a unidirectional DCDC converter with fixed input and output sides.

[0120] In the first and second embodiments, N-channel MOSFETs are used as the semiconductor switches T2 and T4 , but a diode may be used as one or both of them to adopt a diode rectification method.

[0121] In the first and second embodiments, the control unit 12 is mainly composed of a microcomputer, but may be realized by a plurality of hardware circuits other than a microcomputer.

[0122] In the first embodiment, the frequency of the on / off operations of the first and second disconnect switches 71 and 72 (switch S) during intermittent control is set to be greater than the frequency of the on / off operations of the semiconductor switches T1, T2, T3, and T4 during voltage conversion control. However, this is not limiting. The frequency of the on / off operations of the first and second disconnect switches (switches) during intermittent control may be set to be approximately the same as the frequency of the on / off operations of the semiconductor switches during voltage conversion control. Furthermore, the on / off frequencies of the first and second disconnect switches during intermittent control may be different.

[0123] It should be understood that the embodiments disclosed herein are illustrative in all respects, rather than restrictive. The scope of the application is indicated not by the embodiments disclosed herein, but by the claims and the equivalents thereof, and is intended to include all modifications within the scope of the claims and their equivalents.

[0124] BRIEF DESCRIPTION OF DRAWINGS

[0125] 1, 2 … DCDC converter

[0126] 6 … Voltage conversion section

[0127] 7 … Load

[0128] 12 … Control section

[0129] 61 … First external power supply

[0130] 62 … Second external power supply

[0131] 70 … Cut-off switch

[0132] 71 … First cut-off switch

[0133] 71A … Parasitic diode

[0134] 72 … Second cut-off switch

[0135] 72A … Parasitic diode

[0136] 81 … First current detection section

[0137] 82 … Second current detection section

[0138] 83 … Third current detection section

[0139] 91 … First conduction path

[0140] 92 … Second conduction path

[0141] 93 … Reference conduction path

[0142] A1, A2, A3 … Arrow

[0143] C1 … First capacitor

[0144] C2 … Second capacitor

[0145] D1, D2, D3, D4 … Drive switch element

[0146] G … Ground

[0147] L … Inductor

[0148] S … Switch

[0149] S1 … First switch section

[0150] S2… second switch section

[0151] T1, T2, T3, T4… semiconductor switch

[0152] T11, T12, T13, T14… parasitic diode

Claims

1. A DCDC converter comprising: a voltage conversion section provided between a first conductive path and a second conductive path; a capacitor provided between a conductive path of one of the first conductive path and the second conductive path and a reference conductive path; a switch between an external power supply and the capacitor; and a control section that switches the switch between an on state and an off state, current inflow from the external power supply to the capacitor is cut off when the switch is in the off state, and current inflow from the external power supply to the capacitor via the conductive path of one of the first conductive path and the second conductive path is allowed at least when the switch is in the on state, the control section, when switching from cut-off control that maintains the switch in the off state to energization control that maintains the switch in the on state, performs intermittent control that intermittently places the switch in the on state before the energization control, the capacitor includes a first capacitor provided between the first conductive path and the reference conductive path, the external power supply includes a first external power supply connected to the first conductive path, the switch includes a first cut-off switch provided between the first external power supply and the voltage conversion section in the first conductive path, the first cut-off switch is between the first external power supply and the first capacitor, the first cut-off switch allows energization from the first external power supply side to the voltage conversion section side when the first cut-off switch is in the on state, and cuts off energization from the first external power supply side to the voltage conversion section side when the first cut-off switch is in the off state, the control section, when switching from first cut-off control that maintains the first cut-off switch in the off state to first energization control that maintains the first cut-off switch in the on state, performs the intermittent control, that is, first intermittent control, that intermittently places the first cut-off switch in the on state before the first energization control, the voltage conversion section includes a drive switching element, and according to on-off operation of the drive switching element, voltage applied to one of the first conductive path and the second conductive path is boosted or stepped down to apply output voltage to the other, the control section performs voltage conversion control that turns the drive switching element on and off, the frequency of on-off operation of the first cut-off switch in the first intermittent control is greater than the frequency of on-off operation of the drive switching element in the voltage conversion control, and after the first intermittent control ends, the voltage conversion control is performed.

2. The DCDC converter according to claim 1, wherein the capacitor includes a second capacitor provided between the second conductive path and the reference conductive path, the external power supply includes a second external power supply connected to the second conductive path, the switch includes a second cut-off switch provided between the second external power supply and the voltage conversion section in the second conductive path, and the control section performs the intermittent control that intermittently places the second cut-off switch in the on state before the energization control. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ the second cut-off switch allows energization from the second external power supply side to the voltage conversion section when the second cut-off switch is in the on state, the control section, in a case where the second cut-off control that causes the second cut-off switch to be maintained in the off state is switched to a second energization control that causes the second cut-off switch to be maintained in the on state, performs the intermittent control that causes the second cut-off switch to be intermittently in the on state before the second energization control, causes a frequency of on-off operation of the second cut-off switch in the second intermittent control to be higher than a frequency of on-off operation of the driving switching element in the voltage conversion control, and performs the voltage conversion control after the second intermittent control ends.

3. The DCDC converter according to claim 1, wherein the switch includes a semiconductor switch formed as a part of the voltage conversion section.

4. The DCDC converter according to claim 2, wherein the switch includes a semiconductor switch formed as a part of the voltage conversion section.

5. The DCDC converter according to any one of claims 1 to 4, wherein the control section causes an on time of the switch in a part of an entire period in which the intermittent control is performed to be longer than the on time of the switch in a period before the part.

6. The DCDC converter according to any one of claims 1 to 4, wherein the capacitor is a ceramic capacitor.

Images