DC-DC Converter

Abstract

The bootstrap circuit section (20) of the DC-DC converter (1) applies a voltage higher than the first connection point (P1) between the switching elements (T1, T2) to the drive section (8) during the first conversion operation, and applies a voltage higher than the second connection point (P2) between the switching elements (T3, T4) to the drive section (8) during the second conversion operation. The charge pump circuit section (30) of the DC-DC converter (1) boosts the input voltage and applies it to the drive section (8). The drive section (8) sets the voltages of the first drive signal (D1) and the second drive signal (D2) according to the voltage applied by the bootstrap circuit section (20) and the voltage applied by the charge pump circuit section (30). The charge pump circuit section (30) determines the operation period during which the charge pump circuit section (30) applies the output voltage based on the first voltage (V1), the second voltage (V2), the first power supply charging signal (Cs1), and the second power supply charging signal (Cs2).

Description

Technical Field

[0001] The present disclosure relates to a DC-DC converter. Background Art

[0002] When a high-side drive is performed using an N-channel MOSFET as a switching element, it is necessary to make the gate voltage higher than the source voltage. To achieve this, a bootstrap circuit has been conventionally used. The magnitude of the supply voltage from the bootstrap circuit is determined by the charging voltage of a capacitor in the bootstrap circuit.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2004-173481

[0006] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2008-29085

[0007] Patent Document 3: Japanese Unexamined Patent Application Publication No. 2014-11841 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] In Patent Document 3, a configuration using a bootstrap circuit and a charge pump circuit in combination is disclosed. Specifically, the following control method is adopted: the input voltage is monitored, and the charge pump is operated only when it is lower than a predetermined threshold. However, this control method cannot be directly applied to a converter that performs a bidirectional conversion operation. A bidirectional converter must consider other factors in addition to the input voltage when determining the timing at which the charge pump circuit should be operated.

[0010] Therefore, an object of the present disclosure is to provide a DC-DC converter that performs a bidirectional buck-boost operation and includes a charge pump circuit with appropriate operation timing.

[0011] Means for Solving the Problems

[0012] The DCDC converter of the present disclosure includes: a voltage conversion unit that performs bidirectional voltage conversion between a first conductive circuit and a second conductive circuit; a control unit that outputs a control signal for controlling the voltage conversion unit; a drive unit that outputs a drive signal corresponding to the control signal output from the control unit; a first voltage detection unit that detects a first voltage applied to the first conductive circuit; and a second voltage detection unit that detects a second voltage applied to the second conductive circuit. The voltage conversion unit performs a first conversion operation and a second conversion operation. The first conversion operation is at least one of an operation of stepping down the voltage applied to the first conductive circuit and applying the voltage to the second conductive circuit and an operation of stepping up the voltage applied to the second conductive circuit and applying the voltage to the first conductive circuit. The second conversion operation is at least one of an operation of stepping up the voltage applied to the first conductive circuit and applying the voltage to the second conductive circuit and an operation of stepping down the voltage applied to the second conductive circuit and applying the voltage to the first conductive circuit. Among them, the control unit outputs a first control signal for performing the first conversion operation and a second control signal for performing the second conversion operation. The drive unit includes: a first drive unit that outputs a first drive signal corresponding to the first control signal to the voltage conversion unit when the first control signal is output from the control unit; and a second drive unit that outputs a second drive signal corresponding to the second control signal to the voltage conversion unit when the second control signal is output from the control unit. The voltage conversion unit includes: a first switch unit that includes a first high-voltage side element including a switch and a first low-voltage side element including a switch or a diode and is provided with the first drive signal; and a second switch unit that includes a second high-voltage side element including a switch and a second low-voltage side element including a switch or a diode and is provided with the second drive signal. When the first drive signal is provided to the first switch unit, the voltage conversion unit performs the first conversion operation. When the second drive signal is provided to the second switch unit, the voltage conversion unit performs the second conversion operation. The DCDC converter further includes: a bootstrap circuit unit that applies a voltage higher than a first connection point between the first high-voltage side element and the first low-voltage side element to the drive unit during the first conversion operation and applies a voltage higher than a second connection point between the second high-voltage side element and the second low-voltage side element to the drive unit during the second conversion operation;and a charge pump circuit unit that boosts the input voltage and applies an output voltage higher than the input voltage to the driving unit. The driving unit outputs the first driving signal and the second driving signal including voltage signals corresponding to the voltage applied by the bootstrap circuit unit or the voltage applied by the charge pump circuit unit. The charge pump circuit unit determines the operation timing of applying the output voltage based on the first voltage, the second voltage, the state of the first conversion operation, or the state of the second conversion operation.;

[0013] Advantages of the Invention

[0014] According to the present disclosure, a buck-boost DCDC converter with a charge pump circuit having appropriate operation timing can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a circuit diagram showing the DCDC converter of Embodiment 1.

[0016] Figure 2 is a timing diagram showing the operations of the first charge pump circuit and the second charge pump circuit when the input voltage applied to the first conductive circuit changes from a state higher than the voltage of the second conductive circuit to a low state in the case where the DCDC converter of Embodiment 1 outputs to the second conductive circuit based on the input voltage applied to the first conductive circuit.

[0017] Figure 3 is a timing diagram showing the operations of the first charge pump circuit and the second charge pump circuit when the input voltage applied to the second conductive circuit changes from a state lower than the voltage of the first conductive circuit to a high state in the case where the DCDC converter of Embodiment 1 outputs to the first conductive circuit based on the input voltage applied to the second conductive circuit.

[0018] Figure 4 is a timing diagram showing the operations of the first charge pump circuit and the second charge pump circuit when the input voltage applied to the first conductive circuit changes from a state lower than the voltage of the second conductive circuit to a high state in the case where the DCDC converter of Embodiment 1 outputs to the second conductive circuit based on the input voltage applied to the first conductive circuit.

[0019] Figure 5 is a timing diagram showing the operations of the first charge pump circuit and the second charge pump circuit when the input voltage applied to the second conductive circuit changes from a state higher than the voltage of the first conductive circuit to a low state in the case where the DCDC converter of Embodiment 1 outputs to the first conductive circuit based on the input voltage applied to the second conductive circuit.

[0020] Figure 6 is a circuit diagram showing the DCDC converter of Embodiment 2. Detailed implementation manners

[0021] [Description of the embodiments of the present disclosure]

[0022] First, the embodiments of the present disclosure will be enumerated for illustration.

[0023] (1) The DCDC converter of the present disclosure includes a voltage conversion unit, a control unit, a driving unit, a first voltage detection unit, and a second voltage detection unit.

[0024] The voltage conversion unit performs bidirectional voltage conversion between a first conductive circuit and a second conductive circuit. The control unit outputs a control signal for controlling the voltage conversion unit. The driving unit outputs a driving signal corresponding to the control signal output from the control unit. The first voltage detection unit detects a first voltage applied to the first conductive circuit. The second voltage detection unit detects a second voltage applied to the second conductive circuit. The voltage conversion unit performs a first conversion operation and a second conversion operation. The first conversion operation performs at least one of the operations of stepping down the voltage applied to the first conductive circuit and applying the voltage to the second conductive circuit and stepping up the voltage applied to the second conductive circuit and applying the voltage to the first conductive circuit. The second conversion operation performs at least one of the operations of stepping up the voltage applied to the first conductive circuit and applying the voltage to the second conductive circuit and stepping down the voltage applied to the second conductive circuit and applying the voltage to the first conductive circuit. The control unit outputs a first control signal for performing the first conversion operation and a second control signal for performing the second conversion operation.

[0025] The driving unit includes a first driving unit and a second driving unit. The first driving unit outputs a first driving signal corresponding to the first control signal to the voltage conversion unit when the first control signal is output from the control unit. The second driving unit outputs a second driving signal corresponding to the second control signal to the voltage conversion unit when the second control signal is output from the control unit. The voltage conversion unit includes a first switching unit and a second switching unit. The first switching unit includes a first high-voltage side element including a switch and a first low-voltage side element including a switch or a diode, and is provided with the first driving signal. The second switching unit includes a second high-voltage side element including a switch and a second low-voltage side element including a switch or a diode, and is provided with the second driving signal. When the first driving signal is provided to the first switching unit, the voltage conversion unit performs the first conversion operation. When the second driving signal is provided to the second switching unit, the voltage conversion unit performs the second conversion operation, and the structure is configured in the above manner.

[0026] In the present disclosure, the DCDC converter further includes a bootstrap circuit section and a charge pump circuit section. The bootstrap circuit section applies, during a first conversion operation, a voltage higher than a first connection point between a first high-side element and a first low-side element to the drive section. The bootstrap circuit section applies, during a second conversion operation, a voltage higher than a second connection point between a second high-side element and a second low-side element to the drive section. The charge pump circuit section boosts the input voltage and applies an output voltage higher than the input voltage to the drive section. The drive section outputs a first drive signal and a second drive signal including voltage signals corresponding to the voltage applied by the bootstrap circuit section or the voltage applied by the charge pump circuit section. The charge pump circuit section determines an operation period for applying the output voltage based on a first voltage, a second voltage, and a state of the first conversion operation or the second conversion operation.

[0027] During the first conversion operation or the second conversion operation, the DCDC converter can apply, via the bootstrap circuit section, a voltage higher than the first connection point between the first high-side element and the first low-side element or the second connection point between the second high-side element and the second low-side element to the drive section. Further, since the charge pump circuit section can determine the operation period for applying the output voltage based on the first voltage and the second voltage, in a structure capable of bidirectional voltage conversion, during the operation period of the charge pump circuit section, even if the bootstrap circuit cannot apply an appropriate voltage, a higher voltage can be applied via the charge pump circuit section. Moreover, since it is not necessary to always keep the charge pump circuit section operating, it can be made to operate during a necessary period reflecting the state of the first voltage, the second voltage, the first conversion operation, or the second conversion operation, so that power consumption can be suppressed.

[0028] (2) Alternatively, the charge pump circuit section of the DCDC converter according to the present disclosure may apply the output voltage to the first drive section when at least the difference between the first voltage and the second voltage becomes lower than a first threshold in a state where the first conversion operation is being performed.

[0029] If configured in this way, during the first conversion operation of the DCDC converter, the difference between the first voltage and the second voltage is lower than the first threshold, and the risk of not applying an appropriate voltage from the bootstrap circuit section increases. At this time, the charge pump circuit section can be made to operate to apply a voltage to the drive section. Further, regardless of the magnitudes of the absolute values of the first voltage and the second voltage, the operation of the charge pump circuit section is switched based on the relative relationship between the first voltage and the second voltage. Therefore, the output voltage to the first conduction path or the second conduction path is not limited to a specific value and can be applied even if set to a desired magnitude.

[0030] (3) Alternatively, the charge pump circuit section of the DCDC converter according to the present disclosure may apply the output voltage to the second drive section when at least the difference between the first voltage and the second voltage is lower than a second threshold in a state where the second conversion operation is being performed.

[0031] If configured in this way, when the DCDC converter performs the second conversion operation, the difference between the first voltage and the second voltage is lower than the second threshold value, and the risk of not applying an appropriate voltage from the bootstrap circuit section increases. At this time, the charge pump circuit section can be made to operate to apply a voltage to the drive section. In addition, regardless of the magnitudes of the absolute values of the first voltage and the second voltage, the operation of the charge pump circuit section is switched based on the relative relationship between the first voltage and the second voltage. Therefore, the output voltage to the first conduction circuit or the second conduction circuit is not limited to a specific value, and it can be applied even if set to a desired magnitude.

[0032] (4) Alternatively, when the charge pump circuit section of the DCDC converter of the present disclosure performs the first conversion operation in such a manner as to step down the voltage applied to the first conduction circuit and apply the voltage to the second conduction circuit, or performs the second conversion operation in such a manner as to step down the voltage applied to the second conduction circuit and apply the voltage to the first conduction circuit, when the second voltage is greater than the first voltage, the output voltage is applied to the first drive section, and when the first voltage is greater than the second voltage, the output voltage is applied to the second drive section.

[0033] If configured in this way, when a step-down operation is performed between the first conduction circuit and the second conduction circuit, when the first voltage is greater than the second voltage, the second switching section does not perform a switching operation, and thus the risk that the bootstrap circuit section can no longer apply an appropriate voltage to the second drive section and can no longer reliably turn on the second high-side element increases. At this time, the DCDC converter can reliably turn on the second high-side element through the charge pump circuit section. In addition, when the second voltage is greater than the first voltage, the first switching section does not perform a switching operation, and thus the risk that the bootstrap circuit section can no longer apply an appropriate voltage to the first drive section and can no longer reliably turn on the first high-side element increases. At this time, the first high-side element can be reliably turned on through the charge pump circuit section. As a result, the DCDC converter can perform the power exchange between the first conduction circuit and the second conduction circuit well.

[0034] (5) Alternatively, when the charge pump circuit section of the DCDC converter of the present disclosure performs the first conversion operation in such a manner as to step up the voltage applied to the second conduction circuit and apply the voltage to the first conduction circuit, or performs the second conversion operation in such a manner as to step up the voltage applied to the first conduction circuit and apply the voltage to the second conduction circuit, when the first voltage is greater than the second voltage, the output voltage is applied to the second drive section, and when the second voltage is greater than the first voltage, the output voltage is applied to the first drive section.

[0035] If configured in this way, when a boosting operation is performed between the first conduction circuit and the second conduction circuit, when the first voltage is greater than the second voltage, the second switching unit does not perform a switching operation, thereby increasing the risk that the bootstrap circuit unit can no longer apply an appropriate voltage to the second driving unit and can no longer reliably turn on the second high-voltage side element. At this time, the DCDC converter can reliably turn on the second high-voltage side element through the charge pump circuit unit. In addition, when the second voltage is greater than the first voltage, the first switching unit does not perform a switching operation, thereby increasing the risk that the bootstrap circuit unit can no longer apply an appropriate voltage to the first driving unit and can no longer reliably turn on the first high-voltage side element. At this time, the first high-voltage side element can be reliably turned on through the charge pump circuit unit. Thus, the DCDC converter can favorably perform the power exchange between the first conduction circuit and the second conduction circuit.

[0036] (6) The charge pump circuit unit of the DCDC converter of the present disclosure includes a first charge pump circuit, a second charge pump circuit, and an operation control unit. The first charge pump circuit applies a first output voltage to the first driving unit. The second charge pump circuit applies a second output voltage to the second driving unit. The operation control unit controls the operations of the first charge pump circuit and the second charge pump circuit. The operation control unit may also determine the application period of the first output voltage in the first charge pump circuit and the application period of the second output voltage in the second charge pump circuit based on the states of the first voltage, the second voltage, the first conversion operation, or the second conversion operation.

[0037] According to this structure, the DCDC converter can apply voltages to the first driving unit and the second driving unit separately. Therefore, the first switching unit and the second switching unit can be driven separately, and the voltage conversion unit can operate more efficiently.

[0038] (7) The charge pump circuit unit of the DCDC converter of the present disclosure includes a charge pump circuit and an operation control unit. The charge pump circuit performs a first operation of applying a first output voltage to the first driving unit and a second operation of applying a second output voltage to the second driving unit. The operation control unit controls the first operation and the second operation of the charge pump circuit. The operation control unit may also determine the period of the first operation and the period of the second operation based on the states of the first voltage, the second voltage, the first conversion operation, or the second conversion operation.

[0039] According to this structure, the charge pump circuit can switch between performing at least one of the first operation and the second operation through the operation control unit. Therefore, compared with the case where two charge pump circuits are provided corresponding to the first driving unit and the second driving unit, the DCDC converter of the present disclosure can suppress the number of components.

[0040] [Details of the Embodiments of the Present Disclosure]

[0041] <Embodiment 1>

[0042] 〔Overview of the DC-DC Converter〕

[0043] Figure 1 The DC-DC converter 1 shown is configured, for example, as a step-up / step-down DC-DC converter for vehicle use, and is configured to step up or step down the DC voltage applied to one of the first conductive circuit 91 and the second conductive circuit 92 and output it to the other conductive circuit.

[0044] The DC-DC converter 1 includes a first conductive circuit 91 and a second conductive circuit 92 as power lines. The first conductive circuit 91 is a wiring electrically connected to the high-potential side terminal of a first power supply unit (not shown) and conducting with the high-potential side terminal. The first conductive circuit 91 is configured to be applied with a predetermined DC voltage from the first power supply unit. The second conductive circuit 92 is a wiring electrically connected to the high-potential side terminal of a second power supply unit (not shown) and conducting with the high-potential side terminal. The second conductive circuit 92 is configured to be applied with a predetermined DC voltage from the second power supply unit.

[0045] The first power supply unit and the second power supply unit are constituted by known power storage units such as lead-acid batteries, lithium-ion batteries, electric double layer capacitors, lithium-ion capacitors, and other power storage units. The specific values of the output voltage of the first power supply unit and the output voltage of the second power supply unit are not particularly limited, and preferably have the same output voltage. The low-potential side terminals of the first power supply unit and the second power supply unit are electrically connected to a ground portion (not shown) and maintained at a predetermined ground potential (0V).

[0046] The DC-DC converter 1 includes a voltage conversion unit 6, a first voltage detection unit 41, a second voltage detection unit 42, a control unit 12, a drive unit 8, a bootstrap circuit unit 20, and a charge pump circuit unit 30.

[0047] The voltage conversion unit 6 has a function of stepping up or stepping down the input voltage by the on / off operation of the switching elements T1, T2, T3, and T4 and outputting it. The voltage conversion unit 6 is provided between the first conductive circuit 91 and the second conductive circuit 92. The voltage conversion unit 6 can perform a first conversion operation and a second conversion operation. The first conversion operation is at least one of the operation of stepping down the voltage applied to the first conductive circuit 91 and applying the voltage to the second conductive circuit 92 and the operation of stepping up the voltage applied to the second conductive circuit 92 and applying the voltage to the first conductive circuit 91. The second conversion operation is at least one of the operation of stepping up the voltage applied to the first conductive circuit 91 and applying the voltage to the second conductive circuit 92 and the operation of stepping down the voltage applied to the second conductive circuit 92 and applying the voltage to the first conductive circuit 91.

[0048] The voltage conversion unit 6 includes switching elements T1, T2, T3, T4 arranged in an H-bridge configuration and an inductor L, and functions as a DCDC converter that performs so-called bidirectional buck-boost conversion. The switching elements T1, T2, T3, T4 are all configured as N-channel MOSFETs. The switching element T1 is the first high-side element. The switching element T2 is the first low-side element. The switching element T3 is the second high-side element. The switching element T4 is the second low-side element. The switching elements T1 and T2 constitute the first switching unit S1. The switching elements T3 and T4 constitute the second switching unit S2. The inductor L is configured as a known coil having a predetermined inductance.

[0049] In the voltage conversion unit 6, the first conduction path 91 is electrically connected to the drain of the switching element T1, and the drain of the switching element T2 and one end of the inductor L are electrically connected to the source of the switching element T1. The second conduction path 92 is electrically connected to the drain of the switching element T3, and the drain of the switching element T4 and the other end of the inductor L are electrically connected to the source of the switching element T3. The sources of the switching elements T2 and T4 are electrically connected to the ground. First drive signals D1, second drive signals D2, etc. from a drive unit 8 described later are input to the gates of the switching elements T1, T2, T3, T4 respectively.

[0050] The first voltage detection unit 41 and the second voltage detection unit 42 are both configured as known voltage detection circuits. The first voltage detection unit 41 inputs, as a detection value, a value representing the first voltage V1 of the first conduction path 91 (for example, the voltage value of the first conduction path 91, or a value obtained by dividing the voltage value of the first conduction path 91 by a voltage division circuit, etc.) to the operation control unit 33 of the charge pump circuit unit 30. The second voltage detection unit 42 inputs, as a detection value, a value representing the second voltage V2 of the second conduction path 92 (for example, the voltage value of the second conduction path 92, or a value obtained by dividing the voltage value of the second conduction path 92 by a voltage division circuit, etc.) to the operation control unit 33. Based on the value input from the first voltage detection unit 41, the operation control unit 33 can determine the voltage value of the first conduction path 91, and based on the value input from the second voltage detection unit 42, the operation control unit 33 can determine the voltage value of the second conduction path 92.

[0051] The first voltage detection unit 41 is configured to be able to input, as a detection value, a value representing the first voltage V1 of the first conduction path 91 to the control unit 12 (not shown). The second voltage detection unit 42 is configured to be able to input, as a detection value, a value representing the second voltage V2 of the second conduction path 92 to the control unit 12 (not shown).

[0052] The control unit 12 is configured as a microcomputer, for example. Based on the value of the first voltage V1, the value of the second voltage V2, and the target voltage value from the first voltage detection unit 41 and the second voltage detection unit 42, the control unit 12 performs feedback control by a known method to set the duty ratio of the PWM signal supplied to the voltage conversion unit 6. Then, the control unit 12 outputs the set first control signal Con1 and second control signal Con2 to the drive unit 8. The target voltage value can be either a value set by the control unit 12 or a value indicated from an external device such as an external ECU. The target voltage value can be changed to a desired value. Thus, the magnitude of the output voltage to the first conduction path 91 or the second conduction path 92 can be changed to a desired value. It is configured such that a charge selection signal Cs indicating which one of the first power supply unit and the second power supply unit is to be charged is input to the control unit 12 from an external device such as an external ECU. For example, when the charge selection signal Cs indicates charging of the first power supply unit, the control unit 12 sends a first power supply unit charge signal Cs1 for charging the first power supply unit by boosting or bucking from the second conduction path 92 to the first conduction path 91 to the operation control unit 33 of the charge pump circuit unit 30. When the charge selection signal Cs indicates charging of the second power supply unit, the control unit 12 sends a second power supply unit charge signal Cs2 for charging the second power supply unit by boosting or bucking from the first conduction path 91 to the second conduction path 92 to the operation control unit 33 of the charge pump circuit unit 30.

[0053] The drive unit 8 includes a first drive unit 81 and a second drive unit 82. When the first control signal Con1 as a control signal is output from the control unit 12, the first drive unit 81 outputs a first drive signal D1 corresponding to the first control signal Con1 to a first switch unit S1 composed of switch elements T1 and T2. Thereby, the first switch unit S1 starts synchronous rectification control. When the second control signal Con2 as a control signal is output from the control unit 12, the second drive unit 82 outputs a second drive signal D2 corresponding to the second control signal Con2 to a second switch unit S2 composed of switch elements T3 and T4. Thereby, the second switch unit S2 starts synchronous rectification control. Details of the synchronous rectification control will be described later.

[0054] The bootstrap circuit section 20 includes a first bootstrap circuit 21 and a second bootstrap circuit 22. The first bootstrap circuit 21 is disposed between the first drive section 81 and the first switch section S1. The second bootstrap circuit 22 is disposed between the second drive section 82 and the second switch section S2. The first bootstrap circuit 21 is configured to have a structure in which an unillustrated first diode and a capacitor C1 are connected in series. One end of the capacitor C1 is electrically connected to a first connection point P1 that electrically connects the source of the switching element T1 and the drain of the switching element T2. The other end of the capacitor C1 is electrically connected to the cathode of an unillustrated second diode. The anode of the first diode is electrically connected to, for example, the first conduction path 91, and the voltage at the connection point between the cathode of the first diode and the other end of the capacitor C1 (specifically, the voltage at the other end of the capacitor C1) is applied to the first drive section 81.

[0055] The second bootstrap circuit 22 is configured to have a structure in which an unillustrated second diode and a capacitor C2 are connected in series. One end of the capacitor C2 is electrically connected to a second connection point P2 that electrically connects the source of the switching element T3 and the drain of the switching element T4. The other end of the capacitor C2 is electrically connected to the cathode of an unillustrated second diode. The anode of the diode is electrically connected to, for example, the second conduction path 92, and the voltage at the connection point between the cathode of the second diode and the other end of the capacitor C2 (specifically, the voltage at the other end of the capacitor C2) is applied to the second drive section 82.

[0056] During the first switching operation, the first bootstrap circuit 21 applies a voltage higher than the first connection point P1 between the first high-side element (switching element T1) and the first low-side element (switching element T2) to the first drive section 81. Specifically, when the first low-side element (switching element T2) is in the on state, the capacitor C1 is applied with a first voltage V1 and thus stores electricity. Then, when the first high-side element (switching element T1) becomes in the on state, the capacitor C1 supplies the stored charge to the first drive section 81. During the second switching operation, the second bootstrap circuit 22 applies a voltage higher than the second connection point P2 between the second high-side element (switching element T3) and the second low-side element (switching element T4) to the second drive section 82. Specifically, when the second low-side element (switching element T4) is in the on state, the capacitor C2 is applied with a second voltage V2 and thus stores electricity. Then, when the second high-side element (switching element T3) becomes in the on state, the capacitor C2 supplies the stored charge to the second drive section 82.

[0057] The charge pump circuit section 30 includes a first charge pump circuit 31, a second charge pump circuit 32, and an operation control section 33. The first charge pump circuit 31 and the second charge pump circuit 32 are well-known circuits, for example, composed of a plurality of diodes connected in series and a plurality of capacitors respectively connected to connection points of the respective diodes (not shown). The first charge pump circuit 31, for example, boosts the input voltage to the first conduction circuit 91 and the second conduction circuit 92 and applies a first output voltage Vo1 to the first drive section 81. The second charge pump circuit 32, for example, boosts the input voltage to the first conduction circuit 91 and the second conduction circuit 92 and applies a second output voltage Vo2 to the second drive section 82.

[0058] The operation control section 33 is configured to be able to control the operations of the first charge pump circuit 31 and the second charge pump circuit 32. The operation control section 33 is configured to be able to receive a signal corresponding to the magnitude of the first voltage V1 (hereinafter also simply referred to as the first voltage V1) input from the first voltage detection section 41. The operation control section 33 is configured to be able to receive a signal corresponding to the magnitude of the second voltage V2 (hereinafter also simply referred to as the second voltage V2) input from the second voltage detection section 42. Further, the operation control section 33 is configured to be able to receive a signal indicating the state of the first conversion operation or the second conversion operation, that is, the first power supply section charging signal Cs1 or the second power supply section charging signal Cs2, input from the control section 12. Based on these input signals, the operation control section 33 determines the application timing of the first output voltage Vo1 in the first charge pump circuit 31 and the application timing of the second output voltage Vo2 in the second charge pump circuit 32.

[0059] 〔Operation in the DC-DC converter〕

[0060] Next, the operation of the DC-DC converter 1 of the present disclosure will be described.

[0061] 〔Operation of charging the first power supply section〕

[0062] As the operation of the DC-DC converter 1 for charging the first power supply section, there are the following two operations. One is the operation of boosting the voltage applied to the second conduction circuit 92 and applying the voltage to the first conduction circuit 91 in the first conversion operation. The other is the operation of reducing the voltage applied to the second conduction circuit 92 and applying the voltage to the first conduction circuit 91 in the second conversion operation.

[0063] Describe the case of performing the operation of boosting the voltage applied to the second conductive circuit 92 and applying the voltage to the first conductive circuit 91 in the first conversion operation. First, a charging selection signal Cs is input from an external device to the control unit 12. The charging selection signal Cs indicates charging of the first power supply unit. Then, the control unit 12 sends a first power supply unit charging signal Cs1 for boosting or bucking the voltage from the second conductive circuit 92 to the first conductive circuit 91 to the operation control unit 33. The control unit 12 outputs a first control signal Con1 to the first driving unit 81.

[0064] When the first driving unit 81 is output with the first control signal Con1 from the control unit 12, it outputs a first driving signal D1 corresponding to the first control signal Con1 to the voltage conversion unit 6. The first driving signal D1 is a signal that outputs a PWM signal in a form with a dead time set complementarily to each gate of the first switching unit S1 (switching elements T1, T2) of the voltage conversion unit 6. The first switching unit S1 (switching elements T1, T2) performs synchronous rectification control through the first driving signal D1. Specifically, during the period when a turn-on signal (e.g., H-level signal) is output to the switching element T1, a turn-off signal (e.g., L-level signal) is output to the switching element T2. Then, during the period when a turn-on signal (e.g., H-level signal) is output to the switching element T2, a turn-off signal (e.g., L-level signal) is output to the switching element T1, and synchronous rectification control is performed in the above manner.

[0065] The first bootstrap circuit 21 applies a voltage higher than the first connection point P1 between the first high-side element (switching element T1) and the first low-side element (switching element T2) to the first driving unit 81 through the synchronous rectification control of the first switching unit S1. Regarding the first driving signal D1, due to the voltage applied from the first bootstrap circuit 21, the potential of the H-level signal in the PWM signal is higher than the potential of the source voltage of the first high-side element (switching element T1). The H-level signal is a voltage signal. Thus, the first high-side element (switching element T1) can perform the switching operation reliably.

[0066] When the operation control unit 33 is input with the first power supply unit charging signal Cs1, and the first voltage V1 is higher than the second voltage V2, and the difference between the first voltage V1 and the second voltage V2 is equal to or greater than a predetermined first threshold, it outputs a second driving instruction signal Di2 to the second charge pump circuit 32. When the second charge pump circuit 32 is input with the second driving instruction signal Di2, it applies a second output voltage Vo2 to the second driving unit 82. This is to compensate for the function of the second bootstrap circuit 22 that can no longer apply an appropriate voltage to the second driving unit 82 because the switching element T3 of the second switching unit S2 remains in the on state when the first switching unit S1 performs synchronous rectification control.

[0067] When the second charge pump circuit 32 is not input with the second drive indication signal Di2, it does not apply the second output voltage Vo2 to the second drive unit 82. Additionally, when the operation control unit 33 is input with the first power supply unit charging signal Cs1, and the first voltage V1 is higher than the second voltage V2, and the difference between the first voltage V1 and the second voltage V2 is above a predetermined first threshold, it does not output the first drive indication signal Di1 to the first charge pump circuit 31.

[0068] When boosting the DC second voltage V2 (input voltage) applied to the second conduction circuit 92 through this control, an output voltage higher than the second voltage V2 applied to the second conduction circuit 92 is applied to the first conduction circuit 91. The magnitude of the output voltage in the first conduction circuit 91 is approximately the same as the target voltage value used in the control unit 12. The voltage applied as the output voltage to the first conduction circuit 91 is determined according to the duty ratio of the PWM signal (first drive signal D1) supplied to the gate of the switching element T1. At this time, for example, the control unit 12 outputs the second operation maintenance signal Fs2 to the second drive unit 82. After being input with the second operation maintenance signal Fs2, the second drive unit 82 continues to input a turn-on signal to the gate of the switching element T3, maintaining the switching element T3 in the on state. Additionally, after being input with the second operation maintenance signal Fs2, the second drive unit 82 continues to input a turn-off signal to the gate of the switching element T4, maintaining the switching element T4 in the off state.

[0069] Next, the case of performing the operation of reducing the voltage applied to the second conduction circuit 92 and applying the voltage to the first conduction circuit 91 during the second conversion operation will be described. First, the charge selection signal Cs is input from an external device to the control unit 12. The charge selection signal Cs indicates charging of the first power supply unit. Then, the control unit 12 sends the first power supply unit charging signal Cs1 for boosting or reducing the voltage from the second conduction circuit 92 to the first conduction circuit 91 to the operation control unit 33 of the charge pump circuit unit 30. The control unit 12 outputs the second control signal Con2 to the second drive unit 82.

[0070] After the second control signal Con2 is output from the control unit 12, the second drive unit 82 outputs a second drive signal D2 corresponding to the second control signal Con2 to the voltage conversion unit 6. The second drive signal D2 is a signal that outputs a PWM signal in a form with a dead time set complementarily to each gate of the second switching unit S2 (switching elements T3, T4) of the voltage conversion unit 6. The second switching unit S2 (switching elements T3, T4) performs synchronous rectification control through the second drive signal D2. Specifically, during the period when an on signal (e.g., an H-level signal) is output to the switching element T3, an off signal (e.g., an L-level signal) is output to the switching element T4. Then, during the period when an on signal (e.g., an H-level signal) is output to the switching element T4, an off signal (e.g., an L-level signal) is output to the switching element T3, and synchronous rectification control is performed in the above manner.

[0071] The second bootstrap circuit 22 applies a voltage higher than the second connection point P2 between the second high-side element (switching element T3) and the second low-side element (switching element T4) to the second drive unit 82 through the synchronous rectification control of the second switching unit S2. Regarding the second drive signal D2, due to the voltage applied from the second bootstrap circuit 22, the potential of the H-level signal in the PWM signal is higher than the potential of the source voltage of the second high-side element (switching element T3). The H-level signal is a voltage signal. Thus, the second high-side element (switching element T3) can perform a switching operation reliably.

[0072] When the operation control unit 33 is input with the first power supply unit charging signal Cs1, and the first voltage V1 is lower than the second voltage V2, and the difference between the first voltage V1 and the second voltage V2 is equal to or greater than a predetermined second threshold, the operation control unit 33 outputs a first drive instruction signal Di1 to the first charge pump circuit 31. When the first drive instruction signal Di1 is input, the first charge pump circuit 31 applies the first output voltage Vo1 to the first drive unit 81. This is to compensate for the function of the first bootstrap circuit 21 that can no longer apply an appropriate voltage to the first drive unit 81 because the switching element T1 of the first switching unit S1 remains in the on state when the second switching unit S2 performs synchronous rectification control. The first charge pump circuit 31 does not apply the first output voltage Vo1 to the first drive unit 81 when the first drive instruction signal Di1 is not input. In addition, when the operation control unit 33 is input with the first power supply unit charging signal Cs1, and the first voltage V1 is lower than the second voltage V2, and the difference between the first voltage V1 and the second voltage V2 is equal to or greater than a predetermined second threshold, the operation control unit 33 does not output a second drive instruction signal Di2 to the second charge pump circuit 32.

[0073] When the DC second voltage V2 (input voltage) applied to the second conductive circuit 92 is stepped down by this control, an output voltage lower than the second voltage V2 applied to the second conductive circuit 92 is applied to the first conductive circuit 91. The magnitude of the output voltage in the first conductive circuit 91 is substantially the same as the target voltage value used in the control unit 12. The voltage applied to the first conductive circuit 91 as the output voltage is determined according to the duty ratio of the PWM signal (first drive signal D1) supplied to the gate of the switching element T3. At this time, for example, the first operation maintenance signal Fs1 is output from the control unit 12 to the first drive unit 81. When the first operation maintenance signal Fs1 is input, the first drive unit 81 continues to input a turn-on signal to the gate of the switching element T1, maintaining the switching element T1 in the on state. In addition, when the first operation maintenance signal Fs1 is input, the first drive unit 81 continues to input a turn-off signal to the gate of the switching element T2, maintaining the switching element T2 in the off state.

[0074] 〔Operation of charging the second power supply unit〕

[0075] As the operation of the DCDC converter 1 to charge the second power supply unit, there are the following two operations. One is the operation of stepping down the voltage applied to the first conductive circuit 91 and applying the voltage to the second conductive circuit 92 in the first conversion operation. The other is the operation of stepping up the voltage applied to the first conductive circuit 91 and applying the voltage to the second conductive circuit 92 in the second conversion operation.

[0076] The case of explaining the operation of stepping down the voltage applied to the first conductive circuit 91 and applying the voltage to the second conductive circuit 92 in the first conversion operation will be described. First, the charge selection signal Cs is input from an external device to the control unit 12. The charge selection signal Cs indicates charging the second power supply unit. Then, the control unit 12 sends the second power supply unit charge signal Cs2 for stepping up or down from the first conductive circuit 91 to the second conductive circuit 92 to the operation control unit 33. The control unit 12 outputs the first control signal Con1 to the first drive unit 81.

[0077] When the first control signal Con1 is output from the control unit 12, the first drive unit 81 outputs the first drive signal D1 corresponding to the first control signal Con1 to the voltage conversion unit 6. The first switching unit S1 (switching elements T1, T2) performs synchronous rectification control through the first drive signal D1.

[0078] The first bootstrap circuit 21 applies a voltage higher than the voltage at the first connection point P1 between the first high-side element (switching element T1) and the first low-side element (switching element T2) to the first drive unit 81 through synchronous rectification control of the first switch unit S1. Regarding the first drive signal D1, due to the voltage applied from the first bootstrap circuit 21, its potential is higher than the potential of the source voltage of the first high-side element (switching element T1). Thus, the first high-side element (switching element T1) can perform a switching operation reliably.

[0079] When the operation control unit 33 is input with the second power supply unit charging signal Cs2, and the first voltage V1 is higher than the second voltage V2, and the difference between the first voltage V1 and the second voltage V2 is equal to or greater than a predetermined first threshold, the operation control unit 33 outputs a second drive instruction signal Di2 to the second charge pump circuit 32. When the second drive instruction signal Di2 is input, the second charge pump circuit 32 applies the second output voltage Vo2 to the second drive unit 82. This is to compensate for the function of the second bootstrap circuit 22 that can no longer apply an appropriate voltage to the second drive unit 82 because the switching element T3 of the second switch unit S2 is maintained in the on state when the first switch unit S1 performs synchronous rectification control. In addition, when the operation control unit 33 is input with the second power supply unit charging signal Cs2, and the first voltage V1 is higher than the second voltage V2, and the difference between the first voltage V1 and the second voltage V2 is equal to or greater than a predetermined first threshold, the operation control unit 33 does not output the first drive instruction signal Di1 to the first charge pump circuit 31.

[0080] When the DC first voltage V1 (input voltage) applied to the first conduction path 91 is stepped down through this control, an output voltage lower than the first voltage V1 applied to the first conduction path 91 is applied to the second conduction path 92. The magnitude of the output voltage in the second conduction path 92 is approximately the same as the target voltage value used in the control unit 12. At this time, for example, through the second operation maintenance signal Fs2 output from the control unit 12 to the second drive unit 82, the second drive unit 82 continues to input an on signal to the gate of the switching element T3 to maintain the switching element T3 in the on state. In addition, when the second operation maintenance signal Fs2 is input, the second drive unit 82 continues to input an off signal to the gate of the switching element T4 to maintain the switching element T4 in the off state.

[0081] Next, a case will be described where the voltage applied to the first conductive circuit 91 is boosted and the boosted voltage is applied to the second conductive circuit 92 in the second conversion operation. First, a charge selection signal Cs is input from an external device to the control unit 12. The charge selection signal Cs indicates charging of the second power supply unit. Then, the control unit 12 sends a second power supply unit charge signal Cs2 for boosting or bucking from the first conductive circuit 91 to the second conductive circuit 92 to the operation control unit 33. The control unit 12 outputs a second control signal Con2 to the second drive unit 82.

[0082] After the second control signal Con2 is output from the control unit 12, the second drive unit 82 outputs a second drive signal D2 corresponding to the second control signal Con2 to the voltage conversion unit 6. The second switch unit S2 (switching elements T3, T4) performs synchronous rectification control through the second drive signal D2.

[0083] The second bootstrap circuit 22 applies a voltage higher than the second connection point P2 between the second high-voltage side element (switching element T3) and the second low-voltage side element (switching element T4) to the second drive unit 82 through the synchronous rectification control of the second switch unit S2. Regarding the second drive signal D2, due to the voltage applied from the second bootstrap circuit 22, its potential is higher than the potential of the source voltage of the second high-voltage side element (switching element T3). Thus, the second high-voltage side element (switching element T3) can perform a switching operation reliably.

[0084] When the operation control unit 33 is input with the second power supply unit charge signal Cs2, and the first voltage V1 is lower than the second voltage V2, and the difference between the first voltage V1 and the second voltage V2 is equal to or greater than a predetermined second threshold value, the operation control unit 33 outputs a first drive instruction signal Di1 to the first charge pump circuit 31. After the first drive instruction signal Di1 is input, the first charge pump circuit 31 applies a first output voltage Vo1 to the first drive unit 81. This is to compensate for the function of the first bootstrap circuit 21 that can no longer apply an appropriate voltage to the first drive unit 81 because the switching element T1 of the first switch unit S1 is maintained in the on state when the second switch unit S2 performs synchronous rectification control. The first charge pump circuit 31 does not apply the first output voltage Vo1 to the first drive unit 81 when the first drive instruction signal Di1 is not input. In addition, when the operation control unit 33 is input with the second power supply unit charge signal Cs2, and the first voltage V1 is lower than the second voltage V2, and the difference between the first voltage V1 and the second voltage V2 is equal to or greater than a predetermined second threshold value, the operation control unit 33 does not output a second drive instruction signal Di2 to the second charge pump circuit 32.

[0085] When boosting the first DC voltage V1 (input voltage) applied to the first conductive circuit 91 through this control, an output voltage higher than the first voltage V1 applied to the first conductive circuit 91 is applied to the second conductive circuit 92. The magnitude of the output voltage in the second conductive circuit 92 is substantially the same as the target voltage value used in the control unit 12. At this time, for example, through the first operation maintenance signal Fs1 output from the control unit 12 to the first drive unit 81, the first drive unit 81 continues to input a turn-on signal to the gate of the switching element T1, maintaining the switching element T1 in the on state. In addition, after being input with the first operation maintenance signal Fs1, the first drive unit 81 continues to input a turn-off signal to the gate of the switching element T2, maintaining the switching element T2 in the off state.

[0086] 〔Operations of the first charge pump circuit and the second charge pump circuit when the input voltage changes〕

[0087] Next, the operation of the charge pump circuit unit 30 will be described when the input voltage to the first conductive circuit 91 changes from a state higher than the output voltage to the second conductive circuit 92 to a low state when the output voltage is applied to the second conductive circuit 92 based on the input voltage to the first conductive circuit 91.

[0088] First, as Figure 2 shown, at time T1, the first voltage V1 in the first conductive circuit 91 is in a state higher than the second voltage V2 in the second conductive circuit 92, and the difference between the first voltage V1 and the second voltage V2 is equal to or greater than a predetermined threshold Th1 (first threshold). The second power supply unit charging signal Cs2 is input from the control unit 12 to the operation control unit 33. The voltage conversion unit 6 steps down the first voltage V1 in the first conductive circuit 91 and outputs it as the second voltage V2 to the second conductive circuit 92. The first bootstrap circuit 21 applies a voltage higher than the first connection point P1 between the first high-voltage side element (switching element T1) and the first low-voltage side element (switching element T2) to the first drive unit 81 through the synchronous rectification control of the first switch unit S1. Since the first charge pump circuit 31 is not input with the first drive instruction signal Di1, it does not output the first output voltage Vo1 to the first drive unit 81. At this time, the voltage conversion unit 6 performs the first conversion operation. The second charge pump circuit 32 is input with the second drive instruction signal Di2 from the operation control unit 33 and applies the second output voltage Vo2 to the second drive unit 82.

[0089] Next, from time T1 to time T2, the first voltage V1 applied to the first conduction path 91 gradually decreases. At time T2, the difference between the first voltage V1 and the second voltage V2 is lower than a predetermined threshold Th1 (first threshold). At this time, the potential difference between the drain and source of the first high-voltage side element (switching element T1) becomes smaller. At this time, the control unit 12 performs control to make the duty ratio of the PWM signal supplied to the gate of the first high-voltage side element (switching element T1) longer, and the on-state time of the first high-voltage side element (switching element T1) becomes longer. Along with this, the control unit 12 performs control to make the duty ratio of the PWM signal supplied to the gate of the first low-voltage side element (switching element T2) shorter, and the on-state time of the first low-voltage side element (switching element T2) becomes shorter. Therefore, the capacitor C1 of the first bootstrap circuit 21 becomes a state where it is not sufficiently charged, and it is no longer possible to sufficiently supply charge to the first drive unit 81 from the capacitor C1. When the second power supply unit charging signal Cs2 is input from the control unit 12 and the difference between the first voltage V1 and the second voltage V2 is lower than the predetermined threshold Th1 (first threshold), the operation control unit 33 outputs a first drive instruction signal Di1 to the first charge pump circuit 31. When the first drive instruction signal Di1 is input, the first charge pump circuit 31 starts to apply a first output voltage Vo1 to the first drive unit 81. Thereby, the first charge pump circuit 31 compensates for the function of the first bootstrap circuit 21.

[0090] Next, from time T2 to time T3, the first voltage V1 applied to the first conduction path 91 further gradually decreases. Then, at time T3, the magnitude of the first voltage V1 is smaller than the second voltage V2. Then, the voltage conversion unit 6 switches from the first conversion operation to the second conversion operation. Specifically, the first voltage V1 in the first conduction path 91 is boosted, and the voltage is output as the second voltage V2 to the second conduction path 92. At this time, the control unit 12 stops outputting the first control signal Con1 to the first drive unit 81 and starts outputting the second control signal Con2 to the second drive unit 82. Thereby, the synchronous rectification control of the first switch unit S1 stops, and the first bootstrap circuit 21 stops applying voltage to the first drive unit 81. Then, due to the start of the synchronous rectification control of the second switch unit S2, the second bootstrap circuit 22 starts applying a voltage higher than the second connection point P2 between the second high-voltage side element (switching element T3) and the second low-voltage side element (switching element T4) to the second drive unit 82.

[0091] Then, from time T3 to time T4, the first voltage V1 in the first conduction path 91 further gradually decreases. Then, at time T4, the difference between the first voltage V1 and the second voltage V2 becomes equal to or greater than a predetermined threshold Th1 (second threshold). At this time, the voltage applied from the second bootstrap circuit 22 to the second drive unit 82 becomes large enough. Then, the operation control unit 33 stops outputting the second drive instruction signal Di2 that was previously output to the second charge pump circuit 32. The first drive instruction signal Di1 continues to be input to the first charge pump circuit 31, and the first output voltage Vo1 continues to be applied to the first drive unit 81. During the period from time T2 to time T4, the first charge pump circuit 31 and the second charge pump circuit 32 are driven together.

[0092] Next, the operation of the charge pump circuit unit 30 will be described when the input voltage to the second conduction path 92 changes from a state lower than the output voltage to the first conduction path 91 to a state higher than the output voltage while the output voltage is applied to the first conduction path 91 based on the input voltage to the second conduction path 92.

[0093] First, as Figure 3 shown, at time T1, the second voltage V2 in the second conduction path 92 is in a state lower than the first voltage V1 in the first conduction path 91, and the difference between the first voltage V1 and the second voltage V2 is equal to or greater than a predetermined threshold Th1 (first threshold). The first power supply unit charging signal Cs1 is input from the control unit 12 to the operation control unit 33. The voltage conversion unit 6 boosts the second voltage V2 in the second conduction path 92 and outputs it as the first voltage V1 to the first conduction path 91. The first bootstrap circuit 21 applies a voltage higher than the first connection point P1 between the first high-voltage side element (switching element T1) and the first low-voltage side element (switching element T2) to the first drive unit 81 through synchronous rectification control of the first switching unit S1. Since the first charge pump circuit 31 is not input with the first drive instruction signal Di1, the first charge pump circuit 31 does not output the first output voltage Vo1 to the first drive unit 81. At this time, the voltage conversion unit 6 performs a first conversion operation. The second charge pump circuit 32 is input with the second drive instruction signal Di2 from the operation control unit 33, and the second output voltage Vo2 is applied to the second drive unit 82.

[0094] Next, from time T1 to time T2, the second voltage V2 applied to the second conduction circuit 92 gradually increases. At time T2, the difference between the first voltage V1 and the second voltage V2 is lower than a predetermined threshold Th1 (first threshold). At this time, the potential difference between the drain and source of the first high-voltage side element (switching element T1) becomes smaller. At this time, the control unit 12 performs control to make the duty ratio of the PWM signal supplied to the gate of the first high-voltage side element (switching element T1) longer, and the on-state time of the first high-voltage side element (switching element T1) becomes longer. Along with this, the control unit 12 performs control to make the duty ratio of the PWM signal supplied to the gate of the first low-voltage side element (switching element T2) shorter, and the on-state time of the first low-voltage side element (switching element T2) becomes shorter. Therefore, the capacitor C1 of the first bootstrap circuit 21 becomes a state where it is not sufficiently charged, and it is no longer possible to sufficiently supply charge to the first drive unit 81 from the capacitor C1. When the first power supply unit charging signal Cs1 is input from the control unit 12 and the difference between the first voltage V1 and the second voltage V2 is lower than the predetermined threshold Th1 (first threshold), the operation control unit 33 outputs a first drive instruction signal Di1 to the first charge pump circuit 31. When the first drive instruction signal Di1 is input, the first charge pump circuit 31 starts to apply a first output voltage Vo1 to the first drive unit 81. Thereby, the first charge pump circuit 31 compensates for the function of the first bootstrap circuit 21.

[0095] Next, from time T2 to time T3, the second voltage V2 applied to the second conduction circuit 92 further gradually increases. Then, at time T3, the magnitude of the second voltage V2 is greater than the first voltage V1. Then, the voltage conversion unit 6 switches from the first conversion operation to the second conversion operation. Specifically, the second voltage V2 in the second conduction circuit 92 is stepped down, and the voltage is output as the first voltage V1 to the first conduction circuit 91. At this time, the control unit 12 stops outputting the first control signal Con1 to the first drive unit 81 and starts outputting the second control signal Con2 to the second drive unit 82. Thereby, the synchronous rectification control of the first switch unit S1 stops, and the first bootstrap circuit 21 stops applying voltage to the first drive unit 81. Then, due to the start of the synchronous rectification control of the second switch unit S2, the second bootstrap circuit 22 starts applying a voltage higher than the second connection point P2 between the second high-voltage side element (switching element T3) and the second low-voltage side element (switching element T4) to the second drive unit 82.

[0096] Then, from time T3 to time T4, the second voltage V2 in the second conduction circuit 92 gradually increases further. Then, at time T4, the difference between the first voltage V1 and the second voltage V2 becomes equal to or greater than a predetermined threshold Th1 (second threshold). At this time, the voltage applied from the second bootstrap circuit 22 to the second drive unit 82 becomes large enough. Then, the operation control unit 33 stops the output of the second drive instruction signal Di2 that has been output to the second charge pump circuit 32. The first drive instruction signal Di1 continues to be input to the first charge pump circuit 31, and the first output voltage Vo1 continues to be applied to the first drive unit 81. During the period from time T2 to time T4, the first charge pump circuit 31 and the second charge pump circuit 32 are driven together.

[0097] Next, the operation of the charge pump circuit unit 30 will be described when the input voltage to the first conduction circuit 91 changes from a state lower than the output voltage to the second conduction circuit 92 to a higher state when the output voltage is applied to the second conduction circuit 92 based on the input voltage to the first conduction circuit 91.

[0098] First, as Figure 4 shown, at time T1, the first voltage V1 in the first conduction circuit 91 is in a state lower than the second voltage V2 in the second conduction circuit 92, and the difference between the first voltage V1 and the second voltage V2 is equal to or greater than a predetermined threshold Th1 (second threshold). The second power supply unit charging signal Cs2 is input from the control unit 12 to the operation control unit 33. The voltage conversion unit 6 boosts the first voltage V1 in the first conduction circuit 91 and outputs it as the second voltage V2 to the second conduction circuit 92. The second bootstrap circuit 22 applies a voltage higher than the second connection point P2 between the second high-voltage side element (switching element T3) and the second low-voltage side element (switching element T4) to the second drive unit 82 through synchronous rectification control of the second switch unit S2. Since the second charge pump circuit 32 is not input with the second drive instruction signal Di2, the second output voltage Vo2 is not output to the second drive unit 82. At this time, the voltage conversion unit 6 performs a second conversion operation. The first charge pump circuit 31 is input with the first drive instruction signal Di1 from the operation control unit 33, and the first output voltage Vo1 is applied to the first drive unit 81.

[0099] Next, from time T1 to time T2, the first voltage V1 applied to the first conduction path 91 gradually increases. At time T2, the difference between the first voltage V1 and the second voltage V2 is lower than a predetermined threshold Th1 (second threshold). At this time, the potential difference between the drain and the source of the second high-voltage side element (switching element T3) becomes smaller. At this time, the control unit 12 performs control to make the duty ratio of the PWM signal supplied to the gate of the second high-voltage side element (switching element T3) longer, and the on-state time of the second high-voltage side element (switching element T3) becomes longer. Along with this, the control unit 12 performs control to make the duty ratio of the PWM signal supplied to the gate of the second low-voltage side element (switching element T4) shorter, and the on-state time of the second low-voltage side element (switching element T4) becomes shorter. Therefore, the capacitor C2 of the second bootstrap circuit 22 becomes a state where it is not sufficiently charged, and it is no longer possible to sufficiently supply charge to the second drive unit 82 from the capacitor C2. When the second power supply unit charging signal Cs2 is input from the control unit 12 and the difference between the first voltage V1 and the second voltage V2 is lower than the predetermined threshold Th1 (second threshold), the operation control unit 33 outputs a second drive instruction signal Di2 to the second charge pump circuit 32. When the second drive instruction signal Di2 is input, the second charge pump circuit 32 starts to apply the second output voltage Vo2 to the second drive unit 82. Thereby, the second charge pump circuit 32 compensates for the function of the second bootstrap circuit 22.

[0100] Next, from time T2 to time T3, the first voltage V1 applied to the first conduction path 91 further gradually increases. Then, at time T3, the magnitude of the first voltage V1 is greater than the second voltage V2. Then, the voltage conversion unit 6 switches from the second conversion operation to the first conversion operation. Specifically, the first voltage V1 in the first conduction path 91 is stepped down, and the voltage is output as the second voltage V2 to the second conduction path 92. At this time, the control unit 12 stops outputting the second control signal Con2 to the second drive unit 82 and starts outputting the first control signal Con1 to the first drive unit 81. Thereby, the synchronous rectification control of the second switching unit S2 stops, and the second bootstrap circuit 22 stops applying voltage to the second drive unit 82. Then, due to the start of the synchronous rectification control of the first switching unit S1, the first bootstrap circuit 21 starts to apply a voltage higher than the first connection point P1 between the first high-voltage side element (switching element T1) and the first low-voltage side element (switching element T2) to the first drive unit 81.

[0101] Then, from time T3 to time T4, the first voltage V1 in the first conduction path 91 gradually increases further. Then, at time T4, the difference between the first voltage V1 and the second voltage V2 becomes equal to or greater than a predetermined threshold Th1 (first threshold). At this time, the voltage applied from the first bootstrap circuit 21 to the first drive unit 81 becomes large enough. Then, the operation control unit 33 stops the output of the first drive instruction signal Di1 that was previously output to the first charge pump circuit 31. The second drive instruction signal Di2 continues to be input to the second charge pump circuit 32, and the second output voltage Vo2 continues to be applied to the second drive unit 82. During the period from time T2 to time T4, the first charge pump circuit 31 and the second charge pump circuit 32 are driven together.

[0102] Next, the operation of the charge pump circuit unit 30 will be described when the input voltage to the second conduction path 92 changes from a state higher than the output voltage to the first conduction path 91 to a low state when the output voltage is applied to the first conduction path 91 based on the input voltage to the second conduction path 92.

[0103] First, as Figure 5 shown, at time T1, the second voltage V2 in the second conduction path 92 is in a state higher than the first voltage V1 in the first conduction path 91, and the difference between the first voltage V1 and the second voltage V2 is equal to or greater than a predetermined threshold Th1 (second threshold). The first power supply unit charging signal Cs1 is input from the control unit 12 to the operation control unit 33. The voltage conversion unit 6 steps down the second voltage V2 in the second conduction path 92 and outputs it as the first voltage V1 to the first conduction path 91. The second bootstrap circuit 22 applies a voltage higher than the second connection point P2 between the second high-voltage side element (switching element T3) and the second low-voltage side element (switching element T4) to the second drive unit 82 through synchronous rectification control of the second switching unit S2. Since the second drive instruction signal Di2 is not input to the second charge pump circuit 32, the second charge pump circuit 32 does not output the second output voltage Vo2 to the second drive unit 82. At this time, the voltage conversion unit 6 performs a second conversion operation. The first charge pump circuit 31 is input with the first drive instruction signal Di1 from the operation control unit 33, and the first output voltage Vo1 is applied to the first drive unit 81.

[0104] Next, from time T1 to time T2, the second voltage V2 applied to the second conduction circuit 92 gradually decreases. At time T2, the difference between the first voltage V1 and the second voltage V2 is lower than a predetermined threshold Th1 (second threshold). At this time, the potential difference between the drain and source of the second high-voltage side element (switching element T3) becomes smaller. At this time, the control unit 12 performs control to make the duty ratio of the PWM signal supplied to the gate of the second high-voltage side element (switching element T3) longer, and the on-state time of the second high-voltage side element (switching element T3) becomes longer. Along with this, the control unit 12 performs control to make the duty ratio of the PWM signal supplied to the gate of the second low-voltage side element (switching element T4) shorter, and the on-state time of the second low-voltage side element (switching element T4) becomes shorter. Therefore, the capacitor C2 of the second bootstrap circuit 22 becomes a state where it is not sufficiently charged, and it is no longer possible to sufficiently supply charge to the second drive unit 82 from the capacitor C2. When the first power supply unit charging signal Cs1 is input from the control unit 12 and the difference between the first voltage V1 and the second voltage V2 is lower than a predetermined threshold Th1 (second threshold), the operation control unit 33 outputs a second drive instruction signal Di2 to the second charge pump circuit 32. When the second drive instruction signal Di2 is input, the second charge pump circuit 32 starts to apply the second output voltage Vo2 to the second drive unit 82. Thereby, the second charge pump circuit 32 compensates for the function of the second bootstrap circuit 22.

[0105] Next, from time T2 to time T3, the second voltage V2 applied to the second conduction circuit 92 further gradually decreases. Then, at time T3, the magnitude of the second voltage V2 is lower than the first voltage V1. Then, the voltage conversion unit 6 switches from the second conversion operation to the first conversion operation. Specifically, the second voltage V2 in the second conduction circuit 92 is boosted, and the voltage is output as the first voltage V1 to the first conduction circuit 91. At this time, the control unit 12 stops outputting the second control signal Con2 to the second drive unit 82 and starts outputting the first control signal Con1 to the first drive unit 81. Thereby, the synchronous rectification control of the second switch unit S2 stops, and the second bootstrap circuit 22 stops applying voltage to the second drive unit 82. Then, due to the start of the synchronous rectification control of the first switch unit S1, the first bootstrap circuit 21 starts to apply a voltage higher than the first connection point P1 between the first high-voltage side element (switching element T1) and the first low-voltage side element (switching element T2) to the first drive unit 81.

[0106] Then, from time T3 to time T4, the second voltage V2 in the second conduction path 92 further gradually decreases. Then, at time T4, the difference between the first voltage V1 and the second voltage V2 becomes equal to or greater than a predetermined threshold Th1 (first threshold). At this time, the voltage applied from the first bootstrap circuit 21 to the first driving unit 81 becomes large enough. Then, the operation control unit 33 stops outputting the first driving instruction signal Di1 that was previously output to the first charge pump circuit 31. The second driving instruction signal Di2 continues to be input to the second charge pump circuit 32, and the second output voltage Vo2 continues to be applied to the second driving unit 82. During the period from time T2 to time T4, the first charge pump circuit 31 and the second charge pump circuit 32 are driven together.

[0107] Next, the effects of this configuration will be illustrated.

[0108] The DCDC converter 1 of the present disclosure includes a voltage conversion unit 6, a control unit 12, a driving unit 8, a first voltage detection unit 41, and a second voltage detection unit 42.

[0109] The voltage conversion unit 6 performs bidirectional voltage conversion between the first conduction path 91 and the second conduction path 92. The control unit 12 outputs a control signal for controlling the voltage conversion unit 6. The driving unit 8 outputs a first driving signal D1 and a second driving signal D2 corresponding to the first control signal Con1 and the second control signal Con2 output from the control unit 12. The first voltage detection unit 41 detects the first voltage V1 applied to the first conduction path 91. The second voltage detection unit 42 detects the second voltage V2 applied to the second conduction path 92. The voltage conversion unit 6 performs a first conversion operation and a second conversion operation. The first conversion operation performs at least one of the operations of stepping down the voltage applied to the first conduction path 91 and applying the voltage to the second conduction path 92 and stepping up the voltage applied to the second conduction path 92 and applying the voltage to the first conduction path 91. The second conversion operation performs at least one of the operations of stepping up the voltage applied to the first conduction path 91 and applying the voltage to the second conduction path 92 and stepping down the voltage applied to the second conduction path 92 and applying the voltage to the first conduction path 91. The control unit 12 outputs a first control signal Con1 for performing the first conversion operation and a second control signal Con2 for performing the second conversion operation.

[0110] The driving unit 8 includes a first driving unit 81 and a second driving unit 82. When the first control signal Con1 is output from the control unit 12, the first driving unit 81 outputs a first driving signal D1 corresponding to the first control signal Con1 to the voltage conversion unit 6. When the second control signal Con2 is output from the control unit 12, the second driving unit 82 outputs a second driving signal D2 corresponding to the second control signal Con2 to the voltage conversion unit 6. The voltage conversion unit 6 includes a first switching unit S1 and a second switching unit S2. The first switching unit S1 includes a switching element T1 and a switching element T2 and is supplied with the first driving signal D1. The second switching unit S2 includes a switching element T3 and a switching element T4 and is supplied with the second driving signal D2. When the first driving signal D1 is supplied to the first switching unit S1, the voltage conversion unit 6 performs a first conversion operation. When the second driving signal D2 is supplied to the second switching unit S2, the voltage conversion unit 6 performs a second conversion operation, and the structure is configured in the above manner.

[0111] Furthermore, the DCDC converter 1 of the present disclosure includes a bootstrap circuit unit 20 and a charge pump circuit unit 30. The bootstrap circuit unit 20 applies a voltage higher than the first connection point P1 between the switching elements T1 and T2 to the driving unit 8 during the first conversion operation, and applies a voltage higher than the second connection point P2 between the switching elements T3 and T4 to the driving unit 8 during the second conversion operation. The charge pump circuit unit 30 boosts the input voltage and applies an output voltage higher than the input voltage to the driving unit 8. The driving unit 8 outputs the first driving signal D1 and the second driving signal D2 including voltage signals corresponding to the voltage applied by the bootstrap circuit unit 20 or the voltage applied by the charge pump circuit unit 30. The charge pump circuit unit 30 determines the operation period for applying the output voltage based on the first voltage V1, the second voltage V2, the first power supply charging signal Cs1 indicating the state of the first conversion operation or the second conversion operation, and the second power supply charging signal Cs2.

[0112] When the DCDC converter 1 is in the first conversion operation or the second conversion operation, the bootstrap circuit unit 20 can apply a voltage higher than the first connection point P1 between the switching elements T1 and T2 or the second connection point P2 between the switching elements T3 and T4 to the drive unit 8. Further, since the charge pump circuit unit 30 can determine the operation period for applying the output voltage based on the first voltage V1 and the second voltage V2, in a structure capable of bidirectional voltage conversion, even when the bootstrap circuit unit 20 cannot apply an appropriate voltage during the operation period of the charge pump circuit unit 30, the charge pump circuit unit 30 can apply a higher voltage. Moreover, there is no need to always keep the charge pump circuit unit 30 operating continuously, and it can be made to operate during the necessary period in response to the first voltage V1, the second voltage V2, the first power supply charging signal Cs1 indicating the first conversion operation or the second conversion operation state, and the second power supply charging signal Cs2, so that power consumption can be suppressed.

[0113] When the difference between the first voltage V1 and the second voltage V2 is lower than the threshold Th1 (first threshold) in the state where the DCDC converter 1 of the present disclosure is performing the first conversion operation, the charge pump circuit unit 30 applies the output voltage to the first drive unit 81.

[0114] If configured in this way, when the DCDC converter 1 is in the first conversion operation, the difference between the first voltage V1 and the second voltage V2 is lower than the threshold Th1 (first threshold), and the risk of the bootstrap circuit unit 20 not applying an appropriate voltage increases. At this time, the charge pump circuit unit 30 can be made to operate to apply a voltage to the drive unit 8. Specifically, when the difference between the first voltage V1 and the second voltage V2 is lower than the threshold Th1 (first threshold), the duty ratio of the PWM signal supplied to the gate of the first high-side element (switching element T1) becomes longer. Along with this, the duty ratio of the PWM signal supplied to the gate of the first low-side element (switching element T2) becomes shorter, and the on-state time of the first low-side element (switching element T2) becomes shorter. Therefore, when the capacitor C1 of the first bootstrap circuit 21 becomes in a state where it is not sufficiently charged and can no longer supply enough charge to the first drive unit 81 from the capacitor C1, the charge pump circuit 30 is made to operate. In addition, regardless of the magnitudes of the absolute values of the first voltage V1 and the second voltage V2, the operation of the charge pump circuit unit 30 is switched based on the relative relationship between the first voltage V1 and the second voltage V2, so the output voltage to the first conduction path 91 or the second conduction path 92 is not limited to a specific value, and it can be applied even if set to a desired magnitude.

[0115] When the difference between the first voltage V1 and the second voltage V2 is lower than the threshold Th1 (second threshold) in the state where the DCDC converter 1 of the present disclosure is performing the second conversion operation, the charge pump circuit unit 30 applies the output voltage to the second drive unit 82.

[0116] If configured in this way, when the DCDC converter 1 performs the second conversion operation, the difference between the first voltage V1 and the second voltage V2 is lower than the threshold Th1 (second threshold), and the risk of not applying an appropriate voltage from the bootstrap circuit unit 20 increases. At this time, the charge pump circuit unit 30 can be operated to apply a voltage to the drive unit 8. Specifically, when the difference between the first voltage V1 and the second voltage V2 is lower than the threshold Th1 (second threshold), the duty ratio of the PWM signal supplied to the gate of the second high-side element (switching element T3) becomes longer. Along with this, the duty ratio of the PWM signal supplied to the gate of the second low-side element (switching element T4) becomes shorter and the on-state time of the second low-side element (switching element T4) becomes shorter. Therefore, when the capacitor C2 of the second bootstrap circuit 22 becomes a state where it is not sufficiently charged and can no longer supply enough charge to the second drive unit 82 from the capacitor C2, the charge pump circuit 30 is operated. In addition, regardless of the magnitudes of the absolute values of the first voltage V1 and the second voltage V2, the operation of the charge pump circuit unit 30 is switched based on the relative relationship between the first voltage V1 and the second voltage V2. Therefore, the output voltage to the first conduction path 91 or the second conduction path 92 is not limited to a specific value, and can be applied even if set to a desired magnitude.

[0117] When the charge pump circuit unit 30 of the DCDC converter 1 according to the present disclosure performs the first conversion operation in such a manner as to step down the voltage applied to the first conduction path 91 and apply the voltage to the second conduction path 92, or performs the second conversion operation in such a manner as to step down the voltage applied to the second conduction path 92 and apply the voltage to the first conduction path 91, when the second voltage V2 is greater than the first voltage V1, the output voltage is applied to the first drive unit 81, and when the first voltage V1 is greater than the second voltage V2, the output voltage is applied to the second drive unit 82.

[0118] If configured in this way, when the DCDC converter 1 performs a step-down operation between the first conduction path 91 and the second conduction path 92, when the first voltage V1 is greater than the second voltage V2, the second switching unit S2 does not perform a switching operation, so that the second bootstrap circuit 22 can no longer apply an appropriate voltage to the second driving unit 82, and the risk of no longer being able to reliably turn on the second high-side element (switching element T3) increases. At this time, the switching element T3 can be reliably turned on by the second charge pump circuit 32. In addition, when the second voltage V2 is greater than the first voltage V1, the first switching unit S1 does not perform a switching operation, so that the first bootstrap circuit 21 can no longer apply an appropriate voltage to the first driving unit 81, and the risk of no longer being able to reliably turn on the first high-side element (switching element T1) increases. At this time, the switching element T1 can be reliably turned on by the first charge pump circuit 31. Thus, the DCDC converter 1 can perform the power exchange between the first conduction path 91 and the second conduction path 92 well.

[0119] Specifically, when performing the first conversion operation in such a way as to step down the voltage applied to the first conduction path 91 and apply the voltage to the second conduction path 92, the capacitor C2 is no longer charged because the second low-side element (switching element T4) is maintained in the off state. At this time, by applying the second output voltage Vo2 from the second charge pump circuit 32 to the second driving unit 82, the switching element T3 of the second switching unit S2 is reliably turned on. Then, when performing the second conversion operation in such a way as to step down the voltage applied to the second conduction path 92 and apply the voltage to the first conduction path 91, the capacitor C1 is no longer charged because the first low-side element (switching element T2) is maintained in the off state. At this time, by applying the first output voltage Vo1 from the first charge pump circuit 31 to the first driving unit 81, the switching element T1 of the first switching unit S1 is reliably turned on.

[0120] When the charge pump circuit unit 30 of the DCDC converter 1 of the present disclosure performs the first conversion operation in such a way as to boost the voltage applied to the second conduction path 92 and apply the voltage to the first conduction path 91, or when performing the second conversion operation in such a way as to boost the voltage applied to the first conduction path 91 and apply the voltage to the second conduction path 92, when the first voltage V1 is greater than the second voltage V2, the output voltage is applied to the second driving unit 82, and when the second voltage V2 is greater than the first voltage V1, the output voltage is applied to the first driving unit 81.

[0121] If configured in this way, when the DCDC converter 1 performs a boosting operation between the first conduction path 91 and the second conduction path 92, when the first voltage V1 is greater than the second voltage V2, the second switching unit S2 does not perform a switching operation, so that the second bootstrap circuit 22 can no longer apply an appropriate voltage to the second driving unit 82, and the risk of no longer being able to reliably turn on the second high-voltage side element (switching element T3) increases. At this time, the switching element T2 can be reliably turned on by the second charge pump circuit 32. In addition, when the second voltage V2 is greater than the first voltage V1, the first switching unit S1 does not perform a switching operation, so that the first bootstrap circuit 21 can no longer apply an appropriate voltage to the first driving unit 81, and the risk of no longer being able to reliably turn on the first high-voltage side element (switching element T1) increases. At this time, the switching element T1 can be reliably turned on by the first charge pump circuit 31. Thus, the DCDC converter 1 can favorably perform the power exchange between the first conduction path 91 and the second conduction path 92.

[0122] Specifically, when performing the first conversion operation in such a manner that the voltage applied to the second conduction path 92 is boosted and the voltage is applied to the first conduction path 91, the capacitor C2 is no longer charged because the second low-voltage side element (switching element T4) is maintained in an off state. At this time, the second output voltage Vo2 is applied from the second charge pump circuit 32 to the second driving unit 82 to reliably turn on the switching element T2 of the second switching unit S2. Then, when performing the second conversion operation in such a manner that the voltage applied to the first conduction path 91 is boosted and the voltage is applied to the second conduction path 92, the capacitor C1 is no longer charged because the first low-voltage side element (switching element T2) is maintained in an off state. At this time, the first output voltage Vo1 is applied from the first charge pump circuit 31 to the first driving unit 81 to reliably turn on the switching element T1 of the first switching unit S1.

[0123] The charge pump circuit unit 30 of the DCDC converter 1 of the present disclosure includes a first charge pump circuit 31, a second charge pump circuit 32, and an operation control unit 33. The first charge pump circuit 31 applies the first output voltage Vo1 to the first driving unit 81. The second charge pump circuit 32 applies the second output voltage Vo2 to the second driving unit 82. The operation control unit 33 controls the operations of the first charge pump circuit 31 and the second charge pump circuit 32. The operation control unit 33 determines the application timing of the first output voltage Vo1 in the first charge pump circuit 31 and the application timing of the second output voltage Vo2 in the second charge pump circuit 32 based on the first voltage V1, the second voltage V2, the first power supply charging signal Cs1 indicating the state of the first conversion operation or the second conversion operation, and the second power supply charging signal Cs2.

[0124] According to this structure, the DCDC converter 1 can apply voltages to the first driving unit 81 and the second driving unit 82 separately. Therefore, the first switching unit S1 and the second switching unit S2 can be driven separately, and thus the voltage conversion unit 6 can operate more efficiently.

[0125] <Embodiment 2>

[0126] Next, with reference to Figure 6 , the DCDC converter 2 of Embodiment 2 will be described. The DCDC converter 2 is different from Embodiment 1 in that only one charge pump circuit 131 etc. in the charge pump circuit unit 130 is provided. For the same structure, the same reference numerals are added, and the description of the structure, operation, and effects is omitted.

[0127] The charge pump circuit unit 130 of the DCDC converter 2 includes a charge pump circuit 131 and an operation control unit 133. The charge pump circuit 131 is a well-known circuit, and is composed of, for example, a plurality of diodes connected in series and a plurality of capacitors respectively connected to connection points of the respective diodes (not shown). The charge pump circuit 131, for example, boosts the input voltage to the first conductive circuit 91 and the second conductive circuit 92, applies a first output voltage Vo1 to the first driving unit 81, or applies a second output voltage Vo2 to the second driving unit 82. The operation control unit 133 is configured to be able to control the operation of the charge pump circuit 131. The operation control unit 133 is configured to be able to receive a signal equivalent to the first voltage V1 from the first voltage detection unit 41, a signal equivalent to the second voltage V2 from the second voltage detection unit 42, and a first power supply charging signal Cs1 and a second power supply charging signal Cs2 from the control unit 12. The operation control unit 133 determines the application timing of the first output voltage Vo1 and the second output voltage Vo2 in the charge pump circuit 131 based on these input signals.

[0128] 〔Operation in the DCDC Converter〕

[0129] Next, the operation of the DCDC converter 2 of the present disclosure will be described.

[0130] 〔Operation of Charging the First Power Supply〕

[0131] A description will be given of the operation of boosting the voltage applied to the second conductive path 92 and applying the voltage to the first conductive path 91 in the first conversion operation. When the charging selection signal Cs input from an external device to the control unit 12 indicates charging of the first power supply unit, the control unit 12 outputs a first power supply unit charging signal Cs1 to the operation control unit 133. Then, the control unit 12 outputs a first control signal Con1 to the first drive unit 81. When the first control signal Con1 is output from the control unit 12, the first drive unit 81 outputs a first drive signal D1 corresponding to the first control signal Con1 to the voltage conversion unit 6. The first switching unit S1 (switching elements T1, T2) performs synchronous rectification control by the first drive signal D1. The first bootstrap circuit 21 applies a voltage higher than the first connection point P1 between the first high-side element (switching element T1) and the first low-side element (switching element T2) to the first drive unit 81 through the synchronous rectification control of the first switching unit S1.

[0132] When the operation control unit 133 is input with the first power supply unit charging signal Cs1, and the first voltage V1 is higher than the second voltage V2, and the difference between the first voltage V1 and the second voltage V2 is equal to or greater than a predetermined threshold value (first threshold value), the operation control unit 133 outputs a second switching signal Sw2 to the charge pump circuit 131. When the second switching signal Sw2 is input, the charge pump circuit 131 applies a second output voltage Vo2 to the second drive unit 82 and does not apply a first output voltage Vo1 to the first drive unit 81. That is, the charge pump circuit unit 130 performs a second operation of applying the second output voltage Vo2 to the second drive unit 82.

[0133] Next, a description will be given of the operation of reducing the voltage applied to the second conductive path 92 and applying the voltage to the first conductive path 91 in the second conversion operation. When the charging selection signal input from an external device to the control unit 12 indicates charging of the first power supply unit, the control unit 12 outputs a first power supply unit charging signal Cs1 to the operation control unit 133. The control unit 12 outputs a second control signal Con2 to the second drive unit 82. When the second control signal Con2 is output from the control unit 12, the second drive unit 82 outputs a second drive signal D2 corresponding to the second control signal Con2 to the voltage conversion unit 6. The second switching unit S2 (switching elements T3, T4) performs synchronous rectification control by the second drive signal D2. The second bootstrap circuit 22 applies a voltage higher than the second connection point P2 between the second high-side element (switching element T3) and the second low-side element (switching element T4) to the second drive unit 82 through the synchronous rectification control of the second switching unit S2.

[0134] When the operation control unit 133 is input with the first power supply unit charging signal Cs1, and the first voltage V1 is lower than the second voltage V2, and the difference between the first voltage V1 and the second voltage V2 is equal to or greater than a predetermined threshold (second threshold), the operation control unit 133 outputs the first switching signal Sw1 to the charge pump circuit 131. After being input with the first switching signal Sw1, the charge pump circuit 131 applies the first output voltage Vo1 to the first driving unit 81 and does not apply the second output voltage Vo2 to the second driving unit 82. That is, the charge pump circuit unit 130 performs the first operation of applying the first output voltage Vo1 to the first driving unit 81.

[0135] 〔Operation of charging the second power supply unit〕

[0136] The case of explaining the operation of reducing the voltage applied to the first conductive circuit 91 and applying the voltage to the second conductive circuit 92 during the first conversion operation is described. When the charging selection signal Cs input from the external device to the control unit 12 indicates charging of the second power supply unit, the control unit 12 outputs the second power supply unit charging signal Cs2 to the operation control unit 133. The control unit 12 outputs the first control signal Con1 to the first driving unit 81. After the first control signal Con1 is output from the control unit 12, the first driving unit 81 outputs the first driving signal D1 corresponding to the first control signal Con1 to the voltage conversion unit 6. The first switching unit S1 (switching elements T1, T2) performs synchronous rectification control through the first driving signal D1. The first bootstrap circuit 21 applies a voltage higher than the first connection point P1 between the first high-voltage side element (switching element T1) and the first low-voltage side element (switching element T2) to the first driving unit 81 through the synchronous rectification control of the first switching unit S1.

[0137] When the operation control unit 133 is input with the second power supply unit charging signal Cs2, and the first voltage V1 is higher than the second voltage V2, and the difference between the first voltage V1 and the second voltage V2 is equal to or greater than a predetermined threshold (first threshold), the operation control unit 133 outputs the second switching signal Sw2 to the charge pump circuit 131. After being input with the second switching signal Sw2, the charge pump circuit 131 applies the second output voltage Vo2 to the second driving unit 82 and does not apply the first output voltage Vo1 to the first driving unit 81. That is, the charge pump circuit unit 130 performs the second operation of applying the second output voltage Vo2 to the second driving unit 82.

[0138] Next, the case of performing the operation of boosting the voltage applied to the first conductive circuit 91 and applying the voltage to the second conductive circuit 92 in the second conversion operation will be described. When the charging selection signal Cs input from the external device to the control unit 12 indicates charging of the second power supply unit, the control unit 12 outputs a second power supply unit charging signal Cs2 to the operation control unit 133. The control unit 12 outputs a second control signal Con2 to the second drive unit 82. When the second control signal Con2 is output from the control unit 12, the second drive unit 82 outputs a second drive signal D2 corresponding to the second control signal Con2 to the voltage conversion unit 6. The second switch unit S2 (switching elements T3, T4) performs synchronous rectification control through the second drive signal D2. The second bootstrap circuit 22 applies a voltage higher than the second connection point P2 between the second high-voltage side element (switching element T3) and the second low-voltage side element (switching element T4) to the second drive unit 82 through the synchronous rectification control of the second switch unit S2.

[0139] When the operation control unit 133 is input with the second power supply unit charging signal Cs2, and the first voltage V1 is lower than the second voltage V2, and the difference between the first voltage V1 and the second voltage V2 is equal to or greater than a predetermined threshold (second threshold), the operation control unit 133 outputs a first switching signal Sw1 to the charge pump circuit 131. When the first switching signal Sw1 is input, the charge pump circuit 131 applies a first output voltage Vo1 to the first drive unit 81 and does not apply a second output voltage Vo2 to the second drive unit 82. That is, the charge pump circuit unit 130 performs a first operation of applying the first output voltage Vo1 to the first drive unit 81.

[0140] When the operation control unit 133 is input with the first power supply unit charging signal Cs1 or the second power supply unit charging signal Cs2, and the difference between the first voltage V1 and the second voltage V2 is lower than a predetermined threshold (second threshold or first threshold), the operation control unit 133 outputs a third switching signal Sw3 to the charge pump circuit 131. When the third switching signal Sw3 is input, the charge pump circuit 131 applies the first output voltage Vo1 to the first drive unit 81 and applies the second output voltage Vo2 to the second drive unit 82.

[0141] Next, the effects of this structure will be exemplified.

[0142] The charge pump circuit section 130 of the DCDC converter 2 of the present disclosure includes a charge pump circuit 131 and an operation control section 133. The charge pump circuit 131 performs a first operation of applying a first output voltage Vo1 to the first drive section 81 and a second operation of applying a second output voltage Vo2 to the second drive section 82. The operation control section 133 controls the first operation and the second operation of the charge pump circuit 131. The operation control section 133 determines the period of the first operation and the period of the second operation based on a first voltage V1, a second voltage V2, a first power supply section charging signal Cs1 indicating the state of the first conversion operation or the second conversion operation, and a second power supply section charging signal Cs2.

[0143] According to this configuration, the charge pump circuit 131 can switch between performing at least one of the first operation and the second operation through the operation control section 133. Therefore, the DCDC converter 2 can suppress the number of components compared to the case where two charge pump circuits 131 are provided corresponding to the first drive section 81 and the second drive section 82.

[0144] <Other Embodiments>

[0145] This configuration is not limited to the embodiments described above with reference to the description and the drawings. For example, the following embodiments are also included in the technical scope of the present invention.

[0146] In Embodiments 1 and 2, the drive section 8 is illustrated as including a first drive section 81 and a second drive section 82, but it may also be configured such that drive signals are respectively output from one drive section to the first switch section and the second switch section.

[0147] In Embodiments 1 and 2, N-channel MOSFETs are used for the switching elements T2 and T4, but a diode rectification method may be adopted by using a diode for one or both of them.

[0148] In Embodiment 1, the first threshold and the second threshold are both illustrated as the threshold Th1, but the first threshold and the second threshold may also be different values from each other.

[0149] It should be considered that the embodiments disclosed this time are exemplary in all aspects and not restrictive. The scope of the present invention is not limited to the embodiments disclosed this time, but is represented by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0150] Description of Reference Numerals

[0151] 1, 2... DCDC converters

[0152] 6... Voltage conversion section

[0153] 8... Drive section

[0154] 12… Control unit

[0155] 20… Bootstrap circuit section

[0156] 21… First bootstrap circuit

[0157] 22… Second bootstrap circuit

[0158] 30, 130… Charge pump circuit section

[0159] 31… First charge pump circuit

[0160] 32… Second charge pump circuit

[0161] 33, 133… Operation control section

[0162] 41… First voltage detection section

[0163] 42… Second voltage detection section

[0164] 81… First drive section

[0165] 82… Second drive section

[0166] 91… First conduction path

[0167] 92… Second conduction path

[0168] 131… Charge pump circuit

[0169] C1… Capacitor

[0170] C2… Capacitor

[0171] Con1… First control signal

[0172] Con2… Second control signal

[0173] Cs… Charge selection signal

[0174] Cs1… First power supply section charge signal

[0175] Cs2… Second power supply section charge signal

[0176] D1… First drive signal

[0177] D2… Second drive signal

[0178] Di1… First drive indication signal

[0179] Di2… Second drive indication signal

[0180] Fs1… First operation maintenance signal

[0181] Fs2… Second operation maintenance signal

[0182] L…Inductor

[0183] P1…First connection point

[0184] P2…Second connection point

[0185] S1…First switching section

[0186] S2…Second switching section

[0187] Sw1…First switching signal

[0188] Sw2…Second switching signal

[0189] Sw3…Third switching signal

[0190] T1…Switching element (first high-voltage side element)

[0191] T2…Switching element (first low-voltage side element)

[0192] T3…Switching element (second high-voltage side element)

[0193] T4…Switching element (second low-voltage side element)

[0194] Th1…First threshold, second threshold

[0195] V1…First voltage

[0196] V2…Second voltage

[0197] Vo1…First output voltage

[0198] Vo2…Second output voltage.

Claims

1. A DCDC converter, comprising: A voltage conversion unit that performs bidirectional voltage conversion between a first conduction path and a second conduction path; A control unit that outputs a control signal for controlling the voltage conversion unit; A drive unit that outputs a drive signal corresponding to the control signal output from the control unit; A first voltage detection unit that detects a first voltage applied to the first conduction path; And A second voltage detection unit that detects a second voltage applied to the second conduction path, The voltage conversion unit performs a first conversion operation and a second conversion operation, The first conversion operation is at least one of an operation of stepping down the voltage applied to the first conduction path and applying the voltage to the second conduction path and an operation of stepping up the voltage applied to the second conduction path and applying the voltage to the first conduction path, The second conversion operation is at least one of an operation of stepping up the voltage applied to the first conduction path and applying the voltage to the second conduction path and an operation of stepping down the voltage applied to the second conduction path and applying the voltage to the first conduction path. The control unit outputs a first control signal for performing the first conversion operation and a second control signal for performing the second conversion operation, The drive unit has: A first drive unit that outputs a first drive signal corresponding to the first control signal to the voltage conversion unit when the first control signal is output from the control unit; And A second drive unit that outputs a second drive signal corresponding to the second control signal to the voltage conversion unit when the second control signal is output from the control unit, The voltage conversion unit has: A first switch unit that includes a first high-voltage side element including a switch and a first low-voltage side element including a switch or a diode, and is provided with the first drive signal; And A second switch unit that includes a second high-voltage side element including a switch and a second low-voltage side element including a switch or a diode, and is provided with the second drive signal, An inductor is connected between a first connection point of the first high-voltage side element and the first low-voltage side element and a second connection point of the second high-voltage side element and the second low-voltage side element, When the first drive signal is provided to the first switch unit, the voltage conversion unit performs the first conversion operation, When the second drive signal is provided to the second switch unit, the voltage conversion unit performs the second conversion operation, The DCDC converter further includes: A bootstrap circuit unit that applies a voltage higher than the first connection point between the first high-voltage side element and the first low-voltage side element to the drive unit during the first conversion operation, and applies a voltage higher than the second connection point between the second high-voltage side element and the second low-voltage side element to the drive unit during the second conversion operation; And A charge pump circuit unit that steps up the input voltage and applies an output voltage higher than the input voltage to the drive unit, The driving unit outputs the first driving signal and the second driving signal including voltage signals corresponding to the voltage applied by the bootstrap circuit unit or the voltage applied by the charge pump circuit unit. The charge pump circuit unit determines the operation period during which the charge pump circuit unit applies the output voltage based on the first voltage, the second voltage, and the states of the first conversion operation or the second conversion operation.

2. The DCDC converter according to claim 1, wherein when the difference between at least the first voltage and the second voltage is lower than a first threshold in a state where the first conversion operation is being performed, the charge pump circuit unit applies the output voltage to the first driving unit.

3. The DCDC converter according to claim 1, wherein when the difference between at least the first voltage and the second voltage is lower than a second threshold in a state where the second conversion operation is being performed, the charge pump circuit unit applies the output voltage to the second driving unit.

4. The DCDC converter according to claim 1, wherein in a case where the first conversion operation is performed in such a manner that the voltage applied to the first conductive circuit is stepped down and the voltage is applied to the second conductive circuit, or in a case where the second conversion operation is performed in such a manner that the voltage applied to the second conductive circuit is stepped down and the voltage is applied to the first conductive circuit, when the second voltage is greater than the first voltage, the charge pump circuit unit applies the output voltage to the first driving unit, and when the first voltage is greater than the second voltage, the charge pump circuit unit applies the output voltage to the second driving unit.

5. The DCDC converter according to claim 1, wherein in a case where the first conversion operation is performed in such a manner that the voltage applied to the second conductive circuit is stepped up and the voltage is applied to the first conductive circuit, or in a case where the second conversion operation is performed in such a manner that the voltage applied to the first conductive circuit is stepped up and the voltage is applied to the second conductive circuit, when the first voltage is greater than the second voltage, the charge pump circuit unit applies the output voltage to the second driving unit, and when the second voltage is greater than the first voltage, the charge pump circuit unit applies the output voltage to the first driving unit.

6. The DCDC converter according to any one of claims 1 to 5, wherein the charge pump circuit unit includes: a first charge pump circuit that applies a first output voltage to the first driving unit; a second charge pump circuit that applies a second output voltage to the second driving unit; and an operation control unit that controls the operations of the first charge pump circuit and the second charge pump circuit, wherein the operation control unit determines the application period of the first output voltage in the first charge pump circuit and the application period of the second output voltage in the second charge pump circuit based on the first voltage, the second voltage, and the states of the first conversion operation or the second conversion operation.

7. The DCDC converter according to any one of claims 1 to 5, wherein The charge pump circuit section includes: A charge pump circuit that performs a first operation of applying a first output voltage to the first driving section and a second operation of applying a second output voltage to the second driving section; And An operation control section that controls the first operation and the second operation of the charge pump circuit, The operation control section determines the period of the first operation and the period of the second operation based on the state of the first voltage, the second voltage, the first conversion operation, or the second conversion operation.

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