Switching circuits, power generation circuits, and semiconductor devices
The switching circuit generates a floating power supply for high-side drivers using synchronized auxiliary switches and bootstrap circuits, addressing the challenges of component cost and control complexity in existing technologies, enabling efficient and inexpensive power supply.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- SANKEN ELECTRIC CO LTD
- Filing Date
- 2023-03-23
- Publication Date
- 2026-05-19
AI Technical Summary
Existing switching circuits face challenges in generating a floating power supply for high-side drivers without requiring expensive components or complex control methods, especially when the drain terminal potential is high or fluctuates, leading to potential damage and limited control range.
A switching circuit configuration using auxiliary switches and bootstrap circuits synchronized with main switches to generate and supply floating power to high-side drivers, utilizing inexpensive components and simple control signals.
The solution enables a compact, cost-effective power generation circuit that supplies floating power to high-side drivers without complex pre-controls, using small capacitors and diodes with minimal current capacity, suitable for various converter applications.
Smart Images
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Abstract
Description
[Technical Field]
[0001] The present invention relates to a switching circuit and a power supply generation circuit equipped with an N-type switching element that switches the voltage applied to the high-potential main terminal and outputs it to the low-potential main terminal which does not become ground potential. [Background technology]
[0002] Various converters utilize a switching circuit equipped with a switch element 2 that switches the voltage applied to the high-potential main terminal and outputs it to the low-potential main terminal. Such a switch element 2 is called a power element, and semiconductor elements such as MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) and IGBTs (Insulated Gate Bipolar Transistors) are used. In the following explanation, the switch element 2 will be assumed to be an N-type MOSFET.
[0003] When the potential Vs of the source terminal, which is the low-potential main terminal, is at ground potential, the switch element 2 can be driven by the gate drive voltage Vcc of the switch element 2. As shown in Figure 9(a), the switch element 2 can be driven by providing a power supply for the gate drive voltage Vcc and supplying the gate drive voltage Vcc to the low-side driver 5 that drives the switch element 2.
[0004] If there is a period when the potential Vs at the source terminal is at ground potential, the switch element 2 can be driven by a floating power supply generated by the bootstrap circuit 4 using the gate drive voltage Vcc. As shown in Figure 9(b), the bootstrap circuit 4 includes a diode Da and a capacitor Ca connected in series between the gate drive voltage Vcc and the source terminal. During the period when the source terminal is at ground potential, the gate drive voltage Vcc charges the capacitor Ca via the diode Da. The voltage across the capacitor Ca becomes a floating power supply. By supplying this floating power supply to the high-side driver 3 that drives the switch element 2, the switch element 2 can be driven.
[0005] The bootstrap circuit 4 shown in Figure 9(b) cannot perform the desired operation if there is no period during which the potential Vs at the source terminal is at ground potential. Therefore, the switch element 2, whose source terminal is not at ground potential, needs to secure the gate drive voltage Vcc by the following other method.
[0006] As shown in Figure 10(a), there is a method of driving the switch element 2 using a different power supply voltage VCC. By setting the power supply voltage VCC to the value obtained by adding the gate drive voltage Vcc to the potential Vd of the drain terminal, the switch element 2 can be driven directly.
[0007] As shown in Figure 10(b), there is a method of driving the switch element 2 by performing a level shift of the gate control signal G while isolating it with a pulse transformer 6.
[0008] As shown in Figure 10(c), there is a method of driving the switch element 2 using an isolated power supply 7. The isolated power supply 7 can supply the gate drive voltage Vcc to the high-side driver 3 by connecting the low-voltage side output to the source terminal of the switch element 2. [Prior art documents] [Patent Documents]
[0009] [Patent Document 1] Patent No. 6866959 [Overview of the project] [Problems that the invention aims to solve]
[0010] The method using an alternative power supply voltage VCC, as shown in Figure 10(a), is practically effective because when the potential Vd at the drain terminal is low, the power supply voltage VCC can also be low. However, it becomes difficult when the potential Vd at the drain terminal is high. For example, if the potential Vd at the drain terminal is 48V and the gate drive voltage is 10V, a high power supply voltage VCC of 58V is required. Also, if the potential Vs at the source terminal is high when the switch element is off, a large negative voltage is applied between the gate and source, which may damage the gate depending on the withstand capability of the switch element 2.
[0011] The method using the pulse transformer 6 shown in Figure 10(b) can sometimes be implemented with a relatively small number of components depending on the conditions, but because it is a transformer, it cannot produce DC output in principle. Therefore, the range in which the duty cycle can be controlled is narrow. It is said that the practically usable control range is about 20% to 80%, so the control range is also narrow. Another disadvantage is that the lower the drive frequency, the larger the pulse transformer 6 required.
[0012] The method using the isolated power supply 7 shown in Figure 10(c) is not practical considering the cost and size. In other words, because the isolated power supply 7 is expensive and large, it is not practical to provide an isolated power supply 7 solely for driving the switching element 2.
[0013] Furthermore, it has been proposed to provide multiple stages of bootstrap circuits 4 in order to secure floating power supplies to drive each of the multiple switch elements 2 connected in series (see, for example, Patent Document 1). However, in Patent Document 1, in order to charge each floating power supply, it is necessary to drive the switch elements 2 with different special pre-controls before starting normal control, which complicates the control of the switch elements 2.
[0014] This invention was made in view of the aforementioned problems, and its objective is to provide a switching circuit and a power supply generation circuit that can generate a floating power supply with an inexpensive component configuration without having to drive the switching element with different prior controls. [Means for solving the problem]
[0015] To achieve the above objective, the switching circuit according to the present invention is configured as follows. Book The switching circuit according to the invention comprises a first high-side driver and a second high-side driver that drive a first switch element and a second switch element connected in series and complementaryly controlled on / off, respectively, and is a switching circuit in which there is no period during which the low-potential terminal of the second switch element, which is located on the low-potential side, is at ground potential, and comprises a first auxiliary switch and a second auxiliary switch connected in series between ground and the low-potential terminal of the first switch element, a drive voltage source for the first switch element and the second switch element, a first diode and a first capacitor connected in series as a first bootstrap circuit between the connection point of the first auxiliary switch and the second auxiliary switch, and a second bootstrap circuit connected in series between the connection point of the first diode and the first capacitor and the low-potential terminal of the first switch element The device comprises a second diode and a second capacitor connected in a row, a third diode and a third capacitor connected in series as a third bootstrap circuit between the connection point of the first diode and the first capacitor and the low-potential terminal of the second switch element, and a control circuit that synchronizes the first auxiliary switch with the first switch element and controls the on / off state of the second auxiliary switch in synchronization with the second switch element, wherein when the first auxiliary switch is ON, the charge charged to the first capacitor from the drive voltage source is charged to the second capacitor and the third capacitor, respectively, when the second auxiliary switch is ON, and the voltages across the second capacitor and the third capacitor, respectively, are supplied to the first high-side driver and the second high-side driver as floating power supplies. 。 Furthermore, the power generation circuit according to the present invention is a power generation circuit that generates floating power supplies for a first high-side driver and a second high-side driver that drive a first switch element and a second switch element connected in series and complementaryly controlled on / off, wherein there is no period during which the low-potential terminal of the second switch element, which is located on the low-potential side, is at ground potential, and comprises a first auxiliary switch and a second auxiliary switch connected in series between ground and the low-potential terminal of the first switch element, a drive voltage source for the first switch element and the second switch element, a first diode and a first capacitor connected in series as a first bootstrap circuit between the connection point of the first auxiliary switch and the second auxiliary switch, and a second bootstrap circuit between the connection point of the first diode and the first capacitor and the low-potential terminal of the first switch element The system comprises a second diode and a second capacitor connected in series as a third bootstrap circuit, a third diode and a third capacitor connected in series between the connection point of the first diode and the first capacitor and the low-potential terminal of the second switch element, and a control circuit that synchronizes the first auxiliary switch with the first switch element and controls the on / off state of the second auxiliary switch in synchronization with the second switch element, wherein when the first auxiliary switch is ON, the charge charged to the first capacitor from the drive voltage source is charged to the second capacitor and the third capacitor, respectively, when the second auxiliary switch is ON, and the voltages across the second capacitor and the third capacitor, respectively, are supplied to the first high-side driver and the second high-side driver as the floating power supply. [Effects of the Invention]
[0016] The switching circuit of the present invention has the advantage of using a small-sized power generation circuit made of inexpensive components, and generating and supplying a floating power supply to the high-side driver that drives the switching element without driving the switching element with different prior controls. [Brief explanation of the drawing]
[0017] [Figure 1] This is a circuit diagram showing the configuration of a first embodiment of a switching circuit according to the present invention. [Figure 2] This is a waveform diagram showing the sequence of the switching circuit shown in FIG. 1. [Figure 3] This is a circuit diagram showing the configuration of a second embodiment of a switching circuit according to the present invention. [Figure 4] This is a waveform diagram showing the sequence of the switching circuit shown in FIG. 3. [Figure 5] This is a circuit diagram showing the configuration of a third embodiment of a switching circuit according to the present invention. [Figure 6] This is a waveform diagram showing the sequence of the switching circuit shown in FIG. 5. [Figure 7] This is a circuit diagram showing the configuration of the drive circuits of the first auxiliary switch and the second auxiliary switch shown in FIG. 5. [Figure 8] This is a circuit diagram showing the configuration of a fourth embodiment of a switching circuit according to the present invention. [Figure 9] This is a circuit diagram showing the configuration of a conventional switching circuit. [Figure 10] This is a circuit diagram showing the configuration of a conventional switching circuit.
Embodiments for Carrying Out the Invention
[0018] Hereinafter, preferred embodiments of the present invention will be described based on the accompanying drawings.
[0019] The switching circuit 10 of the present embodiment includes an N-type switch element 2, a high-side driver 3, and a power generation circuit 20.
[0020] Switch element 2 is a power element in various converters that switches the voltage applied to the drain terminal D, which is the high-potential main terminal, and outputs it to the source terminal S, which is the low-potential main terminal. Switch element 2 can be a semiconductor device such as a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor). In the following explanation, switch element 2 will be assumed to be a MOSFET.
[0021] The high-side driver 3 includes a level-shifting circuit that shifts the level of the gate control signal G that controls the on / off state of the switch element 2. The high-side driver 3 generates a gate drive signal based on the level-shifted gate control signal G and drives the switch element 2 with the generated gate drive signal.
[0022] The power generation circuit 20 is a circuit for supplying the gate drive voltage Vcc to the high-side driver 3.
[0023] The configurations of the first to fourth embodiments will be described in detail below. Note that components having similar functions will be given the same reference numerals, and their descriptions may be omitted. However, when distinguishing between components, a lowercase alphabet letter will be added to the end of the reference numeral of each component in the description.
[0024] (First Embodiment) The switching circuit 10a of the first embodiment, as shown in Figure 1, comprises an N-type switching element 2a, a high-side driver 3a, a power supply generation circuit 20a, and a control circuit 30a.
[0025] The switch element 2a switches the voltage applied to the drain terminal D and outputs it to the source terminal S by on / off control based on the gate control signal Ga shown in Figure 2(a). The potential of the drain terminal D of the switch element 2a is constant at Vin. The potential at point A connected to the source terminal S of the switch element 2a does not become ground potential, but is Vin when the switch element 2a is ON and Va, which is lower than Vin, when the switch element 2a is OFF, as shown in Figure 2(c).
[0026] The high-side driver 3a generates a gate drive signal based on a level-shifted gate control signal Ga, and drives the switch element 2a by applying the generated gate drive signal between the source terminal S and the control terminal gate terminal of the switch element 2a.
[0027] The power generation circuit 20a may be a semiconductor device integrated on a semiconductor substrate, and is a circuit that generates a floating power supply to be supplied to the high-side driver 3a. The power generation circuit 20a comprises a first auxiliary switch SW1 and a second auxiliary switch SW2, diodes D1 and D2, and capacitors C1 and C2. Hereafter, the forward voltage Vf of diodes D1 and D2 will be assumed to be 0V.
[0028] The series circuit consisting of the first auxiliary switch SW1 and the second auxiliary switch SW2 is connected between ground and point A, which is connected to the source terminal S of the switch element 2a. Point X, to which the first auxiliary switch SW1 and the second auxiliary switch SW2 are connected, is at ground potential when the first auxiliary switch SW1 is ON and the second auxiliary switch SW2 is OFF. Point X is at the potential of point A when the first auxiliary switch SW1 is OFF and the second auxiliary switch SW2 is ON.
[0029] A series circuit consisting of diode D1 and capacitor C1 is connected between the gate drive voltage Vcc and point X, forming the first bootstrap circuit. The anode of diode D1 is connected to the gate drive voltage Vcc, and the cathode is connected to the positive terminal of capacitor C1. The negative terminal of capacitor C1 is connected to point X.
[0030] The series circuit consisting of diode D2 and capacitor C2 is connected between the connection point (point Y) between diode D1 and the positive terminal of capacitor C1 and the source terminal S (point A) of switch element 2a, forming a second bootstrap circuit. Diode D2's anode is connected to the connection point (point Y) between diode D1 and the positive terminal of capacitor C1, and its cathode is connected to the positive terminal of capacitor C2. The negative terminal of capacitor C2 is connected to the source terminal S (point A) of switch element 2a.
[0031] The control circuit 30a outputs a gate control signal Ga that synchronizes the on / off control of the switch element 2a and the first auxiliary switch SW1, and an inverted signal Ga' shown in Figure 2(b), which is the inverted gate control signal Ga. The inverted signal Ga' is a control signal that controls the on / off control of the second auxiliary switch SW2. In other words, the first auxiliary switch SW1 is controlled to turn on and off in synchronization with the switch element 2a, and the second auxiliary switch SW2 is controlled to turn on and off complementaryly with the first auxiliary switch SW1 and the switch element 2a.
[0032] Figure 1(a) shows the operating state of each part during the first charging period T1, when the first auxiliary switch SW1 is ON and the second auxiliary switch SW2 is OFF. During the first charging period T1, the switch element 2a is ON. During the first charging period T1, point X, where the first auxiliary switch SW1 and the second auxiliary switch SW2 are connected, becomes ground potential, as shown in Figure 2(d). Since the negative terminal of capacitor C1 connected to point X becomes ground potential, the first bootstrap circuit operates, and charge is charged to capacitor C1 from the gate drive voltage Vcc through diode D1. As a result, the potential at point Y, connected to the positive terminal of capacitor C1, becomes Vcc, as shown in Figure 2(e), and the voltage across capacitor C1 becomes the gate drive voltage Vcc.
[0033] Figure 1(b) shows the operating states of each part during the second charging period T2, when the first auxiliary switch SW1 is off and the second auxiliary switch SW2 is on. During the second charging period T2, the switch element 2a is off. During the second charging period T2, point X, where the first auxiliary switch SW1 and the second auxiliary switch SW2 are connected, becomes the same potential Va as point A when the switch element 2a is off, as shown in Figure 2(d). In other words, capacitors C1 and C2 are connected in parallel, with their respective negative terminals connected to the same potential Va.
[0034] Since the negative terminal of capacitor C1 connected to point X becomes Va, the potential at point Y connected to the positive terminal of capacitor C1 becomes Vcc + Va, as shown in Figure 2(e). This activates the second bootstrap circuit, and charge is transferred from capacitor C1 to capacitor C2 through diode D2. Capacitor C2 then functions as a floating power supply for driving the switch element 2a, with the voltage across its terminals becoming the gate drive voltage Vcc.
[0035] In the first embodiment, the second auxiliary switch SW2 may be controlled on and off in synchronization with the switch element 2a by a gate control signal Ga, and the first auxiliary switch SW1 may be controlled on and off by an inverting signal Ga'. The series circuit consisting of the first auxiliary switch SW1 and the second auxiliary switch SW2 is connected between ground and the source of the switch element 2a. Therefore, during the second charge period T2, point X becomes the potential Vin of point A when the switch element 2a is ON, and the potential of point Y becomes Vcc + Vin, so the voltage across capacitor C2 becomes the gate drive voltage Vcc.
[0036] According to the first embodiment, a small-sized power generation circuit 20a made of inexpensive components can be used to generate and supply a floating power supply to the high-side driver 3a that drives the switch element 2a without driving the switch element 2a with different prior controls. Capacitors C1 and C2 only need to be able to drive the high-side driver 3a, so their capacitance can be small, and diodes D1 and D2 only need to be able to charge capacitors C1 and C2, so their current capacity can be small. Therefore, although the first auxiliary switch SW1 and the second auxiliary switch SW2 need to withstand a voltage of Vin or higher, the average current flowing through them is only a few mA to a few tens of mA, so small, inexpensive components with small current capacity can be selected. The first auxiliary switch SW1 and the second auxiliary switch SW2 only need to be driven by the gate control signal Ga of the switch element 2a and its inverted signal Ga', so only the normal control of the switch element 2a is required, and no complicated control is necessary.
[0037] (Second Embodiment) The switching circuit 10b of the second embodiment, as shown in Figure 3, comprises an N-type switching element 2b, a high-side driver 3b, a power supply generation circuit 20b, and a control circuit 30b.
[0038] Switch element 2b switches the voltage applied to the drain terminal D and outputs it to the source terminal S by on / off control based on the gate control signal Gb shown in Figure 4(a). Switch element 2b is located on the low side of switch element 2a. Switch element 2a is controlled on / off complementary to switch element 2b based on the gate control signal Ga, which is the inverted signal of the gate control signal Gb. The potential of the drain terminal D of switch element 2a is constant at Vin. As shown in Figure 4(c), the potential at point A, which is the connection point between the source terminal S of switch element 2a and the drain terminal D of switch element 2b, is Vin when switch element 2a is on and switch element 2b is off, and is lower than Vin, Va, when switch element 2a is off and switch element 2b is on. As shown in Figure 4(d), the potential at point B, to which the source terminal S of switch element 2b is connected, is not at ground potential, but is Va when switch element 2b is on, and is lower than Va, Vb, when switch element 2b is off.
[0039] The high-side driver 3b generates a gate drive signal based on the level-shifted gate control signal Gb, and drives the switch element 2b by applying the generated gate drive signal between the source terminal S (point B) and the control terminal gate terminal of the switch element 2b.
[0040] The power generation circuit 20b may be a semiconductor device integrated on a semiconductor substrate, and is a circuit that generates a floating power supply to be supplied to the high-side driver 3b. The power generation circuit 20b comprises a first auxiliary switch SW1 and a second auxiliary switch SW2, diodes D1 and D3, and capacitors C1 and C3. Hereafter, the forward voltage Vf of diodes D1 and D3 will be assumed to be 0V.
[0041] The series circuit consisting of the first auxiliary switch SW1 and the second auxiliary switch SW2 is connected between ground and point A, which is connected to the drain terminal D of the switch element 2b. Point X, to which the first auxiliary switch SW1 and the second auxiliary switch SW2 are connected, is at ground potential when the first auxiliary switch SW1 is ON and the second auxiliary switch SW2 is OFF. Point X is at the potential of point A when the first auxiliary switch SW1 is OFF and the second auxiliary switch SW2 is ON.
[0042] A series circuit consisting of diode D1 and capacitor C1 is connected between the gate drive voltage Vcc and point X, forming the first bootstrap circuit. The anode of diode D1 is connected to the gate drive voltage Vcc, and the cathode is connected to the positive terminal of capacitor C1. The negative terminal of capacitor C1 is connected to point X.
[0043] The series circuit consisting of diode D3 and capacitor C3 is connected between the connection point (point Y) between diode D1 and the positive terminal of capacitor C1 and the source terminal S (point B) of switch element 2b, forming a third bootstrap circuit. Diode D3's anode is connected to the connection point (point Y) between diode D1 and the positive terminal of capacitor C1, and its cathode is connected to the positive terminal of capacitor C3. The negative terminal of capacitor C2 is connected to the source terminal S (point B) of switch element 2b.
[0044] The control circuit 30b outputs a gate control signal Gb that synchronizes the on / off control of the switch element 2b and the second auxiliary switch SW2, and a gate control signal Ga shown in Figure 4(b), which is the inverted gate control signal Gb. The gate control signal Ga is a control signal that synchronizes the on / off control of the first auxiliary switch SW1 with the switch element 2a. That is, the second auxiliary switch SW2 is controlled to turn on and off in synchronization with the switch element 2b, and the first auxiliary switch SW1 is controlled to turn on and off in synchronization with the switch element 2a in a complementary manner to the switch element 2b.
[0045] Figure 3(a) shows the operating states of each part during the first charge period T1, when switch element 2b and the second auxiliary switch SW2 are off, and switch element 2a and the first auxiliary switch SW1 are on. During the first charge period T1, point X, where the first auxiliary switch SW1 and the second auxiliary switch SW2 are connected, becomes ground potential, as shown in Figure 4(e). Since the negative terminal of capacitor C1 connected to point X becomes ground potential, the first bootstrap circuit operates, and charge is charged to capacitor C1 from the gate drive voltage Vcc through diode D1. As a result, the potential at point Y, connected to the positive terminal of capacitor C1, becomes Vcc, as shown in Figure 4(f), and the voltage across capacitor C1 becomes the gate drive voltage Vcc.
[0046] Figure 3(b) shows the operating state of each part during the second charging period T2, when switch element 2b and the second auxiliary switch SW2 are ON, and switch element 2a and the first auxiliary switch SW1 are OFF. During the second charging period T2, point X, where the first auxiliary switch SW1 and the second auxiliary switch SW2 are connected, becomes the same potential Va as point A when switch element 2a is OFF and switch element 2b is ON, as shown in Figure 4(e). In other words, capacitors C1 and C3 are connected in parallel, with their respective negative terminals connected to the same potential Va.
[0047] Since the negative terminal of capacitor C1 connected to point X becomes Va, the potential at point Y connected to the positive terminal of capacitor C1 becomes Vcc + Va, as shown in Figure 4(f). This activates the third bootstrap circuit, and charge is transferred from capacitor C1 to capacitor C3 through diode D3. Capacitor C3 then functions as a floating power supply for driving the switch element 2b, with the voltage across its terminals becoming the gate drive voltage Vcc.
[0048] In the second embodiment, the first auxiliary switch SW1 cannot be controlled on / off in synchronization with the switch element 2b by a gate control signal Gb, and the second auxiliary switch SW2 cannot be controlled on / off in synchronization with the switch element 2a by a gate control signal Ga. The series circuit consisting of the first auxiliary switch SW1 and the second auxiliary switch SW2 is connected between ground and point A. Therefore, when both the second auxiliary switch SW2 and the switch element 2a are ON, point X becomes the potential Vin of point A, and the potential of point Y becomes Vcc + Vin. At this time, since the potential of the negative terminal of capacitor C3 is Vb, the voltage across capacitor C3 becomes a large voltage obtained by adding (Vin - Vb) to the gate drive voltage Vcc.
[0049] According to the second embodiment, a small-sized power generation circuit 20b made of inexpensive components can be used to generate and supply a floating power supply to the high-side driver 3b that drives the switch element 2b without driving the switch element 2b with different prior controls. Capacitors C1 and C3 only need to be small in capacity as they are sufficient to drive the high-side driver 3b, and diodes D1 and D3 only need to be small in current capacity as they are sufficient to charge capacitors C1 and C3. Therefore, although the first auxiliary switch SW1 and the second auxiliary switch SW2 need to withstand a voltage of Vin or higher, the average current flowing through them is only a few mA to a few tens of mA, so small, inexpensive components with small current capacity can be selected. The second auxiliary switch SW2 and the first auxiliary switch SW1 only need to be driven by the gate control signal Gb of the switch element 2b and its inverted gate control signal Ga, respectively, so only the normal control of the switch element 2b is required, and no complicated control is necessary.
[0050] (Third embodiment) The switching circuit 10c of the third embodiment, as shown in Figure 5, comprises N-type switching elements 2a and 2b, high-side drivers 3a and 3b, a power generation circuit 20c, and a control circuit 30c.
[0051] Switch elements 2a and 2b are connected in series. Switch element 2a is controlled on / off based on the gate control signal Ga shown in Figure 6(a), and switch element 2b is controlled on / off complementary to switch element 2a based on the gate control signal Gb shown in Figure 6(b).
[0052] Switch element 2a switches the voltage applied to the drain terminal D and outputs it to the source terminal S. The potential at the drain terminal D of switch element 2a is constant at Vin. As shown in Figure 6(c), the potential at point A, where the source terminal S of switch element 2a and the drain terminal of switch element 2b are connected, is Vin when switch element 2a is ON and switch element 2b is OFF, and is lower than Vin, Va, when switch element 2a is OFF and switch element 2b is ON.
[0053] The switch element 2b switches the voltage applied to the drain terminal D and outputs it to the source terminal S. As shown in Figure 6(d), the potential at point B connected to the source terminal S of the switch element 2b is Va when the switch element 2b is ON, and Vb, which is lower than Va, when the switch element 2b is OFF, without becoming ground potential.
[0054] The high-side driver 3a generates a gate drive signal based on a level-shifted gate control signal Ga, and drives the switch element 2a by applying the generated gate drive signal between the source terminal S and the control terminal gate terminal of the switch element 2a.
[0055] The high-side driver 3b generates a gate drive signal based on the level-shifted gate control signal Gb, and drives the switch element 2b by applying the generated gate drive signal between the source terminal S and the control terminal gate terminal of the switch element 2b.
[0056] The power generation circuit 20c may be a semiconductor device integrated on a semiconductor substrate, and is a circuit that generates floating power supplies to be supplied to the high-side drivers 3a and 3b, respectively. The power generation circuit 20c is configured by adding the third bootstrap circuit (diode D3, capacitor C3) from the power generation circuit 20b of the second embodiment to the power generation circuit 20a of the first embodiment. The power generation circuit 20c includes a first auxiliary switch SW1 and a second auxiliary switch SW2, diodes D1, D2, and D3, and capacitors C1, C2, and C3. Hereafter, the forward voltage Vf of diodes D1, D2, and D3 will be assumed to be 0V.
[0057] The series circuit consisting of the first auxiliary switch SW1 and the second auxiliary switch SW2 is connected between ground and point A, which is connected to the source terminal S of the switch element 2a. Point X, to which the first auxiliary switch SW1 and the second auxiliary switch SW2 are connected, is at ground potential when the first auxiliary switch SW1 is ON and the second auxiliary switch SW2 is OFF. Point X is at the potential of point A when the first auxiliary switch SW1 is OFF and the second auxiliary switch SW2 is ON.
[0058] A series circuit consisting of diode D1 and capacitor C1 is connected between the gate drive voltage Vcc and point X, forming the first bootstrap circuit. The anode of diode D1 is connected to the gate drive voltage Vcc, and the cathode is connected to the positive terminal of capacitor C1. The negative terminal of capacitor C1 is connected to point X.
[0059] The series circuit consisting of diode D2 and capacitor C2 is connected between the connection point (point Y) between diode D1 and the positive terminal of capacitor C1 and the source terminal S (point A) of switch element 2a, forming a second bootstrap circuit. Diode D2's anode is connected to the connection point (point Y) between diode D1 and the positive terminal of capacitor C1, and its cathode is connected to the positive terminal of capacitor C2. The negative terminal of capacitor C2 is connected to the source terminal S (point A) of switch element 2a.
[0060] The series circuit consisting of diode D3 and capacitor C3 is connected between the connection point (point Y) between diode D1 and the positive terminal of capacitor C1 and the source terminal S (point B) of switch element 2b, forming a third bootstrap circuit. Diode D3's anode is connected to the connection point (point Y) between diode D1 and the positive terminal of capacitor C1, and its cathode is connected to the positive terminal of capacitor C3. The negative terminal of capacitor C3 is connected to the source terminal S (point B) of switch element 2b.
[0061] The control circuit 30c outputs a gate control signal Ga that synchronizes the on / off control of the switch element 2a and the first auxiliary switch SW1, and a gate control signal Gb that synchronizes the on / off control of the switch element 2b and the second auxiliary switch SW2. In other words, the first auxiliary switch SW1 is synchronized on / off control with the switch element 2a, and the second auxiliary switch SW2 is synchronized on / off control with the switch element 2b, and the first auxiliary switch SW1 and the second auxiliary switch SW2 are switched on / off complementaryly.
[0062] Figure 5(a) shows the operating states of each part during the first charging period T1, when switch element 2a and the first auxiliary switch SW1 are ON, and switch element 2b and the second auxiliary switch SW2 are OFF. During the first charging period T1, point X, where the first auxiliary switch SW1 and the second auxiliary switch SW2 are connected, becomes ground potential, as shown in Figure 6(e). Since the negative terminal of capacitor C1 connected to point X becomes ground potential, the first bootstrap circuit operates, and charge is charged to capacitor C1 from the gate drive voltage Vcc through diode D1. As a result, the potential at point Y, connected to the positive terminal of capacitor C1, becomes Vcc, as shown in Figure 6(f), and the voltage across capacitor C1 becomes the gate drive voltage Vcc.
[0063] Figure 5(b) shows the operating states of each part during the second charging period T2, when switch element 2a and the first auxiliary switch SW1 are off, and switch element 2b and the second auxiliary switch SW2 are on. During the second charging period T2, point X, where the first auxiliary switch SW1 and the second auxiliary switch SW2 are connected, becomes the same potential Va as point A when switch element 2a is off and switch element 2b is on, as shown in Figure 6(e). That is, capacitors C1, C2, and C3 are connected in parallel, with their respective negative terminals connected to the same potential Va.
[0064] Since the negative terminal of capacitor C1 connected to point X becomes Va, the potential at point Y connected to the positive terminal of capacitor C1 becomes Vcc + Va, as shown in Figure 6(f). As a result, the second and third bootstrap circuits operate, and charge is charged from capacitor C1 to capacitor C2 through diode D2, and from capacitor C1 to capacitor C3 through diode D3. As a result, the voltage across capacitors C2 and C3 becomes the gate drive voltage Vcc, and they function as floating power supplies for driving switch elements 2a and 2b, respectively.
[0065] In the third embodiment, the first auxiliary switch SW1 cannot be controlled on / off in synchronization with the switch element 2b by a gate control signal Gb, and the second auxiliary switch SW2 cannot be controlled on / off in synchronization with the switch element 2a by a gate control signal Ga. The series circuit consisting of the first auxiliary switch SW1 and the second auxiliary switch SW2 is connected between ground and the source terminal S of the switch element 2a (the drain of the switch element 2b). Therefore, when both the second auxiliary switch SW2 and the switch element 2a are ON, point X becomes the potential Vin of point A, and the potential of point Y becomes Vcc + Vin. At this time, since the potential of the negative terminal of capacitor C3 is Vb, the voltage across capacitor C3 becomes a large voltage obtained by adding (Vin - Vb) to the gate drive voltage Vcc.
[0066] According to the third embodiment, a small-sized power generation circuit 20c made of inexpensive components can be used to generate and supply floating power to the high-side drivers 3a and 3b that drive the switch elements 2a and 2b, respectively, without driving the switch elements 2a and 2b with different prior controls. Capacitors C1, C2, and C3 only need to be small in capacity as they are only required to drive the high-side drivers 3a and 3b, and diodes D1, D2, and D3 only need to be small in current capacity as they are only required to charge capacitors C1, C2, and C3. Therefore, although the first auxiliary switch SW1 and the second auxiliary switch SW2 need to withstand a voltage of Vin or higher, the average current flowing through them is only a few mA to a few tens of mA, so small, inexpensive components with small current capacity can be selected. The first auxiliary switch SW1 and the second auxiliary switch SW2 only need to be driven by the gate control signal Ga of switch element 2a and the gate control signal Gb of switch element 2b, respectively, so only the normal control of switch elements 2a and 2b is required, and no complicated control is necessary.
[0067] Figure 7 shows an example configuration of the first auxiliary switch SW1 and the second auxiliary switch SW2, and their drive circuits. The first auxiliary switch SW1 is composed of an NPN bipolar transistor, with its collector connected to point X and its emitter connected to ground. The gate control signal Ga of the switch element 2a is connected to the base of the first auxiliary switch SW1 via the drive circuit 8. SW1 It is input via the drive circuit 8. SW1 This is configured, for example, as an RC parallel circuit, and generates a base current that flows into the base of the first auxiliary switch SW1 when the switch element 2a is turned on, thereby controlling the first auxiliary switch SW1 to be turned on.
[0068] The second auxiliary switch SW2 is composed of a PNP bipolar transistor, with its emitter connected to point A and its collector to point X. The second auxiliary switch SW2 is floating. The gate control signal Gb of the switch element 2b is driven by the drive circuit 8 at the base of the second auxiliary switch SW2. SW2 It is input via the drive circuit 8. SW2 This consists of resistors R1 and R2, a third auxiliary switch SW3 composed of an NPN bipolar transistor, and a drive circuit 8 for the third auxiliary switch SW3. SW3 The circuit comprises a series circuit consisting of resistors R1 and R2 and switch SW3, connected between point A and ground, with the connection point of resistors R1 and R2 connected to the base of the second auxiliary switch SW2. The collector of the third auxiliary switch SW3 is connected to point A via resistors R1 and R2, and the emitter is connected to ground. The gate control signal Gb of the switch element 2b is connected to the base of the third auxiliary switch SW3 via the drive circuit 8 SW3 It is input via the drive circuit 8. SW3 This is composed of, for example, an RC parallel circuit and generates a base current that controls the switch SW3 to turn on when the switch element 2b is turned on. The drive circuit 8 is activated by the drive of the switch SW3. SW2 This generates a base current that flows out from the base of the second auxiliary switch SW2 when the switch element 2b is turned on, thereby controlling the second auxiliary switch SW2 to be turned on.
[0069] (Fourth embodiment) The switching circuit 10d of the fourth embodiment is an Always-Dual-Path Hybrid (ADPH) DC-DC converter. (Source: IEEE C2022: 48 V-to-12 V Always-Dual-Path Hybrid DC-DC Converter for Inductor Current Reduction) Referring to FIG. 8, the switching circuit 10d includes six N-type switch elements 2a to 2f, a flying capacitor C FLY1 , C FLY2 , an inductor L, an output capacitor Co, and a control circuit 30d. Note that the output current is always supplied from two paths. Therefore, the inductor current flowing through the inductor L can be reduced by 50%, and the DCR loss of the inductor L can be reduced by 75%.
[0070] The switch elements 2a, 2b, and 2c are connected between the input terminal and the output terminal as a series circuit. The series circuit composed of the flying capacitor C FLY1 and the switch element 2d is connected between point A, which is the connection point between the switch elements 2a and 2b, and the ground. The series circuit composed of the flying capacitor C FLY2 and the switch element 2e is connected between point B, which is the connection point between the switch elements 2b and 2c, and the ground. The switch element 2f is connected between the connection point of the flying capacitor C FLY2 and the switch element 2e and the output terminal. The inductor L is connected between the connection point of the flying capacitor C FLY1 and the switch element 2d and the output terminal. The output capacitor Co is connected between the output terminal and the ground.
[0071] The control circuit 30d synchronously turns on and off the switch elements 2a, 2c, and 2e, and synchronously turns on and off the switch elements 2b, 2d, and 2f in a complementary manner to the switch elements 2a, 2c, and 2e. FIG. 8(a) shows the state when the switch elements 2a, 2c, and 2e are on and the switch elements 2b, 2d, and 2f are off. FIG. 8(b) shows the state when the switch elements 2a, 2c, and 2e are off and the switch elements 2b, 2d, and 2f are on.
[0072] The voltage conversion ratio (M=Vo / Vin) in the switching circuit 10d operates at a step-down ratio of 1 / 3 or less depending on the duty cycle of the switch elements 2a to 2f. The switching circuit 10d has two circuit states due to the complementary on / off control of the switch elements 2a, 2c, and 2e. Hereafter, the switching circuit 10d will be described as operating at a step-down ratio of 1 / 4, with Vin=48V and Vo=12V.
[0073] The source terminal S of the switch elements 2d and 2e is at ground potential. Therefore, the switching circuit 10d includes a low-side driver 5d that drives the switch element 2d using a gate drive voltage Vcc (hereinafter, Vcc = 10V), and a low-side driver 5e that drives the switch element 2e.
[0074] Since the switching elements 2a, 2b, 2c, and 2f operate in a floating state and the potential of the source terminal S fluctuates, the switching circuit 10d includes high-side drivers 3a, 3b, 3c, and 3f that drive the switching elements 2a, 2b, 2c, and 2f, respectively.
[0075] When the switch element 2e shown in Figure 8(a) is turned on, the source terminal S of the switch element 2f becomes ground potential. Therefore, the switching circuit 10d includes a bootstrap circuit 40f that generates a floating power supply using the gate drive voltage Vcc and supplies it to the high-side driver 3f. The bootstrap circuit 40f includes a diode D4 and a capacitor C4 connected in series between the gate drive voltage Vcc and the source terminal S of the switch element 2f. During the period when the source terminal S is ground potential, the gate drive voltage Vcc charges the capacitor C4 via the diode D4. The voltage across the capacitor C4 becomes a 10V floating power supply.
[0076] Switch elements 2a, 2b, and 2c do not have a period during which their source terminal S is at ground potential. Of these, the source terminal S of switch element 2c is connected to the drain terminal D of switch element 2f, whose source terminal S is at ground potential. Therefore, the switching circuit 10d includes a bootstrap circuit 40c that generates a floating power supply using the 10V voltage across capacitor C4 and supplies it to the high-side driver 3c. The bootstrap circuit 40c includes a diode D5 and a capacitor C5 connected in series between the connection point of capacitor C4 and diode D4 and the source terminal S of switch element 2c. During the period when switch element 2f is ON and the source terminal S of switch element 2c and switch element 2f is Vo=12V, the charge of capacitor C4 is charged to capacitor C5 via diode D5. The voltage across capacitor C5 becomes a 10V floating power supply.
[0077] The switch elements 2a and 2b are connected in series, as in the third embodiment, and the potential of the source terminal S of switch element 2b is never at ground potential. The potential of the drain terminal D of switch element 2a is constant at Vin = 48V. As shown in Figure 8(a), when switch element 2a is on and switch element 2b is off, the potential at point A is Vin = 48V, and the potential at point B is Vo = 12V. As shown in Figure 8(b), when switch element 2a is off and switch element 2b is on, the potential at points A and B is Va = 24V.
[0078] Therefore, the switching circuit 10d includes a power generation circuit 20c of a third embodiment that generates a floating power supply using the gate drive voltage Vcc and supplies it to the high-side drivers 3a and 3b.
[0079] In the first charging period T1 shown in Figure 8(a), point X becomes 0V, so charge is charged to capacitor C1 from the gate drive voltage Vcc through diode D1, and the voltage across capacitor C1 becomes Vcc = 10V. In the second charging period T2 shown in Figure 8(b), point X becomes Va = 24V and point Y becomes Vcc + Va = 34V, so charge is charged from capacitor C1 to capacitor C2 through diode D2, and from capacitor C1 to capacitor C3 through diode D3. As a result, the voltages across capacitors C2 and C3 become Vcc = 10V.
[0080] A floating power supply may be supplied to the high-side driver 3a of the switch element 2a using the power supply generation circuit 20a of the first embodiment or the power supply generation circuit 20b of the second embodiment. A floating power supply may be supplied to the high-side driver 3b of the switch element 2b using the power supply generation circuit 20a or the power supply generation circuit 20b. A floating power supply may be supplied to the high-side driver 3c of the switch element 2c using the power supply generation circuit 20a or the power supply generation circuit 20b. A floating power supply may be supplied to the high-side drivers 3b and 3c of the switch elements 2b and 2c using the power supply generation circuit 20c.
[0081] As described above, this embodiment is a switching circuit 10a equipped with a high-side driver 3a that drives a switch element 2a in which there is no period during which the source terminal S, which is the low-potential side terminal, is at ground potential, comprising: a first auxiliary switch SW1 and a second auxiliary switch SW2 connected in series between ground and the source terminal S (point A) of the switch element 2a; a gate drive voltage Vcc which is the drive voltage source for the switch element 2a; a diode D1 (first diode) and a capacitor C1 (first capacitor) connected in series between the connection point (point X) of the first auxiliary switch SW1 and the second auxiliary switch SW2; and the connection point (point Y) of the diode D1 and the capacitor C1 The system includes a diode D2 (second diode) and a capacitor C2 (second capacitor) connected in series between the switch element 2a and the source terminal S (point A) of the switch element 2a, and a control circuit 30a that synchronizes either the first auxiliary switch SW1 or the second auxiliary switch SW2 with the switch element 2a and complementaryly controls the on / off states of the first auxiliary switch SW1 and the second auxiliary switch SW2. When the first auxiliary switch SW1 is ON, the charge charged to capacitor C1 from the gate drive voltage Vcc is charged to capacitor C2 when the second auxiliary switch SW2 is ON, and the voltage across capacitor C2 is supplied to the high-side driver 3a as a floating power supply. This configuration allows a small power generation circuit 20a, made of inexpensive components, to generate and supply a floating power supply to the high-side driver 3a that drives the switch element 2a without requiring the switch element 2a to be driven by a different control beforehand. Capacitors C1 and C2 only need to be small in capacity as they are sufficient to drive the high-side driver 3a, and diodes D1 and D2 only need to be small in current capacity as they are sufficient to charge capacitors C1 and C2. Therefore, although the first auxiliary switch SW1 and the second auxiliary switch SW2 need to withstand a voltage greater than Vin, the average current flowing through them is only a few mA to a few tens of mA, so small, inexpensive components with small current capacity can be selected. The first auxiliary switch SW1 and the second auxiliary switch SW2 only need to be driven by the gate control signal Ga of the switch element 2a and its inverted signal Ga', so only the normal control of the switch element 2a is required, and no complicated control is necessary.
[0082] Furthermore, this embodiment is a switching circuit 10b equipped with a high-side driver 3b that drives a switch element 2b in which there is no period during which the source terminal S, which is the low-potential side terminal, is at ground potential, and comprises a first auxiliary switch SW1 and a second auxiliary switch SW2 connected in series between ground and the drain terminal D, which is the high-potential side terminal of the switch element 2b, a gate drive voltage Vcc which is the drive voltage source for the switch element 2b, and a diode D1 (first diode) and a capacitor C1 (first capacitor) connected in series between the connection point of the first auxiliary switch SW1 and the second auxiliary switch SW2, and diode D1 and capacitor The circuit includes a diode D3 (second diode) and a capacitor C3 (second capacitor) connected in series between the connection point (point Y) with C1 and the source terminal S of the switch element 2b, and a control circuit 30b that synchronizes the second auxiliary switch SW2 with the switch element 2b and complementaryly controls the on / off states of the first auxiliary switch SW1 and the second auxiliary switch SW2. When the first auxiliary switch SW1 is ON, the charge charged to capacitor C1 from the gate drive voltage Vcc is charged to capacitor C3 when the second auxiliary switch SW2 is ON, and the voltage across capacitor C3 is supplied to the high-side driver 3b as a floating power supply. This configuration allows a small power generation circuit 20b, made of inexpensive components, to generate and supply a floating power supply to the high-side driver 3b that drives the switch element 2b without requiring the switch element 2b to be driven by a different control beforehand. Capacitors C1 and C3 only need to be small in capacity as they are only required to drive the high-side driver 3b, and diodes D1 and D3 only need to be small in current capacity as they are only required to charge capacitors C1 and C3. Therefore, although the first auxiliary switch SW1 and the second auxiliary switch SW2 need to withstand a voltage greater than Vin, the average current flowing through them is only a few mA to a few tens of mA, so small, inexpensive components with small current capacity can be selected. The second auxiliary switch SW2 and the first auxiliary switch SW1 only need to be driven by the gate control signal Gb of the switch element 2b and its inverted gate control signal Ga, respectively, so complex control is not required, only the normal control of the switch element 2b is needed.
[0083] Furthermore, this embodiment includes a high-side driver 3a (first high-side driver) and a high-side driver 3b (second high-side driver) that drive switch elements 2a (first switch element) and 2b (second switch element), respectively, which are connected in series and complementaryly controlled on / off, and a switching circuit 1c in which there is no period in which the source terminal S, which is the low-potential terminal of switch element 2b located on the low-potential side, is at ground potential, and comprises a first auxiliary switch SW1 and a second auxiliary switch SW2 connected in series between ground and the source terminal S of switch element 2a, a gate drive voltage Vcc which is the drive voltage source for switch elements 2a and switch elements 2b, a diode D1 (first diode) and a capacitor C1 (first capacitor) connected in series as a first bootstrap circuit between the connection point (point X) of the first auxiliary switch SW1 and the second auxiliary switch SW2, and the connection point of diode D1 and capacitor C1, and a switch The device includes a diode D2 (second diode) and a capacitor C2 (second capacitor) connected in series as a second bootstrap circuit between element 2a and its source terminal S, a diode D3 (third diode) and a capacitor C3 (third capacitor) connected in series as a third bootstrap circuit between the connection point of diode D1 and capacitor C1 and the source terminal S of switch element 2b, and a control circuit 30c that synchronizes the first auxiliary switch SW1 with switch element 2a and the second auxiliary switch SW2 with switch element 2b to control on / off. When the first auxiliary switch SW1 is ON, the charge charged to capacitor C1 from the gate drive voltage Vcc is charged to capacitor C2 and capacitor C3 respectively when the second auxiliary switch SW2 is ON, and the voltages across capacitor C2 and capacitor C3 are supplied to the high-side drivers 3a and 3b respectively as floating power supplies. This configuration allows for the generation and supply of floating power to the high-side drivers 3a and 3b that drive the switch elements 2a and 2b, respectively, using a small power generation circuit 20c made of inexpensive components, without requiring the switch elements 2a and 2b to be driven by different prior controls. Capacitors C1, C2, and C3 only need to be small in capacity as they are only required to drive the high-side drivers 3a and 3b, and diodes D1, D2, and D3 only need to be small in current capacity as they are only required to charge capacitors C1, C2, and C3. Therefore, although the first auxiliary switch SW1 and the second auxiliary switch SW2 require a voltage rating of Vin or higher, the average current flowing through them is only a few mA to a few tens of mA, so small, inexpensive components with low current capacity can be selected. The first auxiliary switch SW1 and the second auxiliary switch SW2 only need to be driven by the gate control signal Ga of switch element 2a and the gate control signal Gb of switch element 2b, so only the normal control of switch elements 2a and 2b is required, and no complicated control is necessary.
[0084] Furthermore, this embodiment includes low-side drivers 5d and 5e that drive the switch elements 2d and 2e (third switch elements), whose source terminal S is at ground potential, using a gate drive voltage Vcc. This configuration allows the gate drive voltage Vcc of switch elements 2a and 2b, which are connected in series and have no period where their source terminal S is at ground potential, to be shared with the gate drive voltage Vcc of switch elements 2d and 2e, whose source terminal S is at ground potential.
[0085] Furthermore, this embodiment includes a high-side driver 3f (fourth high-side driver) that drives a switch element 2f (fourth switch element) whose source terminal S is connected to the drain terminal D of the switch element 2e, and a bootstrap circuit 40f (fourth bootstrap circuit) consisting of a diode D4 (fourth diode) and a capacitor C4 (fourth capacitor) connected in series between the gate drive voltage Vcc and the source terminal S of the switch element 2f. When the switch element 2e is turned on, the gate drive voltage Vcc charges the capacitor C4, and the voltage across the capacitor C4 is supplied to the high-side driver 5f as a floating power supply. With this configuration, the gate drive voltage Vcc of switch element 2f, whose source terminal S is connected to the drain terminal D of switch element 2e (whose source terminal S is at ground potential), can also be shared with the gate drive voltage Vcc of switch elements 2a and 2b.
[0086] Furthermore, this embodiment includes a high-side driver 5c (fifth high-side driver) that drives a switch element 2c (fifth switch element) whose source terminal S is connected to the drain terminal D of a switch element 2f (fourth switch element), and a bootstrap circuit 40c (fifth bootstrap circuit) consisting of a diode D5 (fifth diode) and a capacitor C5 (fifth capacitor) connected in series between the connection point of diode D4 and capacitor C4 and the source terminal S of switch element 2c. When switch element 2c is turned on, capacitor C4 charges capacitor C5, and the voltage across capacitor C5 is supplied to the high-side driver 5c as a floating power supply. With this configuration, the gate drive voltage Vcc of switch element 2c, whose source terminal S is connected to the drain terminal D of switch element 2f, can also be shared with the gate drive voltage Vcc of switch elements 2a and 2b.
[0087] It is clear that the present invention is not limited to the above embodiments, and that each embodiment can be modified as appropriate within the scope of the technical concept of the present invention. Furthermore, the number, position, shape, etc. of the above-mentioned components are not limited to the above embodiments, and can be set to a number, position, shape, etc. that is suitable for carrying out the present invention. In each figure, the same reference numeral is used for the same component. [Explanation of symbols]
[0088] 2, 2a, 2b, 2c, 2d, 2e, 2f switching elements 3, 3a, 3b, 3c, 3f High-side drivers 5, 5d, 5e Low-side drivers 6. Pulse transformer 7. Isolated power supply 10, 10a, 10b, 10c, 10d switching circuit 20, 20a, 20b, 20c power generation circuit 30a, 30b, 30c, 30d control circuits 40, 40c, 40f bootstrap circuit C1, C2, C3, C4, C5, Ca Capacitor C FLY1 , C FLY2 Flying Capacitor Co output capacitor D1, D2, D3, D4, D5 diodes L Inductor R1, R2 resistance SW1 First Auxiliary Switch SW2 Second Auxiliary Switch SW3 Switch
Claims
1. A switching circuit comprising a first high-side driver and a second high-side driver that drive a first switch element and a second switch element connected in series and complementaryly controlled on / off, wherein there is no period during which the low-potential terminal of the second switch element, which is located on the low-potential side, is at ground potential, A first auxiliary switch and a second auxiliary switch are connected in series between the ground and the low-potential terminal of the first switch element, A first diode and a first capacitor are connected in series as a first bootstrap circuit between the drive voltage sources for the first and second switch elements and the connection point between the first auxiliary switch and the second auxiliary switch, A second diode and a second capacitor are connected in series as a second bootstrap circuit between the connection point of the first diode and the first capacitor and the low-potential terminal of the first switch element, A third diode and a third capacitor are connected in series as a third bootstrap circuit between the connection point of the first diode and the first capacitor and the low-potential terminal of the second switch element, The system includes a control circuit that synchronizes the first auxiliary switch with the first switch element and synchronizes the second auxiliary switch with the second switch element to control its on / off state, A switching circuit characterized in that when the first auxiliary switch is ON, the charge charged from the drive voltage source to the first capacitor is used to charge the second capacitor and the third capacitor, respectively, when the second auxiliary switch is ON, and the voltages across the second capacitor and the third capacitor, respectively, are supplied to the first high-side driver and the second high-side driver as floating power supplies.
2. The switching circuit according to claim 1, further comprising a low-side driver that drives a third switching element whose low-potential terminal is at ground potential using the drive voltage source.
3. A fourth high-side driver drives a fourth switch element, the fourth switch element having its low-potential terminal connected to the high-potential terminal of the third switch element, The fourth bootstrap circuit comprises a fourth diode and a fourth capacitor connected in series between the drive voltage source and the low-potential terminal of the fourth switch element, The switching circuit according to claim 2, characterized in that when the third switching element is ON, the drive voltage source charges the fourth capacitor, and the voltage across the fourth capacitor is supplied to the fourth high-side driver as the floating power supply.
4. A fifth high-side driver drives a fifth switch element, the fourth switch element having a low-potential terminal connected to its high-potential terminal, The fifth bootstrap circuit comprises a fifth diode and a fifth capacitor connected in series between the connection point of the fourth diode and the fourth capacitor and the low-potential terminal of the fifth switch element, The switching circuit according to claim 3, characterized in that when the fourth switching element is ON, the fourth capacitor charges the fifth capacitor, and the voltage across the fifth capacitor is supplied to the fifth high-side driver as the floating power supply.
5. A power generation circuit that generates floating power supplies for a first high-side driver and a second high-side driver, which drive a first switch element and a second switch element connected in series and complementaryly controlled on / off, respectively, There is no period during which the low-potential terminal of the second switch element, which is positioned on the low-potential side, is at ground potential. A first auxiliary switch and a second auxiliary switch are connected in series between the ground and the low-potential terminal of the first switch element, A first diode and a first capacitor are connected in series as a first bootstrap circuit between the drive voltage sources for the first and second switch elements and the connection point between the first auxiliary switch and the second auxiliary switch, A second diode and a second capacitor are connected in series as a second bootstrap circuit between the connection point of the first diode and the first capacitor and the low-potential terminal of the first switch element, A third diode and a third capacitor are connected in series as a third bootstrap circuit between the connection point of the first diode and the first capacitor and the low-potential terminal of the second switch element, The system includes a control circuit that synchronizes the first auxiliary switch with the first switch element and synchronizes the second auxiliary switch with the second switch element to control its on / off state, A power generation circuit characterized in that when the first auxiliary switch is ON, the charge charged from the drive voltage source to the first capacitor is used to charge the second capacitor and the third capacitor, respectively, when the second auxiliary switch is ON, and the voltages across the second capacitor and the third capacitor, respectively, are supplied to the first high-side driver and the second high-side driver, respectively, as the floating power supply.
6. A semiconductor device characterized in that the power generation circuit described in claim 5 is integrated on a substrate.