Auxiliary power supply circuit and power supply device

Abstract

To provide an auxiliary power supply circuit in which power of a switching circuit can be effectively used.SOLUTION: An auxiliary power supply circuit (GDP1) connected to a switching circuit (SWC1) having a high pressure resistant transistor (HVT1) and a low pressure resistant transistor (LVT1) in series, includes a rectifier element (RCT1) and an auxiliary power supply capacitor (GDC1). A connection node between the high pressure resistant transistor (HVT1) and the low pressure resistant transistor (LVT1) is connected to an anode of the rectifier element (RCT1), a cathode of the rectifier element (RCT1) is connected to a positive electrode of the auxiliary power supply capacitor (GDC1), and a negative electrode of the auxiliary power supply capacitor (GDC1) is connected to a reference terminal of the low pressure resistant transistor.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The following disclosure relates to auxiliary power circuits and power supplies. [Background technology]

[0002] Patent Document 1 discloses an example of the configuration of an auxiliary power supply circuit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-220468 Summary of the Invention [Problem to be solved by the invention]

[0004] However, even with such an auxiliary power supply circuit, there is still room for improvement.

[0005] This specification discloses an auxiliary power supply circuit and a power supply device that can effectively utilize the power of a switching circuit. [Means for solving the problem]

[0006] In order to solve the above problems, an auxiliary power supply circuit according to one aspect of the present disclosure is connected to a switching circuit. In the switching circuit, a high-voltage transistor arranged on the high-voltage side and a low-voltage transistor arranged on the low-voltage side are connected in series. The auxiliary power supply circuit includes a rectifying element and an auxiliary power supply capacitor. The connection node between the high-voltage transistor and the low-voltage transistor is connected to the anode of the rectifying element. The cathode of the rectifier element is connected to the positive electrode of the auxiliary power supply capacitor. The negative electrode of the auxiliary power supply capacitor is connected to the reference terminal of the low-voltage transistor. The voltage at the connection node generated when the switching circuit operates is supplied to the auxiliary power supply capacitor.

[0007] In order to solve the above problem, a power supply device according to one aspect of the present disclosure includes the above auxiliary power supply circuit. [Effects of the Invention]

[0008] According to the present disclosure, the power of the switching circuit can be used effectively. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating an auxiliary power supply circuit according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a diagram illustrating an operation of an auxiliary power supply circuit according to an embodiment of the present disclosure. [Figure 3] FIG. 1 illustrates a start-up circuit that can be used in an auxiliary power circuit according to an embodiment of the present disclosure. [Figure 4] 1 is a diagram illustrating a power supply device including an auxiliary power supply circuit according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Embodiment 1] In this specification, as an example of the notation of the symbols in the drawings, the rectifying element RCT1 is also simply referred to as RCT1. The abbreviations used are as follows: MOS is a metal-oxide-semiconductor field-effect transistor, SJMOS is a super-junction metal-oxide-semiconductor field-effect transistor, IGBT is an insulated-gate bipolar transistor, JFET is a junction field effect transistor, HEMT is a high electron mobility transistor, LDO is a low dropout linear regulator, and IC is a semiconductor integrated circuit. A transistor is defined as follows: it has a control terminal, a reference terminal, and a high-voltage terminal. The transistor can be turned on by applying a voltage to the control terminal relative to the reference terminal. When the transistor is turned on, it allows current to flow from the high-voltage terminal to the reference terminal, or from the reference terminal to the high-voltage terminal. When the transistor is off, the high-voltage terminal receives voltage relative to the reference terminal, limiting current conduction. Transistors that meet these definitions include MOS, SJMOS, IGBT, GaN-HEMT, SiC-JFET, etc.

[0011] In this embodiment, an example is shown in which the auxiliary power supply circuit is replaced with a gate drive power supply circuit, the auxiliary power supply capacitor is replaced with a gate drive capacitor, and the Zener diode for the auxiliary power supply capacitor is replaced with a Zener diode for the gate drive capacitor. The auxiliary power supply circuit of this embodiment can be applied to various power supply applications, such as a power supply circuit for a control circuit and a power supply circuit for controlling a mechanical relay, in addition to a gate drive power supply circuit.

[0012] (Gate drive power supply circuit overview) The gate drive power supply circuit GDP1 of the present disclosure will be described with reference to FIG. A common gate drive power supply circuit has an issue with the power consumption of the general auxiliary power supply that serves as the power supply source. The gate drive power supply circuit GDP1 of the present disclosure is configured to receive power from the switching circuit SWC1, which makes effective use of power and reduces the power consumption of the general auxiliary power supply.

[0013] (Main components of the gate drive power supply circuit) 1 shows a lower arm LOS1 that includes SWC1 and GDP1, and an upper arm UPS1 that has the same functions. GDP1 will be explained mainly using LOS1.

[0014] GDP1 is connected to SWC1. SWC1 comprises HVT1 and LVT1, connected in series by connecting the reference terminal of high-voltage transistor HVT1 to the high-voltage terminal of low-voltage transistor LVT1. HVT1 is located on the high-voltage side of bus capacitor BCP1, which is the circuit voltage, and LVT1 is located on the low-voltage side of BCP1. The on and off periods of SWC1 are the same as the on and off periods shared by HVT1 and LVT1. GDP1 includes a rectifier RCT1 and a gate drive capacitor GDC1. The connection node CNN1 between HVT1 and LVT1 is connected to the anode of RCT1, and the cathode of RCT1 is connected to the positive electrode of GDC1. The negative electrode of GDC1 is connected to the reference terminal of LVT1 and the reference node GND1, which is the negative electrode of BCP1.

[0015] With the above main configuration of GDP1, the voltage generated across CNN1 when SWC1 is turned off conducts RCT1, charging GDC1. When the voltage in CNN1 drops from the charged GDC1 when SWC1 is turned on, RCT1 cuts off the current. The repeated on-off switching action of SWC1 supplies DC voltage and power to GDC1. Switching SWC1 on and off is performed by driving the gate of LVT1 using a gate drive IC (GIC1) powered by GDC1.

[0016] (Upper voltage limit for gate drive capacitor GDC1) Unlike typical auxiliary power supplies, the voltage of GDC1 generated by CNN1 has no voltage guarantee and may become an overvoltage. To prevent such overvoltage, the cathode of the Zener diode VLT1 for the gate drive capacitor is connected to the positive electrode of GDC1, and the anode is connected to the negative electrode of GDC1. The Zener voltage of VLT1 defines the upper limit voltage of GDC1, preventing overvoltage beyond that.

[0017] In addition to improving the voltage controllability of GDC1, a Zener diode CVL1 can also be connected in parallel to LVT1 for purposes such as noise reduction.

[0018] (Surge current of gate drive capacitor GDC1 is suppressed by a resistor) The voltage change in CNN1 caused by the switching of SWC1 is steep, which generates a surge current. The surge current propagating to GDC1 becomes noise, which may destabilize the operation of GIC1 connected to GDC1.

[0019] To reduce noise on GDC1, a smoothing capacitor SCP1 and an inrush suppression resistor RSR1 can be added. The positive terminal of SCP1 is connected to the cathode of RCT1, and the negative terminal is connected to the reference terminal of LVT1. RSR1 is interposed in the connection path between the cathode of RCT1 and the positive terminal of GDC1. The addition of SCP1 and RSR1 diverts the surge current generated in CNN1 to SCP1 and returns it to the reference terminal of LVT1. In addition, the propagation of the surge current to GDC1 is limited by RSR1, which stabilizes the operation of GIC1.

[0020] (Surge current of gate drive capacitor GDC1 is suppressed by LDO) To further reduce the noise of GDC1, RSR1 can be replaced with VCT1, an LDO, which can keep the output voltage constant, eliminating the need for VLT1. UPS1 is a circuit in which RSR1 of LOS1 is replaced with VCT1, and VLT1 is omitted. The symbols of the elements of UPS1 that are configured with the same elements as LOS1 are omitted. The VCT1 has an input terminal connected to the cathode of the rectifier element, an output terminal connected to the positive electrode of the gate drive capacitor, and a reference terminal connected to the reference terminal of the low-voltage transistor. VCT1 can further suppress the propagation of surge current to GDC1.

[0021] (Connection of auxiliary power supply AUX1 to gate drive capacitor GDC1) GDP1 cannot supply DC voltage or power to GDC1 when SWC1 is not performing switching operations. Therefore, by supplying power to GDC1 from the general auxiliary power supply AUX1, power can be secured when SWC1 is not performing switching operations. AUX1 is additionally connected to GDP1, the positive terminal of AUX1 is connected to the positive terminal of GDC1, and the negative terminal of AUX1 is connected to the negative terminal of GDC1.

[0022] Ideally, the power from AUX1 should be used only when switching begins, and thereafter the power received by GDP1 from SWC1 should be used effectively. To achieve this, it is preferable that the output voltage of AUX1 is lower than the voltage of GDC1 supplied by GDP1, because GDC1 is charged with the higher power supply voltage, which is then used by GIC1. AUX1 can use a general auxiliary power supply, such as the power supply for a flyback circuit.

[0023] (Voltage supply to gate drive capacitor for high-voltage transistor) When using SJMOS or SiC-MOS for HVT1, it may be necessary to apply voltage to the control terminal. In such cases, a high-voltage transistor gate drive capacitor HCP1 is used. The positive terminal of HCP1 is connected to the control terminal of HVT1, and the negative terminal is connected to the reference terminal of LVT1. Furthermore, by connecting the positive terminal of GDC1 to the positive terminal of HCP1, it is possible to supply voltage from GDC1 to HCP1.

[0024] (Evaluation circuit for gate drive power supply circuit GDP1) The operation of GDP1 will be confirmed using the downconverter circuit DNC1 shown in FIG. DNC1 has LOS1, which uses GND1 as its reference node, and UPS1, which uses switch node SWN1 as its reference node. SWN1 has coil CIL1 and a low-voltage load (not shown) beyond it. UPS1 has bootstrap diode BSD1 instead of AUX1, which LOS1 has. The cathodes of the parasitic diodes in HVT1 and LVT1 are connected to their respective high-voltage terminals.

[0025] The switching of UPS1 and LOS1 controlled by the gate drive IC generates a low voltage load voltage of 200V from the BCP1 voltage of 400V. The carrier frequency of DNC1 is 100KHz. AUX1 is 15V, the Zener voltage of VLT1 is 17V, and the Zener voltage of CVL1 is 30V. The capacitance of GDC1, SCP1, and HCP1 is 0.1μF. The resistance of RSR1 is 100Ω. LVT1 is an N-channel MOS with a withstand voltage of 30V, and HVT1 is an N-channel SJMOS with a withstand voltage of 600V. By setting the withstand voltage of LVT1 to less than one-tenth of the withstand voltage of HVT1, it is possible to keep the voltage of CNN1 low, allowing GDC1 to be charged efficiently.

[0026] (Evaluation of the operation of the gate drive power supply circuit GDP1) Figure 2 shows five graphs of the operating waveforms of each part related to GDP1. The horizontal axis of all five graphs is a common time axis, and the vertical axis has two types of measurements: voltage (Volt) and current (Ampere). V_SWC1 is the voltage of SWC1, and is also the voltage of SWN1 relative to GND1. V_LVG1 is the gate-source voltage of LVT1. For other symbols, symbols beginning with V indicate the voltage of the latter half of the symbol, and I indicates the current of the latter half of the symbol. For example, V_SCP1 is the voltage of SCP1, and I_RCT1 is the current of RCT1.

[0027] At around 1.02E-5Sec, SWC1 turns off, causing the V_SWC1 voltage to rise, and at the same time, V_CNN1 also rises to 19V. The rise in V_CNN1 causes SCP1 to be charged via RCT1 with I_RCT1 at 12A. Meanwhile, I_RSR1, which charges GDC1, is limited to 0.027A, suppressing noise. Furthermore, V_SCP1 rises by 1.5V, but V_GDC1 changes little, demonstrating successful noise suppression. This noise reduction is the result of SCP1 and RSR1. It also shows that VLT1 functions to prevent the gate drive upper limit voltage from exceeding 17V, excluding measurement noise. SCP1, which has a high voltage, continues to charge GDC1 via I_RSR1.

[0028] At around 1.53E-5Sec, SWC1 turns on due to the flywheel current. GIC1 uses GDC1 to make V_LVG1 17V to turn on LVT1 as synchronous rectification. The consumption of V_GDC1 is compensated for by I_RSR1 from V_SCP1. The recovery of GDC1 voltage due to compensation can be confirmed at 1.58E-5Sec. UPS1 can also operate in the same way as LOS1.

[0029] [Embodiment 2] Place AUX1, which was used before SWC1 started, in the startup circuit SUC3. An example of this change will be described with reference to FIG.

[0030] SUC3 includes a startup transistor SUT3, a current limiting resistor CRR3, a gate control resistor GCR3, and a gate controlled Zener diode GCZ3. Terminal FST3 is connected to the positive terminal of GDC1, and terminal SDT3 is connected to the negative terminal of GDC1. Terminal BUT3 is connected to a BUS-Line that can supply power. In this example, BUT3 is connected to the positive terminal of BCP1. This configuration makes it possible to secure power before startup.

[0031] [Embodiment 3] The GDP1 connected to the SWC1 is used to configure the power supply unit PSU4 shown in Figure 4. The PSU4 can reduce power consumption by using the GDP1.

[0032] Please note that the values ​​given above are merely examples. To adjust the circuit operation, it is possible to insert a resistor in the wiring, or add a capacitor between two wirings to increase the capacitance, etc.

[0033] [Additional Notes] The presently contemplated embodiments of the invention disclosed above may be modified in various ways as needed, and it is intended that such modifications, insofar as they fall within the scope of the invention, be incorporated into the appended claims. [Explanation of symbols]

[0034] SWC1 Switching circuit GDP1 Gate drive power supply circuit HVT1 High-Voltage Transistor LVT1 low voltage transistor RCT1 rectifier element GDC1 Gate Drive Capacitor CNN1 connection node VLT1 Zener diode for gate drive capacitor SCP1 smoothing capacitor RSR1 Inrush suppression resistor VCT1 LDO AUX1 Auxiliary power supply SUC3 Startup Circuit HCP1 High-Voltage Transistor Gate Drive Capacitor

Claims

1. An auxiliary power supply circuit connected to a switching circuit, The switching circuit has a high-voltage transistor arranged on the high-voltage side and a low-voltage transistor arranged on the low-voltage side connected in series, the auxiliary power supply circuit includes a rectifying element and an auxiliary power supply capacitor; a connection node between the high-voltage transistor and the low-voltage transistor is connected to the anode of the rectifier element; the cathode of the rectifier element is connected to the positive electrode of the auxiliary power supply capacitor; the negative electrode of the auxiliary power supply capacitor is connected to the reference terminal of the low-voltage transistor; an auxiliary power supply circuit, wherein a voltage at the connection node generated when the switching circuit operates is supplied to the auxiliary power supply capacitor;

2. the auxiliary power supply circuit further comprises a Zener diode for an auxiliary power supply capacitor; The Zener diode for the auxiliary power supply capacitor is The cathode is connected to the positive electrode of the auxiliary power supply capacitor, 2. The auxiliary power supply circuit of claim 1, wherein the anode is connected to the negative terminal of said auxiliary power supply capacitor.

3. The auxiliary power supply circuit further includes a smoothing capacitor and an inrush current suppression resistor, The smoothing capacitor is The positive electrode is connected to the cathode of the rectifying element, The negative electrode is connected to the reference terminal of the low-voltage transistor, 2. The auxiliary power supply circuit according to claim 1, wherein the inrush suppression resistor is disposed in a connection path between the cathode of the rectifier element and the positive electrode of the auxiliary power supply capacitor.

4. The auxiliary power supply circuit further includes a smoothing capacitor and an LDO. The smoothing capacitor is The positive electrode is connected to the cathode of the rectifying element, The negative electrode is connected to the reference terminal of the low-voltage transistor, The above LDO is a capacitor connected to the cathode of the rectifier element and the positive electrode of the auxiliary power supply capacitor; an input terminal connected to the anode of the rectifier; an output terminal connected to the positive electrode of the auxiliary power supply capacitor; 2. The auxiliary power supply circuit according to claim 1, wherein a reference terminal is connected to the reference terminal of said low-voltage transistor.

5. The auxiliary power supply circuit further includes a general auxiliary power supply; The above general auxiliary power supply is The positive electrode is connected to the positive electrode of the auxiliary power supply capacitor, 2. The auxiliary power supply circuit of claim 1, wherein the negative terminal is connected to the negative terminal of said auxiliary power supply capacitor.

6. 6. The auxiliary power supply circuit according to claim 5, wherein the output voltage of said general auxiliary power supply is lower than the voltage of said auxiliary power supply capacitor.

7. The auxiliary power supply circuit further comprises a start-up circuit; 2. The auxiliary power supply circuit of claim 1, wherein the startup circuit charges the auxiliary power supply capacitor before the switching circuit operates.

8. The auxiliary power supply circuit is a gate drive power supply circuit, The auxiliary power capacitor is a gate drive capacitor, the gate drive power supply circuit further comprises a gate drive capacitor for a high-voltage transistor; 2. The auxiliary power supply circuit according to claim 1, wherein a voltage is supplied from said gate drive capacitor to said gate drive capacitor for said high-voltage transistor.

9. A power supply device comprising the auxiliary power supply circuit according to claim 1.

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