Auxiliary power supply circuit and power supply unit

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 an auxiliary power supply circuit and a power supply device.

Background Art

[0002] As an example of the configuration of an auxiliary power supply circuit, Patent Document 1 is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

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

[0005] This specification discloses an auxiliary power supply circuit and a power supply device in which the power of a switching circuit can be effectively utilized.

Means for Solving the Problems

[0006] To solve the above problems, an auxiliary power supply circuit according to one aspect of the present disclosure is connected to a switching circuit. The switching circuit has a high-voltage withstand transistor disposed on the high-voltage side and a low-voltage withstand transistor disposed 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 withstand transistor and the low-voltage withstand transistor is connected to the anode of the rectifying element. The cathode of the rectifying 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 withstand transistor. The voltage generated at the connection node when the above switching circuit is operating is supplied to the above auxiliary power capacitor.

[0007] To solve the above problems, a power supply device according to one aspect of this disclosure includes the above-mentioned auxiliary power supply circuit. [Effects of the Invention]

[0008] According to this disclosure, the power of the switching circuit can be effectively utilized. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows an auxiliary power supply circuit according to one embodiment of the present disclosure. [Figure 2] This figure shows the operation of an auxiliary power supply circuit according to one embodiment of the present disclosure. [Figure 3] This figure shows a startup circuit that can be used in an auxiliary power supply circuit according to one embodiment of the present disclosure. [Figure 4] This figure shows a power supply device equipped with an auxiliary power supply circuit according to one embodiment of the present disclosure. [Modes for carrying out the invention]

[0010] [Embodiment 1] In this specification, the rectifier element RCT1 will also be simply referred to as RCT1 as an example of how to represent the symbols in the figures. The abbreviations used are as follows: MOS stands for metal-oxide-semiconductor field-effect transistor, SJMOS stands for super-junction metal-oxide-semiconductor field-effect transistor, IGBT stands for insulated-gate bipolar transistor, JFET stands for junction field effect transistor, HEMT stands for high electron mobility transistor, LDO stands for low dropout linear regulator, and IC stands for integrated circuit of a semiconductor. 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 with the reference terminal as the reference. When the transistor is turned on, it is possible to pass current from the high-voltage terminal to the reference terminal, or from the reference terminal to the high-voltage terminal. When the transistor is off, it can receive a voltage at the high-voltage terminal with the reference terminal as the reference, thereby limiting current conduction. Transistors include MOS, SJMOS, IGBT, GaN-HEMT, SiC-JFET, and others that meet these definitions.

[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. In addition to gate drive power supply circuits, the auxiliary power supply circuit of this embodiment can be applied to various power supply applications, such as power supply circuits for control circuits and power supply circuits for mechanical relay control.

[0012] (Overview of the gate drive power supply circuit) The gate drive power supply circuit GDP1 of this disclosure will be explained with reference to Figure 1. In a general gate drive power supply circuit, the power consumption of a general auxiliary power supply serving as a power source has been an issue. The gate drive power supply circuit GDP1 of the present disclosure is configured to receive power from a switching circuit SWC1, which enables effective utilization of power and suppresses the power consumption of a general auxiliary power supply.

[0013] (Main components of the gate drive power supply circuit) FIG. 1 includes a lower arm LOS1 containing SWC1 and GDP1, and an upper arm UPS1 having the same function. GDP1 will be mainly described using LOS1.

[0014] GDP1 is connected to SWC1. SWC1 includes a high-voltage transistor HVT1 and a low-voltage transistor LVT1 that are serially connected by connecting the reference terminal of the high-voltage transistor HVT1 and the high-voltage terminal of the low-voltage transistor LVT1. HVT1 is arranged on the high-voltage side of a bus capacitor BCP1 that becomes the voltage of the circuit, and LVT1 is arranged 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 rectifying element RCT1 and a gate drive capacitor GDC1. The connection node CNN1 of 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] Due to the main configuration of GDP1 above, the voltage of CNN1 generated when SWC1 turns off conducts RCT1 to charge GDC1. When CNN1, which has decreased due to the turning on of SWC1, receives power from the charged GDC1, RCT1 blocks the conduction of current. The switching operation of repeatedly turning on and off SWC1 supplies DC voltage and power to GDC1. The on and off switching of SWC1 is implemented by driving the gate of LVT1 by a gate drive IC (GIC1) that uses the power of GDC1.

[0016] (Definition of the upper limit voltage of the gate drive capacitor GDC1) Different from a general auxiliary power supply, the voltage of GDC1 generated from CNN1 without voltage guarantee may become an overvoltage. To prevent such an 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 upper limit voltage of GDC1 is defined by the zener voltage of VLT1, and an overvoltage higher than that can be prevented.

[0017] In addition to improving the voltage controllability of GDC1, a zener diode CVL1 can also be connected in parallel with LVT1 for the purpose of noise reduction and the like.

[0018] (Suppressing the surge current of the gate drive capacitor GDC1 with a resistor) Since the voltage change of CNN1 accompanying the switching of SWC1 is steep, a surge current is generated. The surge current propagating to GDC1 becomes noise and may destabilize the operation of GIC1 connected to GDC1.

[0019] To reduce the noise of GDC1, a smoothing capacitor SCP1 and a surge suppression resistor RSR1 can be added. SCP1 connects its positive electrode to the cathode of RCT1 and its negative electrode to the reference terminal of LVT1. RSR1 is interposed in the connection path between the cathode of RCT1 and the positive electrode of GDC1. The addition of SCP1 and RSR1 bypasses the surge current generated in CNN1 to SCP1 and feeds it back to the reference terminal of LVT1. In addition, since the propagation of the surge current to GDC1 is limited by RSR1, the operation of GIC1 can be stabilized.

[0020] (Suppressing the surge current of the gate drive capacitor GDC1 with an LDO) To further reduce the noise of GDC1, RSR1 can be replaced with an LDO, VCT1. Since the LDO can set the output voltage to a constant voltage, the connection of VLT1 can also be made unnecessary. UPS1 is a circuit that replaces RSR1 with VCT1 in LOS1, and omits VLT1. The elements of UPS1, which are composed of the same elements as LOS1, have their signs omitted. VCT1 has its input terminal connected to the cathode of a rectifier element, its output terminal connected to the positive terminal of a gate drive capacitor, and its reference terminal connected to the reference terminal of a low-voltage transistor. VCT1 further suppresses surge current propagation to GDC1.

[0021] (Connecting auxiliary power supply AUX1 to gate drive capacitor GDC1) GDP1 cannot supply DC voltage and power to GDC1 when SWC1 is not in switching operation. Therefore, power can be supplied to GDC1 from the general auxiliary power supply AUX1 to ensure power is available when SWC1 is not in switching operation. AUX1 is additionally connected to GDP1, with the positive terminal of AUX1 connected to the positive terminal of GDC1, and the negative terminal of AUX1 connected to the negative terminal of GDC1.

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

[0023] (Voltage supply to gate drive capacitors for high-voltage transistors) When using SJMOS, SiC-MOS, or similar transistors 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 becomes possible to supply voltage from GDC1 to HCP1.

[0024] (Evaluation circuit for gate drive power supply circuit GDP1) The operation of GDP1 will be verified using the downconverter circuit DNC1 shown in Figure 1. DNC1 includes LOS1, which uses GND1 as its reference node, and UPS1, which uses the switch node SWN1 as its reference node. SWN1 is equipped with a coil CIL1 and a low-voltage load (not shown) beyond it. UPS1 is equipped with a bootstrap diode BSD1 instead of the AUX1 provided by LOS1. The parasitic diodes provided by HVT1 and LVT1 have their cathodes connected to their respective high-voltage terminals.

[0025] The switching of UPS1 and LOS1, controlled by a gate drive IC, generates a low-voltage load voltage of 200V from the 400V voltage of BCP1. The carrier frequency of DNC1 is 100KHz. AUX1 is 15V, VLT1 has a Zener voltage of 17V, and CVL1 has a Zener voltage of 30V. The capacitances of GDC1, SCP1, and HCP1 are 0.1μF. The resistance of RSR1 is 100Ω. LVT1 is a 30V N-channel MOS, and HVT1 is a 600V N-channel SJMOS. By setting the voltage rating of LVT1 to less than one-tenth of that of HVT1, the voltage of CNN1 can be kept low, allowing for efficient charging of GDC1.

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

[0027] Around 1.02E-5Sec, when SWC1 turns off, the voltage of V_SWC1 rises, and at the same time, V_CNN1 also rises to 19V. The rise in V_CNN1 charges SCP1 via RCT1 with 12A of I_RCT1. Meanwhile, I_RSR1, which charges GDC1, is limited to 0.027A, so noise is suppressed. Furthermore, although the voltage of V_SCP1 rises by 1.5V, the small change in V_GDC1 indicates that noise is suppressed. This reduction in noise is due to the effects of SCP1 and RSR1. Also, excluding measurement noise, it can be seen that VLT1 is functioning to prevent the gate drive voltage from exceeding the upper limit of 17V. The high-voltage SCP1 continues to charge GDC1 via I_RSR1.

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

[0029] [Embodiment 2] The AUX1 that was used before SWC1 started up is placed in the startup circuit SUC3. An example of this substitution will be explained using Figure 3.

[0030] SUC3 comprises a startup transistor SUT3, a current limiting resistor CRR3, a gate control resistor GCR3, and a gate control 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 power supply bus line. Here, BUT3 is connected to the positive terminal of BCP1. This configuration makes it possible to secure power before startup.

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

[0032] Please note that the values ​​mentioned above are merely examples. To adjust the circuit operation, it is possible to add resistors to the wiring or add capacitors between two wires to increase the capacitance.

[0033] [Additional Notes] The embodiments of the invention currently considered as disclosed above can be modified in various ways as needed. Such modifications are intended to be incorporated into the appended claims, as long as they remain within the scope of the present invention. [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 connected nodes 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 above switching circuit has a high-voltage transistor located on the high-voltage side and a low-voltage transistor located on the low-voltage side connected in series. The above auxiliary power supply circuit comprises a rectifier element, a smoothing capacitor, an inrush suppression resistor, an auxiliary power supply capacitor, a Zener diode for the auxiliary power supply capacitor, and a general auxiliary power supply. The 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 terminal of the smoothing capacitor. The positive terminal of the smoothing capacitor is connected to one end of the inrush suppression resistor. One end of the above-mentioned inrush suppression resistor is connected to the positive terminal of the above-mentioned auxiliary power capacitor. The negative terminal of the smoothing capacitor and the negative terminal of the auxiliary power capacitor are connected to the reference terminal of the low-voltage transistor. The Zener diode for the auxiliary power capacitor mentioned above is The cathode is connected to the positive terminal of the auxiliary power capacitor mentioned above. The anode is connected to the negative terminal of the auxiliary power capacitor mentioned above. The above general auxiliary power supply is, The positive terminal is connected to the positive terminal of the auxiliary power capacitor mentioned above. The negative terminal is connected to the negative terminal of the auxiliary power capacitor mentioned above. The output voltage of the above general auxiliary power supply is, Lower than the voltage of the auxiliary power capacitor mentioned above, This value is lower than the Zener voltage of the Zener diode for the auxiliary power supply capacitor mentioned above. An auxiliary power supply circuit in which the voltage at the connection node generated when the above switching circuit is operating is supplied to the above auxiliary power supply capacitor.

2. An auxiliary power supply circuit connected to a switching circuit, The above switching circuit has a high-voltage transistor located on the high-voltage side and a low-voltage transistor located on the low-voltage side connected in series. The above auxiliary power supply circuit comprises a rectifier element, a smoothing capacitor, an LDO, an auxiliary power supply capacitor, and a general auxiliary power supply. The 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 terminal of the smoothing capacitor. The above LDO is, The input terminal is connected to the positive terminal of the smoothing capacitor mentioned above. The output terminal is connected to the positive terminal of the auxiliary power capacitor mentioned above. The reference terminal of the low-voltage transistor is connected to the negative terminal of the smoothing capacitor, the negative terminal of the auxiliary power capacitor, and the reference terminal of the LDO. The above general auxiliary power supply is, The positive terminal is connected to the positive terminal of the auxiliary power capacitor mentioned above. The negative terminal is connected to the negative terminal of the auxiliary power capacitor mentioned above. The output voltage of the above general auxiliary power supply is, Lower than the voltage of the auxiliary power capacitor mentioned above, This value is lower than the output voltage of the above LDO. An auxiliary power supply circuit in which the voltage at the connection node generated when the above switching circuit is operating is supplied to the above auxiliary power supply capacitor.

3. The above auxiliary power supply circuit is a gate drive power supply circuit, The above auxiliary power capacitor is a gate drive capacitor, The gate drive power supply circuit described above is further equipped with a gate drive capacitor for high-voltage transistors. The auxiliary power supply circuit according to claim 1 or 2, wherein a voltage is supplied from the gate drive capacitor to the gate drive capacitor for the high-voltage transistor.

4. A power supply device comprising the auxiliary power supply circuit described in claim 1 or 2.

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