Driving circuit and power supply method of high-voltage silicon carbide half-bridge circuit

Abstract

The application discloses a driving circuit and power supply method of a high-voltage silicon carbide half-bridge circuit. The half-bridge circuit comprises an upper bridge arm switch Sp and a lower bridge arm switch Sn. An auxiliary power supply Vaux1 of the Sn provides positive and negative power supplies to a driving circuit of the Sn through two DC / DC converters. The Vaux1 simultaneously generates an auxiliary power supply Vaux2 through a non-isolated level conversion network. The Vaux2 also provides positive and negative power supplies to a driving circuit of the Sp through two DC / DC converters. The non-isolated level conversion network comprises a diode D1, a current-limiting resistor R1, an energy storage capacitor C1, a common-mode inductor Lcm, differential-mode inductors Ld1 and Ld2, and a filter capacitor C2. The application does not need to use an isolated auxiliary power supply to supply power to the driving circuit of the upper bridge arm switch of the half-bridge circuit, thereby solving the problem that the existing auxiliary power supply scheme needs a high-insulation isolation transformer, and significantly reducing the common-mode current and electromagnetic interference risk, and guaranteeing the safe and stable operation of the system.

Description

Technical Field

[0001] This invention belongs to the field of power semiconductor device driving technology, specifically relating to a driving circuit and power supply method for a high-voltage silicon carbide half-bridge circuit. Background Technology

[0002] Traditional power grids are evolving towards new power systems characterized by the widespread application of power electronics technology. High-efficiency, high-power-density flexible power electronic devices at the megawatt level in medium and high voltage ranges are core equipment in these new power systems, placing high performance demands on high-voltage, high-power devices. However, currently commonly used power devices typically have a withstand voltage of 1200V / 1700V. When applied to medium and high voltage distribution networks above 10kV, multiple devices must be connected in series and parallel, along with an isolation transformer, to construct the power circuit of the flexible device. This results in existing medium and high voltage flexible devices suffering from high cost, low efficiency, large size, and poor reliability, increasing investment costs and operating losses in the distribution network and hindering the large-scale application of next-generation flexible device technology in distribution networks.

[0003] With advancements in high-voltage silicon carbide devices (such as SiC-MOSFETs or SiC-IGBTs) capable of withstanding voltages exceeding 10kV, medium- and high-voltage flexible equipment has ushered in new development opportunities. The drive circuit is a crucial component for ensuring the safe and reliable operation of high-voltage silicon carbide power devices. When applied to medium- and high-voltage power conversion equipment, the drive circuit faces the following challenges:

[0004] 1) The system operating voltage can reach more than 10kV, which requires the isolation voltage withstand capability between the drive circuit and the equipment control circuit (such as digital signal processor circuit) to be more than 10kV;

[0005] 2) High-voltage silicon carbide power devices can achieve switching speeds of up to 100 kV / µs, requiring minimal parasitic capacitance to ground to reduce electromagnetic interference. Since most commonly used medium- and high-voltage power conversion equipment employs multiple half-bridge circuit topologies, each half-bridge circuit includes upper and lower bridge arm switches, and each switch has its own independent drive circuit and isolated auxiliary power supply, the challenges faced by the drive circuits are primarily addressed by the upper bridge arm switches. Existing solutions generally address these challenges by designing isolated auxiliary power supplies with high isolation voltage and low parasitic capacitance. This makes the design of the isolation transformer for the auxiliary power supply particularly difficult, resulting in higher size and cost of the drive circuit. Furthermore, existing solutions cannot completely eliminate common-mode interference generated by parasitic capacitance, producing extremely strong electromagnetic interference to the system control loop and seriously threatening the safe and stable operation of the system. These shortcomings have become one of the main problems hindering the widespread application of high-voltage silicon carbide power devices. Summary of the Invention

[0006] The technical problem to be solved by this invention is: in order to significantly reduce the common-mode current and system electromagnetic interference generated by the upper arm switch of the half-bridge circuit, and improve the safe and stable operation capability of the medium and high voltage power conversion system based on high voltage silicon carbide power devices, a solution is provided to obtain the auxiliary power supply required for the upper arm drive circuit from the lower arm auxiliary power supply, thereby eliminating the need for a dedicated and complex upper arm isolation auxiliary power supply.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical approach:

[0008] This invention first proposes a driving circuit for a high-voltage silicon carbide half-bridge circuit, including an upper bridge arm switch and its driving circuit, and a lower bridge arm switch and its driving circuit. An external auxiliary power supply provides positive and negative power to the driving circuit of the lower bridge arm switch through a first and a second DC / DC converter, respectively. At the same time, the external auxiliary power supply generates a second auxiliary power supply through a non-isolated level conversion network. The second auxiliary power supply provides positive and negative power to the driving circuit of the upper bridge arm switch through a third and a fourth DC / DC converter, respectively. The negative terminal of the auxiliary power supply is connected to the source terminal of the lower bridge arm switch, and the drain terminal of the lower bridge arm switch is connected to the source terminal of the upper bridge arm switch.

[0009] Furthermore, the driving circuit of the high-voltage silicon carbide half-bridge circuit proposed in this invention includes a non-isolated level conversion network comprising a diode, an energy storage capacitor, a common-mode inductor, first and second differential-mode inductors, and a filter capacitor. The positive terminal of the external auxiliary power supply is connected in series with the diode and the common-mode inductor, and then connected to one side of the first differential-mode inductor. The drain of the lower bridge arm switch is connected to one side of the common-mode inductor and the second differential-mode inductor. The two ends of the energy storage capacitor are respectively connected to the cathode of the diode and the drain of the lower bridge arm switch. One end of the filter capacitor is connected to the other side of the first differential-mode inductor, and the other end is connected to the other side of the second differential-mode inductor and the source of the upper bridge arm switch.

[0010] Furthermore, the driving circuit of the high-voltage silicon carbide half-bridge circuit proposed in this invention also includes a current-limiting resistor, the two ends of which are connected to the cathode of the diode and the common-mode inductor, respectively.

[0011] Furthermore, in the high-voltage silicon carbide half-bridge circuit driving circuit proposed in this invention, the first and third DC / DC converters provide positive power, and the second and fourth DC / DC converters provide negative power. All four DC / DC converters are non-isolated topologies, wherein the first and third DC / DC converters are buck converters, and the second and fourth DC / DC converters are inverting converters.

[0012] Furthermore, the driving circuit of the high-voltage silicon carbide half-bridge circuit proposed in this invention comprises a first switch, a first diode, a first filter inductor, and a first capacitor, wherein the normally closed terminal of the first switch is connected to a positive voltage source, and the open and closed terminals are sequentially connected to the cathode of the first diode and one end of the first filter inductor; the other end of the first filter inductor is connected to one end of the first capacitor and the positive voltage input terminal of the driving circuit, and the other end of the first filter inductor and the other end of the first capacitor are respectively connected to a negative voltage source.

[0013] The second and fourth DC / DC converters are composed of a second switch, a second inductor, a third switch, and a second capacitor. The normally closed terminal of the second switch is connected to a positive voltage source, and the open and closed terminals are connected in sequence to one end of the second inductor and the normally closed terminal of the third switch. The open and closed terminals of the third switch are connected to one end of the second capacitor and the negative voltage input terminal of the drive circuit, respectively. The other ends of the second inductor and the second capacitor are connected to the negative voltage source, respectively.

[0014] This invention also proposes a power supply method for the driving circuit of a high-voltage silicon carbide half-bridge circuit, comprising:

[0015] 1) When the lower bridge arm switch is turned on, the upper bridge arm switch is turned off. The drain D and source S of the upper bridge arm switch are shorted. At this time, the diode is turned on, and the auxiliary power supply charges the energy storage capacitor through the diode. After the energy storage capacitor is fully charged, it charges the filter capacitor through the filtering effect of the common mode inductor and the first and second differential mode inductors. The voltage on the filter capacitor is approximately equal to the voltage of the auxiliary power supply. This voltage is used as the auxiliary power supply for the upper bridge arm switch drive circuit.

[0016] 2) When the lower bridge arm switch is off, the upper bridge arm switch is on, and the voltage across the DS terminals of the lower bridge arm switch is high. At this time, the diode is cut off, and the drive circuit of the upper bridge arm switch is directly powered by the filter capacitor.

[0017] Furthermore, in the power supply method for the driving circuit of the high-voltage silicon carbide half-bridge circuit proposed in this invention, the voltage of the filter capacitor is gradually reduced until the upper bridge arm switch changes from on to off. By adjusting the capacitance values ​​of the energy storage capacitor and the filter capacitor, the minimum voltage of the filter capacitor must be higher than the minimum input voltage allowed by the third and fourth DC / DC converters.

[0018] If the withstand voltage of a single diode is less than the voltage it withstands when the lower bridge arm switch is turned off, multiple diodes are connected in series to form a diode series group to replace the single diode until the total withstand voltage is greater than the voltage it withstands when the lower bridge arm switch is turned off.

[0019] The present invention adopts the above technical solution, and has the following beneficial effects compared with the prior art:

[0020] In the power supply method of the driving circuit of the present invention, the driving circuit of the upper bridge arm switch draws power from the auxiliary power supply of the lower bridge arm driving circuit, so that the upper bridge arm driving circuit has no electrical connection with the system control circuit, which significantly reduces the parasitic capacitance on the low-voltage side and high-voltage side of the system, and further significantly reduces the common-mode current and electromagnetic interference generated by the fast switching action of the high-voltage silicon carbide device on the control circuit, thereby improving the safe and stable operation capability of the system. Attached Figure Description

[0021] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the present invention will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the power supply method for the drive circuit of the present invention.

[0023] Figure 2 This is a circuit diagram of the DC / DC converter that generates a positive power supply in this invention.

[0024] Figure 3 This is a circuit diagram of the DC / DC converter that generates a negative power supply in this invention.

[0025] Figure 4 These are the driving waveform of Sn and the voltage waveform on C2 in this invention. Detailed Implementation

[0026] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, what is described is only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] This invention relates to a power supply method for a drive circuit based on a high-voltage silicon carbide half-bridge circuit. The main components of this method are described in detail below with reference to the accompanying drawings. The principle block diagram of the power supply method for the drive circuit of the high-voltage silicon carbide half-bridge circuit is shown below. Figure 1 As shown, the functions and implementation methods of each part are described below.

[0028] The half-bridge circuit consists of an upper bridge arm switch Sp and a lower bridge arm switch Sn. The source of Sp is connected to the drain of Sn. The drive circuit for the high-voltage silicon carbide device requires dual power supplies (positive and negative). Therefore, two DC / DC converters are used to provide the required dual power supplies for Sp and Sn respectively. Figure 1In this invention, DC / DC converters 1 and 3 provide positive power, while DC / DC converters 2 and 4 provide negative power. All four DC / DC converters are non-isolated topologies, which minimizes size, component count, and cost. Optional topologies for DC / DC converters 1 and 3 include, but are not limited to, those listed below. Figure 2 The buck converter shown mainly consists of switch S11, diode D11, filter inductor L11, and capacitor C11. Optional topologies for DC / DC converters 2 and 4 include, but are not limited to, those shown. Figure 3 The inverter shown mainly consists of switch S21, inductor L21, switch S22, and capacitor C21.

[0029] The entire half-bridge circuit's drive circuit requires only one auxiliary power supply, Vaux1. Vaux1 directly powers DC / DC converters 1 and 2, enabling them to generate the required positive and negative dual power supplies for Sn. The negative terminal of Vaux1 is connected to the source terminal of Sn. Since the common-mode interference of the half-bridge circuit is mainly generated by the upper bridge arm switch, Vaux1 only needs to meet isolation requirements; its parasitic capacitances on the low-voltage and high-voltage sides will not generate significant common-mode interference.

[0030] Vaux1 passes through simultaneously Figure 1 The non-isolated level shifting network in the circuit powers the drive circuit of the upper bridge arm switch Sp. This non-isolated level shifting network includes the following components: diode D1, current-limiting resistor R1, energy storage capacitor C1, and common-mode inductor L. cm Differential mode inductors Ld1 and Ld2, and filter capacitor C2. The positive terminal of Vaux1 is connected in series with the anode of D1 and Lcm, and then connected to the left side of Ld1. The drain of Sn is connected to the source of Sp through Lcm and Ld2. C1 is connected between the cathode of D1 and the drain of Sn. C2 is connected between the right side of Ld1 and the source of Sp.

[0031] The principle of the power supply method for the drive circuit of the present invention is as follows:

[0032] 1) When the lower diode Sn is turned on, the upper diode Sp is turned off. With the drain (D) and source (S) of Sn short-circuited (ignoring the forward voltage drop of Sn), diode D1 will conduct, and Vaux1 will charge capacitor C1 through D1. R1 prevents excessive charging current. Lcm, Ld1, Ld2, and C2 act as common-mode and differential-mode harmonic filters on the voltage across C1, reducing interference from the rapid switching of high-voltage silicon carbide devices on the drive circuit. Ignoring the voltage drop of the filters, after full charging, the voltage Vaux2 across C2 is approximately equal to the voltage Vaux1. At this point, the voltage across C2 can serve as the auxiliary power supply for the upper diode Sp drive circuit.

[0033] 2) When the lower diode Sn is off, the upper diode Sp is on. The voltage across the drain-source (DS) terminals of Sn is high (e.g., up to 10kV). At this time, diode D1 is off, and the drive circuit of Sp is directly powered by capacitor C2. Under the filtering effect of Lcm, Ld1, and Ld2, C1 also supports the voltage of C2. Since diode D1 has to withstand the voltage across its DS terminals, it may be as high as 10kV. If the voltage rating of the available diodes is insufficient to withstand 10kV, multiple devices can be used in series as substitutes. In this state, the voltage across capacitor C2 gradually decreases, but the minimum value cannot be lower than the minimum input voltage allowed by DC / DC converters 3 and 4; otherwise, the two DC / DC converters cannot always generate the positive and negative voltages required for Sp. Therefore, when this state ends, i.e., when Sp changes from on to off, the voltage across C2 must not be lower than the minimum input voltage allowed by DC / DC converters 3 and 4. This can be achieved by adjusting the capacitance values ​​of C1 and C2 and selecting a DC / DC converter with a wider input range.

[0034] Therefore, as long as the capacitance values ​​of capacitors C1 and C2 are large enough, the drive circuit of the upper bridge arm switch Sp will always be powered, without the need for an additional dedicated isolation auxiliary power supply, and the common-mode interference caused by the parasitic capacitances on the low-voltage and high-voltage sides of the isolation auxiliary power supply will be eliminated.

[0035] Figure 4 An example waveform of the present invention is given. Vaux1 is 30V, which generates 20V and -5V voltages respectively through two wide-input DC / DC converters. The DC / DC converters used for Sp and Sn are the same. The input voltage range of the two DC / DC converters is 22-36V. The drive power consumption of the two silicon carbide devices is 3W. The current-limiting resistor R1 is 2Ω, the capacitance of capacitor C1 is 10uF, Lcm is 1mH, Ld1 and Ld2 are both 10uH, and C2 is 10uF. Figure 4 The upper part of the waveform is the driving voltage waveform of Sn, with a frequency of 20kHz. The driving voltage waveform of Sp is complementary to the driving voltage of Sn. After using the method of this invention, the voltage waveform across capacitor C2 is as follows: Figure 4 The lower half is shown. It can be seen that when the Sn driving voltage is high (Sn is on), the voltage on C2 gradually charges to 30V and then remains stable. When the Sn driving voltage is low (Sn is off), the voltage on C2 gradually discharges to 29V, always exceeding the minimum input voltage of 22V for the two DC / DC converters of Sp. Therefore, the method of this invention can power the Sp driving circuit without a high-voltage isolation auxiliary power supply.

[0036] In this invention, the high-voltage silicon carbide device is a high-voltage silicon carbide MOSFET device, whose power circuit terminals are named drain and source. The method of this invention is also applicable to high-voltage silicon carbide IGBT devices; only the drain terminal name needs to be changed to collector, and the source terminal name to emitter.

[0037] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above-described embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A driving circuit for a high-voltage silicon carbide half-bridge circuit, suitable for high-voltage silicon carbide devices with a withstand voltage of 10kV or higher, comprising an upper bridge arm switch and its driving circuit, and a lower bridge arm switch and its driving circuit, characterized in that, The external auxiliary power supply provides positive and negative power to the drive circuit of the lower bridge arm switch through the first and second DC / DC converters, respectively. At the same time, the external auxiliary power supply generates a second auxiliary power supply through a non-isolated level conversion network. The second auxiliary power supply provides positive and negative power to the drive circuit of the upper bridge arm switch through the third and fourth DC / DC converters, respectively. The negative terminal of the external auxiliary power supply is connected to the source terminal of the lower bridge arm switch, and the drain terminal of the lower bridge arm switch is connected to the source terminal of the upper bridge arm switch. The non-isolated level conversion network includes a diode, an energy storage capacitor, a common-mode inductor, first and second differential-mode inductors, and a filter capacitor. The positive terminal of the external auxiliary power supply is connected in series with the diode and the common-mode inductor, and then connected to one side of the first differential-mode inductor. The drain of the lower bridge arm switch is connected to one side of the common-mode inductor and the second differential-mode inductor. The two ends of the energy storage capacitor are connected to the cathode of the diode and the drain of the lower bridge arm switch, respectively. One end of the filter capacitor is connected to the other side of the first differential-mode inductor, and the other end is connected to the other side of the second differential-mode inductor and the source of the upper bridge arm switch, respectively.

2. The driving circuit for a high-voltage silicon carbide half-bridge circuit according to claim 1, characterized in that, It also includes a current-limiting resistor, with its two ends connected to the cathode of the diode and the common-mode inductor, respectively.

3. The driving circuit for a high-voltage silicon carbide half-bridge circuit according to claim 1, characterized in that, The first and third DC / DC converters provide positive power, while the second and fourth DC / DC converters provide negative power.

4. The driving circuit for a high-voltage silicon carbide half-bridge circuit according to claim 3, characterized in that, The first to fourth DC / DC converters are all non-isolated topologies, with the first and third DC / DC converters being buck converters and the second and fourth DC / DC converters being inverting converters.

5. A driving circuit for a high-voltage silicon carbide half-bridge circuit according to any one of claims 3 or 4, characterized in that, The first and third DC / DC converters are composed of a first switch, a first diode, a first filter inductor, and a first capacitor. The normally closed terminal of the first switch is connected to a positive voltage source, and the open and closed terminals are connected in sequence to the cathode of the first diode and one end of the first filter inductor. The other end of the first filter inductor is connected to one end of the first capacitor and the positive voltage input terminal of the drive circuit, and the other end of the first filter inductor and the other end of the first capacitor are connected to a negative voltage source.

6. A driving circuit for a high-voltage silicon carbide half-bridge circuit according to any one of claims 3 or 4, characterized in that, The second and fourth DC / DC converters are composed of a second switch, a second inductor, a third switch, and a second capacitor. The normally closed terminal of the second switch is connected to a positive voltage source, and the open and closed terminals are connected in sequence to one end of the second inductor and the normally closed terminal of the third switch. The open and closed terminals of the third switch are connected to one end of the second capacitor and the negative voltage input terminal of the drive circuit, respectively. The other ends of the second inductor and the second capacitor are connected to the negative voltage source, respectively.

7. A power supply method for the driving circuit of the high-voltage silicon carbide half-bridge circuit according to any one of claims 1-6, characterized in that: 1) When the lower bridge arm switch is turned on, the upper bridge arm switch is turned off. The drain D and source S of the upper bridge arm switch are shorted. At this time, the diode is turned on, and the auxiliary power supply charges the energy storage capacitor through the diode. After the energy storage capacitor is fully charged, it charges the filter capacitor through the filtering effect of the common mode inductor and the first and second differential mode inductors. The voltage on the filter capacitor is equal to the voltage of the auxiliary power supply. This voltage is used as the auxiliary power supply for the upper bridge arm switch drive circuit. 2) When the lower bridge arm switch is off, the upper bridge arm switch is on, and the voltage across the DS terminals of the lower bridge arm switch is high. At this time, the diode is cut off, and the drive circuit of the upper bridge arm switch is directly powered by the filter capacitor.

8. The power supply method for the driving circuit of the high-voltage silicon carbide half-bridge circuit according to claim 6, characterized in that: The voltage of the filter capacitor gradually decreases until the upper bridge arm switch changes from on to off. By adjusting the capacitance values ​​of the energy storage capacitor and the filter capacitor, the minimum voltage of the filter capacitor must be higher than the minimum input voltage allowed by the third and fourth DC / DC converters.

9. The power supply method for the driving circuit of a high-voltage silicon carbide half-bridge circuit according to claim 6, characterized in that, If the withstand voltage of a single diode is less than the voltage that the lower bridge arm switch withstands when it is turned off, multiple diodes are connected in series to form a diode series group to replace the single diode until the total withstand voltage is greater than the voltage that the lower bridge arm switch withstands when it is turned off.

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