An RCD energy-fed self-powered power switch tube drive circuit

Abstract

The present invention relates to an RCD energy-fed self-powered power switch tube drive circuit, which includes a power switch tube, an RCD absorption circuit, a buck circuit with negative voltage output, and a power switch tube drive circuit; the RCD absorption circuit is connected in parallel across both ends of the power switch tube, the input of the buck circuit with negative voltage output is connected in parallel across both ends of the capacitor of the RCD absorption circuit, the output of the buck circuit with negative voltage output is connected to the input of the power switch tube drive circuit, and the output of the power switch tube drive circuit is connected to the gate of the power switch tube; the RCD absorption circuit is used to absorb the overshoot voltage of the power switch tube and store energy through the capacitor in the RCD absorption circuit; the buck circuit with negative voltage output is used to convert the energy stored in the RCD absorption circuit into positive and negative voltages for driving the power switch tube; the power switch tube drive circuit is used for driving the power switch tube. The present invention improves the stability of the power switch tube.

Description

Technical Field

[0001] The present invention relates to the field of power electronics, and particularly to an RCD energy-fed self-powered power switch tube drive circuit. Background Art

[0002] The performance of a power converter is largely restricted by the switching performance of power switch tubes MOSFET / IGBT (MOSFET: Metal-Oxide-Semiconductor-Field-Effect Transistor; IGBT: Insulated Gate Bipolar Transistor). Therefore, the drive circuit of MOSFET / IGBT plays a crucial role in a power electronics system. The reliability improvement of power tubes mainly focuses on preventing overvoltage, overcurrent, and reliable turn-off.

[0003] Regarding the overvoltage problem, under normal operating voltages that meet the design requirements, it is mainly the voltage overshoot caused by inductive components. Currently, in various circuit topologies, an RCD (resistor, capacitor, and diode) circuit is usually used to absorb voltage spikes, and when the tube conducts, the energy in the capacitor is dissipated through the resistor, thereby reducing the voltage spike across the switch tube. However, the problem is that the resistor generates heat and the system efficiency is low.

[0004] Regarding the overcurrent problem, when the device current is too large during the conduction of the switch tube, it may cause device damage.

[0005] Regarding the power supply problem of the drive circuit, due to the floating ground problem and the prevention of power interference with signals, the drive circuit of the power switch tube is usually powered separately. Currently, the main methods used are dedicated power supply lines and bootstrap power supply lines, as Figure 2 and Figure 3 shown. Dedicated power supply lines usually require isolation. As the number of switch tubes increases, the auxiliary power supply line becomes more complex. Bootstrap power supply reduces the requirements for auxiliary power supply to a certain extent, but the circuit is still complex, and the supply voltage changes with the pulse width of the switch tube, and the voltage is not stable enough. Summary of the Invention

[0006] The object of the present invention is to provide an RCD energy-fed self-powered power switch tube drive circuit, which improves the stability of the power switch tube.

[0007] To achieve the above object, the present invention provides the following solution:

[0008] An RCD energy-fed self-powered power switch tube drive circuit includes a power switch tube, an RCD absorption circuit, a buck circuit with a negative voltage output, and a power switch tube drive circuit;

[0009] The RCD absorption circuit is connected in parallel across the two ends of the power switch tube. The input of the buck circuit with negative voltage output is connected in parallel across the two ends of the capacitor of the RCD absorption circuit. The output of the buck circuit with negative voltage output is connected to the input of the power switch tube drive circuit, and the output of the power switch tube drive circuit is connected to the gate of the power switch tube;

[0010] The RCD absorption circuit is used to absorb the overshoot voltage of the power switch tube and store energy through the capacitor in the RCD absorption circuit. The buck circuit with negative voltage output is used to convert the energy stored in the RCD absorption circuit into positive and negative voltages for driving the power switch tube. The power switch tube drive circuit is used for driving the power switch tube.

[0011] Optionally, the RCD absorption circuit includes a resistor R1, a capacitor C1, and a diode D1. The positive electrode of the diode D1 is connected to the first pole of the power switch tube. The negative electrode of the diode D1 is respectively connected to the first end of the capacitor C1 and the first end of the resistor R1. The second end of the capacitor C1, the second end of the resistor R1, and the second pole of the power switch tube are all grounded.

[0012] Optionally, the buck circuit with negative voltage output includes a switch tube Q1, a diode D2, a zener diode D3, an inductor L1, capacitors C2, C3, a resistor R2, a resistor R3, a capacitor C14, a first operational amplifier, and a second operational amplifier;

[0013] The first pole of the switch tube Q1 is connected to the first end of the resistor R1. The second pole of the switch tube Q1 is respectively connected to the negative electrode of the diode D2 and the first end of the inductor L1. The gate of the switch tube Q1 is connected to the output end of the second operational amplifier. The positive electrode of the diode D2 is respectively connected to the positive electrode of the zener diode D3 and the first end of the capacitor C2. The second end of the inductor L1 is respectively connected to the first end of the capacitor C3, the first end of the resistor R2, and the first end of the capacitor C14. The second end of the resistor R2 is respectively connected to the first end of the resistor R3 and the first input end of the first operational amplifier. A reference voltage is input to the second input end of the first operational amplifier. The output end of the first operational amplifier is connected to the first input end of the second operational amplifier. A preset sawtooth wave is input to the second input end of the second operational amplifier. The negative electrode of the zener diode D3, the second end of the capacitor C2, the second end of the capacitor C3, and the second end of the resistor R3 are all grounded.

[0014] Optionally, the power switch tube drive circuit is a push-pull drive circuit.

[0015] Optionally, the push-pull drive circuit includes a square wave signal, a transistor Q6, and a transistor Q8; the transistor Q6 is an NPN transistor, and the transistor Q8 is a PNP transistor; the square wave signal is connected to the common base of the transistor Q6 and the transistor Q8, the collector of the transistor Q6 is connected to the first end of the capacitor C14, the collector of the transistor Q8 is connected to the first end of the capacitor C2, and the emitters of the transistor Q6 and the transistor Q8 are both connected to the gate of the power switch transistor.

[0016] Optionally, it further includes a drive current limiting protection circuit, and the drive current limiting protection circuit includes a resistor R7, a resistor R16, a resistor R11, a voltage stabilizing diode D5, and a voltage stabilizing diode D7; the first end of the resistor R7 is connected to the emitter of the transistor Q6, the first end of the resistor R16 is connected to the emitter of the transistor Q8, and the second ends of the resistor R7 and the resistor R16 are both connected to the gate of the power switch transistor; the first end of the resistor R11 and the negative electrode of the voltage stabilizing diode D5 are both connected to the gate of the power switch transistor, the positive electrode of the voltage stabilizing diode D5 is connected to the positive electrode of the voltage stabilizing diode D7, and the second end of the resistor R11 and the negative electrode of the voltage stabilizing diode D7 are both grounded.

[0017] Optionally, the power switch transistor is an IGBT.

[0018] Optionally, the power switch transistor is a MOSFET.

[0019] According to the specific embodiments provided by the present invention, the following technical effects are disclosed by the present invention:

[0020] The present invention absorbs the overshoot voltage of the power switch transistor through the RCD absorption circuit, stores energy through the capacitor in the RCD absorption circuit, and converts the energy stored in the RCD absorption circuit into positive and negative voltages for driving the power switch transistor through a buck circuit with negative voltage output, improving the stability of the power supply voltage of the power switch transistor, reducing the energy consumption and heat generation of the RCD absorption circuit, and improving the energy utilization efficiency of the circuit. Description of the Drawings

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0022] Figure 1 It is a schematic structural diagram of an RCD energy-fed self-powered power switch transistor drive circuit of the present invention;

[0023] Figure 2 Schematic diagram of the dedicated power supply circuit for the power switch tube

[0024] Figure 3 Schematic diagram of the bootstrap power supply circuit for the power switch tube Specific implementation manners

[0025] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0026] The purpose of the present invention is to provide an RCD energy-fed self-powered power switch tube drive circuit, which improves the stability of the power switch tube.

[0027] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0028] Figure 1 Schematic diagram of the structure of an RCD energy-fed self-powered power switch tube drive circuit of the present invention, as Figure 1 shown, an RCD energy-fed self-powered power switch tube drive circuit includes a power switch tube, an RCD absorption circuit 101, a buck circuit 102 with a negative voltage output, and a power switch tube drive circuit 103.

[0029] The RCD absorption circuit 101 is connected in parallel across the two ends of the power switch tube. The input of the buck circuit 102 with a negative voltage output is connected in parallel to the two ends of the capacitor of the RCD absorption circuit 101. The output of the buck circuit 102 with a negative voltage output is connected to the input of the power switch tube drive circuit 103, and the output of the power switch tube drive circuit 103 is connected to the gate of the power switch tube.

[0030] The RCD absorption circuit 101 is used to absorb the overshoot voltage of the power switch tube and store energy through the capacitor in the RCD absorption circuit 101. The buck circuit 102 with a negative voltage output is used to convert the energy stored in the RCD absorption circuit 101 into a positive voltage and a negative voltage for driving the power switch tube. The power switch tube drive circuit 103 is used for driving the power switch tube.

[0031] The power switch tube is an IGBT or the power switch tube is a MOSFET.

[0032] The RCD snubber circuit 101 is applied to various topologies of power converters. In each topology structure, to reduce the voltage overshoot across the power switch (between the drain and source of the MOSFET or between the collector and emitter of the IGBT) caused by inductive loads, the RCD snubber circuit 101 is mainly used to reduce the voltage overshoot. When the power switch turns off, an instantaneous voltage overshoot is generated. At this time, the diode conducts to charge the capacitor. Through the characteristic that the voltage of the capacitor does not change instantaneously, the voltage overshoot is reduced, and the energy of the voltage spike is absorbed to further achieve the soft turn-off of the switch tube; when the switch tube conducts, the diode is cut off, and the capacitor discharges through the resistor, making the capacitor return to a low voltage or zero voltage.

[0033] The buck circuit 102 with negative voltage output is a dual-output buck circuit. The input end of the buck circuit 102 with negative voltage output is connected in parallel across the capacitor of the RCD snubber circuit 101. The resistance value is increased or the resistor is removed, and the energy stored in the capacitor is released through the buck circuit.

[0034] The buck circuit 102 with negative voltage output obtains a stable positive voltage required for the power switch drive circuit 103 at the output end through feedback.

[0035] For the buck circuit 102 with negative voltage output, a series voltage regulator tube and a capacitor parallel circuit are connected in reverse under the freewheeling diode. When the switch tube turns off and the freewheeling diode conducts, a negative voltage common to the ground with the positive voltage is obtained across the voltage regulator tube, and the voltage is maintained through the capacitor.

[0036] The power switch drive circuit 103 mainly adopts a push-pull drive circuit. The upper end of the push-pull drive circuit is connected to the positive output voltage of the buck circuit 102 with negative voltage output, and the lower end is connected to the negative voltage of the buck circuit 102 with negative voltage output. The middle of the two transistors of the push-pull drive circuit is connected to the gate of the power switch through a resistor, and the common base of the push-pull drive circuit is connected to the input square wave signal.

[0037] For the power switch drive circuit 103, when the input square wave signal is at a low level, the lower transistor of the push-pull drive circuit conducts, and the gate of the power switch obtains a negative voltage, making the power switch turn off reliably.

[0038] For the power switch drive circuit 103, when the input square wave signal is at a high level, the upper transistor of the push-pull drive circuit conducts, and the gate of the power switch obtains a positive voltage, making the power switch conduct effectively.

[0039] The RCD absorption circuit 101 includes a resistor R1, a capacitor C1, and a diode D1. The positive electrode of the diode D1 is connected to the first pole of the power switch tube. The negative electrode of the diode D1 is respectively connected to the first end of the capacitor C1 and the first end of the resistor R1. The second end of the capacitor C1, the second end of the resistor R1, and the second pole of the power switch tube are all grounded.

[0040] The buck circuit 102 with a negative voltage output includes a switching tube Q1, a diode D2, a zener diode D3, an inductor L1, a capacitor C2, a capacitor C3, a resistor R2, a resistor R3, a capacitor C14, a first operational amplifier, and a second operational amplifier;

[0041] The first pole of the switching tube Q1 is connected to the first end of the resistor R1. The second pole of the switching tube Q1 is respectively connected to the negative electrode of the diode D2 and the first end of the inductor L1. The gate of the switching tube Q1 is connected to the output end of the second operational amplifier. The positive electrode of the diode D2 is respectively connected to the positive electrode of the zener diode D3 and the first end of the capacitor C2. The second end of the inductor L1 is respectively connected to the first end of the capacitor C3, the first end of the resistor R2, and the first end of the capacitor C14. The second end of the resistor R2 is respectively connected to the first end of the resistor R3 and the first input end of the first operational amplifier. A reference voltage is input to the second input end of the first operational amplifier. The output end of the first operational amplifier is connected to the first input end of the second operational amplifier. A preset sawtooth wave is input to the second input end of the second operational amplifier. The negative electrode of the zener diode D3, the second end of the capacitor C2, the second end of the capacitor C3, and the second end of the resistor R3 are all grounded.

[0042] The push-pull drive circuit includes a square wave signal, a transistor Q6, and a transistor Q8; the transistor Q6 is an NPN transistor, and the transistor Q8 is a PNP transistor; the square wave signal is connected to the common base of the transistor Q6 and the transistor Q8. The collector of the transistor Q6 is connected to the first end of the capacitor C14. The collector of the transistor Q8 is connected to the first end of the capacitor C2. The emitters of the transistor Q6 and the transistor Q8 are both connected to the gate of the power switch tube.

[0043] An RCD energy-fed self-powered power switch tube drive circuit further includes a drive current-limiting protection circuit 104. The drive current-limiting protection circuit 104 includes a resistor R7, a resistor R16, a resistor R11, a zener diode D5, and a zener diode D7; the first end of the resistor R7 is connected to the emitter of the transistor Q6. The first end of the resistor R16 is connected to the emitter of the transistor Q8. The second ends of the resistor R7 and the resistor R16 are both connected to the gate of the power switch tube; the first end of the resistor R11 and the negative electrode of the zener diode D5 are both connected to the gate of the power switch tube. The positive electrode of the zener diode D5 is connected to the positive electrode of the zener diode D7. The second end of the resistor R11 and the negative electrode of the zener diode D7 are both grounded.

[0044] As Figure 1As shown, in the RCD absorption circuit 101, resistor R1 and capacitor C1 are connected in parallel and then in series with diode D1. When the MOSFET switch M1 is turned off, diode D1 conducts, and capacitor C1 causes the voltage between the drain and source of MOSFET switch M1 to rise slowly, achieving the purpose of soft turn-off, while suppressing the overshoot of the voltage between the drain and source. Capacitor C1 stores energy. When switch M1 conducts, diode D1 turns off, and capacitor C1 releases most of its energy through the buck circuit 102 with negative voltage output, and the excess energy is dissipated by the resistor.

[0045] The buck circuit 102 with negative voltage output consists of three parts: a traditional buck circuit, a feedback circuit, and a negative voltage generation circuit. The traditional buck circuit consists of switch Q1, diode D2, inductor L1, and capacitor C3. By modulating switch Q1, diode D2 provides freewheeling for inductor L1, and the required positive voltage is obtained after filtering by inductor L1 and capacitor C1. The feedback circuit consists of voltage sampling, deviation adjustment, generation of the pulse width waveform, and driving of switch Q1. The driving of switch Q1 is Figure 1 the driving circuit in it. Resistors R2 and R3 are used for voltage division to achieve voltage sampling. After comparison with the reference voltage through an operational amplifier and deviation adjustment through a PI section, then comparison with a sawtooth wave through an operational amplifier to obtain the pulse width modulation waveform, and finally driving switch Q1 through the driving circuit.

[0046] For the buck circuit 102 with negative voltage output, the negative voltage generation part includes zener diode D3 and capacitor C2. After zener diode D3 and capacitor C2 are connected in parallel, they are connected in reverse series with freewheeling diode D2. When diode D2 conducts, it enables zener diode D3 to have sufficient current for voltage stabilization, and capacitor C2 stores energy so that the push-pull driving circuit has sufficient negative voltage to turn off power switch M1.

[0047] The push-pull driving circuit is formed by connecting the upper NPN transistor Q6 and the lower PNP transistor Q8. The collector of transistor Q6 is connected to the positive voltage output by the buck circuit 102 with negative voltage output, and the emitter of transistor Q8 is connected to the negative voltage of the buck circuit 102 with negative voltage output. When the driving signal is high level, Q6 conducts, and the push-pull circuit outputs a positive voltage, enabling power switch M1 to conduct effectively. When the driving signal is low level, Q8 conducts, and the push-pull circuit outputs a negative voltage, enabling power switch M1 to turn off reliably.

[0048] The drive current limiting protection circuit 104 includes current limiting resistors R7 and R16, a pull-down resistor R11, clamping zener diodes D5 and D7. The current limiting resistors R7 and R16 prevent excessive drive current from generating oscillations. R7 is responsible for current limiting when the power switch M1 is turned on, and the resistor R16 is responsible for limiting the gate current when the power switch M1 is turned off. The pull-down resistor R11 makes the power switch default to the off state when there is no drive signal. The clamping zener diodes D5 and D7 prevent overvoltage of the positive and negative voltages of the gate of the power switch from damaging the switch.

[0049] Figure 1 In which, both V1 and V2 represent square wave signal generators, and Vref represents a reference voltage.

[0050] The above is Figure 1 the device description of the upper half part, Figure 1 The lower half part also includes an RCD energy-fed self-powered power switch drive circuit, the principle of which is the same as that of Figure 1 the upper half part. The RCD absorption circuit includes diode D9, capacitor C5 and resistor R4. The buck circuit with negative voltage output includes switch Q2, diode D10, zener diode D11, inductor L2, capacitors C6, C7, resistor R5, resistor R6, capacitor C8, the third operational amplifier and the fourth operational amplifier. The push-pull drive circuit includes a square wave signal, transistors Q7 and Q8. The drive current limiting protection circuit includes current limiting resistors R8 and R17, a pull-down resistor R9, clamping zener diodes D6 and D8.

[0051] As Figure 2 shown, each path of the switch tube requires a dedicated power supply line, which requires multiple power supply lines, and the negative voltage is unstable and will change with the pulse width, as Figure 3 shown, the bootstrap power supply method is adopted; the number of auxiliary power supply paths is reduced, but the positive and negative supply voltages of the upper transistor drive will change with the pulse width and are not stable enough.

[0052] An RCD energy-fed self-powered power switch drive circuit of the present invention is an energy-fed power supply line, which effectively solves the complexity of the traditional dedicated power supply circuit and the problem of unstable bootstrap supply voltage. It adopts negative voltage turn-off to ensure the reliability of the power tube turn-off; and effectively avoids the problem of energy consumption and heat generation of the RCD circuit, further improving the system efficiency.

[0053] In this specification, the various embodiments are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other.

[0054] In this text, specific examples are used to illustrate the principles and implementation modes of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation modes and application scopes. In summary, the content of this specification should not be construed as a limitation on the present invention.

Claims

1. An RCD energy-fed self-powered power switch tube drive circuit, characterized in that, It includes a power switch tube, an RCD snubber circuit, a buck circuit with negative voltage output, and a power switch tube drive circuit; The RCD snubber circuit is connected in parallel across the two ends of the power switch tube. The input of the buck circuit with negative voltage output is connected in parallel across the two ends of the capacitor of the RCD snubber circuit. The output of the buck circuit with negative voltage output is connected to the input of the power switch tube drive circuit, and the output of the power switch tube drive circuit is connected to the gate of the power switch tube; The RCD snubber circuit is used to absorb the overshoot voltage of the power switch tube and store energy through the capacitor in the RCD snubber circuit. The buck circuit with negative voltage output is used to convert the energy stored in the RCD snubber circuit into positive and negative voltages for driving the power switch tube. The power switch tube drive circuit is used for driving the power switch tube.

2. The RCD energy-fed self-powered power switch tube drive circuit according to claim 1, characterized in that, The RCD snubber circuit includes a resistor R1, a capacitor C1, and a diode D1. The positive electrode of the diode D1 is connected to the first pole of the power switch tube. The negative electrode of the diode D1 is respectively connected to the first end of the capacitor C1 and the first end of the resistor R1. The second end of the capacitor C1, the second end of the resistor R1, and the second pole of the power switch tube are all grounded.

3. The RCD energy-fed self-powered power switch tube drive circuit according to claim 2, characterized in that, The buck circuit with negative voltage output includes a switching tube Q1, a diode D2, a zener diode D3, an inductor L1, capacitors C2, C3, a resistor R2, a resistor R3, a capacitor C14, a first operational amplifier, and a second operational amplifier; The first pole of the switching tube Q1 is connected to the first end of the resistor R1. The second pole of the switching tube Q1 is respectively connected to the negative electrode of the diode D2 and the first end of the inductor L1. The gate of the switching tube Q1 is connected to the output terminal of the second operational amplifier. The positive electrode of the diode D2 is respectively connected to the positive electrode of the zener diode D3 and the first end of the capacitor C2. The second end of the inductor L1 is respectively connected to the first end of the capacitor C3, the first end of the resistor R2, and the first end of the capacitor C14. The second end of the resistor R2 is respectively connected to the first end of the resistor R3 and the first input terminal of the first operational amplifier. A reference voltage is input to the second input terminal of the first operational amplifier. The output terminal of the first operational amplifier is connected to the first input terminal of the second operational amplifier. A preset sawtooth wave is input to the second input terminal of the second operational amplifier. The negative electrode of the zener diode D3, the second end of the capacitor C2, the second end of the capacitor C3, and the second end of the resistor R3 are all grounded.

4. The RCD energy-fed self-powered power switch tube drive circuit according to claim 3, characterized in that, The power switch tube drive circuit is a push - pull drive circuit.

5. The RCD energy-fed self-powered power switch tube driving circuit according to claim 4, characterized in that, The push-pull drive circuit includes a square wave signal, a transistor Q6, and a transistor Q8; the transistor Q6 is an NPN transistor, and the transistor Q8 is a PNP transistor; the square wave signal is connected to the common base of the transistor Q6 and the transistor Q8, the collector of the transistor Q6 is connected to the first end of the capacitor C14, the collector of the transistor Q8 is connected to the first end of the capacitor C2, and the emitters of the transistor Q6 and the transistor Q8 are both connected to the gate of the power switch transistor.

6. The RCD energy-fed self-powered power switch tube drive circuit according to claim 5, characterized in that, It further includes a drive current limiting and protection circuit, and the drive current limiting and protection circuit includes a resistor R7, a resistor R16, a resistor R11, a zener diode D5, and a zener diode D7; the first end of the resistor R7 is connected to the emitter of the transistor Q6, the first end of the resistor R16 is connected to the emitter of the transistor Q8, the second ends of the resistor R7 and the resistor R16 are both connected to the gate of the power switch transistor; the first end of the resistor R11 and the negative electrode of the zener diode D5 are both connected to the gate of the power switch transistor, the positive electrode of the zener diode D5 is connected to the positive electrode of the zener diode D7, and the second end of the resistor R11 and the negative electrode of the zener diode D7 are both grounded.

7. The RCD energy-fed self-powered power switch tube drive circuit according to claim 1, wherein The power switch transistor is an IGBT.

8. The RCD energy-fed self-powered power switch tube drive circuit according to claim 1, characterized in that The power switch transistor is a MOSFET.

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