Voltage-current source hybrid drive circuit based on coupled inductor

Abstract

The present invention relates to the technical field of drive circuits, and in particular to a voltage-current source hybrid drive circuit based on coupled inductors, comprising: a switch tube S1 and a switch tube S2 are turned on and a switch tube Q is used to drive the drive circuit. p In order to store energy by coupling inductance, before the switch tubes S1 and S2 are turned off, the input capacitors of the switch tubes S1 and S2 are discharged by coupling inductance constant current, and then the switch tubes S1 and S2 are turned off; by setting the opening delay time of the constant current discharge circuit of the series switch tubes S1 and S2, the voltage balance of the series switch tubes S1 and S2 is improved; by setting the time of energy storage by the primary side coupling inductance, the drain-source voltage change rate and the drain current change rate at the moment of turning off the switch tubes S1 and S2 are controlled. The present invention solves the problems that the existing drive circuit of SiC MOSFET cannot solve the series voltage balancing, large loss, limited switching speed, and cannot be closed-loop controlled at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of drive circuits, and in particular to a voltage-current source hybrid drive circuit based on coupled inductors. Background Art

[0002] SiC-based power electronic devices are widely used in distributed energy, medium-voltage DC power grids and other occasions. Currently, the voltage level of commercial SiC MOSFET is limited to 1.7kV. In order to adapt to higher voltage levels, two or more SiC MOSFET switches are required to work in series to increase voltage stress.

[0003] However, the uneven signal delay of the driving circuit, the inconsistency of the device parameters, and the mismatch of parasitic parameters caused by the circuit layout will affect the transient voltage during the switching process of the series switch tube and the steady-state voltage distribution when it is turned on. If no control is applied, the uneven voltage distribution will pose a great threat to the voltage stress and even reliability of the switch tube. In order to fully utilize the advantages brought by the increase in switching frequency and switching speed of SiC MOSFET, the transient and steady-state voltages of the series switch tube need to be adjusted and controlled to improve the voltage balance.

[0004] At present, the methods for controlling the voltage balancing of SiC MOSFET series in the literature mainly include passive buffer circuit, voltage clamp circuit, active drive circuit, single drive circuit, etc. Among them, the passive buffer circuit has a simple structure, but still has large losses; the voltage clamp circuit limits the overvoltage of the series switch tube within a preset safety range, but it is still necessary to use a passive buffer circuit to improve the balance of transient voltage distribution; the single drive circuit only needs one set of drive circuits to drive all parallel switches, thus limiting the further improvement of the switching speed, and it is still necessary to combine a passive buffer circuit to balance the voltage distribution; the active drive circuit generally achieves the purpose of series voltage balancing by compensating the delay of the drive signal, combining digital controllers such as DSP, and high-precision sampling methods for closed-loop control. Summary of the invention

[0005] In view of the deficiencies of the existing circuits, the present invention solves the problems that the existing SiC MOSFET driving circuit cannot simultaneously solve the series voltage balancing, large loss, limited switching speed, and inability to close-loop control.

[0006] The technical solution adopted by the present invention is: a voltage-current source hybrid driving circuit based on coupled inductance includes:

[0007] A primary-side coupled inductor circuit, a first secondary-side coupled inductor constant-current discharge circuit, a first positive-voltage drive circuit, a first negative-voltage drive circuit, a first drive circuit, a second secondary-side coupled inductor constant-current discharge circuit, a second positive-voltage drive circuit, a second negative-voltage drive circuit, and a second drive circuit, wherein;

[0008] When the switch tubes S1 and S2 are turned on, the switch tube Q p In order to store energy by coupling inductance, before the switch tubes S1 and S2 are turned off, the input capacitors of the switch tubes S1 and S2 are discharged by coupling inductance constant current, and then the switch tubes S1 and S2 are turned off; by setting the opening delay time of the constant current discharge circuit of the series switch tubes S1 and S2, the voltage balance of the series switch tubes S1 and S2 is improved; by setting the energy storage time of the primary side coupling inductance, the drain-source voltage change rate and the drain current change rate at the moment of turning off the switch tubes S1 and S2 are controlled.

[0009] As a preferred embodiment of the present invention, the primary coupling inductor circuit includes: a voltage source U s , primary inductance L p And the primary switch tube Q p , L p The lower end of Q p The drain connection, L p The upper end and Q p The source of U s Connect both ends of .

[0010] As a preferred embodiment of the present invention, the first secondary-side coupled inductor constant current discharge circuit comprises: a secondary-side coupled inductor L s1 , auxiliary switch tube Q s1 , diode D1, anti-saturation resistor R s1 , R s1 With L s1 The upper end of the parallel connection is connected to the negative pole of D1, and the positive pole of D1 is connected to Q s1 Source connection.

[0011] As a preferred embodiment of the present invention, the first positive voltage driving circuit includes: a switch tube Q 1+ , driving voltage source U + , driving resistance R gv1 , Q 1+ The source and R gv1 The left end of Q 1+ The drain terminal is connected to U + The positive electrode, U + The negative electrode and L s1 , R s1 The common lower end is connected.

[0012] As a preferred embodiment of the present invention, the first negative pressure driving circuit includes: a switch tube Q 1- , driving voltage source U - , driving resistance R gc1 , Q 1- The drain and Q s1 The drain, R gc1 The left end of Q1- The source terminal is connected to U - The positive pole of U- and the negative pole of L s1 , R s1 The common lower end is connected.

[0013] As a preferred embodiment of the present invention, the first driving circuit includes: a switch tube S1, the gate of S1 and R gc1 , R gv1 The right end of S1 is connected to the source of L s1 , R s1 The common lower end is connected.

[0014] As a preferred embodiment of the present invention, the second secondary-side coupled inductor constant current discharge circuit comprises: a secondary-side coupled inductor L s2 , auxiliary switch tube Q s2 , diode D2, anti-saturation resistor R s2 , R s2 With L s2 The upper end of the parallel connection is connected to the negative pole of D2, and the positive pole of D2 is connected to Q s2 Source connection.

[0015] As a preferred embodiment of the present invention, the second positive pressure driving circuit includes: a switch tube Q 2+ , driving voltage source U + , driving resistance R gv2 , Q 2+ The source and R gv2 The left end of Q 2+ The drain terminal is connected to U + The positive electrode, U + The negative electrode and L s2 , R s2 The common lower end is connected.

[0016] As a preferred embodiment of the present invention, the second negative pressure driving circuit includes: a switch tube Q 2- , driving voltage source U-, driving resistor R gc2 , Q 2- The drain and Q s2 The drain, R gc2 The left end of Q 2- The source terminal is connected to U - The positive electrode, U - The negative electrode and L s2 , R s2 The common lower end is connected.

[0017] As a preferred embodiment of the present invention, the second driving circuit includes: a switch tube S2, the gate of S2 and R gc2 , R gv2 The right end of S2 is connected to the source of Ls2 , R s2 The common lower end of S2 is connected, and the drain of S2 is connected to the source of S1.

[0018] Beneficial effects of the present invention:

[0019] 1. The present invention belongs to an active drive circuit, which is combined with DSP for digital control and can replace the driver part in the original DSP-based digital closed-loop control;

[0020] 2. The present invention provides a coupled inductor detection, voltage and current source hybrid SiC MOSFET series drive circuit, which can not only improve the balance between the steady-state voltage and transient voltage of the SiC MOSFET series, but also achieve low loss, no switching speed restriction, and improve the reliability of the series switch tube;

[0021] 3. Based on the constant current source SiC MOSFET discharge circuit of coupled inductor, energy is stored for the coupled inductor when the series switch is turned on. Before the switch is turned off, the input capacitor of the switch is discharged through the coupled inductor constant current, and then the switch is turned off. By setting the opening delay time of the constant current discharge circuit of the series switch, the voltage balance of the series switch can be improved. By setting the energy storage time of the primary side coupled inductor, the drain-source voltage change rate and drain current change rate at the moment the switch is turned off can be controlled. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a logic block diagram of a voltage-current source hybrid drive circuit based on coupled inductance of the present invention;

[0023] Figure 2 It is a voltage-current source hybrid driving circuit diagram based on coupled inductance of the present invention;

[0024] Figure 3 is the circuit timing waveform of the present invention;

[0025] Figure 4 (a), (b), and (c) are the switching mode diagrams of the positive voltage driving stage, constant current discharge stage, and negative voltage driving stage, respectively;

[0026] Figure 5 It is a schematic diagram of the waveform for adjusting the energy storage time of the primary inductance;

[0027] Figure 6 (a) and (b) are the voltage imbalance distribution and the introduction of Q when no regulation is performed. s1 , Q s2 Schematic diagram of voltage distribution during turn-on delay time. DETAILED DESCRIPTION

[0028] The present invention is further described below in conjunction with the accompanying drawings and embodiments. This figure is a simplified schematic diagram, which only illustrates the basic structure of the present invention in a schematic manner, and therefore it only shows the components related to the present invention.

[0029] like Figure 1 As shown, the voltage-current source hybrid driving circuit based on coupled inductance includes: a primary-side coupled inductance circuit, a first and a second secondary-side coupled inductance constant current discharge circuit (current source), a first and a second positive voltage drive circuit (voltage source), and a first and a second negative voltage drive circuit (voltage source); when the switch tubes S1 and S2 are turned on, the two positive voltage drive circuits provide the switch tubes S1 and S2 with a driving positive voltage, and the switch tubes S1 and S2 are turned on normally, and the primary-side coupled inductance circuit stores energy at the same time; before the switch tubes S1 and S2 are turned off, the constant current of the inductance discharge of the two secondary-side coupled inductance constant current discharge circuits provides a constant current discharge circuit for the switch tubes S1 and S2; the gate-source voltage of S1 and S2 drops to a negative voltage, and the two negative voltage drive circuits are turned on to maintain the switch tubes S1 and S2 in the off state.

[0030] like Figure 2 As shown, the primary coupled inductor circuit includes a voltage source U s , primary inductance L p , primary switch tube Q p ;

[0031] The first secondary-side coupled inductor constant current discharge circuit of the series switch tube S1 includes: a secondary-side coupled inductor L s1 , auxiliary switch tube Q s1 , diode D1, anti-saturation resistor R s1 The first positive voltage driving circuit includes a switch tube Q 1+ , driving voltage source U + , driving resistance R gv1 The first negative pressure driving circuit includes a switch tube Q 1- , driving voltage source U - , driving resistance R gc1 .

[0032] The second secondary coupling inductor constant current discharge circuit of the series switch tube S2 includes: a secondary coupling inductor L s2 , auxiliary switch tube Q s2 , diode D2, anti-saturation resistor R s2 The second positive voltage driving circuit includes a switch tube Q 2+ , driving voltage source U + , driving resistance R gv2 The second negative pressure driving circuit includes a switch tube Q 2- , driving voltage source U - , driving resistance R gc2 .

[0033] The first driving circuit includes: a switch tube S1; the second driving circuit includes: a switch tube S2.

[0034] L p The lower end and Q p The drain connection, L p The upper end and Q p The source of U s The two ends of R s1 With L s1 The upper end of the parallel connection is connected to the negative pole of D1, and the positive pole of D1 is connected to Q s1 The source connection of Q 1+ The source and R gv1 The left end of Q 1+ The drain terminal is connected to U + The positive electrode, U + The negative electrode and L s1 , R s1 The common lower end connection; Q 1- The drain and Q s1 The drain, R gc1 The left end of Q 1- The source terminal is connected to U - The positive electrode, U - The negative electrode and L s1 , R s1 The gate of S1 is connected to R gc1 , R gv1 The right end of S1 is connected to the source of L s1 , R s1 The common lower end is connected.

[0035] R s2 With L s2 The upper end of the parallel connection is connected to the negative pole of D2, and the positive pole of D2 is connected to Q s2 The source connection of Q 2+ The source and R gv2 The left end of Q 2+ The drain terminal is connected to U + The positive electrode, U + The negative electrode and L s2 , R s2 The common lower end connection; Q 2- The drain and Q s2 The drain, R gc2 The left end of Q 2- The source terminal is connected to U - The positive electrode, U - The negative electrode and L s2 , R s2 The gate of S2 is connected to R gc2 , R gv2 The right end of S2 is connected to the source of Ls2 , R s2 The common lower end of S2 is connected, and the drain of S2 is connected to the source of S1.

[0036] Among them, the switch tube Q p , Q s1 , Q s2 , Q 1+ , Q 1- , Q 2+ , Q 2- The model number is SI1480DH, the model numbers of S1 and S2 are CAB450M12XM3, R gv 5Ω, R gc is 0Ω, positive pressure U + is 5V, negative voltage U - is -5V, the primary inductor L p , secondary inductance L s1 and L s2 The inductance value is 500nH.

[0037] Working principle:

[0038] like Figure 3 As shown in the circuit timing waveform, before t0, Q 1+ , Q 2+ Keep it open, two U + The voltage passes through the driving circuit R gv1 Maintain a stable driving current for the series switches S1 and S2.

[0039] At time t0, Figure 4 As shown in (a), open Q p , voltage source U s is the primary inductance L p Charging, L p Energy storage, p rise;

[0040] Rise to maximum value I p for:

[0041]

[0042] At time t1, Figure 4 As shown in (b), turn off Q 1+ , Q 2+ , turn off Q p , open Q s1 , Q s2 , coupled inductor L s1 The constant current in Q s1 , D1, R gc1 To discharge the input capacitor of S1, the coupled inductor L s2 The constant current in Qs2 , D2, R gc2 The input capacitor of S2 is discharged, and the gate-source voltage v GS1 、v GS2 Discharge to near the driving negative pressure;

[0043] Constant current discharge current i s1 and i s2 for:

[0044]

[0045] The rate of change of drain-source voltage during discharge can be written as:

[0046]

[0047] Among them, C iss is the input capacitance of the switches S1 and S2, so by adjusting I p The value of can adjust the drain-source voltage change rate; Figure 5 As shown, the time from t0 to t1 is changed from Δt pre1 Increase to Δt pre2 , so that I p As the value increases, the drain-source voltage change rate increases, and the drain current change rate and the gate-source voltage change rate also increase; therefore, by setting the energy storage time of the primary-side coupled inductor through DSP, the drain-source voltage change rate and the drain current change rate at the moment the switch is turned off can be adjusted.

[0048] At time t2, if Figure 4 As shown in (c), turn off the switch tube Q s1 , Q s2 , open Q 1- , Q 2- , the negative pressure drive circuit remains open, maintaining a stable drive current for the shutdown of the series switches S1 and S2.

[0049] At t3, turn off the switch tube Q 1- , Q 2- , open Q 1+ , Q 2+ , the positive pressure drive circuit opens the switch tube normally again.

[0050] When the series switch tube appears Figure 6 When the voltage is unbalanced as shown in (a), the drain-source voltage v of the switch tube S1 is DS1 and the gate-source voltage v GS1 The voltage rises quickly, resulting in large steady-state voltage and transient voltage overshoots of S1. Therefore, at time t1, the auxiliary tube Q is not turned on at the same time. s1 and auxiliary tube Q s2 , but the auxiliary tube Q is first opened at time t1s2 , discharge the input capacitor of S2 in advance, t1+Δt d Always open auxiliary pipe Q s1 , in order to improve the voltage balance of the two series switches, the voltage balance adjustment principle is as follows Figure 6 As shown in (b); therefore, by setting the turn-on delay time of the constant current discharge circuit (current source circuit) of the series switch tube through DSP, the purpose of improving the voltage balance of the series switch tube can be achieved.

[0051] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A voltage-current source hybrid drive circuit based on coupled inductance, characterized in that: include: A primary-side coupled inductor circuit, a first secondary-side coupled inductor constant-current discharge circuit, a first positive-voltage drive circuit, a first negative-voltage drive circuit, a first drive circuit, a second secondary-side coupled inductor constant-current discharge circuit, a second positive-voltage drive circuit, a second negative-voltage drive circuit, and a second drive circuit, wherein; Switching tube S 1 and S 2. When the switch is turned on, Q p To store energy in coupled inductors, the switch tube S 1 and S 2 Before turning off, the switching tube is fed by the coupled inductor constant current. S 1 and S 2, the input capacitor is discharged, and then the switch is turned off. S 1 and S 2. By setting the series switch tube S 1 and S 2 constant current discharge circuit opening delay time, improve the series switch tube S 1 and S 2 voltage balance; by setting the primary coupling inductor energy storage time, control the switch tube S 1 and S 2. The rate of change of drain-source voltage and drain current at the moment of shutdown; The primary coupled inductor circuit includes: voltage source U s , primary inductance L p And the primary switch Q p , L p The lower end of Q p The drain connection, L p The upper end and Q p The source of U s Connect both ends of the The first secondary-side coupled inductor constant current discharge circuit includes: a secondary-side coupled inductor L s1 , Auxiliary switch tube Q s1 ,diode D 1. Anti-saturation resistor R s1 , R s1 and L s1 The upper end of the parallel D 1 negative connection, D 1's positive electrode and Q s1 Source connection.

2. The voltage-current source hybrid driving circuit based on coupled inductance according to claim 1, characterized in that: The first positive pressure driving circuit includes: a switch tube Q 1+ , driving voltage source U + and drive resistance R gv1 , Q 1+ The source and R gv1 The left end of the connection, Q 1+ The drain terminal U + The positive electrode, U + The negative electrode and L s1 , R s1 The common lower end is connected.

3. The voltage-current source hybrid driving circuit based on coupled inductance according to claim 2, characterized in that: The first negative pressure driving circuit includes: a switch tube Q 1- , driving voltage source U - and drive resistance R gc1 , Q 1- The drain and Q s1 The drain, R gc1 The left end of the connection, Q 1- The source terminal U - The positive electrode, U - The negative electrode and L s1 , R s1 The common lower end is connected.

4. The voltage-current source hybrid driving circuit based on coupled inductance according to claim 3, characterized in that: The first driving circuit includes: a switch tube S 1, S 1 gate and R gc1 , R gv1 The common right end is connected, S 1 source and L s1 , R s1 The common lower end is connected.

5. The voltage-current source hybrid driving circuit based on coupled inductance according to claim 4, characterized in that: The second secondary side coupled inductor constant current discharge circuit includes: a secondary side coupled inductor L s2 , Auxiliary switch tube Q s2 ,diode D 2 and anti-saturation resistor R s2 , R s2 and L s2 The upper end of the parallel D 2 negative connection, D 2's positive electrode and Q s2 Source connection.

6. The voltage-current source hybrid driving circuit based on coupled inductance according to claim 5, characterized in that: The second positive pressure driving circuit includes: a switch tube Q 2+ , driving voltage source U + and drive resistance R gv2 , Q 2+ The source and R gv2 The left end of the connection, Q 2+ The drain terminal U + The positive electrode, U + The negative electrode and L s2 , R s2 The common lower end is connected.

7. The voltage-current source hybrid driving circuit based on coupled inductance according to claim 6, characterized in that: The second negative pressure driving circuit includes: a switch tube Q 2- , driving voltage source U - and drive resistance R gc2 , Q 2- The drain and Q s2 The drain, R gc2 The left end of the connection, Q 2- The source terminal U - The positive electrode, U - The negative electrode and L s2 , R s2 The common lower end is connected.

8. The voltage-current source hybrid driving circuit based on coupled inductance according to claim 7, characterized in that: The second driving circuit includes: a switch tube S 2, S 2 gate and R gc2 , R gv2 The common right end is connected, S 2 source and L s2 , R s2 The common lower end connection, S 2 drain and S 1 source connection.

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