Resonant driving circuit with adjustable switching speed and control method

Abstract

The invention relates to a resonant driving circuit with adjustable switching speed and a control method, a half-bridge circuit structure is designed, the gate-source voltage of a driven power device is clamped through a half-bridge MOS tube, and reliable connection and disconnection of the power tube are ensured; the loss of a diode in a resonant circuit is avoided through the simultaneous switching on and switching off of the resonant bridge arm MOS tubes, the switching loss of the MOS tubes is reduced through a soft switching technology, and the overall system efficiency is improved; the MOS tube is turned off in advance before resonance is finished, and natural follow current is realized through a body diode of the MOS tube, so that over-resonance is avoided; two resonances are adopted to control a resonant charging loop and a resonant discharging loop respectively, and different switching-on and switching-off speeds are adjusted. According to the technical scheme, the system loss is effectively reduced, the stability under frequency mismatch is realized, the switching speed is adjustable, and the anti-interference capability is enhanced.

Description

Technical Field

[0001] The present invention relates to the field of power electronics technology, and particularly to a resonant drive circuit with adjustable switching speed and a control method therefor. Background Art

[0002] With the increase in switching frequency, the power density is enhanced, but this is also accompanied by an increase in power loss. Especially in low-voltage circuits such as point-of-load circuits, the gate drive loss occupies a relatively large proportion. Without control, a further increase in frequency will cause a rapid increase in power loss, thus significantly reducing the overall efficiency of the system. In high-switching-frequency application scenarios, how to effectively reduce the power loss of gate drive has become a key issue in improving system efficiency.

[0003] Traditional gate drivers provide energy through a driving resistor, and nearly half of the energy is lost in the driving resistor. To solve this problem, a resonant drive circuit provides energy for the gate capacitance of the MOSFET through a resonant inductor, thus effectively reducing the drive loss. However, the resonant drive technology still faces the following problems compared with traditional drive schemes:

[0004] 1. The resonant drive circuit is vulnerable to external interference. When there is high-frequency external interference, the interference directly flows through the gate capacitance of the MOSFET, and this interference current causes a voltage change in the drive capacitance, which may lead to mis-switching of the system.

[0005] 2. The resonant drive circuit may have a situation where the resonant frequency does not match the control frequency. When the control frequency does not exactly match the resonant frequency, the system may have problems such as overvoltage, increased loss, and over-resonance, seriously affecting the system reliability.

[0006] 3. The turn-on and turn-off speeds of the resonant drive circuit are usually the same, and it is impossible to independently adjust the switching speed according to specific application requirements. Due to the lack of flexibility, the turn-on and turn-off speeds cannot be optimized under different working conditions, which may lead to reduced efficiency or excessive loss. Summary of the Invention

[0007] In view of the problems existing in the above-mentioned resonant drive circuit, a resonant drive circuit with adjustable switching speed and a control method therefor are proposed, which can effectively reduce system loss, achieve stability under frequency mismatch, have adjustable switching speed, and enhance the anti-interference ability.

[0008] The technical solution of the present invention is: a resonant drive circuit with adjustable switching speed, including a resonant drive circuit and a drive controller, for driving a power device Q 1 ;

[0009] The resonant drive circuit includes a DC voltage source V cc , six MOS transistors S1 , S 2 , S 3 , S 4 , S 5 , S 6 , two resonant inductors L 1 , L 2 , two energy storage capacitors C 1 , C 2 ;

[0010] The MOS transistor S 1 and the MOS transistor S 2 are connected in series in the same direction between V cc and GND to form a clamping half-bridge, and the series connection point is denoted as M; the drain of the MOS transistor S 1 is connected to the DC voltage source V cc , and the source of the MOS transistor S 2 is grounded to GND; the energy storage capacitors C 1 , C 2 are connected in series between V cc and GND, and the series connection point is denoted as point N; one end of the energy storage capacitor C 1 is connected to the DC voltage V cc , and one end of the energy storage capacitor C 2 is grounded to GND;

[0011] The resonant inductor L 1 , the MOS transistor S 3 and the MOS transistor S 4 are connected in series to form a resonant charging bridge arm, which is connected between point N and point M, where the MOS transistor S 3 and the MOS transistor S 4 are connected in series in the reverse direction; the source of the MOS transistor S 3 is connected to the resonant inductor L 1 , and the drain of the MOS transistor S 4 is connected to point M. The other end of the resonant inductor L 1 far from the MOS transistor S 3 is connected to point N;

[0012] The resonant inductor L 2 , the MOS transistor S 5 and the MOS transistor S 6 are connected in series to form a resonant discharging bridge arm, which is connected between point N and point M, where the MOS transistor S 5 and the MOS transistor S 6 are connected in series in the reverse direction; the source of the MOS transistor S 5 is connected to the resonant inductor L 2 , and the drain of the MOS transistor S 6 is connected to point M. The other end of the resonant inductor L 2 far from the MOS transistor S 5 is connected to point N;

[0013] The driving controller includes a half-bridge driver and two dual low-side drivers. The half-bridge driver outputs to drive MOS transistor S 1 and MOS transistor S 2 ; the two dual low-side drivers output to drive MOS transistors S 3 、S 4 、S 5 、S 6 ;

[0014] An equivalent input capacitor C 1 is connected between the gate and the source of the power device Q iss . The source of the power device Q 1 is connected to GND. The M point of the resonant driving circuit is connected to the gate of the power device Q 1 . The resonant driving circuit realizes the on and off control of the power device Q 1 by charging and discharging the C iss of the power device Q 1 .

[0015] Preferably, the energy storage capacitors C 1 、C 2 have the same capacitance value, and the potential of the connection point N is half of V cc .

[0016] Preferably, the resonant inductor L 1 , MOS transistor S 3 and MOS transistor S 4 are connected in series to form a resonant charging loop. The resonant charging time t c is half of the resonant period and can be calculated by formula (1). By adjusting the inductance value of the resonant inductor L 1 , the turn-on speed of the power device Q 1 can be changed.

[0017]

[0018] Preferably, the resonant inductor L 2 , MOS transistor S 5 and MOS transistor S 6 are connected to form a resonant discharge leg. The resonant discharge time t dc is half of the resonant period and can be calculated by formula (2). By adjusting the inductance value of the resonant inductor L 2 , the turn-off speed of the power device Q 1 can be changed.

[0019]

[0020] Preferably, the six-channel input PWM drive control signals of the drive controller are generated by a CPLD, and the six-channel PWM drive control signals are respectively sent to a half-bridge driver and two dual-channel low-side drivers.

[0021] A control method for a resonant drive circuit with adjustable switching speed controls the resonant drive circuit with adjustable switching speed as follows:

[0022] At t 0 -t 1 : Before t 0 , only the MOS transistor S 2 is conducting, and the voltage of the parasitic capacitor C iss is clamped at 0 V through S 2 ; At the moment of t 0 , the MOS transistors S 3 and S 4 are turned on, and the capacitors C 1 , C 2 act as energy storage voltage sources to perform resonant charging on the inductor L 1 ; The current path is C 1 , C 2 -L 1 -S 3 -S 4 -C iss ;

[0023] At t 1 -t 2 : At t 1 , the MOS transistor S 3 is turned off earlier than S 4 , enabling the current to flow through the body diode of S 3 for natural freewheeling; When the current decreases to zero, that is, at t 2 , due to the unidirectional conduction characteristic of the diode, the resonant charging stage ends;

[0024] At t 2 -t 3 : At t 2 , the MOS transistors S 3 and S 4 are in the off state, and the MOS transistor S 1 is turned on; The gate of the power device Q 1 is connected to the DC voltage source V cc , so that the gate-source voltage of the power device Q 1 is clamped at V cc ; At t 2 , the current of the inductor L 1 decreases to zero, and the voltage of C iss rises to V cc , so the MOS transistor S 3and S 4 Turn off in zero - current mode, MOS transistor S 1 Turn on in zero - voltage mode;

[0025] At t 3 -t 4 : At t 3 turn off MOS transistor S 1 and turn on MOS transistors S 5 and S 6 ; C iss starts to discharge, and its current path is C iss -S 6 -S 5 -L 2 -C 1 、C 2 ; The energy stored in C iss is fed back to the energy - storage capacitors C 1 、C 2 ; At t 4 -t 5 : At t 4 compare with S 5 turn off MOS transistor S 6 earlier, so that the current passes through the body diode of S 6 for natural free - wheeling; when the current of inductor L 2 decreases to zero, that is, at t 5 due to the unidirectional conduction characteristic of the diode, the resonant charging stage ends;

[0026] At t 5 -t 6 : At t 5 , similar to that at t 2 -t 3 ; MOS transistors S 5 and S 6 turn off in zero - current mode, switch S 2 turns on in zero - voltage mode, and the gate - source voltage of power device Q 1 is clamped at 0V.

[0027] The beneficial effects of the present invention are as follows: The resonant drive circuit and control method with adjustable switching speed of the present invention design a half - bridge circuit structure. By clamping the gate - source voltage of the driven power device through the MOS transistors of the half - bridge, the reliable conduction and disconnection of the power transistor are ensured; by simultaneously turning on and off the MOS transistors of the resonant leg, the diode loss in the resonant circuit is avoided. The MOS transistor uses soft - switching technology to reduce the switching loss of the MOS transistor, and overall improves the system efficiency; by turning off the MOS transistor in advance before the end of resonance and using the natural free - wheeling of the body diode of the MOS transistor, the over - resonance is avoided; two resonances are used to separately control the resonant charging and discharging circuits to adjust different turn - on and turn - off speeds. Description of the Drawings

[0028] Figure 1 Circuit diagram of the resonant drive circuit with adjustable switching speed of the present invention;

[0029] Figure 2 Control timing waveform diagram of the resonant drive circuit with adjustable switching speed of the present invention;

[0030] Figure 3 Simulation result diagram of the resonant drive circuit with adjustable switching speed of the present invention;

[0031] Figure 4 Block diagram of the MOS transistor drive structure in the circuit of the present invention. Detailed Implementation Manner

[0032] The present invention will be described in detail below with reference to the drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0033] The present invention provides a resonant drive circuit with adjustable switching speed, as shown in the circuit diagram Figure 1 including: a resonant drive circuit and a drive controller for driving the power device Q 1 .

[0034] The resonant drive circuit includes a DC voltage source V cc , six MOS transistors S 1 , S 2 , S 3 , S 4 , S 5 , S 6 , two resonant inductors L 1 , L 2 , and two energy storage capacitors C 1 , C 2 .

[0035] The MOS transistor S 1 and the MOS transistor S 2 are connected in series in the same direction between V cc and GND to form a clamping half-bridge, and the series connection point is denoted as M. The drain of the MOS transistor S 1 is connected to the DC voltage source V cc , and the source of the MOS transistor S 2 is grounded to GND.

[0036] The energy storage capacitors C 1 , C 2 are connected in series between V cc and GND, and the series connection point is denoted as point N. The energy storage capacitor C 1One end is connected to a DC voltage V cc , and the energy storage capacitor C 2 has one end grounded to GND.

[0037] The resonant inductor L 1 , the MOS transistor S 3 and the MOS transistor S 4 are connected in series to form a resonant charging bridge arm, which is connected between point N and point M. Among them, the MOS transistor S 3 and the MOS transistor S 4 are connected in reverse series. The source electrode of the MOS transistor S 3 is connected to the resonant inductor L 1 , and the drain electrode of the MOS transistor S 4 is connected to point M. The other end of the resonant inductor L 1 far from the MOS transistor S 3 is connected to point N.

[0038] The resonant inductor L 2 , the MOS transistor S 5 and the MOS transistor S 6 are connected in series to form a resonant discharging bridge arm, which is connected between point N and point M. Among them, the MOS transistor S 5 and the MOS transistor S 6 are connected in reverse series. The source electrode of the MOS transistor S 5 is connected to the resonant inductor L 2 , and the drain electrode of the MOS transistor S 6 is connected to point M. The other end of the resonant inductor L 2 far from the MOS transistor S 5 is connected to point N.

[0039] The drive controller includes a half-bridge driver and two dual-channel low-side drivers. The input end of the driver is connected to six-channel PWM drive control signals and a DC voltage source V cc . The half-bridge driver outputs to drive the MOS transistor S 1 and the MOS transistor S 2 . The two dual-channel low-side drivers output to drive the MOS transistors S 3 , S 4 , S 5 , S 6 . The six-channel PWM drive control signals can be implemented by a CPLD.

[0040] An equivalent input capacitor C 1 is connected between the gate and the source of the power device Q iss . The source of the power device Q 1 is connected to GND. Point M of the resonant drive circuit is connected to the gate of the power device Q 1 . The resonant drive circuit charges the equivalent input capacitor C 1 of the power device Q issPerform charge and discharge operations to achieve the on and off control of the power device.

[0041] Turn on S 1 Turn off S 2 When, the power device Q 1 The gate-source potential is clamped to V cc Turn on S 2 Turn off S 1 When, the power device Q 1 The gate-source potential is clamped to 0V.

[0042] The energy storage capacitors C 1 , C 2 Have the same capacitance value, and the potential of the connection point N is half of V cc .

[0043] The resonant inductor L 1 , the MOS transistor S 3 And the MOS transistor S 4 Are connected in series to form a resonant charging circuit. The resonant charging time t c Is half of the resonant period and can be calculated by formula (1). With the power device Q 1 Determined, adjust the inductance value of the resonant inductor L 1 To change the turn-on speed of the power device Q 1 .

[0044]

[0045] The resonant inductor L 2 , the MOS transistor S 5 And the MOS transistor S 6 Are connected to form a resonant discharge bridge arm. The resonant discharge time t dc Is half of the resonant period and can be calculated by formula (2). With the power device Q 1 Determined, adjust the inductance value of the resonant inductor L 2 To change the turn-off speed of the power device Q 1 .

[0046]

[0047] The working process of the resonant drive circuit provided by the present invention will be further described below.

[0048] Figure 2 This is a schematic diagram of the control timing waveform provided for the implementation of a resonant drive circuit with adjustable switching speed according to the present invention. From top to bottom, they are: the output voltage waveform at the gate-source terminal of the MOS transistor S 1 , the output voltage waveform at the gate-source terminal of the MOS transistor S 2 , the output voltage waveform at the gate-source terminal of the MOS transistor S 3The output voltage waveform of the gate-source terminal of MOS transistor S 4 The output voltage waveform of the gate-source terminal of MOS transistor S 5 The output voltage waveform of the gate-source terminal of MOS transistor S 6 The output voltage waveform of the gate-source terminal. The horizontal axis of each waveform diagram is time t, which are t 0 、t 1 、t 2 、t 3 、t 4 、t 5 、t 6 in sequence. The vertical axis is voltage. The following will be further described in conjunction with Figure 2 .

[0049] At t 0 -t 1 : Before t 0 , only MOS transistor S 2 is conducting, and the voltage of parasitic capacitor C iss is clamped at 0V through S 2 . At the moment of t 0 , MOS transistors S 3 and S 4 are turned on. Capacitors C 1 and C 2 act as energy storage voltage sources to perform resonant charging on inductor L 1 . The current path is currently C 1 , C 2 -L 1 -S 3 -S 4 -C iss .

[0050] At t 1 -t 2 : At t 1 , MOS transistor S 3 turns off earlier than S 4 , causing the current to flow through the body diode of S 3 for natural freewheeling. When the current decreases to zero, that is, at t 2 , due to the unidirectional conduction characteristic of the diode, the resonant charging stage ends.

[0051] At t 2 -t 3 : At t 2 , MOS transistors S 3 and S 4 are in the off state, and MOS transistor S 1 is turned on. The gate of power device Q 1 is connected to DC voltage source V cc , making power device Q1 The gate-source voltage of is clamped at V cc . At t 2 , the current of inductor L 1 decreases to zero, and the voltage of C iss rises to V cc . Therefore, MOS transistors S 3 and S 4 turn off in zero-current mode, and MOS transistor S 1 turns on in zero-voltage mode.

[0052] At t 3 -t 4 : At t 3 , MOS transistor S 1 is turned off, and MOS transistors S 5 and S 6 are turned on. C iss starts to discharge, and its current path is C iss -S 6 -S 5 -L 2 -C 1 , C 2 . The energy stored in C iss is fed back to energy storage capacitors C 1 , C 2 .

[0053] At t 4 -t 5 : At t 4 , compared with S 5 , MOS transistor S 6 is turned off in advance, so that the current naturally freewheels through the body diode of S 6 . When the current of inductor L 2 decreases to zero, that is, at t 5 , due to the unidirectional conduction characteristic of the diode, the resonant charging stage ends.

[0054] At t 5 -t 6 : At t 5 , similar to that at t 2 -t 3 . MOS transistors S 5 and S 6 turn off in zero-current mode, and switch S 2 turns on in zero-voltage mode. The gate-source voltage of power device Q 1 is clamped at 0V.

[0055] To further illustrate the principle and characteristics of the resonant drive circuit, the component parameters in the simulation circuit are set. In Figure 3Shows the output results obtained from the simulation circuit, and the following waveforms are obtained: From top to bottom are the current waveforms of the resonant inductors L 1 and L 2 , the Cvoltage waveforms of the power device Q 1 iss .

[0056] In the simulation, the inductance value of inductor L 1 is four times the inductance value of L 2 . It can be seen from Equations (1) and (2) that the resonant charging speed is half of the resonant discharging speed. Figure 3 The simulation results also prove the consistency with the theory.

[0057] Figure 4 Shows the driving method of the MOS transistors in the circuit. The six input PWM driving control signals are generated by the CPLD, and the driving chip outputs the gate driving signals corresponding to the MOS transistors. The sources of MOS transistors S 1 and S 2 are driven by a half-bridge driving chip. The power supply of the driving chip is provided by the DC voltage source V cc .

[0058] The sources of MOS transistors S 3 and S 4 and S 5 and S 6 are floating in potential. In the case of the circuit design of Figure 1 , the low-side driving chip powered by V cc provides a driving voltage of V cc to the gates of the MOS transistors, and can normally drive MOS transistors S 3 and S 4 and S 5 and S 6 .

[0059] It should be noted that Figure 2 the shown control timing waveforms and Figure 3 the shown inductor current and the C iss voltage waveforms are only used to help understand the working principle of the present invention and do not represent the actual working waveforms. At the same time, during the on or off control stage, the number of switching times of the working modes is not as shown in Figure 3 , and depends on the specific working circuit parameters.

[0060] The above-described embodiments only represent the specific implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A resonant drive circuit with adjustable switching speed, characterized in that: It includes a resonant drive circuit and a drive controller for driving a power device Q1; The resonant driving circuit includes a DC voltage source V cc , six MOS tubes S1, S2, S3, S4, S5, S6, two resonant inductors L1, L2, two energy storage capacitors C1, C2; The MOS tube S1 and the MOS tube S2 are connected in series in the same direction. cc and GND to form a clamping half-bridge, with the series connection point marked as M; the drain of MOS tube S1 is connected to the DC voltage source V cc , the source of MOS tube S2 is grounded GND; the energy storage capacitors C1 and C2 are connected in series at V cc The series connection point between and GND is marked as point N; one end of the energy storage capacitor C1 is connected to a DC voltage V cc , one end of the energy storage capacitor C2 is grounded GND; The resonant inductor L1, MOS transistor S3 and MOS transistor S4 are connected in series to form a resonant charging bridge arm, which is connected between point N and point M, wherein MOS transistor S3 and MOS transistor S4 are connected in reverse series; the source of MOS transistor S3 is connected to the resonant inductor L1, and the drain of MOS transistor S4 is connected to point M. The resonant inductor L1 is far away from the other end point N of MOS transistor S3; The resonant inductor L2, MOS transistor S5 and MOS transistor S6 are connected in series to form a resonant discharge bridge arm, which is connected between point N and point M, wherein MOS transistor S5 and MOS transistor S6 are connected in reverse series; the source of MOS transistor S5 is connected to the resonant inductor L2, and the drain of MOS transistor S6 is connected to point M. The resonant inductor L2 is far away from the other end of MOS transistor S5, which is connected to point N; The drive controller includes a half-bridge driver and two dual-channel low-side drivers, the half-bridge driver output drives MOS tubes S1 and MOS tube S2; the two dual-channel low-side drivers output drives MOS tubes S3, S4, S5, S6; The gate and source of the power device Q1 are connected with an equivalent input capacitor C iss The source of the power device Q1 is connected to GND, and the M point of the resonant drive circuit is connected to the gate of the power device Q1. The resonant drive circuit is connected to the C of the power device Q1. iss Perform charging and discharging operations to realize the on and off control of the power device Q1.

2. The resonant drive circuit with adjustable switching speed according to claim 1, characterized in that: The energy storage capacitors C1 and C2 have the same capacitance value, and the potential of the connection point N is V cc half.

3. The resonant drive circuit with adjustable switching speed according to claim 1, characterized in that: The resonant inductor L1, MOS tube S3 and MOS tube S4 are connected in series to form a resonant charging circuit. The resonant charging time t c is half of the resonant period. By using formula (1), we can calculate that by adjusting the inductance of the resonant inductor L1, we can change the turn-on speed of the power device Q1.

4. The resonant drive circuit with adjustable switching speed according to claim 1, characterized in that: The resonant inductor L2, MOS tube S5 and MOS tube S6 are connected to form a resonant discharge bridge arm. The resonant discharge time t dc is half of the resonant period. By using formula (2), we can calculate that by adjusting the inductance of the resonant inductor L2, we can change the turn-off speed of the power device Q1.

5. The resonant drive circuit with adjustable switching speed according to any one of claims 1 to 4, characterized in that: The six-channel input PWM drive control signals of the drive controller are generated by CPLD, and the six-channel PWM drive control signals are respectively sent to the half-bridge driver and two dual-channel low-side drivers.

6. A method for controlling a resonant drive circuit with adjustable switching speed, characterized in that: The resonant drive circuit with adjustable switching speed as claimed in claim 5 is controlled as follows: At t0-t1: Before t0, only MOS tube S2 is turned on, and the parasitic capacitor C iss The voltage of is clamped at 0V by S2; at time t0, MOS tubes S3 and S4 are turned on, and capacitors C1 and C2 act as energy storage voltage sources to resonantly charge inductors L1 and L2; the current path is C1, C2-L1-S3-S4-C iss ; At t1-t2: At t1, MOS tube S3 is turned off earlier than S4, so that the current flows naturally through the body diode of S3; when the current decreases to zero, that is, at t2, due to the unidirectional conduction characteristics of the diode, the resonant charging stage ends; At t2-t3: At t2, MOS tubes S3 and S4 are in the off state, and MOS tube S1 is turned on; the gate of power device Q1 is connected to the DC voltage source V cc The gate-source voltage of the power device Q1 is clamped at V cc ; At t2, the current of inductor L1 decreases to zero, C iss The voltage rises to V cc , so MOS tubes S3 and S4 are turned off in zero current mode, and MOS tube S1 is turned on in zero voltage mode; At t3-t4: At t3, MOS tube S1 is turned off, and MOS tubes S5 and S6 are turned on; C iss Start discharging, and the current path is C iss -S6-S5-L2-C1, C2; stored in C iss The energy in the capacitor is fed back to the energy storage capacitors C1 and C2; at t4-t5: at t4, the MOS tube S6 is turned off earlier than S5, so that the current flows naturally through the body diode of S6; when the current of the inductor L2 decreases to zero, that is, at t5, due to the unidirectional conduction characteristics of the diode, the resonant charging stage ends; At t5-t6: At t5, similar to t2-t3, MOS tubes S5 and S6 are disconnected in the zero current mode, switch S2 is turned on in the zero voltage mode, and the gate-source voltage of the power device Q1 is clamped at 0V.

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