A VGaN driving circuit

Abstract

The present invention discloses a VGaN driving circuit, comprising a first switch module, a second switch module, a fourth switch module, a fifth switch module, a charge and discharge control signal input terminal, an input power supply, a current limiting resistor and a VGaN; wherein: the first drain of the VGaN is connected to the negative terminal of the battery, the first switch module and the second switch module, the second drain of the VGaN is connected to the negative terminal of the load and the fourth switch module, the input power supply is connected to the gate of the VGaN via the current limiting resistor, and the input power supply is connected to the first drain of the VGaN via a voltage divider; the first switch module is connected to the second switch module, and the fourth switch module is connected to the fifth switch module; the discharge control signal input terminal is used to input a discharge control signal to the first switch module, and the charge control signal input terminal is used to input a charge control signal to the fifth switch module.

Description

Technical Field

[0001] The invention relates to a VGaN driving circuit, belonging to the technical field of electronic circuits. Background Art

[0002] VGaN is the main gallium nitride product of Innoscience. It is an enhancement-mode gallium nitride power transistor with bidirectional blocking and bidirectional conduction functions, developed and produced based on the 30V~100V low-voltage gallium nitride technology platform.

[0003] VGaN is an enhancement transistor - a normally closed power switch, with extremely high switching frequency, zero reverse recovery charge, ultra-low on-resistance, support for bidirectional conduction and bidirectional blocking, small package size, small parasitic parameters, and strong SOA robustness. It can also replace two back-to-back MOSFETs with a bidirectional gallium nitride device. VGaN has great advantages in the high-side load switch circuit of BMS battery protection and in the switch circuit application in multi-power systems.

[0004] Please refer to Figure 1 , VGaN has a gate (G), drain 1 (D1) and drain 2 (D2), and its minimum turn-on voltage Vgdxth (x=1 or 2) is generally between 1V and 2.5V. When the gate voltage is higher than the turn-on threshold voltage of the drain voltage at either end (Vgdx>Vgdxth), VGaN is in a bidirectional conduction state; when the gate voltage is lower than the voltage of drain 1 and drain 2 at the same time, VGaN is in a bidirectional blocking state.

[0005] According to the above working principle, when VGaN is applied to the high-side cut-off protection of BMS, the charge and discharge protection can be realized by simply pulling the gate down to B-. Figure 2 , Figure 2 It is a simplified charging and discharging schematic diagram of the battery pack--VGaN--load side. When V1-Vbt2>Vgd2th, the battery pack BT2 discharges to the load RL, and can also charge the battery pack BT2; when V1=0, the outside world cannot charge or discharge the battery pack BT2. Among them, V1 is the voltage across the controlled source controlled by VGaN, and Vbt2 is the voltage of the battery pack BT2.

[0006] However, when VGaN is used in the low-side cut-off protection of BMS, the driving circuit is extremely complex, such as the driving circuit designed by Innoscience for VGaN chips. There is a need for improvement. Summary of the invention

[0007] The main purpose of the present invention is to propose a VGaN driving circuit, which realizes the low-side protection function of VGaN in BMS through extremely simple discrete components, thereby solving the problem of extremely complex driving circuit when VGaN is applied to low-side cut-off protection of BMS.

[0008] The present invention adopts the following technical solutions to solve the above problems:

[0009] A VGaN driving circuit is used to realize a BMS low-side protection function, comprising: a first switch module, a second switch module, a fourth switch module, a fifth switch module, a charging control signal input terminal, a discharging control signal input terminal, an input power supply, a current limiting resistor and a VGaN; wherein: a first drain of the VGaN is connected to a negative terminal of a battery, the first switch module and the second switch module, a second drain of the VGaN is connected to a negative terminal of a load and the fourth switch module, the input power supply is connected to a gate of the VGaN via the current limiting resistor, and the input power supply is connected to the first drain of the VGaN via a voltage divider; the first switch module is connected to the second switch module, and the fourth switch module is connected to the fifth switch module; the discharging control signal input terminal is used to input a discharging control signal to the first switch module, and the charging control signal input terminal is used to input a charging control signal to the fifth switch module.

[0010] Furthermore, the discharge control signal is sent to the control end of the first switch module through voltage division to control the on and off of the first switch module.

[0011] Furthermore, the first switch module includes a first switch tube, a first resistor and a second resistor, the first resistor is connected between the discharge control signal input end and the base of the first switch tube, the second resistor is connected between the base of the first switch tube and the negative terminal of the battery, the emitter of the first switch tube is connected to the negative terminal of the battery, and the collector of the first switch tube is connected to the control end of the second switch module.

[0012] Furthermore, the input power is sent to the control end of the second switch module after voltage division to control the conduction of the second switch module; the second switch module is disconnected when the first switch module is turned on.

[0013] Furthermore, the second switch module includes a second switch tube, a second diode, a third resistor and a fourth resistor, the third resistor is connected between the base of the second switch tube and the input power supply, the fourth resistor is connected between the base of the second switch tube and the negative terminal of the battery, the cathode of the second diode is connected to the collector of the second switch tube, the anode is connected to the input power supply via a fifth resistor, and the emitter of the second switch tube is connected to the negative terminal of the battery.

[0014] Further, the fifth switch module is connected to the input power supply, and the control end of the fifth switch module is connected to the charging control signal input end via a first diode; when the charging control signal is at a high level, the first diode is turned on and the fifth switch module is turned off; when the charging control signal is at a low level or a high impedance state, the first diode is turned off and the fifth switch module is turned on.

[0015] Further, the control end of the fourth switch module is connected to the fifth switch module, and the fourth switch module is turned on when the fifth switch module is turned on, and is turned off when the fifth switch module is turned off.

[0016] Further, the fourth switch module includes a fourth switch tube, a third diode, an eighth resistor and a ninth resistor; the fifth switch module includes a fifth switch tube, the first diode and a tenth resistor; the anode of the third diode is connected to the emitter of the fourth switch tube, and the cathode is connected to the negative end of the load, the eighth resistor is connected between the anode of the third diode and the base of the fourth switch tube, the ninth resistor is connected between the base of the fourth switch tube and the emitter of the fifth switch tube, the collector of the fourth switch tube is connected to the input power supply via a fifth resistor, the emitter of the fifth switch tube is connected to the input power supply, the base of the fifth switch tube is connected to the negative end of the battery via the tenth resistor, the anode of the first diode is connected to the charging control signal input end, and the cathode is connected to the base of the fifth switch tube.

[0017] Furthermore, a seventh resistor is included which is connected between the gate of VGaN and the fifth resistor.

[0018] The VGaN driving circuit proposed in the technical solution of the present invention realizes the low-side protection control of VGaN in the BMS by a simpler circuit constructed with discrete components, and reduces the voltage drop loss when a single tube is turned on. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the schematic diagram of VGaN.

[0020] Figure 2 It is a simplified charging and discharging schematic diagram in BMS.

[0021] Figure 3 4 is a diagram of a VGaN driving circuit proposed in an embodiment of the present invention. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation methods.

[0023] The embodiment of the present invention provides a VGaN (enhanced bidirectional gallium nitride power tube) driving circuit, which implements low-side protection control of a BMS (battery management system) with extremely simple discrete components, aiming to solve the problem of complex structure of existing low-side protection circuits.

[0024] The VGaN driving circuit proposed in the embodiment of the present invention uses four switch modules in conjunction with the charge and discharge control signal and the input power supply to realize the driving control of VGaN (Q3), so that the BMS has multiple working states. For details, please refer to Figure 3 The driving circuit includes a first switch module 10, a second switch module 20, a fourth switch module 40, a fifth switch module 50, a charging control signal input terminal, a discharging control signal input terminal, an input power supply, VGaN Q3, current limiting resistors R5 and R7, and the current limiting resistors R5 and R7 are connected in series between the input power supply and the gate G of VGaN. The charging control signal input terminal is used to provide a charging control signal CHG, and the discharging control signal input terminal is used to provide a discharging control signal DSG; the input power supply 5V is obtained by stepping down the BAT, and LDO or DCDC can be realized. CHG and DSG can be AFE (Analog Front End) output or MCU (microcontroller unit) output. It should be noted that the high level output of CHG needs to be ≥5V, and the insufficient level needs to be converted. The high level of CHG realizes the closing of VGaN and the low level realizes the disconnection of VGaN.

[0025] Continue to refer Figure 3 In some embodiments, the first switch module 10 includes a switch tube Q1, voltage-dividing resistors R1 and R2, the second switch module 20 includes a switch tube Q2, a diode DS2, voltage-dividing resistors R3 and R4, the fourth switch module 40 includes a switch tube Q4, a diode DS3, voltage-dividing resistors R8 and R9, and the fifth switch module 50 includes a switch tube Q5, a diode DS1, and a pull-down resistor R10. Wherein:

[0026] The base of the switch tube Q1 is connected to the discharge control signal input terminal through the voltage-dividing resistor R1 on the one hand, and is also connected to the negative terminal B- of the battery BT1 through the voltage-dividing resistor R2 on the other hand. The emitter of the switch tube Q1 is directly connected to the negative terminal B- of the battery. The DSG signal is sent to the Vbe of Q1 after voltage division to control the on and off of Q1.

[0027] The voltage-dividing resistors R3 and R4 are connected in series between the input power supply 5V and the negative terminal B- of the battery. The collector of the switch tube Q1 is connected to the base of the switch tube Q2 and the two are connected between the voltage-dividing resistors R3 and R4. The emitter of the switch tube Q2 is connected to the negative terminal B- of the battery. The input power supply 5V is divided by R3 and sent to the Vbe of Q2 to control the conduction of Q2. The Vce of Q1 is connected in parallel with R4. Therefore, when Q1 is turned on, Q2 is turned off.

[0028] The diode DS2 is used as a clamping diode, with its positive electrode connected between the current limiting resistors R5 and R7 and its negative electrode connected to the collector of the switch tube Q2; the current limiting resistor R5 can prevent the 5V power supply from being overloaded by Q2 or Q4, and the current limiting resistor R7 is used to suppress the junction capacitance impact current when Q3 is turned on and off; the clamping diode DS2 is used to provide a certain voltage drop and clamp the drain voltage on both sides of VGaN;

[0029] The collector of the switch tube Q4 is connected between the current limiting resistors R5 and R7, the emitter is connected to the positive electrode of the diode DS3, the base is connected to one end of the voltage divider resistors R8 and R9, the other end of the voltage divider resistor R8 is connected to the positive electrode of the diode DS3, the other end of the voltage divider resistor R9 is connected to the collector of the switch tube Q5, and the negative electrode of the diode DS3 is connected to the negative terminal P- of the load RL; the emitter of the switch tube Q5 is connected to the input power supply 5V, the base is connected to one end of the pull-down resistor R10 and the negative electrode of the diode DS1, the other end of the pull-down resistor R10 is connected to the negative terminal B- of the battery, and the positive electrode of the diode DS1 is connected to the charging control signal input terminal. The two drains D1 and D2 of VGaN Q3 are connected to the negative terminal B- of the battery and the negative terminal P- of the load respectively. Among them, DS1 is a Schottky diode to prevent the 5V input power supply from flowing back to CHG through the Vbe of Q5. R10 is used as a pull-down resistor to turn on Q5 when CHG is low or high impedance. The voltage divider resistors R9 and R8 are used to turn on Q4. DS3 is a diode, which is used to prevent backflow (after Q3 is turned off, the P- level will be pulled to P+ / B+ by the load RL) and to clamp the voltage.

[0030] So:

[0031] ① When the charging control signal CHG and the discharging control signal DSG are both at high levels, Q1 is turned on and Q5 is turned off, causing Q2 and Q4 to be turned off. At this time, the gate voltage of VGaN Q3 is 5V through the current limiting resistors R5 and R7, making VGaN Q3 bidirectionally conductive, and the BMS is in a state of both charging and discharging, which can charge the battery BT1 and discharge the load RL.

[0032] ② When the charging control signal CHG is at a high level and the discharging control signal DSG is at a low level or in a high-impedance state, both Q1 and Q5 are turned off, causing Q2 to conduct and Q4 to turn off. Then, the gate voltage of Q3 will be clamped to the voltage drop Vds2 of diode DS2, where Vds2 is not higher than 1V. At this time, the voltage drop Vgd1 between the gate G and the drain D1 of Q3 is Vds2 < Vgd1th, and Q3 is turned off. When a P- external RL load is connected, the P- voltage will be pulled up by RL, resulting in a voltage drop Vgd2 between the gate G and the drain D2 of Q3 being less than Vgd2th, and Q3 is turned off at this time. When a P- external charger is connected, the P- voltage will be pulled down (B + B- will be between P + P-, and P- will be lower than B-). When Vr l (charger voltage) - Vbt1 (battery voltage) + Vds2 = Vgd2th, Q3 conducts from D2 to D1, and at this time, the charger can charge the battery. This is the state of not discharging but being able to charge.

[0033] In the above state of being able to charge but not discharge, Q3 needs to bear the voltage drop loss of Vgd2th - Vds2. Therefore, the type selection and quantity of DS2 can be changed according to requirements to reduce its voltage drop loss. Specifically, according to the threshold voltage Vgdth value of the actually selected VGaN, if its minimum value is 1V and there is a 0.2V margin, a signal diode with a voltage drop of about 0.55V can be selected in series with a Schottky diode with a voltage drop of about 0.25V, so as to control the voltage drop to 0.8V, realizing that when charging VGAN in the non-discharging situation, it only needs to bear a voltage drop loss of 0.2V.

[0034] ③ When the charging control signal CHG is at a low level or in a high-impedance state and the discharging control signal DSG is at a high level, both Q1 and Q5 are turned on, causing Q2 to turn off and Q4 to conduct. Then, the gate voltage of VGaN Q3 will be clamped to Vgd2 = Vds3 (Vds3 is the voltage drop of diode DS3 and is not higher than 1V, with P- as the reference), and Q3 is turned off. At this time, there is also Vgd2 = Vds3 < Vgd2th. However, when a P- external RL load is connected, the P- voltage will be pulled up by RL. When Vr l (load voltage) = Vbt1 (battery voltage) - Vgd1th + Vds3, Vgd1 = Vgd1th, Q3 will clamp P- at the same time. At this time, Q3 needs to bear the voltage drop loss of Vgd1th - Vds3, and the type selection and quantity of DS3 can be changed according to requirements to reduce its voltage drop loss. At the same time, Q3 conducts from D1 to D2, and at this time, the battery can discharge to the load. When a P- external charger is connected, the P- potential is pulled down, Vgd1 < Vgd1th, and Q3 is turned off, and charging is not possible at this time. This is the state of being able to discharge but not charge.

[0035] ④When the charging control signal CHG and the discharging control signal DSG are both at low level or high impedance, Q1 is cut off and Q5 is turned on, causing Q2 and Q4 to be turned on. If P- is an external load, the P- voltage will be pulled up by RL, Vgd1=Vds2<Vgd1th and Vgd2<Vgd2th, then there will be no connection between D1 and D2 of Q3, and charging and discharging will not be possible. If an external charger is used, the P- potential will be pulled down, Vgd2=Vds3<Vgd2th and Vgd1<Vgd1th, there will be no connection between D1 and D2 of Q3, and charging and discharging will not be possible. In this case, VGaN is bidirectionally cut off, and the BMS is in a state where it can neither charge nor discharge.

[0036] It should be understood that the diodes DS1, DS2 and DS3 in the above embodiment can be replaced by other devices with diode characteristics without affecting the function of the invention.

[0037] The above-mentioned switch tubes Q1, Q2, Q4 and Q5 can be replaced by other devices such as electronic tubes or relays with switches without affecting the function of the invention.

[0038] The above-mentioned 5V power supply can be replaced by an external power supply without affecting the functions of the invention.

[0039] The above-mentioned 5V power supply can be replaced by a suitable driving voltage such as 4.8V, 4.5V, etc. without affecting the function of the invention.

[0040] The function of the invention can be affected by exchanging the order of the series connection of DS2 and Q2.

[0041] The function of the invention can be affected by exchanging the order of the series connection of DS3 and Q4.

[0042] The above-mentioned addition of parallel number of Q3 does not affect the function of the modified invention.

[0043] The driving circuit of the embodiment of the present invention is a discrete device with a simple structure and low price. The discrete device is simple to adjust the clamping voltage and set the threshold, and has strong compatibility. The triode is the preferred signal tube for fast signal transmission. A series diode is added to reduce its unidirectional conduction voltage drop loss. The number of devices is reduced to reduce the probability of failure.

[0044] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art of the present invention, several equivalent substitutions or obvious variations can be made without departing from the concept of the present invention, and the performance or use is the same, which should be regarded as belonging to the protection scope of the present invention.

Claims

1. A VGaN driving circuit for realizing a BMS low-side protection function, characterized in that: include: A first switch module, a second switch module, a fourth switch module, a fifth switch module, a charging control signal input terminal, a discharging control signal input terminal, an input power supply, a current limiting resistor and VGaN; wherein: the first drain of VGaN is connected to the negative terminal of the battery, the first switch module and the second switch module, the second drain of VGaN is connected to the negative terminal of the load and the fourth switch module, the input power supply is connected to the gate of VGaN via the current limiting resistor, and the input power supply is connected to the first drain of VGaN via voltage division; the first switch module is connected to the second switch module, and the fourth switch module is connected to the fifth switch module; the discharging control signal input terminal is used to input a discharging control signal to the first switch module, and the charging control signal input terminal is used to input a charging control signal to the fifth switch module; The driving circuit realizes driving control of VGaN through the cooperation of the first switch module, the second switch module, the fourth switch module, the fifth switch module, the charge and discharge control signal and the input power supply, so that the BMS has multiple working states.

2. The driving circuit according to claim 1, characterized in that: The discharge control signal is sent to the control end of the first switch module through voltage division to control the on and off of the first switch module.

3. The driving circuit according to claim 2, characterized in that: The first switch module includes a first switch tube, a first resistor and a second resistor, the first resistor is connected between the discharge control signal input terminal and the base of the first switch tube, the second resistor is connected between the base of the first switch tube and the negative terminal of the battery, the emitter of the first switch tube is connected to the negative terminal of the battery, and the collector of the first switch tube is connected to the control terminal of the second switch module.

4. The driving circuit according to claim 2, characterized in that: The input power is sent to the control end of the second switch module after voltage division to control the conduction of the second switch module; the second switch module is disconnected when the first switch module is turned on.

5. The driving circuit according to claim 4, characterized in that: The second switch module includes a second switch tube, a second diode, a third resistor and a fourth resistor, the third resistor is connected between the base of the second switch tube and the input power supply, the fourth resistor is connected between the base of the second switch tube and the negative terminal of the battery, the cathode of the second diode is connected to the collector of the second switch tube, the anode is connected to the input power supply via a fifth resistor, and the emitter of the second switch tube is connected to the negative terminal of the battery.

6. The driving circuit according to claim 4, characterized in that: The fifth switch module is connected to the input power supply, and the control end of the fifth switch module is connected to the charging control signal input end via a first diode; when the charging control signal is at a high level, the first diode is turned on and the fifth switch module is turned off; when the charging control signal is at a low level or a high impedance state, the first diode is turned off and the fifth switch module is turned on.

7. The driving circuit according to claim 6, characterized in that: The control end of the fourth switch module is connected to the fifth switch module. The fourth switch module is turned on when the fifth switch module is turned on, and is turned off when the fifth switch module is turned off.

8. The driving circuit according to claim 7, characterized in that: The fourth switch module includes a fourth switch tube, a third diode, an eighth resistor and a ninth resistor; the fifth switch module includes a fifth switch tube, the first diode and a tenth resistor; the anode of the third diode is connected to the emitter of the fourth switch tube, and the cathode is connected to the negative end of the load, the eighth resistor is connected between the anode of the third diode and the base of the fourth switch tube, the ninth resistor is connected between the base of the fourth switch tube and the emitter of the fifth switch tube, the collector of the fourth switch tube is connected to the input power supply via a fifth resistor, the emitter of the fifth switch tube is connected to the input power supply, the base of the fifth switch tube is connected to the negative end of the battery via the tenth resistor, the anode of the first diode is connected to the charging control signal input end, and the cathode is connected to the base of the fifth switch tube.

9. The driving circuit according to claim 8, characterized in that: A seventh resistor is also included, which is connected between the gate of the VGaN and the fifth resistor.

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