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CN-122026895-A - MOS tube light isolation driver based on triode push-pull accelerating circuit

CN122026895ACN 122026895 ACN122026895 ACN 122026895ACN-122026895-A

Abstract

The invention discloses an MOS tube light isolation driver based on a triode push-pull acceleration circuit, and belongs to the field of power electronic driving. The driver comprises a signal isolation stage, an intermediate driving stage and a push-pull output stage, wherein the signal isolation stage realizes electric isolation of an input control signal and a power driving circuit through photoelectric coupling, the intermediate driving stage converts a weak signal output by an optical coupler into a high-level driving signal, and the push-pull output stage forms symmetrical push-pull output by utilizing the current amplification characteristic of a complementary triode. According to the invention, through the Q2/Q3 push-pull circuit, the grid charging current is raised to 300mA (provided by Q2), the discharging current is raised to 200mA (provided by Q3), the switching delay is reduced to be less than or equal to 400ns when being conducted, less than or equal to 600ns when being turned off, and the switching frequency of the maximum 800kHz is supported.

Inventors

  • HE WEI

Assignees

  • 十堰市志强电子科技有限公司

Dates

Publication Date
20260512
Application Date
20260122

Claims (4)

  1. 1. The MOS transistor optical isolation driver based on the triode push-pull acceleration circuit is characterized by comprising a signal isolation stage, an intermediate driving stage and a push-pull output stage; The signal isolation stage realizes the electrical isolation of an input control signal and a power driving circuit through photoelectric coupling, and the isolation voltage is more than or equal to 2.5kVrms; The intermediate driving stage converts weak signals output by the optocoupler into high-level driving signals to realize level conversion and power amplification of control logic; the push-pull output stage forms symmetrical push-pull output by utilizing the current amplification characteristic of the complementary triode, and accelerates the charge and discharge process of the MOS tube grid capacitor.
  2. 2. The MOS transistor light isolation driver based on the triode push-pull acceleration circuit according to claim 1, wherein the signal isolation stage adopts a low-speed optocoupler U1, the input end of the low-speed optocoupler U1 is connected in series with a current limiting resistor R1, a capacitor C1 is connected with a control signal, the output end ③ of the low-speed optocoupler U1 is directly grounded, and the ④ is connected with the input end of the intermediate driving stage.
  3. 3. The MOS transistor optoisolation driver based on the triode push-pull acceleration circuit according to claim 1, wherein the intermediate driving stage comprises a PNP triode Q1, the base of which is connected to the ④ pin of the low-speed optocoupler U1, and simultaneously is connected to a 12V power supply through a bias resistor R2, the emitter is connected to a 12V power supply, the collector is connected in series with pull-down resistors R3 to GND, and the collector output signal is used as the driving signal of the push-pull output stage.
  4. 4. The MOS transistor light isolation driver based on the triode push-pull acceleration circuit according to claim 1, wherein the push-pull output stage comprises an NPN triode Q2 and a PNP triode Q3, bases of the Q2 and the Q3 are connected in parallel and then connected with a collector of the intermediate driving stage Q1, the collector of the Q2 is connected with a 12V power supply, the collector of the Q3 is connected with GND, emitters of the Q2 and the Q3 are connected in parallel and then used as output ends, the output ends are connected with a damping resistor R4 in series and connected with voltage stabilizing diodes D1 to GND in parallel, and finally connected to a grid electrode of the MOS transistor.

Description

MOS tube light isolation driver based on triode push-pull accelerating circuit Technical Field The invention relates to power electronic driving, in particular to an MOS tube light isolation driver based on a triode push-pull accelerating circuit. Background In the fields of industrial control, switching power supply, BMS bidirectional flyback, motor driving and the like, MOS tubes are widely used as power switching devices due to excellent high-frequency characteristics and low conduction loss. To achieve electrical isolation of a control circuit (e.g., MCU) from a high voltage power circuit, an optocoupler isolation drive scheme is typically employed. The conventional optocoupler driving has the following disadvantages: The switching speed is low, the output current of a low-speed optocoupler (such as PC 817) is small (typical value is 50 mA), the MOS transistor grid capacitor can not be rapidly driven to charge and discharge, the switching delay is caused (the conduction is more than or equal to 2 mu s, the disconnection is more than or equal to 3 mu s), and the high-frequency application scene is limited. When the optocoupler is directly driven, the gate charging current is insufficient, so that the MOS transistor turn-on loss is easily increased, and the MOS transistor is more obvious in a capacitive load (> 10 nF) scene. The circuit compatibility is poor, the cost of a plurality of special isolation driving chips (such as HCPL-3120) is high (about 5-8 yuan/chip), and an auxiliary power supply is required to be additionally configured, so that the complexity of the system is increased. Disclosure of Invention The invention aims to provide a light isolation MOS tube driver with low cost, high speed and strong driving capability. The MOS transistor optical isolation driver based on the triode push-pull acceleration circuit comprises a signal isolation stage, an intermediate driving stage and a push-pull output stage; The signal isolation stage realizes the electrical isolation of an input control signal and a power driving circuit through photoelectric coupling, and the isolation voltage is more than or equal to 2.5kVrms; The intermediate driving stage converts weak signals output by the optocoupler into high-level driving signals to realize level conversion and power amplification of control logic; the push-pull output stage forms symmetrical push-pull output by utilizing the current amplification characteristic of the complementary triode, and accelerates the charge and discharge process of the MOS tube grid capacitor. Furthermore, a low-speed optocoupler U1 (such as PC 817) is adopted, the input end of the low-speed optocoupler U1 is connected in series with a current-limiting resistor R1 (1 kΩ -10 kΩ), a capacitor C1 (100 PF-1 UF) is connected with a control signal (MCU PWM), the output end ③ is directly grounded, and the ④ is connected with the input end of the intermediate driving stage. Further, the intermediate driving stage includes a PNP transistor Q1 (e.g., S8550), a base (B-pole) thereof is connected to the ④ pin of the optocoupler U1, and meanwhile, the base (B-pole) is connected to a 12V power supply through a bias resistor R2 (120Ω), an emitter (E-pole) is connected to a 12V power supply, a collector (C-pole) is connected in series with a pull-down resistor R3 (1 kΩ to 10kΩ) to GND, and a collector output signal is used as a driving signal of the push-pull output stage. Further, the push-pull output stage includes an NPN triode Q2 (e.g. S8050) and a PNP triode Q3 (e.g. S8550), bases (B poles) of the Q2 and Q3 are connected in parallel and then connected to a collector of the intermediate driving stage Q1, a collector (C pole) of the Q2 is connected to a 12V power supply, a collector (C pole) of the Q3 is connected to GND, emitters (E poles) of the Q2 and Q3 are connected in parallel and then used as an output end, the output end is connected in series with a damping resistor R4 (10Ω), and is connected in parallel with a zener diode D1 (18V) to GND, and finally connected to a gate (G pole) of the MOS transistor. The beneficial effects are that: (1) According to the invention, through the Q2/Q3 push-pull circuit, the grid charging current is raised to 300mA (provided by Q2), the discharging current is raised to 200mA (provided by Q3), the switching delay is reduced to be less than or equal to 400ns when being conducted, less than or equal to 600ns when being turned off, and the switching frequency of the maximum 800kHz is supported. (2) The invention can drive the medium and high power MOS tube (such as IRF 540) with the grid capacitance less than or equal to 20nF, and is suitable for industrial grade power scenes. (3) The invention adopts a1 optocoupler+3 triode architecture, and the total cost is less than or equal to 0.3 yuan, which is only 1/5 of that of a special driving chip. (4) The isolation voltage of the optical coupler is more than or equal to 2.5kVrms, and the common mode rejecti