Brushless motor driving circuit and method

[0021]The present invention will be described in further detail below in conjunction with the accompanying drawings:

[0022]Such asfigure 1 Shown is the brushless motor drive circuit of the present invention, which includes a soft-start delay speed regulation circuit, a bus voltage suppression circuit and a three-phase bridge inverter circuit.

[0023]001 is the positive terminal of the voltage source, and 002 is the negative terminal of the voltage source.

[0024]The soft-start delay speed regulation circuit includes a transistor Q1, a capacitor C1, a capacitor C2, a capacitor C3, an adjustable resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a motor control chip U1 and a motor adapter.

[0025]The soft-start control signal is connected to the base of the transistor Q1. The emitter of the transistor Q1 is connected to the first terminal of the capacitor C1, the first terminal of the adjustable resistor R1 and the negative terminal of the voltage source power supply. The collector of the transistor Q1 is connected to the second terminal of the capacitor C1, The second end of the adjustable resistor R1 is connected to the first end of the resistor R2 and then connected to the motor control chip U1, and the second end of the resistor R2 is connected to the positive terminal of the voltage source.

[0026]The motor control chip U1 includes an error amplifier, a first comparator, and a gate drive signal modulation circuit. The collector of the transistor Q1 is connected to the non-inverting input end of the error amplifier. The inverting input end of the error amplifier is connected to the first end of the capacitor C2 and the first end of the resistor R3. One end is connected, the second end of the capacitor C2 and the second end of the resistor R3 are connected to the output end of the error amplifier, the output end of the motor adapter is connected to the inverting input end of the error amplifier through the connection resistor R4, the motor adapter sends out a speed proportional to the motor speed Broaden the wave signal. The output terminal of the error amplifier is connected to the inverting input terminal of the first comparator to output an error signal for comparison. The first end of the resistor R5 is connected to the positive terminal of the voltage source power supply, the second end of the resistor R5 is connected to the non-inverting input terminal of the first comparator and the first terminal of the capacitor C3, and the second terminal of the capacitor C3 is connected to the negative terminal of the voltage source power supply to generate an error signal A triangular wave signal for comparison; the output terminal of the first comparator is connected to the input terminal of the gate drive signal modulation circuit, and the output terminal of the gate drive signal modulation circuit is connected to the input terminal of the three-phase bridge inverter. The gate drive signal modulation circuit generates 6 gate drive signals: AH, BH, CH, AL, BL and CL.

[0027]In the traditional motor control process, the motor bus voltage is not detected and protected. When the bus voltage rises, the motor control system and the motor itself will be damaged or even damaged. Therefore, the bus voltage suppression circuit is used to discharge the bus current through the power load. Avoid excessive bus voltage.

[0028]The bus voltage suppression circuit includes resistor R6, resistor R7, resistor R8, resistor R9, resistor R10, resistor R11, resistor R12, second comparator, PMOS tube T7, transistor Q2 and square wave generator;

[0029]The first end of the resistor R6 and the output end of the gate drive signal modulation circuit are connected to the positive bus voltage VP, the second end of the resistor R6 is connected to the non-inverting input end of the second comparator and the first end of the resistor R7, and the second end of the resistor R7 is grounded. The reverse input terminal of the second comparator is connected to the first terminal of the resistor R8 and the first terminal of the resistor R9, the second terminal of the resistor R8 is connected to the positive terminal of the voltage source power supply, and the second terminal of the resistor R9 is connected to the negative terminal of the voltage source power supply. The output terminals of the two comparators are connected to the reset terminal of the square wave generator, the PWM signal at the output of the square wave generator is connected to the base of the transistor Q2, the emitter of the transistor Q2 is connected to the negative terminal of the voltage source, the collector of the transistor Q2 and the resistor R10 The first end of the resistor R10 is connected to the first end of the resistor R11 and the gate of the PMOS transistor T7. The source of the PMOS transistor T7 and the second end of the resistor R11 are connected to the positive bus voltage VP, and the second end of the PMOS transistor T7 The drain is connected to the first end of the resistor R12, and the second end of the resistor R12 is connected to the negative terminal of the voltage source.

[0030]Both the triode Q1 and the triode Q2 adopt NPN type triode.

[0031]The positive terminal of the voltage source power supply is connected to the VCC terminal of the square wave generator, the DIS terminal of the square wave generator, the THR terminal of the square wave generator, the TRIG terminal of the square wave generator, the capacitor C4 and the ground; the DIS terminal of the square wave generator A resistor R13 is connected to the positive terminal of the voltage source power supply, a resistor R14 is connected between the THR terminal of the square wave generator and the positive terminal of the voltage source power supply, the GND terminal of the square wave generator is grounded, and the COUNT terminal of the square wave generator passes through The capacitor C5 is connected to the GND terminal of the square wave generator.

[0032]The square wave generator can be generated by connecting CD40106, CD4049, NE555, etc. as a multi-resonant circuit, and can adjust and change the duty cycle and frequency of the PWM wave to adapt to different bus voltage working conditions. Set the operating frequency and duty cycle of the NE556 timer through the peripheral resistor and capacitor. When the timer detects the bus voltage detection signal, it outputs the PWM signal corresponding to the frequency and duty cycle.

[0033]In the three-phase bridge inverter circuit, the AH, BH, CH, AL, BL, CL signals are respectively connected to the gates of the VDMOS tube T1, VDMOS tube T2, VDMOS tube T3, VDMOS tube T4, VDMOS tube T5 and VDMOS tube T6 . The drains of the VDMOS tube T1, the VDMOS tube T2 and the VDMOS tube T3 are connected to the positive pole VP of the bus voltage source. The source of the VDMOS tube T1 is connected to the drain of the VDMOS tube T3, which is the bridge A phase output; the source of the VDMOS tube T2 is connected to the drain of the VDMOS tube T5, which is the bridge B phase output; the VDMOS tube T3 The source is connected to the drain of the VDMOS tube T6, which is the bridge C-phase output; the sources of the VDMOS tube T4, VDMOS tube T5, and VDMOS tube T6 are connected to the negative terminal of the bus voltage source. Through AH, BH, CH, AL, BL, CL to control the on-off time of VDMOS tube T1, VDMOS tube T2, VDMOS tube T3, VDMOS tube T4, VDMOS tube T5 and VDMOS tube T6 in the three-phase bridge, adjust the motor speed, Finally, the motor speed is consistent with the system set speed.

[0034]When the soft start control signal is low and effective, the NPN transistor Q1 stops conducting, and the capacitor C1 starts to charge. The voltage signal is sent to the non-inverting input of the error amplifier in the motor control chip U1, and the inverting input of the error amplifier receives the motor speed. The proportional speed widening wave signal fT is passed through the integration network composed of resistor R3, capacitor C2 and error amplifier to produce an error voltage signal for comparison. When the error voltage signal output by the error amplifier rises to the low level of the triangular wave signal determined by the capacitor C3 and the resistor R5, the comparator outputs a PWM pulse modulation signal, which passes through the gate drive signal modulation circuit of U1 to generate 6 gate drive signals , Adjust the motor speed, and finally make the motor speed consistent with the system set speed.

[0035]The soft start delay speed regulating circuit can change the start delay time of the soft start by adjusting the resistance R2, the capacitor C1 and the adjustable resistance R1 to meet the working conditions of different motors and different load driving requirements.

[0036]The delay start time t is determined by the following formula:

[0037]

[0038]VCC represents the value of the positive terminal (001) of the voltage source power supply, Vt represents the low level of the triangular wave, e is the natural index, R1 is the resistance of the resistor R1, R2 is the resistance of the resistor R2, and the C1 is the capacitance of the capacitor C1.

[0039]The circuit structure of the brushless motor drive circuit with the functions of soft start and bus voltage suppression disclosed in the present invention is simple. The soft start part can reduce the starting current of the motor while ensuring the starting time and starting with load, thereby improving the operation of the drive and the system performance. At the same time, the bus voltage suppression function can detect and ensure that the bus voltage will not be higher than the set value in time, and further improve the reliability, stability and speed regulation accuracy of the brushless motor driver circuit. This circuit has been used in three-phase bridge drivers with good results.

[0040]The above content is only to illustrate the technical ideas of the present invention, and cannot be used to limit the scope of protection of the present invention. Any changes made on the basis of the technical solutions based on the technical ideas proposed by the present invention shall fall into the claims of the present invention. Within the scope of protection.