Soft switching control module and brushless DC motor drive system

Abstract

A soft-switching control module is characterized in that an ADJ control unit is connected with a time-delay unit and a comparator so as to obtain rotating speed signals of a direct-current brushless motor, obtain speed regulation signals according to the rotating speed signals, input the speed regulation signals to a first input end of the comparator, respectively obtain soft-switching current falling and rising time according to the speed regulation signals and send the soft-switching current falling and rising time to the time-delay unit; an OSC oscillator is connected with the comparator so as to generate sawtooth signals of a preset period and input the sawtooth signals to a second input end of the comparator; the time-delay unit is connected with a logic unit so as to delay the soft-switching current falling and rising time by means of obtained switch-controlled logic signals of at least one power switch tube; the comparator is connected with the logic unit so as to compare the speed regulation signals with the sawtooth signals to generate a PWM waveform; the logic unit is connected with a driving unit so as to modulating the driving unit according to output of the time-delay unit and the comparator; and the driving unit is connected with the power switch tube so as to control the soft-switching of the power switch tube. According to the invention, ultra-low noises and electro-magnetic interference (EMI) are realized, and the efficiency is prevented from decreasing.

Description

technical field [0001] The invention relates to the technical field of DC brushless motor drive, in particular to a soft switch control module with gradually changing duty ratio applied to a DC brushless motor drive circuit and a DC brushless motor drive system. Background technique [0002] In the design of brushless DC motor drive circuit, for unidirectional motor drive, just use a high-power triode or FET or relay to directly drive the motor; for bidirectional motor drive, you can use four power components The H-bridge circuit or use a double-pole double-throw relay; if speed regulation is required, switching elements such as transistors and field effect transistors can be used to achieve PWM (pulse width modulation) speed regulation. [0003] refer to figure 1 , a simplified schematic diagram of a typical brushless DC single-phase motor drive circuit. Such as figure 1 As shown, the motor (simplified as an inductance Motor in the schematic diagram) is connected between...

AI Technical Summary

Problems solved by technology

The advantage is that the current changes slowly and the noise is small; the disadvantage is that the current changes linearly, the dead time is fixed, and there is a problem of efficiency drop for motors with different currents and speeds.

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