In a larger power brushless motor, the drive circuit and the control circuit can be integrated separately. The drive circuit outputs electric power, drives the armature winding of the motor, and is controlled by the control circuit. At present, the driving circuit has changed from a linear amplification state to a pulse width modulation switching state, and the corresponding circuit composition has also changed from a transistor discrete circuit to a modular integrated circuit. Modular integrated circuits are composed of power bipolar transistors, power field effect transistors and isolated gate field effect bipolar transistors. Although the isolation gate field effect bipolar transistor is more expensive, it is more suitable to choose it from the point of view of reliability, safety and performance.
The control circuit is used to control the speed, steering, current (or torque) of the brushless motor, and to protect the motor from overcurrent, overvoltage, and overheating. The above parameters are easily converted into analog signals, which are relatively simple to control, but from the perspective of development, the parameters of the motor should be converted into digital quantities, and the motor should be controlled by a digital control circuit. At present, the control circuit has three types of composition, such as application-specific integrated circuit, microprocessor and digital signal processor. In the occasions where the requirements for motor control are not high, it is a simple and practical way to form a control circuit with an application-specific integrated circuit. The use of digital signal processors to form control circuits is the future development direction. The digital signal processors will be introduced in the following AC synchronous servo motors.
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