Back-EMF Motor Control Circuit for Adaptive PWM Frequency
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Solution Overview
Problem
Existing brushless motor control systems face inefficiencies in maintaining accurate motor operation at high speeds and high torque due to excessive switching losses and temperature rise in power devices, as conventional PWM frequency adjustments do not accurately reflect the motor's working conditions.
Innovation Solution
A motor control circuit and method utilizing a reverse electromotive force detection circuit to obtain parameters that correlate with PWM signal frequencies, enabling precise frequency adjustments based on detected electromotive force changes or current freewheeling times to optimize motor operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If PWM frequency is increased to meet high-speed motor requirements, then motor running capability is improved, but switching loss and temperature increase significantly
Solution Approach 1:
The patent applies dynamics by making the PWM frequency adjustable and adaptive rather than fixed. The control unit dynamically changes PWM frequency based on real-time motor operating conditions (current and speed), allowing the system to optimize between high-speed capability and low switching loss by selecting appropriate frequency levels during different operating phases.
Solution Approach 2:
The patent implements parameter changes by varying the PWM frequency parameter according to motor operating conditions. The control unit adjusts the frequency parameter based on detected current and speed values, transforming the system from static frequency operation to adaptive frequency operation that reduces switching loss while maintaining speed performance.
2Loss of energy
If motor power is used to determine PWM frequency, then switching loss can be suppressed, but measurement accuracy is poor due to indirect reflection of working conditions
Solution Approach 1:
The patent uses current detection as an intermediary parameter to infer motor working conditions. By detecting the current flowing through the motor and using it as a mediator to determine appropriate PWM frequency, the system achieves better measurement accuracy compared to using motor power directly, while still effectively suppressing switching loss through adaptive frequency selection.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves high-accuracy motor control with reduced power consumption by dynamically adjusting PWM frequencies according to motor conditions, ensuring efficient operation at high speeds and loads while minimizing power device stress.
Implementation Method 1
a reverse electromotive force detection circuit; wherein the controller is connected to the motor through the reverse electromotive force detection circuit to obtain a reverse electromotive force parameter
Data Source
AI summary
Disclosed are a motor control circuit and a control method. The control circuit includes: a power supply; a drive circuit; a pulse width modulation (PWM) signal generation circuit; a controller; and a reverse electromotive force detection circuit. The power supply is connected to the motor through the drive circuit; the drive circuit is connected to the controller through the PWM signal generation circuit; the controller is configured to control the drive circuit by changing a PWM signal frequency; the controller is connected to the motor through the reverse electromotive force detection circuit to obtain a reverse electromotive force parameter; the controller stores a correspondence between the reverse electromotive force parameter and the PWM signal frequency; the controller is further configured to receive the reverse electromotive force parameter and send the PWM signal frequency corresponding to the reverse electromotive force parameter to the drive circuit, for driving the motor.