Brushless Motor Speed Control Circuit for Ceiling Fans
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Solution Overview
Problem
Conventional ceiling fan speed control systems using constant PWM duties are inadequate for varying fan sizes, shapes, and materials, leading to potential motor overload and overheating when different fans are installed, as they fail to adjust effectively to dynamic loading conditions.
Innovation Solution
A method that incorporates a motor PWM duty consumption sampling unit and a motor speed sampling unit, connected to a central processing unit, which dynamically adjusts the PWM duty and speed control by comparing sensed parameters to preset maximum values, switching between PWM duty control and constant-speed control based on motor conditions to prevent overload.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If constant-speed control system with fixed PWM duties is used, then the control program provides variable settings according to fan loadings, but the ceiling fan cannot work according to original setting when fans are replaced by different types, leading to motor overload and overheating
Solution Approach 1:
The patent implements dynamic speed adjustment by transitioning from fixed PWM duty control to a system that continuously monitors motor current and adjusts PWM duty cycle in real-time. The control unit dynamically modifies the PWM signal based on detected motor conditions, enabling the system to adapt to different fan loadings and prevent motor overload while maintaining reliable operation across various fan configurations.
Solution Approach 2:
The patent incorporates a feedback mechanism where the control unit continuously detects motor current and speed, then adjusts PWM duty cycle based on this feedback. The system monitors motor operating conditions and automatically adjusts power delivery to maintain optimal performance and prevent overload, creating a closed-loop control system that ensures reliability across different fan types.
2Speed
If PWM duty is increased to maintain speed with heavier fans, then the fan rotation speed is maintained, but the motor may burn because of overheat and overload
Solution Approach 1:
The control unit continuously monitors motor current and temperature conditions through feedback sensors. When the motor approaches overload or overheating thresholds, the system automatically reduces PWM duty cycle to limit power delivery, preventing motor damage while maintaining fan rotation speed within safe operating parameters.
Solution Approach 2:
The patent dynamically changes the PWM duty cycle parameter based on real-time motor conditions. Instead of using fixed high PWM duty to maintain speed, the system adjusts this parameter adaptively - increasing it when motor capacity allows and reducing it when thermal or electrical limits are approached, thereby maintaining speed without causing overheating or overload.
3Ease of operation
If constant PWM duty is used for different fan loadings, then the control program provides variable settings, but the system fails to adjust effectively to dynamic loading conditions
Solution Approach 1:
The control system performs self-adjustment by automatically detecting fan loading conditions and modifying PWM duty cycle without requiring manual reconfiguration. The system serves itself by monitoring motor current and speed, then autonomously optimizing power delivery for different fan types and loadings, eliminating the need for complex manual control program adjustments while maintaining ease of operation.
Solution Approach 2:
The patent transforms the static control program into a dynamic system that automatically adapts to varying load conditions. The control unit continuously adjusts PWM parameters based on real-time motor feedback, enabling the system to handle different fan configurations and loading scenarios without requiring changes to control program settings, thereby achieving both ease of operation and adaptability.
Data Source
AI summary
The present invention relates to a method and a circuit of controlling a speed of a brushless motor of a ceiling fan. The circuit includes a motor PWM duty consumption sampling unit and a motor speed sampling to sense a PWM duty and a speed of the brushless motor. A central processing unit is provided to compare the PWM duty and the speed of the brushless motor to a preset maximum PWM duty and a preset maximum speed. When the PWM duty reaches to the preset maximum PWM duty first, the central processing unit sets the current speed to be a maximum speed, and speeds of each level are calculated according to the maximum speed. If the speed reaches to the preset maximum speed first, a constant-speed control will take over to control the brushless motor, and speeds of each level are according to the preset speeds.