Brushless DC Motor Motor-Locked Protective Circuit
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Solution Overview
Problem
Brushless DC motors often unexpectedly enter high-speed mode during startup, leading to increased operational temperatures and potential damage due to excessive heat and vibration, and when jammed, they operate in high-speed mode unnecessarily, causing further stress on components.
Innovation Solution
A motor-locked protective circuit is implemented, where a RD signal line connects between the PWM drive IC member and the PWM converter circuit, allowing jammed RD signals to build a predetermined voltage that controls the PWM drive IC to maintain the motor at a predetermined-speed mode, preventing rapid temperature increases and inrush currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the motor is designed to operate in high-speed mode during startup, then the motor can reach operating speed quickly, but the operational temperature increases rapidly and components may be damaged
Solution Approach 1:
The patent applies dynamics by making the motor speed variable rather than fixed. The motor operates in high-speed mode during normal operation but automatically switches to low-speed mode when jamming is detected through the RD signal. This dynamic speed adjustment based on operational conditions resolves the contradiction by allowing fast startup when needed while preventing excessive temperature rise when the motor is jammed.
Solution Approach 2:
The patent implements feedback through the rotational detection (RD) signal line that continuously monitors motor rotation status and feeds this information back to the PWM drive IC. When the motor is jammed and rotation stops, the RD signal changes state, triggering the PWM drive IC to switch from high-speed mode to low-speed mode. This feedback mechanism enables automatic speed adjustment to prevent overheating while maintaining high-speed capability during normal operation.
2Power
If the motor operates in high-speed mode when jammed, then the motor can maintain power output, but excessive stress is placed on components reducing lifespan
Solution Approach 1:
The patent makes the motor speed dynamic based on operational conditions. During normal operation, the motor runs at high speed for maximum power output. When jamming is detected via the RD signal, the system automatically transitions to low-speed mode, reducing mechanical stress on components while maintaining sufficient power for the application. This dynamic adjustment preserves component lifespan without permanently sacrificing power capability.
Solution Approach 2:
The patent changes the operating parameter (speed) based on the motor's rotational state. The PWM drive IC receives the RD signal and adjusts the speed parameter accordingly - maintaining high speed when the motor rotates normally, and switching to low speed when rotation stops due to jamming. This parameter change protects components from excessive stress during jammed conditions while preserving high-power capability during normal operation.
3Reliability
If a RD signal line is added to connect between PWM drive IC member and PWM converter circuit, then the motor can be maintained at predetermined-speed mode when jammed, but the device complexity increases
Solution Approach 1:
The patent applies universality by making the existing RD signal line serve multiple functions. The RD signal line not only detects motor rotation status for normal control operations but also triggers the protective function by switching the motor from high-speed to low-speed mode when jamming is detected. This multi-functionality allows the patent to add motor protection capability without requiring separate dedicated protection circuits, thereby minimizing the increase in device complexity.
Solution Approach 2:
The patent implements self-service by enabling the motor control system to automatically detect and respond to jamming conditions without external intervention. The RD signal line continuously monitors motor rotation and automatically triggers the speed reduction protective mode when jamming is detected, allowing the system to protect itself. This self-service approach eliminates the need for additional protection circuits or manual monitoring, adding reliability with minimal complexity increase.
Data Source
AI summary
A brushless dc motor includes a PWM drive IC member, a Hall IC member, a PWM converter circuit and a Rotational Detection (RD) signal line. The PWM drive IC member electrically connects with the Hall IC member, the PWM drive IC member further includes a pin electrically connected with the PWM converter circuit. The RD signal line connects between the pin of the PWM drive IC member and the PWM converter circuit, and further connects with a RD signal source to supply RD signals to the pin of the PWM drive IC member. When the motor is jammed, the jammed RD signals can build a predetermined voltage which can determine the PWM drive IC member to be restarted or operated at a predetermined-speed mode. In this circumstance, no inrush current of the jammed motor will occur.