Adaptive PWM Motor Driver for Variable-Resistance Startup
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Solution Overview
Problem
Conventional motor drivers output a constant duty cycle driving signal, which is not applicable for motors with varying resistances, leading to unsuccessful startup of motors with large resistances due to insufficient current flow.
Innovation Solution
A motor driver that includes a motor driving circuit, current limiting circuit, and duty cycle detecting circuit, which senses and adjusts the duty cycle of pulse width modulation signals based on current values to calculate motor resistance and set appropriate starting torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a constant duty cycle driving signal is output to drive the high-side switch, then the control circuit is simple, but the motor cannot be successfully started up when having large resistance due to insufficient current flow
Solution Approach 1:
The patent implements a feedback mechanism where the duty cycle detecting circuit monitors the actual duty cycle of PWM signals and feeds this information back to the control circuit. The control circuit adjusts the PWM duty cycle dynamically based on feedback from the duty cycle detected signal, enabling adaptive current control that ensures reliable motor startup across different resistance values while maintaining circuit simplicity.
2Reliability
If the duty cycle is increased to provide sufficient current for motors with large resistance, then motor startup reliability improves, but the driving signal becomes inappropriate for motors with small resistance
Solution Approach 1:
The patent transforms the static constant duty cycle approach into a dynamic adaptive system. The control circuit continuously adjusts the PWM duty cycle based on real-time feedback from the duty cycle detecting circuit, allowing the system to optimize current delivery for each specific motor resistance value. This dynamic adjustment ensures both high startup reliability and broad adaptability across different motor types.
Solution Approach 2:
The patent changes the duty cycle parameter dynamically rather than keeping it constant. By monitoring the duty cycle detected signal and adjusting the PWM duty cycle accordingly, the system adapts the electrical parameter (duty cycle) to match the specific resistance characteristics of different motors, ensuring optimal performance across varying conditions.
3Reliability
If multiple current sensing and duty cycle adjustments are implemented, then motor startup reliability for any resistance improves, but the device complexity increases
Solution Approach 1:
The duty cycle detecting circuit serves multiple functions: it monitors PWM duty cycle, generates duty cycle detected signals for control feedback, and enables adaptive current limiting. By making this circuit multi-functional, the patent achieves high startup reliability across all motor resistances without proportionally increasing overall system complexity, as the same circuit structure supports multiple control objectives.
Data Source
AI summary
A motor driver for starting up a motor having any resistance is provided. The motor driver outputs a motor startup signal to the motor according to an initial startup duty cycle, senses a current value of a current signal of the motor multiple times, compares the current value of the motor that is sensed for multiple times with a reference current value and accordingly sets a plurality of pulse waves of a pulse width modulation signal. Then, the motor driver detects duty cycles of the pulse waves of the pulse width modulation signal as startup detection duty cycles. Then, the motor driver outputs a motor startup signal to the motor according to the startup detection duty cycles.