Brushless DC Motor Driver Using Dual Hysteresis Comparators
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Solution Overview
Problem
Existing brushless DC motor systems face challenges with commutation detection under weak magnetic or back electromotive force, leading to misjudged time points and increased system volume and manufacturing costs due to reliance on Hall sensors, which are prone to errors and inefficiencies.
Innovation Solution
A motor driving device and method utilizing two hysteresis comparators with different hysteresis voltages for start and operating states, along with a logic circuit and control unit, to accurately detect commutation points and improve efficiency without external sensors, thereby preventing commutation delays and noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Hall sensor is used for commutation detection, then the motor system can detect rotor position, but the system volume and manufacturing costs increase
Solution Approach 1:
The patent extracts the commutation detection function from the Hall sensor and implements it through sensorless driving using back electromotive force detection. The Hall sensor is removed from the system, and its detection function is replaced by analyzing the voltage signals generated during motor operation, thereby reducing system volume and manufacturing costs while maintaining commutation detection capability
Solution Approach 2:
The motor system uses its own back electromotive force signals for commutation detection without requiring external sensors. The detection is performed self-service style by analyzing voltages that are naturally generated during motor operation, eliminating the need for separate sensing components
2Measurement precision
If a Hall sensor is used for commutation detection, then rotor position can be detected, but sensing accuracy is lowered and malfunction may occur in extreme environments
Solution Approach 1:
The patent replaces the mechanical/electronic Hall sensor system with a signal processing-based sensorless detection system. Instead of using a physical sensor that can be affected by temperature and environmental factors, the system uses voltage signal analysis and hysteresis comparison to detect commutation points, thereby improving reliability in extreme environments while maintaining detection accuracy
3Device complexity
If the same hysteresis voltage is used in both starting and operating modes, then the detection circuit is simple, but commutation falls behind under weak magnetic or back electromotive force
Solution Approach 1:
The patent implements dynamic adjustment of hysteresis voltage based on motor operating conditions. The detection circuit switches between a first hysteresis voltage during starting mode and a second hysteresis voltage during operating mode. This dynamic adaptation allows the system to maintain accurate commutation timing across different operational phases without overly complicating the detection circuit
Solution Approach 2:
The patent changes the hysteresis voltage parameter according to the motor's operational state. During starting, a first hysteresis voltage is used that is suitable for initial commutation detection, while during normal operation, a second hysteresis voltage is applied. This parameter change enables accurate commutation detection under varying magnetic and back electromotive force conditions
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 enables precise commutation detection and improved motor efficiency across varying conditions, reducing errors and costs associated with sensor-based systems while maintaining consistent performance in mass production.
Implementation Method 1
a first hysteresis comparator having a first hysteresis voltage to compare a first input signal with a second input signal, and correspondingly output a first output signal according to a comparison result
Implementation Method 2
a second hysteresis comparator having a second hysteresis voltage to compare the first input signal with the second input signal, and correspondingly output a second output signal according to a comparison result
Data Source
AI summary
A motor driving device includes a first hysteresis comparator, a second hysteresis comparator, a logic circuit, a control unit, and an inverter circuit. The logic circuit receives a start signal or a start completion signal to output the first output signal as a commutation signal according to the start signal, or to output the second output signal as the commutation signal according to the start completion signal, clamps the second output signal by the first output signal, stops outputting the commutation signal after the potential state of the commutation signal is changed, and unclamps the second output signal with the first output signal and outputs the commutation signal in response to a difference voltage between the first input signal and the second input signal being greater than a positive value of the first hysteresis voltage or less than a negative value of the first hysteresis voltage.