Sensorless Motor Driving Circuit Using Dynamic Integration for Back-EMF Detection
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Solution Overview
Problem
Existing brushless DC motor systems face noise interference issues during zero-point detection of back EMF, leading to incorrect commutation points and motor malfunction, especially in environments with high temperatures, and require costly Hall sensors for accurate positioning.
Innovation Solution
A motor driving circuit and method that includes a starting unit, driving unit, floating phase selecting unit, hysteresis comparator, integration circuit, and control circuit to generate and compare floating phase and neutral point voltage signals, using integration to average noise and adjust integration time based on motor speed for precise commutation point detection without sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Hall sensor is used to detect rotor position for accurate commutation, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts and eliminates the Hall sensor from the motor control system, replacing sensor-based position detection with sensorless back-EMF zero-point detection. This removes the problematic component while maintaining the essential function of rotor position detection through alternative means (detecting zero points of back EMF voltage signals during commutation transitions).
Solution Approach 2:
The patent uses voltage sampling and signal processing to create an electrical representation of rotor position information without physical contact or additional sensors. By sampling phase voltages and detecting zero-crossing points of back-EMF signals, the system creates a virtual position signal that replicates the function of Hall sensor output without requiring the sensor hardware.
2Reliability
If noise filtering is increased to reduce voltage disturbances during zero-point detection, then reliability is improved, but response time increases
Solution Approach 1:
The patent implements dynamic adjustment of the integration time period based on motor operating conditions. The control circuit adapts the filtering duration according to motor speed and load conditions, using longer integration periods at lower speeds where noise has greater impact and shorter periods at higher speeds where response time is more critical. This dynamic approach maintains reliability while minimizing time loss across varying operating conditions.
Solution Approach 2:
The patent changes the integration time parameter dynamically based on motor operating state. By adjusting this parameter according to motor speed and commutation phase, the system optimizes the balance between noise filtering effectiveness and detection speed, ensuring reliable zero-point detection without excessive time delay.
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
This solution reduces noise interference and ensures accurate commutation point detection across varying speeds, eliminating the need for costly sensors and improving motor reliability and efficiency.
Implementation Method 1
an integration circuit configured to integrate the comparison result signal within a time period to generate an integration result signal
Implementation Method 2
a hysteresis comparator configured to compare the floating phase voltage signal with a neutral point voltage signal corresponding to the motor to output a comparison result signal
Data Source
AI summary
A motor driving circuit and a motor driving method are provided. The motor driving circuit is used to drive a motor, and includes a starting unit, a driving unit, a floating phase selecting unit, a hysteresis comparator, an integration circuit, a first comparator and a control circuit. The control circuit controls the floating phase selecting unit to select a floating phase to output a floating phase voltage signal, and controls, in response to an initial starting signal, the integration circuit to use a first integration time, and determine whether the motor has been successfully started. In response to a successful start, the control circuit controls the integration circuit to use a second integration time, and controls the starting unit to be switched to an operation mode to control the driving unit to drive the motor. The first integration time is greater than the second integration time.