Hall Sensor Noise Suppression in PWM Brushless DC Motors
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Solution Overview
Problem
Hall-effect sensors in PWM-driven motor systems experience noise spikes due to the leading and trailing edges of PWM signals, which interfere with accurate rotational position and speed measurements.
Innovation Solution
A noise suppression method and circuit arrangement that precedes PWM drive signals by a predetermined time period, detects edges, and holds signal levels for a duration that covers the transient noise period, using a single substrate with integrated sampling, edge detection, and pulse generation circuits to isolate and eliminate noise from Hall-effect sensor outputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Hall-effect sensors are used to detect rotational position and speed in PWM-driven motors, then measurement capability is provided, but noise spikes are induced by PWM signal edges
Solution Approach 1:
The patent applies preliminary action by generating a preliminary PWM signal that precedes the actual PWM drive signal by a predetermined time period. This preliminary signal triggers edge detection and activates the noise suppression mechanism before the actual PWM edges occur, allowing the system to preemptively hold or filter the Hall sensor outputs during the expected noise periods, thus preventing noise spikes from corrupting the measurement signals.
2Productivity
If PWM drive signals are used to control motor speed, then motor control capability is improved, but transient noise appears on Hall-effect sensor outputs
Solution Approach 1:
The patent introduces an intermediary preliminary PWM signal that acts as a mediator between the main PWM drive signal and the Hall sensor readings. This intermediary signal triggers the edge detector circuit, which then activates the noise suppression logic. The intermediary mechanism allows the system to maintain full PWM motor control capability while reliably identifying and suppressing noise periods in the sensor outputs without directly interfering with the motor drive operation.
3Object-affected harmful factors
If noise suppression is implemented by holding signal levels during PWM edges, then noise is eliminated, but signal updates are delayed
Solution Approach 1:
The patent applies periodic action by using the regular, periodic PWM drive signal to trigger corresponding periodic noise suppression events. The preliminary PWM signal is generated at the same frequency and phase relationship as the main PWM signal, creating a synchronized periodic pattern. This allows the noise suppression to occur only during the necessary PWM edge periods while maintaining normal signal updating during non-PWM periods, thus minimizing overall time loss while effectively suppressing noise.
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
Effectively suppresses PWM-induced noise in Hall-effect sensor outputs, providing clean signals that accurately represent motor rotational position and speed without interference, enhancing the reliability of motor control systems.
Implementation Method 1
Hall-effect type sensors and amplifiers are utilized to generate signals to determine the rotational position and speed of the motor
Data Source
AI summary
A method and apparatus is provided for processing signals from a Hall-effect device arrangement coupled to a monolithic brushless DC motor where the motor is driven by a PWM circuit providing PWM drive signals.