Motor Control Circuit Noise Filtering via State Machine Validation
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Solution Overview
Problem
Existing BLDC motor control circuits face inaccuracies due to noise sensitivity in Hall effect sensors, leading to motor slowdowns and shutdowns, as they struggle to accurately determine the rotational position and speed of the motor.
Innovation Solution
An electronic circuit that includes a magnetic field sensing circuit, a position and speed sensing circuit, and a gate driver circuit, which generates qualified control signals based on valid state changes of magnetic field signals to drive the motor accurately, ignoring invalid state changes until the motor direction is correctly set, thereby reducing noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Hall effect sensors are used to sense motor rotation, then rotational position and speed can be detected, but noise sensitivity causes output glitches leading to inaccurate drive signals
Solution Approach 1:
A state machine is introduced as an intermediary between the Hall effect sensors and the drive signal generation. The state machine receives raw sensor signals, processes them through defined state transitions, and outputs validated position information. This intermediary filters out noise-induced glitches by only accepting state changes that conform to the expected rotational sequence, thereby resolving the contradiction between measurement precision and reliability.
2Ease of operation
If drive signals are generated based on sensed position, then motor control is achieved, but noise-induced inaccuracies cause motor slowdown and shutdown conditions
Solution Approach 1:
The state machine implements feedback by continuously monitoring the sequence of Hall sensor states and comparing them against expected rotational patterns. When noise causes an unexpected state transition, the feedback mechanism detects the inconsistency and prevents it from triggering incorrect drive signals. This feedback loop ensures motor operation stability while maintaining full control capability.
3Speed
If all state changes of magnetic field signals are processed, then real-time motor control is achieved, but invalid state changes due to noise lead to control errors
Solution Approach 1:
The state machine performs preliminary validation of state changes before they are used to generate drive signals. Each detected state change is checked against the expected rotational sequence in advance. Only validated state changes that conform to the predetermined state transition map are processed further. This preliminary action maintains real-time control response while filtering out invalid changes caused by 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
The solution ensures accurate sensing of rotational position and direction, even with large current steps or transients, preventing motor slowdowns and shutdowns by filtering out noise and ensuring precise motor control.
Implementation Method 1
A magnetic field sensing circuit responsive to a plurality of magnetic field sensing elements disposed to sense rotation of the motor and generates a respective plurality of magnetic field signals
Data Source
AI summary
Described embodiments provide an electronic circuit for controlling a motor. The electronic circuit includes a magnetic field sensing circuit responsive to magnetic field sensing elements disposed to sense rotation of the motor. The magnetic field sensing elements generate magnetic field signals, each having a state indicative of at least one of the rotational position and a rotation speed of the motor. A position and speed sensing circuit generates a signal representative of the rotational position of the motor and tracks state changes of the magnetic field signals. A gate driver circuit generates motor drive signals that drive the motor based upon the sensed rotational position. The position and speed sensing circuit generates a qualified control signal based upon a determined valid state change of the magnetic field signals. The gate driver circuit generates the motor drive signals based, at least in part, upon the qualified control signal.