Rotation Speed Detection Circuit for Brushless Motor Drive
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for lead angle control in brushless motor drive control are affected by switching noise and instability due to the use of phase current sensing resistors, leading to inefficiencies in motor drive efficiency.
Innovation Solution
A rotation speed detection circuit that generates an internal clock signal based on a Hall signal or FG signal, allowing for precise digital data signal output without relying on phase current sensing resistors, enabling stable lead angle control and improved motor drive efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If phase current sensing resistors are used for lead angle control, then motor output torque control is achieved, but switching noise affects stability and control performance
Solution Approach 1:
The patent extracts the rotation speed detection function from the phase current sensing resistor circuit and implements it through a dedicated rotation speed detection circuit that counts pulses of the period signal. This separates the speed detection function from the current sensing function, eliminating the noise interference that affected the combined approach.
Solution Approach 2:
The patent introduces an intermediary rotation speed detection circuit that uses a counter to count pulses of the period signal generated by Hall sensors or FG sensors. This intermediary circuit provides a clean digital signal for lead angle control without being directly affected by the switching noise in the power circuit.
2Ease of operation
If phase current sensing resistors are used for lead angle control, then motor torque control is achieved, but switching noise causes instability
Solution Approach 1:
The patent replaces the analog measurement approach using phase current sensing resistors with a digital counting approach. The rotation speed detection circuit counts pulses of the period signal and generates digital data signals that are used for lead angle control, eliminating the analog noise susceptibility of the resistor-based method.
3Measurement precision
If internal clock signal with predetermined number of pulses is generated, then rotation speed detection precision is improved, but device complexity increases
Solution Approach 1:
The rotation speed detection circuit uses the existing period signal from Hall sensors or FG sensors that are already part of the motor control system. The counter unit reuses these signals to generate rotation speed information, eliminating the need for separate sensing components and minimizing additional circuit complexity.
Solution Approach 2:
The patent changes the parameter being measured from phase current (analog) to period signal pulses (digital). By counting the number of pulses in a predetermined time period or measuring the period between pulses, the system achieves precise rotation speed detection using digital logic rather than analog sensing.
Data Source
AI summary
A rotation speed detection circuit includes an internal clock generation portion which receives an input of a period signal whose period varies in accordance with rotation speed of a motor and generates an internal clock signal having a predetermined number of pulses in one period of the period signal, and an internal clock counter portion which counts the number of pulses of the internal clock signal for a predetermined period every one period of the period signal and delivers a count value thereof as a digital data signal.