Motor Speed Control Circuit Temperature Compensation
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Solution Overview
Problem
Conventional motor speed control circuits fail to maintain a constant rotation speed of fan motors relative to temperature changes, even when a PWM signal is input to minimize speed, leading to inefficient cooling of CPUs due to varying motor speeds with temperature fluctuations.
Innovation Solution
A motor speed control circuit that includes a voltage generating circuit to adjust reference and speed voltages based on temperature, a comparison circuit to match speed voltage to reference voltage, and a driving circuit to control motor speed, ensuring linear speed control relative to PWM duty ratio and temperature changes, with the ability to reduce motor speed to zero when the PWM duty ratio is zero.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional motor speed control circuit is used, then the motor speed can be controlled relative to PWM duty ratio, but the rotation speed changes as temperature changes even when PWM duty ratio is constant
Solution Approach 1:
The patent changes the reference voltage parameter based on temperature to compensate for motor speed variations. Specifically, the reference voltage is adjusted according to temperature changes so that the motor speed remains stable despite temperature fluctuations, resolving the contradiction between speed control and speed stability.
2Use of energy by moving object
If the PWM duty ratio is set to minimize motor speed, then energy consumption is reduced, but the motor speed still varies with temperature changes
Solution Approach 1:
The patent adjusts the reference voltage parameter according to temperature even when PWM duty ratio is at minimum, preventing unwanted motor speed variations while maintaining low energy consumption state.
3Stability of the object's composition
If temperature compensation is added to maintain constant speed, then speed stability improves, but device complexity increases
Solution Approach 1:
The patent merges the temperature compensation function into the existing reference voltage circuit. The reference voltage is generated by combining a basic reference voltage with a temperature-dependent voltage component, achieving speed stability without adding separate complex compensation circuits.
Solution Approach 2:
The reference voltage circuit serves multiple functions: providing the basic reference for PWM comparison and simultaneously providing temperature compensation. This multi-functionality achieves speed stability without increasing overall device complexity.
Data Source
AI summary
A motor speed control circuit includes: a voltage generating circuit configured to change either a reference voltage corresponding to a target rotation speed of a motor or a speed voltage corresponding to a rotation speed of the motor, according to a temperature, and output the reference voltage and the speed voltage, either one of which is changed; a comparison circuit configured to compare the speed voltage output from the voltage generating circuit with the reference voltage output from the voltage generating circuit; and a driving circuit configured to drive the motor so as to match a level of the speed voltage to a level of the reference voltage, based on a comparison result from the comparison circuit.