Motor Driving Apparatus PWM Control Linearity
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Solution Overview
Problem
Existing motor driving apparatuses for fan motors experience reduced performance due to heat generation and friction losses, leading to non-linear rotational speed control and inefficient cooling in high-speed operations.
Innovation Solution
A PWM motor driving apparatus with a rotational speed control terminal and a switching circuit that adjusts the oscillator voltage slope to improve linearity between control input and rotational speed, using a capacitor and resistors to determine the slope and frequency of the oscillator voltage, and a digital pulse width modulator to generate control pulses for optimal fan motor operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the operation speed of LSI is increased to improve computation performance, then productivity is improved, but heat generation increases causing thermal runaway
Solution Approach 1:
The patent converts the harmful heat generated by high-speed LSI operation into a useful control parameter. By using temperature sensors to detect heat and feeding this information back to the fan motor control system, the harmful thermal effect is transformed into a beneficial cooling response, where the fan speed is automatically adjusted based on actual temperature conditions to prevent thermal runaway while maintaining computation performance
2Temperature
If a cooling fan is used to cool the LSI, then temperature control is improved, but the rotational speed control becomes non-linear due to heat generation and friction losses
Solution Approach 1:
The patent implements a feedback control system where temperature sensors continuously monitor the LSI temperature and fan motor rotation speed. This feedback information is processed by the control system to dynamically adjust the PWM duty ratio, compensating for non-linearities caused by heat generation and friction losses. The feedback mechanism ensures that the rotational speed control remains linear and accurate across different operating conditions, while maintaining effective temperature control
Solution Approach 2:
The patent changes the control parameter from direct rotational speed control to PWM duty ratio control based on temperature feedback. By using PWM modulation with variable duty ratios adjusted according to temperature conditions, the system achieves linear rotational speed control despite the non-linear effects of heat generation and friction. The parameter change allows the control system to compensate for losses and maintain precision across the operating range
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 provides improved linearity in rotational speed control and optimal correction characteristics, enhancing the motor driving apparatus's performance by adjusting the slope and frequency of the oscillator voltage, thus addressing the inefficiencies caused by heat generation and friction.
Implementation Method 1
a capacitor and a discharging resistor are connected in parallel between the first oscillator terminal and a ground; a charging resistor... to determine the slope and frequency of the oscillator voltage
Implementation Method 2
a switching circuit that turns off the first switch when an oscillator voltage that occurs at the first oscillator terminal reaches an upper-side threshold value, and that turns on the first switch when the oscillator voltage falls to a lower-side threshold value
Data Source
AI summary
A TH terminal receives an analog control voltage VTH which indicates a rotational speed. With a first platform, a capacitor and a discharging resistor are connected in parallel between an OSC terminal and the ground. A charging resistor and a first switch are arranged in series between the OSC terminal and a reference voltage line via which a stabilized voltage is supplied. When an oscillator voltage VOSC that occurs at the OSC terminal reaches an upper-side threshold VH, a switching circuit turns off the first switch. When the oscillator voltage VOSC falls to a lower-side threshold value VL, the switching circuit turns on the first switch. The oscillator voltage VOSC is compared with the voltage at the TH terminal, so as to generate a pulse-modulated control pulse S3.