Heater Power Control Using Variable PWM to Cut Noise
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Solution Overview
Problem
Current temperature control methods in semiconductor manufacturing equipment face challenges in reducing radio frequency noise and reactive power while maintaining precision, with phase angle control generating noise and degrading durability, and PWM control having limitations in response speed and precision.
Innovation Solution
A temperature control apparatus and method that uses a controller to supply power to a heater or cooler in variable periods with alternating on and off duty cycles, calculated based on a set temperature profile, incorporating a processor for PID control and zero-cross detection to minimize noise and reactive power, and optimize power efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase angle control method is used to continuously change output power value, then temperature control precision is improved, but radio frequency and noise are generated and reactive power increases causing power loss
Solution Approach 1:
The patent applies periodic action by using pulse width modulation (PWM) to switch the heater power supply on and off in periodic cycles. Instead of continuously varying output power like phase angle control, the system uses periodic switching with different duty cycles to achieve temperature control, thereby avoiding radio frequency and noise generation while maintaining control precision.
Solution Approach 2:
The patent substitutes the phase angle control mechanism with a PWM switching mechanism. By replacing the continuous power variation approach with discrete on/off switching controlled by duty cycle, the system eliminates the harmful radio frequency and noise effects while achieving equivalent or better temperature control precision.
2Loss of energy
If PWM fixed-period control is used to minimize reactive power, then reactive power is reduced, but control period becomes long and response speed decreases
Solution Approach 1:
The patent applies dynamics by making the PWM control period adaptive rather than fixed. The control system dynamically adjusts the period length based on the heater's thermal state and control requirements, allowing short periods for fast response when needed and longer periods for energy efficiency, thus resolving the contradiction between response speed and reactive power minimization.
3Measurement precision
If PWM variable-period control is used to improve control precision, then temperature control precision is improved, but the number of variable periods is limited and control precision decreases compared to phase angle control
Solution Approach 1:
The patent applies segmentation by dividing the temperature control range into multiple segments or zones, each with optimized PWM parameters. This allows the system to use different control strategies for different temperature ranges, achieving high precision across the entire control range while maintaining adaptability through the segmented approach.
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 effectively reduces noise and reactive power, enhances power efficiency, and maintains high precision in temperature control, preventing equipment degradation and improving control stability.
Implementation Method 1
a heater of which a temperature increases in response to receiving power
Data Source
AI summary
A temperature control apparatus includes a heater of which a temperature increases in response to receiving power, a power source supplying alternating current (AC) power to the heater, a temperature sensor sensing the temperature of the heater and outputting a measured temperature value, and a controller controlling the power supply to the heater so that the heater follows a set temperature profile, wherein the controller supplies the power to the heater for first one control period in a variable period consisting of a plurality number of times of control periods (on duty), and stops the power supply to the heater during remaining control periods until the variable period is finished (off duty).