Heating Element Power Control Circuit
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Solution Overview
Problem
Temperature control systems often require closed-loop feedback, which is unnecessary in systems where thermal characteristics are known a priori, and existing solutions fail to efficiently manage power to heating elements with variable impedance loads.
Innovation Solution
An open-loop controller that generates constant power by measuring applied voltage and current, dispensing power in pulse trains of precisely controlled time periods, allowing for predictable temperature control without thermal feedback, using a microprocessor to adjust power on time based on instantaneous power and load resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If closed-loop control systems are used for temperature control, then temperature accuracy is improved, but system complexity increases due to required thermal feedback sensors and control circuitry
Solution Approach 1:
The patent extracts the temperature sensor and thermal feedback components from the system, creating an open-loop control architecture. The controller determines power delivery timing based on predetermined algorithms and load characteristics rather than real-time temperature feedback, thereby eliminating the complexity of closed-loop sensing and control while maintaining acceptable temperature control through mathematical modeling of the heating process
Solution Approach 2:
The patent changes the control parameter from real-time temperature feedback to timed power delivery pulses. By controlling the duration and timing of power delivery to the heating element based on predetermined algorithms, the system achieves temperature control without requiring temperature sensors or feedback circuitry, thus reducing system complexity while maintaining control accuracy
2Productivity
If power is continuously supplied to heating element, then heating efficiency is improved, but temperature control precision deteriorates due to thermal lag and overshoot
Solution Approach 1:
The patent implements periodic pulsed power delivery to the heating element rather than continuous power supply. The controller delivers power in controlled pulses with specific on-times and off-times, allowing the heating element to reach target temperatures efficiently while preventing thermal overshoot. This periodic action enables precise temperature control by adjusting pulse duration and frequency based on predetermined algorithms
Solution Approach 2:
The controller performs preliminary calculation of required power delivery timing based on desired temperature, load characteristics, and thermal properties before actual heating begins. By predetermined the optimal pulse timing and duration, the system prepares the exact power delivery schedule needed to reach target temperature without overshoot, improving both heating efficiency and temperature control precision
3Adaptability or versatility
If variable impedance loads are connected to power source, then system adaptability is improved, but power delivery stability deteriorates due to impedance variations
Solution Approach 1:
The patent implements current sensing feedback during power delivery pulses to monitor actual current flow through the heating element. The controller measures instantaneous current and uses this feedback information to adjust subsequent pulse timing and duration, compensating for variations in load impedance. This feedback mechanism maintains stable power delivery despite changes in heating element resistance due to temperature changes or manufacturing tolerances
Solution Approach 2:
The patent makes the power delivery timing dynamic rather than fixed, adjusting pulse on-times and off-times in real-time based on measured current and load conditions. The controller dynamically modifies the power delivery schedule to accommodate variable impedance loads, maintaining optimal heating performance across different operating conditions and load variations
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
Enables predictable temperature rise or differential in systems without thermal feedback, maintaining constant heat or power over time, even with varying load impedance, and can be applied to battery-powered systems with dropping voltage.
Implementation Method 1
a controller, a temperature sensor and a control element such as a resistive heater load
Data Source
AI summary
A control circuit and associated method for dynamically controlling power to one or more heating elements are provided. A power source supplies power to a load through one or more current pass elements, which is controlled by a control signal. A processor determines a time period (T) having a time cycle beginning at Ton and a Time cycle end at Toff, where the Time cycle end is less than the time period (T), variable, and generates the control signal or signals each time period (T), thereby electrically connecting the power source to the load and the current sensing element each time period (T) to dispense precisely predetermined quantities of energy per pulse.