Multi-Heater PWM Temperature Control With One Sensor
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Solution Overview
Problem
Existing heating apparatuses with multiple heaters struggle to maintain uniform temperatures across different areas due to varying heater impedances, leading to inefficiencies and increased complexity when using multiple temperature sensors for temperature control.
Innovation Solution
A heating apparatus and temperature control circuit that utilizes a single temperature sensor to regulate the powers of multiple heaters through a series of switches, ramp signal generation circuits, and pulse width modulation signals, ensuring a predetermined ratio between the average powers of the heaters to achieve uniform temperature levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If multiple temperature sensors are installed to ensure uniform temperatures of different heaters, then temperature uniformity is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent applies universality by using a single temperature sensor to control multiple heaters through PWM signals. The temperature sensor serves as a universal monitoring point for the entire heating system, while the controller distributes appropriate power signals to each heater based on its impedance characteristics, making one sensor perform the function that would traditionally require multiple sensors.
Solution Approach 2:
The patent changes the control parameter from direct temperature measurement at each heater to PWM duty cycle control. By adjusting the PWM duty cycle ratios according to heater impedance ratios, the system achieves uniform temperature distribution without needing multiple temperature sensors, thus resolving the contradiction between temperature uniformity and control complexity.
2Temperature
If multiple temperature sensors are installed to ensure uniform temperatures of different heaters, then temperature uniformity is improved, but manufacturing cost increases
Solution Approach 1:
The patent applies universality by using a single temperature sensor to control multiple heaters through PWM signals. The temperature sensor serves as a universal monitoring point for the entire heating system, while the controller distributes appropriate power signals to each heater based on its impedance characteristics, making one sensor perform the function that would traditionally require multiple sensors.
Solution Approach 2:
The patent employs a cost-effective approach by using a single inexpensive temperature sensor instead of multiple sensors. This reduces the overall manufacturing cost while maintaining temperature uniformity through intelligent PWM control that compensates for the limited sensing coverage.
3Device complexity
If heaters are coupled in parallel or series with a common power supply, then device complexity is reduced, but temperature uniformity deteriorates due to different heater impedances
Solution Approach 1:
The patent applies dynamics by transitioning from static power supply connection to dynamic PWM control. The system uses real-time temperature feedback and adjusts the PWM duty cycles dynamically for each heater based on its impedance characteristics, enabling temperature uniformity while maintaining relatively simple circuit connectivity.
Solution Approach 2:
The patent implements feedback control by using the temperature sensor to monitor the heating system state and adjusting the PWM signals accordingly. The controller receives temperature feedback and modifies the power distribution to each heater to achieve uniform temperatures, resolving the contradiction between control simplicity and temperature uniformity.
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
This solution allows for efficient and cost-effective temperature regulation of multiple heaters using a single temperature sensor, reducing complexity and manufacturing costs while maintaining uniform temperatures across different areas.
Implementation Method 1
a signal processor circuit, which is configured to operably sense a temperature to generate a temperature-related signal according to the temperature
Implementation Method 2
a first heater and a second heater; a first switch coupled in series to the first heater... to control a first output current flowing through the first heater
Data Source
AI summary
A heating apparatus includes: first and second heaters, first and second switches, first and second ramp signal generation circuits, a signal processor circuit, first and second comparison circuits, and a switch control circuit. The first and second ramp signal generation circuits generate first and second ramp signals according to first and second output currents, respectively. The signal processor circuit senses a temperature to generate a temperature-related signal. The first and second comparison circuits compare the first and second ramp signals with the temperature-related signal, to generate a first PWM signal and a second PWM signal for controlling the first and second switches respectively, to determine the first and second output currents so that there is a predetermined ratio between average powers of the first heater and the second heater.