TEG Output Power Control Circuit Using PWM Duty Cycle Adjustment
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Solution Overview
Problem
Thermoelectric generators (TEGs) face challenges in dynamically maintaining optimal power extraction as temperatures and loads vary, requiring a method to control output voltage to maximize power delivery without complex electronics or digital processing.
Innovation Solution
An output power tracking control system using a switching voltage converter and pulse width modulator, where the duty cycle of pulses is adjusted based on the difference between the loaded output voltage and a predetermined fraction of the open circuit voltage (Voc), maintaining the loaded voltage within a tolerance range to achieve maximum power, typically at Voc/2, utilizing sample and hold circuitry, temperature sensing, and digital signal processing for calibration and linearization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex electronics or digital processing are used to dynamically maintain optimal power extraction, then power tracking precision is improved, but device complexity increases
Solution Approach 1:
The system uses the TEG's own open-circuit voltage as the reference signal for PWM control, eliminating the need for external voltage references or complex sensing circuits. The TEG automatically provides its own feedback signal when disconnected, enabling self-regulating maximum power point tracking without external processing electronics
Solution Approach 2:
The TEG is periodically disconnected from the load to sample its open-circuit voltage, creating a pulsed measurement cycle. This periodic disconnection allows the system to obtain reference voltage information without continuous complex monitoring, simplifying the control architecture while maintaining tracking accuracy
Solution Approach 3:
A capacitor is introduced as an intermediary energy storage element that maintains voltage during the TEG disconnection period. This capacitor bridges the gap between the TEG and load, allowing voltage sampling without requiring complex switching control or digital processing circuits
2Measurement precision
If the TEG is periodically disconnected to sample Voc, then voltage reference accuracy is improved, but power delivery continuity deteriorates
Solution Approach 1:
The TEG is disconnected briefly to sample its open-circuit voltage before reconnecting to deliver power. This preliminary sampling action occurs in advance of the power delivery phase, allowing the control system to prepare the appropriate duty cycle setting without interrupting the overall power transfer process
Solution Approach 2:
The system dynamically adjusts the duty cycle of the PWM signal based on the sampled Voc to maintain optimal power transfer. The switching converter continuously adapts its operation between the sampling phase and power delivery phase, optimizing performance throughout the cycle rather than using fixed parameters
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 system effectively maintains the loaded voltage at a predetermined fraction of Voc, ensuring maximum output power within a tolerance range, enhancing manufacturability and efficiency while being compatible with various loads and converter architectures.
Implementation Method 1
A thermoelectric generator (TEG) is configured to develop a voltage between an output terminal and a common terminal based on a temperature difference between hot and cold portions of the TEG
Data Source
AI summary
An output power tracking control system for a thermoelectric generator (TEG) is described. The output terminal of the TEG is coupled to the input terminal of the switching voltage converter. The system also includes control circuitry including a pulse width modulator (PWM) having at least one PWM output terminal coupled to the switching control terminal of the switching voltage converter. The PWM generates pulses at the PWM output terminal having a duty cycle that varies based on a difference between a loaded output voltage of the TEG and a predetermined fraction of an unloaded open circuit voltage of the TEG, Voc. The duty cycle of the pulses is configured to maintain the loaded voltage at the output terminal of the TEG to within a tolerance range of the fraction of Voc.