Peltier Cooling Circuit With Temperature-Adaptive Current Control
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Solution Overview
Problem
Existing Peltier element cooling control systems face challenges in accurately controlling a small number of Peltier elements with a simple structure, especially when ambient temperature varies, leading to complex circuits and inhibited control due to lead wires and connectors, and result in insufficient generated voltage.
Innovation Solution
A cooling control circuit comprising a current detection resistor, first and second amplification circuits, and a current control circuit that uses operational amplifiers and thermistors to detect and control current based on ambient temperature, ensuring constant current at high temperatures and adjusting current based on temperature characteristics at lower temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If constant voltage control is used for Peltier elements, then the control circuit is simple, but the generated voltage is small and lead wires and connectors inhibit accurate control
Solution Approach 1:
The patent replaces voltage-based control with current-based control. By using a current control circuit that directly controls the current flowing through the Peltier element, the system eliminates the influence of lead wire resistance and connector contact resistance on control accuracy. The current control circuit measures the actual current through a detection resistor and adjusts the driving voltage accordingly, ensuring precise control regardless of connection variations.
Solution Approach 2:
The patent implements a feedback mechanism where the current control circuit continuously monitors the current flowing through the Peltier element using a detection resistor. The circuit compares the measured current with the target current and adjusts the driving voltage to maintain the desired current level. This feedback loop compensates for variations in lead wire resistance and connector contact resistance, ensuring accurate control.
2Measurement precision
If cooling control is adjusted according to ambient temperature, then cooling accuracy is improved, but the control circuit becomes complicated
Solution Approach 1:
The patent uses a thermistor to detect ambient temperature and automatically adjusts the target current value based on temperature characteristics. The control circuit includes a temperature detection section that converts temperature changes into resistance changes, which are then used to modify the current control setpoint. This allows the system to adapt to ambient temperature variations without requiring complex multi-mode control logic or additional switching circuits.
Solution Approach 2:
The patent integrates multiple functions into a single current control circuit. The circuit simultaneously performs current measurement, temperature compensation, and current regulation functions. The thermistor serves dual purposes as both a temperature sensor and a component that influences the control characteristics. This multi-functional design achieves temperature-adaptive control without significantly increasing circuit complexity.
3Device complexity
If the number of Peltier elements is small, then the device structure is simple, but the generated voltage is insufficient for accurate control
Solution Approach 1:
The patent employs a dynamic control approach where the driving voltage is continuously adjusted based on the actual current measurement. The current control circuit dynamically modifies the output voltage to maintain the desired current level, compensating for the low voltage generation capability of few Peltier elements. This dynamic adjustment ensures sufficient power delivery and control accuracy even with a small number of elements.
Solution Approach 2:
The patent introduces a current detection resistor as an intermediary element in the control loop. This resistor enables precise current measurement by converting current into a measurable voltage drop. The measurement signal is then used by the control circuit to adjust the driving voltage, effectively bridging the gap between the limited voltage generation capability and the required control precision.
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 allows for accurate and simple control of Peltier element cooling, maintaining constant current at high temperatures and adjusting current at lower temperatures to prevent freezing and ensure stable electrostatic atomization, thereby prolonging Peltier element life and maintaining effective condensed water generation.
Implementation Method 1
The first resistor includes a thermistor and connected between the inverting input terminal of the first operational amplifier and the output terminal of the first amplifier
Implementation Method 2
The first amplification circuit includes a first operational amplifier, a first resistor, and a second resistor. The first operational amplifier has a non-inverting input terminal, which is connected to the first terminal of the current detection resistor
Implementation Method 3
the cooling of Peltier elements is controlled to appropriately cool a discharge electrode and the moisture in the air. This generates condensed water on the discharge electrode
Data Source
AI summary
A Peltier element cooling control circuit that accurately controls a small number of elements with a simple structure. First and second amplification circuits are connected between a current detection resistor detecting current of a Peltier element and a current control circuit performing current control on the Peltier element based on voltage proportional to the current. One of two resistors determines the amplification rate of the first amplification circuit includes a thermistor. When the ambient temperature is equal to a predetermined temperature or greater, the output voltage of the second amplification circuit is supplied to the current control circuit to control the current of the Peltier element so as to be constant. When the ambient temperature is less than the predetermined temperature, the output voltage of the first amplification circuit is supplied to the current control circuit to control the current of the Peltier element in accordance with the temperature characteristics.