Peltier Cooling Circuit Using Thermistor-Adjusted 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 due to the influence of lead wires and connectors, and require complex circuits to adjust for ambient temperature, leading to inefficient cooling and potential damage from high or low temperatures.
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, allowing for constant current control at high temperatures and temperature-dependent current control at low temperatures, thereby simplifying the structure and extending Peltier element life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If constant voltage control is used for Peltier elements, then the control method is simple, but the generated voltage is small and lead wires and connectors affect and inhibit accurate control
Solution Approach 1:
The patent replaces voltage control with current control. By using a current control circuit that detects the actual current flowing through the Peltier element and adjusts it accordingly, the system achieves accurate control independent of lead wire and connector resistance. This substitution of control parameter (from voltage to current) resolves the contradiction between simplicity and accuracy.
2Measurement precision
If cooling control is adjusted according to ambient temperature, then accurate temperature control is achieved, but the circuit becomes complicated
Solution Approach 1:
The patent employs a thermistor with specific temperature characteristics that automatically adjusts the control signal based on ambient temperature. The thermistor's resistance changes with temperature, and this change is directly translated into appropriate current control signals without requiring external temperature sensors, microcontrollers, or complex switching circuits. This self-adjusting mechanism achieves accurate temperature-dependent control while keeping the circuit simple.
3Quantity of substance
If a small number of Peltier elements are used, then the device size is reduced, but the generated voltage is small and accurate control is inhibited
Solution Approach 1:
The patent substitutes voltage-based control with current-based control. The current control circuit directly measures and regulates the current through each Peltier element, making the control accuracy independent of the total voltage generated by the limited number of elements. This approach enables precise control of small numbers of Peltier elements by focusing on current regulation rather than voltage generation.
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 enables accurate and efficient cooling control of Peltier elements, ensuring stable operation across varying temperatures, preventing damage from high temperatures and maintaining effective condensed water generation for electrostatic atomization, while simplifying the circuit structure and eliminating the need for microcomputers.
Implementation Method 1
The first resistor (R2) 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
In the prior art, Japanese Laid-Open Patent Publication No. 2006-26629 describes controlling the cooling of Peltier elements to generate condensed water from the moisture in the air
Data Source
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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 (2, 3) are connected between a current detection resistor (R1) detecting current of a Peltier element and a current control circuit (IC) performing current control on the Peltier element (1) 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 (3) is supplied to the current control circuit (IC) to control the current of the Peltier element (1) so as to be constant. When the ambient temperature is less than the predetermined temperature, the output voltage of the first amplification circuit (2) is supplied to the current control circuit (IC) to control the current of the Peltier element (1) in accordance with the temperature characteristics.