Cooling control circuit for peltier element

• US 8,689,569 B2
• Filed: 09/21/2010
• Issued: 04/08/2014
• Est. Priority Date: 09/25/2009
• Status: Active Grant

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Uratani, Yutaka, Yamashita, Mikihiro
• Primary Examiner(s): Ali, Mohammad M
• Application Number:
  US13/393,021
• Publication Number:
  US 20120151940A1
• Time in Patent Office: 1,295 Days
• Field of Search: 62/32, 62/37, 622/592, 361/79, 361/86, 361/87, 374/13, 374/20, 324/522, 324/713, 257/E27.008, 257/930
• US Class Current: 62/3.2
• CPC Class Codes: G05D 23/1919 characterised by the type of controller
• CPC Class Codes: G05D 23/24 the sensing element having a resistance varying with temperature, e.g. a thermistor

Abstract

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.

Claims

1. A cooling control circuit for a Peltier element, the cooling control circuit comprising:

a current detection resistor used to detect current flowing to the Peltier element and including a first terminal, which is connected to the Peltier element, and a second terminal;

a first amplification circuit including;

a first operational amplifier having a non-inverting input terminal, which is connected to the first terminal of the current detection resistor, an inverting input terminal, and an output terminal;

a first resistor including a thermistor and connected between the inverting input terminal of the first operational amplifier and the output terminal of the first amplifier; and

a second resistor connected between the second terminal of the current detection resistor and the inverting input terminal of the first operational amplifier;

a second amplification circuit including;

a second operational amplifier having a non-inverting input terminal, which is connected to the first terminal of the current detection resistor, an inverting input terminal, and an output terminal;

a third resistor connected between the inverting input terminal of the second operational amplifier and the output terminal of the second amplifier; and

a fourth resistor connected between the second terminal of the current detection resistor and the inverting input terminal of the second operational amplifier; and

a current control circuit that receives output voltage of the second amplification circuit when the ambient temperature is greater than or equal to a predetermined temperature and controls the current flowing to the Peltier element so as to be constant based on the output voltage of the second amplification circuit, and receives output voltage of the first amplification circuit that is in accordance with the temperature characteristics of the thermistor when the ambient temperature is less than the predetermined temperature and controls the current flowing to the Peltier element based on the output voltage of the first amplification circuit.

2. The cooling control circuit according to claim 1, wherein the first and second amplification circuits are configured so that the output voltage of the second amplification circuit is greater than the output voltage of the first amplification circuit when the ambient temperature is greater than or equal to the predetermined temperature and the output voltage of the first amplification circuit is greater than the output voltage of the second amplification circuit when the ambient temperature is less than the predetermined temperature.

3. The cooling control circuit according to claim 1, wherein the first to fourth resistors have resistances set so that the output voltage of the second amplification circuit is greater than the output voltage of the first amplification circuit when the ambient temperature is greater than or equal to the predetermined temperature and the output voltage of the first amplification circuit is greater than the output voltage of the second amplification circuit when the ambient temperature is less than the predetermined temperature.

4. The cooling control circuit according to claim 1, wherein the temperature characteristics of the thermistor are set so that the current flowing to the Peltier element decreases as the ambient temperature decreases when the ambient temperature is less than the predetermined temperature.

5. The cooling control circuit according to claim 1, wherein the first amplification circuit amplifies a voltage that is proportional to the current detected by the current detection resistor in accordance with an amplification rate determined by a resistance corresponding to the temperature characteristics of the thermistor and a resistance of the second resistor, and the second amplification circuit amplifies the voltage that is proportional to the current detected by the current detection resistor with an amplification rate determined by resistances of the third and fourth resistors.

6. The cooling control circuit according to claim 5, wherein the temperature characteristics of the thermistor are set so that the current flowing to the Peltier element decreases as the ambient temperature decreases when the ambient temperature is less than the predetermined temperature.