JPH0812568B2 - Temperature control device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a temperature control device that operates stably over a wide temperature range for keeping the temperature of various elements, electronic parts, optical parts, etc. constant. Therefore, it can be used for temperature stabilization of high-precision oscillators that require constant temperature, electronic components and optical components that are easily affected by temperature.

2. Description of the Related Art A Peltier element is used as an electrothermal exchange element as a temperature control element in order to stabilize the temperature of electronic components and optical components. Since this element can be used for both heat absorption and heat generation depending on the direction of current, it is widely used as a thermostatic device. An example of a temperature control device using this Peltier element is shown in FIG. The temperature of the controlled object is detected by the thermistor 21, the error between the voltage and the reference voltage corresponding to the set temperature is detected by the detection unit 22, and the current amplified by the amplification unit 23 is controlled by the Peltier element 24. In this way, the temperature of the controlled object is stabilized (S.56.
Proceedings 2219).

Problems to be Solved by the Invention In the configuration of the conventional example, the temperature on the heat radiation side of the Peltier element,
If the temperature difference of the controlled object becomes large, the response to the temperature change becomes very slow.

These problems are that when the temperature difference between the radiating side of the Peltier element and the controlled part increases, the amount of heat flowing into the controlled part increases and the amount of heat is dissipated to the outside, and the Peltier element current increases. Become. Therefore, the Joule heat of the Peltier element itself increases, and the effective heat absorption on the heat absorption side of the Peltier element decreases. (In this system, the response speed to thermal fluctuation is the heat absorption / heat generation of the Peltier element. Quantity, the heat capacity of the controlled part, and the gain of the amplifier circuit).

Therefore, as an example, when the temperature of the controlled object is kept at about room temperature, when the outside air temperature or the heat radiation temperature becomes high, and as another example, the outside air temperature is about room temperature When you need to keep it at a low temperature,
The response becomes slow and the temperature controllability deteriorates.

The present invention has been made in order to provide a temperature control device which is stable and has good controllability in a wide temperature range.

Means for Solving the Problems According to the present invention, the gain of an amplifier circuit that amplifies a difference between a temperature detection element output and a reference value is variable according to a temperature difference between both ends of a Peltier element or a current flowing through the Peltier element. It is a temperature control device having a function to do.

Function As described above, the present invention changes the gain of the amplifier in response to the temperature difference across the Peltier element or the Peltier element current in order to maintain good temperature controllability over a wide temperature range, and thus the effective Peltier element is changed. By compensating for the fluctuation of the response speed due to the change of the amount of heat absorption and heat generation of the element, it is intended to always obtain good temperature controllability.

Practical Example FIG. 1 is a schematic block diagram of a temperature control device according to a first example of the present invention. One end of the Peltier element 1 is thermally coupled to the control target portion 4 surrounded by the heat insulating portion 5 via the heat sink 2, and the other end is thermally coupled to the heat radiation portion 3. The temperature at one end of the Peltier element 1 is detected by a first temperature detecting element 6 thermally coupled to the heat sink 2, such as a thermocouple, thermistor, or semiconductor temperature detecting element, and converted into a voltage by the first temperature detecting section 8. To be done. The temperature at the other end is detected by the second temperature detecting element 7 which is thermally coupled to the heat radiating section 3 and converted into a voltage by the second temperature detecting section 9. The output of the first temperature detection unit 8 and the output of the reference voltage generation unit 11 corresponding to the set temperature are input to the variable gain amplifier 12 having a differential input unit. In addition, the first temperature detection unit 8
Of the second temperature detector 9 is subtracted from the output of the second temperature detector 9 by the subtraction circuit 10, and according to the output of the subtraction circuit 10, the variable gain amplifier
Twelve gains are determined. The output of the variable gain amplifier 12 drives the Peltier element 1. At this time, the Peltier element current flows so that the output voltage of the first temperature detection unit 8 and the output of the reference voltage generation unit 11 coincide with each other, and as a result, the temperature of the control target unit 4 is kept constant. Also variable gain amplifier
The gain of 12 is (second temperature detector output)-
It is set to increase when the value of (first temperature detector output) is positive and increases.

At this time, for example, when the temperature of the controlled part is set to 25 ° C, the outside air temperature (which is considered to be almost equal to the temperature of the heat sink)
It is also assumed that the gain of the variable gain amplifier is optimally set at about 25 ° C. As the outside air temperature rises, a large amount of current flows through the Peltier element, and the Peltier element 1 absorbs the amount of heat flowing into the control target section 4 and heat is generated on the heat radiation section side. The amount of heat absorbed by the Peltier element 1 due to the Peltier effect increases in direct proportion to the current flowing through the Peltier element 1, but at the same time Joule heat is also generated. for that reason,
The effective increase in the amount of absorbed heat decreases as the Peltier current increases, and becomes zero at a certain current value. If the current value is increased from this, the amount of heat absorption will decrease.

As a result, when the outside air temperature rises, the Peltier element current increases and the effective amount of heat absorption decreases.

On the other hand, the response speed for correcting the temperature change of the controlled object portion is determined by the heat capacity of the controlled object portion including the heat sink and the effective heat absorption amount of the Peltier element 1. Further, in the negative feedback control system as in this example, the response speed also changes depending on the gain of the feedback amplifier, and the larger the gain, the faster the response. In the present embodiment, the delay of the response due to the reduction of the effective heat absorption amount of the Peltier element is compensated by increasing the gain of the amplifier.

In this example, the method of detecting the temperature difference between both ends of the Peltier element 1 and changing the gain of the amplifier has been described, but the effective heat absorption amount of the Peltier element also changes depending on the current flowing through the Peltier element. The case where the amount of heat absorption increases is defined as the positive direction of the current. Therefore, the same effect can be obtained by detecting the Peltier element current and changing the gain of the variable amplifier correspondingly. An embodiment in this case is shown in FIG. The difference from the first embodiment is that the gain of the variable gain amplifier 12 is changed by the output of the current detection section 13 instead of the second temperature detection element 7, the second temperature detection section 9 and the subtraction circuit 10. That is. Other than this, it is exactly the same as FIG. The advantage of this embodiment is that current detection is easier than temperature detection.

Next, as a third embodiment, FIG. 3 shows what can be realized with a very simple structure. FIG. 3 shows only a circuit diagram. The temperature is converted into a voltage by the temperature detection element 14 and the temperature detection unit 15 that detect the temperature of the controlled object part. The output of the reference voltage generator 16 which generates the reference voltage corresponding to the set temperature is connected to the input of the ordinary differential amplifier 17. On the other hand, the output of the temperature detector is connected to the input of the differential amplifier via the resistor 20. The amplifier output drives the Peltier element 18. A positive thermistor 19 for negative feedback is used to determine the gain of this system. The gain is the ratio of the resistance value of the positive thermistor 19 and the resistance value of the resistor 20.
This positive thermistor is thermally coupled to the heat dissipation plate of the Peltier element. In this case, assuming that the voltage of the reference voltage generator is constant (that is, when the set temperature is always constant), if only the temperature of the heat sink is detected, the temperature difference across the Peltier element will be You will understand. In this embodiment, the temperature of the heat sink is detected by the positive thermistor, and the gain of the amplifier is changed by utilizing the fact that the resistance value changes depending on the temperature. The gain increases as the heat sink temperature increases. Also, a similar function can be provided by using a resistor instead of the positive thermistor 19 and an ordinary thermistor instead of the resistor 20.

Further, as described above, the amount of increase in the heat absorption amount with respect to the increase in the current of the Peltier element becomes zero at a certain current value, but if a current larger than this amount flows into the Peltier element, the operation becomes unstable. In particular, in the present invention, the gain of the amplifier becomes large when the Peltier current is large, so if a slight temperature fluctuation occurs in that state, the Peltier current will transiently enter the unstable region in many cases. Therefore, by providing a current limiting mechanism so that the Peltier element current does not become larger than that value, it is possible to prevent the operation from becoming unstable.

Effects of the Invention As described above, according to the present invention, it is possible to provide a temperature control device that is stable and has good controllability over a wide temperature range.

[Brief description of drawings]

1 is a block diagram of a temperature control device according to an embodiment of the present invention, FIG. 2 is a block diagram of a temperature control device according to a second embodiment of the present invention, and FIG. 3 is a third embodiment of the present invention. FIG. 4 is a circuit diagram of the temperature control device of FIG. 4, and FIG. 4 is a circuit diagram of a temperature control device of a conventional example. 1 ... Peltier element, 4 ... Controlled part, 6, 7 ... First,
Second temperature detecting element, 11 ... Reference voltage generating section, 12 ... Variable gain amplifier, 13 ... Current detecting section.

Claims (2)

[Claims] Claim: What is claimed is: 1. Two temperature detecting elements for detecting temperatures at both ends of an electrothermal exchange element, and a difference between an output of a temperature detecting element on the temperature controlled side of the temperature detecting elements and a reference value. It has an amplifying circuit for amplifying and a temperature controlling electrothermal exchange element driven by the amplifying circuit, and the amplification degree of the amplifying circuit changes so as to increase when the temperature difference between both ends of the electrothermal exchange element increases. A temperature control device having a function to perform. 2. A temperature detecting element thermally coupled to a controlled object, an amplifying circuit for amplifying a difference between an output of the temperature detecting element and a reference value, and a temperature controlling electrothermal driven by the amplifying circuit output. With an exchange element, the amplification degree of the amplification circuit is
A temperature control device having a function of changing to increase when a current flowing through the electrothermal exchange element increases in a positive direction.