JPS59139654A - Control circuit for temperature - Google Patents

Abstract

PURPOSE:To make the temperature of a material to be controlled such as a sample constant by connecting a current-heat conversion element to an output circuit for a complementary type transistor amplifier and applying the change of an electric signal based on the temperature change of a thermo-sensitive element to a control electrode for the amplifier. CONSTITUTION:A thermistor 2 is connected between the base-collector of a transistor 5 as a voltage dividing resistor, and determines base potential together with a variable resistance element 3 connected between the base of the transistor 5 and a negative power supply V<->. An emitter of the transistor 5 is connected to the negative power supply V<-> through a resistor RL1. Outputs from an amplification circuit are each applied to the positive and negative input terminals of a differential amplifier 6 through resistors RS1 and RS2. A feedback resistor RF determines the gains of an operational amplifier together with the input resistors RS1, RS2. An output from the operational amplifier is applied to each base electrode of an N-P-N type transistor 7 and a P-N-P type transistor 8 in common. A collector of the transistor 7 is connected to a positive power supply V<+> and a collector of the transistor 8 to the negative power supply V<->, each emitter is connected in common, and a Peltier element 9 is connected in between ground and transistors.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a temperature control circuit, and particularly to a temperature control circuit for semiconductor devices and the like.

[Background of the invention]

In recent years, semiconductor devices such as m-v compounds are increasingly being applied to communication systems, but in this case, the problem is that the device characteristics are highly dependent on temperature. −
Taking a GaAIS semiconductor laser as an example, it is known that the oscillation spectrum of the semiconductor laser changes with temperature fluctuations of around 1° C., which induces noise in optical fiber transmission. To solve such problems, it is necessary to keep the temperature of the device constant with high precision.

A small Peltier element is suitable for changing the temperature of a sample. Peltier elements can be cooled or heated depending on the direction of the current injected. Therefore, by controlling the injection current of the Peltier element, the temperature of the sample can be kept constant over a wide range of ambient temperatures. Conventionally, the injection current was switched using relays, switches, etc. However, when a relay switch is used, the device becomes complicated and large, and the driving power required for the device becomes large, which is not desirable especially in an optical communication system that uses a large number of light emitting elements.

[Purpose of the invention]

Therefore, an object of the present invention is to realize a temperature control circuit that keeps the temperature of the sample constant using an extremely simple and compact electric circuit.

[Summary of the invention]

In order to achieve the above object, the present invention provides a temperature control circuit equipped with a current/thermal conversion element capable of both heating and cooling depending on the polarity of injected power. The temperature of the object to be controlled, such as the sample, is kept constant by connecting the control electrode to the control electrode of the amplifier and applying a change in the electrical signal based on the temperature change of the thermosensitive element to the control electrode of the amplifier.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 1 shows the configuration of an embodiment of a temperature control circuit according to the present invention. In the figure, 1 is a sample whose temperature is to be kept constant, 2 is a thermistor which is a heat sensitive element, and 9 is a Peltier element which is an electric/thermal conversion element.

The thermistor is connected as a voltage dividing resistor between the base and collector of the transistor 5, and determines the base potential together with the variable resistance element 3 connected between the base of the transistor 5 and the torpedo tAv-. Further, the emitter of the transistor 5 is connected to the negative power supply V- via a resistor R1j. Transistor 4 and resistor RL2 have the same characteristics as the amplifier circuit including transistor 5, and are connected in parallel. Output of these amplifier circuits (emitter potential)
are connected to the differential amplifier 6 through resistors RH and Rsz, respectively.
is applied to the positive and negative input terminals of The feedback resistor RF together with the input resistor RS''y R52 determines the gain of the operational amplifier. The output of the operational amplifier is commonly applied to the base electrodes of the NPN transistor 7 and the PNP transistor 8. is connected to the positive power supply V+, the collector of the transistor 8 is connected to the negative power supply V-, their emitters are connected in common, and a Peltier element 9 is connected between the common connection point and ground.

In the above circuit, when the temperature of the semiconductor laser 1 is maintained at a predetermined value, the current flowing through the thermistor 9 is also constant, resulting in a thermally equilibrium state, that is, absorption of heat based on the difference between the sample 1 and the outside temperature. .

Radiation and heat radiation and absorption from the Peltier element are balanced. For example, the values of each circuit element may be set so that no current flows through the Peltier element 9 when the outside air temperature and the desired temperature To of the sample match.

Now, the temperature of sample 1 is the desired temperature T. When the temperature fluctuates, the temperature fluctuation causes a change in resistance due to the thermistor 2, and the base potential of the transistor 5 fluctuates. Since a constant reference voltage is applied to the base electrode of the transistor 4, the potential difference between the two voltages of the differential amplifier 6 decreases (in some cases increases), causing its output to vary. That is, when the temperature of the sample 1 changes to become higher than the desired temperature, a current is caused to flow through the Peltier element 9 in a direction to cool it. For example, if we cool the current flowing to the left in the diagram, when the temperature rises,
It is sufficient that the output potential of the differential amplifier 7 becomes low, cutting off the transistor 7 and making the transistor 8 conductive. It is also clear that when the temperature falls below the desired temperature To, the operation is opposite to that described above.

The desired temperature To of the sample, ie, the initial setting value, varies depending on the application for which the laser is used, ambient conditions, etc., but these can be arbitrarily set by adjusting the base voltage VR or the variable resistor 3.

FIG. 2 shows the measurement results of the ambient temperature T5, the sample temperature, and the current flowing through the Peltier element using the circuit of the above embodiment. It can be seen from this figure that the Peltier current ITE is switched when Ta=To.

In the embodiment shown in FIG. 1, the current switching drive circuit has been described as an example of a bipolar transistor, but it is clear that it may be constructed of an MO8 field effect transistor (FET).

That is, the gates and drains of the N-type MO8FET and P-type MO8FET are connected in common, a power supply is connected between both source electrodes, a Peltier element is connected between the drain terminal and the ground electrode, and a complementary amplifier circuit is constructed. It can be constructed in the same manner as in the above embodiment by converting the temperature fluctuation into the fluctuation of the gate electrode voltage.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the configuration of an embodiment of a temperature control circuit according to the present invention, and FIG. 2 is a diagram showing measurement results of ambient temperature, sample temperature, and current of an electrothermal conversion element according to the above embodiment. .

Claims (1)

[Claims] 1. In a temperature control circuit equipped with an electrothermal conversion element capable of both heating and cooling depending on the polarity of the injected current, conduction and interruption are controlled by an input signal, and the above-mentioned type/thermal conversion element is connected to the output circuit. 1. A temperature control circuit comprising a complementary 1-transistor circuit connected thereto and means for applying an electrical signal based on temperature fluctuations as the input signal of the transistor circuit.