JPS5965324A - Temperature control circuit - Google Patents

Abstract

PURPOSE:To decrease power consumption, by cutting off a current to a Peltier element in case the input detection voltage is set between two different levels of comparison voltage. CONSTITUTION:A Peltier element 5 which performs endothermic and exothermic functions is provided between transistors TR1-3 and TR2-4 which constitute a differential amplifying circuit. A power supply +V is connected to an end of the element 5, and the differential amplifying circuit is driven by the detecting voltage VD to control an optical element, for example, to a prescribed temperature. The voltage VD is compared with comparison voltage Vr1 and Vr2 (Vr1>Vr2) through DC amplifiers 6 and 7 and then amplified to drive TR1-4 of the differential amplifying circuit. In this case, the TR2 and the TR4 of one side are driven through constant voltage diodes 8 and 9. Thus the element 5 can have three modes, i.e., both positive and negative directions (cooling and heating states) and an off-state, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control circuit for a temperature control element, and more particularly to a control circuit used for heating and cooling control of a temperature control element to keep the temperature of an element constant in an optical communication system.

Conventionally, temperature control VC of elements in optical communication systems,
In this case, a thermoelectric cooling element is used, which is small in size and easy to incorporate into a circuit, and is mainly used for stabilizing the characteristics of the laser diode (the amount of light output per oscillation wave, etc.). #:
fVc% long wavelength? In the case of i (1.3 μm to 1.6 μm) laser diodes, there is little practical experience of the element itself.
x (s) Due to the rapid deterioration of the threshold current and the large temperature coefficient, cooling has been a necessary condition for reducing the characteristics. As the IG system progresses and is introduced, single-mode fibers with a wide transmission band are used for a long time, and a strange problem arises. The Mototomonobu system using fiber optics requires high Vc precision. ゛ The core diameter of single mode fiber is about 10 μm, which is about 10 μm compared to that of multimode fiber.
This is because when the laser source is incident on the order of 15 degrees, it becomes extremely unstable due to mechanical deviations in one position due to temperature and temperature fluctuations in the oscillation transverse mode of the laser diode. In addition, the laser diode VC has wavelength temperature dependence (for example, a laser diode with a diameter of 1.3 μm has a
There is a wavelength fluctuation of ~5A/"O), and the wavelength characteristics of the loss of the transmission line (the fiber loss differs depending on the wavelength) and the wavelength characteristics of the band (the fiber transmission band differs depending on the wavelength). Transmission characteristics change significantly with temperature than K. In particular, in long-distance, large-capacity optical transmission systems, loss fluctuations and band fluctuations become a problem, so stabilizing the wavelength of the laser diode is also an important element. .

Therefore, recently there has been a demand for temperature control to keep the temperature constant by lowering the temperature of the laser diode.

The electronic cooling device used to control the temperature of elements such as laser diodes is usually a custom-made Beltier device that utilizes the Beltier effect. This element has the property of absorbing heat and generating heat, and by changing the direction of the current flowing through the element, it can perform both cooling and heating effects.

The path for controlling the electronic cooling element is shown in Figure 1 (
One circuit as shown in a) and (b) is used. Figure (a) shows the positive and negative power supply voltages (±v)? 11- In the example used, transistors 1 and 2 are fully connected to the non-inverting and inverting side output terminals of the DC amplifier 6, which uses the detection voltage VD and comparison voltage vr for temperature control detected from the semiconductor laser device as input signals, respectively. This is a circuit that completely changes the current flowing through the reversible thermoelectric cooling element (Bertier element) 5 at the same level and in magnitude.This circuit allows the control circuit to be constructed relatively easily and is considered to be economical. A temperature control circuit using a Beltier element requires a 5R current of about IA, which makes it uneconomical to prepare two high-output power supplies. Figure (b) shows a single power supply. In this example, the voltage (+v)i is used, and the circuit includes two differential transistor circuits and a constant voltage diode 8.9, and changes the direction and magnitude of the current of the Bertier element 5. In this case, the transistor 2.
4, the current flowing from the power supply is always a certain amount (the maximum required current of the Beltier element) regardless of whether there is a current flowing through the Beltier element (the magnitude of the detection voltage VD).
Therefore, from the point of view of energy saving, it is unsuitable for use in the latest optical communication systems.As mentioned above, conventional temperature control circuits require positive and negative class 2A power supplies, and even with a single power supply, it is not suitable for use in the latest optical communication systems. The drawback was that the current consumption was large.

SUMMARY OF THE INVENTION An object of the present invention is to provide a temperature control circuit that overcomes the above-mentioned drawbacks.

According to the present invention &CL, the first and second transistors whose one ends are connected to the power supply VC and form a differential amplifier circuit, and the front iL[G1 . The other end of the second transistor is connected to VC, and one end of the second transistor is connected to an element that performs heat absorption and heat generation, and is grounded to form a differential amplifier circuit. a fourth transistor; third and fourth transistors are connected to the other ends of the first and second transistors, respectively, and control signals are applied to the emitters of the transistors; In the temperature control circuit that controls the predetermined temperature of the optical system element, the detection signal corresponding to the temperature of Motogaku Yuiko and the first comparison voltage obtained by fully considering the temperature characteristics of Kuyuko A first DC amplifier that detects the detection signal and a second DC amplifier that compares and detects the detection signal with a second comparison voltage that is smaller than the first comparison voltage and is obtained by fully considering the anal characteristics of Yuiko Motogaku. The outputs of the two DC amplifiers cause the first and fourth transistors to conduct, and the second and fourth transistors to conduct. , a first state in which the third transistor is non-conductive, a second state in which all the first to fourth transistors are non-conductive, and a second state in which the first and fourth transistors are non-conductive and the second and third transistors are non-conductive. There is obtained a temperature control circuit characterized in that the temperature control circuit is controlled to one of the third states in which the transistor becomes conductive.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.

FIGS. 2(a) to 2(d) are circuit diagrams showing embodiments of the temperature control circuit of the present invention, and FIGS. 3(a) to (c) show operating states of the transistor circuit section in the circuit of FIG. Diagram for explanation,
FIG. 4 is a diagram for explaining the switching operation of each transistor for input detection width EEvDVc.

FIG. 2(a) In this example, the comparison voltage vr1°V, which is determined by fully considering the temperature dependence of the laser source, is used in the IC.
rz s (Vr, )Vr2) and semiconductor laser x
Two DC amplifiers 6 whose output polarities are opposite to each other are compared and detected with the detection voltage vD input from w, and are controlled by their outputs to completely control the magnitude and magnitude of the current f flowing through the Bertier element 5. NPN transistors 1 to 4,
Pace side of transistor 2.4 [connected image width mIJ
It consists of a limited voltage regulating diode 8°9.

In the above temperature control circuit, the detection voltage VD is the specific soft voltage Vr.
When the voltage (>Vr2) is large, the output of DC amplifier 6 is at a low level, and the output of DC amplifier 7 is at a high level.At this time, transistors 1 and 4 are turned on, transistors 2 and 3 are turned off, and the Beltier wire 5Vc current is turned on. In Figure 3 (a), the flow of the nru' turtle flow is in the direction of the bow. Of course, the magnitude of this current is controlled by the base voltage of the transistor 1.4, that is, the magnitude of the detection voltage vD. Detection voltage VD
When A is smaller than the comparison voltage vr, (<Vr, . Therefore, the electric current flowing through the Bertier element 5 flows in the direction shown in FIG. 3(b). When the detected l voltage vD is at a level between the comparison voltages vr1 and vrl, the outputs of the DC amplifiers 6 and 7 are both low level, and the transistor 1
~4 are all UFi='' Therefore, Fig. 3 (c
), no current flows through the circuit.

The operation of transistors 1 to 4 with respect to the magnitude of detection voltage Vu in the three cases described above is summarized as shown in FIG.
Since all transistors are OFF when the size is between 511? −, no current flows and no current is supplied from the power supply. Therefore, do not waste energy.

Figure 2(b) is a circuit in which the output polarity of the DC amplifier and the direction of the foot voltage diodes in Figure 2(a) of the VC are reversed, and transistors 1 to 4 are all replaced with PNP type ones, and the detection voltage vD1C is It is clear that the operations of transistors 1 to 4 and the current flowing through Peltier element 5 are exactly the same as in the circuit of FIG. 2(a).

Fig. 2(C) shows a circuit using a circuit 7 having two output terminals with different polarities in the DC booster 6.7, a transistor 1.3kPNP type, and an NPN type transistor 2.4, and detects a voltage VD. Transistor 1 for the size of
The operations in steps 4 to 4 are exactly the same as those shown in FIGS. 2(a) and 2(b) described in MiJ.

Figure 2(d) shows transistors 1 and 3 in Figure 2(c).
In this circuit, transistors 1 to 4 are NPN type and 2.4 transistors are PNP type, and the polarity of the base voltage of each transistor is reversed.
The operation is exactly the same as in the case shown in FIG.

As explained above, the temperature control (b) path according to the present invention is
The temperature dependence of the laser source is fully taken into account with two different sizes.
Using two comparison voltages, when the level of the input detection voltage is between the two comparison voltages, all the transistors that control the current to the Bertier element are turned off, making it economical because no current flows from a single power supply. An optical communication system can be realized.

[Brief explanation of the drawing]

1(a) and 1(b) are schematic diagrams showing examples of conventional temperature control circuits, FIGS. 2(a) to 2(d) are circuit diagrams showing embodiments of the temperature control circuit of the present invention, and FIG. Figures (a) to (C) are the second
FIG. 4 is a diagram for explaining the operation of the transistor circuit in the figure, and FIG. 4 is a diagram for explaining the switching operation of the transistor with respect to the detected voltage. 1.2.3.4... Group transistor, 5...
Beltier I-ko, 6.7...DC amplifier, 7,8
・National voltage diode. (aan<b) leather I prisoner (d) 1st 21i (C) θF Vr2jishichiga'VQ

Claims (1)

[Claims] The first and second transistors, whose one ends are connected to the power supply VC and form a differential amplifier circuit, and the first transistor in iJ.
It includes an element that is connected to the other end of the second transistor and performs a heat absorption/heating action, and a third and fourth transistor whose one end is coupled and grounded to form a differential amplifier circuit. ．． The other ends of the fourth transistor are all connected to the other ends of the first and second transistors 7'1. connection,
In a temperature control circuit that applies a control signal to the emitter of each transistor to control the temperature of all optical elements to a predetermined temperature, a detection signal corresponding to the temperature d of the optical element and a custom temperature of the optical element are taken into consideration. a first DC amplifier that performs total comparison detection with a comparison voltage of Ml set by The output of the two DC amplifiers causes the first and fourth transistors to pass through four times, and the second and third transistors to become non-conductive. 6. The first state, the second state in which all transistors are non-conducting VC, and the first state. The fourth transistor is non-conducting and the front d
Pi 2nd. A temperature control circuit characterized in that the third transistor controls any one of four third states.