JPH0521898Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a semiconductor laser device used in a compact disc player, a video disc player, or the like.

[Conventional technology]

In general, a semiconductor laser device used in an optical pickup of a compact disc player or a video disc player is configured such that a semiconductor laser element is housed in a case having a laser beam exit window, and a semiconductor laser element is housed in a case having a laser beam exit window. A driving current from a DC power supply is supplied to the laser element through the pin terminal, and the laser element oscillates to emit laser light through the emission window.

By the way, in conventional semiconductor laser devices of this type, a protection circuit consisting of a temperature sensor, a switch, and a control means for the switch is provided in order to ensure safe operation of the semiconductor laser element. When the ambient temperature is detected and the temperature of the laser element derived based on the detected temperature is equal to or higher than the safe operating limit temperature, the control means turns on or off a switch to cut off the energization path to the laser element. However, oscillation of the laser element is forcibly stopped to prevent damage caused by use at a temperature above the safe operating limit temperature of the laser element.

[Problem that the invention attempts to solve]

However, in this case, the protection circuit is created separately from the semiconductor laser device and then attached to the outside of the semiconductor laser device, which leads to an increase in the size of the device, and the protection circuit itself has many parts, making it expensive. There is a problem in that a surge current flows due to the switching of the switch in the protection circuit and damages the semiconductor laser device.

Therefore, the technical objective of this invention is to prevent damage to the semiconductor laser element due to oscillation at abnormally high temperatures with a small and simple configuration.

[Means for solving problems]

This invention was made with the above points in mind, and includes a metal support block inside the case, a heat resistance effect element with a positive characteristic fixed to the support block, and a heat resistance effect element with one side attached to the heat resistance effect element. and a semiconductor laser element to which the electrode surfaces of the semiconductor laser element are directly bonded, and the semiconductor laser element is connected via a path from the other electrode of the semiconductor laser element to the semiconductor laser element, the thermal resistance effect element, and the support block. This is a semiconductor laser device characterized by passing a driving current.

[Effect]

Therefore, according to this invention, when the temperature of the semiconductor laser element and the thermal resistance effect element becomes abnormally high, the resistance value of the thermal resistance effect element suddenly changes, and the drive current to the semiconductor laser element decreases. The oscillation of the semiconductor laser device is controlled to be below the oscillation threshold, and the oscillation of the semiconductor laser device is forcibly stopped.The drive current to the semiconductor laser device is cut off by a protection circuit installed outside the semiconductor laser device as in the past, and the semiconductor laser device is stopped. The thermal resistance effect element performs the same function as stopping the oscillation of a laser element, thereby preventing damage to the semiconductor laser element due to oscillation at abnormally high temperatures. Since one electrode surface of the element is directly bonded, the thermal coupling between the thermoresistance effect element and the semiconductor laser element is extremely high, and the electrical connection between the two elements is also established at the same time.

〔Example〕

Next, this invention will be explained in detail with reference to drawings showing embodiments thereof.

First, FIGS. 1 to 3 showing the first embodiment will be explained.

In FIG. 1, 1 is a cover plate that closes the rear surface of a case (not shown) having an exit window on the front surface; 2;
3 and 4 are connection pin terminals implanted on the rear surface of the cover plate 1, 5 is a metal support block fixed to the front surface of the cover plate 1 and electrically connected to the pin terminal 3, and 6 is the upper surface of the block 5. A positive characteristic thermal resistance effect element (hereinafter referred to as a POSISTOR) made of a valence-controlled semiconductor such as barium titanate [BaTiO ₃ ] is fixed to the front end; It is a semiconductor laser element provided in a case, and the upper electrode surface is connected to the pin terminal 2 by a lead wire 8. A current from the DC power supply flows through the path, and the laser element 7
is driven to cause laser oscillation, and laser light from the front end face of the laser element 7 is emitted through the exit window of the case.

Reference numeral 9 denotes a monitor photodiode, which is disposed behind the laser element 7 and fixed to the front surface of the cover plate 1 at a slight angle, and is connected to the pin terminal 4 via a lead wire 10.
It receives the laser light from the rear end face of the laser element 7, outputs an output monitor signal of the laser element 7, and, based on the monitor signal, controls the laser so that the output of the laser element 7 reaches a predetermined value. The drive current to the element 7 is controlled.

Note that the resistance value of POSISTOR 6 increases rapidly near the safe operating limit temperature of laser element 7, which is approximately 60 to 70°C.
It is assumed that the laser element 7 has temperature-resistance characteristics such that the drive current to the laser element 7 is controlled to be below the oscillation threshold.

By the way, the equivalent circuit of the laser element 7 and the POSISTOR 6 is shown in FIG. Current will be passed through it.

In addition, the temperature-resistance characteristic of a normal positive temperature coefficient thermistor is as shown in Figure 3, for example, and in the case of Figure 3, the resistance value increases rapidly when the temperature rises above 60 to 70 degrees Celsius. . However, the rate of change in resistance on the vertical axis in FIG. 3 indicates the ratio of the resistance value at each temperature when the resistance value at 25° C. is assumed to be "1".

Therefore, the resistance value of the POSISTOR 6 increases rapidly near the safe operating limit temperature of the laser element 7, so that when the ambient temperature exceeds the safe operating limit temperature of the laser element 7, the POSISTOR 6 and the laser element 7 When the temperature exceeds the safe operating limit temperature, POSISTOR 6
The resistance value of the laser element 7 increases rapidly, and the current flowing through the series circuit of the laser element 7 and the POSISTOR 6 shown in FIG.
below the oscillation threshold, the oscillation of the laser element 7 is forcibly stopped, and as the ambient temperature decreases, the temperature of the laser element 7 and the POSISTOR 6 decreases, and the resistance value of the POSISTOR 6 decreases. The drive current to the laser element 7 gradually increases, and the laser element 7 oscillates again.

At this time, the drive current to the laser element 7 decreases continuously due to the change in the resistance value of the POSISTOR 6, so the surge current caused by switching the switch of the conventional protection circuit does not flow to the laser element 7, and the surge Damage to the laser element 7 due to current can be prevented.

Furthermore, since the POSISTOR 6 and one electrode surface of the laser element 7 are directly bonded, the thermal coupling between the POSISTOR 6 and the laser element 7 is extremely high, and
Electrical connection between both elements 6 and 7 is also made at the same time.

[Effect of idea]

As described above, according to the semiconductor laser device of this invention, when the temperature of the semiconductor laser element and the thermal resistance effect element becomes abnormally high, the resistance value of the thermal resistance effect element suddenly changes and the resistance value to the semiconductor laser element becomes abnormally high. Since the driving current is controlled to be below the oscillation threshold of the laser device, the oscillation of the semiconductor laser device can be forcibly stopped. The thermal resistance effect element performs the same function as stopping the oscillation of the semiconductor laser element by cutting off the drive current to the laser element, and with its small size and simple configuration, it can be used to prevent abnormally high temperatures of the semiconductor laser element. It is possible to prevent damage to the semiconductor laser element due to oscillation, and also to prevent damage to the semiconductor laser element due to surge current when switching the switch of the protection circuit.

[Brief explanation of the drawing]

The drawings show an embodiment of the semiconductor laser device of this invention, and FIGS. 1 to 3 show the first embodiment. FIG. 1 is a right side view, FIG. 2 is an equivalent circuit diagram, and FIG. It is a temperature-resistance characteristic diagram of a POSISTOR. 6...Posistor, 7...Semiconductor laser element, 1
2...Thermistor.

Claims (1)

[Claims for Utility Model Registration] A metal support block within the case, a heat resistance effect element with positive characteristics fixed to the support block,
a semiconductor laser element with one electrode surface directly bonded to the thermal resistance effect element, and a path from the other electrode of the semiconductor laser element to the semiconductor laser element, the thermal resistance effect element, and the support block. A semiconductor laser device characterized in that a driving current for the semiconductor laser element is passed through the semiconductor laser element.