JPS61216384A - Apparatus for driving semiconductor light emitting element - Google Patents

Abstract

PURPOSE:To avoid breakdown of a semiconductor light emitting element caused by an excessive current by a method wherein respective electrodes of the semiconductor light emitting element and a photoelectric conversion element are connected to an integrated connector and this integrated connector is mated with a connector receptacle provided on the side of a control means. CONSTITUTION:A connector receptacle 29 with which a connector 25 is mated is provided in a driving circuit 22. Respective electrodes of a laser diode 26 and a P-I-N photodiode 27 are connected to the driving circuit 22 by an integrated connector 25 which is so designed as to make all terminals 24a, 24b and 24c connected or disconnected together in accordance with mating and unmating of the connector 25 with the receptacle 29. Therefore, such a situation hardly occurs that the terminal of the laser diode 26 is connected while the terminals of the P-I-N photodiode 27 are disconnected. Therefore, breakdown of the laser diode 26 caused by an excessive current can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a driving device for a semiconductor light emitting device that prevents a semiconductor laser or the like from being destroyed by overcurrent during attachment and detachment.

[Technical background of the invention and its problems] In recent years, optical information recording and reproducing devices that use a light beam to record on and reproduce information from a disc-shaped recording medium without using a magnetic head have attracted attention. Ta.

According to this optical information recording/reproducing device, since it is possible to record at high density, it is possible to store a large amount of information on a small-diameter recording medium (disk), and it also has the advantage of being able to read out at high speed. It has the potential to respond to increasing amounts of information. There is also an optical information reproducing device exclusively for reproducing information that uses a light beam to read out information recorded at high density. .

In the above-mentioned optical recording or reproducing apparatus, semiconductor lasers, which can be made compact and have a long life, are widely used as light sources.

The emission intensity of the semiconductor laser changes depending on the current flowing through the semiconductor laser and the temperature, so generally an automatic output & control (APC) circuit is used to monitor the emission output using an integrated bin photo. The current supplied to the semiconductor laser is controlled based on the signal detected by the diode, and the laser is maintained at an appropriate light output level.

FIG. 5 shows a conventional driving device 1 for a semiconductor light emitting device.

That is, the semiconductor laser 2 includes a laser diode 3 as a semiconductor light emitting element and a pin photodiode 4 as a semiconductor photoelectric conversion element that receives the light emission output of the laser diode 3.

The laser diode 3 is configured to be supplied with current from a constant current circuit 5 forming a laser drive circuit by attaching a connector 3A to which each electrode of the laser diode 3 is connected to a connector receiver 3B.

On the other hand, the pin photodiode 4 that receives the light emission output of the laser diode 3 connects the connector 4A to the connector receiver 4.
By attaching it to B, this photoelectric conversion output is connected to the other terminal of the resistor R1, one end of which is connected to the negative voltage terminal -E,
This output is applied to the grounded terminal and the output of the comparator (CM
P) Shift the potential of one input terminal A (eg, non-inverting input terminal) of 7.

The other input terminal B (for example, inverting input terminal) of this comparator 7 is connected to a grounded O potential and a negative potential -E through a resistor R2, Ra
The photoelectric conversion is compared with this reference level, and an error voltage corresponding to the deviation from this reference level is amplified by an amplifier (AMP) 8. It is input to circuit 5.

The constant current circuit 5 has a differential amplifier 5A and an output transistor 5B connected to its output terminal, and applies the output of the amplifier 8 to the inverting input terminal of the differential amplifier 5A. Therefore, the non-inverting input terminal of the differential amplifier 5B is grounded, and the non-inverting input terminal is connected to the output transistor 5 via the resistor R.
It is connected to the emitter of the amplifier 8 and inverts and amplifies the signal input from the amplifier 8 to control the current on the load side.

In other words, the input voltage is between zero level and below zero level (
The more the photoelectric conversion output shifts to the negative side (that is, the lower the photoelectric conversion output input to one input terminal of the comparator 7 is than the reference level), the larger the current is applied to the laser diode 3 connected to the connector receiver 3B, and the photoelectric conversion A negative feedback circuit is formed so that the output level is maintained almost at the reference level.

By the way, the semiconductor laser 2 has connectors 3A that can be attached and detached from the connector receivers 38 and 48 on the drive circuit side.
, 4A are properly installed and used, the laser diode 3 is controlled to provide an appropriate light emission output by the negative feedback circuit having the above-mentioned APC function.

However, in the above conventional example, the connector 3A,
4A is a separate connector receiver 3B.

4B, so for example connector 3
A is attached to connector receiver 3B, but connector 4
A situation may also occur in which connector A is not attached to connector receiver 4B. When the power is turned on in this situation, the reference potential level side at both input terminals A and B of the comparator 7 becomes a high level, so the constant current circuit 5 increases the current flowing to the laser diode 3 by the output of the comparator 7. do.

However, even if the light emitting output of the laser diode 3 increases and reaches the specified value, the input state of the comparator 7 does not change, and therefore, an even larger current flows through the laser diode 3. A runaway state occurs in which an excessive current flows, and the laser diode 3 is destroyed by the excessive current.

[Object of the Invention] The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a driving device for a semiconductor light emitting device that can prevent the semiconductor light emitting device from being destroyed by excessive current.

[Summary of the Invention] The present invention provides a drive circuit that connects an electrode of a semiconductor light emitting element and an electrode of a photoelectric conversion element that receives the amount of oscillated light of the light emitting element to an integrated connector, and controls the amount of oscillated light of the connector. By attaching the pixel elements to the connector receiver provided on the side, the pixel elements can be attached and detached at the same time, thereby making it possible to prevent the semiconductor light emitting elements from being destroyed by overcurrent.

[Embodiments of the invention] Hereinafter, the present invention will be specifically explained with reference to the drawings.

1 and 2 relate to a first embodiment of the present invention, FIG. 1 shows the circuit configuration of the driving device of the first embodiment, and FIG. 2 shows the external appearance of the semiconductor laser device in the first embodiment. show.

The (semiconductor laser) driving device 21 of the first embodiment includes a (semiconductor laser) driving circuit 22 and a semiconductor laser device section 23 that is detachably attached to the driving circuit 22.

This semiconductor laser device section 23 includes a semiconductor laser 24 and a connector 25 for connecting the semiconductor laser 24 to the drive circuit 3 via a lead wire connected to an electrode of the semiconductor laser 24.

The semiconductor laser 24 used in the first embodiment is generally widely available on the market, and has an external shape as shown in FIG.

In this semiconductor laser 24, a laser diode 26 as a semiconductor light emitting element and a bin photodiode 27 as a semiconductor photoelectric conversion element for monitoring are housed in the same package, and as shown in the circuit of FIG. A first terminal 24a that has both the anode of the laser diode 26 and the cathode of the bin photodiode 27 in common, and a second terminal 24b that is connected to the cathode of the laser diode 26.
.

The third one connected to the anode of the bin photodiode 27
A total of three terminals, terminal 24C, are pulled out.

The three terminals 24a, 24b, and 24c are each terminal 25a of the connector 25, which has three terminals 25a, 25b, and 25G via lead wires, respectively.

25b and 25C, respectively. It should be noted that these lead wires are braided wires so as to reduce noise mixed in.

On the other hand, the drive circuit 22 has a configuration as shown in FIG.
A connector receiver 29 to which the connector 25 is mounted is provided.

Each terminal 29a, 29b of the connector receiver 29.

29C is each terminal 25a, 25b of the connector 25.

25c can be connected.

The first terminal 29a of the connector receiver 29 is grounded,
The second terminal 29b is the output transistor 5 of the constant current circuit 5.
The third terminal 29c is connected to the collector of the comparator 7.
is connected to one input terminal A of the.

The circuit configuration of the drive circuit 22 except for the connector receiver 29 to which the connector 25 on the semiconductor laser 24 side is detachably attached is the same as that of the conventional example described above.

That is, when the connector 25 is attached to the connector 29, the output of the bin photodiode 27 is output to the comparator 7.
is applied to one input terminal A of the comparator 7, and compared with the reference potential level of the other input terminal B of the comparator 7. The difference between these re-input potential levels is detected by the comparator 7, and its output is input to the constant current circuit 5 via the amplifier 8, and flows to the laser diode 26 connected to the load side of the constant current circuit 5. Automatic output control is performed by controlling lfl and performing negative feedback so that the light emission output of the laser diode 26 becomes a constant value.

According to the first embodiment, when the electrodes of the laser diode 26 and the bin photodiode 27 are connected to and removed from the corresponding connector receivers 29 by using the integrated connector receiver 25, the terminals 24a, 24b, 24G are connected as a whole (rather than individually) or (rather than individually)
It is set to a state where it is not connected as a whole. Therefore, the situation where the laser diode 26 side is connected but the bin photodiode 27 side is not connected (which can occur in the conventional example) hardly occurs, and the laser diode 26 is not damaged by excessive current. It can be prevented.

Further, according to the first embodiment, there is an advantage that only one attachment/detachment operation is required.

FIG. 3 shows a second embodiment of the invention. The drive device 31 of this second embodiment is the connector 25 of the first embodiment. The connector receiver 29 is connected to a connector 32 consisting of five terminals. Next to the connector receiver 33.

Therefore, the first to third terminals 32 of the connector 32
a, 32b, 32c are connected to the semiconductor laser 24 as in the first embodiment, and fourth and fifth terminals 32d, 32e
are connected to each other.

On the other hand, in the connector receiver 33, the first. Third terminal 33
a, 33c are the same as in the first embodiment, and the second
The terminal 33b is connected to the fourth terminal 33d, and the fifth terminal 33
e is connected to the output transistor 5B.

Therefore, when the connector 32 is attached to the connector receiver 33, the bin photodiode 27 is attached to the first. Third terminal 328.
32C is connected to the corresponding terminals 33a and 33C, the operating state is set, but the laser diode 26 is connected to the corresponding terminal 33a, 33C.
In addition to the terminal 32a, the second. 4th. If the fifth terminal is not connected, no current will flow, so it is possible to more reliably prevent only the laser diode 26 side from being electrically connected, such as when the connection is insufficient.

FIG. 4 shows a third embodiment of the invention. In this third embodiment, the comparator 7 in the first embodiment is replaced by a window type comparator 7'. Therefore, the second reference potential ■2 is applied to the third input terminal of this comparator 7- via resistors R6 and R7, and this potential ■2 is higher than the reference potential (denoted as Vz) mentioned above. It's set at a fairly low level.

Therefore, when the level applied to the input terminal A is higher than the reference potential V2, this comparator 7'
The operation of the embodiment is performed, but when the level of the input terminal A is lower than the reference potential 'V2, the output of the comparator 7' becomes, for example, a high level state, and the inverting input terminal of the constant current circuit 5 passes through the amplifier 8. The laser diode 26 is held above the zero level.
This is to prevent current from flowing.

Therefore, when the connector 25 is connected, even if the terminal 25G connected to the 7th node of the bin photodiode 27
When the terminal 29G of the connector receiver 29 has a poor contact, the 1N current will not flow through the laser diode 26, so that the laser diode 26 can be protected.

Note that the present invention is not limited to the structure of the semiconductor laser 24 shown in FIG. 1 or FIG. It can be widely applied to devices that are connected to a connector receiver on the drive circuit side through a connector in which each electrode with a conversion element is integrated.

Further, the semiconductor light emitting device is not limited to a laser diode, but can be similarly applied to a light emitting diode used in cases where a weak light emission output is sufficient, such as in the case of reproduction, for example. Further, the configuration of the drive circuit that controls the light emission output is not limited to that shown in the drawings, and other circuit configurations can be widely applied.

[Effects of the Invention] As described above, according to the present invention, a semiconductor light emitting device;
Since the light receiving element that monitors the light emitting output of the semiconductor light emitting element is connected to the drive circuit that controls the amount of oscillated light of the light emitting element through an integrated connection means, only the semiconductor light emitting element side is electrically connected. It is possible to reliably prevent connections from occurring. Therefore, it is possible to prevent the semiconductor light emitting device from being destroyed by excessive current flowing through it.

[Brief explanation of drawings]

1 and 2 relate to a first embodiment of the present invention, FIG. 1 is a circuit diagram showing the configuration of the first embodiment, FIG. 2 is a perspective view showing a semiconductor laser device section, and FIG. 3 is a circuit diagram showing the configuration of the first embodiment. FIG. 4 is a circuit diagram showing a second embodiment of the invention, FIG. 4 is a circuit diagram showing a third embodiment of the invention, and FIG. 5 is a circuit diagram showing a conventional example. 5... Constant current circuit 7... Comparator 8... Amplifier 21... Semiconductor laser drive device 22... Drive circuit 23... Semiconductor laser device section 24... Semiconductor laser 25... Connector 26...Laser diode 2
7...Bin photodiode 29...Connector receiver Fig. 1 2I Fig. 2 Fig. 3

Claims (1)

[Claims] A semiconductor light emitting element, a photoelectric conversion element that converts a part of light from the semiconductor light emitting element into an electrical signal, and a control means that controls the amount of oscillated light of the semiconductor light emitting element to an appropriate amount using the electrical signal of the photoelectric conversion element. In the driving device for a semiconductor light emitting element, an integrated connector is provided to which the electrode of the semiconductor light emitting element and each electrode of the photoelectric conversion element are connected, and the connector is mounted on a connector receiver provided on the control means side. A driving device for a semiconductor light emitting device, characterized in that: