JPH06215399A - Detecting circuit for life of laser diode - Google Patents

Abstract

PURPOSE:To obtain a detecting circuit for the life of a laser diode capable of detecting the life of the laser diode with proper timing. CONSTITUTION:A current detecting means R1 is connected between a power source Vcc and a laser diode and detects the amount of currents flowing through the relevant laser diode. A comparing means 24 outputs a prescribed signal when the amount of currents detected by the current detecting means R1 exceeds a prescribed value.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a laser diode (L
D) The life detection circuit.

[0002]

2. Description of the Related Art Conventionally, an LD for projecting light is incorporated in an optical pickup such as a CD player. The LD deteriorates as it is used, and the luminous intensity of the LD decreases. Therefore, L
The driver circuit that drives D increases the amount of current flowing through the LD when it detects a decrease in the luminous intensity of the LD, and maintains a predetermined luminous intensity. When the deterioration of the LD further progresses (about 5000 hours), the light emission is stopped and the data cannot be read out. In the case of the CD player, the sound jump occurs or the reproduction becomes impossible at the end, so the LD is replaced.

[0003]

However, the conventional device incorporating the LD has the following problems. For example, in the case of a CD player, since the circuit for detecting the life of the LD is not provided, the life of the LD cannot be detected until a sound jump or a reproduction impossible state occurs. for that reason,
There is a possibility that a sound jump or a non-reproducible state may occur while reading important data or reproducing sound. Therefore, the present invention can detect the life of the LD at an appropriate timing.
It is an object of the present invention to provide a life detection circuit of the.

[0004]

In order to solve the above problems, the present invention has the following constitution. That is, a current detection means connected between the power supply and the laser diode for detecting the amount of current flowing through the laser diode, and a predetermined signal when the amount of current detected by the current detection means exceeds a predetermined value. And a comparison means for outputting. For example, the current detecting unit may be a resistor that converts a current flowing through the laser diode into a voltage, and the comparing unit may use a comparator that compares the voltage appearing across the resistor with a reference voltage. Further, the comparator may be provided with a reference voltage adjusting means for adjusting the reference voltage.

[0005]

[Operation] The operation will be described. The amount of current flowing through the laser diode is detected by the current detecting means. Therefore,
The deterioration of the laser diode progresses, the amount of current flowing through the laser diode increases, and when the amount exceeds a predetermined amount, the comparison means outputs a predetermined signal. Therefore, the life of the laser diode can be detected by detecting the signal. . In particular, if a resistor for converting the current flowing through the laser diode into a voltage is used as the current detecting means and a comparator for comparing the voltage appearing across the resistance with a reference voltage is used as the comparing means, the laser output changes due to the laser The life of the diode can be detected. Further, if the comparator is provided with the reference voltage adjusting means, it becomes possible to adjust even if the current amount varies among the laser diodes.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 shows a block diagram of an essential part of an optical pickup for a CD player in which a life detecting circuit 12 for a laser diode (LD) 10 of this embodiment is incorporated, and FIG. 2 shows a circuit diagram of the life detecting circuit 12 for the LD 10. Show. In FIG. 1, reference numeral 14 is a power supply circuit, which supplies DC + 5 V as a power supply voltage (Vcc), for example. Reference numeral 16 denotes an LD driver circuit, which causes the current supplied from the power supply circuit 14 to flow to the LD 10. Further, it has a built-in means for detecting the luminous intensity of the LD 10, and in order to keep the luminous intensity constant, when the luminous intensity decreases, the LD 10
It has the function of increasing the amount of current flowing to.

Although details of the detection circuit 12 will be described later, the detection circuit 12 is connected between the power supply circuit 14 and the LD 10. The detection circuit 12 detects the amount of current flowing through the LD 10, and when the amount of detected current exceeds a predetermined value, the LD 10
A predetermined signal indicating that the life of the is reached is output. 1
An LED driver circuit 8 blinks the LED 20 when the predetermined signal is sent from the detection circuit 12 to notify the user that the life of the LD 10 has expired. LD
LE is a means to notify that the life of 10 has come
Not limited to D20, for example, a buzzer sound signal may be used for notification.

Next, an example of the detection circuit 12 will be described with reference to FIG. R1 is a resistor which is an example of a current detecting means, and is connected between the power supply circuit 14 and the LD driver circuit 16. The resistor R1 converts the current flowing through the LD10 into a voltage. Therefore, the current flowing through the LD 10 can be detected by detecting the voltage appearing across the resistor R1. R2 is a resistor and is connected in parallel to the resistor R1. The resistor R2 is connected in parallel to the resistor R1 in order to reduce the resistance value between the power supply circuit 14 and the LD driver circuit 16.

Numeral 22 is an open / close switch, which has resistors R1 and L
The circuit with the D driver circuit 16 is opened and closed. Therefore,
When the open / close switch 22 is open (state of FIG. 2), the resistance R
Since 2 is not in the closed circuit, the resistance value between the power supply circuit 14 and the LD driver circuit 16 is high. on the other hand,
When the open / close switch 22 is closed, the resistors R1 and R2 are in a parallel state, so that the resistance value between the power supply circuit 14 and the LD driver circuit 16 is low. Reference numeral 24 is a comparator which is an example of a comparison means. When the open / close switch 22 is in an open state, the voltage appearing across the resistor R1 is input to the non-inverting input terminal and the reference voltage is input to the inverting input terminal. If the voltage input to the non-inverting input terminal is higher than the voltage input to the inverting input terminal, the comparator 24 turns High.
It outputs DC +5 volts which is the h signal. On the other hand, if the voltage input to the non-inverting input terminal is lower than the voltage input to the inverting input terminal, the comparator 24 outputs a low signal of approximately 0 volt.

RV is a variable resistor which is an example of reference voltage adjusting means, and the voltage appearing at both ends is applied to the inverting input terminal of the comparator 24 as a reference voltage. Variable resistance RV
By using, the reference voltage can be adjusted. The variable resistor RV is provided so that the reference voltage can be adjusted because the light emission intensity of the LD 10 is set to a predetermined light intensity at the start of use. Milliampere), LD1
This is because the reference voltage set to detect the arrival of the life of 0 also differs for each LD 10.

Next, the operation of this embodiment will be described.
First, the open / close switch 22 is opened and the power supply circuit 1
4 and the LD driver circuit 16 have a high resistance value. That is, the voltage applied to the non-inverting input terminal of the comparator 24, that is, the voltage appearing across the resistor R1 is set to a high state, and the variable resistor RV is adjusted to adjust the comparator 2.
4 outputs DC + 5V which is a High signal. This completes the setting of the reference voltage. Then, the open / close switch 22 is closed. When the open / close switch 22 is closed, the resistance value between the power supply circuit 14 and the LD driver circuit 16 is low. Then, the voltage applied to the non-inverting input terminal of the comparator 24, that is, the voltage appearing across the resistor R1 decreases, and the comparator 24 outputs a low signal of 0 volt.
The reference voltage value (voltage appearing across the variable resistor RV)
Is a voltage value that is higher than the voltage appearing at the resistor R1 by a predetermined amount (for example, 10%) when the opening / closing switch 22 is closed at this initial time.

When the LD 10 deteriorates during use in this state and the luminous intensity of the emitted light falls below a predetermined luminous intensity, the LD
The driver circuit 16 increases the amount of current. Due to this increase in current, the voltage appearing across the resistor R1 rises. Eventually, when the LD10 reaches the end of its life, the current flowing through the LD10 further increases, and the voltage appearing across the resistor R1 exceeds the reference voltage (voltage exceeding the initial value by 10%). As a result,
If the voltage input to the non-inverting input terminal of the comparator 24 is higher than the voltage input to the inverting input terminal, the comparator 24 outputs DC + 5 V which is a High signal. That is, this DC + 5 V is a signal indicating the end of the life of the LD 10.

When DC + 5V is output from the comparator 24, the LED driver circuit 18 blinks the LED 20 to notify the user of the end of the life of the LD 10. Although the preferred embodiments of the present invention have been described above in detail, the present invention is not limited to the above-described embodiments, and it goes without saying that many modifications can be made without departing from the spirit of the invention.

[0014]

When the laser diode life detecting circuit according to the present invention is used, the amount of current flowing through the laser diode is detected by the current detecting means. Therefore, the deterioration of the laser diode progresses, the amount of current flowing through the laser diode increases, and when the amount exceeds a predetermined amount, the comparison unit outputs a predetermined signal, so the life of the laser diode can be detected by detecting the signal. Therefore, it is possible to surely prevent the occurrence of the sound jump and the non-reproducible state during the reading of the data and the reproduction of the sound.

[Brief description of drawings]

FIG. 1 is a block diagram of an essential part of an optical pickup for a CD player in which an LD life detection circuit according to the present invention is incorporated.

FIG. 2 is a circuit diagram of a life detection circuit for the LD shown in FIG.

[Explanation of symbols]

 10 LD 12 Life Detecting Path 14 Power Supply Circuit 16 LD Driver Circuit 18 LED Driver Circuit 20 LED 22 Open / Close Switch 24 Comparator R1 Resistor R2 Resistor RV Variable Resistor

Claims (3)

[Claims] 1. A current detecting means connected between a power source and a laser diode for detecting the amount of current flowing through the laser diode, and a predetermined value when the amount of current detected by the current detecting means exceeds a predetermined value. And a comparison means for outputting the signal of 1. 2. The current detecting means is a resistor for converting a current flowing through the laser diode into a voltage, and the comparing means is a comparator for comparing a voltage appearing across the resistor with a reference voltage. The laser diode life detection circuit according to claim 1. 3. The laser diode life detecting circuit according to claim 2, wherein the comparator is provided with a reference voltage adjusting means for adjusting the reference voltage.