JPH05144063A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To provide an optical memory device which has the circuit simplified and has a high reliability by resolving the problem that a semiconductor laser monitor circuit of the optical memory device is complicated because of a need of two monitor circuits for monitor of the current flowing to a semiconductor laser itself and for monitor of reflected light of light emitted from the semiconductor laser and the problem that the reliability of the monitor circuit is reduced because of an occasional failure of proportion between the light emission level of the semiconductor laser and the operation current. CONSTITUTION:The optical memory device uses a voltage drop detecting circuit 102 and detects the voltage drop of a semiconductor laser drive circuit 101 to detect the operation current flowing to the semiconductor laser and compares this detection output with a reference signal 115 to monitor the operation state of the semiconductor laser.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing apparatus. More specifically, it relates to an improved configuration of a semiconductor laser operation protection circuit.

[0002]

2. Description of the Related Art In an optical information recording / reproducing apparatus, a semiconductor laser is used for recording / reproducing information. This semiconductor laser is vulnerable to disturbances such as noise and static electricity and is easily destroyed. Moreover, when recording information on the optical disc,
Since the device is used near the maximum value of the operating current, a circuit for monitoring the abnormality of the operating current flowing through the semiconductor laser is required.

In the conventional abnormal operation monitoring circuit, the semiconductor laser is monitored by two detecting means, that is, the current flowing through the semiconductor laser itself and the irradiation power of the semiconductor laser light (reflected light from the optical disk).

FIG. 3 shows a monitoring circuit for abnormal operation of a semiconductor laser in a conventional optical information recording / reproducing apparatus. The optical sensor 120 is means for detecting the reflected light from the optical disk of the semiconductor laser. Semiconductor laser 1
The optical sensor 120 detects the light 130 reflected from the optical disk by irradiating the laser light from 05. The detected signal 131 is converted into a voltage by the first current-voltage detection circuit 121. Converted detection signal 132
Is compared with the first reference signal 133 by the first comparator 123 to detect an abnormal state (abnormal light emission) of the semiconductor laser. On the other hand, the current 1 supplied to the semiconductor laser 105
35 is converted into a voltage by the second current-voltage detection circuit 122. The converted detection signal 135 is compared with the second reference signal 137 by the second comparator 124 to detect an abnormal current flowing through the semiconductor laser. The output 134 of the first comparator 123 and the output 13 of the second comparator 124
Both are supplied to the semiconductor laser control circuit 104. When the output of either comparator exceeds the level of the reference signal, the semiconductor laser control circuit 104 recognizes that the semiconductor laser is in an abnormal state, outputs the reset signal 114, and shuts off the semiconductor laser drive circuit 101. .. These two detecting means monitor and protect the abnormal state of the semiconductor laser.

[0005]

However, in this conventional method, it is necessary to detect abnormal light emission of the semiconductor laser, an abnormal current supplied to the semiconductor laser, and two types of abnormal times. It becomes complicated.
Moreover, since the emission level of the semiconductor laser and the operating current are not necessarily proportional to each other, an abnormal state of the semiconductor laser cannot be reliably detected, and the semiconductor laser may sometimes be destroyed.

[0006]

The optical information recording / reproducing apparatus of the present invention is an optical information recording / reproducing apparatus for recording / reproducing and erasing information by using a semiconductor laser. The power supply of the semiconductor laser drive circuit is separated from other power supply systems and turned on / off by the control circuit in order to protect it from noise caused by turning the power supply on / off, and the current consumption of the semiconductor laser drive circuit is low. Paying attention to the fact that most of them are consumed by the semiconductor laser itself, current detecting means for detecting an abnormal current flowing through the semiconductor laser by utilizing the voltage drop of the semiconductor laser drive circuit, and b) the current detecting means. It consists of a comparator that compares the output with a reference level, and c) a cutoff circuit that cuts off the semiconductor laser drive circuit depending on the level of the comparator. Things and said.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. In the figure, the same parts as those in the conventional example are indicated by the same reference numerals. FIG. 1 is a block diagram showing the configuration of the optical information recording / reproducing apparatus of the present invention. The semiconductor laser driving circuit 101 boosts the voltage 110 supplied from the terminal 106 to obtain a stable power source as a semiconductor laser driving power source, and a semiconductor laser driving power source for turning ON / OFF the other power source. It is composed of a semiconductor laser reset circuit for separating from the ON / OFF operation of. The semiconductor laser drive circuit 101 is
Reset signal 11 from the semiconductor laser control circuit 104
Upon receipt of 4, the driving power supply 116 is supplied to the semiconductor laser 105. The voltage drop detection circuit 102 detects the voltage drop 111 of the semiconductor laser drive power supply and differentially amplifies it with the drive power supply voltage (reference voltage) before the voltage drop. The differentially amplified signal 112 is compared with the reference signal 115 supplied from the terminal 107 by the comparator 103. When the differentially amplified signal 112 shows a value larger than the reference signal 115, it is determined that the semiconductor laser is operating abnormally, and the comparator 1
03 outputs the abnormality detection signal 113. Abnormality detection signal 1
The semiconductor laser control circuit 104 that has received 13 outputs the semiconductor laser reset signal 114, shuts off the semiconductor laser drive circuit 101, and protects the semiconductor laser.

FIG. 2 is a circuit diagram of an embodiment of the optical information recording / reproducing apparatus of the present invention. Part 101 surrounded by a dotted line in the figure
Is a semiconductor laser drive circuit, and 102 is a voltage drop detection circuit. The semiconductor laser drive circuit 101 will be described. This circuit is composed of a power boost circuit and a semiconductor laser reset circuit. The power boost circuit
It is composed of an operational amplifier 150, a transistor 151, a resistor 152, and a capacitor 153, and the power supply voltage 110 input to the terminal 106 is boosted and stabilized by the operational amplifier 150 and the transistor 151. The semiconductor laser reset circuit is composed of transistors 156, 157, a diode 154, and a resistor 155.
A reset signal 114 output from the semiconductor laser control circuit 104 switches the transistors 156 and 157 to turn on / off the driving power supply voltage of the semiconductor laser.
To do. The diode 154 emits an extra voltage remaining in the circuit when the semiconductor laser drive power is turned off.

Next, the voltage drop detection circuit 102 will be described. When a current flows through the semiconductor laser 105, the voltages appearing at both ends 166 and 167 of the minute resistor (about several Ω) 158 differ from each other. By knowing the voltage difference,
It is possible to know the current value flowing in the semiconductor laser. The current value can be expressed as follows.

(V ₀ −V _L ) · R _D = I _L where V ₀ : reference power supply voltage (voltage appearing at terminal 166) _VL : voltage after voltage drop (voltage appearing at terminal 167) _RD : resistance The resistance value I _{L of} 158 is the current value flowing in the semiconductor laser.

Here, both ends 166 of the resistor 158 are
The voltage difference appearing at 167 is differentially amplified by the operational amplifier 165 to detect it more significantly. Here, the operational amplifier 16
5, the resistors 159, 160, 162 and 164 and the capacitors 161 and 163 form a differential amplifier. Resistance 1
The amplification factor of the differential amplifier is determined by the ratio of 59, 162 (resistors 160, 164).

The signal 11 output from the operational amplifier 165
2 is input to the comparator 103 and compared with the reference signal 115 supplied from the terminal 107. Differential output signal 112
Is larger than the reference signal 115, the comparator 1
Reference numeral 03 outputs an abnormality detection signal 113, assuming that an abnormal current has flown into the semiconductor laser. The semiconductor laser control circuit 104 receiving this abnormality detection signal outputs the semiconductor laser reset signal 114 (actually, the reset signal is OF
F ) Is performed by the transistors 156, 1
57 is switched, the semiconductor laser drive circuit 101 is cut off, and the operation of the semiconductor laser 105 is stopped and protected.

[0013]

As described above, according to the present invention, the abnormal current flowing through the semiconductor laser can be monitored by monitoring the voltage drop of the semiconductor laser drive circuit. As a result, unlike the conventional circuit that requires two monitoring circuits for monitoring the current flowing through the semiconductor laser itself and for monitoring the reflected light of the light emitted from the semiconductor laser,
It is possible to simplify the semiconductor laser monitoring circuit. Moreover, since it is possible to comprehensively capture the operating current flowing through the semiconductor laser, there is almost no monitoring error,
It becomes possible to monitor more reliably. Therefore, the number of monitoring circuits can be significantly reduced, and the reliability is improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an optical memory device of the present invention.

FIG. 2 is a circuit diagram of an optical memory device that is an embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a conventional optical memory device.

[Explanation of symbols]

 101 semiconductor laser drive circuit 102 voltage drop detection circuit 103 comparator 104 semiconductor laser control circuit 105 semiconductor laser 115 reference comparison signal 156 high speed transistor 157 high speed transistor 165 high speed operational amplifier

Claims (1)

[Claims] 1. Recording of information using a semiconductor laser,
In an optical information recording / reproducing apparatus for reproducing and erasing, a) In order to protect a semiconductor laser from noise caused by turning on / off a power source, a power source of a semiconductor laser driving circuit is separated from other power source system and a control circuit is provided. It is turned on and off by the semiconductor laser drive circuit, and the current consumption of the semiconductor laser drive circuit is mostly consumed by the semiconductor laser itself. A current detection means for detecting an abnormal current flowing, b) a comparator for comparing the output of the current detection means with a reference level, and c) a cutoff circuit for cutting off the semiconductor laser drive circuit according to the level of the comparator. A characteristic optical information recording / reproducing device.