JP2808630B2 - Current control circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical disk device for recording and reproducing a digitized video signal, and more particularly, to a recording circuit thereof.

2. Description of the Related Art Conventionally, as shown in FIG. 2, a recording circuit of this type has a differential amplifier 9 for driving a laser diode, a constant current source 8 of the differential amplifier 9 and a control signal for the constant current source 8. The output of the adder 10 and the monitor output of the laser diode as an input of the adder 10 and the control signal WRITE (L) receive VR1 and
An analog switch 3 for switching the output of VR2, an amplifier for receiving and amplifying the output of the analog switch 3 and inputting it to the adder 10, and an analog for receiving the signal WRITE (L) and turning on the constant current source 8 It consists of a switch 6.

The reason for switching between VR1 and VR2 as described above is as follows. That is, when the VR1 is only turned on / off, the output level of the amplifier 4 becomes 0 V when the VR1 is off, the monitor output of the laser diode becomes positive in the output at the time of reading, and the output of the adder drops to -VCC.

When VR1 is turned on in this state, the output of the adder rises from -VCC, so that the recording current has a delay in rising. To improve this, VR2 is selected at the time of reading, VR2 is adjusted so that the output of the adder is the same as at the time of recording, and the output of the adder is output from the recording level instead of -VCC during recording, and the recording current converges. Hastened.

[Problems to be Solved by the Invention] In the above-described conventional technology, the volume is switched at the time of reading to make the output of the adder equal to that at the time of recording in order to accelerate the convergence of the recording current. As a result, there is a problem that it takes time to adjust the volume. Adjustment of the volume at the time of reading has an optimum point.If it is too small, the start-up is delayed, and if it is too large, overshorting may occur and the laser diode may be destroyed. I was

[Means for Solving the Problems] The gist of the present invention is to provide a regulator for adjusting a recording current, a first amplifier for receiving and amplifying an output of the regulator, a monitor output of a laser diode, and the first amplifier. Adder having an output of the adder as an input, a control circuit for generating a control signal in response to a recording on / off control signal, and a first analog for conducting / cutting off an output of the adder in response to the control signal A switch, a constant current source for changing a passing current in response to an output of the adder supplied through the first analog switch, and a first transistor and a fixed voltage source connected to the laser diode. And a differential amplifier that sends a current passing through the first transistor and a current passing through the second transistor to the constant current source in response to an input signal. A second amplifier for receiving a monitor output of the laser diode in the current control circuit and amplifying the monitor output at an amplification factor corresponding to a ratio between a read output of the laser diode and a write output of the laser diode; A second amplifier is provided between an input of the adder and an input of the adder, and supplies / blocks an output of the second amplifier to the input of the adder in response to an inverted signal of the control signal output from the control circuit. And a second analog switch.

Example Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention. The volume adjuster 1 adjusts the level of the recording current, the output of which is amplified by the amplifier 2 and applied to the adder 3 via the resistor R2. Monitor output VM of laser diode is amplifier 4
Is added to the adder 3 via the resistor RM. The gain of the amplifier 4 is determined by the ratio between the recording output and the reading output of the laser diode.

The output of the amplifier 4 becomes the input of the analog switch 5,
The analog switch 5 turns off when the output of the inverter 6 is at a high level, turns on when the output is at a low level, and is applied to the adder 3 via a resistor RM. The analog switch 8 receives the output of the adder 3 as an input, and is turned off when the output of the inverter 7 is at a high level, and turned on when the output of the inverter 7 is at a low level. The constant current source 9 receives the output of the adder 3 via the analog switch 8, determines the level of the recording current, and drives the differential amplifier 10.

The point of the present invention is to make the output of the adder 3 the same at the time of recording and at the time of reading. Since the analog switch 5 is turned off during recording, the input of the adder 3 becomes the monitor output of the laser diode and the output of the amplifier 2. Assuming that each output is VM and VR, the output V0 of the adder 3 is Becomes Rf is a feedback resistance of the adder 3.

At the time of reading, the monitor output of the laser diode decreases in proportion to the output of the laser diode.

Assuming that this ratio is k, the output of the adder 3 is Becomes

 Here, K is the gain of the amplifier 4.

To make the output of the adder 3 the same as at the time of recording, k + kK = 1, that is, It is good. Recording output 8.2 [mW], readout 3.3
If [mW], k0.4 and K = 1.5.

If the relationship described above is maintained, the output level of the adder 3 during recording and reading will be the same.

[Effects of the Invention] As described above, according to the present invention, the recording output of the laser diode and the voltage source having a gain corresponding to the read output are added at the time of reading, so that the rising of the recording ionization can be quickly performed and the volume adjustment can be performed. It has the effect of removing time and effort.

[Brief description of the drawings]

 FIG. 1 is a block diagram showing one embodiment of the present invention. 1 ... Volume for adjusting recording current, 2 ... Amplifier, 3 ... Adder, 4 ... Amplifier, 5,8 ... Analog switch, 6,7 ... Inverter, 9 ... Constant current source, 10 ... FIG. 2 is a block diagram showing a conventional example. 1… Volume for adjusting the recording current, 2… Volume for adjusting the output of the adder at the time of reading, 3,6 …… Analog switch, 4 …… Amplifier, 5 …… Resistance, 7 …… Inverter, 8 …… Constant current source , 9 ... Differential amplifier, 10 ... Adder.

Claims (1)

(57) [Claims] An adjuster for adjusting a recording current; a first amplifier for receiving and amplifying an output of the adjuster; an adder for inputting a monitor output of a laser diode and an output of the first amplifier; A control circuit for generating a control signal in response to a recording on / off control signal; a first analog switch for conducting / cutting off an output of an adder in response to the control signal; A constant current source that changes a passing current in response to the supplied output of the adder; a first transistor connected to the laser diode and a second transistor connected to a fixed voltage source;
In a current control circuit having a differential amplifier for sending a current passing through the first transistor and a current passing through the second transistor to the constant current source in response to an input signal, a monitor output of the laser diode is provided. And a second amplifier for amplifying the monitor output with an amplification factor corresponding to a ratio between a read output of the laser diode and a write output of the laser diode, and a second amplifier between the second amplifier and an input of the adder. And a second analog switch for supplying / interrupting an output of a second amplifier to the input of the adder in response to an inverted signal of the control signal output from the control circuit. Current control circuit.