JPH04123327A - Laser driving circuit - Google Patents

Abstract

PURPOSE:To perform the control of momentary rise to a designated high power by providing a bias reference means, a reproducing bias holding means, and a laser output means which selectively takes each bias outputted from the bias reference means as the input to it as output laser light. CONSTITUTION:A monitor signal 2 from a monitor photo diode 1 is compared with a reproduced command voltage PR 5 by a comparator 3 with coincidence output on the reproducing bias side,and the result is sent to an up/down counter 11 on the reproducing bias side. A digital reproducing bias 14 as the output is subjected to D/A conversion and is sent to an LD-drive circuit 25, and a laser current starts to flow. A recording/erasing high-power bias is preliminarily held as a digital value and is corrected in real time even for the change of temperature. Thus, the control of momentary rise from the low power for repro ducing to the designated high power is possible.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to a laser drive circuit that controls the output of laser light in optical disk drives, magneto-optical disk drives, etc. used for document files and data files. be.

(b) Prior Art Conventionally, this type of laser drive circuit has had a configuration as shown in FIG. In Figure 6, the APC loop that keeps the optical output constant is the output (2) of the monitor diode (1).
) and the command voltage sent from the switch circuit (53) are sent to the comparison amplifier (50), and the difference between the two patterns is detected by the comparison amplifier (50).
) and output as a bias value. During playback, the signal passes through the sample hold (51), the switch circuit (21), and the laser drive circuit (5).
2) causes current to flow through the laser (23), which becomes laser light again and is fed back to the monitor diode (1) built into the pickup. In the case of power bias used during recording/erasing, the output switching signal (
13), the switch circuit (53) is switched to change the command voltage sent to the amplifier (50) to the high power voltage (
6). The switch circuit (21) and sample hold (51) are also switched by the output switching signal (13), and the increased output of the amplifier (50) is directly input to the laser drive (52), and a large current is applied to the laser (23). flows. The high-power laser beam is fed back to a monitor diode (1) built into the pickup, and the output (2) from the monitor diode (1) increases to balance the amplifier. (Unexamined Japanese Patent Publication No. 1-22
(Refer to Publication No. 3641) (c) Problems to be Solved by the Invention In the conventional control circuit, from the regeneration mode, the output switching signal (13) causes the switch (53) to switch from the regeneration voltage (5) to the high power voltage (6). When switching to high power mode, the time from the moment of switching until the high power bias stabilizes is limited by the characteristics of the amplifier (50).
The problem was that delays occurred.

Also, the moment the high power voltage (6) is switched to the reproduction voltage (5), the output of the emitted laser light will overshoot and will not stabilize immediately, so the reproduction bias can be adjusted by referring to the sample hold (51) e. , trying to stabilize the system after switching. However, due to the droop characteristic of the sample hold (51) itself, the bias level decreases over time, resulting in the problem that an appropriate bias value cannot be obtained when switching from high power mode to playback mode. have. As the bias level decreases in this way, it is necessary to resample the reproduction bias before the decrease in bias level affects circuit operation, which limits the duration of the high power state. It had some problems.

In view of the above-mentioned problems, the present invention eliminates the time delay from switching the output switching signal (13) until the high power bias and reproduction bias become stable, and the duration of time to maintain high power without decreasing the bias level. This is the purpose.

(d) Means for Solving the Problems The present invention provides a high power bias holding means for holding the high power bias value used for recording and erasing as a digital value at the initial stage of laser startup, and a high power bias holding means that is compatible with temperature changes during use. a reproduction bias holding means for holding the reproduction bias value as a digital value, and recording/erasing by referring to the output of the high power bias holding means and the output of the reproduction bias holding means when switching from the reproduction mode to the high power mode. A bias reference means is provided which corrects the bias, that is, sets it by using an addition/subtraction circuit based on the reproduction bias.

(E) Effect In the above configuration, if the circuit of the present invention is used, the recording/erasing bias is maintained by the initial setting performed at the beginning of the laser startup, and the startup speed to the high power mode becomes extremely fast. Furthermore, since the reproduction bias is also maintained, the switching speed from the high power mode to the reproduction mode is also very slow.

When switching from playback mode to high power mode in response to temperature changes, the recording/erasing bias is corrected in real time, so you can always switch to high power voltage with the optimal bias.

(f) Example FIG. 1 shows the laser drive circuit of the present invention.

This will be explained with reference to FIGS. 2, 3, 4, and 5.

FIG. 1 shows a laser drive circuit in one embodiment of the present invention. FIG. 2 shows the laser output waveform at the time of initial setting when using the laser drive circuit of the present invention. FIG. 3 shows a flowchart at the time of initial setting. FIG. 4 shows the laser characteristic curve. FIG. 5 shows the relationship between temperature and laser bias. In Figure 1, (1) is the monitor photodiode, (2) is the output of the monitor photodiode, and (3) is the monitor photodiode.
(4) is a comparator with a -spread output, (5) is a reproduction command voltage, (6) is a high power command voltage, (7) is a reproduction output arrival signal, (8) is a high power output arrival signal, and (9) is Laser lighting command signal, (10) is a counter clock, (11) and (12) are up/down counters that up and down the output and hold the output value as a digital value under the control of the output matching comparator (13)
) is a high power/low power switching signal that switches between high power used during recording/erasing and low power used during playback, (14) is a digital playback bias, (1
5) is a digital high-power bias, (16) is an adder that adds the digital reproduction bias and the digital high-power bias, and (17) and (18) convert the input digital bias into an analog bias. D/A converter, (19) is analog playback bias, (20) is analog high power bias, (21)
(22) is the laser bias selected by the bias selection switch. (23) is the laser. (24) is the modulation data.
5) is a laser drive circuit for oscillating the laser (23).

The operation of the laser drive circuit configured as above will be explained.

First, a laser lighting command signal (9) for controlling laser lighting is activated. At this time, the π/WE signal (13) that controls switching between low power and high power is in R1, that is, read mode, so the up/down counter (11) on the reproduction bias side becomes operational, and the high power bias side up-down counter (1
2) is in a state where the operation is stopped. The monitor signal (2) from the monitor photodiode (1) is the reproduction command voltage PR.
(5) and a comparator with matching output on the playback bias side (3
), and the result is sent to the up/down counter (II) on the reproduction bias side. The output of the digital playback bias (14) is the D/
It is D/A converted by an A converter (17) and sent as a laser bias (22) to an LD-drive circuit (25), which is a laser drive circuit, via a switch circuit (21), and a laser current begins to flow. At the beginning of operation, the laser output is in a rising state, rising in a stepwise manner as shown in Figure z (26), and stops when it matches the command value shown in Figure 2 b (32), and the regeneration begins. An R-OK multiplied signal 7) which is an output arrival signal is output. Next, at c (33) in Figs. 2 and 3, the R/WE signal (13)
becomes H, the up/down counter (11) on the playback bias side stops operating, and the high power bias side becomes operational.The switch (21) also switches to the playback bias side. is switched from the D/A conversion @ (17) to the high power bias side D/A converter (18).High power command voltage pHl
Since the output of monitor signal (2) is lower than /E (6),
Converter with matching output on high power bias side (4)
sends the UP command to the up/down counter (12) on the high power bias side. Up-down counter (12)
The digital high power bias value (15) from Ru. The result is converted into an analog high power bias (20) by the D/A converter (18) on the high power bias side, and sent to the LD-drive (25), which is a laser drive circuit, via the switch (21). Laser current begins to increase. The laser rises in a stepwise manner as shown in Figure 2 (28), and stops when it matches the command value shown in Figure 2 d (34), and the W/E-OK signal, which is a high power output arrival signal, is output. Output signal 8).

At e(35) in FIGS. 2 and 3, the R/WE signal (
13) is switched from the high power mode to the reproduction mode, and as shown in FIG. 2(3o), the reproduction bias value held at the time of c(33) in FIG.
7) can be obtained. After that, even if a switching command to high power is issued, the up/down callan 9-(12) on the high power bias side retains the digital high power bias value, so the result will be as shown in Figure 2 (28). It does not follow a step-like process (it instantly rises to the high power state shown in Figure 2 (29). Also, when a temperature change occurs, the laser normally exhibits the characteristics as shown in Figures 4 and 5. is known. To illustrate this characteristic, if the temperature is 2
When the temperature rises from 5°C to 50°C, the reproducing laser current flowing to the laser in the reproducing mode is as shown in Figure 4 IRI (38)
to IR2 (40) in FIG. In this case, since the laser output is always monitored by the comparator with coincidence output (3), the up/down counter (11)
is controlled by repeatedly going up and down. The laser bias is set from VRI (44) in Figure 5 to VR2 (44) in Figure 5.
6) in FIG. 5 by ΔVR (48). At this time, the laser bias in the high power mode is also shown in Figure 5, since the laser current moves almost in parallel due to the relationship shown in Figure 4.
From I (45) to Figure 5 VWE2 (47) Figure 5 ΔVW
E(49) portions, that is, ΔVR(48) portions may be eaten.

The up/down counter (11) on the playback bias side displays the digital playback bias value (14) held at the time of initial setting.
) and the digital high power bias value (15) are added by the adder (16), and the optimal bias is output as an analog high power bias (20) from the D/A converter 41NS (18) on the high power bias side. I'm waiting.

As a result, the rise speed to high power is extremely fast, and the recording/erasing bias is corrected in real time according to temperature changes, so it is possible to always switch to high power voltage with the optimal bias.

(G) Effects of the Invention In the present invention, the high power bias for recording and erasing is held as a digital value in advance, and correction is made in real time for temperature changes, so that the low power for reproduction is changed to the specified high power. It can be started up and controlled instantly, and its effects are great.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment of the present invention, FIG. 2 is a laser output waveform diagram at the time of initial setting when using the laser drive circuit of the present invention, FIG. 3 is a flowchart at the time of initial setting, and FIG. The figure is a laser characteristic curve diagram, FIG. 5 is a relationship diagram between temperature and laser bias, and FIG. 6 is a conventional laser drive circuit diagram. 1...Photodiode, 2...Monitor output,
3.4... - Comparator with scattered output, 5... Reproduction command voltage (analog), 6... High power command voltage (analog), 7... Reproduction output arrival signal (digital) , 8... High power output arrival signal (digital), 9... Laser lighting command (digital), 1
0... Counter clock, 11.12...
Up/down counter 13...High power/low power switching signal, 14...Reproduction bias (digital), 15...High power bias (digital), 16...Adder, 17.18 ...D/A converter, 19... Reproduction bias (analog), 20.
...High power bias (analog), 21...
Switch, 22... Laser bias, 23...
・Laser 24...Modulation data, 25...Laser drive circuit, 26...Reproduction output during initial rise, 27.30...Reproduction output, 28...Reproduction output during initial rise High power output, 29... High power output,
31-35...Each point during initial rise, 36...
...Characteristic curve at 25°C, 37...Characteristic curve at 50°C, 38.40...Reproduction via Xl/l current, 39.41...High power bias current, 42.
43...Bias voltage characteristic curve, 44-47...
・Bias voltage, 48.49...Difference in bias voltage due to temperature change, 5o・mountain amplifier, 51...Sample/hold, 52...Laser drive circuit, 53
····switch.

Claims (1)

[Claims] (1) In a laser drive circuit attached to an optical disk device that records and reproduces information on a rotating recording medium using a laser beam, a high power bias holding means is used that determines and holds a recording/erasing bias at the initial stage of laser startup. a reproduction bias holding means for holding a reproduction bias value corresponding to temperature changes during use, and a recording method corresponding to temperature changes during use by referring to the output of the high power bias holding means and the output of the reproduction bias holding means. - A bias reference means for outputting an erasing bias, and a laser output means for selectively inputting each bias output from the reproduction bias holding means and the bias reference means and outputting it as a laser beam. laser drive circuit.