JPH02306678A - Semiconductor laser drive controller - Google Patents

Abstract

PURPOSE:To stably operate the laser diode even if a power source voltage is set to a low value by controlling a normal driving current by a drive element for controlling the driving current, and providing a start detecting means for operating a soft start of a starting point by the element and a control means. CONSTITUTION:A driving means 18 for controlling a current flowing to a laser diode De, a control means 300 for supplying a control signal instructing energization or interruption of the diode De, and a start detecting means 100 for detecting application of a power source voltage Vcc to the means 300 and outputting an energization start signal for blocking a surge current to the diode De for a predetermined period of time are provided. An energization start signal is so supplied to the means 300 as to gradually increase the current flow amount from the means 100 at the time of turning ON of the power source to invalidate a light emitting amount set signal, and the diode De is driven by the means 18 according to the energization start signal. Thus, it is operated stably with a low power source voltage to prevent the diode De from damaging.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an active circuit for a laser diode.

In particular, the present invention relates to a half-body laser swelling control device that protects a laser diode from surge current applied when power is turned on.

[Prior Art] Laser diodes are used as light sources for code reading devices, document reading devices, and various other office equipment and information processing equipment.

This type of laser diode can be destroyed by the surge current that flows when the device is turned on.
A laser diode drive circuit is usually equipped with a protection circuit to protect the laser diode from surge currents.

FIG. 2 is a configuration diagram showing the main parts of a semiconductor laser turbulence device according to the prior art, in which De is a laser diode, 72
73 is a current limiting resistor; 74 is a control unit; 75 is an NPN transistor used to protect the laser diode De; and 76 is an activation detection unit.

In the figure, a transistor 72 and a resistor 73 are connected in series to the laser diode De, which controls the drive current necessary to obtain a predetermined amount of light from the diode De. The output of a control section 74 for controlling this drive current is supplied to the drive current.

The amount of light emitted from the laser diode De is controlled by a drive current value that corresponds to the impedance value between the collector and emitter of the transistor 72 in accordance with the output value of the control section 74 that is supplied with a light emission amount setting signal from an external device (not shown).

With only the above configuration, the laser diode De may be destroyed by the surge current generated when the power is turned on.As a countermeasure, a transistor 75 for protective operation is added to the series circuit of the laser diode De, the collector emitter of the transistor 72, and the resistor 73. The collector-emitter of the transistor 75 is inserted in series, detects when the power is turned on, and lowers the impedance between the collector-emitter of the transistor 75 relatively slowly over a predetermined period of time, thereby gradually increasing the drive current to perform normal lighting operation. It is designed to perform a so-called slow start operation that delays the

[Problems to be Solved by the Invention] In the above conventional configuration for performing slow start operation, the transistor 72 for driving the current of the laser diode De, the transistor 75 for protection operation, and the current limiting resistor 73 are connected in series. However, in normal operation, a power supply voltage twice as high as that between the emitter and the collector is required, so there is a problem that a semiconductor laser driving device that is required to operate at a low power supply voltage cannot be obtained.

Therefore, the technical object of the present invention is to provide a semiconductor laser driving device that solves this problem and prevents the laser diode De from being destroyed.

[Means for Solving the Problems] In order to solve the above-mentioned technical problems, the present invention provides a laser diode De that outputs a laser beam with a current supplied from the power supply VCC, and a current flowing through the laser diode De. a series-connected drive means 18 for controlling the laser diode De; The present invention is characterized in that it includes a start-up detection means 100 that detects that the power supply Vcc is turned on and outputs a energization start signal for blocking surge current to the laser diode De for a predetermined period of time.

[Function] When the power is turned on, an energization start signal that gradually increases the amount of energization from the activation detection means 100 is supplied to the control means 300, the light emission amount setting signal is invalidated, and the driving means 18 operates the laser diode according to the energization start signal. Since De is driven, it is possible to provide a semiconductor laser driving device that prevents damage to the laser diode De with a low power supply voltage.

[Example] Examples of the present invention will be described in detail below based on the drawings.

FIG. 1 is a wiring diagram showing a circuit configuration of the present invention used in an optical reading device or the like.

In the figure, 1, 3, 5, 6, 7, 9, 14, 15°19
．． 21, 25, 26 are resistors, 2, 16, 24 are capacitors, 4, 8, 18, 20, 27 are NPN bipolar transistors, 10.11 is a two-terminal input type operational amplifier, 12.13 is a diode, 17 is a light emitting diode unit with a built-in monitor diode, 22 is a thermistor for temperature detection, 23 is a Zener diode, De is a laser diode, Dm is a photodiode, 100 is a startup detection section, 200 is an operation detection section, 300 is a control section , 400 indicate an operating voltage generating section, respectively.

First, to explain the configuration, the light emitting diode unit 17
A laser diode De for irradiating the optical recording medium with a laser beam and a pin-type photodiode Dm for monitoring the amount of light emitted from the laser diode De are arranged. The anode of the laser diode De is connected to the cathode of a photodiode Dm.

Anode of laser diode De and photodiode D
Power supply voltage Vcc is applied to the connection point of the cathode of m. The anode of the photodiode Dm is connected to a comparison input point B for controlling the amount of light emitted from a laser diode De provided in a control section 300, which will be described later.

The cathode of this laser diode De is connected to the collector of a driving NPN type transistor 18 in order to control the current flowing through the laser diode De. The emitter of this transistor 18 is connected to an operation detecting section 3 which will be described later.
It is grounded via a resistor 19 for detecting the current value of 00. The base of the transistor 18 is configured as a command signal input point E to which a protection command and a signal for energization amount command outputted from both the operation detection section 200 and the control section 300, which will be described later, are supplied. On the other hand, the temperature generated from the energized laser diode De is transmitted to the thermistor 22 for temperature detection.

A power supply voltage Vcc is applied to one end of this thermistor 22 via a resistor 21. The connection point between the thermistor 22 and the resistor 21 is connected in parallel with a Zener diode 23 whose cathode side is connected in order to generate a constant voltage, and a capacitor 24 which similarly bypasses the alternating current component. and grounded. The other end of the thermistor 22 is grounded via a resistor 26 provided in an operation detection section 200, which will be described later, for detecting a current value that increases in response to a rise in temperature of the thermistor 22.

In the activation detection unit 100, a resistor 1 and a capacitor 2 are connected in series between a power supply terminal Vcc to which a positive power supply voltage Vcc is applied and a common ground line GND to which a negative power supply voltage Vcc is applied. A common connection point A between the resistor 1 and the capacitor 2 is connected to the base of an NPN transistor 4. The emitter of this transistor 4 is
It is grounded, and one end of a resistor 3 is connected to its collector. A power supply voltage Vcc is applied to the other end of this resistor 3 via a resistor 5 whose resistance value is set to be extremely higher than that of the resistor 3. The connection point between the resistor 5 and the resistor 3 is an output terminal of the startup detection section 100, and the voltage value applied to the comparison input point B of the control section 300, which will be described later, is determined at the time when the power supply voltage Vcc is applied. to the power supply value V c only for a time dependent on the time constants of resistor 1 and capacitor 2.
It is configured to raise the voltage to a value extremely close to V c and output a start-up determination signal that drops relatively slowly at the time the power supply V c is turned on to prevent damage to the laser diode De.

At each connection point between the resistor 19 of the operation detection section 200 and the emitter of the transistor 18, and between the resistor 26 and the thermistor 22, there is an N
The bases of PN type transistors 20 and 27 are connected to each other. These transistors 20 and 27 are connected to the power supply voltage c through a pull-up resistor 25 on each collector.
c is applied, and each emitter is both grounded. The connection point F between the respective collectors of the transistors 20 and 27 and the resistor 25 is connected to the rt L l+ level by determining the excessive current value that increases in accordance with the excessive increase in the current flowing to the laser diode De and the temperature rise in the thermistor 22. It is configured to supply the abnormality detection signal to a non-inverting input terminal which is a comparison input terminal of the operational amplifier 11. This 11 L 7
The operational amplifier 11 to which Lebel's abnormality detection signal is supplied is
The operational amplifier 11 is configured to operate as a comparator with a latch that holds the output state at the "L" level until it is reset.The non-inverting input terminal and output terminal of this operational amplifier 11 are connected to a diode that conducts a positive feedback current. 12 anodes and cathodes are connected respectively.This operational amplifier 1
The inverting input terminal of No. 1 is connected to an operating voltage generating section 40, which will be described later.
0 to a base voltage value Vref indicating a threshold value which is a limit value for normal operation of the laser diode De, and a reset voltage value v5 from a transistor 8 to be described later. The output terminal of this operational amplifier 11 is connected to the cathode of a diode 13 that prevents the "H'" level of this output terminal from being transmitted to the command signal input point E, and this anode is connected to the output terminal of the operational amplifier. is u
One end of a resistor 15 is connected to limit the current value passed when the current is at the L+t level, and the other end is connected to a transistor 18.
It is connected to command signal input point E, which is the base of . The current flowing through the series circuit of the resistor 15 and the diode 13 starts flowing in the forward direction between the bases and emitters of the transistors 20 and 27 when the compared voltage value Vin corresponding to the voltage drop of the resistors 19 and 26, which are signal sources, starts flowing. At this time, the voltage value at the connection point F through transistors 20 and 27, which perform a detection operation having rectifying and voltage dividing functions, exceeds the voltage value Vbe applied to the operational amplifier 11. , the output terminal of the operational amplifier 11 is held at It L 7 level only until the reset voltage value Vs is applied to the inverting input terminal - of the operational amplifier 11, and the output terminal of the operational amplifier 11 is held at the It L 7 level, and the command signal input point E is input from the control section 300. It is configured to serve as a protection command signal that invalidates the applied energization amount command signal.

The operational amplifier 10 of the control section 300 is
A reference voltage value applied from an operating voltage generating section 400, which will be described later, is applied to a non-inverting input terminal of the operational amplifier IO, and a start detection signal of the start detecting section 100, an anode of the photodiode Dm, a resistor 3, and a resistor are connected to the inverting input terminal of the operational amplifier IO. When the voltage value applied to the comparison input point B of the control unit 300 connected to
It is configured as a comparator that outputs the level. The output terminal of the operational amplifier 10 is grounded via a resistor 14 and a capacitor 16. Resistor 14 of control unit 300
The connection point E between the capacitor 16 and the laser diode De
It is connected to the base of the transistor 18 that drives the . This series circuit of the resistor 14 and the capacitor 16 is configured as an integrating circuit that outputs a DC voltage value proportional to the proportion of time that the output terminal of the operational amplifier 10 outputs the 11 HN level.

In the operating voltage generating means 400, a series circuit of a resistor 6, a resistor 7, and a resistor 8 is connected between a power supply Vcc and a ground IIAGND. From the connection point C between the resistor 6 and the resistor 7, a voltage value indicating the amount of light emitted from the laser diode De is output from the operational amplifier 1.
0 non-inverting input terminal. From the connection point G between the resistor 7 and the resistor 8, a voltage value indicating the holding and releasing operations is supplied to the inverting input terminal - of the operational amplifier 11. The collector of the reset transistor 8 is also connected to this connection point G. The emitter of this transistor 8 is grounded, and the transistor 8
The collector and emitter of the transistor 8 are configured to be in a low impedance state while an "H" level reset signal is applied to the base of the transistor 8. While the “L” level reset signal is applied to the base of the transistor 8, the reference voltage value Vcf indicating the center value of the amount of light emitted from the laser diode Oe is applied from the connection point C, and the holding operation of the operational amplifier 11 is applied from the connection point G. Reference voltage value V indicating the threshold value of
It is configured to output ref. While the "H" level reset signal is being applied to the base of the transistor 8, a voltage value Ver indicating the center value of the laser diode De and a lower amount of light emitted from the connection point C and an operational amplifier 11 from the connection point G are applied. It is configured to output a reset voltage value Vs that instructs an operation to release the held state.

The operation of the above configuration will be explained below.

First, when the power is turned on to the optical reading device, the potential of the non-inverting input terminal + (connection point C) of the operational amplifier 10 becomes equal to the power supply V.
At the same time as cc is turned on, the reference voltage value Vcf, which indicates the center value of the light emission amount of the laser diode De, is reached as expressed by the following equation.

Vcf=Vcc・(R7+R9)/(R6+R7+R9
) On the other hand, the potential at the inverting input terminal - (connection point B) of the operational amplifier 10 is such that the potential at the connection point A increases with a predetermined characteristic with a constant time constant determined by a time constant circuit consisting of a resistor 1 and a capacitor 2. As the potential of the connection point A rises, a start-up determination current Isd is generated along the path of power supply Vcc → resistor 5 → resistor 3 → collector to emitter of transistor 4 → ground line GND.
is energized. This start-up determination current Isd is generated when the capacitor 2 is charged and the voltage V e b 4 applied between the base and emitter of the transistor 4 is a predetermined value (for example, +,
The base current 1be4 is energized by reaching 06V).
Corresponding to, the current amplification factor hf of resistor 1 and transistor 4
It increases relatively slowly until it reaches saturation depending on a. The potential at the connection point B, which increases according to the increasing characteristic of the base current value Ice4, is divided between the resistor 5 set to a relatively high resistance value, the resistor 3 set to a relatively low resistance value, and the collector emitter of the transistor 4. Pressure connection point C
The voltage drops to a potential slightly lower than the reference voltage value Vcf. Correspondingly, the potential at the connection point E gradually increases depending on the rate at which the resistor 1 and the capacitor 2 are charged, and the time ratio at which the output terminal of the operational amplifier 10 is output at the rr H+j level increases, and the laser diode De The drive current value that provides a slightly larger amount of light than the center value of the amount of light emitted increases toward the voltage value that allows energization. Therefore, the drive current value of the laser diode De does not suddenly increase when the power is turned on, but a so-called soft start operation is performed, and the drive current value increases at an appropriate speed until a predetermined amount of light emission is obtained.

When the amount of light emitted from the laser diode De is detected by the photodiode Drri and is larger than the set amount of light, the connection point B is set at a higher potential than the reference voltage value Vcf applied to the connection point C, as described later. As shown in FIG. Similarly, if the amount of light is less than the set amount of light, the reference voltage value V applied to the connection point C
Negative feedback is provided from the photodiode Dm so that the potential of the connection point B is lower than c f, the voltage value of the connection point E increases, and the amount of light emitted per unit increases. Therefore, the amount of light irradiated from the laser diode De to the optical recording medium is in a steady state according to the reference voltage value V c f applied to the connection point C.

Photodiode D to which a bias voltage is applied in the reverse direction
m is inversely proportional to the increase in the amount of light illuminated on the photodiode Dm, and the reverse impedance RIDm generated between the cathode and the anode decreases. Then, as the impedance RIDm decreases, the monitor current Im flowing through the path from the power supply Vcc to the anode to the cathode of the photodiode Dm to the resistor 3 to the collector to the transistor 4 to the emitter to the ground @GND is changed to the cathode of the photodiode Dm. - monitor current I conducted in the path between the anodes;
m increases. This monitor current value Im (A) is constant when the base current value Ib8, which is limited by the resistance value R1 (Ω) of the resistor 1 that is passed between the base and emitter of the transistor 4, is saturated when the voltage across the capacitor 2 is saturated. Assuming that, the power supply voltage value is Vcc (V), the internal resistance of the power supply is Rcc (Ω), and the cathode of the photodiode Dm is
The reverse impedance between the anodes is RIDm (Ω)
, the resistance value of resistor 3 is R3 (Ω), and the voltage value divided between the collector and emitter of transistor 4 at this time is Vce.
4 (V), and the collector-emitter internal resistance of transistor 4 at this time is Rcc8 (Ω), the negative feedback value is expressed by the following equation.

I m= (Vcc - Vce4)/(RI Dm+
R3+ Rcc8) At the same time, the base of transistor 4 -
When the base current value Ib8, which is limited by the resistance value R1 (Ω) of the resistor 1 that is passed between the emitters, is constant when the voltage across the capacitor 2 is saturated, the power supply V c c → the resistor 5 →
The start-up determination current l5d (A) passed from the collector of the resistor 3 to the transistor 4 to the emitter to the ground line GND has a value expressed by the following equation when the resistance value of the resistor 5 is R5 (Ω).

I sd= (Vcc - Vce4)/(R, 3+ R
5+ Rcc8) Therefore, the potential V at connection point B in steady state
B (V) is the startup judgment current Isd and the monitor current value Im
The composite current value Isd+Im is passed through the path from the resistor 3 to the transistor 4 collector to the emitter to the ground WGND, and is controlled in a closed loop to approach the reference voltage value at the connection point C to a value shown in the following equation.

VB=(rsd+Im)(R3+R5+Rce8)+V
ce4 Next, a protection operation in a state where an excessive drive current value IDe is applied to the laser diode De will be explained.

The drive current value IDe is the power supply Vcc→laser diode D
Electricity is supplied through the path from the anode to the cathode of e, the collector to the emitter of the transistor 18, the resistor 19, and the ground line GND. When the drive current value IDe is in an excessive state, for example, when the command signal VE from the control unit 300 is applied at a high potential for some reason, an excessive current value that tends to destroy the laser diode De is applied. At this time, the current detection signal VR19 generated across the resistor 19 corresponding to the voltage value Vin to be compared rises to a level exceeding the base-emitter voltage V b e 20 of the transistor 20, and the current detection signal VR19 is generated between the base and emitter of the transistor 20. Current Ibe20
is energized. Then, an excessive current detection value Ice20 according to the value of the base current Ibe20 is applied to the path from the power supply Vcc to the resistor 25 to the collector of the transistor 20 to the emitter to the ground line GND. Therefore, the potential of the connection point F to which this excessive current detection value Ice20 is applied is as follows.

The reference voltage applied to the inverting input of the operational amplifier 11 is below the positive value V r e f . Therefore, the output terminal of the operational amplifier 11 shifts to the 11 L jj level and is held there.

A protection command signal is applied to connection point E. The driving current to the laser diode De in a state where the protection command signal is applied is such that the energization amount command signal applied from the control unit 300 to the command signal input point E is from the resistor 15 to the anode of the diode 13 to the cathode to the operational amplifier 11. As a result of energization from the output terminal of the terminal to the negative power supply terminal (not shown) to the ground line GND, the potential of the connection point E is reduced, and the base current Ibe18 of the transistor 18 is not energized, so it is cut off. Enters a protected operating state that is disabled. At the same time as this protective operation state is entered, a positive feedback current is passed through a path from the power supply Vcc to the anode of the diode 12 to the cathode and the output terminal of the operational amplifier 11 to a negative power supply terminal (not shown) to the ground line GND. Then, the collector of the transistor 20, 26, the resistor 25 and the diode 1
In the holding operation state in which a positive feedback current is conducted through the common connection point F of the anodes of the transistors 2 and 2, even if the current detection signal VR19 is lower than the base-emitter voltage Vbe20 of the transistor 20, the non-inverting input terminal of the operational amplifier 11 The potential applied to - never exceeds the reference voltage value Vref. Note that in this state, even if a voltage higher than the reference voltage value V r e f is applied to the base of the transistor 19.26, it is not transmitted to the collector of the transistor 19.26, so the holding operation continues to be maintained. .

Next, a description will be given of a protective operation in a state where the temperature of the laser diode De approaches its destruction. Even if the laser diode De is supplied with a driving current value IDe that is less than the excess current, there is a high possibility that the laser diode De will be destroyed as the temperature rises. This temperature rise is transmitted to the thermistor 22, and the thermistor 22
The impedance value of decreases. This thermistor 2
2, the power supply voltage value Vcc is made into a constant voltage by a constant voltage circuit including a resistor 21, a Zener diode 23, and a capacitor 24, and this constant voltage value is divided by the added value of the dropped impedance value of the thermistor 22 and the resistor 26. Excess current is applied. At this time, the current detection signal generated across the resistor 26 corresponding to the voltage value Vin to be compared is
7, and a base current Ibe27 is passed between the base and emitter of the transistor 27. Resistance 25 in this state
→ From collector to emitter of transistor 27 → Ground line G
An excess current detection value according to the value of the base current Ibe27 is applied to the ND path.

Therefore, the potential of the connection point F to which this excess current detection value is applied is lower than the reference voltage value Vref applied to the inverting input - of the operational amplifier 11. Therefore, the output terminal of the operational amplifier 11 shifts to L'' level and is held there, and the protection command signal is applied to the connection point E.The drive current to the laser diode De with the protection command signal applied is as follows. The energization amount command signal applied from the control unit 300 to the command signal input point E is energized through the path of the resistor 15 -> the anode and cathode of the diode 13 - the output terminal of the operational amplifier 11 -> the negative power supply terminal (not shown) -> the installation line GND. Since the base current Ibe18 of the transistor 18 is not energized, it is cut off and enters the protective operation state.Furthermore, in this state, the voltage g V c c → from the anode of the diode 12 to the cathode and from the output terminal of the operational amplifier 11 A holding current is passed through the path from a negative power supply terminal (not shown) to the ground line GND, and the potential at the connection point F is a forward voltage value VFD12 that is divided between the anode and cathode of the diode 12.
Therefore, since the reference voltage value V e r f applied to the inverting input terminal - of the operational amplifier 11 is not exceeded, the same protection operation due to overcurrent is maintained.

Next, a reset operation for restoring the protective operation state maintained due to overcurrent and overheating described above will be explained. A pulse signal of LL HI+ level supplied from a reset command circuit (not shown) is applied to the reset terminal, for example, by manual operation or the like. With this pulse signal, the collector-emitter of the transistor 8 becomes energized. The reset voltage value Vs (V) applied to the inverting input terminal - of the operational amplifier 11, which is the potential of the connection point G, is determined by the resistor 6
The resistance value of resistor 7 is R6 (Ω), the resistance value of resistor 7 is R7 (Ω),
When the voltage value divided between the collector and emitter of the transistor 8 in the energized state is Vce8 (V), the voltage value Vce8 (V) is obtained as shown by the following equation.

Vs = Vcc - (R6 + R7) (Vcc - Vce
8)/(R6+R7) Once this reset voltage value Vs (V) is applied to the operational amplifier 11, the reset voltage value Vs (V) is lower than the forward voltage value VFD12 applied to the non-inverting input terminal +. Therefore, the output terminal is II HI
Transition to I level and the holding state is reset. While the reset voltage value Vs (V) is being applied to the operational amplifier 11, the potential Vcr (V) at the connection point C is lower than the reference voltage value Vcf that indicates the center light emission amount of the laser diode De, as shown in the following equation. This value indicates the amount of light emitted.

Ver=Vce8+(Vcc-Vce8)・R7/
(R6+R7) The control unit 300, to which the reference voltage value Ver instructing this low light emission amount is applied, supplies the driving current IDe of the laser diode De to the base of the transistor 18.
A command signal is supplied to restart the machine while holding it low.

Then, when the reset terminal returns to the 17 LI+ level, a command signal instructing steady state light emission is supplied from the control section 300. Therefore, in the restart state, a command signal that increases step by step from the base voltage value Ver, which instructs a low light emission amount, to the reference voltage value Vef, which instructs a steady state light emission amount, is supplied to the laser diode De. Less stress. Furthermore, if the malfunction state is detected by the operation detection unit 200 again in this state, if the drive function of the transistor 18 is normal, the drive current IDe is cut off while the stress applied to the laser diode De is small. .

The startup detection unit 100 described in the above embodiment has a configuration that integrates the applied power supply voltage to obtain a startup command signal when the power is turned on. However, the configuration is not limited to this. It is also possible to change to a digital circuit that generates a start command signal for performing a predetermined soft start operation.

Further, the activation command signal of the activation detection unit 100 and the negative feedback value from the monitor diode Dm are both supplied to the inverting input terminal - (connection point B) which is the control input terminal of the control unit 300 explained in the above embodiment. However, if the design is changed to change the polarity of the activation command signal of the activation detection unit 100, the control unit 3
Needless to say, it can be changed to the non-inverting input terminal side of 00.

Note that even if the resistor 19 connected in series with the laser diode De for detecting the collective current value IDe is set to a relatively small resistance value compared to the current limiting resistor 73 of the conventional example, the resistance of the monitor diode Dm Since the current is controlled by the transistor 18 based on the negative feedback value, it operates without problems.

The semiconductor laser drive device configured in this way is
Since the current is limited by the transistor 18,
Since it operates stably even with a relatively low power supply voltage value Vcc, it is extremely convenient to be applied to hand belt type equipment, and its practical range is widened.

[Effects of the Invention] As explained above, in the semiconductor laser driving device of the present invention, the drive element 18 that controls the drive current controls the normal drive current, and this element 18 performs the soft start operation at the time of startup. Since the detection means 100 and the control means 300 are configured, the voltage divided in series with the laser diode De is not wasted, and the applied power supply voltage can be used efficiently, so the power supply voltage can be lowered. It can be operated stably even after setting.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention, and FIG. 2 is a configuration diagram showing a conventional example. 1.3,5,14,19...Resistance, 2,16...
...Capacitor, 4,18,20...Transistor. 1o... operational amplifier, 17... light emitting diode unit with built-in monitor diode, De...
... Laser diode, Dm ... Photo diode, 100 ... Startup detection section, 200.
...Motion detection section, 300...Control section, 4
00...Operating voltage generator. Figure 2

Claims (1)

[Scope of Claims] A laser diode De that outputs a laser beam using a current supplied from a power supply Vcc, a series-connected drive means 18 that controls the current flowing through the laser diode De, and a drive means 18 provided in the drive means 18. a control means 300 for supplying a control signal supporting energization and cut-off of the laser diode De to an input terminal B of the laser diode De; A semiconductor laser drive control device comprising: activation detection means 100 for outputting an energization start signal to prevent surge current from flowing to the semiconductor laser.