JP7259954B2 - Semiconductor laser device - Google Patents

Description

The present disclosure relates to a semiconductor laser device having a semiconductor laser element and its peripheral circuit, and more particularly to a semiconductor laser device that drives a semiconductor laser element by a peripheral circuit including an avalanche transistor.

In order to drive a semiconductor laser device, a peripheral circuit including a switching element (avalanche transistor) having an avalanche breakdown characteristic is sometimes used, as disclosed in Patent Document 1 and Non-Patent Document 1, for example.

Patent Document 1 discloses a pulse power supply device that operates a semiconductor laser element as a pulse light source. Here, the anode of the semiconductor laser element is connected to the emitter of the avalanche transistor, and the cathode of the semiconductor laser element is grounded. Also, the collector of the avalanche transistor is connected to the power supply via a resistor and another switching element (field effect transistor), and grounded via a capacitor.

In the circuit of U.S. Pat. No. 5,700,000, the capacitor is charged to the voltage of the power supply when the avalanche transistor is turned off and the field effect transistor is turned on. The voltage of the power supply is set by the capacitor so that a voltage higher than the breakdown voltage BVceo between the collector and emitter of the avalanche transistor is applied between the collector and emitter of the avalanche transistor. When the capacitor is charged to the voltage of the power supply, the field effect transistor is turned off. Now, when an avalanche breakdown is triggered by a control signal applied to the base of the avalanche transistor, the avalanche transistor is turned on and collector current flows rapidly. This collector current drives the semiconductor laser device connected in series with the avalanche transistor, thereby lighting the semiconductor laser device. Since this collector current is mainly derived from charges accumulated in the capacitor, the potential of the collector decreases as the collector current flows. When the potential of the collector drops until the collector-emitter voltage of the avalanche transistor becomes lower than the breakdown voltage BVceo, the avalanche breakdown stops and the avalanche transistor is turned off. After that, the capacitor is charged again to the voltage of the power supply and the series of operations is repeated.

Thus, by using an avalanche transistor, a semiconductor laser device can be driven to repeatedly generate intense light having a short duration.

Japanese Patent Application Laid-Open No. 2007-042731

N. Chadderton, "The ZTX415 Avalanche Mode Transistor: An Introduction to Characteristics, Performance and Applications", Zetex Application Note 8, Zetex, Issue 2 January 1996.

In the circuit of Patent Document 1, the following timing restrictions are imposed on the operations of the avalanche transistor and the field effect transistor.

The first timing constraint requires that the field effect transistor be turned on for a sufficient length of time to charge the capacitor to the voltage of the power supply. If the length of time during which the field effect transistor is turned on is insufficient, the power supplied from the capacitor to the semiconductor laser element will decrease, and the amount of light emitted from the semiconductor laser element will decrease.

Also, after the capacitor is charged to the voltage of the power supply, when both the avalanche transistor and the field effect transistor are turned off, leakage current in the avalanche transistor causes the collector potential to drop. In this case also, the power supplied from the capacitor to the semiconductor laser element is reduced, and the light emission amount of the semiconductor laser element is reduced. Therefore, a second timing constraint is required to turn off the field effect transistor just before turning on the avalanche transistor.

For example, it may be required to turn on a semiconductor laser element at a variable repetition rate (multirate). However, due to the above timing restrictions, the repetition rate of lighting of the semiconductor laser element is limited. Therefore, it is required to drive the semiconductor laser device with a high degree of freedom without reducing the amount of light emitted from the semiconductor laser device.

SUMMARY OF THE INVENTION An object of the present disclosure is to provide a semiconductor laser that can drive a semiconductor laser element with a simple circuit configuration without reducing the amount of light emitted from the semiconductor laser element and by relaxing the timing restrictions of the peripheral circuits of the semiconductor laser element. It is to provide a device.

A semiconductor laser device according to one aspect of the present disclosure includes:
a semiconductor laser element;
a capacitor;
a drive circuit;
first and second charge control circuits connected in parallel between a power source and the capacitor;
An NPN type having a collector connected to a node between the first and second charge control circuits and the capacitor, an emitter connected to the anode of the semiconductor laser element, and a base connected to the drive circuit. and a first switching element that is an avalanche transistor,
The drive circuit controls the first switching element to turn on the first switching element by avalanche breakdown, and blocks current from the power supply when the first switching element is on. and controlling the first charging control circuit to pass or block current from the power supply when the first switching element is off;
The first charging control circuit controls charging of the capacitor by current from the power supply flowing through the first charging control circuit,
The second charge control circuit holds the potential of the capacitor when the first switching element is turned off and the first charge control circuit blocks current from the power supply. , controlling the charging of the capacitor by current from the power source flowing through the second charge control circuit.

As a result, the semiconductor laser device can be driven by relaxing the timing restrictions of the peripheral circuits of the semiconductor laser device without reducing the amount of light emitted from the semiconductor laser device with a simple circuit configuration.

A semiconductor laser device according to one aspect of the present disclosure includes:
The first charging control circuit includes a second switching element and a first resistor connected in series with each other.

This makes it possible to easily control the charging of the capacitor by the current from the power supply flowing through the first charge control circuit under the control of the drive circuit.

A semiconductor laser device according to one aspect of the present disclosure includes:
The first charge control circuit includes a constant current circuit that supplies a constant current from the power supply to the capacitor to charge the capacitor.

As a result, it is possible to improve the repetition rate of lighting of the semiconductor laser element, and furthermore, it is possible to relax the timing restrictions of lighting of the semiconductor laser element.

A semiconductor laser device according to one aspect of the present disclosure includes:
The constant current circuit includes a current mirror circuit.

As a result, when the potential of the capacitor becomes substantially equal to the potential of the power supply, the charging of the capacitor can be automatically stopped, and the timing restrictions when the drive circuit controls the constant current circuit can be relaxed. .

A semiconductor laser device according to one aspect of the present disclosure includes:
The second charge control circuit includes a second resistor.

This makes it possible to easily control the charging of the capacitor by the current from the power supply flowing through the second charge control circuit.

According to the semiconductor laser device according to one aspect of the present disclosure, the semiconductor laser device has a simple circuit configuration and relaxes the timing restrictions of the peripheral circuits of the semiconductor laser device without reducing the light emission amount of the semiconductor laser device. can drive.

1 is a circuit diagram showing the configuration of a semiconductor laser device according to a first embodiment; FIG. 2 is a timing chart showing the operation of the semiconductor laser device of FIG. 1; 2 is a circuit diagram showing the configuration of a semiconductor laser device according to a second embodiment; FIG. 4 is a timing chart showing the operation of the semiconductor laser device of FIG. 3; FIG. 10 is a circuit diagram showing the configuration of a semiconductor laser device according to an implementation example of the second embodiment;

An embodiment (hereinafter also referred to as "the present embodiment") according to one aspect of the present disclosure will be described below with reference to the drawings. In each drawing, the same reference numerals denote similar components.

[First embodiment]
[Configuration of the first embodiment]
FIG. 1 is a circuit diagram showing the configuration of the semiconductor laser device according to the first embodiment. The semiconductor laser device of FIG. 1 includes a semiconductor laser element LD1, a switching element Q1, a switching element MN1, a power source V1, a resistor R1, a resistor R2, a capacitor C1, and a drive circuit 1.

In this specification, the node between the resistor R1 and the capacitor C1 is called "node N1", the node between the switching element Q1 and the semiconductor laser element LD1 is called "node N2", and the positive electrode of the power supply V1 is called "node N3". ”, and the node between the switching element MN1 and the resistor R2 is called “node N4”.

The semiconductor laser element LD1 is a laser diode. The anode of the semiconductor laser device LD1 is connected to the emitter of the switching device Q1, and the cathode of the semiconductor laser device LD1 is grounded.

The switching element Q1 is an NPN avalanche transistor. The switching element Q1 has a collector connected to a node N1 between the resistor R1 and the capacitor C1, an emitter connected to the anode of the semiconductor laser element LD1, and a base connected to the driving circuit 1. Switching element Q1 has an avalanche breakdown characteristic and has a predetermined collector-emitter breakdown voltage BVceo. The avalanche transistor is turned on by applying a control signal that triggers avalanche breakdown to the base when a voltage higher than the collector-emitter breakdown voltage BVceo is applied between the collector and emitter. Once the avalanche transistor causes an avalanche breakdown (also called "first breakdown"), it immediately transitions to a low impedance state (also called "second breakdown"). By using this phenomenon, high-speed switching on the order of several nanoseconds is realized.

The switching element MN1 is, for example, an enhancement-type N-channel field effect transistor. The switching element MN1 has a drain connected to the power supply V1, a source connected to the node N1 via the resistor R1, and a gate connected to the driving circuit 1.

A resistor R2 is connected between the power supply V1 and the capacitor C1. In other words, resistor R2 is connected in parallel with switching element MN1 and resistor R1 between power supply V1 and capacitor C1.

The power supply V1 is a DC power supply that generates a predetermined voltage. The positive electrode of the power source V1 is connected to the capacitor C1 via the resistor R2, the positive electrode of the power source V1 is further connected to the capacitor C1 via the switching element MN1 and the resistor R1, and the negative electrode of the power source V1 is grounded. One end of the capacitor C1 is a hot end (terminal to which a varying potential is applied) connected to the collector of the switching element Q1, and the other end of the capacitor C1 is a grounded cold end (to which a stable potential is applied). terminal).

The emitter of switching element Q1 and the anode of semiconductor laser element LD1 are connected to each other, and switching element Q1 and semiconductor laser element LD1 are connected to each other in series. The voltage of the capacitor C1 is applied across the switching element Q1 and the semiconductor laser element LD1, that is, across the collector of the switching element Q1 and the cathode of the semiconductor laser element LD1. When the switching element Q1 is turned off, no driving current flows through the semiconductor laser element LD1, so that no forward voltage is generated, and therefore the voltage of the capacitor C1 is applied between the collector and emitter of the switching element Q1. . The voltage of the power supply V1 is set higher than the collector-emitter breakdown voltage BVceo of the switching element Q1.

The drive circuit 1 applies a control signal to the base of the switching element Q1 that triggers the avalanche breakdown of the switching element Q1. When the avalache breakdown of the switching element Q1 is triggered, the switching element Q1 is turned on, and the semiconductor laser element LD1 is driven by discharging the electric power charged in the capacitor C1. Further, the drive circuit 1 applies a control signal for turning on/off the switching element MN1 to the gate of the switching element MN1. The drive circuit 1 controls the switching element MN1 to block the current from the power supply V1 when the switching element Q1 is on, and allows or passes the current from the power supply V1 when the switching element Q1 is off. Control the switching element MN1 to block.

Switching element MN1 and resistor R1, under the control of drive circuit 1, control charging of capacitor C1 by current from power source V1 flowing through switching element MN1 and resistor R1.

Resistor R2 allows current from power supply V1 to flow through resistor R2 so as to hold the potential of capacitor C1 when switching element Q1 is turned off and switching element MN1 blocks current from power supply V1. controls the charging of capacitor C1 by .

The power supply V1 generates at least a voltage higher than the breakdown voltage BVceo of the avalanche transistor, eg, 170-260V.

Resistor R2 may have a much higher resistance value than that of resistor R1, for example 100 times the resistance value.

In this specification, the switching element Q1 is also called "first switching element", and the switching element MN1 is also called "second switching element". Further, in this specification, the switching element MN1 and the resistor R1 are also referred to as a “first charging control circuit” or a “first charging circuit”, and the resistor R2 is referred to as a “second charging control circuit” or a “second charging circuit”. Also called charging circuit.

Switching element MN1 may be a P-channel field effect transistor instead of an N-channel field effect transistor, or any other switchable element.

[Operation of the first embodiment]
FIG. 2 is a timing chart showing the operation of the semiconductor laser device of FIG. The semiconductor laser device of FIG. 1 operates as follows.

The first row in FIG. 2 shows the control signal applied from the driving circuit 1 to the gate of the switching element MN1. The second row in FIG. 2 shows the potential of capacitor C1 at node N1. The third row in FIG. 2 shows the control signal applied from the drive circuit 1 to the base of the switching element Q1. The fourth row in FIG. 2 shows the amount of light emitted from the semiconductor laser element LD1.

In the initial state (time t1), the avalanche breakdown of switching element Q1 does not occur (that is, switching element Q1 is turned off).

During the time periods (time t1-t2, time t4-t5, and time t8-t9) in which the switching element Q1 is turned off and the switching element MN1 is turned on, the power supply V1 flows through the switching element MN1 and the resistor R1. The capacitor C1 is charged by the current from , and the potential of the capacitor C1 rises almost to the potential of the power supply V1, as shown in the second row of FIG. As a result, a voltage higher than the breakdown voltage BVceo of the switching element Q1 is applied between the collector and the emitter of the switching element Q1 by the capacitor C1.

When the potential of capacitor C1 rises sufficiently (time t2, t5, and t9), switching element MN1 is turned off. Even after the switching element MN1 is turned off, the potential of the capacitor C1 is held by the current from the power supply V1 flowing through the resistor R2 (time t5-t6).

Here, when an avalanche breakdown is triggered by a control signal applied to the base of the switching element Q1 (time t2, t6, and t9), an avalanche breakdown (first breakdown) due to free electrons occurs in the switching element Q1. (that is, the switching element Q1 is turned on) and the collector current flows rapidly. The semiconductor laser element LD1 is lit by this collector current. Since the collector current of switching element Q1 is mainly derived from the charges accumulated in capacitor C1, the potential of capacitor C1 decreases as the collector current flows. Even if the potential of the capacitor C1 drops, the switching element Q1 has a low impedance ( second yield).

When the charge accumulated in the capacitor C1 decreases and the potential of the capacitor C1 drops until the collector-emitter voltage of the switching element Q1 becomes lower than the breakdown voltage BVceo, the avalanche breakdown ends and the switching element Q1 is turned off. be.

After that, the capacitor C1 is again charged by the current from the power supply V1 flowing through the switching element MN1 and the resistor R1, the potential of the capacitor C1 rises almost to the potential of the power supply V1, and thereafter a series of operations are repeated.

Thus, by using the switching element Q1, which is an avalanche transistor, the semiconductor laser element LD1 can be driven to repeatedly generate strong light having a short duration.

The base of switching element Q1 is assumed to be floating. A potential difference based on the built-in potential is maintained between the base and emitter of the switching element Q1. A high reverse bias voltage is applied between the base and collector of the switching element Q1 to expand the depletion layer and generate a strong electric field. The collector current (that is, leakage current) that flows at this time consists of the current due to the potential difference between the collector and the emitter and the current due to the diffusion of holes from the emitter to the base (that is, the current amplification factor h _FE times the base current). collector current). Therefore, a large (on the order of several μA to several tens of μA) and fluctuating leakage current is generated.

The magnitude of the leakage current of switching element Q1 depends on the resistance value of resistor R1. Also, the repetition rate of lighting of the semiconductor laser element LD1 depends on the time constant of the resistor R1 and the capacitor C1. Since the power supplied to the semiconductor laser element LD1 depends on the voltage of the power source V1 and the capacitance value of the capacitor C1, when the semiconductor laser element LD1 is to be lit with a predetermined amount of light emission, the capacitor C1 is used to set a desired repetition rate. The range in which the capacitance value of C1 can be changed is limited. Therefore, the repetition rate mainly depends on the resistance value of resistor R1. In this case, if the resistance value is increased to reduce the leakage current, the repetition rate will decrease, and conversely, if the resistance value is decreased to increase the repetition rate, the leakage current will increase.

According to the prior art (for example, Patent Document 1), as mentioned above, a timing constraint is imposed to turn on the switching element MN1 for a sufficient length of time to charge the capacitor C1 to the voltage of the power supply V1. Further, according to the prior art (for example, Patent Document 1), in order to reduce the influence of leakage current, as described above, the timing constraint is imposed that the switching element MN1 is turned off immediately before the switching element Q1 is turned on. . According to the semiconductor laser device of FIG. 1, even after the switching element MN1 is turned off, the potential of the capacitor C1 is held by the current from the power supply V1 flowing through the resistor R2. Therefore, according to the semiconductor laser device of FIG. 1, the capacitor C1 can be charged during any part of the time period during which the switching element Q1 is turned off. As described above, according to the semiconductor laser device of FIG. 1, timing restrictions on the peripheral circuits of the semiconductor laser element LD1 can be relaxed.

[Effects of the first embodiment]
The semiconductor laser device of FIG. 1 can rapidly charge the capacitor C1 through the switching element MN1 and the resistor R1 (first charging control circuit). Further, since the semiconductor laser device of FIG. 1 includes the resistor R2 (second charge control circuit), the potential of the capacitor C1 can be held even when the switching elements Q1 and MN1 are off. can. As described above, the semiconductor laser device of FIG. 1 is provided with two charge control circuits, so that timing restrictions on the peripheral circuits of the semiconductor laser element LD1 can be relaxed without reducing the light emission amount of the semiconductor laser element LD1. The semiconductor laser element LD1 can be driven. As a result, for example, it is possible to easily realize a semiconductor laser device in which the semiconductor laser element LD1 is lit at a variable repetition rate.

Since the semiconductor laser device of FIG. 1 has a very simple circuit configuration, for example, a monolithic cathode-common semiconductor laser device including a plurality of semiconductor laser elements to be driven can be easily realized.

As described above, according to the semiconductor laser device according to the first embodiment, although the circuit configuration is simple, the timing restriction of the peripheral circuit of the semiconductor laser element LD1 can be reduced without reducing the light emission amount of the semiconductor laser element LD1. The semiconductor laser device LD1 can be driven with relaxation.

[Second embodiment]
[Configuration of Second Embodiment]
FIG. 3 is a circuit diagram showing the configuration of the semiconductor laser device according to the second embodiment. The semiconductor laser device of FIG. 3 includes a constant current circuit I1 and a drive circuit 1A instead of the switching element MN1, resistor R1 and drive circuit 1 of FIG.

The constant current circuit I1 is connected between the power supply V1 and the capacitor C1, and controls charging of the capacitor C1 by current from the power supply V1 flowing through the constant current circuit I1. The constant current circuit I1 supplies a constant current from the power source V1 to the capacitor C1 to charge it.

In this specification, the constant current circuit I1 is also referred to as a "first charging control circuit".

The drive circuit 1A, like the drive circuit 1 of FIG. 1, applies to the base of the switching element Q1 a control signal that triggers the avalanche breakdown of the switching element Q1. Further, the drive circuit 1A controls the constant current circuit I1 to block the current from the power supply V1 when the switching element Q1 is on, and controls the current from the power supply V1 when the switching element Q1 is off. is controlled to pass or block the constant current circuit I1.

[Operation of Second Embodiment]
FIG. 4 is a timing chart showing the operation of the semiconductor laser device of FIG. The semiconductor laser device of FIG. 3 operates as follows.

The third row in FIG. 2 shows the control signal applied from the drive circuit 1 to the constant current circuit I1. The first, second, and fourth rows of FIG. 4 are the same as the corresponding parts of FIG.

In the initial state (time t11), the avalanche breakdown of switching element Q1 does not occur (that is, switching element Q1 is turned off).

During the time periods (time t11-t12, time t14-t15, and time t18-t19) in which the switching element Q1 is turned off and the constant current circuit I1 is turned on, the current flows from the power supply V1 through the constant current circuit I1. A constant current charges the capacitor C1, and the potential of the capacitor C1 rises almost to the potential of the power supply V1, as shown in the second row of FIG. As a result, a voltage higher than the breakdown voltage BVceo of the switching element Q1 is applied between the collector and the emitter of the switching element Q1 by the capacitor C1. At this time, since a constant current is supplied to the capacitor C1, the potential of the capacitor C1 changes as a ramp function.

When the potential of capacitor C1 rises sufficiently (time t12, t15, and t19), constant current circuit I1 is turned off. Even after the constant current circuit I1 is turned off, the potential of the capacitor C1 is held by the current from the power supply V1 flowing through the resistor R2 (time t15-t16).

Here, when an avalanche breakdown is triggered by a control signal applied to the base of the switching element Q1 (time t12, t16, and t19), an avalanche breakdown (first breakdown) due to free electrons occurs in the switching element Q1. (that is, the switching element Q1 is turned on) and the collector current flows rapidly. The semiconductor laser element LD1 is lit by this collector current. Since the collector current of switching element Q1 is mainly derived from the charges accumulated in capacitor C1, the potential of capacitor C1 decreases as the collector current flows. Even if the potential of the capacitor C1 drops, the switching element Q1 has a low impedance ( second yield).

When the charge accumulated in the capacitor C1 decreases and the potential of the capacitor C1 drops until the collector-emitter voltage of the switching element Q1 becomes lower than the breakdown voltage BVceo, the avalanche breakdown ends and the switching element Q1 is turned off. be.

After that, the capacitor C1 is again charged by the current from the power supply V1 flowing through the constant current circuit I1, the potential of the capacitor C1 rises almost to the potential of the power supply V1, and thereafter a series of operations are repeated.

Thus, by using the switching element Q1, which is an avalanche transistor, the semiconductor laser element LD1 can be driven to repeatedly generate strong light having a short duration.

According to the semiconductor laser device of FIG. 3, since the capacitor C1 is charged with a constant current flowing from the power source V1 through the constant current circuit I1, the charging time of the capacitor C1 is shortened as compared with the semiconductor laser device of FIG. can do. As a result, the repetition rate of lighting of the semiconductor laser element LD1 can be improved, and furthermore, the restriction on the timing of lighting of the semiconductor laser element LD1 can be relaxed. Also, by adjusting the magnitude of the current flowing through the constant current circuit I1, the capacitor C1 can be effectively charged.

Further, according to the semiconductor laser device of FIG. 3, as in the semiconductor laser device of FIG. 1, even after the constant current circuit I1 is turned off, the current from the power source V1 that flows through the resistor R2 maintains the potential of the capacitor C1. is retained. Therefore, according to the semiconductor laser device of FIG. 3, the capacitor C1 can be charged during any part of the time period during which the switching element Q1 is turned off.

As described above, according to the semiconductor laser device of FIG. 3, the repetition rate of lighting of the semiconductor laser element LD1 can be improved, and the timing restrictions of the peripheral circuits of the semiconductor laser element LD1 can be relaxed.

Leakage current tends to flow through the avalanche transistor, so it is difficult to reduce the resistance value of the resistor R1 in FIG. On the other hand, since the power supplied to the semiconductor laser element LD1 is determined by the capacity of the capacitor C1, it is also difficult to reduce the capacity of the capacitor C1. According to the semiconductor laser device of FIG. 3, since the constant current circuit I1 is provided, the charging time of the capacitor C1 can be shortened without increasing the leakage current.

[Example of implementation of the second embodiment]
FIG. 5 is a circuit diagram showing the configuration of a semiconductor laser device according to an implementation example of the second embodiment. The constant current circuit I1 in FIG. 3 includes, for example, field effect transistors MP1 and MP2, a switching element SW1, and a constant current source I1a. The field effect transistors MP1 and MP2 are, for example, P-channel field effect transistors and constitute a current mirror circuit. The switching element SW1 is turned on/off under the control of the drive circuit 1A. When the switching element SW1 is turned on, a current having the same magnitude as the current flowing through the constant current source I1a is supplied from the power supply V1 to the capacitor C1.

According to the semiconductor laser device of FIG. 5, since the current mirror circuit of the field effect transistors MP1 and MP2 is provided, the current flowing through the field effect transistor MP1 is mirrored by the field effect transistor MP2, and the capacitor C1 is charged by this current. be done. When the charging of the capacitor C1 approaches the end and the potential of the capacitor C1 becomes substantially equal to the potential of the power source V1, the mirror relationship between the currents of the field effect transistors MP1 and MP2 is broken and the current of the field effect transistor MP2 automatically becomes , and thus the charging of capacitor C1 can be automatically stopped. Since the drive circuit 1A does not need to generate a control signal to stop charging the capacitor C1, it is possible to relax the timing constraint when the drive circuit 1A controls the constant current circuit I1.

[Effect of Second Embodiment]
The semiconductor laser devices of FIGS. 3 and 5 can rapidly charge the capacitor C1 through the constant current circuit I1 (first charge control circuit). In addition, the semiconductor laser devices of FIGS. 3 and 5 are provided with the resistor R2 (second charge control circuit), so that even when the switching element Q1 and the constant current circuit I1 are off, the capacitor C1 is kept charged. A potential can be held. As described above, the semiconductor laser devices of FIGS. 3 and 5 are provided with two charging control circuits, thereby improving the lighting repetition rate of the semiconductor laser element LD1 without reducing the light emission amount of the semiconductor laser element LD1. In addition, the semiconductor laser device LD1 can be driven by relaxing the timing restrictions on the peripheral circuits of the semiconductor laser device LD1. As a result, for example, it is possible to easily realize a semiconductor laser device in which the semiconductor laser element LD1 is lit at a variable repetition rate.

Since the semiconductor laser devices of FIGS. 3 and 5 have a very simple circuit configuration, for example, a monolithic cathode-common semiconductor laser device including a plurality of semiconductor laser elements to be driven can be easily realized.

As described above, according to the semiconductor laser device according to the second embodiment, although the circuit configuration is simple, the timing restriction of the peripheral circuit of the semiconductor laser element LD1 can be reduced without reducing the light emission amount of the semiconductor laser element LD1. The semiconductor laser device LD1 can be driven with relaxation.

[Example]
The semiconductor laser device according to each embodiment of the present disclosure is applicable to, for example, a LiDAR (Light Detection and Ranging) rangefinder. According to the LiDAR technology, TOF (Time of Flight) is roughly classified into either direct TOF by transmission/reception of pulsed light or indirect TOF by transmission/reception of continuous light. The semiconductor laser device according to each embodiment of the present disclosure can be applied to a LiDAR ranging device using direct TOF, and in particular, can be applied to effectively transmit pulsed light.

According to the semiconductor laser device according to each embodiment of the present disclosure, it is possible to transmit pulsed light having a short duration (e.g., full width at half maximum of 5 nanoseconds or less) and high peak power (e.g., peak value of 100 W). , which enables direct TOF measurement with high accuracy.

Further, according to the semiconductor laser device according to each embodiment of the present disclosure, when transmitting pulsed light having a wavelength from visible light to near-infrared light, the power of the transmitted pulsed light is adjusted so as to satisfy eye-safe constraints. can be controlled.

Further, according to the semiconductor laser device according to each embodiment of the present disclosure, the transmitted pulsed light is adjusted so as to compensate for the characteristics of the semiconductor laser element (laser diode) that varies depending on the environment or due to deterioration. Power can be controlled. For example, the voltage of the power supply V1 may be set higher according to deterioration of the semiconductor laser element.

Further, according to the semiconductor laser device according to each embodiment of the present disclosure, by increasing the repetition rate of transmitting pulsed light (for example, a repetition rate higher than 100 kHz), the number of direct TOF measurements per unit time is increased. and the measurement accuracy of LiDAR can be improved.

Further, according to the semiconductor laser device according to each embodiment of the present disclosure, it is possible to easily realize a semiconductor laser device in which the semiconductor laser element is lit at a variable repetition rate.

Further, according to the semiconductor laser device according to each embodiment of the present disclosure, in order to expand the measurement range of LiDAR, for example, a LiDAR ranging device including a cathode common semiconductor laser device including a plurality of semiconductor laser elements can be provided.

Also, the semiconductor laser device according to each embodiment of the present disclosure can be applied to a processing device using pulsed laser light. The energy of laser light generated by the semiconductor laser device according to each embodiment of the present disclosure may be directly used to process an object. Further, the laser light generated by the semiconductor laser device according to each embodiment of the present disclosure may be used as a trigger signal to generate laser light with higher energy to process the object.

[summary]
A semiconductor laser device according to each aspect of the present disclosure may be expressed as follows.

A semiconductor laser device according to a first aspect of the present disclosure includes a semiconductor laser element LD1, a first switching element Q1, a power source V1, first and second charge control circuits, a capacitor C1, and drive circuits 1 and 1A. . The first and second charge control circuits are connected in parallel with each other between the power supply V1 and the capacitor C1. The first switching element Q1 has a collector connected to a node between the first and second charge control circuits and the capacitor C1, an emitter connected to the anode of the semiconductor laser element LD1, and the driving circuits 1 and 1A. NPN avalanche transistor with base connected. The drive circuits 1 and 1A control the first switching element Q1 so as to turn on the first switching element Q1 by avalanche breakdown, and when the first switching element Q1 is on, the current from the power supply V1 is and control the first charging control circuit to pass or block the current from the power source V1 when the first switching element Q1 is off. The first charge control circuit controls charging of the capacitor C1 with current from the power supply V1 flowing through the first charge control circuit. The second charge control circuit maintains the potential of the capacitor C1 when the first switching element Q1 is turned off and the first charge control circuit blocks the current from the power source V1. 2 control the charging of the capacitor C1 by the current from the power supply V1 flowing through the charge control circuit 2;

According to the semiconductor laser device according to the second aspect of the present disclosure, in the semiconductor laser device according to the first aspect, the first charging control circuit includes the second switching element MN1 and the first switching element MN1 connected in series with each other. Includes resistor R1.

According to the semiconductor laser device according to the third aspect of the present disclosure, in the semiconductor laser device according to the first aspect, the first charging control circuit supplies a constant current from the power supply V1 to the capacitor C1 to charge the capacitor C1. It includes a constant current circuit I1.

According to the semiconductor laser device according to the fourth aspect of the present disclosure, in the semiconductor laser device according to the third aspect, the constant current circuit I1 includes a current mirror circuit.

According to the semiconductor laser device according to the fifth aspect of the present disclosure, in the semiconductor laser device according to one of the first to fourth aspects, the second charging control circuit includes the second resistor R2.

A semiconductor laser device according to one aspect of the present disclosure can be applied to, for example, a LiDAR ranging device, and can be applied to a processing device using pulsed laser light.

1, 1A... drive circuit,
C1... Capacitor,
I1... constant current circuit,
I1a... constant current source,
LD1... semiconductor laser element,
MP1, MP2...field effect transistors Q1, MN1, SW1...switching elements,
R1, R2... Resistance,
V1 . . . power supply.

Claims (5)

a semiconductor laser element;
a capacitor;
a drive circuit;
first and second charge control circuits connected in parallel between a power source and the capacitor;
An NPN type having a collector connected to a node between the first and second charge control circuits and the capacitor, an emitter connected to the anode of the semiconductor laser element, and a base connected to the drive circuit. and a first switching element that is an avalanche transistor,
The drive circuit controls the first switching element to turn on the first switching element by avalanche breakdown, and blocks current from the power supply when the first switching element is on. and controlling the first charging control circuit to pass or block current from the power supply when the first switching element is off;
The first charging control circuit controls charging of the capacitor by current from the power supply flowing through the first charging control circuit,
The second charge control circuit holds the potential of the capacitor when the first switching element is turned off and the first charge control circuit blocks current from the power supply. , controlling charging of the capacitor by current from the power source flowing through the second charge control circuit;
Semiconductor laser device. wherein the first charging control circuit includes a second switching element and a first resistor connected in series with each other;
2. The semiconductor laser device according to claim 1. The first charging control circuit includes a constant current circuit that supplies a constant current from the power supply to the capacitor to charge the capacitor.
2. The semiconductor laser device according to claim 1. the constant current circuit includes a current mirror circuit;
4. The semiconductor laser device according to claim 3. the second charging control circuit includes a second resistor;
5. The semiconductor laser device according to claim 1.

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