JP7231025B2 - 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 transistor having an avalanche breakdown characteristic (avalanche transistor) may be used as disclosed in Patent Document 1 and Non-Patent Document 1, for example. In this case, for example, 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 grounded via a capacitor.

In circuits containing avalanche transistors as described above, when the avalanche transistor is turned off, the capacitor is charged to the voltage of the power supply. 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. 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.

The power supplied to the semiconductor laser element depends on the power charged in the capacitor, and the power charged in the capacitor depends on the voltage of the power supply and the capacitance value of the capacitor. The voltage of the power supply must be set at least higher than the breakdown voltage BVceo of the avalanche transistor. Also, the breakdown voltage BVceo is determined according to the characteristics of the avalanche transistor that is actually used. As described above, there is a problem that the controllable range of the amount of light emitted from the semiconductor laser element is narrow and difficult to control due to the restrictions on the voltage of the power supply and the breakdown voltage BVceo of the avalanche transistor.

The magnitude of the leakage current of the avalanche transistor depends on the resistance value of the resistor connected to the collector of the avalanche transistor. Further, the repetition rate of lighting of the semiconductor laser element depends on the time constant (the product of the resistance value of the resistor and the capacitance of the capacitor) of the resistor and capacitor connected to the collector of the avalanche transistor. As described above, the power supplied to the semiconductor laser device depends on the voltage of the power source and the capacitance value of the capacitor. The range in which the capacitance value of the capacitor can be changed is limited. Therefore, the repetition rate mainly depends on the resistance value of the resistor. In this case, if the resistance value is increased in order to reduce the leakage current, the repetition rate will decrease. Conversely, if the resistance value is decreased in order to increase the repetition rate, the leakage current will increase.

In order to increase the repetition rate without increasing the leak current, for example, it is conceivable to connect in parallel a plurality of drive circuits operating in different phases to one semiconductor laser device. However, when such a circuit configuration is adopted, the scale of the circuit becomes very large. In addition, since a very high voltage is applied to each circuit component to cause the avalanche breakdown of the avalanche transistor, the breakdown voltage of each circuit component can be ensured without mounting a large number of circuit components in a narrow area. Implementation constraints are imposed as follows. Furthermore, it is difficult to realize a monolithic common-cathode semiconductor laser device including a plurality of semiconductor laser elements to be driven.

An object of the present disclosure is to control the amount of light emitted from a semiconductor laser device over a wider range than in the past with a simple circuit configuration, and to achieve a higher repetition rate than in the past without increasing leakage current. An object of the present invention is to provide a semiconductor laser device capable of lighting a laser element.

A semiconductor laser device according to one aspect of the present disclosure includes:
A semiconductor laser device, a switching device, first and second power supplies, first and second charge control circuits, first and second capacitors, a diode, and a drive circuit,
The first charge control circuit is connected between the first power supply and the first capacitor, and the first charge control circuit is powered by a current from the first power supply flowing through the first charge control circuit. controls the charging of the capacitor,
The second charge control circuit is connected between the second power supply and the second capacitor, and the second charge control circuit is powered by current from the second power supply flowing through the second charge control circuit. controls the charging of the capacitor,
The diode has a cathode connected to a node between the first charge control circuit and the first capacitor, and an anode connected to a node between the second charge control circuit and the second capacitor. and
The switching element has a collector connected to a node between the first charge control circuit and the first capacitor, an emitter connected to the anode of the semiconductor laser element, and a base connected to the drive circuit. is an NPN-type avalanche transistor having

As a result, the amount of light emitted from the semiconductor laser element can be controlled over a wider range than in the past with a simple circuit configuration, and the semiconductor laser element can be operated at a higher repetition rate than before without increasing leakage current. can be lit.

According to the semiconductor laser device according to one aspect of the present disclosure,
The first power supply applies a voltage higher than the voltage applied by the second power supply to the second capacitor through the second charge control circuit to the first capacitor through the first charge control circuit. is applied to the capacitor of

This allows the first and second capacitors to be charged independently of each other. The voltage applied between the collector and emitter of the switching element when the first breakdown occurs in the switching element and the power supplied to the semiconductor laser element when the switching element is in the second breakdown state are independent of each other. can be adjusted to

According to the semiconductor laser device according to one aspect of the present disclosure,
The second capacitor has a capacity equal to or greater than that of the first capacitor.

As a result, since the power for driving the semiconductor laser element is mainly supplied from the second capacitor, the voltage of the second power supply and the capacity of the second capacitor can be appropriately set to drive the semiconductor laser element. The amount of light emitted can be easily controlled over a wide range. Further, since the power for driving the semiconductor laser element is mainly supplied from the second capacitor, even if the resistance value of the first charge control circuit is increased to reduce the leakage current, the first capacitor can be set smaller. Therefore, by setting the time constants of the first charge control circuit and the first capacitor small, the repetition rate of lighting of the semiconductor laser element can be increased.

According to the semiconductor laser device according to one aspect of the present disclosure,
The first charge control circuit includes a first resistor.

Thereby, the charging of the first capacitor by the current from the first power supply can be controlled.

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

As a result, the time required for charging the first capacitor can be shortened, and the repetition rate of lighting of the semiconductor laser element can be improved.

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

Thereby, the charging of the second capacitor by the current from the second power supply can be controlled.

According to the semiconductor laser device according to one aspect of the present disclosure,
The second charging control circuit includes a constant current circuit that supplies a constant current from the second power supply to the second capacitor to charge the second capacitor.

Thereby, the time required for charging the second capacitor can be shortened, and the repetition rate of lighting of the semiconductor laser element can be improved.

According to the semiconductor laser device according to one aspect of the present disclosure,
Said diode is a Schottky barrier diode.

As a result, the reverse recovery current that flows when a reverse bias voltage is applied to the diode can be reduced, and the semiconductor laser device can be driven at high speed and reliably.

According to the semiconductor laser device according to one aspect of the present disclosure, it is possible to control the amount of light emitted from the semiconductor laser element over a wider range than in the past with a simple circuit configuration, without increasing leakage current. A semiconductor laser element can be lit at a higher repetition rate than conventionally.

1 is a circuit diagram showing the configuration of a semiconductor laser device according to a first embodiment; FIG. FIG. 3 is a circuit diagram showing the configuration of a semiconductor laser device according to a comparative example; 2 is a circuit diagram showing the configuration of a semiconductor laser device according to a second embodiment; FIG. FIG. 4 is a graph schematically showing temporal changes in voltages at nodes N1 and N5 of FIG. 3; FIG. FIG. 10 is a circuit diagram showing the configuration of a semiconductor laser device according to a third embodiment; 6 is a graph schematically showing temporal changes in voltages at nodes N1 and N5 of FIG. 5; FIG. 11 is a circuit diagram showing the configuration of a semiconductor laser device according to a fourth embodiment; FIG. 8 is a graph schematically showing temporal changes in voltages at nodes N1 and N5 of FIG. 7; FIG.

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 power source V1, a resistor R1, a capacitor C1, a power source V2, a resistor R2, a capacitor C2, a diode D1, 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". , the positive terminal of the power supply V2 is also called “node N4”, and the node between the resistor R2 and the capacitor C2 is called “node N5”.

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 power supply V1 is a DC power supply that generates a predetermined voltage. The positive terminal of power supply V1 is connected to capacitor C1 via resistor R1, and the negative terminal of power supply V1 is grounded. A resistor R1 is connected between the power supply V1 and the capacitor C1 and controls the charging of the capacitor C1 by current from the power supply V1 flowing through the resistor R1. 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 power supply V2 is a DC power supply that generates a predetermined voltage. The positive terminal of power supply V2 is connected to capacitor C2 through resistor R2, and the negative terminal of power supply V2 is grounded. A resistor R2 is connected between the power source V2 and the capacitor C2 and controls the charging of the capacitor C2 by current from the power source V2 flowing through the resistor R2. One end of capacitor C2 is a hot end connected to the collector of switching element Q1 via diode D1, and the other end of capacitor C2 is a grounded cold end.

Diode D1 has a cathode connected to node N1 between resistor R1 and capacitor C1, and an anode connected to node N5 between resistor R2 and capacitor C2. Diode D1 is a steering diode that allows current to flow only from node N5 toward node N1 when a forward bias voltage is applied.

When the potential of node N1 drops below the potential of node N5, the voltage of capacitor C2 is applied across switching element Q1 and semiconductor laser element LD1 via diode D1. Therefore, the voltage of the power supply V2 is set by the capacitor C2 such that a voltage higher than the breakdown voltage BVceo of the switching element Q1 is applied between the collector and emitter 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 capacitors C1 and C2.

Power supplies V1 and V2 generate at least a voltage higher than the breakdown voltage BVceo of the avalanche transistor, eg, 170-260V. The power source V1 may apply to the capacitor C1 via the resistor R1 a voltage equal to or higher than the voltage that the power source V2 applies to the capacitor C2 via the resistor R2. In this case, when the switching element Q1 is turned off, the potential of the node N1 becomes equal to or higher than the potential of the node N5, and the diode D1 is turned off.

Capacitor C2 may have a capacitance greater than or equal to that of capacitor C1, eg, 5 to 10 times as large. In this case, power for driving the semiconductor laser device LD1 is mainly supplied from the capacitor C2.

Diode D1 may be a Schottky barrier diode. Diode D1 may also be a fast recovery diode.

In this specification, the power supply V1 is also called "first power supply", and the power supply V2 is also called "second power supply". Further, in this specification, the resistor R1 is 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 Further, in this specification, the capacitor C1 is also referred to as the "first capacitor", and the capacitor C2 is also referred to as the "second capacitor".

[Configuration and Operation of Comparative Example]
FIG. 2 is a circuit diagram showing the configuration of a semiconductor laser device according to a comparative example. The semiconductor laser device of FIG. 2 shows the circuit disclosed in Patent Document 1 and Non-Patent Document 1. FIG.

The semiconductor laser device of FIG. 2 includes a semiconductor laser element LD1, a switching element Q1, a power source V1, a resistor R1, a capacitor C1, and a drive circuit 1. Each component of the semiconductor laser device of FIG. 2 is configured in the same manner as the corresponding component of the semiconductor laser device of FIG.

The semiconductor laser device of FIG. 2 operates as follows.

When the avalanche breakdown of the switching element Q1 does not occur (that is, when the switching element Q1 is turned off), the current from the power supply V1 flowing through the resistor R1 charges the capacitor C1, and the potential of the node N1 becomes It rises almost to the potential of the power supply V1. 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.

Here, when an avalanche breakdown is triggered by a control signal applied to the base of the switching element Q1, an avalanche breakdown (first breakdown) due to free electrons occurs in the switching element Q1 (that is, the switching element Q1 turns on). ) and the collector current flows rapidly. Since this collector current is mainly derived from charges accumulated in capacitor C1, the potential of node N1 decreases as the collector current flows. Even if the potential of the node N1 drops, as long as a voltage higher than the breakdown voltage BVceo of the switching element Q1 is applied between the collector and emitter of the switching element Q1, the switching element Q1 has a low impedance ( second yield).

When the electric charge accumulated in the capacitor C1 decreases and the potential of the node N1 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 resistor R1, the potential of the node N1 rises almost to the potential of the power supply V1, and thereafter a series of operations are repeated.

The power supplied to the semiconductor laser element LD1 depends on the power charged in the capacitor C1, and the power charged in the capacitor C1 depends on the voltage of the power supply V1 and the capacitance value of the capacitor C1. The voltage of the power supply V1 must be set at least to a value exceeding the breakdown voltage BVceo of the switching element Q1, and the breakdown voltage BVceo is determined according to the characteristics of the switching element Q1 actually used. As described above, the controllable range of the light emission amount of the semiconductor laser element LD1 is narrow and difficult to control due to the restrictions on the voltage of the power supply V1 and the breakdown voltage BVceo of the switching element Q1. .

When the switching element Q1 is turned off, the base of the switching element Q1 is considered 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). This results in a large and fluctuating leakage current.

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. As described above, the power supplied to the semiconductor laser device LD1 depends on the voltage of the power source V1 and the capacitance value of the capacitor C1. The range in which the capacitance value of capacitor C1 can be changed for setting is limited. Therefore, the repetition rate mainly depends on the resistance value of resistor R1. In this case, if the resistance value is increased in order to reduce the leakage current, the repetition rate will decrease. Conversely, if the resistance value is decreased in order to increase the repetition rate, the leakage current will increase. Specifically, the magnitude of the leakage current is on the order of 10 μA at maximum, and the repetition rate of lighting of the semiconductor laser element LD1 is limited to the order of several tens of kHz at maximum.

In order to increase the repetition rate (for example, to exceed several 100 kHz) without increasing the leak current, for example, a plurality of drive circuits operating in different phases are connected in parallel to one semiconductor laser element LD1. It is conceivable to connect However, when such a circuit configuration is adopted, the scale of the circuit becomes very large. In addition, since a very high voltage is applied to each circuit component to cause an avalanche breakdown of the switching element Q1, the breakdown voltage of each circuit component can be ensured without mounting a large number of circuit components in a narrow area. Implementation constraints are imposed as follows. Furthermore, it may be difficult to realize a monolithic common cathode semiconductor laser device including a plurality of semiconductor laser elements LD1 to be driven.

In each of the embodiments of the present disclosure, although the circuit configuration is simple, the light emission amount of the semiconductor laser element LD1 can be controlled over a wider range than in the conventional art, and the repetition rate is higher than in the conventional art without increasing the leakage current. Provided is a semiconductor laser device capable of lighting a semiconductor laser element LD1 at a high rate.

[Operation of the first embodiment]
The semiconductor laser device of FIG. 1 operates as follows.

When the avalanche breakdown of the switching element Q1 does not occur (that is, when the switching element Q1 is turned off), the current from the power supply V1 flowing through the resistor R1 charges the capacitor C1, and the potential of the node N1 becomes It rises almost to the potential of the power supply V1. 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 the same time, the capacitor C2 is charged by the current from the power supply V2 flowing through the resistor R2, and the potential of the node N5 rises almost to the potential of the power supply V2. As previously described, the voltages of power supplies V1 and V2 are set such that power supply V1 applies a voltage to capacitor C1 through resistor R1 that is greater than or equal to the voltage that power supply V2 applies to capacitor C2 through resistor R2. . Therefore, at this time, the potential of the node N1 becomes equal to or higher than the potential of the node N5, and the diode D1 is turned off.

Here, when an avalanche breakdown is triggered by a control signal applied to the base of the switching element Q1, an avalanche breakdown (first breakdown) due to free electrons occurs in the switching element Q1 (that is, the switching element Q1 turns on). ) and the collector current flows rapidly. Since this collector current is derived from the charge accumulated in capacitor C1, the potential of node N1 decreases as the collector current flows. When the charge stored in the capacitor C1 decreases and the potential of the node N1 becomes lower than the potential of the node N5, a forward bias voltage is applied to the diode D1 to turn it on. When the diode D1 is turned on, the current derived from the charge accumulated in the capacitor C2 flows through the diode D1 and is added to the collector current of the switching element Q1. Even if the potential of the node N1 drops, as long as a voltage higher than the breakdown voltage BVceo of the switching element Q1 is applied between the collector and emitter of the switching element Q1, the switching element Q1 has a low impedance ( second yield).

When the charges stored in the capacitors C1 and C2 decrease and the potential of the node N1 drops until the collector-emitter voltage of the switching element Q1 becomes lower than the breakdown voltage BVceo, the avalanche breakdown stops and the switching element Q1 turned off. After that, the capacitor C1 is again charged by the current from the power supply V1 flowing through the resistor R1, and the potential of the node N1 rises almost to the potential of the power supply V1. At the same time, the capacitor C2 is charged by the current from the power supply V2 flowing through the resistor R2, and the potential of the node N5 rises almost to the potential of the power supply V2.

Here, the time constant τ2 of the resistor R2 and the capacitor C2 is set to be equal to or greater than the time constant τ1 of the resistor R1 and the capacitor C1. As a result, the potential of the node N1 is more likely to rise than the potential of the node N5, and during most of the period in which the switching element Q1 is off, the potential of the node N1 is equal to or higher than the potential of the node N5, and the diode D1 is turned off. be done. Capacitors C1 and C2 are thus charged independently of each other.

After that, a series of operations are repeated.

[Effects of the first embodiment]
The semiconductor laser device of FIG. 1 includes a power source V1, a resistor R1, and a capacitor C1 for supplying power to the semiconductor laser element LD1 when a first breakdown occurs in the switching element Q1. A power supply V2, a resistor R2 and a capacitor C2 are provided for powering the semiconductor laser device LD1 when in breakdown. As a result, the voltage applied between the collector and the emitter of the switching element Q1 when the first breakdown occurs in the switching element Q1 and the voltage supplied to the semiconductor laser element LD1 when the switching element Q1 is in the second breakdown state power can be adjusted independently of each other. Therefore, the amount of light emitted from the semiconductor laser element LD1 can be controlled over a wider range than conventionally.

According to the semiconductor laser device of FIG. 1, the power for driving the semiconductor laser element LD1 is mainly supplied from the capacitor C2. The amount of light emitted from the device LD1 can be easily controlled over a wide range. Moreover, since the time constants of the resistor R2 and the capacitor C2 can be selected in a wide range, the lighting repetition rate of the semiconductor laser element LD1 can be set in a wide range.

According to the semiconductor laser device of FIG. 1, power for driving the semiconductor laser element LD1 is mainly supplied from the capacitor C2. The capacity of C1 can be set small. Therefore, according to the semiconductor laser device of FIG. 1, the time constants of the resistor R1 and the capacitor C1 can be reduced without increasing the leakage current, and the semiconductor laser element LD1 can be lit at a higher repetition rate. Alternatively, according to the semiconductor laser device of FIG. 1, the leak current can be reduced without lowering the lighting repetition rate of the semiconductor laser element LD1.

According to the semiconductor laser device of FIG. 1, for example, the leakage current can be increased by a simple circuit configuration without connecting in parallel a plurality of drive circuits operating in different phases for one semiconductor laser element LD1. The repetition rate can be increased without Therefore, for example, a monolithic cathode-common semiconductor laser device including a plurality of semiconductor laser elements to be driven can be realized.

According to the semiconductor laser device of FIG. 1, connection/disconnection of the nodes N1 and N5 is realized by the diode D1 without using a switching element to which a control signal is applied from the outside. Therefore, the desired operation can be realized with a simple circuit configuration without requiring complicated timing control of the switching elements.

According to the semiconductor laser device of FIG. 1, by using a Schottky barrier diode or a fast recovery diode as the diode D1, the reverse recovery current that flows when a reverse bias voltage is applied to the diode D1 is reduced, and the semiconductor laser element LD1 is reduced. can be driven at high speed and reliably.

As described above, according to the semiconductor laser device of the first embodiment, the light emission amount of the semiconductor laser element LD1 can be controlled over a wider range than in the prior art with a simple circuit configuration, and the leakage current can be reduced. It is possible to light the semiconductor laser element LD1 at a higher repetition rate than before without increasing .

[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 in place of the resistor R1 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".

Here, the time constant τ2 of the resistor R2 and the capacitor C2 is set to be equal to or greater than the time constant τ1 of the constant current circuit I1 and the capacitor C1. As a result, the potential of the node N1 is more likely to rise than the potential of the node N5, and during most of the period in which the switching element Q1 is off, the potential of the node N1 is equal to or higher than the potential of the node N5, and the diode D1 is turned off. be done. Therefore, capacitors C1 and C2 are charged independently of each other, as in the case of the semiconductor laser device of FIG.

FIG. 4 is a graph schematically showing temporal changes in voltages at nodes N1 and N5 of FIG. The time required to charge the capacitor C1 limits the repetition rate of lighting of the semiconductor laser element LD1. Therefore, shortening the time required for charging the capacitor C1 contributes to improving the lighting repetition rate of the semiconductor laser element LD1. According to the semiconductor laser device of FIG. 3, by using the constant current circuit I1, the potential of the node N1 rises rapidly, and the time required for charging the capacitor C1 can be shortened.

Since the constant current circuit I1 can also serve as a supply source of the leakage current of the switching element Q1, the charging operation may be terminated promptly when the charging of the capacitor C1 is completed.

According to the semiconductor laser device of the second embodiment, the time required for charging the capacitor C1 can be shortened as compared with the semiconductor laser device of the first embodiment. lighting repetition rate can be improved.

[Third embodiment]
FIG. 5 is a circuit diagram showing the configuration of a semiconductor laser device according to the third embodiment. The semiconductor laser device of FIG. 5 has a constant current circuit I2 in place of the resistor R2 of FIG. The constant current circuit I2 is connected between the power supply V2 and the capacitor C2, and controls charging of the capacitor C2 by current from the power supply V2 flowing through the constant current circuit I2. The constant current circuit I2 supplies a constant current from the power supply V2 to the capacitor C2 to charge it.

In this specification, the constant current circuit I2 is also referred to as a "second charging control circuit".

Here, the time constant τ2 of the constant current circuit I2 and the capacitor C2 is set to be equal to or greater than the time constant τ1 of the resistor R1 and the capacitor C1. As a result, the potential of the node N1 is more likely to rise than the potential of the node N5, and during most of the period in which the switching element Q1 is off, the potential of the node N1 is equal to or higher than the potential of the node N5, and the diode D1 is turned off. be done. Therefore, capacitors C1 and C2 are charged independently of each other, as in the case of the semiconductor laser device of FIG.

FIG. 6 is a graph schematically showing temporal changes in voltages at nodes N1 and N5 of FIG. The time it takes to charge the capacitor C2 also limits the repetition rate of the lighting of the semiconductor laser device LD1. Also, the capacitor C2 has a larger capacitance than the capacitance of the capacitor C1. Therefore, shortening the time required for charging the capacitor C2 contributes to improving the lighting repetition rate of the semiconductor laser element LD1. According to the semiconductor laser device of FIG. 5, by using the constant current circuit I2, the potential of the node N5 rises rapidly, and the time required for charging the capacitor C2 can be shortened.

According to the semiconductor laser device according to the third embodiment, the time required for charging the capacitor C2 can be shortened as compared with the semiconductor laser device according to the first embodiment. lighting repetition rate can be improved.

[Fourth embodiment]
FIG. 7 is a circuit diagram showing the configuration of a semiconductor laser device according to the fourth embodiment. The semiconductor laser device of FIG. 7 includes a constant current circuit I1 instead of the resistor R1 of FIG. 1, and a constant current circuit I2 instead of the resistor R2 of FIG. The constant current circuit I1 of FIG. 7 is configured similarly to the constant current circuit I1 of FIG. 3, and the constant current circuit I2 of FIG. 7 is configured similarly to the constant current circuit I2 of FIG.

Here, the time constant τ2 of the constant current circuit I2 and the capacitor C2 is set to be equal to or greater than the time constant τ1 of the constant current circuit I1 and the capacitor C1. As a result, the potential of the node N1 is more likely to rise than the potential of the node N5, and during most of the period in which the switching element Q1 is off, the potential of the node N1 is equal to or higher than the potential of the node N5, and the diode D1 is turned off. be done. Therefore, capacitors C1 and C2 are charged independently of each other, as in the case of the semiconductor laser device of FIG.

FIG. 8 is a graph schematically showing temporal changes in voltages at nodes N1 and N5 of FIG. According to the semiconductor laser device of FIG. 7, by using the constant current circuits I1 and I2, the potentials of the nodes N1 and N5 rise rapidly, and the time required for charging the capacitors C1 and C2 can be shortened.

According to the semiconductor laser device according to the fourth embodiment, the time required for charging the capacitors C1 and C2 can be shortened as compared with the semiconductor laser device according to the first embodiment. The repetition rate of lighting of the element LD1 can be improved.

[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 voltages of the power supplies V1 and V2 may be set higher according to the 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, the number of direct TOF measurements per unit time is increased, and the LiDAR measurement accuracy is improved. be able to.

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 switching element Q1, a first power source V1, a first charging control circuit, a first capacitor C1, a second power source V2, a second , a second capacitor C2, a diode D1, and a drive circuit 1. The first charge control circuit is connected between the first power supply V1 and the first capacitor C1, and charges the first capacitor C1 with current from the first power supply V1 flowing through the first charge control circuit. Control charging. The second charge control circuit is connected between the second power supply V2 and the second capacitor C2, and charges the second capacitor C2 with current from the second power supply V2 flowing through the second charge control circuit. Control charging. A diode D1 has a cathode connected to a node between the first charge control circuit and the first capacitor C1 and an anode connected to a node between the second charge control circuit and the second capacitor C2. have. The switching element Q1 has a collector connected to a node between the first charge control circuit and the first capacitor C1, an emitter connected to the anode of the semiconductor laser element LD1, and a base connected to the driving circuit 1. is an NPN-type avalanche transistor.

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 power supply V1 and the second power supply V2 are supplied to the second power supply V2 via the second charging control circuit. 2 is applied to the first capacitor C1 via the first charging control circuit.

According to the semiconductor laser device according to the third aspect of the present disclosure, in the semiconductor laser device according to the first or second aspect, the second capacitor C2 has a capacitance equal to or greater than that of the first capacitor C1.

According to the semiconductor laser device according to the fourth aspect of the present disclosure, in the semiconductor laser device according to one of the first to third aspects, the first charging control circuit includes the first resistor R1.

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 third aspects, the first charging control circuit controls the power supply from the first power supply V1 to the first includes a constant current circuit I1 for charging the capacitor C1 by supplying a constant current to it.

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

According to the semiconductor laser device according to the seventh aspect of the present disclosure, in the semiconductor laser device according to one of the first to fifth aspects, the second charge control circuit controls the second power supply V2 to the second power supply V2. includes a constant current circuit I2 for charging the capacitor C2 by supplying a constant current to it.

According to the semiconductor laser device according to the eighth aspect of the present disclosure, in the semiconductor laser device according to one of the first to seventh aspects, the diode D1 is a Schottky barrier diode.

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... drive circuit,
C1, C2...capacitors,
D1... Diode,
I1, I2...constant current circuits,
LD1... semiconductor laser element,
Q1... switching element,
R1, R2... Resistance,
V1, V2 . . . power supplies.

Claims (7)

A semiconductor laser device, a switching device, first and second power supplies, first and second charge control circuits, first and second capacitors, a diode, and a drive circuit,
The first charge control circuit is connected between the first power supply and the first capacitor, and the first charge control circuit is powered by a current from the first power supply flowing through the first charge control circuit. controls the charging of the capacitor,
The second charge control circuit is connected between the second power supply and the second capacitor, and the second charge control circuit is powered by current from the second power supply flowing through the second charge control circuit. controls the charging of the capacitor,
The diode has a cathode connected to a node between the first charge control circuit and the first capacitor, and an anode connected to a node between the second charge control circuit and the second capacitor. and
The switching element has a collector connected to a node between the first charge control circuit and the first capacitor, an emitter connected to the anode of the semiconductor laser element, and a base connected to the drive circuit. is an NPN-type avalanche transistor having
The first power supply applies a voltage higher than the voltage applied by the second power supply to the second capacitor through the second charge control circuit to the first capacitor through the first charge control circuit. applied to a capacitor of
Semiconductor laser device. The second capacitor has a capacity equal to or greater than the capacity of the first capacitor,
2. The semiconductor laser device according to claim 1 . the first charging control circuit includes a first resistor;
3. 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 first power supply to the first capacitor to charge the first capacitor.
3. The semiconductor laser device according to claim 1 . the second charging control circuit includes a second resistor;
The semiconductor laser device according to claim 1 . The second charge control circuit includes a constant current circuit that supplies a constant current from the second power supply to the second capacitor to charge the second capacitor.
The semiconductor laser device according to claim 1 . the diode is a Schottky barrier diode,
The semiconductor laser device according to claim 1 .

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