JP7370892B2 - Light emitting device, fiber laser device, integrated light emitting device, and control method for light emitting element - Google Patents

Description

The present invention relates to a light emitting device, a fiber laser device, an integrated light emitting device, and a method of controlling a light emitting element.

Conventionally, a light emitting device including a semiconductor laser diode as a light emitting element has been disclosed (see Patent Document 1). This light emitting device is used as an excitation light source in a fiber laser device. The drive current flowing through the light emitting element is changed by controlling the switching element. Pulse width modulation (PWM) control is used to control the switching elements. The switching element may be a transistor.

Patent No. 5694711

When a transistor is used for its original switching operation, such as PWM control, the current flowing through the transistor becomes pulsed, so the power loss in the transistor is reduced compared to when controlling only with DC current, and the heat generated by the transistor is suppressed. may be done. This pulsed current flows through a smoothing circuit, is smoothed to some extent, and is supplied to the light emitting element. However, since the current flowing through the transistor under PWM control has a steep change in current value over time, an induced electromotive voltage is generated. In particular, when the current value is large, the induced electromotive voltage generated becomes high, which may have an adverse effect such as deteriorating the transistor.

The present invention has been made in view of the above, and provides a light emitting device, a fiber laser device, an integrated light emitting device, and a fiber laser device capable of suppressing the temperature of a transistor to an acceptable level and suppressing the generation of a high induced electromotive voltage. An object of the present invention is to provide a method for controlling a light emitting element.

In order to solve the above-mentioned problems and achieve the objects, a light-emitting device according to one embodiment of the present invention includes a light-emitting element, a DC power supply that supplies current to the light-emitting element, and a DC power supply that supplies current to the light-emitting element, and The control unit includes a transistor that controls a current flowing through a light emitting element, and a control unit that sets the control voltage applied to the transistor, and the control unit sets the control voltage to a pulse based on temperature index information of the transistor. It is characterized by being set to width modulation voltage or DC voltage.

In the light-emitting device according to one aspect of the present invention, the control unit sets the control voltage so that a current having a set current value flows through the light-emitting element, and the temperature index information includes the set current value. It is characterized by including.

In the light emitting device according to one aspect of the present invention, the control unit may control the set current value to be equal to or higher than a first current value or lower than the first current value so that the temperature of the transistor is equal to or lower than a predetermined value. If the current value is smaller than the second current value, the control voltage is set to a DC voltage, and if the set current value is smaller than the first current value and larger than the second current value, the control voltage is set to a DC voltage. It is characterized in that it is set to a modulation voltage.

In the light emitting device according to one aspect of the present invention, when the set current value is equal to or higher than a first current value, the control unit adjusts the control voltage so that the temperature of the transistor becomes equal to or lower than a predetermined value. The control voltage is set to a DC voltage, and if the set current value is smaller than the first current value, the control voltage is set to a pulse width modulation voltage.

A light emitting device according to one aspect of the present invention includes a temperature sensor that detects a junction temperature of the transistor, and the temperature index information includes the temperature detected by the temperature sensor.

In the light emitting device according to one aspect of the present invention, in a state where the control voltage is set to a pulse width modulation voltage, if the detected temperature is higher than a first temperature, The present invention is characterized in that the control voltage is changed so that the current value of the peak value of the pulse width modulated voltage is high and the duty is low.

The light emitting device according to one aspect of the present invention includes a temperature sensor that detects a junction temperature of the transistor, the temperature index information includes the temperature detected by the temperature sensor, and the control unit converts the control voltage into a direct current. If the detected temperature is higher than the first temperature in a state where the control voltage is set to a voltage, the setting of the control voltage is switched to a pulse width modulation voltage.

The light emitting device according to one aspect of the present invention includes at least two of the transistors, and the control unit sets the control voltages applied to the two transistors to pulse width modulated control voltages having mutually opposite phases. It is characterized by

A fiber laser device according to one aspect of the present invention includes the light emitting device, and the plurality of light emitting elements are excitation light sources for an optical amplification fiber.

An integrated light emitting device according to one aspect of the present invention includes a plurality of the light emitting devices and an integrated control section that outputs an instruction signal regarding the control voltage to each of the control sections of the plurality of light emitting devices, The control unit is characterized in that it outputs the instruction signal according to a predetermined condition to each of the control units in accordance with a required value of light output for the integrated light emitting device.

In the integrated light emitting device according to one aspect of the present invention, the predetermined condition is such that the number of the light emitting devices for which the control voltage is set to a pulse width modulation voltage is smaller than the total number of the light emitting devices. Features.

In the integrated light emitting device according to one aspect of the present invention, the predetermined condition is such that the average value of light conversion efficiency in the light emitting devices in which the control voltage is set to a value larger than zero is such that the light conversion efficiency in all of the light emitting devices is It is characterized by a condition in which the efficiency is higher than the average value.

An integrated light emitting device according to one aspect of the present invention is characterized in that it includes an optical amplification fiber into which light output from the plurality of light emitting devices is input.

A method for controlling a light emitting element according to one aspect of the present invention includes a setting step of setting a control voltage to be applied to a transistor, and a control step of controlling a current flowing through the light emitting element according to the control voltage, The setting step is characterized in that the control voltage is set to a pulse width modulated voltage or a DC voltage based on temperature index information of the transistor.

Advantageous Effects of Invention According to the present invention, it is possible to suppress the temperature of the transistor to an allowable level and to suppress the generation of high induced electromotive voltage.

FIG. 1 is a schematic configuration diagram of a light emitting device according to Embodiment 1. FIG. 2 is a diagram illustrating an example of the relationship between current flowing through a transistor and junction temperature. FIG. 3 is a diagram illustrating setting of the control voltage. FIG. 4 is a diagram illustrating current flowing through a transistor and a light emitting section. FIG. 5 is a diagram showing an example of the junction temperature in the first embodiment. FIG. 6 is a flow diagram of control example 1. FIG. 7 is a diagram illustrating an example of characteristics of a light emitting device according to a comparative embodiment. FIG. 8 is a diagram showing an example of the characteristics of the light emitting device according to the first embodiment. FIG. 9 is a diagram showing another example of the characteristics of the light emitting device according to the first embodiment. FIG. 10 is a schematic configuration diagram of a light emitting device according to Embodiment 2. FIG. 11 is a flow diagram of control example 2. FIG. 12 is a schematic configuration diagram of a light emitting device according to Embodiment 3. FIG. 13 is a schematic configuration diagram of a fiber laser device according to Embodiment 4. FIG. 14 is a schematic configuration diagram of a fiber laser facility that is an example of an integrated light emitting device according to Embodiment 5. FIG. 15 is a diagram showing an example of the relationship between the drive current of the LD, the optical output, and the optical conversion efficiency. FIG. 16 is a diagram showing a map of the average value of light conversion efficiency in the first light-emitting device and the second light-emitting device with respect to the combination of the first current value in the first light-emitting device and the second current value in the second light-emitting device. be. FIG. 17 is a diagram showing an example of a control flow for outputting a set current value.

Embodiments of the present invention will be described in detail below with reference to the drawings. Note that the present invention is not limited to this embodiment. Further, in each drawing, the same or corresponding elements are given the same reference numerals as appropriate, and redundant explanation will be omitted.

(Embodiment 1)
FIG. 1 is a schematic configuration diagram of a light emitting device according to Embodiment 1. As shown in FIG. 1(a), the light emitting device 10 includes a light emitting section 1, a DC power supply 2, a transistor 3, a PWM signal generator 4, a control section 5, a current sensor 6, and capacitors 7a and 7d. , a diode 7b, and a coil 7c.

The light emitting unit 1 includes one or more light emitting elements, and in this embodiment, four light emitting elements are connected in series. Although the light emitting element is not particularly limited, in this embodiment, the light emitting element is assumed to be an LD.

The DC power supply 2 is a known DC power supply connected to supply current to each light emitting element of the light emitting section 1.

The transistor 3 is a field effect transistor (FET), and in this embodiment is an NMOS type FET. The transistor 3 is provided between the DC power supply 2 and the light emitting section 1, and is connected in series with the light emitting section 1. The drain-source current of the transistor 3 changes depending on the control voltage applied to the gate. Thereby, the transistor 3 can perform a control process of controlling the current flowing through the light emitting section 1 according to the applied control voltage.

The PWM signal generator 4 uses a control voltage signal Sg that applies a control voltage to the transistor 3 as a control voltage signal that is a pulse width modulated voltage (PWM control voltage signal) or a control voltage signal that is a DC voltage (DC control voltage signal). is configured to be output to the gate of the transistor 3.

The control section 5 includes a calculation section and a storage section. The calculation unit performs various calculation processes for the control executed by the control unit 5, and is composed of, for example, a CPU (Central Processing Unit). The storage unit includes a part that stores various programs and data used by the calculation unit to perform calculation processing, for example, a ROM (Read Only Memory), and a work space when the calculation unit performs calculation processing. and a portion constituted by, for example, RAM (Random Access Memory), which is used for storing the results of calculation processing by the calculation section. The control function of the control section 5 is realized in software by the functions of a calculation section and a storage section. Further, the control unit 5 may include a digital-to-analog converter (DAC) or an analog-to-digital converter (ADC) as appropriate.

The control unit 5 outputs control signals SV, Sf, and SD to the PWM signal generator 4 and performs a setting step of setting the characteristics of the control voltage signal Sg output by the PWM signal generator 4.

FIG. 1(b) shows a case where the control voltage signal Sg is a PWM voltage signal. V is the peak value of the voltage. t is the pulse width of the pulse voltage. T is the repetition period of the pulse voltage, and f is the repetition frequency. The duty of the PWM signal is defined as t/T. Note that when t=T, the duty is 100% and the signal becomes a DC signal. Control signals SV, Sf, and SD outputted from the control unit 5 to the PWM signal generator 4 are signals for setting the peak value, repetition period, and duty, respectively. The PWM signal generator 4 outputs a control voltage signal Sg having a peak value, repetition period, and duty set based on the control signals SV, Sf, and SD. The relationship between the control signals SV, Sf, and SD and the current flowing through the transistor 3 accordingly is stored in the storage section of the control section 5.

The current sensor 6 is connected in series to the cathode side of the light emitting section 1. The current sensor 6 includes a sense resistor, and outputs the amount of voltage drop caused by the sense resistor to the control unit 5 as a monitor signal Sm. The control unit 5 detects the current value of the current flowing through the light emitting unit 1 based on the input monitor signal Sm. The control unit 5 performs feedback control to control the control signals SV, Sf, and SD output to the PWM signal generator 4 so that the detected current value becomes constant.

Capacitors 7a, 7d and diode 7b are connected in parallel with light emitting section 1, and coil 7c is connected in series with light emitting section 1. Capacitors 7a, 7d and coil 7c constitute a smoothing circuit. Diode 7b functions as a freewheeling diode for coil 7c.

(About transistor heat generation)
The output of the LD of the light emitting unit 1 has increased in recent years, and the current to be supplied has accordingly increased. As the current to be supplied increases, the amount of heat generated by the transistor 3 also increases.

In the light emitting device 10, if the voltage applied by the DC power supply 2 is Vpower, and the current flowing through the light emitting section 1 is I, then Vpower is, for example, (forward voltage Vf(I) of the light emitting section 1) + (drain of the transistor 3). −source voltage Vds)+(voltage drop due to current sensor 6). When the current sensor 6 is composed of a sense resistor having a resistance value Rs, the following formula (1) holds true.
Vds=Vpower-Vf(I)-Rs×I (1)
Further, if the power consumption of the transistor 3 is P, P is expressed by equation (2).
P=I×Vds (2)
Then, the junction temperature Tj of the transistor 3 is expressed by equation (3). Note that Tr is the on-resistance of the transistor 3, and Ths is a parameter representing the contribution of the heat sink to the junction temperature of the transistor 3.
Tj=P×Tr+Ths
=I×Vds×Tr+Ths
=I×(Vpower−Vf(I)−Rs×I)×Tr
+Ths (3)

Further, power consumption W in the light emitting section 1 is expressed by equation (4). This W corresponds to the total optical output intensity.
W=I×Vf(I) (4)

Here, since the IV characteristic of the LD included in the light emitting section 1 is not linear, the drain-source voltage Vds of the transistor 3 is also not linear with respect to I. As a result, depending on the IL characteristics of the LD and the Vpower conditions, the load of the transistor 3 may have a maximum value with respect to the current. In this case, for example, as shown in FIG. 2, in a graph in which the horizontal axis is the current I and the vertical axis is the junction temperature of the transistor 3, the junction temperature has a maximum value. In such a case, when adjusting I in the range of 0A to 15A, for example, the maximum value of I, that is, the I at which the light emitting section 1 has the maximum light output, and the I at which the load on the transistor 3 is at the maximum will deviate. . Further, in FIG. 2, Tlim indicates the allowable upper limit temperature of the junction temperature of the transistor 3. When the junction temperature reaches its maximum value, it may exceed the allowable upper limit temperature.

On the other hand, in the light emitting device 10, as shown in FIG. 3, a threshold value Tth, which is a value equal to or less than Tlim, is set as a predetermined temperature with respect to the junction temperature of the transistor 3. Then, among the current values that become Tth, the larger one is set as IH, which is the first current value, and the smaller one is set as IL, which is the second current value.With IH and IL as the boundary shown by the dashed line, the current region is defined as region A, The transistor 3 is controlled by dividing into B and C. IH and IL are stored in the storage section of the control section 5, and are called up and used as appropriate.

Specifically, the control unit 5 receives a setting signal for a current value to be passed through the light emitting unit 1 from the outside, and uses the current value (set current value) according to the setting signal as temperature index information of the transistor 3 to generate a PWM signal. Control signals SV, Sf, and SD of predetermined values are output to the generator 4, and the control voltage signal Sg is set to a PWM voltage or a DC voltage.

FIG. 4A shows a case where the set current value is in region A. In this case, the control voltage signal Sg is a DC voltage. As a result, the current flowing through the transistor 3 and the light emitting section 1 becomes a DC current corresponding to the set current value as shown by the solid line, but since it is below IL, the junction temperature becomes below Tth.

FIG. 4B shows a case where the set current value is in region B. In this case, the control voltage signal Sg is a PWM voltage. As a result, the current flowing through the transistor 3 has a pulse width ta according to the PWM voltage, and becomes a rectangular pulsed current I1a that repeats a Hi state and a Lo state. In this case, the current flowing through the light emitting section 1 is smoothed and becomes a current I2a having a value corresponding to the set current value. In this case, the current flowing through transistor 3 is below IL or above IH. As a result, the junction temperature becomes equal to or lower than Tth.

Note that, as shown in FIG. 4(b), when the pulse width of the PWM voltage is increased while maintaining the repetition period, the current flowing through the transistor 3 becomes a rectangular pulse whose pulse width is tb, which is larger than ta, according to the PWM voltage. The current I1b is as follows. In this case, the current flowing through the light emitting section 1 is smoothed and becomes a current I2b that corresponds to the set current value and is larger than the current I1a. Also in this case, since the current flowing through the transistor 3 is below IL or above IH, the junction temperature becomes below Tth.

FIG. 4(c) shows a case where the set current value is in region C. In this case, the control voltage signal Sg is a DC voltage. As a result, the current flowing through the transistor 3 and the light emitting section 1 becomes a DC current corresponding to the set current value as shown by the solid line, but since it is higher than IH, the junction temperature is lower than Tth.

As a result, in the light emitting device 10, as shown in FIG. 5, when the set current is in region A or region C, the junction temperature becomes equal to or lower than Tlim, as in FIGS. 3 and 4. In addition, when the set current is in region B, the current flowing through the light emitting part 1 is set to the current value of region B, but the transistor 3 has a current value of region A and region C, as shown in FIG. 4(b). can be made to flow. As a result, even when the set current is in region B, the junction temperature can be kept below Tlim as shown by the arrow. Thereby, the temperature of the transistor 3 can be suppressed to below Tlim.

Furthermore, when the set current is in region C, the current value is large, so if the transistor 3 is PWM controlled, a high induced electromotive voltage may be generated. However, since the light emitting device 10 is DC controlled, a high induced electromotive voltage is generated. can be suppressed.

A control example of the control unit 5 in the first embodiment will be described as a control example 1 with reference to FIG. 6. First, when a setting signal is input, the control unit 5 acquires a current value based on the setting signal (step S101). Next, the control unit 5 uses the acquired current value as temperature index information to determine whether the current value is in region A or C (step S102). If the acquired current value is in region A or C (step S102, Yes), the control unit 5 sets the DC control voltage so that the set current flows through the light emitting unit 1, and executes DC control (step S103). ), the control flow returns to step S101. If the acquired current value is not in region A or C, that is, in region B (step S102, No), the control unit 5 sets the PWM control voltage so that the set current flows to the light emitting unit 1, and performs PWM control. is executed (step S104), and the control flow returns to step S101.

As described above, according to the light emitting device 10 according to the first embodiment, the temperature of the transistor 3 can be suppressed to an acceptable level, and generation of a high induced electromotive voltage can be suppressed.

FIG. 7 is a diagram illustrating an example of characteristics of a light emitting device according to a comparative embodiment having the same configuration as the light emitting device according to Embodiment 1. However, in Comparative Form 1, as shown in FIG. 7(a), the control voltage signal to transistor 3 increases stepwise as time passes from 0, t1, t2, t3, t4, t5, and t6. However, it is not PWM control but DC control. In the case of such a control voltage, the current flowing through the light emitting section 1 increases in a stepwise manner according to the shape of the control voltage, as shown in FIG. 7(b). As a result, as shown in FIG. 7C, the junction temperature of the transistor 3 changes in accordance with the change in current in the same manner as in FIG. 2, and may exceed Tlim.

On the other hand, FIG. 8 is a diagram showing an example of the characteristics of the light emitting device 10 according to the first embodiment. As shown in FIG. 8A, the control voltage signal to the transistor 3 is controlled to increase stepwise as time passes from 0 to t2 and from t4 to t6. On the other hand, the control voltage signal is controlled to be a PWM control voltage from time t2 to t3, and from t3 to t4 to be a PWM control signal having the same repetition period and duty as the time from t2 to t3 and having a high peak value. In the case of such a control voltage, the current flowing through the light emitting part 1 increases stepwise according to the shape of the control voltage as shown in FIG. The current becomes a ripple. Here, from t2 to t3 and from t3 to t4, the current value is greater than or equal to IL and less than IH. However, unlike the case of FIG. 7(c), the junction temperature of the transistor 3 changes so as not to exceed Tlim, as shown in FIG. 8(c).

Furthermore, FIG. 9 is a diagram showing another example of the characteristics of the light emitting device 10 according to the first embodiment. As shown in FIG. 9(a), the control voltage signal to the transistor 3 is controlled to increase stepwise as time passes from 0 to t2 and from t4 to t6. On the other hand, the control voltage signal is controlled to be a PWM control voltage from t2 to t3, and from t3 to t4 to be a PWM control signal with the same peak value and short repetition period as that from t2 to t3. In the case of such a control voltage, the current flowing through the light emitting part 1 increases stepwise according to the shape of the control voltage as shown in FIG. The current becomes a ripple. Here, from t2 to t3 and from t3 to t4, the current value is greater than or equal to IL and less than IH. In this example, as in the case of FIG. 8(c), the junction temperature of the transistor 3 changes so as not to exceed Tlim, as shown in FIG. 9(c).

(Embodiment 2)
FIG. 10 is a schematic configuration diagram of a light emitting device according to Embodiment 2. The light emitting device 10A has a configuration in which a temperature sensor 8 is added to the light emitting device 10 shown in FIG.

The temperature sensor 8 includes, for example, a thermistor, and outputs a current according to the temperature to the control unit 5 as a monitor signal Smt. The control unit 5 detects the junction temperature of the transistor 3 based on the input monitor signal Smt.

In the light emitting device 10A as well, the transistor 3 is controlled by dividing the current region into regions A, B, and C using IH and IL as boundaries. In the light emitting device 10A, the temperature detected by the temperature sensor 8 is also used for control.

The control unit 5 outputs control signals SV, Sf, and SD of predetermined values to the PWM signal generator 4, using the set current value as one of the information included in the temperature index information of the transistor 3, and outputs control signals SV, Sf, and SD of predetermined values to the PWM signal generator 4, and outputs a control voltage signal Sg. , PWM voltage or DC voltage. Further, the control unit 5 uses the temperature detected by the temperature sensor 8 for control.

For example, in the transistor 3, the characteristic curve of junction temperature with respect to flowing current as shown in FIG. 2 may differ or fluctuate due to individual differences, deterioration over time, ambient temperature, and the like. Therefore, in the light emitting device 10A, by using the temperature detected by the temperature sensor 8 for control, even if the characteristic curve of the junction temperature has large variations due to individual differences, aging deterioration, ambient temperature, etc. The temperature can be suppressed to an acceptable level.

Control using the temperature detected by the temperature sensor 8 can be performed in various ways.

For example, in a state in which the set current value is in region B and the control voltage is set to the PWM voltage, if the detected temperature is higher than the first temperature, the peak value of the PWM voltage is The control voltage may be changed so that it is higher than the state and the Duty is lower than the state. The first temperature is, for example, Tlim. If the detected temperature is higher than Tlim, it is necessary to lower the junction temperature of transistor 3. Therefore, by setting the peak value higher than the current value, in the Hi state of PWM control, the current value can be set to a current value in region C that is further away from region B, and in the Lo state of PWM control, the current value can be set to a current value in region A. The current value can be set further away from region B. Furthermore, since increasing the peak value increases the current flowing through the light emitting section 1, the Duty is changed to a lower value. As a result, the junction temperature of the transistor 3 can be lowered while maintaining the current value of the current flowing through the light emitting section 1.

Further, in a state where the set current value is in region A or C and the control voltage is set to DC voltage, if the detected temperature is higher than the first temperature, the control unit 5 changes the setting of the control voltage. It is also possible to switch to PWM voltage. The first temperature is, for example, Tlim. If the detected temperature is higher than Tlim, it is necessary to lower the junction temperature of transistor 3. Therefore, by switching the control voltage setting to a PWM voltage, the junction temperature of the transistor 3 can be lowered. In this case, although initially set in region A or C, the set current value may be changed to region B such that the detected temperature becomes equal to or higher than the first temperature. Such changes can be implemented by updating the IH and IL values stored in the storage section of the control section 5.

A control example of the control unit 5 in the second embodiment will be described as a control example 2 with reference to FIG. 11. First, when a setting signal is input, the control unit 5 acquires a current value based on the setting signal (step S201). Next, the control unit 5 uses the acquired current value as temperature index information to determine whether the current value is in region A or C (step S202). If the acquired current value is in region A or C (step S202, Yes), the control flow advances to step S203. In step S203, the control unit 5 determines whether the detected temperature is equal to or lower than a predetermined value (first temperature). If it is below the predetermined value (Step S203, Yes), the control unit 5 sets the DC control voltage so that the set current flows to the light emitting unit 1 and executes the DC control (Step S204), and the control flow is as follows. Return to step S201. On the other hand, if the acquired current value is not in region A or C, that is, in region B (step S202, No), and if the detected temperature is higher than the predetermined value (step S203, No), the control unit 5 The PWM control voltage is set so that a current flows through the light emitting section 1, and PWM control is executed (step S205), and the control flow returns to step S201.

As described above, according to the light emitting device 10 according to the second embodiment, the temperature of the transistor 3 can be suppressed to an acceptable level, and generation of a high induced electromotive voltage can be suppressed. Further, even if there are large variations due to individual differences in the transistors 3, deterioration over time, ambient temperature, etc., the junction temperature of the transistors 3 can be suppressed to an allowable level.

(Embodiment 3)
FIG. 12 is a schematic configuration diagram of a light emitting device according to Embodiment 3. As shown in FIG. 12(a), a light emitting device 10B includes a transistor 3B, a diode 7Bb, a coil 7Bc, and a capacitor 7Bd added to the light emitting device 10 shown in FIG. It has a configuration replaced with 4B.

The transistor 3B is provided between the DC power supply 2 and the light emitting section 1, and is connected in series with the light emitting section 1. Further, the transistor 3B is connected in parallel with the transistor 3. The diode 7Bb is connected in parallel with the light emitting section 1. Further, diode 7Bb is connected in parallel with diode 7b. The coil 7Bc is connected in series with the light emitting section 1. Further, the coil 7Bc is connected in parallel with the coil 7c. Capacitor 7Bd is connected in parallel with capacitor 7d. Coil 7Bc constitutes a smoothing circuit. Diode 7Bb functions as a freewheeling diode for coil 7Bc.

The PWM signal generator 4B sets the control voltages applied to the two transistors 3 and 3B to PWM control voltages whose phases are opposite to each other, as shown in FIG. 12(b). As a result, ripples generated in the current due to PWM control cancel each other out, and the ripple in the current flowing through the light emitting section 1 can be suppressed as shown in FIG. 13(b).

(Embodiment 4)
FIG. 13 is a schematic diagram of a fiber laser device according to Embodiment 4. The fiber laser device 1000 is configured as a fiber laser device for laser processing, and includes a plurality of fiber laser devices 100, an optical multiplexing coupler 1001, and a processing head 1002.

The fiber laser device 100 includes a light emitting device 10, a TFB (Tapered Fiber Bundle) 20 that is an optical multiplexer, a fiber Bragg grating (FBG) 30, an optical amplification fiber 40, an FBG 50, and a TFB 60.

The light emitting unit 1 of the light emitting device 10 is an excitation light source for the optical amplification fiber 40 and outputs excitation light. The wavelength of the excitation light is, for example, 915 nm. The intensity of the excitation light is a value that corresponds to a set current value based on a set signal input from the outside.

The TFB 20 multiplexes and outputs the excitation light output from the light emitting section 1. The FBG 30 transmits excitation light. The optical amplification fiber 40 includes an optical amplification medium (for example, ytterbium ions) that is optically excited by the wavelength of the excitation light, and is optically excited by the excitation light that has passed through the FBG 30 and emits fluorescence. A component of a predetermined wavelength of the fluorescence is lased by the action of the optical resonator constituted by the FBG 30 and the FBG 50 and the optical amplification fiber 40, and the FBG 50 oscillates as a laser beam (for example, a laser beam in the 1.1 μm wavelength band). is output from. The optical multiplexing coupler 1001 multiplexes the laser beams output from each fiber laser device 100 and outputs the multiplexed laser beams to the processing head 1002 via the delivery fiber. The processing head 1002 irradiates the object to be processed with the combined laser light. Laser processing is thereby performed.

In the fiber laser device 1000, the temperature of the transistor 3 of the light emitting device 10 can be suppressed to an acceptable level, and generation of a high induced electromotive voltage can be suppressed. As a result, the reliability of the fiber laser device 1000 increases.

(Embodiment 5)
FIG. 14 is a schematic diagram of a fiber laser facility that is an example of an integrated light emitting device according to Embodiment 5. The fiber laser equipment 1000A has a configuration in which an integrated control section 1010 is added to the configuration of the fiber laser device 1000 shown in FIG.

The integrated control unit 1010 outputs a setting signal to each fiber laser device 100. The setting signal is a signal containing information on the setting current value. The setting signal is an example of an instruction signal regarding the control voltage.

The integrated control unit 1010 includes a calculation unit 1011, a storage unit 1012, and an input/output unit 1013. The calculation unit 1011 performs various calculation processes for the control executed by the integrated control unit 1010, and is composed of, for example, a CPU (Central Processing Unit). The storage unit 1012 includes a part that stores various programs, data, etc. used by the calculation unit 1011 to perform calculation processing, and includes a ROM (Read Only Memory), for example. It includes a work space and a section composed of, for example, RAM (Random Access Memory), which is used for storing the results of arithmetic processing of the arithmetic section. The control function of the integrated control unit 1010 is realized in software by the functions of the calculation unit 1011 and the storage unit 1012. The input/output unit 1013 is an interface unit that outputs setting signals to each fiber laser device 100 and receives input of instruction signals from a host device. Note that the integrated control unit 1010 may include a DAC or ADC as appropriate. Note that the input/output unit 1013 may include an operating device such as a mouse and a keyboard, and a display unit such as a liquid crystal display.

The integrated control unit 1010 receives a requested value of optical output for the fiber laser equipment 1000A through an instruction signal from a host device, an input operation from an operating device, or the like. The required value of the optical output is, for example, the required value for the power of the laser beam output from the processing head 1002.

The integrated control unit 1010 outputs an instruction signal to each of the control units 5 of each fiber laser device 100 in accordance with the required value of the optical output so that the required value of the optical output is realized. That is, the integrated control unit 1010 outputs an instruction signal for realizing the set current value that is required to flow through the light emitting unit 1 of each fiber laser device 100 in order to realize the required value.

The instruction signal (set current value) can be determined according to various predetermined conditions. For example, it can be determined according to conditions related to the light conversion efficiency of the light emitting section 1. The light conversion efficiency is the ratio of the power converted into light to the power given to the light emitting section 1.

FIG. 15 is a diagram showing an example of the relationship between the drive current, which is the current flowing through the LD, and the optical output and optical conversion efficiency of the LD. Curves P, Q, and R show the relationship between light output and light conversion efficiency for different LDs. The optical output of the LD increases as the drive current increases, but the light conversion efficiency changes to reach a maximum value at a certain drive current. In FIG. 15, for example, if the light conversion efficiency is 0.45, it is considered that the light conversion efficiency is high. Note that, as shown by curves P, Q, and R, due to variations in the characteristics of the LD, the shape of the curve showing the optical output and light conversion efficiency of the LD with respect to the drive current shown in FIG. It differs for each device 10.

For example, the integrated control unit 1010 can set the same set current value for each light emitting device 10 in order to achieve the required value of light output, but for example, as described below, the integrated control unit 1010 can You may decide to do so. In the following description, for simplicity, a case will be described in which there are two fiber laser devices 100. The light emitting devices of the two fiber laser apparatuses 100 will be referred to as a first light emitting device and a second light emitting device, respectively.

FIG. 16 shows the optical conversion in the first light emitting device and the second light emitting device for the combination of the set current value (first current value) in the first light emitting device and the set current value (second current value) in the second light emitting device. It is a figure showing the map of the average value of efficiency. In the figure, the shaded area is the area where the average value of the light conversion efficiency is 0.45 or more. A broken line L1 is a case where the same set current value is set for the first light emitting device and the second light emitting device. On the other hand, the broken line L2 is a case where a set current value is set so that the first light emitting device and the second light emitting device have substantially equal light output. When setting current values for the first light emitting device and the second light emitting device, for example, different settings may be made so that the average value of light conversion efficiency is 0.45 or more on the broken line L2. A current value may also be set. Alternatively, different set current values may be set so that the average value of the light conversion efficiency is maximized on the broken line L2. In addition, in FIG. 16, a region YX (Y, 3 shows a method of controlling the light emitting device when each of the values is set to a specific value. For example, the area where X=A and Y=A is area AA. In the case of the region where X=A or C, the first light emitting device emits light under DC control, and in the case of the region where X=B, the first light emitting device emits light under PWM control. Similarly, when Y=A or C, the second light emitting device emits light under DC control, and when Y=B, the second light emitting device emits light under PWM control.

The integrated control unit 1010 operates under the condition that the control voltage is set to a pulse width modulation voltage, that is, the number of light emitting devices 10 whose set current value is set in region B in FIG. 3 is less than the total number of light emitting devices 10. , a set current value can be set (first condition). When achieving a required value of predetermined light output using a plurality of light emitting devices 10, it is preferable that the number of light emitting devices 10 that perform PWM control is smaller in terms of suppressing current ripples flowing through the light emitting devices 10. Note that it is more preferable to set the condition that the number of light emitting devices 10 whose set current value is set in region B is less than 1/2 of the total number of light emitting devices 10, and less than 1/3 of the total number of light emitting devices 10. It is more preferable to set the conditions such that the amount of energy decreases.

FIG. 17 is a diagram showing an example of a control flow for outputting a set current value in the integrated control unit 1010. First, in step S301, the integrated control unit 1010 obtains a required value of optical output from, for example, a higher-level device.

Subsequently, in step S302, the integrated control unit 1010 calculates a combination with a smaller number of light emitting devices 10 having a set current value corresponding to region B. This calculation is performed using, for example, a data table stored in the storage unit 1012. This data table includes data on the light conversion efficiency, light output, and heat generation amount with respect to the drive current for the LD included in each light emitting device 10. The calculation unit 1011 reads necessary data from the data table stored in the storage unit 1012 and performs calculations.

This calculation is performed, for example, as follows. When there are N light-emitting devices 10 (N is an integer greater than 1), first, a combination of set current values that achieves the required value of light output but does not correspond to region B (combination 1) is selected. Calculate whether it exists. Once it is confirmed that combination 1 exists, the calculation ends. Once it is confirmed that combination 1 does not exist, it is next determined whether there is a combination (combination 2) in which only one set current value is the set current value corresponding to region B while realizing the required value of optical output. calculate. Once it is confirmed that combination 2 exists, the calculation ends. Once it is confirmed that combination 2 does not exist, it is next determined whether there is a combination (combination 3) in which only two set current values are set current values corresponding to region B while realizing the required value of optical output. calculate. By repeating this process, if it is confirmed that there is no combination in which N-1 light emitting devices 10 are set to the set current value corresponding to region B, all N light emitting devices 10 are set to the set current value corresponding to region B. It is determined that the settings need to be made, and the calculation ends. By repeating calculations in this way, if there is a combination that can achieve the required light output value without setting all the light emitting devices 10 to the set current value corresponding to region B, the set current corresponding to region B can be set. Combinations with a small number of light-emitting devices 10 can be calculated.

Subsequently, in step S303, the integrated control unit 1010 outputs an instruction signal corresponding to the set current value to each light emitting device 10. The flow then ends.

Further, the predetermined condition is that the average value of the light conversion efficiency of the light-emitting devices 10 whose control voltage is set to a value larger than zero is higher than a predetermined value, for example, the average value of the light conversion efficiency of all the light-emitting devices 10. It may be a condition (second condition). The light emitting device 10 whose control voltage is set to a value greater than zero means the light emitting device 10 through which a drive current flows. Under such conditions, the light conversion efficiency of the fiber laser equipment 1000A as a whole can be made higher than when a drive current is passed through all of the light emitting devices 10. Further, by combining the first condition and the second condition, it is possible to achieve the required value of light output and increase the light conversion efficiency while suppressing the induced electromotive voltage. More specifically, for example, in the control flow shown in FIG. 17, the average value of light conversion efficiency in the light emitting device 10 in which the control voltage is set to a value greater than zero before step S302 or between steps S302 and S303. is a predetermined value or more (an example of the second condition, condition A), and in step S303, the set current value of each light emitting device 10 that satisfies both the combination calculated in step S302 and the condition A is set. A corresponding instruction signal may also be output. In such a case, for example, combinations of set current values that satisfy condition A may be stored in the storage unit 1012 in association with respective required values of optical output, and may be referenced as needed.

As other predetermined conditions, for example, among the light emitting devices 10, a set current value may be set in order of increasing light conversion efficiency, so that the light conversion efficiency of the light emitting devices 10 is at least a predetermined value or a maximum value. . In this case as well, the optical conversion efficiency of the fiber laser equipment 1000A as a whole can be increased while achieving the required value of optical output.

In the above embodiment, when the set current value is equal to or higher than IH or lower than IL, that is, in the case of region A or region C, the control voltage is set to a DC voltage, and when the set current value is smaller than IH and IL In the case of the larger region B, the control voltage is set to the PWM voltage. However, if the set current value is in region C greater than IH, the control voltage is set to DC voltage, and if the set current value is in region A or B smaller than IH, the control voltage is set to PWM voltage. You may. Even if such control is performed, the temperature of the transistor can be suppressed to an acceptable level, and generation of a high induced electromotive voltage can be suppressed.

Furthermore, the present invention is not limited to the above embodiments. The present invention also includes configurations in which the above-mentioned components are appropriately combined. For example, a temperature sensor 8 may be added to the light emitting device 10B according to the third embodiment, as in the light emitting device 10A according to the second embodiment, and control as shown in FIG. 11 may be performed, for example. Moreover, further effects and modifications can be easily derived by those skilled in the art. Accordingly, the broader aspects of the invention are not limited to the embodiments described above, but are capable of various modifications.

1 Light emitting section 2 DC power supply 3, 3B Transistor 4, 4B PWM signal generator 5 Control section 6 Current sensor 7a Capacitor 7b, 7Bb Diode 7c, 7Bc Coil 8 Temperature sensor 10, 10A, 10B Light emitting device 20, 60 TFB
30, 50 FBG
40 Optical amplification fiber 100 Fiber laser device 1000 Fiber laser 1001 Optical multiplexing coupler 1002 Processing heads A, B, C Regions I1a, I2a, I2b Currents SD, SV, Sf Control signal Sg Control voltage signal Sm, Smt Monitor signal

Claims (12)

A light emitting element,
a DC power source that supplies current to the light emitting element;
a transistor that controls a current flowing through the light emitting element according to an applied control voltage;
a control unit that sets the control voltage applied to the transistor;
Equipped with
The control unit sets the control voltage so that a current having a set current value flows through the light emitting element , and sets the control voltage so that the set current value is set to a first value so that the temperature of the transistor becomes equal to or lower than a predetermined value. If the current value is greater than or equal to the second current value that is smaller than the first current value, the control voltage is set to a DC voltage, and the set current value is smaller than the first current value and is the second current value. If the control voltage is larger than that, the light emitting device is characterized in that the control voltage is set to a pulse width modulation voltage . A light emitting element,
a DC power source that supplies current to the light emitting element;
a transistor that controls a current flowing through the light emitting element according to an applied control voltage;
a control unit that sets the control voltage applied to the transistor;
Equipped with
The control unit sets the control voltage so that a current having a set current value flows through the light emitting element, and sets the control voltage so that the set current value is set to a first value so that the temperature of the transistor becomes equal to or lower than a predetermined value. If the current value is equal to or higher than the first current value, the control voltage is set to a DC voltage, and if the set current value is smaller than the first current value, the control voltage is set to a pulse width modulated voltage. A light emitting device. comprising a temperature sensor that detects a junction temperature of the transistor,
When the temperature detected by the temperature sensor is higher than a first temperature in a state in which the control voltage is set to a pulse width modulation voltage, the control unit sets the pulse height of the pulse width modulation voltage to be higher than in the state. , and changing the control voltage so that the Duty becomes lower,
The light emitting device according to claim 1 or 2 , characterized in that: comprising a temperature sensor that detects a junction temperature of the transistor,
The control unit is characterized in that when the temperature detected by the temperature sensor is higher than a first temperature while the control voltage is set to a DC voltage, the control unit switches the setting of the control voltage to a pulse width modulated voltage. The light emitting device according to claim 1 or 2 . Claims 1 to 4 , wherein at least two of the transistors are provided, and the control unit sets the control voltages applied to the two transistors to pulse width modulated control voltages having phases opposite to each other. The light emitting device according to any one of. A fiber laser device comprising the light emitting device according to claim 1 , wherein the light emitting element is an excitation light source for an optical amplification fiber. A plurality of light emitting devices according to any one of claims 1 to 5 ,
an integrated control unit that outputs an instruction signal regarding the control voltage to each of the control units of the plurality of light emitting devices;
Equipped with
The integrated light emitting device, wherein the integrated control section outputs the instruction signal according to a predetermined condition to each of the control sections, depending on a required value of light output for the light emitting device. The integrated light emitting device according to claim 7 , wherein the predetermined condition is a condition in which the number of the light emitting devices for which the control voltage is set to a pulse width modulation voltage is smaller than the total number of the light emitting devices. . The predetermined condition is a condition in which the average value of light conversion efficiency of the light-emitting devices for which the control voltage is set to a value greater than zero is higher than the average value of light conversion efficiency of all of the light-emitting devices. The integrated light emitting device according to claim 7 , characterized in that: The integrated light emitting device according to any one of claims 7 to 9 , further comprising an optical amplification fiber into which the light output from the plurality of light emitting devices is input. a setting step of setting a control voltage to be applied to the transistor;
a control step of controlling a current flowing through the light emitting element according to the control voltage;
In the setting step, the control voltage is set so that a current having a set current value flows through the light emitting element , and the set current value is set so that the temperature of the transistor becomes equal to or lower than a predetermined value. is equal to or greater than a first current value or equal to or less than a second current value smaller than the first current value, the control voltage is set to a DC voltage, and the set current value is smaller than the first current value and the second current value is smaller than the first current value. 2. A method for controlling a light emitting device, characterized in that when the current value is larger than 2, the control voltage is set to a pulse width modulation voltage . a setting step of setting a control voltage to be applied to the transistor;
a control step of controlling a current flowing through the light emitting element according to the control voltage;
In the setting step, the control voltage is set so that a current having a set current value flows through the light emitting element, and the set current value is set so that the temperature of the transistor becomes equal to or lower than a predetermined value. is a first current value or more, the control voltage is set to a DC voltage, and when the set current value is smaller than the first current value, the control voltage is set to a pulse width modulation voltage. Characteristic control method for light emitting elements.

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