JP6889995B2 - Light source system and vehicle lighting - Google Patents

Description

The present invention relates to a light source system including a semiconductor laser and a vehicle lamp.

Semiconductor lasers are light sources used for various purposes, and in recent years, they are also used for lighting applications such as floodlights and head wraps for vehicles. For example, when a semiconductor laser is used as a light source for illumination, light of a desired wavelength (emission color) is extracted to the outside as illumination light by incident light emitted from the semiconductor laser on a phosphor. For example, Patent Document 1 discloses a light emitting device including an excitation light source such as a semiconductor laser and a light conversion member including a phosphor.

Patent No. 5155555

While semiconductor lasers are small and high-power light sources, they are known to cause COD (Catastrophic Optical Damage), which is sudden optical damage to the end face of light emitted. When a semiconductor laser is used as a light source, a system configuration that takes into account the generation of COD is required.

The present invention has been made in view of the above points, and the operation of the semiconductor laser light source is monitored to predict the occurrence of a failure such as COD, and the laser element to be driven is set to another laser element before the failure occurs. It is an object of the present invention to provide a highly reliable light source system and vehicle lighting equipment that can be switched to.

In the light source system according to the present invention, a light source device having a laser light source including a plurality of semiconductor laser elements and one semiconductor laser element among the plurality of semiconductor laser elements are driven targets, and one semiconductor laser element is subjected to constant light. With respect to the drive circuit driven in the constant output drive mode that keeps the output and the time-dependent change I _{op (t) of the drive current I op} of 1 semiconductor laser element by the drive circuit, the drive current value at the start of driving of 1 semiconductor laser element. Is I _c , the constant is k, the time is t, and the exponent is α.

に示す式に従って経時変化したと判定し、式（１）の指数αが、α＞１であり、かつｄα／ｄｔ＞０を満たす変化状態が所定時間続いた場合に、１の半導体レーザ素子における光学損傷の発生を予測する故障予測回路と、を有し、故障予測回路によって１の半導体レーザ素子の光学損傷の発生が予測された場合、駆動回路は、複数の半導体レーザ素子のうちの他の半導体レーザ素子を駆動対象とすることを特徴としている。

When it is determined that the change over time is performed according to the equation shown in the above, and the change state in which the index α of the equation (1) is α> 1 and the change state satisfying dα / dt> 0 continues for a predetermined time, the semiconductor laser device of 1 is used. When a failure prediction circuit that predicts the occurrence of optical damage is provided and the failure prediction circuit predicts the occurrence of optical damage of one semiconductor laser device, the drive circuit is the other of the plurality of semiconductor laser devices. It is characterized in that it targets a semiconductor laser element as a drive target.

Further, in the light source system according to the present invention, a light source device having a laser light source including a plurality of semiconductor laser elements and one semiconductor laser element among the plurality of semiconductor laser elements are driven targets, and one semiconductor laser element is fixed. With respect to the drive circuit driven in the constant current drive mode that maintains the drive current of 1 and the time-dependent change P _{out (t) of the optical output P out} of 1 semiconductor laser element, the optical output at the start of driving of 1 semiconductor laser element is P. ₀ , constant is k, time is t, exponent is α

に示す式に従って経時変化したと判定し、式（２）の指数αが、α＞１であり、かつｄα／ｄｔ＞０を満たす変化状態が所定時間続いた場合に、１の半導体レーザ素子における光学損傷の発生を予測する故障予測回路と、を有し、故障予測回路によって１の半導体レーザ素子の光学損傷の発生が予測された場合、駆動回路は、複数の半導体レーザ素子のうちの他の半導体レーザ素子を駆動対象とすることを特徴としている。

When it is determined that the change over time is performed according to the equation shown in the above, and the change state in which the index α of the equation (2) is α> 1 and the change state satisfying dα / dt> 0 continues for a predetermined time, the semiconductor laser device of 1 is used. When a failure prediction circuit that predicts the occurrence of optical damage is provided and the failure prediction circuit predicts the occurrence of optical damage of one semiconductor laser device, the drive circuit is the other of the plurality of semiconductor laser devices. It is characterized in that it targets a semiconductor laser element as a drive target.

Further, the light source system according to the present invention is a light source device including a laser light source including a plurality of semiconductor laser elements optically coupled and juxtaposed with each other, and a wavelength conversion device for converting the wavelength of the laser light from the laser light source. A drive circuit that drives one semiconductor laser element out of a plurality of semiconductor laser elements as a drive target and drives one semiconductor laser element in a constant current drive mode that maintains a constant drive current, and one semiconductor laser element or Regarding the time-dependent change P _out (t) of the optical output P _out of the wavelength converter, the optical output at the start of driving of the semiconductor laser device or the wavelength converter 1 is P ₀ , the constant is k, the time is t, and the exponent is α. ,

に示す式に従って経時変化したと判定し、数式（２）の指数αが、α＞１であり、かつｄα／ｄｔ＞０を満たす変化状態が所定時間続いた場合に、１の半導体レーザ素子における光学損傷の発生を予測する故障予測回路と、を有し、故障予測回路によって１の半導体レーザ素子の光学損傷の発生が予測された場合、駆動回路は、複数の半導体レーザ素子のうちの他の半導体レーザ素子を駆動対象とすることを特徴としている。

When it is determined that the change over time is performed according to the equation shown in the above, and the change state in which the index α of the equation (2) is α> 1 and the change state satisfying dα / dt> 0 continues for a predetermined time, the semiconductor laser device of 1 is used. When a failure prediction circuit that predicts the occurrence of optical damage is provided and the failure prediction circuit predicts the occurrence of optical damage of one semiconductor laser device, the drive circuit is the other of the plurality of semiconductor laser devices. It is characterized in that it targets a semiconductor laser element as a drive target.

It is a figure which shows typically the structure of the light source system which concerns on Example 1. FIG. (A) is a schematic perspective view of a laser light source in the light source system according to the first embodiment, and (b) is a block diagram showing a configuration of a control circuit. (A) and (b) are diagrams schematically showing an exponential function model used when the failure prediction circuit of the light source system according to the first embodiment determines the occurrence of COD. (A) and (b) are diagrams schematically showing an exponential function model used when the failure prediction circuit of the light source system according to the first embodiment determines the occurrence of COD. It is a schematic perspective view of the laser light source in the light source system which concerns on the modification of Example 1. FIG.

Hereinafter, examples of the present invention will be described in detail.

FIG. 1 is a diagram schematically showing the configuration of the light source system 10 according to the first embodiment. The light source system 10 includes a light source device 20, a drive circuit 30 that drives the light source device 20, and a control circuit 40 that controls drive of the drive circuit 30. The light source system 10 constitutes, for example, a vehicle lamp. The light source system 10 constitutes, for example, a headlamp system for an automobile.

In this embodiment, the light source device 20 includes a laser light source 21 that generates and emits laser light L1, a wavelength conversion device 22 that converts the wavelength of the laser light L1 to generate wavelength conversion light L2, and a wavelength conversion light L2. Includes a lens 23 that forms the molding light L3 to generate the molding light L3. In this embodiment, the light source device 20 has a housing 24 that houses the laser light source 21, the wavelength conversion device 22, and the lens 23. Further, the molding light L3 molded by the lens 23 is taken out from the light source device 20 to the outside. That is, the lens 23 outputs the molded wavelength conversion light L2, which is the molding light L3, to the outside.

The drive circuit 30 drives the laser light source 21. Specifically, the drive circuit 30 generates a drive current (drive signal) DC that drives the laser light source 21. The laser light source 21 is driven by a drive current applied by the drive circuit 30 (performs a light emitting operation).

The control circuit 40 monitors the output light LO (laser light L1 or wavelength conversion light L2) from the laser light source 21 or the wavelength conversion device 22 and the drive current DC of the laser light source 21 generated by the drive circuit 30. The drive of the laser light source 21 is controlled by the drive circuit 30 based on the monitoring result of.

FIG. 2A is a schematic perspective view of the laser light source 21. The laser light source 21 includes a plurality of semiconductor laser elements (two semiconductor laser elements LE1 and LE2 in this embodiment) housed in a package (not shown). In this embodiment, the laser light source 21 includes a plurality of semiconductor laser elements (first and second semiconductor laser elements) LE1 and LE2 that are optically coupled to each other and juxtaposed with each other.

More specifically, the laser light source 21 has a mounting substrate 51 and a semiconductor structural layer 52 common to the semiconductor laser elements (hereinafter, simply referred to as laser elements) LE1 and LE2. The semiconductor structure layer 52 is formed on the mounting substrate 51, and constitutes a resonator by end faces ES1 and ES2 facing each other. In this embodiment, the laser light source 21 is arranged so that the end face ES1 is the emission surface of the laser beam L1 and the end face ES1 faces the incident surface of the wavelength conversion device 22 and the lens 23. A reflecting mirror (not shown) may be formed on each of the end faces ES1 and ES2 in order to obtain a desired reflectance.

In this embodiment, the mounting substrate 51 is a semiconductor substrate having an n-type conductive type (first conductive type). Further, the semiconductor structure layer 52 has a structure in which an n-type semiconductor layer 52A, a light emitting layer 52B, and a p-type (second conductive type) semiconductor layer 52C are sequentially laminated on the mounting substrate 51 in this order.

Further, the laser light source 21 corresponds to each of the laser elements LE1 and LE2, and is formed on the upper surface of the semiconductor structure layer 52, and a plurality of ridge portions (first and second) extending in a stripe shape between the opposite end faces ES1 and ES2. Ridge portion) 54A and 54B. In this embodiment, the ridge portions 54A and 54B are two striped convex portions formed on the upper surface of the p-type semiconductor layer 52C and extending between the end faces ES1 and ES2.

The ridge portions 54A and 54B are formed in parallel with each other separated by a distance W. The extending direction of the ridge portions 54A and 54B, that is, the opposite direction of the end faces ES1 and ES2 is the cavity length direction (optical resonance direction) RD of the laser elements LE1 and LE2.

Further, an insulating layer 53 is formed on the upper surface of the semiconductor structure layer 52 excluding the ridge portions 54A and 54B. Further, the laser light source 21 is formed on the ridge portions 54A and 54B, respectively, and is formed on the individual electrodes 55A and 55B corresponding to the laser elements LE1 and LE2 and on the mounting substrate 51, and is common to the laser elements LE1 and LE2. It has an electrode 56. In this embodiment, the individual electrodes 55A and 55B are p-electrodes, respectively, and the common electrode 56 is an n-electrode.

The individual electrodes 55A and 55B are separated from each other and are insulated from each other. Therefore, the laser elements LE1 and LE2 independently perform the light emitting operation depending on whether the current is applied between the individual electrodes 55A and the common electrode 56 or the current is applied between the individual electrodes 55B and the common electrode 56. It is configured to do. As described above, the laser light source 21 includes two laser elements LE1 and LE2 that can be driven independently.

Further, the drive circuit 30 is configured to drive the laser element of one of the laser elements LE1 and LE2 as a drive target. Further, the drive circuit 30 drives the element to be driven in a constant output drive mode (APC (Automatic Power Control) mode), which is a drive mode for maintaining a constant optical output, or drives with a constant drive current value. It is configured to be driven in a constant current drive mode (ACC (Automatic Current Control) mode), which is a mode.

The constant output drive mode is, for example, a drive mode in which the drive current is increased or decreased so as to keep the light output of the output light LO from the laser light source 21 constant. Further, the constant current drive mode is a drive mode in which the drive current DC is kept constant. Further, in the present embodiment, the selection of the drive target and the selection of the drive mode of the drive circuit 30 are performed by the control signal CS from the control circuit 40 as described later.

The distance W between the ridge portions 54A and 54B is 140 μm or less. By setting the interval W to 140 μm or less, the lens 23 can be shared by the laser elements LE1 and LE2. That is, the laser light L1 from either the laser elements LE1 or LE2 can be formed into the same light distribution shape by using one lens 23. Therefore, the light source system 10 is miniaturized.

In this embodiment, the laser light source 21 is made of a GaN-based semiconductor material. The mounting substrate 51 has, for example, a GaN composition. The semiconductor structure layer 52 has a composition of, for example, AlxInyGa1-x-yN (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1).

The wavelength conversion device 22 is a phosphor plate containing a phosphor made of, for example, yttrium aluminum garnet (YAG). That is, in this embodiment, the laser light L1 emitted from the laser light source 21 is blue light. Further, the wavelength conversion light L2 emitted from the wavelength conversion device 22 is white light generated by mixing the blue light which is the laser light L1 and the yellow light generated by the incident of the laser light on the phosphor. ..

FIG. 2B is a block diagram showing the configuration of the control circuit 40. The control circuit 40 drives the output light monitoring circuit 41 that monitors the output light LO (laser light L1 or wavelength conversion light L2) from the laser light source 21 or the wavelength conversion device 22, and the laser light source 21 generated by the drive circuit 42. It has a drive current monitoring circuit 42 that monitors the current DC. The output light monitoring circuit 41 includes, for example, a photodetector. The drive current monitoring circuit 42 includes, for example, an ammeter.

Further, the control circuit 40 includes a failure prediction circuit 43 that predicts COD (Catastrophic Optical Damage), which is optical damage of the laser element LE1 or LE2, based on the time-dependent change of the output light LO and the time-dependent change of the drive current DC. The failure prediction circuit 43 predicts that COD will be generated in the laser element driven by the drive circuit 30 based on the time-dependent change of the optical output of the output light LO and / or the time-dependent change of the current value of the drive current DC. ..

Further, the control circuit 40 includes a drive control circuit 44 that controls the drive of the laser light source 21 by the drive circuit 30 based on the prediction result of the failure prediction circuit 43. The drive control circuit 44 generates a control signal CS that controls (selects) the drive target element of the laser light source 21, and supplies the control signal CS to the drive circuit 30.

Specifically, in this embodiment, the laser light source 21 has a redundant configuration in which any of the laser elements LE1 and LE2 is used as a drive target element (active element) and the other laser element is used as a spare element (standby element). Has. For example, the drive control circuit 44 controls the drive circuit 30 to select and drive another laser element as a drive target when a failure of the laser element to be driven is predicted by the failure prediction circuit 43.

Therefore, when the failure prediction circuit 43 predicts the occurrence of optical damage to the laser element to be driven (for example, the laser element LE1), the drive circuit 30 uses the other lasers of the laser elements LE1 and LE2 in the laser light source 21. The element (for example, the laser element LE2) is driven as a driving target.

Further, the control circuit 40 has a notification circuit 45 that notifies the outside of information indicating that COD is predicted to occur in the drive target element by the failure prediction circuit 43. For example, the notification circuit 45 externally (for example,) indicates that the laser element being driven is just before the occurrence of COD, another laser element has become the element to be driven, and the replacement time of the laser light source 21 is approaching. Notify the driver of the car, etc.).

In this embodiment, the drive control circuit 44 supplies the drive circuit 30 with a control signal CS that controls the switching of the drive mode in addition to the switching control of the drive target of the laser light source 21. In this embodiment, the drive control circuit 44 drives the selected laser element (drive target element) with respect to the drive circuit 30 in the constant output drive mode (APC mode), or the constant current drive mode (ACC mode). Controls to instruct whether to drive with.

Further, the drive control circuit 44 controls the drive circuit 30 to set an initial drive target element (drive target element at system startup) and an initial drive mode (drive mode at system startup) of the laser light source 21. Do. For example, the drive control circuit 44 can control the drive circuit 30 so that the initial drive target element is the laser element LE1 and the initial drive mode is the constant output drive mode.

Next, the details of the failure prediction operation by the failure prediction circuit 43 will be described with reference to FIGS. 3 (a) and 3 (b) and FIGS. 4 (a) and 4 (b). First, the failure prediction circuit 43 has different prediction criteria depending on the drive mode of the laser light source 21, and the failure prediction of the drive target element is performed based on the prediction criteria.
[When driving in constant output drive mode (APC mode)]
First, when the drive target element in the laser light source 21 (in this embodiment, one laser element of the laser elements LE1 and LE2) is driven in the constant output drive mode (APC mode), that is, the drive control circuit 44 When the drive circuit 30 is driven in the constant output drive mode, the failure prediction circuit 43 predicts the occurrence of COD of the element to be driven when the drive current DC increases at an accelerating rate.

Specifically, in the case of the constant output drive mode, the failure prediction circuit 43 describes the current of the drive current DC at the start of driving of the drive target element with respect to the time-dependent change I _{op (t) of the drive current value I op of the drive target element.} Assuming that the value is I _c , the constant is k, the time is t, and the exponent is α, it is determined that the time has changed according to the following equation (1).

そして、故障予測回路４３は、所定の時間ｔを基準とした時間経過及び駆動電流値Ｉｏｐの変化（Ｉ_op（ｔ））を記録することで、指数αを求める。故障予測回路４３は、この指数αが、α＞１であり（予測条件１）、かつｄα／ｄｔ＞０を満たす変化状態が所定時間続いた（予測条件２）場合、駆動対象素子におけるＣＯＤの発生を予測する（すなわちＣＯＤが発生する直前であると判定する）。

Then, the failure prediction circuit 43 obtains the index α by recording the passage of time and the change in the drive current value Iop (I _{op (t)) with respect to the predetermined time t.} When the index α is α> 1 (prediction condition 1) and the change state satisfying dα / dt> 0 continues for a predetermined time (prediction condition 2), the failure prediction circuit 43 determines the COD in the drive target element. Predict the occurrence (that is, determine that it is just before the occurrence of COD).

Regarding the prediction condition 2, for example, the relationship of dα / dt> 0 is satisfied when the change of the index α is calculated to the first decimal place with the determination period (corresponding to the above “predetermined period”) as 1 hour (corresponding to the above “predetermined period”). For example, the occurrence of COD can be predicted when dα / dt> 0 occurs more than once within 1 hour). Further, this determination period is set, for example, in the range of 0.1 hour to 100 hours, considering that the occurrence of COD is surely predicted (that is, the above determination is performed before the actual occurrence of COD). Is preferable.

FIG. 3A is a diagram showing the ratio of increase of _{the drive current value I op} with time according to the change of the index α in the equation (1). For example, when α = 0, the drive current I _op does not increase or decrease. When α = 1, the drive current value I _op increases linearly. However, when α exceeds 1, the drive current value I _op increases exponentially. The failure prediction circuit 43 _obtains the index α of the equation (1) by recording the change (I _op (t)) of the drive current I op at predetermined time intervals, and determines that the change with time according to the obtained index α. Continue to do.

FIG. 3B is a diagram modeling an example of time-dependent changes _{in the drive current value I op} determined by the failure prediction circuit 43. In the failure prediction circuit 43, for example, the drive current value I _op hardly changes _{from the start of the drive to the time t1 (the state of I op} (t) = I _c continues), and this period is expressed by the equation (1). ) Approximately the period of index α = 0. Since the prediction condition 1 is not satisfied during this period, the failure prediction circuit 43 does not predict the occurrence of COD.

_{The failure prediction circuit 43 approximates the index α and models the current value change I op} (t) based on the change in the _{drive current value I op} at predetermined time intervals even after the time t1. Then, in the example shown in FIG. 3B, after the time t3, the drive current value I _op increases exponentially at shorter intervals than before, and the approximated index α gradually increases. .. The failure prediction circuit 43 predicts and determines that both the above-mentioned prediction conditions 1 and 2 are satisfied and COD is generated in the drive target element at the timing of t4.

In the period of time t2 to t3, the index α is obtained as α = 1.3 and satisfies the prediction condition 1, but the index α maintains the state of 1.3 for a certain period of time (state of dα / dt = 0). Does not satisfy the prediction condition 2 because (is continued for a certain period of time). Similarly, even in the period from time t3 to t4, since α is 1.4, the prediction condition 1 is satisfied, but the state where the index α is 1.4 is maintained longer than the condition period of the prediction condition 2, so that the prediction is made. Condition 2 is not satisfied. Therefore, the failure prediction circuit 43 does not predict a failure at the timing of time t2 or t3. That is, the failure prediction circuit 43 determines that the timing of the time t2 or t3 is not yet immediately before the occurrence of COD.

When the semiconductor laser is driven in the constant output drive mode, it is known that the failure of the semiconductor laser is caused not only by COD but also by thermal runaway. On the other hand, the inventor of the present application has found that _{a device failure due to thermal runaway occurs at a predetermined drive current value If.} Specifically, the drive current value (thermal runaway generated current value) _{If that causes a failure of the laser element due to thermal runaway is T 0 for} the characteristic temperature of the laser element (drive target element) _{, R th for} the thermal resistance, and electricity. Assuming that the resistance (series resistance) is R, it can be expressed by the following equation (3).

また、図３（ｂ）に示すように、故障予測回路４３を用いて上記したようなＣＯＤの発生予測を行う場合、この熱暴走が発生するタイミング（熱暴走が発生し得る駆動電流値Ｉ_fに達するタイミング）は、ＣＯＤの予測タイミングよりも遅い。従って、故障予測回路４３は、上記した予測条件１及び２に加え、駆動電流値Ｉ_dが所定の電流値未満である（駆動電流値Ｉ_d＜熱暴走発生電流値Ｉ_f（予測条件３）を満たす）場合にＣＯＤの発生の予測を確定する。

Further, as shown in FIG. 3B, when predicting the occurrence of COD as described above using the failure prediction circuit 43, the timing at which this thermal runaway occurs (the drive current value I _{f at which thermal runaway can occur)} The timing to reach) is later than the predicted timing of COD. Therefore, in the failure prediction circuit 43, in addition to the prediction conditions 1 and 2 described above, the drive current value I _d is less than a predetermined current value (drive current value I _d <thermal runaway generation current value _If (prediction condition 3)). If), the prediction of the occurrence of COD is confirmed.

As a result, the accuracy of COD prediction is improved, and the occurrence of COD can be predicted more reliably. Thus, the failure prediction circuit 43, when the drive current value I _op did not meet predicted conditions 1 and 2 until it reaches the thermal runaway generation current value I _f, it is possible to predict failure of the driven element due to thermal runaway ..
[When driving in constant current drive mode (ACC mode)]
Next, when the drive target element of the laser light source 21 is driven in the constant current drive mode (ACC mode), that is, when the drive circuit 30 is driven in the constant current drive mode by the drive control circuit 44, a failure occurs. The prediction circuit 43 predicts that COD will be generated in the drive target element when _{the light output P out of the output light LO decreases at an accelerating rate.}

Specifically, in the case of the constant current drive mode, the failure prediction circuit 43 of the drive target element or the wavelength conversion device 22 with respect to the time-dependent change P _{out (t) of the optical output P out} of the drive target element or the wavelength conversion device 22. Assuming that the optical output at the start of driving is P ₀ , the constant is k, the time is t, and the exponent is α, it is determined that the time has changed according to the following equation (2).

そして、故障予測回路４３は、所定の時間ｔを基準とした時間経過及び光出力Ｐ_outの変化（Ｐ_out（ｔ））を記録することで、指数αを求める。故障予測回路４３は、この指数αが、α＞１であり（予測条件４）、かつｄα／ｄｔ＞０を満たす変化状態が所定時間続いた（予測条件５）場合、駆動対象素子におけるＣＯＤの発生を予測する（すなわちＣＯＤが発生する直前であると判定する）。

Then, the failure prediction circuit 43 obtains the index α by recording the passage of time and the change in the _{optical output P out (P out (t)) with respect to the predetermined time t.} When the index α is α> 1 (prediction condition 4) and the change state satisfying dα / dt> 0 continues for a predetermined time (prediction condition 5), the failure prediction circuit 43 determines the COD in the drive target element. Predict the occurrence (that is, determine that it is just before the occurrence of COD).

Regarding the prediction condition 5, for example, the relationship of dα / dt> 0 is satisfied when the change of the index α is calculated to the first decimal place with the determination period (corresponding to the above “predetermined period”) as 1 hour (corresponding to the above “predetermined period”). For example, the occurrence of COD can be predicted when dα / dt> 0 occurs more than once within 1 hour). Further, this determination period is set, for example, in the range of 0.1 hour to 100 hours, considering that the occurrence of COD is surely predicted (that is, the above determination is performed before the actual occurrence of COD). Is preferable.

FIG. 4A is a diagram showing the ratio of decrease of _{the optical output P out} with time according to the change of the index α in the formula (2). For example, when α = 1, the light output P _out decreases linearly. However, when α exceeds 1, the optical output P _out decreases exponentially. The failure prediction circuit 43 _obtains the index α of the equation (2) by recording the change (P _out (t)) of the optical output P out at predetermined time intervals, and determines that the change with time according to the obtained index α. Continue to do.

FIG. 4B is a diagram modeling an example of time-dependent changes _{in the optical output P out} determined by the failure prediction circuit 43. In the failure prediction circuit 43, for example, there is almost no change in the _{optical output P out} from the start of driving to the time t1 when the driving time t _{(the state of P out} (t) = P ₀ continues), and this period is in the equation (2). Approximately the period of index α = 0. Since the prediction condition 4 is not satisfied during this period, the failure prediction circuit 43 does not predict the occurrence of COD.

_{The failure prediction circuit 43 approximates the index α and models the optical output change P out} (t) based on the change in the _{optical output P out} at predetermined time intervals even after the time t1. Then, in the example shown in FIG. 4B, after the time t3, the optical output P _out decreases exponentially at short intervals, and the approximated index α increases. The failure prediction circuit 43 predicts that all of the above-mentioned prediction conditions 4 and 5 are satisfied at the timing of t4, and that COD is generated in the drive target element.

As in the constant output drive mode, the failure prediction circuit 43 does not predict the occurrence of COD unless both the prediction conditions 4 and 5 are satisfied. Further, in the constant current drive mode, element failure due to thermal runaway is unlikely to occur. Therefore, in the constant current mode, the occurrence of COD can be predicted with high accuracy according to the prediction conditions 4 and 5.

In this embodiment, the case where the light source device 20 has the wavelength conversion device 22 and the lens 23 has been described, but the light source device 20 is not limited to the case where the light source device 20 has the wavelength conversion device 22 and the lens 23. The light source device 20 may have a laser light source 21. For example, the light source device 20 does not have a wavelength conversion device 22, and may be composed of a laser light source 21 and a lens 23. In this case, the lens 23 may output the laser beam L1 to the outside. Further, the optical output monitoring circuit 41 of the control circuit 40 may monitor the laser beam L1 from the laser light source 21 as the light to be monitored.

As described above, in the present embodiment, the light source system 10 includes a laser light source 21 including a plurality of semiconductor laser devices LE1 and LE2 that can be driven independently, and any one of the plurality of semiconductor laser devices LE1 and LE2. Predicts optical damage to the drive target element based on the drive circuit 30 that drives one laser element as the drive target element and the time course of the drive current DC of the drive target element by the drive circuit 30 or the output light LO from the drive target element. A control circuit 40 that controls switching of a drive target element with respect to the drive circuit 30 based on the prediction.

The failure prediction circuit 43 of the control circuit 40 determines the sign of COD before it occurs in the drive target element from the time-dependent changes of the drive current DC and the output light LO. Therefore, it is possible to switch the drive target to another element before the COD actually occurs, that is, before the laser element being driven fails. Therefore, for example, it is possible to prevent the lighting from being suddenly turned off.

For example, when the light source system 10 is used for a vehicle lamp (for example, a headlamp), it is expected that sudden turning off of the laser light source 21 will directly lead to a traffic accident. Therefore, the light source system 10 has a plurality of laser elements LE1 and LE2, and the failure prediction circuit 43 predicts the COD and switches the element to be driven before the occurrence of the COD, so that the vehicle can travel safely. Can be provided. Therefore, it is preferable to use the light source system 10 to configure the vehicle lamp.

When the laser elements LE1 and LE2 are optically coupled to each other and juxtaposed as in this embodiment, the undriven laser element (laser element LE2 when the drive target element is the laser element LE1) is output light. It can be used as a light receiving element of the monitoring circuit 41. Specifically, when driving the laser element LE1, a part of the output light LO from the laser element LE1 propagates to the laser element LE1. Therefore, by detecting (monitoring) the current between the p electrode 55B and the n electrode 56 of the laser element LE2, the laser element LE2 can function as a photodetector of the output light monitoring circuit 41.

In other words, in the present embodiment, the output light monitoring circuit 41 monitors the output light LO by using the undriven laser element among the plurality of laser elements LE1 and LE2 in the laser light source 21 as the light receiving element. To do. As a result, for example, it is not necessary to provide a photodetector for the output light monitoring circuit 41, and the system configuration is simplified and miniaturized.

FIG. 5 is a schematic perspective view of the laser light source 21A of the light source device 20A in the light source system according to the modified example of the first embodiment. Similar to the laser light source 21, the laser light source 21A has a plurality of laser elements LE1 and LE2 optically coupled and juxtaposed with each other, but the detailed configuration thereof is different from that of the laser light source 21. First, the case where the laser light source 21 has the semiconductor structure layer 52 common to the laser elements LE1 and LE2 has been described, but the laser light source 21A has separate semiconductor structure layers 62 and 72 in the laser elements LE1 and LE2. That is, the laser light source 21A has a plurality of semiconductor structural layers 62 and 72 corresponding to each of the laser elements LE1 and LE2 and forming a resonator by end faces facing each other.

Further, the laser light source 21A corresponds to each of the laser elements LE1 and LE2, and has ridge portions 64 and 74 formed on the upper surfaces of the semiconductor structure layers 62 and 72, respectively, and extending in a stripe shape between the opposite end faces. Further, the ridge portions 64 and 74 of the semiconductor structure layers 62 and 72 are arranged so that the distance between the ridge portions 64 and 74 and the adjacent ridge portions is 140 μm or less.

More specifically, the laser light source 21A has a semiconductor structure layer 62 (n-type semiconductor layer 62A, light emitting layer 62B and p-type semiconductor layer 62C), an insulating layer 63, and a ridge portion 64 as the laser element LE1 on the mounting substrate 61. , P-electrode 65 and n-electrode 66 are mounted. In this modification, the laser element LE2 is formed on the laser element LE1 via the bonding layer 67.

Specifically, a bonding layer 67 is formed on the laser element LE1 so as to cover the upper surfaces of the p-type semiconductor layer 62C, the ridge portion 64, and the p electrode 65. On the bonding layer 67, as the laser element LE2, a semiconductor structure layer 72 (p-type semiconductor layer 72C, light emitting layer 72B and n-type semiconductor layer 72A) including an insulating layer 73, a p electrode 75, and a ridge portion 74, and an n electrode 76. Is formed.

The semiconductor structure layer 62 of the laser element LE1 constitutes a resonator in which the end faces ES11 and ES12 facing each other form a resonator long direction RD between the end faces. Similarly, the semiconductor structure layer 72 of the laser element LE2 constitutes a resonator in which the end faces ES21 and ES22 facing each other form a resonator long direction RD between the end faces.

In this modification, the laser light source 21A has a structure in which the semiconductor structure layers 62 and 72 are joined so that the ridge portions 64 and 74 are alternately arranged with the insulating layer 73 interposed therebetween. Therefore, the distance between the light emitting portions of the laser elements LE1 and LE2 can be reduced (for example, 140 μm or less), and the molding light L3 (extracted light) having a desired shape can be formed by one lens 23 regardless of which laser element is driven. ) Can be generated.

As described above, in the laser light source 21 or 21A including the plurality of semiconductor laser elements LE1 and LE2, the drive circuit 30 drives any of the semiconductor laser elements LE1 and LE2 as a drive target. Further, the failure prediction circuit 43 measures the time-dependent change of the optical output LO of the drive target element or the time-dependent change of the drive current DC of the drive target element according to the drive mode of the drive target element, and optically damages the drive target element. Predict. When the failure prediction circuit 43 predicts the occurrence of optical damage to the drive target element, the drive circuit 30 uses the laser light source 21 or the other undriven lasers of the plurality of laser elements LE1 and LE2 in the 21A. The element is driven as a driving target. Therefore, the drive target can be switched to another element before the COD of the drive target element is generated, and a highly reliable light source system can be provided.

10 Light source system 20 Light source device 21, 21A Laser light source LE1, LE2 Semiconductor laser element 30 Drive circuit 43 Failure prediction circuit 44 Drive control circuit

Claims (15)

A light source device having a laser light source including a plurality of semiconductor laser elements,
A drive circuit in which one of the plurality of semiconductor laser elements is driven and the semiconductor laser element is driven in a constant output drive mode for maintaining a constant light output.
The elapsed time t and the time-dependent change I _op (t) _{of the drive current I op} of the semiconductor laser device of the above 1 by the drive circuit are recorded, and the drive current value at the start of the drive of the semiconductor laser device of the above 1 is I _c. The following equation (1) showing the time-dependent change I _op (t) of the drive current, where k is a constant.

To thus determine the index alpha, the index alpha of the formula (1) is, alpha> 1, and if a change condition satisfying dα / dt> 0 becomes equal to or more than a predetermined time continues Kukamatawa predetermined plurality of times , anda failure prediction circuit for determining the occurrence of optical damage in the semiconductor laser element of the 1,
When the occurrence of optical damage of the semiconductor laser element of the 1 is determined by the failure prediction circuit, wherein the drive circuit, and characterized in that the other semiconductor laser element of the plurality of semiconductor laser elements and driven Light source system. A light source device having a laser light source including a plurality of semiconductor laser elements,
A drive circuit in which one of the plurality of semiconductor laser elements is driven and the semiconductor laser element is driven in a constant output drive mode for maintaining a constant light output.
The elapsed time t and the time-dependent change I _{op (t) of the drive current I op} of the semiconductor laser device of the above 1 by the drive circuit are recorded, and the drive current value at the start of the drive of the semiconductor laser device of the above 1 is I _c. The following equation (1) showing the _{time-dependent change I op} (t) of the drive current, where k is a constant.

The exponent α is obtained according to the above equation (1), and the change state in which the exponent α of the formula (1) is α> 1 and satisfies dα / dt> 0 continues for a predetermined time or becomes a predetermined plurality of times or more . It has a failure prediction circuit that determines that optical damage has occurred in the semiconductor laser element of 1 when the drive current value of the semiconductor laser element is less than a predetermined current value.
When the occurrence of optical damage of the semiconductor laser element of 1 is determined by the failure prediction circuit, the drive circuit is characterized in that the other semiconductor laser element of the plurality of semiconductor laser elements is driven. light source system. The light source system according to claim 1 or 2, wherein the plurality of semiconductor laser elements are optically coupled and juxtaposed with each other. The laser light source is
A semiconductor structural layer that is common to the plurality of semiconductor laser elements and constitutes a resonator by end faces facing each other,
It has a plurality of ridge portions corresponding to each of the plurality of semiconductor laser elements, formed on the upper surface of the semiconductor structural layer, and extending in a stripe shape between the opposing end faces.
The light source system according to claim 3, wherein the distance between adjacent ridge portions of the plurality of ridge portions is 140 μm or less. The laser light source is
A plurality of semiconductor structural layers corresponding to each of the plurality of semiconductor laser elements and forming a resonator by end faces facing each other,
It has a ridge portion corresponding to each of the plurality of semiconductor laser elements, formed on the upper surface of each of the plurality of semiconductor structural layers, and extending in a stripe shape between the opposing end faces.
The light source system according to claim 3, wherein the ridge portion of each of the plurality of semiconductor structural layers is arranged so that the distance between the ridge portion and the adjacent ridge portion is 140 μm or less. Light source system according to any one of claims 1 to 5, characterized in that it has a notification circuit for notifying the occurrence of the optical damage of the semiconductor laser element of the 1 by the failure prediction circuit is determined externally .. A vehicle lamp including the light source system according to any one of claims 1 to 6.
The light source device is a vehicle lamp having a lens that outputs a laser beam from the laser light source to the outside. A light source device having a laser light source including a plurality of semiconductor laser elements,
A drive circuit that targets one of the plurality of semiconductor laser elements to be driven and drives the semiconductor laser element in a constant current drive mode that maintains a constant drive current.
The elapsed time t of driving the semiconductor laser element of 1 and the time-dependent change P _out (t) of the optical output P _out by the drive circuit are recorded, and the optical output at the start of driving of the semiconductor laser element of 1 is P ₀ . The following equation (2) showing the time-dependent change _{Pout (t) of the optical output, where k is a constant.}

To thus determine the index alpha, the index alpha of the formula (2) is, alpha> 1, and if a change condition satisfying dα / dt> 0 becomes equal to or more than a predetermined time continues Kukamatawa predetermined plurality of times , anda failure prediction circuit for determining the occurrence of optical damage in the semiconductor laser element of the 1,
When the occurrence of optical damage of the semiconductor laser element of the 1 is determined by the failure prediction circuit, wherein the drive circuit, and characterized in that the other semiconductor laser element of the plurality of semiconductor laser elements and driven Light source system. The light source system according to claim 8, wherein the plurality of semiconductor laser elements are optically coupled and juxtaposed with each other. It has an output light monitoring circuit that monitors the output light from the semiconductor laser device of 1.
The light source system according to claim 9, wherein the output light monitoring circuit monitors the output light by using an undriven semiconductor laser element among the plurality of semiconductor laser elements as a light receiving element. The laser light source is
A semiconductor structural layer that is common to the plurality of semiconductor laser elements and constitutes a resonator by end faces facing each other,
It has a plurality of ridge portions corresponding to each of the plurality of semiconductor laser elements, formed on the upper surface of the semiconductor structural layer, and extending in a stripe shape between the opposing end faces.
The light source system according to claim 9 or 10, wherein the distance between adjacent ridge portions of the plurality of ridge portions is 140 μm or less. The laser light source is
A plurality of semiconductor structural layers corresponding to each of the plurality of semiconductor laser elements and forming a resonator by end faces facing each other,
It has a ridge portion corresponding to each of the plurality of semiconductor laser elements, formed on the upper surface of each of the plurality of semiconductor structural layers, and extending in a stripe shape between the opposing end faces.
The light source system according to claim 9 or 10, wherein the ridge portion of each of the plurality of semiconductor structural layers is arranged so that the distance between the ridge portion and the adjacent ridge portion is 140 μm or less. .. A vehicle lamp comprising the light source system according to any one of claims 8 to 12.
The light source device is a vehicle lamp having a lens that outputs a laser beam from the laser light source to the outside. A light source device including a laser light source including a plurality of semiconductor laser elements optically coupled and juxtaposed to each other, and a wavelength conversion device for converting the wavelength of the laser light from the laser light source.
A drive circuit that targets one of the plurality of semiconductor laser elements to be driven and drives the semiconductor laser element in a constant current drive mode that maintains a constant drive current.
The elapsed time t of driving the semiconductor laser element of 1 and the time-dependent change P _out (t) of the optical output P _out by the drive circuit are recorded, and the optical output at the start of driving of the semiconductor laser element of 1 is P ₀ . The following equation (2) showing the time-dependent change _{Pout (t) of the optical output, where k is a constant.}

To thus determine the index alpha, the index alpha of the formula (2) is, alpha> 1, and if a change condition satisfying dα / dt> 0 becomes equal to or more than a predetermined time continues Kukamatawa predetermined plurality of times , anda failure prediction circuit for determining the occurrence of optical damage in the semiconductor laser element of the 1,
When the occurrence of optical damage of the semiconductor laser element of the 1 is determined by the failure prediction circuit, wherein the drive circuit, and characterized in that the other semiconductor laser element of the plurality of semiconductor laser elements and driven Light source system. A vehicle lamp comprising the light source system according to claim 14.
The light source device is a vehicle lamp having a lens that outputs wavelength conversion light from the wavelength conversion device to the outside.

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