Light emitting device

Abstract

The invention provides a light-emitting device capable of lighting a plurality of light sources through a simple structure. The light-emitting device comprises n light sources, wherein n is greater than or equal to 2; the n power supply circuits are respectively arranged for the n light sources; and a switch provided between a node on a ground side of each of the n light sources and a ground, the power supply circuit generating a power supply voltage for a corresponding one of the n light sources according to a first signal and stopping the generation of the power supply voltage according to a second signal, and when the power supply voltage for the one light source is generated, generating a power supply voltage for the one light source according to the second signal. The switch is turned on according to a light-on instruction and turned off according to a light-off instruction.

Description

Technical Field

[0001] The present invention relates to a light emitting device. Background Art

[0002] In a measuring device that measures the distance to an object based on light emitted from a light emitting element such as a laser diode, a driving circuit that drives the light emitting element is generally provided (for example, Patent Document 1). Prior art literature

[0003] Patent Document 1: Japanese Patent Publication No. 2021-28924

[0004] The driving circuit disclosed in Patent Document 1 is provided with a level shift circuit, so the structure of the driving circuit is generally complicated. Summary of the invention

[0005] The present invention has been made in view of the above-mentioned conventional problems, and a main object of the present invention is to provide a light emitting device capable of lighting a plurality of light sources with a simple structure.

[0006] A light-emitting device of one embodiment of the present invention includes: n (n≥2) light sources; n power supply circuits respectively set for the n light sources; and a switch set between a node on the ground side of each of the n light sources and the ground, wherein the power supply circuit generates a power supply voltage for a corresponding one of the n light sources according to a first signal, and stops generating the power supply voltage according to a second signal, and when generating the power supply voltage for the one light source, the switch is turned on according to a lighting indication, and is turned off according to a lighting off indication.

[0007] According to the present invention, it is possible to provide a light emitting device capable of lighting a plurality of light sources with a simple structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a diagram showing an example of the measuring device 10 . Figure 2 It is a diagram showing an example of the light emitting device 20a. Figure 3 1 is a diagram showing an example of the structure of the light source D0. Figure 4 It is a diagram showing an example of the light emitting device 20b. Figure 5 It is a diagram for explaining signals S10 to S19. Figure 6 It is a diagram for explaining the operation of the light emitting device 20b. Figure 7 1 is a diagram showing an example of a current waveform of the light emitting device 20 b . Figure 8 It is a diagram showing an example of the light emitting device 20c. Fig. 9 This is a diagram showing an example of a current waveform of the light emitting device 20c. DETAILED DESCRIPTION

[0009] At least the following contents can be understood from the description of this specification and the drawings. In addition, the same reference numerals are used for the same or equivalent structural elements, components, etc. shown in the respective drawings, and repeated descriptions are appropriately omitted.

[0010] ======Present Implementation Method====== <<Overview of Measurement Device 10>> The measuring device 10 has a function as a so-called LiDAR (Light Detection and Ranging, Laser Imaging Detection and Ranging), and is a device for measuring the distance to the object 11. Specifically, the measuring device 10 emits measurement light and measures the distance to the object 11 based on a TOF method (Time of flight) for detecting reflected light reflected on the surface of the object 11. The measuring device 10 is provided on a vehicle (not shown), for example, and includes a light emitting device 20, a light receiving device 21, and a control device 22.

[0011] The object 11 is, for example, a vehicle different from the vehicle on which the measurement device 10 is installed, a person, a street light, or a structure such as a building.

[0012] The light emitting device 20 emits measurement light toward the object 11 based on control from a control device 22 (described later). The light emitting device 20 will be described in detail later.

[0013] The light receiving device 21 receives reflected light from the object 11 , and outputs information on the reflected light (for example, timing and level) to the control device 22 .

[0014] The control device 22 is a device that performs overall control of the measuring device 10. Specifically, the control device 22 controls the emission of the measuring light from the light emitting device 20, and measures the distance to the object 11 in a TOF (Time of Flight) method based on the output from the light receiving device 21. Although not shown in the figure, the control device 22 includes, for example, a storage device and a computing device that executes a program stored in the storage device.

[0015] <<Details of Light Emitting Device 20a>> Figure 2 2 is a diagram showing an example of a structure of a general light emitting device 20a. The light emitting device 20a includes light sources D0 to D9, a capacitor 40, power supply circuits 50 to 59, and a control circuit 60. Figure 2In the figure, for the sake of easy understanding, part of the structure of the light emitting device 20a (light sources D2 to D8, power supply circuits 52 to 58) is omitted.

[0016] ==About light source== The light source D0 includes, for example, a vertical cavity surface emitting laser that can emit infrared measurement light. Figure 3 For example, the optical member 120 for adjusting the light distribution of the laser diodes 100 to 115 is included.

[0017] The cathodes and anodes of the laser diodes 100 to 115 are common. Therefore, the light emitted from each laser diode 100 to 115 becomes the measurement light from one light source D0. Here, the light source D0 includes 16 laser diodes 100 to 115, but it may be another number (e.g., 8 or 32).

[0018] The optical component 120 is, for example, an optical diffusion element (LSD: Light Shaping Diffuser), which is a component that diffuses (i.e., adjusts) the light emitted from each laser diode 100 to 115 so that the light distribution from the light source D0 becomes a desired pattern. In addition, here, LSD is used as the optical component 120, but any component can be used as long as the light distribution from the light source D0 becomes a desired pattern.

[0019] Since light sources D1 to D9 respectively include the same surface emitting laser (hereinafter referred to as "VCSEL") and optical component 120 as light source D0, detailed description is omitted here. In addition, the nine light sources D0 to D9 are equivalent to n (n is an integer greater than 2) light sources. In addition, for convenience, light source D0 is sometimes described as VCSEL.

[0020] ==About capacitor 40== The capacitor 40 is an element for stabilizing a predetermined power supply voltage Vdd1 (for example, several tens of V) supplied to the power supply circuits 50 to 59. The predetermined power supply voltage Vdd1 is applied to the capacitor 40.

[0021] ==Details of Power Supply Circuit 50== The power supply circuit 50 is a circuit that generates a power supply voltage V0 for lighting the light source D0 based on the power supply voltage Vdd1 and the signal S0 from the control circuit 60. Specifically, if a high-level (hereinafter, "H-level") signal S0 is input from the control circuit 60 to light the light source D0, the power supply circuit 50 generates the power supply voltage V0. On the other hand, if a low-level (hereinafter, "L-level") signal S0 is input from the control circuit 60 to turn off the light source D0, the power supply circuit 50 stops generating the power supply voltage V0.

[0022] The power circuit 50 includes a diode 200 , a capacitor 201 , a buffer 210 , a transformer 211 , an integrated circuit (IC) 212 , and a resistor 213 .

[0023] The diode 200 is an element that generates a power supply voltage for operating an IC 212 (described later) together with the capacitor 201. A power supply voltage Vdd2 (eg, 5V) is applied to the anode of the diode 200, and the cathode of the diode 200 is connected to the capacitor 201.

[0024] When the current from the diode 200 charges the capacitor 201 , a power supply voltage for operating the IC 212 is generated on the capacitor 201 .

[0025] The buffer 210 outputs a signal Sa0 of the same logic level as the signal S0 to the transformer 211. Specifically, the buffer 210 outputs the signal Sa0 of an H level according to the signal S0 of an H level, and outputs the signal Sa0 of an L level according to the signal S0 of an L level. Here, the signal S0 is a signal for controlling the on / off of a driving transistor 231 (described later) of the IC 212, and the L level of the signal S0 is, for example, 0V, and the H level is, for example, 3V.

[0026] The transformer 211 is an insulating transformer that maintains the amplitude of an input signal and converts the DC level for output, and includes a primary coil 220 and a secondary coil 221 electromagnetically coupled to the primary coil 220 .

[0027] Here, the transformer 211 functions as a so-called level shift circuit. Therefore, the transformer 211 converts the signal Sa0 whose logic level changes with respect to the ground voltage (0V) into the signal Sb0 whose logic level changes with respect to the power supply voltage V0. That is, when the signal Sa0 is at an H level, the transformer 211 causes the secondary coil 221 to generate the signal Sb0 at an H level, and when the signal Sa0 is at an L level, the transformer causes the secondary coil 221 to generate the signal Sb0 at an L level.

[0028] Here, the transformer 211 is used as a so-called level shift circuit, but the present invention is not limited to this, and other structures (for example, a circuit including a photocoupler, etc.) may be used.

[0029] IC212 generates power supply voltage V0 for light source D0 when signal Sb0 from secondary coil 221 is at H level, and stops generating power supply voltage V0 when signal Sb0 is at L level. IC212 includes a buffer 230 and a driving transistor 231 .

[0030] The buffer 230 outputs a signal of the same logic level as the signal Sb0 to the driving transistor 231. Specifically, when the signal Sb0 of the H level is output from the secondary coil 221, the buffer 230 outputs the signal of the H level to the driving transistor 231. As a result, the driving transistor 231 is turned on.

[0031] On the other hand, when the L-level signal Sb0 is output from the secondary coil 221, the buffer 230 outputs the L-level signal to the driving transistor 231. As a result, the driving transistor 231 is turned off.

[0032] Here, when the driving transistor 231 is turned on, the power supply voltage V0 of the line L0 on the anode side of the light source D0 rises to approximately the power supply voltage Vdd1. Since the high-level power supply voltage V0 is applied to the line L0 on the anode side of the light source D0, the light source D0 lights up (emits measurement light).

[0033] In addition, the resistor 213 is an element for limiting the current flowing through the light source D0. In addition, if the driving transistor 231 is turned on, the voltage of the line L0 connected to the source of the driving transistor 231 rises to approximately the power supply voltage Vdd1 (for example, tens of V). Therefore, in order to maintain the on state of the driving transistor 231, it is necessary to continuously apply a voltage higher than the voltage of the line L0 by the threshold of the driving transistor 231 to the gate of the driving transistor 231.

[0034] exist Figure 2 In the power supply circuit 50, the transformer 211 shifts the DC level of the signal Sa0 and outputs it to the secondary side as the signal Sb0. Therefore, the logic level (H level or L level) of the signal Sb0 on the secondary side of the transformer 211 changes with the voltage of the line L0 as a reference. As a result, in the power supply circuit 50, the on / off of the driving transistor 231 can be controlled based on the signal S0 that changes with the ground voltage (0V) as a reference.

[0035] When the signal S0 becomes L level and the driving transistor 231 is turned off, the power supply circuit 50 stops generating the power supply voltage V0. As a result, the supply of the power supply voltage V0 to the light source D0 also stops, so the light source D0 turns off.

[0036] ==About power supply circuits 51 to 59== The power supply circuits 51 to 59 generate power supply voltages V1 to V9 for the light sources D1 to D9 based on the signals S1 to S9, respectively, similarly to the power supply circuit 50. Therefore, the detailed description of the power supply circuits 51 to 59 is omitted here.

[0037] == About Control Circuit 60 == The control circuit 60 is based on Figure 1 The control device 22 starts lighting instructions, and controls each power circuit 50 to 59 so that the light sources D0 to D9 are sequentially lit. Here, "the light sources D0 to D9 are sequentially lit" means that among the 10 light sources D0 to D9, for example, in the order of light sources D0, D1, ... D9, the light sources are lit one by one. Therefore, among the light sources D0 to D9, for example, when the light source D0 is lit, the other light sources D1 to D9 are turned off, and for example, when the light source D1 is lit, the light sources D0, D2 to D9 are turned off.

[0038] Therefore, the control circuit 60 sets the level of one signal corresponding to the light source to be turned on among the signals S0 to S9 to the H level, and sets the levels of the other nine signals to the L level. By outputting such signals S0 to S9, the light sources D0 to D9 are turned on sequentially.

[0039] But, Figure 2 The power supply circuits 50 to 59 of the light emitting device 20a include a plurality of components such as a transformer 211 and an IC 212. Therefore, in the light emitting device 20a, the mounting space occupied by the power supply circuits 50 to 59 is usually increased.

[0040] Furthermore, since the transformer 211 for level shifting the signal S0 and the capacitor 201 for generating the power supply voltage of the buffer 230 have relatively large parasitic inductance and parasitic capacitance, the accuracy of the power supply voltage V0 of the light source D0 deteriorates. Here, in the measuring device 10 of this embodiment, a light emitting device 20b operating with a simple structure is used.

[0041] <<Details of light emitting device 20b>> Figure 4 The light emitting device 20b shown is a device that turns on the light sources D0 to D9 according to the lighting start instruction from the control device 22, and includes the light sources D0 to D9, a capacitor 40, an IC 41, power supply circuits 70 to 79, and a control circuit 80. Figure 4 , Figure 2 The structures marked with the same reference numerals are the same. Therefore, here, the description will be centered on IC41, power supply circuits 70 to 79, and control circuit 80. Figure 4 In the figure, for the sake of easy understanding, part of the structure of the light emitting device 20b (light sources D2 to D8 and power supply circuits 72 to 78) is omitted.

[0042] ==About IC41== IC41 is a circuit for lighting the light source to which the power supply voltage is applied among the light sources D0 to D9. IC41 of this embodiment is provided between the node on the ground side of each light source D0 to D9 and the ground. In addition, the "node on the ground side of the light source D0" is, for example, a node to which the cathodes of the laser diodes 100 to 115 constituting the light source D0 are connected.

[0043] IC41 is Figure 2 The same circuit as IC212 includes a buffer 300 and a driving transistor 301.

[0044] The buffer 300 outputs a signal of the same logic level as the input signal to the driving transistor 301, similarly to the buffer 230. In the present embodiment, a signal S20 from a control circuit 80 (described later) is input to the buffer 300. Therefore, the buffer 300 turns on the driving transistor 301 in response to the signal S20 at an H level, and turns off the driving transistor 301 in response to the signal S20 at an L level.

[0045] The signal S20 at an H level corresponds to a “lighting instruction” for lighting the light source, and the signal S20 at an L level corresponds to a “lighting off instruction” for turning off the light source.

[0046] The drain of the driving transistor 301 is connected to the node on the ground side of the light sources D0 to D9, and the source is grounded. Therefore, when the driving transistor 301 is turned on, a current flows through the light sources D0 to D9 to which the power supply voltage is applied, thereby lighting up. In addition, when the driving transistor 301 is turned off, the path of the current flowing from the light sources D0 to D9 to the ground is cut off, so that all the light sources D0 to D9 are turned off.

[0047] The driving transistor 301 of this embodiment is equivalent to a “switch.” In this embodiment, the driving transistor 301 uses a Ga (gallium nitride) N-type FET (Field effect transistor) as a “switch,” but other compound transistors, common MOS transistors, and bipolar transistors may also be used.

[0048] ==Details of Power Supply Circuit 70== The power circuit 70 generates a power voltage V10 for lighting the light source D0 based on the signal S10. Specifically, the power circuit 70 generates the power voltage V10 when the signal S10 at an H level is input, and stops generating the power voltage V10 when the signal S10 at an L level is input.

[0049] The power supply circuit 70 includes a buffer 310 , a PMOS transistor 311 , an NMOS transistor 312 , a resistor 313 , and a capacitor 314 .

[0050] The buffer 310 operates as an inverter that outputs a signal Sc0 obtained by inverting the logic level of the signal S10. Therefore, the buffer 310 outputs the signal Sc0 at an L level in response to the S10 at an H level, and outputs the signal Sc0 at an H level in response to the S10 at an L level.

[0051] The gate of the PMOS transistor 311 is connected to the gate of the NMOS transistor 312, and the drain of the PMOS transistor 311 is connected to the drain of the NMOS transistor 312. Therefore, the PMOS transistor 311 and the NMOS transistor 312 constitute a so-called push-pull circuit.

[0052] In the present embodiment, when the signal Sc0 is at the L level, the PMOS transistor 311 is turned on and the NMOS transistor 312 is turned off. As a result, the capacitor 314 is charged and the voltage rises to approximately the power supply voltage Vdd1 (eg, several tens of V).

[0053] When the signal Sc0 is at the H level, the PMOS transistor 311 is turned off and the NMOS transistor 312 is turned on, so that the capacitor 314 is discharged. At this time, the charging voltage of the capacitor 314 decreases to approximately 0V.

[0054] Here, in the present embodiment, one end of the capacitor 314 is connected to the anode of the light source D0 via the line L10 . Therefore, the charging voltage of the capacitor 314 becomes the power supply voltage V10 generated by the power supply circuit 70 .

[0055] In this way, the power supply circuit 70 can generate the power supply voltage V10 for lighting the light source D0 or stop generating the power supply voltage V10 according to the logic level of the signal S10.

[0056] In addition, in this embodiment, the buffer 310, the PMOS transistor 311, and the NMOS transistor 312 are equivalent to a "charge and discharge circuit" for charging and discharging the capacitor 314. In addition, the resistor 313 provided between the above-mentioned push-pull circuit and the capacitor 314 is an element for limiting the current of charging and discharging the capacitor 314. Moreover, the power supply circuit 70 is equivalent to a circuit for generating a power supply voltage V10 for "a corresponding one light source D0" among the light sources D0 to D9. In addition, the capacitor 314 is equivalent to the "first capacitor".

[0057] ==About Power Supply Circuits 71 to 79== Each power circuit 71 to 79 generates power voltages V11 to V19 for light sources D11 to D19 based on signals S11 to S19, similarly to the power circuit 70. Therefore, detailed description of the power circuits 71 to 79 is omitted here. In the present embodiment, the power circuits 70 to 79 are provided for light sources D0 to D9, respectively.

[0058] == About Control Circuit 80 == The control circuit 80 is based on Figure 1 The control device 22 starts lighting, and controls each power circuit 70 to 79 so that the light sources D0 to D9 are lit in sequence. Specifically, the control circuit 80 sets the level of the signal of the power circuit corresponding to the light source to be lit among the signals S10 to S19 to the H level, and sets the levels of the other nine signals to the L level.

[0059] Furthermore, when the lighting start instruction is input, the control circuit 80 outputs an H-level signal S20 (lighting instruction) at the timing of lighting the target light source, and outputs an L-level signal S20 (lighting off instruction) at the timing of lighting off.

[0060] ==Operation of the control circuit 80 and main waveforms of the light emitting device 20b== Figure 5 It is a diagram showing an example of the waveforms of signals S10 to S19. Figure 6 2 is a diagram showing an example of the main waveform of the light emitting device 20b when the light source D0 is turned on. Figure 5 In the figure, for ease of understanding, only signals S10, S11, and S19 are shown.

[0061] first, Figure 4 The control circuit 80 changes the signal S10 from the L level to the H level at time t0, so the power supply circuit 70 starts to generate the power supply voltage V10. As a result, Figure 6 As shown, the power supply voltage V10 rises from 0 V to the level of the power supply voltage Vdd1. In fact, the power supply voltage V10 rises slightly later than the source t0 of the signal S10, but the delay is omitted here for convenience.

[0062] Furthermore, the control circuit 80 sets the signals S11 to S19 to the L level at time t0 , respectively. Therefore, the power supply circuits 71 to 79 stop generating the power supply voltages V11 to VB19 .

[0063] When a predetermined period of time Ta has elapsed from time t0 to time t1 (see Figure 6 ), the control circuit 80 outputs a signal S20 of H level in order to turn on the light source D0. As a result, Figure 4 The driving transistor 301 of the IC 41 is turned on. Therefore, the current I0 flows through the light source D0, and the light source D0 is turned on.

[0064] In the present embodiment, the predetermined period Ta is longer than the period from when the power supply voltage V10 level changes from 0 V to the power supply voltage Vdd1. When the current I0 flows through the light source D0, the capacitor 40 is discharged, so the power supply voltage V10 drops from the power supply voltage Vdd1.

[0065] Then, if you arrive Figure 6 At time t2, the control circuit 80 changes the signal S20 to the L level in order to turn off the light source D0. As a result, the driving transistor 301 is turned off. Therefore, since the current I0 of the light source D0 is cut off, the light source D0 is turned off. In addition, at time t2, since the current I0 is cut off, the discharge of the capacitor 40 stops, and the power supply voltage V10 rises to reach the power supply voltage Vdd1.

[0066] Then, at time t3, the control circuit 80 changes the signal S20 to the H level, and the light source D0 is turned on again. In addition, in this embodiment, after time t3, the operation from time t1 to time t2 is repeated four times. In addition, when the power supply voltage V10 is generated, it is assumed that the light source D0 is turned on five times, but the number of times the light source D0 is turned on is only an example.

[0067] Furthermore, at time t11, the control circuit 80 changes the signal S10 to the L level in order to stop the generation of the power supply voltage V10. As a result, Figure 4 The capacitor 314 is discharged by the resistor 313 and the NMOS transistor 312, so the power supply voltage V10 gradually decreases. In fact, the power supply voltage V10 decreases slightly later than the falling timing t11 of the signal S10, but the delay is omitted here for convenience.

[0068] In addition, if Figure 5 As shown, at time t11, control circuit 80 changes signal S11 to H level in order to generate power supply voltage V11. As a result, capacitor 314 (not shown) of power supply circuit 71 is gradually charged, so that power supply voltage V11 rises.

[0069] In addition, in this embodiment, for example Figure 5 As shown at time t11, the timing of the discharge start of the capacitor 314 of the power supply circuit 70 is the same as the timing of the charge start of the capacitor 314 (not shown) of the power supply circuit 71. That is, in this embodiment, the control circuit 80 controls the power supply circuits 70 and 71 so that the capacitor 314 (not shown) of the power supply circuit 71 is charged when the capacitor 314 of the power supply circuit 70 is discharged.

[0070] However, it is also possible that the capacitor 314 (not shown) of the power supply circuit 71 is charged after the capacitor 314 of the power supply circuit 70 is discharged and the power supply voltage V10 becomes almost 0V. Figure 5 and Figure 6 After time t12, the signal S11 becomes H level, so the timing of lighting the light source D1 is also delayed.

[0071] In this embodiment, when the capacitor 314 of the power supply circuit 70 is discharged (i.e., when the power supply voltage V10 level decreases and exceeds 0 V), the capacitor 314 of the power supply circuit 71 that is to be lit next starts to be charged. Therefore, in this embodiment, the light source can be lit at a shorter interval.

[0072] In addition, despite the Figure 5 Although not shown in the figure, the control circuit 80 outputs the H-level signal S20 five times when the predetermined period Ta has passed since time t11, similarly to the case where the predetermined period Ta has passed since time t0 (see Figure 6 As a result, the light source D1 is also turned on five times at the same timing as the light source D0. Here, the operation when the control circuit 80 turns on the light sources D0 and D1 is described, but the same applies to the other light sources D2 to D9.

[0073] so, Figure 4 The power supply circuit 70 of this embodiment does not include Figure 2 The power supply circuit 50 includes a diode 200, a capacitor 201, a transformer 211, and an IC 212. In addition, the light emitting device 20b is provided with an IC 41 between the grounding node of the light sources D0 to D9 and the ground, thereby controlling the lighting and extinguishing of the light sources D0 to D9. Therefore, in this embodiment, the lighting of multiple light sources can be controlled by a simple structure.

[0074] In this embodiment, H level signals S10 to S19 correspond to “first signals” and L level signals S10 to S19 correspond to “second signals.” For example, power supply circuit 70 corresponds to “first power supply circuit” and power supply circuit 71 corresponds to “second power supply circuit.”

[0075] However, in order to increase the distance to the object 11 that the measuring device 10 can measure (hereinafter referred to as "measurement distance"), it is necessary to strengthen the light emitted from the light source D0. In addition, in order to strengthen the light emitted from the light source D0, it is necessary to increase the current I0 that turns on the light source D0. Figure 4 In the light emitting device 20b, the discharge current of the capacitor 314 of the power supply circuit 70 becomes the current I0 for lighting the light source D0. Therefore, if the capacitance of the capacitor 314 is increased, the measuring distance of the measuring device 10 can be lengthened.

[0076] However, if the capacitance of the capacitor 314 is increased, the variation between the capacitors 314 included in each of the power supply circuits 70 to 79 generally increases. Figure 7 1 is a diagram showing an example of waveforms of currents I0 to I2 when the capacitance of the capacitor 314 of each of the power supply circuits 70 to 72 is 2200 pF, 2000 pF, and 1800 pF.

[0077] In addition, Figure 7 In the figure, the solid line represents the current I0 from the 2200 pF capacitor 314, the dashed line with larger intervals represents the current I1 from the 2000 pF capacitor 314, and the dashed line with smaller intervals represents the current I2 from the 1800 pF capacitor 314.

[0078] In addition, Figure 7 , the timing of turning on the driving transistor 301 when the currents I0 to I2 are generated is depicted in conjunction with time t20 so that the waveforms of the currents I0 to I2 can be compared.

[0079] Here, if the current I0 is used as an example for explanation, since the driving transistor 301 is turned on at time t20, the current I0 increases. Furthermore, if the capacitor 314 of the power supply circuit 70 is discharged, the current I0 decreases to zero. Subsequently, the driving transistor 301 is turned off at a predetermined timing. In addition, the current I0 is used as an example for explanation, but the currents I1 and I2 are also the same.

[0080] In this embodiment, if Figure 7 As shown, when the capacitance of the capacitor 314 is as large as 2200pF, the peak value of the current I0 for lighting the light source (approximately 18A) is larger than the peak values ​​of the current values ​​I1 and I2 (approximately 17.5A, approximately 17A). Therefore, in the light emitting device 20b, when the capacitors 314 with small variations are used in the power supply circuits 70 to 79, the light sources D0 to D9 can be lit with high accuracy. In addition, by using capacitors with small capacitance values ​​(for example, capacitors smaller than 1000pF) for the plurality of capacitors 314, the variations among the plurality of capacitors 314 can be suppressed.

[0081] <<Details of Light Emitting Device 20c>> Figure 8 The light emitting device 20c shown is a device that can increase the peak values ​​of the currents I0 to I9 and suppress the deviation of the currents I0 to I9. The light emitting device 20c includes light sources D0 to D9, capacitors 40 and 400, IC 41, power supply circuits 70 to 79, a control circuit 80, and a resistor 401. Figure 8 and Figure 4 Therefore, the capacitor 400 and the resistor 401, and the capacitor 314 included in each of the power supply circuits 70 to 79 will be mainly described here.

[0082] The capacitor 400 is an element for determining the current value (especially the peak value) of the currents I0 to I9 for lighting the light sources D0 to D9, and is provided between the grounding node of each light source D0 to D9 and the driving transistor 301. Specifically, one end of the capacitor 400 is connected to the grounding node of each light source D0 to D9, and the other end is connected to the drain of the driving transistor 301.

[0083] The resistor 401 is an element for discharging the charge of the capacitor 400. One end of the resistor 401 is connected to the node on the ground side of each light source D0 to D9, and the other end is connected to the drain of the driving transistor 301. Therefore, the resistor 401 and the capacitor 400 are connected in parallel. In addition, the capacitor 400 is equivalent to the "second capacitor".

[0084] ==About the current waveform of the light emitting device 20c== Here, the waveform of the current flowing through the light source of the light emitting device 20c is described. In this embodiment, the capacitance of the capacitor 400 is, for example, 2000 pF, and the capacitor 314 of each of the power supply circuits 70 to 79 uses a capacitor having a capacitance sufficiently larger than 2000 pF (for example, 0.1 μF).

[0085] However, capacitors 314 of power circuits 70 to 79 vary. In this embodiment, the capacitance of capacitor 314 of power circuit 70 is 0.11 μF, the capacitance of capacitor 314 of power circuit 71 is 0.1 μF, and the capacitance of capacitor 314 of power circuit 72 is 0.09 μF.

[0086] In addition, here is the reference Fig. 9 The currents I0 to I2 flowing through the light sources D0 to D2 are described. Fig. 9 In the figure, the current I0 is represented by a solid line, the current I1 is represented by a dotted line with a large interval, and the current I2 is represented by a dotted line with a small interval. The details will be described later. In this embodiment, since the waveforms of the currents I0 to I2 are substantially the same, Fig. 9 The three current waveforms overlap.

[0087] exist Figure 8 In the state where the power supply circuit 70 generates the power supply voltage V10 (that is, the state where the signal S10 is at the H level), for example, Fig. 9 At time t30, if the signal S20 is at the H level, the driving transistor 301 is turned on.

[0088] As a result, the capacitor 314 of the power supply circuit 70 is discharged, and the charging current for charging the capacitor 400 increases. In this embodiment, since the charging current of the capacitor 400 reaches the current I0 for lighting the light source D0, the current I0 increases.

[0089] Then, if the capacitor 400 is gradually charged and the current I0 reaches a peak value, the current I0 decreases. Then, since the discharged capacitor 314 is charged, the current I0 decreases to substantially zero. Then, the driving transistor 301 is turned off at a predetermined timing. In addition, if the driving transistor 301 is turned off, the capacitor 400 is discharged via the resistor 401.

[0090] Here, the current I0 when the power supply circuit 70 generates the power supply voltage V10 is described, but Fig. 9 As shown in FIG. 1 , the waveforms of the currents I1 and I2 when the power supply circuits 71 and 72 generate the power supply voltages V11 and V12, respectively, also become the charging currents of the capacitor 400. Fig. 9 As shown, the waveforms of currents I0 to I2 are substantially the same.

[0091] Thus, in the light emitting device 20c, when the capacitance of the capacitor 314 included in the power supply circuits 70 to 79 is sufficiently larger than the capacitance of the capacitor 400, the waveforms and peak values ​​of the currents I0 to I9 are determined by the capacitance of the capacitor 400. Therefore, even when the measurement distance is increased in the light emitting device 20c, the deviation of the currents I0 to I9 can be suppressed.

[0092] In addition, when the measuring distance is relatively short, the Figure 4 In this case, since the variation of the plurality of capacitors 314 of the power supply circuits 70 to 79 is generally small, the variation of the intensity of the light emitted from the light sources D0 to D9 is also small. Therefore, when the measurement distance is relatively short, the light emitting device 20b can be used.

[0093] ===Other Implementation Methods=== In this embodiment, VCSELs are used for light sources D0 to D9, but the present invention is not limited thereto and light emitting diodes may be used. When light emitting diodes are used as light sources D0 to D9, a light emitting device can be realized with a simple structure as in this embodiment.

[0094] ===Overview=== The above is a description of the measuring device 10 of the present embodiment. In the light emitting device 20b, a driving transistor 301 is provided between the ground-side node of the light sources D0 to D9 and the ground. Therefore, when the power supply voltage is supplied to the light source to be emitted, if the driving transistor 301 is turned on, the light source to be emitted can be turned on. Therefore, the number of components in the light emitting device 20b is small, and a plurality of light sources can be turned on with a simple structure.

[0095] In addition, in the light emitting device 20b, for example, when the power supply circuit 70 generates the power supply voltage V10, the power supply circuits 71 to 79 discharge the respective internal capacitors 314 (not shown). Therefore, when the driving transistor 301 is turned on, only the desired light source can be turned on among the plurality of light sources. In addition, when the measurement distance is relatively short, the deviation of the capacitors 314 of the power supply circuits 71 to 79 becomes small. Therefore, in this case, the light emitting device 20b can be used.

[0096] In addition, in the power supply circuit 70, a resistor 313 is provided between the push-pull circuit composed of the PMOS transistor 311 and the NMOS transistor 312 and the capacitor 314. Therefore, the charging current and the discharging current of the capacitor 314 can be limited to appropriate current values. Moreover, compared with the components constituting the power supply circuit 50, the components constituting the power supply circuit 70 can use low-power components.

[0097] In addition, for example Figure 4 and Figure 5 As shown, the control circuit 80 controls the power supply circuits 70 and 71 so that the capacitor 314 (not shown) of the power supply circuit 71 is charged when the capacitor 314 of the power supply circuit 70 is discharged. That is, according to this embodiment, since the power supply voltage V11 is generated before the power supply voltage V10 becomes 0V, the light source D1 can be smoothly turned on after the light source D0 is turned off.

[0098] In the light emitting device 20c, the capacitor 400 and the resistor 401 are provided between the light sources D0 to D9 and the driving transistor 301. Therefore, in the light emitting device 20c, since the charging current of the capacitor 400 becomes the currents I0 to I9, the variation of the currents I0 to I9 can be suppressed.

[0099] Furthermore, in the light emitting device 20c, the capacitance of the capacitor 314 of each of the power supply circuits 70 to 79 is larger than the capacitance of the capacitor 400. Therefore, the capacitor 314 can supply a sufficient current to the capacitor 400.

[0100] In addition, for example, in the light emitting device 20c, the capacitance of the capacitor 400 is set to 1000 pF or more. As a result, the peak values ​​of the currents I0 to I9 can be increased in the light emitting device 20c, so that the measuring distance can be extended.

[0101] Furthermore, as the light source D0 , a VCSEL may be used, but, for example, a light emitting diode having a cathode and an anode similar to the VCSEL may also be used. In this case, the light source D0 includes a light emitting diode and an optical member 120 .

[0102] The above-mentioned embodiments are for facilitating understanding of the present invention, and are not intended to limit or explain the present invention. In addition, the present invention may be modified and improved without departing from the scope of the inventive concept, and the present invention includes substantially the same technical solutions.

[0103] This international application claims priority based on Japanese Patent Application No. 2022-093042 filed on June 8, 2022, and Japanese Patent Application No. 2022-112517 filed on July 13, 2022, and the entire contents of Japanese Patent Application No. 2022-093042 and Japanese Patent Application No. 2022-112517 are therefore incorporated by reference into this international application.

[0104] The above description of specific embodiments of the present invention is provided for illustrative purposes. It is not intended to be exhaustive or to limit the present invention in the manner described. It is obvious to those skilled in the art that many variations or modifications can be made based on the above description. Description of Reference Numerals

[0105] 10 Measurement device 11 Object 20, 20a, 20b Light emitting device 21 Light receiving device 22 Control device 40, 201, 314, 400 capacitors 41, 212IC 50~59 power supply circuit 60 control circuit 100~115 laser diode 120 Optical components 200 diodes 210, 230, 300, 310 buffers 211 Transformer 213, 313, 401 resistors 220 Primary coil 221 Secondary Coil 231, 301 driving transistor 312NMOS transistor 311PMOS transistor D0~D9 light source

Claims

1. A light emitting device, characterized in that include: n light sources, n ≥ 2; The n power supply circuits are respectively provided for the n light sources; as well as A switch is provided between a node on the ground side of each of the n light sources and the ground, The power supply circuit generates a power supply voltage for a corresponding one of the n light sources according to the first signal, and stops generating the power supply voltage according to the second signal. When the power supply voltage for the one light source is generated, the switch is turned on according to a lighting instruction, and is turned off according to a lighting off instruction.

2. The light emitting device according to claim 1, characterized in that: The power supply circuit comprises: a first capacitor generating the power supply voltage; and The charging and discharging circuit charges the first capacitor according to the first signal and discharges the first capacitor according to the second signal.

3. The light emitting device according to claim 2, characterized in that: A resistor is included which is arranged between the charge and discharge circuit and the first capacitor.

4. The light emitting device according to claim 3, characterized in that: A control circuit is provided, wherein the control circuit outputs the first signal and the second signal to the n power supply circuits respectively, thereby controlling the n power supply circuits respectively. The control circuit controls the first power supply circuit and the second power supply circuit so that the first capacitor of the second power supply circuit is charged when the first capacitor of the first power supply circuit among the n power supply circuits is discharged.

5. The light emitting device according to claim 2, characterized in that include: A second capacitor is arranged between a node on the ground side of each of the n light sources and the switch; as well as A resistor is connected in parallel with the second capacitor.

6. The light emitting device according to claim 5, characterized in that: The capacitance of the first capacitor is greater than the capacitance of the second capacitor.

7. The light emitting device according to claim 6, characterized in that: The capacitance of the second capacitor is greater than or equal to 1000 pF.

8. The light emitting device according to any one of claims 1 to 7, characterized in that: The light source includes an element selected from the group consisting of a laser diode and a light emitting diode, and an optical member for adjusting light distribution of light emitted from the element.

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