WO2021059756A1 - Light source device - Google Patents

Abstract

The purpose of the present invention is to appropriately protect a light-emitting element in the case where the light-emitting element and a driver circuit therefor are realized in a semiconductor chip in a light source device. A light source device according to the present invention has: a light-emitting element for emitting a prescribed amount of light as a result of being supplied with a prescribed drive current; a drive unit for supplying the drive current to the light-emitting element; a reference-level generation unit for generating a reference level serving as a reference for detecting an overcurrent pertaining to the drive current; a comparison unit for comparing the drive current with the reference level and outputting the result of the comparison as an output signal; and a level shift unit for shifting and outputting the level of the output signal of the comparison unit. The light source device detects an overcurrent of the drive current on the basis of the output of the level shift unit.

Description

Light source device

This disclosure relates to a light source device.

A light emitting element such as a laser diode that emits light according to an electric current is known. If a current (overcurrent) that greatly exceeds the design value flows through such a light emitting element due to a defect in the power supply system or the like, light may be emitted with an unexpectedly large amount of light. In addition, there is a risk of causing destruction of the light emitting element itself. Therefore, a circuit that monitors the current flowing through the light emitting element and protects the light emitting element has been proposed.

For example, in Patent Document 1, the voltage on the anode side of the laser diode, the threshold voltage, and the comparator are compared, and the drive current of the laser diode is controlled based on the comparison result. Further, in Patent Document 2, a comparator and a current limiter are used to monitor the drive current of the laser diode.

Japanese Unexamined Patent Publication No. 58-107692 Japanese Unexamined Patent Publication No. 2004-355697

When the light emitting element and its driver circuit are realized in a semiconductor chip, the power supply voltage level may be increased. In that case, there is room for improvement in protecting the light emitting element.

Therefore, the present disclosure proposes a light source device capable of appropriately protecting the light emitting element when the light emitting element and its driver circuit are realized in a semiconductor chip.

The light source device according to the present disclosure has a light emitting element that emits light with a predetermined amount of light when a predetermined drive current is supplied, a drive unit that supplies the drive current to the light emitting element, and an overcurrent for the drive current. A reference level generator that generates a reference level that serves as a reference for detection, a comparison unit that compares the drive current with the reference level and outputs the comparison result as an output signal, and an output signal level of the comparison unit. It has a level shift unit that shifts and outputs the current, and detects an overcurrent of the drive current based on the output of the level shift unit.

It is a block diagram which shows the structure of an example of the light source apparatus applicable to each embodiment of this disclosure. It is a figure which shows the structure of the driver of the light source device of the comparative example. It is a figure which shows the driver of the light source apparatus by 1st Embodiment of this disclosure. It is a figure which shows the structure of the example of the driver which concerns on the 1st modification of 1st Embodiment. It is a figure which shows the structure of the example of the driver which concerns on the 2nd modification of 1st Embodiment. It is a figure which shows the example of the level shift part. It is a figure which shows the example of the level shift part. It is a figure which shows the 1st example of the structure in the case of driving a plurality of laser diodes which concerns on 4th Embodiment. It is a figure which shows the 2nd example of the structure in the case of driving a plurality of laser diodes which concerns on 4th Embodiment. It is a figure which shows the 1st implementation example of the structure in the case of driving a plurality of laser diodes which concerns on 5th Embodiment. It is a figure which shows the 2nd implementation example of the structure in the case of driving a plurality of laser diodes which concerns on 5th Embodiment. It is a figure which shows the 3rd implementation example of the structure in the case of driving a plurality of laser diodes which concerns on 5th Embodiment. It is a figure for demonstrating the example of the arrangement on the LDD chip of each element included in a driver which concerns on 5th Embodiment. It is a figure for demonstrating the example of the arrangement on the LDD chip of each element included in a driver which concerns on 5th Embodiment. It is a figure for demonstrating the example of the case where the capacitor is further arranged with respect to the LDD chip which concerns on 5th Embodiment. It is a figure for demonstrating the example of the case where the capacitor is further arranged with respect to the LDD chip which concerns on 5th Embodiment. It is a figure for demonstrating the example of the case where the capacitor is further arranged with respect to the LDD chip which concerns on 5th Embodiment. It is a block diagram which shows the structure of an example of the distance measuring apparatus which concerns on 6th Embodiment. It is a figure which shows the histogram of an example based on the time when the light receiving part received light, which is applicable to 6th Embodiment.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In each of the following embodiments, the same parts are designated by the same reference numerals, so that duplicate description will be omitted.

In addition, the present disclosure will be described according to the order of items shown below.
0. Configuration common to each embodiment 0.1 Comparative example 1. First Embodiment 1.1 Configuration 1.2 Operation 1.3 First Modification Example of First Embodiment 1.4 Second Modification Example of First Embodiment 1.5 Effect 2. Second Embodiment 2.1 Configuration 2, 2 Operation 2.3 Effect 3. Third Embodiment 3.1 Configuration 3.2 Operation 3.3 Effect 4. Fourth embodiment 5. Fifth embodiment 6. Sixth Embodiment 7. Summary

(0. Configuration common to each embodiment)
The present disclosure relates to the control of a light emitting element that emits light in response to an electric current, such as a laser diode. FIG. 1 is a block diagram showing a configuration of an example of a light source device applicable to each embodiment of the present disclosure.

In the following, it will be described assuming that the light emitting element is a laser diode (LD). Laser diodes are excellent in straightness and light collection, have a high response speed, and take advantage of their characteristics such as low power consumption in various fields such as distance measurement, optical transmission, and electrophotographic printers. It is used in. The light emitting device applicable to the present disclosure is not limited to the laser diode. For example, an LED (Light Emitting Diode) can be applied as a light emitting element.

In FIG. 1, the light source device 1 includes a driver 10 and a laser diode (LD) 12. The controller 11 may be included in the light source device 1. The driver 10 drives the laser diode 12 under the control of the controller 11 to cause the laser diode 12 to emit light. The controller 11 includes, for example, a CPU (Central Processing Unit) and a memory, and supplies a control signal 40 generated by the CPU according to a program stored in the memory in advance to the driver 10 to control the driver 10. Further, the controller 11 determines whether or not an overcurrent is supplied to the laser diode 12 based on the detection signal 42 output from the driver 10. When the controller 11 determines that an overcurrent is being supplied to the laser diode 12, it generates a control signal 43 indicating that fact and supplies the control signal 43 to the driver 10.

It is assumed that the overcurrent is a current larger than the current for causing the laser diode 12 to emit light with a predetermined amount of light, and the difference is equal to or more than the threshold value.

The driver 10 includes a drive unit 20 and a detection unit 21. The drive unit 20 generates a drive current for causing the laser diode 12 to emit light according to the control signal 40 supplied from the controller 11, and supplies the generated drive current to the laser diode 12. Further, the drive unit 20 can control the on / off of the light emission of the laser diode 12 according to the control signal 43 supplied from the controller 11. Further, the drive unit 20 supplies the detection unit 21 with a signal 41 indicating the current value of the drive current that drives the laser diode 12. The detection unit 21 supplies the detection signal 42 based on the signal 41 supplied from the drive unit 20 to the controller 11.

It is also possible for the detection unit 21 to determine whether or not an overcurrent is supplied to the laser diode 12. For example, the detection unit 21 determines whether or not an overcurrent is supplied to the laser diode 12 based on the signal 41 supplied from the drive unit 20. When the detection unit 21 determines that an overcurrent is being supplied to the laser diode 12 as a result, the detection unit 21 supplies a signal 44 indicating that fact to the drive unit 20. The drive unit 20 stops the light emission of the laser diode 12, for example, in response to the signal 44. In this way, the response speed can be further increased by directly supplying the signal 44 indicating that the overcurrent is supplied to the laser diode 12 from the detection unit 21 to the drive unit 20.

[0.1 Comparative Example]
In order to facilitate understanding of the embodiments of the present disclosure, comparative examples will be described first. FIG. 2 is a diagram showing a configuration of a driver 10 of a light source device of a comparative example. In FIG. 2, the driver 10 of the comparative example has a drive unit 20, a replica unit 20R, a level shift unit 13a, 13b, a laser diode 12 as a light emitting element, and current sources 103, 104, 113, 114, which are low. It has a region passing filter 105 and a comparison unit 110.

The laser diode 12 emits light with a predetermined amount of light when a predetermined drive current is supplied. The coupling portions 100a and 100b are provided to connect the laser diode 12 and the driver 10 when they have different configurations. For example, the driver 10 is configured on one semiconductor chip, and the laser diode 12 is configured as a unit 120 separate from the semiconductor chip. The laser diode 12 and the driver 10 are electrically connected by the coupling portions 100a and 100b.

The drive unit 20 supplies the drive current to the laser diode 12. The drive unit 20 includes _{a transistor 101 for supplying a drive current due to the power supply voltage VDD} to the laser diode 12, and a transistor 111 for outputting a voltage corresponding to the drive current by the source follower. The transistors 101 and 111 are P-channel MOS (Metal Oxide Semiconductor) transistors.

In the present embodiment, the replica unit 20R has a configuration that imitates the drive unit 20. The replica unit 20R has a transistor 102 corresponding to the transistor 101 and a transistor 112 corresponding to the transistor 111. Transistors 102 and 112 are P-channel MOS transistors. The transistors 101 and 102 are configured so that their on-resistors R _ON-1 and R _ON-2 are equal. For example, the transistors 101 and 102 are formed in the same size. Further, it is more preferable to arrange the transistors 101 and 102 at positions thermally close to each other. The replica unit 20R functions as a reference level generation unit that generates a reference level that serves as a reference for detecting an overcurrent with respect to the drive current. A voltage source that generates a reference level may be used instead of the replica unit 20R.

The drain of the transistor 101 is connected to the anode of the laser diode 12 via the coupling portion 100a. The cathode of the laser diode 12 is connected to the current source 103 via the coupling portion 100b. On the other hand, the drain of the transistor 102 is connected to the current source 104. _{The voltage V 1} is taken out at the connection point where the drain of the transistor 101 and the anode of the laser diode 12 are connected, and is supplied to the comparison unit 110. _{Further, the voltage V 2} is taken out at the connection point where the drain of the transistor 102 and the current source 104 are connected, and is supplied to the comparison unit 110.

Each source of transistors 101 and 102 is connected to a _{common power supply voltage VDD.} The drain of the transistor 101 is connected to the anode of the laser diode 12 via the coupling portion 100a. The drain of the transistor 102 is connected to the current source 104. _{The voltage V 1} at the connection point where the drain of the transistor 101 and the anode of the laser diode 12 are connected is taken out. _{Then, the voltage V 3} obtained by subtracting the gate-source voltage of the transistor 111 from the voltage V ₁ is taken out. The voltage V ₃ is supplied to the comparison unit 110 via the level shift unit 13a and the low-pass filter 105. _{Further, the voltage V 2} is taken out at the connection point where the drain of the transistor 102 and the current source 104 are connected. _{Then, the voltage V 4} obtained by subtracting the gate-source voltage of the transistor 112 from the voltage V ₂ is taken out. The voltage V ₄ is supplied to the comparison unit 110 via the level shift unit 13b. The cathode of the laser diode 12 is connected to the current source 103 via the coupling portion 100b.

Here, it is assumed that the on-resistance R _ON-1 of the transistor 101 and the on-resistance R _ON-2 of the transistor 102 have substantially the same resistance value. Hereinafter, the on-resistors R _ON-1 and R _ON-2 will be described as the on-resistors R _ON.

In such a configuration, the voltages V ₁ and V ₂ are obtained by the following equations (1) and (2).
V ₁ = V _DD -R _ON × ( _IL + Δ)… (1)
_{V 2 = V DD -R ON ×} (I L + I offset) ... (2)
In the formula (1) and (2), the current I _L is the current supplied to the laser diode 12, the current I _offset is over-current component of the current to the current I _L.

The level shift unit 13a from voltages V ₁ corresponding to the drive current output from the drive unit 20, an input voltage obtained by subtracting the gate-source voltage of the transistor 111. The level shift unit 13b, an input voltage output from the replica unit 20R, that is, the voltage obtained by subtracting the gate-source voltage of the transistor 112 from the voltage V _2. The current sources 113 and 114 operate so that a predetermined current flows through the level shift portions 13a and 13b. The level shift units 13a and 13b shift the voltage level so that the voltage is within the range of the power supply voltage at which the comparison unit 110 operates. Here, as will be described later, in the case of a structure in which the laser diode array is laminated on the semiconductor chip of the laser diode driver, it is necessary to pass a large current. In order to pass a large current, it is necessary to raise the power supply voltage level. However, considering the withstand voltage of the transistor, it is difficult to apply a high voltage. Therefore, it is necessary to provide the level shift portions 13a and 13b to change the voltage level, that is, to shift the level.

The low-pass filter 105 inputs the voltage level-shifted by the level shift unit 13a. The low-pass filter 105 removes high-frequency components. The current flowing through the laser diode 12 changes at a predetermined cycle, and the high frequency component is removed by the low-pass filter 105. Therefore, the output of the low-pass filter 105 becomes a DC voltage corresponding to the average value of the currents flowing through the laser diode 12. Therefore, the low-pass filter 105 functions as an averaging circuit that outputs an average value of the input signal within a predetermined time. The low-pass filter 105 is realized, for example, by a time constant circuit with a resistor and a capacitor.

The comparison unit 110 compares the output level of the low-pass filter 105 with the reference level signal level-shifted by the level shift unit 13b. The comparison unit 110 outputs different signals depending on whether the output level of the low-pass filter 105 exceeds the reference level signal or not. For example, the comparison unit 110 outputs an output signal having a relatively high voltage (high level) when the output level of the low-pass filter 105 exceeds the reference level, and the output level of the low-pass filter 105 is the reference. When it is below the level, an output signal with a relatively low voltage (low level) is output. Therefore, the comparison unit 110 can determine that an overcurrent is being supplied to the laser diode 12. Therefore, the comparison unit 110 functions as the detection unit 21 in FIG.

Here, the power supply voltage _VDD and the operating voltage range of the comparison unit 110 may be different. For example, while the power supply voltage _VDD is + 5V and the ground level is 0V, the operating voltage range of the comparison unit 110 may be + 2V to + 5V. Even in such a case, if the level shift units 13a and 13b perform level shift so as to be within the operating voltage range of the comparison unit 110, an appropriate voltage after the level shift can be input to the comparison unit 110. it can. This makes it possible to detect an overcurrent with respect to the drive current.

In FIG. 2, the driver 10 of the comparative example uses _{a path (referred to as a main line) for supplying the current IL} to the laser diode 12 by the drive unit 20 and a replication path (referred to as a replica path) by the replica unit 20R. The current of this replica path is regarded as the current flowing through the laser diode 12.

Current source 103 supplies a current I _L. Current I _L supplied current source 103 is a current for lighting the laser diode 12 at a predetermined light amount. The current I _L + delta supplied to the laser diode 12, when the overcurrent is not equal to the current I _L.

The current value supplied by the current source 104 can be changed. Current source 104 supplies a current _{I c.} Current _{I c} is the current plus the current I _offset to the current I _L. That is, the current source 104 supplies a current I _L + I _offset to be the threshold value that is over-current to the laser diode 12. In other words, the current I _L + I _offset is a current obtained by adding the current I _offset overcurrent component with respect to the current I _L.

The level shift unit 13a has transistors 13 ₁₁ , 13 ₁₂ and 13 ₁₃ . Transistors 13 ₁₁ to 13 ₁₃ are respectively diode-connected, and resistance is generated by the PN junction. A resistor is realized by connecting a plurality of stages of the transistors 13 ₁₁ to 13 _{13 connected by diodes.} The level shift unit 13b has transistors 13 ₂₁ , 13 ₂₂ and 13 ₂₃ . The transistors 13 ₂₁ to 13 ₂₃ are respectively diode-connected, and resistance is generated by the PN junction. A resistor is realized by connecting a plurality of stages of _{transistors 13 21} to 13 ₂₃ connected by diodes.

Here, since the number of the level shift unit 13a and the level shift unit 13b connected to the diode is the same, the _{resistance value of the transistors 13 11} to 13 ₁₃ and the resistance value of the transistors 13 ₂₁ to 13 ₂₃ are the same. Should be. However, when the variation of the transistors (for example, the variation in manufacturing) is large, the _{resistance value by the transistors 13 11} to 13 ₁₃ and the resistance value by the transistors 13 ₂₁ to 13 ₂₃ are not the same, and the main line side by the level shift portion 13a There is a possibility that the level shift amount of the above and the level shift amount on the replica path side by the level shift unit 13b do not match. This may reduce the accuracy of overcurrent detection. The area of the level shift portion may be increased in order to suppress a decrease in the accuracy of overcurrent detection. However, when the mounting area of the level shift portion is limited, it may be difficult to increase the area, and as a result, it may be difficult to reduce the variation.

Further, as will be described later, when the laser diode array is laminated on the semiconductor chip of the laser diode driver, a large current may flow. In order to pass a large current, it is necessary to increase the area of the semiconductor chip.

(1. First Embodiment)
Next, the first embodiment of the present disclosure will be described. FIG. 3 is a diagram showing a driver 10a of a light source device according to the first embodiment of the present disclosure.

[1.1 Configuration]
In the driver 10a shown in FIG. 3, the output signal of the drive unit 20 is input to the comparison unit 110a via the low-pass filter 105 without level shifting. The output signal of the replica unit 20R is also input to the comparison unit 110a without level shifting. Then, the output of the comparison unit 110a is level-shifted by the level shift unit 130. That is, the difference between the driver 10a of the light source device shown in FIG. 3 and the comparative example described with reference to FIG. 2 is the position of the level shift unit 130.

The operating voltage range of the comparison unit 110a is different from the operating voltage range of the comparison unit 110 described with reference to FIG. In the above example, the power supply voltage _VDD is + 5V and the ground level is 0V, whereas the operating voltage range of the comparison unit 110 is + 2V to + 5V. On the other hand, the operating voltage range of the comparison unit 110a is, for example, + 5V to 0V. As a result, the comparison unit 110a can appropriately perform the comparison operation.

[1.2 Operation]
The comparison unit 110a compares the output signal of the drive unit 20 with the output signal of the replica unit 20R. The comparison unit 110a outputs a high level signal, for example, when the voltage level of the output signal of the drive unit 20 is lower than the voltage level of the output signal of the replica unit 20R (when an overcurrent is flowing). The comparison unit 110a outputs a low level signal, for example, when the voltage level of the output signal of the drive unit 20 is higher than the voltage level of the output signal of the replica unit 20R (when no overcurrent is flowing). That is, the comparison unit 110a outputs a high level or low level output signal depending on whether or not the threshold value for detecting an overcurrent is exceeded.

The level shift unit 130 performs level shift to match the voltage level of a circuit in the subsequent stage (not shown), that is, a circuit to which the output signal is transferred. As a result, even if the arrangement of the comparison unit 110a and the level shift unit 130 is different from the above-mentioned comparative example, the output signal can be passed.

The level shift unit 130 changes the voltage level of a high level or low level output signal indicating the result of the comparison operation by the comparison unit 110a. The level shift unit 130 similarly shifts the voltage level for the high level output signal and the low level output signal, and the level shift unit 130 changes the high level, which is the result of the comparison operation, to the low level. On the contrary, it does not change. Therefore, even if the level shift unit 130 performs the level shift, the accuracy of the comparison operation by the comparison unit 110a is not affected.

In the comparative example described with reference to FIG. 2, the comparison is performed by the comparison unit 110 after the level shift is performed using the two level shift units 13a and 13b. Therefore, there is a possibility that the transistors constituting the level shift portions 13a and 13b may have variations due to a manufacturing process or the like. If there is such a variation, there is a limit to the accuracy of comparison by the comparison unit 110. On the other hand, in the first embodiment, after the comparison is performed by the comparison unit 110a, the level shift is performed by the level shift unit 130. Therefore, the above variation does not affect the accuracy of the comparison operation by the comparison unit 110a.

[1.3 First Modified Example of First Embodiment]
Next, a first modification of the first embodiment will be described. _{In the first modification of the first embodiment, the on-resistance R ON-2} of the transistor 102 is increased in the replica path with respect to the configuration of the driver 10a according to the first embodiment described with reference to FIG. At the same time, the current supplied by the current source 104 is reduced.

FIG. 4 is a diagram showing a configuration of an example of the driver 10b according to the first modification of the first embodiment. Since the connection relationship of each element shown in FIG. 4 is the same as that of the driver 10a shown in FIG. 3, the description thereof is omitted here. In FIG. 4, the driver 10b sets the on-resistance of the transistor 102'of the replica path to a resistance value larger than _{the on-resistance R ON-2 of the transistor 102 shown in FIG.} In the example of FIG. 4, the on-resistance of the transistor 102'is a resistor R _ON-2 × N (N is an integer of 2 or more).

Further, in the driver 10b, the current supplied by the current source 104 of the replica path is set to a small current according to _{the on-resistance R ON-2 × N of the transistor 102'.} In the example of FIG. 4, the current source 104 'is supplying current _{(I L + I offset) /} N. Since the current supplied by the current source 104'is smaller than that of the configuration of FIG. 3, the power consumption of the driver 10b can be reduced with respect to the driver 10a of FIG.

[1.4 Example of Second Modification of First Embodiment]
Next, a second modification of the first embodiment will be described. FIG. 5 is a diagram showing a configuration of an example of the driver 10b'related to the second modification of the first embodiment. Since the connection relationship of each element shown in FIG. 5 is the same as that of the driver 10a shown in FIG. 3, the description thereof is omitted here. In the driver 10b'shown in FIG. 5, a capacitor 140 connected between the drain of the transistor 101 and the ground potential is further added to the configuration of FIG. The capacitor 140 stores an electric charge corresponding to _{the voltage V DD} of the power supply supplied via the transistor 101. For example, when the current source 103 supplies the current to the laser diode 12 by PWM (Pulse Width Modulation) drive, the electric charge accumulated in the capacitor 140 is used to supply the current to the laser diode 12.

That is, the voltage V _DD of the power supply is supplied from the external substrate of the LDD chip 1000 to the pad 1001 on the LDD chip 1000 by wire bonding, for example. When a steep voltage change occurs due to PWM drive, a large voltage drop occurs due to the inductance of the wire used for this wire bonding. Therefore, for each laser diode 12 ₁ ~ 12 _n, by supplying the current I _L on the basis of the charge stored in the capacitor 140, it is possible to avoid the influence of this voltage drop.

[1.5 effect]
According to the first embodiment, it is possible to eliminate variations due to the provision of a plurality of level shift portions, and it is possible to improve the determination accuracy without increasing the area.

(2. Second embodiment)
A second embodiment of the present disclosure will be described. FIG. 6 is a diagram showing an example of the level shift unit 130a.

[2.1 Configuration]
The level shift unit 130a shown in FIG. 6 includes resistors 131 and 132 connected in series, a transistor 133, and an inverting circuit 139.

One end of the resistor 131 through the transistor 133 is connected to the power supply voltage _{V DD} is a predetermined potential. The other end of the resistor 131 is connected to one end of the resistor 132. The other end of the resistor 132 is connected to the reference voltage. The output signal of the comparison unit 110 is input to the gate of the transistor 133 as an input signal IN. The transistor 133 is turned on or off based on the output signal of the comparison unit 110. The reference voltage is a voltage that serves as a reference for the voltage divided by the resistors 131 and 132, which are voltage dividing resistors. For example, ground can be used as a reference voltage, but the reference voltage is not limited thereto. The inverting circuit 139 inverts and outputs the voltage divided by the resistors 131 and 132.

[2.2 Operation]
The transistor 133 is turned on or off based on the output signal of the comparison unit 110. When the transistor 133 is on, the resistors 131 and 132 function as voltage dividing resistors. The level shift unit 130a inverts the voltage divided by the voltage dividing resistance by the resistors 131 and 132 by the inverting circuit 139 and outputs the voltage. That is, the level shift unit 130a outputs the voltage corresponding to the voltage divided by the voltage dividing resistor as the output signal OUT after the level shift. That is, the level shift unit 130a outputs a level-shifted output signal OUT with respect to the input signal IN.

[2.3 effect]
According to the second embodiment, since the level shift can be realized by a simple configuration, the increase in the mounting area due to the provision of the level shift portion 130a can be minimized.

(3. Third Embodiment)
A third embodiment of the present disclosure will be described. FIG. 7 is a diagram showing an example of the level shift unit 130b.

[3.1 Configuration]
The level shift unit 130b shown in FIG. 7 includes a flip-flop unit FF, buffer units BF1 and BF2, transistors 134a and 134b, and an output unit 135. The buffer unit BF1 and the buffer unit BF2 receive an input signal IN as an input. The input signal IN is an output signal of the comparison unit 110.

As shown in FIG. 7, the flip-flop unit FF is composed of four transistors. The flip-flop unit FF has either a first state of outputting a relatively high voltage (high level) output signal or a second state of outputting a relatively low voltage (low level) output signal. Become in a state.

_{A power supply voltage V DDH} is applied to the flip-flop portion FF via the transistors 134a or 134b. The flip-flop unit FF has transistors F1 and F2 that are turned on by either one, and transistors F3 and F4 that are turned on by _{the power supply voltage V DDM.} The flip-flop unit FF is in the first state of outputting a high-level output signal or the second state of outputting a low-level output signal. The output signal of the flip-flop unit FF is input to the output unit 135. The output unit 135 has a CMOS inverter with transistors C1 and C2.

The buffer units BF1 and BF2, the transistors 134a and 134b are operated by the _{power supply voltage V DDH} and the reference voltage V _SSH. The flip-flop unit FF operates by the power supply voltage V _DDM and the reference voltage V _SSL . The output unit 135 operates by the power supply voltage V _DDL and the reference voltage V _SSL . Therefore, the flip-flop unit FF and the output unit 135 operate with different power supply voltages.

Here, the power supply voltage V _DDH is a voltage higher than the _{power supply voltage V DDM} and the power supply voltage V _DDL. The power supply voltage V _DDM is a voltage lower than the power supply voltage V _DDH and higher than the power supply voltage V _DDL. The power supply voltage V _DDL is a voltage lower than the _{power supply voltage V DDM} and the power supply voltage V _DDH. The reference voltage V _SSH is a voltage higher than the reference voltage V _SSL.

[3.2 Operation]
The buffer unit BF1 outputs the input signal IN without inverting it. The buffer unit BF2 inverts the input signal IN and outputs it. The output signal of the buffer unit BF1 is input to the gate of the transistor 134a. The output signal of the buffer unit BF2 is input to the gate of the transistor 134b. Therefore, when the transistor 134a is in the on state, the transistor 134b is in the on state. Further, when the transistor 134a is in the off state, the transistor 134b is in the on state.

When the transistor 134a is in the ON state, the power supply voltage _VDDH is applied to the flip-flop section FF via the transistor 134a, and the output of the flip-flop section FF is in the first state. For example, the output signal of the flip-flop section FF becomes a high level. On the other hand, when the transistor 134b is in the ON state, the power supply voltage _VDDH is applied to the flip-flop section FF via the transistor 134b, and the output of the flip-flop section FF is in the second state. For example, the output signal of the flip-flop section FF becomes low level. That is, the flip-flop unit FF is set to the first state or the second state based on the output signal of the comparison unit 110.

The output signal of the flip-flop unit FF is input to the output unit 135. The output unit 135 inverts the output signal of the flip-flop unit FF and outputs it as an output signal OUT. That is, the output unit 135 outputs a voltage corresponding to the state of the flip-flop unit FF. The output unit 135 outputs an output signal OUT that is level-shifted with respect to the input signal IN.

[3.3 effect]
According to the third embodiment, it is possible to eliminate variations due to the provision of a plurality of level shift portions, and it is possible to improve the determination accuracy without increasing the area.

(4. Fourth Embodiment)
Next, a fourth embodiment will be described. In the first to third embodiments described above, and in each modification, a configuration in which each driver drives one laser diode 12 has been described. On the other hand, the driver according to the fourth embodiment drives a plurality of laser diodes 12.

8A and 8B are diagrams showing a first example and a second example of a configuration for driving a plurality of laser diodes 12 according to a fourth embodiment. In FIGS. 8A and 8B, the configurations of the transistors 102 and 112, the current source 104, the low-pass filter 105, and the comparison unit 110 are the same as those of FIG. 3 described above, and detailed description thereof will be omitted. ..

8A, 8B, respectively, the laser diode 12 _1, 12 ₂ more with respect to the drain of the transistor 101, ..., LD (laser diode) arrays 1200a and 1200b are connected, including a 12 _n. The LD arrays 1200a and 1200b are, for example, VCSELs (Vertical Cavity Surface Emitting LASER).

Each of the laser diodes 12 ₁ , 12 ₂ , ..., 12 _n is connected to each of the independently controllable current sources 103 ₁ , 103 ₂ , ..., 103 _n on a one-to-one basis. That is, by controlling, for example, on / off of _{each of the current sources 103 1} , 103 ₂ , ..., 103 _n by a drive circuit (not shown), one-to-one with _{each of the current sources 103 1} , 103 ₂ , ..., 103 _n. The light emission of each of the corresponding laser diodes 12 ₁ , 12 ₂ , ..., 12 _n can be controlled independently.

FIG. 8A is a diagram showing a configuration example of the driver 10c according to the first example in the case of driving a plurality of laser diodes 12 according to the fourth embodiment. Figure 8A, each laser diode 12 _1, 12 _2, ..., show examples of LD arrays 1200a to each anode and each cathode is independent of the 12 _n. In LD array 1200a, the laser diode 12 _1, 12 _2, ..., each anode of the 12 _n, coupling portions 100a _1, 100a _2, ..., are connected to the drain of the transistor 101 through the 100a _n. In the driver 10c, the respective coupling portions 100a _1, 100a _2, ..., and 100a _n, the voltage at the node where the drain of the transistor 101 is connected to the voltage _{V 1.} The voltage V ₃ obtained by subtracting the gate-source voltage of the transistor 111 from the _{voltage V 1} is taken out. The voltage V ₃ is supplied to the comparison unit 110 via the low-pass filter 105.

Further, the _{cathodes of the laser diodes 12 1} , 12 ₂ , ..., 12 _n are connected to the coupling portions 100b ₁ , 100b ₂ , ..., _{100 b n,} and the current sources 103 ₁ , 103 ₂ , ..., 103. _{It is connected to n} on a one-to-one basis.

FIG. 8B is a diagram showing a configuration example of the driver 10d according to the second example in the case of driving a plurality of laser diodes 12 according to the fourth embodiment. FIG. 8B shows an example of an LD array 1200b in which the anodes of the _{laser diodes 12 1} , 12 ₂ , ..., 12 _{n are commonly connected and the cathodes are independent.} In the LD array 1200b, the _{anodes of the laser diodes 12 1} , 12 ₂ , ..., 12 _n are commonly connected to the coupling portion 100a, and are connected to the drain of the transistor 101 via the coupling portion 100a. _{In the driver 10d, the voltage V 1} is taken out from the connection point where the coupling portion 100a and the drain of the transistor 101 are connected. _{Then, the voltage V 3} obtained by subtracting the gate-source voltage of the transistor 111 from the voltage V ₁ is taken out. The voltage V ₃ is supplied to the comparison unit 110 via the low-pass filter 105.

Also, each laser diode 12 _1, 12 _2, ..., 12 each cathode of _n is, the coupling portion 100b _1, 100b _2, ..., 100b _n, via a respective current source 103 _1, 103 _2, ..., 103 _n Is connected one-to-one.

In any of the examples of FIGS. 8A and 8B, voltages V ₁ to be taken out in the main line, each laser diode 12 _1, 12 _2, ..., a voltage corresponding to the sum of the currents flowing through 12 _n. Thus, the current source 104 in the replica routing also, it is necessary to supply a current I _L + I _offset that corresponds to the current of the summation.

Not limited to this, for example, it is also possible _{to individually control each current source 103 1} , 103 ₂ , ..., 103 _{n and detect an overcurrent every 12 n 1} , 12 ₂ , ..., 12 n of the laser diode. is there.

Thus, a plurality of laser diodes 12 _1, 12 _2, ..., even if the 12 _n are connected, the laser diode 12 _1, 12 _2, ..., it is possible to detect the overcurrent for 12 _n.

(5. Fifth Embodiment)
Next, a fifth embodiment will be described. A fifth embodiment relates to mounting the drivers 10c and 10d and the LD arrays 1200a and 1200b according to the fourth embodiment described above.

In the following, the driver 10d described with reference to FIG. 8B and the LD array 1200b having a common anode for _{each of the laser diodes 12 1} to 12 _{N will be described as an example.} In this case, the transistor 101 includes a plurality of transistors connected in parallel, and the transistor 102 includes a plurality of transistors connected in parallel in the same manner.

9A to 9C are diagrams schematically showing first to third mounting examples of the driver 10d and the LD array 1200b according to the fifth embodiment. In the fourth embodiment, the LD array 1200b and other configurations included in the driver 10d are formed on another substrate.

FIG. 9A is a diagram schematically showing how the LD array 1200b is arranged on the LDD (laser diode driver) chip 1000 in which each element included in the driver 10d is arranged, which is applicable to the fifth embodiment. is there. FIG. 9A shows the LDD chip 1000 and the LD array 1200b viewed from the surface (upper surface) on which the light emitting portion of each laser diode 12 included in the LD array 1200b is arranged. In FIG. 9A and FIG. 9B described later, the LD array 1200b is shown in a state where the side (back surface) connected to the LDD chip 1000 is seen through from the upper surface side where the light emitting portion of the laser diode 12 is arranged. There is.

The LDD chip 1000 is one semiconductor chip, and is connected to an external circuit by wire bonding to a plurality of pads 1001 arranged in a peripheral portion. For example, the LDD chip 1000 is supplied with a _{voltage V DD from the outside via the pad 1001.} Further, the voltages V ₁ and V ₂ in FIG. 8B are supplied to the comparison unit 110 provided outside the LDD chip 1000 via the pad 1001. The comparison unit 110 may be provided anywhere. The comparison unit 110 may be provided inside the LDD chip 1000.

FIG. 9B is a diagram schematically showing the configuration of the LD array 1200b applicable to the fifth embodiment. As shown in FIG. 9B, the cathode terminals 1201 of each of the plurality of laser diodes 12 included in the LD array 1200b and the anode terminals 1202 common to the plurality of laser diodes 12 are aligned with respect to the back surface of the LD array 1200b. Be placed.

In the example of FIG. 9B, when the horizontal direction of the figure is a row and the vertical direction is a column, the cathode terminals 1201 are arranged in the central portion of the LD array 1200b by a grid-like arrangement of C rows × L columns. That is, in this example, (C × L) laser diodes 12 are arranged with respect to the LD array 1200b. Further, the anode terminals 1202 are arranged in a grid pattern of _{C rows × A 1} column on the left end side of the LD array 1200b and C rows × A _{2 columns on the right end side.}

Here, each cathode terminal 1201 corresponds to, for example, the coupling portions 100b ₁ , 100b ₂ , ..., 100b _n in FIG. 8B. In addition, each anode terminal 1202 collectively corresponds to, for example, the coupling portion 100a in FIG. 8B. By forming a plurality of coupling portions 100a in which the anodes of the laser diodes 12 are commonly connected by the plurality of anode terminals 1202, it is possible to suppress the connection resistance when connecting each anode to the LDD chip 1000. Become.

FIG. 9C is a side view of the structure including the LDD chip 1000 and the LD array 1200b applicable to the fifth embodiment as viewed from the lower end side of FIG. 9A. As described above, the LDD chip 1000 and the LD array 1200b have a structure in which the LD array 1200b is laminated on the LDD chip 1000. Each cathode terminal 1201 and each anode terminal 1202 are connected to the LDD chip 1000 by, for example, micro bumps.

Next, an example of arranging each element included in the driver 10d on the LDD chip 1000 will be described with reference to FIGS. 10A and 10B.

FIG. 10A is a diagram corresponding to FIG. 8B described above. In the example of FIG. 10A, the driver 10e makes the size of the transistor 102 of FIG. 8B smaller than the size of the transistor 101. For example, a transistor 101 is composed of _{a plurality of transistors 101 1} , ..., 101 _N , which are connected in parallel to one transistor 102 and can be independently turned on / off. In the example of FIG. 10A, N / 10 transistors 102 are used for _{N transistors 101 1} to 101 N. For example, if N = 10, the number of transistors 102 is one.

As a result, the on-resistance R _ON-2 of the transistor 102 can be made higher than the on-resistance R _ON-1 by the entire transistors 101 ₁ to 101 _N. Further, the current I _L + I _offset current source 104 in the replica path, the size of the transistors 102 (number), the size (number) of the whole of the transistors 101 ₁ ~ 101 _N, can be reduced based on the ratio of ..

In the example of FIG. 10A, the current current source 104 is supplied, to the current _{I c} of the current source 104 in the example of FIG. 8B (i.e. _{I L + I offset), 1} /10 of the current _{(I L + I offset) /} 10 It is said. According to equation (2) described above, the on-resistance R _ON-2 of the transistor 102 is 10 times, even 1/10 current I _L + I _offset, the value of the voltage V ₂ obtained it can be seen that unchanged. Since the current of the replica path can be reduced in this way, the power consumption of the LDD chip 1000 can be reduced. In the example of FIG. 10A, the size of the transistor 102 is increased by 10 times and the amount of current in the replica path is set to 1/10, but the power consumption can be further reduced by the same method.

Although the transistor 102 is shown as one element in FIG. 10A, the transistor 102 may also be configured by using a plurality of transistors that are connected in parallel and can be independently turned on / off. Good.

FIG. 10B is a diagram showing an example of arrangement of each element of the driver 10e on the LDD chip 1000, which is applicable to the fourth embodiment. In each region 1300, 1301, 1302, and 1303 in FIG. 10B, each element shown by a dotted line frame corresponding to each region 1300, 1301, 1302, and 1303 in FIG. 10A is arranged.

Specifically, in the example of FIG. 10B, the region 1300 includes current sources 103 ₁ , 103 ₂ , ..., 103 _n . In the example of FIG. 10B, the LD array 1200b is arranged in the region 1310 corresponding to this region 1300. In FIG. 10B, the area 1301 and the area 1302 are arranged on the long side side of the area 1300. Region 1301 includes transistors 101 ₁ to 101 _N. Further, the region 1302 includes the transistor 102. In the example of FIG. 10B, in the region 1301, _{two regions 1301 including each of the transistors 101 1} to 101 _N divided into two groups are arranged on both sides of the region 1302. Thus, to close the transistor 102 relative to transistors 101 ₁ ~ 101 _N, and, by arranging so as to sandwich, can close the characteristics of the transistors 101 ₁ ~ 101 _N, and characteristics of the transistor 102, the ..

In the example of FIG. 10B, the region 1303 including the current source 104 is further arranged on the short side side of the region 1300.

_{In FIG. 10B, the region 1300 including the current sources 103 1} to 103 _n is arranged with respect to the region 1310 in which the LD array 1200b is arranged, but the present invention is not limited to this example. For example, in the region 1310, other elements may be arranged in addition to the region 1300 including _{the current sources 103 1} to 103 _n. Further, the region 1300 including the current sources 103 ₁ to 103 _n may be arranged at another position of the LDD chip 1000. Further, a drive circuit (not shown) for driving each of the current sources 1031 to 103n and the like may be arranged on the LDD chip 1000.

[Example when arranging capacitors]
Next, an example of the driver 10f in which the capacitor is further arranged with respect to the LDD chip 1000 will be described with reference to FIGS. 11A, 11B and 11C. FIG. 11A is a diagram showing an example in which a capacitor 140 commonly connected to the drain of _{each transistor 101 1} to 101 _n is added to the configuration of FIG. 10A described above.

As described with reference to FIG. 5, the capacitor 140 accumulates an electric charge corresponding to _{the voltage V DD} of the power supply supplied via _{each of the transistors 101 1} to 101 _{n. When the currents are supplied to the laser diodes 12 1} to 12 _n included in the LD array 1200b by the current sources 103 ₁ to 103 _n by PWM drive, the electric charge accumulated in the capacitor 140 is used. A current is supplied to each laser diode 12 ₁ to 12 _n.

That is, the voltage V _DD of the power supply is supplied from the external substrate of the LDD chip 1000 to the pad 1001 on the LDD chip 1000 by wire bonding. When a steep voltage change occurs due to PWM drive, a large voltage drop occurs due to the inductance of the wire used for this wire bonding. Therefore, for each laser diode 12 ₁ ~ 12 _n, by supplying the current I _L on the basis of the charge stored in the capacitor 140, it is possible to avoid the influence of this voltage drop.

FIG. 11B is a diagram showing an example in which the region 1304 including the capacitor 140 is arranged on the LDD chip 1000. The capacitor 140 has a relatively large size as compared with, for example, transistors 101 ₁ to 101 _{n, transistors 102, and the like.} Therefore, in the example of FIG. 11B, the region 1304 including the capacitor 140 is arranged at a position corresponding to the region 1310 in which the LD array 1200b is arranged. As described above, since the region 1304 including the capacitor 140 has a relatively large size, such an arrangement facilitates the layout design of the LDD chip 1000.

Further, in the example of FIG. 11B, the _{region 1300 including each current source 103 1} to 103 _n is divided into two and arranged outside the long sides on both sides of the region 1304.

In the example of FIG. 11B, the entire region 1304 including the capacitor 140 is shown to be included in the region 1310 in which the LD array 1200b is arranged, but this is not limited to this example. For example, the area 1304 may be arranged so that a part thereof is included in the area 1310. When the size of the area 1304 is smaller than that of the area 1310, other elements may be arranged together with the area 1304 at a position corresponding to the area 1310.

FIG. 11C shows an example in which the region 1304 including the capacitor 140 shown in FIG. 11B is arranged on the LDD chip 1000, and the _{region 1301 including each transistor 101 1} to 101 _n is divided into a plurality of regions 1301 and the transistor 102 is divided into a plurality of regions 1301. It is a figure which shows the example which included the region is also divided into a plurality of regions 1302. In this case, it is assumed that the transistor 102 is also configured by using a plurality of transistors that are connected in parallel and can be independently turned on / off, like the _{transistors 101 1} to 101 _n.

Here, when _{the overall size of each transistor 101 1} to 101 _n or the size of the transistor 102 composed of a plurality of transistors is relatively large, variations due to a manufacturing process or the like occur for each transistor. there is a possibility. In the example of FIG. 11C, the _{region 1301 including each transistor 101 1} to 101 _n and the region 1302 including a plurality of transistors constituting the transistor 102 are divided into finer units, and each divided region 1301 is further divided. And each region 1302 are aligned and arranged alternately. As a result, _{it is possible to suppress variations in the transistors 101 1} to 101 _n and the plurality of transistors constituting the transistor 102.

In addition, in FIG. 10A and FIG. 11A described above, the configuration corresponding to FIG. 6 described above is applied, and the voltages V ₁ and V ₂ are taken out directly in the main line and the replica path, respectively. Not limited to the example. That is, the configurations described with reference to FIGS. 3 to 5 can be applied to the configurations of FIGS. 10A and 11A.

Further, instead of the LD array 1200b, the LD array 1200a to which the laser diodes 12 ₁ to 12 _n described in FIG. 8A are independently connected may be used.

(6. Sixth Embodiment)
Next, the sixth embodiment will be described. The sixth embodiment is an example in which the light source device 1 according to each of the above-described embodiments and modifications of each embodiment is applied to a distance measuring device that performs distance measuring using a laser beam.

FIG. 12 is a block diagram showing a configuration of an example of the distance measuring device according to the sixth embodiment. In the following, the drivers 10a to 10d, the drivers 10d', and the drivers 10e (a) to 10e (c) according to the above-described embodiments and modifications of the embodiments will be described as represented by the driver 10. .. Similarly, the laser diode 12, the laser diode 12 ₁ to 12 _n , the laser diode 12 ₁ to 12 _{N, and the} like will be described by being represented by the laser diode 12. More preferably, it is conceivable to apply the configuration described with reference to FIG. 11B or FIG. 11C.

In FIG. 12, the distance measuring device 70 as an electronic device according to the sixth embodiment includes a driver 10, a laser diode 12, a controller 11, a distance measuring unit 51, and a light receiving unit 302. The driver 10 generates a drive signal that drives the laser diode 12 to emit light in a pulsed manner in response to the control signal supplied from the controller 11, and causes the laser diode 12 to emit light based on the generated drive signal. The driver 10 passes a signal indicating the timing at which the laser diode 12 is made to emit light to the ranging unit 51.

The controller 11 determines whether or not an overcurrent is supplied to the laser diode 12 based on the detection signal 42 supplied from the driver 10. When the controller 11 determines that an overcurrent is being supplied to the laser diode 12, the controller 11 outputs a control signal 43 for stopping the light emission of the laser diode 12 to the driver 10 and supplies the overcurrent. The indicated error signal is output. The controller 11 can output an error signal to, for example, the outside of the distance measuring device 70.

The light receiving unit 302 includes a light receiving element that outputs a light receiving signal by photoelectric conversion based on the received laser light. As the light receiving element, for example, a single photon avalanche diode can be applied. The single photon avalanche diode is also called SPAD (Single Photon Avalanche Diode), and has a characteristic that electrons generated in response to the incident of one photon cause avalanche multiplication and a large current flows. By utilizing this characteristic of SPAD, the incident of one photon can be detected with high sensitivity. The light receiving element 302 to which the light receiving unit 302 can be applied is not limited to SPAD, but an avalanche photodiode (APD) or an ordinary photodiode can also be applied.

The distance measuring unit 51 calculates the distance D between the object 61 and the object 61 based _{on the time t 0} when the laser beam is emitted from the laser diode 12 _{and the time t 1} when the light is received by the light receiving unit 302.

In the above configuration, the laser beam 60 emitted from the laser diode 12 at _{the timing of time t 0} is reflected by the object 61, for example, and is received by the light receiving unit 302 at the timing of _{time t 1 as the reflected light 62.} .. The ranging unit 51 determines the distance D to the object 61 based on the difference between the _{time t 1} when the reflected light 62 is received by the light receiving unit 302 and _{the time t 0} when the laser light is emitted by the laser diode 12. Ask. The distance D is calculated by the following equation (3) the constant c as light velocity ^{(2.9979 × 10 8 [m /} sec]).
D = (c / 2) × (t ₁ −t ₀ )… (3)

The ranging unit 51 repeats the above-mentioned processing a plurality of times. The distance D may be calculated based on each light receiving timing in which the light receiving unit 302 includes a plurality of light receiving elements and the reflected light 62 is received by each light receiving element. The ranging unit 51 _{classifies the time t m} (called the light receiving time t _{m ) from the light emitting timing time t 0} to the light receiving timing when the light is received by the light receiving unit 302 based on the class (bins). Generate a histogram.

The light received by the light receiving unit 302 during the light receiving time t _m is not limited to the reflected light 62 in which the light emitted by the laser diode 12 is reflected by the object to be measured. For example, the ambient light around the light receiving unit 302 is also received by the light receiving unit 302.

FIG. 13 is a diagram showing an example histogram based on the time when the light receiving unit 302 receives light, which is applicable to the sixth embodiment. In FIG. 13, the horizontal axis indicates the bin and the vertical axis indicates the frequency for each bin. The bins are obtained by classifying the light receiving time t _m for each predetermined unit time d. Specifically, bin # 0 is 0 ≦ t _m <d, bin # 1 is d ≦ t _m <2 × d, bin # 2 is 2 × d ≦ t _m <3 × d, ..., Bin # (N). -2) is (N-2) × d ≦ t _m <(N-1) × d. When the exposure time of the light receiving unit 302 is time t _ep , t _ep = N × d.

The ranging unit 51 counts the number of times the light receiving time t _m is acquired based on the bins to obtain the frequency 310 for each bin, and generates a histogram. Here, the light receiving unit 302 also receives light other than the reflected light reflected from the light emitted from the laser diode 12. As an example of such light other than the target reflected light, there is the above-mentioned ambient light. The portion indicated by the range 311 in the histogram includes the ambient light component due to the ambient light. The ambient light is light that is randomly incident on the light receiving unit 302 and becomes noise with respect to the reflected light of interest.

On the other hand, the target reflected light is light received according to a specific distance, and appears as an active light component 312 in the histogram. The bin corresponding to the frequency of the peak in the active light component 312 becomes the bin corresponding to the distance D of the object to be measured 303. The distance measuring unit 51 acquires the representative time of the bottle (for example, the time in the center of the bottle) as the time t ₁ described above, and calculates the distance D to the object to be measured 303 according to the above formula (3). be able to. In this way, by using a plurality of light receiving results, it is possible to perform appropriate distance measurement for random noise.

As described above, by applying the driver 10 according to the present disclosure to the distance measuring device 70 that directly measures the distance by the ToF (Time-of-Flight) method, whether or not an overcurrent is supplied to the laser diode 12. Can be detected with higher accuracy. By controlling the light emission of the laser diode 12 based on this detection result, it is possible to suppress the influence on the eyes when, for example, a laser diode stronger than expected due to an overcurrent is emitted from the laser diode 12. Further, it is possible to prevent the element itself of the laser diode 12 from being destroyed due to an overcurrent, and it is possible to improve the reliability of the distance measuring device 70.

(7. Summary)
The light source device 1 includes a light emitting element, a drive unit 20, a reference level generation unit, a comparison unit 110, and a level shift unit 130. The light emitting element emits light with a predetermined amount of light when a predetermined drive current is supplied. The drive unit 20 supplies a drive current to the light emitting element. The reference level generator generates a reference level as a reference for detecting an overcurrent with respect to the drive current. The comparison unit 110 compares the drive current with the reference level and outputs the comparison result as an output signal. The level shift unit 130 shifts the level of the output signal of the comparison unit 110 and outputs the signal. The overcurrent of the drive current is detected based on the output of the level shift unit 130.

As a result, the light source device 1 performs a level shift on the comparison result by the comparison unit 110, so that it is possible to eliminate variations due to the provision of a plurality of level shift units, and when the level shift is performed before the comparison by the comparison unit 110. Compared with this, the accuracy of overcurrent detection can be improved.

The drive unit 20 of the light source device 1 includes a first resistor. The first resistor is connected to a predetermined potential and is connected in series with the light emitting element. The reference level generation unit is a replica unit 20R that imitates the drive unit 20. The replica unit 20R includes a second resistor. The second resistor is connected to a predetermined potential. Further, the light source device 1 includes a first current source. The first current source supplies a current connected in series with the second resistor, which is the drive current plus the current of the overcurrent. The comparison unit 110 compares the drive current with the reference level generated by the replica unit 20R.

Thereby, the light source device 1 can appropriately detect the overcurrent.

The light source device 1 further has an averaging circuit that outputs an average value of the drive current within a predetermined time, and the comparison unit 110 compares the average value output from the averaging circuit with the reference level.

Thereby, the light source device 1 can detect the overcurrent based on the average value of the drive currents flowing through the light emitting element.

The level shift unit 130a of the light source device 1 may have a voltage dividing resistor by the resistors 131 and 132 and a transistor 133 that gives a predetermined potential to the voltage dividing resistor. The voltage dividing resistor divides the voltage between the predetermined potential and the reference voltage. The transistor 133 is turned on or off based on the output signal of the comparison unit 110. The level shift unit 130 outputs a voltage corresponding to the voltage divided by the voltage dividing resistor as the voltage after the level shift.

As a result, the light source device 1 can perform level shift by the voltage dividing resistor.

The level shift unit 130b of the light source device 1 may have a flip-flop unit FF and an output unit 135. The flip-flop unit FF operates by the first power supply voltage V _DDH and V _SSH , and is set to either the first state or the second state based on the output signal of the comparison unit 110. The output unit 135 operates by a second power supply voltage V _DDL and V _SSL different from the first power supply voltage V _DDH and V _SSH, and outputs a voltage corresponding to the state of the flip flop unit FF. The level shift unit 130 outputs the output of the output unit 135 as the voltage after the level shift.

As a result, the light source device 1 can perform level shift based on the first state or the second state of the flip-flop unit FF.

The light emitting element of the light source device 1 may be configured as an element array 1200a in which a plurality of elements that emit light independently are arranged. The first current source supplies a predetermined drive current according to the number of light emitting elements among the plurality of elements included in the element array 1200a.

As a result, the light source device 1 can detect an overcurrent for a plurality of elements of the element array that emit light independently of each other.

The light source device 1 may further include a plurality of second current sources that independently supply a plurality of drive currents for driving the plurality of elements to each of the plurality of elements. A first semiconductor chip in which a first resistor, a second resistor, a first current source, and a plurality of second current sources are arranged, and a second semiconductor chip including an element array. The second semiconductor chip may be laminated on the first semiconductor chip.

The light source device 1 may further include a plurality of second current sources that independently supply a plurality of drive currents for driving the plurality of elements to each of the plurality of elements. A second semiconductor including a first semiconductor chip in which a first resistor, a second resistor, a first current source, and the plurality of second current sources are arranged, and an element array. The second semiconductor chip, including the chip, may be laminated on the first semiconductor chip. Each of the plurality of elements included in the element array arranged on the second semiconductor chip and each of the plurality of second current sources arranged on the first semiconductor chip may be connected one-to-one.

As a result, the light source device 1 can independently control the light emission of each element corresponding to the current source on a one-to-one basis by controlling the on / off of each current source by the drive circuit.

A plurality of second current sources of the light source device 1 may be arranged in a predetermined region on the first semiconductor chip, and the element array may be stacked and arranged in a region corresponding to the predetermined region on the first semiconductor chip. ..

Thereby, the light source device 1 can detect an overcurrent when the element array is laminated on the first semiconductor chip.

The first resistor of the light source device 1 may include a plurality of resistors connected in parallel, and the plurality of resistors may be divided into a plurality of blocks and arranged on the first semiconductor chip.

As a result, the light source device 1 can arrange the plurality of resistors on the semiconductor chip even when a plurality of resistors for causing the light emitting element to emit light are connected in parallel.

The second resistor of the light source device 1 may include a plurality of resistors connected in parallel, and the plurality of resistors may be divided into a plurality of blocks and arranged on the first semiconductor chip. Further, each of the plurality of blocks in which the plurality of resistors included in the first resistor is divided and each of the plurality of blocks in which the plurality of resistors included in the second resistor are divided alternate with each other. , They may be aligned and arranged on the first semiconductor chip.

As a result, the light source device 1 can arrange the plurality of resistors on the semiconductor chip even when a plurality of resistors for causing the light emitting element to emit light are connected in parallel.

The light source device 1 may further include a capacitor arranged in a predetermined region on the first semiconductor chip and connected to the first resistor. The element arrays may be stacked and arranged in a predetermined region on the first semiconductor chip.

As a result, the mounting area does not increase even when a capacitor with a large capacity is required.

The first resistor and the second resistor of the light source device 1 may be the resistance between the source and the drain of the MOS transistor in the ON state, respectively.

Thereby, the light source device 1 can be formed on the semiconductor chip.

The averaging circuit of the light source device 1 may include a low-pass filter 105 for removing the high-frequency component of the drive current, and output the drive current from which the high-pass component has been removed by the low-pass filter 105 as an average value. ..

Thereby, the light source device 1 can detect the overcurrent based on the average value of the drive currents flowing through the light emitting element.

Note that the effects described in this specification are merely examples and are not limited, and other effects may be obtained. In addition, the configurations described in the present specification can be combined as appropriate.

The present technology can also have the following configurations.
(1)
A light emitting element that emits light with a predetermined amount of light when a predetermined drive current is supplied, and
A drive unit that supplies the drive current to the light emitting element,
A reference level generator that generates a reference level that serves as a reference for detecting an overcurrent with respect to the drive current, and a reference level generator.
A comparison unit that compares the drive current with the reference level and outputs the comparison result as an output signal.
A level shift unit that shifts the level of the output signal of the comparison unit and outputs it,
Have,
A light source device that detects an overcurrent of the drive current based on the output of the level shift unit.
(2)
The drive unit
It comprises a first resistor connected to a predetermined potential and connected in series with the light emitting element.
The reference level generator
It is a replica unit that includes a second resistor connected to the predetermined potential and imitates the drive unit.
further,
It includes a first current source connected in series with the second resistor to supply a current obtained by adding a current corresponding to an overcurrent to the drive current.
The light source device according to (1) above, wherein the comparison unit compares the drive current with a reference level generated by the replica unit.
(3)
It further has an averaging circuit that outputs an average value of the drive current within a predetermined time.
The light source device according to (1) or (2), wherein the comparison unit compares the average value output from the averaging circuit with the reference level.
(4)
The level shift unit is
A voltage dividing resistor that divides the voltage between the predetermined potential and the reference voltage,
A transistor that turns on or off based on the output signal of the comparison unit and gives the predetermined potential to the voltage dividing resistor when it is turned on.
Have,
The light source device according to any one of (1) to (3) above, which outputs a voltage corresponding to the voltage divided by the voltage dividing resistor as a voltage after level shifting.
(5)
The level shift unit is
A flip-flop unit that operates by the first power supply voltage and is set to either the first state or the second state based on the output signal of the comparison unit.
It operates with a second power supply voltage different from the first power supply voltage, and has an output unit that outputs a voltage corresponding to the state of the flip-flop unit.
The light source device according to any one of (1) to (3) above, which outputs the output of the output unit as a voltage after level shifting.
(6)
The light emitting element is
It is configured as an element array in which a plurality of elements that emit light independently are arranged.
The first current source is
The light source device according to (2), wherein the predetermined drive current is supplied according to the number of light emitting elements among the plurality of elements included in the element array.
(7)
A plurality of second current sources for independently supplying a plurality of drive currents for driving each of the plurality of elements to each of the plurality of elements are further provided.
A first semiconductor chip in which the first resistor, the second resistor, the first current source, and the plurality of second current sources are arranged.
A second semiconductor chip laminated on the first semiconductor chip, which comprises the element array, and
Including
Each of the plurality of elements included in the element array arranged on the second semiconductor chip and each of the plurality of second current sources arranged on the first semiconductor chip are connected one-to-one. The light source device according to (6) above.
(8)
The plurality of second current sources
Arranged in a predetermined region on the first semiconductor chip,
The element array is
The light source device according to (7) above, which is laminated and arranged in a region corresponding to the predetermined region on the first semiconductor chip.
(9)
The first resistor is
The light source device according to (7), wherein the light source device includes a plurality of resistors connected in parallel, and the plurality of resistors are divided into a plurality of blocks and arranged on the first semiconductor chip.
(10)
The light source device according to (9) above, wherein the first resistor is divided into two blocks arranged in an aligned manner, and the second resistor is arranged between the two blocks.
(11)
The second resistor is
A plurality of resistors connected in parallel are included, and the plurality of resistors are divided into a plurality of blocks and arranged on the first semiconductor chip.
Each of the plurality of blocks in which the plurality of resistors included in the first resistor is divided and each of the plurality of blocks in which the plurality of resistors contained in the second resistor are divided are The light source device according to (10) above, which is alternately arranged and arranged on the first semiconductor chip.
(12)
Further comprising a capacitor arranged in a predetermined region on the first semiconductor chip and connected to the first resistor.
The element array is
The light source device according to (7), which is laminated and arranged in the predetermined region on the first semiconductor chip.
(13)
The first resistor and the second resistor are
The light source device according to (7) above, each of which is a resistance between the source and drain of a MOS (Metal Oxide Semiconductor) type transistor in the on state.
(14)
The averaging circuit
The light source device according to (3), wherein the light source device includes a low-pass filter for removing a high-frequency component of the drive current, and outputs a drive current from which the high-frequency component has been removed by the low-pass filter as the average value.

1 Light source device 10, 10a to 10f Driver 11 Controller 12 Laser diode 13a, 13b Level shift unit 20 Drive unit 20R Replica unit 21 Detection unit 51 Distance measurement unit 61 Object 70 Distance measurement device 101, 102, 111, 112, 133, 134a,
134b, 137, C1, C2, F1 to F4, M1, M2 Transistors 103, 104, 113, 136 Current source 105 Low- pass filter 110, 110a Comparison unit 130, 130a, 130b Level shift unit 131, 132 Resistance 135 Output unit 138 ₁ to 138 ₄ Inverter 140 Capacitor 302 Light receiving part 1381, 1382, BF1, BF2 Buffer part CM Current mirror part FF Flip-flop part

Claims (14)

1. A light emitting element that emits light with a predetermined amount of light when a predetermined drive current is supplied, and
   A drive unit that supplies the drive current to the light emitting element,
   A reference level generator that generates a reference level that serves as a reference for detecting an overcurrent with respect to the drive current, and a reference level generator.
   A comparison unit that compares the drive current with the reference level and outputs the comparison result as an output signal.
   A level shift unit that shifts the level of the output signal of the comparison unit and outputs it,
   Have,
   A light source device that detects an overcurrent of the drive current based on the output of the level shift unit.
2. The drive unit
   It comprises a first resistor connected to a predetermined potential and connected in series with the light emitting element.
   The reference level generator
   It is a replica unit that includes a second resistor connected to the predetermined potential and imitates the drive unit.
   further,
   It includes a first current source connected in series with the second resistor to supply a current obtained by adding a current corresponding to an overcurrent to the drive current.
   The light source device according to claim 1, wherein the comparison unit compares the drive current with a reference level generated by the replica unit.
3. It further has an averaging circuit that outputs an average value of the drive current within a predetermined time.
   The light source device according to claim 1, wherein the comparison unit compares the average value output from the averaging circuit with the reference level.
4. The level shift unit is
   A voltage dividing resistor that divides the voltage between the predetermined potential and the reference voltage,
   A transistor that turns on or off based on the output signal of the comparison unit and gives the predetermined potential to the voltage dividing resistor when it is turned on.
   Have,
   The light source device according to claim 1, wherein a voltage corresponding to the voltage divided by the voltage dividing resistor is output as a voltage after level shifting.
5. The level shift unit is
   A flip-flop unit that operates by the first power supply voltage and is set to either the first state or the second state based on the output signal of the comparison unit.
   It operates with a second power supply voltage different from the first power supply voltage, and has an output unit that outputs a voltage corresponding to the state of the flip-flop unit.
   The light source device according to claim 1, wherein the output of the output unit is output as a voltage after level shifting.
6. The light emitting element is
   It is configured as an element array in which a plurality of elements that emit light independently are arranged.
   The first current source is
   The light source device according to claim 2, wherein the predetermined drive current is supplied according to the number of elements to emit light among the plurality of elements included in the element array.
7. A plurality of second current sources for independently supplying a plurality of drive currents for driving each of the plurality of elements to each of the plurality of elements are further provided.
   A first semiconductor chip in which the first resistor, the second resistor, the first current source, and the plurality of second current sources are arranged.
   A second semiconductor chip laminated on the first semiconductor chip, which comprises the element array, and
   Including
   Each of the plurality of elements included in the element array arranged on the second semiconductor chip and each of the plurality of second current sources arranged on the first semiconductor chip are connected one-to-one. The light source device according to claim 6.
8. The plurality of second current sources
   Arranged in a predetermined region on the first semiconductor chip,
   The element array is
   The light source device according to claim 7, wherein the light source device is arranged so as to be laminated on a region corresponding to the predetermined region on the first semiconductor chip.
9. The first resistor is
   The light source device according to claim 7, further comprising a plurality of resistors connected in parallel, the plurality of resistors being divided into a plurality of blocks and arranged on the first semiconductor chip.
10. The light source device according to claim 9, wherein the first resistor is divided into two blocks arranged in an aligned manner, and the second resistor is arranged between the two blocks.
11. The second resistor is
    A plurality of resistors connected in parallel are included, and the plurality of resistors are divided into a plurality of blocks and arranged on the first semiconductor chip.
    Each of the plurality of blocks in which the plurality of resistors included in the first resistor is divided and each of the plurality of blocks in which the plurality of resistors contained in the second resistor are divided are The light source device according to claim 10, wherein the light source devices are alternately arranged and arranged on the first semiconductor chip.
12. Further comprising a capacitor arranged in a predetermined region on the first semiconductor chip and connected to the first resistor.
    The element array is
    The light source device according to claim 7, wherein the light source device is stacked and arranged in the predetermined region on the first semiconductor chip.
13. The first resistor and the second resistor are
    The light source device according to claim 7, wherein each is a resistance between the source and drain of a MOS (Metal Oxide Semiconductor) type transistor in the on state.
14. The averaging circuit
    The light source device according to claim 3, further comprising a low-pass filter for removing a high-frequency component of the drive current, and outputting the drive current from which the high-frequency component has been removed by the low-pass filter as the average value.

Images