Single-point VCSEL (Vertical Cavity Surface Emitting Laser) driving circuit and laser equipment

Abstract

The invention discloses a single-point VCSEL laser driving circuit, and the circuit comprises a charging circuit which is electrically connected with a voltage source, the charging circuit is provided with a capacitor, the charge of the voltage source is stored in the capacitor, and the charge in the capacitor is outputted to a single-point VCSEL laser; the discharging circuit is provided with a switching device which can be turned on and turned off within the nanosecond pulse width, and after the switching device is turned on, charges stored in a capacitor lighten the single-point VCSEL laser; the grid circuit outputs current to the switching device so as to control the switching device to be closed; and the control circuit is used for controlling the grid circuit to output current to the switching device after receiving the instruction signal. The single-point VCSEL laser driving circuit is used for driving a VCSEL chip with a single light-emitting hole to emit light, the lasting time of ultra-narrow pulses (0.5 nanosecond) is short, the power consumption required by light emitting of the VCSEL chip is low, the driving current is small, and the driving cost is low.

Description

Technical Field

[0001] The present application mainly relates to the field of electronic chips, and specifically to a single-point VCSEL laser driving circuit and laser equipment. Background Art

[0002] VCSEL (Vertical Cavity Surface Emitting Laser) chip is a semiconductor laser used in optical communication, sensing, optical storage and other fields. VCSEL laser is mainly composed of a light-emitting unit and a driving circuit. The driving circuit is used to supply power to the light-emitting unit to light up the VCSEL laser. VCSEL lasers are used in consumer electronics as a light source for face recognition, such as in mobile phones and face payment; or they are used in consumer electronics as a light source for obstacle recognition, such as in obstacle avoidance solutions for service robots (sweeping robots).

[0003] The obstacle avoidance solutions for service robots currently mostly use EEL (Edge-Emitting Laser) chips. EEL chips are semiconductor devices that emit laser beams from the edge of the laser. Their advantages are high power density, but their disadvantages are high production costs and difficulty in consistency. EEL is used in service robots and has a large driving current. Summary of the invention

[0004] One advantage of the present application is that it provides a single-point VCSEL laser driving circuit, wherein the single-point VCSEL laser driving circuit is used to drive a VCSEL chip of a single light-emitting hole to emit light, achieving an extremely narrow pulse (0.5 nanoseconds) with a short duration, low power consumption required for the VCSEL chip to emit light, small driving current, and low driving cost.

[0005] Another advantage of the present application is that it provides a single-point VCSEL laser driving circuit, in which the VCSEL chip is lit for a short time, generates less heat during operation, has a higher peak power, a long detection distance, and can be adapted to more different models of SPADs.

[0006] A charging circuit is electrically connected to the voltage source, the charging circuit has a capacitor, the charge of the voltage source is stored in the capacitor, and the charge in the capacitor is output to the single-point VCSEL laser;

[0007] A discharge circuit, wherein the discharge circuit has a switch device capable of being turned on and off within a nanosecond pulse width, and after the switch device is closed, the charge stored in the capacitor lights up the single-point VCSEL laser;

[0008] A gate circuit, which outputs current to the switch device to control the switch device to close;

[0009] A control circuit controls the gate circuit to output current to the switch device after receiving the instruction signal.

[0010] In the single-point VCSEL laser driving circuit according to the present application, the opening and closing pulse widths of the switch device are within 1.0 nanosecond.

[0011] In the single-point VCSEL laser driving circuit described in the present application, the gate circuit has a current output device. After the control circuit inputs a high level to the current output device, the current output device outputs current to the switch device in the form of outputting a high level.

[0012] In the single-point VCSEL laser driving circuit described in the present application, the gate circuit includes a line-to-line regulator and a magnetic bead for filtering voltage noise, and the voltage provided to the current output device is first filtered by the line-to-line regulator and then filtered twice by the magnetic bead.

[0013] In the single-point VCSEL laser driving circuit according to the present application, the gate circuit has at least two sub-capacitors for storing charges, and the charges in the sub-capacitors are output to the current output device.

[0014] In the single-point VCSEL laser driving circuit described in the present application, the control circuit is provided with a resistor R2 and a resistor R3 connected in parallel with the resistor R2.

[0015] In the single-point VCSEL laser driving circuit described in the present application, the charging circuit includes a voltage-stabilizing capacitor and a storage capacitor composed of multiple capacitor devices to reduce the parasitic inductance of the entire charging circuit, and the charge in the storage capacitor is output to the single-point VCSEL laser.

[0016] In the single-point VCSEL laser driving circuit described in the present application, a charging resistor R1 is provided between the energy storage capacitor and the voltage dividing capacitor.

[0017] The single-point VCSEL laser driving circuit according to the present application also includes a signal feedback circuit for indicating that the single-point VCSEL laser is lit.

[0018] In the single-point VCSEL laser driving circuit described in the present application, the switch is an NMOS switch.

[0019] According to another aspect of the present application, the present application provides a laser device, comprising:

[0020] A laser projection device for projecting laser light, wherein the laser projection device comprises a single-point VCSEL laser and any single-point VCSEL laser driving circuit as described above;

[0021] a laser receiving device for receiving a laser signal; and

[0022] A processor is communicatively connected to the laser projection device and the laser receiving device.

[0023] Further objectives and advantages of the present application will be fully reflected through understanding of the following description and drawings.

[0024] These and other objects, features and advantages of the present application are fully reflected in the following detailed description, drawings and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 Schematic diagram of a single-point VCSEL laser driving circuit of this application.

[0027] Figure 2 This is a circuit simulation of the buffer device of the single-point VCSEL laser driving circuit of this application. The simulation conditions in the circuit simulation diagram are: input voltage 25V, input pulse width of the trigger signal 1.5ns, energy storage capacitor 68pF; simulation results: pulse current 0.804A, pulse width 0.85ns.

[0028] Figure 3 Another schematic diagram of the single-point VCSEL laser driving circuit of the present application.

[0029] Figure 4 The circuit simulation of the gate drive chip of the single-point VCSEL laser drive circuit of this application, the simulation conditions of the circuit are: input voltage 25V, input pulse width of the trigger signal 1.5ns,, energy storage capacitor 68pF; simulation results: pulse current 0.83A, pulse width 1.6ns.

[0030] Figure 5 It is a schematic diagram of the single-point VCSEL laser structure of this application. DETAILED DESCRIPTION

[0031] In order to make the purpose, features, and advantages of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the embodiments described below are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0032] The present application is further explained below in conjunction with the accompanying drawings and specific embodiments.

[0033] In the description of the present application, it should be understood that the terms "upper", "lower", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0034] Application Overview

[0035] VCSEL (Vertical Cavity Surface Emitting Laser) laser is an infrared laser emitter, which is widely used in consumer electronics, data communications, laser equipment and other fields. VCSEL lasers have the advantages of less temperature drift, low cost and easy integration, and are suitable for obstacle avoidance light sources in service robots. The single-point VCSEL laser driving circuit of the present application is used to light up the single-point VCSEL laser of the obstacle avoidance solution on the service robot. The single-point VCSEL laser is lit in an extremely narrow pulse of 0.5-0.8 nanoseconds, and its driving current is small and the cost is lower. VCSEL lasers are used in service robots and have the advantages of less heat generation, high peak power, long detection distance and high obstacle avoidance accuracy.

[0036] Schematic single-point VCSEL laser and driving circuit of single-point VCSEL laser

[0037] like Figure 1 and Figure 3As shown, the VCSEL laser and the driving circuit of the present application are presented in the form of a driving circuit board, and the VCSEL laser is fixed on the driving circuit board in the form of a module; in other embodiments, the VCSEL laser can also be fixed on the driving circuit board in the form of a bare VCSEL chip. The VCSEL laser has a cathode pin and an anode pin, the DC rectifier input end of the driving circuit is electrically connected to the anode pin of the VCSEL laser, and the current output end of the driving circuit is electrically connected to the cathode pin of the VCSEL laser. The driving circuit is opened and closed by an NMOS switch with an extremely narrow nanosecond pulse frequency, and the actual VCSEL laser is lit at an extremely narrow nanosecond frequency.

[0038] The driving circuit for lighting a single-point VCSEL laser includes a charging circuit 11 electrically connected to the anode pin of the VCSEL laser, a discharge circuit 12 electrically connected to the cathode pin of the VCSEL laser, a gate circuit 13, a control circuit 14, and a signal feedback circuit 15 for feeding back to the entire control system when the VCSEL laser is lit. The charging circuit includes an energy storage capacitor C1, a charging resistor R1, and a plurality of voltage-dividing capacitors C2. The energy storage capacitor C1 inputs the charge received from the voltage source VCC so as to quickly release energy when needed. In the driving circuit of the VCSEL laser, the fast discharge capability of the energy storage capacitor is crucial for generating nanosecond pulses. The input voltage source VCC is stored in the energy storage capacitor C1 and then output through the input end. The voltage of the voltage source VCC is divided through the charging resistor R1 to form a divided charge. The voltage of the voltage source after the voltage division enters the divided capacitor C2 respectively and is temporarily stored in the divided capacitor C2 to wait for the discharge circuit 12 to be closed. The charge in the divided capacitor C2 is output to the anode pin of the VCSEL to light up the VCSEL laser. The use of the voltage-dividing capacitor C2 in parallel can reduce the overall equivalent series resistance (ESR) of the circuit, reduce voltage drop and energy loss. In the present application, the number of the voltage-dividing capacitors C2 is three, and the three voltage-dividing capacitors are connected in parallel; multiple parallel voltage-dividing capacitors reduce the parasitic inductance on the charging circuit 11 and reduce the voltage consumed by the charging circuit 11. In other embodiments, the number of the voltage-dividing capacitors C2 can be more than three, and the increase in the number can better reduce the parasitic inductance of the charging circuit 11 and reduce the voltage consumed by the charging circuit 11. The number of voltage-dividing capacitors C2 can be adjusted as needed to optimize circuit performance. Of course, in other embodiments, the voltage of the voltage source VCC can be directly output by the energy storage capacitor C1 to the anode pin of the VCSEL to light up the VCSEL laser.

[0039] The discharge circuit 12 turns on the VCSEL laser by closing the NMOS switch, and turns off the VCSEL by disconnecting the NMOS switch. The NMOS switch is a switch device that controls the VCSEL chip to be turned on and off. The on-off frequency of the NMOS switch determines the frequency of the VCSEL chip being turned on within 1.0 nanoseconds. The NMOS (N-Channel Metal-Oxide-Semiconductor) switch is a field effect transistor used to control the flow of current. In the driving circuit of the VCSEL laser, the fast on-off capability of the NMOS switch determines the fast on-off and off of the laser. The input end of the discharge circuit 12 is electrically connected to the cathode pin of the VCSEL laser, and the current passing through the VCSEL laser is output through the discharge circuit 12. The current required for the NMOS switch to turn on and off is provided by the gate circuit 13 connected in parallel to the voltage source. The gate circuit 13 is used to eliminate noise in the voltage and ensure that the NMOS switch obtains a stable voltage supply. In the driving circuit of the VCSEL laser, the design of the gate circuit 13 needs to take into account the voltage stability and response speed to meet the requirements of nanosecond pulses.

[0040] The gate circuit 13 supplies voltage to the NMOS switch and also filters the noise of the voltage supplied to the NMOS switch, keeping the voltage supplied to the NMOS switch at 5V. The gate circuit 13 includes a first capacitor C9, a line regulator, a second capacitor C8, a magnetic bead L1, a third capacitor C7, and a fourth capacitor C6. The voltage source provided is input into the first capacitor C9 to eliminate the noise of part of the voltage source. The voltage in the first capacitor C9 passes through the line regulator and is then stored in the second capacitor C8. The charge in the second capacitor C8 passes through the magnetic bead L1 to filter out the interference factors of the voltage to keep the voltage fluctuating around 5V. The voltage is divided into the third capacitor and the fourth capacitor and temporarily stored in the third capacitor C7 and the fourth capacitor C6. The charge stored in the third capacitor C7 and the fourth capacitor C8 is output to the control circuit 14, and the control circuit 14 controls the opening and closing of the NMOS switch.

[0041] The control circuit 14 is responsible for generating a control signal to adjust the opening and closing of the NMOS switch, thereby controlling the working state of the VCSEL laser. The control circuit 14 includes a current output device 141 and a signal control circuit. When the current output device 141 receives a nanosecond pulse signal from the signal control circuit, it inputs a 5A current to the NMOS switch, so that the NMOS switch is closed and the discharge circuit 12 is closed to light up the VCSEL laser. The signal control circuit includes at least two parallel resistors, resistor R2 and resistor R3. The high level is input from the outside and then input to the current output device 141 through resistor R2 and resistor R3, and the current output device 141 is controlled to control the NMOS switch. Figure 3As shown, in this embodiment, the current output device 141 is a buffer device; or as Figure 2 As shown, the current output device 141 is within the gate driver, and then the current is input to the NMOS switch through the gate driver.

[0042] The signal feedback circuit 15 is used to provide the control system with information about the working state of the VCSEL laser. This feedback mechanism is very important for achieving precise control and fault diagnosis.

[0043] like Figure 5 As shown, the present application also discloses a single-point VCSEL laser, the VCSEL laser includes a light-emitting point, and the light-emitting point is a VCSEL unit with an independent light-emitting hole. The light-emitting point includes an epitaxial structure, a first electrode 31, and a second electrode 37; the first electrode 31 is an N-type metal layer, and the first electrode 31 is an N-type doped alloy composed of three metals: platinum, gold, and nickel. The first electrode 31 is in ohmic contact with the bottom of the epitaxial structure, serving as the cathode of the VCSEL laser; when the VCSEL laser is composed of multiple light-emitting points, the multiple light-emitting points share the same first electrode 31, that is, the VCSEL laser is a common cathode VCSEL.

[0044] The second electrode 37 is a P-type doped alloy composed of three metals: platinum, gold, and nickel. In other embodiments, the second electrode 37 can be other metals, such as gold (Au). The second electrode 37 is in ohmic contact with the top surface of the epitaxial structure, and the second electrode 37 is used as an anode of a light-emitting point or a light-emitting unit. The second electrode 37 is electrically contacted with a metal electrode, and the metal electrode is attached to the second electrode 37 by electroplating, sputtering, or evaporation. The metal electrode is made of a metal with excellent conductivity, such as platinum and gold, among which gold is preferred.

[0045] The epitaxial structure includes, from bottom to top, a substrate layer 32, a first Bragg reflector 33, an active region 34, a current limiting layer 36 having a limiting hole 361, and a second Bragg reflector 35. The substrate layer 32 is an N-type doped gallium arsenide substrate; or in other modified embodiments, the substrate layer 32 is a P-type doped gallium arsenide substrate. The substrate layer 32 can be made of a doping material such as InP, GaN, and GaAs. The second electrode 37 is in ohmic contact with the top surface of the second Bragg reflector 35. The second Bragg reflector 35 is grown to the top surface of the active region 34 by MOCVD. The second Bragg reflector 35 is a P-DBR, which is formed by alternating stacking of multiple P-type doped high aluminum content AlxGa1-xAs (x=1~0) and P-type doped low aluminum content AlxGa1-xAs (x=1~0).

[0046] Correspondingly, the first Bragg reflector 33 is grown to the top surface of the substrate layer 32 by MOCVD. The first Bragg reflector 33 is an N-DBR, which is formed by alternating stacking of N-type doped AlxGa1-xAs (x=1~0) with a high aluminum content and N-type doped AlxGa1-xAs (x=1~0) with a low aluminum content. It is worth mentioning that the material selection of the alternating layer depends on the working wavelength of the laser emitted by the light-emitting point, and the optical thickness of the alternating layer is equal to or approximately equal to 1 / 4 of the working wavelength of the laser.

[0047] In other modified embodiments, the difference between the reflectivity of the first Bragg reflector 33 and the reflectivity of the second Bragg reflector 35 is controlled by designing and configuring the first Bragg reflector 33 and the second Bragg reflector 35, so as to control the light emission direction of the laser; for example, the reflectivity of the second Bragg reflector 35 is controlled to be higher than that of the first Bragg reflector 33, that is, the second Bragg reflector 35 is an N-DBR, and the first Bragg reflector 33 is a P-DBR. Since the refractive index of the second Bragg reflector 35 is higher than that of the first Bragg reflector 33, the laser generated by it is emitted in the direction toward the substrate layer 32. The active region 34 is located between the first Bragg reflector 33 and the second Bragg reflector 35 to form a resonant cavity. After being excited, photons are reflected back and forth in the resonant cavity and repeatedly amplified to form laser oscillation, thereby forming a laser.

[0048] In summary, the single-point VCSEL laser and the driving circuit for realizing nanosecond-level circular lighting of the VCSEL laser are explained.

[0049] Schematic laser equipment

[0050] According to another aspect of the present application, a laser device is also provided. The working principle of the laser device is: using laser as a medium, emitting laser to the target to be measured, and receiving laser reflected by the target to be measured, based on the time difference between the emitted laser and the received laser pulse (or the phase difference between the emitted laser and the received reflected laser), the relative position and distance between the target to be measured and the laser device are obtained, thereby realizing the detection, tracking and identification of the object to be measured in the target area.

[0051] Accordingly, the laser device includes: a laser projection device for projecting laser, a laser receiving device for receiving laser signals, and a processor communicatively connected to the laser projection device and the laser receiving device, wherein the laser projection device includes the single-point VCSEL laser as described above and a driving circuit for driving the single-point VCSEL laser.

[0052] It should be noted that in the apparatus and method of the present application, the components or steps in different embodiments can be decomposed and / or recombined without departing from the principles of the present application. Such decomposition and / or recombination should be considered to be included in the inventive concept of the present application.

[0053] The basic principles of the present application are described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, effects, etc. mentioned in the present application are only examples and not limitations, and it cannot be considered that these advantages, strengths, effects, etc. are required by each embodiment of the present application. In addition, the specific details disclosed above are only for the purpose of illustration and ease of understanding, not for limitation, and the above details do not limit the present application to being implemented by adopting the above specific details.

Claims

1. Single-point VCSEL laser driving circuit, characterized in that: include A charging circuit is electrically connected to the voltage source, the charging circuit has a capacitor, the charge of the voltage source is stored in the capacitor, and the charge in the capacitor is output to the single-point VCSEL laser; A discharge circuit, wherein the discharge circuit has a switch device capable of being turned on and off within a nanosecond pulse width, and after the switch device is closed, the charge stored in the capacitor lights up the single-point VCSEL laser; A gate circuit, which outputs current to the switch device to control the switch device to close; A control circuit controls the gate circuit to output current to the switch device after receiving the instruction signal.

2. The single-point VCSEL laser driving circuit according to claim 1, wherein: The switch device has a turn-on and turn-off pulse width of less than 1.0 nanosecond.

3. The single-point VCSEL laser driving circuit according to claim 1, wherein: The gate circuit is provided with a current output device. After the control circuit inputs a high level to the current output device, the current output device outputs current to the switch device in a high level manner.

4. The single-point VCSEL laser driving circuit according to claim 3, wherein: The gate circuit includes a line-to-line regulator and a magnetic bead for filtering voltage noise. The voltage provided to the current output device is first filtered by the line-to-line regulator for noise filtering, and then filtered twice by the magnetic bead.

5. The single-point VCSEL laser driving circuit according to claim 3, wherein: The gate circuit has at least two sub-capacitors for storing charges, and the charges in the sub-capacitors are output to the current output device.

6. The single-point VCSEL laser driving circuit according to claim 3, wherein: The control circuit is provided with a resistor R2 and a resistor R3 connected in parallel with the resistor R2.

7. The single-point VCSEL laser driving circuit according to claim 1, wherein the charging circuit comprises a voltage-stabilizing capacitor and an energy storage capacitor composed of a plurality of capacitor devices to reduce the parasitic inductance of the entire charging circuit, and the charge in the energy storage capacitor is output to the single-point VCSEL laser.

8. The single-point VCSEL laser driving circuit according to claim 7, wherein: A charging resistor R1 is provided between the energy storage capacitor and the voltage dividing capacitor.

9. The single-point VCSEL laser driving circuit according to claim 1, wherein: Also included is a signal feedback circuit for indicating that the single-point VCSEL laser is lit.

10. The single-point VCSEL laser driving circuit according to claim 1, wherein: The switch is an NMOS switch.

11. A laser device, characterized in that: include: A laser projection device for projecting laser light, wherein the laser projection device comprises a single-point VCSEL laser and any single-point VCSEL laser driving circuit as claimed in claims 1 to 10; a laser receiving device for receiving a laser signal; and A processor is communicatively connected to the laser projection device and the laser receiving device.

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