A constant power driving circuit for semiconductor laser

Abstract

The present invention provides a semiconductor laser constant power drive circuit, which relates to the field of semiconductor laser technology, and includes a diode module, a sampling module, a drive module, and a voltage compensation module; the diode module is connected to the sampling module, the sampling module is connected to the voltage compensation module, the voltage compensation module is connected to the drive module, and the drive module is connected to the diode module. The present invention realizes sampling, amplification, DC compensation and calibration of photodiode PD current, and an inverting compensation current drive circuit.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor lasers, and in particular to a semiconductor laser constant power driving circuit. Background Art

[0002] Semiconductor lasers (also known as laser diodes) use semiconductor materials as working materials, can emit lasers of specific wavelengths and powers, and have the advantages of small size and long life. In recent years, with the increasing maturity of semiconductor technology, semiconductor lasers have become one of the mainstream laser light sources and are widely used in consumer electronics, medical beauty, automotive aviation and other fields.

[0003] However, the electrical and optical properties of semiconductor lasers are limited by the properties of the semiconductor itself, and the temperature characteristics are poor. When the heat dissipation conditions are not good, the semiconductor laser is prone to light decay, that is, its UI characteristics and PI characteristics are offset. At this time, using a traditional current source drive, the laser brightness will drop significantly. Therefore, in order to meet the requirements of a light source with constant brightness, it is necessary to build an automatic power control circuit (APC) to compensate for light decay in real time to drive the semiconductor laser to work stably.

[0004] At present, the power-controlled light source driving circuit can be roughly divided into two categories: ① electrical power control; ② optical power control. The two types of driving are similar in structure, namely collecting real-time power, amplifying processing, reverse compensation and driving. The difference is:

[0005] 1) The electric power control driving circuit generally collects the current and voltage drop when the light source is working, and inversely compensates the current and voltage of the driving circuit. For example, the driving scheme proposed in the publication number CN116056284A collects the real-time voltage and current of the infrared light source, calculates the real-time power, and outputs the target voltage after comparison to achieve the adjustment of the driving voltage. This control method mainly compensates for the change of UI characteristics with temperature when the semiconductor laser is working. It has a simple structure and low cost, but it cannot compensate for the change of PI characteristics.

[0006] 2) The optical power control driving circuit generally uses a photoelectric device to collect the optical power of the light source when it is working, converts it into a current or voltage value, and then inverts the compensation driving circuit. This control method can simultaneously compensate for the changes in the UI and PI characteristics of the semiconductor laser, and therefore has become the mainstream of the APC circuit. For example, the patent disclosed in the publication number CN201178510Y includes a current-voltage conversion (I / V conversion) circuit composed of a sampling resistor, which is used to convert the current signal of the monitoring photodiode into a voltage signal; an integral amplifier circuit composed of an operational amplifier, which is used to differentially amplify a given reference voltage and feedback value; a voltage-controlled current driving circuit composed of a transistor, and the driving output current can be controlled by the output voltage of the pre-stage amplifier circuit. When changes, the driving current changes in reverse phase, thereby realizing the automatic adjustment of the output power of the semiconductor laser. However, this solution has the following problems to be optimized:

[0007] i) Insufficient sampling accuracy: The output current of the monitoring photodiode (PD) is generally very small, and the sampling accuracy requirement is high. The sampling resistor has a limited effect in the I / V conversion of tiny currents.

[0008] ii) Difficulty in debugging the reference voltage: Since the feedback voltage signal includes the monitoring current and its real-time fluctuation value when the diode works at the target power, in order to make the output value of the differential amplifier directly serve as the input of the voltage-controlled current source, it is necessary to: ① eliminate the reference monitoring current; ② compensate the reference voltage of the voltage-controlled current source when the laser diode works normally. The variable debugging point has a small value, high density, and high precision, which makes it difficult to use a general programmable voltage source.

[0009] iii) Voltage-controlled current drive to be optimized: The current drive circuit composed of PNP transistors utilizes the current control characteristics of the transistor. In this scheme, the collector of the transistor is connected to the load. Since the voltage difference between the collector and the base is constant, the change in the collector voltage will cause the voltage drop of the input resistance to change, thereby changing the input current. The current amplification characteristics of the transistor are then used to compensate for the load current. This scheme uses the load voltage as the feedback value and compensates for the load current, ignoring the offset of the UI curve (change in resistance) of the laser diode during operation.

[0010] Therefore, a semiconductor laser constant power driving circuit is proposed. Summary of the invention

[0011] The present specification provides a semiconductor laser constant power driving circuit, which realizes sampling, amplification, DC compensation and calibration of photodiode PD current, and an inverting compensation current driving circuit.

[0012] This specification provides a semiconductor laser constant power driving circuit, including: a diode module, a sampling module, a driving module, and a voltage compensation module;

[0013] The diode module is connected to the sampling module, the sampling module is connected to the voltage compensation module, the voltage compensation module is connected to the driving module, and the driving module is connected to the diode module.

[0014] Optionally, the diode module includes a semiconductor laser that integrates a laser diode LD and a photodiode PD.

[0015] Optionally, the sampling module includes an operational amplifier U1, a sliding rheostat R5, and a protective resistor R3. The inverting input terminal of the operational amplifier U1 is connected to the diode module, the non-inverting input terminal of the operational amplifier U1 is grounded through the protective resistor R3, and the sliding rheostat R5 is connected between the inverting input terminal and the output terminal of the operational amplifier U1.

[0016] Optionally, the gain of the sampling module is determined by:

[0017] U I / V =I PD ×R5+U PD

[0018] Among them, U I / V is the output voltage signal of the sampling module, I PD is the photocurrent collected by the photodiode PD, R5 is the resistance value of the sliding resistor R5, U PD is the voltage across the photodiode PD.

[0019] Optionally, the voltage compensation module includes an adding unit and a differential unit;

[0020] The adding unit includes an operational amplifier U3, a resistor R10, a resistor R14, a resistor R16, a resistor R17, and a resistor R18;

[0021] The resistor R14, the resistor R17, and the resistor R18 are connected in parallel to the non-inverting input terminal of the operational amplifier U3. The resistor R14 is grounded, and the resistor R17 is connected to the compensation voltage V com , the resistor R18 is connected to the reference voltage V set The inverting input terminal of the operational amplifier U3 is grounded through the resistor R16, and the resistor R10 is connected between the inverting input terminal and the output terminal of the operational amplifier U3.

[0022] Optionally, the differential unit includes an operational amplifier U2, a resistor R11, a resistor R12, a resistor R13, and a resistor R15;

[0023] The resistor R11 and the resistor R13 are connected in parallel to the non-inverting input terminal of the operational amplifier U2, the resistor R11 is also connected to the output terminal of the operational amplifier U3, and the resistor R13 is grounded; the inverting input terminal of the operational amplifier U2 is connected to the sampling module through the resistor R12, and the resistor R15 is connected between the inverting input terminal and the output terminal of the operational amplifier U2.

[0024] Optionally, the driving module includes an operational amplifier U5 and a sampling resistor R1;

[0025] The non-inverting input terminal of the operational amplifier U5 is connected to the voltage compensation module, and the inverting input terminal of the operational amplifier U5 is connected to the diode module through the sampling resistor R1.

[0026] Optionally, the operational amplifier U5 transmits the voltage formed by the voltage compensation module to the sampling resistor R1, including:

[0027] U REF =U DIFF =V com +V set -U I / V =I LD ×R1

[0028] I LD =U REE / R1

[0029] Among them, U RRF is the voltage at the non-inverting input terminal of operational amplifier U5, U DIFF is the compensated and calibrated signal of the output voltage of the sampling module (200), V com is the compensation voltage, V set is the reference voltage, U I / V is the output voltage signal of the sampling module (200), I LD is the current collected by the laser diode LD, and R1 is the resistance value of the sampling resistor R1.

[0030] The present invention has at least the following advantages:

[0031] 1. Using operational amplifiers to complete PD microcurrent sampling and I / V conversion can meet the needs of PD current conversion and amplification, with low cost and high precision;

[0032] 2. Using a sliding rheostat to adjust the magnification also provides convenience for debugging and can be applied to different types of semiconductor lasers;

[0033] 3. Provide two intuitive and adjustable voltage interfaces: laser tube DC drive and DC compensation. Laser tube DC drive is used to set the reference voltage for LD to work; DC compensation is used to compensate for the brightness drop caused by temperature of the laser tube under DC drive;

[0034] 4. The voltage output by the sampling photodiode is directly fed back to the driving circuit, avoiding the phase shift and spectrum attenuation problems that occur when the traditional constant power circuit uses a filter circuit for AC compensation. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments 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 creative work.

[0036] Figure 1 A schematic diagram of the structure of a semiconductor laser constant power driving circuit provided in an embodiment of this specification;

[0037] Figure 2 An overall circuit diagram of a semiconductor laser constant power drive circuit provided in an embodiment of this specification;

[0038] Figure 3 A partial circuit diagram of a diode module provided in an embodiment of this specification;

[0039] Figure 4 A partial circuit diagram of a sampling module provided in an embodiment of this specification;

[0040] Figure 5 A partial circuit diagram of a driving module provided in an embodiment of this specification;

[0041] Figure 6 A partial circuit diagram of a voltage compensation module provided in an embodiment of this specification.

[0042] The accompanying drawings illustrate: 100, diode module; 200, sampling module; 300, driving module; 400, voltage compensation module; 410, adding unit; 420, differential unit. DETAILED DESCRIPTION

[0043] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art can think of other obvious variations. The basic principles of the present invention defined in the following description can be applied to other embodiments, variations, improvements, equivalents, and other technical solutions that do not deviate from the spirit and scope of the present invention.

[0044] The following is combined with Figure 1-6 The exemplary embodiments of the present invention are described more fully. However, the exemplary embodiments can be implemented in various forms, and it should not be understood that the present invention is limited to the embodiments set forth herein. On the contrary, providing these exemplary embodiments can make the present invention more comprehensive and complete, and it is more convenient to fully convey the inventive concept to those skilled in the art. The same reference numerals in the figures represent the same or similar elements, components or parts, and thus their repeated description will be omitted.

[0045] Under the premise of being consistent with the technical concept of the present invention, the features, structures, characteristics or other details described in a specific embodiment do not exclude that they can be combined in one or more other embodiments in a suitable manner.

[0046] In the description of specific embodiments, the features, structures, characteristics or other details described in the present invention are intended to enable those skilled in the art to fully understand the embodiments. However, it does not exclude that those skilled in the art can practice the technical solutions of the present invention without one or more of the specific features, structures, characteristics or other details.

[0047] The flowcharts shown in the accompanying drawings are only exemplary and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps can be decomposed, and some operations / steps can be combined or partially combined, so the actual execution order may change according to actual conditions.

[0048] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities may be implemented in software form, or in one or more hardware modules or integrated circuits, or in different networks and / or processor devices and / or microcontroller devices.

[0049] The term "and / or" or "and / or" includes all combinations of any one or more of the associated listed items.

[0050] Figure 1A schematic diagram of the structure of a semiconductor laser constant power driving circuit provided in an embodiment of the present specification, the circuit includes: a diode module 100, a sampling module 200, a driving module 300, and a voltage compensation module 400; the diode module 100 is connected to the sampling module 200, the sampling module 200 is connected to the voltage compensation module 400, the voltage compensation module 400 is connected to the driving module 300, and the driving module 300 is connected to the diode module 100. The diode module 100 includes a semiconductor laser integrating a laser diode LD and a photodiode PD. The diode module 100 receives power from the driving module 300 to generate laser light, which irradiates the photodiode PD to form a photocurrent. Afterwards, the photocurrent is transmitted to the sampling module 200, and the sampling module 200 converts the photocurrent into a photovoltage in order to compensate for the influence of temperature on the light-emitting performance and fluctuation of the laser diode.

[0051] The anode of the laser diode LD is connected to the cathode of the photodiode PD, that is, when the laser diode LD works in the forward conduction state, the photodiode PD works in the reverse bias state. This common-pole design is easy to operate and saves costs.

[0052] The sampling module 200 includes an operational amplifier U1, a sliding rheostat R5, and a protective resistor R3. The inverting input terminal of the operational amplifier U1 is connected to the diode module 100, the non-inverting input terminal of the operational amplifier U1 is grounded through the protective resistor R3, and the sliding rheostat R5 is connected between the inverting input terminal and the output terminal of the operational amplifier U1. Optionally, the gain of the sampling module 200 is determined by:

[0053] U I / v =I PD ×R5+U PD

[0054] Among them, U I / V is the output voltage signal of the sampling module 200, I PD is the photocurrent collected by the photodiode PD, R5 is the resistance value of the sliding resistor R5, U PD is the voltage across the photodiode PD. This module amplifies the tiny current in the photodiode PD into a voltage signal by a certain multiple, and its gain is determined by the resistance value of the sliding rheostat R5. The sampling module 200 converts the photocurrent into a photovoltage, which includes a DC and AC part. Among them, the DC part reflects the luminous performance of the laser diode LD under constant current drive (including the influence of temperature on luminescence), and the AC part reflects the fluctuation of the laser diode LD under constant current drive.

[0055] The voltage compensation module 400 includes an adding unit 410 and a differential unit 420; the adding unit 410 includes an operational amplifier U3, a resistor R10, a resistor R14, a resistor R16, a resistor R17, and a resistor R18; the in-phase input terminal of the operational amplifier U3 is connected in parallel with resistors R14, R17, and R18, the resistor R14 is grounded, and the resistor R17 is connected to the compensation voltage V com , resistor R18 is connected to the reference voltage V set The inverting input terminal of the operational amplifier U3 is grounded through the resistor R16, and the resistor R10 is connected between the inverting input terminal and the output terminal of the operational amplifier U3. It is worth noting that when R14=R18=R17=R16=2R10:

[0056] U ADJ =V com +V set

[0057] Among them, U ADJ is the calibration level.

[0058] Since the compensation voltage V com and reference voltage V set During the debugging process, high precision and high debugging density are required. Here, the output of a DC / DC power chip is connected, and this voltage is output to the voltage regulator to form a reference voltage. Connect sliding resistors to the two reference voltage interfaces respectively, and the V can be adjusted by changing the voltage divider of the resistor. com and V set The value of , greatly increases the feasibility of debugging.

[0059] The differential unit 420 includes an operational amplifier U2, a resistor R11, a resistor R12, a resistor R13, and a resistor R15; the non-inverting input terminal of the operational amplifier U2 is connected in parallel with resistors R11 and R13, and resistor R11 is also connected to the output terminal of the operational amplifier U3, and resistor R13 is grounded; the inverting input terminal of the operational amplifier U2 is connected to the sampling module 200 through resistor R12, and resistor R15 is connected between the inverting input terminal and the output terminal of the operational amplifier U2. The driving module 300 includes an operational amplifier U5 and a sampling resistor R1; the non-inverting input terminal of the operational amplifier U5 is connected to the voltage compensation module 400, and the inverting input terminal of the operational amplifier U5 is connected to the diode module 100 through the sampling resistor R1. It is worth noting that when R11=R12=R13=R15:

[0060] U DIFF =U ADJ -U I / V

[0061] The operational amplifier U5 transmits the voltage formed by the voltage compensation module 400 to the sampling resistor R1, including:

[0062] U REF =U DIFF =V com +V set -U I / V =I LD ×R1

[0063] I LD =U REF / R1

[0064] Among them, U REF is the voltage at the non-inverting input terminal of operational amplifier U5, U DIFF is the compensated and calibrated signal of the output voltage of the sampling module (200), V com is the compensation voltage, V set is the reference voltage, U I / V is the output voltage signal of the sampling module (200), I LD is the current collected by the laser diode LD, and R1 is the resistance value of the sampling resistor R1.

[0065] The voltage compensation module 400 performs the following compensation: (1) The differential unit 410 completes the U I / V Therefore, the fluctuations generated by the light source can be fed back to the constant current circuit; that is, when the light is large, the reverse compensation reduces the driving current to reduce the light, and when the light is small, the direction compensation increases the driving current to increase the light. (2) Adjust V com The DC compensation voltage can be set to compensate for the decrease in brightness of the laser diode LD due to temperature. (3) Adjust V set A basic driving constant current can be set, which can make the laser diode LD work in a constant current mode.

[0066] The present invention can also add a control module, using a field effect tube connected between the sampling resistor R1 and the laser diode LD, and the gate level is connected to the control signal. When the control signal is high, the circuit works normally and the LD works in the automatic light power control mode; when the control signal is low, no current flows and the LD does not work. The control module can realize: 1. digitally controllable light source switch, 2. high-frequency PWM to adjust the laser intensity.

[0067] The present invention has at least the following advantages:

[0068] 1. Using operational amplifiers to complete PD microcurrent sampling and I / V conversion can meet the needs of PD current conversion and amplification, with low cost and high precision;

[0069] 2. Using a sliding rheostat to adjust the magnification also provides convenience for debugging and can be applied to different types of semiconductor lasers;

[0070] 3. Provide two intuitive and adjustable voltage interfaces: laser tube DC drive and DC compensation. Laser tube DC drive is used to set the reference voltage for LD to work; DC compensation is used to compensate for the brightness drop caused by temperature of the laser tube under DC drive;

[0071] 4. The voltage output by the sampling photodiode is directly fed back to the driving circuit, avoiding the phase shift and spectrum attenuation problems that occur when the traditional constant power circuit uses a filter circuit for AC compensation.

[0072] The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the present invention is not inherently related to any specific computer, virtual device or electronic device, and various general devices can also implement the present invention. The above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

[0073] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0074] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A semiconductor laser constant power drive circuit, characterized in that: include: A diode module (100), a sampling module (200), a driving module (300), and a voltage compensation module (400); the diode module (100) is connected to the sampling module (200), the sampling module (200) is connected to the voltage compensation module (400), the voltage compensation module (400) is connected to the driving module (300), and the driving module (300) is connected to the diode module (100); The diode module (100) comprises a semiconductor laser including an integrated laser diode LD and a photodiode PD; The sampling module (200) comprises an operational amplifier U1, a sliding rheostat R5, and a protective resistor R3; the inverting input terminal of the operational amplifier U1 is connected to the diode module (100); the non-inverting input terminal of the operational amplifier U1 is grounded via the protective resistor R3; the sliding rheostat R5 is connected between the inverting input terminal and the output terminal of the operational amplifier U1; the operational amplifier U5 transmits the voltage formed by the voltage compensation module (400) to the sampling resistor R1, and comprises: U REF =U DIFF =V com +V set -U I / V =I LD ×R1 I LD =U REF / R1 Among them, U REF is the voltage at the non-inverting input terminal of operational amplifier U5, U DIFF is the compensated and calibrated signal of the output voltage of the sampling module (200), V com is the compensation voltage, V set is the reference voltage, U I / V is the output voltage signal of the sampling module (200), I LD is the current collected by the laser diode LD, and R1 is the resistance value of the sampling resistor R1; The method for determining the gain of the sampling module (200) includes: IN I / V =I PD ×R5+U PD Among them, U I / V is the output voltage signal of the sampling module (200), I PD is the photocurrent collected by the photodiode PD, R5 is the resistance value of the sliding resistor R5, U PD is the voltage across the photodiode PD; The driving module (300) comprises an operational amplifier U5 and a sampling resistor R1; The non-inverting input terminal of the operational amplifier U5 is connected to the voltage compensation module (400), and the inverting input terminal of the operational amplifier U5 is connected to the diode module (100) via the sampling resistor R1; The voltage compensation module (400) comprises an adding unit (410) and a differential unit (420); The adding unit (410) comprises an operational amplifier U3, a resistor R10, a resistor R14, a resistor R16, a resistor R17, and a resistor R18; The resistor R14, the resistor R17, and the resistor R18 are connected in parallel to the non-inverting input terminal of the operational amplifier U3. The resistor R14 is grounded, and the resistor R17 is connected to the compensation voltage V com , the resistor R18 is connected to the reference voltage V set The inverting input terminal of the operational amplifier U3 is grounded through the resistor R16, and the resistor R10 is connected between the inverting input terminal and the output terminal of the operational amplifier U3; The differential unit (420) comprises an operational amplifier U2, a resistor R11, a resistor R12, a resistor R13, and a resistor R15; the resistor R11 and the resistor R13 are connected in parallel to the in-phase input terminal of the operational amplifier U2, the resistor R11 is also connected to the output terminal of the operational amplifier U3, and the resistor R13 is grounded; the inverting input terminal of the operational amplifier U2 is connected to the sampling module (200) via the resistor R12, and the resistor R15 is connected between the inverting input terminal and the output terminal of the operational amplifier U2.

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