Semiconductor laser constant current driving circuit

Abstract

The invention belongs to the technical field of laser emission, and provides a semiconductor laser constant-current driving circuit which solves the problem of constant-current driving of a laser diode, and the driving circuit comprises a reference voltage output circuit which is used for providing stable and accurate reference voltage to act on a digital potentiometer; the digital potentiometer is used for adjusting resistance so as to provide driving current required by the semiconductor laser and inputting the driving current into the constant-current control circuit; the constant current control circuit is used for controlling the MOS tube, guaranteeing the stability of output current and driving the semiconductor laser; and the push-pull circuit enables the TTL / PWM signal to be directly input into the constant current control circuit, and is used for carrying out frequency modulation on the output signal of the semiconductor laser and improving the modulation frequency of the signal. The invention is suitable for various semiconductor lasers.

Description

Technical Field

[0001] The invention belongs to the technical field of laser emission, and in particular relates to a semiconductor laser constant current drive circuit. Background Art

[0002] With the development and application of fiber optic technology in the field of light transmission, semiconductor lasers are considered to be an excellent light source due to their high output power. At the same time, the laser driving circuit is also an important component of the fiber optic transceiver module. The speed at which the driving circuit outputs the signal and the quality of the signal will affect the transmission quality of the signal in the fiber optic transmission system. Traditional laser driving circuits are generally implemented using a switching current source, but the switching current source is difficult to ensure a constant current, and the switch will also introduce a lot of noise, thereby affecting the quality of the signal. Therefore, adopting an effective constant current drive design is of great significance to improving the stability of the overall operation of the system. Summary of the invention

[0003] The purpose of the present invention is to provide a semiconductor laser constant current drive circuit, which solves the constant current drive problem of the laser diode, reduces noise interference, and improves the quality of the output signal.

[0004] The technical solution of the present invention is: a semiconductor laser constant current driving circuit, comprising

[0005] Reference voltage output circuit, used to provide stable and accurate reference voltage;

[0006] A digital potentiometer, used to adjust the resistance to provide the driving current required by the semiconductor laser;

[0007] Constant current control circuit, used to control MOS tube to ensure output current stability;

[0008] Electrostatic protection circuit to prevent static electricity from damaging semiconductor lasers;

[0009] A push-pull circuit is used to frequency modulate a semiconductor laser.

[0010] The reference voltage output circuit includes a reference voltage source chip TL431, a resistor R1, and a capacitor C;

[0011] The cathode (K terminal) and the reference terminal (R terminal) of the reference voltage source TL431 are connected to the positive pole of the power supply through the current limiting resistor R1, the anode (A terminal) is connected to the ground terminal of the digital potentiometer and grounded, and the other branch of the cathode (K terminal) is grounded through the capacitor C.

[0012] The reference voltage source TL431 is equivalent to a 2.5V voltage regulator tube, and outputs a 2.5V reference voltage from the cathode (K terminal) to the digital potentiometer B1 terminal.

[0013] The digital potentiometer B1 end is connected to the cathode of the reference voltage source, the A1 and W1 ends are connected to the positive pole of the operational amplifier and the output end of the push-pull circuit, the VDD interface is connected to the power supply VCC, and the CS, SDI and CLK interfaces receive signals from the microprocessor;

[0014] The constant current control circuit includes an operational amplifier LM321, a MOS tube Q3, and a resistor R5. The 2nd terminal of the operational amplifier LM321 is grounded, the 5th terminal is connected to the power supply Vcc, the negative electrode (the 3rd terminal) is respectively connected to the 2nd terminal of the resistor R5 and the 3rd terminal of the MOS tube, and the 4th terminal is connected to the 1st terminal of the MOS tube Q3;

[0015] The push-pull circuit includes a switch SW, resistors R2, R3, R4, and MOS tubes Q1 and Q2. One section of the switch SW is connected to the positive electrode of the power supply, and two sections are connected to one end of the resistor R2. Two ends of the resistor R2 are respectively connected to the IO interface, one end of the resistor R3, and one end of the MOS tube Q1. Two ends of the resistor R3 are connected to three ends of the MOS tube Q1. Two ends of the MOS tube Q1 are respectively connected to one end of the resistor R4 and one end of the MOS tube Q2. Two ends of the resistor R4 are connected to the power supply Vcc. Two ends of the MOS tube Q2 are connected to the positive electrode (one end) of the operational amplifier.

[0016] The electrostatic protection circuit includes a transient voltage suppression diode TVS, one end of the transient voltage suppression diode TVS is connected to the two ends of the MOS tube Q3 and the cathode (two ends) of the laser diode LD, and the two ends of the transient voltage suppression diode TVS are connected to the positive electrode of the power supply and one end of the laser diode LD.

[0017] When the circuit is working, 3.3V and GND are connected to the power supply respectively, the SW switch is closed, and the IO interface inputs the QWM / TTL signal. When the input voltage is in the positive half cycle, the MOS tube Q1 is turned on, the MOS tube Q2 is turned off, and the reference voltage source outputs a 2.5V reference voltage. The operational amplifier LM321 is driven by the digital potentiometer F to control the N-MOS tube Q3, so that the output current is stable, thereby realizing constant current driving of the laser diode LD.

[0018] In the semiconductor laser constant current drive circuit, the cathode (K terminal) of the reference voltage source TL431 is connected to the positive electrode of the power supply through the current limiting resistor R1, and the anode (A terminal) is connected to the negative electrode of the power supply. At this time, the reference voltage source TL431 is equivalent to a 2.5V voltage regulator tube, outputting a 2.5V reference voltage. The reference voltage obtains a constant current through the digital potentiometer. The MOS tube Q3 is controlled by the operational amplifier LM321 to ensure the stability of the output current.

[0019] The beneficial effects of the present invention are as follows: the push-pull circuit receives the TTL / PWM signal from the microcontroller unit (MCU) and directly inputs it into the operational amplifier LM321, so that the output waveform of the module has a shorter rise time, thereby increasing the modulation frequency. At the same time, the output signal can be modulated at a specific frequency to improve the anti-interference ability during signal transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A circuit diagram of an implementation of the present application. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Please refer to Figure 1 , this embodiment of a semiconductor laser constant current drive circuit, comprising:

[0023] The reference voltage source is used to provide a stable and accurate reference voltage. In this embodiment, the TL431 chip is selected as the reference voltage source. The cathode (K terminal) of the reference voltage source TL431 is connected to the positive pole of the power supply through the current limiting resistor R1, and the anode (A terminal) is connected to the negative pole of the power supply. At this time, the reference voltage source TL431 is equivalent to a 2.5V voltage regulator tube, outputting a 2.5V reference voltage.

[0024] The digital potentiometer is used to adjust the resistance to provide the driving current required by the semiconductor laser. In this implementation, the AD8400 digital potentiometer is selected because of its flexible use, high adjustment accuracy, small size and anti-interference.

[0025] Operational amplifier, used to control the MOS tube to ensure the stability of the output current. In this implementation, the LM321 operational amplifier is selected;

[0026] Transient voltage suppression diode TVS, to prevent static electricity from damaging semiconductor lasers;

[0027] The push-pull circuit is used to perform frequency modulation on the semiconductor laser. In this embodiment, the microcontroller unit (MCU) inputs a TTL / QWM signal, and the frequency modulation of the output signal is realized through TTL modulation, thereby improving the anti-interference ability during signal transmission.

[0028] The two ends of the resistor R1 are connected to a 3.3V power supply, and the one end is connected to the cathode (K end) and the reference end (R end) of the reference voltage source TL431 respectively;

[0029] The cathode (K terminal) of the reference voltage source TL431 is connected to the 2 terminals of the capacitor C, and the anode (A terminal) is connected to the digital potentiometer F;

[0030] End 1 of the capacitor C is grounded, end 2 is connected to end 1 of the digital potentiometer, end 2 of the digital potentiometer is grounded, segment 7 is connected to end 8, and then respectively connected to segment 1 of the operational amplifier LM321 and end 2 of the MOS tube Q2, ends 3, 4 and 5 of the digital potentiometer are provided with required signals by the microprocessor, and end 6 of the digital potentiometer is connected to the power supply Vcc;

[0031] The first section of the switch SW is connected to a 3.3V power supply, and the second section is connected to the first end of the resistor R2;

[0032] The two ends of the resistor R2 are respectively connected to the IO interface, one end of the resistor R3 and one end of the MOS tube Q1;

[0033] The 2nd terminal of the resistor R3 is connected to the 3rd terminal of the MOS tube Q1;

[0034] Two ends of the MOS tube Q1 are connected to one end of the resistor R4 and one end of the MOS tube Q2 respectively;

[0035] Two ends of the resistor R4 are connected to a power source Vcc;

[0036] The 2 ends of the MOS tube Q2 are connected to the positive electrode (1 end) of the operational amplifier;

[0037] The operational amplifier LM321 has a 2-terminal connected to the ground, a 5-terminal connected to the power supply Vcc, a negative electrode (3-terminal) connected to the 2-terminal of the resistor R5 and the 3-terminal of the MOS tube respectively, and a 4-terminal connected to the 1-terminal of the MOS tube Q3;

[0038] The two ends of the MOS tube Q3 are connected to the cathode (the two ends) of the laser diode LD and the one end of the transient voltage suppression diode TVS respectively, and the three ends of the MOS tube Q3 are connected to the two ends of the resistor R5;

[0039] The cathode (2 ends) of the laser diode LD are respectively connected to 1 end of the transient voltage suppression diode TVS and 2 ends of the MOS tube Q3, and the anode (1 end) of the laser diode LD is respectively connected to a 3.3V power supply and 2 ends of the transient voltage suppression diode TVS;

[0040] One end of the resistor R5 is grounded;

[0041] When the circuit is working, 3.3V and GND are connected to the power supply respectively, the SW switch is closed, and the IO interface inputs the PWM / TTL signal. When the input voltage is in the positive half cycle, the MOS tube Q1 is turned on, the MOS tube Q2 is turned off, and the reference voltage source outputs a 2.5V reference voltage. The digital potentiometer F drives the operational amplifier LM321 to control the N-MOS tube Q3, so that the output current is stable, and the constant current drive of the laser diode LD is realized;

[0042] The circuit can meet the driving current requirements of laser diodes of different models by adjusting the resistance value of the digital potentiometer;

[0043] The circuit can modulate the output signal of the laser diode to meet a specific frequency by adjusting the frequency of the input PWM signal.

[0044] The above is only a specific embodiment of the present invention, and the present invention is described in detail. The unexplained part is a conventional technology. However, the protection scope of the present invention is not limited to this. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. The protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A semiconductor laser constant current drive circuit, characterized in that: include The reference voltage output circuit is used to provide a stable and accurate reference voltage to act on the digital potentiometer; A digital potentiometer is used to adjust the resistance so as to provide the driving current required by the semiconductor laser and input into the constant current control circuit; Constant current control circuit, used to control MOS tube, ensure output current stability, and drive semiconductor laser; The push-pull circuit allows the TTL / PWM signal to be directly input into the constant current control circuit, which is used to frequency modulate the output signal of the semiconductor laser and increase the modulation frequency of the signal.

2. The semiconductor laser constant current driving circuit according to claim 1, characterized in that: The reference voltage output circuit includes a reference voltage source chip TL431, a resistor R1, and a capacitor C; The cathode and reference end of the reference voltage source TL431 are connected to the positive pole of the power supply through the current limiting resistor R1, the anode is connected to the ground terminal of the digital potentiometer and grounded, and the other branch of the cathode is grounded through the capacitor C.

3. The semiconductor laser constant current driving circuit according to claim 2, characterized in that: The reference voltage source TL431 is equivalent to a 2.5V voltage regulator tube, and outputs a 2.5V reference voltage from the cathode to the digital potentiometer B1 terminal.

4. The semiconductor laser constant current driving circuit according to claim 1, characterized in that: The digital potentiometer B1 end is connected to the cathode of the reference voltage source, A1 and W1 ends are connected to the positive pole of the operational amplifier and the output end of the push-pull circuit, the VDD interface is connected to the power supply VCC, and the CS, SDI and CLK interfaces receive signals from the microprocessor.

5. The semiconductor laser constant current driving circuit according to claim 1, characterized in that: The constant current control circuit includes an operational amplifier LM321, a MOS tube Q3, and a resistor R5. Terminal 2 of the operational amplifier LM321 is grounded, terminal 5 is connected to the power supply Vcc, the negative electrode is respectively connected to terminals 2 of the resistor R5 and terminal 3 of the MOS tube, and terminal 4 is connected to terminal 1 of the MOS tube Q3.

6. The semiconductor laser constant current driving circuit according to claim 1, characterized in that: The push-pull circuit includes a switch SW, resistors R2, R3, R4, and MOS tubes Q1 and Q2. One section of the switch SW is connected to the positive electrode of the power supply, and two sections are connected to one end of the resistor R2. Two ends of the resistor R2 are respectively connected to the IO interface, one end of the resistor R3, and one end of the MOS tube Q1. Two ends of the resistor R3 are connected to three ends of the MOS tube Q1. Two ends of the MOS tube Q1 are respectively connected to one end of the resistor R4 and one end of the MOS tube Q2. Two ends of the resistor R4 are connected to the power supply Vcc. Two ends of the MOS tube Q2 are connected to the positive electrode of the operational amplifier.

7. The semiconductor laser constant current driving circuit according to claim 1, characterized in that: Also includes: Electrostatic protection circuit to prevent static electricity from damaging semiconductor lasers.

8. The semiconductor laser constant current driving circuit according to claim 7, characterized in that: The electrostatic protection circuit includes a transient voltage suppression diode TVS, one end of the transient voltage suppression diode TVS is connected to the two ends of the MOS tube Q3 and the cathode of the laser diode LD, and the two ends of the transient voltage suppression diode TVS are connected to the positive pole of the power supply and one end of the laser diode LD.

9. The semiconductor laser constant current driving circuit according to any one of claims 2 to 8, characterized in that: When the circuit is working, 3.3V and GND are connected to the power supply respectively, the SW switch is closed, and the IO interface inputs the PWM / TTL signal. When the input voltage is in the positive half cycle, the MOS tube Q1 is turned on, the MOS tube Q2 is turned off, and the reference voltage source outputs a 2.5V reference voltage. The digital potentiometer F drives the operational amplifier LM321 to control the N-MOS tube Q3, so that the output current is stable, thereby realizing constant current driving of the laser diode LD.

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