A constant temperature and constant current semiconductor laser driving circuit with negative voltage overcurrent protection

Abstract

The present invention discloses a constant temperature and constant current semiconductor laser driving circuit with negative voltage overcurrent protection, which mainly includes: a constant current source circuit, a temperature control circuit and an overcurrent protection circuit; the constant current source circuit is used to provide a stable driving current for the semiconductor laser; the temperature control circuit is used to achieve high-precision temperature control of the semiconductor laser; the overcurrent protection circuit is used to protect the semiconductor laser from being damaged due to excessive driving current setting or current surge. The present invention is designed for a negative voltage overcurrent protection circuit with a negative voltage, has a wider range of applications, high reliability, and has high stability driving current control and temperature control for semiconductor lasers.

Description

Technical Field

[0001] The invention belongs to the technical field of laser driving, and in particular relates to a constant-temperature and constant-current semiconductor laser driving circuit with negative voltage overcurrent protection. Background Art

[0002] Semiconductor lasers (LDs) have the advantages of small size, high conversion efficiency, and long service life. They are widely used in communications, lidar, optical sensing, medical equipment, and precision measurement. It is often necessary to modulate the output of LD to achieve modulation and demodulation of optical signals. The modulation of LD output includes internal modulation and external modulation. Both internal and external modulation require stable driving current and temperature to ensure the normal operation of LD, so the design of LD drive is crucial.

[0003] LD is a relatively fragile junction device. Slight changes in current and temperature will affect the parameters of the LD's output light and may even damage the laser. Therefore, it is necessary to design a stable constant current source circuit to drive the LD, a high-precision temperature control circuit to control the temperature, and an overcurrent protection circuit to prevent the current surge caused by the load and the damage to the LD caused by the working current design exceeding the limit value. In addition, due to the different use ranges of LD, the internal diode anode pin will be considered to be short-circuited or isolated from the tube shell ground in the process design. If the diode anode pin is short-circuited with the tube shell ground, a negative voltage needs to be provided to the diode cathode for the laser to work normally. If it is isolated from the tube shell ground, the design can be designed in two ways: providing a positive voltage at the diode anode and grounding the cathode or providing a negative voltage at the diode cathode and grounding the anode. Therefore, in view of the different existing LD pin designs, the design of negative voltage drive has a wider range of applications.

[0004] Semiconductor laser drivers need to provide a stable driving current and a constant temperature for LD. In terms of providing a stable driving current, the traditional voltage-controlled constant current source circuit generally adopts the Howland constant current source circuit or adds a triode on this basis to enhance the output current capability. However, the load carried by the traditional Howland constant current source circuit cannot be too large, otherwise it will affect the efficiency and accuracy. Precision op amps with high output current and slew rate can solve this problem, but its cost is relatively high; adding a triode on this basis can solve this problem efficiently, but the triode is a current-controlled current device. However, after the triode is turned on, the current flowing through the sampling resistor is not entirely the load current, but also the base current. Therefore, for a high-precision constant current source, the use of the triode will have a certain error. In terms of temperature control, the existing temperature control has higher accuracy, but its control algorithm is relatively complex and the circuit structure is relatively complex. In terms of protecting LD, the existing research on the overcurrent protection function, whether it is a forward feedback type or a backward feedback type protection circuit, is generally judged based on the positive voltage feedback point, and is rarely involved in the negative voltage driven laser diode circuit.

[0005] In summary, in the constant current source circuit, the traditional Howland constant current source has high requirements for the selection of op amps, and the constant current source circuit composed of op amps and triodes will have certain errors in accuracy; in the temperature control circuit, the existing control algorithm and circuit structure are relatively complex; in the overcurrent protection circuit, negative voltage feedback is rarely involved. Therefore, the defects of the existing technology are the problems that need to be solved urgently for laser driving. Summary of the invention

[0006] The present invention aims to solve the deficiencies of the prior art and provides the following solutions:

[0007] A constant temperature and constant current semiconductor laser driving circuit with negative voltage overcurrent protection, comprising: a constant current source circuit, a temperature control circuit and an overcurrent protection circuit;

[0008] The constant current source circuit is used to provide a stable driving current for the semiconductor laser;

[0009] The temperature control circuit is used to achieve high-precision temperature control of the semiconductor laser;

[0010] The overcurrent protection circuit is used to protect the semiconductor laser from being damaged due to excessive drive current setting or current surge.

[0011] Preferably, the constant current source circuit includes: a first operational amplifier U1, a first peripheral proportional resistor R1, a second peripheral proportional resistor R2, a third peripheral proportional resistor R3, a fourth peripheral proportional resistor R4, a sampling resistor R test and MOS tubes;

[0012] The first peripheral proportional resistor R1 is connected to the second peripheral proportional resistor R2 and the inverting input terminal of the first operational amplifier U1 respectively;

[0013] The second peripheral proportional resistor R2 is also connected to the sampling resistor R test connect;

[0014] The sampling resistor R test Also connected to the drain of the MOS tube;

[0015] The third peripheral proportional resistor R3 is connected to the fourth peripheral proportional resistor R4 and the in-phase input terminal of the first operational amplifier U1 respectively;

[0016] The output end of the first operational amplifier U1 is connected to the gate of the MOS tube;

[0017] The fourth peripheral proportional resistor R4 is also connected to the drain of the MOS tube;

[0018] The sampling resistor R test The connection point between the fourth peripheral proportional resistor R4 and the drain of the MOS tube forms a voltage feedback point FB.

[0019] Preferably, the temperature control circuit adopts MAX1978 integrated temperature control chip.

[0020] Preferably, the overcurrent protection circuit includes: a second operational amplifier U2, a third operational amplifier U3, a fourth operational amplifier U4, a first voltage comparator U5, a second voltage comparator U6, a first Schottky diode D1, a second Schottky diode D2, a first resistor R5, a second resistor R6, a third resistor R7, a fourth resistor R8, a fifth resistor R9, a pull-down resistor R 10 , transistor Q3 and relay K1;

[0021] The non-inverting input terminal of the second operational amplifier U2 is connected to the voltage feedback point FB, the output terminal of the second operational amplifier U2 is connected to the first resistor R5, and the inverting input terminal of the second operational amplifier U2 is connected to the path between the output terminal of the second operational amplifier U2 and the first resistor R5;

[0022] The non-inverting input terminal of the third operational amplifier U3 is grounded, the inverting input terminal of the third operational amplifier U3 is connected to the first resistor R5, and the output terminal of the third operational amplifier U3 is connected to the first Schottky diode D1 and the second Schottky diode D2;

[0023] The first resistor R5 is also connected to the second resistor R6 and the third resistor R7 respectively, the second resistor R6 is also connected to the first Schottky diode D1 and the fourth resistor R8 respectively, and the third resistor R7 is also connected to the second Schottky diode D2 and the non-inverting input terminal of the fourth operational amplifier U4 respectively;

[0024] The inverting input terminal of the fourth operational amplifier U4 is connected to the fourth resistor R8 and the fifth resistor R9 respectively, and the output terminal of the fourth operational amplifier U4 is connected to the fifth resistor R9 and the non-inverting input terminal of the first voltage comparator U5 respectively;

[0025] The inverting input terminal of the first voltage comparator U5 inputs the current limiting voltage V 限流电压 The output end of the first voltage comparator U5 is respectively connected to the base of the transistor Q3 and the pull-down resistor R 10 connect;

[0026] The non-inverting input terminal of the second voltage comparator U6 inputs the setting voltage V in The inverting input terminal of the second voltage comparator U6 inputs the current limiting voltage V 限流电压 The output end of the second voltage comparator U6 is connected to the base of the transistor Q3 and the pull-down resistor R 10 connect;

[0027] The collector of the transistor Q3 is connected to the relay K1, and the emitter of the transistor Q3 is grounded;

[0028] The controlled end of the relay K1 is connected to the semiconductor laser.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The negative voltage overcurrent protection circuit designed for a bias circuit with a negative voltage has a wider application range, high reliability, and high-stability driving current control and temperature control for semiconductor lasers. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0032] Figure 1 is a circuit diagram of a constant current source circuit according to an embodiment of the present invention;

[0033] Figure 2is a circuit diagram of a conventional Howland current source according to an embodiment of the present invention;

[0034] Figure 3 A circuit diagram of a constant current source circuit composed of an operational amplifier and a triode according to an embodiment of the present invention;

[0035] Figure 4 A circuit diagram of a MAX1978 temperature control circuit according to an embodiment of the present invention;

[0036] Figure 5 4 is a circuit diagram of an overcurrent protection circuit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0037] 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.

[0038] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] Embodiment 1

[0040] In this embodiment, a constant temperature and constant current semiconductor laser driving circuit with negative voltage overcurrent protection includes: a constant current source circuit, a temperature control circuit and an overcurrent protection circuit.

[0041] The constant current source circuit is used to provide a stable driving current for the semiconductor laser.

[0042] In this embodiment, if Figure 1 As shown, the constant current source circuit includes: a first operational amplifier U1, a first peripheral proportional resistor R1, a second peripheral proportional resistor R2, a third peripheral proportional resistor R3, a fourth peripheral proportional resistor R4, a sampling resistor R test and MOS tube; the first peripheral proportional resistor R1 is connected to the second peripheral proportional resistor R2 and the inverting input terminal of the first operational amplifier U1 respectively; the second peripheral proportional resistor R2 is also connected to the sampling resistor R test Connection: sampling resistor R test The third peripheral proportional resistor R3 is connected to the fourth peripheral proportional resistor R4 and the in-phase input terminal of the first operational amplifier U1 respectively; the output terminal of the first operational amplifier U1 is connected to the gate of the MOS tube; the fourth peripheral proportional resistor R4 is also connected to the drain of the MOS tube; the sampling resistor R testThe connection point between the fourth peripheral proportional resistor R4 and the drain of the MOS tube forms a voltage feedback point FB.

[0043] Specifically, the design ideas of the constant current source circuit include:

[0044] First consider the traditional constant current source circuit. The traditional constant current source circuit can adopt the Howland constant current source circuit as shown in Figure 2 As shown. U1 is the first operational amplifier; R1, R2, R3 and R4 are the first peripheral proportional resistor, the second peripheral proportional resistor, the third peripheral proportional resistor and the fourth peripheral proportional resistor respectively. test is the sampling resistor, R L is the load resistance; VCC is the positive voltage, VEE is the negative voltage, V in It is the setting voltage for regulating the output current.

[0045] The output current of the Howland current source circuit is controlled by the input voltage. In the design, the resistors R1 = R3 and R2 = R4 make the resistance ratio of the two arms equal. According to the virtual short and virtual open properties of the operational amplifier, the current flowing through the load resistor can be deduced as follows:

[0046]

[0047] However, the disadvantage of the traditional Howland constant current source circuit is that the output current of the general precision op amp is small, and the load cannot be too large, otherwise it will affect the efficiency and accuracy of the constant current source. The use of precision op amps with high output current and slew rate can solve this problem, but its cost is high. Therefore, in order to improve the output current capability, a transistor Q1 can be added to the Howland constant current source circuit, such as Figure 3 As shown. It can be seen that this circuit is Figure 2 The transistor Q1 is added to the circuit to expand the current. The actual principle is that when the sampling resistor R test When the voltage changes, it is directly fed back to the inverting input of the operational amplifier. The difference between the voltage and the non-inverting input voltage is amplified by the operational amplifier, and the output controls the base current of the transistor to change the internal resistance of the transistor, thereby changing the voltage drop between the emitter and the collector, so that the voltage of the sampling resistor remains unchanged, so as to achieve the purpose of constant load current. The current flowing through the load (here is the laser diode) is still the same as formula (1). However, the transistor is a current-controlled current device. After the transistor is turned on, the current flowing through the sampling resistor is not entirely the load current, but also the base current. Therefore, for a high-precision constant current source, the use of the transistor will have a certain error. This problem can be solved by using MOS tubes, because MOS tubes are voltage-controlled voltage devices, and their on-resistance is very small, basically at the milliohm level. Compared with transistors, their power consumption will be smaller. At the same time, it has a wider range of applications for laser drive design. The circuit is designed as a negative voltage drive. Its schematic diagram is as follows Figure 1 As shown: Q2 is a MOS tube. It can be seen that the circuit changes the voltage range from positive voltage to negative voltage, but the current direction does not change. The current flowing through the laser diode is still the same as formula (1). This embodiment adopts an operational amplifier + MOS tube negative voltage constant current source circuit, and the setting voltage for adjusting the output current can be provided by a reference voltage source or by using an external MCU to control a digital-to-analog converter. This embodiment is mainly designed for a semiconductor laser (LD) in a butterfly package (DFB), and the DC bias current required by a general LD ​​is in the range of 35-150mA, so the driving current range of this embodiment is in the range of 0-150mA, but the driving current range can be modified according to different laser requirements.

[0048] The temperature control circuit is used to realize high-precision temperature control of semiconductor lasers. The temperature control circuit adopts MAX1978 integrated temperature control chip.

[0049] In this embodiment, the change in temperature will cause a certain drift in the wavelength and power of the light. As the temperature increases, the output wavelength of the DFB laser will also change, and its typical change value is about 0.3-0.4nm / ℃, and the optical power will also decrease. Therefore, it is very necessary to control the temperature stability of the LD and set the temperature with high precision. A negative temperature coefficient (NTC) thermistor is generally integrated inside the LD. The feedback voltage of the thermistor can be obtained through a bridge circuit and compared with the reference voltage of the set temperature. According to the comparison result, the current size and flow direction of the built-in semiconductor refrigeration chip (TEC) can be accurately adjusted, thereby realizing the cooling or heating of the TEC to control the temperature of the LD.

[0050] MAX1978 is an integrated temperature control chip with the advantages of small size, safety, high precision, and complete TEC control module. MAX1978 also integrates an ultra-low drift chopper amplifier and a high-precision integral amplifier to form a proportional integral differential (PID) controller to maintain a temperature stability of ±0.001°C. The instrumentation amplifier can be connected to an external NTC or PTC thermistor, thermocouple, or semiconductor temperature sensor to provide analog output to monitor the temperature and current of the TEC. The feedback voltage value of the thermistor is compared with the set temperature voltage value, and then compensated by the PID controller and then enters the pulse width modulation controller to drive the field effect tube to control the TEC to achieve temperature control. The specific temperature control schematic diagram is as follows Figure 4 shown.

[0051] The overcurrent protection circuit is used to protect the semiconductor laser from being damaged by drastic changes in current.

[0052] The overcurrent protection circuit includes: a second operational amplifier U2, a third operational amplifier U3, a fourth operational amplifier U4, a first voltage comparator U5, a second voltage comparator U6, a first Schottky diode D1, a second Schottky diode D2, a first resistor R5, a second resistor R6, a third resistor R7, a fourth resistor R8, a fifth resistor R9, a pull-down resistor R 10 , transistor Q3 and relay K1.

[0053] The non-inverting input terminal of the second operational amplifier U2 is connected to the voltage feedback point, the output terminal of the second operational amplifier U2 is connected to the first resistor R5, and the inverting input terminal of the second operational amplifier U2 is connected to the path between the output terminal of the second operational amplifier U2 and the first resistor R5; the non-inverting input terminal of the third operational amplifier U3 is grounded, the inverting input terminal of the third operational amplifier U3 is connected to the first resistor R5, and the output terminal of the third operational amplifier U3 is connected to the first Schottky diode D1 and the second Schottky diode D2; the first resistor R5 is also connected to the second resistor R6 and the third resistor R7 respectively, the second resistor R6 is also connected to the first Schottky diode D1 and the fourth resistor R8 respectively, and the third resistor R7 is also connected to the second Schottky diode D2 and the non-inverting input terminal of the fourth operational amplifier U4 respectively; the inverting input terminal of the fourth operational amplifier U4 is connected to the fourth resistor R8 and the fifth resistor R9 respectively, and the output terminal of the fourth operational amplifier U4 is connected to the fifth resistor R9 and the non-inverting input terminal of the first voltage comparator U5 respectively; the inverting input terminal of the first voltage comparator U5 inputs the current limiting voltage V 限流电压 The output terminal of the first voltage comparator U5 is connected to the base of the transistor Q3 and the pull-down resistor R 10 Connect; Input the setting voltage V to the non-inverting input terminal of the second voltage comparator U6 in The inverting input terminal of the second voltage comparator U6 inputs the current limiting voltage V 限流电压 The output terminal of the second voltage comparator U6 is connected to the base of the transistor Q3 and the pull-down resistor R 10 The collector of the transistor Q3 is connected to the relay K1, and the emitter of the transistor Q3 is grounded; the controlled end of the relay K1 is connected to the semiconductor laser.

[0054] In this embodiment, the overcurrent protection circuit is divided into two parts, one part is the front-end protection, i.e. the delayed power-on circuit, and the other part is the back-end protection, i.e. the overcurrent protection circuit. At the front end, in order to prevent the peaks and pulses of the current waveform from damaging the LD at the moment of power-on, the zero-output zero-state response of the resistor-capacitor circuit and the charging and discharging principle of the capacitor are used to make the voltage rise in a buffered manner during the start-up process of the circuit to protect the LD. The focus of this invention is to provide overcurrent protection for the LD at the load end, connect the LD in parallel with another branch of the controlled end with relay K1, when the load end current is within the normal range, the transistor Q3 is in a high-impedance state, the relay K1 is in a normally open state, and the laser works normally; when the load end current exceeds the set protection current value, the overcurrent protection circuit will immediately turn on the transistor Q3, the relay K1 branch is turned on, and the LD is short-circuited, thereby protecting the LD. The overcurrent protection circuit is as follows Figure 5 As shown, its input FB is the negative voltage side voltage feedback point, U2, U3 and U4 are the second operational amplifier, the third operational amplifier and the fourth operational amplifier respectively, D1 and D2 are the first Schottky diode and the second Schottky diode respectively, U5 and U6 are the first voltage comparator and the second voltage comparator respectively, Q3 is a transistor, K1 is a relay, R 10 is a pull-down resistor to ensure that the initial level is low. In this embodiment, U2 is used as a voltage follower, and U2, U3, U4, D1, D2, R5, R6, R7, R8 and R9 constitute an absolute value circuit.

[0055] Overcurrent protection mainly has two aspects. On the one hand, at the front end setting voltage, there is a setting voltage for adjusting the output current in the constant current source circuit. From formula (1), it can be known that the output current I load The voltage V in Because this voltage is a positive voltage, in order to prevent the set current from being greater than the limit current value, the set voltage corresponding to the adjusted output current is compared with the voltage value corresponding to the limit current through the first voltage comparator U5 to control the disconnection of the transistor Q3, that is, the opening and closing of the relay K1 to protect the LD; on the other hand, feedback is performed at the load end. If the front-end voltage is set within the safety range, but the output end suddenly encounters an excessive current, feedback can be performed from the negative voltage side. After the feedback point, the voltage follower U2 is used. Its high input impedance and low output impedance characteristics can play a good buffering and isolation role. Since the voltage is extracted from the negative voltage side, an absolute value circuit is added to rectify the voltage into a positive voltage, and then the voltage value is compared through the second voltage comparator U6 to control the disconnection of the transistor Q3, thereby controlling the opening and closing of the relay K1 branch to protect the LD.

[0056] Embodiment 2

[0057] In this embodiment, the constant current source circuit and the overcurrent protection circuit are analyzed. Since the temperature control circuit uses the integrated temperature control chip MAX1978, the feedback voltage of the thermistor is obtained through the bridge circuit and compared with the reference voltage of the set temperature to achieve temperature control, no detailed explanation is needed.

[0058] 1. Constant current source circuit analysis

[0059] First, the output current of the constant current source is adjusted by controlling the DAC output voltage through an external reference voltage source or an external MCU, and then the constant current source is composed of an op amp and a MOS tube to achieve a stable constant current output. Figure 1 In the figure, V- is the inverting input voltage of the first operational amplifier U1, V + is the voltage at the non-inverting input terminal of the first operational amplifier U1, V test is the sampling resistor R test The high potential voltage, V FB is the sampling resistor R test The low potential voltage is the feedback voltage point, from which feedback is given to the overcurrent protection circuit. According to the virtual short and virtual open characteristics of the operational amplifier, the current through the first peripheral proportional resistor R1 and the second peripheral proportional resistor R2 are of the same magnitude and direction, so it can be listed as follows:

[0060]

[0061] Similarly, the currents passing through the third peripheral proportional resistor R3 and the fourth peripheral proportional resistor R4 have the same magnitude and direction, which can be listed as follows:

[0062]

[0063] Arranging formulas (2) and (3) yields:

[0064]

[0065] Because of the virtual short and virtual break characteristics, V + =V - When R2 / R1=R4 / R3, we can deduce:

[0066]

[0067] Then the sampling resistor R test The voltage across both ends can be obtained, so when the second peripheral proportional resistor R2 is much larger than the load internal resistance in parameter setting, the current passing through the load can be obtained as:

[0068]

[0069] Because V GND=0, so the load current, i.e. the current passing through LD, can be obtained as formula (1). At this time, the voltage at the feedback point should be:

[0070] V FB =VEE+V DS (7)

[0071] Among them, V DS is the voltage between the drain and source of the MOS tube. The principle of constant current is: when the sampling resistor R test When the voltage changes, it is fed back to the inverting input terminal of the op amp, and the difference between the voltage and the non-inverting input terminal is amplified by the op amp, and the output controls the gate voltage of the MOS tube to change the voltage between the drain and the source, thereby making the sampling resistor R test The voltage across the terminals remains constant, keeping the load current constant.

[0072] 2. Overcurrent protection circuit analysis

[0073] The schematic diagram of the overcurrent protection circuit is Figure 5 , the overcurrent protection circuit at the load end first protects Figure 3 The feedback voltage point FB in the circuit is input into the voltage follower U2, whose high input impedance and low output impedance can play a buffering and isolating role, ensuring that the load current is not disturbed by the subsequent stage. The voltage values ​​of the input and output of the voltage follower are approximately equal, and the feedback voltage value is extracted and entered into the absolute value circuit.

[0074] Absolute value circuit principle: When the input voltage is positive, since the third operational amplifier U3, the first resistor R5 and the second resistor R6 form an inverting amplifier circuit, the output of the third operational amplifier U3 is a negative voltage, then the second Schottky diode D2 is turned off, the first Schottky diode D1 is turned on, and the in-phase input of the fourth operational amplifier U4 is in a high impedance state, and the current will not flow through the following branch. In the overcurrent protection circuit diagram, R5=R6=R7=R8=R9, so the third operational amplifier U3 and the fourth operational amplifier U4 are two 1:1 inverting amplifier circuits, then after two reverses, the output is still a positive voltage of the same voltage value; when the input voltage is negative, after passing through the inverting amplifier circuit of the third operational amplifier U3, the voltage at the output of the third operational amplifier U3 is a positive voltage, then the second Schottky diode D2 is turned on, the first Schottky diode D1 is turned off, and the current of the first resistor R5 is output by the output terminal V of the fourth operational amplifier U4 o The sum of the current from the output of the third operational amplifier U3 to the inverting input terminal of the third operational amplifier U3 and the current from the output of the third operational amplifier U3 to the inverting input terminal of the third operational amplifier U3, and the non-inverting input terminal of the third operational amplifier U3 is grounded. According to the virtual short and virtual break characteristics of the operational amplifier, it can be obtained:

[0075]

[0076] The output voltage is the opposite of the input voltage. This realizes the absolute value circuit. After passing through the absolute value circuit, it enters the comparator and is compared with the set voltage value corresponding to the protection current to control the transistor to turn off, thereby controlling the relay K1 to open and close to protect LD. At the front end setting voltage, the set voltage is directly compared with the set voltage value corresponding to the protection current to control the transistor Q3 to turn off and the relay K1 to open and close, thereby protecting LD.

[0077] Embodiment 3

[0078] In this embodiment, the laser driving circuit designed by the present invention is tested. In the constant current source output current stability test, due to R test The load laser diode is in the same path, so by measuring R test The voltage at both ends can be converted to the corresponding output current, and a constant current stability test is performed on it for 1 hour. The output current is set to 76.96mA. After statistical analysis, the average LD current is 76.96296mA and the standard deviation is 0.036264; the output current is set to 88.80mA, the average output current is 88.797mA, and the standard deviation is 0.031764. In the temperature stability test, the laser temperature is set to 25℃, and the data is collected for 1 hour. The laser temperature fluctuates within 0.01℃; in the LD overcurrent protection test, when the output current setting voltage exceeds the protection current limiting voltage setting value, the laser is short-circuited, which is consistent with the expected design.

[0079] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A constant temperature and constant current semiconductor laser drive circuit with negative voltage overcurrent protection, characterized in that: include: Constant current source circuit, temperature control circuit and overcurrent protection circuit; The constant current source circuit is used to provide a stable driving current for the semiconductor laser; The temperature control circuit is used to achieve high-precision temperature control of the semiconductor laser; The overcurrent protection circuit is used to protect the semiconductor laser from being damaged due to excessive drive current or sudden current increase; The constant current source circuit includes: a first operational amplifier U1, a first peripheral proportional resistor R1, a second peripheral proportional resistor R2, a third peripheral proportional resistor R3, a fourth peripheral proportional resistor R4, a sampling resistor R test and MOS tubes; The first peripheral proportional resistor R1 is connected to the second peripheral proportional resistor R2 and the inverting input terminal of the first operational amplifier U1 respectively; The second peripheral proportional resistor R2 is also connected to the sampling resistor R test connect; The sampling resistor R test Also connected to the drain of the MOS tube; The third peripheral proportional resistor R3 is connected to the fourth peripheral proportional resistor R4 and the in-phase input terminal of the first operational amplifier U1 respectively; The output end of the first operational amplifier U1 is connected to the gate of the MOS tube; The fourth peripheral proportional resistor R4 is also connected to the drain of the MOS tube; The sampling resistor R test , the connection point between the fourth peripheral proportional resistor R4 and the drain of the MOS tube forms a voltage feedback point FB; The cathode of the semiconductor laser is connected to the second peripheral proportional resistor R2 and the sampling resistor R test A path therebetween, the positive electrode of the semiconductor laser is grounded; The voltage feedback point FB is input to the overcurrent protection circuit.

2. A constant temperature and constant current semiconductor laser driving circuit with negative voltage overcurrent protection according to claim 1, characterized in that: The temperature control circuit adopts the MAX1978 integrated temperature control chip.

3. The constant temperature and constant current semiconductor laser driving circuit with negative voltage overcurrent protection according to claim 1, characterized in that: The overcurrent protection circuit includes: a second operational amplifier U2, a third operational amplifier U3, a fourth operational amplifier U4, a first voltage comparator U5, a second voltage comparator U6, a first Schottky diode D1, a second Schottky diode D2, a first resistor R5, a second resistor R6, a third resistor R7, a fourth resistor R8, a fifth resistor R9, a pull-down resistor R 10 , transistor Q3 and relay K1; The non-inverting input terminal of the second operational amplifier U2 is connected to the voltage feedback point FB, the output terminal of the second operational amplifier U2 is connected to the first resistor R5, and the inverting input terminal of the second operational amplifier U2 is connected to the path between the output terminal of the second operational amplifier U2 and the first resistor R5; The non-inverting input terminal of the third operational amplifier U3 is grounded, the inverting input terminal of the third operational amplifier U3 is connected to the first resistor R5, and the output terminal of the third operational amplifier U3 is connected to the first Schottky diode D1 and the second Schottky diode D2; The first resistor R5 is also connected to the second resistor R6 and the third resistor R7 respectively, the second resistor R6 is also connected to the first Schottky diode D1 and the fourth resistor R8 respectively, and the third resistor R7 is also connected to the second Schottky diode D2 and the non-inverting input terminal of the fourth operational amplifier U4 respectively; The inverting input terminal of the fourth operational amplifier U4 is connected to the fourth resistor R8 and the fifth resistor R9 respectively, and the output terminal of the fourth operational amplifier U4 is connected to the fifth resistor R9 and the non-inverting input terminal of the first voltage comparator U5 respectively; The inverting input terminal of the first voltage comparator U5 inputs the current limiting voltage V 限流电压 The output end of the first voltage comparator U5 is respectively connected to the base of the transistor Q3 and the pull-down resistor R 10 connect; The non-inverting input terminal of the second voltage comparator U6 inputs the setting voltage V in The inverting input terminal of the second voltage comparator U6 inputs the current limiting voltage V 限流电压 The output end of the second voltage comparator U6 is connected to the base of the transistor Q3 and the pull-down resistor R 10 connect; The collector of the transistor Q3 is connected to the relay K1, and the emitter of the transistor Q3 is grounded; The controlled end of the relay K1 is connected to the semiconductor laser.

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