阅读说明：本技术 电压自适应激光器驱动电路及其控制方法 (Voltage adaptive laser driving circuit and control method thereof ) 是由 胡肖松 骈冰 戢冰 张武杰 于 2021-02-25 设计创作，主要内容包括：本申请公开了一种电压自适应激光器驱动电路及其控制方法,电路包括：开关电源(1),激光器(2),恒流驱动电路(3),电流设置电路(4),MCU控制电路(5),电压采集电路(6),电压设置电路(7)；所述开关电源(1),分别与所述激光器(2)和所述电压设置电路(7)相连,用于为所述激光器(2)和所述电压设置电路(7)提供电能；所述激光器(2),分别与所述开关电源(1)和所述恒流驱动电路(3)相连,用于产生激光。本发明通过MCU控制电路对电压采集电路和电压设置电路的PID调节,实现开关电源的输出电压根据激光器和恒流电路的工作状态自适应变化,以及通过MCU控制电路对电流设置电路的调节实现PWM高速频闪功能。(The application discloses voltage self-adaptation laser drive circuit and control method thereof, the circuit includes: the device comprises a switching power supply (1), a laser (2), a constant current driving circuit (3), a current setting circuit (4), an MCU control circuit (5), a voltage acquisition circuit (6) and a voltage setting circuit (7); the switching power supply (1) is respectively connected with the laser (2) and the voltage setting circuit (7) and is used for providing electric energy for the laser (2) and the voltage setting circuit (7); the laser (2) is respectively connected with the switching power supply (1) and the constant current driving circuit (3) and is used for generating laser. According to the invention, the MCU control circuit is used for PID regulation of the voltage acquisition circuit and the voltage setting circuit, so that the output voltage of the switching power supply can be changed in a self-adaptive manner according to the working states of the laser and the constant current circuit, and the MCU control circuit is used for regulating the current setting circuit so as to realize the PWM high-speed stroboscopic function.)

1. A voltage adaptive laser driver circuit, comprising: the device comprises a switching power supply (1), a laser (2), a constant current driving circuit (3), a current setting circuit (4), an MCU control circuit (5), a voltage acquisition circuit (6) and a voltage setting circuit (7);

the switching power supply (1) is respectively connected with the laser (2) and the voltage setting circuit (7) and is used for providing electric energy for the laser (2) and the voltage setting circuit (7);

the laser (2) is respectively connected with the switching power supply (1) and the constant current driving circuit (3) and is used for generating light;

the constant current driving circuit (3) is respectively connected with the laser (2) and the current setting circuit (4) and is used for controlling the current flowing through the laser (2) to be constant current;

the current setting circuit (4) is respectively connected with the constant current driving circuit (3) and the MCU control circuit (5) and is used for correspondingly outputting analog voltage according to the output current of the constant current driving circuit (3);

the MCU control circuit (5) is respectively connected with the current setting circuit (4), the voltage acquisition circuit (6) and the voltage setting circuit (7) and is used for realizing numerical control adjustment of the voltage self-adaptive laser driving circuit;

the voltage acquisition circuit (6) is connected with the MCU control circuit (5) and is used for acquiring analog voltage to realize digital control;

and the voltage setting circuit (7) is respectively connected with the MCU control circuit (5) and the switching power supply (1) and is used for outputting voltage to the switching power supply (1) to realize linear regulation of the output voltage.

2. The voltage adaptive laser driving circuit according to claim 1, wherein the current setting circuit (4) further comprises a digitally controlled analog voltage setting circuit and a selection output circuit; the current setting circuit (4) further comprises a multi-channel DA chip and a multi-channel analog switch chip, and the DA chip outputs voltage to the analog switch chip.

3. The voltage adaptive laser driving circuit according to claim 1, wherein the constant current driving circuit (3) is a current series negative feedback structure; the voltage of the current sampling resistor is connected to the input cathode of the operational amplifier; the output signal of the current setting circuit (4) is connected to one end of a current limiting resistor, the other end of the current limiting resistor is connected to the input anode of the operational amplifier, and the output signal of the operational amplifier is connected to the grid electrode of the power MOS tube.

4. The voltage adaptive laser driving circuit according to claim 1, wherein the constant current driving circuit (3) is a current parallel negative feedback structure; one end of the parallel resistor is connected with the negative input end of the operational amplifier, and the other end of the parallel resistor is connected with the input end of the current sampling resistor; one end of the current-limiting resistor is connected with an output signal of the analog switch chip, the other end of the current-limiting resistor is connected with an input cathode of the operational amplifier, an anode of the operational amplifier is connected with an output terminal of the reference voltage chip, and an output signal of the operational amplifier is connected with a grid electrode of the power MOS tube.

5. The voltage adaptive laser driving circuit according to claim 1, wherein the MCU control circuit (5) is further configured to perform PID setting on the output voltages of the voltage setting circuit (7) and the switching power supply (1).

6. The voltage adaptive laser driving circuit according to claim 1, wherein the switching power supply (1) further comprises: the input voltage VCC, the output voltage OUT, the RESET signal RESET, and the voltage regulation pin FB.

7. The voltage adaptive laser driving circuit according to claim 1, wherein the laser (2) is a laser driven by a constant current.

8. The voltage adaptive laser driving circuit according to claim 1, wherein the constant current driving circuit (3) is configured in a linear constant current control manner, and the topological structure of the constant current driving circuit is a current series negative feedback structure or a current parallel negative feedback structure.

9. The voltage adaptive laser driving circuit according to claim 1, wherein the voltage setting circuit (7) further comprises: and the output end of the DA conversion circuit is connected with one end of a voltage setting resistor, and the other end of the voltage setting resistor is connected with the switching power supply (1).

10. A control method of a voltage adaptive laser driving circuit is characterized by comprising the following steps:

step 1, after starting up, the input voltage VFB of the switching power supply (1) is 0V, and the output voltage Vout of the switching power supply (1) is set to be the maximum value at the moment;

step 2, selecting the maximum output step current Imax in the step current flowing through the laser (2) according to the step current value configured by the user, and controlling the output voltage in the period;

step 3, a voltage acquisition circuit (6) acquires input voltage VLD + of the laser (2), output voltage VLD-of the laser (2), and voltage VRS of a sampling resistor of the constant current drive circuit (3), and calculates working voltage VLD at two ends of the laser (2);

step 4, calculating the power heat dissipation of an MOS tube in the constant current driving circuit (3);

step 5, determining the voltage drop VDS of the drain electrode and the source electrode of the MOS tube according to the preset value PH of the power heat dissipation of the MOS tube in the constant current driving circuit (3);

step 6, calculating the output voltage Vout of the switching power supply (1);

7, calculating the value of the output voltage VT of the DA chip of the voltage setting circuit (7), and then controlling the output voltage VT of the DA chip of the voltage setting circuit (7) by the MCU control circuit (5) in a way of gradually increasing the VT;

and 8, controlling the voltage acquisition circuit (6) to sample the working voltage of each point again through the MCU control circuit (5), and comparing the actual power consumption and the preset power consumption of the MOS tube according to the output voltage Vout of the switching power supply (1) and the VT value of the DA chip of the voltage setting circuit (7) to realize the closed-loop control of the output voltage value PID.

11. The control method of the voltage adaptive laser driving circuit according to claim 10, wherein the closed-loop control of the output voltage value PID is realized, and further comprising a MCU control circuit (5) controlling the switching power supply (1), the laser (2), the constant current driving circuit (3), the voltage acquisition circuit (6), and the voltage setting circuit (7) to output the voltage and realize the circuit regulation.

Technical Field

The invention relates to the technical field of laser driving circuits, in particular to a voltage-adaptive numerical control laser constant-current driving circuit and a control method thereof.

Background

Lasers are currently widely used in people's daily life, industrial production, medical instruments, aerospace, special equipment or military weapons. The laser is usually an LD semiconductor laser, and has been widely used in the fields of long-distance fiber communication, wireless communication, laser marking, laser ranging, laser radar, laser weapons, and the like because of its mature production process and relatively low cost.

The LD laser is generally driven by a constant current, generally, the output current of the laser is a constant current or a PWM modulated current signal, and the amplitude of the driving current is generally constant; in addition, the general laser has poor surge resistance, and a large surge current or current overshoot occurs during operation, which tends to reduce the lifetime of the laser or damage the laser.

In some special application occasions, such as laser marking, laser radar and laser weapons, the pulse width of the driving constant current of a laser is often required to be controllable, and the current value of the driving constant current is adjustable. In other application occasions, the constant current driving circuit of the laser is required to be capable of meeting the requirement that lasers of different types are directly connected for use, or a plurality of lasers are required to be connected in series to improve the output power of laser of the whole system, so that the circuit is required to be capable of using the working voltage of the lasers of different types and outputting adjustable current and pulse.

Products or schemes in the prior art involve constant current drive circuits for some lasers. For example, document CN109950790A "a laser control circuit, a laser device" proposes a constant current driving circuit for realizing laser operations with different junction voltages, but this scheme can only output a constant current, and the power supply voltage adjustment is adjusted by an external adjustable resistor; document CN111355121A "double-pulse laser driving system, driving circuit and driving method" proposes a circuit and method for constant current driving of double-pulse LD laser, but the power supply of this scheme is not adjustable, and two input signals are needed to control to generate double pulses, which limits the application thereof; document CN110445011A "a laser power supply constant current driving circuit and method" mainly solves the problems of stability and service life of the laser, and does not consider the working efficiency of the laser and the application of PWM pulse width modulation; document CN105208739B "constant current driving device for laser light source" proposes a constant current output laser driving circuit powered by DC/DC power supply, which does not implement the adjustment of laser voltage and the PWM pulse width modulation of laser.

Disclosure of Invention

The invention aims to solve the technical problem of providing a laser constant current driving circuit which is adaptive to the working voltage of a laser and has a PWM (pulse width modulation) output function. The circuit adopts four AD chips to collect input power supply voltage, laser anode voltage, laser cathode voltage and voltage on a sampling resistor, the voltage is input to the MCU after voltage following and AD sampling as parameters of PID adjustment, and the output voltage of the switching power supply is fed back and controlled to control the voltage drop of a power MOS tube in a constant current driving circuit, thereby reducing heat dissipation and realizing higher efficiency; meanwhile, an analog switch chip is used as a control switch of a PWM signal, the output voltage of the multi-path DA conversion circuit is used as a reference value of output current, and the pulse width and frequency setting is realized by adopting the MCU, so that stroboflash and step current regulation can be easily realized.

In order to solve the above technical problem, the present invention further provides a voltage adaptive laser driving circuit, including: the device comprises a switching power supply 1, a laser 2, a constant current driving circuit 3, a current setting circuit 4, an MCU control circuit 5, a voltage acquisition circuit 6 and a voltage setting circuit 7;

the switching power supply 1 is respectively connected with the laser 2 and the voltage setting circuit 7 and is used for providing electric energy for the laser 2 and the voltage setting circuit 7;

the laser 2 is respectively connected with the switching power supply 1 and the constant current driving circuit 3 and is used for generating light;

the constant current driving circuit 3 is respectively connected with the laser 2 and the current setting circuit 4, and is used for controlling the current flowing through the laser 2 to be constant current;

the current setting circuit 4 is respectively connected with the constant current driving circuit 3 and the MCU control circuit 5, and is used for correspondingly outputting analog voltage according to the output current of the constant current driving circuit 3;

the MCU control circuit 5 is respectively connected with the current setting circuit 4, the voltage acquisition circuit 6 and the voltage setting circuit 7 and is used for realizing numerical control adjustment of the voltage adaptive laser driving circuit;

the voltage acquisition circuit 6 acquires the output voltage of the switching power supply 1, the input voltage of the laser 2, the output voltage of the laser 2 and the voltage of the sampling resistor in the constant current drive circuit 3, supplies the acquired voltages to the MCU control circuit 5, and is used for acquiring analog voltage to realize digital control;

and the voltage setting circuit 7 is respectively connected with the MCU control circuit 5 and the switching power supply 1 and is used for outputting voltage to the switching power supply 1 to realize linear regulation of the output voltage.

Preferably, the current setting circuit 4 further comprises a digitally controlled analog voltage setting and selection output circuit; the current setting circuit 4 further comprises a multi-channel DA chip and a multi-channel analog switch chip, wherein the DA chip outputs voltage to the analog switch chip.

Preferably, the constant current driving circuit 3 is a current series negative feedback structure; the voltage of the current sampling resistor is connected to the input cathode of the operational amplifier; the output signal of the current setting circuit 4 is connected to one end of a current limiting resistor, the other end of the current limiting resistor is connected to the input anode of the operational amplifier, and the output signal of the operational amplifier is connected to the grid electrode of the power MOS tube.

Preferably, the constant current driving circuit 3 is a current parallel negative feedback structure; one end of the parallel resistor is connected with the negative input end of the operational amplifier, and the other end of the parallel resistor is connected with the input end of the current sampling resistor; one end of the current-limiting resistor is connected with an output signal of the analog switch chip, the other end of the current-limiting resistor is connected with an input cathode of the operational amplifier, an anode of the operational amplifier is connected with an output terminal of the reference voltage chip, and an output signal of the operational amplifier is connected with a grid electrode of the power MOS tube.

Preferably, the MCU control circuit 5 is further configured to perform PID setting on the output voltages of the voltage setting circuit 7 and the switching power supply 1.

Preferably, the switching power supply 1 further includes: the input voltage VCC, the output voltage OUT, the RESET signal RESET, and the voltage regulation pin FB.

Preferably, the laser 2 is a laser driven by a constant current.

Preferably, the constant current driving circuit 3 is set in a linear constant current control manner, and the topological structure thereof is a current series negative feedback structure or a current parallel negative feedback structure.

Preferably, the voltage setting circuit 7 further includes: and the output end of the DA conversion circuit is connected with one end of a voltage setting resistor, and the other end of the voltage setting resistor is connected with the switching power supply 1.

In order to solve the above technical problem, the present invention further provides a method for controlling a voltage adaptive laser driving circuit, comprising the following steps:

step 1, after starting up, the input voltage VFB of the switching power supply 1 is 0V, and at this time, the output voltage Vout of the switching power supply 1 is set to be the maximum value;

step 2, selecting the maximum output step current Imax in the step current flowing through the laser 2 according to the step current value configured by the user, and controlling the output voltage in the period;

step 3, the voltage acquisition circuit 6 acquires the input voltage VLD + of the laser 2, the output voltage VLD + of the laser 2 and the voltage VRS of the sampling resistor of the constant current drive circuit 3, and calculates the working voltage VLD at two ends of the laser 2;

step 4, calculating the power heat dissipation of the MOS tube in the constant current driving circuit 3;

step 5, determining the voltage drop VDS of the drain and the source of the MOS tube according to the preset value PH of the power heat dissipation of the MOS tube in the constant current driving circuit 3;

step 6, calculating the output voltage Vout of the switching power supply 1;

step 7, calculating the value of the output voltage VT of the DA chip of the voltage setting circuit 7, and then controlling the output voltage VT of the DA chip of the voltage setting circuit 7 by the MCU control circuit 5 in a way of gradually increasing the VT;

and 8, controlling the voltage acquisition circuit 6 to sample the working voltage of each point again through the MCU control circuit 5, and comparing the actual power consumption and the preset power consumption of the MOS tube according to the output voltage Vout of the switching power supply 1 and the VT value of the DA chip of the voltage setting circuit 7 to realize the closed-loop control of the output voltage value PID.

Wherein: VFB is the input voltage of the switching power supply 1; vout is the output voltage of the switching power supply 1; imax is the maximum output step current of the step currents flowing through the laser 2; VLD + is the laser 2 input voltage; VLD-is the laser 2 output voltage; VRS is the voltage of the sampling resistor of the constant current driving circuit 3; VLD is the operating voltage across the laser 2; the VDS is the voltage drop of the drain electrode and the source electrode of the MOS tube in the constant current driving circuit 3; VT is the output voltage of the DA chip of the voltage setting circuit 7.

Preferably, the closed-loop control for realizing the output voltage value PID further comprises an MCU control circuit 5 controlling the switching power supply 1, the laser 2, the constant current driving circuit 3, the voltage collecting circuit 6, and the voltage setting circuit 7 to output the voltage and realize the circuit regulation.

The beneficial effects of the invention include:

(1) the current setting circuit adopts the output voltage of the multi-channel DA conversion circuit as the reference value of the output current, the pulse width and the current are selected through the analog switch circuit, the pulse amplitude of the laser is adjusted by step current, the pulse width is independently set, and the amplitude, the pulse width and the frequency of the output current can be accurately controlled through the MCU.

(2) The MCU control circuit controls the voltage setting circuit and the output voltage of the switching power supply to perform PID feedback regulation, and controls the switching power supply, the laser, the constant current driving circuit, the voltage acquisition circuit and the voltage setting circuit to perform switching power supply output voltage regulation.

(3) The voltage acquisition circuit acquires four paths of AD voltages and feeds the four paths of AD voltages back to the MCU for numerical control PID adjustment, so that the output voltage of the switching power supply can be automatically adjusted according to the working voltage of the laser and the voltage drop of the drain electrode and the source electrode of the MOS tube, and the characteristic of high efficiency is achieved.

(4) Two constant current source control circuits are provided, one is a current series negative feedback circuit, and the other is a current parallel negative feedback output circuit, so that the application of most linear constant current driving in a laser can be met.

Drawings

In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below, it is obvious that the drawings in the following description are only a part of the embodiments or prior art, and other similar or related drawings can be obtained by those skilled in the art without creative efforts.

Fig. 1 is a block diagram of a voltage adaptive laser driving circuit according to an embodiment of the present invention.

Fig. 2 is a circuit diagram of an implementation manner of the voltage adaptive laser driving circuit according to the embodiment of the invention.

Fig. 3 is a circuit diagram of a second implementation manner of the voltage adaptive laser driving circuit according to the embodiment of the invention.

Fig. 4 is a block diagram of an internal implementation of the switching power supply according to the embodiment of the present invention.

Fig. 5 is a flowchart of a control method for adjusting the digital control function of the output voltage according to the embodiment of the present invention.

Detailed Description

The present invention will be described in detail with reference to examples. The present invention will be described in further detail below to make the objects, aspects and advantages of the present invention clearer and more clear, but the present invention is not limited to these examples.

The invention relates to a voltage self-adaptive constant-current driving circuit of a numerical control laser, which comprises a switching power supply 1, a laser 2, a constant-current driving circuit 3, a current setting circuit 4, an MCU (microprogrammed control unit) control circuit 5, a voltage acquisition circuit 6 and a voltage setting circuit 7, wherein the switching power supply is connected with the laser 2 through the MCU control circuit; the MCU control circuit 5 realizes the numerical control adjustment of the system, the voltage acquisition circuit 6 is a digital control four-channel analog voltage acquisition circuit, the current setting circuit 4 provides output voltage for the constant current drive circuit to realize constant current output, and the voltage setting circuit 7 outputs voltage for the switching power supply to realize self-adaptive adjustment according to the characteristics of the working voltage of the laser. According to the invention, the MCU control circuit is used for PID regulation of the voltage acquisition circuit and the voltage setting circuit, so that the output voltage of the switching power supply can be changed in a self-adaptive manner according to the working states of the laser and the constant current circuit, and the MCU control circuit is used for regulating the current setting circuit so as to realize the PWM high-speed stroboscopic function.

The voltage acquisition circuit 6 acquires the output voltage of the switching power supply 1, the input voltage of the laser 2, the output voltage of the laser 2 and the voltage of the sampling resistor in the constant current drive circuit 3, supplies the acquired voltages to the MCU control circuit 5, and is used for acquiring analog voltages to realize digital control.

Example 1:

fig. 1 is a block diagram of a voltage adaptive laser driving circuit according to an embodiment of the present invention. The laser driving circuit comprises a switching power supply 1, a laser 2, a constant current driving circuit 3, a current setting circuit 4, an MCU control circuit 5, a voltage acquisition circuit 6 and a voltage setting circuit 7.

The switching power supply supplies power to the laser, the implementation mode of the switching power supply can be in various modes, a non-isolated topological structure or an isolated switching power supply topological structure can be adopted, and the switching power supply is characterized in that the external representation of the switching power supply comprises an input voltage VCC, an output voltage OUT, a RESET signal RESET and a voltage regulation pin FB.

The laser is an LD laser or other type of laser driven by constant current; the laser can also adopt the external terminal form, by the laser instrument of user's access its needs according to the demand.

The constant current driving circuit controls the current flowing through the laser to be constant current, adopts a linear constant current control mode, and can be in a current series negative feedback structure or a current parallel negative feedback structure in a topological structure.

The current setting circuit is a digital control analog voltage setting and selecting output circuit, the current setting circuit is composed of a multi-channel DA chip and a multi-channel analog switch, and the output voltage of the DA chip is provided for the input of the analog switch chip. The number of output channels of the DA chip is corresponding to the number of input channels of the analog switch chip, and the current setting circuit is controlled by the MCU in a communication mode.

The MCU control circuit can be a micro-processing circuit, a CUP circuit, an ARM circuit or an FPGA circuit.

The voltage acquisition circuit is digital control four-channel analog voltage acquisition circuit, four ways AD chip has gathered input power supply voltage, the positive voltage of laser instrument, laser instrument negative pole voltage, the voltage on the sampling resistor, give MCU as the parameter that PID adjusted with voltage input, feedback control switching power supply's output voltage, adopt software to realize PID feedback signal's regulation, thereby come the pressure drop of MOS pipe among the control constant current drive circuit, thereby heat dissipation has been reduced, realize higher efficiency.

The voltage setting circuit controls the output voltage of the voltage setting circuit to the switching power supply through MCU communication, so that the output voltage of the switching power supply is controlled to be linearly adjusted.

Fig. 2 is a circuit diagram of a voltage adaptive laser driving circuit according to an embodiment of the present invention. The switch power supply external interface comprises VCC, OUT, RESET and FB, wherein input voltage VCC is connected with an external power supply, output voltage OUT is connected with the input anode of the laser, a RESET signal RESET is connected with one pin P17 of the MCU control circuit, and a voltage regulation pin FB is connected with one terminal of an output resistor R1 of the voltage regulation circuit.

The constant current driving circuit is a current series negative feedback structure, a linear constant current power tube is M1, a current sampling resistor is R31, the voltage of the sampling resistor is connected to the input negative electrode of the operational amplifier U11, the output signal of the analog switch circuit 4 is connected to one end of the resistor R14, the other end of the resistor R14 is connected to the input positive electrode of the operational amplifier U11, the output signal of the operational amplifier U11 is connected to the grid electrode of the power MOS tube, and the calculation formula of the output current is as follows:

equation 1

In formula 1, VD is the voltage at the connection point of the resistor R14 and the analog switch circuit, and RS is the resistance of the sampling resistor R31.

The core chip of the current setting circuit adopts an 8-path 12-bit DA chip, output voltage signals are Vout0, Vout1, Vout2, Vout3, Vout4, Vout5, Vout6 and Vout7, the current setting circuit adopts an SPI interface to communicate with the MCU, communication signals are SCLK, SYNC, SDI, SDO, LDAC and RESET, wherein the SCLK, SYNC, SDI and SDO are respectively connected with resistors R17, R20, R22 and R24 in series and then connected into the MCU. The analog switch chip adopts an 8-to-1 analog switch, the channel selection control signals are three-position A2, A1 and A0 signals which are respectively connected with resistors R30, R29 and R28 in series and then are connected to a control terminal of the MCU; the 8-path signal input terminals of the analog switch chip are S8, S7, S6, S5, S4, S3, S2 and S1, and are respectively connected with the output signals of the DA chip; the output signal terminal of the analog switch chip is D, and the output signal is provided for the constant current driving circuit.

The MCU control circuit can be selectively accessed to a display circuit, a communication circuit and a control circuit, the display circuit is used for displaying the working state and the output condition of the circuit, the communication circuit is used for communicating with an upper computer or performing remote control, and the control circuit is used for configuring the working state and the output value.

The signal pins P06, P07 and P10 of the MCU control circuit are respectively connected with the analog switch circuit signal selection terminals A2, A1 and A0 through series resistors R30, R29 and R28, the signal pins P00 and P01 are respectively connected with LDAC and RESET of the current setting circuit, the signal pins P02, P03, P04 and P05 are respectively connected with SDO, SDI, SYNC and SCLK of the current setting circuit through resistors R24, R22, R20 and R17, the signal pins P11, P12, P13 and P14 are respectively connected with CONVST, ALERT, SDA and SCL of the voltage acquisition circuit, and the signal pins P15, P16 and P17 are connected with A0, SDA and SCL of the voltage setting circuit.

The voltage acquisition circuit adopts a four-way DA voltage conversion chip U6 of an I2C interface, signals SCL, SDA, ALERT and CONVEST of U6 are connected to terminals P14, P13, P12 and P11 of the MCU control circuit, and signal pins SCL, SDA and ALERT are pulled up to 3.3V voltage through resistors R6, R7 and R8.

The resistors R126 and R27 obtain the constant current driving circuit sampling resistor voltage VRS and divide the voltage, and the divided signal is provided to the operational amplifier U12 to follow and input to Vin1 of U6.

The resistors R11 and R12 acquire and divide the cathode voltage VLED of the LED light source, and the divided signal is provided to the operational amplifier U8 to be followed by the Vin2 input to the U6.

The resistors R2 and R3 obtain and divide the input voltage VCC of the switching power supply, and the divided signal is provided to the operational amplifier U2 to be followed and then input to the Vin3 of the U6.

The resistors R9 and R10 acquire and divide the anode voltage VLED + of the LED light source, and the divided signal is provided to the operational amplifier U4 to be followed and then input to the Vin4 of the U6.

The voltage setting circuit adopts a single-circuit DA chip, an I2C interface is adopted for input control signals, signal pins are SCL and SDA, the input signals are connected with a communication pin of the MCU and are respectively pulled up by resistors R4 and R5, output signals are connected with one end of a resistor R1, and the other end of the resistor R1 is connected with an FB pin of the switching power supply.

Example 2:

fig. 3 is a circuit diagram of a second implementation manner of the voltage adaptive laser driving circuit according to the embodiment of the present invention. Different from the embodiment 1, the constant current driving circuit 3 is a current parallel negative feedback structure, the linear constant current power transistor is M1, the current sampling resistor R31, one end of the resistor R32 is connected to the input negative terminal of the operational amplifier, the other end is connected to the input terminal of the current sampling resistor R31, one end of the resistor R14 is connected to the output signal of the current setting circuit 4, the other end of the resistor R14 is connected to the input negative terminal of the operational amplifier U11, the positive terminal of the operational amplifier U11 is connected to the output terminal of the reference voltage chip U13, the output signal of the operational amplifier U11 is connected to the gate of the power MOS transistor M1, and the calculation formula of the output current at this time is:

equation 2

In formula 2, VD is the voltage at the connection point of the resistor R14 and the analog switch chip, RS is the resistance of the sampling resistor R31, VREF is the reference voltage value of the anode of the operational amplifier U11, and K1 is the ratio of the resistor R32 to the resistor R14.

Example 3:

fig. 4 is a block diagram of an internal implementation of the switching power supply according to the embodiment of the present invention. In embodiment 1 or embodiment 2, the MCU control circuit controls the voltage setting circuit and the output voltage of the switching power supply to perform setting, an internal circuit diagram of the switching power supply is shown in fig. 4, and a calculation formula of the open-loop setting of the output voltage at this time is as follows:

equation 3

In formula 3, Vout is the output voltage of the switching power supply; VT is the output voltage of the DA conversion circuit in the voltage setting circuit; the VFB is an input voltage of the switching power supply circuit, is a reference pin of the output voltage Vout, also called an output feedback pin, and is connected to an input end of the internal error amplifier to set the output voltage; k2 is the ratio of resistance R13 and resistance R16, and K3 is the ratio of resistance R13 and resistance R1.

Example 4:

fig. 5 is a flowchart of a control method of the output voltage regulation numerical control function according to an embodiment of the present invention. In the method, the MCU control circuit controls the switching power supply, the laser, the constant current drive circuit, the voltage acquisition circuit and the voltage setting circuit to carry out the switching power supply output voltage regulation circuit, and the method specifically comprises the following steps:

step 1, after the computer is started, the output voltage VFB of the voltage setting circuit is 0, and Vout is set to be the maximum value.

And 2, selecting the maximum output step current Imax in the step currents according to the step current value configured by the user, and controlling the output voltage in the period.

And 3, acquiring output voltages VLD +, VLD-and VRS by the voltage acquisition circuit, and calculating working voltages VLD at two ends of the LD light source:

equation 4

And 4, calculating the power consumption of the MOS tube as follows:

equation 5

Step 5, determining the voltage drop VDS of the drain and the source of the power MOS tube according to the preset value PH of the power heat dissipation of the MOS tube:

equation 6

Step 6, calculating output voltage Vout:

equation 7

And 7, calculating the value of VT according to the formula 3 and the formula 7, and then controlling the output voltage VT of the voltage setting circuit 7 by the MCU control circuit 5 in a mode of gradually increasing VT.

And 8, controlling the voltage acquisition circuit to sample the working voltage of each point again through the MCU, and comparing the actual power consumption of the MOS tube with the preset power consumption Ph according to the numerical values of Vout and VT to realize the closed-loop control of the output voltage numerical value PID.

Wherein: VFB is the input voltage of the switching power supply 1; vout is the output voltage of the switching power supply 1; imax is the maximum output step current of the step currents flowing through the laser 2; VLD + is the laser 2 input voltage; VLD-is the laser 2 output voltage; VRS is the voltage of the sampling resistor of the constant current driving circuit 3; VLD is the operating voltage across the laser 2; the VDS is the voltage drop of the drain electrode and the source electrode of the MOS tube in the constant current driving circuit 3; VT is the output voltage of the DA chip of the voltage setting circuit 7.

Although the present invention has been described with reference to a few embodiments, it should be understood that the present invention is not limited to the above embodiments, but rather, the present invention is not limited to the above embodiments, and those skilled in the art can make various changes and modifications without departing from the scope of the invention.