Feed-forward control model, system and method for driving power supply of linear high-power semiconductor laser

Abstract

The invention provides a feed-forward control model, system and method for a driving power supply of a linear high-power semiconductor laser. The model comprises semiconductor laser internal resistance # imgabs0 #, semiconductor laser internal parasitic inductance, inductance # imgabs1 # equivalent to wiring inductance caused by wiring, and equivalent capacitance # imgabs2 # formed by combined action of semiconductor laser internal parasitic capacitance and parasitic capacitance caused by a driving circuit. The second-order control model provided by the invention not only realizes the correspondence with the actual test current waveform, but also avoids the complex control and difficult engineering application of the traditionally provided high-order model.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor laser driving power supplies, and in particular relates to a linear high-power semiconductor laser driving power supply feedforward control model, system and method. Background Art

[0002] The driving power supplies for high-power semiconductor lasers and fiber lasers are usually switching power supplies and linear power supplies. Among them, linear power supplies have relatively fast response speed and low driving current ripple, and are widely used.

[0003] Among the many performance indicators of high-power laser driver power supplies, the driving current response speed is an important requirement. The invention patent application with application number 202210646981.1 describes a segmented control method, which provides an effective means to accelerate the current response of the laser driver power supply. However, due to the different parasitic parameters of lasers from different manufacturers and models, and even the length and routing of the power wiring of the whole machine manufacturer, the overall performance of the laser drive will be affected. The hardware power supply regulation circuit of the laser driver power supply cannot be widely adapted to a variety of laser models, resulting in overshoot or even oscillation of the driving current of some models of lasers, such as Figure 1 as shown; or the expected current response time is not achieved, which reduces its performance. Summary of the invention

[0004] In view of the above technical problems, the present invention proposes a linear high-power semiconductor laser drive power supply feedforward control model, system and method. A high-power semiconductor laser second-order control model is proposed, and a feedforward control method based on the model is implemented on the basis of the model, which effectively speeds up the current response time and reduces the overshoot.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A linear high-power semiconductor laser drive power supply feedforward control model, including: semiconductor laser internal resistance , the inductance equivalent to the parasitic inductance inside the semiconductor laser and the wiring inductance caused by the wiring , the equivalent capacitance formed by the parasitic capacitance inside the semiconductor laser and the parasitic capacitance caused by the driving circuit .

[0007] A linear high-power semiconductor laser drive power supply feedforward control system, comprising:

[0008] Output current closed-loop controller, through which the output current feedback and the current input R(s) are subtracted, and the difference is calculated by the PID controller to output the current closed-loop output control quantity;

[0009] A current feedforward controller, which calculates the current input R(s) through a linear high-power semiconductor laser driving power supply feedforward control model F(s), and outputs a feedforward control quantity;

[0010] After the current closed-loop output control quantity is added to the feedforward control quantity output by the linear high-power semiconductor laser driving power supply feedforward control model F(s), the driving power supply is controlled to generate a driving current for driving the semiconductor laser.

[0011] A linear high-power semiconductor laser driving power supply feedforward control method is performed by a linear high-power semiconductor laser driving power supply feedforward control system, comprising:

[0012] Step 1: The current input R(s) is calculated by the linear high-power semiconductor laser driving power supply feedforward control model F(s) through the current feedforward controller, and the feedforward control quantity is output;

[0013] Step 2: The output current closed-loop controller makes a difference between the output current feedback and the current input R(s), and the difference is calculated by the PID controller to output the current closed-loop output control quantity;

[0014] Step 3: After adding the current closed-loop output control quantity to the feedforward control quantity output by the linear high-power semiconductor laser driving power supply feedforward control model F(s), the driving power supply is controlled to generate a driving current for driving the semiconductor laser.

[0015] Beneficial effects:

[0016] The present invention proposes a second-order model based on high-power laser drive, which avoids the inconsistency between the traditional first-order system and the actual current output response waveform of the project, or the complexity of the traditional high-order system, which makes it difficult to analyze. According to the model, the present invention designs a feedforward controller based on load characteristics, which effectively speeds up the response time of the drive current and reduces the system overshoot. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is the semiconductor laser driving current overshoot and oscillation waveform in the prior art;

[0018] Figure 2 This is the electrical schematic diagram of the semiconductor laser drive power supply in the linear high-power semiconductor laser drive power supply feedforward control model;

[0019] Figure 3 It is the small signal schematic diagram of semiconductor laser driving power supply in the linear high-power semiconductor laser driving power supply feedforward control model;

[0020] Figure 4 This is the equivalent small signal schematic diagram of the semiconductor laser drive power supply in the linear high-power semiconductor laser drive power supply feedforward control model;

[0021] Figure 5 A control schematic diagram for adding feedforward control to the feedforward control system of a linear high-power semiconductor laser drive power supply;

[0022] Figure 6 Semiconductor laser driving current waveform after adding feedforward control. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0024] The present invention provides a linear high-power semiconductor laser driving power supply feedforward control model and a feedforward control method based on the model. The segmented control method described in the invention patent application number 202210646981.1 is applied. In the second output stage, i.e., the closed-loop output stage, the single-chip microcomputer output DAC is used to multiply the discretized feedforward model by a certain coefficient and output it according to the sampling frequency, and the adder and the closed-loop feedback compensation value are added to jointly control the current output of the driving power supply.

[0025] The equivalent electrical schematic diagram of a high-power semiconductor laser linear drive power supply considering parasitic parameters is as follows: Figure 2 As shown, is the input control voltage; It is the constant pressure source of the front stage; It is the inductance equivalent to the wiring inductance caused by wiring; LD is a semiconductor laser; is the internal resistance of the semiconductor laser, is the MOSFET gate drive resistor; Q is the N-channel MOSFET; is the comprehensive parasitic capacitance of the semiconductor laser; Cgs is the gate-drain parasitic capacitance of the MOSFET; Cdg is the gate-source parasitic capacitance; Cds is the source-drain parasitic capacitance, and Csc is the equivalent capacitance formed by the internal parasitic capacitance of the semiconductor laser and the parasitic capacitance caused by the driving circuit.

[0026] When MOSFET works in the saturation region, the output current output relationship is:

[0027] ;

[0028] Where: K: is the transfer gain, is the input control voltage, which is also the gate drive voltage. : MOSFET turn-on threshold voltage.

[0029] Apply the segmented control method described in invention patent application No. 202210646981.1, Figure 2 The equivalent small signal circuit is Figure 3 shown.

[0030] According to the experimental results, the capacitance values ​​of capacitors Cgs and Cdg are much smaller than those of Cds and Csc, so the small signal equivalent circuit can ignore them. Considering Cds and Csc together, the small signal circuit can be equivalent to: Figure 4 .

[0031] According to an embodiment of the present invention, a linear high-power semiconductor laser driving power supply feedforward control model is provided. Figure 4 The schematic diagram of the structure of the model is shown in Figure 2. Figure 4 As shown, the model includes the internal resistance of the semiconductor laser , the inductance equivalent to the parasitic inductance inside the semiconductor laser and the wiring inductance caused by the wiring , the equivalent capacitance formed by the parasitic capacitance inside the semiconductor laser and the parasitic capacitance caused by the driving circuit .

[0032] Figure 4 The model shown in can be referred to as the small signal model. Under the small signal model, the MOSFET output current is:

[0033] (1)

[0034] in:

[0035] (2)

[0036] The above linear high-power semiconductor laser drive power supply feedforward control model provides the laser current. According to Kirchhoff's current law, the laser current for:

[0037] (3)

[0038] in is the parasitic capacitance current.

[0039] in addition:

[0040] (4)

[0041] (5)

[0042] in, is the MOSFET source voltage, It is the inductance value of the inductance equivalent to the wiring inductance caused by the wiring. is the resistance value of the semiconductor laser internal resistance, is the equivalent parasitic capacitance.

[0043] Substituting equations (1) and (5) into equation (3), we can obtain:

[0044] (6)

[0045] in, is the small signal of the laser driving current, It is the small signal of MOSFET driving voltage.

[0046] The laser current The open loop transfer function is:

[0047] (7)

[0048] This model is a typical second-order system. When the damping coefficient When < 1, the system exhibits the characteristics of damped oscillation, and its oscillation angular frequency is: , which corresponds to the actual engineering phenomenon.

[0049] Based on the second-order system drive model, a control system with feedforward compensation is proposed. Its principle is as follows: Figure 5 As shown. Figure 5 As shown, the control system includes:

[0050] Output current closed-loop controller, through which the output current feedback and the current input R(s) are subtracted, and the difference is calculated by the PID controller to output the current closed-loop output control quantity;

[0051] A current feedforward controller, which calculates the current input R(s) through a linear high-power semiconductor laser driving power supply feedforward control model F(s), and outputs a feedforward control quantity;

[0052] After the current closed-loop output control quantity is added to the feedforward control quantity output by the linear high-power semiconductor laser driving power supply feedforward control model F(s), the driving power supply is controlled to generate a driving current for driving the laser.

[0053] Figure 5 In is the feedforward compensation model based on the controlled object, which is the inverse of the controlled object. Then, from formula (7), we can get:

[0054] (8)

[0055] In formula (8) is the MOSFET drive voltage required for the drive current output by the model.

[0056] In order to reduce the impact of the high-frequency part of the feedforward term on the system, a second-level low-pass filter is added to the output drive current. From equation (8), we get:

[0057] (9)

[0058] Among them, τ is a parameter related to the target bandwidth of the system design, and s is the Laplace operator.

[0059] Although the added low-pass filter weakens the effect of feedforward, it improves the stability of the system. Overall, the response and overshoot of the system are improved. The current response curve after adding feedforward is as follows: Figure 6 As shown. And Figure 1 In comparison, the overshoot and adjustment time are significantly reduced.

[0060] According to an embodiment of the present invention, a linear high-power semiconductor laser drive power supply feedforward control method is provided. The method comprises:

[0061] Step 1: The current input R(s) is calculated by the linear high-power semiconductor laser driving power supply feedforward control model F(s) through the current feedforward controller, and the feedforward control quantity is output;

[0062] Step 2: The output current closed-loop controller makes a difference between the output current feedback and the current input R(s), and the difference is calculated by the PID controller to output the current closed-loop output control quantity;

[0063] Step 3: After adding the current closed-loop output control quantity to the feedforward control quantity output by the linear high-power semiconductor laser driving power supply feedforward control model F(s), the driving power supply is controlled to generate a driving current for driving the laser.

[0064] The present invention is not limited to the above-mentioned specific implementation modes. Any implementation modes slightly modified or changed by a person skilled in the art based on the disclosure of the present implementation modes or the accompanying drawings shall fall within the protection scope of the present invention.

Claims

1. A linear high-power semiconductor laser drive power supply feedforward control model, characterized in that: include: Semiconductor laser internal resistance , the inductance equivalent to the parasitic inductance inside the semiconductor laser and the wiring inductance caused by the wiring , the equivalent capacitance formed by the parasitic capacitance inside the semiconductor laser and the parasitic capacitance caused by the driving circuit .

2. The linear high-power semiconductor laser driving power supply feedforward control model according to claim 1, characterized in that: The linear high-power semiconductor laser driver power supply calculates the semiconductor laser current based on the linear high-power semiconductor laser driver power supply feedforward control model. The control quantity is: （9） in, is the feedforward control quantity, , K: transfer gain, : is the MOSFET turn-on voltage threshold of the driving power supply, is the input control voltage, It is the inductance value of the inductance equivalent to the wiring inductance caused by the wiring. is the internal resistance of the semiconductor laser, is the equivalent capacitance, is the semiconductor laser current.

3. A linear high-power semiconductor laser drive power supply feedforward control system, characterized in that: include: Output current closed-loop controller, through which the output current feedback is subtracted from the current input R(s), and the difference is calculated by the PID controller to output the current closed-loop output control quantity; A current feedforward controller, which outputs a feedforward control value after calculating the current input R(s) using the linear high-power semiconductor laser driving power supply feedforward control model F(s) as claimed in claim 1 or 2; After the current closed-loop output control quantity is added to the feedforward control quantity output by the linear high-power semiconductor laser driving power supply feedforward control model F(s), the driving power supply is controlled to generate a driving current for driving the semiconductor laser.

4. A linear high-power semiconductor laser drive power supply feedforward control method, characterized in that: The method is performed by the linear high-power semiconductor laser driving power supply feedforward control system according to claim 3, comprising: Step 1: The current input R(s) is calculated by the linear high-power semiconductor laser driving power supply feedforward control model F(s) through the current feedforward controller, and the feedforward control quantity is output; Step 2: The output current closed-loop controller makes a difference between the output current feedback and the current input R(s), and the difference is calculated by the PID controller to output the current closed-loop output control quantity; Step 3: After adding the current closed-loop output control quantity to the feedforward control quantity output by the linear high-power semiconductor laser driving power supply feedforward control model F(s), the driving power supply is controlled to generate a driving current for driving the semiconductor laser.

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