A control circuit and method for semiconductor laser linear drive power supply

Abstract

The present invention discloses a control circuit and method for a semiconductor laser linear drive power supply, wherein the control circuit comprises a differential circuit, a delay circuit, a PID adjustment circuit, a starting current setting circuit, a drive circuit, and an MCU. The present invention uses a staged control method to adjust the control circuit, wherein the staged control method comprises setting two stages, wherein the two stages are stage one as a starting delay stage and stage two as an inertia stage. The present invention realizes segmented control of the drive process by analyzing the working characteristics of the semiconductor laser drive system, thereby ensuring the rapid response of the drive power supply and avoiding the waste of energy caused by the starting current at power-on.

Description

Technical Field

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

[0002] The common driving power supplies for semiconductor lasers and fiber lasers are 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 laser drive power supply, the driving current response speed is one of its important requirements. The factors affecting the response speed of linear drive power supply include the response speed of linear drive power supply power device (the influencing factors include the internal driving resistance of the device, parasitic capacitance, etc.), system parasitic inductance (including parasitic inductance of connecting wires, parasitic inductance of semiconductor lasers, etc.), junction capacitance of semiconductor laser body, etc. The influence of these factors on the response speed can be divided into two categories. One is the delay link caused by factors such as parasitic capacitance of power devices and junction capacitance of semiconductor lasers; the other is the inertia link caused by factors such as internal driving resistance of power devices and line inductance.

[0004] At present, there are two main ways for semiconductor drive power to solve the above problems. One is the traditional processing method that equates the delay link to the inertia link. This method has stable system output and simple control loop debugging. However, when the delay link is not much smaller than the inertia link, it will cause the system response speed to be slow, at least the rising edge of the driving current is relatively slow.

[0005] The second is to output a small current (hereinafter referred to as the startup current) when the drive power system is powered on, so that the drive power has current output, but the semiconductor laser does not output laser. When there is a light signal, the drive system increases the output current to the set current. This control method effectively avoids the delay link and improves the system response speed, but due to the existence of small currents, it causes energy waste; and in high-power applications, due to the influence of factors such as nonlinearity, the inconsistency of the device is particularly obvious at small currents. In addition, due to the influence of factors such as temperature drift, each device needs to be debugged repeatedly, which is not conducive to mass production. Summary of the invention

[0006] In view of the above technical problems, the present invention proposes a control circuit and method for a semiconductor laser linear drive power supply. The control circuit divides the semiconductor laser linear drive power supply into two stages for control. Stage one is the initial delay stage; stage two is the inertia stage. While avoiding the starting current output when the power supply is started, the current rise time is reduced, thereby improving the performance of the drive power supply.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A control circuit of a semiconductor laser linear drive power supply comprises a differential circuit, a delay circuit, a PID regulation circuit, an addition circuit, a drive circuit, and an MCU; wherein the differential circuit and the delay circuit are added before the PID regulation circuit; the differential circuit and the delay circuit are connected in parallel as inputs of the PID regulation circuit; the PID regulation circuit and the starting current setting circuit are added in parallel as inputs of the drive circuit; and the drive circuit drives a power device Q to output current.

[0009] The present invention also provides a control method for a control circuit of a semiconductor laser linear drive power supply, which uses a staged control method to adjust the control circuit. The staged control method includes setting two stages, the two stages being stage one as a starting delay stage and stage two as an inertia stage;

[0010] The first stage is open-loop control. When the MCU detects the light output signal, the starting current setting UFbSet is output through the DAC to complete the starting current output. At this time, the laser light output signal delay signal GateDelay is high, the UDelta signal is 0, and the output of the PID adjustment circuit is also 0; the power device Q outputs only the starting current set by UFbSet;

[0011] The delay of the second stage is stored and timed by the MCU, and the laser light output signal delay signal GateDelay is set low. The PID adjustment circuit starts to work and adjusts the output working current of the power device Q based on UFbSet to ensure that it responds quickly to the set current.

[0012] Beneficial effects:

[0013] The present invention realizes controlling the driving process in stages by analyzing the working characteristics of the semiconductor laser driving system, which not only ensures the rapid response of the driving power supply, but also avoids the waste of energy caused by the starting current when the power is turned on. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A control circuit principle block diagram of a semiconductor laser linear drive power supply of the present invention;

[0015] Figure 2 It is a schematic diagram of the staged and PID regulation circuit of the present invention;

[0016] Figure 3 It is a schematic diagram of the adding circuit and the driving circuit of the present invention. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and 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.

[0018] The present invention provides a control circuit and method for a semiconductor laser linear drive power supply, wherein the control circuit divides the semiconductor laser linear drive power supply into two stages for control. Among them, stage one is the initial delay stage; stage two is the inertia stage. The staged control method of the present invention is implemented by MCU control, and the system delay time and starting current setting UFbSet can be obtained according to the experiment, and the results are stored in the MCU. The MCU triggers the timer to start timing according to the light output signal, and outputs the laser light output signal delay signal GateDelay after the system delay is reached, thereby realizing the stage switching of the control circuit.

[0019] The control circuit of the present invention is realized by a differential circuit, a delay circuit, a PID adjustment circuit, an addition circuit, a drive circuit, and an MCU. The control circuit principle block diagram is shown in FIG. Figure 1 As shown. The differential circuit and the delay circuit are added before the PID adjustment circuit; the differential circuit and the delay circuit are connected in parallel as the input of the PID adjustment circuit; the PID adjustment circuit and the starting current setting circuit are connected in parallel and added as the input of the driving circuit; the driving circuit drives the power output device Q contained therein to output current. The control circuit also includes a semiconductor laser DL, wherein IFed is the feedback current, ISet is the set current, GateDelay is the delay signal of the laser light output signal, UFbSet is the starting current setting, UDelta is the differential signal of the set current ISet and the feedback current IFed, Qg is the delay signal, and UDriver is the power device drive signal.

[0020] In stage one, when the MCU detects the light output signal, the startup current setting UFbSet is output through the DAC to complete the startup current output. At this time, the laser light output signal delay signal GateDelay is high, the UDelta signal is 0, and the PID adjustment circuit output is also 0. At this time, UDriver only contains the startup current setting UFbSet, and this is the current open-loop control. When the MCU determines the delay time, it sets the laser light output signal delay signal GateDelay to low, and the PID adjustment circuit starts working, entering stage two. The power output device Q of the drive circuit outputs the working current, and the drive control circuit forms a current closed-loop control.

[0021] Since the system forms a closed-loop control in the second stage, the closed-loop regulation PID regulation circuit does not include a delay link, and the system response time must be fast, at least the current rise time must be fast. At the same time, the output current starts from the moment the light is emitted, avoiding energy waste. It should be further explained that most of the current semiconductor laser applications are optical power open-loop control, so the delayed open-loop start-up added by the present invention has the same effect as the traditional control method of starting current at power-on, and the output rise time of the drive has the same effect, but for the optical power closed-loop system, the present invention is not applicable.

[0022] The present invention inserts a delay circuit into the traditional PID regulation circuit to ensure that the integral PID circuit does not work in stage one, otherwise the staged control cannot be achieved. The specific staged and PID regulation circuit schematic diagram is as follows Figure 2 shown.

[0023] exist Figure 2 In the first stage, the delay signal GateDelay and the fault signal Err generated by the MCU are ORed by the tube D2, and the transistor Q2 is driven to pull down the output UDelta of the differential adjustment circuit operational amplifier U4A to 0. Further, the output signal USet of the PID adjustment circuit operational amplifier U2B is 0. In the second stage and when no fault occurs, the transistor Q2 is driven to be cut off, and the output UDelta of the differential adjustment circuit operational amplifier U4A is a normal output. Further, the output signal USet of the PID adjustment circuit operational amplifier U2B makes the power output device Q quickly output the set current. And -ISet is the inverse of the set current ISet, the resistor R14=R18, R11< <R12,R12=R16。

[0024] Then the output equation of the differential signal UDelta between the set current ISet and the feedback current IFed is:

[0025] UDelta=R19 / R14(ISet-IFed) (1)

[0026] Among them, R19 / R14 is the proportional gain.

[0027] The output equation of USet is:

[0028]

[0029] Among them, USet is the output of PID regulation circuit; is the proportional gain; is the integral gain;

[0030] R16C17 is the differential gain.

[0031] When the laser output light signal delay signal GateDelay is low, UDelta=0, then from formula (2), USet=0, ensuring that the PID adjustment circuit output USet in the delay link is 0.

[0032] exist Figure 3 In the process, the light-emitting signal Gate and the fault Err signal are controlled by the transistor D1 after being phase-ORed. That is, when there is no light-emitting command or there is a fault, the transistor Q3 is turned on and the start-up current setting signal UFbSet is pulled down to 0. At this time, the output signal UDriver of the driving circuit operational amplifier U3 is 0, and the output of the power output device Q is 0. When there is a light-emitting signal and there is no fault, in stage 1, the transistor Q3 is turned off, and the signal of the start-up current setting UFbSet is output normally, and the output Figure 2 The PID regulation circuit outputs the USet signal as 0, and the power output device Q outputs the starting current; in stage 2, the starting current setting signal UFbSet and Figure 2 The USet signal output by the PID control circuit is added, and the power output device Q outputs the set current.

[0033] Figure 3 The light output signal Gate is negative logic, the light output is low, and the light off is high; -UFbSet is the inversion of the starting current setting, a negative value; Err is a fault signal, high effective; and the resistor R10 = R17.

[0034] In the first stage, USet=0, and the output equation of the power output device Q drive signal UDriver is:

[0035] UDriver=R13 / R17UFbSet (3)

[0036] Among them: UFbSet is the starting current setting. At this time, the power output device Q only outputs the starting current.

[0037] In the second stage, the laser light output signal delay signal GateDelay is low, and the PID regulation circuit takes effect. At this time, the UDriver output equation is formula (4), realizing the closed-loop regulation function to ensure the rapid rise of the output current and the current accuracy.

[0038]

[0039] Where: UFbSet is the starting current setting; USet is the PID adjustment output of formula (2); is the starting current amplification factor.

[0040] When the MCU detects a fault, including overcurrent, overtemperature, etc., the fault signal Err is set high. At this time, USet and -UFbSet are both 0, and the UDriver output is 0, achieving rapid shutdown of the drive output.

[0041] The present invention is not limited to the above-mentioned specific implementation modes. Any implementation modes slightly modified, altered or transformed by a person skilled in the art based on the disclosure of this implementation mode or the accompanying drawings fall within the protection scope of the present invention.

Claims

1. A control circuit for a semiconductor laser linear drive power supply, Features: It includes a differential circuit, a delay circuit, a PID adjustment circuit, a starting current setting circuit, a drive circuit and an MCU; wherein the control circuit sets the differential circuit and the delay circuit before the PID adjustment circuit; the differential circuit and the delay circuit are connected in parallel as the input of the PID adjustment circuit; the PID adjustment circuit and the starting current setting circuit are connected in parallel and added as the input of the drive circuit; the drive circuit drives the power output device Q to output current; The control circuit divides the semiconductor laser linear drive power supply into two stages for control; the first stage is the initial delay stage; the second stage is the inertia stage; The first stage is open-loop control. When the MCU detects the light output signal, the DAC outputs the starting current setting UFbSet to complete the starting current output. At this time, the laser light output signal delay signal GateDelay is high, the differential signal UDelta between the setting current ISet and the feedback current IFed is 0, and the output of the PID adjustment circuit is also 0; the output of the power output device Q only has the starting current set by the starting current setting UFbSet; When the MCU determines the delay time, the delay time of the second stage is triggered by the MCU timing, the laser light output signal delay signal GateDelay is set low, and the PID adjustment circuit starts to work. Based on the starting current setting UFbSet, the power output device Q outputs the working current to ensure that it responds to the set current.

2. The control method of a control circuit of a semiconductor laser linear drive power supply according to claim 1, Features: The control circuit is adjusted by a staged control method, wherein the staged control method includes setting two stages, the two stages being stage one as a starting delay stage and stage two as an inertia stage; The first stage is open-loop control. When the MCU detects the light output signal, the DAC outputs the starting current setting UFbSet to complete the starting current output. At this time, the laser light output signal delay signal GateDelay is high, the differential signal UDelta between the setting current ISet and the feedback current IFed is 0, and the output of the PID adjustment circuit is also 0; the output of the power output device Q only has the starting current set by the starting current setting UFbSet; When the MCU determines the delay time, the delay time of the second stage is triggered by the MCU timing, the laser light output signal delay signal GateDelay is set low, and the PID adjustment circuit starts to work. Based on the starting current setting UFbSet, the power output device Q outputs the working current to ensure that it responds to the set current.

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