Research And Design Of Small Information Semiconductor Laser Driving System

With the rapid development of Internet of Things and optoelectronic information industry,semiconductor lasers,as excellent non-contact measurement light sources,have demonstrated their strong market competitiveness in non-contact measurement fields such as medicine and military.The working conditions of a semiconductor laser are very strict.The working current and temperature of the core are the main factors that affect the change of the center wavelength.The existing driving research focuses on high-power semiconductor lasers,and the research on the driver of low-power information semiconductor lasers is still insufficient.Therefore,a stable,precise and suitable driver is the basis for its wide application.First,this paper introduces its working principle and working characteristics.The central wavelength is an important index in the non-contact measurement fields.But,its variation of current and temperature will bring the impacts of 0.01 nm/mA and 0.1nm/℃ respectively.Based on the above two influencing factors and the packaging structure of the semiconductor laser,this paper independently designs a small,stable and accurate semiconductor laser driving system.It mainly consists of two parts:the operating current control and the die temperature control.(1)The operating current control part determines the output power of the semiconductor laser and is the control core of the entire driving system.The working current control part adopts a constant current circuit combined with the digital incremental PID algorithm for the double closed-loop control method of the module.In the research work of this paper,considering the common characteristics of the semiconductor laser and the individual characteristics of the FLD5FCX-E series information laser,the power supply filtering slow-start circuit and negative feedback circuit are improved respectively.The digital incremental PID algorithm is completed by the microprocessor STM32F103xE chip,and the current value is corrected to reduce the balance time.The improved power supply filtering slow-start circuit improves the conventional two-stage LC filter structure into a one-stage LC filter structure that incorporates inductor beads.Simulated and verified by Multisim software,transient analysis of the filter slow-start circuit at the instant of power supply is more effective than the traditional start-up circuit.In view of the improved negative feedback circuit,we proposes to use the instrumentation amplifier instead of the operational amplifier.Through the theoretical derivation,the driving current is linearly expressed by voltage.The circuit is feasibility.In this design,the improved negative feedback circuit consists of a dual instrumentation amplifier,a semiconductor field effect-transistor and a high-precision sampling resistor,which is the core part of constant-current control.The improved negative feedback circuit has been tested,verified and analyzed by the physical object.The linearity of the current control part is good,the maximum error of the current control is ±0.5mA.And the one-hour stability is about 1.2%.(2)The temperature control part of the die adopts a dedicated temperature control chip to control the temperature through the thermistor and the thermoelectric cooler.By comparing and analyzing the existing three special chips on the market in this paper,the LTC1923 is selected as the control chip and exchanges data with the microprocessor through the A/D converter and the D/A converter.Finally,the temperature control part of the die has been physically tested,verified and analyzed.The maximum error in temperature control is ±0.3 ℃.The initial temperature rise is removed,and the one-hour stability is about 1.4%.