The Design And Study Of Power For Quantum Cascade Laser Applied In The CO Gas Detection System

Carbon monoxide gas concentrations detector has great significance for productionsafety underground the coal mine. Infrared light source is needed in the infrared gasdetection system, Quantum cascade laser is an ideal light source within the wavelengthrange of2.5~25μm infrared gas detection, as it has high reliability, high luminous efficacyand temperature stability, flexible design wavelength, fast inherent corresponding speed.The performance of the quantum cascade laser supply is an important factor. Quantumcascade lasers can only work in pulse mode, so the goal of this paper is to design a stableperformance digital pulse drive power which comes from the national863project “thedesign of infrared CO gas detection system used in mine coal”.According to the parameter of operation requirement of quantum cascade lasers, thepaper designs a set of adjustable pulse constant current driving power and a set ofadjustable pulse constant voltage driving power. The hardware circuit of the systemincludes source circuit, DSP controller circuit, pulse generating circuit, switch modulationcircuit, voltage controlled pulse constant current source circuit, pulse shaping circuit,constant voltage source circuit, analog-to-digital conversion circuit, key array and liquidcrystal display circuit, serial communication circuit and protection circuit, etc. Softwaredesign includes system initialization program, interrupt program, PWM generation, D/Ainterface procedures, LCD display, serial communication program, etc.The paper uses ORCAD CAPTURE to simulate the circuit and uses PSPICE tocreate model to study the effect of various device parameters on the output of loaderdriver. A lot of experiments had been made to test the influence of parasitic inductanceand capacitance, and it proves that parasitic inductance could cause overshoot andparasitic capacitance can improve overshoot of output when the capacitance has a propersize.At last, we test the performance parameters of the two sets of driving power. The setof adjustable pulse constant current driver works in pulse mode with frequency range of1K~10KHz, pulse width of0.2μs~10μs, current amplitude of0~3.0A, current accuracy is 2×10-2A and the average rise time and fall time are about20~46ns and20~200ns, themaximum output voltage amplitude is20V, edge overshot is less than5%. The set ofadjustable pulse constant voltage driver works in pulse mode with frequency range of1K~10KHz, pulse width of0.2μs~4μs, voltage stability is2.25×10-2V, the maximumoutput current amplitude is3A, the average rise time and fall time are about70ns and90ns. After a long period of performance tests, the two sets of power supply work stably.