The Design Of DFB Laser Driver And Temperature Controller Applied In CO Gas Detection System

CO is a kind of colorless, tasteless, toxic and dangerous gas. People always getpoisoned with no awareness of it. However, in recent years, CO leakages due to gasexplosion and furnace door lax sealing happened frequently in steel making, coking,cement production, kiln process in industrial production. These accidents have seizedhundreds of people’s lives. Therefore, to develope a set of effective CO gas detectionwarning system will provide an important protection in industrial production.In this paper, I design a laser driver with high temperature control accuracy basedon the DFB laser applied in CO gas detection system. In the design of hardwarecircuit, the programmable waveform generator provide driving waveform comprisedof triangle wave and sine wave to the voltage controlled constant current source.Using the thermoelectric cooler controller LTC1923to drive the TEC to maintaine theDFB laser at a constant temperature. Laser protection circuit includes power supplysoft start circuit, over-current protection circuit, surge protection circuit and so on. Alow noise and high precision regulated power supplies power to the system to makethe driver system work more stability. The interactive part includes a LCD displaycircuit, a serial communication circuit, a key array. The software design containswaveform generating program, D/A interface program, A/D sampling program,system initializing program, the interrupting program, LCD display program, keyprogram and serial communication program.In this research, the DFB laser driver and temperature controller’s performaceindicators are as follows:(1)A linear power with low ripple and noise supplies power to the system. Whenthe output is+5V, the ripple amplitude is2mV and the ripple coefficient is0.04%.(2)The double DDSs can synchronously output frequency and amplitudeadjustable triangle and sine wave.(3)The voltage controlled constant current source with good linearity and stability outputs in the range of0mA-200mA.(4)The temperature controller can make the DFB laser work at a temperaturerange of [6℃，50℃] with a response time of10seconds. The long-term temperaturecontrol precision is±0.01℃.(5)The protection for DFB laser includes power soft start, over-current protection,over-temperature protection, thermal resistance protection, TEC protection andanti-surge measure.