Temperature Control System For Lazer Diode Based On Thermal Electrical Cooler

Based on the laser absorption spectroscopy, gas monitoring system plays an important role in coal production and usage. To ensure these kinds of laser diodes’s output power and wavelength is less affected, laser diodes are needed to keep working in high stable temperature. At the same time, because laser diodes are usually very expensive, good temperature control system is necessary for protecting laser diodes from damaged by large instantaneous current. Thus, a highly integrated, tiny size, high temperature stability control system is very crucial to solve those problems.In the designing system, the negative temperature coefficient (NTC) thermal resistor is used as high precision temperature sensor; thermal electronic cooler (TEC) is able to cool/heat laser diodes as an execute unit of system; H-bridge circuit eliminates temperature drift on measuring error voltage; MAX1978is a good choice for temperature control module with an error amplifier and TEC driver circuit. In order to select appropriate TEC, designing TEC module is necessary to analyse cooling/heating effect. To change the working temperature of laser diodes and control system, it is always used by setting preset voltage related with expecting temperature by using D/A converter. What’s more, designing appropriate PID-controller through analysing mathematical model and using PID control theory, make control system working more efficient. MCU and FPGA work together to ensure that control system works well, to sample voltage signals about temperature and temperature stability, to communicate with upper computer by RS-232port, and to display data with LCD. By using LabVIEW, control software of upper computer is able to monitor control procedure, save sampling data, and plot data curves.After designing schematic diagram and simulating system, real circuits system can be made. If analysing the results of series of experiments, the conclusion demonstrate that the temperature stability of5m℃. Control system is working well in an efficient way.