The Study And Design Of SLED Driving System Based On USB Communication

The development of semiconductor lasers has accelerated the application pace of optical fiber sensing technology.As the main device in the optoelectronic system,the semiconductor lasers' work performance has a great impact on the whole system.So how to ensure the semiconductor lasers' high-efficient,stable and safely working performance has great significance for research and development.The design of the high-precision and reliability temperature controlling system is the most important part in driving system,because many working parameters of semiconductor laser have relationship to the temperature.In this paper, the design of driving system based on our laboratory's actual requirement for the semiconductor laser.This paper first list the current research situation on driving the semiconductor lasers' at home and abroad,then explain the temperature has many influence on the performance parameters of semiconductor lasers.We make our own design proposal from the significance of the study of constant-temperature controlling system and the analysis of the current research situation.With the merits of large number of supported equipments,easy to expand,high speed transmission and stability,the Universal Serial Bus was chose to communicate the target board and PC.The USB bus controller can facilitate the interconnection of equipment in the extensive use of computer peripherals.Although it is less used in laser-driven systems,with the decrease in PC slots number and limitation in PC address and interrupt resources,it will become a trend to use the USB as the communication means between PC and the driving system.This paper made use of USB communication protocol to complete collecting and sending data.In the software design of the computer's display terminal,a friendly interface was designed in the VC++6.0 development environment to receive electrical signals from the sensor and send values to control the work state of semiconductor laser by the USB bus.The programming language is C++ language,which has been widely applied in the data acquisition field because the powerful features,reliability,scalability,maintainability and so on.This paper used the MSP430 single chip microcomputer as controlling core in hardware designs.The temperature signal,detected by the temperature detecting circuit,was collected by the internal 12-bit accuracy AD converter.In view of the Thermoelectric Cooler(TEC) characteristics,after the converted digital data was calculated by PID algorithm,the MSP430 made PWM pulse to control the work performance of the TEC.In order to make sure the laser's driven current more stable,we design a constant current source with the deep negative feedback circuit.To sum up,this paper engaged in both software and hardware system designing.With the help of the USB communication protocol,the system's anti-interference ability was increased.And the VC project had successfully controlled the work state of TEC.So for the deeper and more extensive research in future,this paper provides a strong platform and reference.