The Development Of Pulse Driver For Medium And Small Power Laser Diode

A driver applied for pulsed and continuously operating laser diode on medium and small power states is investigated and manufactured. This driver consists of a current driving control module and a temperature control module. And for the working mode of Pulsed/Continuous, it is able to make the output of light wavelength and light power of laser diode controlled steadily.The pulsed current driving module is composed of current source and pulse generator and modulating circuit. Based on the principle of series negative feedback, closed loop control of controlled parameters are realized by current source and the stability of the driving system is improved. According to different feedback parameter, the current source is divided into automatic current control and automatic power control, which are fit for steadying afflux current and the output of light power, respectively. The pulse generator is implemented using FPGA, which enhances integration of system and flexibility of design. Using a pulse signal as a control variable and high-speed switching characteristic of field effect transistor, the modulating circuit implements pulsed laser diode driver. 250/500mA range switch for practical application is achieved by using a range choosing circuit. And bidirectional driving of both laser diode and photo diode is achieved by the current driving module, which using a multi-polarities control circuit. Besides, as for security of an operating laser diode, active measure of static safeguard, limiting extent, extent frequency protection and slow start are taken in order to ensure the use of the laser diode.The temperature control module for laser diode built-in thermistor and thermoelectric cooler is designed according to the idea of constant temperature control. It is composed of temperature sampling circuit and thermoelectric cooler driver. Double-constant current source is adopted in the temperature sampling circuit and internal temperature high-precision sampling of laser diode is implemented by the temperature sampling circuit, which not only completes RTH/V conversion, but also eliminates the effects of lead resistance from system. The driver adjusts the quantity of cooling and warming of the thermoelectric cooler by controlling magnitude and direction of the current injected in the thermoelectric cooler. Moreover, the internal serial negative feedback of driving circuit realizes laser diode internal temperature's changes in the rapid response and control. In addition, the temperature control module employs a protecting circuit for the thermoelectric cooler to prevent the fact that the performing apparatus is demolished by an excessive current.Aiming at the main factors by which the stability of the driver system is affected, relevant actions are taken to guarantee the stability of the system and a driving system is developed on the basis of considering the electro magnetic compatibility. In the evaluation by a corresponding experiment, current stability and other performance parameters of this driver are satisfied with design request.