Design and Development of Current Controlled SMPS for Laser Application

Abstract

LASER diode, a constituent in many applications, is sensitive to excessive energy input. It becomes essential to drive high rating laser diodes with accurate and precise control otherwise optical damage may occur due to an unintentional current spike. One of the controls for laser diode is control through a current source. For such a need, current controlled SMPS provides a better controlling solution, as it affords reasonable transient response and a short circuit protection compared to the voltage mode control. The report of major project is based on designing a current control based SMPS for the LASER diode applications. The SMPS takes input from 230 V single phase utility mains and delivers a regulated current to the diode. The current in continuous mode is design up to 20A supporting a output voltage of 10V. The SMPS is a IGBT based push pull converter operated in current mode control with two feedback loop. Peak current mode control implements the inner loop and the voltage mode control as the outer loop provide the constant output voltage if any change in input supply side. The duty cycle of the gate pulses is varied by sensing the change in output current and voltage, which provide the constant current output. The feedback control IC senses the load current and voltage which is used both for metering purpose and closing the outer loop in current mode. The decided high switching frequency of 30kHz has advantages like small size, reduced weight, low ripple and faster dynamic response. The driver card provide the proper isolation to control circuit and power circuit. Such a diode driver find applications in many fields including ophthalmologic laser, laser marker e.g. Laser cutting and welding application.