Design and development of switch mode power supply for 3.0 kW solid state RF amplifier

A 3 kW Solid State Amplifier (SSA) has been indigenously designed and developed for a 37.8 MHz re- buncher of The Rare Ion Beam (RIB) facility at VECC. This power amplifier of 3.0 kW at 37.8 MHz has been designed and developed with combining of four amplifier modules of 800 W. The maximum requirement of voltage and current to drive the each amplifier module is 50 V and 30 A. A DC power supply (rated 55V/150A) has been designed and developed indigenously at VECC Kolkata for biasing of this amplifier system. This is current/voltage controlled (cv/cc) switched mode power supply, it works on the principle of pulse width modulation technique using buck converter topology and regulated by using PI controller with require phase and gain margin. In this power supply three phase line voltage (415V, 50Hz.) is fed to three phase step down transformer to achieve 55 volt AC, this AC voltage rectified with 3-phase full wave rectifier and filtered with LC filter to get around 74V DC. The rectified output is switched at high frequency (20 KHz) by buck converter circuit by using IGBT as a switching element to get pulsating DC. LC filter is used for smoothing the pulsating DC to obtain 55V DC at output. The voltage regulation is achieved by comparing the sampled output voltage with stable reference voltage. The error signal is fed to the built in error amplifier of PWM IC (SG 3525) which in terms varies the duty cycle depending upon error signal, which drive IGBT through Opto-isolator (TLP 250). For current control a shunt resistance is used as a feedback in series with the load. The simulation is performed in MATLAB and PSIM both in order to utilize the high end computational mechanics from MATLAB and special power electronics featured of PSIM. The experimental result is presented for the verification of mathematical analysis. In this paper, circuit topology, function of system components, key system specifications and experimental result of power supply are discussed. (author)