Development of variable charging system for voltage adjustment

Compact pulsed power generators have been used in fields such as biology, environment, and agriculture. Functions required by researchers include miniaturization, weight saving, safety, and ease-of-use. Recently, control systems using microcomputers or field programmable gate arrays (FPGA) have been studied for flexibility in changing circuits and greater control of pulse power. Because various uses are conducted under different parameters such as conductivity, humidity, pressure, and temperature, different conditions require specific energies and thus requires flexibility in the pulsed power generator. Our work aims to utilize the primary capacitor through an FPGA for charging time so as to control pulsed power energy output. Our compact pulsed power generator consists of a charger, a magnetic pulse compression (MPC) circuit and a controller using a FPGA. Design specifications of the controller are: Verilog HDL, Xilinx ISE 14.7, and FPGA (Spartan-3). Maximum charging voltage is 1.5 kV to the primary capacitor of 2.24 μF. Repetition rate is up to 500 pulses per second, and charging energy is a maximum of 1.0 J/pulse. Voltage was measured by a high voltage probe (Tektronix Model P6015A) for pulse power and mid-range voltage probe (Tektronix Model P5100) for charger. The load has a resistance of 100 Ω. The inhibit signal turns off when the frequency turns on. At this time, charging of the primary capacitor starts. After that, the inhibit signal turns on, and trigger signal to turn on for 200 μs, and generated the pulsed power.