Comparison of the energy performance of pulse generation circuits for PEF

Abstract

Pulse shaped voltages are required for preservation of food with PEF. Several pulse forms generated by a variety of circuits are compared with respect to required energy. The analysis includes square pulses, trapezoidal pulses, exponential decay pulses and oscillatory and over-damped oscillatory pulses. The base of comparison is the establishment of a certain minimum voltage level during certain minimum time. The comparison concerns the dissipation in a resistive load, which is considered to be representative for a category of loads, including PEF. Furthermore, the ratio between initial capacitor voltage and corresponding threshold voltage is compared as this parameter reflects the required hold voltage of the switch in the circuit. The analysis shows that the efficiency approaches 100% for hard switched circuits and circuits with transmission lines. For highly damped RLC-circuits with capacitor C, inductor L and load resistance R the maximum obtainable efficiency is between 37 and 47% where the capacitor C has to be charged to 1.6–1.8 times the desired threshold voltage. For oscillating damped sinusoids the maximum efficiency is between 47 and 52%, however, the capacitor has to be charged to 1.8–3 times the threshold voltage. Graphs with an example are provided to determine circuit parameters from a certain pulse specification.