Chapter 21 - Power electronics in capacitor charging applications

Abstract

Conventional dc power supplies operate at a given dc output voltage into a constant or near constant load. Pulse loads such as lasers, flashlamps, railguns, and radar, however, require short but intense bursts of energy. Recharging the capacitor voltage to a specified voltage is tasked to a capacitor charging power supply (CCPS). The role of power electronics devices, topologies, and charging strategies for capacitor charging applications is presented. The CCPS has three modes of operation. The first mode is the charging mode in which the capacitor is charged from an initial voltage of zero to a specified final voltage. The duration of the charging mode is determined by the capacitance of the energy storage capacitor and the rate at which the CCPS delivers energy. The next mode of operation is the refresh mode, which can be considered a “standby mode” where the stored energy is simply maintained. When the output voltage drops below a predetermined value, the CCPS should turn on and deliver the energy necessary to compensate for capacitor leakage. The final mode of operation is the discharge mode where the load is actively discharging the capacitor. The CCPS does not supply any energy to the load in this mode. The amount of time the CCPS remains in this mode is determined by how quickly the load can discharge the capacitor.