Reset Circuits With Energy Recovery for Solid-State Modulators

In power modulators for pulses in the microsecond range, transformers are often used for generating high output voltages. With standard topologies, the transformer is usually only excited in a unipolar direction, i.e., the flux density B swings between zero and a value close to the saturation flux density. By applying a reset circuit, the flux density B in the transformer is set to a value close to the negative saturation flux density before the pulse, so that the flux density could swing between the negative and positive saturation values during the pulse. This allows one to halve the core area and reduce the core volume/weight as well as the losses. In this paper, the operating modes of three different reset circuit topologies (the standard and a new advanced passive as well as an active one) and the corresponding waveforms are explained. Furthermore, the three topologies are compared with respect to the losses/complexity based on a design for a solid-state modulator with 20-MW output power and 200-kV output voltage..