Droop compensation with soft switching for High Voltage Converter Modulator (HVCM)

High Voltage Converter Modulators (HVCM) offer significant performance advantages over conventional modulator technologies for long pulse applications. One of the key advantages of HVCM technology is the ability to compensate for capacitor bank droop. Achieving droop compensation without incurring significant additional switching loss has not been possible in existing designs. This paper presents an analysis of the “Y-point” variant of the HVCM topology using the Combined Phase and Frequency Modulation (CPFM) technique. This, combined with the addition of a ‘lossless’ snubber circuit, enables droop compensation while achieving soft switching over the entire pulse duration. The rise time and overshoot of the output voltage is optimised using an iterative extreme seeking algorithm. The optimisation reduces the rise time from 100μs to 50μs with no overshoot. This will lead to an increase in overall accelerator efficiency.