Parameters optimization for improved dynamics of voltage multipliers for space

Voltage multipliers for the generation of high voltages (HV) are widely employed aboard space vehicles and new applications open-up. One is the drive of ionic motors. The characteristics of such loads, as well as those of many others, require special care to the dynamics and to robustness performances of the voltage supply. After recalling the dynamic characterization of the Cockroft-Walton (CW) cell as a linear three-port network in the small signal approximation, the n-cell chain is characterized and the possibility of reaching simplified expression of its transfer functions is put into evidence. The good accuracy of the model is supported by experimental results. The CW chain with identical capacitors in its cells is compared with the CW chain whose capacitor values are gradually decreased from the first to the last cell. Such an assignment has been used already for obtaining a minimization of the ripple. It is shown that it can improve the dynamic behavior too. Tables of the transfer functions for voltage gain, input admittance, output impedance and current gain are given for aiding the design of the voltage multipliers. The usefulness of the described modeling technique goes beyond the space applications.