Capacitor current feedback for output filter damping in switched-mode magnet power supplies

Abstract

In magnet power supplies for a particle accelerator system, a second-order low-pass filter is used to reduce the output current ripple content within specifications. The output filter must be properly damped in order to avoid any large amplification at the resonant frequency and large transient responses of voltages and currents at the step change of the line voltage. Conventionally, a series combination of resistance and capacitance is added in parallel with the filter capacitor to provide the required damping. This approach, however, requires a large dc-blocking capacitor which has to be several times larger than the filter capacitor. In this paper, a filter damping technique using capacitor current feedback is presented. The basic concept of the capacitor current feedback is established using a linear model of the converter involved, and then a sampled-data model of the converter is used to analyze the filter damping technique. The filter damping effect of the capacitor current feedback is verified experimentally.

Output Filter with Adaptive Damping for Interleaved Converters with Low Ripple and High Dynamics

“…This topology has the advantage of damping the resonance between output filter C out and load inductance L load without affecting the steady state performance of the converter. However, the value C damp must be adapted to the load parameters and often leads to a bulky damping capacitor C damp [8]. Moreover, the damping capacitor branch compromises the transient behavior of the load current i load , since it increases the effective output capacitance, to achieve a sufficiently damped performance.…”

“…R load -L load ) to ensure sufficient ripple attenuation without compromising the dynamic performance of the system [4]. However, simply the inclusion of a low output capacitance is often not enough since the formation of the L load -C out with a low resistance R load could lead to resonances that are triggered during the converter's transient [8]. As a result, the output stage usually consists of an output filter combined with a damping filter, as highlighted in Fig.…”