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Reducing COSS Switching Loss in a GaN-based Resonant Cockcroft-Walton Converter Using Resonant Charge Redistribution


By applying resonant charge redistribution (RCR) to the parasitic capacitances of a switched-capacitor converter, COSS-related dynamic switching losses can be significantly reduced. The proposed technique demonstrates adiabatic mitigation of all primary loss mechanisms in a transformer-less resonant Cockcroft-Walton (CW) converter's forward power path, with only the gate drivers exhibiting conventional hard-charged CV2f losses. Two inductors are used: a large primary inductance directly in the forward power path to mitigate transient inrush currents, and a second small inductance to perform Coss charge redistribution prior to initialization of subsequent phases. The second inductor can be small while still exhibiting high Q-factor as it only interacts with switch parasitics. A discrete 1:5 prototype using GaN-FETs and diodes achieves a power density of 181.8 kW/liter (2.98 kW/inch3) and a peak efficiency of 96.2% with RCR contributing a measured 61% reduction in total losses at light load for a 0.74% increase in solution volume.

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