High-frequency current transducers in a control system for quasiresonant power convertors

After a short review of zero-current-switched quasiresonant power conversion principles, some drawbacks associated with the full-wave operation mode are described. In particular, those aspects connected with the power switch on-time control are analysed. The paper demonstrates the suitability of using across-the-switch current detection in a control system which ensures zero-current switching under various operating conditions. Some simple, low-cost measurement systems realised for instantaneous current transduction in a power MOSFET resonant switch are then described. The systems considered are based on Hall-effect probes, current-sensing power MOSFETs, and resistive shunts. Experimental results carried out with a test circuit are reported and discussed. Finally, the performance and the advantages obtained from the use of a shunt-based measurement system in power-convertor control are described