Fast-Transient PCCM Switching Converter With Freewheel Switching Control

This brief presents a new switching converter operating in pseudo-continuous-conduction mode (PCCM) with freewheel switching control. Compared with conventional discontinuous-conduction mode (DCM) converters, this converter demonstrates much improved current handling capability with reduced current and voltage ripples. The control-to-output transfer function exhibits a single-pole behavior, making the load transient response much faster than its CCM counterparts. Simulation and experimental results show that, with a 6-V, 6-W load and a 10-V unregulated supply, the PCCM converter has a current ripple of only 1.1 A and a ripple voltage of only 58 mV, while a DCM converter has a current ripple of 2.2 A and a ripple voltage of 220 mV. In addition, the PCCM converter takes only 25 mus to respond to a 500-mA load current change while a CCM one requires 1.4 ms.