A thorough efficiency analysis of a boost PWM converter taking into account the conduction losses, the diode power loss, the switching losses, the gate-drive loss and the capacitive switching loss, for both continuous conduction mode and discontinuous conduction mode is presented. The analysis is extended in the synchronous rectification case where a self driven transistor instead of the diode rectifier is adopted. The expressions of the converter efficiency can be used to predict the circuit behaviour for both a constant input and constant output voltage operation. The model has been validated using SPECTRE simulator and a 0.35 µm CMOS process, and error always lower than 2% were found. Copyright © 2005 John Wiley & Sons, Ltd.