Efficiency is the essential figure that reflects the quality of a switching regulator, and it is directly measured as:
Efficiency = ΣPOUT/ΣPIN = Σ(VOUT*IOUT)/Σ(VIN*IIN) < 100%,
where ΣPOUT – ΣPIN is the total power loss.
In switching regulators, there are different types of power losses contributed by various factors. The losses in buck converters are discussed here, and the losses for other topologies can be analyzed in a similar fashion.
1. Conduction Loss
Conduction loss is straight forward and exists on both HS and LS MOSFET; it is the IRMS2*Rds(on) loss when a MOSFET conducts current during its on time. For a buck with average current Iavg, peak-to-peak current ripple Iripple, and duty cycle D, the RMS current for HS is given by:
IRMS = sqrt((D/3)*((I
