Abstract <p>An analytical calculation and analysis has been performed for the four main operating ranges of a quasiPWM step-down converter within the switching frequency period. Conditions required for stable converter operation in a soft switching mode with current resonance when the power switch is turned on have been determined. Based on the calculation of the voltage across the resonant capacitor averaged throughout the switching period, an analytical relationship for the DC voltage conversion coefficient of the step-down converter has been obtained. It is shown that, in the general case, the conversion coefficient is represented by a complex function of three variables such as the switching frequency, the PWM adjustment coefficient, and the load current. When choosing the load current as a parameter, at a constant switching frequency, an relationship is obtained for calculating the adjustment characteristics of the converter. Upon choosing the adjustment coefficient as a parameter, at a constant switching frequency, a relationship for the estimation of load characteristics has been obtained. Experimental results that confirm the correctness of the basic theoretical calculations are presented. The limit of current and voltage are estimated for the key components of the circuit.</p>