Abstract-This letter describes an enhancement to a previously reported single-stage transformer-leakage-inductance based power-factor-corrected isolated power supply. An improved switch timing calculation algorithm is developed to achieve zero current switch on of the active rectifier switches. The algorithm is based on an analytical model of the system relating the gate timing to the input and output voltages and control inputs. Remarkably, a closed form expression for the switch timing can be derived and used to calculate and apply the timings in real-time without the need for high speed measurements or resonant structures. A prototype 1.25 kW prototype power supply is implemented using the proposed technique and performance measurements presented.