Abstract: A transformer includes a bobbin with spacers extending inwardly from the bobbin and a barrier extending outwardly from the bobbin. A ferrite core positioned within the bobbin is separated by the spacers to provide a controlled air gap. Primary windings wound around the bobbin are separated into series connected windings by the barrier. The barrier is aligned with spacers so as to prevent any wound portion of the primary windings from overlapping the air gap in the ferrite core.

Abstract: When a main switching transistor of a zero voltage switching power supply is conductive, a voltage is developed in a current sensing resistor coupled in series with the transistor. The voltage in the current sensing resistor is coupled to a first input of a comparator of the control circuit. A second input of the comparator is coupled to a capacitor that develops a voltage that varies in accordance with an output voltage of the power supply. During a given conduction interval of the transistor, the comparator is triggered in accordance with the difference between the current sensing resistor voltage and the capacitor voltage. An output of the comparator is coupled to the base of the transistor for controlling the turn off instant of the transistor on a current pulse-by-current pulse basis. Under overload condition, when the transistor is turned off, a reverse collector current flows through the base-collector junction of the transistor.