Abstract: A wide range single-phase/polyphase switching power supply is presented. The power supply comprises first and second full wave bridge circuits. The rectified outputs of the bridge circuits are connected to a preregulator circuit, i.e., a FET circuit, where the primary input voltage from bridge circuits is limited. The output of the preregulator circuit is presented to a filter circuit. A current mode controller circuit operates at a fixed frequency with a variable duty cycle. An output of the current mode controller circuit drives the gate of a switching FET, at the fixed frequency and variable duty cycle. The aforementioned filtered voltage signal and the drain of the switching FET are connected across a first winding on the primary side of a flyback transformer. A second winding on the primary side of the flyback transformer is connected across Vcc, the supply voltage of the current mode controller circuit.

Abstract: A multi-loop controller for controlling a quasi-resonant converter having a power switch, a filter inductor and an output voltage. The controller includes a sensor circuit for sensing the output voltage of the converter. A detector monitors the filter inductor current of the converter. The output voltage is compared with a known reference voltage to develop a control error voltage when the output voltage exceeds the reference voltage. A comparing circuit then compares the inductor current with the control error voltage and produces a control signal when a predetermination relationship has been detected. Finally, an activating circuit responsive to the control signal turns the power switch on.