Secondary side switching regulator having a phase lock loop control circuit

Abstract

A switching power converter for producing regulated D.C. power at two or more voltages. First and second regulation circuits including switching elements are connected across the secondary side of a transformer. A control circuit including a phase lock loop provides a first timing signal in leading relation to the AC input, and a delay circuit which provides a second timing circuit in delayed relation to the first timing signal. A logic circuit is responsive to the first and second timing signals to provide drive signals for the switching elements. The regulation circuits each include a first switching element having a power terminal coupled to the secondary winding and another power terminal is coupled to an intermediate node. A second switching element has a power terminal coupled to the intermediate node and another power terminal coupled to a common node. An inductor is coupled from the intermediate node to an output node. The control circuit delivers drive signals to control terminals of the switching elements to switch the switching elements on and off such that first and second regulated voltages appear between the first and second output nodes and the common node, respectively.