Analysis of a DC Power Supply to Regulate on an Open-Loop Basis

Telephone equipment being used for data transmission, and housed on telephone customer premises, requires miniature ac to dc power supplies. The miniaturization of a dc power supply associated with this equipment has been facilitated by the use of pulse modulation techniques. An analysis is presented of an open-loop regulated dc power supply operating from a commercial ac source. The analysis illustrates how open-loop regulation has been achieved through the use of pulse modulation techniques. The pulse modulation is achieved with a parallel inverter operating into a 2-core transformer at a 20-kHz switching rate. The analysis includes the cases where 1) under ideal conditions there is no error in the pulse duration, 2) the error in pulse duration is a constant finite amount, and 3) pulse duration error varies on a periodic basis. Both calculated and measured results are presented based on tests made on a breadboard model of the open-loop inverter regulator.