Low Power Multiple Output DC Supply -Part I: Flyback Converter with Wide Input Voltage Range

The paper deals with a front-end topology of a low power switched-mode power supply intended for a plug and play use. During its design, a special attention has been paid to a simple and cost effective solution confronted with a wide input line-voltage range (57 ÷ 3× 240)·(1 ± 0.2) VRMS and with the frequency range from 40 Hz to 65 Hz. Such extreme demands are particularly of interest in industrial applications where devices should be supplied either from the single- two- or three-phase network. In order to reduce human errors and production cost, no mechanical switches are allowed. The paper proposes a novel concept of the Flyback converter that solves the designated task with variable turns ratio of the transformer, while keeping the switching frequency constant. The implemented transformer with its control circuit enables on-line adaptation to the temporary value of input phase-voltage. As a consequence, voltage stress of implemented switching transistors is also reduced.