Electronic switching power supply

Abstract

An electronic switching power supply for supplying power to a load from an input voltage source, including a flyback converter with a transformer having its primary coil connected in series with the collector-emitter circuit of a first transistor in parallel arrangement with the input voltage source, while its secondary coil is connected in series with the load and a first diode, with the emitter of the first transistor being connected to chassis or reference potential through a first resistor while the base of the first transistor is connected to a control circuit (St), with a capacitor in parallel arrangement with the load, with the voltage across the junction (B) of the capacitor at the side remote from reference potential being of the same polarity as the voltage across the junction (A) of the first resistor and the first transistor. The power supply also includes a first circuit, including a second resistor, that is placed between the junction (A) of the first resistor (8) and the first transistor and the junction (B) of the capacitor at the side remote from reference potential, the first circuit serving to reduce a total effective resistance between the emitter of the first transistor and the reference or chassis potential when a voltage across said capacitor is below a predetermined value.