Circuit arrangement for switching the power factor of the switch power supply pCircuit arrangement for improving the power factor of the switch power supply

摘要

The invention relates to a circuit for achieving higher power factor in a switched-mode power supply in which there is a coupling (A) between the full-wave rectifier (DB) and the primary circuit (C, W1, S1) for feeding the energy from the rectifier (DB) to the transformer (M). According to the invention the coupling (A) is formed by an inductance (L) and a diode (D), connected in series, and is connected in the primary circuit (C, W1, S1) to a point between the switch (S1) and the filter capacitor (C) in such a way that at least a part of the primary winding (W1) is between the point and the filter capacitor (C). Preferably, the coupling (A) is connected to a point between the switch (S1) and the primary winding (W1). By this simple circuit a power factor of the order of 0.9 ... 0.96 is easily achieved. The circuit is able to operate within a wide mains voltage range, and is not sensitive to variations in the switching frequency or the load (LD). IMAGE