Power supply unit for the dc power supply of an electrical appliance which is fed from an ac mains

摘要

It is a power supply unit for the dc power supply of an electrical appliance which is fed from an ac mains proposed, in particular a power supply unit for a power tool which can be driven by a universal motor, such as, for example, a percussion drilling machine. The required constant voltage source contains the series circuit of a constant voltage element (40), of an equally richter element (48) and a protective resistor (44, 46), which at least partially (44), together with the constant voltage element (40) by means of a buffer capacitor (52) is bridged. As a result, the buffer capacity at a significantly higher voltage level than the required direct voltage (u), as a result of which is provided on the one hand, to significantly more rapidly and, on the other hand, has only a very low pulsation. Such a dc voltage (u) is very well suited both for supplying a control unit of the electrical appliance, such as also for the supply of additional consumers, wherein the low pulsation of the dc voltage, for example, in the case of the feeding of light-emitting diodes as the additional loads, the variation of the light intensity at least is reduced to such an extent that they can be used for the human eye is no longer visible (fig.).