transformerless mains power supply - space saving and cost effective

space saving and cost effective Warning! This circuit needs to be constructed and wired with the greatest care as the full mains voltage is present at several points. The pulsating direct voltage provided by rectifier D1 . . . D4 has a peak value of 310 V. This voltage is ap- plied to the drain of power MOSFET T1 via limiting resistor R9. A control circuit ensures that the MOSFET only conducts during the short times just before and after the mains voltage goes through zero. During these times the momentary value of the pulsating direct voltage 7-76 transformerless mains power supply does not exceed 5 V. In the same short times smoothing capacitor C2 is charged: during the remainder of the time it provides the output cur- rent. Consequently, this capacitor has a very high value: 10 000 II. The load-current pulses have a peak value, if only for a brief moment, of the order of 4 A! The stability of the output voltage is essentially dependent upon the load. The output current may be 1...