mains power supply with primary regulation

401011011, LI 40 pH 3AC93AR1 4, pH 3A L3 mm470n 7W 400V 40 3A 10 19 12 220 V 240 V C1 C3 R2 iemm 4700P/63V 100n 914 BC 557 5k "see text LM317T adj T 22011 16V R3 10n mains power supply with primary regulation L2 B50 C5000/3500 r) IC2 LM 317 adj. R17 C10 RR= P1 L4 R113 m 40 pH R4 226D 15 100n 95 C4 470 400V IC3 TIL 119 5 The unusual circuit shown in figure 1 has an unusual efficiency: according to SGS, this amounts to no less than 37 per cent at an output voltage of 3 V and output current of 2 A. With tra- ditional secondary regulation, an ef- ficiency of about 8 per cent would have been normal. The output voltage can be varied over the range 1.2 ...25 V, and the output current can be 1.5 A at any of these voltages, provided IC2is mounted on a suitable heat sink. Another advantage of primary regu- lation is that the power supply is pro- tected against variations in the mains supply. This aspect is normally ignored with secondary regulation, as it is assumed that primary fluctuation...