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Surge Protected Cheap Transformerless Hi Watt LED Driver Circuit

This circuit is just a proof of concept just to show that the good old 555 timer can still be used for a modern and quite demanding application. It is by no means an optimized circuit that can be readily used for mass production. It appears relatively big by today's standard because I used only through hole components. You may shrink it to 50 % of its original size if you use modern SMD parts. You may also be able to increase the efficiency of this circuit. Unfortunately I didnt't have time to do extensive measurements with all sorts of inductors. There may be some room for optimizations.


Parts list

R1 2.2 kΩ / 0.1 W
R2 10 kΩ / 0.1 W
R3 100 kΩ / 0.1 W
R4 470 Ω / 0.1 W
R5 1 kΩ / 0.1 W
R6 2 Ω / 0.25W
C1 220 pF NPO ceramic disc capacitor
C2 10 µF / 16 V electrolytic
C3, C4 470 µF / 6.3 V, low ESR
L1 custom made transformer, see text
L2 47 µH / 2 A (TDK SLF 12575 / Fastron PIS4728 series)
D1 1N4148
D2 SB240 (SB360, MBRS240, MBRD650)
D3 BZX55C 4V7, 4.7 V Zener Diode
D4 1 W High Power LED
T1 BC 337-40 (2N2222A)
T2 BC547B (2N3904)
T3 2SK2869 (IRLR2905, IRLZ 34N)
IC1 ICM7555 (TLC555, HA17555)