Continue to Site

Welcome to

Welcome to our site! is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Dimming a high power tungsten bulb


Advanced Member level 5
Jun 13, 2021
Reaction score
Trophy points
Activity points
We are working on a small lighthouse at a small marina. There have been crashes into a sand bank of late. We need to dim a tungsten bulb from 200W to 500W.
We have 240VAC mains supply.
Solution must accord with EN61000-3-2 mains harmonics regs, and flicker regs.
Mains isolation not required.

Thinking BuckBoost PFC.....but is there a cheaper/smaller way?
Also, Buckboost PFC gives DC output....not good for the arc-over that will occur when the bulb eventually fails.

What about Standard fluorescent half bridge resonant fluorescent ballast circuit...with preceeding Boost PFC?...this gives a high frequency AC current output...which gives advantageous zero crossings for extinguishment of arc-over......but does that apply at frequencies that are well above 50Hz?.....because the current soon rises again after crossing zero.

What about standard high frequency PWM into the bulb, with an inductor in series with it? a class D amp
If this is a one-off then a surplus Variac would be ideal.

Or you could have a plurality of bulbs and a bank of switches, for
a few levels and dirt, dirt cheap. Maybe have to put the bulbs in
series for your 240V if that's not common bulb voltage "over there".
Is the load unchanging? Inductive drop could do the job. As choke or coupled inductor.

coupled inductor reduces 230VAC (w pfc cap) to bulb 200W.png

Alternatively a choke consisting of a single inductor 400 mH.

LaTeX Commands Quick-Menu:

Similar threads

Part and Inventory Search

Welcome to