Dimming a high power tungsten bulb

[cupoftea]

Hi,
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?...like a class D amp

 

[D.A.(Tony)Stewart]

How about a Triac with 2 stage choke filters. You don't have any cost specs.

 

[Easy peasy]

transformer, or variac .....

 

[betwixt]

Its tungsten and has a long thermal time constant so I would go with phase control and filtering as Tony suggests. A triac would be FAR cheaper than a PSU with PFC or any PWM driver.

Brian.

 

[dick_freebird]

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".

 

[Easy peasy]

as far as light houses go - reliability is key, hence auto Tx or variac

 

[BradtheRad]

Is the load unchanging? Inductive drop could do the job. As choke or coupled inductor.

Alternatively a choke consisting of a single inductor 400 mH.