Driving High Power Lamp Using MOSFET or RELAY?

mosfet as relay

I am wondering to drive high power lamp using Mosfet or Relay?
Could anyone explain the main difference between these two schemes?
Thanks a lot!

Yoy did not mention what power source will bu used: AC or DC.

If it is DC you can use both a power mosfet or a relay. However, relays for DC applications have limited applications as you will have so called "welding effect" at the contacts. On the other hand switching with MOSFET ie efficient and fast..

For AC light you can not use MOSFET but you can use a relay (or contactor) or you can use a triac. Other option will be "solid state" relay which basically a triac trigged by "zero crossing" device..

IanP said:

For AC light you can not use MOSFET but you can use a relay (or contactor) or you can use a triac. Other option will be "solid state" relay which basically a triac trigged by "zero crossing" device..

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I am using AC light. I don't know why MOSFET can't be used in AC light application.

the main differance is of switching speed. relay's speed is many times less than a mosfet

MOSFETs can not switch ac loads. They can be used only in dc applications.
As far as semoconductors are concerned, SCRS and triacs are the devices specially designed for ac applications. They can switch significant currents and can be trigged at "zero crossing" thus not causing any spikes in th supply lines (as relays will do).

IanP said:

For AC light you can not use MOSFET but you can use a relay (or contactor) or you can use a triac. Other option will be "solid state" relay which basically a triac trigged by "zero crossing" device..

Click to expand...

Hello Ianp,
What is so called "zero crossing" device?
Can 555 timer output drive triac directly?
If a triac which can bear 12A current can be soldered on board?

the main differance is of switching speed. relay's speed is many times less than a mosfet

Click to expand...

Switching speed does not affect anything in normal lamp on-off action. There are cases where the lamp needs more time to glow than the relay to activate. Mosfet's speed is used in lamp dimming, through PWM (pulse with modulation), a method that only the mosfet (or transistor) can offer.

What is so called "zero crossing" device?

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This is used in AC lamp control, on-off or dimming. It synchronises the control device (Triac or thyristor) with the time that the AC supply (sinusoidal) voltage reaches the zero value. This is done in order too minimise RF interferance caused when switching is perfomed while the voltage is not at a zero value.

Can 555 timer output drive triac directly?

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Yes and No. Depends on the voltage of the cct. Common practice and safety states that we should isolate high voltages from parts of the cct that cannot handle them in case of a fault.

If a triac which can bear 12A current can be soldered on board?

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Yes. Just have in mind that the PCB tracks must be sized accordingly in order to handle the 12A. If the board is already made and tracks are not thick enough you can put solder in the whole track's run in order to strenghten it.

I hope i help a little. I am expecting the answer from IanP who is more experience than me.

Try google: "zero crossing"+triac+driver
You will find scores of sites such as this one..
https://www.fairchildsemi.com/an/AN/AN-3003.pdf
If you think you don't need "zero crossing" use any other optocoupler as for safety reason you may need isolation from HV..

On some pcb that operate with high currents you can see a silver- or tin-plated copper wire soldered on top of the existing track. This solves the problem with conducting currents and the width of a truck..