Regulated Power Supply for LED Spot Light

Hi Bheema,

Please be aware that the lifetime limiting factor of your design (as always) will be the electrolytic capacitors. Make sure that you use 105 C types with sufficient basic lifetime / ripple current . In order to make a good assumprion of the exspected lifetime to must measure the ripple current through the elcaps and measure the surrounding temperature. The elcap supplier will give you a lifetime calulation equation to incorporate these figures to calcuate for exspected liftime.

Best regards,

Enrico Migchels

Hi Bheema,

Please be aware that the lifetime limiting factor of your design (as always) will be the electrolytic capacitors. Make sure that you use 105 C types with sufficient basic lifetime / ripple current . In order to make a good assumprion of the exspected lifetime to must measure the ripple current through the elcaps and measure the surrounding temperature. The elcap supplier will give you a lifetime calulation equation to incorporate these figures to calcuate for exspected liftime.

Best regards,

Enrico Migchels

Hi Enrico,

Thanks for the suggestion on capacitor selection.

but down the line how often should we take care about the temperature rating of Elcaps (i mean to say the derating of elcaps life time WRT temperature)

for example if i want 18V regulated output then what should be value of cap and voltage rating.

Best Rdgs

Bheema

Hi Bheema,

For a give brand and type (i use lelon RXK quite often):

Your selection procedure should go like this: voltage range selection (in your case 25V, but be aware that the voltage can rise in fault mode).

Measure or calulate the ripple current through the elcap. Select 'maximum permisseble current' parameter. If for the given ESR and ripple current the output ripple voltage is too high add a second L/C filter or use a lower ESR type capacitor (brand NCC, type KZH is very good).

You see. Capacitance is not the main parameter, it is not important.

Best regards,

Enrico Migchels

HI Enrico,

yes i should consider the surge current at fault condition, probably i can go with 48V capacitor instead of 25V.

and also i will be using an Bridge rectifier (BR) module with 1A current rating.

suppose i use a T/f of rating 18-0-18 i.e 18V step down voltage i will be getting, this is feed to BR which gives me roughly 1.41 times the o/p which is 25V.

Best Rdgs

Bheema

Bheema,

Have you considered just using an off the shelf existing LED driver for your application instead of building your own?

-Kent

Hi Kent,

I have selected  LM3404MALM3404MA LED driver which is available in market

but for power supply i have planned to design on my own.

Best Rdgs

Bheema

Thanks Bheema.

If you are interested in comparing the cost / performance of a standard commercial ac/dc supply (or dc/dc) to power the LED driver please let me know. It may be worth a quick comparison for you.

Kent Smith

Applications Engineer

ksmith@xppower.com

Hi Kent,

Yes i would be interested in comparision on different standard commercial ac/dc supply (or dc/dc) to power the LED driver.

and also as a simple regulated power supply i have selected LM350 which is an variable output one.

Best Rdgs

Bheema

Bheema,

Please send me an email to ksmith@xppower.com and I can get your contact information to the correct people to work with you in selecting the best products to show you for your comparison purposes.

Thanks,

-Kent Smith

XP Power