Halogen lamp 12V power adapter, please help

tbx8192

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I am making a halogen desk lamp that uses DC power supply. My plan is to find a notebook power adapter to drive 12V bi-pin bulb. For a desk lamp, 36W is enough power. That is 3A current. A 12V notebook AC power adapter can supply up to 5A current. So there is no problem.

My worry is lamp's startup current. For a incandescent bulb, its startup current is usually 10 times larger. But I do not want a 12V 30A adapter. It is big, heavy and hard to find.

So my question is:
(1) Is a 12V5A notebook power adapter capable of starting a 12V3A halogen bulb?
(2) If yes, does it hurt the adapter?
(3) If still yes, should I add some protection? (a inductance? How many H should it be?)
 

jrmcferren

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The 12 volt 5 amp adapter is more than enough. The inrush for startup is so short that the power supply would not notice it. If you are really worried about it, switch the DC side instead of the AC side and that way the filter capacitor is always charged up when switching the light on and will absorb the startup surge without difficulty.
 

Gauss163

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The 12 volt 5 amp adapter is more than enough.

Whether or not it will work will depends on the design of the PSU. For example a Dell DA2 (12V/18A) may trip even when you hot-plug some low-power devices (like an Opus BT-C3100 charger) due to the high inrush current when capacitors charge.
 
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tbx8192

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Whether or not it will work will depends on the design of the PSU. For example a Dell DA2 (12V/18A) may trip even when you hot-plug some low-power devices (like an Opus BT-C3100 charger) due to the high inrush current when capacitors charge.

Thanks. I will avoid this type.
 

tbx8192

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The 12 volt 5 amp adapter is more than enough. The inrush for startup is so short that the power supply would not notice it. If you are really worried about it, switch the DC side instead of the AC side and that way the filter capacitor is always charged up when switching the light on and will absorb the startup surge without difficulty.

Thanks. So it is due to capacitor in the power adapter. I will try.
 
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