I need help with modifying the power supply for some LED room lighting.
I am trying to replace some 12V halogen spotlights with 12V LED spotlights, but am having trouble with the power supply. The original Power supply is incompatible with LED. The LED lamps take about 300 mA each, and in total there are 12 of them. I am using a 5A 12.4V switched mode power supply. When I connected the power supply to just one lamp it lights beautifully without flickering, and there does not seem to be any problem with a minimum current requirement with this power supply. However with all lamps connected, the lamps flicker (all in synchrony); it seems the flickering gets worse and at lower frequency, the more lamps are connected. It looks like there is a feedback oscillation problem somewhere between the power supply and the lamps.
Under some conditions the flickering vanishes: eg if there is one 50W halogen lamp in the circuit; also if the lights are turned on shortly AFTER the 50W lamp was connected and then disconnected - but naturally the advantage disappears the second time the lights are turned on.
All this makes me sure that a trivial modification to the power supply should be able to correct the problem - such as a resister or capacitor. I tried first a 1.69K Ohm resistor and then a 240 Ohm resistor connected acros the 12V output - I expected that to help, but neither worked. Maybe some kind of capacitor across the output is what I need? A capacitor should short-circuit the AC component in the oscillation.
If I connect a multimeter across the 240 Ohm resistor with all 12 LED lamps connected and no halogen (and therefore with the lamps flickering), surprisingly I find only 9.3 V coming from the power supply (with only one lamp directly connected it was 12.4V). AC current across the 240 Ohm resistor is 0. However if I replace one of the lamps with the 50W halogen all the lamps burn very brightly (all LEDs and the halogen) without flickering, and there is 12.4V DC and 26V AC across the 240 Ohm resistor!!!
Now I am confused!!!
Can anyone help me please?
I am trying to replace some 12V halogen spotlights with 12V LED spotlights, but am having trouble with the power supply. The original Power supply is incompatible with LED. The LED lamps take about 300 mA each, and in total there are 12 of them. I am using a 5A 12.4V switched mode power supply. When I connected the power supply to just one lamp it lights beautifully without flickering, and there does not seem to be any problem with a minimum current requirement with this power supply. However with all lamps connected, the lamps flicker (all in synchrony); it seems the flickering gets worse and at lower frequency, the more lamps are connected. It looks like there is a feedback oscillation problem somewhere between the power supply and the lamps.
Under some conditions the flickering vanishes: eg if there is one 50W halogen lamp in the circuit; also if the lights are turned on shortly AFTER the 50W lamp was connected and then disconnected - but naturally the advantage disappears the second time the lights are turned on.
All this makes me sure that a trivial modification to the power supply should be able to correct the problem - such as a resister or capacitor. I tried first a 1.69K Ohm resistor and then a 240 Ohm resistor connected acros the 12V output - I expected that to help, but neither worked. Maybe some kind of capacitor across the output is what I need? A capacitor should short-circuit the AC component in the oscillation.
If I connect a multimeter across the 240 Ohm resistor with all 12 LED lamps connected and no halogen (and therefore with the lamps flickering), surprisingly I find only 9.3 V coming from the power supply (with only one lamp directly connected it was 12.4V). AC current across the 240 Ohm resistor is 0. However if I replace one of the lamps with the 50W halogen all the lamps burn very brightly (all LEDs and the halogen) without flickering, and there is 12.4V DC and 26V AC across the 240 Ohm resistor!!!
Now I am confused!!!
Can anyone help me please?
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