Today I bought an LED bulb from a local shop that starts with T and ends in O it's one of there own brand according to its packaging it should consume 9 watts and give the same light as a real 60 watt bulb. Anyhow I took it to my shack a to test how much RFI it made I was pleasantly surprised that it only seemed to give a little rectifier noise on the higher bands name 15 and 10 meters. The noise disappeared completely when I connected my digital multimeter on AC volts between the metal lamp base and earth just to see how much leakage voltage was on the metal base it was around 11 volts one way and around 8 volts the other way polarity reversed by swapping the supply wires. Next I thought ide try the lamp on DC not expecting it to work but surprise surprise it worked fine fed with around 230 VDC from a full wave rectifier it worked fine pulling around 27 mA adding a capacitor for a bit of smoothing gave 330 VDC and the lamp remained lit for a couple of seconds while the cap ran down. Final test was running it on AC of 240 volts it took 70mA from the mains I will re check the figures tomorrow as I don't get why there would be the difference in current. Finally after running the lamp for around 40 minutes the plastic base of the lamp was too hot to touch other than that it seemed fine
Almost all of these lamps use DC internally, the mains is rectified by a full wave bridge and then somewhat smoothed with a reservoir capacitor. Therefore DC input will be fine.
The OPTIMUM DC input is generally higher than the RMS AC input. This is because the internal DC voltage within the lamp tends to approach the peak of the of the AC mains, rather than the RMS figure.
OTOH, many of these lamps work over a very wide range of input voltage.
The wattage input should be roughly constant at any voltage AC or DC on which the lamp works correctly. The current input will be a lot higher on AC than with DC. This is because on an AC supply the input current will be very peaky.
Consider as an example, that the internal capacitor charges to 320 volts. Current will only flow into this capacitor when the momentary voltage of the mains exceeds 320 volts, this is only for a small part of each mains cycle. Therefore a relatively large current must flow for this small part of the cycle.
Almost all of these lamps use DC internally, the mains is rectified by a full wave bridge and then somewhat smoothed with a reservoir capacitor. Therefore DC input will be fine.
The OPTIMUM DC input is generally higher than the RMS AC input. This is because the internal DC voltage within the lamp tends to approach the peak of the of the AC mains, rather than the RMS figure.
OTOH, many of these lamps work over a very wide range of input voltage.
The wattage input should be roughly constant at any voltage AC or DC on which the lamp works correctly. The current input will be a lot higher on AC than with DC. This is because on an AC supply the input current will be very peaky.
Consider as an example, that the internal capacitor charges to 320 volts. Current will only flow into this capacitor when the momentary voltage of the mains exceeds 320 volts, this is only for a small part of each mains cycle. Therefore a relatively large current must flow for this small part of the cycle.
