How can these led Christmas lights be 3V or 2.5V bulbs but its connected to 120V supply with no transformer? Why doesn't it blow them out?
- StevenLv 78 months ago
Multiple LEDs are wired in series and require a current limiting device for that string, which may be just a resistor. Some LED lamps use a switching low voltage power supply. But it is important to understand that LEDs do not have resistance in the normal sense. They have a "forward voltage" below which they conduct nothing and above which they conduct an unlimited current and burn out, so the current must be controlled by a resistor or controller chip. LEDs also require a rectifier because their reverse voltage capability is not enough by themselves.
- rogerLv 78 months ago
Because there are 40 of them connected in series. They drop 3 volts each. there is also a limiting resistor in the string.
- PhilomelLv 78 months ago
Each LED is 3V@~10mA= 300Ω. 120V/3v= ~40 LED's in the string of lights.
- M.Lv 78 months ago
Series string to divide the voltage.
- What do you think of the answers? You can sign in to give your opinion on the answer.
- derframLv 78 months ago
Because 40 - 50 of them are connected in series. If you have 40 bulbs rated at 3 volts each in series, the applied voltage would need to be 40 * 3 = 120 V.
- ?Lv 78 months ago
120v is the maximum available voltage. it doesn't mean that's what everything attached to it draws. Your house is connected to a water supply system that moves thousands of gallons an hour, that doesnt mean it all tries to come out your kitchen tap when you turn it on.
- 異域秦後人Lv 78 months ago
THEY ARE JOINED IN SERIES TO MAKE UP AS A 120V LIGHT BULB,. tHEN IT CAN BE POWERED DIRECTLY WITH 120V WITHOUT BURNING DOWN.
3V BULB*40 PIECES = 120V BULB