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21 votes
Accepted

Why aren't AC LED lamps as simple as a huge LED array in series?

For the same reason that you never connect a single LED directly to a voltage source: LEDs are current controlled devices, not voltage controlled. You want to send a specific amount of current ...
  • 63.1k
8 votes
Accepted

Why connecting the LED to the source instead of the drain does not work?

The MOSFET is controlled by the voltage between the MOSFET gate and the MOSFET source. Further, you have a high voltage MOSFET that takes about +4V to start to turn on, and +10V (from gate to source) ...
6 votes

Candle light flashing LED (max. 5V) burnt by attaching LiPo battery (3.7V)

The burned LED is what should be the expectation by connecting it directly to battery. You seem to have a misunderstanding about the LED. The lithium battery won't be 3.7V. It will be about 4.2V when ...
  • 104k
6 votes
Accepted

Candle light flashing LED (max. 5V) burnt by attaching LiPo battery (3.7V)

Perhaps you connected it backwards. This kind of part has an internal IC that should operate from a 3.6V battery directly, at least by my reading of the current datasheet downloaded from the ...
5 votes

Why connecting the LED to the source instead of the drain does not work?

An NMOS is controlled by the voltage DIFFERENCE between the gate and source terminal. It is not controlled by the gate voltage relative to ground because there is no way it can know what ground is. It ...
  • 50.9k
5 votes

Candle light flashing LED (max. 5V) burnt by attaching LiPo battery (3.7V)

According to the datasheet the LED should take anything from 2.5 to 5V ... Correct. So, if the forward voltage of the LED is only 2.5 V then a very large current will flow and destroy the LED. A ...
  • 165k
5 votes

Why aren't AC LED lamps as simple as a huge LED array in series?

Why exactly wouldn't a simple 100+ LED array direct connected to AC work? If you replace the resistor with a linear current regulator then you would have a typical American light bulb. The regulator ...
3 votes

Candle light flashing LED (max. 5V) burnt by attaching LiPo battery (3.7V)

Did you put a resistor in series to the circuit for the current limitation? A battery provide 3.7V, and without a resistor which limit the current, the current will exceed the maximum rating of the ...
  • 43
1 vote

Help with a constant-voltage LED driver

A replacement constant current driver should be both of the following: Rated for the same or lower current Rated for the same or larger voltage range In this case the voltage range of the new ...

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