But it is impossible to get 300mA at 0 volts.

Consider a piece of wire...

 

But it is impossible to get 300mA at 0 volts.

0V=short. It is possible to send 300mA into a short.

 

But it is impossible to get 300mA at 0 volts.

Every heard of superconductor electro magnetics?

 

Every heard of superconductor electro magnetics?

Assuming it's impossible to reach absolute zero then there must be some resistance hence some voltage no? I thought it was because the detector reached its lower limit (infinitesimal quantity).

 

UNCLE!

 

A good LED driver should not blow smoke if the diodes (LEDs) get shorted out. Most of my drivers continued to push the rated current into a short. Some dropped back to hiccup mode, where they drove rated current for a 1mS then gave up for a while them tried again.

 

The problem is, if the LEDs need 30mA each, then 10 will work properly and 1 will let out the magic smoke.

Not even close.

ak

 

Not even close.

ak

Could you elaborate?

 

The power supply is a constant current LED supply. The forward voltage of white LEDs is about 3.5 volts, so at a current of 300mA, about 1 watt we be supplied to an LED bead. The voltage range of 25 – 90 volts covers series strings from 7 to 27 LEDs. For any number of LEDs in series from 7 to 27, the current through each will be 300mA, with the voltage varying as required to maintain 300mA in the circuit.

Wrapping your head around a constant current supply can be tough. Say you have a 10mA constant current supply. The supply will do everything it can to put 10mA through a circuit. If you put a 100 ohm resistor across the output, the supply will make the output voltage 1 volt to maintain 10mA in the circuit. If you put 500 ohm resistor across the output, the supply will put out 5 volts to force 10mA through the circuit. A dead short will cause the voltage to drop to nearly zero, to maintain the 10mA current flow.

So what happens if the circuit is open? The constant current supply will try its best to keep 10mA flowing by raising its output voltage as high as it can but of course it can't raise it any higher than the voltage it has to work with.

 

For very large values of 0, it is possible.

Like 0.0000000?

 

Like 0.0000000?

It's a riff on "2 + 2 = 5 for very large value values of 2 and very small values of 5."