does this make sense

[docb]

I see a company with a 3watt driver that says 750ma, and a 5 watt driver says 950ma.

I ordered a 5watt, for my LED which is ok up to 1000ma.

Does it sound normal that 5w is fact no more than 950ma, so I'm safe using it?

 

[garden]

I don't really understand what you are trying to say. Watt in no way related to amps. Amp is just the current, watt is current + voltage, overall power...

 

[docb]

How do you know whether to use a 3watt or a 5watt driver with an LED like
Cree XRE?

The 5watt driver says 950ma. The 3watt says 750ma in the specs.

 

[garden]

Assuming that the voltage complies with the manufacturer suggestion, you can drive it with the 5W driver. The voltage on the driver is about 5.26, since AMP*VOLT=WATT. The current is suitable.

 

[docb]

Do you mean the LED will now see 5.26v?????
in other words.. if a Cree XRE specs are 1000ma 3.7vfd, then is this 5w 950ma the wrong driver???

I have used the 750ma/ 3w, with this same LED.

(Am I mixed up - meaning that theoretically there might be a 3 watt 700 and 3 watt 950, and the only diff would be the 950 would make it brighter? The only difference between 3 and 5 is how much they COULD source if I was using more than one LED per driver?)

 

[Curt R]

If the driver is limited to 1000 mA of output current and the voltage is higher than the voltage drop across
the LED everything is good. The driver may produce 100 volts and limited at 1000 mA and everything
is still good. That would be a 100 watt driver, but if the current output is still limited to 1000 mA from the
driver the LED would still be fine.

If the voltage drop across the LED is 3.5 volts and the driver can output only 3 volts at 50 amps of current,
the LED will never see 1000 mA of current. It then may only see 650 mA of current from a 150 watt driver.

However if the driver is not current output limited and the voltage is higher than the voltage drop across
the LED, the 5 watt driver may produce more than the listed 5 watts of output. I have seen 2.87 amps of
current output from a driver that is listed to produce only 1.2 amps of current during a board test. From
a TI63000 IC that is a voltage limited output driver. I stopped that test when the solder holding the
IC on the board started to get shinny.

Curt