J
John Fields
Guest
On Tue, 24 Jan 2012 21:11:23 -0800, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:
Pretty close, though, once you get past the knee.
---
Inadvisedly so, unless the source voltage can never rise high enough
to over-current the LED.
---
All that says is that if the voltage from the constant-voltage low
impedance source is high enough to over-current the LED, then the
source's impedance won't stop the destruction of, or enhance the
limited life of, the LED.
--
JF
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:
---On Tue, 24 Jan 2012 20:17:17 -0500, Tom Biasi <tombiasi@optonline.net
wrote:
On Tue, 24 Jan 2012 15:56:48 -0800 (PST), Bill Bowden
I've seen LED flashlights with 2 white 3 volt LEDs wired directly in
parallel across two AA batteries.
-Bill
They rely heavily on the battery's internal resistance and luck.
LEDs have a current:voltage slope that's not a brick wall.
Pretty close, though, once you get past the knee.
---
---They can be
run at constant voltage, and often are.
Inadvisedly so, unless the source voltage can never rise high enough
to over-current the LED.
---
---The dynamic impedance of a flashlight-type LED is a lot higher than
the impedance of an AA battery.
All that says is that if the voltage from the constant-voltage low
impedance source is high enough to over-current the LED, then the
source's impedance won't stop the destruction of, or enhance the
limited life of, the LED.
--
JF