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LEDs are not constant current devices. They are diodes with non-linear I-V characteristic curve. The question of supplying LEDs with CC or CV power supply is o
by megous 8y ago
LEDs are not constant current devices. They are diodes with non-linear I-V characteristic curve.
The question of supplying LEDs with CC or CV power supply is only the question of efficiency and cost.
Most LED strips are made as a serial/parallel combination of LEDs with an added resistor for each segment, to get the desired current through the LEDs in a segment from a ~12V CV power supply.
You don't really have that much choice when it comes to LED strips. CC power supply would need to generate thousands of volts or you'd need a bunch of them. And that would be costly.
- phoenix3200 8y agoLEDs are better modeled as constant current because it's the I part of the curve which is typically more unreliable. The junction voltage is largely consistent, but due to the exponential increase in current, to balance the amount of power it's easier to regulate the I component of P=I*V for consistency than it is the V portion.
- megous 8y agoYou can run any current through the LED. (well, up to a point :D) It's one way to regulate the brightness. I'm not sure what "modeled as constant current" really means when talking about a passive device. If anything I simplify leds as maintaining a "constant voltage", no matter the current I send through them (in the right direction). Just like other diodes. > it's easier to regulate the I component of P=I*V for consistency than it is the V portion. I understand, and we're on the same page. But it doesn't change the fact that almost no led strips do this. You can iron out over individual LED differences by putting 3-4 in the series, and regulate the current using a resistor. In fact, most of the LED indicators you'll see are driven like this. LED + resistor [+ optionally PWM or multiplexing]. Only for power LEDs you'll usually see anything more complicated invlving DC/DC CC switching power supplies.