The current–voltage characteristic of an LED is similar to other diodes, in that the current is dependent exponentially on the voltage (see Shockley diode equation). This means that a small change in voltage can cause a large change in current. If the applied voltage exceeds the LED's forward voltage drop by a small amount, the current rating may be exceeded by a large amount, potentially damaging or destroying the LED. The typical solution is to use constant-current power supplies to keep the current below the LED's maximum current rating. Since most common power sources (batteries, mains) are constant-voltage sources, most LED fixtures must include a power converter, at least a current-limiting resistor. However, the high resistance of three-volt coin cells combined with the high differential resistance of nitride-based LEDs makes it possible to power such an LED from such a coin cell without an external resistor.
The current – voltage characteristic of an LED is similar to other diodes , in that the current is dependent exponentially on the voltage ( see Shockley diode equation ) . This means that a small change in voltage can cause a large change in current . If the applied voltage exceeds the LED 's forward voltage drop by a small amount , the current rating may be exceeded by a large amount , potentially damaging or destroying the LED . The typical solution is to use constant - current power supplies to keep the current below the LED 's maximum current rating . Since most common power sources ( batteries , mains ) are constant - voltage sources , most LED fixtures must include a power converter , at least a current - limiting resistor . However , the high resistance of three - volt coin cells combined with the high differential resistance of nitride - based LEDs makes it possible to power such an LED from such a coin cell without an external resistor .
What feature do most LED fixtures need to have?
What feature do most LED fixtures need to have ?
a power converter
a power converter