High-voltage LEDs offer optimum solution for indoor retrofit lamps (MAGAZINE)

April 27, 2011
High-voltage (HV) LEDs have a turn-on voltage that is closer to the mains supply than conventional high-current LEDs. This eliminates components, notably the driver, and offers other advantages, as Epistar’s ALEXANDER WANG explains.
A high-voltage (HV) LED, as indicated by the name, is a DC-driven LED with a turn-on voltage greater than 20V, which is much higher than the 2-3V turn-on voltage of conventional LEDs. An HV-LED chip is usually constructed from many small LED cells, which are electrically connected in series. Fig. 1a shows a blue HV-LED chip containing fifteen cells connected in series. The operating current is 20 mA, and the total turn-on voltage across all fifteen cells in series is 48V. This blue HV-LED consumes around 1W in full operation. Fig. 1b shows a red HV-LED chip containing ten cells, again connected in series. The forward current is 20 mA and the overall turn-on voltage is 20V, so the power consumption is around 0.4W.

A major advantage of HV-LEDs over conventional LEDs is the forward current, which is typically an order of magnitude smaller in the HV-LED. Low current is favored in LED chip designs due to the better current-spreading effect.


This article was published in the April/May 2011 issue of LEDs Magazine. To read the full version of this article, please visit our magazine page, where you can download FREE electronic PDF versions of all issues of LEDs Magazine. you can also request a print copy of LEDs Magazine (available by paid subscription) and sign up for our free weekly email newsletter.