Abstract:Both high voltage LED and AC LED increase their break over voltage by connecting dozens of LED in series, and high voltage LED can be considered as a special form of AC LED in structure. Driving circuit models of high voltage LED and AC LED were introduced, and their similarity is that they both own a current limiting resistance connected in series with the light source. The output characteristics of high voltage LED and AC LED were measured by adjusting current limiting resistor, the number and connecting form of LEDs. It is indicated that with the same LED number and operating current, both the luminous efficiency and luminous flux of high voltage LED are all higher than that of AC LED, but the luminous efficiency of parallel high voltage LED is lower than that of the series one, while the luminous efficiency is on the contrary. According to the measurement, it is verified that the luminous efficiency of AC LED is irrelevant for the current limiting resistance.