This paper proposes a novel line-frequency multistage conduction LED driver with current-limiting mechanism. By operating the LED driver in multistage conduction, the number of LEDs can be automatically adjusted to be driven with low AC voltage, which increases the LED utilization rate. The current-limiting mechanism offers overcurrent protection to the LEDs. With the aim of shaping the input current into a sinusoidal waveform, the number of LEDs and the current-limit values are determined by the proposed analysis methods; these steps improve the power factor (PF) and the total harmonic distortion of input current (THDi). Finally, two prototype circuits --two-stage conduction and three-stage conduction LED drivers --are built to verify the performances, such as LED utilization rate, THDi, PF, and system efficiency.

In this paper, a line-frequency dual input-voltagelevel LED driver is proposed. The conventional AC LED topologies are operated with single input voltage level, which cannot be suitable for both two major utility voltage levels of 110 V and 220 V. The proposed LED driver utilizes the automatic parallel/series switching mechanism to achieve the compatibility with the input voltages of 110 V and 220 V. Since the LED driver possesses the current-limiting mechanism, it can prevent LEDs from overcurrent no matter what the input voltage is. Finally, the prototype circuit of line-frequency dual input-voltage-level LED driver is built to verify the performances.978-1-4799-6735-3/15/$31.00 ©2015 IEEE

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