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A high‐efficiency multi‐string LED driver based on constant current bus with time‐multiplexing control scheme is proposed and analysed. Each LED string is connected to the constant current bus, which is provided by the output of a front‐end high‐efficiency converter. The current of each LED string can be independently controlled by the turn on duty ratio of its time‐multiplexing switch. A capacitor is connected to the current bus to provide a current flowing path for constant bus current when none of the LED string is connected to the current bus. It needs only one output filter capacitor, which makes circuit volume small and cost low. Finally, a 7.2 W two‐string LED driver is provided to verify the studied results. [ABSTRACT FROM AUTHOR]

A resonant two‐string LED driver with power factor correction and passive current sharing is proposed. By controlling one output current, the other output current of the two‐string LED driver can be controlled via passive current sharing, which makes its control simple. The proposed converter uses only one active switch and one magnetic component with single‐stage power conversion, thus it benefits from low cost, small volume, light weight and high efficiency. The proposed converter is studied and experimental results of a 75 W two‐string LED driver are provided to verify the studied results. [ABSTRACT FROM AUTHOR]

A flicker‐free transformerless light emitting diode (LED) driving circuit based on a quadratic buck power factor correction (PFC) converter is proposed. It combines a cascaded input buck PFC converter and an output buck dc–dc converter with a single switch. The proposed LED driving circuit can not only achieve high PFC to comply with the EN61000‐3‐2 standard and low output voltage without a high step‐down transformer, but also reduces second‐order line frequency current ripple flowing through the LED to eliminate light flicker of the LED. Experimental results of a 7 W prototype are presented to verify the analysis results of the proposed converter. [ABSTRACT FROM AUTHOR]