LED switching circuit for varying input voltage source

摘要

An LED array switching apparatus comprises: a plurality of LED segments D1 to Dn connected in series, each LED segment having a forward voltage; a voltage supply coupled to the plurality of LED segments; and a plurality of constant current sources G1 to Gn coupled to outputs of the LED segments D1 to Dn respectively. Each of the constant current sources is switchable between a current regulating state and an open state so that as the voltage of the voltage supply increases, the LED segments are switched on and lit to form a higher forward voltage LED string, and as the voltage of the voltage supply decreases, the LED segments are switched off and removed from the LED string starting with the most recently lit segment.