Patent ID: 8508140

Claim:
An LED array switching apparatus, comprising: a plurality of LED segments (D 1 ) 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 (G 1 ) to (Gn), coupled to outputs of LED segments (D 1 ) to (Dn), respectively, each of the constant current sources being switchable between a current regulating state and an open state such that as the voltage of the voltage supply increases, LED segments are switched on and lit to form a higher forward voltage LED string, and as the voltage of the voltage supply decreases, segments are switched off and removed from the LED string starting with the most recently lit segment, wherein the voltage supply includes a triac dimmer having an RC timing circuit, and the LED array switching apparatus further comprises: a bleeder circuit coupled to the voltage supply and the constant current sources, the bleeder circuit including a bypass resistor, the bleeder circuit being operable to connect the bypass resistor across the input voltage, to allow sufficient charging current to be supplied to the RC timing circuit, when the rectified input voltage is low enough to indicate that the triac is off, and to disconnect the bypass resistor when the input voltage is high enough to indicate that the triac is on.