LED Switch Circuitry for Varying Input Voltage Source

A method of driving an LED array switching apparatus that includes 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 LED segments (D1) to (Dn), respectively, 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,
• the method comprising:
• (a) when the voltage of the voltage supply is increasing:
• switching on successive ones of the constant current sources, so as to form a higher forward voltage LED string of the LED segments and disabling others of the constant current sources, such that only one of the plurality of constant current sources supplies current to the LED segments forming the LED string at any given time;
• and
• (b) when the voltage of the voltage supply is decreasing,
• switching on successive ones of the constant current sources, in reverse order from the switching on performed in step (a), so as to form a lower forward voltage string of the LED segments and disabling others of the constant current sources, such that only one of the plurality of constant current sources supplies current to the LED segments forming the LED string at any given time.