| 主权项 |
1. An apparatus for driving a plurality of LEDs, comprising:
a plurality of LEDs divided into a plurality of LED segments connected in series, each of said plurality LED segments having a positive end and a negative end, and a switching device connected in parallel between the positive and negative ends; an input voltage connected to the positive end of a leading LED segment of said plurality of LED segments; a switching voltage detector having a first end connected to the negative end of a trailing LED segment of said plurality of LED segments, and generating a first mode change signal when said input voltage increases and a second mode change signal when said input voltage decreases; a current limiting device having a first end connected to a second end of said switching voltage detector and a second end connected to ground; and a switch controller receiving said input voltage and said first and second mode change signals and generating a plurality of switching control signals for respectively controlling the switching devices of said plurality of LED segments; wherein said switching voltage detector includes a delta voltage detector, said delta voltage detector comprising:
a first voltage controlled current limiting device having a first terminal, a second terminal connected to a first bias voltage through a bias voltage switching device, a third terminal connected to a common node through a first current sensing device, and a by-pass switching device connected between said second terminal and said common node, said first terminal and said common node being connected respectively to the first end and the second end of said switching voltage detector;a second voltage controlled current limiting device having a first terminal, a second terminal connected to a second bias voltage and a third terminal connected to said common node through a second current sensing device;a third voltage controlled current limiting device having a first terminal, a second terminal connected to a third bias voltage through a bias voltage switching device, a third terminal connected to said common node through a third current sensing device, and a by-pass switching device connected between the second terminal of said third voltage controlled current limiting device and said common node;one or more LEDs connected in series between the first terminals of said first and second voltage controlled current limiting devices; andone or more LEDs connected in series between the first terminals of said second and third voltage controlled current limiting devices. |
