| 主权项 |
1. An LED driver circuit comprising:
at least one string of light emitting diodes (LEDs) connected in series, and a power supply for converting a mains voltage into an output voltage to be applied to said at least one string of LEDs, the power supply including a single-stage boost converter adapted to directly convert the mains voltage into the output voltage, wherein the boost converter is a multi-level converter having a switch and a capacitor respectively associated with each level, the capacitors of the various levels being connected in series, and a respective said string of LEDs being connected in parallel with each of the capacitors, wherein the converter includes an inductor and further comprising a controller adapted to operate the switches in a critical discontinuous mode, in which a current flowing through the inductor of the converter is allowed to drop to zero only momentarily, wherein the converter is adapted to generate, across each of the capacitors, a terminal voltage that is of the same order of magnitude or smaller than the peak level of a rectified mains voltage, and wherein the controller has a first mode of operation in which the switches are opened simultaneously and closed simultaneously, and at least one further mode of operation in which at least one switch is switched ON during an OFF period of at least one other switch. |
