LOSSLESS PRELOAD FOR LED DRIVER WITH EXTENDED DIMMING

摘要

A quasi-phase active preload circuit to be coupled at the output of a non-isolated LED driver converter having a pre-stage phase-angle control dimmer circuit, such as a commonly used leading-edge control Triac dimmer, is disclosed. The quasi-phase active preload circuit may include a preload resistor coupled to a current-controlled current source configured to draw a sinking current through the preload resistor based on a peak detect signal. The peak detect signal may be, in one example, representative of a leading-edge peak voltage of an output of the Triac dimmer circuit, which may be representative of a conduction angle of the Triac dimmer circuit. During normal operating conditions, no sinking current is drawn through the preload resistor. During low dimming conditions, a sinking current that is responsive to the peak detect signal is drawn through the preload resistor. During deep dimming or when used with a leaky Triac dimmer, a maximum sinking current may be drawn through the preload resistor by the current-controlled current source.

主权项

1. An active preload circuit configured to be coupled to an output of a non-isolated light-emitting diode (LED) driver converter having a phase-angle control dimmer circuit, the active preload circuit comprising:
a preload resistor coupled to the output of the non-isolated LED driver converter; and a current-controlled current source coupled to receive a peak detect signal representative of a conduction angle of the phase-angle control dimmer circuit, wherein the current-controlled current source is configured to draw a variable sinking current through the preload resistor, and wherein a value of the sinking current is based on the peak detect signal.