Importance

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Abstract

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.

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First Claim