Indirect line voltage conduction angle sensing for a chopper dimmed ballast

摘要

A ballast includes a rectifier, DC to DC converter, a dimming sensor, and a light source driver circuit. The rectifier provides rectified power from an AC power source modified by a chopper dimmer. The converter includes a boost inductor having a primary winding and a detection winding. The converter receives the rectified power from the rectifier and provides a DC power rail. The dimming sensor monitors a voltage of the detection winding of the boost inductor and provides a dimming signal as a function of the monitored voltage. The light source driver circuit receives the dimming signal, receives the DC power rail, and provides power from the DC power rail to the light source as a function of the dimming signal. An amount of power provided to the light source by the light source driver circuit corresponds to a dimming level indicated by the dimming signal.

主权项

1. A ballast operable to provide power to a light source from an alternating current (AC) power source modified by a chopper dimmer, the ballast comprising:
a rectifier operable to receive AC power from the AC power source and provide rectified power; a DC to DC converter comprising a boost inductor having a primary winding and a detection winding, wherein the DC to DC converter is operable to receive the rectified power from the rectifier and provide a DC power rail; a dimming sensor operable to monitor a voltage of the detection winding of the boost inductor of the DC to DC converter and provide a dimming signal as a function of the monitored voltage; a light source driver circuit operable to receive the dimming signal from the dimming sensor, receive the DC power rail from the DC to DC converter, and provide power from the DC power rail to the light source as a function of the dimming signal, wherein an amount of power provided to the light source from the DC power rail by the light source driver circuit corresponds to a dimming level indicated by the dimming signal;
wherein a first terminal of the detection winding is connected to a circuit ground; the DC to DC converter further comprises a voltage regulator operable to provide a bias voltage; and the dimming sensor comprises
an input capacitor having a first terminal connected to a second terminal of the detection winding of the boost inductor,an input diode having an anode connected to a second terminal of the input capacitor, anda switch having an input connected to a cathode of the input diode, a low side connected to the circuit ground, and a high side connected to voltage regulator to receive the bias voltage.