Indirect line voltage conduction angle sensing for a chopper dimmed ballast

A light fixture functional to receive power from an alternating current (AC) power source modified by a chopper dimmer and provide light, said light fixture comprising:

• a light source effective to provide light in response to receiving power;
• a ballast operable to provide power to the light source from the AC power source modified by the chopper dimmer, the ballast comprising
• a rectifier operable to connect to the AC power source, 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, and
• 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;
• and
• a housing connected to the light source and the ballast;
• 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, and
• a 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.