Dimmer conduction angle detection circuit and system incorporating the same

A conduction angle detection circuit to receive a gate drive signal from a power factor correction circuit and to provide a dimmer reference level signal representative of a dimmer setting of a dimmer circuit in response to the gate drive signal, the conduction angle detection circuit comprising:

• a comparator having a first input and a second input, the comparator configured to provide a pulse-width modulated output in response to comparison of signals at the first input with signals at the second input, the pulse width modulated output having a pulse width representative of the dimmer setting of the dimmer circuit;
• an input network coupled to the comparator and configured to receive the gate drive signal and to provide an output in response to the gate drive signal, wherein the input network provides the output to the first input of the comparator;
• a threshold supply circuit configured to provide a threshold voltage to the second input of the comparator;
• and
• a filter coupled to the comparator, the filter being configured to convert the pulse-width modulated output of the comparator to the dimmer reference level signal.

A method of dimming a light source driven by a ballast, comprising:

• controlling a switch of a switching converter using a gate drive output of a power factor correction circuit to provide a regulated voltage output to a power conversion circuit;
• coupling the gate drive output to a conduction angle detection circuit, wherein the conduction angle detection circuit is configured to provide a dimmer reference level signal corresponding to a dimmer setting of a dimmer circuit in response to the gate drive output;
• and
• coupling the dimmer reference level signal to the power conversion circuit, the power conversion circuit being configured to provide an output to the light source in response to the dimmer reference level signal to establish a light output level corresponding to the dimmer setting.