Capacitive drop power supply for lighting control

A circuit, comprising:

• a capacitor-drop power supply that includes a series combination of a resistor and a first capacitor, the capacitor-drop power supply including an output, and the capacitor-drop power supply adapted to be coupled to a light source;
• a second capacitor coupled to the output of the capacitor-drop power supply;
• a switch coupled in parallel with the series combination of the resistor and the first capacitor, the switch configured to cause the light source to illuminate;
• an active clamp circuit coupled to the capacitor-drop power supply, the active clamp circuit configured to:
• cause the capacitor-drop power supply to operate in a first state responsive to a voltage across the second capacitor being less than a reference voltage, and in the first state, the capacitor-drop power supply provides charging current to the second capacitor;
• and
• cause the capacitor-drop power supply to operate in a second state responsive to a voltage across the second capacitor being greater than the reference voltage, and in the second state, the capacitor-drop power supply provides a current path through at least one of the switch or the series combination of resistor and first capacitor and, while the capacitor-drop power supply is in the second state, the second capacitor does not receive current.

A circuit, comprising:

• a resistor;
• a first capacitor coupled in series with the resistor;
• a first diode coupled to the first capacitor;
• a second diode coupled to the resistor;
• a first transistor coupled to the first diode, the first transistor having a control input;
• a second transistor coupled to the second diode, the second transistor having a control input;
• a second capacitor coupled to the first and second diodes and to the first and second transistors;
• a switch coupled in parallel with the series coupling of the resistor and the first capacitor;
• and
• a comparator having an input and an output, the input coupled to the second capacitor and the output coupled to the control inputs of the first and second transistors.