Phase-control power controller with digital RMS load voltage regulation

1. A phase-control power controller that converts a line voltage to an RMS load voltage, the controller comprising:

line terminals for a line voltage and load terminals for a load voltage;

a phase-control circuit connected to said line and load terminals and having a potentiometer and a capacitor that clip the load voltage;

a load sensing circuit connected across said load terminals that senses the load voltage and provides a DC signal that is related to an RMS load voltage; and

a comparator circuit connected to said phase-control circuit and said load sensing circuit and that compares the DC signal to a reference and adjusts a resistance of said potentiometer in response to the comparison to control the RMS load voltage.

2. The controller of claim 1 , wherein said load sensing circuit comprises a full-wave bridge that sets the DC signal to a peak of the clipped load voltage.

3. The controller of claim 1 , wherein said comparator circuit comprises a comparator that receives the DC signal and the reference, and wherein said potentiometer is a digital potentiometer that receives an output from said comparator that controls the resistance of said digital potentiometer.

4. The controller of claim 1 , wherein said phase-control circuit further comprises a diac and a triac that is triggered by said diac.

5. The controller of claim 1 , wherein said phase-control circuit further comprises an insulated gate bipolar transistor (IGBT).

6. The controller of claim 1 in an integrated circuit that is connected between a terminal of a lamp and a light emitting element of said lamp.

7. The controller of claim 1 , wherein said comparator circuit varies the resistance of said potentiometer so as to maintain the RMS load voltage substantially constant.