Patent ID: 7489094

Claim:
A load control device for controlling a speed of an AC motor to be driven from an AC supply voltage of an AC power source, the load control device comprising: a first capacitor and a second capacitor, each of the first and second capacitors adapted to be coupled in series electrical connection between the AC power source and the AC motor; a first controllably conductive switch coupled in series electrical connection with the first capacitor and a second controllably conductive switch coupled in series electrical connection with the second capacitor; a control circuit operable to control the first and second controllably conductive switches to provide a plurality of discrete speeds of the AC motor; and a zero cross detect circuit operable to provide to the control circuit a signal representative of the zero-crossings of the AC supply voltage; wherein the control circuit is operable to change the speed of the AC motor by rendering the first switch conductive at a first zero-crossing of the AC supply voltage to allow the first capacitor to substantially charge to a first predetermined voltage; rendering the second switch conductive at a second zero-crossing of the AC supply voltage to allow the second capacitor to substantially charge to a second predetermined voltage; and rendering the first and second switches conductive at a predetermined time after a third zero-crossing of the AC supply voltage.