Patent ID: 7671549

Claim:
A load control device for controlling the 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; and a control circuit operable to control the first and second controllably conductive switches to provide a plurality of discrete speeds of the AC motor, the control circuit operable to render both of the first and second switches non-conductive to turn off the motor, the control circuit operable to render the first switch conductive and the second switch non-conductive to couple only the first capacitor in series electrical connection between the AC power source and the AC motor to control the speed of the motor to a first discrete speed, the control circuit operable to render the second switch conductive and the first switch non-conductive to couple only the second capacitor in series electrical connection between the AC power source and the AC motor to control the speed of the motor to a second discrete speed, the control circuit further operable to render both of the first and second switches conductive to couple the parallel combination of the first and second capacitors in series electrical connection between the AC power source and the AC motor to control the speed of the motor to a third discrete speed; wherein the control circuit is operable to change the speed of the AC motor to the third speed by rendering the first switch conductive during a first line cycle of the AC supply voltage to allow the first capacitor to charge to approximately a first predetermined voltage; rendering the second switch conductive during a second subsequent line cycle of the AC supply voltage to allow the second capacitor to charge to approximately a second predetermined voltage; and rendering the first and second switches conductive at approximately the same time during a third subsequent line cycle of the AC supply voltage.