Patent ID: 6507157
Filing Date: 2003-01-14
Classification: H05B,Y02B,Y10S

Abstract:
Control circuitry for controlling the output power of an electronic ballast system having a power supply branch circuit having power lines comprising a line voltage line and a common line, and a ballast stage having (i) inputs connected to the power lines for providing power to an arc discharge lamp, (ii) internal power control feedback circuitry that defines a feedback loop for controlling the amount of power applied to the arc discharge lamp, and (iii) a control signal input for receiving a control signal that affects operation the internal power control feedback circuitry and the level of power outputted by the ballast stage, the control circuitry comprising:a first circuit having an input for connection to one of the power lines, the first circuit generating a control signal for input into the control input of the ballast stage, the control signal having a first predetermined magnitude when one of the power lines is connected to the input of the first circuit and a second predetermined magnitude when the power lines are isolated from the input of the first circuit; and a second circuit having a first state for reducing the first and second predetermined magnitudes of the control signal by a predetermined increment so as to effect step dimming of the arc discharge lamp and a second state that maintains the first and second predetermined magnitudes of the control signal.