Method and apparatus for determining a target light intensity from a phase-control signal
AssigneeLutron Electronics Co., Inc.
InventorDonald F. Hausman, Jr.
Life of this patent
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Abstract
A dimmable ballast circuit for a compact fluorescent lamp controls the intensity of a lamp tube in response to a phase-control voltage received from a dimmer switch. The ballast circuit comprises a phase-control-to-DC converter circuit that receives the phase-control voltage, which is characterized by a duty cycle defining a target intensity of the lamp tube, and generates a DC voltage representative of the duty cycle of the phase-control voltage. Changes in the duty cycle of the phase-control voltage that are below a threshold amount are filtered out by the converter circuit, while intentional changes in the duty cycle of the phase-control voltage are reflected in changes in the target intensity level and thereby the intensity level of the lamp tube.
Claims30
A load control circuit for controlling a target intensity level of a lighting load, said load control circuit comprising:
- a bus-voltage-generating circuit receiving a phase-control voltage having a duty cycle and producing a DC bus voltage;
- a load regulation circuit receiving said DC bus voltage and adapted to be coupled to said lighting load for adjusting the intensity of said lighting load;
- and
- a control circuit operable to determine said target intensity level of said lighting load in response to said duty cycle of said phase-control voltage, said control circuit controlling said load regulation circuit to adjust the intensity level of said lighting load in response to said duty cycle of said phase-control voltage and an actual-intensity signal related to the actual intensity level of said lighting load;
- wherein said control circuit adjusts said target intensity level of said lighting load using a slow time constant in response to changes in said duty cycle of said phase-control voltage that are below a threshold amount, and adjusts said target intensity level of said lighting load using a fast time constant less than said first time constant in response to intentional changes in said duty cycle of said phase-control voltage.
A control circuit for a load control circuit for a lighting load, said load control circuit receiving a phase-control voltage that is characterized by a duty cycle set by a dimmer switch that operates according to either a forward phase-control method or reverse phase-control method, said control circuit comprising:
- a phase-control-voltage converter circuit for converting said phase-control voltage into a target signal for determining a target intensity level of said lighting load;
- and
- an error amplifier circuit for comparing said target signal and an actual-intensity signal related to the actual intensity level of said lighting load and generating a drive control signal for controlling said lighting load to said target intensity level;
- wherein said phase-control-voltage converter circuit adjusts said target intensity level of said lighting load using a slow time constant in response to changes in said duty cycle of said phase-control voltage that are below a threshold amount, and adjusts said target intensity level of said lamp using a fast time constant less than said first time constant in response to intentional changes in said duty cycle of said phase-control voltage.
A lighting control system receiving power from an AC power source, said lighting control system comprising:
- a dimmable high-efficiency lighting load comprising a light source and a load regulation circuit for illuminating said light source;
- and
- a two-wire dimmer switch adapted to be coupled in series electrical connection between said AC power source and said dimmable high-efficiency lighting load for generating a phase-control voltage characterized by a duty cycle;
- wherein said load regulation circuit receives said phase-control voltage and illuminates said light source in response to said phase-control voltage, said load regulation circuit comprising a control circuit operable to determine a target intensity level of said light source in response to said duty cycle of said phase-control voltage, said control circuit operable to control said load regulation circuit to adjust the intensity of said light source towards said target intensity level, said control circuit adjusting said target intensity level of said light source using a slow time constant in response to changes in said duty cycle of said phase-control voltage that are below a threshold amount, and adjusting said target intensity level of said light source using a fast time constant less than said first time constant in response to intentional changes in said duty cycle of said phase-control voltage.
A method of controlling a compact fluorescent lamp comprising:
- receiving a phase-control voltage characterized by a duty cycle set by a dimmer switch that operates according to either a forward phase-control method or reverse phase-control method;
- determine a target intensity level of said lamp in response to said duty cycle of said phase-control voltage;
- providing a sinusoidal output voltage to said lamp for illuminating said lamp to said target intensity level;
- adjusting said target intensity level of said lamp using a slow time constant in response to changes in said duty cycle of said phase-control voltage that are below a threshold amount;
- and
- adjusting said target intensity level of said lamp using a fast time constant less than said first time constant in response to intentional changes in said duty cycle of said phase-control voltage.
Dependencies are inferred from the claim text.