Method and apparatus for determining a target light intensity from a phase-control signal
AssigneeLutron Technology Company LLC
InventorDonald F. Hausman, Jr.
Life of this patent
Estimating the term…
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.
Claims20
An apparatus for controlling an intensity level of a lighting load, the apparatus configured to receive a phase-control voltage characterized by a duty cycle, the apparatus comprising:
- a load regulation circuit configured to receive a drive control signal and to control an intensity level of the lighting load in response to the drive control signal;
- and
- a control circuit configured to receive a scaled version of the phase-control voltage, and to generate the drive control signal to cause the load regulation circuit to adjust the intensity level of the lighting load towards a target level;
- wherein the control circuit is configured to:
- measure a duty cycle of the scaled version of the phase-control voltage;
- determine a requested level in response to the duty cycle of the scaled version of the phase-control voltage;
- determine a change in the duty cycle of the scaled version of the phase-control voltage by calculating a difference between the requested level and the target level;
- adjust the target level for the lighting load using a first time constant when the difference between the requested level and the target level is less than a threshold;
- and
- adjust the target level for the lighting load using a second time constant when the difference between the requested level and the target level is greater than the threshold, where the second time constant is less than the first time constant.
A lamp configured to receive a phase-control voltage characterized by a duty cycle, the lamp comprising:
- a lighting load;
- a load regulation circuit configured to receive a drive control signal and to control an intensity level of the lighting load in response to the drive control signal;
- and
- a control circuit configured to receive a scaled version of the phase-control voltage, and to generate the drive control signal to cause the load regulation circuit to adjust the intensity level of the lighting load towards a target level;
- an enclosure for housing the load regulation circuit;
- and
- a screw-in base adapted to be coupled to a standard Edison socket;
- wherein the control circuit is configured to:
- measure a duty cycle of the scaled version of the phase-control voltage;
- determine a requested level in response to the duty cycle of the scaled version of the phase-control voltage;
- determine a change in the duty cycle of the scaled version of the phase-control voltage by calculating a difference between the requested level and the target level;
- adjust the target level for the lighting load using a first time constant when the difference between the requested level and the target level is less than a threshold;
- and
- adjust the target level for the lighting load using a second time constant when the difference between the requested level and the target level is greater than the threshold, where the second time constant is less than the first time constant.
A method of controlling an intensity level of a lighting load in response to a phase-control voltage, the method comprising:
- determining a target level for the lighting load;
- receiving a scaled version of the phase-control voltage;
- measuring a duty cycle of the scaled version of the phase-control voltage;
- determining a requested level in response to the duty cycle of the scaled version of the phase-control voltage;
- determining a change in the duty cycle of the scaled version of the phase-control voltage by calculating a difference between the requested level and the target level;
- adjusting the target level for the lighting load using a first time constant when the difference between the requested level and the target level is less than a threshold;
- adjusting the target level for the lighting load using a second time constant when the difference between the requested level and the target level is greater than the threshold, where the second time constant is less than the first time constant;
- and
- controlling the intensity level of the lighting load towards the target level.
Dependencies are inferred from the claim text.