Triac dimmable compact fluorescent lamp with dimming interface

Details Triac dimmable compact fluorescent lamp with dimming interface Triac dimmable compact fluorescent lamp with dimming interface

1997-04-10

2001-01-16

Kinkead, Arnold (Department: 2817)

Electric lamp and discharge devices: systems

Regulation of the control current and/or potential applied...

C315SDIG004, C315S307000

Reexamination Certificate

active

06175195

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates generally to a ballast for a triac dimmable fluorescent lamp, and more particularly to the dimming interface of a triac dimmable fluorescent lamp.
A triac dimmable compact fluorescent lamp includes a triac dimmer and a compact fluorescent lamp. The triac dimmer controls the amount of power supplied to and thereby the level of illumination provided by the compact fluorescent lamp. Triac dimmers are characterized by a cut-in angle, that is, a firing angle for turning on the triac. A minimum cut-in angle corresponds to maximum lamp light output. There is, however, no one minimum cut-in angle for turning on all triac dimmers. Effective interface with a compact fluorescent lamp is therefore difficult because of the variation in the minimum cut-in angle among different triac dimmers.
Accordingly, it is desirable to provide an improved compact fluorescent lamp which can effectively interface with triac dimmers having different minimum cut-in angles. The interface should translate the different minimum cut-in angles as representing a maximum lamp light output.
SUMMARY OF THE INVENTION
Generally speaking, in accordance with a first aspect of the invention, a ballast for powering at least one lamp in combination with a triac dimmer having a cut-in angle includes a driver for controlling the level of lamp illumination based on a dimming signal; and a dimming interface for supplying the dimming signal to the interface based on the cut-in angle. The driver includes a threshold device for establishing a minimum cut-in angle corresponding to a maximum level for the dimming signal by reduction in the voltage of a signal representing the cut-in angle. The threshold device produces a modified signal representing the cut-in angle of the triac dimmer but with the minimum cut-in angle being imposed.
Variations in the dimming signal arising from differences in the minimum cut-in angle of different triac dimmers are limited by the threshold device to within a range of voltages which can be readily interpreted by the driver. Consequently, the threshold device establishes a minimum cut-in angle (e.g. 25-30 degrees) corresponding to a maximum dimming voltage signal.
The triac dimmer based on the cut-in angle produces a pulse. The dimming interface includes converting means for converting the width of the pulse into a proportional average rectified voltage. The proportional average rectified voltage serves as the dimming signal. Generally, the threshold device includes a zener diode. The dimming interface can also include a translating device for translating the cut-in angle into a signal representing duty cycle. The translating device typically includes a zener diode.
In accordance with a second aspect of the invention, a method for powering at least one lamp includes controlling the level of lamp illumination based on a dimming signal supplied to an inverter driver; supplying the dimming signal as an input to the inverter driver based on a cut-in angle of a triac dimmer; and reducing the voltage level of a signal representing the cut-in angle and thereby establishing a minimum cut-in angle corresponding to a maximum level for the dimming signal.
Accordingly, it is an object of the invention to provide an improved compact fluorescent lamp which can effectively interface with triac dimmers having different minimum cut-in angles.
It is another object of the invention to provide an improved ballast having an interface which translates different minimum cut-in angles as representing a maximum lamp light output.
Still other objects and advantages of the invention, will, in part, be obvious and will, in part, be apparent from the specification.
The invention accordingly comprises several steps in a relation of one or more of such steps with respect to each of the others, and the device embodying features of construction, a combination of elements and arrangement of parts which are adapted to effect such steps, all is exemplified in the following detailed disclosure and the scope of the invention will be indicated in the claims.


REFERENCES:
patent: 5559395 (1996-09-01), Venkitasubrahmanian et al.
patent: 5691605 (1997-11-01), Xia et al.

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