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US 6,229,271 B1Granted
Low distortion line dimmer and dimming ballast
AssigneeOsram Sylvania Inc.
InventorGuang Liu
Life of this patent
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Abstract
A line dimmer has a limited maximum firing angle to limit a total harmonic distortion within a powering signal. A dimming ballast generates a pulse width modulated signal based on a firing angle of the powering signal, generates a dimming command signal based on the pulse width modulated signal, and dims a lamp based on the dimming command signal. The maximum firing angle may be limited to 30 degrees, 25 degrees, or 20 degrees, for example, to limit a resulting total harmonic distortion.
Claims19
A dimming ballast apparatus comprising:
- a firing-angle-to-pulse-width-modulation converter to generate a pulse width modulated signal based on a firing angle of a powering signal from a power-line phase angle dimmer control, wherein the firing angle of each half cycle of the powering signal from the power-line phase angle dimmer control is less than or equal to 30 degrees;
- and
- a filter to generate a dimming command signal based on the pulse width modulated signal.
A method comprising:
- generating a pulse width modulated signal based on a firing angle of a powering signal from a power-line phase angle dimmer control, wherein the firing angle of each half cycle of the powering signal from the power-line phase angle dimmer control is less than or equal to 30 degrees;
- generating a dimming command signal based on the pulse width modulated signal;
- and
- dimming a lamp based on the dimming command signal.
1 more element
Dependencies are inferred from the claim text.