continued from part 1 - Controller General of Patents, Designs, and ...

(12) PATENT APPLICATION PUBLICATION (21) Application No.6424/DELNP/2008 A
(19) INDIA
(22) Date of filing of Application :22/07/2008 (43) Publication Date : 24/10/2008
(54) Title of the invention : "ELETRONIC BALLAST HAVING ADAPTIVE FREQUENCY SHIFTING"
(51) International classification :H05B 41/392 (71)Name of Applicant :
(31) Priority Document No :11/352,962 1)LUTRON ELECTRONICS CO., INC.
(32) Priority Date :13/02/2006
Address of Applicant :7200 SUTER ROAD,
(33) Name of priority country :U.S.A.
COOPERSBURG, PENNSYLVANIA 18036, UNITED STATE
(86) International Application No
:PCT/US07/002655 OF AMERICA. U.S.A.
Filing Date
:29/01/2007 (72)Name of Inventor :
(87) International Publication No :WO 2007/094971 1)MARK S. TAIPALE
(61) Patent of Addition to Application
Number
Filing Date
:NA
:NA
(62) Divisional to Application Number :NA
Filing Date
:NA
(57) Abstract :
An electronic ballast for driving a gas discharge lamp avoids mercury pumping in the lamp by adaptively changing an operating
frequency of an inverter of the ballast when operating near high-end. The inverter of the ballast generates a high-frequency AC
voltage, which is characterized by the operating frequency and an operating duty cycle. The ballast also comprises a resonant tank for
coupling the high-frequency AC voltage to the lamp to generate a present lamp current through the lamp, and a current sense circuit
for determining the magnitude of the present lamp current. A hybrid analog/digital control circuit controls both the operating
frequency and the operating duty cycle of the inverter with closed-loop techniques. The control circuit adjusts the duty cycle of the
inverter in response to a target lamp current and the present lamp current. To avoid mercury pumping, the control circuit attempts to
maximize the duty cycle of the inverter when operating at high-end. Specifically, the control circuit adjusts the operating frequency of
the inverter in response to the target lamp current signal, the duty cycle of the inverter, and a target duty cycle in order to drive the
operating duty cycle toward the target duty cycle.
No. of Pages : 40 No. of Claims : 41
The Patent Office Journal 24/10/2008 25919