The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 09, 2007
Filed:
Feb. 27, 2006
Jeffrey Doyle Mullin, Wellington, CO (US);
Yan Yin, Longmont, CO (US);
Jeffrey Doyle Mullin, Wellington, CO (US);
Yan Yin, Longmont, CO (US);
National Semiconductor Corporation, Santa Clara, CA (US);
Abstract
A driver circuit for an electroluminescent (EL) lamp that consumes less power and reduces electromagnetic interference (EMI). Electrical charge is stored during a discharge cycle of an AC signal employed to illuminate an EL lamp, and subsequently reused during the AC signal's charging cycle. The reuse of electrical charge enables the driver circuitry to illuminate the EL lamp while drawing the least amount of power from a power supply, such as a battery. Also, multiple charge pumps can be sequentially/serially turned off during the discharge cycles of the AC signal driving the EL Lamp. By sequentially discharging the EL lamp, a waveform for the AC signal can be synthesized that more closely resembles a relatively symmetrical sinusoidal shape. The relatively symmetrical shape of the synthesized AC waveform serves at least in part to reduce spurious emissions of electromagnetic interference (EMI), audio noise, and improve the efficiency of the driver circuitry.