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US006583580B2
(12) United States Patent ao) Patent No.: us 6,583,580 B2
Shimoda et al. (45) Date of Patent: Jun. 24,2003
(54) EL ELEMENT DRIVING CIRCUIT AND
METHOD, AND ELECTRONIC APPARATUS
(75) Inventors: Tatsuya Shimoda, Suwa (JP); Satoru Miyashita, Suwa (JP); Satoshi Inoue, Suwa (JP)
(73) Assignee: Seiko Epson Corporation (JP)
( * ) Notice: Subject to any disclaimer, the term ol this patent is extended or adjusted under 35 U.S.C. 154(b) by 0 days.
(21) Appl. No.: 09/900,758
(22) Filed: Jul. 6, 2001
(65) Prior Publication Data
US 2002/0140363 Al Oct. 3, 2002 (30) Foreign Application Priority Data
Jul. 7, 2000 (JP) 2000-207393
(51) Int. C I. H05K 7/02
(52) U.S. CI 315/169.3; 361/782; 315/169.1
(58) Field of Search 315/169.1-169.4,
315/165, 167; 345/60, 64, 71, 72, 75, 76, 80; 323/222, 282; 361/762-764, 782
(56) References Cited
U.S. PATENT DOCUMENTS
5,545,291 A 8/1996 Smith et al 156/655.1
5,783,856 A 7/1998 Smith et al 257/618
5,824,186 A 10/1998 Smith et al 156/655.1
5,904,545 A 5/1999 Smith et al 438/455
5,959,846 A * 9/1999 Noguchi et al 361/782
6,297,622 Bl * 10/2001 Yatabe 323/222
* cited by examiner
Primary Examiner—Don Wong
Assistant Examiner—-Wilson Lee
(74) Attorney, Agent, or Firm—Harness, Dickey & Pierce, PL.C.
(57) ABSTRACT
An EL driving circuit which can operate at a satisfactory operation speed is disclosed. A voltage higher than the voltage for operating the EL element is input, and the input voltage is stepped down by the voltage step-down circuit (2) which is provided in each unit block (1). The stepped-down voltage is then supplied to a transistor (3) functioning as the driving element for driving the EL element. Therefore, even when the number of EL elements increases, sufficient source voltage can be supplied to each unit block.
8 Claims, 6 Drawing Sheets
