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:
Dec. 03, 2013
Filed:
Nov. 02, 2010
Yoshikazu Sasaki, Kyoto, JP;
Kenichi Fukumoto, Kyoto, JP;
Yoshikazu Sasaki, Kyoto, JP;
Kenichi Fukumoto, Kyoto, JP;
Rohm Co., Ltd., , JP;
Abstract
An LED driving circuit drives a display backlight LED string including multiple LEDs connected in series. A power supply supplies a driving voltage from an output terminal thereof to a first end of the LED string. A detection resistor is arranged between a second end of the LED string and a fixed voltage terminal. The LED driving circuit receives a pulse modulation signal having a duty ratio that corresponds to the luminance. In the on period, in which the PDIM signal is the first level, the LED driving circuit controls the power supply such that the voltage drop across the detection resistor approaches a predetermined target value. In the off period, in which the PDIM signal is the second level, the LED driving circuit stops the control operation for the power supply.