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:
Nov. 23, 2004
Filed:
Dec. 29, 2003
Rohm Co., Ltd., Kyoto, JP;
Abstract
An electronic apparatus is equipped with light emitting elements ( ) such as LEDs. The light emitting elements are driven by a power supply circuit of the drive device ( ) at a high step-up voltage (Vh). The drive device ( ) has a multiplicity of constant-current drivers ( ), a selection circuit ( ), and a control circuit ( ). The drivers are turned ON or OFF in accordance with respective instruction signals (S S ) supplied thereto to provide associated series with currents to activate the series for emission of light when associated drivers are turned ON. The selection circuit ( ) selects the lowest one of the voltages impressed on the drivers and outputs the selected lowest voltage as a detection voltage. The control circuit ( ) automatically controls the voltage Vh so as to equilibrate the detection voltage with a low reference voltage at which the drivers can perform required constant-current operations. Thus, the drive device can fully activate the light emitting elements for emission of light while suppressing energy loss in the drivers.