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:
Jan. 15, 2019
Filed:
Sep. 08, 2015
Citizen Watch Co., Ltd., Nishitokyo-shi, JP;
Citizen Electronics Co., Ltd., Fujiyoshida-shi, Yamanashi, JP;
Takashi Akiyama, Sayama, JP;
Citizen Watch Co., Ltd., Tokyo, JP;
Citizen Electronics Co., Ltd., Fujiyoshida-shi, Yamanashi, JP;
Abstract
Provided is an LED drive circuit whereby the light emission color is easily changed when dimming by adjusting the current that drives the LED. The LED drive circuit has: a variable constant current source; a first LED row having a plurality of LEDs connected in series and emitting light in a first light emission color; a second LED row having a plurality of LEDs connected in series and emitting light in a second light emission color; and a current limiting circuit including a current detection element and a switch element. The LED drive circuit is characterized by: the threshold voltage for the first LED row being larger than the threshold voltage for the second LED row; the first LED row and the second LED row being connected in parallel to the variable constant current source; and the current limiting circuit limiting the current flowing to the second LED row, on the basis of the current flowing to the current detection element via the first LED row.