公开(公告)号：US20170347414A1

公开(公告)日：2017-11-30

申请号：US15606169

申请日：2017-05-26

Applicant: Panasonic Intellectual Property Management Co., Ltd.

Inventor： Kazuhiko HARADA ,  Akira NAKAJO

IPC: H05B33/08

CPC classification number: H05B33/089 ,  H05B33/0815 ,  H05B33/0845 ,  Y02B20/341

Abstract: The lighting device includes a power conversion circuit and a control circuit. The power conversion circuit includes a high voltage side output terminal and a low voltage side output terminal to be connected to a light source, and a step-down chopper circuit. The control circuit performs a lighting operation of controlling the power conversion circuit to develop a DC output voltage between the high voltage side output terminal and the low voltage side output terminal. The control circuit starts a protective operation of limiting a current to be supplied to the light source when the output voltage is equal to or higher than a threshold value. The threshold value is in a range of 1.2 to 1.3 times a rated voltage of the light source.