US Patent No. 10,194,499

LIGHTING DEVICE


Patent No. 10,194,499
Issue Date January 29, 2019
Title Lighting Device
Inventorship Noboru Takizawa, Kyoto (JP)
Masaaki Nakayama, Kyoto (JP)
Assignee Rohm Co., Ltd., Kyoto (JP)

Claim of US Patent No. 10,194,499

1. A lighting device comprising:at least one dimmer configured to adjust a light emission current flowing in a light emitting element group;
a light emission controller configured to control the dimmer by detecting a magnitude relationship between a drive voltage and a light emission reference voltage; and
a power supply circuit configured to supply the drive voltage,
wherein the light emission controller
enables the dimmer to generate the light emission current when the drive voltage is higher than the light emission reference voltage, and
disables the dimmer from generating the light emission current when the drive voltage is lower than the light emission reference voltage,
wherein the light emitting element group includes a plurality of light emitting elements connected in series with each other which emit light as a result of the light emission current flowing therein when a light emission voltage based on the drive voltage and equal to or higher than the light emission reference voltage is applied to the light emitting element group,
wherein the light emission controller includes:
a comparing circuit configured to output a comparison result signal by comparing a comparison voltage based on the drive voltage with a predetermined reference voltage; and
a control switch configured to be turned on and off in accordance with the comparison result signal,
wherein the dimmer is enabled to generate and disabled from generating the light emission current as a result of the control switch being turned on and off.