US Patent No. 10,368,409

LIGHT EMITTING DEVICE AND LED LIGHT BULB


Patent No. 10,368,409
Issue Date July 30, 2019
Title Light Emitting Device And Led Light Bulb
Inventorship Hiroyasu Kondo, Yokohama (JP)
Masahiko Yamakawa, Yokohama (JP)
Yasuhiro Shirakawa, Yokohama (JP)
Ryoji Tsuda, Yokohama (JP)
Atsuji Nakagawa, Himeji (JP)
Toshitaka Fujii, Himeji (JP)
Tomohiko Inoue, Himeji (JP)
Assignee Toshiba Materials Co., Ltd., Yokohama-Shi (JP)

Claim of US Patent No. 10,368,409

1. A light emitting device comprising:a first light source configured to emit a first white light and including a plurality of first diode groups, each first diode group having N pieces of first white light emitting diodes where N is a natural number equal to or more than 2, the first white light emitting diodes of each first diode group being connected in series to one another in a forward direction, the series-connected diodes of one of the first diode groups being connected in parallel with the series-connected diodes of another one of the first diode groups, the first white light having a first color temperature; and
a second light source connected in parallel to the first light source, configured to emit a second white light, and including a plurality of second diode groups and a first resistance element, each second diode group having M pieces of second white light emitting diodes where M is a natural number less than N, the second white light emitting diodes of each second diode group being connected in series to one another in a forward direction, the series-connected diodes of one of the second diode groups being connected in parallel with the series-connected diodes of another one of the second diode groups, the first resistance element being connected in series to the series-connected diodes of each second diode group and having a first resistance value, and the second white light having a second color temperature lower than the first color temperature,
wherein each of the first white light emitting diodes and the second white light emitting diodes has a phosphor film, the film containing a silicone resin and a phosphor dispersed in the resin,
wherein the device is configured to emit a mixed white light of the first white light and the second white light,
wherein a ratio of a drive current of the first light source to a drive current of the second light source is 10 or more,
wherein a drive voltage of the first light source is higher than a drive voltage of the second light source, and
wherein a color temperature of the mixed white light is higher as a total luminous flux of the mixed white light is higher.