Light emitting device and illumination apparatus

• US 8,820,950 B2
• Filed: 03/11/2011
• Issued: 09/02/2014
• Est. Priority Date: 03/12/2010
• Status: Expired due to Fees

• Current Assignee: Toshiba Lighting & Technology Corporation (Toshiba Corporation)
• Original Assignee: Toshiba Lighting & Technology Corporation (Toshiba Corporation)
• Inventors: Matsuda, Shuhei, Shibusawa, Soichi, Betsuda, Nobuhiko, Nishimura, Kiyoshi
• Primary Examiner(s): Ward, John A
• Application Number:
  US13/045,787
• Publication Number:
  US 20110222264A1
• Time in Patent Office: 1,271 Days
• Field of Search: 362/617, 362/231, 362/249.01, 362/249.02
• US Class Current: 362/84
• CPC Class Codes: F21K 9/00 Light sources using semiconductor devices as light-generating elements, e.g. using light-emitting diodes [LED] or lasers
• CPC Class Codes: F21K 9/232 specially adapted for generating an essentially omnidirectional light distribution, e.g. with a glass bulb
• CPC Class Codes: F21S 8/026 intended to be recessed in a ceiling or like overhead structure, e.g. suspended ceiling
• CPC Class Codes: F21Y 2105/10 comprising a two-dimensional array of point-like light-generating elements
• CPC Class Codes: F21Y 2105/12 characterised by the geometrical disposition of the light-generating elements, e.g. arranging light-generating elements in differing patterns or densities
• CPC Class Codes: F21Y 2113/13 comprising an assembly of point-like light sources
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 2320/06 Adjustment of display parameters
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48137 the bodies being arranged next to each other, e.g. on a common substrate
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 33/48 characterised by the semiconductor body packages
• CPC Class Codes: H01L 33/50 Wavelength conversion elements
• CPC Class Codes: H05B 45/28 using temperature feedback
• CPC Class Codes: H05B 45/56 involving measures to prevent abnormal temperature of the LEDs

Abstract

According to one embodiment, a light emitting device which is attached to an illumination apparatus and radiates light having a correlated color temperature of 2900 to 3600K is provided. The light emitting device includes a substrate, blue light emitting LED elements and red light emitting LED elements mounted on the substrate, and a wavelength converting unit. The red light emitting LED elements have a luminous intensity of 0.2 to 2.5 times as large as that of the blue light emitting LED elements at normal use temperature in a state where the light emitting device is attached to the illumination apparatus. The wavelength converting unit is excited by light emitted from the blue light emitting LED elements and converts the light to light having a peak wavelength within a range of 500 to 600 nm.

Claims

1. A light emitting device which is attached to an illumination apparatus configured to control a light, the light emitting device configured to radiate light having a correlated color temperature of 2400 to 3600K, the device comprising:

a substrate;

blue light emitting diode (LED) elements mounted on the substrate;

red LED elements mounted on the substrate, the red LED elements having reduction rates of luminous intensity according to temperature rise that are higher than reduction rates of luminous intensity of the blue LED elements according to temperature rise;

a wavelength converting unit configured to be excited by light emitted from the blue LED elements and convert the light emitted from the blue LED elements to light having a peak wavelength within a range of 500 to 600 nm; and

a lighting circuit configured to control current to both the blue LED elements and the red LED elements to perform dimming control such that a ratio of a current to the blue LED elements to a current to the red LED elements is constant when the light output is controlled at less than full intensity;

wherein

a luminous intensity of the red LED elements is from 0.2 to 2.5 times a luminous intensity of the blue LED elements; and

when junction temperatures of the blue LED elements and the red LED elements are 120°

C. or lower and the light output is dimmed from full intensity to less than full intensity, a color temperature rises, as an intensity of the red LED elements increases relative to the blue LED elements, within a range of 2400K-3600K.

2. The light emitting device according to claim 1, further comprising series circuits in which the blue LED elements and the red LED elements are connected in series.

3. The light emitting device according to claim 1, wherein the plurality of blue LED elements and the plurality of red LED elements are mounted on the substrate and arranged alternately.

4. An illumination apparatus comprising:

an apparatus body; and

the light emitting device according to claim 1 disposed on the apparatus body.

5. The light emitting device according to claim 1 comprising:

a first series circuit in which the plurality of blue LED elements is connected in series;

a second series circuit in which the plurality of red LED elements is connected in series; and

a pair of power supply terminals connected to the first series circuit and the second series circuit in parallel.

6. The light emitting device according to claim 5, wherein a sum of a forward voltage of the blue LED elements in the first series circuit and a sum of a forward voltage of the red LED elements in the second series circuit are equal.

7. The light emitting device according to claim 5 comprising a temperature detecting unit disposed on the substrate, wherein the lighting circuit is configured to control current flowing through the first series circuit and the second series circuit based on the temperature detected by the temperature detecting unit.

8. The light emitting device according to claim 1, wherein:

the blue LED elements are mounted on a central portion of the substrate, and

the red LED elements are mounted on a portion of the substrate outside the blue LED elements.

9. The light emitting device according to claim 1, wherein the wavelength converting unit comprises:

a first translucent sealing member comprising a phosphor covering the blue LED elements; and

a second translucent sealing member covering the read LED elements.

10. The light emitting device according to claim 9, wherein one of the first sealing member and the second sealing member is arranged so as to surround the other one of the first sealing member and the second sealing member.

11. An illumination apparatus comprising:

an apparatus body;

a lighting circuit configured to control a light emitting device; and

the light emitting device disposed on the apparatus body and configured to radiate light having a correlated color temperature of 2400 to 3600K, the light emitting device comprising;

a substrate;

blue LED elements mounted on the substrate;

red LED elements mounted on the substrate, the red LED elements having reduction rates of luminous intensity according to temperature rise that are higher than reduction rates of luminous intensity of the blue LED elements according to temperature rise; and

a wavelength converting unit configured to be excited by light emitted from the blue LED elements and convert the light emitted from the blue LED elements to light having a peak wavelength within a range of 500 to 600 nm;

wherein

the lighting circuit is configured to control current to both the blue LED elements and the red LED elements to perform dimming control such that a ratio of a current to the blue LED elements to a current to the red LED elements is constant when the light output is controlled at less than full intensity,

when junction temperatures of the blue LED elements and the red LED elements are 120°

C. or lower and the light output is dimmed from full intensity to less than full intensity, a color temperature rises, as an intensity of the red LED elements increases relative to the blue LED elements, within the range of 2400K-3600K; and

a luminous intensity of the red LED elements is from 0.2 to 2.5 times a luminous intensity of the blue LED elements.