Patent Application
20120087130
1. Technical Field
The disclosure relates to LED illumination apparatuses, and particularly to an alternating current LED illumination apparatus.
2. Description of the Related Art
LEDs' many advantages, such as high luminosity, low operational voltage, low power consumption, compatibility with integrated circuits, easy driving, long term reliability, and environmental friendliness have promoted their wide use as a light source. Now, LEDs are commonly applied in environmental lighting.
The luminous intensity of LED is in direct proportion to the injection current. Thus, LED is commonly driven by direct current. However, the luminous efficiency decreases with increasing injection current. The junction temperature of LED increases with the injection current increasing. It is well known that the lifetime of the LED will decrease with the junction temperature of LED increasing. In order to decrease the temperature of LED during the operating period, Pulse Width Modulation Dimming (PWM Dimming) can be used to control the LED. However, the PWM operates with constant current. Thus, the driving circuit of LED has to include at least one AC (alternating current) to DC (direct current) converter, decreasing utilization efficiency of the LED illumination apparatus and increasing costs.
Therefore, it is desirable to provide an alternating current LED illumination apparatus which can overcome the described limitations.
Many aspects of the disclosure can be better understood with reference to the drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present alternating current LED illumination apparatus. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the views.
Embodiments of an alternating current LED illumination apparatus as disclosed are described in detail here with reference to the drawings.
Referring to
The heat dissipating plate 10 can be high thermal conductive and electrically insulating material, such as Si3N4, SiC, ZrO2, B4C, TiB2, AlxOy, AlN, BeO, or a combination thereof. Moreover, the heat dissipating plate 10 can be an electrical conductive substrate coated with electrically insulating material.
The plurality of LED chips 20 is mounted on one surface of the heat dissipating plate 10 and thermally connecting to the heat dissipating plate 10. The distance between adjacent LED chips 20 exceeds 500 μm, preferably, not less than 900 μm. The length of the LED chips 20 should not exceed 350 μm. Preferably, the length of the LED chips 20 should not exceed 150 μm. The LED chips 20 can be yellow light LED, blue light LED, or UV LED.
The circuit layer 30 can be deposited on the heat dissipating plate 10 by chemical vapor deposition or sputtering. The positive and negative electrodes (not shown) of each LED chip 20 electrically connect to the circuit layer 30.
The electrodes 40 are mounted on the heat dissipating substrate 10. In this embodiment, the electrodes 40 are mounted on the surface of the heat dissipating substrate 10 having the LED chips 20. The electrodes 40 electrically connect to the circuit layer 30.
The encapsulation layer 50 covering the plurality of LED chips 20 and a part of the circuit layer 30 is mounted on the heat dissipating substrate 10. The electrodes 40 are exposed beyond the encapsulation layer 50. The encapsulation 50 can be silicone, epoxy resin, PMMA, or plastic. The encapsulation 50 can be doped with at least one fluorescent material, such as sulfides, aluminates, oxides, silicates, or nitrides. The commonly used fluorescent materials are YAG (yttrium aluminum garnet) and TAG (terbium aluminum garnet).
Referring to
An end of the switch 62 connecting selectivity to the end c or one of the tapping 612 of the secondary coil N2 changes the output driving voltage to provide power to different numbers of LED chips 20. When the output voltage increases, more LED chips 20 can be turned on or the brightness of the LED chips 20 enhanced. The nearer the coil numbers of the tapping 612 of the secondary coil N2 is, the more tendered dimming effect is.
The plurality of LED chips 20 is connected first anti-parallel to every two chips and then in series in this embodiment. In other words, the LED chips 20 are divided into a plurality of pairs. Twelve pairs are shown in
The driving element 60 of the alternating LED illumination apparatus 100 connects directly to the AC power to drive the plurality of LED chips 20. The driving element 60 is simpler than the common driving circuit. Furthermore, the alternating LED illumination apparatus 100 requires no AC-DC converters, and power utilization efficiency of the alternating LED illumination apparatus 100 is increased.
Moreover, the switch 62 of the driving element 60 selectively connects to the output terminal of the transformer 61. Thus, the driving element 60 outputs different driving voltage to the plurality of LED chips 20. According to needs, that can adjust the luminous intensity of the plurality of LED chips 20.
The operating current is not greater than 50 mA. Preferably, the operating current is not greater than 30 mA.
Referring to
While the disclosure has been described by way of example and in terms of exemplary embodiment, it is to be understood that the disclosure is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.
