Patent Application
20070246729
Embodiments of the present invention will be described in connection with accompanying drawings.
By making a parallel connection of the Zener diode 110 and the LED 115, the Zener diode can prevent damage caused by static electricity when the current is applied in the reverse direction. The Zener diode is also called a “voltage regulator diode,” which is one of the semiconductor PN junction diodes. Designed to show operation properties in a breakdown area of PN junction, the Zener diode is mostly used for voltage regulation. The Zener diode obtains a certain voltage by use of the Zener recovery phenomenon. It operates in about 10 mA of current in the p-n junction of silicon, and can achieve about 3V to about 12V of voltage regulation, depending on the type. The Zener diode 110 can be mounted directly on the substrate or by use of the lead frame as shown in
The Zener diode 110, however, has a problem of absorbing the light emitted by the LED 115, since it is located near the LED 115. In other words, the light-emitting efficiency of the LED package becomes lower as the Zener diode 110 absorbs some of the light of the LED 115 that is directed to the Zener diode 110.
In one embodiment of the present invention, a shielding dam is formed between the LED and the voltage regulator diode to prevent the light emitted by the LED being absorbed by the voltage regulator diode. The shielding dam can be shaped to have a certain angle to reflect the light emitted by the LED to the outside, and can be made of a reflective material or formed with a reflective side to increase reflectivity. Moreover, the LED package can have a reflecting part to increase the luminosity of the light emitted by the LED. The reflecting part can be formed in accordance with the angle of the shielding dam, that is, the section can have a tapered shape.
Certain embodiments of a high efficiency LED will be described with reference to the accompanying drawings. In the drawings, identical elements will be given the same reference numeral regardless of the figure number, and any redundant description regarding the same element will not be provided. Mainly, three embodiments are described here, based on the shape of the shielding dam formed between the LED and the voltage regulator diode. Although the side view type of LED package will be described, at least one embodiment of the present invention can be also applied to other LED packages, such as a top view type, a type used in a flash light, a power LED used in a light. Moreover, although the Zener diode is used to describe the voltage regulator diode, it shall be evident that any device (e.g. an avalanche diode) having an effect of voltage regulation can be applied in embodiments of the present invention.
For the LED 215, a typical LED can be used, for example, from the GaN group. A GaN line of light-emitting chip is designed to irradiate a wavelength band of blue color when emitting light. By applying a fluorescent material producing the light of yellow wavelength band on top of the light-emitting chip, the white light can be made. Here, it is also possible to make the white light by using red, green, and blue fluorescent materials.
The LED package may include i) the LED 215, which is disposed inside the projectile body 205 and irradiates light when electricity is applied, ii) a voltage regulator diode 210, which is for preventing damage caused by static electricity by making a parallel connection with the LED 215, and iii) a reflecting part 250, which reflects the light emitted by the LED 215 to the outside. The projectile body 205 can be made of plastic, especially of poly parabanic acid resin (referred to as “PPA” hereinafter), which has a high mechanical strength and a high reflectivity. The reflecting part 245 is formed on the substrate, surrounding the LED 215, the voltage regulator diode 210, and the shielding dam 213, and can be formed in one body with the projectile body 205 or separately from the projectile body 205. On one side of the projectile body are the anode lead frames 235 and 236 and the cathode lead frames 240 and 241, each of which are protruded. The anode lead frames 235 and 236 and the cathode lead frames 240 and 241 are electrically connected. The voltage regulator diode 210, the shielding dam 213, the LED 215, the first wire 220, the second wire 225, and the third wire 230 are protected by resin, for example, epoxy resin.
The anode lead frame 235 is mounted with the voltage regulator diode 210, and the cathode lead frame 240 with the LED 215. The voltage regulator diode 210 and/or the LED 215 can be mounted by the die bonding method with a conductive epoxy.
The LED can be electrically connected to the anode lead frame 235 through the second wire 225. Therefore, the light can be irradiated from the LED 215 by applying the forward-direction current applied to the cathode lead frame 235 to the LED 215. The highly conductive gold (Au) can be used for the second wire 225.
The voltage regulator diode 210 has a physical property of electrostatic resist pressure against reverse-direction currents. Thus, if reverse-direction currents are applied to the LED 215 by, for example, static electricity, the currents are bypassed by the voltage regulator diode 210, preventing damage by the static electricity. Although the voltage regulator diode 210 includes a Zener diode, any device, such as an avalanche diode, a switching diode, and a schottky diode, having the effect of regulating the voltage can be included.
The voltage regulator diode 210 may include the first wire 220, which is extended from the voltage regulator diode 210 and wire-bonded to the cathode lead frame 240. Here, the first wire 220 can be connected to the third wire 230, which is extended form the LED 215, making a parallel connection of the voltage regulator diode 210 to the LED 210.
The shielding dam 213 may be located between the voltage regulator diode 210 and the LED 215, and can substantially prevent the light emitted from the LED 215 from directly irradiating on the voltage regulator diode 210 and being reflected directly to or absorbed by the voltage regulator diode 210. Thus, the shielding dam 210 can be made of a reflective material, or the side of the exterior including the side facing the LED 210 can be coated with a reflective material, such that the light emitted by the LED 215 can be efficiently emitted to the outside.
The reflective material forming or coated on the shielding dam 213 can be aluminum (Al) or silver (Ag), which are highly reflective, or can be the highly reflective PPA, which is used to form the projectile body 205, or the highly reflective nylon. If the shielding dam 213 is made of the same material as the material forming the projectile body 205, the shielding dam 213 and the projectile body 205 can be formed by the same process, simplifying the manufacturing process.
A typical LED package having both the voltages regulator diode 210 and the LED 215 generates the light of 1 cd if the LED of 1 cd is used. With the shielding dam 210, however, the light of about 1.1 cd can be generated. To increase the reflection efficiency, the reflecting part 245 of the shielding dam 213 can be formed at an angle from the substrate.
When the forward-direction current is applied to the LED package, the current is supplied to the LED 215 via the anode lead frame 235 and the first wire 220, making the LED 215 irradiate the light having R, G, and B colors. Since the Zener diode is in the reverse direction, it is electrically open, and thus protects the LED 215 by being short when it is over a certain voltage. Therefore, the LED 215 can have a stable irradiation of light by maintaining the supply of current with the forward-direction voltage (anode to cathode) within a certain range to the LED 215.
If a reverse-direction voltage is applied due to, for example, static electricity, the reverse-direction voltage is supplied to the voltage regulator diode 210, which is electrically a forward direction. The LED 215 is electrically open. Here, if the voltage is applied in the reverse direction, the voltage regulator diode 210 bypasses the current by being short, preventing the LED 215 from being damaged. Therefore, by making a parallel arrangement of the voltage regulator diode 210 with the LED 215, the damage to the LED by the forward-direction and reverse-direction currents can be prevented.
The shielding dam 713 is tilted to an angle such that the light emitted by the LED 715 can be efficiently irradiated to the outside. That is, the side on which the shielding dam 713 faces the LED 715 can be tilted at an angle to the substrate (i.e. the anode lead frame 735, the cathode lead frame 740, and the insulation area 745). The tilted side can be a portion of the side or the entire side. The tilt can be formed at an angle by which the reflection efficiency of the light is good. Therefore, the section of the shielding dam 713 can be a shape of a polygon, for example, a rectangle or a triangle.
The shielding dam 813 can have a shape of a plate which is bent in the middle. That is, to irradiate the light emitted by the LED 815 to the outside efficiently, the shielding dam 813 is shaped as if a plate is bent, requiring less material to form the shielding dam 813. It is evident that any other shape that can efficiently reflect the light emitted by the LED 815 can be applied to the present invention. For example, the entire shielding dam can be slanted to one side, as in a “\” shape.
While the above description has pointed out novel features of the invention as applied to various embodiments, the skilled person will understand that various omissions, substitutions, and changes in the form and details of the device or process illustrated may be made without departing from the scope of the invention. Therefore, the scope of the invention is defined by the appended claims rather than by the foregoing description. All variations coming within the meaning and range of equivalency of the claims are embraced within their scope.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2006-0035782 | Apr 2006 | KR | national |
