LED lamp

An LED lamp includes a heat dissipation apparatus with a base, an LED module mounted on the base, and an AC-DC converter electrically connected to the LED module. The AC-DC converter is mounted on the base near the LED module. Heat generated by the LED module and heat-generating components of the AC-DC converter is transferred to the base from which the heat is dissipated by the heat dissipation apparatus. Heat pipes are embedded in the base of the heat dissipation apparatus.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an LED lamp, and particularly to an LED lamp having a heat dissipation apparatus for heat dissipation.

2. Description of Related Art

Significant advances have been made in the technology of light emitting diodes (LEDs). LEDs are commercially available which generate 10-15 lumens/watt. This is comparable to the performance of incandescent bulbs. In addition, LEDs offer other advantages such as longer operating life, shock/vibration resistance and design flexibility because of their small size. As a result, LEDs are replacing traditional incandescent sources for illumination applications such as signage, and pathway lighting.

Typically, LED performance is affected by the driving current and by the ambient temperature surrounding the LED. Both of these parameters contribute to the junction temperature of the LED, which affects the performance. When applying LEDs for display backlighting or other illumination applications, there are two reasons to drive them with constant current: one is to avoid violating the absolute maximum current rating and compromising the reliability; the second is to obtain predictable and matched luminous intensity and chromaticity from each LED.

The power source for an LED is a direct current (DC) and low voltage power; therefore, the traditional power source of high voltage, alternating current (AC) power which is used to power the tungsten lamp or daylight lamp can not be directly used in powering the LED lamps. Therefore, an LED lamp generally includes an AC/DC converter that converts an AC, high voltage power to a DC, low voltage power to be supplied to the LEDs. The AC/DC converter will generate a significant amount of heat that must be dissipated to ensure reliable operation of the LED lamp. Furthermore, the LED lamp usually uses a plurality of closely packed LEDs, and most of the LEDs are driven at the same time, which results in a quick rise in temperature of the LED lamp.

However, since generally the LED lamp does not have heat dissipation devices with good heat dissipating efficiencies, operation of the general LED lamp has a problem of instability because of the rapid buildup of heat. Consequently, the light from the LED lamp often flickers, which degrades the quality of the illumination. Furthermore, if the LED lamp is used in a hot state for a long time, the life time thereof is consequently shortened.

What is needed, therefore, is an LED lamp which has a greater heat-dissipation capability.

SUMMARY OF THE INVENTION

An LED lamp comprises a heat dissipation apparatus with a base, an LED module mounted on the base, and an AC-DC converter electrically connected to the LED module. The AC-DC converter is mounted on the base near the LED module. A plurality of heat pipes is embedded in the base of the heat dissipation apparatus. Heat generated by the LED module and the AC-DC converter is transferred to the base and the heat pipes from which the heat is transferred to fins of the heat dissipation apparatus to be dissipated to ambient air.

DETAILED DESCRIPTION OF THE INVENTION

Referring toFIG. 1, an LED lamp of a preferred embodiment of the invention comprises a heat dissipation apparatus100, an LED module200and two AC/DC converters300. The LED module200and the converters300are mounted on a top surface of the heat dissipation apparatus100, and cooled by the heat dissipation apparatus100.

Referring toFIG. 2, the heat dissipation apparatus100comprises a heat sink110and a plurality of heat pipes120embedded in the heat sink110. The heat sink110comprises a rectangular base112and a plurality of fins114parallelly mounted on a bottom surface of the base112. In a top surface of the base112, a plurality of parallel grooves1120is formed. The grooves1120extend within the base112along a direction from a front end to a rear end of the base112. In detail, the grooves1120extend from an area adjacent to the front end of the base112to an area adjacent to the rear end of the base112.

The heat pipes120are installed and retained in corresponding grooves1120, so that the heat pipes120extend within the base112along the corresponding grooves1120. The heat pipes120are flattened, and top surfaces of the heat pipes120are coplanar with the top surface of the base112. The base112further defines a plurality of screw holes1122in sides of the grooves1120. Screws (not shown) extend through the LED module200and threadedly engage into corresponding screw holes1122to secure the LED module200on the top surface of the base112.

The LED module200comprises a plurality of elongated printed circuit boards210positioned at middle and rear portions of the top surface of the base112. The LED module200further comprises a plurality of evenly spaced LEDs220mounted on each printed circuit board210. The printed circuit boards210together with the LEDs220are juxtaposed on the top surface of the base112in such a manner that each printed circuit board210is arranged over one heat pipe120, and front ends of the heat pipes120located close to the front end of the base112extend beyond the printed circuit boards120. The printed circuit board210can be secured on the top surface of the base112via the screws extending therethrough to threadedly engage into corresponding screw holes1122of the base112. By such design, heat produced by the LEDs220can be conducted downwardly and absorbed by the heat pipes120, when the LEDs220are powered to lighten by the converters300.

The converters300each are electrically connected to several printed circuit boards210and convert an AC, high voltage power from a conventional power outlet to a DC, low voltage power which is supplied to the LEDs220. In general, the AC/DC converters300are well known. The AC/DC converter300may be any conventional converter that is small enough to fit in the LED lamp near the printed circuit boards210.

As shown inFIGS. 2-3, each converter300comprises a driver printed circuit board310having a driver circuit (not shown) formed thereon, a plurality of capacitors320, and a plurality of heat-generating driver components330, such as MOSFETs. The capacitors320are mounted on a top surface of the driver printed circuit board310, and the heat-generating driver components330are positioned on a bottom surface of the driver printed circuit board310. The driver printed circuit boards310of the two converters300are juxtaposed on a front portion of the top surface of the base112near a front end of the LED module200. The heat-generating driver components330are in direct contact with the top surfaces of the base112and the heat pipes120, so that heat originated from the heat-generating driver components330is directly absorbed by the base112and the heat pipes120, simultaneously. Therefore, heat produced by the heat-generating driver components330can be quickly removed away to keep the converters300within acceptable temperature range. Thermal interface material such as thermal grease or thermal tapes can be applied to a bottom face of each of the heat driver components330, whereby the heat driver components330can have an intimate contact with the heat pipes120and the top face of the base112. Thus, heat generated by the heat driver components330can be effectively transferred to the heat pipes120and the top face of the base112.

As described above, both of the printed circuit boards210and the driver printed circuit boards310are arranged on the top surface of the base112with the heat pipes120located below the driver printed circuit boards310and the printed circuit boards210. In other words, the heat pipe120comprises a first portion positioned between the LED module200and the base112, and a second portion positioned between the base112and the bottom surface of the driver printed circuit board310. Heat produced by the LEDs220and the heat-generating driver components330is absorbed by the base112and the heat pipes120, and then conducted to the fins114to be dissipated. Therefore, the LED lamp can work within an acceptable temperature range.

Referring toFIGS. 4-6, an LED lamp of another preferred embodiment of the invention is shown. The second embodiment has a structure similar to that of the previous embodiment, except two AC/DC converters300a. The main difference between the converters300aand the converters300is that capacitors320aand heat-generating driver components330aof the converter300aare mounted on a top surface of a driver printed circuit board310aof the converter300a. A heat dissipation apparatus100acomprises a plurality of thermal conductors130a, such as thermal tapes or heat conducting blocks, which is positioned on a front portion of a top face of a base112aof the heat dissipation apparatus100a. When the converters300aand an LED module (not shown) are positioned on the top surface of the base112ain a similar manner to that of the previous embodiment, the thermal conductors130aare located just below corresponding heat-generating driver components330a. Therefore, heat produced by the heat-generating driver components330ais transferred to the thermal conductors130a, which have a high heat conductivity and quickly transfer the heat from the converters300ato the base112aand the heat pipes120a, whereby the heat can be dissipated to ambient air via fins of the heat dissipation apparatus100a.