1. Field of the Invention
The present invention relates to an LED lamp, more particularly to an LED lamp having a heat sink enclosed in an envelope for dissipating heat generated by LEDs of the LED lamp.
2. Description of Related Art
The high power LED light devices produce considerable amount of heat, which may cause performance degrade or even damage if the heat is not removed from the LED chips efficiently. In an LED light device, the core is an LED chip mounted on a substrate. A transparent top covering the LED chip serves as a lens for modifying the direction of the emitted light. Although there are many different designs, the major heat dissipation route for the heat produced by the LED chip usually is managed through the base to which the LED chip is mounted or through an additional metal heat sink below the base and then to an outer heat sink.
Traditional adoption of the fans for active cooling system not only introduces noise problems but also brings risk of damage to an LED lamp if the fan is out of order. In contrast, passive cooling with natural convection is quite, continuous and time-unlimited. But since a natural convection system is relative weak for heat dissipation, to solve this problem, a large surface area is needed to enhance heat dissipation capacity. Most passive cooling devices for LED lamps adopt highly heat-conductive materials, such as copper or aluminum, with extended surfaces for heat dissipation. However, to facilitate flowage of airflow through the fins, fins of the heat sink of the LED lamp are commonly exposed to outside of the housing; this makes the fins in a risk of being broken and hurting users of the LED lamp. Furthermore, dust or rainwater on the fins may creep along the heat sink to cause the LEDs to have a contamination by the dust or a short circuit by the rainwater.
What is needed therefore is a LED lamp having an improved structure which overcomes above mentioned disadvantages.