| 摘要 |
A LED lamp has a tubular metal body 1 having bayonet fitting lugs 2 and a central insulated contact 3 at its base. The top 4 of the body is angled and has a small metal plate 5 set in potting compound 6 arranged flush with the angled top 4. The plate 5 has two arrays 7,8 of LEDs mounted on it. The LEDs are protected by a layer of transparent encapsulant 9. The LEDs 7 are visible light LEDs, and up to two hundred of them are arranged in a series/parallel array 70. The LEDs 8 are infra-red LEDs, with four arranged in a series parallel array 80. The cathodes 71 of the LEDs 7 on the cathode side of the array 70 and the anodes 82 of the LEDs 8 on the anode side of the array 80 are commonly connected via leads 11 to the body 1. The anodes 72 on the anode side of the array 70 are connected via a current limiting resistor 12 to the central contact 3. Similarly the cathodes 81 on the cathode side of the array 80 are connected via a reverse voltage limiting diode 13 and a current limiting resistor 14 to the central contact 3. When the central contact has a positive voltage applied to it of say 28 volts, the VL LEDs 7 are excited, and emit light; whilst the IR LEDs 8 are not excited. When the polarity is reversed, the IR LEDs are excited and emit IR light and the VL LEDs are not excited. |
