| 摘要 |
An LED assembly has a tubular metal body 101 with bayonet fitting lugs 102 and a central insulated contact 103 at its base. The end 104 of the body is at right angles to its length and carries a small metal plate 105. To this is adhered a ceramic substrate 106 for two arrays of LEDs 107,108 mounted on it. They are protected by a layer of transparent potting material 109. The substrate is of beryllium oxide, whilst the plate is of steel, in order to provide compatibility of thermal expansion. A pair of contact leads 110,111 extend back from the substrate, through the plate 105 and a further backing plate 112, via apertures with insulating bushes 113. The plates 105,112 are clipped to the body end 104 by a crimped band 114, which ensures good electrical contact between the plate 105 and the body 104. On a circuit board 120 for electrical protection devices, there is arranged a 12R forward voltage regulation resistor 121 in series with the IR LEDs. A 4.7R (for red and yellow LEDs) or 6.8R (for green LEDs) forward voltage regulation resistor 122 is connected in series with the VL LEDs, as is an integrated circuit, forward current limiting device 123. Not only does it limit the forward current through the LED array, it progressively restricts this current if the lamp overheats for any reason above 150‹C For its protection, it is provided with reverse voltage protection diodes 124 and an anti-oscillation capacitor 125. |
