High Frequency Operation of Metal-halide Lamp Controlled by Microcomputer

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  • メタルハライドランプの高周波点灯のマイクロコンピュータ制御
  • メタル ハライド ランプ ノ コウシュウハ テントウ ノ マイクロコンピュータ

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Description

When HID lamp is operated at high frequencies (several kHz to 100 kHz), arc instability caused by accoustic resonance occurs. Especially in metal-halide lamp, the frequency regions for the stable operation are narrow and vary with the operating condition. Therefore high frequency operation of the metal-halide lamp with fixed frequency is difficult.<BR>In this paper, a microcomputer (CPU and memories) is used to detect the instability of discharge and control the operating frequency.<BR>A CPU monitors the lamp voltage for detecting the instability. When the discharge is unstable, the frequency is swept to search the frequncy region of stable discharge. If the stable region is found, the value of the frequency at the lower edge of the region (f1) and that at the upper edge (f2) are stored in the memory (RAM). Then the frequency is set at the average value of f1 and f2, and the lamp operates in the middle in the frequency region of stable discharge. If the discharge become unstable, the above process is repeated to search the region of stable discharge.<BR>This procedure has an advantage that the interference with communication system is little compared with the operation with frequency modulation or square wave.

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