| 摘要 |
<P>PROBLEM TO BE SOLVED: To suppress noise generation caused by characteristics of light emitting diodes in the primary side voltage of a transformer, in a lighting system equipped with the transformer to the primary side of which an almost sine wave AC voltage is supplied and the light emitting diodes connected to its secondary side. Ž<P>SOLUTION: An impedance circuit Z1 is connected to light emitting diodes D1, D2 in series, and an impedance circuit Z2 is connected to light emitting diodes D3-D18 in series. Therefore, if an AC voltage is impressed on the secondary side of the transformer, no current passes through the light emitting diodes unless the impressed voltage reaches the minimum light emitting voltage or higher, and if the voltage reaches the minimum light emitting voltage or higher, both end voltages are almost fixed regardless of the current, a voltage drop is thereby caused according to the current in the impedance circuits although a voltage waveform becomes close to a rectangular wave. Accordingly, both end voltage waveform on the secondary side of the transformer and both end voltage waveform on the primary side of the transformer become close to a sine wave. Therefore, noise generation in the primary side voltage of the transformer can be suppressed. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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