| 摘要 |
PURPOSE:To improve the conversion efficiency of an external supply power without damaging the reproducibility of a frequency signal at the time of reduction of the reception level. CONSTITUTION:A switching element 4 which turns on/of a bypass circuit connected in parallel to a capacitor 2 which is connected in series to a reception coil 1 to form a resonance circuit is provided. When the reception level is low, the switching element 4 is made non-conductive by a reception voltage monitor circuit 3 to turn off the bypass circuit of the capacitor 2, and the resonance circuit is formed to improve the rectification efficiency. When the reception level is high, the switching element 4 is made conductive to turn on the bypass circuit of the capacitor 2, and the formation of the resonance circuit is released to receive the signal with a high reproducibility. |
