| 摘要 |
PURPOSE:To optimize the capacitance of a capacitor for elimination ripples. CONSTITUTION:The output voltage of a rectifier 3 is detected by a voltage detection circuit 17. When the detected voltage is low ( due to a weak reception radio wave or a remote distance), a controller 20 turns off a switch 16 to connect only a capacitor 14 to the output of the rectifier 3 and to decrease the capacitance of the capacitor thereby increasing the rising speed of a power supply voltage. On the other hand, when the detected voltage is higher than a prescribed voltage (due to a strong reception radio wave or a near distance), the controller 20 turns on the switch 16 to connect capacitors 14, 15 to the output of the rectifier 3 in parallel and to increase the combined capacitance of the capacitors thereby eliminating ripple sufficiently. Accordingly, malfunction due to a ripple component is prevented and the communication is conducted. |
