POWER SUPPLY NOISE REDUCING FILTER, POWER UNIT, METHOD FOR DESIGNING THE POWER SUPPLY NOISE REDUCING FILTER, AND CHOKE COIL WITH RESISTANCE COMPONENT

摘要

PROBLEM TO BE SOLVED: To provide a power supply noise reducing filter which enables a reproduced sound to be surely outputted from a loudspeaker without deteriorating sound quality while reducing power supply noise even when, for example, there is load fluctuation such as output volume fluctuation of the loudspeaker in a car audio system.;SOLUTION: Circuit conditions of the filter are designed so that impedance Z_AB of the filter near a cutoff frequency f_c does not increase abruptly. Namely, the cutoff frequency f_c exists within an audible sound band and while carrying out noise reduction, predetermined attenuation characteristics can be satisfactorily realized in a frequency band of or higher than the cutoff frequency f_c. Furthermore, a power supply noise reducing filter 110A is composed of a choke coil 11a capable of suppressing the abrupt increase in impedance in the frequency of the audible sound band and having new inductance and a capacitor 12a having capacitance.;COPYRIGHT: (C)2005,JPO&NCIPI