VARIABLE FREQUENCY SWITCHING AMPLIFIER AND METHOD THEREFOR

摘要

A switching amplifier (20) generates noise at its switching frequency and harmonics thereof. The noise at these harmonics, for an audio amplifier, will be generated with significant amplitude in the AM band. Thus, an AM tuner (12) will experience interference problems if the tuner frequency is sufficiently close to one of these harmonics. To avoid this problem the switching frequency of the switching amplifier is chosen based on the tuner frequency. Thus, the switching frequency is chosen to avoid having harmonics at or too near the chosen tuner frequency. The switching amplifier is disabled when the tuner is in seek or scan mode. Instead of using the tuner frequency to determine what switching frequency should be used to avoid interference, the interference can be detected directly to cause a change in the switching frequency and thus remove the interference.