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US 7,010,271 B2Granted
Circuits and methods for reducing interference from switched mode circuits
AssigneeCirrus Logic, Inc.
InventorJohn Laurence Melanson
Life of this patent
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Abstract
A system 100 including a radio receiver 101/108 and switched mode circuitry 114/115 operating at a selected switching frequency is disclosed. Circuitry 207–209 sets the switching-circuitry of the switched mode circuitry 114/115 as a function of a frequency of a signal being received by a radio receiver 101/108.
Claims11
A system comprising:
- an AM radio receiver;
- switched mode circuitry comprising an audio amplifier for driving an audio channel of said radio receiver and operating at a selected switching frequency, the audio amplifier including pulse width modulation circuitry operating in response to a clock signal of a selected frequency and another clock signal having a frequency of a selected frequency divide ratio to the frequency of the clock signal, the pulse width modulation circuitry outputting a pulse width modulated signal at said selected switching frequency and changing operating characteristics in response to a change in said divide ratio including changing a zero point of the pulse of the pulse width modulated signal;
- and
- circuitry for setting said switching frequency of said switched mode circuitry by setting said divide ratio as a function of a frequency of an AM signal being received by said radio receiver.
1 more element
A system comprising:
- an radio receiver;
- an audio amplifier for driving an audio channel of said redio receiver and operating at a switching frequency, the audio amplifier including pulse width modulation circuitry operating in response to a clock signal and another clock signal of a frequency of selected divide ratio to the frequency of the clock signal and outputting a pulse width modulated signal at the switching frequency, a change in the divide ratio changing operating characteristics of the pulse width modulation circuitry including varying distortion correction operations in response to a change in the divide ratio and the switching frequency;
- and
- circuitry for setting said switching frequency by changing the divide ratio including a divider for dividing the frequency of the clock signal to generate the freguency of the another clock signal of the selected divide ratio.
1 more element
Dependencies are inferred from the claim text.