Dual mode class D amplifiers
First Claim
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1. A class D amplifier comprising:
- an integrator having a plurality of inputs including an audio input, an audio feedback input, and a digital feedback input;
a comparator for receiving the output of the integrator and generating a series of pulses, each pulse corresponding to one of two states of the comparator and having a width proportional to the slope of the output of the integrator;
a driver circuit for receiving the pulse output of the comparator and generating gate drive signals proportional in duration to the width of the pulses;
a bridge circuit comprising two or more MOSFETS, each MOSFET having its gate coupled to a corresponding one of the gate drive signals;
a low pass filter coupled to the output of the bridge for converting an output of the bridge circuit into a power signal representative of the audio input signal; and
means coupled to the comparator for eliminating harmonics of an input AM signal from the output.
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Abstract
Pulse width modulated (“Class D”) amplifiers and controllers switching in the 50 khz to 2 MHz range generate harmonics that interfere with AM radio reception. This interference has precluded wide spread acceptance of class D amplifiers in products that include an AM radio. The amplifier described here uses a a harmonic avoidance modulator when operating with an AM radio to avoid generating harmonics at the receiver selected frequency or the intermediate (IF) frequency thereof.
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Citations
4 Claims
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1. A class D amplifier comprising:
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an integrator having a plurality of inputs including an audio input, an audio feedback input, and a digital feedback input;
a comparator for receiving the output of the integrator and generating a series of pulses, each pulse corresponding to one of two states of the comparator and having a width proportional to the slope of the output of the integrator;
a driver circuit for receiving the pulse output of the comparator and generating gate drive signals proportional in duration to the width of the pulses;
a bridge circuit comprising two or more MOSFETS, each MOSFET having its gate coupled to a corresponding one of the gate drive signals;
a low pass filter coupled to the output of the bridge for converting an output of the bridge circuit into a power signal representative of the audio input signal; and
means coupled to the comparator for eliminating harmonics of an input AM signal from the output. - View Dependent Claims (2, 3, 4)
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Specification