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US 2003/0194970 A1Published application
Dual mode class D amplifiers
OwnerDavid Hoyt, Stuart W. Pullen +3inventors
InventorsDavid Hoyt, Stuart W. Pullen, Patrick A. Begley, Arecio A. Hernandez, Jeffrey M. Strang
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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.
Claims4
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.
4 more elements
Dependencies are inferred from the claim text.