Digital pulse width modulation for half bridge amplifiers
First Claim
1. A switching amplifier circuit capable of driving a half bridge switching amplifier stage, comprising:
- a variable frequency generator for generating a variable frequency reference pulse width modulated signal, wherein the variable frequency generator varies a frequency of the frequency reference pulse width modulated signal to generate a varying frequency reference pulse width modulated signal; and
a digital integral noise shaping circuit for converting a digitally modulated digital input to an output digital pulse width modulated signal with a variable switching frequency, the digital integral noise shaping circuit comprising a digital integrator for producing the output pulse width modulated signal by digitally integrating the digitally modulated digital input, the variable frequency reference pulse width modulated signal and an inverse of the output digital pulse width modulated signal, wherein the output digital pulse width modulated signal is available to drive the half bridge switching amplifier stage.
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Abstract
A switching amplifier drives a load or audio transducer. A digital integral noise shaping circuit converts a digital input such as audio content to an output digital pulse width modulated signal using an integrator. The integrator integrates the digital input, a variable frequency reference pulse width modulated signal and an inverse of the output digital pulse width modulated signal. A half bridge amplifier receives the output digital pulse width modulated signal and drives the load or audio transducer. A variable frequency generator generates the variable frequency reference pulse width modulated signal with an approximately equal duty ratio or alternatively varies the variable frequency pulse width modulated signal above and below about a fifty percent duty ratio.
17 Citations
20 Claims
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1. A switching amplifier circuit capable of driving a half bridge switching amplifier stage, comprising:
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a variable frequency generator for generating a variable frequency reference pulse width modulated signal, wherein the variable frequency generator varies a frequency of the frequency reference pulse width modulated signal to generate a varying frequency reference pulse width modulated signal; and a digital integral noise shaping circuit for converting a digitally modulated digital input to an output digital pulse width modulated signal with a variable switching frequency, the digital integral noise shaping circuit comprising a digital integrator for producing the output pulse width modulated signal by digitally integrating the digitally modulated digital input, the variable frequency reference pulse width modulated signal and an inverse of the output digital pulse width modulated signal, wherein the output digital pulse width modulated signal is available to drive the half bridge switching amplifier stage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A switching amplifier circuit capable of driving a half bridge switching amplifier stage, comprising:
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a variable frequency generator for generating a variable frequency reference pulse width modulated signal; a digital circuit for converting a digital input to an output digital pulse width modulated signal with a variable switching frequency, the digital circuit comprising an integrator for producing the output pulse width modulated signal by integrating the digital input, the variable frequency reference pulse width modulated signal and an inverse of the output digital pulse width modulated signal, wherein the output digital pulse width modulated signal is available to drive the half bridge switching amplifier stage; a summer operatively coupled to sum an output of the integrator and the digital input; and a multi-bit quantizer coupled to an output of the summer to produce the output digital pulse width modulated signal. - View Dependent Claims (13, 14, 15, 16)
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17. A method for amplifying a digital input and drive a load via a half bridge, the method comprising the steps of:
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(a) generating a variable frequency reference pulse width modulated signal; (b) converting the digital input to an output digital pulse width modulated signal with a variable switching frequency by integrating the digital input, the variable frequency reference pulse width modulated signal and an inverse of the output digital pulse width modulated signal; (c) summing an output of the integrator and the digital input; (d) quantizing an output of the summer to produce the output digital pulse width modulated signal; and (e) driving the half bridge with the output digital pulse width modulated signal. - View Dependent Claims (18, 19, 20)
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Specification