Multi level Class-D amplifier by means of 2 physical layers
First Claim
1. A circuit to generate virtual multi-level output pulses for a Class-D Amplifier with only 2 physical levels, where the resulting time-voltage-area corresponds to a multiple of digital levels, comprising:
- means to convert the input signal into a PDM (Pulse Density Modulated) signal;
means to generate the output of said PDM (Pulse Density Modulated) as a signal, representing the desired multiple of pulse areas values;
means to determine the required length-ratio of positive and negative pulse portions within one sampling period, where said pulse length ratio represents said multiple pulse-area values;
means to define a set of output pulse-area values, one for each step of said multiple pulse-area values;
means to control the time of pulse phase changes within one sampling period. a pulse generator providing the virtual multi-level output pulses to a power driver, using said pulse length controlled signal;
means for a Class-D power driver to drive voltage into an output load, controlled by said power driver pulses, typically a Complementary-Pair-Driver or an equivalent circuit; and
means for an output load as the amplifier'"'"'s output target.
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Abstract
Introduce a pulse length control mechanism to generate virtual multi-level output pulses for a Class-D Amplifier, which has only 2 physical output levels. Typically a Sigma-Delta-Modulator converts the input signal into high frequency low bit rate. The disclosed invention adds functions to transform the SDM signal into pulses with equivalent multi-level time-voltage areas and adds a pulse-length-control mechanism to produce various output pulse patterns, where the summations of the positive and negative pulses, within one sampling period, result in time-voltage area values, corresponding to 3 or more digital levels. Thus the invention produces higher signal quality at lower sampling rates.
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Citations
42 Claims
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1. A circuit to generate virtual multi-level output pulses for a Class-D Amplifier with only 2 physical levels, where the resulting time-voltage-area corresponds to a multiple of digital levels, comprising:
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means to convert the input signal into a PDM (Pulse Density Modulated) signal;
means to generate the output of said PDM (Pulse Density Modulated) as a signal, representing the desired multiple of pulse areas values;
means to determine the required length-ratio of positive and negative pulse portions within one sampling period, where said pulse length ratio represents said multiple pulse-area values;
means to define a set of output pulse-area values, one for each step of said multiple pulse-area values;
means to control the time of pulse phase changes within one sampling period. a pulse generator providing the virtual multi-level output pulses to a power driver, using said pulse length controlled signal;
means for a Class-D power driver to drive voltage into an output load, controlled by said power driver pulses, typically a Complementary-Pair-Driver or an equivalent circuit; and
means for an output load as the amplifier'"'"'s output target. - View Dependent Claims (2, 3, 4, 6, 7, 8, 9, 10, 13, 15, 16, 17, 18, 19, 20, 21, 22)
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5. The circuit of claim I wherein said means to generate the output of said PDM (Pulse Density Modulated) as a signal, representing the desired multiple of pulse areas values is implemented in a digital signal processor as an integrated part together with the Sigma Delta Modulator
- 11. The circuit of claim I wherein said means to define a set of output pulse-area values assumes a set of fixed and a priori known magnitudes.
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14. The circuit of claim I wherein said means to convert said PDM (Pulse Density Modulated) signal is implemented as an integrated digital logic function.
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23. A method to generate virtual multi-level output pulses for a Class-D Amplifier with only 2 physical levels, where the resulting time-voltage-area corresponds to a multiple of digital levels, comprising:
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providing means to convert the input signal into ideal PDM (Pulse Density Modulated) control pulses, means to generate the output of said PDM (Pulse Density Modulated) converter as a signal, representing the desired multiple of values of pulse areas, means to define a set of output pulse-area values, means to determine the required length-ratio of positive and negative pulse portions within a sampling period, means to control the time of pulse phase changes, a pulse generator providing the virtual multi-level output pulses to a power driver, means for a Class-D power driver to drive voltage into an output load and means for an output load;
converting said input signal into ideal PDM (Pulse Density Modulated) control pulses;
generating the output of said PDM signal converter as a multiple of values, representing the desired pulse areas;
determining said length-ratio of positive and negative pulse portions within one sampling period, where said pulse length ratio represents said multiple pulse-area values;
defining a set of output pulse-area values, one for each step of said multiple pulse-area values;
controlling the time to change the pulse phase within a sampling period, based on the desired pulse length ratio, with an appropriate time control mechanism;
generating said virtual multi-level output pulses under control of the signal, which changes said pulse phase;
applying said virtual multi-level output pulses to said Class-D power driver; and
driving said power driver'"'"'s output voltage to the output load (typically a loudspeaker). - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42)
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Specification