Class D amplifier
First Claim
1. A bit-flipping sigma-delta modulator for a class D amplifier and comprising:
- a quantiser coupled to a bit-flipping means;
one or more look-ahead quantisers; and
a controller having inputs from the quantiser and the look-ahead quantiser and arranged to enable the bit-flipping means to provide a different output from that of the quantiser in order to reduce the quantised output transition rate of the modulator;
a feedback circuit arranged to add a portion of the quantiser output to the input signal path of the modulator, and further comprising an integrator circuit in the input signal path between the input and the quantiser, the integrator circuit having a compensation circuit for adjusting the input to the quantiser when said previous modulator output has been changed by the bit flipping means from said previous quantiser output.
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Accused Products
Abstract
The present invention relates to Class-D amplifiers, and in particular to bit-flipping sigma-delta modulator (SDM) implementations of such amplifiers. Such amplifiers are particularly although not exclusively suitable for audio equipment such as hi-fi and personal music amplifiers. The present invention provides a bit flipping sigma delta modulator (BF SDM) having a multiple feedback loop filter structure. The modulator comprises a quantiser coupled to a bit flipping means, a look ahead quantiser to determine the next quantiser output, and a controller which determines whether to change the output of the bit flipping means. The modulator comprises a feedback loop arranged to add feedback from the output of the modulator to its input. The modulator comprises compensation means to adjust the states of the modulator in order to correct for bit flipping of the output of the quantiser. This adjusts the input to the quantiser to correspond to an input having feedback from a non bit flipped quantiser output.
68 Citations
21 Claims
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1. A bit-flipping sigma-delta modulator for a class D amplifier and comprising:
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a quantiser coupled to a bit-flipping means;
one or more look-ahead quantisers; and
a controller having inputs from the quantiser and the look-ahead quantiser and arranged to enable the bit-flipping means to provide a different output from that of the quantiser in order to reduce the quantised output transition rate of the modulator;
a feedback circuit arranged to add a portion of the quantiser output to the input signal path of the modulator, and further comprising an integrator circuit in the input signal path between the input and the quantiser, the integrator circuit having a compensation circuit for adjusting the input to the quantiser when said previous modulator output has been changed by the bit flipping means from said previous quantiser output. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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Specification