Common mode voltage dynamic modulation circuit, method thereof and class-D audio power amplifier
The disclosure provides a common mode voltage dynamic modulation circuit, a method thereof and a class-D audio power amplifier. The modulation circuit includes: a signal input terminal and a common mode voltage dynamic adjustment module. The signal input terminal is used to receive an audio signal and output a differential audio signal to the common mode voltage dynamic adjustment module. The common mode voltage dynamic adjustment module is used to dynamically adjust a common mode voltage of the differential audio signal according to a preset static common mode bias and a normalized processing result of a swing of the audio signal, track an amplitude of an input audio signal in real time and obtain a continuously adjusted common mode voltage.
1 . A common mode voltage dynamic modulation circuit, comprising a signal input terminal and a common mode voltage dynamic adjustment module, wherein
the signal input terminal is configured to receive an audio signal and output a differential audio signal to the common mode voltage dynamic adjustment module;
the common mode voltage dynamic adjustment module is configured to dynamically adjust a common mode voltage of the differential audio signal according to a preset static common mode bias and a normalized processing result of a swing of the audio signal to obtain a current common mode voltage;
an expression of the current common mode voltage after normalization is:
V COM /V TRI =1−abs( V IN )/ V TRI −α;
V COM /V TRI is the current common mode voltage after normalization, abs (V IN )/V TRI is the swing of the audio signal after normalization, abs (V IN ) is an absolute value of an input voltage V IN , V COM is the current common mode voltage, V TRI is a maximum voltage of a triangular wave, and α is the preset static common mode bias.
2 . The common mode voltage dynamic modulation circuit according to claim 1 , further comprising an anti-clipping-off feedback adjustment module, configured to collect the differential audio signal after superimposing the current common mode voltage in real time, and determine a feedback adjustment voltage according to an amplitude of the differential audio signal after superimposing the current common mode voltage, wherein
the feedback adjustment voltage is configured to give feedback and adjust the current common mode voltage.
3 . The common mode voltage dynamic modulation circuit according to claim 2 , further comprising a first adder, wherein
the first adder is configured to add the current common mode voltage and the feedback adjustment voltage to obtain a current common mode voltage after the feedback adjustment.
4 . The common mode voltage dynamic modulation circuit according to claim 1 , wherein
when the signal input terminal is single-ended, the signal input terminal comprises an inverter to invert the audio signal.
5 . The common mode voltage dynamic modulation circuit according to claim 1 , further comprising a PWM comparator, wherein
the PWM comparator is configured to compare a received preset triangular wave signal with the differential audio signal after superimposing the current common mode voltage, and output an audio PWM modulation signal.
6 . The common mode voltage dynamic modulation circuit according to claim 1 , further comprising a second adder and a third adder, wherein
the second adder is configured to superimpose a positive terminal signal of the differential audio signal and the current common mode voltage, and output the positive terminal signal of the differential audio signal after superimposing the current common mode voltage;
the third adder is configured to superimpose a negative terminal signal of the differential audio signal and the current common mode voltage, and output the negative terminal signal of the differential audio signal after superimposing the current common mode voltage.
7 . The common mode voltage dynamic modulation circuit according to claim 1 , wherein
the preset static common mode bias is a real number greater than 0 and less than or equal to 0.5.
8 . A dynamic modulation method of a common mode voltage, configured to a dynamic adjustment of the common mode voltage using the common mode voltage dynamic modulation circuit according to claim 1 , comprising:
receiving the audio signal and outputting the differential audio signal;
normalizing the swing of the differential audio signal through the common mode voltage adjustment module, and determining the current common mode signal according to the obtained normalized input signal and the preset static common mode bias.
9 . The dynamic modulation method of the common mode voltage according to claim 8 , further comprising:
collecting the differential audio signal after superimposing the current common mode signal in real time through an anti-clipping-off feedback adjustment module, determining a feedback adjustment voltage according to an amplitude of the differential audio signal after superimposing the current common mode signal, and obtaining a current common mode signal after the determining the feedback adjustment voltage.
10 . A class-D audio power amplifier, comprising the common mode voltage dynamic modulation circuit according to claim 1 .
11 . The class-D audio power amplifier according to claim 10 , further comprising an output power amplifier module, wherein
an input terminal of the output power amplifier module is connected with an output terminal of the common mode voltage dynamic modulation circuit.
12 . The class-D audio power amplifier according to claim 11 , further comprising a low-pass filter, wherein
the low-pass filter is connected with an output terminal of the output power amplifier module.
13 . The class-D audio power amplifier according to claim 11 , further comprising a power amplifier gain module;
an input terminal of the power amplifier gain module is connected with an output terminal of a signal input module, and an output terminal of the power amplifier gain module is connected with an input terminal of the common mode voltage dynamic adjustment module;
an output signal of the output power amplifier module is fed back to the input terminal of the power amplifier gain module.