A board-level noise elimination circuit and audio output device for analog signals

Abstract

The invention provides a board-level noise elimination circuit for analog signals and an audio output device. The circuit includes a digital-to-analog conversion circuit and a signal drive circuit arranged on an audio processing chip. The digital-to-analog conversion circuit outputs a differential signal to the signal drive circuit, and the signal drives The circuit outputs signals to the output coupling capacitor arranged on the circuit board; wherein, the audio processing chip is also provided with a reference voltage generating circuit, the reference voltage generating circuit receives the reference voltage, and the reference voltage generating circuit also receives the input coupling capacitor arranged on the circuit board For the output signal, the reference voltage generating circuit outputs the reference voltage to the signal driving circuit. The audio output device includes a circuit board on which an audio processing chip is arranged, and the above-mentioned board-level noise elimination circuit for analog signals is also arranged on the circuit board. The invention has a simple structure and can effectively eliminate the noise and interference generated by the grounding of the circuit board on the analog signal.

Description

technical field [0001] The present invention relates to the technical field of analog signal processing, in particular to a board-level noise elimination circuit for analog signals and an audio output device with such a circuit. Background technique [0002] At present, most smart terminal devices such as smart phones and tablet computers have the function of playing audio. Therefore, earphones have become a standard configuration of smart terminal devices, and the smart terminal devices output audio signals to the earphones. Usually, a circuit board is arranged in the smart terminal device, an audio processing chip is arranged on the circuit board, and a digital-to-analog conversion circuit is arranged on the audio processing chip, and the digital-to-analog conversion circuit is used to receive the digital signal output by the processor and convert the digital signal into an analog signal and output the analog signal to the headphones. Since the power of the analog signal ...

AI Technical Summary

Problems solved by technology

If the single-ended analog signal is directly output to the earphone, the single-ended analog signal will generate DC loss, reduce efficiency and even damage the earphone. Therefore, it is necessary to install a large coupling capacitor on the circuit board to cut off the DC bias voltage. The other end of the will be connected to the ground of the circuit board

[0006] Usually, the power supply and grounding in the audio processing chip will be better RC filtered, and the interference signal of the circuit board will be complicated, so there will be a difference between the grounding inside the audio processing chip and the grounding near the connecting socket on the circuit board. At this time, if there is noise and interference near the ground of the circuit board, there will be noise during the playback of the earphone, which does not meet the application requirements of the product.

Existing solutions mainly focus on dealing with the noise caused by the charging and discharging of output coupling capacitors or Zobel capacitors during power-on and power-off, and there is no solution for noise near the ground on the circuit board.

[0007] For example, the notification number is CN101933224A, which discloses an audio processing circuit, which outputs the reference voltage Vref through the second operational amplifier as the reference voltage of the first operational amplifier, but this solution cannot eliminate the noise near the ground of the circuit board and noise caused by interference, the effect of earphone sound playback is not ideal

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