CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of Taiwan application Serial No. 105109883, filed Mar. 29, 2016, the disclosure of which is incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention relates to a noise suppression circuit, and more particularly, to a noise suppression circuit for touch-panel driver circuits.

BACKGROUND OF THE INVENTION

In a touch-panel driver circuit, an analog front-end (AFE) uses operational amplifiers to amplify a weak response signal from a touch sensor and filters to filter a part of noise in the response signal; after that, the amplified and filtered response signal can be conducted to analog-to-digital converters (ADC) and digital signal processors (DSP) in the back-end unit of the touch panel, so as to generate a digitized touch-sensor signal with a better signal-to-noise ratio (SNR). Generally, the operational amplifier is provided with a DC reference voltage generated by a reference-voltage generator.

However, noises often accompany the DC reference voltage during the generation of the DC reference voltage, so that those noises would be amplified by the AFE and thus deteriorate the total SNR of the driver circuit. Therefore, it is in need of new noise suppression means in the touch-panel driver circuit.

SUMMARY OF THE INVENTION

According to one aspect of the present disclosure, one embodiment provides a noise suppression circuit for suppressing a noise in a voltage signal, comprising: a switch unit having a first terminal receiving the voltage signal and a second terminal; a capacitor having a first terminal connected to the first terminal of the switch unit and a second terminal grounded; and an analog front-end unit including an operational amplifier with a signal input terminal and a reference-voltage input terminal electrically connected to the second terminal of the switch unit; wherein the switch unit is controlled by a pulse signal.

According to another aspect of the present disclosure, another embodiment provides a noise suppression circuit for suppressing a noise in a voltage signal, comprising: a switch unit having a first terminal receiving the voltage signal and a second terminal; a capacitor having a first terminal connected to the first terminal of the switch unit and a second terminal grounded; and an analog front-end unit including an operational amplifier with a signal input terminal and a reference-voltage input terminal electrically connected to the second terminal of the switch unit; wherein the switch unit is controlled by a pulse signal, and the analog front-end unit further includes a second reference-voltage generator with an input terminal connected to the second terminal of the switch unit and an output terminal connected to the reference-voltage input terminal of the operational amplifier.

According to still another aspect of the present disclosure, another embodiment provides a noise suppression circuit for suppressing a noise in a voltage signal, comprising: a switch unit having a first terminal receiving the voltage signal and a second terminal; a capacitor having a first terminal connected to the first terminal of the switch unit and a second terminal grounded; and an analog front-end unit including an operational amplifier with a signal input terminal and a reference-voltage input terminal electrically connected to the second terminal of the switch unit; wherein the switch unit is controlled by a pulse signal, the voltage signal is a DC voltage generated by a third reference-voltage generator with an output terminal connected to the first terminal of the switch unit, and the noise suppression circuit further includes a fourth reference-voltage generator with an input terminal connected to the output terminal of the third reference-voltage generator and an output terminal connected to the first terminal of the switch unit.

Further scope of applicability of the present application will become more apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

