Pseudo-Differential AFE Circuit for Low-Distortion Image Signals
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Solution Overview
Problem
Existing display systems face signal distortion issues during the conversion of single-ended analog image signals to differential signals, which can be exacerbated by poor layout and power configuration in ICs, leading to increased component count and pin count, affecting image quality.
Innovation Solution
A pseudo-differential analog front-end circuit is introduced, comprising a clamper, input buffer, and analog-to-digital converter (ADC) with a common comparing voltage, reducing the number of components and pins while improving signal quality by using a pseudo-differential input structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If single-ended analog image signals are converted to differential signals in the interior of LCD controllers, then noise immunity is improved, but signal distortion occurs due to different reference ground levels
Solution Approach 1:
The patent introduces a pseudo-differential conversion circuit as an intermediary between the single-ended signal input and the differential signal processing. This circuit uses a clamper to establish a common reference voltage level and generates complementary signals, serving as a mediator that enables differential processing without direct single-ended to differential conversion that causes distortion.
Solution Approach 2:
The conversion process is segmented into distinct functional blocks: a clamper circuit for reference voltage establishment, a pseudo-differential conversion circuit for signal transformation, and subsequent differential processing stages. This segmentation allows each block to be optimized independently, with the clamper handling reference levels and the conversion circuit handling signal transformation.
2Manufacturing precision
If a fully-differential input structure is used in the AFE circuit, then signal distortion is reduced, but the number of components and package pins increases
Solution Approach 1:
The patent employs an asymmetric pseudo-differential structure where only one side of the differential pair requires external input pins, while the other side is generated internally through the clamper and conversion circuit. This asymmetric design achieves differential signal benefits without requiring symmetric dual input connections, reducing pin count and component requirements.
Solution Approach 2:
The patent merges the reference voltage generation and signal conversion functions into integrated circuits within the AFE. The clamper circuit and pseudo-differential conversion circuit are combined to generate both differential signals and reference voltages internally, eliminating the need for separate external components and reducing overall device complexity.
3Manufacturing precision
If more power pins and ground pins are added to the IC (such as AD 9887), then signal distortion is reduced, but the device complexity and pin count increase
Solution Approach 1:
The AFE circuit is designed to self-generate its reference voltage levels and internal ground references through the clamper circuit, eliminating the need for multiple external power and ground pins. The circuit serves itself by creating stable reference levels internally, reducing dependency on external pin connections for power and ground stabilization.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The pseudo-differential AFE circuit effectively minimizes signal distortion, reduces power consumption and size, and enhances image quality by approximating fully-differential inputs with fewer components and pins, resulting in improved image processing.
Implementation Method 1
The clamper receives the analog image signal and restores a DC voltage level of the analog image signal to generate a first restored signal
Implementation Method 2
The ADC converts a voltage difference between the two input terminals into the digital signal
Data Source
AI summary
An image processing device is provided which includes a pseudo differential analog front end circuit for receiving at least one image analog signal and generating at least one digital signal. The pseudo differential analog front end circuit includes at least a converting circuit, each of which includes a clamper, an input buffer and an analog-to-digital converter. All of the analog-to-digital converters receive a common comparing voltage if the number of the converting circuits is greater than one.