Fingerprint Display Panel Differential Signal Circuit
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Solution Overview
Problem
Common mode interference between the output signal and reference ground in fingerprint recognition circuits reduces the accuracy of fingerprint recognition in display devices.
Innovation Solution
A display panel with fingerprint recognition circuits that include a light sense signal obtaining unit generating two light sense voltage values under different power voltage values, with a subtractor eliminating the common mode interference to produce a light sense data value for improved recognition accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fingerprint recognition circuit is implemented in a display device, then user privacy protection and operation simplicity are improved, but common mode interference occurs between the output signal and reference ground which reduces fingerprint recognition accuracy
Solution Approach 1:
The fingerprint recognition circuit is divided into multiple independent sensing units, each with its own signal processing path. This segmentation allows the common mode interference to be isolated and eliminated in each channel independently through differential signaling, while maintaining the overall simplicity of the fingerprint recognition operation.
Solution Approach 2:
A differential signaling mechanism is introduced as an intermediary between the fingerprint sensing element and the processing circuitry. This differential signal path acts as a mediator that rejects common mode interference while preserving the fingerprint signal, thereby improving recognition accuracy without complicating the user operation.
2Adaptability or versatility
If the fingerprint recognition circuit operates with current-carrying conductors, then the fingerprint recognition function is achieved, but potential difference between output signal and reference ground causes common mode interference
Solution Approach 1:
The circuit design establishes equipotential relationships between signal paths and reference grounds through careful layout and shielding. By maintaining equal potential levels across adjacent conductors carrying differential signals, the potential difference that causes common mode interference is eliminated, allowing the fingerprint recognition function to operate without harmful interference.
Solution Approach 2:
The common mode interference, which initially appears as a harmful effect, is converted into a beneficial feature through differential signaling. The interference signal appears equally on both differential lines and is therefore rejected by the differential amplifier, while the actual fingerprint signal appears as a differential voltage that is amplified. This transforms the harmful common mode interference into a demonstration of the differential signal's noise rejection capability.
Data Source
AI summary
The present disclosure provides a display panel and a display device. The display panel includes a plurality of fingerprint recognition circuits. At least one of the plurality of fingerprint recognition circuits includes a light sense signal obtaining unit and a subtracted. The light sense signal obtaining unit is configured to obtain a first light sense voltage value and a second light sense voltage value, the first light sense voltage value is related to a first power voltage value, the second light sense voltage value is related to a second power voltage value, and the first power voltage value is greater than the second power voltage value. The subtracted is configured to subtract the second light sense voltage value from the first light sense voltage value to obtain a light sense data value.