Ultrasonic Induction Circuit Threshold Voltage Compensation
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Solution Overview
Problem
Current ultrasonic sensor circuits in display devices face errors in determining fingerprint ridges and valleys due to the influence of threshold voltage variations in transistors, affecting touch performance.
Innovation Solution
The ultrasonic induction circuit incorporates a first potential supply sub-circuit, a compensation sub-circuit, and a signal output sub-circuit, with a second potential supply terminal providing a fixed potential that compensates for the threshold voltage, ensuring the output voltage signal is independent of the transistor's threshold voltage, thereby stabilizing the touch operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional ultrasonic sensor circuit is used, then the circuit structure is simple, but the output voltage signal is affected by threshold voltage variations causing errors in fingerprint ridge and valley determination
Solution Approach 1:
The circuit is divided into distinct functional modules: a first potential supply sub-circuit for providing a first potential, a compensation sub-circuit with a second potential supply terminal for providing a second potential that compensates for threshold voltage, and a signal output sub-circuit. This segmentation allows each module to be optimized independently, with the compensation sub-circuit specifically addressing the threshold voltage issue without redesigning the entire system.
Solution Approach 2:
The second potential supply terminal acts as an intermediary element that introduces a compensating potential to offset the threshold voltage of the transistor. This intermediary potential (Vr2) is added to the signal path to counterbalance the unwanted threshold voltage effect, thereby improving measurement accuracy without requiring fundamental changes to the transistor itself.
2Reliability
If the output voltage signal depends on transistor threshold voltage, then the circuit design is straightforward, but the touch performance is affected due to threshold voltage variations
Solution Approach 1:
The compensation for threshold voltage is performed in advance by providing a second potential (Vr2) from the second potential supply terminal before the signal processing stage. This preliminary compensation ensures that the threshold voltage effect is counterbalanced before it can degrade the signal quality, thereby improving reliability without adding complex real-time adjustment mechanisms.
Solution Approach 2:
The circuit utilizes parameter changes in the potential supplied to the ultrasonic sensor electrode. By varying the potential (introducing Vr2 from the second potential supply terminal) to compensate for threshold voltage variations, the system adapts to different transistor characteristics and maintains stable touch operation across different operating conditions.
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
This configuration effectively eliminates the impact of threshold voltage variations on the output voltage signal, improving the accuracy of fingerprint recognition and touch performance by maintaining a stable voltage signal independent of transistor threshold voltages.
Implementation Method 1
the ultrasonic sensor comprises a first electrode, a second electrode and a piezoelectric film layer arranged between the first electrode and the second electrode
Data Source
AI summary
An ultrasonic induction circuit is provided, a first electrode of an ultrasonic sensor is electrically connected with a first terminal of the ultrasonic sensing circuit, a second electrode is electrically connected with a second terminal of a first potential supply sub-circuit, and the first terminal of the first potential supply sub-circuit is electrically connected with a first potential supply end. A gate of M1 is electrically connected with the second electrode and the second terminal of the compensation sub-circuit. The second electrode is electrically connected with the first terminal of the compensation sub-circuit. The first electrode is coupled to the second potential supply end. The first terminal of the signal output sub-circuit is electrically connected to the second electrode of the first transistor, and the second terminal is electrically connected to the second terminal of the ultrasonic induction circuit.