Sampling-and-Hold Circuit With Feedback for TFT Printhead Timing
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Solution Overview
Problem
Thin film transistors (TFTs) used in print head driving circuits for inkjet printers exhibit higher leakage current and longer signal rising and falling times compared to CMOS devices, leading to operational issues such as data loss and overlapping driving signals, which affect print quality and reliability.
Innovation Solution
The implementation of a sampling and holding circuit with a feedback unit and an output buffer, utilizing thin film transistors, helps stabilize input signals and control the rising and falling times of driving signals, reducing leakage current and preventing signal overlap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If thin film transistors are used in print head driving circuits, then large-area circuits can be manufactured with ease, but leakage current increases and signal timing deteriorates
Solution Approach 1:
The driving circuit is divided into multiple sub-circuits, each driving a specific group of nozzles. This segmentation allows independent optimization of each sub-circuit's timing characteristics while maintaining the overall large-area manufacturing advantage of TFT technology.
Solution Approach 2:
The circuit pre-charges capacitive loads before actual switching operations. By preparing the electrical state in advance, the circuit compensates for TFT's slow switching characteristics, ensuring accurate signal timing without requiring faster transistor performance.
2Ease of manufacture
If thin film transistors are used in print head driving circuits, then large-area circuits can be manufactured, but data loss occurs due to higher leakage current
Solution Approach 1:
The circuit employs periodic refresh operations to reinitialize signal states before nozzle firing. This periodic action counteracts the cumulative effect of leakage current, ensuring data integrity is maintained throughout the printing cycle despite TFT's higher leakage characteristics.
Solution Approach 2:
The circuit monitors signal states and implements feedback mechanisms to detect and correct errors caused by leakage current. By continuously verifying signal integrity, the system prevents data loss without requiring lower-leakage transistors, thus maintaining manufacturing simplicity.
3Ease of manufacture
If thin film transistors are used in print head driving circuits, then large-area circuits can be manufactured, but overlapping driving signals occur due to longer falling time
Solution Approach 1:
The circuit dynamically adjusts timing parameters based on actual signal conditions and nozzle response characteristics. By adaptively modifying rise and fall times, the system prevents signal overlap while maintaining the manufacturing advantages of TFT technology for large-area circuits.
Solution Approach 2:
The circuit incorporates timing margins and buffer zones between consecutive driving signals. This beforehand cushioning prevents overlap by ensuring sufficient separation between signal transitions, compensating for TFT's prolonged falling time without affecting manufacturing simplicity.
Data Source
AI summary
An electronic device includes a heater, and a sampling and holding circuit coupled to the heater. The sampling and holding circuit includes a sampling unit, a register unit and a feedback unit. The sampling unit is for receiving a data signal. The register unit has an input terminal and an output terminal. The input terminal is coupled to the sampling unit, and the output terminal is for outputting a first signal. The feedback unit is coupled to the input terminal and the output terminal of the register unit. When the feedback unit is turned on, the feedback unit feeds the first signal to the input terminal.