Piezoelectric Printhead Overcurrent Isolation for Faulty Ejectors
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Solution Overview
Problem
In inkjet printheads with piezoelectrically controlled ink ejectors, electrical shorts and overcurrent conditions can occur due to defects or deterioration in the connections between ASICs and piezoelectric materials, leading to damage and inoperativity of multiple ink nozzles.
Innovation Solution
A fluid ejection system with a transistor connected to a piezoelectric actuator, a diode, and detection circuits that detect overcurrent conditions and disable the transistor to prevent further damage, thereby isolating the faulty ejector unit and preventing cascading failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If multiple ink ejectors are packed into a small area with ASIC connections, then device integration and compactness are improved, but electrical shorts and overcurrent conditions occur more frequently
Solution Approach 1:
The patent divides the inkjet printhead into independently controllable ejector units, each with its own protection circuit. When an electrical short is detected in one unit, only that specific unit is disabled while other units remain operational. This segmentation isolates failures and prevents cascading damage across the entire device.
Solution Approach 2:
The patent implements preliminary protective measures by incorporating overcurrent detection circuits and disabling mechanisms before electrical shorts can cause widespread damage. The detection circuit continuously monitors current levels and preemptively disables faulty ejector units, preventing the propagation of electrical failures to adjacent components.
2Reliability
If overcurrent detection and disabling circuits are added to each ejector unit, then reliability and failure isolation are improved, but device complexity increases
Solution Approach 1:
The protection circuit is segmented into modular units, with each ink ejector having its own integrated detection and disabling circuitry. This modular approach allows the protection functionality to be distributed across multiple simple units rather than requiring a single complex centralized protection system.
Solution Approach 2:
Each ejector unit is equipped with self-diagnostic and self-protection capabilities through integrated overcurrent detection circuits. When a fault is detected, the unit automatically disables itself without requiring external intervention, thereby simplifying the overall control architecture while maintaining high reliability.
3Reliability
If individual ejector units are disabled upon overcurrent detection, then collateral damage to other nozzles is prevented, but the number of operational nozzles decreases
Solution Approach 1:
The inkjet printhead is divided into independently controllable ejector units, allowing selective disabling of only the faulty unit while maintaining operation of all other units. This segmentation ensures that a failure in one location does not compromise the functionality of other locations, thereby preserving overall productivity.
Solution Approach 2:
The patent converts the harmful effect of electrical shorts into a beneficial isolation mechanism. By detecting overcurrent conditions and automatically disabling only the affected ejector unit, the system transforms a potential catastrophic failure into a localized event that protects the remaining operational units, ultimately benefiting overall system productivity.
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 solution effectively prevents collateral damage to other ink nozzles by disabling the affected unit, reducing the need for head replacement and maintaining functionality of the remaining fluid ejection units.
Implementation Method 1
each including a pumping chamber connected to a nozzle. The piezoelectric material can be electrically coupled to an application-specific integrated circuit (ASIC). The ASIC drives the piezoelectric material, which actuates the pumping chamber and ejects the ink from the associated nozzle.
Implementation Method 2
a detection circuit configured to detect whether a voltage at the drain of the transistor is above a predefined voltage
Data Source
AI summary
An apparatus, method, and a fluid ejection system for detecting electrical shorts in piezoelectric printheads are described. An apparatus includes a piezoelectric actuator, a transistor whose drain is connected to the piezoelectric actuator, a diode that is connected to a source and the drain of the transistor, a detection circuit configured to detect whether a voltage at the drain of the transistor is above a predefined voltage, and a disabling circuit configured to turning off the transistor in response to detecting that voltage at the drain of the transistor is above the predefined voltage.