Printhead Ground Wiring Segmentation for Ringing Suppression
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Solution Overview
Problem
In inkjet printheads, the long wiring lengths in full-line configurations lead to increased parasitic inductance, causing ringing and potential differences that can activate parasitic transistors, resulting in malfunctions of driving elements and logic circuits due to electromagnetic noise and current fluctuations.
Innovation Solution
A printhead configuration with separate ground wirings for the transistor source and back gate, and a capacitive element connected between these ground wirings to suppress ringing and prevent malfunctions, including a power supply wiring connected to the printing element and a transistor to drive it, with the capacitive element placed on the print circuit board to reduce parasitic inductance effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the wiring length is increased to achieve full-line printhead configuration, then the print width is improved, but the parasitic inductance increases causing ringing and potential differences
Solution Approach 1:
The ground wiring is segmented into multiple separate ground wirings (first ground wiring connected to source, second ground wiring connected to back gate) to reduce the loop area and parasitic inductance. This segmentation prevents the formation of large current loops that would generate electromagnetic noise and ringing, thereby maintaining reliability in full-line printhead configurations.
Solution Approach 2:
A capacitive element is introduced as an intermediary component connected between the first and second ground wirings. This capacitor provides a low-impedance path for high-frequency noise currents, suppressing ringing and potential differences caused by parasitic inductance. The capacitor acts as a mediator that stabilizes the potential difference between different ground references without requiring physical shortening of the wiring.
2Reliability
If separate ground wirings are used for heater and logic circuit, then electromagnetic noise propagation is prevented, but the device complexity increases
Solution Approach 1:
The separate ground wirings serve multiple functions: they provide independent reference potentials for the heater and logic circuit (preventing noise propagation), and they work in conjunction with the capacitive element to suppress ringing. This multi-functionality justifies the increased wiring complexity by delivering enhanced reliability and noise immunity.
3Reliability
If a capacitive element is added between ground wirings, then ringing is suppressed and potential difference is stabilized, but the device complexity increases
Solution Approach 1:
The capacitive element changes the electrical parameters of the ground wiring system by providing a low-impedance path for high-frequency currents. This parameter change (adding capacitance) suppresses ringing and stabilizes the potential difference between ground wirings. The single capacitive component provides significant noise suppression with minimal impact on overall device complexity.
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 suppresses ringing and prevents malfunctions of both logic circuits and driving elements, enhancing the reliability of the printhead by maintaining a stable potential difference and reducing the risk of parasitic transistor activation.
Implementation Method 1
a first capacitive element configured to be electrically connected, at one terminal thereof, to the first ground wiring and electrically connected, at another terminal thereof, to the second ground wiring
Implementation Method 2
a heater in order to achieve stable discharge characteristics in an inkjet printhead that discharges ink from a plurality of discharge ports using thermal energy
Data Source
AI summary
A printhead includes a printing element; a first power supply wiring configured to be electrically connected to one terminal of the printing element and supply power to the printing element; a transistor configured to be electrically connected to another terminal of the printing element and drive the printing element; a first ground wiring configured to be electrically connected to a source of the transistor; a second ground wiring configured to be electrically connected to a back gate of the transistor; and a first capacitive element configured to be electrically connected, at one terminal thereof, to the first ground wiring and electrically connected at another terminal thereof, to the second ground wiring.