Thermal Printhead Structure with XOR Logic Control
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Solution Overview
Problem
Existing thermal printhead structures suffer from high conductive pattern density, undesirable butterfly-like dot shapes, and leakage currents due to the center-tap arrangement, and diode-based solutions face implementation challenges and increased costs, while diode-less systems generate residual heat affecting printing quality.
Innovation Solution
A new printhead structure with conductive leads connected to either the power supply or ground via a driver IC switch, utilizing exclusive-OR (XOR) logic for control, reduces conductive lead density and eliminates leakage current, and a driver IC with SPDT switches and built-in XOR gates for flexible operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a center-tap arrangement is used with conductive paths connected to both ends of each heater element, then the heater elements can be controlled to generate Joule's heat, but the density of the conductive pattern becomes twice the resolution of the printed dots and the printed dots take an undesirable butterfly-like shape
Solution Approach 1:
The patent extracts the center-tap conductive path from the heater element structure, connecting conductive paths only to one end of each heater element instead of both ends. This extraction reduces the conductive pattern density from twice the dot resolution to the same as dot resolution, eliminating the butterfly-like shape while maintaining heater control functionality through the driver IC switching mechanism.
2Object-generated harmful factors
If diodes are added in the upstream conductive path to prevent leakage current, then reverse-flowing current is prevented, but the space for mounting diode arrays becomes constrained and manufacturing cost increases
Solution Approach 1:
The patent replaces the mechanical/diode-based current blocking system with an electronic switching system. Instead of using diodes to prevent reverse current flow, the driver IC uses electronic switches that can actively control current direction and prevent leakage current through intelligent switching, eliminating the need for physical diode arrays and their associated space and cost constraints.
3Ease of manufacture
If a diode-less alternated conductive lead system is used, then diode arrays are removed, but undesirable leakage current still flows through neighboring nibs generating residual heat
Solution Approach 1:
The patent replaces the passive alternated conductive lead system with an active electronic switching system. Instead of relying on physical diodes or alternated lead configurations to prevent leakage, the driver IC uses electronically controlled switches that can precisely control current flow, preventing leakage current through neighboring nibs while maintaining ease of manufacture.
4Manufacturing precision
If the conductive leads are connected to both power supply and ground through switches, then leakage current is eliminated and dot shape consistency is improved, but the driver IC complexity increases with SPDT switches and XOR logic
Solution Approach 1:
The patent merges the switch control functions into a unified driver IC structure that integrates SPDT switches and XOR logic gates. By combining multiple control functions (power supply connection, ground connection, leakage prevention) into a single integrated circuit, the overall system complexity is managed more efficiently despite the increased IC functionality, achieving improved dot shape consistency.
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 new structure achieves reduced conductive lead density, eliminates leakage current, and maintains high printing speed with improved dot shape consistency and uniformity, suitable for high-resolution and edge-type thermal heads.
Implementation Method 1
Joule's heat is generated by applying a voltage across and flowing the current through the heater element
Implementation Method 2
due to high thermal conductivity of gold, heat escapes from the conductive pattern in the center portion toward the electrodes
Data Source
AI summary
A new structure (FIG. 11) for a thick-film thermal printhead and a variety of implementation approaches for controlling such a printhead. In the structure of the invention, the conductive lead at each end of the heater element is switched to either the power supply (Vhd) or ground, depending on the corresponding nib data bit. The improvement over a traditional center-tap structure (FIG. 1) is the reduction of density of conductive leads to achieve the resolution of printed dots. Compared to the printhead structure of alternated conductive system, either with diodes (FIG. 2) or without diodes (FIG. 4), which both suffer from the introduction of undesirable leaking currents, the printhead structure of the invention provides the advantage of eliminating leakage current completely. Control of the thermal printhead according to the invention is based on the sequential exclusive-OR (XOR) logic operation applied to the shifted-in nib data bit stream. The XOR functionality may be incorporated in the driver IC, embedded in the raster data processing FPGA (Field Programming Gate Array), or implemented in the form of a lookup table in the memory block of a main processor system. All prior art advanced controls based on a multi-pulse strategy can be applied directly from those used in prior art printhead structures to the controls for the thermal printhead for this invention without modification. A new driver IC (FIG. 26) is also disclosed according to the invention in which the outputs are SPDT (Single-Pole-Double-Throw) switches and the built-in XOR gates can be configured to act in the pass-through mode, if required, so that the new driver IC may be used as a traditional driver IC.