Thermal Print Head Driver Device Voltage Level Shifting
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Solution Overview
Problem
Conventional thermal print heads face challenges with high on-state resistance variations in MOS transistors, which hinder downsizing and increase the dimensions of driver devices due to the need for correction circuits and larger gate widths to compensate for voltage and resistance variations.
Innovation Solution
The introduction of a driver device with n transistors, a data storage, and n level shifters that convert first voltages into higher second voltages, reducing on-state resistance stability and allowing for smaller gate widths, and a regulator to produce these higher voltages for the driver devices, eliminating the need for correction circuits and enabling downsizing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MOS transistors with larger gate widths are used to compensate for resistance variations, then current stability is improved, but driver device dimensions increase
Solution Approach 1:
The invention changes the voltage parameter by introducing level shifters that convert first voltages to higher second voltages. This voltage transformation allows the use of transistors with smaller gate widths while maintaining current stability, as the higher voltage compensates for the reduced transistor size. The regulator circuit maintains stable voltage output despite variations in transistor characteristics, resolving the contradiction between current stability and device size.
2Manufacturing precision
If correction circuits are added to compensate for process variations and wiring resistance, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The invention merges the voltage regulation function with the existing level shifter circuitry. The regulator circuit is integrated into the driver device structure, combining multiple functions (voltage conversion, regulation, and transistor control) into a unified system. This integration achieves precise current control without adding separate, complex correction circuits, as the regulator works in conjunction with the level shifters to compensate for process variations and wiring resistance.
3Stability of the object's composition
If more transistors with stable characteristics are used to reduce resistance variations, then on-state resistance stability is improved, but the number of components and device area increase
Solution Approach 1:
Instead of increasing the number of transistors or their gate widths to improve stability, the invention changes the operating voltage parameter. The level shifters convert first voltages to higher second voltages, which stabilizes the on-state resistance by operating the transistors in a regime where resistance variations are minimized. This approach achieves stability through parameter optimization rather than component proliferation.
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 solution stabilizes on-state resistance and reduces current variations through resistive elements, allowing for smaller driver device dimensions and eliminating the need for correction circuits, thus facilitating the downsizing of thermal print heads.
Implementation Method 1
a regulator for converting a first voltage into a higher second voltage
Implementation Method 2
n level shifters for converting first voltages into higher second voltages and outputting the higher second voltages to control electrodes of the n transistors
Implementation Method 3
n transistors for individually driving n heating elements
Data Source
AI summary
A print head has m driver devices 1 that are fed with a supply voltage VDD and that control the driving of resistive elements acting as heaters and a regulator 2 that is fed with a supply voltage VH higher than the supply voltage VDD and that converts the supply voltage VH into a supply voltage VG, which the regulator 2 then feeds to the individual driver devices 1.