Liquid Crystal Driving Circuit Ramp Signal Noise Reduction
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Solution Overview
Problem
Liquid crystal driving circuits face a trade-off between display quality and circuit board area and current consumption due to the need for large capacitors to absorb spike noise, which can result in defective displays if output impedance is not sufficiently small.
Innovation Solution
A liquid crystal driving circuit with resistors connected in series and voltage follower circuits that impedance-convert intermediate potentials, allowing common and segment signals to change in a ramp form, reducing spike noise and slew rate while minimizing current consumption and circuit area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large capacitors are used to absorb spike noise, then display quality is improved, but circuit board area and current consumption increase
Solution Approach 1:
The patent changes the parameter of signal potential transition from abrupt to ramp form. By controlling the potential to change gradually rather than abruptly, the spike noise is reduced without requiring large capacitors for noise absorption, thus decreasing circuit board area while maintaining display quality
Solution Approach 2:
The patent introduces dynamic control of signal potential transitions. The potential is changed in a ramp form based on timing control, allowing the system to adaptively manage noise generation. This dynamic approach reduces spike noise during potential transitions without requiring static large capacitors for noise filtering
2Reliability
If large capacitors are used to absorb spike noise, then display quality is improved, but current consumption increases
Solution Approach 1:
The patent changes the parameter of signal potential transition from abrupt to ramp form. By controlling the potential to change gradually rather than abruptly, the spike noise is reduced without requiring large capacitors for noise absorption, thus decreasing circuit board area while maintaining display quality
Solution Approach 2:
The patent introduces dynamic control of signal potential transitions. The potential is changed in a ramp form based on timing control, allowing the system to adaptively manage noise generation. This dynamic approach reduces spike noise during potential transitions without requiring static large capacitors for noise filtering
3Reliability
If output impedance is made sufficiently small to reduce spike noise, then display quality is improved, but current consumption increases
Solution Approach 1:
The patent changes the parameter of signal potential transition from abrupt to ramp form. By controlling the potential to change gradually rather than abruptly, the spike noise is reduced without requiring large capacitors for noise absorption, thus decreasing circuit board area while maintaining display quality
Solution Approach 2:
The patent introduces dynamic control of signal potential transitions. The potential is changed in a ramp form based on timing control, allowing the system to adaptively manage noise generation. This dynamic approach reduces spike noise during potential transitions without requiring static large capacitors for noise filtering
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 reduces spike noise and slew rate, ensuring favorable display quality while minimizing current consumption and circuit board area, by changing signal potentials in a ramp form with a maximum potential difference.
Implementation Method 1
one or more voltage follower circuits configured to impedance-convert one or more intermediate potentials between the first potential and the second potential, to be outputted, respectively, the one or more intermediate potentials generated at one or more connection points between the plurality of resistors, respectively
Implementation Method 2
beard-like spike noise might be generated in one of the signals, which is caused by a change in potential of the other of the signals. Thus, in the liquid crystal driving circuit illustrated in FIG. 7, similarly to FIG. 4 in Japanese Patent Laid-Open Publication No. H10-10491, capacitors C1 and C2 are used as stabilizing capacities so as to absorb the spike noise
Data Source
AI summary
A liquid-crystal-driving circuit includes: a plurality of resistors connected in series between a first and second potentials; one or more voltage follower circuits to impedance-convert one or more intermediate potentials between the first and second potentials, to be outputted, respectively, the intermediate potentials generated at one or more connection points between the resistors, respectively; a common-signal-output circuit to supply common signals to common electrodes of a liquid-crystal panel, respectively, the common signals each being at the first and second potentials, and the intermediate potentials; and a segment-signal-output circuit to supply segment signals to segment electrodes of the panel, respectively, the segment signals each being at the first and second potentials, and the intermediate potentials according to the common signals, the segment-signal output circuit to change the potentials of the segment signals in a ramp form, at least if the potentials of the segment signals are changed with a maximum-possible-potential difference.