LCD Driving Circuit Using Periodic Pulse High-Voltage Signals
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Solution Overview
Problem
Liquid crystal displays (LCDs) face issues with flicker phenomena and image sticking due to asymmetrical voltage applications, which lead to uneven transmittance and increased power consumption, and the presence of impurity ions that migrate under voltage, causing image sticking.
Innovation Solution
A liquid crystal display driving apparatus using a unidirectional voltage signal applied to the pixel electrode and a corresponding common voltage signal, along with a periodical pulse high-voltage signal, to control the tilt of liquid crystal molecules and maintain impurity ions in a saturation state, reducing power consumption and eliminating flicker and image sticking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bidirectional voltage is applied to prevent liquid crystal aging, then liquid crystal material aging is prevented, but power consumption increases and requires two sets of gamma resistors
Solution Approach 1:
The patent applies periodic pulse high-voltage signals to the common electrode instead of continuous bidirectional voltage. The pulse signals are applied at specific intervals (e.g., every few frames) to reorient liquid crystal molecules and prevent aging, while maintaining unidirectional drive during normal operation to reduce power consumption.
Solution Approach 2:
The patent changes the voltage application parameters by using unidirectional voltage with periodic pulse interruptions rather than continuous bidirectional voltage. The pulse width, amplitude, and frequency are optimized to achieve aging prevention with minimal power consumption impact.
2Stability of the object's composition
If bidirectional voltage is applied to display images, then liquid crystal molecules are tilted in opposite directions, but transmittance becomes uneven and flicker occurs
Solution Approach 1:
The patent intentionally uses asymmetric voltage application - unidirectional voltage for normal display combined with periodic pulse high-voltage signals. This asymmetric approach creates sufficient electric field strength during pulses to reorient molecules and prevent aging without creating the transmittance unevenness and flicker associated with continuous bidirectional voltage.
Solution Approach 2:
Periodic pulse high-voltage signals are applied to the common electrode at controlled intervals. These pulses create strong electric fields that temporarily reorient liquid crystal molecules to prevent aging, while the unidirectional voltage between pulses maintains stable transmittance and eliminates flicker.
3Ease of operation
If two sets of gamma resistors are used to provide positive and negative voltages, then pixel voltage control is achieved, but PCB and COF space increases and cost increases
Solution Approach 1:
The patent extracts the need for negative voltage generation by using unidirectional voltage drive. Only one set of gamma resistors is required on the COF to generate positive voltages, eliminating the second set that would be needed for bidirectional drive. The periodic pulse high-voltage signals are generated through circuit switching rather than additional resistors.
Solution Approach 2:
The single set of gamma resistors serves multiple functions by working in conjunction with the periodic pulse high-voltage signal generation circuit. The same resistor network that controls normal pixel voltages also works with the pulse circuit to achieve aging prevention, eliminating the need for separate negative voltage generation components.
4Use of energy by moving object
If unidirectional voltage is applied to reduce power consumption, then power consumption decreases, but liquid crystal aging occurs
Solution Approach 1:
Periodic pulse high-voltage signals are superimposed on the unidirectional voltage drive. These pulses occur at intervals (e.g., every 2-10 frames) with sufficient amplitude and duration to reorient liquid crystal molecules and prevent aging, while the majority of the time the system operates in low-power unidirectional mode.
Solution Approach 2:
The voltage parameters are dynamically changed between normal unidirectional operation and pulse high-voltage application. During normal operation, low-power unidirectional voltage is applied. During pulse intervals, high-voltage signals are applied to achieve molecular reorientation and prevent aging, optimizing both power consumption and reliability.
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 constrains flicker phenomena and reduces power consumption by applying a unidirectional voltage and periodical pulse high-voltage signals, preventing image sticking by maintaining impurity ions in a saturation state, thus improving the quality and longevity of the liquid crystal display.
Implementation Method 1
applying a periodical pulse high-voltage signal so as to form a bias field opposite to the electric field
Implementation Method 2
an electric field for tilting liquid crystal is formed between the pixel electrode and the common electrode by the unidirectional voltage signal and the common voltage signal
Data Source
AI summary
A liquid crystal display driving apparatus including a pixel voltage driving circuit for providing a periodical pulse high-voltage signal is provided. The liquid crystal display driving apparatus includes: a gate driving unit, a source driving unit, and a gate line and a date line intersected with each other to define a pixel region, in which a pixel electrode is provided, wherein the source driving unit includes: a pixel voltage driving circuit for providing a unidirectional voltage signal applied to the pixel electrode in the pixel region and for providing a periodical pulse high-voltage signal; and a common voltage driving circuit for providing a common voltage signal which corresponds to the unidirectional voltage signal provided by the pixel voltage driving circuit.