LCD Gate Driver Level Shifter With Pre-Charge Voltage Transition
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Solution Overview
Problem
Conventional liquid crystal display (LCD) gate driver level shifter circuits consume high current due to the need for a wide voltage swing range, which increases power consumption and is inefficient in portable devices.
Innovation Solution
A level shifter circuit that controls voltage levels of clock and inverted clock signals using pre-charge signals to switch between external voltage levels and power supply or ground voltage levels for a predetermined period, reducing current consumption by optimizing voltage transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional level shifter circuits are used to drive gate lines with wide voltage swing range, then the gate lines can be driven effectively, but current consumption increases significantly
Solution Approach 1:
The patent applies preliminary action by pre-charging the clock signal to an intermediate voltage level before the actual level transition. The pre-charge signal activates transistors to charge the clock signal to an intermediate voltage (e.g., 0V or VDD/2) before the main level shifter operates, reducing the voltage swing required during the actual switching operation and thereby reducing current consumption.
Solution Approach 2:
The patent changes the voltage parameter dynamically by introducing an intermediate voltage level for pre-charging. Instead of directly switching between extreme voltage levels (e.g., -VEE to VDD), the system first transitions to an intermediate level, then to the final level, effectively reducing the instantaneous voltage swing and associated current consumption during level shifting operations.
2Use of energy by moving object
If the voltage swing range is reduced to lower current consumption, then energy efficiency improves, but the gate driver may not be able to drive the gate lines effectively
Solution Approach 1:
The patent segments the voltage transition into multiple stages: a pre-charge stage that transitions the clock signal to an intermediate voltage level, and a main switching stage that completes the transition to the final voltage level. This segmentation allows each stage to operate with smaller voltage swings, reducing current consumption while ensuring the gate lines are still driven to the required voltage levels for effective operation.
Solution Approach 2:
The patent introduces an intermediate voltage level as a mediator in the level shifting process. The pre-charge signal creates this intermediate state, acting as a bridge between the input and output voltage levels. This intermediary approach allows the system to achieve the required voltage swing for gate line driving while minimizing the instantaneous current draw during transitions.
Data Source
AI summary
Provided are a level shifter circuit and a corresponding method for controlling voltage levels of a clock signal and an inverted clock signal for driving gate lines of a ASG thin film transistor liquid crystal display panel, where the level shifter circuit includes first and second level shifters, the first level shifter controls the voltage level of the clock signal to swing between a negative external voltage level and a positive external voltage level in response to a clock activating signal, and increases the voltage level of the clock signal from the negative external voltage level to a power supply voltage level or decreases it from the positive external voltage level to a ground voltage level while a pre-charge clock activating signal is activated, the second level shifter controls the voltage level of the inverted clock signal to swing between the negative external voltage level and the positive external voltage level in response to an inverted clock activating signal, and increases the voltage level of the inverted clock signal from the negative external voltage level to the power supply voltage level or decreases it from the positive external voltage level to the ground voltage level while an inverted pre-charge clock activating signal is activated, and the level shifter circuit increases or decreases the voltage levels of the clock signal and inverted clock signal using a battery voltage or a ground voltage, thereby reducing current consumption caused by the increase or decrease in the voltage level.