Column Driver Offset Compensation for Display Devices
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Solution Overview
Problem
Display devices face challenges in maintaining consistent output among column driver circuits due to variations in threshold voltage of source follower transistors, affecting display quality and operation speed.
Innovation Solution
Incorporating an offset signal holding unit and a current supply unit with a comparator and switch between the input and output nodes of the column driver circuit to suppress offset differences and enhance operation speed by dynamically adjusting current supply based on voltage comparisons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a source follower circuit is used as the output buffer of the column driver circuit, then the circuit structure is simple, but the output potential varies among columns due to threshold voltage variations
Solution Approach 1:
The offset signal holding unit stores the offset signal in advance before it is needed for compensation. By pre-acquiring and storing the offset signal that corresponds to the threshold voltage variation, the system can quickly compensate for potential variations without adding complex real-time measurement circuits, thus maintaining circuit simplicity while improving output consistency.
Solution Approach 2:
An offset signal holding unit is introduced as an intermediary component between the input and output of the column driver circuit. This unit stores and provides offset signals that compensate for threshold voltage variations, acting as a mediator that corrects the potential variations without requiring complex circuit modifications to the source follower itself.
2Manufacturing precision
If the offset component is canceled using a source follower circuit, then the variation in output potential among columns is suppressed, but the operation speed is limited
Solution Approach 1:
The offset signal is acquired and stored in advance in the offset signal holding unit before the column driver circuit needs to operate at high speed. This preliminary preparation allows the circuit to switch to high-speed operation mode without being burdened by real-time offset calculation, thus resolving the contradiction between precision and speed.
Solution Approach 2:
The system dynamically switches between different operational modes: during the offset signal acquisition period, the system focuses on precision by storing offset signals; during the image signal output period, the system switches to high-speed operation using the pre-stored offset signals. This dynamic operation allows both precision and speed requirements to be met at different times.
3Productivity
If the display device operates at high speed, then the productivity is improved, but the power consumption increases
Solution Approach 1:
The system uses periodic action by dividing operation into distinct phases: an offset signal acquisition period where the switch is connected to store offset signals, and an image signal output period where high-speed operation occurs. This periodic structure allows the system to achieve high productivity during the output period while keeping power consumption manageable by limiting high-current operation to specific time windows.
Solution Approach 2:
By preliminarily acquiring and storing offset signals before high-speed operation, the system enables high-speed operation without requiring continuous high power consumption for offset management. The pre-stored offset signals allow the circuit to maintain precision during high-speed operation without additional power-intensive compensation mechanisms.
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 configuration effectively suppresses variations among column driver circuits, enabling high-speed operation while reducing power consumption and improving display quality by quickly responding to voltage changes.
Implementation Method 1
an amplifier arranged between the input node and the output node
Implementation Method 2
an offset signal holding unit arranged between the input node and the amplifier and configured to suppress a difference in offset of the amplifier among the plurality of column driver circuits
Implementation Method 3
a current supply unit including a first terminal connected to the input node and a second terminal connected to the output node, and configured to supply a current to the output node based on a voltage at the first terminal and a voltage at the second terminal
Implementation Method 4
a switch arranged between the input node and the first terminal
Data Source
AI summary
A display device including pixels and column drivers configured to supply an image signal to the pixels is provided. The column drivers includes: an input node and an output node; an amplifier arranged between the input node and the output node; an offset signal holding unit arranged between the input node and the amplifier and configured to suppress a difference in offset of the amplifier among the column drivers; a current supply unit including a first terminal connected to the input node and a second terminal connected to the output node and configured to supply a current to the output node based on a voltage at the first terminal and the second terminal; and a switch arranged between the input node and the first terminal. The offset signal holding unit and the switch are connected in parallel to the input node.