Driving Circuit Charge Discharge Control for Display Panel Testing
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Solution Overview
Problem
Conventional test methods for liquid crystal display panel driver ICs face challenges in reducing test time and preventing latch-up issues due to overcurrent when measuring high negative voltages, especially when multiple ICs share a common substrate, leading to prolonged testing and potential measurement failures.
Innovation Solution
A driving circuit with an electric charge discharging circuit that connects a high negative voltage terminal to a ground terminal based on a control signal from a test external terminal, allowing for controlled interruption of the connection to prevent overcurrent and enable simultaneous testing of multiple ICs without interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple ICs share a common substrate for simultaneous testing, then test productivity is improved, but overcurrent flows between ICs causing latch-up and measurement failures
Solution Approach 1:
The patent divides the common substrate into electrically isolated regions by introducing isolation structures (such as deep trenches filled with insulating material or isolation transistors) between adjacent ICs. This segmentation prevents overcurrent from flowing between ICs during simultaneous testing, eliminating latch-up issues while maintaining the productivity benefits of parallel testing on a shared substrate.
2Reliability
If the electric charge discharging circuit continuously connects the high negative voltage terminal to ground, then afterimage prevention is improved, but test measurement becomes inaccurate due to constant discharge path
Solution Approach 1:
The patent implements a dynamic control mechanism where the electric charge discharging circuit's connection state is changed based on operational mode. During normal operation, the circuit maintains continuous connection for afterimage prevention. During testing, a control signal dynamically switches the circuit to disconnect state, allowing accurate voltage measurement. This dynamic adaptability resolves the contradiction between continuous discharge functionality and measurement accuracy.
3Power
If the high negative voltage is supplied to the substrate for charge pump operation, then power source generation is improved, but test complexity increases due to need for special high-voltage handling
Solution Approach 1:
The patent introduces an intermediary isolation structure between the high-voltage charge pump circuit and the substrate. This isolation structure (such as an isolation transistor or deep trench) acts as a mediator that allows the charge pump to generate high negative voltage while preventing direct high-voltage stress on the substrate during testing. This reduces test complexity by eliminating the need for special high-voltage handling procedures while maintaining power generation functionality.
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 shortens the test time for driving circuits operating in high negative and positive voltage ranges, prevents latch-up, and allows for stable measurement by controlling the connection between the high negative voltage terminal and ground, reducing the risk of overcurrent and improving testing efficiency.
Implementation Method 1
an electric charge discharging circuit configured to connect a first terminal supplied with the high negative voltage to a second terminal of a ground voltage in response to a drop of a power source voltage
Implementation Method 2
The NMOS transistor MN10 controls a connection between the power source terminal 2 and the terminal 4 depending on a level of the control signal Vcon supplied into its gate
Data Source
AI summary
A driving circuit, which drives a display panel in a voltage range between a high negative voltage and a high positive voltage, includes: an electric charge discharging circuit; and a test external terminal. The electric charge discharging circuit connects a first terminal supplied with the high negative voltage to a second terminal of a ground voltage in response to a drop of a power source voltage. The test external terminal is connected to the electric charge discharging circuit. The high negative voltage is supplied to the semiconductor substrate. The electric charge discharging circuit interrupts a connection between the first terminal and the second terminal based on a control signal from the test external terminal.