Display Driver Output Stage With Gate-Source Voltage Limiting
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Solution Overview
Problem
The high-voltage process used in traditional gate drivers for LCDs increases manufacturing costs and risks damage to transistors due to large voltage differences, necessitating a reduction in the number of high-voltage process transistors used.
Innovation Solution
A driving module design that employs transistors with a special process and a voltage generating unit to limit voltage differences between the gate and source, generating appropriate voltages at nodes to prevent transistor damage, thereby reducing the need for high-voltage process components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional high-voltage process transistors are used in the gate driver output stage, then the transistor can withstand large voltage differences, but the manufacturing cost significantly increases
Solution Approach 1:
The patent changes the voltage parameters at the gate and source nodes of the output transistors by introducing a voltage generating unit. This unit dynamically adjusts the voltages VN1 and VN2 to ensure that the voltage differences VGS1 and VGS2 across the transistor gates and sources remain within safe thresholds, allowing standard low-voltage transistors to operate reliably in a high-voltage environment.
Solution Approach 2:
The voltage generating unit acts as an intermediary between the high-voltage power sources (VGH, VGL) and the output transistors (MP1, MN1). It generates intermediate control voltages VN1 and VN2 that mediate the voltage differences, preventing direct exposure of the transistors to damaging voltage spikes while still enabling the generation of large voltage swing output signals.
2Reliability
If traditional high-voltage process transistors are used in the gate driver output stage, then the transistor can withstand large voltage differences, but the device complexity increases
Solution Approach 1:
Instead of using specialized high-voltage transistors, the patent changes the voltage parameters supplied to standard transistors through the voltage generating unit. This approach maintains transistor reliability by controlling voltage differences while avoiding the need for complex high-voltage process components.
Solution Approach 2:
The patent substitutes the mechanical/physical solution of using specialized high-voltage transistors with an electrical control solution. The voltage generating unit uses standard transistors (MP2, MN2, MP3, MN3) and resistors to electrically control and limit voltage differences, replacing the need for physically robust high-voltage components.
3Reliability
If voltage differences across transistors are limited, then transistor damage risk decreases, but the device complexity increases due to additional voltage generating components
Solution Approach 1:
The voltage generating unit performs multiple functions: it generates control voltages VN1 and VN2, limits voltage differences across output transistors, and enables the gate driver to produce large voltage swing output signals. By making these components multi-functional, the patent reduces the need for separate protection circuits, thereby limiting the increase in device complexity.
Solution Approach 2:
The patent merges the voltage control and transistor protection functions into the existing gate driver structure. The voltage generating unit is integrated with the output stage, combining signal generation and voltage protection in a unified circuit design, which minimizes additional complexity compared to separate protection circuits.
Data Source
AI summary
A driving module for a display device includes a first transistor, comprising a gate coupled to a first node, a drain coupled to an output end, and a source coupled to a first positive voltage source; a second transistor, comprising a gate coupled to a second node, a drain coupled to output end, and a source coupled to a first negative voltage source; and a voltage generating unit, coupled to an input end, a second positive voltage source and a second negative voltage source for generating a first voltage at first node and a second voltage at second node according to a control signal from input end; wherein voltage difference between a first positive voltage of first positive voltage source and first voltage is smaller than first threshold and voltage difference between a first negative voltage of first negative voltage source and second voltage is smaller than second threshold.