LCD Source Driver AMP Output Protection for Charge Sharing
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Solution Overview
Problem
The existing AMP output stage circuits for LCD panel source drivers face issues where the diodes within the PMOS/NMOS amplifiers can be turned on if the output voltage exceeds or falls below HVDD, leading to increased die area and power consumption due to the need for additional body bias control and protective diodes.
Innovation Solution
An AMP output protective circuit is introduced, utilizing a first and second amplifier biased by different power sources, input and output switching units, and Schottky barrier diodes to equalize input and output voltages to HVDD, eliminating the need for a body bias control circuit and enhancing protection during charge sharing intervals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protective diodes are added to prevent AMP output voltage from exceeding HVDD, then circuit protection is improved, but die area increases
Solution Approach 1:
The patent introduces switching units as intermediary components that control the connection between the AMP output and the protective diodes. These switches act as mediators that selectively enable or disable the protective diodes based on operational conditions, allowing protection functionality to be activated only when needed rather than being permanently present, thus reducing the effective die area usage.
Solution Approach 2:
The protective circuit transitions from a static configuration to a dynamic one where switching units change the circuit topology based on voltage conditions. The switches dynamically connect or disconnect the protective diodes from the AMP output, allowing the circuit to adapt its protection mechanism only when voltage excursions occur, thereby optimizing die area utilization.
2Reliability
If body bias control circuit is added to handle threshold voltage issues, then amplifier performance is improved, but die area increases
Solution Approach 1:
The switching units serve as intermediary components that manage the body bias control circuit's activation. Instead of having the body bias control circuit continuously active, the switches mediate its engagement only when threshold voltage issues are detected, reducing the operational burden and effective area requirement of the body bias control circuit.
Solution Approach 2:
The body bias control circuit operates periodically rather than continuously, activated by switching units when specific voltage conditions are met. This periodic activation reduces the average power consumption and effective area utilization of the body bias control circuit while maintaining amplifier performance when needed.
3Reliability
If protective diode size is increased to ensure adequate protection, then circuit protection is improved, but die area increases
Solution Approach 1:
The protective diodes transition from being permanently connected to being dynamically connected through switching units. The switches enable or disable the protective diodes based on real-time voltage monitoring, allowing smaller diodes to provide adequate protection only when voltage excursions occur, rather than requiring oversized diodes for continuous protection.
Solution Approach 2:
The circuit changes the operational parameters of the protective diodes by controlling their connection state through switching units. When voltage excursions are detected, the switches change the diode's connection parameter from disconnected to connected, enabling protection only when necessary and allowing the use of smaller diode structures.
4Reliability
If additional switching units are added to control AMP protection, then circuit protection is improved, but device complexity increases
Solution Approach 1:
The switching units are designed with multi-functionality, serving both as protection control elements and as signal routing components. Each switching unit can simultaneously manage protective diode connection, body bias control activation, and output signal routing, reducing the need for separate dedicated components and thereby limiting the increase in device complexity.
Solution Approach 2:
The patent merges multiple control functions into unified switching units that handle both protection mechanisms and signal routing. By combining what could be separate control circuits into integrated switching elements, the overall device complexity is minimized while maintaining comprehensive AMP protection 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 reduces die area and power consumption, prevents diode turn-on issues, and provides safer protection for the AMP circuit by using Schottky barrier diodes with lower turn-on voltages than internal PMOS/NMOS diodes, ensuring circuit speed is maintained.
Implementation Method 1
Schottky barrier diodes with lower turn-on voltages than internal PMOS/NMOS diodes
Data Source
AI summary
An AMP output protective circuit for an LCD panel source driver is disclosed. To solve a problem that internal diodes of PMOS/NMOS of an AMP output circuit are turned on, embodiments are characterized in making input and output voltages of the AMP in a charge sharing interval equal to HVDD and short-circuiting outputs of PAMP and NAMP with VRST_GH and VRST_GL lines, respectively. Accordingly, since there is no increase of voltage (Vth) attributed to a body effect, a speed is not reduced. An additional body bias control circuit is unnecessary. Power consumption can be reduced. Also, an AMP circuit can be more safely protected by adding an output reset function and an AMP protecting circuit.