Level Shifter Dynamic Gate Control for EMI Reduction
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Solution Overview
Problem
The existing level shifters in flat panel display driving circuits face challenges in reducing electromagnetic interference (EMI) and minimizing differences in transition times of output signals due to variations in transistor threshold voltages, which affect charging times and image quality.
Innovation Solution
A level shifter comprising a first transistor to increase output signal voltage, a second transistor to decrease output signal voltage, and drivers to vary gate voltages of these transistors within transition times, controlling the gate-source voltage to reduce on-resistance and slew rate, thereby minimizing EMI and transition time differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the slew rate of the output waveform is reduced to improve EMI, then electromagnetic interference is improved, but the transition time difference between output signals increases due to transistor threshold voltage variations
Solution Approach 1:
The patent dynamically adjusts the gate-source voltage of transistors during the transition period to compensate for threshold voltage variations. By changing the voltage parameter in real-time, the circuit maintains consistent transition times across different transistors while operating at reduced slew rates to minimize EMI.
Solution Approach 2:
The patent implements a feedback mechanism that monitors the transition time of output signals and adjusts the gate voltage accordingly. This feedback loop ensures that transition time differences caused by transistor threshold voltage variations are compensated, maintaining signal consistency while operating at lower slew rates for reduced EMI.
2Object-affected harmful factors
If the slope of the control signal is reduced to lower EMI, then electromagnetic interference is improved, but the charging time consistency of pixels deteriorates
Solution Approach 1:
The patent dynamically modifies the gate-source voltage parameter during the transition period to compensate for the effects of reduced control signal slope. This parameter adjustment ensures that pixels receive consistent charging times even when the control signal has a reduced slope for EMI mitigation.
Solution Approach 2:
The patent uses feedback to monitor pixel charging times and adjusts the gate voltage of output transistors accordingly. This feedback mechanism ensures that all pixels receive consistent charging times despite the reduced control signal slope, maintaining display reliability while reducing EMI.
3Reliability
If the gate-source voltage is varied within transition time to reduce on-resistance, then transistor performance is improved, but the circuit complexity increases
Solution Approach 1:
The patent applies dynamic control to the gate-source voltage of transistors during the transition period. By making the gate voltage time-dependent rather than static, the circuit optimizes transistor on-resistance dynamically, improving performance without requiring complex additional circuitry.
Solution Approach 2:
The patent prepares and applies the varied gate-source voltage signal in advance during the transition period before the main signal transmission. This preliminary action ensures optimal transistor performance is achieved without requiring complex real-time adjustment mechanisms during critical signal transmission phases.
Data Source
AI summary
The present disclosure relates to a level shifter and a display device using the same, and the level shifter includes a first transistor configured to increase a voltage of an output signal, a second transistor configured to lower a voltage of the output signal, a first driver configured to vary a gate voltage of the first transistor in response to a first Vgs signal being varied within a transition time of the output signal, and a second driver configured to vary a gate voltage of the second transistor in response to a second Vgs signal being varied within a transition time of the output signal.