Display Level Shifter With Overlapping Control to Cut EMI
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Solution Overview
Problem
Existing level shifters in display devices suffer from electromagnetic interference (EMI) due to harmonics and peak currents generated during rapid voltage changes, leading to increased power consumption and chip size, and existing EMI reduction methods are inadequate.
Innovation Solution
A level shifter design that utilizes multiple power input terminals and control signals with overlapping on-intervals to manage current flow, reducing EMI by minimizing dead time and controlling slew rates at voltage transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an EMI filter is added to the output stage of the level shifter, then EMI is reduced, but power consumption increases and chip size increases
Solution Approach 1:
The patent extracts the EMI filtering function from a separate physical EMI filter component and implements it within the level shifter circuit itself using the third switch element and third power input terminal. This integration eliminates the need for external EMI filter components, reducing chip size while maintaining EMI reduction effectiveness.
Solution Approach 2:
The level shifter circuit is designed to perform multiple functions: voltage level shifting, EMI reduction, and power management. The third switch element and third power input terminal serve dual purposes of controlling the output signal and filtering EMI, while also enabling the circuit to operate in different modes (high-speed mode and EMI-reduced mode) depending on the control signals applied.
2Object-affected harmful factors
If an EMI filter is added to the output stage of the level shifter, then EMI is reduced, but chip size increases
Solution Approach 1:
The patent merges the EMI filtering function with the level shifter circuit by integrating the third switch element and third power input terminal directly into the existing circuit architecture. This combination eliminates the need for separate EMI filter components, thereby reducing overall chip size while maintaining EMI reduction capabilities.
Solution Approach 2:
The level shifter circuit is designed to perform multiple functions: voltage level shifting, EMI reduction, and power management. The third switch element and third power input terminal serve dual purposes of controlling the output signal and filtering EMI, while also enabling the circuit to operate in different modes (high-speed mode and EMI-reduced mode) depending on the control signals applied.
3Object-affected harmful factors
If dead time is reduced between switch element on/off timings, then EMI reduction effect is improved, but control complexity increases
Solution Approach 1:
The patent applies different control strategies to different switch elements based on their specific functions. The first and second switch elements operate with traditional non-overlapping control for basic level shifting, while the third switch element uses overlapping control intervals specifically targeted at EMI reduction. This localized approach to control complexity allows EMI reduction without requiring complete redesign of the entire control system.
Solution Approach 2:
The control signals for the switch elements are designed with dynamic timing characteristics where the on-intervals of control signals overlap. This dynamic timing approach allows the circuit to naturally reduce EMI through controlled current flow during overlapping periods, eliminating the need for complex dead-time management while maintaining EMI reduction effectiveness.
4Object-affected harmful factors
If control signals have overlapping on-intervals, then slew rate is reduced and EMI is minimized, but circuit operation complexity increases
Solution Approach 1:
The patent applies different control strategies to different switch elements based on their specific functions. The first and second switch elements operate with traditional non-overlapping control for basic level shifting, while the third switch element uses overlapping control intervals specifically targeted at EMI reduction. This localized approach to control complexity allows EMI reduction without requiring complete redesign of the entire control system.
Solution Approach 2:
The control signals for the switch elements are designed with dynamic timing characteristics where the on-intervals of control signals overlap. This dynamic timing approach allows the circuit to naturally reduce EMI through controlled current flow during overlapping periods, eliminating the need for complex dead-time management while maintaining EMI reduction effectiveness.
Data Source
AI summary
A level shifter includes a first power input terminal to which a first gate voltage may be applied; a second power input terminal to which a second gate voltage may be applied; a third power input terminal to which a third gate voltage may be applied; an output terminal; a first switch element configured to electrically connect the first power input terminal to the output terminal in response to a voltage of on-intervals of a first control signal; a second switch element configured to electrically connect the second power input terminal to the output terminal in response to a voltage of on-intervals of a second control signal; and a third switch element configured to electrically connect the third power input terminal to the output terminal in response to a voltage of on-intervals of a third control signal.