LED Ghost Image Removal via Parasitic Capacitance Discharge
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Solution Overview
Problem
Multiplexed LED arrays suffer from ghost images due to parasitic capacitances, which existing systems attempt to address with additional dedicated circuitry for resistive discharge, but this is inefficient and requires dead time for discharge.
Innovation Solution
The proposed solution involves a timing sequence for switching operations of power and current switches to discharge parasitic capacitances without additional circuitry, ensuring that LEDs are properly switched on and off to prevent ghost images, using a controller to manage the switching sequence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional dedicated circuitry is used to provide resistive discharge path, then ghost images are prevented, but device complexity increases
Solution Approach 1:
The patent merges the ghost image prevention function into the existing multiplexed LED circuit structure by utilizing the anode and cathode connections that already exist for LED control. The resistive discharge paths are formed by combining existing circuit elements (anodes, cathodes, and resistors) rather than adding dedicated discharge circuitry, thus preventing ghost images without increasing device complexity
Solution Approach 2:
The anodes and cathodes in the multiplexed LED circuit serve multiple functions: they control LED illumination during active periods and simultaneously provide resistive discharge paths during inactive periods. This multi-functionality eliminates the need for separate dedicated discharge circuitry while maintaining ghost image prevention
2Reliability
If resistive discharge path is implemented, then parasitic capacitance is discharged, but dead time is required reducing productivity
Solution Approach 1:
The patent ensures continuous discharge of parasitic capacitance by maintaining resistive discharge paths through the anodes and cathodes during the entire off-period between LED activations. This continuous action eliminates the need for dedicated dead time intervals, allowing the system to transition smoothly between states without reducing productivity
Solution Approach 2:
The resistive discharge paths are established in advance through the existing anode and cathode connections before the LED switching transitions occur. This preliminary configuration of discharge paths ensures that parasitic capacitance is continuously discharged without requiring additional dead time, maintaining operational efficiency
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 approach effectively eliminates ghost images without the need for extra components, reducing dead time and enhancing the operational efficiency of multiplexed LED arrays.
Implementation Method 1
the first current switch is arranged to discharge the one or more parasitic capacitances when the first current switch is in the on state
Data Source
AI summary
A light emitting diode (LED) circuit for preventing parasitic current flow through a first LED when the first LED is in an off state is described, where the parasitic current flow is a result of one or more parasitic capacitances, the LED circuit comprising the first LED, and a first current switch coupled to the first LED and arranged to enable a current flow through the first LED when the first current switch is in an on state, where the first current switch is arranged to discharge the one or more parasitic capacitances when the first current switch is in the on state.