Leakage Reduction Circuit for Power Adapters
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Solution Overview
Problem
Mobile devices experience touch malfunction and user discomfort due to high voltage leakage during AC to DC power conversion, which introduces common mode noise and perceptible electrical current.
Innovation Solution
A leakage reduction circuit using an arrangement of capacitors provides a noise return path in power adapters, reducing high voltage leakage from AC to DC conversion, eliminating perceptible electrical current and improving user experience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If AC to DC power conversion is performed using conventional power supply circuitry, then power conversion functionality is achieved, but high voltage leakage and common mode noise are introduced causing touch malfunction and user discomfort
Solution Approach 1:
A capacitor is introduced as an intermediary component connected between the secondary ground and AC line input. This capacitor provides a return path for common mode noise current, diverting it away from the touch circuitry and preventing both touch malfunction and high voltage leakage to the user.
2Object-affected harmful factors
If a noise return path is created using a capacitor between secondary ground and AC line input, then common mode noise is reduced, but high voltage leakage current increases
Solution Approach 1:
The patent converts the potentially harmful leakage current into a beneficial noise suppression mechanism. By carefully selecting the capacitor value, the leakage current is controlled to provide a low-impedance return path for common mode noise, effectively suppressing EMI while keeping leakage below perceptible levels.
3Object-affected harmful factors
If a three-prong power adapter with ground connection is used, then high voltage leakage is reduced, but device complexity and cost increase
Solution Approach 1:
The patent extracts the ground connection requirement from the physical three-prong plug structure and replaces it with an electrical ground reference created by the capacitor between secondary ground and AC line input. This eliminates the need for a physical ground pin while maintaining the electrical benefits of grounding.
4Object-generated harmful factors
If capacitor value in noise return path is reduced to limit leakage current, then high voltage leakage is reduced, but common mode noise increases causing touchscreen malfunction
Solution Approach 1:
The patent optimizes the capacitor value parameter to achieve a balance between two opposing requirements. The selected capacitance value creates a capacitive reactance that is low enough to provide an effective noise return path but high enough to limit leakage current to non-perceptible levels, resolving the trade-off between noise suppression and leakage reduction.
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
The solution effectively reduces high voltage leakage, eliminating user discomfort and touch malfunction issues, while allowing for a two-prong power adapter design that is economical and suitable for more regions, including Japan and Korea.
Implementation Method 1
Embodiments of the disclosed leakage reduction circuit include an arrangement of capacitors that provides a noise return path (e.g., for common mode noise)
Implementation Method 2
reducing high voltage leakage that may occur from a high voltage AC input to a lower voltage DC output
Data Source
AI summary
A leakage reduction circuit is described herein that is configured to reduce high voltage leakage that may occur in electrical power step-down scenarios. The leakage reduction circuit, for instance, may be employed in a power adapter for a client device, such as a mobile computing device. For example, a power adapter may include a high voltage alternating current (AC) input, and circuitry for converting the AC input into lower voltage direct current (DC) for output to a client device. Implementations of the disclosed leakage reduction circuit include an arrangement of capacitors that provides a noise return path (e.g., for common mode noise) in a power adapter, while reducing high voltage leakage that may occur from a high voltage AC input to a lower voltage DC output of the power adapter.