Leakage Current Suppression Circuit for AC-DC Power Supplies
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Solution Overview
Problem
Conventional AC-to-DC power supplies face challenges in suppressing leakage current while effectively managing electromagnetic interference (EMI), as increased capacitance for EMI suppression leads to higher leakage currents, failing to meet regulatory standards.
Innovation Solution
A leakage current suppression circuit is introduced, comprising first and second impedance units connected between the capacitor and input/output ends of the power supply, allowing for the effective splitting and attenuation of leakage currents through carefully determined impedance ratios, thereby reducing the measured leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the capacitance of the Y-type capacitor is increased to suppress electromagnetic interference, then the EMI suppression effect is improved, but the leakage current increases and fails to meet regulatory standards
Solution Approach 1:
The patent divides the single capacitor into multiple capacitors (first capacitor between P5 and P3, second capacitor between P5 and P7, third capacitor between P4 and P3, fourth capacitor between P4 and P6). This segmentation allows the total capacitance to be distributed across multiple paths, reducing the leakage current through each individual capacitor while maintaining the overall EMI suppression capability. The leakage current is thus segmented and reduced without sacrificing EMI protection.
2Object-affected harmful factors
If the capacitance of the Y-type capacitor is increased, then the electromagnetic interference suppression is enhanced, but the device complexity increases due to additional components and circuit configuration
Solution Approach 1:
The patent makes the capacitor network serve multiple functions simultaneously: EMI suppression through capacitive coupling, leakage current reduction through distributed capacitance paths, and grounding reference establishment. By designing the capacitor network to fulfill multiple roles, the patent avoids adding separate components for each function, thereby managing device complexity while achieving enhanced EMI suppression.
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 significantly suppresses leakage currents, allowing for increased capacitance flexibility to meet EMI suppression requirements, achieving up to 95% reduction in measured leakage current while maintaining compliance with regulatory standards.
Implementation Method 1
a capacitor having two terminals, one of which is coupled to the second output terminal of the bridge rectifier
Implementation Method 2
a first impedance unit to be coupled between the other of the terminals of the capacitor and the third end of the input unit; and a second impedance unit to be coupled between the other of the terminals of the capacitor and the second output end of the DC-to-DC converter
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A leakage current suppression circuit (5) is for use with an AC-to-DC power supply (10) that includes a bridge rectifier 2 converting an AC input voltage into a DC voltage and outputting the DC voltage through a first output terminal (P4) and a grounded second output terminal (P5) thereof, a DC-to-DC converter 3 converting the DC voltage into a DC output voltage and outputting the DC output voltage, and a capacitor (Cy) coupled to the second output terminal (P5) of the bridge rectifier 2. The leakage current suppression circuit (5) includes a first impedance unit (51) and a second impedance unit (52) each coupled in parallel between the other terminal of the capacitor (Cy) and ground.