DC-Side Power Supply Filtering for Switching Noise Suppression
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Solution Overview
Problem
Existing power supply apparatuses with power switching circuitry face challenges in efficiently suppressing switching noise, leading to electromagnetic interference (EMI) and heat dissipation issues due to lossy resistive elements used in typical EMI suppression devices.
Innovation Solution
The power supply apparatus configures an electrical filter downstream of the power conversion portion, utilizing an inductive element to block switching noises. This configuration operates the electrical filter in a DC mode, reducing power loss and allowing for a more compact design while effectively suppressing noise closer to the source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If typical EMI suppression devices with lossy resistive elements are used, then electromagnetic interference is suppressed, but power loss increases and heat dissipation becomes a problem
Solution Approach 1:
The patent changes the operating parameter of the electrical filter from AC mode to DC mode by positioning it downstream of the power conversion portion. This parameter change reduces the RMS current through the filter, thereby reducing resistive power loss while maintaining noise suppression effectiveness.
Solution Approach 2:
The patent extracts the electrical filter from the AC input stage and relocates it to the DC output stage of the power conversion circuit. This separation allows the filter to operate in DC mode with reduced current, minimizing power loss while still suppressing switching noise at its source.
2Object-affected harmful factors
If the electrical filter is configured upstream of the power conversion portion, then noise suppression is provided, but power loss increases due to AC mode operation
Solution Approach 1:
Instead of placing the electrical filter at the conventional upstream AC input position, the patent inverts the arrangement by positioning the filter downstream at the DC output position. This inversion allows the filter to operate in DC mode rather than AC mode, significantly reducing power loss while maintaining noise suppression capability.
3Loss of energy
If a larger common-mode choke is used to reduce resistive loss, then power loss decreases, but the apparatus becomes bulkier
Solution Approach 1:
The patent changes the operating mode parameter from AC to DC, which reduces the RMS current through the electrical filter. This parameter change reduces resistive power loss without requiring a larger common-mode choke, thereby avoiding increased apparatus size.
4Object-affected harmful factors
If the electrical filter is positioned upstream, then noise suppression is provided, but noise leakage back to the input port occurs
Solution Approach 1:
The patent positions the electrical filter downstream of the power conversion portion, which is closer to the noise source. This preliminary positioning allows the filter to suppress switching noise at its origin before it can propagate and cause interference elsewhere in the circuit, including back to the input port.
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 configuration achieves a high power factor, minimizes power loss, and reduces the risk of noise leakage, thereby enhancing the efficiency and compactness of the power supply apparatus while effectively suppressing switching noise.
Implementation Method 1
An electrical filter typically comprises an inductive element which is configured to block switching noises
Data Source
AI summary
A power supply apparatus comprising a power input portion, a rectifying portion, a power conversion portion, a power output portion and an electrical filter is disclosed. The electrical filter is connected intermediate the rectifying portion and the power output portion for reduction of switching noise generated during power switching operations of the power switching circuitry. With such an arrangement, the electrical filter operates in the DC portion of the apparatus and power loss is significantly reduced while switching noise is suppressed nearer the source compared to conventional arrangement. In addition, switching noises due to stray or parasitic capacitance to the metal casing when the power supply is enclosed in a metallic casing to form a power supply module are also mitigated nearer the source.