Switching Converter EMI Reduction via Auxiliary Switch Node
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Solution Overview
Problem
Conventional buck-type switching converters experience significant ringing at the switch node due to parasitic loops, leading to undesired electromagnetic interference (EMI) that can cause faulty operation or failure in electronic devices.
Innovation Solution
The implementation of an additional auxiliary switch S3, inductor LR, and capacitor CR, along with a modified controller for pulse width modulation (PWM) control, which includes an error and comparator network to minimize switch ringing and EMI by employing zero voltage and zero current switching techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional buck-type switching converters are used, then voltage conversion functionality is achieved, but significant ringing and electromagnetic interference occur due to parasitic loops
Solution Approach 1:
An auxiliary switch node is introduced as an intermediary between the input voltage node and the main switch node. This intermediary node provides an alternative current path that bypasses the parasitic loop formed by the lower switch, thereby reducing electromagnetic interference without fundamentally changing the converter's core structure
Solution Approach 2:
The switching network is segmented into multiple switch nodes (input voltage node, auxiliary switch node, and main switch node) with associated switches. This segmentation allows independent control of current paths, enabling the system to route current through different paths to avoid parasitic loops while maintaining voltage conversion functionality
2Object-affected harmful factors
If additional auxiliary components are added to reduce ringing and EMI, then electromagnetic interference is reduced, but device complexity increases
Solution Approach 1:
The auxiliary switch node and its associated switch are designed to serve multiple functions: providing an alternative current path during switching transitions, absorbing voltage spikes, and reducing ringing. This multi-functionality allows the system to achieve EMI reduction without adding proportionally complex circuitry
3Object-affected harmful factors
If zero voltage and zero current switching techniques are employed, then EMI emissions are reduced, but control complexity increases
Solution Approach 1:
The controller monitors the states of switches and adjusts the timing of auxiliary switch activation based on feedback from the switching network. This feedback mechanism enables precise control of switching transitions to achieve zero voltage and zero current switching, reducing EMI while maintaining manageable control complexity through adaptive timing adjustment
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 effectively reduces switching ringing and EMI emissions, ensuring reliable operation of sensitive electronic devices by minimizing parasitic loop effects and electromagnetic interference.
Implementation Method 1
System and method for active electromagnetic interference reduction for a switching converter
Implementation Method 2
Conventional buck-type switching converters experience significant ringing at the switch node due to parasitic loops
Data Source
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AI summary
An EMI reduction network for a converter, the converter including upper and lower power switches provided between an input voltage node and a reference node. An inductance is coupled between the input voltage node and the upper switch at a first node, a capacitance and an auxiliary power switch are coupled in series between the first and reference nodes, and a controller is provided to control switching. The controller switches the upper switch based on a PWM signal. The controller keeps the lower switch turned on until the phase node goes positive while the upper switch is on. The controller turns the auxiliary switch on after the lower power switch is turned off and turns the auxiliary switch off after the upper power switch is turned off. The lower and auxiliary switches may be zero voltage switched, and the upper switch may be zero current switched.