Active Choke Circuit for EMI Suppression in Power Converters
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Solution Overview
Problem
Conventional switching power supplies generate significant electromagnetic interference (EMI) due to common mode currents, which are typically suppressed using large and inefficient common mode chokes, leading to power supply efficiency losses and increased physical size.
Innovation Solution
An active choke circuit comprising a three-winding choke and an amplifier, where the choke's inductance is amplified by the amplifier, reducing the physical size and increasing efficiency while maintaining EMI suppression, by using a smaller choke and incorporating a differential amplifier with variable resistors and capacitors to adjust impedance based on monitored signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a common mode choke is used to suppress EMI, then EMI suppression is improved, but power supply efficiency deteriorates and physical size increases
Solution Approach 1:
The patent replaces the passive mechanical/common mode choke with an active electronic circuit consisting of an operational amplifier and impedance network. This active circuit electronically generates the common mode impedance needed for EMI suppression without the physical choke, thereby eliminating the efficiency losses and size penalties associated with traditional common mode chokes.
Solution Approach 2:
The patent changes the impedance parameters dynamically using an operational amplifier circuit that can adjust the effective common mode impedance based on operating conditions. By using variable resistors and capacitors in the impedance network, the circuit adapts its parameters to maintain optimal EMI suppression across different power supply operating points while minimizing power loss.
2Object-affected harmful factors
If a common mode choke is used to suppress EMI, then EMI suppression is improved, but physical size increases
Solution Approach 1:
The patent replaces the physical common mode choke with an active electronic circuit using an operational amplifier and passive components. This substitution eliminates the need for large magnetic cores and windings, reducing the physical footprint from what would be required for a choke providing equivalent EMI suppression to a compact integrated circuit implementation.
Solution Approach 2:
The operational amplifier circuit serves multiple functions: it provides EMI suppression through virtual common mode impedance, enables impedance matching, and can adapt to different operating conditions. This multi-functionality consolidates what would otherwise require separate components into a single integrated active circuit, further reducing overall physical size.
3Volume of moving object
If a smaller choke is used to reduce physical size, then physical size is improved, but EMI suppression deteriorates
Solution Approach 1:
The patent completely replaces the choke-based EMI suppression mechanism with an active electronic system. The operational amplifier, configured with specific feedback impedances, creates a virtual common mode impedance that provides EMI suppression equivalent to or better than a physical choke of the same size, effectively decoupling EMI performance from physical dimensions.
Solution Approach 2:
The patent uses parameter transformation by converting physical inductance requirements into active electronic impedance synthesis. The operational amplifier circuit synthesizes the required common mode impedance through its feedback network, allowing EMI suppression performance to be maintained or improved while using minimal physical components.
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 active choke circuit effectively reduces common mode currents and EMI emissions while minimizing power supply efficiency losses and physical size, achieving comparable EMI suppression with a smaller, more efficient design.
Implementation Method 1
a first three-winding choke; a second three-winding choke; and an amplifier; wherein a first winding of the first three-winding choke is electrically coupled in series with a first winding of the second three-winding choke
Data Source
AI summary
In general, one aspect disclosed features an active choke circuit, including a first three-winding choke; a second three-winding choke; and an amplifier; wherein a first winding of the first three-winding choke is electrically coupled in series with a first winding of the second three-winding choke; wherein a second winding of the first three-winding choke is electrically coupled in series with a second winding of the second three-winding choke; wherein a third winding of the first three-winding choke is electrically coupled to an input of the amplifier; and wherein a third winding of the second three-winding choke is electrically coupled to an output of the amplifier.