Bridgeless Boost PFC Circuit Common Mode EMI Reduction
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Solution Overview
Problem
Conventional bridgeless boost power factor correction (PFC) systems generate significant common mode electromagnetic interference (EMI), which can disrupt electronic devices and degrade power system performance.
Innovation Solution
The system incorporates a common mode choke and X capacitors between input and output lines, presenting high impedance to boost chokes and bypassing input lines with low impedance to reduce high-frequency potential differences, thereby minimizing common mode conducted EMI. Additionally, the use of a low-loss transformer ferrite and cost-effective materials reduces core loss and space requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional bridgeless boost PFC system is used, then power factor correction is achieved, but common mode EMI is generated which disrupts electronic devices
Solution Approach 1:
A common mode choke is introduced as an intermediary component between the input AC lines and the boost chokes. This choke presents high impedance to common mode noise currents, blocking their propagation while allowing differential mode power current to pass through unaffected, thus reducing common mode EMI without compromising PFC performance
Solution Approach 2:
The harmful common mode EMI is extracted and isolated from the main power circuit by routing it through the common mode choke, which separates the noise current path from the useful power transmission path, effectively removing the harmful effect while preserving the beneficial PFC function
2Object-generated harmful factors
If high impedance is presented to boost chokes to reduce EMI, then common mode conducted EMI is minimized, but voltage boosting operations must be maintained
Solution Approach 1:
The common mode choke provides high impedance locally at common mode noise frequencies while maintaining low impedance for differential mode power current. This frequency-selective impedance characteristic allows the choke to block EMI without interfering with the voltage boosting operation that requires low impedance power transmission
Solution Approach 2:
The common mode choke dynamically adapts its impedance based on the current type: it presents high impedance to common mode noise currents to block EMI, while presenting low impedance to differential mode power current to allow voltage boosting operations to proceed normally
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 results in a compact, efficient, and cost-effective PFC system with significantly reduced common mode conducted EMI, allowing for effective power factor correction without disrupting voltage boosting operations.
Implementation Method 1
A common mode choke is coupled between the first and second input and the first and second boost choke
Implementation Method 2
A first X capacitor is coupled between the first input and the output and a second X capacitor coupled between the second input and the output
Implementation Method 3
a first boost choke coupled to the first input and a second boost choke coupled to the second input
Data Source
AI summary
According to one example embodiment, a bridgeless boost power factor correction (PFC) system includes a first input for connection to a first line of an alternating current (AC) source and a second input for connection to a second line of the AC source. The PFC system includes an output for delivering an output of the bridgeless boost PFC system, a first boost choke coupled to the first input and a second boost choke coupled to the second input. A common mode choke is coupled between the first and second input and the first and second boost choke. A first X capacitor is coupled between the first input and the output and a second X capacitor coupled between the second input and the output.