PFC Current Sensing With Magnetic Coupling for Low-Loss Control
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Solution Overview
Problem
Power supply systems face challenges in achieving high power factor and reducing harmonic distortion in AC input current, leading to inefficiencies and power losses, particularly due to the phase difference between AC input voltage and current, and significant power loss in current measurement operations.
Innovation Solution
The implementation of a power factor correction (PFC) circuit with a controller that includes a ramp generation circuit, comparator, and PWM generation circuit, which adjusts the switching cycle of a switch in the PFC circuit based on voltage and current measurements to minimize phase difference and harmonic distortion, using magnetic coupling for current measurement to reduce power loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional current measurement methods are used in PFC circuits, then current sensing can be achieved, but significant power loss occurs during measurement operations
Solution Approach 1:
The patent replaces traditional resistive current sensing with magnetic field-based sensing using a current transformer. The current transformer couples magnetically to the switch current terminal and provides an isolated measurement signal, eliminating the need for direct electrical contact and reducing power loss while maintaining measurement precision through magnetic coupling.
2Device complexity
If phase difference between AC input voltage and current is not corrected, then system complexity is reduced, but power factor deteriorates and harmonic distortion increases
Solution Approach 1:
The patent implements a feedback control mechanism where the controller receives voltage and current measurement signals, compares them to detect phase difference and harmonic content, and adjusts the switch timing accordingly. This closed-loop feedback enables power factor correction and harmonic reduction while maintaining manageable system complexity through integrated control.
3Loss of energy
If switching frequency is increased to improve power transfer efficiency, then power loss is reduced, but electromagnetic interference and switching losses increase
Solution Approach 1:
The patent employs periodic switching of the PFC circuit switch at an optimized frequency that balances power transfer efficiency with electromagnetic interference management. The controller generates periodic gate drive signals that switch the PFC switch in sync with the AC input waveform, achieving efficient power transfer while limiting EMI through controlled periodic operation rather than high-frequency switching.
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 improves the power factor and reduces harmonic distortion in AC input current, enhancing the efficiency of power transfer and minimizing power loss in the power supply system.
Implementation Method 1
The current measurement circuit is magnetically coupled to the current terminal and having a current measurement output
Data Source
AI summary
In some examples, an apparatus includes: a ramp generation circuit having a ramp control input and a ramp output, the ramp control input coupled to a power factor correction (PFC) output terminal; a comparator having a comparator output and first and second comparator inputs, the first comparator input coupled to the ramp output, the second comparator input coupled to a PFC switch current sensing terminal; and a pulse width modulation (PWM) generation circuit having a PWM control input and a PWM output, the PWM control input coupled to the comparator output, and the PWM output coupled to a PFC switch control terminal.