PFC Circuit Common Measuring Point for Boost Converter Control
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Solution Overview
Problem
Existing power factor correction circuits for AC/DC converters face challenges in maintaining trouble-free operation under non-normal conditions, such as overcurrent, extreme load changes, or mains voltage drops, due to indirect monitoring of parameters like zero crossing of discharge current and actual DC output voltage.
Innovation Solution
A power factor correction method and circuit that uses a common measuring point connected via resistors to both the inductance and diode, allowing direct or indirect measurement of output voltage and zero crossing of discharge current, enabling the control unit to determine switch-off time and detect overcurrent without additional monitoring pins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a common measuring point with resistors is used to directly measure output voltage and discharge current zero crossing, then measurement precision and reliability under special conditions is improved, but device complexity increases due to additional circuit components
Solution Approach 1:
The common measuring point circuit is designed to perform multiple measurement functions simultaneously: it measures the output voltage level, detects the zero crossing moment of the discharge current, and provides timing information for switch-off events. By using a single measuring point with strategically placed resistors, the circuit achieves multi-functionality without requiring separate monitoring pins for each parameter, thus improving measurement precision while limiting the increase in device complexity.
Solution Approach 2:
Resistors are introduced as intermediary elements in the measuring circuit to enable direct measurement of voltage and current parameters. The resistors convert electrical parameters into measurable voltage signals at the common measuring point, allowing the control unit to accurately detect output voltage levels and discharge current zero crossings without direct access to multiple separate points.
2Device complexity
If indirect monitoring through voltage divider center tap is used, then device complexity is reduced, but reliability under special conditions deteriorates
Solution Approach 1:
The invention extracts the measurement function from the traditional voltage divider center tap configuration and relocates it to a common measuring point that directly monitors the critical parameters. By taking out the measurement function from its conventional location and placing it where it can directly observe output voltage and discharge current zero crossing, the circuit achieves reliable detection under special conditions while maintaining manageable complexity through shared circuit elements.
Solution Approach 2:
The common measuring point establishes a direct feedback path to the control unit, providing real-time information about output voltage levels and discharge current zero crossings. This feedback mechanism enables the control unit to make accurate switching decisions and detect abnormal conditions, significantly improving reliability under special conditions compared to indirect monitoring methods.
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 approach ensures stable operation by directly measuring critical parameters, enhancing the circuit's ability to handle special conditions and maintain sinusoidal current draw, thereby reducing harmonic currents in the supply network.
Implementation Method 1
a DC voltage or rectified input AC voltage feeds an inductance, the inductance repeatedly using a switch clocked by a control unit by closing and opening the same is magnetized and demagnetized
Implementation Method 2
the discharge current of the inductance is fed to an output via a diode
Data Source
AI summary
The invention relates to a method and circuit for correcting a power factor in an alternating current/direct current power transformer. The circuit has an inductor (L) fed by a rectified AC voltage (VIN), and a switch (S) by means of which the inductor (L) can be magnetized and demagnetized by closing and opening the switch, and further comprises a diode (D) by means of which the discharge current of the inductor (L) is fed to the output of the circuit. The following are directly or indirectly measured at a common measurement point (Pinsens) connected to a control unit (PFC): the voltage (Vout) at the output and the point in time at which the zero line of the discharge current of the inductor (L) is reached when the switch (S) is open; as well as the voltage (Vout) at the output and the current (ishunt) flowing through the switch (S) when the switch (S) is closed.