Power Factor Correction Circuit Single Pin Switch-Off Time Calculation
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Solution Overview
Problem
Existing power factor correction circuits require multiple monitoring pins and complex voltage measurement systems to determine switch-off times, which can lead to errors and inefficiencies in harmonics reduction.
Innovation Solution
A method and circuit that utilize a single monitoring pin to measure output voltage and switch current thresholds, allowing for the calculation of switch-off times using a control unit, thereby simplifying the measurement process and reducing the need for multiple pins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple monitoring pins and complex voltage measurement systems are used to determine switch-off times, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple measurement functions (output voltage monitoring and switch current threshold detection) into a single monitoring pin. The control unit integrates the processing of multiple parameters (output voltage, switch current, switch-on time) to calculate switch-off time, replacing the need for separate monitoring pins and measurement circuits.
Solution Approach 2:
The single monitoring pin serves multiple functions: it monitors output voltage when the switch is open and detects switch current threshold when the switch is closed. The control unit universally processes these different signals and performs calculations to determine switch-off times, making the monitoring system multi-functional rather than requiring dedicated pins for each measurement.
2Device complexity
If a single monitoring pin is used to measure multiple parameters, then device complexity is reduced, but measurement precision may deteriorate
Solution Approach 1:
The control unit acts as an intermediary that processes the single monitoring pin's signals. It distinguishes between different measurement modes (voltage monitoring when switch is open, current threshold detection when switch is closed) and performs calculations based on the appropriate parameters, ensuring precise switch-off time determination despite using a single pin.
Solution Approach 2:
The control unit stores the switch-on time and output voltage in advance, and has predetermined current thresholds programmed. When the switch-off moment arrives, it quickly calculates the switch-off time using these pre-prepared data and the current monitoring pin reading, ensuring accurate timing without requiring complex real-time measurement systems.
Data Source
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AI summary
The invention relates to a method and a circuit for correcting a power factor in an alternating current / direct current power transformer. The circuit has an inductance (L) fed by a rectified AC voltage (VIN), and a switch (FET) by means of which the inductance (L) can be charged and discharged by closing and opening the switch, and further comprises a diode (D) by means of which the discharge current of the inductance (L) is fed to the output of the circuit. At a measurement point connected in common to a control unit (PFC), the following are measured directly or indirectly: - a voltage corresponding to the output voltage (VBUS) of the transformer when the switch (FET) is open, and a voltage corresponding to the current (IFET) through the switch (FET) when the switch is closed, wherein the elapsed time (TON) is measured from the point of time of closing the switch (FET) until the switch current reaches a prescribed threshold value (IT). The switch-off time (TOFF) for the switch (FET) is finally determined numerically by evaluating the threshold value (IT), the output voltage (VBUS), and the switch-on time (TON).