Power Factor Correction Circuit Using Voltage Derivative Control
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Solution Overview
Problem
Power factor correction circuits face challenges in effectively suppressing harmonics and reducing current peaks when input voltage rises, especially without modifying capacitances in the input region.
Innovation Solution
A power factor correction circuit that adjusts the switching time based on the sign of the input voltage's time derivative, extending the Ton time by different additional intervals depending on whether the input voltage is increasing or decreasing, thereby controlling current consumption and reducing current peaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional power factor correction circuits are used with fixed switching time, then the circuit structure remains simple, but current peaks occur when input voltage rises and harmonics are not effectively suppressed
Solution Approach 1:
The patent applies dynamics by making the switching time (Ton) variable instead of fixed. The control device adjusts Ton based on the time derivative of the input voltage, allowing the circuit to adapt its switching behavior dynamically to changing voltage conditions, thereby suppressing current peaks and harmonics effectively.
Solution Approach 2:
The patent implements feedback by using the time derivative of the input voltage as a control signal. The control device continuously monitors the input voltage, calculates its time derivative, and uses this information to adjust the switching time, creating a closed-loop control system that actively suppresses harmful current characteristics.
2Object-generated harmful factors
If input capacitances are increased to reduce current peaks, then current peak amplitude decreases, but the circuit complexity and component changes increase
Solution Approach 1:
The patent applies parameter changes by modifying the switching time parameter (Ton) based on the time derivative of the input voltage. Instead of changing physical component values like capacitances, the patent changes the operational parameter (switching duration) to achieve current peak suppression, avoiding additional components and circuit modifications.
Solution Approach 2:
The patent substitutes the mechanical approach of increasing capacitance values with an electronic control approach. Rather than physically modifying the input circuit with larger capacitors, the patent uses electronic switching control based on voltage derivative detection to achieve the same current peak suppression effect.
3Object-generated harmful factors
If the switching time is extended uniformly to reduce harmonics, then harmonic suppression improves, but the response to changing voltage conditions deteriorates
Solution Approach 1:
The patent makes the switching time dynamic by basing it on the time derivative of the input voltage. This allows the circuit to automatically adapt its switching behavior to changing voltage conditions, achieving both harmonic suppression and good adaptability to voltage variations without uniform extension.
Solution Approach 2:
The patent applies preliminary anti-action by detecting the time derivative of the input voltage in advance and using this information to preemptively adjust the switching time. This allows the control device to counteract upcoming current peaks and harmonic generation before they occur, improving both suppression effectiveness and adaptability.
Data Source
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Figure 3~4
AI summary
A power factor correction circuit (11) comprises an input for receiving an input voltage (UIN), an inductance (21) coupled to the input, a switching means (24) that is coupled to the inductance (21) and that is controllable in order to either charge or discharge the inductance (21), and a control device (14). The control device (14) is set up in order to produce a control signal (Ctrl) for controlling the switching means (24) on the basis of a parameter value. The control device (14) is set up in order to ascertain the parameter value on the basis of an arithmetic sign of a time derivation for the input voltage (UIN).