Power Factor Correction Switch On-Time Control for Harmonic Distortion
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Solution Overview
Problem
Real power factor correction circuits experience losses due to parasitic capacitance, leading to distorted current profiles and increased total harmonic distortion, especially at lower input voltage levels.
Innovation Solution
The method involves setting the on-time of the switch in a power factor correction circuit to include two on-time periods, where the first on-time is dependent on the control signal and the second on-time is proportional to the reciprocal of the input voltage, compensating for parasitic effects and reducing harmonic distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the on-time is extended to compensate for parasitic capacitance losses, then the current profile distortion is reduced, but the device complexity increases due to the need for additional control mechanisms
Solution Approach 1:
The patent applies dynamics by making the on-time variable rather than fixed. The on-time is dynamically adjusted based on the instantaneous input voltage value, allowing the system to adapt to changing conditions and compensate for parasitic losses without requiring complex additional hardware. The control mechanism modifies the switching parameters in real-time based on voltage detection.
Solution Approach 2:
The patent changes the parameter of on-time duration based on the instantaneous input voltage. By varying the on-time parameter according to voltage levels (extending it at lower voltages where parasitic losses are more significant), the system compensates for energy losses and maintains a sinusoidal current profile without adding complex circuitry.
2Loss of energy
If the on-time is extended to compensate for losses, then the energy transfer efficiency improves, but the power consumption increases
Solution Approach 1:
The patent applies local quality by extending the on-time only during specific portions of the voltage cycle where parasitic losses are most significant (at lower instantaneous voltage values). Rather than uniformly extending on-time across all operating conditions, the control mechanism selectively adjusts the duty cycle based on the instantaneous voltage, compensating for losses where they occur most while minimizing unnecessary energy consumption during other phases.
Data Source
AI summary
The document describes a method and an actuating circuit for actuating a switch regulating the power consumption in a power factor correction circuit which has input terminals for applying an input voltage and output terminals for providing an output voltage. In this case, the switch is cyclically turned on for an on-time and turned off for an off-time, respectively, with the on-time having a first on-time period and a second on-time period which is directly adjacent to the first on-time period. A length for the first on-time period is in this case dependent on the control signal, and a length for the second on-time period is proportional, at least for a prescribed range of values for an instantaneous value of the input voltage, to a quotient with a first first-degree function for this instantaneous value in the denominator and a second first-degree function for the instantaneous value in the numerator, with function values for the first function increasing as the instantaneous value rises.