Active PFC Converter Window Modulation for Low Power Operation
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Solution Overview
Problem
Active PFC converters experience high standby and no-load power consumption due to continuous switching of semiconductors, even at low loads, leading to increased harmonics and acoustic noise.
Innovation Solution
Implement a method where the PFC converter is continuously clocked at full or partial loads above a specified power value, and operates with a constant duty cycle proportional to power consumption at low loads, reducing peak current and standby consumption by limiting clocking to specific periods within the input voltage half-cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the PFC converter continuously switches semiconductors to maintain power factor correction, then the power factor remains within legal range, but standby and no-load power consumption increases
Solution Approach 1:
The patent applies periodic action by switching the PFC converter on and off in periodic intervals based on the AC input voltage cycle. Instead of continuous switching, the converter operates only during specific portions of the voltage half-cycles, creating a periodic switching pattern that reduces standby power consumption while maintaining power factor correction during active operation.
Solution Approach 2:
The patent implements dynamics by making the switching behavior adaptive to load conditions. The control unit dynamically adjusts the switching strategy based on detected power consumption levels - using continuous clocking at full load, window modulation at partial load, and reduced switching at low load. This dynamic adaptation resolves the contradiction between maintaining correction quality and reducing standby losses.
2Loss of energy
If the PFC converter reduces switching time window at low load to decrease standby losses, then energy efficiency improves, but peak current increases causing acoustic noise
Solution Approach 1:
The patent uses dynamic switching strategies that adapt to load conditions. At low load, it employs window modulation with open-loop width control that dynamically adjusts the switching window based on the AC voltage cycle, reducing peak current and acoustic noise while maintaining energy efficiency. The system transitions between different operating modes (continuous clocking, window modulation, reduced switching) based on real-time load detection.
Solution Approach 2:
The patent changes operating parameters based on load conditions. It modifies the switching frequency, duty cycle, and clocking behavior according to the detected power consumption level. At low load, it uses a constant duty cycle with period proportional to power consumption, and at very low load, it reduces switching to specific periods within the voltage half-cycle, thereby controlling peak current and acoustic noise while maintaining standby efficiency.
3Loss of energy
If the PFC converter operates with window modulation at low load, then standby losses reduce, but harmonics reappear due to high peak current
Solution Approach 1:
The patent implements a dynamic multi-mode operating strategy that transitions between continuous clocking, window modulation, and reduced switching based on load detection. This dynamic approach maintains continuous clocking at full load to prevent harmonics, uses window modulation at partial load to reduce standby losses, and applies reduced switching at very low load with controlled peak current to minimize both harmonics and acoustic noise.
Solution Approach 2:
The patent changes key operating parameters based on load conditions: at full load it uses continuous clocking with PWM control, at partial load it transitions to window modulation with adjusted duty cycle, and at low load it uses reduced switching with constant duty cycle and period proportional to power consumption. These parameter changes resolve the contradiction by adapting the switching behavior to maintain harmonic suppression while reducing standby losses.
Data Source
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AI summary
The method involves operating a PFC converter based on the power consumption of a consumer which is below a predetermined value, when an input current is clocked to an input power only for a period of a half-shaft. The output current is continuously clocked to an output power (Pout), and the PFC converter is controlled when the power consumption is above the predetermined value. The PFC converter is not current controlled when the power consumption is below the predetermined value, and a time period is clocked proportional to the power consumption. An independent claim is included for a device for operating an active PFC converter for converting an AC input voltage into a predetermined DC output voltage supplied to a connected load.