Quasi-Resonant PFC Circuit Controller for Switching Loss Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Modern switched mode power supplies face challenges in maintaining a high power factor and minimizing switching losses and electromagnetic interferences due to varying input voltages and loads, which can result in undesirably high switching frequencies.
Innovation Solution
A power factor correction circuit that includes a first inductor and a semiconductor switch, controlled by a controller circuit which monitors feedback signals to switch on at the N-th local minimum and adjusts the on-time, maintaining the switching frequency within a defined range by using a quasi-resonant switching scheme.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the switching frequency is increased to handle wide input voltage and load ranges, then the power factor correction capability is improved, but switching losses and electromagnetic interferences increase
Solution Approach 1:
The patent implements dynamic switching frequency adjustment by detecting the resonant frequency of the circuit and adapting the switching frequency accordingly. The controller dynamically modifies the switching frequency based on real-time circuit conditions, allowing the system to maintain high power factor correction capability while operating at lower switching frequencies to reduce switching losses and electromagnetic interferences.
2Reliability
If the switching frequency is increased to maintain performance under varying loads, then the power factor is maintained, but electromagnetic interferences increase
Solution Approach 1:
The system dynamically adjusts the switching frequency to track the resonant frequency of the circuit, enabling reliable power factor maintenance across varying load conditions while minimizing electromagnetic interferences by operating at lower, resonance-aligned frequencies rather than high fixed frequencies.
Solution Approach 2:
The patent employs feedback mechanisms where the controller continuously monitors circuit parameters and adjusts the switching frequency based on detected resonant conditions. This feedback loop ensures that the power factor is maintained reliably while the switching frequency is optimized to reduce electromagnetic interferences.
3Loss of energy
If the switching frequency is reduced to minimize losses, then switching losses are decreased, but the ability to handle varying input voltages and loads is compromised
Solution Approach 1:
The patent resolves this contradiction by implementing dynamic switching frequency adjustment that allows the system to operate at lower frequencies to minimize switching losses while simultaneously adapting to varying input voltages and load conditions through real-time resonant frequency detection and tracking.
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 low switching losses and electromagnetic interferences while maintaining a high power factor, even with varying input voltages and loads, by keeping the switching frequency within a narrower range, thus enhancing efficiency and reducing electromagnetic interferences.
Implementation Method 1
The controller circuit is configured to monitor a feedback signal representing the voltage drop across the load current path of the semiconductor switch, to detect at least one local minimum in the feedback signal while the semi-conductor switch is off
Implementation Method 2
The PFC circuit further includes a semiconductor switch that has a load current path coupled in series to the first inductor. An output terminal is coupled to the inductor and operably providing an output voltage and an output current
Data Source
AI summary
A power factor correction (PFC) circuit includes a first inductor, which is operably supplied with an input voltage and an input current. The input voltage is a rectified AC line voltage. A semiconductor switch has a load current path coupled in series with the first inductor. An output terminal is coupled to the inductor and operably providing an output voltage and an output current. A controller circuit controls the cyclic switching operation of the semiconductor switch. The controller circuit is configured to monitor a feedback signal representing the voltage drop across the load current path of the semiconductor switch, to detect at least one local minimum in the feedback signal while the semiconductor switch is off, and to switch on the semiconductor switch in response to detecting the N-th local minimum in the feedback signal.