Dual Buck-Boost PFC Circuit Reducing Conduction Losses
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Solution Overview
Problem
Conventional single-phase dual buck-boost/buck power factor correction (PFC) circuits experience higher conduction losses due to the boost diode when operating in buck mode, which affects efficiency and total harmonic distortion (THD) in three-phase systems.
Innovation Solution
The implementation of a dual buck-boost/buck PFC circuit topology with three independent single-phase circuits, each comprising a buck-boost and a buck circuit, connected through a neutral line, allowing for independent operation and reduced conduction losses by controlling the input current in boost and buck modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional single-phase dual buck-boost/buck PFC circuit operates in buck mode, then the circuit can handle input voltage higher than output voltage, but the boost diode experiences higher conduction losses
Solution Approach 1:
The circuit is divided into two separate PFC circuits: a buck-boost PFC circuit and a buck PFC circuit. Each circuit handles specific voltage ranges independently, allowing the system to adapt to wide voltage fluctuations while minimizing conduction losses by selecting the appropriate circuit for each operating condition
Solution Approach 2:
The invention changes the operating parameters by switching between two different PFC circuit configurations based on the input-output voltage relationship. When input voltage exceeds output voltage, the buck PFC circuit is activated; otherwise, the buck-boost PFC circuit operates, optimizing efficiency across different voltage conditions
2Reliability
If a single-phase three-level buck-boost PFC circuit is used, then the input current can track the input voltage with low THD, but the circuit complexity increases
Solution Approach 1:
The three-level PFC circuit is segmented into two independent single-phase PFC circuits (buck-boost and buck), each with simpler control characteristics. This segmentation maintains good current tracking performance while reducing the complexity of control strategies compared to a unified three-level buck-boost circuit
3Reliability
If three independent single-phase PFC circuits are used in a three-phase system, then each phase can be controlled independently for reduced THD, but the device complexity increases
Solution Approach 1:
The three-phase system is segmented into three independent single-phase dual PFC circuits, allowing each phase to be controlled independently for optimal THD performance. The modular structure enables separate control strategies for each phase while maintaining overall system coordination
Solution Approach 2:
Each single-phase dual PFC circuit module serves multiple functions: it handles both buck and buck-boost operations, provides independent phase control, and can operate autonomously. This multi-functionality reduces the need for additional components and control mechanisms in the three-phase system
Data Source
AI summary
The configurations of a single-phase dual buck-boost/buck power factor correction (PFC) circuit and a controlling method thereof are provided in the present invention. The proposed circuit includes a single-phase three-level buck-boost PFC circuit receiving an input voltage and having a first output terminal, a neutral-point and a second output terminal for outputting a first and a second output voltages, a single-phase three-level buck PFC circuit receiving the input voltage and coupled to the first output terminal, the neutral-point and the second output terminal, a first output capacitor coupled to the first output terminal and the neutral-point, a second output capacitor coupled to the neutral-point and the second output terminal, and a neutral line coupled to the neutral-point.