Three-Phase Vienna PFC Circuit Alternating Capacitor Charging
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Solution Overview
Problem
Three-phase Vienna PFC circuits suffer from capacitor ripples, which existing technologies have been unable to effectively reduce, affecting the performance of components in UPS systems.
Innovation Solution
A circuit with four bridge arm units and two capacitors, where each bridge arm unit includes diodes, an inductor, and a switching transistor, configured to alternately charge capacitors, thereby improving switching frequency and reducing magnetic and filtering parameters, and switching ripples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a three-phase Vienna PFC circuit uses conventional single-capacitor configuration, then the circuit structure is simple, but capacitor ripples are large affecting component performance
Solution Approach 1:
The patent divides the single capacitor into two separate capacitors (C1 and C2) connected to different bridge arm units. Each capacitor handles ripple current independently, segmenting the harmful ripple effect and preventing it from affecting the entire circuit. This segmentation reduces capacitor ripples while maintaining a relatively simple circuit structure.
Solution Approach 2:
The patent combines multiple bridge arm units (first, second, third, and fourth bridge arm units) working in parallel with alternating charging cycles. By merging the functionality of multiple bridge arms to charge capacitors alternately, the system reduces the ripple current burden on each individual capacitor while maintaining overall circuit performance.
2Object-generated harmful factors
If the circuit uses four bridge arm units with alternating capacitor charging, then capacitor ripples are reduced, but the device complexity increases
Solution Approach 1:
The patent implements periodic action by having the four bridge arm units charge the two capacitors in alternating cycles. Each bridge arm unit operates periodically, with Q1 and Q3 charging C1 while Q2 and Q4 charge C2, and vice versa in subsequent cycles. This periodic operation reduces capacitor ripples through distributed charging while managing device complexity through systematic control.
Solution Approach 2:
The patent ensures continuity of useful action by maintaining that at least one bridge arm unit is always charging a capacitor. The alternating charging mechanism ensures that capacitor charging continues without interruption, improving ripple reduction effectiveness while the systematic operation helps manage the complexity of having multiple bridge arm units.
3Ease of manufacture
If conventional Vienna PFC circuit is used, then the circuit design is straightforward, but component performance is affected by ripples
Solution Approach 1:
By segmenting the capacitor into two separate capacitors and assigning them to different bridge arm units, the patent reduces the ripple current each capacitor must handle. This segmentation improves component reliability and performance while maintaining a circuit design that builds upon the conventional Vienna PFC structure, making it relatively straightforward to implement.
Solution Approach 2:
The patent introduces multiple bridge arm units as intermediaries between the power supply and the capacitors. These bridge arm units with switching transistors (Q1-Q4) and diodes (D1-D6) act as mediators that distribute and control the charging current, reducing direct ripple impact on capacitors and improving component performance while maintaining manageable circuit design.
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 configuration effectively reduces capacitor ripples, enhances the usage of components, and improves the overall performance of the circuit by alternately charging capacitors, leading to better magnetic and filtering parameter management.
Implementation Method 1
once Q1 is turned on, the flow direction of a current is: Phase A of the mains supply flows along AC(A) -> K1-> L1 -> Q1 -> N
Implementation Method 2
once Q1 is turned off, the flow direction of the current is: AC(A) -> K1-> L1 -> D1 -> C1 -> N
Data Source
Figure 1~3
Figure 4
AI summary
The present invention discloses a circuit, including a first bridge arm unit, a second bridge arm unit, a third bridge arm unit, a fourth bridge arm unit, a first capacitor, and a second capacitor, where: the first bridge arm unit is configured to input a first-phase alternating current of a three-phase power supply, the second bridge arm unit and the third bridge arm unit are configured to input a second-phase alternating current of the two-phase power supply, and the fourth bridge arm unit is configured to input a third-phase alternating current of the three-phase power supply. In alternating current working mode, the first capacitor and the second capacitor are charged by turning on the switching transistor of the second bridge arm unit and the switching transistor of the third bridge arm unit alternately, thereby reducing ripples of the capacitor; in battery working mode, the second bridge arm unit and the third bridge arm unit can still charge the capacitor, and no component of the circuit is idle, thereby improving usage of components.