Power Converter Start Circuit for Flying Capacitor Pre-Charge
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Solution Overview
Problem
Conventional power conversion circuits with resonant and duty-cycle-expandable topologies face challenges in controlling the start process and pre-charging of flying and output capacitors, leading to potential damage from large currents and the need for high-cost, high-current-resistant electronic components.
Innovation Solution
A power conversion system that includes a start circuit to pre-charge flying and output capacitors using a third winding, an inductor, and switch elements, allowing for electromagnetic coupling to gradually charge capacitors, reducing the impact of large currents and enabling the use of cost-effective components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the power conversion circuit is started without pre-charging the flying capacitor and output capacitor, then the circuit can start immediately, but a large current is generated that damages electronic components
Solution Approach 1:
The patent applies preliminary action by introducing a start circuit that pre-charges the flying capacitor and output capacitor before the main power conversion circuit operates. This preliminary charging action prevents large inrush currents from damaging electronic components when the circuit starts, while still enabling relatively quick startup through controlled charging paths.
2Reliability
If electronic components with high current-resistant properties are used to protect against large currents, then component reliability is improved, but the cost increases
Solution Approach 1:
By pre-charging capacitors before main operation, the patent eliminates the need for expensive high-current-resistant components. The preliminary charging action ensures that when the main circuit starts, currents remain within normal operating ranges, allowing the use of standard, cost-effective electronic components while maintaining high reliability.
3Reliability
If a start circuit with electromagnetic coupling is used to pre-charge capacitors, then component protection is improved, but device complexity increases
Solution Approach 1:
The patent uses electromagnetic coupling as an intermediary mechanism to transfer energy from the input voltage to the flying capacitor and output capacitor during startup. This intermediary approach provides isolated, controlled charging paths that protect main circuit components while adding only moderate complexity through the use of coupled inductors or transformers.
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
The system effectively reduces the risk of component damage from large currents and allows for the use of cost-effective electronic components by ensuring capacitors are charged to a preset voltage before the power conversion circuit starts, enhancing operational safety and reducing component costs.
Implementation Method 1
The two first windings are electromagnetically coupled with each other. The third winding is electromagnetically coupled with the two first windings.
Data Source
AI summary
A power conversion system includes a power conversion circuit and a start circuit. The power conversion circuit includes a first terminal, a second terminal, an output capacitor, at least one switch unit, a flying capacitor and a magnetic element. The flying capacitor is connected between the first terminal and the second terminal. The output capacitor is electrically connected with the first terminal or the second terminal. The start circuit is configured to control the power conversion circuit to pre-charge. A first terminal of the start circuit is electrically connected with the first terminal, and a second terminal of the start circuit is electrically connected with the second terminal. During a start process of the power conversion circuit, the at least one flying capacitor and the output capacitor are pre-charged by the start circuit.