Flying Capacitor Boost Circuit Precharge for Overvoltage Protection
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Solution Overview
Problem
Existing flying capacitor boost circuits face issues with high system costs, running losses, and increased control logic due to overvoltage protection mechanisms that increase complexity and require additional control resources, particularly in photovoltaic applications.
Innovation Solution
A boost circuit structure is formed by a switch circuit, main boost circuit, and branch boost circuit, with functional circuits connected to the flying capacitor and diodes to protect switches and diodes from overvoltage during power-on, using passive and active devices for precharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active devices are used to disconnect the flying capacitor loop for overvoltage protection, then device voltage is clamped and overvoltage is protected, but overall running loss increases and control resources increase
Solution Approach 1:
The patent extracts the overvoltage protection function from the main power circuit by using a separate precharging circuit with a precharging switch. This allows the main boost circuit to operate independently during normal operation without the protection circuit interfering, thereby minimizing running losses while maintaining overvoltage protection capability during power-on.
Solution Approach 2:
The patent implements preliminary action by precharging the flying capacitor before the main boost circuit operates. The precharging circuit activates first to charge the capacitor to a safe voltage level, preventing overvoltage damage to switches and diodes during power-on, while the main circuit remains inactive during this precharging phase.
2Reliability
If voltage division is performed by using capacitors to clamp device voltage, then overvoltage is protected, but system costs increase and system coupling degree increases
Solution Approach 1:
The patent segments the power circuit into distinct functional modules: a precharging circuit for overvoltage protection and a main boost circuit for normal operation. The precharging circuit includes its own switch and control logic, separated from the main circuit, reducing system coupling while maintaining protection functionality.
Solution Approach 2:
The patent introduces a precharging switch as an intermediary component that mediates between the power source and the flying capacitor during power-on. This intermediary controls the charging process independently, protecting the main circuit components without requiring direct coupling between protection and main circuits.
3Reliability
If precharging of flying capacitor is implemented before main topology power-on, then overvoltage damage is prevented, but control logic and system complexity increase
Solution Approach 1:
The patent implements periodic action through sequential activation of circuits: first the precharging circuit is activated to charge the flying capacitor, then after a predetermined time delay, the main boost circuit is activated. This time-sequenced operation simplifies control logic by using a simple timer-based approach rather than complex inter-circuit coordination.
Data Source
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AI summary
This application is applicable to the field of electronic circuit technologies, and specifically provides a boost circuit structure, an inverter apparatus, and a photovoltaic power generation system. The structure includes a switch circuit, a main boost circuit, a branch boost circuit, a first functional circuit, and a second functional circuit. In this application, a boost circuit structure frame is formed by the switch circuit, the main boost circuit, and the branch boost circuit, and then the first functional circuit is connected to a flying capacitor and a second input terminal, to charge the flying capacitor in a process of powering on an input side of the boost circuit, thereby protecting a second controllable switch from an overvoltage. In addition, the second functional circuit is connected to a second diode in parallel, to charge the flying capacitor in a process of powering on an output side of the boost circuit, thereby protecting the second diode from an overvoltage.