Flying Capacitor Pre-Charging in Multi-Level Topology Circuits
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Solution Overview
Problem
Existing flying capacitor charging solutions for multi-level topology circuits are costly and have limited applicability, especially in high-voltage systems where quick charging is required, as they necessitate large power resistors or numerous resistors in parallel, leading to increased space occupation and higher system power consumption.
Innovation Solution
The method involves using the existing structure of the multi-level topology circuit to charge flying capacitors without an additional charging circuit, allowing for charging on either the input or output side by connecting an external DC power source or a soft-start resistor, thereby reducing costs and enhancing applicability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an additional charging circuit with resistors is used to pre-charge the flying capacitor, then the flying capacitor can be charged before power-on, but the system cost increases and the occupation area becomes excessively large in high-voltage systems
Solution Approach 1:
The patent merges the charging function into the existing multi-level topology circuit structure by utilizing the inherent switches and capacitors. The flying capacitor is charged through the existing circuit paths during normal operation rather than requiring a separate dedicated charging circuit, thereby eliminating the need for additional resistors and reducing occupation area.
Solution Approach 2:
The existing switches and capacitors in the multi-level topology circuit are made to serve dual purposes: their primary function in voltage conversion and their secondary function in charging the flying capacitor. The input capacitor and output capacitor are utilized as charging sources for the flying capacitor through controlled switch operations, making the circuit elements universal in their functionality.
2Productivity
If a large-power resistor or multiple resistors in parallel are used for quick charging in high-voltage systems, then the charging speed increases, but the occupation area and system power consumption increase excessively
Solution Approach 1:
The circuit uses its own stored energy in the input and output capacitors to charge the flying capacitor, rather than relying on external high-power resistors. The switches are controlled to transfer energy from the input/output capacitors to the flying capacitor, enabling the system to self-charge without additional power consumption from dedicated charging resistors.
Solution Approach 2:
The charging process is implemented as a periodic operation controlled by the switch states during normal circuit operation. The flying capacitor is charged in periodic cycles through controlled switch operations, allowing efficient energy transfer without requiring continuous high-power resistor operation, thus reducing overall power consumption.
3Reliability
If an additional charging circuit is used to pre-charge the flying capacitor, then the flying capacitor can be charged before power-on, but the device complexity and system cost increase
Solution Approach 1:
The patent combines the overvoltage protection function with the existing circuit structure. The flying capacitor charging is integrated into the normal operation of the multi-level topology circuit, where the same switches and capacitors used for voltage conversion also perform the charging function. This eliminates the need for a separate dedicated charging circuit and reduces overall device complexity.
4Power
If multiple flying capacitors are present in parallel topologies, then the system power increases, but the number of resistors needed increases proportionally, leading to excessive occupation area
Solution Approach 1:
In parallel topologies with multiple flying capacitors, each capacitor leverages the input and output capacitors as shared charging sources through controlled switch operations. The same input and output capacitors serve multiple flying capacitors sequentially or simultaneously depending on switch configurations, eliminating the need for dedicated resistors for each flying capacitor and reducing the total occupation area proportionally.
Data Source
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AI summary
This application provides a flying capacitor charging method and apparatus, applied to a multi-level topology circuit, to provide a flying capacitor charging solution with a small occupation area and strong applicability. The circuit is connected to an input power source by using a first switch, and is connected to an output power source by using a second switch. A first end of a first capacitor in flying capacitors in the circuit is connected to a first electrode of a first semiconductor switch transistor, a second end of the first capacitor in the flying capacitors in the circuit is connected to a second electrode of a second semiconductor switch transistor, and a second electrode of the first semiconductor switch transistor is connected to a first electrode of the second semiconductor switch transistor by using a second capacitor. The second capacitor is an input capacitor, an output capacitor, or another flying capacitor. The method includes: closing the first semiconductor switch transistor and the second semiconductor switch transistor, to connect the first capacitor to the second capacitor in parallel; charging the first capacitor and the second capacitor to a first specified voltage value; opening the first semiconductor switch transistor and the second semiconductor switch transistor; and charging the second capacitor to a second specified voltage value.