Flying Capacitor Converter Voltage Division for High-Voltage Stress
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Solution Overview
Problem
Conventional flying capacitor converters face challenges with the withstand voltage of the second switch S2 and the second diode D2, particularly when dealing with high input voltages, leading to potential breakdown and inefficiencies.
Innovation Solution
The improved flying capacitor converter incorporates additional capacitors and diodes, along with a transient voltage suppressor, to create voltage division and provide charging paths that reduce the voltage stress on these components, ensuring they do not need to withstand the full magnitude of the input voltage, thereby enhancing their withstand voltage capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional flying capacitor converter topology is used, then circuit simplicity is maintained, but the second switch S2 and second diode D2 cannot withstand high input voltages leading to breakdown
Solution Approach 1:
The patent divides the voltage blocking function into multiple segments by introducing a first capacitor C1 and a second capacitor C2 in series between the input voltage and the second switch S2. The first capacitor C1 blocks a first voltage and the second capacitor C2 blocks a second voltage, collectively enabling the circuit to withstand high input voltages without requiring the second switch S2 and second diode D2 to handle the full voltage stress.
2Reliability
If standard components are used in conventional FCC, then cost is reduced, but components break down under high voltage stress
Solution Approach 1:
The patent introduces intermediary components (first capacitor C1 and second capacitor C2) that act as voltage buffers between the high-voltage input source and the sensitive second switch S2 and second diode D2. These capacitors absorb and distribute the voltage stress, protecting the standard components from breakdown while allowing them to operate within their rated voltage limits.
3Reliability
If high-voltage diodes are used to prevent breakdown, then reliability improves, but efficiency decreases
Solution Approach 1:
Instead of using a single high-voltage diode that would reduce efficiency, the patent segments the voltage handling function across multiple standard-voltage diodes (second diode D2 and third diode D3) combined with capacitive voltage division. This allows each diode to operate at lower voltage stress with higher efficiency while collectively providing the necessary voltage blocking capability.
Data Source
Figure 1~2
Figure 3~4
Figure 5A~5B
AI summary
A flying capacitor converter includes an inductor (L), a first switch (S1) and a second switch (S2), a first diode (D1) and a second diode (D2), a first capacitor (CB1) and a second capacitor (CB2), a flying capacitor (CF1), a third diode (DC1) and a third capacitor (Cc), a fourth diode (DC2), and a fifth diode (DC3). The inductor (L) is coupled to a first node (PL). The first switch (S1) and the second switch (S2) are commonly connected to a second node (PS). The first diode (D1) and the second diode (D2) are commonly connected to a third node (PD). The first capacitor (CB1) and the second capacitor (CB2) are commonly connected to a fourth node (PC). The flying capacitor (CF1) is coupled to the second node (PS) and the third node (PD). The third diode (DC1) and the third capacitor (Cc) are commonly connected to a fifth node (PE). The fifth diode (DC3) is coupled to the third node (PD) and the fourth node (PC).