Flying-Capacitor Inverter Phase-Shift Control for Lower Switch Stress
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Solution Overview
Problem
Conventional flying-capacitor inverters and multi-level phase-shift converters face high switching and conduction losses, as well as excessive stress on switches due to dynamic voltage increases, which are not effectively managed by existing control methods.
Innovation Solution
A flying-capacitor inverter with a switch leg of four switches and a flying capacitor, employing phase-shift modulation to control switch states and transitions, ensuring no time-overlap of switches and using duty cycle control to maintain the flying capacitor voltage at half the input voltage, thereby reducing losses and stress on switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional flying-capacitor inverter control methods are used, then the inverter can operate, but switching losses and conduction losses are high
Solution Approach 1:
The patent implements dynamic switching control where the switching states of the four switches are dynamically adjusted based on phase-shift modulation. The switching signals for switch pairs (S1,S4) and (S2,S3) are phase-shifted relative to each other, creating dynamic transitions that reduce overlapping conduction periods and minimize both switching and conduction losses while maintaining efficient power conversion.
Solution Approach 2:
The patent changes the switching parameters by introducing phase-shift modulation between different switch pairs. By adjusting the phase shift angle and duty cycle dynamically, the control device optimizes the switching timing to reduce losses. The flying capacitor voltage is maintained at a specific parameter level (half of input voltage) through this parameter adjustment, achieving low loss operation.
2Strength
If the flying capacitor voltage is not controlled, then the inverter structure is simple, but the switches experience excessive stress and dynamic voltage increases
Solution Approach 1:
The control device implements feedback control to maintain the flying capacitor voltage at the desired level (half of input voltage). By monitoring the voltage and adjusting the switching signals accordingly, the system prevents excessive voltage buildup that would stress the switches. This feedback mechanism ensures switch protection while managing the complexity through intelligent control rather than additional hardware.
Solution Approach 2:
The flying capacitor acts as an intermediary energy storage element that buffers voltage fluctuations. By controlling the capacitor voltage to remain at half the input voltage, it mediates the voltage stress on the switches, preventing direct exposure to full input voltage dynamics. This intermediary function protects the switches without requiring complex protection circuits.
3Loss of energy
If phase-shift modulation is employed to reduce losses, then switching and conduction losses decrease, but the control complexity increases
Solution Approach 1:
The control device performs multiple functions through a single integrated control mechanism: it generates phase-shifted switching signals for all four switches, maintains flying capacitor voltage regulation, and optimizes power transfer. By consolidating these control tasks into one multi-functional control device using phase-shift modulation, the patent reduces overall system complexity while achieving low loss operation.
Data Source
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AI summary
The invention concerns a flying-capacitor inverter (1), comprising a switch leg (2) with four switches (S1, S2, S3, S4), a flying capacitor (3) connected to the switch leg (2), an output (5) between pairs of the switches (S1, S2; S3, S4), and a control device (200) connected to each of the four switches (S1, S2, S3, S4), wherein the control device (200) is configured to employ phase-shift modulation to switch the four switches (S1, S2, S3, S4) such that switching signals for a first switch (S1) and a fourth switch (S4) of the four switches (S1, S2, S3, S4) are phase shifted to the switching signals for a second switch (S2) and a third switch (S3) of the four switches (S1, S2, S3, S4). The invention also concerns a multi-level phase-shift converter (100) comprising the flying-capacitor inverter (1), as well as a method for controlling the flying-capacitor inverter (1) and/or the multi-level phase-shift converter (100).