Flying-Capacitor Inverter Phase-Shift Control for Lower Switch Loss
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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.
Innovation Solution
A flying-capacitor inverter with a switch leg of four switches and a flying capacitor, controlled using phase-shift modulation to balance switch states and reduce overlap, ensuring low switching and conduction losses, and maintaining a stable voltage by alternating current sequences through the capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional switching control is used in flying-capacitor inverters, then the inverter can operate, but switching losses and conduction losses are high
Solution Approach 1:
The patent implements dynamic voltage balancing control that continuously adjusts the switching states of the four switches based on real-time flying capacitor voltage detection. The control device dynamically selects between different switching sequences (A+, A-, B+, B-) to maintain optimal operating conditions, thereby minimizing switching and conduction losses while adapting to varying load and input voltage conditions.
Solution Approach 2:
The patent changes the switching parameters by introducing phase-shift modulation between complementary switch pairs. By adjusting the phase shift angle and duty cycle dynamically, the control device optimizes the switching timing to reduce overlap losses and conduction losses, transforming the fixed switching pattern into an adaptive parameter control strategy.
2Reliability
If the flying capacitor voltage is not controlled, then the circuit is simpler, but the switch voltage stress increases and becomes unstable
Solution Approach 1:
The patent implements a feedback control mechanism where the control device continuously monitors the flying capacitor voltage and adjusts the switching states accordingly. When the voltage deviates from the target value (Vin/2), the control device selects appropriate switching sequences to charge or discharge the capacitor, thereby stabilizing the voltage and reducing switch stress through closed-loop feedback.
Solution Approach 2:
The flying capacitor itself acts as an intermediary energy storage element that smooths voltage variations. The control device uses the capacitor's natural charging/discharging behavior as a mediator to balance the voltage, reducing the need for complex external voltage regulation circuits while maintaining stable switch operating conditions.
3Loss of energy
If phase-shift modulation is implemented to reduce losses, then switching and conduction losses decrease, but the control complexity increases
Solution Approach 1:
The patent segments the control into four distinct switching sequences (A+, A-, B+, B-), each optimized for specific operating conditions. The control device selects among these pre-defined sequences based on the current state, breaking down the complex phase-shift modulation into manageable discrete states that reduce the computational burden while maintaining loss optimization benefits.
Data Source
AI summary
The disclosure concerns a flying-capacitor inverter, comprising a switch leg with four switches, a flying capacitor connected to the switch leg, an output between pairs of the switches, and a control device connected to each of the four switches, wherein the control device is configured to employ phase-shift modulation to switch the four switches such that switching signals for a first switch and a fourth switch of the four switches are phase shifted to the switching signals for a second switch and a third switch of the four switches. The disclosure also concerns a multi-level phase-shift converter comprising the flying-capacitor inverter, as well as a method for controlling the flying-capacitor inverter and/or the multi-level phase-shift converter.