An FPGA-based, single transducer, active balancing scheme for a 5-level flying capacitor converter with 1 MHz effective switching frequency

This paper presents an active balancing scheme for a 5-level flying capacitor converter operating with an effective switching frequency of 1 MHz. The proposed technique utilises only a single voltage transducer to sense the multilevel waveform. The states of the flying capacitor and bus voltages are estimated from multiple samples of the multilevel waveform over one switching period (4 μs for a single level). The FPGA responsible for modulation of the switches updates the state estimation and applies duty cycle corrections at the effective switching frequency (1 MHz) to drive the flying capacitor voltages towards balance. The technique is demonstrated experimentally utilising a 5-level half-bridge module based on GaN FETs.