Generate clean sinusoidal waveforms up to 2kV from a low-voltage DC bus, with variable frequency. The previous linear amplifier approach was massive and ran hot.
The Solution
Cascaded H-bridge inverter where each stage adds its output voltage in series, reaching 2kV with lower-voltage MOSFETs per module. Identical PCBs stack mechanically and electrically. Staggered switching instants push harmonic content to higher frequencies where it's easier to filter. Inter-stage isolation at 2kV requires isolated gate drivers and strict creepage management.
Results
The client now offers 500V, 1kV, and 2kV variants of their instrument using 1, 2, or 4 stacked modules from the same PCB design.
How the modules stack
Identical modules in series. Each module adds its own output voltage, so one PCB design builds the 500 V, 1 kV and 2 kV versions with one, two or four modules. Isolated gate drivers and strict creepage keep the stages apart at 2 kV.Why stacking cleans up the waveform. Each module switches against its own carrier, shifted by a fraction of a cycle from the next, so their switching harmonics cancel and the first remaining cluster moves up in frequency with every module added. Four modules push it out to around twice the order of a single bridge, and the THD falls from 61% to 13%, which leaves a much smaller output filter to reach a clean sine at 2 kV.
Have a Similar Challenge?
High-voltage power electronics are part of the regular workload.
