Inverter for a low frequency amplifier with high drive voltage, high power density, high efficiency, and wide bandwidth operation
A low frequency direct drive amplifier is disclosed which can simultaneously achieve high drive voltages, high power density, high efficiency, and wide bandwidth operation is disclosed. The power circuit structure includes an input DC-DC converter and an output multi-level DC-AC inverter. The input DC-DC converter's circuit topology is commonly referred to as the phase shifted full bridge, which includes input capacitors, a Gallium Nitride (GaN) based full bridge, an isolation transformer, two rectifying diodes, and two series stacked output capacitors. The output DC-AC inverter includes two series stacked input capacitors (same as the input DC-DC converter's output capacitors), four Silicon Carbide (SiC) semiconductors, four Silicon IGBTs, and an output filter. The disclosure's features the combination of the output multi-level DC-AC inverter circuit topology paired with 1.7 kV SiC semiconductors, allowing for a high voltage direct drive design without a low frequency boost transformer.
1. An inverter for delivering power with a desired output voltage waveform with an output frequency content between 600 Hz to 1100 Hz to a load, the inverter comprising:
a plurality of series stacked half-bridge circuits, each in parallel with capacitors, configured to convert a greater than 2 kV DC voltage into a modulated unipolar voltage waveform, wherein each half-bridge circuit operates independently at a switching frequency that is greater than five times the inverter's output frequency;
a full bridge circuit is connected to the plurality of series stacked half-bridge circuits and the full bridge circuit is configured to convert the unipolar voltage waveform into a modulated bipolar voltage waveform having a positive amplitude and a negative amplitude, wherein the full bridge circuit switches at zero amplitude crossing points of the modulated bipolar voltage waveform to achieve the modulated bipolar voltage waveform; and
an output filter is connected the full bridge circuit and is connected to the load, wherein the output filter converts the modulated bipolar voltage waveform into the desired output voltage waveform with frequency content between 600 Hz and 1100 Hz.
2. The inverter of claim 1 , wherein the plurality of series stacked half-bridge circuits are two series stacked half-bridge circuits comprising a plurality of 1.7 kV rated SiC semiconductors.
3. The inverter of claim 2 , wherein the plurality of 1.7 kV rated SiC semiconductors in each series stacked half-bridge circuit consists of two 1.7 kV rated SiC semiconductors.
4. The inverter of claim 1 , wherein the full bridge circuit consists of a plurality semiconductors with voltage ratings greater than 2 kV.
5. The inverter of claim 4 , wherein the plurality of semiconductors consists of four IGBTs with voltage ratings of 2.4 kV.