A small open half-bridge built as the inverter of his DRSSTC 0.5, a 75 mm coil started in 2017. The sheet is signed “futurist’s TO-247 mini halfbridge”, Rev 1.1, dated 2017-04-11, with highvoltageforum.net in the title block. It was drawn in KiCad 4.0.6 and exported through Eeschema-PDF. Four FGH40N60 IGBTs in TO-247, two paralleled per switch (the “double half-bridge” he describes in his own build log). Each has an STPS340U Schottky across it, a 10 Ω gate resistor and an SM6T30CA bidirectional TVS clamping its gate. Bus snubbing is two 1 µF caps with two more positions left unfitted, and the sheet gives the exact part he used: R75LN41004000K. Gates leave on two headers, GDTA for G1/G2 and GDTB for G3/G4.
The sheet also covers what has to happen off the board. A boxed note draws the GDT phasing (one primary, two secondaries, the second pair crossed so the lower switch gets the opposite sense). Two instructions follow. One reads “Install 10kohm resistor across the output of the inverter!”. The other is a 0.1 µF capacitor from BUS- to ground labelled “Steve’s primary strike protection”, so Ward’s trick is named on the drawing.
From his own write-up: a 300 A over-current trip, and two 1000 µF 400 V bus capacitors behind a KBPC5010 1000 V 50 A bridge rectifier, straight off 240 V mains with no voltage doubler. The coil supports are laser-cut and 3D-printed so it can be copied. He credits Steve Ward and Gao Guangyan, among others, for the write-ups he learned from. No photograph of the assembled board exists. The thread has the KiCad project and two other archives and no images at all. The only photo in his earlier DRSSTC1 thread shows that coil whole, not this board.
Schematics and photos
schematic: “futurist’s TO-247 mini halfbridge”, Rev 1.1, 11 Apr 2017 (KiCad, from to247hb.zip)
Sources
- highvoltageforum.net: Futurist’s DRSSTC 0.5
- highvoltageforum.net: Futurist’s DRSSTC1 (the earlier coil)
This is the card from the driver tree, written from what the builder published. Send corrections through the forum.