An independent design by Ray Ring, a professional electrical engineer (ex General Dynamics) who writes the Circuit Salad blog. It has no connection to Ward's or Burnett's lineages and turned up in a search for half-bridge drivers. It self-oscillates off a current-sense transformer on the secondary feedback path. The signal is phase-shifted through an adjustable RC network and a 74HC14 inverter chain so switching happens near the zero-crossing rather than on it, then goes to a pair of UCC27321 gate drivers through a hand-wound pulse transformer. PGnd is deliberately isolated from the control-circuit ground, and an HCPL-M456 optocoupler carries the interrupter signal across. It was first built on IRFP4229 MOSFETs. Two months later he moved it to STGW35HF60W IGBTs, after noting that MOSFET conduction losses rise faster than IGBT losses as current climbs. The IGBTs ran warmer (about 10 W at 10 A against 4 W for the MOSFETs) but, in his words, "they do not overheat with the small heat sinks and switching losses are low... I have not blown any up yet."
Schematics and photos
schematic (Circuit Salad, Rev 1.0)
Sources
- circuitsalad.com: Optimised Half-Bridge Tesla Coil Driver
- circuitsalad.com: IGBTs in my Optimized Half Bridge Tesla Coil
This is the card from the driver tree, written from what the builder published. Send corrections through the forum.