IndustrialDriveDataDrive Board & Diagnostic Database
Gate-drive circuit

Emerson TD900 IGBT Turn-Off Drive Stage

A documented TD900 gate-drive observation shows a 3120 driver arrangement using a diode/resistor/capacitor network to improve IGBT turn-off charge removal where no negative gate supply is used.

Functional path

Driver output
Turn-off diode path
Gate resistor / capacitor network
IGBT gate-emitter junction

Diagnostic signals and checkpoints

Driver-stage integrityDiode open-circuit conditionGate resistor damageReplacement module protection

Technician notes

  • A diode in this path can require out-of-circuit confirmation because parallel resistance may disguise an open-circuit failure.
  • This circuit deserves inspection whenever a power module failed or the repaired drive fails to produce output correctly.