IndustrialDriveDataDrive Board & Diagnostic Database
Electronics supply

VFD auxiliary SMPS and control-power path

Maps the auxiliary supply route that powers the CPU, keypad, I/O, relay logic, fan control and often isolated driver supplies.

Functional path

DC bus or auxiliary input
Startup feed
SMPS switch/controller
Transformer / secondary rectifiers
Feedback regulation
24 V / 15 V / 5 V branches
Control board loads

Diagnostic signals and checkpoints

Dark keypadPulsing displayClicking relayFan twitchLow-voltage rail collapse

Technician notes

  • A shorted downstream branch can collapse the supply.
  • Old electrolytics may cause weak startup.
  • Keypad replacement is premature until supply evidence is known.