We have encountered a flaw in the Argon firmware that puts drive power stage transistors in danger if safe torque off (STO) was activated in certain conditions. This issue has been fixed in a firmware version 1.0.3 available here. Please upgrade FW before continuing use of the drives!

The bug endangered only the drive itself. Regardless of this issue, STO function has always worked without compromising user or machine safety. STO is based on hardware circuits thus software can’t defeat it even if it wanted so.

Safe torque off testing once STO2 activated. When STO2 is activated, the gate drive voltage will be removed from the power stage forcing motor driving transistors in non-conductive state. Traces: green=gate supply voltage, red=PWM signal from DSP to power stage, yellow=under voltage fault from power stage, blue=output voltage of power stage (measured at motor terminal). From the traces we see that STO2 reacted within 300 µs from activation.

The technical background in this issue was that the power stage module’s built-in under voltage lock-out protects only half of the transistors inside. The other half of transistors are able to run despite gate voltage being too low which could cause high heat dissipation and transistor melt down. This has been fixed by shutting down the controlling PWM signal once power stage’s undervoltage fault becomes active.

In the other news, we finally received more Argon in stock! All pending orders will ship on Monday.

Update 26.9.2013: The users who had drives damaged due to this bug have been successfully served by repairing or replacing the drives for free. Such faults are always covered by warranty.