Can the USB Port Maintain Logic Power for the A6 Servo Drive During an E-Stop When Main Power is Cut?

First, let's examine the USB port on the A6 servo drive:

Its primary function is to connect to the drive software for parameter debugging. The power specification provided by this port to the drive is 5V.

So, when the main power is cut during an emergency stop, but the USB port remains connected, is the 5V voltage sufficient to power the logic supply?

It is strongly discouraged and prohibited to operate in this manner!

The specific reasons are as follows:

• Insufficient Power: The USB port (5V/0.5A) provides very limited power and may be insufficient to stably power the drive's core logic circuits, encoder feedback circuit, and communication interface simultaneously.
• Violation of Power Sequencing: Servo drives have strict power-on/power-off sequences. During normal operation, the logic power is typically applied first, followed by the main power. The sequence is reversed during shutdown. Using the USB port to maintain logic power during an E-Stop disrupts this sequence, potentially causing internal state machine confusion, register errors, or communication abnormalities within the drive.
• Prevention of Proper System Reset: After an emergency stop, the system requires a clear "reset" operation to clear fault statuses and reinitialize the drive. If the logic power remains continuously on, the drive might not complete a full power-off/on cycle. This could prevent some latched faults or states from being cleared, thereby hindering the system's normal recovery.

Updated on: 28/11/2025