Electrical – How does this part of the schematic control the torque


This is a part of the schematic for a chinese built TB6600 stepper driver. The TQ pin (torque setting) can be either LOW when the torque is reduced to 30% or HIGH when its 100%. How does this part of the schematic work? STEP signal is the clock signal that turns the motor by a single step. No part numbers for the transistors were provided but I'm guessing they are something similar to a 2N3906(?).

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Best Answer

Looks like those transistors simply delay the step signal and apply it as the current demand.

If you step fast enough it will stay in high current, and if you single step it goes into holding current mode shortly after each step.