eBay TB6560 Stepper Motor Driver Boards

[williamturner1]

The when the current pulse is turned off the inductance of the winding tries to maintain current flow so generates a large reverse voltage. The protection diodes are there to clip this reverse voltage and absorb the current from the motor in discharging the winding inductance.

So is it that Mr ChinaMan's circuit doesn't provide enough protection be it through poor design or poor component choice

[1113562]

So is it that Mr ChinaMan's circuit doesn't provide enough protection be it through poor design or poor component choice

The H bridge in the chip itself is designed to discharge the inductance but the board has external diodes as well as protection. I cant see that the problem is the enternal diodes fitted to the board. You could measure to see if the board diodes on the blown chip motor output pins are damaged, If they are not then this implies these were not the reason for the failure of the chip. The diodes are FR307 which are 3A fast recovery diodes. These are rated at 1000V VR witha 200A surge and a 1.3V Vf and can withstand an average of 3 Amps continuously.

Hope this helps