I am new to engineering, and now I am puzzled. My friend bought the product and he gave me the circuit diagram. But I don't know the purpose of diodes D10-D17. Can anyone give me an answer?
A slight correction to what was already posted: inductivities don't really "create a voltage" that needs to be shorted when shut off. Rather they maintain the current flowing through them until the energy in their magnetic field has been consumed. Clamping diodes will let the current continue while consuming the energy just fine. Here the clamping diodes are connected to VCC and GND which means that the switch-off current will be retained and work not just against the drop-down voltage of the diodes and coil resistance but also against the power supply voltage. Which is almost good and should deplete the field energy fast while burning only a minor part of the energy in the diodes, except that the power rails must be able to actually sink that current. If the circuitry does not consume it on its own, the power supply needs to be able to deal with back current. A capacity of proper dimension after voltage regulation might be enough, or your voltage regulation circuit needs to be able to feed back current.
It's not a part of this circuit diagram but you need to keep this in mind for the power supply.