should a driver board need negative voltaje???

[patriciooholegu]

Hey people.
There is something rolling around in my head since a few days now, because making a job of reverse engineering on a Ricoh stepper driver pcb, and found that:
1 of the connectors of the board needs 24 volts for motor powering.
1 connector it is 100% sure for ground.
1 of the connectors goes to a PNP transistor and also motor powering and that’s my question:

If found a PNP transistor on the board, obviously together at the side with 24v, should I suspect that I need negative voltage on that?
Should be of the same current rating than 24v?

The device is 2SB1031 and here is the datasheet (The symbol –, negative, is everywhere):

2SB1031 pdf, 2SB1031 description, 2SB1031 datasheets, 2SB1031 view ::: ALLDATASHEET :::

Please be advice that im not talking about ground connections here.

Please Help!!!

[george4657]

It sounds like this is an H bridge circuit.
Google H-bridge BJT and you will find circuits that use npn transistors to drive motors.
And no you do not need a negative voltage for this.

George

[patriciooholegu]

Originally Posted by george4657 It sounds like this is an H bridge circuit. Google H-bridge BJT and you will find circuits that use npn transistors to drive motors. And no you do not need a negative voltage for this. George

This particular board have a PNP transistor. Not NPN.
On the 24 volt connector it is a rectifier diode.
both, the rectifier and the PNP transistor end up at going to motor power mosfets

[vanjast]

That link goes to the 2SD1435 ?

An PNP does require the Base voltage to be -ve relative to the Emitter, to turn on. This does not mean that the base voltage has to be -ve wrt ground/0-volts. The datasheet probably refers to relative voltages, not absolute.

It sounds like the PNP is being used as a gate driver for N-type mosfet.
It's another (cheaper) way to switching the mosfet on faster. It is more advisable to use a mosfet driver chip for this purpose.

The diode could either be a blocking diode (preventing voltage going back into the circuit causing damage) or a freewheeling diode (connected to the drain) to suppress the power spikes from the motor. If connected to the gate, it's probably a clamping zener diode as mosfet gates are usually limited to 20V max.

Google 'driving mosfets'.. there are plently app-notes on this.