PMOS Driver in 3-Phase Switch-Mode Inverter

[[email protected]]

I'm working on a motor drive for a 3 phase AC electric motor. I have
a 48VDC supply. I am using six N-Channel mosfets to drive the three
phase inverter that supplys power to the motor and Im using six P-
Channel mosfets for regenerative braking (to act as a three phase
rectifier).
Are there P-Channel power mosfet drivers on the market? Everything
I've seen as far as mosfet drivers go seem to be designed for N-
Channel mosfets. Because P-channel mosfets require a 'negative'
voltage on the gate I was hoping someone could direct me to a driver
that could supply 2A (10V) to the gate of a PMOS for switching
frequencies up to 1kHz.
I know my description is quite brief so if you need any clarification
message back.

 

[[email protected]]

I'm working on a motor drive for a 3 phase AC electric motor. �I have
a 48VDC supply. �I am using six N-Channel mosfets to drive the three
phase inverter that supplys power to the motor

Good so far.

and Im using six P-

Channel mosfets for regenerative braking (to act as a three phase
rectifier).

WHY?? your existing mosfets will do the regenerating for you. You need
to dump power from the dc bus into a resistor during braking. A little
research will save you a lot of grief.

 

[[email protected]]

WHY?? your existing mosfets will do the regenerating for you. You need
to dump power from the dc bus into a resistor during braking. A little
research will save you a lot of grief.

I have researched this a bit. If im trying to put energy back on the
batteries dont I need P-Channel Mosfets to allow current to flow in
the reverse direction? If you have any references on this subject
that would help me I would greatly appreciate it.

-Greg

 

[Nobody]

I have researched this a bit. If im trying to put energy back on the
batteries dont I need P-Channel Mosfets to allow current to flow in
the reverse direction?

No. MOSFETs allow current to flow in either direction (although they can
normally only block current in one direction due to the intrinsic diode).
H-bridge motor drivers often use this to perform synchronous rectification
during freewheeling (the voltage drop across a fully-conducting MOSFET is
often less than across a diode).

At the simplest level, regenerative braking just requires reversing the
polarity. When driving the motor normally, you apply voltage so as to
increase (or at least maintain) the motor current. If you reverse the
polarity, apart from decreasing the current, the existing current will
flow back into the battery.

There's some useful introductory material at:

http://robots.freehostia.com/

It deals primarily with DC motors (the author mainly uses modified
auto starter motors), but much of it can also be applied to driving
3-phase motors.

 

[Jim Thompson]

No. MOSFETs allow current to flow in either direction (although they can
normally only block current in one direction due to the intrinsic diode).
H-bridge motor drivers often use this to perform synchronous rectification
during freewheeling (the voltage drop across a fully-conducting MOSFET is
often less than across a diode).

At the simplest level, regenerative braking just requires reversing the
polarity. When driving the motor normally, you apply voltage so as to
increase (or at least maintain) the motor current. If you reverse the
polarity, apart from decreasing the current, the existing current will
flow back into the battery.

There's some useful introductory material at:

http://robots.freehostia.com/

It deals primarily with DC motors (the author mainly uses modified
auto starter motors), but much of it can also be applied to driving
3-phase motors.

For some pointers, see....

PerfectDiodeForChargerIsolation.pdf

on the S.E.D/Schematics page of my website.

...Jim Thompson

 

[[email protected]]

I have researched this a bit.

Not enough it would seem.


�If im trying to put energy back on the

batteries

That will happen with just your existing 6 devices.


dont I need P-Channel Mosfets to allow current to flow in

the reverse direction?

No, research "inversion"

�If you have any references on this subject

that would help me I would greatly appreciate it.

Too many to list, 5 mins with google should do it.