sircube

modified 8 years ago

High-side MOSFET driver

340

09:43:09

This circuit is one of the ways to create a floating power supply, to drive the upper two MOSFETs of an H-Bridge (see my last circuit). Notice the ground not being connected to the secondary winding of the transformer, which is referenced to the Source of the power MOSFET.

Ps: wait for the blue channel to set before trying to toggle the switch. 

Edit: the push-pull stage is not referenced to ground, but to the Source of the mosfet.

published 8 years ago

hurz

8 years ago

A push pull stage is sometimes also called "voltage follower" for a good reason the emitter follows the base voltage minus Ube

sircube

8 years ago

Yes, I made that to achieve low impedance, and to discharge the parasitic capacitor Cg faster, resulting in faster switching speed

hurz

8 years ago

Voltage follower!!!! 24V in at base cause 24-Ube out at emitter!!!!

sircube

8 years ago

I still do not understand, what's the problem?

hurz

8 years ago

Measure the gate voltage and see its a little below 24V

sircube

8 years ago

I made a mistake, thank you: the push-pull stage is now referenced to the source of the mosfet, and now it is correct I think.

hurz

8 years ago

And have you measured the gate voltage? Suppose also a Vto of at least 2V

sircube

8 years ago

Another mistake... I am not concentrated today... the signal must be taken from the floating supply, not the main supply. Thanks again

hurz

8 years ago

You are welcome! Next you need an interface to TTL or arduino 3.3V as slow OC driver?

sircube

8 years ago

Yes, somethig like an OC should do the trick

hurz

8 years ago

How about this http://everycircuit.com/circuit/5484157090660352

sircube

8 years ago

That is with bootstrap capacitor and diode, isn't it? Anyway, that works fine too

sircube

8 years ago

In one of my projects I used my version, because I had got integrated insulated switching supplies. (They are as big as a small relay)

hurz

8 years ago

This without transformer is working fine but has the limitation of frequency, its not working for to low switching frequency or "static" cuz of leakage current of MOS Igs. The bootstrap voltage will drop

sircube

8 years ago

Exactly, and I needed duty cycle from 0 to 100, wich are basically DC and that won'work. But that solution is valid in many cases, especially for the fact it uses few components :)

hurz

8 years ago

For what do you need 100% duty cycle? Isn't 90-99% much enough for your application?

sircube

8 years ago

Two 250W DC motors, in fact 90 % would be enough but I wanted full control.

hurz

8 years ago

Truck wiper motors?

sircube

8 years ago

They are from electric bikes, I am using them on a segway

hurz

8 years ago

DC motors and ?PWM?, hmmmmm

hurz

8 years ago

How is the PWM project going?

sircube

8 years ago

I am designing the PCB

hurz

8 years ago

Good, i will follow your new yt broadcast ;-)

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