Step down voltage from 36V to 12V for EV

[Assurena]

Hello ,

i have to design a step down circuit from 36V/48V to 12V that compatible for Electric Vehicle.
Where my circuit need to charge the 12V battery.

I need an opinion how to control all the MOSFET.
After done the simulation, i have failed to get the right result.
Thank you.

 

[donkey]

I have to counter this question with another, how many amps we talking? if its to start a car engine you need about 100 cranking amps which most step downs won't be able to do.
just stepping down a voltage is not the only thing you need to look at, also look at current ratingand let us know what that is

 

[(*steve*)]

Leaving all those mosfet's gates disconnected seems like a problem.

 

[Assurena]

the specifications of the cct are:
Vin=12V
Vo=1.5V
Io=40A
fs=50Hz

From the circuit i would like to modify the input and also the output since I have to step down from 48V/36V to 12V and i have to charge the 12V battery.

From my understanding, i cant use PWM rite? since i have fix pattern to turn on every each of the MOSFETs.
As attached is the details of my project.

 

[Assurena]

during the simulation, i have connect it with a comparator circuit. The circuit is working but i didnt get the rite result. I have to control all the MOSFETs by using PIC? This is the pattern of each of my MOSFETs in order to make the circuit works at it should be.

 

[(*steve*)]

Remember that the source of each mosfet is at a different (and varying) voltage.

Vgs is the important value.

I also have no idea what that circuit is supposed to do. Did you come up with it yourself?

 

[Assurena]

nope. i got it from journal. After did some research. is it true that i have to use PIC sir?
I have to do my own program to get the waveform?/

 

[(*steve*)]

Please see to the right about calling me "sir"

<----

You probably don't have to use a PIC, but that is *a* way to generate this sort of waveform.

As I've suggested, getting the appropriate voltages to the gates won't be as simple as wiring them up to the output of the PIC though.

You will almost certainly need gate drivers to allow the mosfets to switch rapidly enough, and beware of any delays which might allow crowbar currents to flow.

Gate drivers might also assist with the voltage you need to drive the gates.

 

[BobK]

Look up buck converter. Your circuit is way over complicated. There are buck converter controller chips that will do this quite well. All you need to add is an external MOSFET, inductor and a few passive compoents.

Bob