help me making dc to dc converter

[amrshata]

I JUST WONDERING if any one could help me making dc to dc converter where the input is 48 volt and the outputs are 12 and 5 volts ( 50 ampere ) .

 

[goldsmith]

Dear amrshata
Hi
it is simple . you'll be able to do it , with a simple LM2576 and one optocoupler and one mosfet and some other things .
Best Wishes
Goldsmith

 

[amrshata]

LM2576 has maximum voltage of 40 volt

 

[steveelliott]

Well actually the LM2576HV has a 60V rating. But it's internal switch is rated at 3A, not 50A. What are the output currents?

 

[goldsmith]

Dear amrshata And steveelliott
Hi
As steveelliott said the HV series , can support your aim .
And about the current : as i told , you can use an opto coupler after your IC ( in series with a resistor ) .
Then you can switch a mosftet ( high power , such as IRFZ44N ( 45 A at least , 65 volts ) or another mosfets in parallel .
And then using a famous filter of buck regulator after that mosfet and then taking feed back . I did this way to achieve 100A simply and with good efficiency .
Good luck
Goldsmith

 

[Tahmid]

You can use a buck converter.

For this, you can use a dedicated controller for such a purpose or you can use a general-purpose PWM chip like UC3845.
If you use the second suggestion, you need to design a start-up section which can be a simple resistor. You can use the UC3845 to drive N-channel MOSFETs in high-side configuration. For this you will need high-side drivers such as IR2117. You would need an inductor and capacitor. Then, you'll need a feedback section to keep the output fixed.

If you use buck-converter, you would need 2 buck converters, one for 12V and one for 5V.

Another thing you can do is, use a transformer-isolated converter, so you can use one controller and a MOSFET stage driving a transformer with two output windings (and maybe an auxiliary for powering the controller or you can use the output 12V for powering the controller). A simple circuit would be an SG3525 driving 2 MOSFETs in push-pull configuration.

Hope this helps.
Tahmid.

 

[amrshata]

thanks guys you were really helpful