DC-DC converter with single source of voltage
Hi
I am actually working on a telecom project to convert -48VDC to +24VDC with a maximum of 1.2A as current. I do not have a any other supply available except for the -48V supply. I need a dc-dc converter to do the job for me but i cannot find any schematics anywhere. Your help will be appreciated. Thanking you all.
Comments
Thx for ur reply. If i use a buck-boost converter, earth will be the positive input terminal and -48V the negative input terminal. So the output will be measured w.r.t -48V. In fact, in the available 48V supply. the +ve terminal has been earthed. I need the output with the -ve terminal earthed so that i can get the +24V....it is not possible with a buck-boost converter. I need an isolation scheme to achieve it.
It is possible to use the buck boost... Just shift the switch and the diode on the negative side and voila you have the earth reference as you want it. see attached schematic.
If you want to use isolated topology then use a flyback topology. Use a full bridge at the input and you'll get an isolated 24 V at the output.
Thx Sir. But how can i control the switching of the MOSFET? I have only the -48V supply which is available to me :( can i use the -48V via a circuit to obtain PWM to control the switching of my MOSFET Sir? Thx
The DPASwitch has an integrated PWM controller along with the MOSFET. All you need to do is supply feedback to the control pin. The chip does the PWM function and derives gate drive for the internal MOSFET. PLease read the DPAswitch application note and datasheet for details... See some design examples on the website also to get an idea of what I am saying.
http://www.powerint.com/sites/default/files/PDFFiles/der112.pdf
Do you need the outputs to share the same ground? If so you need a buck-boost converter to get the toggled output (negative to positive)