Need schematic of a DC-DC down converter

Hi,
I am new to power electronics. I would like to design DC-DC down converter from around 300V to either 5V or 3.3V. The output voltage should not be constantly controlled at fixed level. If the voltage level of input is reduced, the voltage level of level must also be reduced appropriately. Can anyone help with the schematic design?

Thanks and regards,
Mukesh

DC-DC down converter

Hi,
It depends on what you intend to use this for and the required current. If this is to be a reference for some circuit, a non-isolated voltage divider will do:


If you require this to drive some current, then you need to design an SMPS with something like TOP, TNY, DPA, VIPER, UC384x or some similar controller.

Hope this helps.
Tahmid.

Re: DC-DC down converter

Hi Tahmid,

Actually I want to measure the voltage level of the DC source using electronics circuit but at such high voltage electronics does not work. Therefore, I want to decrease the voltage level to 5V or 3.3 V. If the DC source voltage is lower, the output of my circuit is also lower accordingly. This is the only application.

By the way, can you give me the equation of how to derive resistors' value for different DC source voltages?

Thanks
Mukesh

Tahmid said:

Hi,
It depends on what you intend to use this for and the required current. If this is to be a reference for some circuit, a non-isolated voltage divider will do:


If you require this to drive some current, then you need to design an SMPS with something like TOP, TNY, DPA, VIPER, UC384x or some similar controller.

Hope this helps.
Tahmid.

Click to expand...

DC-DC down converter

Hi,
The formula goes:
Vout = (Vin * R2) / (R2 + R1)

For your requirement, this circuit is enough.

Hope this helps.
Tahmid.

Re: DC-DC down converter

Hi Tahmid,

But this circuit may not work at high current. I need to design to measure the voltage at very high current level, ranging from 1 A to 25 A.

Thanks
Mukesh

Tahmid said:

Hi,
The formula goes:
Vout = (Vin * R2) / (R2 + R1)

For your requirement, this circuit is enough.

Hope this helps.
Tahmid.

Click to expand...

DC-DC down converter

Hi,
The high current is going to the load(a few kWs), not flowing through the resistors, so this is fine.

Hope this helps.
Tahmid.

Re: DC-DC down converter

Tahmid said:

Hi,
The high current is going to the load(a few kWs), not flowing through the resistors, so this is fine.

Hope this helps.
Tahmid.

Click to expand...

Yeap Agree with Tahmid! As long as your load resistance is much much smaller than the resistances of the potential divider than it should work well.

Anyway your input and output voltage is a fixed or varying voltage?