Help High Voltage DCDC Buck

[mystamo]

Hey Guys,

Need help with a little project that I'm working on.

I need to make a DC DC buck converter for an input of 24v-160v and I need it to output 5v at 200ma (Maybe 500ma)

I've been trying to model a circuit after Roman Black. He has a website with some
2-transistor Black Regulator

Anyone have any links or quick circuits they can draw up to make such a thing happen? Is it even possible to have such a wide range of input voltage?


I've also read about people using high voltage P Fets in conjunction with a regular switcher. The idea is you use the switcher to switch the P fet gate while powering up the switcher with a power resistor or zener dropped down from your main voltage.

I'm not exactly sure how that works.

Any support would be greatly appreciated.

 

[blueroomelectronics]

160v is not going to be easy, why such a high voltage?

If 24-70 then an LM2574-5HV would fit the bill.

 

[Mr RB]

Maybe he wants to have to option of running from rectified 110v AC mains, which is about 160v DC? I've seen people with wind generators etc and having large Vin ranges.

If you want to run the 2-tran buck circuit from higher voltages, and need a wide range of Vin, then it really helps to put a constant current driver between the bottom transistor and the main switching transistor (Q1) in the base circuit. That establishes a fixed and reliable ON-state base current for Q1, regardless of what the Vin is. (The original simple circuit has varying ON-state base current depending on Vin, so it needs a limited range of Vin variance).

Then of course all the parts exposed to high voltages like 160v need to be rated for >160v to allow for switching transients, I would suggest rating for 300v or so. Those parts include all the transistors, the Vin electro cap, and the inductor (which needs to also be a larger inductance value).

And finally, if you have not got much experience in designing high voltage (>40v) SMPS circuits this might not be the project for you, there will be lots of chances to blow parts up.