Can a buck converter be used to convert a 100ms pulse properly?

Thread Starter

guilhermep

Joined Mar 1, 2018
8
So, here is my issue, I have a device that takes 24Vdc as input and works during 100ms and uses 200W of power. The issue is, I'll have to adapt it to work using 48V and I've been tasked to step it down to 24V. I'm having trouble looking for an IC that accommodates these sepcs, but that got me thinking, will a buck converter even cut it? I know the voltage rises with a delay due to the inductor, so if it can only be fed during 100ms, will the voltage even reach the desire voltage? Any suggestions?
 

SteveSh

Joined Nov 5, 2019
92
Some clarification -

You have constant load, and want to pulse 24V across it for 100 ms?

Why not just let the buck run continously, and then switch the 24V output of the buck across the load with another pass transistor - a FET? You'll need a fair amount of capacitance on the output of the buck to hold up the voltage so that it doesn't droop, until the buck's control loop can respond.
 

crutschow

Joined Mar 14, 2008
23,507
It would be difficult to get a buck converter to provide a clean 100ms pulse.
Better to do as Steve suggested and let the converter run continuously while switching the output with a power MOSFET.
 

Thread Starter

guilhermep

Joined Mar 1, 2018
8
Some clarification -

You have constant load, and want to pulse 24V across it for 100 ms?

Why not just let the buck run continously, and then switch the 24V output of the buck across the load with another pass transistor - a FET? You'll need a fair amount of capacitance on the output of the buck to hold up the voltage so that it doesn't droop, until the buck's control loop can respond.
Thanks man, do you happen to know a good IC for that? I looked into some of them but I couldn't find one that would accommodate the specs. The closer I got to it was the XL4016 from XLSEMI, but the maximum input is 40Vdc.
 

SteveSh

Joined Nov 5, 2019
92
Thanks man, do you happen to know a good IC for that? I looked into some of them but I couldn't find one that would accommodate the specs. The closer I got to it was the XL4016 from XLSEMI, but the maximum input is 40Vdc.
Not off the top of my head. But there are tons of 48V input power supplies out there.
 

Thread Starter

guilhermep

Joined Mar 1, 2018
8
Not off the top of my head. But there are tons of 48V input power supplies out there.
Yeah, but when I take the 200W factor into account (the 8ish Ampere) it eliminates most of them. I guess I'll be looking around some more, right now I'm just plainly googling it, is there any sort of database/aggregator where it would be easier for me to find stuff like this? Thanks for the help so far btw.
 

Thread Starter

guilhermep

Joined Mar 1, 2018
8
What about one of these?
I don't live in the US. So I was hoping to find out the IC needed and build the circuit around it. I don't think it would be viable to pay/wait for the shipping of a single converter. That's why I'm looking for which IC I would have to use. But thanks for the suggestion.
 

SteveSh

Joined Nov 5, 2019
92
How long does this thing have to pulse? 1 minute? 1 hour? Days?

48V batteries are used for electric bicycles, among other uses. Did you consider them? 48V is also the standard voltage for telecon equipment, ot at least it used to be IIRC. Or how bout 4 automotive batteries in series?
 

Thread Starter

guilhermep

Joined Mar 1, 2018
8
How long does this thing have to pulse? 1 minute? 1 hour? Days?

48V batteries are used for electric bicycles, among other uses. Did you consider them? 48V is also the standard voltage for telecon equipment, ot at least it used to be IIRC. Or how bout 4 automotive batteries in series?
Oh, it's supposed to pulse for a duration of 100ms. The 48Vdc are supplied by a battery bank, but I have to step it down because the equipment only uses 24Vdc. I can't change the battery banks.


And how am I to know that?
I'm sorry I guess. I didn't mean to imply you had to know or was supposed to know that.

Do you any experience in designing high current switch-mode circuits?
If not, I suggest you continue searching for a built module.

Can you order from Ali Express?
Not exactly, I did design a few circuits to control/measure high current/voltage circuits successfully. I guess I could order from Ali, I did find the conversor you recommended there. I was just looking for the optimal price/time. Thanks for the help anyway.
 
Top