I know this is a little off topic, but people in this forum seem quite knowledgeable about the construction of DC-DC converters, so please, please don't roast me =)
I need to build a dc-dc converter that takes an input that constantly varies from ~18-24v and outputs 12vdc at ~12 amps continuous. The voltage may go transiently go to 36v or it may drop to 0v at times. Below an input of 14v or so it should shut off and it should also have over current/thermal protection if the current gets too high. The input voltage will be 18-24v most of the time. Precise regulation of the output voltage is not important.
Efficiency of this circuit is the most important to me, followed by low part count, then cost. It also needs to practically design itself since I'm pretty unskilled when it comes to circuit design=)
My current plan is to use a few LM2677's in parallel with a 555 timer as suggested by "n-channel": here:
http://www.diyaudio.com/forums/showthread.php?postid=167812#post167812
Does anyone have any better suggestions for IC's? Something more efficient or less complex? How about whole circuits that are ready to go?
I need to build a dc-dc converter that takes an input that constantly varies from ~18-24v and outputs 12vdc at ~12 amps continuous. The voltage may go transiently go to 36v or it may drop to 0v at times. Below an input of 14v or so it should shut off and it should also have over current/thermal protection if the current gets too high. The input voltage will be 18-24v most of the time. Precise regulation of the output voltage is not important.
Efficiency of this circuit is the most important to me, followed by low part count, then cost. It also needs to practically design itself since I'm pretty unskilled when it comes to circuit design=)
My current plan is to use a few LM2677's in parallel with a 555 timer as suggested by "n-channel": here:
http://www.diyaudio.com/forums/showthread.php?postid=167812#post167812
Does anyone have any better suggestions for IC's? Something more efficient or less complex? How about whole circuits that are ready to go?
Hello
I did a google search: http://www.google.com/search?hl=da&q="Synchronous+Buck+Controller"++40V&lr=
I'm sure you can find something that will work.
\Jens
I did a google search: http://www.google.com/search?hl=da&q="Synchronous+Buck+Controller"++40V&lr=
I'm sure you can find something that will work.
\Jens
Hi,
This looks like it could be ok in your application:
http://focus.ti.com/lit/ds/symlink/tps40057.pdf
When you do the layout, be sure to seperate the noisy part of the circuit from the feedback part.
That will secure proper circuit operation.
Best of luck
\Jens
This looks like it could be ok in your application:
http://focus.ti.com/lit/ds/symlink/tps40057.pdf
When you do the layout, be sure to seperate the noisy part of the circuit from the feedback part.
That will secure proper circuit operation.
Best of luck
\Jens
Thanks Guys,
stef1777:
These converters and others I've seen like them have a minimum voltage of 36v and 48v is needed to power up. I need a lower minimum like 14v.
JensRasmussen:
The tps40057 looks good, even though it's more complicated than I had hoped.
Any suggestions for an efficient switching mosfet to pair with this chip?
stef1777:
These converters and others I've seen like them have a minimum voltage of 36v and 48v is needed to power up. I need a lower minimum like 14v.
JensRasmussen:
The tps40057 looks good, even though it's more complicated than I had hoped.
Any suggestions for an efficient switching mosfet to pair with this chip?
pulexirritans said:
Hi,
I would go for something you can hand solder so Dpack or D2pack type mosfets is a place to start.
The TOP mosfet (switches from Vin) may be a single mosfet for this converter, but for the bottom mosfet (Active diode) it might be a good idea to parallel two devices to get the conduction losses down.
I would look at 30V-40V N-channel mosfets from:
Onsemi
Vishay
IR
Fairchild
ST
Low Qg and Low Rds is what you want.
What about inductor?
Switching frequency?
Remember that the ripple current in the inductor only is related to L, Vin, Vout and Fswitch.
In and output capacitor(s) (Ceramics are great here)
Some of the things to consider
There is no easy way to convert 100+ W with little loss
\\\Jens
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