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DC-DC Buck Converter Questions

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Ultron81:
I'm replacing the linear power supply in a game console to save space and get rid of the large heat sink. The supply is a 7805, and I would say normal conditions draw 800mA, maybe max current draw is 1A. The input to the console is ~17VDC unregulated, coming from a wallwart. I plan on redesigning the power board, since it has a RF modulator on it that I don't plan on using in my new design.

I've never really dealt with the design of a buck converter before. I did do a lot of reading online, but I'm still a little confused.

I see there are non-synchronous and synchronous converters. What would be the best to use in my case? I've been looking in the 5V/1.5A-2A range.

The part that really throws me for a loop is the switching frequency. I see some switchers at 150kHz, but then also a lot at 1.4MHz. What would be a good all-around frequency to use?

I was looking at this part, but couldn't find much information on anyone's experience with it - http://www.ti.com/product/TPS5405

I also saw this, looks like a direct 7805 replacement, though expensive - https://www.digikey.com/product-detail/en/murata-power-solutions-inc/OKI-78SR-5-1.5-W36-C/811-2196-5-ND/2259781

Thanks in advance!

noname4me:
https://uk.farnell.com/wurth-elektronik/173010578/dc-dc-conv-buck-5v-300khz-sip/dp/2577479?st=Magi3c%205v

Even simpler?

It's a pin for pin compatible replacement for the 7805...

Sent from my SM-N960F using Tapatalk

Ultron81:
Thanks, I'll check these out

Buriedcode:

--- Quote from: blueskull on August 30, 2019, 01:07:38 am ---Keep it simple and stupid, and cheap.

https://www.amazon.com/dp/B01MQGMOKI

--- End quote ---

I would be wary of those modules.  I have no doubt the IC does what it claims, but the IO caps tend to be grossly insufficient.  I would at least test the device with your average input and output voltage, and maximum current to see what the ripple and regulation are like.  The few of those I have tried were good up to about 600mA but lost regulation beyond it.

wraper:
As you don't know much about them, better stay with lower frequencies. High frequency DC/DC converters are finicky and very sensitive to board layout.

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