DC-DC Buck Converter Questions

[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...

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[Ultron81]

Thanks, I'll check these out

[Buriedcode]

Keep it simple and stupid, and cheap.

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

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.

[wraper]

Keep it simple and stupid, and cheap.

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

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.

Caps of such size should be sufficient because of 1.5 MHz switching frequency. Actual capacitance may be lower than needed though. I would suggest converter with non regulated output voltage. 3-12V range is questionable and should be sub-optimal in most of range.

[yashrk]

Keep it simple and stupid, and cheap.

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

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.

Caps of such size should be sufficient because of 1.5 MHz switching frequency. Actual capacitance may be lower than needed though. I would suggest converter with non regulated output voltage. 3-12V range is questionable and should be sub-optimal in most of range.

He is replacing an existing linear regulator so it must have external capacitors already available onboard which he can replace to get the requisite capacitance.