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[SOLVED] Low Cost 12v to 5v DC to DC switching reg alternatives to LM7805

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castingflame:
I have a requirement for some 12VDC to 5VDC switching (buck) converters to replace the ubiquitous fixed linear LM7805 regulator.

I currently use the Traco TSR1-2450 and there are similar modules available from Murata and Recom. They are perfect for what I need but the downside is cost. They normally come out at around £6 to £12 delivered. I am looking for something closer to £2-£3 delivered.


Requirements

* Pin compatible drop in replacement for the linear 78 series regulators.
* £2-£3 delivered.
* Existing module or homebrew tiny footprint pcb is okay if similar to 7805/Traco footprint.
* 800mA min up to 2Amp max.
* For more detailed spec requirements look at the Traco TSR1-2450.
I am happy to buy an existing module like the above or alternatives. Additionally,
I am happy to create a tiny PCB with SMD components and make the units myself if need be.

I don't want to get into the dark art realms of switching designs, so any new design will need to be based on existing schematics.




Thanks




Gyro:
Sorry to say that you're always going to be onto a cost loser trying to fit a pin-compatible switching regulator drop-in for a linear part. The only completely cost-effective way is to modify your board design to include the revised regulator circuit on board.

I understand your nervousness about getting into a switching design but this is a pretty much jellybean application these days, a switching chip, inductor, rectifier and a few caps. A lot more compact if your existing board is smd. All switchmode IC datasheets will include a sample circuit, and many, an example layout too, though the pinout usually makes this self evident.

Your though about building your own tiny smd board is the second best solution. You can prototype it with minimal risk to your product. This ebay listing shows the minimal level of complexity.. https://www.ebay.co.uk/itm/1X-MURATA-POWER-SOLUTIONS-7805SR-C-IC-SWITCHING-REGULATOR/392356245046?hash=item5b5a412e36:g:sP8AAOSwtV1dOjvW  (that is a high quality one by the way). It still won't be as cheap overall as integrating it into your main board due to cost of header, separate PCB, additional assembly etc, but that really depends on your volume.

You can probably easily meet your £2-3 goal if you purchase less tightly specified PCB modules from China but I wouldn't really recommend that path.


P.S. Ignore the details of that ebay listing - it's from one of those unscrupulous ebay sellers who re-list RS and Farnell parts at twice the price, it was simply an easy-to-hand photo to demonstrate the board complexity. That one has a lot of capacitance on board, whether you need that much really depends on the noise sensitivity of a circuit originally expecting a linear regulator - hard to comment without knowing more details of your board / product.

Zero999:
There was a thread a couple of days ago about a Chinese DC:DC converter module, which appears to be suitable for replacing the LM7805, at a lower cost, especially given that no heatsink is required. I haven't tried it, but don't expect 3A of output current, keep it to 1.5A maximum.
https://www.eevblog.com/forum/chat/has-anyone-tried-this-buck-converter-board-42-cents-each/
https://www.aliexpress.com/item/32884011122.html

voltsandjolts:

--- Quote from: castingflame on October 14, 2019, 08:31:36 am ---I am looking for something closer to £2-£3 delivered.

--- End quote ---

2.60+VAT at quantity 1
https://uk.farnell.com/2760747

mariush:
Make your own, using dc-dc regulator ICs like

AOZ6662 (35 cents each if you get 25): https://www.digikey.com/product-detail/en/alpha-omega-semiconductor-inc/AOZ6662DI-01/785-1858-1-ND/10258157
AP65111: https://www.digikey.com/product-detail/en/diodes-incorporated/AP65111AWU-7/AP65111AWU-7DICT-ND/7652826
AP65211: https://www.digikey.com/product-detail/en/diodes-incorporated/AP65211AWU-7/AP65211AWU-7DICT-ND/7652825

examples of fixed voltage regulators:
AP1509 : https://www.digikey.com/product-detail/en/diodes-incorporated/AP1509-50SG-13/AP1509-50SGDIDKR-ND/1301964
AP63205 : https://www.digikey.com/product-detail/en/diodes-incorporated/AP63205WU-7/AP63205WU-7DIDKR-ND/9858432

Add an inductor that's 50 cents or less, a diode, a couple ceramic resistors and capacitors

PCBs can be ordered at jlpcb for 2$ for 5-10pcs, or you could probably order a big panel with 50-100 to-220 sized circuit boards for something like 10-20$

With the first regulator, it's running at high enough frequency that you'd be able to use smaller ceramic inductors and capacitors, so basically you could make your whole board surface mount and put solder paste on pads then components on top of pads and heat the tiny circuit board with a hot air gun or even go as far as to heat it on a metal plate on the kitchen stove

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