https://www.banggood.com/DC-DC-Step-Down-Power-Supply-Adjustable-Module-With-LCD-Display-With-Housing-Case-p-1038740.html?rmmds=buy&cur_warehouse=CN

Calibration method:

Under power off situation, Holdind left button and power the supply,when the display begin flashing, release left button, with multimeter measuring the output voltage, by press the left and right button ,adjust the multimeter measuring voltage near 5V, such as 5.00V ,4.98V or 5.02V is ok too,at this situation,please ignore the displaying on this item. After adjustment,please power off it and then power to it again, then the calibration is completed. Errors can be calibrated in 0.04V, if the error is greater, you can try to calibrate it again.

a little adjustable power supply, purchased off ebay for dirt cheap.

It can take between 4.5 and 23V in (recommended to stay below 20V) and has a 1.5V drop-out.

It’s claimed that it can source up to 2A continuous (with 3A surges)… I dunno

Winners Adjustable DC Power Supply (from ebay): review and demo
https://www.youtube.com/watch?v=Hh0tqsXY7P8

Buck-boost module teardown & test
https://www.edn.com/electronics-blogs/benchtalk/4460293/Buck-boost-module-teardown—test?utm_source=Aspencore&utm_medium=EDN&utm_campaign=social

A whole series of interesting and seemingly well-designed and -made power supply modules have come out of Rui Deng (Hangzhou Ruideng Technologies) of China over the last year or two.

The outputs aren’t super-quiet, but fine for general use. I may add output filters.

The LTC1871 on the little daughtercard is a boost converter running at a bit over 100 kHz.

The XL7005A is a buck switcher-on-a-chip, running at 150 kHz. In fact, the output switch is a Sziklai pair

The TL594 is a general PWM control IC, similar to the classic TL494, and runs at 68 kHz

The STM32F100C8 is an ARM Cortex-M3 microcontroller with all the usual trimmings.

What’s conspicuous by its absence? Yeah…switching MOSFETs. There are two SMT parts clamped under the bottom edge of the heatsink. I think we’ve found our transistors. No…I’m not removing the sink.

As I said, this crazy arrangement of three switching converters had me perplexed at first. I originally assumed there’d be one switcher

Yes… It seems the input (6-40 V) is converted to an intermediate 35.7-40 V, which is then stepped down to the desired output. That’s a bit surprising, given that losses tend to be exacerbated with high buck step-down ratios. I guess the designer felt this to be the best trade-off. If it works, who am I to complain?

That third switcher, the XL7005A? It appears to generate 5V, and there are two (I think) 3.3V linear regulators as well. The µC, LCD, and op-amp need juice too.

The MP2307 is a monolithic synchronous buck regulator. The device integrates 100mΩ MOSFETS that provide 3A of continuous load current over a wide operating input voltage of 4.75V to 23V.