@demef758

One of the problems with ALL of these modules, real or fake, is that the catch diode is only rated for 1A while the spec says that the maximum output current is 3A. The catch diode rating must be rated for the same current as the output current. Pull 3A out of these modules and you will notice the catch diode gets real hot! Replace the diode with a 3A/40V Schottky.

A second issue is the use of aluminum capacitors in a switcher application. If these caps are switcher grade, they have much lower ESR (equivalent series resistance) than typical cheap aluminum capacitors. The former are rated for switching applications, the latter are rated for 120 Hz applications. Switchers create a lot of high frequency triangular current waveforms that must pass through these capacitors. If the ESR is high, then the capacitor will generate a lot of I^2*R power loss and heat up the capacitor, limiting its useful life. I seriously doubt that a cheap $1 module uses switcher-rated aluminum capacitors! The ESR of the output capacitor has a significant effect on the ripple output voltage. Again, a lower ESR filter capacitor will lower the output ripple. Better yet, tack on a decent 1uF/35V ceramic capacitor (has almost zero ESR) across both the input and output capacitors and you will see both the input and output ripple voltages drop significantly, and the switching waveforms will be much more stable!

EDIT: the uber-slow switching speed is also the result of these cheap aluminum input and output capacitors. Parallel ceramic capacitors (with voltages rated for the input/output voltages) and you should then see much smaller ripple voltages as well as the switching frequency increasing. However, one thing I have seen in some of these cheap buck converters is the typical Chinese modus operandi, where they wipe clean the controller chip's markings and laser etch a different part number on it.  There is another National switcher that runs at 52 kHz, I think it is, and that's what you will get on the board! It SHOULD be an LM2596, but it's actually it's this much slower chip. Hey ... what do you expect for $1?

@jamesbrown99991

LM2575 has 52kHz switching frequency. It's possible you have some rebadged LM2575, or rebadged fake LM2575.

@Bapate-rh9be

I bought a whole bunch of these exact buck converters 1 year ago and I use them for a lot of applications. Most of these applications do not require anything spectecular (i.e. power a bunch of 12V fans after upgrading a 3D printer to 24V). They perform quite well in these applications. I remember measuring the ripple on the output and I do not recall anything quite that high. I suppose they might have changed the IC in the meantime, as back then they were also quite a bit more expensive.

@AccessAccess

Read the whole datasheet.  Many of these converters are designed to skip cycles or "beats" and will do so when operating at lower current draw.  National refers to this as "discontinuous mode", other manufacturers may use "burst mode" or some other terminology.  If the inductor value is not properly chosen for the operating parameters of the supply (voltages, current draw, etc.), the circuit may only be capable of discontinuous mode rather than being able to transition between the two modes as necessary.  So while the IC may be counterfeit, it might be performing like the real thing, only that the inductor on the module is too low resulting in the converter skipping cycles and the ripple being quite high.  Or perhaps the ripple may be elevated due to their being no load, or insufficient loading (very little current draw) on the circuit, and it will drop to better levels once an actual load is applied.

@foogod4237

I wonder if the reason it gets so hot is because they used a circuit design intended for 150 kHz but the fake chip is only running it at 50 kHz.  That would make the choice of inductor and other components not well tuned to the frequency they're being driven at, which could result in increased inefficiency and heat generation than the circuit is supposed to produce.

@JoseGustavoAbreuMurta

To identify the frequency of the internal oscillator you can scope pin 2 of the LM2596. Thank you for sharing this information.
I tested 6 modules LM2596 . All  are fake with 50 KHz from China!

@p4spooky

Excellent video. Will be very useful if you can show what happens when you install the original  IC to max current/ripple and switching frequency and temperature measurements

@uwepolifka4583

Very informative video.
I bought some of these modules a few years ago. At only 1,1 A and from 38V down to 30V the coil becomes so hot that it melts.

@PeterM-PeterM

I have used this module before in a small, non critical application with no issue. I was about to start using them to power some sensitive electronics... I can't thank you enough for the demonstration. I will be looking for a different device for my sensitive equipment.

@beforebefore

Never run electrolytic capacitors at their rated voltage - if you want it to last reasonably well. The nor. Al design guideline is to not exceed 89% of the rated voltage.

@EJEuth

This IC is in fact the LM2576 that runs at 52KHz, per TI’s datasheet. So, it is “re-baptized ” as LM2596, but the IC doesn’t know it should now oscillate at the remarked frequency of 150KHz.

@lohikarhu734

this kind of very low frequency,  with big ripple, can sometimes be traced back to your test setup.
if you are running a fairly high load current and have insufficient input capacitance, or too much resistance, or poor regulation, in your bench power supply, the device will "motorboat", not actually reaching a stable operating point, it keeps "re-starting", as its soft start can't get it running, and it just keeps re-trying to start, and 15-50 kHz is pretty common.

@tttuberc

Great video.  I've always wondered why these modules are so cheap compared to cost of parts I buy from Digikey

@ABehrooz

You're using the wrong datasheet. The input limit for DIP LM2596 is 37V +/- 4%.  You also killed the output cap. which contributes to the voltage deviation. the frequency is not guaranteed since you have no consumer and the output cap is broken. there are output ESR constraints that are probably not met with the dead cap. The HVS version with 63v input cap can accept up to 58 volts. and no more than 28 volts is recommended for the S version. The packaging and font is not necessarily fake because there are multiple package factories. source: I've used dozens of these. all versions.

@copernicofelinis

From my experience, markings on ICs and transistors bought from Chinese resellers on the marketplace are just... decorations. They have nothing to do with what's inside the case. Also, you need to convert from Chinese units to SI units by diving by 2. If it says it will withstand 1 Chinese ampere, it will only withstand one half SI ampere.
They can still be useful, tho.

@konradgrima2872

As usual great educational videos, keep up the good work.

@beakytwitch7905

I use these without problem, well within the supposedmaximum specifications.  To solve the output ripple I use both ferrites for high frequency switching noise, and resistive regulators for the 50 kHz ripple.  The result is reliable, clean, stabilized volt factories.

@1djbecker

I'm surprised that this wasn't about the knock-off chips being marked as the HV variant.  Rather than working up to 60V, these fail at 30v-40v with an internal short that applies full input voltage to the output.

I'll use them, but not anywhere close to their claimed input voltage.

I'll have to check the still-working modules I have to see what the switching frequency is.

@Noname-hc4hc

This chip is a remarked lm2576. The spec matches quite well.

@FixitEasyDIY

Excellent brother 😊 Thanks for the great video ❤