Universal Adjustable Voltage Converter Powered by USB with QC Mode Support

Not long ago, I ordered an interesting little gadget from AliExpress. I didn’t have any particular use in mind—I just bought it because it was inexpensive and had some unusual features. But as usual, it’s best to read all about it in the review. I hope you’ll find it interesting.


Price: $4.23 + $1.77 shipping to my country

This converter is marketed as a heavily simplified “bench power supply” powered by a USB power adapter.
Brief specifications:
Input voltage: 4–13 V
Output voltage: 0.5–30 V
Output current: 0–2 A
Output power: up to 15 W
Voltage display: 0.1 V resolution, ±0.1 V accuracy
Current display: 0.01 A resolution, ±0.05 A accuracy over the 0.05–2.2 A range
Power display: 0–15 W
Overtemperature protection: shuts down above 100 degrees; press the power button again to turn it back on.
Quiescent current: 30 mA
Short-circuit protection
Weight: 52 g

The converter arrived in a compact foam box. The packaging reminded me a bit of RDtech products.


It’s designed like a “flash drive”: the module has a USB plug that connects to a power adapter. As before, I have to say I’m not too happy with the design: the board is completely exposed on one side, so anything could get inside, including something conductive.


I thought my USB tester was pretty large, but I was wrong—apparently there are even bigger USB devices.


1. A four-digit, seven-segment LED display is on top. To its right are two LEDs indicating that the converter is on and that it has entered CC mode (current limiting).
There are also two trimmer potentiometers to the right: the lower one adjusts the current, and the upper one adjusts the voltage.
2. The bottom only has the model name and input/output ratings.
3. The front has a USB plug and two USB ports, USB Type-C and microUSB, so there are three ways to supply power.
4. On the opposite side is a button for selecting QC, AFC, FCP, SCP, and automatic control mode for power adapters with fast-charging support.
5. On the end, next to the display, are two more buttons. The left one turns the unit on and off and also resets the overload mode; the right one selects what to display: voltage, current, or power.
6. There are no connectors or controls on the other side, just the converter components.


There’s a matte protective film on the top (and bottom). I removed it later, but the display still isn’t very easy to read, in my opinion, because the case is made of clear rather than tinted plastic. The photo on the right shows it without the top panel; with the panel on and the film removed, it’s a little easier to read—not much, though.


That’s why I did all the tests and demonstrations that follow with a piece of red filter film over the display. I think it looks much better that way.

When power is applied, the display shows “Auto.” The Chinese developers really do a number on the letter t: I’ve seen a version where it was displayed as r, making it read “Auro.” It would have been much simpler to show a t in a simplified form, without the left-hand part of the horizontal stroke.


1–3. Voltage, current, and power display. Press the Select button to cycle through them; the fourth press starts automatic cycling, but in practice this mode is very inconvenient.
4–8. Manually select the power adapter control mode for fast-charging protocols.
9, 10. Off mode. But it doesn’t actually turn off completely: the output voltage is disconnected, but the display stays lit and shows zero output voltage. In other words, the controls and display keep running independently.
11, 12. Minimum and maximum output voltage.


1, 2. The unit’s own current consumption when on and off is about 60 and 15 mA, respectively.
3, 4. The converter was connected to a QC charger and automatically selected a 12 V output, but you can also set any voltage manually without a problem.


As I’ve already mentioned, the case design is simple and basic: two pieces of plastic with a circuit board between them.


The circuit board looks neat, though, and for a device in this price range, it’s excellent.


The TM1650 LED display driver is mounted on the bottom, with a microcontroller underneath the display itself. Or rather, I’m assuming it’s a microcontroller, since I didn’t desolder the display, but there’s definitely a chip there.


1, 2. USB connectors. I can't speak for the extreme ends, but the USB plug looks well made.
3. The power supply rails use ordinary, probably the cheapest, capacitors: 220 µF 16 V on the input and 100×35 on the output.
4. Near the output terminal block and current-sense shunt is an LM358 op-amp, presumably responsible for amplifying the shunt voltage and the output-voltage measurement signal.


And here is the “heart” of this board: the universal converter itself, built around a SEPIC topology. Don't confuse it with StepUP-StepDown designs, where the voltage is first stepped up and then stepped down (usually using two separate PWM controllers and two inductors), or with a universal converter that has one PWM controller and one inductor.

I've talked about SEPIC converter topology many times, and even suggested a simple way to modify a StepUp converter by adding a few components. These converters are usually easy to identify by the presence of one PWM controller and two identical (this is important) inductors.

This converter can both step voltage up and step it down, which is why, with an input voltage of 4–13 V, it can output 0.5–31 V.

It's controlled by an FP5139 PWM controller and an NCE6075 power transistor. Notably, there's an inductor on the output to reduce ripple, followed by an additional capacitor.


Since in practice we don't set the voltage directly, but simply adjust it while watching the voltmeter, this is really a test of the voltmeter and ammeter's measurement accuracy.

In short, across the entire range the voltmeter reads 0.1–0.2 V low, which is more than the stated 0.1 V error. I wouldn't call that critical—this isn't a precision instrument, after all. And claiming 0.1 V accuracy with a resolution of 0.1 V is rather optimistic, since that's simply not realistic.


While adjusting the output current, I ran into a few “glitches.”
1, 2. For example, with no load connected and the current adjustment knob turned fully counterclockwise, the output voltage jumped from 0.5–1 V up to 4–7 V.
3. The same thing could happen with a load connected and the voltage knob turned fully counterclockwise: the current could jump from 300 mA to 4 A, even though the converter is rated for a 2 A limit. In other words, the limit simply wasn't working in this case. Be careful.


The current readings are much like the voltage readings: the ammeter reads about 0.06 A low, despite a stated error of 0.05 A. It only settles down at currents above 2 A. The maximum output current is 2.3 A; beyond that, it simply won't let you adjust any further.
I think it might be possible to improve this, though you'd have to change the current feedback divider, power transistor, and inductors, and possibly the capacitors too. The meter itself can display higher currents, as you can see in the previous photo.


The remaining tests were run with this setup: QC-capable power supply, USB tester, the converter under test, and a ZKE EBC-A10H electronic load.


Because this is a SEPIC, I ended up with a ton of graphs. Tests were run at two input voltages (5 and 12 V) and four output voltages (5, 12, 20, and 30 V). The current was increased until the converter either shut off its output or dropped the voltage to the load's cutoff threshold (0.8 V).


I'll tuck the rest of the graphs under a spoiler, since I couldn't think of a more compact way to present them :(


When the current limit was exceeded, the converter simply went into current limiting. When the power limit was exceeded, it shut off the output and displayed an overload message. It could be turned back on either by pressing the power button or by disconnecting and reconnecting the input voltage.


Since the USB tester measures voltage before the shunt—that is, at the power supply output—I connected a second tester to the output of the first to get a more accurate efficiency measurement. It measured the voltage at its own output, which is almost at the converter input. “Almost” because there is also a voltage drop across the connector contacts, so the graph shows a slightly worse result than the actual one. I think we can ignore that in this case.


I ended up with two graphs. The first is for an input voltage of 5 V.


The second is for 12 V. The load was operating in constant-power mode, so the values at the bottom of the scale correspond to power in watts.


Ripple measurements at the converter output in different operating modes. Ideally, of course, I should have powered it from a linear power supply to eliminate any influence from the power supply itself, but unfortunately I don't have that option right now.

No-load operation, modes:
5-5
5-20
12-5
12-20


Input: 5 V; output voltage and load, respectively:
1, 2. 5 V, 5 and 10 W
3, 4. 12 V, 5 and 10 W
5, 6. 20 V, 5 and 10 W


Input: 12 V; output voltage:
1, 2. 5 V, 5 and 10 W
3, 4. 12 V, 5 and 14 W
5, 6. 20 V, 5 and 14 W


Just as an extra test, I checked operation with 5 V at the input and 30 V at the output, at 9 W. I also happened to catch a strange waveform at the output with a particular combination of settings: in this case, 12 V input, 20 V output, and 10 W. I didn't see it in any other mode.


So, what do we have in the end?
This converter is definitely intriguing and, in its own way, quite interesting. I'm not entirely sure who the target audience is, but it works and displays not only voltage and current, but power as well. It can step voltage up or down, control QC, AFC, FCP, and SCP modes, and adjust the output voltage and current. You could even use it as a charger or a basic “bench power supply,” though its power is limited to 15 W.
Speaking of power, at an output voltage of 5 V, for example, the maximum will be around 10–11 W because of the current limit. In other words, the converter has two limits—current and power—and whichever is reached first determines the maximum. At voltages above 7–7.5 V, you can get the full 15 W. You can power it via USB-A, USB-C, or microUSB, which is convenient.
The output current and voltage aren't set digitally; you simply adjust them while monitoring the voltmeter or ammeter.
It has short-circuit and overload protection. Overtemperature protection is claimed but wasn't tested. There's also a fuse on the board.

In short, it's an interesting device, especially at this price, but I still don't know what I'd use it for.

That's all from me. I hope you found this useful.