New RuiDeng RK6006 Adjustable Converter

About a month and a half ago, I posted a preview of a new model of RuiDeng’s adjustable converter, the RK6006. Not long ago, I finally received it, tested it, and today I’ll share my thoughts.

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First, here’s a list of all the converters from this company that I’ve had a chance to try.
DPH5005
DPS8005
DPS5020
RD6006
RD6012
RD6018
RD6006P
RD6012P
RD6024

I actually ordered the converter back at the end of April, but it was shipped considerably later because of the holidays. To make matters worse, it arrived in Kyiv, then went to... Lviv, then back to Kyiv, and only after that made it to Kharkiv. I don’t think I need to explain why that happened; anyone from Ukraine will understand.
But in any case, it did eventually reach me, which of course makes me very happy :)

To get ahead of myself, I’ll say that several people who bought this converter during the promotion received theirs a long time ago, and judging by the reviews, they seem to be happy with it. So I hope the information really was useful.

Let’s get to the review.
I picked up the familiar polystyrene box at the post office, and as always, I’ll give this company a thumbs-up: at least they take care to make sure the device arrives undamaged.
Inside was a neat, fairly small box, noticeably smaller than the ones used for models like the DPS5005.


Here are the converter’s technical specifications.


I ordered the top configuration, which differs from the standard one only by including a Bluetooth module. Everything else is the same: the converter, a temperature sensor, and a fuse.


The temperature sensor and fuse are the same as those included with the RD60xx series modules. By the way, there’s only one fuse here too.


The module looks somewhat similar to the DPS/DPH series converters, but to me it has a more stylish appearance. The manufacturer seems to have tried to follow the design of the higher-end series.


As I noted, and as some buyers later pointed out, a huge advantage is that the dimensions are exactly the same as those of the older DPS/DPH series models. That means you can upgrade your old converter without any modifications. Just take out the old model, disconnect it, connect the new one in exactly the same way, and put it in the same place. How great is that?


The front panel has the same four buttons as the previous models, but there are some major changes here too: the buttons are now like those on the RD60xx models—soft rubber buttons with backlighting. They’re a pleasure to press, and I think anyone who’s used the older models will really appreciate this.
Otherwise, everything is straightforward: the buttons on the left select voltage and current adjustment modes, there’s a menu button, an encoder on the right, an output-enable button, and yes, a USB port. If you don’t remember, the older models had the USB port on a separate board that had to be installed somewhere else.
As far as I can tell, there’s galvanic isolation, though the previous models always had it too.


There’s a removable terminal block on the back, with the module’s input and output connections brought out to it.
A Bluetooth submodule board is tucked away on the side, along with the input capacitors: 150 + 220 µF, rated for 80 V.
The communications submodule is removable, but it’s not very convenient to install: the connector is tiny and sits deep inside the case.


The layout is really compact. Honestly, I’m impressed by the determination of this company’s engineers, who managed to cram all the electronics into such a small space.
You can see a transistor on the board. Based on my experience analyzing previous models, I’d guess it’s for reverse-polarity protection.
,There’s a fuse holder next to it, but there’s only one fuse here, on the output. That makes sense, since it’s much harder to blow the input fuse—and if you do, the repair probably won’t be easy. On the other hand, you can blow the output fuse by connecting a battery with the wrong polarity. Overall, everything looks good.
We can also see a couple of two-pin connectors: the one on the left is for the temperature sensor, and the one in the center is for the fan. That’s genuinely good, because fan control is definitely useful.

The fan turns on either when the current exceeds 4 A or when the temperature rises above 45 degrees, and turns off when the current drops below 3.9 A or the temperature falls below 45 degrees. The only downside is that the fan needs to be rated for 5 V and no more than 200 mA. But I think anyone who needs more will come up with something.


1. The PWM controller and all its supporting components are on a separate submodule. The circuit design looks no different from that of the RD6006.
2. There’s a heatsink on the board with two G080N10 transistors mounted on it, with an on-resistance of 11.2 mΩ. That’s also great: first, this is clearly a synchronous rectifier converter, and second, it uses N-channel transistors, which have better characteristics than P-channel ones, still sometimes used because they’re easier to drive.
3. The output has a pair of 330 µF, 63 V capacitors and a power inductor. There’s also an inductor on the board to reduce output ripple, so kudos to the designers for that too. Yes, 660 µF is certainly a bit much, and LED power supply enthusiasts will exclaim, “Our LEDs are doomed!” Well, yes, I basically agree. In that case, buy either a linear power supply or an RD60xxP. For such a compact, inexpensive device, this is normal.
4. There’s a heatsink on the board, and you can see an optocoupler on the right. I just didn’t quite understand what it’s for, since it clearly belongs to the power board, not the “brains” board.


Speaking of the brains, let’s take a look at them. To do that, we’ll remove the power board. I don’t recommend removing it at all; I’ll explain why later, although it comes out fairly easily.


There’s nothing interesting on the underside of the power board.


But the control board has a lot of components—I’d even say a whole lot.
There’s a microcontroller, ADC chips (if I understood correctly), and a tiny, annoying buzzer, which I disabled right away.



The photos didn’t turn out very well: the case reflects the flash, but I hope you can make out what’s installed.
1. The buzzer is at the top; thankfully, you can disable it in the menu. The power converter is there too.
2. Another power converter; the circuit probably uses two supply voltages.


Let’s put it back together and see what’s new in the converter’s software.
1–3. When you turn it on, the manufacturer’s splash screen appears, then the converter switches to normal operation. And here’s something odd: the first time I turned it on, the display showed some current and voltage, even though the output was off and, judging by the input current, no power was going anywhere at the output. I nudged the board and it seemed to go away; then I raised the supply voltage, and everything was fine. It hasn’t happened again since. The first power-up was after disassembly, and most likely the connector didn’t seat properly the first time. That’s exactly why I don’t recommend taking the converter apart: putting the board back in is almost a blind operation.
4–6. The information display design is almost an exact copy of its bigger siblings in the RD-60xx series—so similar that you can’t tell them apart at a glance. The only thing missing here is a real-time clock.

Honestly, well done. They’ve managed to fit everything that used to be shown on the large display onto the small one, including temperature, capacity in mAh and mWh, operating modes, input and output voltage, current and power, as well as the set values. And I wouldn’t say anything is hard to read; the varying symbol sizes and colors make it easy to read.

As for the controls, pressing the encoder changes the setting increment, but for voltage the largest increment is one volt, and for current it’s one amp, i.e. You can't adjust it in 10 V increments, but maybe that's a good thing.

What's more, the buttons light up green when active, and the three buttons on the left are also faintly lit in white, presumably by the display backlight. Looks great.



For anyone who's used similar devices, the menu is intuitive. The only item that stumped me was the Take Out setting. I looked up its description in the manual, which is very detailed, though in English. You can download it here.
When the Take Out option is enabled, the converter is supposed to save the current and voltage settings when switched off. But it behaves strangely; I still haven't figured out exactly how it works, even though I've tried enabling it. I'll investigate further.
Otherwise, this is a cut-down version of the RD60xx menu, though I wouldn't say it's cut down that much. You can set the maximum output power and screen brightness, adjust how information is displayed, choose from three font combinations, and pick from a whole bunch of color schemes.

So, as I wrote earlier, this converter is basically an RD6006 on a budget: the menu has been simplified a little, the clock and battery-charging output have been removed, and everything has been packed into a more compact case. The result is a great little unit.


Let's move on to the tests. For convenience, I'll present them in the same order as in my other reviews of adjustable converters.
Test zero.
1. Just a photo showing another font option; I later switched back to the one I'm more used to.
2–4. No-load power consumption at different input voltages, along with a quick check of input-voltage measurement accuracy. No issues here: at an input of 12 V, the maximum cutoff reading was 12.03 V, which seems fine to me.


Test one: output-voltage setting accuracy and the accuracy of the built-in voltmeter. I checked at 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, and 55 V.
The manufacturer specifies setting accuracy of +/- 0.3% +3 digits. In practice, the maximum deviation I got was 2 least significant digits; I didn't even get to percentage-level error. Five points.


Test two: the same thing, but this time setting and measuring current.
The results are much the same. The only noticeable error occurs at the lowest settings, 0.01–0.05 A. Otherwise, an easy five points: the converter stayed within the specified tolerance in least significant digits and never even reached percentage-level error.


While taking measurements, I got curious about the losses in this mode at different input voltages (12, 24, and 61 V). It turned out that the higher the voltage, the greater the losses; at an input of 61 V, they came to 5.75 W.

While preparing the review, I looked at this photo and realized why the converter had seemed so similar to the previous versions: they reused not only the component layout design, but also the color scheme. That's exactly why the new model looks like a scaled-down version.


Test three: how output voltage varies with load current.
I checked the voltage with no load and at a current of 6 A, at output voltages of 3.3, 5, 12, and 24 V.

Yes, there is some variation, but come on: 10 mV across a range of 44 mA to 6 A is a pretty good result, in my opinion.


Test four: the minimum input/output voltage difference at which the converter can still regulate.
1, 2. Input voltage was about 35.6 V; at a current of about 6 A, the output was 3.6 V.
3, 4. Input voltage was 54.6 V; at the same current, the difference was 5 V.

Honestly, I expected better results here. Even the hybrid RD6006P does better, so keep this in mind when choosing the upstream power supply.
Speaking of the upstream power supply, the manufacturer specifies a maximum input voltage of 58 V. I should point out that to get the specified 61 V output, you'll need a power supply rated for 66–68 V.
I'm often asked about using an upstream source with a conventional transformer. Yes, you can, but there's a problem: you have to design the transformer so that with no load and an input of 240–250 V, its output is no more than 68 V. But then, under load and with an input of 198 V, you won't get 61 V at the output. That's why using regulated power supplies is simpler and more convenient.

You can improve things a little by shorting the reverse-polarity protection transistor. You won't gain much, of course, but still.


Test five: measuring output-voltage ripple.

The test was performed at currents of 0, 1.25, 2.5, 3.75, 5, and 6 A, with an output voltage of 30 V, i.e. half the maximum. The probe was connected directly to the output terminals, with no additional capacitors.

The manufacturer specifies ripple of up to 100 mV peak-to-peak, and notes that the measurement was taken using -

I did exactly the same thing, except I didn't add a 0.1 µF capacitor, so in my case the ripple should be higher.

In the test, under the conditions listed above, I got a peak-to-peak value of about 60–65 mV, which is well within the stated specifications.


The current was the same throughout this test—6 A—but I varied the output voltage: 3.3, 5.0, 12, 25, 40, and 55 V. The largest peak-to-peak value was at an output of 55 V, but it still came in under the specified 100 mV, even with the “spikes.”


Test six: response to transients.

As always, I tested it in several operating modes:
1, 2. Applying/removing 5 V at the output.
3, 4. Response to connecting/disconnecting a load. The output was set to 12 V, with a 30 Ω resistor connected continuously and a 3.3 Ω resistor connected in parallel with it (or disconnected). So this tests the response to a current step from 0.4 to 4 A and from 4 to 0.4 A.
5, 6. Switching from CV mode to CC mode and back. Voltage was 14 V, load current was 4.5 A, and the current limit was set to 3 A.

No complaints about the transient response. In fact, everything looks fine to me here. I will note, though, that the voltage drops very gradually when switched off with no load. I noticed this while just playing around: unlike the RD60xx series converters, when you lower the voltage or switch the output off, it doesn't drop abruptly but rather gradually. The graph shows the voltage falling smoothly from 5 V to zero over about 0.8 seconds; from a higher voltage, the time will increase proportionally. Apparently, either there is no discharge circuit here—in essence, a current regulator that speeds up the discharge of the output capacitors—or it has very low power. It's not critical; I just noticed it.
By the way, startup isn't particularly fast either, although it's noticeably faster than shutdown, of course.


Test seven: using a TS-100 soldering iron as the load.
Overall, I think it did great. The control loop handles current fluctuations from about 0 to 50% load well. Models like the RD6006 and RD6012 had noticeable problems with this test.


Test seven: measuring the converter's efficiency.
Input voltage was about 60–61 V, load current was 6 A, and output voltage was 5, 12, 24, 36, 48, and 54 V.

Output voltage — efficiency — power loss
5 V — 83.4% — 6.3 W
12 V — 91.8% — 6.4 W
24 V — 95.3% — 7.0 W
36 V — 96.8% — 7.2 W
48 V — 97.6% — 7.1 W
56 V — 97.9% — 6.8 W

As you can see, the efficiency is quite good. The maximum power loss in this test was 7.2 W, but as I mentioned above, losses will be higher with the output shorted.


I checked the thermal performance in two operating modes: input voltage of 60–61 V, output voltage of 42 and 24 V, and load current of about 6 A, giving output power of 255 and 325 W, respectively.
And here I can tell you that the hottest component is... the current-sense shunt resistor, at around 100 degrees. The heatsink reached about 70–80 degrees, while the inductor was cooler still.
But keep in mind that the converter was sitting on the table; it will get noticeably hotter inside an enclosure. So I definitely recommend installing a fan if you want to draw more than 200 W for extended periods. At that power, though, you'll need a fan anyway, at least for the power supply.


In the comments on the announcement, I was asked to test for voltage “overshoot” while adjusting it. The request covered different operating modes. I checked a couple, but not because I was too lazy to do more—there was simply no point.
The screenshot shows the adjustment from 1 V to 10 V. You can see that the voltage rises fairly smoothly, so there's simply nothing you can do to make it “overshoot.” I tried turning the encoder as fast as I could.


A few words about the software. First, the PC version: you can download the latest software and manuals here.
This version also almost completely (if not entirely) mirrors the software for the RD60xx models. They even carried over the option to change the startup image.


There's a handy feature for programming automatic voltage changes: set the starting voltage, ending voltage, step size, and rate of change. The RD60xx had this too, though.


But I didn't mention this feature for no reason—there's a bug. For example, if you set it to adjust from zero to some voltage, but the converter already has a voltage set, it will first output that voltage, then zero the output, and only then start adjusting.
That is, If you set the adjustment range to 0–5 V when it was previously set to 50, the output will first go to 50, then drop to zero, and only then will adjustment begin. Be careful!!!!


The Android software is available as an APK file. There’s also an outdated version floating around there, possibly with a bug, so download the one without the word “delete.”

It installed without any problems and found the converter’s Bluetooth module just as easily. The only snag was the password: I tried 0000 first, but 1234 worked.


The software has fewer features here, but you can still control the converter just fine. I liked the handy feature for quickly choosing which graph parameters to display. The graph can show only two parameters at a time, and the four buttons below let you quickly choose which ones to view.
Otherwise, the software is mainly for quick adjustments; the PC version is more capable.

Yes, the front panel is locked whether you’re using a PC or a smartphone. So far, I think I’ve seen only one converter model that allows simultaneous control from both the software and the panel.




Conclusions.
In my opinion, this is one of those very rare cases where reality exceeded expectations. I mean, I’ve tested almost every converter model from this company, except the really old ones, so I had a pretty good idea of what to expect. But subjectively, I can say for sure that I didn’t expect it to be this good.
Sure, someone will say I’m praising it too much. But why not? It’s compact, has a good feature set, decent power and performance, precise adjustment, behaves well in dynamic tests, and its ripple is lower than specified.
The one thing I wish this converter had is a battery charging mode—that is, a feature that stops charging when the charging current drops below a certain threshold. Especially since this could be implemented in software.
There was something else I wanted, I think, but I can’t remember now. It must not have been that important.
One thing I can fault it for is the relatively large voltage drop. The manufacturer specifies a minimum difference of 3.2 V, but for some reason I measured about 5 V. Strangely, the difference was smaller at an input voltage of 36 V than, for example, at 60 V.

Otherwise, I’m happy with it and can definitely recommend buying one.

That’s all for now. I hope you found this useful. Comments and questions are welcome.