Adjustable voltage converter RD6006P (not a review)

RuiDeng continues to develop its RD60xx series of adjustable voltage converters, and information about a new model appeared not long ago. But instead of the expected RD6024 with a 24 A output current, which was supposed to be the next model after the RD6018, they decided to take a small "step back" and return to the 6006.

As before, this post isn't an advertisement, and apart from a link to a Taobao page with some information, but effectively no way to buy it (unless you're willing to shell out $15k), there's nothing yet. Although it's already available on AliExpress.

But this looks like an interesting model, so I decided to take a closer look at how it differs from the previous ones, and just discuss whether it's worth it.

So, externally, it's the same familiar design as the RD6006, 6012 and 6018 models: a panel that fits into the same cases, the same control buttons, terminals, and so on.


And according to the main specifications, the unit has the same parameters as the RD6006: output voltage up to 60 V, current up to 6 A, and therefore power up to 360 W.


It also looks like there are no planned changes to connecting it to a PC or smartphone. So there are three options: USB, which all models have, or, using separate modules, either Wi-Fi or RS485.
By the way, here's a question that's been nagging at me: will the developer ever implement a simple way to assign a local network address for access over Wi-Fi? The connection does work now, but in practice it's often a real "song and dance".

It could all be much simpler: let the address be set manually or assigned via DHCP, but have the software find the device automatically and locate it on the local network. Or, again, let the software accept a static address for the converter...




I've gotten sidetracked. So, the first key change: the current and voltage setting/measurement resolution has been increased tenfold compared with the RD6006. The minimum step is now 100 µA instead of 1 mA, and 1 mV instead of 10 mV.
Presumably, all measurements are now made using a separate ADC rather than the one built into the microcontroller. The question of how current and voltage are set remains open, though. As I understand it, there should also be a separate DAC, but in this case, "that's not certain."

In any case, I consider this change either a key one or close to it. I also think we can expect at least an 6012P model, with 12 A and a 1 mA step instead of 10 mA.
There is, however, a second complication that I've mentioned several times before: with a two-wire connection, all the benefits of setting the voltage this precisely are lost. Though, if you think about it, setting the voltage with 1 mV accuracy isn't all that useful anyway.


Naturally, they had to find room for the extra digit on the voltmeter and ammeter, so the display has been tweaked a little. The previous series is on the left, the new model on the right.
And speaking of the display, why not add a menu option for temperature units and show the reading in both Celsius and Fahrenheit? There's no point in that, and it takes up space...


The settings menu has changed too. It looks like they've also decided to add an option for setting the maximum output power, as on the 6018 model, which I think is a good thing.
They've also added options for choosing the font color. And if you look at the bottom of the screenshot, you'll see that there are more languages: French, German and Russian have been added to the familiar English and Chinese. And for some reason, I even have a pretty good idea who had a hand in that :)


In addition to the color, you can choose different display styles and fonts. Here, too, I think we should thank the user with the nickname UniSoft, who got this process started on their own.


But what interested me personally was the second, and in my opinion, fundamental change. This is a change to the power supply topology, which turns it from a switching supply into a hybrid one.
If you look closely at the circuit board photo, you can see that the developers have not only significantly rearranged the components, but also added another heatsink.


The PWM regulator components are mounted on one heatsink, and the linear regulator components on the other. At first, I thought the linear regulator components were on the heatsink on the right, and even started estimating the voltage drop across it.
But on closer inspection, I noticed that there are two components on the right-hand heatsink, in different packages: a standard one and an insulated one. The linear regulator only needs one transistor.
So most likely, the PWM regulator's transistor and diode assembly have been moved to the right-hand heatsink, while the linear regulator is on the heatsink with the fan. That means there's a chance the voltage difference will be at least 1–1.5 V. In addition, this cooling design gives us reason to hope for a 6012P version too, which would be simply fantastic.

The main PWM controller is most likely still the same TL594. On the right, you can also see the input reverse-polarity protection transistor and the PWM regulator that powers the entire unit.



Among the other changes, they’ve fitted a different current-sense shunt, presumably with a lower TCR (although it’s still a two-wire type); otherwise, increasing the current measurement resolution would make little sense. There’s also an added optocoupler, most likely somewhere in the linear regulator circuit, and an unidentified black rectangular component near the edge of the board by the fan.
The location of the resettable fuse is a little questionable, though maybe I’m just nitpicking at this point.


So, there are clearly significant changes to both the software and hardware. Of course, I’d like to see a higher current rating—not 18 A, but 12 A would be quite enough. In my view, though, the most significant change is the move to a hybrid topology. The ripple will most likely be higher than with a fully linear power supply, but lower than with a switching one, although this mainly affects the reduction in output capacitance.

And of course, I’d like to hear what everyone thinks of this unit. If you have any corrections, please let me know—I’ve only been able to assess it based on the photos.