Modifying Drok Buck Converter for Computer Control

[Crossphased]

So I needed a couple new power supplies for my lab, and my budget is tight.  I also need them to be capable of high current and low noise. I've got a couple 60 V transformers, just need to convert and regulate them to chosen voltages. I decided the best way to do this was to use a buck converter followed by a linear regulator.

I looked around and picked up a couple Drok converters off Amazon:
https://www.amazon.com/gp/product/B071LGTTRN/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

They actually work pretty darn good. The interface is not pleasant however, takes awhile to select a voltage. I want everything controlled by my microcontroller. So I made a schematic of the Drok converter, and modified the feedback circuit.

Here's top level function of the converter:



Relevant Components:


There is a riser board with LED read out and buttons that is easily removable. It just pulls out, no de-soldering. I pulled it out for these pictures. Here is the circuit for the voltage setting/sensing:


I have a feeling the Drok controller is using PWM to set the voltage, based on the multiple RC filters in the path R32, R33, R34, R22. The Drok controller is a STM8S103.
Here are some of the components in the above schematic:


To control the converter I'm using a DAC to inject a desired voltage in the circuit. I removed the resistor R33 to de-couple the Drok MCU control:


To set the voltage I injected various voltages and noted the output vs input relationship. Here's some data:


So if you're looking for a cheap power supply under digital control, it should be pretty easy to remove a resistor, solder a jumper wire, and hook it up to a DAC to set the output voltage. Hope this makes somebody's life easier! Cheers!

[Crossphased]

Also if you are curious, here is the pinout of the riser connection to the LED readout and buttons. The STM8 MCU is located on this riser board:

[Cata Lin]

Yes, your work made somebody's life easier
I have a remote location where I spend sometimes my weekends, there is no electricity and I am using the DROK DKP6012 PSU to charge my batteries from the photovoltaic panels, I found an interesting project, OSPController (https://github.com/opensolarproject/OSPController/wiki/Step-1-Parts-List#new-now-supports-multiple-power-supplies) and seems to work fine. Or for me worked fine for a while.
I have 2 photovoltaic panels, each one has output voltage open circuit 41.3 Vdc, I connected them in series so in ideal sunlight these can deliver a max of 82.6 Vdc (I have a 48 Vdc inverter, that is why I had to connect in series the 2 panels). The maximum input voltage for the DROK DKP6012 is 75 Vdc in specs. I checked the main parts for the buck converter, MOSFET, diodes, caps, all are rated for 100 Vdc, so they should handle well my 82.6 Vdc.
(Also the OSPController project mentioned that DROK DKP6012 can handle this extra voltage well)
When I tested first time the setup, all worked fine, my panels supplied 73 Vdc (winter sun), but a weekend ago, the panels were able to supply 78 Vdc (summer sun is coming) and I had a nasty surprise to see the input voltage 78 Vdc at the output, somehow the N channel MOSFET died (MPN is IPP045N10N3G from Infineon) and output was not regulated anymore.
I found here on the forum your reverse engineering work on DROK DKP6012 PSU and I wonder if you can have an advice on which parts / functional blocks can limit the input voltage at 75 Vdc on this PSU.
Can be the driver block for the MOSFET? Can be the feedback loop? Can be the PSU buck block for the control block (microcontroller PCBA)? Do you have some schematic for these blocks? Thanks!

[Pineapple Dan]

I am familiar with this OSP project. But I wonder would it not be less effort in the long run to make one's own buck converter instead of relying on Drok? I don't think the design of the Drok is that fantastic to make it worth the bother.

[rin67630]

Hi,
you may want to have a look at my project
https://github.com/rin67630/Drok-Juntek-on-steroids

It is up and running for quite a bench of Drok/Juntek converters.
Your post here helped me to understand how the Drok converters work.
Regards
Laszlo