KORAD KA3005P Schematic Design Details and Teardown
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- čas přidán 5. 04. 2024
- NOT Another KORAD Teardown !! :-)
Well no, not even close. Today's videos is me ans you going through the Schematics and the Electronics Design of my Trusty KORAD KA3005P that I have since 2015, Highlighting the good and the less good Design Decisions and how it Works.
I this Video are of-course some Brain Farts too :-) for ex. I called the Optocouplers on the Interface Boars 3N45 which are in reality 4N25.
Please don’t forget to like and subscribe. Thanks for watching...
!!! Thank you to all my subscribers !!!
#korad
#powersupply
#linear - Věda a technologie
excellent analysis
Thankyou !
The way how output transistors (power board Q1, Q2) are controlled by main board seems fascinating. The main board's supply seems to bootstrap itself to float on top of (power board) Q3's base by controlling the current through (main board's) Q4.
Nuvoton sounds quite foreign for many of us, but it's a very popular brand because they have such a wide variety of chips they sell at large volume that you can both get a chip ideally suited for your use & get it cheap. It's a spin-off of Winbond, the manufacturer we most often see making motherboard IC's and EEPROM/Flash or RAM
Hi Anna, Thankyou!
U5b & u7B pin 5 should be tied to ground with a 10nF cap.
The op-amps have an UNBALANCE frequency response between the two inputs - A BIG NONO!!!!!!!!!!!!
It likely will help with your "crazy" response to TESLA coil issue.
Hi Steven, Thankyou !
This PS is old, it's 2013 or older, maybe at that time the dacs weren't as cheap as now, now you can get those under $1usd in single unit quantities, maybe even weren't available in China at all at that time. Now there are some switching power supplies from China that includes 16bit TI dacs. Great vid, subscribed.
Hi , Thankbyou, the spoken dac is from the early 2000’s was just an example, the developers would have used a 12bit dac made for the asian Market like the Nuvoton mcu’s.
@@KonstantinGrigoriadis most of the nuvoton mcu's used for this have the ability to put out 12bit on their own DACs. They very likely ended up going the way you can see here due to either preexisting designs that were retrofitted with a newer MCU, or the lack of R&D money, or some strange limitation that is due to architectural differences between the Nuvoton and whatever the Nuvoton ripped off. That latter issue can make them behave weird, and it cripples the GigaDevice ADC's unless you hack in workarounds or code with their own API for an example.
On another note, the shift registers you noted are sub-cent parts at times. The DAC's with sufficient performance can definitely reach tens of cents.
Hi Anna, probably they just used a dac design the had used before and they had the code for it proven and tested. Even if the shift registers are dirt cheap, using more than 60 components to build just 2 12 bit dacs is ridiculus , this makes the design susceptible to noise for no real benefit.
@@KonstantinGrigoriadis I suspected as much!
The rationale seems on point. Replacing a proven firmware with parallel drive to a book DAC with a serial I2C drive could have been the difference between a working product and a warranty neightmare.
I can imagine the discussions between the engineers and the product manager
Thanks for the very nice and detailed walk through.
To answer the question "why an externa EEPROM ?" I think it takes quite a beating even under regular use.
The settings memory is dead in mine, so I have to replace this EEPROM.
The issue shows up this way:
- If at startup, the values show up correctly, the power supply will work normally until next power up.
- If at startup, the values do NOT show up correctly, the power supply will continue displaying garbled data no matter what operation you perform and lock up within 20s
I can not confirm this as I haven't had time to perform the swap yet.
I have to be absolutely sure to read the old data in case there would be calibration data in there.
Hi Daniel, Thankyou! Yes Probably its easier to change the EEPROm than the MCU if the EEPROM Memory of it fails, Of course they could optimize when to absolute necessary to Write, but its easier and safer like that! hope there are no cal data there!
Hello I have just bought the 10 amp version of this PSU, it is a beast. It has a much beefier fan heatsink arrangement and transformer , but otherwise very similar. Thank you for posting circuit diagram, never know when I might need it? Great analysis too, pity about the vast resistor array, I did wonder of it's purpose. I have learned a lot from your post, Regards Graham
Hi Graham, Thankyou ! Cheers, Konstantin
They could have made a DAC with excellent linearity by filtering down slow PWM. It’s one of the approaches used in the design of metrology-grade voltage sources. The resistor array is cute looking though.
Hi, yes it looks interesting of course :-)
Thank you for the video. Probably going to pick one of these up. They seem more quality made vs the ones you can buy for $40 less. Hanmatek branded, switching supplies. I don't need the serial communication, so I'll go for the D variant.
Hello, I have it since 2015 and works fine :-)
@@KonstantinGrigoriadis I hope mine lasts just as long. Only using it for voltage injection, finding shorts in macbook logic boards.
muy buena explicacion una pregunta que diferencia tiene esta fuente con las que son copias de la misma es el traformador o que es
Hello Jose, Thankyou, for what I know, there is no real Difference to the other Differently name Branded Versions of the KORAD except of the Name. The others ones are not Copies but Rebranded OEM Versions of it.
Cheers, Konstantin
I have one of those supplies and reverse engineered it several years ago. I too was surprised that they used such an old design for the A/D.
Other than the lazy design, it has worked for me!
One thing I did not like is the way the wires are routed between the power transformer to the back power board. The sheet metal baffle is SHARP and can cut the wires, so I re-routed the wires and cleaned up the edge of the sheet metal so it wasn't sharp, and put a piece of tape on the edge.
Where did you find the schematic?
Hi, yes the metal sheet in the middle is sharp and can damage the cables, therefore i put the cables in a Protective sleeve. I found the schematics in the internet, cheers, Konstantin
I wonder how the output voltage of those DAC's get calibrated ?
Hi Laszlo, good Question. In this Design there is only doing it by software either by :
1) adding a correction list(Array) over the DAC Range by sampling a number of Points in the Line and correcting the Output accordingly.
2) or by reading back the output of the 2 Dacs and correcting the Output accordingly. (by dont see anything in the Schematics for that)
This is one further Disadvantage of this Discrete Design Because of the Resistor Value Errors and thermal Drift. Even the Reference Voltage for the R2R Ladder is from a simple LDO.
I like your presentation. Where did you get the schematics from?
Thankyou ! The schematics are from a private CN forum.
Does anyone know if it's possible to buy a new main board? The microcontroller on mine died.
Hi, i have not seen one yet being sold , cheers, Konstantin
I have the same power supply (branded Velleman LABPS3005D) One annoying thing with it is it rounds up the voltage shown on the display when the voltage is a little below the set voltage. When charging a LiPo battery with settings 4.2 V and 1 A, the voltage is shown correctly for a while as the voltage rises towards 4.2V. But around 4,10V (or thereabouts) the voltage suddenly jumps up to 4,20 on the display when the actual voltage is lower. The PSU nevertheless delivers the full 1 A until the voltage actually reaches 4,20V. Why did they do it like that? It is silly. Is it the same bug on the Korad?
Hi, I never used the KORAD as a charger, normally this should not happen bcs as seen in the schematics the Regulation Loop is purely Analog and not through the MCU. Seems to be only a Display Issue the has to do with the Internal 12Bit ADC or the code driving it, when the jump occurs, did you measure the real Output Voltage ?
Can't confirm. My Korad KA3005D behaves correctly in such a case
Hello, In what case ? Inductive loads or High EMC Pulses ?
@@KonstantinGrigoriadis I answered to the upper message. No issue with charging of li-ion batteries
@@hrandib Ah, OK Thankyou!
Thanks for the upload and greetings! Are the resistor array maybe old design they just kept?
Hello Arve, Thankyou, discrete R2R Dac (except in high end Audio) is gone since the 80‘s , the only reason I can Imagine is that they had the code ready for a proven working Design and used it, to speed up development.
@@KonstantinGrigoriadis yes makes sense. No one had to hand solder it😀😀 just computer design and pcb robots.
Wonder if it comes down to cheapness, 5c for all those resistors vs cost of the DAC? At least too you'd never have trouble of not being able to source the DAC :)
The 52 resistors the 3 74hc595 and a dual opamp, I dont think thats really cheaper than the 2 dacs i mentioned.
But wait, no need to use big brand dacs, they can use cheap dacs made for the asian market, like the nuvoton mcu’s
BTW Paul, if you want the Schematics, send me an Email, Friday this Week when I am back i can send it to you
Can we increase amp of this psu .i have 5 amp version
Hello, no bcs of many reasons, 1) the software does not support more, 2) the transformer is for 5a, 3) the power stage is not designed for higher currents, Cheers, Konstantin
@@KonstantinGrigoriadis thank you for explaining. ...
Where did you get schematic please share link
Hello,send me a Mail to send you the files.
Cheers,
Konstantin
can you share schematic pdf? thank you.
Hello, Yes, send me a mail to reply you.Cheers, Konstantin
Посмотри PSL-3604
Hi, thankyou I know this Design, for some Years, I like it and his other Designs, Cheers, Konstantin
Subscribed, very well presented.
Thankyou and Thankyou :-)