QC 3.0 controller for repairing a charger

Not too long ago, I posted a review of a QC 3.0 charger. It was very cheap when I bought it, but turned out not to be fully functional. Specifically, the QC feature itself didn't work. I found the right chip on Taobao, ordered it, repaired the charger, and decided to report back in case it might be useful to someone.


Lately I've been seeing quite a few reviews of counterfeit components: relabeled parts, faulty components, outright fakes, and even empty packages with leads. So even though the price here wasn't very high, I was still a little worried.

As I mentioned, I needed a QC chip. It would be a shame to lose that feature in the charger, and since I was putting together another order anyway, I decided to add some of these too.
I needed a specific chip, which I mentioned in my previous review: NT6008. I couldn't find it locally or on AliExpress, but I saw plenty of them on Taobao and decided to save a little more. When searching, I selected free shipping. Shipping to the forwarding agent usually costs $1.9, and sometimes as much as $7–8, though in that case it was probably just a seller's trick.
And I did find them. The search returned three options, but I didn't like one store's name, and another one was selling plumbing supplies or something. In the end, I chose the ones priced at 2 yuan (about 30 cents).


At first I wanted to order three, just in case I broke one and lost another, but after a while I got a message in the forwarding agent's chat saying the seller would ship a minimum of 10 pcs. I figured they might come in handy later and agreed, although of course that made it more expensive.


Eventually I received a large package with a second, smaller one inside from the seller. Given how little the chips weigh, I think most of what I paid went toward shipping the packages.


Inside was a standard tape with ten chips. So far, so good.


The marking matches the listing: PGZ6A1. The chip in my charger was marked PGZ691, but that doesn't really matter; the important thing is that it has PGZ6.
The package is TSOT23-8, but this chip is also available in an MSOP-10L package, so be sure to check the photos too.


This controller supports QC 2.0 and QC 3.0 Class A.


The Class A designation means that, unlike full QC 3.0, the maximum output voltage is limited to 12 V rather than 20 V.


The application is pretty simple and basic: this controller sits between the output terminals going to the load and the PWM controller's feedback input. Technically, it works as a "spoof", since the PWM controller doesn't even know what the actual output voltage is.
That's exactly why I agreed to buy more chips: I'm planning to make some small chargers of my own, but not the ordinary step-down converters that are already everywhere for about a dollar and a half. Instead, I want to combine a SEPIC converter with QC, which would effectively let me get 5–12 V from 5–20 V in any combination.


The datasheet shows an example circuit using this controller; I've highlighted it in red. It works here with the NT3875A PWM controller, and judging by its description, its feedback is set for an output voltage of 5.2 V. Anything higher is achieved thanks to the QC chip.
In very simplified terms, it works like this:
1. Your smartphone wants 12 V.
2. The smartphone sends a command to the QC chip: I want 12 V.
3. The chip receives it and "shorts" the lower resistor in the converter's feedback divider.
4. The converter thinks, oh, the voltage has dropped; I need to raise it.
5. The voltage rises until it reaches 12 V.
6. The QC chip maintains this steady state, and we get the required 12 V at the output.

Basically, you could probably modify just about any converter this way. I'd love to find similar chips that support 20 V. Has anyone come across any?


Here are the patient and the medicine. Time to start the treatment :)


The chip is buried deep inside, but the important thing is that it's the right one. The rest is just a matter of technique.


I picked up the soldering iron and started desoldering it, but it was very awkward, even though it was doable.


After inspecting the board carefully, I realized the heatsink could be removed. The USB connector next to the chip was still in the way, of course, but it made the job much easier.


1. First, I add a drop of solder to each side of the chip to melt the original solder. This helps heat the contacts faster, and the extra thermal mass makes it possible to remove the chip from the board by heating the sides one at a time. In some cases the chip may be glued down, but I was lucky this time: it came off relatively easily. Low-melting-point solder can also help sometimes: it dissolves the original solder and lowers the overall melting temperature.
2. Then we need some alcohol, cotton wool and tweezers. The last two can be replaced with a cotton swab, and the alcohol with acetone, but you need to be a little more careful with acetone than with alcohol, even though it cleans more easily and effectively.
3. Use the soldering iron to remove the excess solder, but it's best to leave a little on the pads so it'll be easier to solder the new chip in place later. Clean the work area with alcohol.
4. Next, we need some flux. I'm using our F-3, from an old stockpile.


1. Apply flux to the contact pads. Don't skimp too much, but don't flood them either. A small brush works well for this. I usually use fiberglass sticks, but this time I just applied it with tweezers.
2. Use tweezers to position the chip and solder any one of its pins in place. It doesn't matter which one or how the joint looks; the important thing is that the chip sits straight. Two pins bridged together when I soldered them, but they are actually connected on the board anyway.
3. Apply a little more flux and carefully solder the remaining pins, then touch up the first joint.
4. Once again, use alcohol and cotton wool to remove the flux from the board and the chip. And that's the whole process.


The moment of truth: could it really be a fake? No, everything is working fine so far. The output is 5 V; before the repair it was around 8 V because the chip was faulty. I only fitted the heatsink here for the photo; otherwise, the board kept falling over. You can leave it off while testing, so you won't have to remove it again if something goes wrong.


1. List of supported protocols.
2. Switch to manual control mode. The default is 5.21 V; apparently, the feedback circuit is configured here the same way as in the example above.
3. The minimum setting is 3.8 V.
4. The maximum is 12.13 V.
5, 6. In QC 2.0 mode, you can select only fixed values: 9 and 12 V, plus the standard 5 V, of course. QC 3.0 allows finer voltage adjustment, which is essentially what sets it apart from QC 2.0.


That wraps up the repair. I often see people say that you need special equipment for this kind of work: a soldering station, hot-air gun, desoldering pump, desoldering braid, and so on.
The photo shows everything I used for the replacement, right down to a piece of cotton wool. No special tools at all.


The same goes for the soldering iron: no T12, Quick or anything like that, just a basic Solomon. Below is a photo of its tip next to the old chip.

Why did I take this photo? People often ask me, “Which soldering iron or station should I buy? Which tips should I use?” I find those questions hard to answer because I'm used to working with all kinds of tools, and what works for me may not work for you.



And that's about it. The charger is repaired. At the very least, the replacement chip is working; at best, all the others are too. The price was more than reasonable. According to the weighing at the forwarding agent, it came to 2 grams, and since that was just a drop in the ocean compared with the rest of the shipment, shipping was practically free. Of course, ordering just these chips would have been very expensive, and it would have been easier to buy another charger.
For now, I've tossed the other chips into my desk drawer, but I want to make some small boards that can be added to other converters (any kind) to give them QC. Might come in handy someday :)

I hope you found this review useful.