i have multiple power supplies in series that charge multiple different vehicles of different voltages.
We’re clogging up this thread, taking it to PM.
My apologies everyone, went too far before I realized how many posts we had.
1 Like
Anything move on this?
Usual disclaimer: non-expert, speculation, don’t take this as gospel
I’m a bit hesitant trusting myself to design power electronics for >10w, especially when the device on the other end has a propensity for fire. So I was just looking for a combination of prebuilt modules rather than an original design.
Get a USB PD dev board like this lad (not a spoofer, they seem to be just for triggering one voltage so they’re less universal) to negotiate between a few different input voltages depending on which supply you’re using.
Attach it to something like this, set your output voltage and current, then glue/silicone over the trim pots so it can’t get bumped. Probably add a digital panel meter so you can check it, and stick em all in a 3d printed enclosure
Two main downsides (which at present make it questionably useful)
-
The USB negotiation board can’t communicate with the boost converter. So if you set your boost converter output for 50.4V-1A, you’re probably fine with a 20V-3.25A input. But if the charger only supplies 15V or it does 20V but can only give 45W, the boost converter doesn’t know that and has a high chance of pulling too much current. As a result this “dumb” setup would need to be set with a very conservative output. You’d be leaving power on the table if a 100W supply was connected but only drawing ~45W, but at least it would trickle charge off a wider range of supplies. You could get around this by using a simpler 20V spoofer module so it would only work off higher power USB PD supplies but it would at least be at >1A
-
The only boost modules I can find that go above ~36V tend to be built for much higher power so they’re big. Hilariously big when you consider you’re likely to be getting <1A charging out of them.
Not super important numbers:
The power available at 15V or 12V is (almost always) lower than at 20V. Common voltage-current combinations are 9V-3A (27W), 12V-3A (36W), 15V-3A (45W).
Then 20V has a bit more variability, some supplies do 2.25A (45W), some 3.25A (65W), some 5A (100W). The headline spec is always the maximum supply power, but a 65W charger can’t usually deliver 65W at its lower voltages. There are exceptions just to keep you guessing, in my experience the most common source of this weirdness is phone chargers, particularly from Xiaomi and their derivatives. They like to do weird shit like 11V-3A.
1 Like
I haven’t actively developed anything further on this, but I have tinkered enough with my own PD negotiator board that I got the FW implemented to the point where I can communicate with a PD source device, enumerate the power profiles, choose one of them and request it. In my development I have tested with a Lenovo 60W PD charger that I bought with my own money and I tested a HP PD 60w charger at the office also and it also works (enumerated, reads power profiles and is able to choose one).
The main IC is a STM32G0-series MCU with the hardware peripheral for the USB PD comms, although you need a logical layer in the firmware to actually do anything with it. There’s also a lot of other things that I wanted to test with this board initially and that’s why there is a lot of stuff on it. It’s also a bit dusty as it’s been sitting on my work table for some time.
Basically you’d just implement a boost/buck-boost SMPS after the USB-C connector behind a protective FET (or other switch between the USB-C connector and the input of the converter), so you can then convert the supplied voltage from the USB for the wanted load and make sure you have enough feedback to monitor that the input power from the USB side stays within the negotiated limit. I would be able to implement this with my current knowledge and the new max 240W support with the PD 3.1 would make it actually pretty good power wise.
4 Likes
Hey Simo, any plans on making this available to purchase? 