Simple DC to USB-C PD (power delivery) 100W  - Page 1
Forum section: electronics / projects

author: flaviu
author_rank: Newbie
timestamp: March 27, 2022, 01:45:17 pm
content: Hi, I need a little bit of help from a genius mind.What I need to achieve is an USB-C adapter which should work from a fixed 20V 5A power supply.Basically the USB-C adapter should get the power from the fixed 20V DC and depending on the consumer to deliver over the USB-C PD all the voltages ( 5, 9, 15, and 20 V at 5A)The biggest problem I have is that I have to keep the BOM between 1 and 3 USD (excluding the 20V power supply and the USB-C receptacle)What I am looking is either a recomandation for a chip which can do what I need (having the mosfets integrated) or some other solution with external mosfets but to remain in the 1 -3 USD price pointIdeal would be a working schematic for the entire project.Is there anybody on this forum who could help me achieve the above?

author: Boscoe
author_rank: Frequent Contributor
timestamp: March 28, 2022, 06:54:56 pm
content: What you're really talking about is a three IC solution. One for the negotiation along the CC lines, a buck regulator and an MCU to coordinate everything. Remember, the buck needs to be a programmable type. The ACT2831 is a fantastic SEPIC solution but will consume a lot of your budget on its own.Don't forget, the power on USB is a minefield mishmash of standards which are impossible to achieve in one solution. For example, you have the 'non-standard' tying up of the USB data lines to indicate an amount of power that can be delivered. On top of that you have the USB 2 power negotiation up to 2.5W (some devices will not consume it, if they cannot negotiate) and then USB PD on top of all that.

author: bugrobotics
author_rank: Regular Contributor
timestamp: March 29, 2022, 02:43:08 pm
content: I'm not sure about your BOM cost but the OnSemi CYPD3177 is gonna do what you want as far as simple control. I've messed with it and it is one of the simpler PD interfaces. Good luck finding USB PD stuff at the moment.

author: thm_w
author_rank: Super Contributor
timestamp: March 29, 2022, 09:13:06 pm
content: Quote from: flaviu on March 27, 2022, 01:45:17 pmWhy? Do you not have access to 110V?edit: I meant mains voltage for those being pedantic.

author: tooki
author_rank: Super Contributor
timestamp: March 30, 2022, 03:24:36 am
content: Quote from: thm_w on March 29, 2022, 09:13:06 pmWell, no. They’re in the UK, so 240V.(Not that North America is 110V, either: we’ve been officially 120V, not 110V, since the 1950s.)

author: flaviu
author_rank: Newbie
timestamp: April 04, 2022, 02:17:39 pm
content: Thanks all for the answers.I am not sure I was very clear in my initial post, so I am ammending my initial post.What I need to do is a small device which has a specific function (which is not related to this post). Because I don't want all these devices to have each an individual power supply my plan is to chain multiple devices to share the same power adapter.USB-C power supply -> device 1 -> device 2 -> device 3 -> device Nbecause these devices needs 20V as an input I was thinking each device to have an input USB-C from where it gets 20V and an output on USB-C with a 20V output so that I can connect the next device into the output of the previous device.Each individual device will have an MCU and is not part of the current BOM constrain.What I need is a schematic in which a device negociate with the upstrem power supply to get 20V at max I (Amps) and to negociate further to the next device to deliver 20V and remaining Amps (taking in coniseration the actual device consumption - which probably is in the order of miliamps)my limitation is in the BOM costsIs there anybody having the time to help me do this? I am willing to pay for the work.

author: Fredderic
author_rank: Regular Contributor
timestamp: April 04, 2022, 03:42:43 pm
content: I don't know a darned thing about USB-C… Except that it's a rite pita, and the chips you get usually either give you power from USB-C, or give you USB-C from power, so you're probably going to need one of each, per device.But I'm feeling it's not going to stay 20V through all those devices, unless you boost it back up again. Or get a higher voltage, and drop it down. Either way, in each device.Easier, would probably to use a dumb power supply that puts out a suitable voltage a little higher than you need, on a simple plug, pass that through your device chain, and buck it down in each device. Give it enough head room for a little loss at each step.

author: thm_w
author_rank: Super Contributor
timestamp: April 04, 2022, 11:11:30 pm
content: Quote from: flaviu on April 04, 2022, 02:17:39 pmIn the future start by drawing a system diagram of what you are trying to do. By not fully explaining your original need and what devices you are using it causes confusion.Fredderic pointed out a good solution, whats wrong with that?Or why not have a squid cable that supplies power to each small device, instead of having a series chain cable?I'm not sure why this power supply has to be USBC, and can't just be a two wire 20V power cable that connects between devices:20V↑↓A <---> B <---> C

author: flaviu
author_rank: Newbie
timestamp: April 05, 2022, 10:27:22 am
content: Hi,You are right, I could have post a more clear question/request from the begining. Unfortunately at that time I didn't realized that my question will not be clear enough.What Fredrerinc propose may be a cheap solution, but in order to reduce the e-waste footprint I would like to use a standard USB-C adapter which can be reused for something else, or repurpose from something else and used with my device.

author: Someone
author_rank: Super Contributor
timestamp: April 05, 2022, 12:23:18 pm
content: Quote from: flaviu on April 05, 2022, 10:27:22 amSo you're stuck with the expense of the (non-trivial) silicon to support the complex PD protocol.Focusing too much on one characteristic of the system and hoping/demanding it will all fall into place around it doesn't work. Sometimes a more expensive cable mated with cheaper connectors is the better solution, sometimes the opposite. I get the attraction of volume produced 100W power supplies with commodity pricing, but you're not going to get access to the symmetric commodity sink/device parts (or you wouldn't be asking here, the rep would have provided you with the design kit). Time to leverage the existing CPU you have to drive the PD protocol and come up with some clever arrangement to shuffle the power.

author: flaviu
author_rank: Newbie
timestamp: April 05, 2022, 12:58:39 pm
content: that's why I asked for help here.... hopeing somebody with a genius mind could help me.

author: Someone
author_rank: Super Contributor
timestamp: April 05, 2022, 01:34:39 pm
content: Quote from: flaviu on April 05, 2022, 12:58:39 pmI saved a meme for just that:https://www.eevblog.com/forum/chat/mods-are-asleep-post-eevmemes/msg3384958/#msg3384958* removed direct image posting after the OP says this isnt a commercial/for profit project. Yet has a super tight BOM cost...

author: flaviu
author_rank: Newbie
timestamp: April 06, 2022, 09:06:16 am
content: Someone, this is very rude of you.I am not doing this for money, it is a hobby project for me. I have almost no experience doing any electronics and I am trying to learn, also as you could see in my post above, I have offered to pay for this work.

author: thm_w
author_rank: Super Contributor
timestamp: April 06, 2022, 11:13:22 pm
content: Maybe rude, but assumptions are made when details are left out. Knowing if the project is hobby or business is useful info to provide.It also doesn't make a ton of sense to me either, to be willing to pay for a design, but then have a BOM cost limitation of $1-3.Anyway, for the sink side:-HUSB238-IP2721- A premade STM32sink modulefound on Ali for ~$1, then solder to your boardFor the source side, that is just not possible for $3. The control IC alone costs that much.You can look at:https://www.digikey.com/reference-designs/en/power-management/usb-power-delivery/2583

author: flaviu
author_rank: Newbie
timestamp: April 08, 2022, 09:34:10 am
content: Thanks thm_w,Your recomandations are very good. Especially the HUSB328. They also have a USC-C PD source which is in the ~1 USD + MosfetI really appreciate your recomandation.THank you,