Powering a display and RPi Zero of a single source

Recently purchased “https://www.ebay.com.au/itm/362919391987” and a RPi Zero, connected them up and powered them separately without any issues. Both the screen and RPi started up without issue.

Though when powering them both (or even just the screen) from a “2-way Fast Charge Buck Module” the screen fails to start up (starts, but resets a moment after the backlight comes one). After working through the issue with the eBay seller their suggestion is that it’s not getting enough power, they recommend 12v 1.5a 18w.

The buck should be able to handle this based off it’s specs and a couple times it has and also the screen works when using an old phone USB C phone charger.

Any suggestions on what might be going on here or possible alternate ideas would be great.


Hi Andrew,

All Raspberry Pi boards are officially documented as 5.1VDC devices, it seems a bit odd when most people can get them to work on 5VDC just fine but there are caveats and gotchas to be aware of, there was a long discussion on it in this thread which you may find relavant.

The 2-way Fast Charge Buck Module is a bit of an odd device because it is trying to use a charger as a power supply which are two very different design goals.
The first problem will be that the Pi Zero doesn’t support a fast charging protocol so it will just appear as a dumb 5V device to the charger. I suspect the display won’t use these protocols either and wants 12V.
I’m not sure that this buck module will support two different outputs, especially when neither have the protocol to request their preferred voltage supply.

What kind of power input socket does your display use? We can help you come up with a power supply solution better suited to these devices.


Hi Andrew, that fast charging module max output is 3.4A between 2 ports or 1.7A per port. I am not sure if the 3.4A will be proportionally distributed.

The Zero may consume a max of 1.5 watts with HDMI signal output. So it would not have any issues with power.

The ebay listing for the display is sparse on the power consumption during working. Gives only the standby consumption. If it works with a USB C phone charger, it might need full 2A (That is the lowest I have seen with my Samsung charger with USB A port. The USB C charger is 3A). What you can get is a power delivery optimized charger with a USB C port (3A) and a USB A port and give it a try. Try Anker PD charger. The description assures 2.4A at 5V per port.
Anker is a reliable manufacturer. I use their products.
Just test the display with A 2A USB A charger. If it works it will work with the Anker product.


Hi guys
The old favourite has come up again. Trying to use battery/phone chargers as power supplies.
Two entirely different devices.

If what you need is a power supply then use a power supply.
If what you need is a battery/phone charger then use one of those.
Don’t get the two mixed up.
If you need 5V and 12V there are plenty of dual output power supplies out there. MeanWell make a selection and they seem to be an OK product.
Cheers Bob


Hi Andrew,

I suspect you’re getting tripped up with fast charging protocols. The problem with USB these days is there are many different standards and protocols that all use the same USB connectors.

Looking at the eBay listing, it’s actually unclear what USB variant they’ve implemented for the screen - especially when they describe the power input as ‘HDMI Type C’, while the images clearly show a USB C connector for power.


I suspect that you’ll need to use a ‘dumb’ power supply to power this screen, like the official Pi Power supply - which just provides power and does not attempt to protect the device attached from drawing too much power.

Fundamentally, I think you’re trying to use smart power supplies which require the device to politely ask for more power or voltage, and won’t give it unless nicely asked. Your devices aren’t capable of asking nicely, so they won’t get the power they need.

You need a supply that doesn’t care about manners and protocol and will give your device as much power as it will take - even if that much could burn up the device.

You also need it to be a nice clean and stable 5v. Battery chargers take a rough and dirty 5v and clean it up themselves. You need your supply to give you a clean input - this is what Bob’s referring to above about the difference between a ‘Battery/Phone Charger’ and a ‘Power Supply’.


The title of the 2-way Fast Charge Buck Module will lead people to think it can be used as a power supply. It is designed as a fast charger !!!

Because it can change its output voltage, I would be very hesitant to use it other than as a charger. Especially to power a Raspberry Pi. (Compatible with Raspberry Pi 4B & Jetson Nano) should be removed from the title and a warning saying it is a Fast charger only added; then threads like this would not exist. While it probably can be used as a 5V source it is not intended to be used that way.

@Andrew4045 Suggest you find a power supply that has 5V and 12V outputs at enough current to power screen and Pi; as @Robert93820 has said. AND is compatible with HDMI Type-C power connector.

As @Oliver has shown the display has a Type-C Power Supply and uses it in the HDMI format. As I understand it Type-C format is complex and not all manufacturers support all the formats. I don’t think the 2-way Fast Charge Buck Module is going to do what you want.

With respect to Type-C, always use the manufacturer supplied cables and devices, other cheaper cable I have bought have not worked.



Ahh, that’s another new one! I didn’t realise the HDMI forum had jumped on the Type-C connector bandwagon too. This only makes life more confusing for consumers - what a labyrinth USB is these days!

I knew there was a A Billboard Device Class, Audio/Video Device Class, and a USB Monitor Control Class in the USB specs, and that USB 4 allows for Display port tunnelling - all of which are used by different devices for image display, but today I also learned that the USB Type-C connector has also been adopted by both the HDMI Forum and the Display Port forum for raw transmission of their data via Alt-Mode.

It’s certainly a Universal connector! If only all its features were Universally supported as well!


Hi All
Re the controller board for that display.
What an extremely clever piece of work. I assume the type C connector in the middle is for some sort of communication and oh goody, right alongside this is a type C power connector.

Now I have no idea what voltage is expected on this power connector, nor am I likely to find out or worry about it. Just doing something like this is a complete turn off for me and I would steer clear of anything from this manufacturer. I find purchasing from China directly takes far too long and personally I try to purchase locally and somehow hope the items in question are not made there.

Maybe swapping connectors will not do any harm, then maybe it will. I am afraid I have not got a lot of sympathy for anyone who purchases anything made like this so if this characteristic results in smoke think of it as a lesson.
Cheers Bob


Did some poking around in the US ebay site and found the similar product from the same vendor. It has a bit more info on power in the photos and also the connection sequence. Attaching those photos for a quicker look-see.
Power supply suggestion: (18W PD)

Connection sequence:

Unfortunately, the 30pin connector product has same lack of information in the US ebay site as well (sold as a bundle with a 10.1 inch screen)


That would be a couple more reasons not to purchase it
Cheers Bob

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Thanks for the replies, going to run through a couple of the suggestions and try and see how it goes.

Was hoping the USB C port would make it simpler, oh well.


Keep us posted. I am sure all involved are interested to see your solution.
Cheers Bob


Did some testing with a couple charges/power supplies and found it will run as low as 5v/2.1A. So just need a power supply that can output 5v/2.1A for two USB devices (one for the screen and one for the Pi).

Ideally I want to try and power this from a single source and split once inside the device. Having a look around, would something like this do the job (https://core-electronics.com.au/5v-3a-dual-usb-step-down-buck-converter-module.html)? Can wire up an external connector and then use the two USB connections to power the screen and PI.

Also, if anyone has suggestions on where to get screens like this from somewhere more reliable that would be great.



2.1 + 2.1 = 4.2. you are short about 1A for a start.
You still have to input 8V to 32V input to this device and allow for conversion efficiency.

Looking at all this what in the hell is wrong with getting a power supply which will do the job. Say 5V at something like 5A or more and all your troubles would be over in one go.

You have shown that 2 supplies of about 2A will work then what is your problem. Just go ahead and do what I suggest above. Get a supply at 5V at 5A or more and be done with it.
Cheers Bob


I’m sure that one will work and think I’ve probably got one laying around, only reason I ask is just to make the final solution a bit cleaner by not have extra cables running around and a longer cable with a barrel jack is simpler then messing around with multiple USB extension cables.

The end solution will all be enclosed and if possible only having a single power cable would be ideal. If not, then a power supply and two USB cables will do the job.

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Hi Andrew
If it is to be enclosed then hard wire your 2 units to one connector.
Cheers Bob


Unfortunately it’s the way things are headed at present. The USB-C connector is used for everything these days - the one bit of good news is that (assuming things comply with standards) you can’t blow something up by plugging the wrong thing into a USB connector. It just won’t work instead.

I’m sure it’s a complete nightmare for the engineers though.

He might not be all that short. The Pi Zero can run off a few hundred mA if its USB ports aren’t loaded up.

Still probably a bit tight though if the screen’s pulling 2.1A at steady state.

@Andrew4045 Bob’s advice of going with a 25W 5v supply is solid I reckon. You can power a pi zero via the 5v on on the GPIO header without any issue, which means you only need three one USB connector.

You could even use a little USB breakout board if you wanted.

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Hi Oliver

The trouble is they nearly always finish getting loaded up. Then everything is short a few mA. Why not make provision for a few extra eventualities right from the start.

I have learned a philosophy or two when starting on something like this. Start by working out how much power you might need for everything (in Watts). Try to stay away from all these buck and boost converters. You lose 15% to 20% and sometimes more every time you convert. Only do this if you really have to. Then add a fudge factor of at least 50% or more likely 100%. Select a power supply the next size UP from that. Keep away from power banks and phone chargers. May use smaller supply on individual components as a temporary measure for a short time. You can go back to volts and milliamps (or Amps) at the end of the day when power requirement is finalised.

Doing that means I usually have none or very little trouble with this aspect of things. That is why recently I have been playing with Neo Pixel LED strips for XMAS lights. So far I have 2 X 5 metre strips. BUT I have a 14A power supply to run them. Room for expansion??? I believe I am not going to have any power problems.

Example: One of the later projects I was involved in while working required everything to be de-rated to 50ºC. Now when performance figures are usually quoted at 25ºC you may be surprised at what happens when you do this. A 60W power supply rapidly becomes 120W or even 150W to guarantee the required 60W at 50ºC. Resistors and similar components suffer too. A 1/2 W resistor will be rated at 1/4 W and so it goes on. The real world may surprise some.

Cheers Bob


The step down buck I linked before says that it can do 5v/3a on both USB ports “Its two USB ports can output 5V/3A at the same time”. Would have though that’d do the job unless I’m missing something.

With the powering the pi via the gpio, and then only needing the single USB port, where would I be patching the 5v for the pie from? Thinking I’m missing a part with that idea.

And definitely in future gonna do more planning around power. Was actually hoping this one would be simple just using ‘standard’ USB connections. Oh well, live and learn.


Btw, thanks for all the help.on this one, still getting my head around the electronic side of these projects.