PocketPD - USB-C Portable Bench Power Supply

We are very happy to introduce the project page on CrowdSupply. Please sign up so we know how many people is expect the product so we can plan the manufacturing accordingly. Also, don't miss the part where you can pre-order the unit at launch!

Another firmware pre-release (V0.9.5). We now has a Menu to select between different profile! The firmware is still under test for edge cases.

Long press VOLT/AMP button to enter the MENU. If you change your mind, just hold the VOLT/AMP button again to cancel. Use the encoder to scroll through the menu and long press the encoder to select your desire profile.

At Boot, default is still PPS profile at 5V and 1V limit.

We are actively working on the firmware update so that our complete prototype user will have the best experience! 

Some feature that we are now support:

• Press any button to skip booting and capability display.
• Blinking cursor so you know which digit and which parameter you are changing.
• Fix encoder skipping step

Note: We just happen to test on older hardware. Don't worry, the pinout is the same!

A refined version of the PCB has arrived. This version will support 5A, seem cool to touch under our recent 5A load test. Firmware is under development for this newer board to provide profile selection and better control response via encoder. Other component like case and lid are arriving a bit later in the month. The product will be online for purchase on June 30th.

We will be presenting at CrowdSupply 2024 - Portland, OR on June 23rd, 2024! If you are around, come and check out the project in person. We will also have other products on demo like PPSTrigger and AndroidAuto Fast Charge Injector.

Unlocking more ability from your USB-C Charger

A big thanks to our beta user for your feedback. We have incorporate many of the suggestion into the newer layout and design. Here is some sneak peak on our recent layout update:

• Standard 19.05 mm spacing for banana clip
• Optional footprint under XT-60 for standard 5.5x2.1mm DC jack
• Input capacitance meet USB-PD sink standard
• Dimmer Status LED
• Support 5A full USB-C PD current

Beside hardware, we have a long task list for the next firmware version that will add extra menu to provide protocol selection.

After a long wait from our PCB vendor, the boards are already here. This is the first batch to confirm our wiring, mechanical test, electrical and thermal performance.

It is good news that the wiring is all good. The board boots up with some code modification from the previous design. We can work more on the mechanical design but overall it will FIT inside a case!

The port layout works a bit better than we expected. The buttons' spring force and height are just right. The screen height is low enough not to shadow the button labels.

The initial thermal test shows that the output switch selected is good for 3A continuous. We will also move the location of the status LED so that it can be used at night without being too bright.

The next step for these 4 boards is to design a case for them. Let us know if you want to be our beta user and explore the application with USB PPS!

It requires some modification to the AP33772 Library but it seems like the current limit is working on our device.

Here you can see the current limit (small font) is at 1.3A and we are reading 1.32A. The voltage will change when you are in current limit mode. During this mode, the voltage encoder knob will not react if you increase the voltage as the voltage is capped by the current.

The prototype version of PocketPD utilizes a sense resistor of 10mOhm to measure the current reading of the load. Here is the configuration for V.Prototype:

The power goes directly from USB-C VBUS, and passes through the sense resistor, thru the PMOS output switch to the banana jack terminals.

Issue: VBUS reading is higher than VOUT, more than expected. There must be more voltage drop somewhere.

It was a bit surprising that Ron is consistent across multiple input voltages as Vgs and Ron are dependent on each other. Further investigation is needed

Conclusion: The resistance of PMOS (68mOhm) is higher than expected (18mOhm) which causes the discrepancy between the OLED measured and the Banana jack output. 

Solution:

• Use the known resistance drop across the PMOS. Calculate the expected voltage drop with current. Display the adjusted VBUS value
• Move the current sensing to just before the banana jack. This will take care if there need to be component changes on PMOS due to part shortage or part upgrade. 

But !... The current reading is now calibrated. We are getting the correct amperage report through the Rsense resistor!