PocketPD is a small but brilliant idea: a USB-C powered benchtop power supply that literally fits in your pocket, designed to go anywhere without sacrificing fine-tuning of voltage and current. It began as an open-source project after a long process of iterations , refining both the hardware and firmware with the help of the community to get the most out of the USB Power Delivery standard and, in particular, the Programmable Power Supply ( PPS) mode .
With a modern charger or compatible power bank, this power "solicitor" negotiates the best possible profile and gives you a fully adjustable output, with built-in protections and a clear interface based on an OLED screen and physical controls. No complicated frills: just buttons, an encoder, and real-time data readings to do what you need without distractions.
What is PocketPD and why is it different?
The key to PocketPD is that it doesn't use buck/boost converters on the board: it directly leverages USB-C's Power Supply Points (PPS) negotiation to request the desired voltage and current from the charger. This allows for a lighter and more compact design, with less power loss and less heat, making it ideal as a portable power supply or for bench testing in the field. Furthermore, it acts as a PD 3.0 profile tester , making it a doubly useful tool for anyone working with USB-C.
Its usage philosophy is pragmatic: if you connect a modern charger or battery with PPS (many popular brands like Anker, Ugreen, or Baseus already support it), the device lets you request precise voltage and current values. And if PPS isn't available, the firmware gracefully switches to a standard 5V profile (PDO) and allows you to adjust the profile with a long press of the Volt/Amp button to maintain usability in almost any scenario.
The role of PPS within USB Power Delivery
The Programmable Power Supply mode was introduced with USB PD 3.0 to fine-tune battery charging by reducing conversion losses. In practice, PPS allows the consuming device to request the exact voltage and current limit it needs from the power supply, adjusting the values in very fine steps . Thus, with PocketPD, you can operate it like a real bench power supply, conveniently regulating parameters without adding unnecessary conversion stages.
An important note: the actual capacity depends on every link in the chain. The final power output is limited by the weakest component ; for example, if your charger delivers 5A but the cable is only rated for 3A, the system will not exceed 3A. Similarly, the PPS voltage range varies depending on the charger: typically it's 3,3–11V or 3,3–21V , and PocketPD adapts to whatever each power source negotiates.
Output ranges, CV/CC modes, and adjustment granularity
With a compatible power supply, you can adjust the voltage from 3,3 V up to the charger's maximum (typically 20–21 V) in 20 mV increments —a level of control usually found in laboratory power supplies. For current, the configurable limit starts at 1 A and goes up to the available PPS maximum in 50 mA increments , perfect for protecting sensitive prototypes or keeping tests within safe limits.
It's important to note a particularity of PPS mode in this project: current limitation below 1 A is not supported in DC when working in PPS mode. If you need to test very low loads with fine current control, you'll have to consider this limitation in your testing methodology to avoid any surprises.
Compatible with chargers, power banks and car
The versatility of the PocketPD is evident in its power supply: it accepts USB-C inputs between 3,3 and 21 V and up to 5 A , allowing it to work with wall chargers, power banks, and car chargers. In field scenarios, carrying a PPS power bank in your backpack solves many problems without relying on mains electricity, and in the workshop, a good PD charger will give you the necessary headroom for more demanding tests.
If you're unsure about compatibility, it's best to check the charger's specifications: it should mention PD 3.0 (or later) with PPS . Chargers without PPS will still work with a 5V PDO profile, but you'll lose the continuous voltage adjustment. And don't forget: use cables certified for the current you need; it's a common problem for the cable to be the bottleneck in the system and limit you without you even realizing it.
Display, controls, and profile memory
The interface features a 0,96″ OLED screen that provides clear voltage, current, and status readings, along with physical controls (encoder and buttons) for straightforward navigation between parameters. It's simple to use, with immediate response and no complicated menus, which is a major advantage when you're taking measurements and don't want to waste time.
A practical detail: the selected profile (voltage and current limit) is saved in the microcontroller's flash memory and is recalled upon reboot. This means you can turn it off, turn it back on, and resume exactly where you left off—something that, in everyday use, is more appreciated than you might think.
Internal architecture and electronics
At the heart of the system is a Raspberry Pi RP2040 (Cortex-M0+) with 16 MB of QSPI flash memory, responsible for the logic, UI, and negotiation control. An AP33772 sink controller is used as the USB PD protocol brain , managing the dialogue with the charger to fine-tune the PPS parameters with precision and reliability.
For power and measurement, the design integrates an onboard current and voltage sensor and a 5A (23V max.) "ideal diode" load switch, which reduces voltage drops and improves efficiency. This approach, combined with the absence of DC-DC converters on the board, minimizes heat and simplifies the path between the power supply and your circuit under test.
Protections and security
Since this power supply is intended for prototypes and sensitive electronics, protection features are essential. At the input, there is TVS/ESD protection on the DC, USB 2.0, and VBUS ports to cover spikes and surges; at the output, there is TVS/ESD protection on the VOUT port along with flyback diode protection for inductive loads, as well as protection against short circuits, reverse current, and, in documented versions, reverse voltage on the rail.
Overall, the security system is designed so that minor errors won't ruin your session or damage your hardware. Even so, the manufacturer's recommendation is clear: respect the limits of your charger, cable, and the PocketPD itself , and always verify the settings before connecting sensitive devices.
Physical design, assembly and dissipation
The chassis and encoder knob are 3D printed with high-temperature material (PETG in the documented versions), which helps it withstand the heat of summer or demanding test benches. The design prioritizes simplicity and the repairability typical of the maker world.
One interesting feature is the integrated magnet on the back: it allows you to attach it to metal surfaces (like a bench bar) and, incidentally, acts as a passive heatsink , helping to dissipate heat during extended use. This simple feature is very useful in workshops and laboratories where you need to have the power supply readily available and easily visible.
Output connectivity and variants
PocketPD comes standard with pre-soldered banana plugs , ready for use with standard instruments. Two variants are also available: one with an added removable screw block , and another that includes two additional unsoldered connectors, allowing you to choose between Anderson Powerpole PP15/45 or XT60 . This flexible design adapts to your setup without restricting you to a single standard.
Please note that, as specified, all outputs share the same internal rail; that is, they are not independent channels. This is important to avoid simultaneous connections that could introduce unwanted feedback or unhygienic ground loops.
Key specs
For those who want to get straight to the point, here's a technical summary of the most relevant information. Remember that the maximum negotiable voltage depends on your PPS charger and that the current is limited by the weakest link in the chain (charger/cable):
- Entrada: USB Type-C3,3–21 V up to 5 A
- Starting time: 3,3–20/21 V up to 5 A (depending on available PPS)
- Modes: CV (20 mV/step) and CC (50 mA/step, minimum 1 A in PPS)
- Screen: 0,96″ OLED
- MCU: RP2040 + 16 MB QSPI
- IC protocol: AP33772 (PD sink)
- Protections: short circuit, reverse current, TVS/ESDflyback; variants include reverse voltage
- Dimensions 86 × 55 × 21 mm; weight: 63 gr
Regarding operating temperature, there are references to two ranges in different technical notes: 0–80 °C and 0–45 °C . If you are going to stress it near the upper limit, use the magnet/heatsink and monitor the environment to maintain reasonable margins.
Truly open source: firmware, hardware, and casing
The software is released under the MIT license , combining proprietary libraries with third-party community resources. The schematic and PCB were developed in KiCad 9.x and will be released under CC BY-SA 4.0 , while the 3D-printed enclosure is also available for you to customize. In other words, you can study, modify, and contribute to both the code and the electronics and mechanics.
If you'd like to learn more about PPS, there are references in the community to content from GreatScott! and ElectricArc240 , which are very useful for understanding the fundamentals and getting the most out of it in your own projects. The repository also includes Gerber files and firmware ready for you to build your own unit if you're into DIY projects.
Field use and professional profile
The team behind PocketPD comes from the world of remote sensing and field instrumentation. This background explains design choices such as a focus on physical controls , clear readability, a rear magnet, and a compact body that, without being flashy, works when you need it . Whether you're a professional, an engineering student, or a maker, this is a versatile tool that won't take up much space in your backpack.
Another advantage is that PocketPD also functions as a PD profile tester , useful for validating chargers and cables and verifying what you're negotiating in each case. This dual power supply/tester functionality is especially practical in teaching labs and maintenance kits, where time is of the essence and you don't want to carry around half a shelf.
Manufacturing, quality control and materials
Production and assembly are handled by Elecrow , specialists in rapid production runs who have accelerated development through several iterations. Each unit undergoes functional testing before shipping to ensure it arrives in perfect working order from the factory—something that, when it comes to a power supply, is noticeable from the very first use.
The packaging has been designed to reduce waste without sacrificing protection, avoiding excess foam . The casing and knob are 3D printed with high-temperature filament to withstand warm environments and long sessions, a practical and sustainable decision in line with the open-source ethos.
Logistics and availability
After each production batch, shipments are routed through Crowd Supply's fulfillment partner, Mouser Electronics , for global distribution. If you're interested in staying up-to-date, the team has announced an improved version and is sharing progress and updates through the project's channels so you don't miss a thing.
Project maturity, risks and evolution
The design has undergone several rounds of refinement to ensure robustness and reliability . The core functionality has been stable for some time, and firmware updates focus on improving control and user experience. Regarding supply, a flexible bill of materials minimizes the impact of potential stock shortages of key components.
As with any electronic product, there's always some risk involved , but preventative measures have been taken and the product has been successfully validated through a pre-production run. For the average user, the biggest real "risk" is pairing it with an incompatible charger/cable; that's why we emphasize: choose the right power supply and cable to fully enjoy its potential.
PPS, PD and Quick Charge: clarifying concepts
Within the zoo of charging standards, PD and QC are the best known. USB Power Delivery is the umbrella term that allows for high power outputs in USB-C (up to 100W in classic versions), with predefined profiles and, since PD 3.0, the PPS mode for fine-tuning . Quick Charge (Qualcomm), on the other hand, is a proprietary fast-charging technology for mobile devices; recent versions have improved PD compatibility, but their focus is not on acting as a power bank.
The advantage of PPS over fixed profiles lies in reducing losses and heat by requesting precisely what's needed at any given moment. For batteries, this means less thermal stress and a longer lifespan; for a tool like PocketPD, it means fine-tuned control without the need for additional converters that complicate the system.
Compatibility tips and equipment that supports PPS
There are increasingly more chargers and power banks on the market with Power Point Switching (PPS). In addition to those already mentioned from Anker, Ugreen, and Baseus, several high-end smartphones (such as recent Samsung Galaxy models) and modern laptops support it, which encourages charger manufacturers to include this mode in their devices. Even so, always check the technical specifications to ensure you have the 3,3–11 V or 3,3–21 V range you need and the required current.
If you connect a power supply without PPS, PocketPD will switch to 5V PDO . You'll be able to work with 5V loads and adjust available profiles, but you'll lose the magic of dynamic voltage adjustment. It's perfectly usable for 5V electronics, but if your goal is to regulate between 3,3 and 20/21V in 20mV steps, you absolutely need PPS.
Just to avoid confusion: GPD Pocket is not PocketPD
On the web, you'll see references to the GPD Pocket , a 7-inch mini-laptop with Windows 10, an Atom x7 processor, 8 GB of RAM, eMMC storage, WiFi-AC, and USB-A/C and microHDMI ports. It's an interesting device in terms of size and design, but it's unrelated to the PocketPD beyond the name. If you're looking for a programmable USB-C power supply with PPS, focus on the PocketPD; if you want a mini-computer, then yes, the GPD Pocket is a different story.
That laptop, by the way, stands out for its alloy chassis, 1920×1200 IPS touchscreen, 7000 mAh battery and a compact keyboard with trackpoint, but it has nothing to do with the power supply, protection or PD negotiation functions that concern us here.
PocketPD combines fine voltage and current control via PPS, comprehensive protections, a clear interface, flexible connectivity, and an open-source approach that encourages learning, modification, and improvement. With a compatible USB-C PD 3.0+ charger/cable, you carry a benchtop power supply in your pocket, ready for labs, classrooms, or fieldwork, with the peace of mind that comes from careful manufacturing and a community that drives the project forward.
