Do you know how to steal power from a USB Type C power source for your hobby electronics projects? If not, this article is for you. I also wanted to know more about USB Type C power delivery (USB-C PD) tricks.
This is not a USB-C primer. This is an introduction to the USB-C Power Delivery. An in-depth article on USB-C will be posted later, so visit this site regularly for updates.
USB Type C & Power Delivery
The USB Type C connector is designed to provide a number of features when compared to previous generations. Enhancements include a smaller package size, greater signal bandwidths, more conductors, higher voltage ratings and higher current ratings. The plugs and receptacles can be connected either right-side up or up-side down, allowing for faster and easier insertion of plugs into receptacles.
A typical USB Type C connector employs 24 contacts and there are four power and ground contacts to aggregately carry a current of 5A. The connector is also rated up to 20V between the power and ground pins, allowing for 100 Watts of power transfer!
The USB Power Delivery specifications provide information regarding the implementation of the higher levels of power delivery available through USB Type C connectors. Note that a USB Type C connector is designed to support the USB PD standard. The device’s host controller and cable must also be configured to support the standard (https://en.wikipedia.org/wiki/USB-C).
The features provided by USB-C are many. Since so many features in a single port comes with complex management, we need a dedicated port controller for using USB-C port effectively. There are various controllers available in the market, but we have to choose the appropriate controller depending on the actual requirement. I will discuss these in a later post. Now, let’s see how to steal power from a USB-C port.
USB-C Power Delivery & Hobby Power Supply
USB-C has become the new trend after its introduction. All the latest laptops, notebooks, smart phones, tablets, power banks and travel chargers tend to be installed with USB-C ports. We can see even the USB-C port in a cheap USB-C travel charger has an ability to cater DC voltages up to 12V!
How can we exploit that? Plugging a common USB-C male connector breakout board into the USB-C socket will give you nothing, not even the minimum 5 Volts!
To exploit the promised features, the plugs and connectors have additional configuration pins to allow devices to negotiate their state. Supporting the configuration channels may seem like a cumbersome task, but it can be achieved simply for basic applications. Let us take a quick look into this!
The easiest method is to use two 5.1KΩ pull-down resistors on the Configuration Channel (CC) lines (A5 = CC1 & B5 = CC2). The CC1 and CC2 pins are critical for basic USB Type-C operation. Resistors are attached to the CC pins in various configurations depending on whether the application is a downstream facing port (DFP), upstream facing port (UFP), or an electronically marked/active cable. Remember, an upstream facing port must connect a valid pull-down resistor to GND to both CC1 and CC2 pins. The 5.1KΩ ± 10% is the only acceptable resistor if USB Type-C charging of 1.5A@5V or 3.0A@5V is used.
It is also important to note that USB Power Delivery allows power configuration of a USB connection to be dynamically modified. The default 5V on VBUS can be reconfigured up to any level up to 20V. The maximum current supplying capability can also be raised to a maximum of 5A with a 100W compatible electronically marked USB PD Type C cable.
Therefore, in order to draw 5VDC from a USB-C port gently, you can either solder a pair of 5.1KΩ pull-down resistors on the CC pins of a regular USB-C male (or female) breakout board or you can pick up a special USB-C breakout board that comes with pre-soldered 5.1KΩ pull-down resistors.
Following is a simple schematic for those want to design and build their own USB-C breakout board for hobby power applications. I can’t give the PCB artwork because it’s not ready yet, sorry.
When considering today’s implementations, it is worth learning more about USB Power Delivery designs. This is a good post on that topic https://www.digikey.com/en/articles/designing-in-usb-type-c-and-using-power-delivery-for-rapid-charging
Since I already have many Pololu USB Type-C connector breakout boards, I tried the Hobby Power concept with it and it worked like a charm.
The Pololu breakout board is really helpful as it provides access to the tightly-spaced connector’s pins for power (VBUS and GND), USB 2.0 differential data (D+ and D−), Configuration Channel (CC), and Sideband Use (SBU). Each of these pins is broken out into a 1×8 row of 0.1″ spaced pins on the board, along with duplicate VBUS and GND pins for high-current applications. However, this board does not expose the Type-C connector’s USB 3.1 SuperSpeed differential pairs (TX and RX signals), so it only supports USB 2.0 Low-Speed, Full-Speed, and High-Speed communication!
For the first experiment, I selected my USB-C power bank and a DVM and extended the dc supply from the power bank to the breakout board using a USB-C (power and data) cable. Below you can see a casual snapshot of my quick test setup that provides a 5 Volt DC output.
I have seen many Chinese breakout boards with a single 56KΩ pull-up resistor as the one shown below. They are not suitable for this project (It’s actually tailored for USB type-C male to USB type-A female adapters).
As can be seen in the below table, 56KΩ ± 20% is the recommended “DFP Rp Pull-Up Resistor” for Default USB Power (500mA for USB2.0, 900mA for USB3.0).
USB-C In-depth https://www.mouser.in/datasheet/2/813/USB-C_Datasheet-1534377.pdf
Even though most USB-C power banks and travel chargers can cater dc voltages up to 12V, the above demoed trick won’t let you take more than 5V. Luckily that’s also fairly easy because you can now buy various models of cheap USB-C PD tester/trigger/decoy modules from many Chinese online vendors. Just make sure you also got a USB-C cable and power source that can handle the requirements, though doing it this way is a bit unsafe!
Along the lines of being a bit unsafe, it’s worth pointing there are some module makers out there that have intentionally exploited the USB Type-C standards outside of the intended specification. Beware! See this (slightly older) post https://www.scorpia.co.uk/2019/06/28/pi4-not-working-with-some-chargers-or-why-you-need-two-cc-resistors /
Below you can see the close up of an unsoldered USB Type C connector (Thanks to Pololu).
Now you know more about stealing power from a USB-C power source with just two resistors. Get ready to get into USB-C Power Delivery to play around with getting higher voltages and watts. Leading players like TI, STM and Cypress have USB Type-C controller chip solutions that can do all of this for you.
Finally, I hope this little guide is helpful for hobbyists looking to run their designs up with USB Type-C power. Trust me, I’ve a few more ideas in mind which I have yet to play around with. Time to read some great USB-C PD projects and the latest datasheets. See you then!