USB Type-C and Power Delivery – How straightforward is it?
Using USB-C for charging and powering our modern devices has become second nature – plug it in, and it works. No need to think about it. Connect a cable between the wall adapter and the device, and on comes the charging light. Simple, right? Unknown to most, there is a sequence of back-and-forth communication between the charger and the charged, like a fast tango, ensuring both devices operate safely, efficiently and within their limits.
But sometimes that charging light might turn on yet your device charges at a snail’s pace or that light doesn’t even turn on at all. Diving deeper into the standards, it’s clear that not all chargers, nor cables, were created equal. In this article, we look at the history of USB Power Delivery, how the latest standard has taken over, things to watch out for, and how USB-C charging can be successfully implemented in modern products.
A quick history of USB power standards
The Universal Serial Bus (USB) was first introduced as a data connector and commonly used for low-speed and low-power devices, such as keyboards, mice, or flash drives. The maximum output current would be 100mA, extended to 500mA (or even 900mA for USB 3.x) for high power ports. With the increasing power demand of connected devices, the USB Implementers Forum (USB-IF) developed the Battery Charging (BC) protocol in 2010 to allow for higher currents to come from a USB port, at 1.5A. This protocol uses the data lines (D+/D-) for signalling higher current capability.
Qualcomm developed its own proprietary protocol in 2013, Quick Charge, which unlocked higher charging powers (>7.5W) by using negotiated voltage levels. Further revisions to Quick Charge expanded the power capabilities and added features such as finer voltage adjustments. While Quick Charge was only available for devices with Qualcomm Snapdragon System on Chips (SoCs), the USB-IF were simultaneously developing a universal USB Power Delivery standard.
Many separate mobile phone companies were also developing and using their own standards to increase the charging speeds of their devices, such as Oppo’s VOOC, Xiaomi’s HyperCharge, and Huawei’s SuperCharge. If not already confusing enough, a collection of Chinese mobile phone manufacturers introduced the Universal Fast Charging Specification (UFCS) in 2022, and UFCS 2.0 in 2025. By that time, USB Power Delivery had already become much more mainstream and common, making it difficult for UFCS to truly become “universal”.
For above 7.5W of power, manufacturers created their own charging protocols.
USB Power Delivery - The beginning
USB Power Delivery has since become the common standard for powering and charging portable devices at over 7.5W. The first Power Delivery standard developed in 2012, PD1.0, communicated via frequency shift keying (FSK) on the VBUS line. The USB PD provider constantly advertises its source capabilities until a consumer makes a request, and then the power levels are negotiated. The given power profiles for PD1.0 are 5V, 12V, and 20V, at 1.5A, 3A, or 5A.
In this period of early development, Microchip chipped in with their own recommendation for ensuring safe PD1.0 compatibility. They suggested that the cables and receptacles should have additional features to access powers above 5V / 1.5A. These may be elongated shields or internal cable markers like resistors between pins or capacitors on ID pins. Microchip’s idea never gained traction as it was only compatible with their own PD controller ICs and caused further Power Delivery fragmentation. Shortly afterwards, the USB-IF introduced the USB-C connector and the PD2.0 standard which provided a more unified solution.
USB Type-C
In 2014, the USB-IF created the USB Type-C connector which superseded all previous USB connectors and is still in use today. A key benefit of this connector is reversibility, meaning it can be plugged in in either orientation, plus it features 24 pins which include other purposes alongside D+/D- and power. The accompanying Power Delivery 2.0 standard updated the power profiles and the method of negotiation. An important change with USB-C is that it is a “cold” socket, meaning that power is only provided after some form of negotiation by the sink device, unlike USB-A which will typically provide a “hot” 5V from power-up, regardless of whether a device is connected.
The USB-C negotiation now happens via the two dedicated Configuration Channel (CC) pins, and with digital signalling using Bi-phase Mark Code (BMC) rather than analogue modulation. This provided a more robust solution than the analogue VBUS FSK communication in PD1.0, which was susceptible to interference and noise. The power profiles for PD2.0 are slightly different to those for PD1.0, at 5V, 9V, 15V, 20V and up to 3A or 5A.
From Power Delivery version 3.0, additional features were added, such as Programmable Power Supply (PPS). This feature enabled voltage and current profiles to be programmed in 20mV and 50mA steps between 3.3V to 21V. PPS has great benefits for battery charging, as the voltage and current can be adjusted in real time by the charger source, leading to greater charging efficiency and reduced internal heat generation.
With Power Delivery 3.1, additional power profiles were added of 28V, 36V, and 48V which make up the Extended Power Range (EPR). The maximum current is still 5A, and at 48V this enables a power of up to 240W. PD3.1 also introduced Adjustable Voltage Supply (AVS), a method of controlling the voltage in the EPR in 100mV increments. The latest revision, USB PD3.2, expands AVS control into the Standard Power Range (SPR) down to 9V. Other changes in PD3.2 involve protocol refinements, while the power profiles and maximum power remain the same.
The difference between PPS and AVS is subtle and each has their own best use case. The finer control of PPS best suits battery charging situations. The 20mV resolution and more frequent adjustments allow for higher efficiency and less thermal stress in the battery. AVS, on the other hand, is coarser and only controls voltage, in 100mV steps, without a programmable maximum current. AVS would be more suitable for replacing a DC barrel jack and providing a specific and constant voltage rail.
Negotiation must take place before a USB-C port switches its output on.
USB PD3.2 source voltage levels [Texas Instruments]
EU Regulations – A Common Charger
In November 2022, the EU Common Charger Directive 2022/2380 stated that all new battery powered “radio equipment” devices that could be recharged via wired charging sold from 28 December 2024 has to include USB Type-C charging.
Such devices include “handheld mobile phones, tablets, digital cameras, headphones or headsets, handheld videogame consoles, portable speakers, e-readers, keyboards, mice, portable navigation systems, and earbuds”. These rules were subsequently extended to laptops as of 28 April 2026.
This Directive requires that USB-C devices using a charging power of up to 15W must support at least one of the USB charging options: USB 2.0, USB 3.2, USB 4, USB BC1.2, USB Type-C Current 1.5 A, USB Type-C Current 3.0 A, or USB PD. For devices charging above 15W, the full functionality of USB PD must be supported along with any additional proprietary protocols that the manufacturer may wish to include. Proprietary charging receptacles, such as Lenovo’s Slim Tip connector, are allowed for any device and power level but must be complemented by a USB-C connector which can provide an equal power level. For high power devices above 240W, USB-C PD must be included at 240W, and other custom protocols can be implemented to achieve >240W.
Another benefit of the EU Common Charger Directive is the coexistence between the USB Power Delivery standard and any other proprietary manufacturer specific protocols. The directive states that “the full functionality of USB PD must not be hampered by additional charging protocols”, meaning that the availability of the maximum power must not be exclusive to manufacturer-specific charging protocols. One example could be Motorola’s 68W charger, which has a proprietary 11V and 6.2A profile, but still includes standard power delivery profiles up to 68W (at 20V and 3.4A).
While the EU legislation has now come into effect, many of us still own legacy electronics, which require different charging cables and charge at different speeds. The harmonisation of USB-C across portable devices and the adoption of USB Power Delivery has provided a huge step forward but not without issue. Cables and chargers are still a point of concern, where misleading marketing or false assumptions may result in consumers having a poor user experience.
Cables, cables, cables – what’s their cable-ability?
Not only do the charger and the device need to both be happy with the same charging protocol, the cable between the two needs to agree as well.
USB-A to USB-C cables are not uncommon but need to be understood. USB-A does not have any CC connections, so only negotiation via data or power line modulation is available. Claims of “up to 100W charging” via such cables is technically allowed, under USB PD1.0, but is rarely implemented as PD2.0 and Type-C took over shortly after PD1.0 was introduced.
The power of USB-A to USB-C cables is limited to 4.5W as default at 5V and 0.9A, 7.5W at 1.5A for USB BC1.2, or higher for proprietary protocols like Quick Charge at 18W or SuperCharge at 22.5W. USB2.0 and USB3.0 ports default to 500mA or 900mA respectively using data ports. The USB BC1.2 specification allows for Dedicated Charging Ports (DCP) to reach 1.5A by shorting D+ and D-, while USB3.2 dual-lane pushes the default to the same value without modifying the D+/D- lines.
USB-A to USB-C cables include their own pull-up resistors, which advertise to the sink device the current capability. As per the USB Cable Specification, any USB-C to non-USB-C cable is required to incorporate a 56kΩ pull-up on the CC line to indicate “default current”. This is because the cable assembly does not know the capability of the source and is only allowed to advertise the default currents. Other pull-up values are not permitted as they can overload the legacy power source. Any higher currents must be negotiated for, such as using the D+/D- data lines in line with the BC1.2 specification.So, the reason why your 100W USB-A to USB-C cable doesn’t ever reach 100W, let alone the 45W that your new phone can cope with, is that the power level is only permitted to reach 7.5W without implementing a vendor specific protocol. The same applies to your 22.5W USB-A power bank, as that maximum power may only be accessible if you happen to own a specific brand of phone.
To unlock higher powers via a USB-C to USB-C cable without using any specific protocol such as USB Power Delivery, pull-up or pull-down resistors are used on the CC lines to signal the current capabilities of the source – default current (500mA or 900mA), 1.5A, or 3A. To access 5A capabilities, the cable must have an active e-marker chip which advertises that the cable is 5A capable. At these higher currents, the quality of the cable is important to prevent damage to itself and ensure safe operation. The aforementioned e-marker chip is located inside the cable assembly, sitting on the CC lines, and contains cable capability information. It is not required for all cables; only for those above 100W and 5A or including other features such as USB3.2 or alternate modes like DisplayPort.
Sometimes, you might encounter a USB-C device that only charges with the cable in one orientation. It’s usual to assume that the cable is at fault. However, it is actually the device or charger where the problem lies. A cable normally only includes one CC connection by design and relies on the source and sink having a symmetrical CC1/2 termination. If the device does not include both CC1/2 resistors, power will only work with the cable in one orientation.
Proprietary, often manufacturer specific, non-PD protocols may allow for higher currents than the USB PD 5A maximum. In these cases, it is important to have a properly rated cable - Motorola, for example, use a higher current of 6.5A which is only available when using their specific chargers with their specific e-marked cables.
Modern USB Power Delivery requires a USB Type-C to Type-C cable which may contain internal electronics to allow maximum power transfer.
It’s not all so easy
So, all you need to do is go out and buy a USB PD3.0 or higher rated charger and it will presumably provide all the voltage levels defined by the PD standards and output 100W? It doesn’t quite work that way – the Power Delivery standards do not guarantee the power outputs; they just specify the communication protocols and the rules on how the power profiles can be used. For example, a PD3.1 30W charger must have 5V at 3A, 9V at 3A, and 15V at 2A profiles (specified in Table 3.1 of the USB-PD specification). USB PD3.2 has changed the profile rules slightly, disallowing a 20V profile, whereas earlier Power Delivery versions allowed optional higher voltage levels, like 20V at 1.5A to make 30W. Equally, not all PD3.0 and above rated chargers provide PPS or AVS – these are optional in the standards, so would have to be explicitly listed in the charger product details.
A common marketing trick used by some USB charger manufacturers is to advertise the sum total of each port’s power as the maximum power of the charger. While this may be true when multiple devices are connected, it does not hold for the power output of just one port. It is easy to fall for such obfuscation, especially with legacy USB-A to USB-C cables, so it is helpful to understand the intricacies of Power Delivery.
How is this all implemented?
There exists a plethora of USB Power Delivery controller chips on the market, all capable of communicating with a PD source to negotiate for a specific voltage and current limit. Some of these chips offer a full USB-C interface, controlling data paths and extra modes, whereas others simply act as a PD sink to request power from a source. Simpler chips can be controlled via specially selected external components to set a specific input voltage and current requirement, or via an I²C interface for dynamic programming and setting a specific level using PPS/AVS. Integrating a battery charge controller and a PD sink chip allows the source power supply to do the heavy lifting of voltage conversion and its associated heat generation, while letting the battery charge optimally without excessive internal voltage converter losses.
A USB-C power sink must implement a 5.1kΩ pull down resistor on each of the CC pins. This helps indicate the current capability to the sink by using a voltage divider formed with the pull up pins on the source for basic Type-C functionality. For example, when the source pull up resistor is 22kΩ, the 5.1kΩ pull down voltage divider will indicate a voltage of 0.94V, which signals to the sink that 1.5A is available. Tables 4-27 and 4-28 in the USB-C Cable Specification provide a comprehensive overview of the resistor values and the currents they represent. Typically, a USB-C to USB-C cable only has one CC connection passed through which can be used to indicate cable orientation - the pull-up and pull-down resistors on the source and sink should be symmetrical for electrical reversibility. Table 4-10 in the Specification describes the meaning when both CC1/2 are connected through the cable, and Figure 4-42 in that same document shows how an internal e-marker is connected too.
It is very easy to get sucked into the vast catalogue of available Power Delivery controllers, so it is important to have defined requirements. A dedicated PD controller chip may not even be required for low power devices under 15W, where the standard USB-C current capability is sufficient, and product BOM cost can be reduced by using a less capable chip or by omitting a controller chip entirely.
If a PD-controller chip is used, care must be taken if the device is expected to charge when connected to legacy supplies. For example, while it may be beneficial for a device with a large battery to take advantage of higher supply currents when available from USB-PD supplies, it is perfectly valid for a user who only has a legacy USB-A source available to accept the option of slow charging over no charging – analogous to charging an electric vehicle from a standard mains plug. Our experience is that not all PD-controller chips offer full backwards compatibility: they may successfully negotiate high power rates from a compatible source and fall back to a lower charging rate from a non-PD USB-C source, but can remain inactive if connected to a USB-A source where the configuration is not detected.
If the product is to work with legacy ports other than USB-C, it will have to intelligently limit the current that it draws when operating from a legacy port. If the product is plugged into a 500mA capable port on a PC, for example, and it attempts to draw more than this current, the results can vary between a warning message and a damaged USB port, neither of which is desirable.
Legacy compatibility can, of course, be mitigated with careful selection of the controller chip or the use of additional external circuitry, but these examples of potential issues illustrate how DCA’s approach of prioritising a detailed requirements specification and then testing thoroughly against these requirements in early design iterations avoids unexpected problems when the product reaches a user’s hands.
How this shapes the way for rechargeable devices
Along with the common charger EU Directive 2022/2380, Article 11 of the EU Regulation 2023/1542, which concerns the removability and replacement of portable batteries, sets a clear path for the future for our portable electronics. While there are design challenges to overcome when they are both in effect, the harmonised USB-C charging protocol will provide a useful starting point across rechargeable portable devices, accelerating the design of future products.
Another clear benefit of having a common charger standard is the reduction in e-waste with a consolidation of cables and chargers. With a sufficiently rated charger, most household devices can be charged from the same plug-in charger with the same cable.
Conclusion
The history of powering and charging devices over USB has not been a straight line. As the power demand of portable devices has increased, a unified solution was required. USB Type-C and Power Delivery quickly became the standard, and EU regulation ensured the widespread rollout in our modern devices.
Designing your product to accept power via USB-C has clear advantages. It makes the product compatible with a large existing power supply infrastructure, so users do not require a dedicated power supply for the product, and in some cases is required for regulatory compliance. The maturity of USB-C Power Delivery and widespread availability of integrated Power Delivery controller chips means that meeting EU regulations in future designs can be achieved relatively painlessly while also reducing project risk and effort compared with the development of a completely bespoke power supply design.
However, as we have discussed in this article, there are subtleties and details that must be understood to select the right implementation in the product electronic design, as well as the power source and cable to specify or supply for it. It is vital to understand these details when designing a product so that the requirements are fully captured; the design is correctly positioned in terms of cost, capability and backwards compatibility; and that these requirements are successfully met in the product implementation.
Here at DCA Design International, our team understands these details. Our experience in this area, together with our complementary multidisciplinary skills in the design of low-power, rechargeable portable devices is perfectly positioned to serve our clients with their product design needs in this space.
Written by Martin Bowers, Electronics Engineer
It is vital to understand the design details of USB Power Delivery to meet modern product requirements.
