USB Type-C® and USB Power Delivery: Designed for extended power range and battery-powered systems

USB Type-C® (USB-C®) is an industry-wide universal connector that supports data and power transfer over a single interface for applications such as personal electronics, automotive, industrial, and enterprise systems. USB Power Delivery (PD) is a standard that uses the USB-C connector to increase the functionality and features of the USB-C interface . Until recently, the USB PD 3.0 specification allowed up to 100W of power (20V, 5A) to flow in both directions, which is now known as the Standard Power Range (SPR). The latest USB PD 3.1 specification increases the power range to 240W (48V, 5A) over a USB-C cable, which is now known as the Extended Power Range (EPR).

Table 1 shows the comparison between EPR and SPR.

EPR supports up to 240W of power (28V, 36V, and 48V @ 5A). The EPR mode requires the receiver to evaluate and respond to new source capability messages in the same way as in a typical USB PD contract negotiation. After entering EPR mode, the port begins negotiating a power delivery object (PDO) of up to 240W (48V, 5A). The 48V limit represents a practical limit when considering design safety margins.

In addition to the fixed voltage level extension in EPR mode, the power supply must also follow the specifications of the adjustable voltage supply (AVS). In EPR mode, AVS enables the sink to fine-tune the voltage between 15V and 48V in 100mV steps to improve performance and thermal efficiency. AVS also gives the sink the flexibility to accept voltage from any charger, eliminating the need for custom adapters and providing a consistent user experience within the electronics ecosystem.

Figure 1 shows the Programmable Power Supply (PPS) and AVS ranges in relation to SPR and EPR power levels. While both PPS and AVS have programmable step sizes, they are not the same and are used for different purposes. AVS acts as a constant voltage source and provides a stable DC voltage to the system for improved efficiency. PPS has a smaller step size window (20mV) and can charge the battery directly, bypassing the battery charger in the connected device. The main difference between AVS and PPS is that when using PPS, the negotiated voltage will continue to change over time. As the battery charges, the required PPS charging voltage will increase. AVS is intended to be used as a constant power source, providing a system input voltage level that is closer to the voltage level required by the entire system.

Figure 1: USB PD 3.2 voltages required on the power supply side

Battery-Powered Products and Next-Generation Solutions

The adoption of USB-C is beneficial for portable battery-powered products such as Bluetooth® speakers and power tools. Implementing USB-C for these types of products allows them to both charge through the USB-C port and use the same port to power connected devices. Products that use single or multi-cell battery chargers can now be used with a USB-C or USB PD controller, allowing the application to provide and receive power through the USB-C port.

Figure 2 shows the typical architecture of a device transitioning to USB-C and USB PD.

Figure 2: USB-C battery-powered product block diagram

To help simplify the design of USB PD ports for battery-powered products, Texas Instruments' USB PD controllers have added I2C host support to directly control the battery charger. This integrated I2C host control enables a two-chip solution without the need for an external microcontroller (MCU). The USB PD controller will automatically update the charging parameters of the battery charger via I2C based on the power negotiation conducted over the USB PD port. In addition, no firmware development is required to add a USB PD port to a battery-powered product. The TPS25751 and TPS26750 are two USB PD controllers for USB-C plus battery charger pairing.

The TPS25751 is an SPR PD controller, while the TPS26750 is an EPR PD controller capable of negotiating the full 240W EPR. Table 2 shows the recommended pairings of USB PD controllers and battery chargers. With these paired reference designs, you can “copy and paste” the designs into your application.

Table 2 USB PD controller and battery charger pairing

Reference Design

To support the full 240W extended power range, the 240W USB Type-C PD3.1 EPR battery charger reference design pairs the TPS26750 with our BQ25756 bidirectional buck/boost charge controller. As shown in Figure 3, the reference design combines these two devices on the same printed circuit board, eliminating the need for an external MCU and custom firmware to achieve a bidirectional 240W solution.

Figure 3: EPR battery charger reference design block diagram

This battery charger reference design is an integrated USB PD and charging reference design for 7 to 14 battery cells in products such as power tools, vacuum cleaners, mobile power stations and e-bikes. The TPS26750 works with the BQ25756 through simple I2C communication, requiring no firmware development. The TPS26750 can be easily programmed using the application customization tool for TI USB PD controllers.

The battery charger reference design supports charging the battery at up to 240W from a USB PD 3.1 compliant input source and provides up to 48V, 5A output in On-The-Go mode. The BQ25756 implements a four-switch buck/boost charger that can switch between buck, buck/boost, and boost modes. The high level of integration and simple design will reduce bill of materials costs, size, and time to market.

Conclusion

With the recent increase in maximum power range, USB-C is emerging as the universal connector of the future. Although USB-C may be viewed as a challenging new technology, Texas Instruments solutions simplify your design process by enabling integration from both a software and hardware perspective. Our USB PD controllers paired with battery chargers, combined with our reference designs, enable smaller solution size and faster time to market.