The reference design helps engineers create power solutions using GaN technology, improving performance and reducing losses for charging applications…
The 65-W USB Power Delivery (PD) 3.0 adapter reference design from Texas Instruments enables design engineers to develop compact power solutions for various charging applications, including mobile phones, laptops, and tablets. The reference design utilises integrated gallium nitride (GaN) technology, enabling higher switching frequencies with reduced losses and enhancing efficiency and power density. The quasi-resonant flyback topology further improves efficiency by balancing simplicity and low switching losses, dynamically adjusting the switching frequency to minimise drain voltage on the primary field-effect transistor (FET). The design also features a GaN device integrated with sense emulation, which enables virtually lossless current sensing, further boosting the system’s overall efficiency.
This reference design allows engineers to optimise their power delivery solutions for space-constrained applications, as the high-frequency GaN technology enables smaller inductors, reduced core sizes, and fewer primary windings. The compact design suits mobile wall chargers, USB wall power outlets, and auxiliary power supplies. Engineers can minimise transformer size by integrating the LMG3624, a 170-mΩ GaN FET with current sensing and switching capabilities while improving system efficiency. The elimination of traditional shunt resistors through integrated current sensing helps reduce power losses and lower costs, making the design more cost-effective.
Engineers can also optimise transformer design for high-frequency operation, which is essential for maintaining efficiency in high-density designs. In the quasi-resonant converter, high switching frequencies minimise the size of the transformer, but engineers must select the right switching device to avoid significant power loss penalties. When selecting switching devices, the reference design provides a clear framework for considering frequency-dependent and current-dependent conduction losses. Additionally, the board comes with a USB Type-C PD controller, and engineers can connect it to a USB Type-C PD load through the onboard connector to adjust the output voltage to 5V, 9V, 15V, or 20V, depending on the application. Engineers will need a USB Type-C PD load that communicates to fully utilise the variable output voltage, such as the PM125 USB Power Delivery Tester and PassMark Software.
For testing different outputs, a standard USB Type-C cable can be used to draw up to 3.00A at 5V, 9V, or 15V, but an E-marker USB Type-C cable is required to achieve 3.25A at the 20V output. The board’s flexibility allows engineers to test various configurations and explore the limits of their power delivery designs, making it a versatile tool for developing efficient, high-performance power solutions.
Some of the key features of the reference design include:
- 25.29 W/in³ power density for compact designs
- 92.83% efficiency at full load, 90 Vac
- 94.09% efficiency at full load, 115 Vac
- 94.32% efficiency at full load, 230 Vac
- 70 mW loss reduction with integrated current sensing
- 30 mW standby power at 115 Vac
- Low temperatures for easy thermal management
- Universal AC input voltage support
TI has tested this reference design. It comes with a bill of materials (BOM), schematics, assembly drawing, printed circuit board (PCB) layout, and more. The company’s website has additional data about the reference design. To read more about this reference design, click here.
