Benchmark Power Density Achieved Using ‘All-GaN’ Design for USB PD3.1 Reference Design

Article By : Efficient Power Conversion (EPC)

EPC's EPC9171 reference design can deliver 240W maximum output power at 48V output voltage and 5A load current.

Efficient Power Conversion (EPC) has launched the EPC9171, a 90V–260V universal AC input to 15V–48V DC output power supply designed for USB PD3.1 ultra-fast chargers. This reference design can deliver 240W maximum output power at 48V output voltage and 5A load current. A power density of about 1.1W/cm3 is achieved by employing gallium nitride (GaN) power switches operating at high switching frequencies in both the primary and secondary circuits.

This 240W reference design measures a mere 83.7-by-83.7mm and shows 79% higher power density, which is more than recently released 140W USB PD3.1 slim chargers, while providing 240W of output power – 100W more power!

The power supply topology used in the design of the EPC9171 consists of a two-phase interleaving boost converter power factor correction (PFC) stage and an isolated LCC resonant power stage. Unlike the well-known LLC resonant power stages, which suffer from limited output voltage range, the LCC resonant converters are ideal for wide output voltage range multi-point applications.

The EPC9171 is an ‘all-GaN’ solution using GaN devices for PFC, LCC and secondary synchronous rectification. The GaN solution switches at two to three times the frequency of standard silicon MOSFET solutions, which enables the very high-power density.

For the PFC, GaN power switches operate well above 200kHz allowing small physical dimension PFC inductors. The LCC resonant converter operates in the frequency range of 350 to 580kHz, which helps to reduce the size of the power transformer as well as that of the other passive components in the resonant circuit.

The synchronous rectifier stage employs a pair of 100V rated, 3.2mΩ EPC2218 GaN FETs on the secondary side of the LCC stage. The GaN FETs are driven by fast synchronous rectifier controllers to minimize the losses over the whole output voltage and current range and allow a simple yet effective thermal design.

With 240W power, this solution can be adopted not only for ultra-fast USB charging for laptops, notebooks, and smartphones, but can extend USB charging to other applications requiring 240W, such as gaming PCs, eBikes, and eScooters. As the cost for 48V batteries continues to decrease, additional applications for AC/DC/SMPS charger applications are emerging.

eGaN FETs and ICs provide the fast switching, small size, and high efficiency needed to further reduce the size and weight, while decreasing charging time for USB PD3.1 fast chargers,” said Alex Lidow, CEO of EPC. “The EPC9171 is an ideal example of how GaN technology enables miniaturization, very high efficiency, and excellent thermal performance for high-volume charger applications using devices that are lower cost and in stock for immediate delivery.”


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