Figure 1 on the lower left shows a CCM totem-pole PFC circuit that uses GaN in the Fast Leg section. Figure 2 on the lower right shows the efficiency at this time. An efficiency of close to 97% at 115Vac and over 98% at 230Vac is achieved.

The totem-pole PFC circuit achieves high efficiency by replacing the bridge diode, which was the main cause of power loss in the PFC circuit, with an active switch and by using GaN, which is compatible with higher frequencies.

The figure below shows a schematic diagram of a 1kW power supply that includes the above CCM totem-pole PFC circuit, an LLC circuit, and a secondary-side SR controller.

At this time, with an output of 50V/20A, as shown in the figure below, high efficiency of 93.6% at 115Vac and 96.1% at 230Vac is achieved.

In the schematic, NCP1681 is the totem pole PFC controller, NCP58921 is the GaN power switch with integrated driver, NCP51561 is the isolated gate driver and NCP51530 is the gate driver.

ON Semiconductor offers a variety of evaluation boards and user guides, including evaluation boards for totem pole PFC circuits, evaluation boards for 240W and 500W power supplies, and an evaluation board for the 1kW power supply shown above in efficiency data. Please feel free to contact us for more information.

Finally, GaN power switch products including NCP58921 [This section explains the features of NCP58920/NCP58921/NCP58922.

・ Gate driver + E-mode GaN Built-in driver and GaN It is possible to minimize the wiring inductance between the dv/dt Resistance, PCB This simplifies the design layout. (See the diagram on the right.)
- 6 V internal clamp GaN Built-in gate drive.
・On resistance: 50m Ω /78m Ω /150m Ω
・ 650V Breakdown Voltage
・ 30ns (typ.) Propagation Delay Time
・ 2.75mm Creepage distance
・TQFN26 8x8 Bottom Side Cool package
・ Silicon Carbide It is difficult to deal with 1MHz(max) Supports high-speed switching