ON Semiconductor Introduces Innovative Ultra-High Density Offline Power Solutions

     ON Semiconductor has introduced the industry's first dedicated critical conduction mode (CrM) totem-pole PFC controller, a new addition to the company's ultra-high-density offline power solution portfolio.

     In a conventional PFC circuit, the loss of the rectifier bridge diode in a 240 W power supply is about 4 W, accounting for about 20% of the total loss. In comparison, the energy efficiency of the PFC stage is typically 97%, and the LLC circuit achieves similar performance. However, replacing the lossy diodes with switches in a "totem pole" configuration, and pulling in the boost PFC function, reduces bridge losses and significantly improves overall energy efficiency. In addition, the NCP1680 can be used with any switch type, whether it is a superjunction silicon MOSFET or a wide bandgap switch such as silicon carbide (SiC) or gallium nitride (GaN).

     The new NCP1680 CrM totem-pole PFC controller uses a novel current limit architecture and line phase detection, combined with proven control algorithms, to provide a cost-effective totem-pole PFC solution without compromising performance. At the heart of this IC is an internally compensated digital loop control. This innovative device uses a constant-on-time CrM architecture with valley switching. Due to the built-in discontinuous conduction mode (DCM), the valley is synchronously turned on during frequency flyback operation, so it can meet modern energy efficiency standards, including those that require high energy efficiency at light loads.

     This highly integrated device enables power supply designs to operate at recommended power levels up to 350 W from universal power supplies (90 to 265 Vac). The NCP1680-based PFC circuit is able to achieve nearly 99% energy efficiency at 300 W at 230 Vac power input. A fully functional totem-pole PFC can be implemented with just a few simple components externally, saving space and component cost. Further reduction in device count enables cycle-by-cycle current limiting without the need for Hall-effect sensors.Available in a small SOIC-16 package, the NCP1680 can also be used as part of an evaluation platform to support rapid development and debugging of advanced totem-pole PFC designs.

     According to the totem pole switching technology, there are two high-speed half-bridges and low-speed half-bridges. On the high-speed half-bridge, the NCP1680 can be combined with the NCP51820 half-bridge GaN high electron mobility transistor (HEMT) gate driver or the NCP51561 isolated SiC MOSFET gate drivers are used together. The NCP51561 is an isolated dual gate driver with 4.5 A source and 9 A peak sink capability. The new devices are suitable for fast switching of silicon power MOSFETs and SiC-based MOSFET devices, providing short and matched propagation delays. Two independent 5 kVRMS (UL1577 rated) galvanically isolated gate driver channels can be used as two low bridges, two high bridge switches or one half bridge driver with programmable dead time. An enable pin will shut down both outputs simultaneously, and the NCP51561 provides other important protection features such as independent undervoltage lockout (UVLO) and enable functions for both gate drivers.

     ON Semiconductor offers a broad lineup of SiC MOSFETs that offer higher energy efficiency than silicon MOSFETs. Low on-resistance (RDS(on)) and small die size ensure low capacitance and gate charge (Qg) for maximum energy efficiency in a smaller system size for increased power density. ON Semiconductor has released 650 V SiC MOSFETs in TO-247-4L and D2PAK-7L packages and will continue to ramp up the product line. In addition, ON Semiconductor offers a complete portfolio of silicon-based 650 V SUPERFET III MOSFETs.