The NCP1901 integrated circuit from On Semiconductor combines both a power factor correction (PFC) controller and a resonant half-bridge controller in one package. This high level of integration facilitates the creation of small form-factor off-line adapters that meet worldwide efficiency standards such as Energy Star v2.0, California Energy Commission (CEC), European Code of Conduct, and China Standard Certification Center (CSC).
The NCP1901 sports an innovative combination of a PFC controller operating in a critical conduction mode (CRM) and a resonant half-bridge controller. Overall voltage regulation is maintained by adjusting the PFC output voltage. This allows for the use of a fixed-frequency resonant controller, reducing transformer size and maximizing efficiency.
Using the company’s proprietary high-voltage technology reduces the need for external discrete components and minimizes board footprint. The resonant controller has an integrated half-bridge driver rated at 600 V, eliminating the need for an external driver or gate drive transformer. A 600-V startup circuit allows direct connection to the bulk capacitor, improving efficiency at light loads through the absence of startup resistors.
Combining both controllers in a single package ensures correct sequencing and operation between the PFC and half-bridge stages. As a result, robust power supplies with key protection features can be designed quickly while still maintaining design flexibility.