The FAN7621 resonant controller from Fairchild Semiconductor simplifies design, reduces bill of materials, and provides advanced protection functions, according to the company. It integrates a high-side gate-drive circuit, a current-controlled oscillator, a frequency-limit circuit, soft start, and numerous protection functions in a 16-pin small-outline package/dual-inline package (SOP/DIP) package.
This controller eliminates the need for expensive external circuitry such as pulse transformers to conserve board space and reduce the cost of the overall design, Fairchild says. Its internal high-side gate-drive circuit is designed to provide common-noise cancellation for excellent noise immunity, enabling the application to meet stringent electromagnetic-interference (EMI) specifications.
For further noise immunity, the FAN7621 offers a zero voltage switching (ZVS) technique that reduces switching noise and allows the use of a smaller and less expensive EMI filter. It features overvoltage protection (OVP), overcurrent protection (OCP), abnormal OCP, and internal thermal shutdown without the need for additional components, reducing design time and overall system costs.
The ZVS technique reduces switching losses in MOSFETs and rectifiers. Compared to conventional hard-switching converter topologies, efficiency is improved by 10%. For applications like PDP-TVs, efficiency reaches 97%. The ZVS technique also reduces switching noise by at least 5 dB compared to hard-switching techniques. The FAN7621 costs $0.50 each in 1000-unit lots. Samples are available now, with delivery in 12 weeks.