The STR-W6765 is a quasi-resonant topology IC designed for SMPS applications. It shows lower EMI noise characteristics than conventional PWM solutions, especially at greater than 2 MHz. It also provides a soft-switching operation to turn on the internal MOSFET at close to zero voltage (VDS bottom point) by use of the resonant characteristic of primary inductance and a resonant capacitor.
The package is a fully molded TO-220, which contains the controller chip (MIC) and MOSFET, enabling output power up to 52 W with universal input or 110 W with a 230 Vac input. The bottom-skip function skips the first bottom of VDS and turns on the MOSFET at the second bottom point, to minimize an increase of operational frequency at light output load, improving system-level efficiency over the entire load range.
There are two standby functions available to reduce the input power under very light load conditions. The first is an auto-burst mode operation that is internally triggered by periodic sensing, and the other is a manual standby mode, which is executed by clamping the secondary output. In general applications, the manual standby mode reduces the input power further compared to the auto-burst mode.
The soft-start function minimizes surge voltage and reduces power stress to the MOSFET and to the secondary rectifying diodes during the start-up sequence. Various protections such as overvoltage, overload, overcurrent, maximum on-time protections and avalanche-energy-guaranteed MOSFET secure good systemlevel reliability.