FSBH0170

The highly integrated FSBH series consists of anintegrated current-mode Pulse Width Modulator (PWM)and an avalanche-rugged 700V SenseFET. It isspecifically designed for high-performance off-lineSwitch Mode Power Supplies (SMPS) with minimalexternal components.

The integrated PWM controller FSBH series features include aproprietary green-mode function that provides off-timemodulation to linearly decrease the switching frequencyat light-load conditions to minimize standby powerconsumption. To avoid acoustic-noise problems, theminimum PWM frequency is set above 18kHz. Thisgreen-mode function enables the power supply to meetinternational power conservation requirements. ThePWM controller is manufactured using the BiCMOSprocess to further reduce power consumption. TheFSBH series turns off some internal circuit to improvepower saving when V_FB is lower than 1.6V, which allowsan operating current of only 2.5mA.

The FSBH series has built-in synchronized slopecompensation to achieve stable peak-current-modecontrol. The proprietary external line compensationensures constant output power limit over a wide ACinput voltage range, from 90V_AC to 264V_AC.

The FSBH series provides many protection functions. Inaddition to cycle-by-cycle current limiting, the internalopen-loop protection circuit ensures safety when anopen-loop or output short occurs. PWM output isdisabled until V_DD drops below the V_TH-OLP, then thecontroller starts again. As long as V_DD exceeds 28V, theinternal OVP circuit is triggered.

Compared with a discrete MOSFET and controller orRCC switching converter solution, the FSBH seriesreduces total component count, design size, andweight; while increasing efficiency, productivity, andsystem reliability. FSBH series provide a basicplatform well suited for design of cost-effective flybackconverters, such as in PC auxiliary power supplies.