SG6742W: Green-Mode PWM Controller for Flyback Converter, 65KHz

The highly integrated SG6742WMR PWM controller provides several features to enhance the performance of flyback converters.

To minimize standby power consumption, a proprietary Green-Mode function provides off-time modulation that linearly decreases the switching frequency at light-load conditions. To avoid acoustic-noise problems, the minimum PWM frequency is set above 22KHz. Green Mode enables the power supply to meet international power conservation requirements. With the internal high-voltage startup circuitry, the power loss due to bleeding resistors is also eliminated. To further reduce power consumption, SG6742WMR is manufactured using the BiCMOS process, which allows an operating current of only 2.7mA.

SG6742WMR integrates an asynchronous frequency-hopping function that helps reduce EMI emission of a power supply with minimum line filters. Synchronized slope compensation achieves stable peak-current-mode control. The proprietary, internal line compensation ensures constant output power limit over a wide AC input voltage range, from 90VAC to 264VAC.

SG6742WMR provides many protection functions. In addition to cycle-by-cycle current limiting, the internal open-loop protection circuit ensures safety should an open-loop or output short-circuit failure occur. PWM output is disabled until VDD drops below the UVLO lower limit, when the controller starts up again. As long as VDD exceeds ~26V, the internal OVP circuit is triggered.

SG6742WMR is available in an 8-pin SOP package.

Application Notes