SG6741

The highly integrated SG6741 series of PWM controllers provides several features to enhance the performance of flyback converters.

To minimize standby power consumption, a proprietary green-mode function provides off-time modulation to linearly decrease the switching frequency at light-load conditions. To avoid acoustic-noise problems, the minimum PWM frequency is set above 18KHz.This green-mode function enables the power supply to meet international power conservation requirements.With the internal high-voltage start-up circuitry, the power loss due to bleeding resistors is also eliminated.To further reduce power consumption, SG6741 is manufactured using the BiCMOS process, which allows operating current as low as 4mA.

SG6741 integrates a frequency-hopping function that helps reduce EMI emission of a power supply with minimum line filters.Its built-in synchronized slope compensation achieves stable peak-current-mode control.The proprietary internal line compensation ensures constant output power limit over a wide range of AC input voltages, from 90VAC to 264VAC.

SG6741 provides many protection functions. In addition to cycle-by-cycle current limiting,the internal open-loop protection circuit ensures safety when an open-loop or output short-circuit failure occurs.PWM output is disabled until V_DD drops below the UVLO lower limit; then the controller starts again.As long as V_DD exceeds about 26V, the internal OVP circuit is triggered.

SG6741 is available in an 8-pin DIP or SOP package.