Description
The highly integrated SG6741A 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 startup circuitry, the power loss due to bleeding resistors is eliminated. To further reduce power consumption, SG6741A is manufactured using the BiCMOS process, which allows an operating current of only 4mA.

FEATUREs
ƒ High-Voltage Startup
ƒ Low Operating Current: 4mA
ƒ Linearly Decreasing PWM Frequency to 18kHz
ƒ Frequency Hopping to Reduce EMI Emissions
ƒ Peak-Current-Mode Control
ƒ Cycle-by-Cycle Current Limiting
ƒ Leading-Edge Blanking (LEB)
ƒ Synchronized Slope Compensation
ƒ GATE Output Maximum Voltage Clamp: 18V
ƒ VDD Over-Voltage Protection (Auto Restart)
ƒ VDD Under-Voltage Lockout (UVLO)
ƒ Internal Open-Loop Protection
ƒ Constant Power Limit (Full AC Input Range)

APPLICATIONs
General-purpose switch-mode power supplies and flyback power converters, including:
ƒ Power Adapters
ƒ Open-Frame SMPS