SG6741A

SG6741A — Highly Integrated Green-Mode PWM Controller April 2008 SG6741A — Highly Integrated Green-Mode PWM Controller Features ƒ ƒ ƒ ƒ ƒ ƒ ƒ ƒ ƒ ƒ ƒ ƒ ƒ High-voltage Startup Low Operating Current: 4mA Linearly Decreasing PWM Frequency to 18kHz Frequency Hopping to Reduce EMI Emissions Peak-current-mode Control Cycle-by-cycle Current Limiting Leading-edge Blanking (LEB) Synchronized Slope Compensation GATE Output Maximum Voltage Clamp: 18V VDD Over-voltage Protection (Auto Restart) VDD Under-voltage Lockout (UVLO) Internal Open-loop Protection Constant Power Limit (Full AC Input Range) 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. SG6741A integrates a frequency-hopping function internally to reduce EMI emission of a power supply with minimum line filters. A built-in synchronized slope compe...