DESCRIPTION

The highly integrated SG6742 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 22KHz. 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 eliminated. To further reduce power consumption, SG6742 is manufactured using the BiCMOS process, which allows an operating current of 4mA.

FEATURES

„ High-voltage start-up

„ Low operating current (4mA)

„ Linearly decreasing PWM frequency to 22KHz

„ Frequency jittering to reduce EMI emission

„ Fixed PWM frequency (65KHz)

„ Peak-current-mode control

„ Cycle-by-cycle current limiting

„ Leading-edge blanking

„ Synchronized slope compensation

„ Internal open-loop protection

„ GATE output maximum voltage clamp (18V)

„ VDDunder-voltage lockout (UVLO)

„ VDDover voltage protection (OVP)

„ Programmable over-temperature protection (RT)

„ Internal latch circuit (OVP, RT)

„ Constant power limit (full AC input range)

„ Internal OTP sensor with hysteresis

APPLICATIONS

General-purpose switch-mode power supplies and flyback power converters, including:

„ Power Adapters

„ Open-Frame SMPS