FAN6756: mWSaver™ PWM Controller for Flyback Converter, 65KHz, X-Cap discharge

The FAN6756 is a next-generation Green Mode PWM controller with innovative mWSaver™ technology, which dramatically reduces standby and no-load power consumption, enabling conformance to worldwide Standby Mode efficiency guidelines.

An innovative AX-CAP™ method minimizes losses in the EMI filter stage by eliminating the X-cap discharge resistors while meeting IEC61010-1 safety requirements. Standby Mode clamps feedback voltage and modulates feedback impedance with a impedance modulator during Burst Mode operation, which forces the system to operate in a “deep” Burst Mode with minimum switching losses.

Protections ensure safe operation of power system in various abnormal conditions. Proprietary asynchronous jitter decreases EMI emission and built-in synchronized slope compensation allows more stable Peak-Current-Mode control over wide range of input voltage and load conditions. The proprietary internal line compensation ensures constant output power limit over entire universal line voltage range.

Requiring a minimum number of external components, FAN6756 provides a basic platform that is well suited for cost-effective flyback converter designs that require extremely low standby power consumption.

Features

• Achieves Low No-Load Power Consumption: Less than 30mW at 230V_AC (EMI Filter Loss Included)
• Eliminates X Capacitor Discharge Resistor Loss with AX-CAP™ Technology
• Linearly Decreases Switching Frequency to 23KHz
• Burst Mode Operation at Light-Load Condition
• Impedance Modulation in Standby Mode for “Deep” Burst Mode Operation
• Low Operating Current (450µA) in Standby Mode
• 500V High-Voltage JFET Startup Circuit to Eliminate Startup Resistor Loss
• Proprietary Asynchronous-Jitter to Reduce EMI
• High-Voltage Sampling to Detect Input Voltage
• Peak-Current-Mode Control with Slope Compensation
• Cycle-by-Cycle Current Limiting with Line Compensation
• Leading Edge Blanking (LEB)
• Built-In 8ms Soft-Start
• Brown-In/Brownout Recovery
• Internal Overload/Open-Loop Protection (OLP)
• V_DD Under-Voltage Lockout (UVLO)
• V_DD Over-Voltage Protection (VDD OVP)
• Over-Temperature Protection (OTP)
• Current-Sense Short-Circuit Protection (SSCP)

Application Notes