This highly integrated PWM controller provides several features to enhance the performance of low-power flyback converters. To minimize standby power consumption, a proprietary green-mode function provides off-time modulation to linearly decrease the switching frequency under light-load and zero-load conditions. This green mode enables the power supply to meet international power conservation requirements. The supply voltage V_DD is also used for feedback compensation, to regulate the output voltage without requiring a conventional TL431 and a photo-coupler. Another advantage of the FAN400A is that the typical startup current is only 8µA, while the typical operating current can be as low as 3.6mA. A large startup resistance can be used to achieve even higher power conversion efficiency.

FAN400A integrates a frequency hopping function internally to reduce EMI emissions with minimum line filters. Built-in synchronized slope compensation maintains the stability of peak current-mode control. Proprietary internal compensation ensures constant output power limiting over a universal range of AC input voltages, from 90V_AC to 264V_AC.

The FAN400A provides many protection functions. Pulse-by-pulse current limiting ensures constant output current, even if a short circuit occurs. The internal protection circuit disables PWM output if V_DD exceeds 22.7V. The gate output is clamped at 17V to protect the power MOS from over-voltage damage. The built-in over-temperature protection (OTP) function shuts down the controller at 140°C with a 30°C hysteresis.

The FAN400A is designed to provide a low-cost total solution for flyback converters. It is available in a small-footprint, 6-pin, SOT-26 package.

• Linearly Decreasing PWM Frequency
• Green Mode Under Light-Load and Zero-Load Conditions
• Constant Voltage (CV) and Constant Current (CC)
• No Secondary Feedback
• Low Startup Current: 8µA
• Low Operating Current: 3.6mA
• Leading-Edge Blanking
• Constant Power Limit
• Universal AC Input Range
• Synchronized Slope Compensation
• 140°C OTP Sensor with Hysteresis
• V_DD Over-Voltage Clamping
• Cycle-by-Cycle Current Limiting
• Under-Voltage Lockout (UVLO)
• Fixed PWM Frequency with Hopping
• Gate Output Maximum Voltage Clamped at 17V
• Small SOT-26 Package

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

• Battery Chargers for Cellular Phones, Cordless Phones, PDAs, Digital Cameras, Power Tools
• Power Adapters for Ink Jet Printers, Video Game Consoles, Portable Audio Players
• Open-frame SMPS for TV/DVD Standby and Auxiliary Supplies, Home Appliances, Consumer Electronics
• Replacement for Linear Transformers and RCC SMPS
• PC 5V Standby Power