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 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 90VThe 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 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.
●Features
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● 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
● VDD Over-Voltage Clamping
● Cycle-by-Cycle Current Limiting
● Under-Voltage Lockout (UVLO)
● Gate Output Maximum Voltage Clamped at 17V
● Fixed PWM Frequency with Hopping
● Small SOT-26 Package
