FSL137H: 700V Integrated Power Switch for 19Watt offline flyback converters, 100kHz, Brown In/Out Protection

The highly integrated FSL137H consists of an integrated current mode Pulse Width Modulator (PWM) and an avalanche-rugged 700V SenseFET. It is specifically designed for high-performance offline Switch Mode Power Supplies (SMPS) with minimal external components.

The integrated PWM controller features include a proprietary green-mode function that provides off-time modulation to linearly decrease the switching frequency at light-load conditions to minimize standby power consumption. To avoid acoustic noise problems, the minimum PWM frequency is set above 18KHz. The 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 also eliminated. To further reduce power consumption, the PWM controller is manufactured using the BiCMOS process, which allows an operating current of only 3.5mA.

The FSL137H built-in synchronized slope compensation achieves stable peak-current-mode control. The proprietary external line compensation ensures constant output power limit over a wide AC input voltage range, from 90VAC to 264VAC.

The FSL137H provides many protection functions. In addition to cycle-by-cycle current limiting, the internal open-loop protection circuit ensures safety when an open-loop or output short-circuit failure occurs. PWM output is disabled until VDD drops below the UVLO lower limit, when the controller starts up again. As long as VDD exceeds ~28V, the internal OVP circuit is triggered.

Compared to a discrete MOSFET and controller or RCC switching converter solution, the FSL137H reduces total component count, design size, and weight while increasing efficiency, productivity, and system reliability. These devices provide a basic platform well suited for design of cost-effective flyback converters.

Features

• Built-in 5ms Soft-Start Function
• Internal Avalanche Rugged 700V SenseFET
• Low Audio Noise
• High-Voltage Startup
• Fixed PWM Frequency at 100KHz
• Linearly Decreasing PWM Frequency to 18KHz
• Peak-Current-Mode Control
• Cycle-by-Cycle Current Limiting
• Leading-Edge Blanking (LEB)
• Synchronized Slope Compensation
• Internal Open-loop Protection (OLP)
• V_DD Under-Voltage Lockout (UVLO)
• V_DD Over-Voltage Protection (OVP)
• Constant Power Limit (Full AC Input Range)
• Internal OTP Sensor with Hysteresis

Application Notes