HF500A-20 Flyback Controller

HF500A-20 Flyback Controller

The HF500A-20 is a fixed-frequency, flyback, controller with current control mode and internal slope compensation.

Key Specifications

Features

• Fixed Frequency, Current Mode Control, and Internal Slope Compensation
• 700V/2.6Ω Integrated MOSFET
• Frequency Foldback Down to 25kHz at Light Loads
• Burst Mode for Low Standby Power Consumption
• Frequency Jittering (fJITTER) for Reduced Electromagnetic Interference (EMI)
• Over-Power Compensation (OPC)
• Internal High-Voltage Current Source
• VCC Under-Voltage Lockout (UVLO) Protection with Hysteresis
• Configurable VIN Brownout Protection and Input Over-Voltage Protection (OVP)
• VCC Over-Voltage Protection (OVP)

Typical Application Circuit

Applications

• Home Appliance Power Supplies
• Set-Top Boxes
• Standby and Auxiliary Power

Design Notes

• The PFC inductor must support the maximum duty cycle at the lowest line voltage, which is where saturation risk peaks.
• High-voltage startup and X-capacitor discharge paths dominate no-load standby loss; verify them against the efficiency target.
• Leakage inductance and the RCD clamp set the turn-off loss — snubber values are a thermal trade-off, not a fixed recipe.
• Synchronous rectification timing must track the primary switching; a mistimed SR FET conducts through its body diode and fails hot.

Common Questions