HF500-40 Flyback Regulator

HF500-40 Flyback Regulator

The HF500-40 is a fixed-frequency, current- mode regulator with built-in slope compensation.

Key Specifications

Features

• 700V/1Ω Integrated MOSFET
• Fixed-Frequency, Current-Mode Control Operation with Built-In Slope Compensation
• Frequency Foldback Down to 25kHz at Light Load
• Burst Mode for Low Standby Power Consumption
• Frequency Jittering for a Reduced EMI Signature
• Over-Power Compensation
• Internal High-Voltage Current Source
• VCC Under-Voltage Lockout (UVLO) with Hysteresis
• Programmable Input B/O and Over-Voltage Protection (OVP)
• VCC Over-Voltage Protection (OVP)

Typical Application Circuit

Applications

• Power Supplies for Home Appliances
• 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