HF81 X Capacitor Bleeder SOIC8

HF81 X Capacitor Bleeder SOIC8

HF81 is an innovative two-terminal IC that automatically discharges an X capacitor while eliminating power losses and allowing power supplies to comply with safety standards.

Key Specifications

Features

• Disconnect series discharge resistors from L-N when AC voltage is applied
• Connect series discharge resistors with L-N to discharge the X capacitor when AC voltage is unplugged
• Supplied by AC voltage directly and doesn't need external bias
• Meets safety standards for use before or after input fuse
• No external ground pin leads to high common mode surge immunity
• 1000V internal JFET inside leads to high differential surge immunity
• >4mm creepage on package and PCB
• Compliant to IEC 60950-1

Typical Application Circuit

Applications

• AC/DC converters with X capacitors larger than 0.1μF
• All converters requiring ultra-low no-load consumption and low standby power
• Appliances requiring EuP Lot 6 compliance
• Appliances requiring Energy Star V2.0
• White Goods (For example, Dishwasher, Washing Machine, Air-Conditioner and etc.)

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