X-CAP Bleeder

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Product Description

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. The HF81 acts as a smart high-voltage switch when placed in series with discharge resistors (alternatively bleed resistors). In the presence of an AC voltage, the HF81 blocks current flow in the safety discharge resistors to reduce the power loss in these components to zero at 230 VAC. When disconnected from the AC voltage, the HF81 automatically and safely discharges the X capacitor by closing the circuit through the bleed resistors and directing the energy away from the exposed AC plug. Table 1: Component Selection Table PN X Capacitance Total Series Resistance Power Saving(1) HF81 ≤500nF 1.5MΩ 750nF 1MΩ 66mW 1μF 780kΩ 86mW 1.5μF 480kΩ 142mW 2μF 360kΩ 191mW 2.5μF 300kΩ 230mW 3.5μF 200kΩ 347mW 5μF 150kΩ 464mW.

Product 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


  • Power Range DefinedNo
  • GradeCatalog
  • PackageDIP8, SOIC-8
  • Vbr (V)1000
  • Isupply (µA)15
  • Isc (mA)1.7
Quality Policy, Certificates & Reliability Reports
All MPS parts are lead-free, halogen-free and adhere to the RoHS directive. See Environmental section for details.