HF81

X Capacitor Bleeder

HF81 Rev. 1.12

www.MonolithicPower.com

1

11/15/2012

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© 2012 MPS. All Rights Reserved.

The Future of Analog IC Technology

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

Notes:

1) The values are calculated at Vin=265Vac

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

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.)

 Server Power, Telecom Power, ATX Power

All MPS parts are lead-free and adhere to the RoHS directive. For MPS green

status, please visit MPS website under Quality Assurance. “MPS” and “The

Future of Analog IC Technology” are Registered Trademarks of Monolithic

Power Systems, Inc.

TYPICAL APPLICATION