SG6961 查看數據表（PDF） - Fairchild Semiconductor

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SG6961

Power Factor Controller

Fairchild Semiconductor 

Power Factor Controller

Product Specification

SG6961

Zero Current Detection

The zero current detection of the inductor is achieved

using its auxiliary winding. When the stored energy of

the inductor is fully released to output, the voltage on

ZCD goes down and a new switching cycle is enabled

after a ZCD trigger. The power MOSFET is always

turned on with zero inductor current, such that turn-on

loss and noise can be minimized. The converter works

in boundary mode, such that the peak inductor current is

always exactly twice of the average current. Moreover,

a natural power factor correction function is achieved

with the low-bandwidth on time modulation. An

inherent maximum off-time is built in to ensure proper

start-up operation. In addition, this pin can be used as a

synchronous input.

Noise Immunity

Noise on the current sense or control signal can cause

significant pulse-width jitter, particularly in the

boundary-mode operation. Slope compensation and

built-in debounce circuitry alleviate this problem. Note

that the SG6961 has a single ground pin; therefore, high

sink current at the output cannot be returned separately.

Good high-frequency or RF layout practices should be

followed. Avoid long PCB traces and component leads.

Locating compensation and filter components near to

the SG6961 and increasing the power MOSFET gate

resistance improve performance.

© System General Corp.

Version 1.3.1 (IRO33.0028.B6)

-9-

www.sg.com.tw • www.fairchildsemi.com

September 24, 2007

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