SG6961 Fairchild Semiconductor, SG6961 Datasheet - Page 9

• Manufacturer Part Number: SG6961
• Description: Power Factor Controller
• Manufacturer: Fairchild Semiconductor

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Power Factor Controller
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.
© System General Corp.
Version 1.3.1 (IRO33.0028.B6)
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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.
www.sg.com.tw • www.fairchildsemi.com
Product Specification
September 24, 2007
SG6961