SEMICONDUCTOR

TECHNICAL DATA

FC9931

2012. 10. 31

1/6

Revision No : 0

Features

Constant output current

Large step-down ratio

Unity power factor

Low input current harmonic distortion

Fixed frequency or

fixed off-time operation

Internal 450V linear regulator

Input and output current sensing

Input current limit

Enable, PWM and phase dimming

Applications

Offline LED lamps and fixtures

Street lamps

T

raffic signals

Decorative lighting

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General Description

The FC9931 is a

fixed frequency PWM controller IC designed

to control an

LED lamp driver using a single-stage PFC

buckboost-buck topology. It can

achieve a unity power factor

and a

very high step-down ratio that enables driving a single

high-brightness

LED from the 85-264VAC input without a

need for a power transformer. This topology allows reducing

the

filter capacitors and using non-electrolytic capacitors to

improve reliability. The FC9931 uses open-loop peak current

control to regulate both the input and the output current. This

control technique eliminates a need for loop compensation,

limits the input inrush current, and is inherently protected from

input under-voltage condition.

Capacitive isolation protects the LED Lamp from failure of the

switching MOSFET.

FC9931 provides a low-frequency PWM

dimming input that can accept an external control signal with a

duty ratio of 0-100% and a frequency of up to a few kilohertz.

The PWM dimming capability enables FC9931 phase control

solutions that can work with standard wall dimmers.

Typical Application Circuit

VIN

GATE

CS1

CS2

VDD

PWM

D

RT

GN

D

R

ref2

R

ref1

R

CS1

R

CS2

C2

L1

L2

C1

Q1

D3

R

S1

R

S2

D4

VO

+

-

D1

D2

~AC

~AC

C

IN

R

T

FC9931

Unity Power Factor LED Lamp Driver