LC5540LF Series

Description

LC5540LF series is a quasi-resonant topology switching

power supply IC, designed for input capacitorless applica-

tions, and making it possible for systems to comply with the

harmonics standard (IEC61000-3-2 class C). It incorporates

separate controller and power MOSFET chips. The control-

ler adapts the average current control method for realizing

high power factors, and the quasi-resonant topology contrib-

utes to high efficiency and low EMI noise. The rich set of

protection features helps to realize low component counts,

and high performance-to-cost power supply.

The LC5540LF devices are intended for isolated designs.

650 V (LC5546LF and LC5547LF) to 800 V (LC5549LF).

(LC5546LF). It is capable of a maximum output power

of 80 W on 230 VAC supply to 55 W on universal supply

(LC5547LF) based on the thermal rating. Note that the

maximum output power can be up to 120% to 140% of this

value. However, it may be limited in applications with low

output voltage or short duty cycle.

Features and Benefits

• Integrated on-width control circuit (it realizes high power

factor by average current control)

• Integrated startup circuit (no external startup

circuit necessary)

• Integrated soft-start circuit (reduces power stress during

start-up on the incorporated power MOSFET and rectifier)

• Integrated bias assist circuit (improves the startup

operation, allows reduction of VCC capacitor value as well

as use of a ceramic capacitor)

• Integrated Leading Edge Blanking (LEB) circuit

• Integrated maximum on-time limit circuit

• Dual-chip structure, with an avalanche-guaranteed power

MOSFET (allows simplified surge suppressing circuits)

• Protection features:

▫ Overcurrent protection (OCP): pulse-by-pulse

▫ Overvoltage protection (OVP): latched shutdown

▫ Overload protection (OLP): latched shutdown

▫ Thermal shutdown (TSD): latched shutdown

Single-Stage Power Factor Corrected

Off-Line Switching Regulators

Typical Application

Applications

• LED lighting fixtures

• LED light bulbs

C2

C6

C5

C3

D8

+

-

PC1

U2

DZ1

D1

D3

D2

D4

F1

L1

C1

Q1

D5

C4

T1

D6

D7

DZ2

PC2

L2

LED

R1

PC2

D9

R8

R9

R10

R11

R12

R13

R14

R15

R16

R17

R18

R19 R20

(Rocp)

R2

R3

R4

R5

R6

VAC

PC1

R7

C7

C8

C10

C9

C11

C12

C13

C14

C15

C16

C17

D/ST S/GND VCC

Control

Part

OCP

OVP

NC

FB

U1

LC554xLF

7

6

5

4

3

2

1

Packages: 7-pin TO-220F

Not to scale

LF 3052

LF 3054

LF 3051

LC5540LF-DS

SANKEN ELECTRIC CO., LTD.