FC2338 datasheet(7/9 Pages) FS

7 / 9 page

Internal Block Diagram

OVP

VREF

UVLO

&VREF

Current

Sense

PFC

Control

DRAIN

VCC

COMP

GND 2

5, 6

Driver

Thermal

Regulation

Logic &

Protection

Startup

& Power

Supply

Demag

Figure 5. FC2338 Internal Block Diagram

Application Information

The FC2338 integrating a 600V power MOSFET,

is a high precision non-isolated buck APFC LED

driver, specially designed for universal mains with

constant current control. The driver with on-chip PFC

circuit achieves high power factor, low THD and high

efficiency.

1 Start Up

After system powered on, the capacitor on VCC pin is

charged up by the internal JFET. When the VCC pin

voltage reaches the turn on threshold, the internal

circuits start working. The COMP pin voltage is

pulled up to 1.6V quickly, then the system starts

switching from 7kHz frequency at the beginning, the

COMP voltage rises up gradually, and the inductor

peak current also rises up. The LED current hence

achieves a soft start without overshoot.

2 Constant Current Control

The FC2338 utilizes patent pending floating ground

structure. The inductor current is sensed during the

whole switching cycle, thus it achieves high precision

output current control and also excellent line and load

regulation.

The LED current can be calculated by the equation:

Rcs

OUT

REF

≈

Where,

VREF: Internal reference voltage

Rcs: Value of the current sensing resistor

3 Feedback Network

The FB pin is used to detect output voltage, the OVP

threshold voltage is 1.65V. The ratio of FB upper

FC2338

2019. 10. 02

7/9

Revision No : 0

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