AN-6846 Datasheet, PDF (1/8 Pages) Fairchild Semiconductor – Control a Flyback Power Supply with Surge Current Output

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AN-6846
Applying SG6846 to Control a Flyback Power Supply with
Surge Current Output
Summary
This application note describes a detailed design strategy for
a high-efficiency, compact flyback converter. Design
considerations, mathematical equations, and guidelines for
printed circuit board layout are presented.
Applications
General-purpose switch-mode power supplies and flyback
power converters, including:
ƒ Power Adapters
ƒ Open-frame SMPS
ƒ SMPS with Surge-current Output, such as for Printers,
Scanners, Motor Drivers
0.9V/0.7V
VIN 3
Over-Power Compensation
1.18-0.08 VX IN
Figure 1. Pin Configuration
RI
4
VDD
Soft
Driver
8 GATE
VDD ⁷
RT ⁵
VDD -TH-G
UVLO
16.5V/10.5V
Latch
23.6V
I_RT
1.05V
Internal
BIAS
QS
R
Debounce
OCP
Delay
OSC
Green
Mode
+
1R
Slope
Compensation
1R
1R
/2R
6V
R
3R
Blanking
Circuit
2 FB
6 SENSE
1.15V
1
GND
Figure 2. Block Diagram
© 2008 Fairchild Semiconductor Corporation
Rev. 1.3.2 • 9/26/08
www.fairchildsemi.com