AN-6032| Application Note
www.fairchildsemi.com
Application Note AN6032
FAN4800 Combo Controller Applications
General Description
This application note shows the step-by-step process to design a high-performance supply. The equations shown in this document can also be used for different output voltages and total power. The complete power supply circuits shown in Figures 6 and 7 demonstrate the FAN4800's ability to manage high output power while complying with international requirements regarding AC line quality. The PFC section provides 380VDC to a dual-transistor current-mode forward converter. The output of the converter delivers +12V at up to 8.4 amps. The circuit operates from 85 to 265VAC with both power sections switching at 100kHz.
The PFC Stage
Powering the FAN4800
The FAN4800 is initialized once C12 is charged to 13V through R27 and R28. PFC switching action boosts the voltage on C5 to 380V via L1's inductance. T2 then supplies a well-regulated 13V for the FAN4800 from its secondary winding. T2's primary-to-secondary turns ratio (NPRI / NSEC) is 18.8:1. For proper circuit operation, high-frequency bypassing with low-ESR ceramic or film capacitors on VCC and VREF is provided. Orderly PFC operation upon start-up is achieved when D2 quick charges the boost capacitor to the peak AC line voltage before the boost switch Q1 is turned on. This ensures the boost inductor current is zero before
D3 RGF1J
F1 3.15A
L1 BR1 4A, 600V KBL06 R2A 453k R1A 500k R27 75k
D2 1N5406
D1 ISL9R460P2
VDC / +380V Q1G Q2G
C5 100uF 450V R7A 178k R17 33 C25 0.1uF R28 240 T1B C12 10uF 35V R7B 178k D7 MMBZ5245B R30 4.7k Q2 FQPF 6N50 D5 RGF1J
AC INPUT C1 85 TO 265Vac 0.68uF
Q1 FQPF9N50 D9 MBRS 140
C4 10nF
ISENSE
R5D R5C 1.2 R5B 1.2 R5A 1.2 1.2 R2B 453k C3 0.1uF R1B 500k R3 110k C2 0.47uF R4 15.4k
R21 22
C30 330uF 25V
Q3G
R6 41.7k R10 6.2k C7 NOT USED C6 1.5nF R14 33 C20 1uF R15 3 Q3 FQPF6N50
T2 D6 RGF1J
RAMP2 / DC ILIMIT
R20A 2.2 R19 220 R9 1.1k R20B 2.2
R31 100
R12 71.5k
T1A
U1
FAN4800
1 2 3 4 5 6
IEAO IAC ISENSE VRMS SS VDC RAMP1 RAMP2
VEAO VFB VREF VCC PFC OUT PWM OUT GND DC ILIMIT
16 15 14 13 12 11 10 9
VFB
Q4 MMBT3904 D4 MMBZ5245B
VREF
R13 10k
VCC
RAMP1
R11 845k D8 MBRS 140 R16 10k C16 1uF C15 10nF C13 0.1uF C14 1uF C8 68nF C9 10nF
C10 15uF
7 8
D10 MBRS 140 R8 2.37k C31 1nF
D12 1N5401 D13 1N5401 C26 100nF C19 1uF C18 470pF C11 10nF C17 220pF
VDC
PRI GND
Figure 1. The PFC Stage
2006 Fairchild Semiconductor Corporation FAN4800 Rev. 1.0.2 12/07/06 www.fairchildsemi.com
AN-6032 Application Note fairchild Download PDF
Add this permalink to your bookmarks for future download of AN-6032 ApplicationNote
Permalink: http://application.emcelettronica.com/fairchild/AN-6032
