SG6903SZ Fairchild Semiconductor, SG6903SZ Datasheet - Page 15

• Manufacturer Part Number: SG6903SZ
• Description: IC PFC CONTROLLER 16SOIC
• Manufacturer: Fairchild Semiconductor

Specifications of SG6903SZ

• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (3.9mm Width)
• Output Voltage: 1.5 V to 8 V
• Switching Frequency: 65 KHz
• Operating Temperature Range: - 20 C to + 85 C
• Mounting Style: SMD/SMT
• Duty Cycle (max): 83 %
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Supply: -
• Operating Temperature: -
• Frequency - Switching: -
• Mode: -
• Current - Startup: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Green Mode PFC/Flyback-PWM Controller
R2 and maximum of Rs can be determined since I
should not exceed the specified maximum value.
value of the sense resistor Rs. The value of Rs should be
small to reduce power consumption, but it should be large
enough to maintain the resolution. A current transformer
(CT) may be used to improve the efficiency of high power
converters.
and V
to Equation (4). In other words, good RC filtering for
V
frequency) for voltage loop are suggested for better input
current shaping. The trans-conductance error amplifier
has output impedance Z
10µF) should be connected to ground. This establishes a
dominant pole f1 (Equation (6)) for the voltage loop.
© System General Corp.
Version 1.0.1 (IAO33.0061.B0)
RMS
According to Equation (5), the minimum value of
There are different concerns in determining the
To achieve good power factor, the voltage for V
EA
and narrow bandwidth (lower than the line
should be kept as constant as possible according
O
and a capacitor C
FIG.5 Average current mode control loop
EA
(1µF ~
RMS
MO
- 15 -
error amplifier, actually controls the total input power and
hence the power delivered to the load.
The average total input power can be expressed as:
From Equation (7), V
Pin
∝
∝
∝
=
f
1
=
V
V
V
2
RMS
RMS
RMS
2
=
π
×
Vin(rms)
×
×
×
×
R
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V
Z
EA
I
AC
I
R
Vin
1
MO
AC
O
V
AC
V
×
RMS
×
RMS
C
×
V
×
EA
2
V
EA
2
Iin(rms)
EA
EA
, the output of the voltage
---------------------- (6)
Product Specification
---------------- (7)
September 28, 2007
SG6903