SG6980DZ Fairchild Semiconductor, SG6980DZ Datasheet - Page 13

• Manufacturer Part Number: SG6980DZ
• Description: IC PFC CTRLR AVERAGE CURR 16DIP
• Manufacturer: Fairchild Semiconductor

Specifications of SG6980DZ

• Mode: Average Current
• Frequency - Switching: 65kHz
• Current - Startup: 10µA
• Voltage - Supply: 12.5 V ~ 20 V
• Operating Temperature: -20°C ~ 125°C
• Mounting Type: Through Hole
• Package / Case: 16-DIP (0.300", 7.62mm)
• Output Voltage: 0.3 V to 25 V
• Switching Frequency: 68 KHz
• Operating Temperature Range: - 20 C to + 125 C
• Mounting Style: Through Hole
• Duty Cycle (max): 98 %
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Single-Stage PFC Controller
ON/OFF
For ON/OFF control, the SG6980D is disabled
immediately if the voltage at this pin is below 1V. Usually,
the pin opens when turn off can have the best power saving.
The operating current during turn off is less than 35µA.
SYNC Signal Section
The SG6980D can synchronize half frequency of the
SYNC signal and the synchronize signal provided by
second stage. This reduces switching noise and the ripple
on the output voltage. Figure 3 shows the relationship
between the OUT and SYNC signals.
FIG.3 Synchronized Interleaving-Switching
RDY Signal Section
SG6980D provides a RDY pin to inform the next stage and
other applications. RDY signal is high impedance when the
FB voltage goes up to 2.7V and the delay around 5ms. Use
the pin to turn on the second stage PWM when the bulk
capacitor voltage is high enough. The RDY pin (open-drain
structure) is used for the next-stage-ready signal.
PFC Operation
The purpose of a boost active power factor corrector (PFC)
is to shape the input current of a power supply. The input
current waveform and phase follow that of the input
voltage. Using SG6980D, average-current-mode control is
utilized for continuous current mode for the PFC booster.
With the innovative multi-vector control for voltage loop
and switching-charge multiplier/divider for current
reference, excellent input power factor is achieved with
good noise immunity and transient response. Figure 4
shows the total control loop for the average-current-mode
control circuit of SG6980D.
© System General Corp.
Version 1.0.1 (IAO33.0071.B0
- 13 -
FIG.4 Multiplier and Control Loop of PFC Stage
The current source output from the switching-charge
multiplier/divider can be expressed as:
I
I
sources. R
high the operating point of the IMP and ICS pins if the
voltage across R
Through the differential amplification of the signal across
R
compared with an internal sawtooth and the pulse width for
PFC is determined. Through the average current-mode
control loop, the input current I
According to Equation 5, the minimum value of R2 and
maximum of R
exceed the specified maximum value.
There are different concerns in determining the value of the
sense resistor R
to reduce power consumption, but large enough to maintain
the resolution. A current transformer (CT) may be used to
improve the efficiency of high-power converters.
To achieve a good power factor, the voltage for V
V
Equation 4. Good RC filtering for V
bandwidth (lower than the line frequency) for voltage loop
are suggested for better input current shaping. The
transconductance error amplifier has output impedance R
and a capacitor C
(as shown in FIG. 4). This establishes a dominant pole f1
(Equation 6) for the voltage loop.
I
I
IMP
MO
MO
MO
S
EA
, better noise immunity is achieved. The output of IEA is
, the current output from IMP pin, is the summation of
and I
should be kept as DC as possible according to
u
R
K
MR1
2
2
u
and R
I
. I
AC
S
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V
S I
S
S
MR1
can be determined because I
. The value of R
RMS
goes negative with respect to ground.
3
u
u
EA
are also identical. They are used to pull
and I
R
V
(1µF ~ 10µF) connected to ground
EA
S
2
---------------
MR2
(
µA
are identical fixed current
S
)
Product Specification
is proportional to I
S
-----------------
should be small enough
September 17, 2007
RMS
MO
SG6980D
and narrow
should not
RMS
MO
.
and
(4)
(5)
O