SG6980DZ Fairchild Semiconductor, SG6980DZ Datasheet - Page 12

• 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 SG6980 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 SG6980 can synchronize the OUT and synchronize
signals provided by second stage, which reduces switching
noise and the ripple on output voltage. Figure 3 shows the
relationship between the OUT and SYNC signals.
FIG.3 Synchronized Interleaving-Switching
RDY Signal Section
SG6980 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 delays around 5ms.
Use the pin to turn on the second stage PWM when the
bulk capacitor voltage is high enough. In SG6980, the
RDY
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 SG6980, average-current-mode control is
utilized for continuous-current-mode operation 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
average-current-mode control circuit of SG6980.
© System General Corp.
Version 1.0.1 (IAO33.0064.B0)
shows
pin
(open-drain
the
total
control
structure)
loop
is
used
for
for
the
- 12 -
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
Rs, better noise immunity is achieved. The output of IEA
is 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 R
maximum of R
not exceed the specified maximum value.
There are different concerns in determining the value of
the sense resistor, R
enough to reduce power consumption, 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
(as shown in Figure 4). This establishes a dominant pole
f1 (per Equation 6) for the voltage loop.
I
I
MO
MP
MO
MO
O
EA
, the current output from IMP pin, is the summation of
and a capacitor C
and I
should be kept as DC as possible, according to
u
R
K
2
MR1
2
u
and R
I
. I
AC
I
V
S
www.sg.com.tw • www.fairchildsemi.com
S
MR1
RMS
u
S
u
3
can be determined because I
goes negative with respect to ground.
V
are also identical. They are used to pull
R
and I
2
EA
EA
S
S
. The value of R
---------------
(1µF ~ 10µF) connected to ground
(
µA
MR2
)
are identical, fixed-current
-----------------
S
Product Specification
is proportional to I
September 17, 2007
S
RMS
should be small
and narrow
SG6980
MO
RMS
should
MO
2
and
and
(4)
:
(5)