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PDF KA7526 Data sheet ( Hoja de datos )
| Número de pieza | KA7526 | |
| Descripción | Power Factor Correction Controller | |
| Fabricantes | Fairchild | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de KA7526 (archivo pdf) en la parte inferior de esta página. Total 22 Páginas | ||
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KA7526
Power Factor Correction Controller
www.fairchildsemi.com
Features
• Internal Startup Timer
• Internal R/C filter which eliminates the Need for an
External R/C filter
• Overvoltage Comparator eliminates Runaway Output
Voltage
• Zero Current Detector
• One Quadrant Multiplier
• Trimmed 1.5% Internal Bandgap Reference
• Under Voltage Lock Out with 5V of Hysteresis
• Totem Pole Output with High State Clamp
• Low Startup and Operating Current
• 8-Pin DIP or 8-Pin SOP
Applications
• Electronic Ballast
• SMPS
Descriptions
The KA7526 provides simple and high performance active
power factor correction. KA7526 is optimized for electronic
ballast and low power, high density power supplies requiring
a minimum board area, reduced component count and low
power dissipation. Addition of internal R/C filter eliminates
the need for an external R/C filter. Internal clamping of the
error amplifier and multiplier outputs improves turn on over-
shoot characteristics and current limiting. Special circuitry
has also been added to prevent no load runaway conditions.
The output drive clamping circuit limits overshoot of the
power MOSFET gate drive Independent of supply voltage,
so that it greatly enhance the system reliability.
8-DIP
8-SOP
1
1
©2000 Fairchild Semiconductor International
Rev. 5.0
1 page  
KA7526
Electrical Characteristics
Unless otherwise specified, for typical values Vcc=12V, Ta=25oC, for Min/Max values Ta is the operating ambient temperature range
with -25oC ≤ Ta ≤ 125oC.
Parameter
Symbol
UNDER VOLTAGE LOCK OUT SECTION
Start Threshold Voltage
Vth (st)
UVLO Hysteresis
HY(st)
Supply Zener Voltage
Vz
SUPPLY CURRENT SECTION
Start Up Supply Current
Ist
Operating Supply Current
ICC
Dynamic Operating Supply Current
Idcc
ERROR AMPLIFIER SECTION
Voltage Feedback Input Threshold
Vref
Line Regulation
Load Regulation (Note1)
Temperature Stability of Vref (Note2)
Input Bias Current
Output Source Current
Output Sink Current
Output Voltage Range (Note2)
Slew Rate
MULTIPLIER SECTION
Input Bias Current (pin3)
M1 Input Voltage Range (pin3)
M2 Input Voltage Range (pin2)
Multiplier Gain (Note3)
∆Vref1
∆Vref2
∆Vref3
Ib(ea)
Isource
Isink
∆Veao
SR
Ib(m)
∆Vm1
∆Vm2
K
Maximum Multiplier Output Voltage
Temperature Stability of K (Note2)
Vomax(m)
∆K/∆T
Condition
VCC Increasing
-
ICC=10mA
VCC<Vth(st)
Output not switching
50kHz, CI=1nF
Iref=0mA,-
25oC≤Ta≤125oC
12V≤Vcc≤25V
0mA≤Iref≤2mA
-25oC≤Ta≤125oC
-
Vm2=3V
Vm2=2V
No Load on E.A Output
-
-
-
-
Vm1=1V,
∆Vm2=2.7 to 3.3V
Vea(-)=0V, Vm1=2V
-25oC≤Ta≤125oC
Min. Typ.
12 13
45
30 36
- 0.3
-4
-5
2.44 -
- 0.1
- 0.1
- 20
-0.5 -
-2 -4.5
3 4.5
1.2 -
- 0.6
-0.5 -
0-
Vref -
0.49 0.62
1.55 1.65
- -0.2
Max. Unit
14 V
6V
-V
0.4 mA
8 mA
10 mA
2.56 V
10 mV
10 mV
- mV
0.5 µA
- mA
- mA
5.6 V
- V/µs
0.5
3.8
Vref+2
µA
V
V
0.74 1/V
1.75
-
V
%/oC
5
5 Page 
KA7526
Error Amplifier
An Error Amplifier with access to the inverting input and output is provided. The noninverting input is internally biased at
2.5V and is not pinned out. The output voltage of the power factor converter is typically divided down and monitored by the
inverting input. The error amp output is internally connected to the multiplier and is pinned out for external loop compensa-
tion. Typically, the loopbandwidth is set below 20Hz, so that the amplifer’s output voltage is relatively constant over a given ac
line cycle. In effect, the error amp monitors the average output voltage of the converter over several line cycles. Input bias cur-
rent(0.5uA, max) can cause an output voltage error that is equal to the product of the input bias current and the value of the
upper divider resistor, R1 in Fig. 2.1.
1.8V
Over Voltage To Drive
+Comparator Output Shutdown
R1 -
+
R2 Vref
+
R3 1
INV
-
Vref
_
+x
To Multiplier
Band width= 1/(2π×R1×Ccomp)
2
Ccomp EA OUT
Fig.2.1 Error Amp and Over Voltage Comparator
Over Voltage Protection
The low bandwidth (typically below 20Hz) characteristic of Error Amplifier control loop results in output voltage runaway
condition. This condition can occur during initial start-up, sudden load removal, or during output arcing. The over voltage
comparator monitors the output voltage of the error amplifier. When load is removed, error amp output swings lower than
1.8V, comparator is triggered high and output driver is turned off till the error amp inverting input voltage drops below 2.5V.
At this point, the error amp output swings positive, turns the output driver back on. .
Multiplier
A single quadrant, two input multiplier is the critical element that enables this device to get power factor correction. One input
of multiplier(Pin 3) is connected to an external resistor divider which monitors the rectified ac line. The other input is inter-
nally driven by a DC voltage which is the difference of error amplifier output (Pin 2) and reference voltage, Vref. The multi-
plier is designed to have an extremely linear transfer curve over a wide dynamic range, 0V to 3.8V for Pin 3, and 2.5V to 4.5V
for error amplifier output under all line and load conditions.
The multiplier output controls the current sense comparator threshold as the ac voltage traverses sinusoidally from zero to
peak line. This allows the inductor peak current to follow the ac line thus forcing the average input current to be sinusoidal. In
other words, this has the effect of forcing the MOSFET on-time to track the input line voltage, resulting in a fixed drive output
on-time, thus making the preconverter load appear to be resistive to the ac line.
The equation below describes the relationship between multiplier output and inputs.
Vmo = K × Vm1 × (Vm2-Vref)
K : Multiplier gain
Vm1: Voltage at Pin 3
Vm2: Error amp output voltage
Vmo: Multiplier output voltage
11
11 Page | ||
| Páginas | Total 22 Páginas | |
| PDF Descargar | [ Datasheet KA7526.PDF ] | |
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