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PDF KA7525B Data sheet ( Hoja de datos )
| Número de pieza | KA7525B | |
| Descripción | Power Factor Correction Controller | |
| Fabricantes | Fairchild | |
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KA7525B
Power Factor Correction Controller
www.fairchildsemi.com
Features
• Internal Start-up Timer
• Internal Current Sense Blanking 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 2.1V of Hysteresis
• Totem Pole Output with High State Clamp
• Low Start-up and Operating Current
• 8-Pin DIP or 8-Pin SOP.
Applications
• Electronic Ballast
• SMPS
Description
The KA7525B provides simple and high performance active
power factor correction. KA7525B 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 current sense blanking (Internal R,C) eliminates the
need for an external R/C filter. Internal clamping of the error
amplifier and multiplier outputs improves turn on overshoot
characteristics and current limiting. Special circuitry has also
been added to prevent no load runaway conditions. Output
drive clamps limiting power MOSFET gate drive
independent of supply voltage greatly enhance the products
practical application.
8-DIP
1
8-SOP
1
©2002 Fairchild Semiconductor Corporation
Rev.1.0.1
1 page  
KA7525B
Electrical Characteristics (Continued)
Parameter
CURRENT SENSE SECTION
Symbol
Conditions
Min. Typ. Max. Unit
Input Offset Voltage (Note2)
Input Bias Current
Current Sense Delay to Output (Note2)
Vio(cs)
Ib(cs)
td(cs)
Vm1 = 0V, Vm2 = 2.2V
0V ≤ Vcs ≤ 1.7V
-
-10 3 10 mV
-1 -0.3 1 µA
- 200 500 ns
ZERO CURRENT DETECT SECTION
Detect Input Threshold
Detect Hysteresis
Vth(det) Vdet Increasing
HY(det)
-
1.65 1.8 1.95 V
180 240 300 mV
Input Low Clamp Voltage
Input High Clamp Voltage
Input Bias Current
Input High/Low Clamp Diode
Current(Note2)
OUTPUT DRIVER SECTION
Output Voltage High
Output Voltage Low
Rising Time(Note2)
Falling Time(Note2)
Vclamp(I)
Vclamp(h)
Ib(det)
Idet = -100uA
Idet = 3mA
1V ≤ Vdet ≤ 6V
Iclamp(d)
-
Voh IO = -10mA, VCC = 12V
Vol IO = 10mA, VCC = 12V
tr CI = 1nF
tf CI = 1nF
0.45 0.75
6.7 7.5
-1 -0.2
1
8.3
1
V
V
µA
- - ±3 mA
8.5 9 - V
- 0.8 1 V
- 130 200 ns
- 50 120 ns
Maximum Output Voltage
Vomax(o) VCC = 20V
12 13 15 V
Output Voltage With UVLO Activated Vomin(o) VCC = 5V, IO = 100µA
- - 1V
RESTART TIMER SECTION
Restart Time Delay
td(rst) Vm1 = 1V, Vm2 = 3.5V
- 300 - µs
OVER VOLTAGE PROTECTION SECTION
Voltage Feedback Input Threshold
Vth(ovp) Vcs= -0.5V, Vm1=1V , Vdet=0V 1.7 1.8 1.9 V
Notes :
1. Because the reference is not brought out externally, this specification cannot be tested on the package part. It is guaranteed
by design.
2. These parameters, although guaranteed, are not 100% tested in production.
Pin4 Threshold
3. K =
Vm1×(Vm2-Vref)
(Vm1=Vpin3, Vm2=Vpin2)
5
5 Page 
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
KA7525B
Current Sense
Comparator
-
+
CS
4
+
1.24V
Vref
3
MULT
Vm1
Vmo
Error Amp.
- Vm2 +
+
+-
2
EA OUT
Figure 3.1 Multiplier Block
1
INV
Current Sense Comparator
The current sense comparator RS latch configuration used ensures that only a single pulse appears at the drive output during a
given cycle. MOSFET drain current is converted to voltage using an external sense resistor in series with the external power
MOSFET. When sense voltage exceeds the threshold set by the multiplier output, the current sense comparator terminates the
gate drive to the MOSFET and resets the PWM latch. The latch insures that the output remains in a low state after the MOS-
FET drain current falls back to zero.
The peak inductor current under normal operating conditions is controlled by the multiplier output, Vmo.
Abnormal operating conditions occur during preconverter start-up at extremely high line or if output voltage sensing is lost.
Under these conditions, the multiplier output and current sense threshold will be internally clamped to 1.24V. Therefore, the
maximum peak switch current is limited to:
Ipk(max) = 1.24V / Rsense
Internal R,C filter has been included to attenuate any high frequency noise that may be present on the current waveform. These
circuit block eliminate the need for an external RC filter otherwise required for proper operation of the circuit.
LEB Delay(KA7525R)C filter
cs
+4
- Rsense
1.24V
Multiplier
Output
Low Pass Filter can be
eliminated
Figure 4.1 Current Sense Circuit
11
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet KA7525B.PDF ] | |
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