IR2166 International Rectifier, IR2166 Datasheet - Page 27

• Manufacturer Part Number: IR2166
• Description: IC PFC/BALLAST CONTROL 16-DIP
• Manufacturer: International Rectifier
• Type: PFC/Ballast Controllerr

Specifications of IR2166

• Frequency: 39 ~ 50 kHz
• Current - Supply: 10mA
• Current - Output: 400mA
• Voltage - Supply: 11.5 V ~ 15.6 V
• Operating Temperature: -25°C ~ 125°C
• Package / Case: 16-DIP (0.300", 7.62mm)
• Package: 16-pin DIP
• Circuit: Fluorescent Ballast IC
• Offset Voltage (v): 600
• Output Source Current Min (ma): 250
• Output Sink Current Min (ma): 400
• Vcc Range (v): 10-25V with UVLO
• Output Voltage Min (v): 10
• Output Voltage Max (v): 25
• Pbf: PbF Option Available
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: *IR2166

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During lamp ignition, the DC bus can drop below
the rectified AC line voltage causing current to
conduct directly from the output of the rectifier,
through the PFC inductor and diode, to the DC
bus capacitor. This results in a low-frequency offset
of current in the PFC inductor. Since the zero-
crossing detection circuit only detects the high-
frequency zero-crossing of the inductor current,
the PFC MOSFET will turn on again each cycle
before the inductor current has reached zero. This
causes the PFC to work in a continuous conduction
mode and the sum of the low-frequency and high-
frequency components of current can saturate the
PFC inductor and/or damage the PFC MOSFET.
To protect against these conditions, a current
sense resistor (RS) can be inserted between the
source on the PFC MOSFET and ground, and a
diode (D4) connected from the top of this current-
sensing resistor to the VBUS pin (Figure 13).
13, External over-current protection circuit
Should high currents occur, the voltage across
the current-sensing resistor (RS) will exceed the
4.3V over-voltage protection threshold at the VBUS
pin and the PFC MOSFET will turn off safely
limiting the current. The watch-dog timer will then
Rectified
AC line
Current
Ground
High
RS
1
1N4148
D4
COMP
VBUS
CPH
RPH
PFC
RT
CT
ZX
1
2
3
4
5
7
6
7
8
16
15
14
13
12
11
10
9
VS
LO
HO
VCC
CS
VB
COM
SD/EOL
Ground
Device
restart the PFC as normal (Figure 14). The current
sensing resistor value should be selected such
that the over-current protection does not false trip
during normal operation over the entire line voltage
range and load range. A current-sensing resistor
value, for example, of 1.0 W will set the over-
current protection threshold to about 5 A peak.
Figure 14, PFC inductor current limited using over-
current protection circuit (upper trace: DC Bus,
100V/div; middle trace: AC line input voltage, 100V/
div; lower trace: PFC inductor current 1A/div).
The effect that these line and load conditions have
on the performance of the ballast depends on the
saturation level of the PFC inductor, the selection
of the PFC MOSFET, the DC bus capacitor value,
the maximum on-time limit set by DZCOMP, and,
how fast VCC decreases below UVLO- when the
DC bus drops during ignition (the 3V reset on the
VBUS pin does not become active until RUN mode).
For these reasons, the ballast designer should
perform these mains interrupt and ignition tests
carefully to determine the robustness of their final
design and to decide if this additional over-current
protection circuit is necessary.
IR2166 & (PbF)
27