IR21571S International Rectifier, IR21571S Datasheet - Page 14

• Manufacturer Part Number: IR21571S
• Description: IC BALLAST CONTROL 16-SOIC
• Manufacturer: International Rectifier
• Type: Ballast Controllerr

Specifications of IR21571S

• Frequency: 45.5 ~ 50.5 kHz
• Current - Supply: 5.5mA
• Current - Output: 500mA
• Voltage - Supply: 11.4 V ~ 15.6 V
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 16-SOIC (3.9mm Width)
• Package: 16-lead SOIC Narrow
• Circuit: Fluorescent Ballast IC
• Offset Voltage (v): 625
• 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
• Special Ic: Fully Integrated
• Pbf: PbF Option Available
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: *IR21571S

Thus, for a lamp removal and replacement, the ballast
automatically restarts the lamp in the proper manner,
maximizing lamp life and minimizing stress on the
power MOSFETs or IGBTs. The SD lead contains an
internal 7.5V zener diode clamp, thereby reducing
the number of external components required.
The third lead used for protection is the CS lead,
which is normally connected to a resistor in the source
of the lower power MOSFET, as shown in Figure 14.
The CS lead is used to sense fault conditions such
as failure of a lamp to strike, over-current during
normal operation, hard switching, no load, and
operation below resonance. If any one of these
conditions is sensed, the fault latch is set, the oscillator
is disabled, the gate driver outputs go low, and the
chip is put into the micropower mode. The CS lead
performs its sensing functions on a cycle-by-cycle
basis in order to maximize ballast reliability.
switching
programmable, positive-going CS+ threshold is
IR21571 (S) & (PbF)
14
For the over-current, failure-to-strike, and hard
R
VDC
CPH
RPH
RUN
OC
OC
Half-Bridge Current Sensing and
RT
CT
DT
Figure 14: Half-bridge current sensing circuit
1
2
3
4
5
6
7
8
fault
connection (shaded area)
16
15
14
13
12
11
10
9
VCC
COM
HO
CS
SD
VS
VB
LO
Protection
conditions,
C
D
R
BOOT
BOOT
GHS
AC line
rectifie
R
GLS
d
R
C
SUPPLY
R3
VCC
D1
V
BUS
+V
BUS
return
Q1
Q2
R
an
CS
externally
C
D2
SNUBBER
1
/
2
output
Bridge
enabled at the end of the preheat time. The level of
this positive-going threshold is determined by the
value of the resistor ROC. The value of the resistor
ROC is determined by the following formula:
For the under-current and under-resonance
conditions, there is a negative-going CS- threshold
of 0.2V which is enabled at the onset of the run mode.
The sensing of this CS- threshold is synchronized
with the falling edge of the LO output.
Figures 15, 16 and 17 are oscillographs of fault
conditions. Figure 15 shows a failure of the lamp to
strike, Figure 16 shows a hard switching condition
and Figure 17 shows an under-current condition.
R
V
OC
CS
Figure 15: Lamp failure to strike
+ =
=
50E -6 - R
50E - 6
V
CS
+
or
OC
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