IR2159 International Rectifier, IR2159 Datasheet - Page 19

• Manufacturer Part Number: IR2159
• Description: IC BALLAST CONTROL DIM 16-DIP
• Manufacturer: International Rectifier
• Type: Ballast Controllerr

Specifications of IR2159

• Frequency: 25 ~ 95 kHz
• Current - Supply: 10mA
• Voltage - Supply: 12.5 V ~ 15.6 V
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 16-DIP (0.300", 7.62mm)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Current - Output: -

and the IR2159 enters DIM mode and the phase
control loop is closed.
For a reliable ignition with minimal start-up flash,
the resistor on FMIN should be set to 5kHz lower
than the ignition frequency or the 100% brightness
dimming frequency, whichever is lower.
Ignition-to-Dim (IGN-to-DIM)
When the VCO decreases below VDIMTH, the
IR2159 enters dim mode. The phase control loop
is closed and the phase of the load current is
regulated against the user control input on pin DIM.
To control the rate at which the dim setting
changes from maximum brightness to the user
setting (IGN-TO-DIM time, Figure 10), pin DIM is
connected internally to pin CPH when the IR2159
enters DIM mode. The resistor on pin DIM (RDIM)
discharges the capacitor on pin CPH down to the
user dim setting. The resistor can be selected for
a fast time constant to minimize the amount of
flash visible over the lamp just after ignition, or, a
long time constant such that the brightness ramps
www.irf.com
V
5.1V
V
V
CPH
VCO
DIM
Figure 10, IR2159 ignition timing diagram.
PH
IGN
R
TIME CONSTANT
DIM
& C
DIM
IGN-TO-DIM
TPH
TIME
t
t
down smoothly to the user setting. Should the
ignition-to-dim time be too fast, however, the loop
can respond faster than the ionization constant
of the lamp (milliseconds) causing the VCO to
over-shoot. This can result in a frequency that is
higher than the minimum brightness frequency and
can extinguish the lamp. The capacitor on pin
CPH serves multiple functions by setting the
preheat time, the travel rate just after ignition
(together with resistor RDIM), and, serving as a
filter capacitor on pin DIM during dimming to
increase high-frequency noise immunity and
minimize component count.
Dimming (DIM)
To regulate lamp power, the error between the
reference phase and the phase of the output stage
current forces the VCO to steer the frequency in
the proper direction, as determined by the transfer
function of the output stage, such that the error is
forced to zero. An internal 15uA current source is
connected to pin VCO during dimming mode
(Figure 11) to discharge the VCO capacitor and
decrease the frequency towards lock.
0.5 to 5V
V
V
BUS
BUS
(+)
(-)
C
C
R
R
R
VCO
CPH
MAX
DIM
MIN
Figure 11, IR2159 dimming circuitry.
CPH
VCO
MAX
DIM
MIN
IR2159/IR21591
2
3
4
5
6
16uA
R
7.6V
FB
VCC
CONTROL
PHASE
INTERFACE
VCO
DIM
FAULT
LOGIC
Half
Bridge
Driver
IR2159
1.6V
16
15
11
10
12
HO
CS
COM
VS
LO
Q2
Q2
RCS
Load
Return
Half
Bridge
Output
I
LOAD
( S )
19