OMO ElectronicOMO Electronic
Expand menu
Hello, Sign inMy Account
0 Cart

IR21593STRPBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P26
IR21592/IR21593
(
S
)
&
(
PbF
)
16 www.irf.com
Brown-out Protection
In addition to the voltage on VCC being above
the start-up threshold, pin VDC must also be
above 5.1V for HO and LO to begin oscillating. A
voltage divider (R3,RVDC) from the rectified AC
line connected to pin VDC measures the rectified
AC line input voltage to the ballast and programs
the turn-on and turn-off line voltages. A filter
capacitor (CVDC) is also connected to pin VDC
that must be chosen such that the ripple is low
enough and the lower turn-off threshold of 3V is
not crossed during normal line conditions. This
detection is necessary due to the possibility of
the lamp extinguishing during low-line conditions
before the IC is properly reset. Should a brown-
out occur, the DC bus can drop to a level below
the minimum required for the tank circuit to
maintain the necessary lamp voltage. This
detection will insure a clean turn-off before the
DC bus drops too low and properly resets the
IC to the preheat mode when the line returns.
Preheat (PH)
The IR21592/IR21593 enters preheat mode
when VCC exceeds the UVLO+ threshold and
VDC exceeds 5.1V. HO and LO begin to
oscillate at the maximum operating frequency
with 50% duty cycle and at the internally set
dead-time of 2us (IR21592) or 1µs (IR21593). Pin
CPH is disconnected from COM and an internal
1uA current source (Figure 7) charges the external
timing capacitor on CPH linearly.
3
7.6V
2
1uA
7
8
CPH
FMIN
IPH
VCO
11
12
COM
LO
10
CS
1uA
60uA
I
FMIN
1/R
FMIN
5.1V
Q2
RCS
VCO
PH
LOGIC
16
HO
Q2
15
VS
R
FMIN
R
IPH
C
CPH
C
VCO
Half
Bridge
Output
I
LOAD
V
BUS
(+)
V
BUS
(-)
Load
Return
Half
Bridge
Driver
IR21592/IR21593
Figure 7, IR21592/IR21593 preheat circuitry.
An internal 1uA current source slowly discharges
the external capacitor on pin VCO and the voltage
on pin VCO begins to decrease. This decreases
the frequency, which, for operating frequencies
above resonance, increases the load current.
When the peak voltage measured on pin CS,
produced by a portion of the load current flowing
through an external sense resistor (RCS), exceeds
the voltage level on pin IPH, a 60uA internal
current source is connected to pin VCO and the
capacitor charges (Figure 8). This forces the
frequency to increase and the load current to
decrease. When the voltage on pin CS decreases
below the voltge on pin IPH, the 60uA current
source is disconnected and the frequency
decreases again.
IR21592/IR21593
(
S
)
&
(
PbF
)
www.irf.com 17
60uA
-1uA
t
t
t
t
V
CVCO
I
CVCO
V
RCS
VS
LO
HO
V
IPH
Figure 8, Peak load current regulation timing diagram.
This feedback keeps the peak preheat current
regulated to the user-programmable setting on pin
IPH for the duration of the preheat time. An
internal current source connected to an external
resistor on pin IPH sets a voltage reference for
the peak pre-heat current. The pre-heat time
continues until the voltage on pin CPH exceeds
5V.
Ignition (IGN)
The IR21592/IR21593 enters ignition mode when
the voltage on pin CPH exceeds 5V. The peak
current regulation reference voltage is
disconnected from the user-programmable
setting on pin IPH and is connected to a higher
internal threshold of 1.6V (Figure 9).
3
7.6V
2
1uA
4
CPH
DIM
VCO
11
12
COM
LO
10
CS
1uA
1.6V
Q2
RCS
VCO
PH
LOGIC
16
HO
Q2
15
VS
R
DIM
C
CPH
C
VCO
Half
Bridge
Output
I
LOAD
V
BUS
(+)
V
BUS
(-)
Load
Return
Half
Bridge
Driver
IR21592/IR21593
DIM
INTERFACE
0.5 to 5V
PHASE
CONTROL
FAULT
LOGIC
Figure 9, IR21592/IR21593 ignition circuitry.
The ignition ramp is then initiated as the
capacitor on pin VCO discharges linearly
through an internal 1uA current source. The
frequency decreases linearly towards the
resonance frequency of the high-Q ballast output
stage, causing the lamp voltage and load current
to increase (Figure 10). The frequency
continues to decrease until the lamp ignites or
the current limit of the IR21592/IR21593 is
reached. If the current limit is reached, the
IR21592/IR21593 enters FAULT mode. The 1.6V
threshold together with the external current
sensing resistor on pin CS determine the
maximum allowable peak ignition current (and
therefore peak ignition voltage) of the ballast
output stage. The peak ignition current must not
exceed the maximum allowable current ratings
of the output stage MOSFETs or IGBTs, and,
the resonant inductor must not saturate at
any time.
To prevent a "flash" across the lamp during
ignition at low dim settings, an ignition detection
IR21592/IR21593
(
S
)
&
(
PbF
)
18 www.irf.com
circuit measures the voltage at the CS pin and
compares it against the voltage at the IPH pin.
During the rising ignition ramp, the voltage at
the IPH pin is increased to 20% above its value
5.1V
V
CPH
V
VCO
t
t
PH
IGN
DIM
V
DIM
R
DIM
& C
TPH
TIME CONSTANT
IGN-TO-DIM
TIME
Figure 10, IR21592/IR21593 ignition detection.
during preheat mode. When the voltage on the
CS pin exceeds this voltage, the voltage on the
IPH pin is decreased to VIPH Pre-Heat +10% and
the ignition detection circuit is then active (See
Figure 10). When the lamp ignites, the voltage on
the CS pin will then fall below the voltage on the
IPH pin and the IC enters DIM Mode and the phase
control loop is closed. In order for the ignition
detection circuit to function properly and for the IC
to enter DIM mode, the voltage on the CS pin must
first rise above VIPH Pre-Heat + 20% during the
ignition ramp to activate the circuit, and then
decrease below VIPH Pre-Heat +10% when the lamp
ignites.
Ignition-to-Dim (IGN-to-DIM)
When the IR21592/IR21593 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 11),
pin DIM is connected internally to pin CPH when
the IR21592/IR21593 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 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
Figure 11, IR21592/IR21593 ignition timing diagram.
V
IPH
V
IPH
+ 20%
V
IPH
+ 10%
CS
PH IGN DIM
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P26

IR21593STRPBF

Mfr. #:
Buy IR21593STRPBF
Manufacturer:
Infineon / IR
Description:
LED Display Drivers Dim Ballast Cntrl 1.8us Deadtime
Lifecycle:
New from this manufacturer.
Delivery:
DHL FedEx Ups TNT EMS
Payment:
T/T Paypal Visa MoneyGram Western Union

Products related to this Datasheet