Application Note AN-1037
IR2167: Universal Input Dual Lamp Ballast
Parallel Configuration for T8/32W and T8/36W
Table of Contents
Page
1. Features, Description, Introduction .............................................................. 1
2. Electrical Characteristics ............................................................................... 2
3. Functional Description ................................................................................... 3
4. Demo Board Bill of Materials ......................................................................... 6
5. Inductor Specifications .................................................................................. 7
6. Setup................................................................................................................ 9
6.1 Power Factor Correction Section ............................................................... 9
6.2 Protections .................................................................................................. 10
6.3 IR2167 Block Diagram ................................................................................ 10
6.4 Operating Sequence ................................................................................... 12
6.5 Startup Mode ............................................................................................... 12
6.6 Preheat Mode .............................................................................................. 13
6.7 Ignition Ramp Mode.................................................................................... 13
6.8 Run Mode..................................................................................................... 13
7. Control Circuit............................................................................................... 15
7.1 Additional Control Circuit for auto-restart after lamp replacement........ 15
8. Fault Protection Characteristics.................................................................. 17
8.1 Additional Control Circuit to avoid cold strike......................................... 18
8.2 Additional Control Circuit to avoid striations during start-up ................ 18
8.3 Improved End of Life solution ................................................................... 19
8.4 Improved End-of-life circuit ....................................................................... 19
This Application Note describes the IR2167 demo board for driving one or two
fluorescent lamp types. The design contains an EMI filter, active power factor correction
and a ballast control circuit.
APPLICATION NOTE
AN-1037
International Rectifier • 233 Kansas Street El Segundo CA 90245 USA
IR2167: Universal Input Dual Lamp Ballast
Parallel Configuration forT8/32W and T8/36W
By Cecilia Contenti, Masashi Sekine and Peter Green
Topics Covered
Features
Description
Introduction
Functional Description
Schematic Diagram
Bill of Materials
Protections
Control Circuit
Features
!
!
!
!
!
!
Drives 2 x 36W T8 or 2 x 32W T8 Lamp
Can work with 1 or 2 lamps
Universal Input Voltage: 90-250Vac
High Power Factor/Low THD
High Frequency Operation
Lamp Fault Protection in both lamps
(Open filament and broken lamp)
!
!
!
!
!
!
!
Lamp Filament Preheating
Low AC line and low DC bus Protection
Failure to strike Protection
Below resonance operation Protection
End of Life Protection
Thermal overload Protection
IR2167 HVIC Ballast Controller
Description
This Demo Board is a high efficiency, high power factor, fixed output electronic ballast designed for driving one or
two fluorescent lamp types. The design contains an EMI filter, active power factor correction and a ballast control
circuit using the IR2167. The IR2167 allows setting of the design parameters such as ignition voltage, preheat
current and time, running voltage and power through external resistors and capacitors. This demo board is intended to ease the evaluation of the IR2167 Ballast Control IC, demonstrate PCB layout techniques and serve as
an aid in the development of production ballasts using the International Rectifier IR2167.
Introduction
Driving two lamps in parallel as opposed to a series configuration has the advantage of lower voltage stress on the
ballast output stage components, the wiring and the fixture sockets. Additionally, the resonant L and C associated
with the lamps will be less sensitive to components tolerances due to the lower running lamp voltage compared to
the series configuration. Parallel configuration also allows the ballast to continue working when 1 lamp is removed.
For these reasons, the parallel configuration is becoming more popular.
NOTE: This configuration allows one lamp to remain running when the other is removed. This circuit switches off
both lamps when 1 lamp fails, this avoids damaging the other lamp or the ballast. In case of a fault in one lamp you
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AN1037
have to reset the input line voltage, replace or remove the lamp damaged and re-apply the line. Never replace the
lamp without resetting the line as this will not provide the correct preheat, ignition sequence.
In this application note we propose an additional circuit that is needed if automatic restart when replacing a failed
lamp is necessary.
Electrical Characteristics
Parameter
Lamp Type
Input Power
Units
Input Current
Preheat Mode Frequency
Preheat Mode Lamp Voltage
Preheat Time
Ignition Ramp Mode Frequency
Ignition Voltage
Ignition Ramp time
Run Mode Frequency
[Arms]
[kHz]
[Vppk]
[s]
[kHz]
[Vppk]
[ms]
[kHz]
Lamp Run Voltage
[Vppk]
[W]
Input AC Voltage Range
Power Factor
Total Harmonic Distortion
[VACrms]
[%]
Value
36W T8 or 32W T8
74 for 36W T8 and
66 for 32W T8
0.3
54
630
1
42
1600
15
45KHz for 36W T8
48KHz for 32W T8
310 for 36W T8
420 for 32W T8
90..250VAC (50..60Hz)
0.99-0.98
10
Fault Protection Characteristics
Fault
Line voltage low
Upper filament broken
Lower filament broken
Failure to ignite
Open circuit (no lamp)
No 1 lamp
End of Life
2
Ballast
Deactivates
Deactivates
Deactivates
Deactivates
Deactivates
Activates
Deactivates
Restart Operation
Increase line voltage
Reset Line and Lamp exchange
Reset Line and Lamp exchange
Reset Line and Lamp exchange
Reset Line and Lamp exchange
The other lamp stays on
Reset Line and Lamp exchange
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AN1037
Functional Description
Overview
The IR2167 Demo Board consists of an EMI filter, an active power factor correction section, a ballast control
section and a resonant lamp output stage. The output stage is for double lamp, parallel configuration, currentmode heating. The active power factor correction section is a boost converter operating in critical conduction
mode with free-running frequency. The ballast control section provides frequency shifting control of a traditional
RCL lamp resonant output circuit and is easily adaptable to a wide variety of lamp types. The ballast control
section also provides the necessary circuitry to perform lamp fault detection, low line detection and shutdown. The
circuit is designed to work with one or two lamps. If one of the lamps fails the ballast will shutdown and it is
necessary to turn off the line and remove the faulty lamp to continue work with only a single lamp or to replace the
faulty lamp.
Design Procedure to adapt the design to different lamp types
To adapt the design to different types of lamps you need to adjust the values of: LPFC, MPFC, MLO, MHO, CPH,
RT, RPH, RRUN, RCS, ROC, CT, RDT, CRAMP, REOL4, CRES1, CRES2, LRES1 and LRES2. Do not change
any others values !
1)
Use the Ballast Designer Software to set the values of LRES1, LRES2, CRES1, CRES2, MPFC, MLO
and MHO, RDT, CT, CRAMP, CS and to set the starting values of LPFC, CPH, RT, RPH, RRUN and
ROC.
Cross both lamps (i.e. connect a filament or resistor to each lamp cathode position but not a good lamp) and
measure the lamp voltage at ignition using a storage oscilloscope.
1)
2)
3)
4)
Set ROC to get the right ignition voltage ((decrease ROC to decrease the ignition voltage or decrease
RCS to increase the ignition voltage)
Set RT to set the minimum frequency of the oscillator (increase RT to decrease the minimum frequency). Increase RT up to when the over-current protection is working in the worst case (i.e. the ballast
shuts down at ignition) : One lamp connected normally and the second one crossed.
Select CPH to set the preheat time (increase CPH to increase the preheat time)
Set RPH to set the right preheat current (increase RPH to increase the preheat current)
Connect both lamps correctly and measure the input power
5)
Select RRUN to set the correct power, RRUN is required only if the run frequency is above the ignition
frequency (increase RRUN to increase the power on the lamp)
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6)
Verify the value of LPFC at each limit of the line/load range:
Minimum load and maximum input voltage:
If the COMP pin becomes less than 400mV the PF will not operate in a stable manner and it is necessary to
increase LPFC.
Maximum load and minimum input voltage:
If the PF does not operate in a stable manner and audible noise can be heard from LPFC, it is necessary to
decrease LPFC.
7)
Set ROL4 to set the End of life protection to a percentage of the lamp voltage. For example, to set the
protection threshold to 20% of the lamp voltage:
{(Vpklamp) x 20/100} x REOL4 / (REOL4 + REOL1 + REOL2 + REOL3)
should give approximately 7V.
(Fine tuning of this threshold can be done by trying different REOL4 values on the test bench)
4
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AN1037
2167 dual lamp parallel
DPFC
LPFC
LRES2
CDC2
RSUPPLY
RVAC
CRES2
REOL5
L
F1
N
RV1
L1
RVDC
CVDC
C1
BR1
VDC
CPH
CPH
CRAMP
RPH
CBUS
GND
RPH
RT
RVBUS1
C2
RRUN
CT
RVBUS2
COC
2
ROC
4
RUN
5
6
DT
7
OC
CCOMP
COMP
RZX
ZX
19
3
RT
CT
RDT
20
18
IR2167
CY
1
17
16
15
14
8
13
9
12
10
11
REOL6
RHO
HO
MHS
LRES1
VS
VB
CBOOT
DBOOT
VCC
REOL7
CSNUB
RLIM2
CVCC1
COM
DCP2
RLIM3
CRES1
REOL1
CVCC2
LO
RLO
CS
RLIM1
REOL2
MLS
REOL3
DCP1
SD
PFC
CDC1
CCS
VBUS
IC BALLAST
CSD
MPFC
CVBUS
RCS
DEOL1
DEOL2
CEOL
REOL4
RPFC
Note: Thick traces represent high-frequency, high-current paths. Lead
lengths should be minimized to avoid high-frequency noise problems
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Demo Board Schematic
RVBUS
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Demo Board Bill of Materls
Item #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
Total
6
Qt
1
1
1
1
3
1
1
1
1
3
1
2
1
1
1
1
1
1
2
1
2
2
1
2
3
3
1
1
1
1
1
2
1
1
1
2
1
1
1
1
1
1
1
1
6
1
1
1
67
Manufacturer
International Rectifier
Roederstein
Dale
Roederstein
Wima
Panasonic
Panasonic
Panasonic
B.I. technologies
Panasonic
Panasonic
Part Number
DF10S
WY0222MCMBF0K
CW-1/2
F1772433-2200
MKP10
ERZ-V05D471
Digi-key
PCC1900CT-N
Panasonic
Panasonic
Digi-key
Panasonic
Panasonic
Digi-key
Diodes
International Rectifier
ECE-A1HGE02R2
International Rectifier
Panasonic
Panasonic
Panasonic
Panasonic
Panasonic
Yageo
Panasonic
Panasonic
Panasonic
ELF-15N007A
ECJ-2VB1HC104K
ECJ-2YB1C474K
311-1183-1-ND
ECU-V1H471KBN
MURS160DICT-ND
LL4148DICT-ND
IR2167
IRF840
ERJ-8GEYJ22
270KQBK-ND
ERJ-8GEYJ680K
Panasonic
Panasonic
Panasonic
ERJ-8GEYJ1K
Digi-Key
Digi-Key
ZMM5231BDICTND
ZMM5236BDICTND
WAGO
WAGO
235-203
235-207
Description
Bridge Rectifier, 1A 1000V
Capacitor, 2.2nF 275 VAC Y Cap
Resistor, 0.5Ohm, 1/.2W
Capacitor, 0.33uF 275 VAC
Capacitor, 0.1uF 400 VDC
Transient Suppressor
Capacitor, 22uF 450VDC 105C
EMI Inductor, 1X10mH 0.7Apk
PFC Inductor, 0.8mH 2.5Apk
Capacitor, 0.1uF SMT 0805
Capacitor, 0.47uF SMT 0805
Capacitor, 0.47uF SMT 1206
Capacitor, 0.56uF SMT 1206
Capacitor, 4.7uF 16V, SMT 1206
Capacitor, 0.01uF SMT 0805
Capacitor, 2.2uF 50VDC 105C
Capacitor, 0.68uF SMT 1206
Capacitor, 1nF 1KV SMT 1812
Capacitor, 8.2nF 1.6KV
Capacitor, 470pF SMT 0805
Diode, 1A 600V, SMT SMB
Diode, 1N4148 SMT DL35
IC, Ballast Driver /PFC
Inductor, 2.0mH 2.5Apk
Transistor, MOSFET
Resistor, 22 ohm SMT 1206
Resistor, 120K ohm SMT 1206
Resistor, 39Kohm SMT1206
Resistor, 47K ohm SMT 1206
Resistor, 100K ohm SMT 1206
Resistor, 270K ohm 1⁄4 watt
Resistor, 680K ohm SMT 1206
Resistor, 43K ohm SMT 1206
Resistor, 6.8K ohm SMT 1206
Resistor, 22K ohm SMT 1206
Resistor, 10 ohm SMT 1206
Resistor, 1K ohm SMT 1206
Resistor, 0.68 ohm SMT 2010
Resistor, 2.2 megohm 1/4W
Resistor, 22K ohm SMT 1206
5.1V Zener 0.5W SMT
7.5V Zener 0.5W SMT
Resistor, 13Kohm 1% SMT805
Capacitor, 100pF SMT 0805
Resistor, 220K ohm SMT 1206
Resistor, 160K ohm SMT 1206
Connector, 3 terminal
Connector, 7 terminal
Reference
BR1
CY
F1
C1
C2, CDC1, CDC2
RV1
CBUS
L1
LPFC
CBOOT, CVCC1, COC
CSD
CVDC, CRAMP
CPH
CEOL
CVBUS
CVCC2
CCOMP
CSNUB
CRES1, CRES2
CT
DBOOT, DPFC
DCP2, DCP1
IC BALLAST
LRES1, LRES2
MPFC, MHS, MLS
RPFC, RLO, RHO
RVDC
RPH
RRUN for T8 32W lamp
RRUN for T8 36W lamp
RSUPPLY
RVBUS1, RVBUS2
ROC
RDT
RT
RLIM2, RLIM3
RLIM1
RCS
RVAC
RZX
DEOL2
DEOL1
RVBUS
CCS
REOL1, 2, 3, 5, 6, 7
REOL4
X1
X2
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AN1037
Inductor Specifications
INDUCTOR SPECIFICATION
TYPE : LRES1, LRES2
E25/13/7 (EF25)
CORE SIZE
GAP LENGTH
1
PINS
8
HORIZONTAL
BOBBIN
mm
Philips 3C85, Siemens N27 or equivalent
CORE MATERIAL
NOMINAL INDUCTANCE
2
mH
MAXIMUM CURRENT
2
Apk
MAXIMUM CORE TEMPERATURE
100
ºC
WINDING START PIN FINISH PIN TURNS WIRE DIAMETER (mm)
MAIN
ELECTRICAL LAYOUT
1
8
177
4 strands of AWG 32
PHYSICAL LAYOUT
20.05mm
TOP VIEW
5mm
1
2
25mm
TEST
3
4
8
7 5mm
6
5
(TEST FREQUENCY = 50kHz)
MAIN WINDING INDUCTANCE
MIN 1.9
mH
MAIN WINDING RESISTANCE
MAX 1.5
Ohms
MAX 2.1
mH
NOTE : Inductor must not saturate at maximum current and maximum core temperature at given
test frequency.
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AN1037
INDUCTOR SPECIFICATION
TYPE : LPFC
CORE SIZE
BOBBIN
E25/13/7 (EF25)
GAP LENGTH
1
HORIZONTAL
PINS
8
mm
CORE MATERIAL Philips 3C85, Siemens N27 or equivalent
NOMINAL INDUCTANCE
0.8
mH
2
Apk
MAXIMUM CURRENT
MAXIMUM CORE TEMPERATURE
100
ºC
WINDING START PIN FINISH PIN TURNS WIRE DIAMETER (mm)
MAIN
1
6
111
4 strands of AWG 32
ZX
3
8
10
4 strands of AWG 32
ELECTRICAL LAYOUT
PHYSICAL LAYOUT
20.05mm
TOP VIEW
5mm
1
25mm
TEST
8
7 5mm
6
5
2
3
4
(TEST FREQUENCY = 50kHz)
MAIN WINDING INDUCTANCE
MIN 0.7
mH
MAIN WINDING RESISTANCE
MAX 1.5
Ohms
MAX 0.9
mH
NOTE : Inductor must not saturate at maximum current and maximum core temperature at given
test frequency.
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AN1037
Setup
Power Factor Correction Section
The power factor correction section contained in the IR2167 forms the control for a boost topology circuit operating in critical conduction mode. This topology is designed to step-up and regulate the output DC bus voltage while
drawing sinusoidal current from the line (low THD) which is “in phase” with the AC input line voltage resulting in a
high power factor.
Our simplified critical conduction mode power factor control circuitry has only four pins: VBUS which senses the
output voltage from the PFC boost converter, COMP which is the error amplifier compensation pin, ZX which
senses the inductor current and PFC which is the PFC FET gate driver.
No current sense input from the source of the PFC FET is required as our scheme does not use a multiplier and
we do not need to sense the AC line. We also need only a single VCC supply because the PFC and ballast control
are integrated on one IC. These features allow for a very reduced component count and a simplified PCB layout.
The off time is determined from the inductor current detected at the ZX pin.
The on time is determined from the error amplifier which senses the bus voltage detected at the VBUS pin. We
also have a further modulation of the on time in which near to the line zero-crossing it increases to reduce cross
over distortion and therefore give a better THD.
The error amplifier can operate either with a high gain when we need fast response to changes in line or load or
with a low gain when the line and load are constant and we need to optimize the power factor. Initially the gain is
high to allow the DC bus to rise rapidly. The gain is also high during ignition so that the high current surge causes
only a small transient in the DC bus voltage.
I
n RUN mode the gain is low because the load is effectively constant. We do not require rapid changes in the on
time because this needs to remain constant during most of the AC line cycle to provide a good power factor.
In this way we do not need a trade off between bus regulation and good PF.
The power factor section works in conjunction with the ballast control section. The gain can be set high or low
depending on the status of the ballast controller and also if the ballast is in fault mode, the PFC section will be
disabled.
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Protections
The fault logic includes the under voltage lockout and over temperature shutdown built into the IC.
There are three pins that sense the AC line voltage (VDC), the current (CS) and if there is no lamp connected or
external shut down (SD).
Pin VDC is used for low AC line protection. RVDC set the protection threshold:
(RVDC / (RVDC + RVAC)) x VACmin = 5.1V.
Pin CS is used for undercurrent protection to protect for below resonance condition (the undercurrent threshold is
fixed to 0.2V) and for over-current protection to protect for hard switching or current spikes due to failure to strike,
lamp fault or no load.
Pin SD is the external shutdown pin combined with the end of life protection pin. It is internally polarized to 2V and
inside the IC we have a 1 to 3V window comparator for end of life detection.
Ballast Control Section
The ballast control section of the IR2167 Ballast Control IC contains an oscillator, a high voltage half-bridge gate
driver and lamp fault protection circuitry. The following page shows the operating sequence that occurs within the
system.
Following that is a breakdown of the operation of the ballast in all of the different modes of operation.
Initially in the UVLO mode the IC draws very low current. Then VCC rises above the under voltage threshold and
the oscillator starts up.
The oscillator runs initially at a very high start frequency and then it shifts to the preheat frequency until it sweeps
down to ignition.
At ignition the oscillator runs at a frequency close to the resonant frequency of the LC output stage of the ballast
producing a large voltage across the lamp.
After ignition the oscillator goes to the run frequency, which will provide the correct power to the lamp.
The IC will go into FAULT mode shutting down the oscillator if a fault condition occurs (over-current, under-current,
over-temperature or end of life). In the FAULT state the IC is in a latched shutdown and will restart in the UVLO
state only after resetting the line or removing the lamp.
In case of low AC line, low DC bus or low VCC, the IC will go directly back to the UVLO state.
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AN1037
IR2167 Block Diagram
Power Turned On
UVLO Mode
/2 -Bridge Off
PFC off
IQCC ≅ 150µA
CPH = 0V
Oscillator Off
1
VCC > 11.4V (UV+)
and
VDC > 5.1V (AC Line OK)
and
SD < 4.8V (Lamp OK)
and
T J < 160C (Tjmax )
SD > 5.1V
(Lamp Removal)
or
VCC < 9.5V
(Power Turned Off)
FAULT Mode
Fault Latch Set
1
/ 2-Bridge Off
PFC off
IQCC ≅ 150µA
CPH = 0V
VCC = 15.6V
Oscillator Off
T J > 160C
(Over-Temperature)
CS > CS+ Threshold
(Failure to Strike Lamp
or Hard Switching)
and
CS+ Count > 50
or
T J > 160C
(Over-Temperature)
CS > CS+ Threshold
(Over-Current/Hard Switching, single
event)
or
CS < 0.2V
(No-Load/Below Resonance)
or
SD > 3V (End of Life)
or
SD < 1V (End of Life)
or
T J > 160C (Over-Temperature)
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VCC < 9.5V
(VCC Fault or Power Down)
or
VDC < 3.0V
(AC Line Fault or Power Down)
or
SD > 5.1V
(Lamp Removal)
PREHEAT Mode
/2 -Bridge @ f PH
PFC enabled
CPH Charging @ I PH = 1µA
RPH = 0V
RUN = Open Circuit
CS Disabled
1
CPH > 4.0V
(End of PREHEAT Mode)
IGNITION RAMP Mode
f PH ramps to f MIN
CPH Charging @ I PH = 1µA
RPH = Open Circuit
RUN = Open Circuit
CS+ Threshold & Counter Enabled
CPH > 5.1V
(End of IGNITION RAMP)
RUN Mode
f M IN Ramps to f RUN
CPH Charges to 9V Clamp
RPH = Open Circuit
RUN = 0V
CS- Threshold Enabled
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Operating sequence
This figure shows a plot of the half-bridge oscillation frequency as a function of time for all of the normal modes of
operation: Preheat mode, Ignition Ramp mode and Run mode. As shown, there is an initial startup frequency that
is much higher than the steady state Preheat mode frequency that lasts for only a short duration. This is done to
fosc
fPreheat
fRun
fIgnition
t
preheat
ignition
run
insure that the initial voltage appearing across the lamp at the startup of oscillation does not exceed the minimum
lamp ignition voltage. If, at the initiation of oscillation of the half-bridge, the voltage across the lamp is large enough,
a visible flash of the lamp can occur which should be avoided. This in effect is a cold strike of the lamp, which can
reduce the life of the lamp
Startup Mode
When power is initially applied to the ballast, the voltage on the VCC pin of the IR2167 begins to charge up. The
voltage for the IR2167 is derived from the current supplied from the rectified AC line through startup resistor
RSUPPLY. During this initial startup when the VCC voltage of the IC is below its rising under-voltage lock-out
threshold (11.4V), IC1 is in its UVLO and also its micro-power mode. When the voltage on IC1 reaches the rising
under-voltage lockout threshold, the oscillator is enabled (this assumes that there are no fault conditions) and
drives the half-bridge output MOSFETs. When the half-bridge is oscillating, capacitor Csnub, diodes DCP1 and
DCP2 form a snubber /charge pump circuit which limits the rise and fall time at the half-bridge output and also
supplies the current to charge capacitor CVCC2 to the VCC clamp voltage (approx. 15.6V) of IC1. When the rising
under-voltage lockout threshold of IC1 is reached, it starts to oscillate and drive MOSFET MPFC to boost and
regulate the bus voltage to 400 VDC. The power factor control starts only during preheat, so the bus is not yet
boosted when the oscillator starts, this helps to prevent the lamp flash at the start up.
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AN1037
Preheat Mode
When the ballast reaches the end of the UVLO mode, the Preheat mode is entered. At this point the ballast control
oscillator of the IR2167 has begun to operate and the half-bridge output is driving the resonant load (lamp) circuit.
The ballast control section oscillator of the IR2167 is similar to oscillators found in many popular PWM voltage
regulator ICs and consists of a timing capacitor and resistor connected to ground. Resistors RT and RPH program a current which determines the ramp up time of capacitor CT and resistor RDT determines the ramp down
time. The downward ramping time of CT is the deadtime between the switching off of the LO (HO) and the
switching on of the HO (LO) pins on the IR2167. The Preheat mode frequency of oscillation is selected such that
the voltage appearing across the lamp is below the minimum lamp ignition voltage while supplying enough current
to preheat the lamp filaments to the correct emission temperature within the Preheat mode period. The preheating
of the lamp filaments is performed with a constant current during the Preheat mode.
The duration of the Preheat, as well as the mode of operation the ballast is operating in is determined by the
voltage on the CPH pin of IR2167. At the completion of the UVLO mode, Preheat mode is entered and an internal
current source is activated at the CPH pin, which begins to charge up capacitor CPH. The ballast remains in the
Preheat mode until the voltage on the CPH pin exceeds the Ignition Ramp mode threshold (4V).
Ignition Ramp Mode
At the completion of the Preheat (4V < CPH pin < 5.1V) the ballast switches to the Ignition Ramp mode and the
frequency ramps down to the ignition frequency. Resistor RPH is no longer connected directly in parallel with
resistor RT. The shift in frequency does not occur in a step function but rather with an exponential decay because
of capacitor CRAMP in series with resistor RPH to COM. The duration of this frequency ramp is determined by the
time constant of the RC combination of capacitor CRAMP and resistor RPH. The minimum frequency of oscillation occurs at the end of this ramp and is determined by resistor RT and capacitor CT. This minimum frequency
corresponds to the absolute maximum ignition voltage required by the lamp under all conditions. During this
ramping downward of the frequency, the voltage across the lamp increases in magnitude as the frequency approaches the resonant frequency of the LC load circuit until the lamp ignition voltage is exceeded and the lamp
ignites.
During the Ignition Ramp time the voltage on the CPH pin continues to ramp up until the voltage at the CPH pin of
IC1 exceeds the Run mode threshold (5.1V). Over-current sensing, Under-current sensing and End of Life protection are enabled at the beginning of the Ignition Ramp mode.
Run Mode
At the end of the Ignition Ramp mode (CPH pin > 5.1V) the ballast switches to the Run mode at which point the
frequency is shifted to the run frequency. The run frequency is determined by the parallel combination of resistors
RT and RRUN and capacitor CT. The running frequency is that at which the lamp is driven to the lamp manufacturer’s
recommended lamp power rating.
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AN1037
Preheat, Ignition and Run mode voltage in the lamp
Preheat, Ignition with 2 lamps crossed
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AN1037
Preheat and Ignition Ramp with 2 lamps crossed
Control Circuit
If both lamps are removed or one lamp fails, hard switching will occur at the half-bridge and the resulting current
will cause the voltage across the CS pin to trigger the over-current protection and shut-down. If one lamp fails,
excessive voltage will appear across the other lamp and cause the ballast to shut down due to the over-current
protection. If only one lamp is removed, the other will continue to work.
Additional Control Circuit for auto-restart after lamp replacing
The figure in the next page shows the additional control circuitry for lamp presence detection and automatic
restart. The circuit discussed before can operate with only one lamp and, when replacing the other lamp, we will
have cold strike of the lamp. This cold strike is not a problem in this case because of the way we have set the
frequencies. We have verified that it does not cause hard switching and stress in the circuit. However, the cold
strike is a problem when removing both lamps and replacing only one lamp, in this case, a cold strike can damage
the lamp and over-stress the circuit. The circuit discussed before does not start automatically when we remove
both lamps and we replace one lamp. It requires the line to be reset, to avoid cold strike.
In the new circuit in figure, the ballast re-starts automatically when reinserting one lamp. The additional circuit
allows the reset of the IC to allow the ballast start in preheat mode. In this new circuit, when one lamp is replaced
and in good condition, the ballast starts automatically with the right start sequence (start, preheat, ignition and
run). When the second lamp is replaced, we will have a cold strike, however it is not dangerous.
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AN1037
DPFC
LPFC
LRES2
CDC2
RSUPPLY
RVAC
CRES2
REOL5
N
F1
RVDC
RV1
CVDC
C1
L1
BR1
VDC
CPH
CPH
CRAMP
RPH
CBUS
GND
RPH
RT
RVBUS1
C2
RRUN
CT
RVBUS2
COC
RT
ROC
DT
ZX
18
7
COMP
RZX
3
6
OC
CCOMP
19
5
CT
RDT
2
4
RUN
20
IR2167
CY
1
17
16
15
14
8
13
9
12
REOL6
RHO
HO
MHS
LRES1
VS
VB
CBOOT
DBOOT
VCC
DCP2
RLIM3
CRES1
REOL1
CVCC2
LO
RLO
CS
RLIM1
SD
DSD
CCS
REOL7
CSNUB
RLIM2
CVCC1
COM
PFC
CDC1
REOL2
MLS
RPU2
REOL3
RPU1
RSD1
DCP1
RSD2
CSD2
VBUS
10
11
IC BALLAST
CSD1
RVBUS
MPFC
CVBUS
RCS
DEOL1
DEOL2
CEOL
REOL4
RPFC
Note: Thick traces represent high-frequency, high-current paths. Lead
lengths should be minimized to avoid high-frequency noise problems
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AN1037
In case of removal of one or both lamps, an over-current condition causes the IC to go in a fault state (“FAULT” in
the block diagram of the IR2167) where the IC is in latched shutdown. To return to micro-power state and restart
from preheat, it is necessary to pull the SD pin above the threshold 5.1V.
The values of the network RPU1, RPU2, RSD1, RSD2, CSD1 are chose to allow the voltage on the DSD anode
less than 2.6V with only 1 lower cathode connected. In this way, when one or both of the lower cathodes of the 2
lamps are in place, the shutdown pin (SD) is 2V and the DSD diode does not conduct. When both lamps are
removed, VCC pulls the voltage at the anode of DSD high through the pull up resistors (RPU1, RPU2), when this
voltage is more than 2.6V the diode will conduct and the SD pin of the IC is pulled above 5.1V and the IC enters
micro-power mode. When one of the lower filaments is reinserted the SD pin is pulled low through resistor RSD
and the small lower cathode resistance of the lamp so the IC returns to the preheat mode.
Fault Protection Characteristics
Fault
Line voltage low
Upper filament broken
Lower filament broken
Failure to ignite
Open circuit (no lamp)
No 1 lamp
End of Life
Item #
1
2
3
4
Qt
1
1
1
2
5
Total
2
7
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Ballast
Deactivates
Deactivates
Deactivates
Deactivates
Deactivates
Activates
Deactivates
Manufacturer
Panasonic
Part Number
ECJ-2YB1C474K
Diodes
Panasonic
LL4148DICT-ND
ERJ-8GEYJ680K
Restart Operation
Increase line voltage
Lamp exchange
Lamp exchange
Lamp exchange
Lamp exchange
The other lamp stays on
Lamp exchange
Description
Capacitor, 0.47uF
Capacitor, 0.47uF
Diode, 1N4148
Resistor, 100Kohm
Reference
CSD1
CSD2
DSD
RSD1, RSD2
Resistor, 1Mohm
RPU1, RPU2
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AN1037
Additional Control Circuit to avoid cold strike
The SD circuit has to be modified in this way to have auto-restart with preheat when one lamp is re-inserted when
the other lamp is still running.
This figure shows the additional control circuitry for lamp presence detection and automatic restart. When one of
the lamps is removed, the base of the transistor (an NPN bipolar transistor may be used e.g. FMMT2222ACT
Zetex) is pulled high. This turns Q1 on discharging the capacitor, but does not affect SD, which remains at 2V. The
other lamp will therefore remain running. When the lamp is reinserted, Q1 is turned off and a short voltage pulse
appears in the SD pin via the diode (you can use 1N4148 diode). This pulse momentarily pulls SD above the 5.1V
threshold and resets the IR2167. As SD falls back to 2V, the IR2167 is restarted in preheat mode. This ensures
proper heating of the filaments before the lamp is re-ignited.
LRES2
CDC2
CRES2
LRES1
CDC1
CRES1
VCC pin
100KOhm
1Mohm
1Mohm
100KOhm
10nF
100KOhm
SD pin
0.47uF
510KOhm
COM pin
Additional Control Circuit to avoid striations during start-up
After initial start-up you could have some striations (visible dark rings) on the lamps for a short period (a few
minutes) particularly when the lamp has been off for some time and is cold. The simplest way to avoid this
problem is to add a resistor in parallel to CDC1 and a resistor in parallel to CD2. The value should in the order of
100kOhm 0.5W.
During Preheat however, this resistor adds some DC current in the lamp. This small DC component on the
current solves the striations problem, but causes the CEOL capacitor to charge to several volts during preheat
which can cause the end-of-life protection circuit to be triggered at the beginning of run mode when the SD pin
becomes enabled.
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AN1037
A possible solution to this problem is to introduce a delay greater than the preheat time for this protection by
increasing the value of the CEOL capacitor. In this case the capacitor value that is required is large 50-100uF and
the capacitor cannot be polarized since it needs to be able to go negative as well as positive depending on the
direction of the lamp voltage asymmetry caused by the rectifying effect at end of life, unless back to back electrolytics
were to be used.
To avoid the need for such a large capacitor it is possible to place a diode between RPH pin and shutdown pin
(anode to SD pin). This diode will limit the voltage that the capacitor can charge to during preheat (RPH is
switched to 0V inside the IC during preheat then charges to 2V during ignition and stays 2V during run mode).
When the RPH voltage increases to 2V the SD pin is released and operates normally (RPH will not sink current
during in run mode). In this way the value of the CEOL capacitor can be reduced (we did not test this solution in our
lab).
Improved End of Life solution
The same PCB can be used with a different end of life configuration. It is needed to put a capacitor in the place of
DEOL1 diode (100nF), to short DEOL2 (0 Ohm resistor) and to reduce the capacitor in the SD pin CSD1 (100pF).
The resultant circuit is shown in the following figure.
2V
in A
REOL
0V
CRES
CEOL
SD
CSD1
Inside the
IR2167
A
REOL4
in the SD pin
2V
Improved End-of-life circuit
The value of REOL4 is changed so that the lamp voltage during normal running produces a signal with 1.5 Vppk at
the point (A) were the capacitor CEOL connects it to the SD pin. The SD pin is internally biased at 2V with 1Mohm
impedance and therefore at the SD pin a signal varying between 1.25V and 2.75V will normally be present due to
the AC coupling of the 100nF capacitor (CEOL).
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AN1037
During end of life the lamp voltage may increase either symmetrically (AC end of life, due to a similar deterioration
in both cathode) or asymmetrically (DC end of life, due to a deterioration only in one cathode). This circuit has the
advantage of detecting both failure modes.
The peak to peak voltage at the SD pin will increase (with 2V DC offset) in either case until the positive peak
exceeds 3V and/or the negative peak drops below 1V, therefore triggering the window comparator shutdown. The
threshold of end of life can be adjusted by changing the value of REOL4 (usually 30% Vlamp is required).
The following Figure shows the voltage in the SD pin and the voltage on the lamp in these 4 cases: no end of life,
DC end of life (upper cathode deteriorated and lower cathode deteriorated) and AC end of life (both filaments
deteriorated in the same way).
SD pin Voltage
3V
3V
3V
3V
2V
2V
2V
2V
1V
1V
1V
1V
Lamp Voltage
Vspec
0V
Vspec + 30%
0V
-Vspec - 30%
Vspec + 30%
0V
0V
-Vspec - 30%
Vspec = VpK in the spec of the
lamp
Voltage in the SD pin and voltage on the lamp in these 4 cases: no end of life, DC end of life and AC end of life.
WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245 Tel: (310) 252-7105
http://www.irf.com/ Data and specifications subject to change without notice. 3/29/2002
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