IRF IRF730 High power factor/low thd Datasheet

IRPLLNR2
International Rectifier • 233 Kansas Street, El Segundo, CA 90245 USA
IR21571 Ballast Control IC Design Kit
Features
= Drives:
=
=
=
=
=
=
=
1 x 32W T8 Lamp (IRPLLNR2U)
1 x 36W T8 Lamp (IRPLLNR2)
Input:
90-140VAC/60Hz (IRPLLNR2U)
185-265VAC/50Hz (IRPLLNR2)
High Power Factor/Low THD
High Frequency Operation (42kHz)
Lamp Filament Preheating
Lamp Fault Protection with Auto-Restart
Brownout Protection
IR21571 HVIC Ballast Controller
Description
The IRPLLNR2 is a high efficiency, high power factor, fixed output
electronic ballast designed for driving rapid start fluorescent lamp types. The design contains an EMI
filter, active power factor correction and a ballast control circuit using the IR21571. This demo board is
intended to ease the evaluation of the IR21571 Ballast Control IC, demonstrate PCB layout techniques
and serve as an aid in the development of production ballast’s using the International Rectifier IR21571.
Ballast Block Diagram
EMI Filter
Rectifier
PFC
Half-Bridge
Output Stage
Lamp
Line
PFC Control
UVLO
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IR21571
Lamp Fault
1
Electrical Characteristics
Parameter
Lamp Type
Input Power
Input Current
Preheat Mode Frequency
Preheat Mode Lamp Voltage
Preheat Time
Ignition Ramp Mode Frequency
Run Mode Frequency
Lamp Run Current
Input AC Voltage Range
Input DC Voltage Range
Power Factor
Total Harmonic Distortion
Maximum Output Voltage
Units
[W]
[Arms]
[kHz]
[Vrms]
[s]
[kHz]
[kHz]
[Arms]
[VACrms]
[VDC]
[%]
[Vpk]
Value (IRPLLNR2)
36W T8
36
0.300
44
220
0.9
38
42
0.34
185..255/50..60Hz
250..350
0.98
<15
600
Value (IRPLLNR2U)
32W T8
32
0.300
44
220
0.6
38
42
0.34
90..140/50..60Hz
100..180
0.99
<10
600
Note: Measurements performed with input AC line voltage = 120Vrms (IRPLDIM1U)
230Vrms (IRPLDIM1)
Fault Protection Characteristics
Fault
Line voltage low
Upper filament broken
Lower filament broken
Failure to ignite
Open circuit (no lamp)
Ballast
Deactivates
Deactivates
Deactivates
Deactivates
Deactivates
Restart Operation
Increase line voltage
Lamp exchange
Lamp exchange
Lamp exchange
Lamp exchange
Functional Description
Overview
he IRPLDIM1 Demo Board consists of an EMI filter, an active power factor correction front end, a
ballast control section and a resonant lamp output stage. The active power factor correction section
is a boost converter operating in critical mode conduction, free-running frequency mode. The ballast
control section provides frequency modulation 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 closed-loop dimming, lamp fault detection, shutdown and
auto-restart. All functional descriptions refer to the IRPLDIM1 schematic diagram.
2
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IRPLLNR2/IRPLLNR2U
Schematic Diagram
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L2
R8
D2
R12
R1
R14
L1
L
R4
RV1
C2
R11
D3
D1
R2
N
C14
BR1
R13
C9
R5
1
VDC
HO
16
2
CPH
VS
15
3
RPH
VB
14
M2
C8
GND
1
8
2
7
C1
C10
R7
M1
RT
RPH
4
6
CSTART
4
5
5
RUN
6
CT
RSTART
R6
R3
RT
RRUN
C4
CT
R19
D4
VCC
R20
13
C11
COM
12
LO
11
R21
C16
C12
R15
C17
M3
D5
RDT
R16
7
R10
IR21571
3
CRAMP
R9
C6
C7
MC34262
C3
C5
L3
C15
CPH
DT
CS
D6
10
R18
ROC
R17
8
OC
SD
9
C13
COC
Note: Thick traces represent high-frequency, high-current paths. Lead
lengths should be minimized to avoid high-frequency noise problems
RCS
3
IRPLLNR2U Bill Of Materials
Lamp type: T8/32W
Line Input Voltage: 90..140 VAC/50..60 Hz
Note: Different lamp types require different frequency programming components.
Item #
1
Qt
1
Manufacturer
International Rectifier
Part Number
DF10S
Description
Bridge Rectifier, 1A 1000V
BR1
Reference
2
3
1
1
Roederstein
Roederstein
WY0222MCMBF0K
F1772433-2200
Capacitor, 2.2nF 275 VAC Y Cap
Capacitor, 0.33uF 275 VAC
C1
C2
4
1
Wima
MKP10
Capacitor, 0.01uF 400 VDC
C3
5
6
3
3
Panasonic
Panasonic
ECU-V1H103KBM
ECJ-3YB1E474K
Capacitor, 0.01uF SMT 1206
Capacitor, 0.47uF SMT 1206
C4, CRAMP, CSTART
C5, C6, C13
7
5
Panasonic
ECU-V1H104KBM
Capacitor, 0.1uF SMT 1206
C9,CPH, COC, C10, C11
8
9
1
1
Panasonic
Panasonic
EEU-EB2V100
ECU-V1H471KBM
Capacitor, 10uF 350VDC 105C
Capacitor, 470pF SMT 1206
C8
CT
10
11
1
1
Panasonic
Vitramon
ECE-A1HGE010
1812A152KXE
Capacitor, 1uF 50VDC 105C
Capacitor, 1.5nF 1KV SMT 1812
C12
C14
12
1
Wima
MKP10
Capacitor, 0.1uF 400VDC
C15
13
14
15
1
1
1
Vitramon
Panasonic
Panasonic
1812A102KXE
ECW-H16103JV
ECU-V1H101KBM
Capacitor, 1nF 1KV SMT 1812
Capacitor, 0.01uF 1.6KV
Capacitor, 100pF SMT 1206
C16
C17
CCS
16
3
Diodes
LL4148DICT-ND
Diode, 1N4148 SMT DL35
D1, D5, D6
17
2
International Rectifier
10BF60
Diode, SMT SMB
D2, D4
18
19
1
1
Diodes
Motorola
ZMM5250BCT
MC34262
Diode, Zener , 20V SMT DL35
IC, Power Factor Controller
D3
IC1
20
1
International Rectifier
IR21571
IC, Ballast Driver
IC2
21
22
1
1
Panasonic
RG-Allen
ELF-15N007A
EMI Inductor, 1X10mH 0.7Apk
PFC Inductor, 2.0mH 2.0Apk
L1
L2
23
1
RG-Allen
24
3
International Rectifier
Inductor, 2.0mH 2.0Apk
L3
IRF730
Transistor, MOSFET
M1, M2, M3
25
5
Panasonic
ERJ-8GEYJ680K
Resistor, 680K ohm SMT 1206
R1, R2, R4, R5, R17
26
1
Panasonic
ERJ-8GEYJ10K
Resistor, 10K ohm SMT 1206
R3
27
28
1
1
Panasonic
Panasonic
ERJ-8GEYJ12K
ERJ-8GEYJ100K
Resistor, 12K ohm SMT 1206
Resistor, 100K ohm SMT 1206
R6
R7
29
30
3
3
Panasonic
Panasonic
ERJ-8GEYJ22K
ERJ-8GEYJ22
Resistor, 22K ohm SMT 1206
Resistor, 22 ohm SMT 1206
R8, RSTART, RT
R9, R13, R15
31
32
1
1
Dale
Panasonic
CW-1/2
ERJ-8GEYJ130K
Resistor, 0.5 ohm ½ watt
Resistor, 130K ohm SMT 1206
R10
R11
33
34
1
1
Yageo
Dale
2.2MQBK-ND
CW-1/2
Resistor, 2.2megohm ¼ watt
Resistor, 0.68 ohm ½ watt
R12
RCS
35
36
37
38
39
1
1
1
1
1
Panasonic
Panasonic
Panasonic
Panasonic
Yageo
ERJ-8GEYJ5.6K
ERJ-8GEYJ30K
ERJ-8GEYJ91K
ERJ-8GEYJ150K
390KQBK-ND
Resistor, 5.6K ohm SMT 1206
Resistor, 30K ohm SMT 1206
Resistor, 91K ohm SMT 1206
Resistor, 150K ohm SMT 1206
Resistor, 390K ohm ¼ watt
RDT
ROC
RPH
RRUN
R14
40
41
42
43
44
1
1
1
1
2
Panasonic
Panasonic
Yageo
Panasonic
Panasonic
ERJ-8GEYJ1K
ERJ-8GEYJ2.2M
100KQBK-ND
ERZ-V05D471
ERJ-8GEYJ10
Resistor, 1K ohm SMT 1206
Resistor, 2.2megohm SMT 1206
Resistor, 100K ohm ¼ watt
Transient Suppressor
Resistor, 10 ohm SMT 1206
R16
R18
R19
RV1
R20, R21
Total
67
4
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IRPLLNR2 Bill Of Materials
Lamp type: T8/36W
Line Input Voltage: 180..255 VAC/50..60 Hz
Note: Different lamp types require different frequency programming components.
Item #
1
Qt
1
Manufacturer
International Rectifier
Part Number
DF10S
Description
Bridge Rectifier, 1A 1000V
BR1
2
1
Roederstein
3
1
Roederstein
4
5
1
3
6
7
Reference
WY0222MCMBF0K
Capacitor, 2.2nF 275 VAC Y Cap
C1
F1772433-2200
Capacitor, 0.33uF 275 VAC
C2
Wima
Panasonic
MKP10
ECU-V1H103KBM
Capacitor, 0.01uF 400 VDC
Capacitor, 0.01uF SMT 1206
C3
C4, CRAMP, CSTART
3
Panasonic
ECJ-3YB1E474K
Capacitor, 0.47uF SMT 1206
C5, C6, C13
5
Panasonic
ECU-V1H104KBM
Capacitor, 0.1uF SMT 1206
C9,CPH, COC, C10, C11
8
9
1
1
Panasonic
Panasonic
EEU-EB2V100
ECU-V1H471KBM
Capacitor, 10uF 350VDC 105C
Capacitor, 470pF SMT 1206
C8
CT
10
11
1
1
Panasonic
Vitramon
ECE-A1HGE010
1812A152KXE
Capacitor, 1uF 50VDC 105C
Capacitor, 1.5nF 1KV SMT 1812
C12
C14
12
13
1
1
Wima
Vitramon
MKP10
1812A102KXE
Capacitor, 0.1uF 400VDC
Capacitor, 1nF 1KV SMT 1812
C15
C16
14
15
1
1
Panasonic
Panasonic
ECW-H16103JV
ECU-V1H101KBM
Capacitor, 0.01uF 1.6KV
Capacitor, 100pF SMT 1206
C17
CCS
16
17
3
2
Diodes
International Rectifier
LL4148DICT-ND
10BF60
Diode, 1N4148 SMT DL35
Diode, SMT SMB
D1, D5, D6
D2, D4
18
19
1
1
Diodes
Motorola
ZMM5250BCT
MC34262
Diode, Zener 20V SMT DL35
IC, Power Factor Controller
D3
IC1
IC2
20
1
International Rectifier
IR21571
IC, Ballast Driver
21
1
Panasonic
ELF-15N007A
EMI Inductor, 1X10mH 0.7Apk
L1
22
23
1
1
RG-Allen
RG-Allen
PFC Inductor, 2.0mH 2.0Apk
Inductor, 2.0mH 2.0Apk
L2
L3
24
25
3
5
International Rectifier
Panasonic
IRF830
ERJ-8GEYJ680K
Transistor, MOSFET
Resistor, 680K ohm SMT 1206
M1, M2, M3
R1, R2, R4, R5, R17
26
27
1
1
Panasonic
Panasonic
ERJ-8GEYJ10K
ERJ-8GEYJ8.2K
Resistor, 10K ohm SMT 1206
Resistor, 8.2K ohm SMT 1206
R3
R6
28
29
1
3
Panasonic
Panasonic
ERJ-8GEYJ100K
ERJ-8GEYJ22K
Resistor, 100K ohm SMT 1206
Resistor, 22K ohm SMT 1206
R7
R8, RSTART, RT
30
3
Panasonic
ERJ-8GEYJ22
Resistor, 22 ohm SMT 1206
R9, R13, R15
31
1
Dale
CW-1/2
Resistor, 1.0 ohm ½ watt
R10
32
33
34
1
1
1
Panasonic
Yageo
Dale
ERJ-8GEYJ56K
2.2MQBK-ND
CW-1/2
Resistor, 56K ohm SMT 1206
Resistor, 2.2megohm ¼ watt
Resistor, 0.68 ohm ½ watt
R11
R12
RCS
35
36
37
38
39
1
1
1
1
1
Panasonic
Panasonic
Panasonic
Panasonic
Yageo
ERJ-8GEYJ5.6K
ERJ-8GEYJ30K
ERJ-8GEYJ75K
ERJ-8GEYJ150K
390KQBK-ND
Resistor, 5.6K ohm SMT 1206
Resistor, 30K ohm SMT 1206
Resistor, 75K ohm SMT 1206
Resistor, 150K ohm SMT 1206
Resistor, 390K ohm ¼ watt
RDT
ROC
RPH
RRUN
R14
40
41
42
43
44
1
1
1
1
2
Panasonic
Panasonic
Yageo
Panasonic
Panasonic
ERJ-8GEYJ1K
ERJ-8GEYJ2.2M
100KQBK-ND
ERZ-V05D471
ERJ-8GEYJ10
Resistor, 1K ohm SMT 1206
Resistor, 2.2megohm SMT 1206
Resistor, 100K ohm ¼ watt
Transient Suppressor
Resistor, 10 ohm SMT 1206
R16
R18
R19
RV1
R20, R21
Total
65
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5
Power Factor Correction
The power factor correction section consists of the Motorola Semiconductor MC34262 Power Factor
Controller IC (IC1), MOSFET M1, inductor L2, diode D2, capacitor C8 and additional biasing, sensing and compensation components (see schematic diagram). The IC was chosen for its minimal
component count, low start-up supply current and robust error amplifier. This is a boost topology
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 (HPF). The design of the power
factor correction section was taken from the Motorola Semiconductor MC34262 data sheet and
information on the operation and design considerations for the MC34262 are contained therein.
Ballast Control
The ballast control section is built around the IR21571 Ballast Control IC, IC2 of the Demo board.
The IR21571 contains an oscillator, a high voltage half-bridge gate driver and lamp fault protection
circuitry. A block diagram of the IR21571 IC is shown in figure 1 and a state diagram of the IR21571
is shown in figure 2. Following is a breakdown of the operation of the ballast in all of the different
modes of operation.
3.0V
14 VB
VDC 1
5.1V
S
Q
R
Q
LEVEL
SHIFT
PULSE
FILTER &
LATCH
16 HO
1.0uA
15 VS
CPH 2
7.6V
5.1V
4.0V
S
Q
R1
4.0V
RPH 3
2.0V
T
Q
R
Q
13 VCC
R2 Q
11 LO
IRT
RT 4
15.6V
12 COM
2.0V
RUN 5
Q
ICT = IRT
D
0.2V
10 CS
CLK
CT 6
Q
S
Q
R
Q
R
DT 7
7.6V
50uA
OC 8
UNDERVOLTAGE
DETECT
OVERTEMP
DETECT
9
7.6V
2.0V
SD
7.6V
Figure 1: IR21571 Block Diagram
6
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Power Turned On
UVLO Mode
1
/2-Bridge Off
IQCC ≅ 150µA
CPH = 0V
Oscillator Off
VCC > 11.4V (UV+)
and
VDC > 5.1V (Bus OK)
and
SD < 1.7V (Lamp OK)
and
TJ < 140C (Tjmax)
SD > 2.0V
(Lamp Removal)
or
VCC < 9.5V
(Power Turned Off)
FAULT Mode
Fault Latch Set
1
/2-Bridge Off
IQCC ≅ 150µA
CPH = 0V
VCC = 15.6V
Oscillator Off
TJ > 140C
(Over-Temperature)
CS > CS+ Threshold
(Failure to Strike Lamp
or Hard Switching)
or
TJ > 140C
(Over-Temperature)
CS > CS+ Threshold
(Over-Current or Hard Switching)
or
CS < 0.2V
(No-Load or Below Resonance)
or
TJ > 140C
(Over-Temperature)
VCC < 9.5V
(VCC Fault or Power Down)
or
VDC < 3.0V
(dc Bus/ac Line Fault or Power Down)
or
SD > 2.0V
(Lamp Fault or Lamp Removal)
PREHEAT Mode
1
/2-Bridge @ fPH
CPH Charging @ IPH = 1µA
RPH = 0V
RUN = Open Circuit
CS Disabled
CPH > 4.0V
(End of PREHEAT Mode)
IGNITION RAMP Mode
fPH ramps to fMIN
CPH Charging @ IPH = 1µA
RPH = Open Circuit
RUN = Open Circuit
CS+ Threshold Enabled
CPH > 5.1V
(End of IGNITION RAMP)
RUN Mode
fMIN Ramps to fRUN
CPH Charges to 7.6V Clamp
RPH = Open Circuit
RUN = 0V
CS- Threshold Enabled
Figure 2: IR21571 State Diagram
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7
Startup Mode
When power is initially applied to the ballast, the voltage on the VCC pin of IC2 (IR21571) begins to
charge up. The voltage for IC2 is derived from the current supplied from the rectified AC line through
startup resistor R14. During this initial startup when the VCC voltage of IC2 is below its rising undervoltage lock-out threshold (11.4V), IC2 is in its UVLO and also its micro-power mode. The micropower mode of the IC2 allows the use of a large value,
low wattage startup resistor (R14). When the voltage
on IC2 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 (M2 and M3). When the half-bridge is
oscillating, capacitor C16, diodes D5 and D6 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 C12 to the VCC clamp voltage (approx. 15.6V) of IC2. The voltage for IC1 is derived from the current supplied from another snubber/
charge pump circuit formed by capacitor C14 and diodes D1 and D3. When the rising under-voltage lockout threshold of IC1 is reached, it starts to oscillate
and drive MOSFET M1 to boost and regulate the bus
Figure 3: Top trace: Half-bridge output voltage
voltage to 400 VDC. An oscillograph of the startup of
Middle trace: VCC of IC2
the VCC of IC1, VCC of IC2 and half-bridge output
Bottom trace: VCC of IC1
voltage are shown in Figure 3. (For a complete description of the operation of IC1, refer to the Motorola Semiconductor MC34262 data sheet.)
Preheat Mode
When the ballast reaches the end of the UVLO mode, the Preheat mode is entered. At this point the
oscillator of IC2 has begun to operate and the half-bridge output is driving the resonant load (lamp)
circuit. The oscillator section of IC2 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 IC2. 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 waveform in Figure 4 shows the lamp filament
current while Figure 5 shows lamp filament voltage during the normal Startup, Preheat, Ignition
Ramp and Run modes of the ballast.
8
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Figure 4: Lamp filament current during Startup,
Preheat, Ignition Ramp and Run (500mA/div)
Figure 5: Lamp filament voltage during Startup,
Preheat, Ignition Ramp and Run
Figure 6 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 in Figure 6 there
is an initial startup frequency that is much higher than the steady state Preheat mode frequency that
lasts for only a short duration. Components CSTART and RSTART are used to program this initial
startup frequency. This is done to 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
occurs which should be avoided. This in effect is a cold strike of the lamp which could shorten the life
of the lamp. An oscillograph of the lamp voltage at startup is shown in Figures 7 and 8 (next page).
Figure 7 shows the lamp voltage without the high initial startup frequency while Figure 8 shows the
lamp voltage with the high initial frequency startup.
fosc
fPreheat
fRun
fIgnition
t
preheat
ignition
run
Figure 6: Oscillator frequency versus time, Normal operating conditions
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9
Figure 7: Typical lamp voltage at startup;
fStartup = fP reheat
Figure 8: Improved lamp voltage at startup;
fStartup > fP reheat
The duration of the Preheat mode as well as which mode of operation the ballast is operating in is
determined by the voltage on the CPH pin of IC2. At the completion of the UVLO mode, Preheat
mode is entered and an internal current source is activated at the CPH pin of IC2 which begins to
charge up capacitor CPH. The ballast remains in the Preheat mode until the voltage on the CPH
pin of IC2 exceeds the Ignition Ramp mode threshold (4V).
Ignition Ramp Mode
At the completion of the Preheat mode (4V < CPH
pin < 5.1V) the ballast switches to the Ignition Ramp
mode and the frequency ramps down to the ignition
frequency. The frequency ramping is accomplished
by turning off the internal open drain MOSFET on
the RPH pin of IC2 (see Figure 1, IR21571 block
diagram). 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 ground. 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. 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
10
Figure 9: Upper trace: voltage on capacitor
CRAMP during Ignition Ramp mode
Lower trace: Lamp voltage during Ignition
Ramp mode.
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is exceeded and the lamp ignites. Figure 9 shows the ramping of voltage appearing across the lamp
and also the voltage on capacitor CRAMP. Note that the sudden drop in lamp voltage indicates that
the lamp has ignited. Also note that the voltage on capacitor C12 is still increasing at the point when
the lamp has already ignited meaning the frequency is still ramping down to the final minimum
ignition frequency. This minimum frequency corresponds to the absolute maximum ignition voltage
required by the lamp under all conditions.
During the Ignition Ramp mode the voltage on the CPH pin of IC2 continues to ramp up until the
voltage at the CPH pin of IC2 exceeds the Run mode threshold (5.1V). Over-current sensing is also
enabled at the beginning of the Ignition Ramp mode. A full explanation of the functionality of the
over-current sensing is in the section on Fault 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. Resistor RRUN is
connected in parallel by turning on the internal
open drain MOSFET connected to the RUN pin
of IC2 (see Figure 1, IR21571 block diagram).
The sensing of under-current conditions is also
enabled at the beginning of the Run mode. The
full explanation of the functionality of the undercurrent sensing is in the section on Fault Mode.
Figure 10 shows the functionality of the CPH,
RPH and RUN pins of IC2 during Startup, Preheat, Ignition Ramp and Run modes.
Figure 10: Top trace: CPH pin IC2
Middle trace: RPH pine IC2
Bottom trace: RUN pin IC2
The Run mode frequency is that at which the lamp is driven to the lamp manufacturer’s recommended lamp power rating. The running frequency of the lamp resonant output stage for selected
component values is defined as,
frun =
1
2π
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 2VDCbus 
1− 
2



1
1
VLampπ 
 PLamp 
 PLamp 

− 2
− 2
 + 
  −4
2
2
LC
L2C 2
 CV Lamp 
 CV Lamp  
 LC
2 2
2
(3)
11
where,
L
C
PLamp
VLamp
=
=
=
=
Lamp resonant circuit inductor (L3)
Lamp resonant circuit capacitor (C14)
Lamp running power
Lamp running voltage amplitude
(H)
(F)
(W)
(V)
Figure 11 shows the voltage appearing across the lamp while Figure 12 shows the current flowing
through the lamp during Startup, Preheat, Ignition Ramp and Run modes.
Figure 11: Lamp voltage during Startup, Preheat,
Ignition Ramp and Run
Figure 12: Lamp current during Startup, Preheat,
Ignition Ramp and Run (100mA/div.)
Normal Powerdown
A Normal Powerdown occurs when the AC line voltage is disconnected from the ballast. When this
occurs the voltage on the VDC pin of IC2 drops below the line fault threshold (3V) and IC2 shuts
down in a controlled fashion. The oscillator is stopped, the half-bridge driver outputs (LO and HO)
are turned off and capacitors CPH, CRAMP, CSTART and CT are discharged. IC2 also goes into its
UVLO/micro-power mode and the bus voltage begins to collapse.
Fault Mode
Fault mode is when the ballast driver is shutdown due to the detection of a lamp fault. Note that when
the ballast is in this Fault mode the power factor correction section of the ballast is also shutdown
and the bus voltage will drop to the non-boosted/unregulated level. There are several lamp fault
conditions which can put the ballast into the Fault mode. The lamp fault conditions detected include:
near/below resonance (under-current) detection, hard-switching detection and over-current detection. Resistor RCS in the source lead of the low side MOSFET (M3) serves as the current sensing
point for the half-bridge which is used to detect these lamp fault conditions. In operation when the
half-bridge is oscillating, a voltage appears across RCS whenever the low side MOSFET, M3, is
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turned on or the high side MOSFET, M2, is turned off. The magnitude of this voltage directly relates
to the current in the lamp resonant circuit. Figure 13 shows the voltage which appears across resistor RCS during normal Run mode conditions while Figure 14 shows the voltage appearing across the
lamp during the end of Preheat mode, Ignition Ramp mode and the beginning of Run mode. Also
shown in Figure 13 are the gate drive signals for the low side MOSFET (LO pin) and the high side
MOSFET (HO-VS pin).
Figure 13: Normal Run mode, Upper trace: voltage
across RCS, Middle trace: IC2 LO pin voltage,
Lower trace: IC2 HO-VS pin voltage
Figure 14: Normal lamp ignition: Lamp voltage during
the end of Preheat mode, Ignition Ramp mode
and the beginning of the Run mode
During the Preheat mode the voltage across resistor RCS is not measured. However, at the end of
Preheat mode (the beginning of the Ignition Ramp mode) the hard-switching and over-current detection are enabled. If at any time thereafter the voltage magnitude across resistor RCS rises above the
over-current (CS+) threshold of the CS pin of IC2, a lamp fault condition is signaled and the halfbridge output MOSFETs’, (M2 and M3) are turned off and the ballast goes into Fault mode. This can
happen if the lamp fails to ignite or if the upper filament is open. For failure to ignite the lamp, the
current in the half-bridge increases and thus the voltage across resistor RCS increases above the
over-current threshold signaling a fault. Figure 15 shows the voltage across resistor RCS and the
voltage appearing across the lamp when the ballast detects a failure to ignite the lamp and goes into
Fault mode. The CS+ threshold is determined by resistor ROC. An internal current source of 50uA is
connected to the OC pin of IC2 which when applied to resistor ROC sets a voltage at the OC pin.
This voltage is the CS+ threshold of IC2. Figure 16 shows the voltage appearing across the lamp
during the tail end of the Preheat mode and the Ignition Ramp mode for a failure of the lamp to ignite
condition. If the upper filament is open, the half-bridge output hard-switches and each time the low
side MOSFET (M3) is turned on a large current pulse occurs and thus a large voltage pulse occurs
across resistor RCS signaling a fault, Figure 17 shows this hard-switching condition. Figure 18 shows
the lamp voltage during the Preheat mode and beginning of Ignition Ramp mode for this hardswitching condition when the lamp fault condition is detected. The ballast will remain in Fault mode
until either the line voltage is cycled or a lamp replacement is performed.
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Figure 15: Failure of lamp to ignite condition (lamp
filaments good): Upper trace: voltage across
RCS, Lower trace: lamp voltage
Figure 16: Failure of lamp to ignite condition (lamp
filaments good): Lamp voltage during the end
of Preheat and Ignition Ramp modes
Figure 17: Hard-switching condition (upper filament
open): Upper trace: voltage across RCS,
Middle trace: IC2 LO pin voltage,
Lower trace: IC2 HO-VS pin voltage
Figure 18: Hard-switching condition (upper filament open):
Lamp voltage during Preheat mode and beginning of
Ignition Ramp mode when lamp fault is detected
At the completion of the Ignition Ramp mode (beginning of the Run mode) the near/below resonance
(under-current) detection is also enabled. Near/below resonance detection is performed by synchronously sensing the voltage across resistor RCS, which relates to the current flowing in the low side
MOSFET (M3), just prior to the turn off of M3. If this voltage is lower than the near/below resonance
threshold (CS- = 0.2V) of the CS pin of IC2, a lamp fault condition is signaled and the ballast goes
into Fault mode. This could occur if the frequency of oscillation becomes too close to the resonant
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frequency of the load circuit and the current in the load circuit commutates to close to zero. Figure 19
shows a near/below resonance condition where the voltage on resistor RCS falls below the 0.2V
threshold on the CS pin of IC2.
Resistors R17, R18 and capacitor
C13 form a divider/filter network
which is used to detect an open lower
lamp filament and/or lamp replacement. Under normal conditions, the
voltage across C8 is approximately
zero volts. However, if the lower filament becomes open or the lamp is
removed, the voltage across C13 increases above the 2V threshold for
the SD pin of IC2 and signals a lamp
fault condition which in turn puts the
ballast into Fault mode. The ballast
remains in the Fault mode until the
line voltage is cycled or a lamp replacement is performed. If the lamp
is replaced with a lamp with a good
lower filament, the voltage on the SD
Figure 19: Near/Below Resonance conditions
pin of IC2 is pulled back below the
Upper trace: voltage across RCS
2V threshold and the ballast will go
Lower trace: half-bridge output voltage
through a restart. Line voltage cycling
is also used to restart the ballast for all lamp fault conditions. The ballast will go through a full
Preheat, Ignition Ramp and Run modes any time a restart is performed. Note that the SD pin of IC2
is active during all modes of operation.
Another way that the ballast can go into Fault mode is if the AC line voltage falls below approximately
170Vrms. Resistors R11, R12 and capacitor C9 form a voltage divider/filter network which is connected to the VDC pin of IC2 and is used to determine if the line voltage falls below permissible
levels. This happens when the line voltage is cycled or possibly a brownout condition occurs. The
VDC pin of IC2 senses a fault if the voltage at the pin falls below 3 volts and shutdown of the ballast
occurs. The ballast remains shutdown until the voltage at the VDC pin rises above 5.1 volts. At this
time if there are no other fault conditions the ballast will go through a full Preheat, Ignition Ramp and
Run mode. As in the case of the SD pin of IC2, the VDC pin of IC2 is active during all modes of
operation of the ballast.
IR WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245 Tel: (310) 252-7105
Data and specifications subject to change without notice. 10/28/2000
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15
Data Sheets
Lighting Ballast Control IC - Designer’s Manual
16
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