IRPLLNR5 - INTERNATIONAL RECTIFIER

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IRPLLNR5

IRPLLNR5 Wide Range Input Linear Fluorescent Ballast

Reference Design Using the IRS2168D

Table of Contents

Page

1. Features…………………………………………………………………...….2

2. Description.............................................................................................2

3. Electrical Characteristics .......................................................................3

4. Fault Protection Characteristics.............................................................4

5. IRPLLNR5 Schematics…………...……..…………………………………..5

6. PCB Component Placement Diagram and Board Fabrication…………..6

7. Bill of Material and Inductor Specification………………………..………..8

8. Functional Description……….……………………….…………………....11

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1. Features

• Drives 1 x 54 W TL5 Lamp

• Input Voltage: 90-305 VAC

• High Power Factor/Low Total Harmonic Distortion

• High Frequency Operation

• Lamp Filament Preheating

• Lamp Fault Protection with Auto-Restart After Lamp Replacement

• Low AC Line Protection

• Lamp End-of-Life Shutdown

• IRS2168D HVIC Ballast Controller

2. Description

The IRPLLNR5 reference design 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 IRS2168D(S)PbF Ballast Control

IC. This reference design is intended to ease the evaluation of the IRS2168D, demonstrate PCB layout

techniques, and serve as an aid in the development of a production-ready ballast using the IRS2168D.

IRS2168D

Line

Input

UVLO

PFC Control

Half-Bridge Driver

Lamp Fault

Lamp

EMI Filter Rectifier Boost PFC Output Stage

Control IC

Fig. 1: Ballast Block Diagram

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3. Electrical Characteristics

Parameter Units Value

Lamp Type 54 W TL5

Input Power [W] 54

Lamp Running Voltage [Vpp] 400

Run Mode Frequency [kHz] 50

Preheat Mode Frequency [kHz] 85

Preheat Time [s] 1.0

Lamp Preheat Voltage [Vpp] 500

Lamp Ignition Voltage [kVpp] 2.0

Input AC Voltage Range [VAC] 90-305 VAC

Power Factor 0.995 at 120 VAC

0.98 at 220 VAC

Total Harmonic Distortion [%] 10 at 120 VAC

14 at 220 VAC

Table 3.1: Ball ast Par ameters

Vin Pin (W) PF THD (%) DCBUS (V)

90 55.5 0.997 9.15 495

110 52.8 0.996 9.85 495

130 51.8 0.994 11 495

150 51.1 0.992 11.25 495

170 50.8 0.99 12.2 495

190 50.7 0.987 12.8 495

210 50.6 0.983 13.9 495

230 50.5 0.978 14.9 495

250 50.5 0.972 16.1 495

270 50.5 0.964 17.7 495

Table 3.2: PFC Data

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0.96

0.965

0.97

0.975

0.98

0.985

0.99

0.995

90 140 190 240

VIN

THD

PF PM

THD PM

Fig. 2: PFC and THD Performances versus Input Voltage

4. Fault Protection Characteristics

Fault Ballast Restart Operation

Line Voltage Low Deactivates Increase line voltage

Upper Filament Broken Deactivates Lamp exchange

Lower Filament Broken Deactivates Lamp exchange

Failure to Ignite Deactivates Lamp exchange

Open Circuit (no lamp) Deactivates Lamp exchange

End of Life Deactivates Lamp exchange

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5. IRPLLNR5 Schematics

Fig. 3: Schematic Diagram, IRS2168D, Single Lamp, Voltage Mode Heating

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6. PCB Component Placement Diagram and Board Fabrication

Fig. 4: PCB Component Placement Diagram

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Board Fabrication

1) Board size: L = 8.59 inch, W = 1.195 inch

2) No. of copper layers: 1 (bottom layer)

3) Copper: 2 oz.

4) Board material: FR-4

5) Through hole plating: No

6) Solder plating on pads: Yes

7) Solder mask: Green LP1 (bottom layer only)

8) Silk screen layers: Top and bottom

9) Silk screen ink: White epoxy, non-conductive

10) Gerber file: IRPLLNR5.ZIP

11) Gerber file description:

a) IRPLLNR5.apr Apertures

b) IRPLLNR5.DRL NC drill

c) IRPLLNR5.DRR NC drill

d) IRPLLNR5.GBL Bottom layer

e) IRPLLNR5.GBO Silk screen bottom

f) IRPLLNR5.GBS Solder mask bottom

g) IRPLLNR5.GD1 Drill drawing

h) IRPLLNR5.GG1 Drill guide

i) IRPLLNR5.GM1 Mechanical layer

j) IRPLLNR5.GTO Silk-screen top

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7. Bill of Material and Inductor Specification

Item Qty Manufacturer Part Number Description Reference

1 1 Diodes Inc. DF10S Bridge Rectifier, 1 A, 1000 V BR1

2 1 Roederstein WKP222MCPEJ0K Capacitor, 2.2 nF, 305 VAC Y Cap CY

3 1 Dale CW-1/2 Resistor, 0.5 Ω, 1/2 W F1

4 1 Roederstein F1772433-2200 Capacitor, 0.33 µF, 275 VAC C1

5 1 Panasonic ELF-15N007A EMI Inductor, 10 mH, 0.7 A peak L1

6 1 Vishay Dale MKP1841410634 Capacitor, 0.1 µF, 630 VDC C2

7 1 Wima MKP10-.1/400/10 Capacitor, 0.1 µF, 400 VDC CDC

8 1 Panasonic ERZ-V05D471 Transient Suppressor RV1

9 1 VOGT IL 060 320 41 02 PFC Inductor, 2 mH, 2.5 A peak LPFC

10 2 Panasonic EEU-EB2V330S Capacitor, 33 µF, 350 VDC, 105 °C CBUS1, CBUS2

11 2 Panasonic ECJ-3VB1E104K Capacitor, 0.1 µF, SMT 1206 CBS, CVCC

12 2 Panasonic ECU-V1H102JCH Capacitor, 1 nF, SMT 1206 CSD, CEOL (see Note 2)

13 3 Panasonic ECJ-3YB1E105K Capacitor, 1 µF, SMT 1206 CCOMP, CPH, CVCO

14 1 Panasonic ECU-V1H103KBM Capacitor, 0.01 µF, SMT 1206 CVBUS

15 1 Panasonic ECJ-3VB1E334K Capacitor, 0.33 µF, SMT 1206 CSD1

16 1 Panasonic ECE-A1EKG100 Capacitor, 10 µF, 25 VDC, 105 °C CVCC1

17 1 Johanson Dielectrics 102R29W102KV4E Capacitor, 1 nF, 1 kV, SMT 1808 CBS

18 1 WIMA FKP1-3300/2000/5 Capacitor, 3.3 nF, 2 kV CRES

19 2 Panasonic ECU-V1H471KBM Capacitor, 470 pF, SMT 1206 CCS, COC

20 2 Panasonic ECQB1104JFW Capacitor, 0.1 µF, 100 V CH1, CH2

21 1 Diodes Inc. ZMM5240B-7 Zener diode, 10 V, Minimelf, 0.5 W DEOL1

22 1 Diodes Inc. ZMM5232B-7 Zener diode, 5.6 V, Minimelf, 0.5 W DEOL2

23 1 Digi-key MURS160DICT-ND Diode, 1 A, 600 V, SMT SMB DPFC

24 3 Diodes LL4148DICT-ND Diode, 1N4148, SMT DL35 DCP1, DCP2, DSD

25 1 Tyco Electronics/Amp 2-641262-1 DIP 16 IC Socket Through-Hole IC1

26 1 International Rectifier IRS2168D IC, Ballast Driver / PFC IC1

27 1 VOGT IL 060 320 51 01 Resonant Inductor, 2 mH, 2 A peak LRES

28 3 International Rectifier IRFB9N60A Transistor, MOSFET MPFC, MHS, MLS

29 2 > = 22 A.W.G Jumpers J1, J2

30 5 Panasonic ERJ-8GEYJ120V Resistor, 12 Ω, SMT 1206 RPFC, RLO, RHO, RLM1, RLM2

31 1 Panasonic ERJ-8GEYJ474V Resistor, 470 kΩ, SMT1206 RCPH

32 1

Phoenix Passive

Components 5033ED220K0F12AF5 Resistor, 220 kΩ, 1/2 W RVCC

33 2 Panasonic ERJ-8GEYJ684V Resistor, 680 kΩ, SMT 1206 RVBUS1, RVBUS2

34 1 Panasonic ERJ-8GEYJ333V Resistor, 33 kΩ, SMT 1206 RZX

35 2 Panasonic ERJ-8GEYJ102V Resistor, 1 kΩ, SMT 1206 RF1, RF2

36 1 Vishay/Dale RS01A1R500FS70 Resistor, 1.5 Ω, 1%, 1 W RCS

37 1 Digi-Key P0.62W-1BK-ND Resistor, 0.62 Ω, 1 W ROC

38 1 Panasonic ERJ-8ENF1132V Resistor, 11.3 kΩ, 1%, SMT 1206 RVBUS

39 1 Panasonic ERJ-8GEYJ104V Resistor, 100 kΩ, SMT 1206 RSD

40 4 Panasonic ERJ-8GEYJ224V Resistor, 220 kΩ, SMT 1206 REOL1, REOL2, REOL3, RPU

41 1 Panasonic ERJ-8GEYJ203V Resistor, 20 kΩ, 5%, SMT 1206 REOL4 (see Note 3)

42 1 Digi-key 36.0KFRCT-ND Resistor, 36 kΩ, 1%, SMT 1206 RFMIN

43 1 Panasonic ERJ-8GEYJ563V Resistor, 56 kΩ, 1%, SMT 1206 RPH

44 1 WAGO 235-203 Connector, 3 terminal X1

45 1 WAGO 235-207 Connector, 4 terminal X2

Table 1: Bill of Material

Lamp type: 54 W TL5; Line Input Voltage: 80-305 VAC

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Note 1: Different lamp types require different frequency programming components.

Note 2: CEOL and CSD values can be increased up to 470 nF to increase noise immunity.

Note 3: REOL4 value can be increased to 33 kΩ for a more sensitive lamp end-of-life detection

HORIZONTAL

INDUCTOR SPECIFICATION

CORE SIZE

CORE MATERIAL

GAP LENGTH

Fi 324 or equivalent

WINDING START PIN FINISH PIN TURNS WIRE DIAMETER (mm)

MAIN

PHYSICAL LAYOUT

TEST

MAIN WINDING INDUCTANCE INDUCTANCE TOLERANCES: +/- 5%

PART NO.: IL 060 320 41 02 REF DES:

LPFC

(TEST FREQUENCY = 50kHz)

NOMINAL INDUCTANCE

MAXIMUM CURRENT

MAXIMUM CORE TEMPERATURE

Apk

ºC

115

NOTE : Inductor must not saturate at maximum current and maximum core temperature at

given test frequency

ELECTRICAL

LAYOUT

BOBBIN PINS

EVD25 3.5

2.5

TBD

3526

4 strands of AWG 32

AWG 32

5mm

20.05mm

25mm

TOP VIEW

MAIN WINDING INDUCTANCE INDUCTANCE RESISTANCE MAX 3.2 OHM

Fig. 5: Power Factor Inductor Specification

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HORIZONTAL

INDUCTOR SPECIFICATION

CORE SIZE

CORE MATERIAL

GAP LENGTH

Fi 324 or equivalent

WINDING START PIN FINISH PIN

URNS WIRE DIAMETER (mm)

MAIN

PHYSICAL LAYOUT

EST

MAIN WINDING MIN 1.9 MAX 2.1

MAIN WINDING

mH mH

MAX 1.8 Ohms

PART NO.: IL 060 320 51 01 REF DES: LRES

(TEST FREQUENCY = 50kHz)

NOMINAL INDUCTANCE

MAXIMUM CURRENT

MAXIMUM CORE TEMPERATURE

ºC

115

NOTE : Inductor must not saturate at maximum current and maximum core temperature at given

test frequency.

ELECTRICAL

BOBBIN PINS

CATHODE (1)

CATHODE (2)

EVD25 2.82

5mm

20.05mm

25mm

TOP VIEW

1 8185 4 strands of AWG 32

6 7 8 4 strands of AWG 32

4 5 8 4 strands of AWG 32

Fig. 6: Resonant Inductor Specification

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8. Functional Description

The IRPLLNR5 reference design consists of an EMI filter, an active power factor correction section, a

ballast control section, and a resonant lamp output stage. The active power factor correction section is a

boost converter operating in critical 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 lamp fault detection, shutdown, and auto-restart.

Reference Design Overview

This demo-board is designed for a single 54 W TL5 lamp with voltage mode heating. TL5 lamps are

popular due to their low profile and high lumen/watt output. These lamps, however, can be more

difficult to control due to their higher ignition and running voltages. A typical ballast output stage using

current-mode filament heating (filament placed inside L-C tank) will result in excessive filament current

during running. The output stage has therefore been configured for voltage-mode filament heating using

secondary windings off of the resonant inductor LRES. The lamp has been placed outside the under-

damped resonant circuit loop, which consist of LRES and CRES. The filament heating during preheat

can be adjusted with the capacitors CH1 and CH2. The result is a more flexible ballast output stage

necessary for fulfilling the lamp requirements. The DC blocking capacitor, CDC, is also placed outside

the under-damped resonant circuit loop such that it does not influence the natural resonance frequency

of LRES and CRES. The snubber capacitor, CSNUB, serves as EMI reduction and a charge pump for

supplying the IRS2168D.

The IRS2168D ballast control IC is used to program the ballast operating points and protect the ballast

against conditions such as lamp strike failures, low DC bus or lamp failure during normal operations. It

is also used to regulate the DC bus and for power factor correction to give high power factor and low

harmonic distortion of the ballast AC input current.

Power Factor Correction Section

The power factor correction section contained in the IRS2168D controls 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. The power factor correction section also includes over-current protection of the

boost MOSFET to prevent damage that can occur during boost inductor saturation.

Ballast Control Sectio n

The ballast control section of the IRS2168D ballast control IC contains an oscillator, a high-voltage

half-bridge gate driver, and lamp fault protection circuitry. Please refer to the datasheet of this IC for

the block diagram and the state diagram. The following is a breakdown of the different modes of

operation for the ballast.

Startup Mode

When power is initially applied to the ballast, the voltage on the VCC pin of the IRS2168D begins to

increase. The voltage for the IRS2168D is derived from the current supplied from the rectified AC line

through the startup resistor RSUPPLY. During this initial startup when the VCC voltage of the

IRS2168D is below the rising under-voltage lock-out threshold (UVLO+), the IC is in UVLO Mode and

draws micro-power current at VCC. The micro-power current of the IRS2168D allows for the use of a

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large value, low-wattage startup resistor (RSUPPLY). When the voltage on the IRS2168D reaches the

rising under-voltage lockout threshold (12.5 V), the gate driver oscillator is enabled (this assumes that

there are no fault conditions) and drives the half-bridge output MOSFETs (MHS and MLS). 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. 15.6 V). When the rising under-voltage lockout

threshold of the IRS2168D is reached, the power factor control output also starts to oscillate and drives

MOSFET MPFC to boost and regulate the bus voltage to 500 V DC.

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 IRS2168D has begun to operate and the half-bridge output is driving

the resonant load (lamp) circuit.

There is an initial startup frequency that is higher than the preheat frequency that lasts for only a short

duration. This is done to ensure 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 undesired flash of the lamp can occur.

This in effect is a cold strike of the lamp and can shorten the life of the lamp.

The ballast control section oscillator of the IRS2168D consists of an internal timing capacitor and an

external timing resistor (RFMIN). Resistors RFMIN and RPH program a current that determines the

ramp up time of the internal timing capacitor. The preheat frequency is determined by the equivalent

resistance formed by the parallel combination of RFMIN and RPH. The preheat frequency 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 their correct emission temperature within the

Preheat Mode time period. The preheating of the lamp filaments is performed using voltage mode

heating that consists of a constant voltage across the lamp filaments. The waveform in Figure 7 shows

the CPH voltage and lamp voltage during normal Preheat, Ignition, and Run Modes. Figure 8 shows the

half-bridge voltage (VS pin) during Preheat Mode.

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Fig. 7: CPH Pin Voltage (Black) and Lamp Voltage (Blue) During Normal

Preheat, Ignition and Run Modes

Fig. 8: Half-Bridge Mid-Poi nt Voltage (VS Pin) During Preheat Mode

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fosc

Preheat Ignition Run

fPreheat

fRun

Start

Fig. 9: Oscillator Frequency versus Time During Normal Operating Conditions

Figure 9 shows a plot of the half-bridge oscillation frequency as a function of time for normal Preheat,

Ignition and Run ballast operating modes. The duration of the Preheat Mode, as well as all ballast

operating modes, are determined by the voltage on the CPH pin of the IRS2168D. At the end of UVLO

Mode, Preheat Mode is entered and the external capacitor at the CPH pin of the IRS2168D begins to

charge through the external resistor (RCPH) from CPH to VCC. The ballast remains in Preheat Mode

until the voltage on the CPH pin exceeds the End-of-Preheat Mode threshold of 0.67(VCC), at which

time the ballast then enters Ignition Mode.

Ignition Mode

When the IC enters Ignition Mode, CPH is discharged quickly to 0.33(VCC) and RPH is disconnected

from COM via an internal MOSFET at the RPH pin. CPH begins to charge up again from 0.33(VCC)

and the frequency begins to ramp down to the run frequency at a rate determined by the time constant

RPH(CVCO). 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. The maximum ignition voltage that can be generated

is determined from the value of RCS, and the ignition frequency must be higher than the run frequency

so that the frequency sweeps through the resonance frequency to ensure lamp ignition. If the lamp does

not ignite, then the ignition regulation feature of the IRS2168D will regulate the ballast output voltage

to a constant level (programmed by RCS) for the duration of Ignition Mode. Figure 10 shows the lamp

voltage during ignition ramp and ignition regulation during a lamp non-strike condition.

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Fig. 10: CPH Pin Voltage (Bl ack) and Lamp Voltage (Blue) During Lamp

Non-Strike Fault Condition

During Ignition Mode, the voltage on the CPH pin of the IRS2168D continues to ramp up until the

voltage at the CPH pin exceeds 0.67(VCC) a second time and the IC enters Run Mode. The over-current

fault counter is disabled during Ignition Mode due to the ignition regulation feature and enabled again

at the start of Run Mode. During a lamp non-strike condition, the ignition voltage will be regulated for

the duration of Ignition Mode and then unregulated during Run Mode. This means that the ignition

voltage will increase slightly after Ignition Mode (as the frequency decreases towards the run

frequency) until the fault counter times out, after 65 cycles above the over-current threshold, and the

ballast shuts off. The amount of frequency shift and resulting voltage increase is determined by the

value of CVCO. The 5 V shutdown threshold at the SD pin is also disabled during Ignition Mode and

enabled again at the start of Run Mode. A full explanation of the functionality of the over-current

sensing and shutdown functions are in the Fault Mode section.

Run Mode

During Run Mode and after a successful lamp ignition, the frequency is at the final run frequency and

is determined by RFMIN. The 1 V and 3 V end-of-life (EOL) window comparator at the SD/EOL pin,

the 5 V unlatched shutdown threshold at the SD/EOL pin, and the fault counter at the CS pin, are all

enabled in Run Mode. A functional description of the over-current sensing and end-of-life sensing is

given in the Fault Mode section.

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The Run Mode frequency (Figure 11) 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,

fLC P

CV LC P

run Lamp

Lamp

DCbus

Lamp

=−

⎛

⎝

⎜⎞

⎠

⎟+−

⎛

⎝

⎜⎞

⎠

⎟

⎡

⎣

⎢

⎤

⎦

⎥

−

−⎛

⎝

⎜⎞

⎠

⎟

12124

where,

L = Lamp resonant circuit inductor (LRES) (H)

= Lamp resonant circuit capacitor (CRES) (F)

Lamp = Lamp running power (W)

VLamp = Lamp running voltage amplitude (V)

Fig. 11: Half-Bridge Mid-Point Voltage (VS Pin) During Run Mode

Normal Power Down

A normal power down occurs when the AC line voltage is disconnected from the ballast. When this

occurs, the voltage on the VBUS pin of the IRS2168D drops below the VBUS pin under-voltage reset

threshold of 3 V. This will cause VCC to be discharged internally to UVLO- (10.5 V). The IC enters

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UVLO Mode and the PFC and ballast oscillators are disabled, the PFC and half-bridge driver outputs

(PFC, LO, and HO) are turned off, and the IRS2168D consumes micro-power current at VCC.

Lamp Removal and Auto-Restart

Resistors RPU, RSD and capacitor CSD1 form a divider/filter network used to detect an open lower

lamp filament and/or lamp replacement. Under normal conditions, the voltage across CSD1 is close to

zero. If the lower filament becomes open or the lamp is removed, however, the voltage at the SD pin

increases above the 5 V threshold and causes the IC to shutdown (Figure 12). The ballast remains

shutdown until a lamp replacement is performed. If the lamp is replaced with a lamp with a good lower

filament, the voltage on the SD pin of the IRS2168D drops back below the 3 V threshold and the

ballast will restart in Preheat Mode. The ballast will go through the Preheat, Ignition, and Run Mode

sequences each time a restart is performed. Note that the SD pin of the IRS2168D is active during

Preheat and Run Modes and is disabled during Ignition Mode.

Fig. 12: SD Pin Voltage (Black) and Lamp Voltage (Blue) during

Lamp Removal/Auto-Restart Condition

Fault Mode

When a fault is detected at the CS pin or SD/EOL pin, the IC will enter Fault Mode. During Fault

Mode, the ballast section and PFC section are both shutdown. The DC bus voltage will drop to the

non-boosted peak AC line voltage level. There are several lamp fault conditions that can cause the IC

to enter into Fault Mode. These include: hard-switching at the half-bridge mid-point (open load), over-

current (non-strike), lamp voltage shift (end-of-life), and lamp removal (SD/EOL pin). Resistor RCS in

the source lead of the low-side MOSFET (MLS) serves as the current-sensing point for the half-bridge,

and is used to detect hard-switching or over-current. During normal operation when the half-bridge is

oscillating, a voltage appears across RCS when the low-side MOSFET, MLS, is turned on. The

magnitude of this voltage directly relates to the current in the lamp resonant circuit.

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If at any time during Preheat Mode or Run Mode the voltage across resistor RCS rises above the over-

current threshold (1.25 V) for 65 events, the PFC and half-bridge MOSFETs, (MPFC, MHS and MLS)

are turned off and the ballast goes into Fault Mode. During the Ignition Mode, the over-current is

disabled and the ignition regulation feature limits the maximum current flowing in the resonant tank

and half-bridge. An over-current condition can occur if the lamp fails to ignite or the lamp is broken

(an open circuit cathode or broken lamp). If a cathode is broken (open circuit), the half-bridge output

hard-switches. Each time the low-side MOSFET (MLS) is turned on, a large current pulse occurs and

thus a large voltage pulse occurs across resistor RCS signaling a fault. The ballast will remain in Fault

Mode until the AC line voltage is reset or a lamp replacement is performed.

During an end-of-life lamp fault condition, the lamp voltage can increase or decrease asymmetrically.

The resulting excessive voltage across the lamp filaments can cause the lamp ends to reach temperatures

high enough to melt the tube glass. The lamp can then fall out of the fixture and cause harm or damage.

To protect against this condition, resistors REOL1, REOL2, REOL3, REOL4, and zener diodes DEOL1

and DEOL2, are used for end-of-life protection. The end-of-life window comparator at the SD/EOL pin

is enabled in Run Mode. If the voltage on SD/EOL pin falls outside the range of the internal 1 V – 3 V

window comparator, the IC will enter Fault Mode. The SD/EOL pin is internally biased at 2 V with an

internal +/-10 µA OTA. The value of REOL4, DEOL1 and DEOL2 are selected such that the SD/EOL

pin remains at 2 V during normal operation, but increases above 3 V or decreases below 1 V during an

end-of-life fault condition. The lamp voltage end-of-life threshold can be adjusted by changing the value

of resistor REOL4 and/or zener diodes DEOL1 and DEOL2. A threshold of 30% higher than the

nominal running lamp voltage is typical.

PFC Control Section

The IRS2168D contains control circuitry for driving a boost-type power factor correction (PFC) circuit.

This is necessary for producing sinusoidal input current at the mains input that is “in phase” with the

mains voltage and contains minimal total harmonic distortion (THD). It is also convenient to use the

boost converter to regulate the DC bus voltage to a constant DC level. The PFC control is achieved

using five control pins. The DC bus voltage is sensed with a resistor divider at the VBUS pin. The loop

compensation speed is programmed with an external capacitor at the COMP pin. The cycle-by-cycle

zero-crossing of the boost inductor current is detected at the ZX pin. The gate drive for the boost

MOSFET is provided by the PFC pin. The cycle-by-cycle over-current protection is performed by the

OC pin. The following waveforms show the operation of the PFC at 120 VAC (Figure 13) and 290 V

AC (Figure 14) input line conditions.

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Fig. 13: AC Input Current (Green) and AC Input Voltage (Blue) at 120 VAC

Fig. 14: AC Input Current (Green) and AC Input Voltage (Blue) at 290 VAC

PFC Over-Current Protection

The PFC section includes cycle-by-cycle over-current protection. The OC pin senses the current in the

PFC MOSFET via an external sense resistor (ROC). Should the voltage across this resistor exceed the

internal threshold (1.25 V typical), the PFC MOSFET will turn off to limit the instantaneous current

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and will turn on again at the next zero-crossing of the inductor current as detected by the ZX pin. This

over-current condition can occur, for example, during a low-line condition (Figure 15). As the AC line

decreases, the PFC inductor and MOSFET current will increase to keep the DC bus constant for a

given power level. When the peak current reaches the over-current threshold, the cycle-by-cycle

current limit will cause the peak of the MOSFET current to flatten and the DC bus to start to drop. This

current limit is necessary to prevent saturation of the PFC inductor current and to protect the PFC

MOSFET from being damaged.

Fig. 15: OC Pin Voltage (Black) and DC Bus Voltage (Green) During Low-Line Condition

Brown-Out Protection

The IRS2168D includes an under-voltage reset (UVR) function at the VBUS pin. Should the DC bus

decrease too far during a momentary interrupt of the mains input voltage, the ballast should be properly

shutdown and restarted. This will prevent the lamp from extinguishing and will properly preheat and

restart the lamp when the mains voltage returns. If the VBUS pin voltage decreases below 3 V, the

PFC and half-bridge gate drivers will be turned off and VCC will be discharged to UVLO-. The ballast

will then be restarted via the RSUPPLY resistor when the mains voltage reaches a high enough level

again (Figure 16).

RD-0613

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Fig. 16: VBUS Pin (Black), Lamp Voltage (Blue) and DC Bus Voltage (Green) During

Momentary Interruption of the Mains

02/15/2007