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1 Three Dimensional Passive Integrated Electronic Ballast for Low Wattage HID lamps Yan JiangCommittee Members:Dr. Fred C. Lee (Chair)Dr. J. D. van WykDr. Dushan BoroyevichDr. Shuo WangDr. William T. BaumannDr. Carlos T. A. SuchicitalJanuary 27th, 2009
2 Low pressure discharge High (pressure) intensity discharge (HID) Lighting19% of global power consumption and 3% of global oil demand is attributable to lightingIncandescentEfficacy: 15~20 lm/WLife time: 1k~3k hoursStandard Incand.halogenGas dischargeSolid StateLow pressure dischargeHigh (pressure) intensity discharge (HID)Fluorescent (FL)CFLCCFLLow pressure sodiumMetal halide (MH)Ceramic MHMercury vaporHigh pressure sodiumLEDOrganic LEDFor FL and CFL, Technologies on both lamp and ballast are very mature. Simple and low cost ballast have been widely used in residential application and replacing the incandescent lamps.For HID lamps, mainly used in outdoor and high end, due to the large size and high cost of HID ballast.60~200 lm/W8k~18k hours60~150 lm/W8k~40k hours40~160 lm/W50k~60k hours
3 HID ApplicationsTrack lighting for offices and retail environment (20W~39W)Automotive headlights (35W~70W)LCD projectors (100W~150W)Supermarket lighting (175W~400W)Stadium, parking area and roadway/tunnel lighting (400W~2000W)3
4 Need around 4 yr to break even Track LightingHalogenHIDLower efficacyShorter lamp life (≈4kHr)≈70% of market shareLower cost, smaller size(Basically incandescent lamp, doesn’t need ballast)70W halogen≈20W HIDHigher efficacyLonger lamp life (up to 20kHr)<20% of market shareHigher cost, larger size(Needs sophisticated ballast)HID lamp system has higher initial cost, but is more energy efficient in long run.Track lights provide directable beams of high-quality light for use in retail displays, galleries, museums, and residences. They are useful in locations where lights need to be aimed at different angles and where the position of the light may be changed frequently. Until recently, the only light sources that could provide the right kind of illumination for track lighting were inefficient halogen lamps. However, the introduction of low-wattage, metal halide (MH) lamps in the mid-1990s gave designers and specifiers an energy-efficient alternative. These lamps not only reduce energy use but last several times longer than halogen lamps, thus leading to reduced lamp-replacement costs as well. However, costs for MH lamps and fixtures are significantly higher than those for incandescent units, so MH products are most cost-effective in applications with long burn hours and where changing lamps is difficult.Need around 4 yr to break evenMarket requirements for HID ballast:Compact sizeLow cost
5 Ballast for Gas Discharge Lamp VSVABVRVoltage (V)VABLampR+ VR -+ VLamp -VLampCurrent (A)ISSBallast is needed to stabilize the current for gas discharge lampsfs>20kHzLike other gas discharge lamp as fluorescent lamp, HID lamp has negative VI characteristics as shown in this figure. So if an HID lamp can’t directly connected to a voltage source, a small variation of the current may lead to the extinguish or blow up of the lamp. Therefore, a ballast with a positive impedance is needed to compensate the negative impedance , and stabilize the lamp current. This is the first requirement for the HID lamp ballast. HID ballast should also provide a high ignition voltage pulse to start the lamp at the beginning. Provide a constant lamp power during the lamp lifetime. It also should provide a high PF and small input current harmonics, ballast should meet IEC Class C standard, which is the most stringent requirement especially for lighting application.Another special characteristic of HID lamp is a phenomenon called “acoustic resonance” . Acoustic resonance can occur when HID lamp is operating at high frequency from several kHz to several hundred kHz. And it will lead to the fluctuation of the light, variation of the color temperature, decrease the lamp lifetime and in the worst case even crack the discharge cube. The most effective way to eliminate AR is providing the lamp a low frequency square wave current.Since the HID lamp is has the highest efficacy and compact size, the ballast is also needed to have high efficiency and small size.LLampCHigh Q parallel-load series-resonant tank generate high voltage peakTransformer boost voltage pulseIgnitor is needed to initiate the gas discharge
6 From Magnetic to Electronic Ballast Magnetic BallastHF Electronic Ballastfs>20kHzLIgnitorLampL110V/60HzLampHigher costSmall and lightIntegrated ignitorNo reignition, no flickering and audible noiseWith lamp power regulation (more intelligent)Improved lamp efficacySimple, low cost, high reliabilitylarge and heavyExternal ignitorReignition causes line frequency flickeringNo lamp power regulationHF electronic ballast greatly reduce the size and weight of ballast, and greatly improve the lamp performance
7 Most Significant Lighting Advance: CFL .Most Significant Lighting Advance: CFLFL with magnetic ballastTypical CFL ballast circuit:Self-oscillating HB series resonant circuit* from DeltaCompact fluorescent Compact fluorescent lamps (CFLs) are the most significant lighting advance developed for homes in recent years. They combine the efficiency of fluorescent lighting with the convenience and popularity of incandescent fixtures.CFLs can replace incandescents that are roughly three to four times their wattage, saving up to 75% of the initial lighting energy. Although CFLs cost from 10 to 15 times more than comparable incandescent bulbs, they also last 10 to 15 times as long. This energy savings and superior longevity make compact fluorescent lamps an excellent choice for residential use.As previously discussed, CFLs are one of the best energy efficiency investments available. When introduced in the early- to mid-1980s, CFLs were bulky, heavy, and too big for many incandescent fixtures. However, newer models with lighter electronic ballasts are only slightly larger than the incandescent lamps they replace. The new CFLs also produce a better color for the home.CFLs come in integral and modular designs. Integral CFLs have a ballast and a lamp in a single disposable unit.In CFL below 25 W, PFC and constant power control are not often used to achieve low costCFL w/ built-in ballastWhy this topology is not suitable for HID ballast?
8 HID lamp start-up profile CFL v.s. HIDCFL start up profileHID lamp start-up profileRequires lower ignition voltage: 400V~600V, Series resonant parallel loaded circuit is enoughRequires much higher ignition voltage: 1kV~5kV (cold strike), ~20KV (hot strike), Voltage need to be further boosted by transformer or elseLF SQ AC current driving is needed to avoid Acoustic Resonance, additional LF inverter is needed.No Acoustic Resonance, can use HF AC current driving
9 Lamp voltage increase (due to AR) vs. freq. Acoustic ResonanceAcoustic Resonance in HID lamps:standing pressure waves occur on the discharge tube at high frequency (f>4kHz)Normal arcArc with AR1020100200708090Vlamp(V)fs(kHz)Detrimental effect of AR:Light lumens fluctuationLamp color temperature variationArc tube overheatExtinguishLamp voltage increase (due to AR) vs. freq.Acoustic Resonance. At high frequency (f > 4 kHz) operation of HID lamps, standing pressure waves (acoustic resonances) can occur in the discharge tube. This phenomenon may lead to visible arc distortions, resulting in decreased lamp life time and, in some cases, cracking of the discharge tubes. Acoustic resonances are driven by periodic instantaneous lamp power. In conclusion it may be stated that the occurrence of acoustic resonances at high frequency can be considered as a limitation factor for a wide and reliable application of high frequency (< 60kHz) electronic ballasts supplying HID lamps .Acoustic Resonance is due to:Methods (for Ballast) to eliminate AR:Lamp frequency is within AR frequency bandHigh frequency energy is larger than the AR thresholdOperate in non-AR frequencyReduce HF energy to below the threshold* E. Rasch, Osram, 1988
10 Existing Methods to Eliminate AR_1 1. Operate in non-AR frequencyDCUltra HF10kHz20kHz100kHz200kHzARAR-free1) DC-type ballast (*S. Wada, 1987)Etching and asymmetrical eroding of electrodes due to cataphoretic effect2) Operate at AR-free Zone (*E. Rasch, 1988)Difficult to select these windows due to dependency on lamp geometry and physical characteristics.3) Operates at frequency higher than 300kHz (*R. Redl, 1999)High EMI caused by high frequency lamp arc.
11 Existing Methods to Eliminate AR_2 2. Reduce HF energy to below the threshold1) Lamp Power spectrum spreadingfrequency modulation, phase-angle modulation…feedback modulation or random modulationOriginal Lamp voltage:Modulated Lamp voltage:40dBV20dBV0dBV0dBVThreshold varies due to lamp parameter inconsistencyPossible to introduce AR on other frequency point* L. Laskai, 1998
12 Existing Methods to Eliminate AR-3 3. Square-wave current driving1) Low Frequency Square Wave (LFSW) lamp current. (*Janos Melis, 1995)vlampilamp≈x00HzThe only one used in commercial productCompletely eliminate Acoustic Resonance,but has relatively complicated system structure.2) High Frequency Square Wave (HFSW) lamp current. (*M. Ponce, APEC 2001)Flat instantaneous power ideally,due to parasitics, there is still HF energy provided to lamp
13 Requirements for HID Ballast Functions:Stabilize lamp currentProvide high voltage (several kV) pulse for initial startingAcoustic resonance free (LF SW AC current driving)Constant lamp power regulation (maximize lamp life time)Regulations:High power factor (PF>0.9)Small input current harmonics (IEC Class C and ITHD <10% )EMI standard (FCC 18)
14 Typical Electronic HID Ballast Achieve high PF, low ITHDProvide constant lamp power regulationProvide high ignition voltageAvoid Acoustic resonance(10K~500kHz)AC/DCPFCDC/DCBuckRegulatedLF DC/AC Inv& IgnitorUnregulatedVinHigh PF, low ITHDConstant powerAcoustic resonance freeLow Crest FactorTo compete with halogen and CFL in low wattage application, HID ballast need:Compact sizeLow costComplicated circuitLow power densityHigh cost
15 CHID Research Objective A high power density, high performance, low cost solution for HID lamp ballastHID ballastCompact system architectureNovel circuit topologyBuilt-in HID ballastCHIDNovel integration technology3D packaging scheme
17 Dissertation Outline Chapter 1: Introduction Chapter 2: High Density HID Ballast Topology Study, Design and ImplementationChapter 3: High Density 3D Passive Integrated BallastChapter 4: Thermal Modeling, Management and Experimental Verification for Integrated BallastChapter 5: Conclusions and Future Work
18 Chapter 2: High Density HID Ballast Topology Study, Design and ImplementationInvestigation on system architecture for CHID ballastSSPFC AC/DC frond-end designExperimental verification
19 Three-stage HID Ballast Structure LF SW Inv.& IgnitorUnregulatedAC/DCPFCDC/DCBuckVinRegulatedCoL2S2For soft-startS1B1L1Cbvinvlampilamp≈400HzS3S4S5S6IgnitorLampHere is a typical HID lamp ballast can meet the above requirements for HID lamp ballast. It is a three-stage structure. AC/DC PFC stage is to achieve high PF and small input current harmonics, DC/DC stage is to provide the lamp power regulation, buck is the simplest topology here. And DC/AC inverter/ignitor stage is an unregulated inverter to change the DC-link voltage/current to a low frequency square to avoid acoustic resonance. And also also provide high ignition voltage to start the lamp.High PF, low ITHDConstant powerAcoustic resonance freeLow Crest FactorComplicated circuitLow power densityHigh cost*Janos Melis, 1995
20 From Three-stage to Two-stage Structure Full-bridge Buck Converterwith ignitorVinAC/DCPFCDC/AC Inv.DC/DC& IgnitorBCMRegulatedUnregulatedS3S4S5S6IgnitorLampCoL2S2For soft-startS1B1L1CbvinS2S3S4S5LoCoLampLrCr* U.S. patent 5,932,976, MEW20W MH ballast (2.4W/in3)Save 1 switch and controllerBCM Boost-type PFC: unity PF, ITHD<10%,High VB(>Vin,pk), need additional soft-start switch3 HF switchesNeed complicated sensing circuit for constant power control
21 Two-stage HID Ballast_type A *M. Sen, et al, IEEE transaction on IA, 2003*J. Zhao, et al, IAS 2003BoostBuckBoostSave 1 switch and controllerBCM Boost-type PFC: unity PF, low ITHD, High bus voltage(>Vin,pk), need soft-start switch3 HF switchesOnly constant current control is achieved (also need complicated sensing circuit for constant power control)Save 3 switchesBCM Boost-type PFC: unity PF, low ITHDHigh bus voltage(>Vin,pk), Need soft-start switch3 HF switchesOnly constant current control is achievedLarge Cs, Lamp voltage or duty cycle is limited by the Vdc and Vcs
22 Two-stage HID Ballast_Type B DC/DCDC/AC Inv.& Ignitor(Regulated)(Unregulated)AC/DCPFCVinDC/AC Inv.& Ignitor(Regulated)(Unregulated)Single Stage PFC AC/DCVin*Y. Yang, APEC 2005*Y. Jiang, IAS 2000SSPFC:DCM Boost + FlybackLF FB inv.DCM Boost type PFC: ITHD>10% , High bus voltage(>Vin,pk), need additional soft start switchonly 1 HF switch, but with higher current stressDCM Boost type PFC: ITHD>10%, High bus voltage(>Vin,pk), need additional soft start switch,only 1 HF switch, but with higher current stressSave 2 LF switch, but adding passive component: one L winding, one C, and one diode.
23 Two-stage Structure Comparison DC/AC Inv& IgnitorregulatedVinAC/DCPFCLF DC/AC Inv& IgnitorUnregulatedVinSSPFCAC/DCBCM Boost type PFC:unity PF, ITHD <10% ,High bus voltage(>Vin,pk),Need additional-soft start switch3 High Freq. switchesComplex sensing and controlDCM Boost type SSPFC:ITHD >10%High bus voltage(>Vin,pk)Need additional soft-start switchOnly 1 High Freq. switchSimple controlSpecific requirements of SSPFC for Low-wattage HID Ballast:Stringent input current harmonic requirement (ITHD<10%)Low bulk cap voltage under large load range (open-circuit to short-circuit)Load characteristic: constant power regulation , large output voltage range.No isolation requirement
24 DCM Single Stage Single Switch PFC DCM S2PFC is suitable for Low power application due to inherent PFC with simple controlDCM PFC + DCM DC/DC:DCM PFC + CCM DC/DC:DC bus voltage is independent of loadHigher current stressSmall current stressHigher efficiencyHigh voltage stress at light load* M. Madigan, etc, PESC’92
25 DCM S4PFC with DC Bus Voltage Feedback Reduce the bulk cap voltage stressReduce the switch current stressTHD increase due to the dead time in input current (much larger than 10%)* F. Tsai etc. INTELEC’96
26 DCM Flyback + DCM Flyback *Jingrong Qian, Ph.D dissertation, DCM PFC +DCM DC/DCLow bus voltage stresslTHD <10%Unity PF, Low ITHD (<10%)Low and adjustable bus voltageEasy soft startFlyback PFC:DCM PFC+DCM DC/DCFlyback DC/DC:large lamp load range (from open-circuit to short-circuit)DCM Flyback + DCM FlybackThe main stream of S4PFC converter is based on two-cascade-stage PFC converter. It integrates PFC stage and DC/DC stage with a shared switch and its controller. Because the PFC semi-stage and dc/dc semi-stage share a common switch, only one control variable can be controlled. Since the output voltage is required to be regulated. It is required that PFC semi-stage has an inherent PFC function. . It is well known that a DCM boost or Flyback converter can draw a near sinusoidal input current with constant on-time control during a line period. Therefore, A DCM boost or flyback integrated with a dc/dc converter is able to achieve PFC and output regulation simultaneously with simple control.Good PFCLow DC bus voltageHigh current stress on the switch (only suitable for low power application)*Jingrong Qian, Ph.D dissertation,
27 Derivation of proposed SSPFC Converter No isolation requirementDCM Flyback (PFC)DCM Buck-Boost (DC/DC)iav Vin, Unity PF and Low THD can be achieved at constant D and fsConstant Pout meansconstant D and fs
28 SSPFC AC/DC Front-end Benefits +Vb_*CbD2L1aL1b*B1D3L2CoRLSDCM FlybackDCM Buck-BoostBenefitsAutomatic unity PF and very low THD (<10%)Constant and low bulk cap voltage at all load conditionsSimple duty cycle control, constant power regulationEasy soft start, no additional sw needed
29 Implementation Issues-1 VgsIL2Vb=120VVL2*S1D2D3B1L2CoRLL1aL1bCbVoVo=90VD4+-Vo,igi=300V-VD3Since the inductor L2 operates in DCM, when the current through D3 reduced to zero, L2 will resonant with the junction capacitor of D3. If there is no damping, the voltage across L2, VL will reduced to -Vo, and the voltage across D3 will be 2Vo. Consider the load is open circuit, the output voltage is 300V, therefore 600V diode is not enough for the voltage rating. Therefore, Diode D4 is used to clamp VL at -Vb: when VL decreases to - Vb, D4 turns on, and the VL is clamped to - Vb, therefore the maximum voltage across D4 is Vb+Vo=450V. This clamp diode can also reduce the voltage stress of D2 and S1. In our design, this diode won’t work at normal operation mode. Therefore, this diode will not sacrifice the efficiency.+Vo+VbVo,igi+VbHigh voltage stress on D3 due to voltage ringing when IL2 ignition mode (Vo=300V)VD3= -(Vo+VL2)≈2Vo,igi
30 Implementation issue-2 D11bLD2D3****irr of D1+Vo-CCCbbb@ peak(vin > Vo)B1VinCoD4L2S1Large output voltage ripple due to the reverse recovery of D1iD1Irr of D1VoWhen switch turns off, D2 D3 will turn on, and if vin>Vo, D1 will see a reverse bias voltage. During the interval between the switch turn-off and D1’s turn off, a voltage of vin-vo is added to the leakage inductance and stray inductance of the loop of input-B1-L1_d1-D2-D3-Load. Which produce a large di/di.. Especially at high line input, the current through D1 before switch turns off is high, so this di/dt will introduce a large reverse recovery current through D1. Fortunately ,this reverse recovery occurs at switch turn-off, it will not add the switch current stress and switching loss, but it will increase the diode loss, and the This reverse recovery current flow through the load, which results in a large low frequency ripple in the output voltage.Irr of D1iD3Eliminate D1Split S1 to two separate MOSFETsSolution:
31 Two-Switch Version of SSPFC Stage L1aL1bD2D3****S2D4CbB1S1CoRLL2Benefits:Reduce the output voltage ripple (by eliminating the reverse recovery current of D1)Remove the clamping diode D4 by using the body diode of S2Change 1 Mosfet to 2 smaller Mosfet (share the same gate signal), save 2 diodesSeparate the power loss into two switches. S1.S2 can use smaller package (IPAK) and no heat sink is needed
33 Constant Power Control Scheme VVLKIIoVCLKVVomultiplierPIVconPrefPOVO50V300VControl schemeIdeal ballast curveCurrent limiting mode: VCL* KIIO = Pref IO=Const.Constant power mode: KIIO* KVVO = Pref VOIO=Const.Voltage limiting mode: VVL* KVVO = Pref VO=Const.
34 Inverter/Ignitor Steady state: fs=400Hz, D=0.5 Ignition mode: fs=100~200kHz(sweeping), D=0.53rd harmonic resonance is used to reduce the size of Lr (fr=450kHz)Auto-transformer structure is used to reduce the voltage across the cap90Vfs=400HzIgnition ModeSteady state
35 Experimental Results – I PF>99.5%, ITHD<10%@ Vin=120Vac +/-10%
36 Experimental Results-II VlampIlampLow bulk cap voltage at all load conditionsBulk cap voltage is lower than vin,pkVo=89V, Po=19.9WEfficiency = 84.7%(w/o control power)Efficiency 81.3%(with control power)
37 Experimental Results – III Constant power regulation during steady stateCurrent limiting during start-upVoltage limiting before ignition
38 Power Density 2.4W/in3 4.5W/in3 6.0W/in3 (1.8x) (2.5x) Benchmark: Commercial 20W HID ballastNew commercial productCPES PrototypeUse same circuit topology2.4W/in34.5W/in3(1.8x)6.0W/in3(2.5x)
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