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                      SODIUM LAMPS
                  Dos Reis, F. S., IEEE Member; Clima, J. C. M.; Tonkoski Jr., R., IEEE Student Member;
                            Maizonave, G. B., Ceccon, G. B., Bombardieri, A., Dos Reis, R. W.
                       Pontifícia Universidade Católica do Rio Grande do Sul, Porto Alegre, Brazil.
                                                FENG – DEE – LEPUC

Abstract – In the recent years many authors [1-4] are           to be about thirty percent of total consumption of electrical
working to obtain single stage HPF electronic ballast           energy in the country. Because of these, innumerable
for fluorescent and HID lamps to achieve cost                   research groups around the world, like [1-8], have
reduction and to comply with international standard             dedicated their efforts to the development of new
requirements. Usually to obtain HPF in electronic               topologies and new control techniques for different kinds
ballast for high pressure sodium lamps a Power Factor           of discharge lamps.
Corrector (PFC) is used between the mains and the                  Most of magnetic ballast manufacturers had to develop
electronic ballast [5]. In this paper will be reported the      electronic ballasts for discharge lamps to guarantee their
study and implementation of two single stage high               survival in business because the consumers started to
power factor (HPF) electronic ballasts for high                 demand more and more this type of product. It also
pressure sodium (HPS) lamps using a LCC filter, one             simplifies the production line, which has expressive
using a half-bridge inverter and the second one using a         physical reduction and productivity increase in relation the
full-bridge inverter. The main idea in this work is to          line that produces the conventional ballasts. Now, the
present two simple electronic ballasts topologies with          challenges for industries are the reduction of production
HPF for HPS lamps working with a 220 V RMS mains                costs, the reduction of converter size, unitary power factor
voltage. Design criteria, simulation and experimental           and null harmonic distortion which implies in a substantial
results will be also presented. These topologies present        improvement of energy quality consumed by ballasts. In
some drawbacks like moderate THD, lamp power                    Brazil, the development of electronic ballasts for HID
limitation once the converter works as a Buck inverter          lamps is being made by a few groups of researchers.
and it is not an ideal PFC. PF around .95 are easily            However in a close future, these ballasts will be in the
obtained. This paper intends to warn other researchers          production lines of main national manufacturers.
about these structures limitation, but may be an                   In the power electronics group of PUCRS (LEPUC) an
interesting option for some applications.                       smart public illumination system was developed, where an
                                                                electronic ballast with dimming capability is controlled by
                   I. INTRODUCTION                              a central using SMS technology, this ballast, called
                                                                Master, controls a whole neighborhood of slave ballasts
   Nowadays, an important topic of awareness is the             thru a power line communication system. This system is
importance of environment preservation. In this direction,      presented on figure 1.
important efforts have been made in the diverse areas of
knowledge. In electrical engineering field, this
phenomenon has reflected in searching for alternatives
energy systems, higher efficiency on available resources
utilization, losses reduction in equipments and to increase
power quality.
   In the last few years the market was flooded by a great
number of electronic ballasts for fluorescent lamps
operating in high frequency, especially by compact
fluorescent lamps. Its utilization was widely stimulated by
Brazilian media for energy economy, due the fact that
luminous efficiency increases with the frequency for this
kind of lamp. Brazil faced a serious energy crisis in 2001.
Many corrective actions were taken to mitigate this serious
problem. One of them was the energy rationing which
consisted in overtaxing or even cutting energy supply from
consumers which exceeds the prefixed energy quotes. Also            Figure 1. Smart Ilumination System proposed by LEPUC.
many electric energy concessionaires had distributed
gratuitously compact fluorescent lamps for residential            The purpose of this paper is to report the development
consumers, showing the importance of illumination’s             of two low cost single stage HPF electronic ballasts for
segment inside the global energy consumption, estimated
HPS lamps for a 220 VRMS mains voltage developed for               full bridge-inverter was also explored by the same authors
utilization with this system. Each ballast was implemented         in [10], in order to increase the available RMS lamp
using a different converter topology. The design criteria          voltage. The utilization of these topologies will be debated
will be presented in this work for the proposed circuits.          in this paper.
   There are many kind of high intensity discharge lamps;
however, this work will focus only the high-pressure                       II. STUDIED ELECTRONIC BALLASTS
sodium lamps (HPS), widely used in public illumination.
The HPS lamps radiate energy on a great part of the visible           Both studied single stage high power factor electronic
spectrum. Those lamps provide a reasonable color                   ballast for high pressure sodium lamps structure
reproduction (it has IRC 23 color reproduction index).             incorporates a bridge rectifier and an input LC filter to
They are available up to 130 lm/W of luminous efficiency           minimize the EMI generated by the electronic ballast. Two
and color temperature of 2100 K, approximately.                    inverters topologies were proposed to supply the HPS
   The HPS lamps, as any other HID lamps, need ballast to          lamp, using this simple concept to avoid the utilization of
operate correctly. The ballast is an additional equipment          an external PFC.
connected between the power line and the discharge lamp.              Figure 3 shows the electrical diagram of the first
The ballast has two main functions: to guarantee lamps             proposed circuit. In this circuit it was proposed the
ignition through the application of a high voltage pulse           utilization of a half bridge inverter connected to the LCC
between the lamp electrodes and to limit the current that          filter. The capacitor CF in this figure has the main function
will circulate through it. The lamp would be quickly               of receive the reactive current from the electronic ballast.
destroyed without current limitation, due the negative             This arrangement provides high power factor to the
resistance characteristic of the lamp, as can be observed in       electronic ballast because in this case the capacitor CF is
figure 2.                                                          not a bulk capacitor. Actually this is a small capacitor in
   The HPS lamps have many particularities when they               the range of nano Faradays.
operate in high frequency, such as:

           Can be modeled by a resistance in steady state;
           Can have luminous intensity controlled;
           The spectrum color reproduction can be
           Presents the acoustic resonance phenomenon,
            which can result in the arc extinguishing until                  Fig. 3. Half Bridge HPF Electronic Ballast.
            the lamp destruction;
                                                                      The second electronic ballast studied used a full bridge
                                                                   inverter topology as showed in figure 4. The input stage of
                                                                   this topology has the same characteristic as the topology
                                                                   presented on figure 3. The main difference between HB
                                                                   and FB inverters topologies is the available RMS voltage
                                                                   applied to the LCC filter; this crucial difference will affect
                                                                   the application of the topology.

 Figure 2. - Typical voltage versus current curve for HID lamps.

   In order to achieve low cost electronic ballast for HPS
lamps with HPF a single stage converter was conceived.                       Fig. 4. Full Bridge HPF Electronic Ballast.
The idea is very simple: Once, in high frequency, the HPS
lamps have a resistive behavior, why the electronic ballast                   III. BALLAST DESIGN EXAMPLE
(inverter and LCC filter) can not be connected directly to
the full bridge rectifier? This idea will be discussed in this        To verify the performance of the proposed systems LCC
paper.                                                             two electronic ballasts, one for a 250 W HPS lamp and
   In [9], it was studied the possibility of using this concept    another for a 70 W HPS Lamp were designed. The
applied to a half bridge (HB) inverter. Unfortunately, in          nominal lamp voltage (Vlamp) was obtained from the
this arrangement the half bridge inverter reduces the              lamp’s manufacturer datasheet and its value is 100 VRMS
available RMS lamp voltage and therefore, restricts the            for the 250 W HPS Lamp and 70 VRMS for the 70W HPS
maximum output power about 70 W for HPS lamps. The                 Lamp. The electronic ballast input power voltage comes
                                                                   from the output of an input bridge rectifier; consequently,
this input voltage is mains dependent. In the present design                                 2 2 Vmains
example the mains voltage adopted was considered to be                   V1stRMS _( FB )                  198,07 V       (3)
equal to Vmains= 220 VRMS. The switching frequency                                               
chosen was 68 kHz. Assuming the resistive comportment
of the lamp, we can estimate the value of its resistance                If we compare the available RMS voltage for each
(Rx), where x represents the nominal power of the lamp,           topology, for systems with same mains voltages, the full
after ignition using equation 1.                                  bridge topology will generate a higher RMS voltage value
                                                                  than the half bridge inverter as it was expected. As it can
                                                                  be observed in equation 2, the half bridge topology will
                    Vlamp 2        1002
          R250W                        40                     never generate the necessary voltage to achieve the lamp
                      P           250W                      (1)   full rated power, witch impossibilities the design of the HB
                                                                  ballast for most of 250 W HPS lamps with a 220 VRMS
                   Vlamp 2       702
          R70W                      70                        mains, so the half bridge topology is indicated for low
                     P          70W                               power HPS lamps, where the necessary lamp RMS voltage
                                                                  is lower than 100 VRMS. Hence the topology chosen for
where P is the lamps power.                                       the 70 W HPS lamp was the half bridge (HB) one and for
                                                                  the 250 W HPS lamp was the Full Bridge (FB) one.
  As it was indicated in [5], the best relationship between          In this study an expression was obtained to determine
the switching frequency and the tank resonance frequency          the peak voltage across the capacitor CP. This expression,
before the lamp turn on is 0/s = 3, guaranteeing the high       shown in equation (4), is valid before the lamp start up for
voltage generation for the lamp ignition and limiting the         the HB topology. For the FB topology the VCp would be
peak current at the MOSFET to acceptable levels. If it was        twice the value obtained for the HB converter. In this
adopted to work at resonance 0 = s in theory we would           design criteria sample the parameters would be only
have the possibility of an infinite voltage generation over       obtained for the HB topology, considering that for the full
the lamp which could be good for a quickly lamp turn on.          bridge topology there are no difference on this procedure,
On the other hand current would also rise to infinite             only some equations must be adequated for this case.
because the impedance of the circuit formed by L, C S and                                              2  Vmains
CP is null just before the lamp is turned on. This operation                                 Vcp            RESR
mode will result in the MOSFET’s and driver’s                                                        1 e   4 L  F
destruction.                                                         Where, RESR is the circuit equivalent series resistance
                                                                  and F is the switching frequency. Preliminary tests
                                                                  demonstrated that necessary peak voltage (Vopk) to
                                                                  guarantee the lamp ignition is about 3.8 kV. A typical RESR
                                                                  value is 6.5 Ω. Manipulating equation (4) may be obtained
                                                                  the value of inductor L in equation (5) for the HB
        Figure 5. Simplified circuit for the LCC Ballast.                                     RESR
                                                                                    L         4 F         219.5 H
   For the circuit showed in figure 5, in the case of a half                                      2E 
                                                                                        ln 1          
bridge inverter, the voltage Ve is an asymmetrical wave                                          Vopk 
(from 0 to Vpk sin (t)V). In the case of a full bridge                                                                (5)
inverter, the voltage Ve is a symmetrical wave (from Vpk             The resonance frequency may be calculated using
sin (t) to - Vpk sin (t)V). A good simplification to        equation (6).
study the system behavior comes from the frequency                                                    1
                                                                                      Fo 
domain approach. To use this approach the first harmonic                                                    1
                                                                                            2   L 
component for this wave must be knew. Bum & Hee [5]                                                     1     1
presented the first harmonic peak amplitude for a half                                                      
                                                                                                        C p Cs
bridge inverter considering an ideal fixed DC bus voltage                                                                  (6)
(E). In the present case, the first harmonic peak amplitude          Considering the fact that the switching frequency is
was obtained using the same method but the DC bus                 estimated to be three times lesser then the resonance
voltage (E) was replaced by the mains voltage resulting in        frequency and, usually, capacitor CP is, at least, 10 times
expression (2) for a half bridge inverter and in expression       smaller then capacitor CS, equation 6 may be simplified
(3) for a full bridge inverter. The experimental results          into equation 7, because the effect of the capacitance C S is
validate this procedure:                                          almost null.
                                  2 Vmains                                                           6   L  Cp
            V1stRMS _( HB )                  99, 035V     (2)                                                            (7)
  Manipulating equation (7), it can be obtained the value         GLCC (GLCC=70/99 =0.707), for different values of Kc as
for the capacitor CP as it is shown in equation (8).              design parameter. Using the graphic of figure 5, a Kc
                   1                                              =1/32 was adopted. This relationship will allow achieving
    Cp                            2, 767nF
           6   F                                             the desired GLCC relationship in the frequency where the
                                                          (8)     lamp is turned on, hence after the start up the HID lamp is
   To determinate the real value of the RESR, an                  driven at rated power.
experimental circuit using a 220 µH inductor L and a 2,7
nF capacitor CP was stimulated with a 60 V peak-to-peak
square wave signal, which generated a 660 V signal over
the lamp terminals, allowing the determination of RESR
using equation 4. This RESR was obtained experimentally
and its value was 6.5 Ω. Before the lamp startup a leakage
current flows into the lamp. To determine the equivalent
lamp resistance before the startup, the following
measurement was made: a 10 Ω resistor was placed in
series with the lamp. The obtained equivalent lamp
resistance was 100kΩ. If this resistance is taken to account
a new RESR = 5.7 Ω could be easily obtained.
   The reference [2] and our experimental results allow us
to consider that after lamps ignition, the lamp resistance is
too low considering the CP reactance. Therefore, it can be
deduced the equation 9:                                              Figure 7. LCC transfer function for different values of Kc.
                                         // R  R
                                    CP                 (9)
                                                                    With the Kc relationship, the value of CS may be
                                                                  obtained using equation 11 for a GLCC=0.707.
   Consequently, after lamp ignition, the equivalent circuit
                                                                          Cp 1
is showed in figure 6.                                               Kc      Cs  Kc  C p  89,17nF        (12)
                                  L                 Cs                    Cs 32

           Ve                                                 R
                                                                              IV. EXPERIMENTAL RESULTS

                                                                     Two prototypes, one using the HB topology and another
       Figure 6. – Ballast equivalent circuit after ignition.     using the FB topology for 70 W and 250 W HPS lamps
   After lamp ignition the ballast must guaranty that RMS         respectively were built. The main components and
voltage over the lamp do not overcome the nominal value.          parameters used in these implementations are shown in
The RMS lamp voltage Vlamp can be obtained using the              table 1.
well known voltage divider, equation 10 presents this                Table 1. Main components value and design parameters.
result:                                                                                 FulL Bridge Half Bridge
                       Vlamp  Vm                                            Vmains        220 V           220 V
                               Z                       (10)
   The modulus of the impedance of the circuit can be
                                                                              Fs           68 kHz          68 kHz
calculated with equation 10, and is presented in equation
11. To simplify the design of the LCC filter the
                                                                              L            220 uH          220 uH
parameterized LCSR circuit transfer function was obtained
and the result is shown in figure 7.
                                                                              Cp            2,7 nF         2,7 nF
                                     1                 (11)
                  G ( j , K c ) 
                                                       K c                   Cs            55 nF           90 nF
                                       1  K c 2 
   Where Kc is the capacitor relationship factor defined as                   Fmains        60 Hz           60 Hz
Kc = CS/CP,  the relationship of switching frequency and
resonance frequency of the circuit of figure 4, R is the
lamp resistance after startup and τ is the parameterized             A conventional SMPS power line filter with differential
                 2
                                                                  and common mode mitigation paths was used. The EMI
time constant
                  R Cp
                        .                                         Filter topology used is presented on Figure 8 and very
   Figure 7 presents the relationship between the RMS             good results were obtained. Usually a capacitor between
lamp voltage and the RMS first harmonic voltage,                  the line and the filter is used, in this project the input
Vlamp/V1stRMS, called as parameterized lamp voltage gain          capacitor was suppressed once it will block the PLC
                                                                  communications between the other units as schematized in
Fig. 1. The experimental results are presented for the FB
topology, since for the half bridge topology the results
obtained are similar.

          Figure 8. Topology of the EMI Filter used.
   In figure 9, voltage and current in the mains are shown
for the FB ballast. It may be observed that the voltage and
current in these waveforms have almost null displacement             Figure. 10. Voltage and current in the lamp in a low
factor. The current waveform presented would be similar                              frequency period.
to a usual converter operating in the discontinuous
conduction mode if no EMI filter was used. With the
waveforms presented in figure 7, the power factor was
calculated and the value found is PF=0.98, which would be
in conformity with all known ballast standards.

                                                                    Figure 11. Voltage in the DC bus and current in the output of
                                                                                           the rectifiert.

                                                                   Figure 12 presents the harmonic components for the
                                                                 voltage waveform presented in figure 7. The presence of
                                                                 the third, fitth and seventh harmonic components in the
 Figure. 9. Voltage (200 V/Div.) and Current (2 A/Div.) in the
                                                                 mains is observed. The THD obtained was 2,49 %.
                                                                 According to IEEE Std. 519-1992, the THD expected in
   In figure 10 is showed the lamp’s voltage and current. It     the mains is below 5%. The current waveform
may be observed that nearby each zero crossing, the lamp         decomposition in harmonic components from the ballast
is turned off and on, as well as it happens with regular         proposed is shown in figure 13. It was found a moderated
electromagnetic ballasts. This phenomenon is attributed to       harmonic content, the THD obtained was 19,83%,
the non-linear lamps characteristic. During this period the      considering the IEC 61000-3-2, the fifth and seventieth
lamp is reigniting because the voltage available was too         harmonic component exceeds the indicated limits for class
low to keep the arc in the lamp, so the lamp is turned off.      C equipments. For the fifth harmonic, the limit indicated is
This phenomenon reflects into the input current waveform,        10 % and for the seventieth is 3 %.
where in each beginning of semi cycle the current goes
nearby zero causing a flattening in the waveform. The
crest factor obtained was around 2. In Figure 11 is shown
the voltage in the DC bus, where it may be observed that
voltage goes close to zero what causes the extinction of the
lamp’s arc. In the same figure it is observed the current in
the output of the rectifier.

                                                                       Figure 12. Harmonics present in the mains voltage.
                                                                                   VIII. REFERENCES

                                                              [1] Tsai-Fu Wu; Te-Hung Yu; Meng-Chian Chiang; “Single-
                                                              stage electronic ballast with dimming feature and unity power
                                                              factor”; Power Electronics, IEEE Transactions on , Volume: 13 ,
                                                              Issue: 3 , May 1998; Pages:586 – 597.
                                                              [2] Ribas, J.; Alonso, J.M.; Calleja, A.J.; Lopez, E.; Cardesin,
                                                              J.; Garcia, J.; Rico, M.; “Single-stage high-power-factor self-
                                                              oscillating electronic ballast for fluorescent lamps with rapid
                                                              start”; Power Electronics Congress, 2002. Technical Proceedings.
                                                              CIEP 2002. VIII IEEE International , 20-24 Oct. 2002 Pages:15 –
                                                              [3] Martin, F.J.F.; Viejo, C.B.; Anton, J.C.A.; Garcia, M.A.P.;
       Figure 13. Harmonics present in the input current.     Rico-Secades, M.; Alonso, J.M.; “Analysis and design of a high
                                                              power factor, single-stage electronic ballast for high-intensity
                    VI. CONCLUSION                            discharge lamps”; Power Electronics, IEEE Transactions on ,
                                                              Volume: 18, Issue: 2, March 2003; Pages:558 – 569.
                                                              [4] Co, M.A.; Brumatti, M.; Simonetti, D.S.L.; Vieira, J.L.F.;
   The half bridge topology will never generate the           “Single stage electronic ballast for HID lamps”; Industry
necessary voltage to achieve the lamp full rated power 250    Applications Conference, 2003. 38th IAS Annual Meeting.
W with a 220 VRMS mains, witch impossibilities the design     Conference Record of the , Volume: 1 , 12-16 Oct. 2003;
of these ballast in this case, in this case the full bridge   Pages:339 - 344 vol.1
topology will generate the necessary voltage for to a high    [5] Bum Suk Kang; Hee Jun Kim; High Power Factor
power HPS lamp. The half bridge topology is suitable for      Electronic Ballast for High Pressure Sodium Lamp, TENCON
lamps less than 250 W once the main restriction is the        99. Proceedings of the IEEE Region 10 Conference, Volume: 2,
available RMS voltage. This paper described a single stage    Dec 1999, Page(s): 887 -890 vol.2.
high power factor electronic ballast for high pressure        [6] Ben Yaakov, S.; Gulko, M.; “Design and performance of an
                                                              electronic ballast for high-pressure sodium (HPS) lamps,
sodium lamps using half and full bridge inverter. This        Industrial Electronics”, IEEE Transactions on Volume: 44 Issue:
ballast presents a very low cost because it avoids an         4, Aug 1997, Page(s): 486 -491.
external PFP.                                                 [7] Alves, J.A.; Perin, A.J.; Barbi, I.; “An electronic ballast
   The behavior of the full bridge topology and the half      with high power factor for compact fluorescent lamps”; Industry
bridge topology achieved was similar. The phenomenon of       Applications Conference, 1996. Thirty-First IAS Annual
the acoustic resonance was not observed, maybe because        Meeting, IAS '96., Conference Record of the 1996 IEEE
the lamp was excited by a modulated power signal,             ,Volume: 4 , 6-10 Oct. 1996; Pages:2129 - 2135 vol.4.
however an investigation on this subject is encouraged . A    [8] Prado, R.N.D.; Bonafldo, S.A.; “A high-power-factor
very high power factor was obtained. The crest factor         electronic ballast using a flyback push-pull integrated converter”;
                                                              Industrial Electronics, IEEE Transactions on ,Volume: 46 ,
found was not good enough considering fluorescent lamps,      Issue: 4 , Aug. 1999; Pages:796 – 802.
however for HPS lamps this crest factor is not considered     [9] Dos Reis, F.S., Canalli, V.M, Lima, J. C., Tonkoski, R. Jr.,
critical.                                                     Sarmanho, U, Edar, F., Santos, Toss, M, Ramos, F.M., Garcia,
                                                              L.L., Callai, P., Da Silva, N. B.R, Godinho, L.A., Líbano, F.B.,
              VII. ACKNOWLEDGEMENT                            Low Cost High Power Factor Electronic Ballast For High
                                                              Pressure Sodium Lamps, VI Induscon, Joinville, 2004.
The authors gratefully acknowledge the support to this        [10] Dos Reis, F.; Tonkoski, R.; Maizonave, G.B.; Lorenzoni,
work provided by INTRAL S.A. (Ballast and Fixture             L.C.; Sarmanho, U.; Ceccon, G.B..; Lima, J.C.M.. ” Full Bridge
Manufacturer), LEPUC (Power Electronic Laboratory             Single Stage Electronic Ballast for a 250 W High Pressure
                                                              Sodium Lamp”, IEEE 36th Conference of Power Electronics
PUC), CEEE (Companhia Estadual de Energia Elétrica)           Specialists, Recife, 2005, Page(s):1094 – 1099.
and CAPES (Coordenação de Aperfeiçoamento de Pessoal
de Nível Superior).

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