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Full Bridge Single Stage Electronic Ballast for a 250 W
High Pressure Sodium Lamp
F. S. Dos Reis, J. C. M. de Lima, Tonkoski, R L.C. Lorenzoni, U.A. Sarmanho, V. M. Canalli and F.B. Líbano
Pontifícia Universidade Católica do Rio Grande do Sul
Faculdade de Engenharia
Departamento de Engenharia Elétrica
Avenida Ipiranga, 6681 - Porto Alegre – RS
CEP 90619-900 - Brazil
Abstract – In this paper will be reported the study and
compact fluorescent lamps. Its utilization was widely
implementation of a single stage High Power Factor (HPF)
stimulated by Brazilian media for energy economy,
electronic ballast for High Pressure Sodium (HPS) lamps using
a LCC filter. In the recent years many authors are working to
due the fact that luminous efficiency increases with
obtain single stage HPF electronic ballast for fluorescent lamps
the frequency for this kind of lamp. Brazil faced a
[1][2]. Normally to obtain HPF in electronic ballast for high
serious energy crisis in 2001. Many corrective actions
pressure sodium lamps a Power Factor Preregulator (PFP) is
were taken to mitigate this serious problem. One of
used between the mains and the electronic ballast [3]. The
main idea in this work is to present a simple electronic ballast
them was the energy rationing which consisted in
with HPF for HPS lamps. Design criteria and experimental
overtaxing or even cutting energy supply from
results will be also presented in the final paper.
consumers which exceeds the prefixed energy quotes.
Also many electric energy concessionaires had
ACKNOWLEDGMENT
distributed gratuitously compact fluorescent lamps for
residential consumers, showing the importance of
illumination’s segment inside the global energy
KEYWORDS
Electronic Ballast, HID Lamps, High Power Factor.
consumption, estimated to be about thirty percent of
total consumption of electrical energy in the country.
I. INTRODUCTION
Because of these, innumerable research groups
around the world, like [1], [2], [3] and [4], have
dedicated their efforts to the development of new
Nowadays, an important topic of awareness is the
importance of environment preservation. In this
direction, 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 electric energy 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
topologies and new control techniques for different
kinds of discharge lamps.
Most of magnetic ballast manufacturers had to
develop electronic ballasts for discharge lamps to
guarantee their survival in business because the
consumers started to demand more and more this type
of product. It also simplifies the production line,
which
has
expressive
physical
reduction
and
productivity increase in relation the line that produces
the conventional ballasts. Now, the challenges for
industries are the reduction of production costs, the
1
reduction of converter size, unitary power factor and
null
harmonic
distortion which
implies

in a
substantial improvement of energy quality consumed
The spectrum color reproduction can be
modified;

Presents the acoustic resonance phenomenon,
by ballasts. Here in Brazil, the development of
which can result in the arc extinguishing until
electronic ballasts for HID lamps is being made by a
the lamp destruction;
few groups of researchers. However in a close future,
Positive Resistance
these ballasts will be in the production lines of main
Lamp
Current
national manufacturers.
Negative Resistance
The porpoise of this paper is to report the
development of a low cost single stage HPF electronic
Lamp
Voltage
ballast for HPS lamps. The design criteria will be
Breakdown Voltage
presented in this work for the proposed circuit. There
are many kind of high-pressure lamps; however, this
work will focus only the high-pressure sodium lamps
Fig. 1. - Typical voltage x current curve for HID
(HPS), widely used in public illumination. The HPS
lamps.
lamps radiate energy on a great part of the visible
In order to obtain low cost electronic ballast for
spectrum [5]. These lamps provide a reasonable color
HPS lamps with HPF a single stage converter was
reproduction (it has IRC 23 color reproduction index).
conceived. The idea is very simple: Once, in high
They are available up to 130 lm/W of luminous
frequency, the HPS lamps have a resistive behavior
efficiency and color temperature of 2100 K,
why the electronic ballast (full-bridge inverter and
approximately.
LCC filter) can not be connected directly to a full
The HPS lamps, as any other HID lamps, need
ballast to operate correctly. The ballast is additional
bridge rectifier? This idea will be studied in this
paper.
equipment connected between the power line and the
discharge lamp. The ballast has two main functions:
to guarantee lamps ignition through the application of
II. STUDIED ELECTRONIC BALLAST
a high voltage pulse between the lamp electrodes and
to limit the current that will circulate through it. The
The studied single stage high power factor
lamp would be quickly destroyed without current
electronic ballast for high pressure sodium lamps
limitation, due the negative resistance characteristic
structure incorporates a bridge rectifier and an input
of the lamp, as can be observed in figure 1.
LC filter to minimize the EMI generated by the
The HPS lamps have many particularities when
they operate in high frequency, such as:
electronic ballast. Figure 2 shows an electrical
diagram of the proposed circuit. Similar circuits have
been proposed by other authors using fluorescent


Can be modeled by a resistance in steady
lamps. but any paper using this topology for HPS
state;
lamps was not found. The capacitor CF in this figure
Can have luminous intensity controlled;
has two main functions first of all is to receive the
2
reactive current from the electronic ballast and work
ignition and limiting the peak current at the MOSFET
as line filter with the inductor L. This arrangement
to acceptable levels. If it was adopted to work at
provides high power factor to the electronic ballast
resonance ω0 = ωs in theory we would have the
because in this case the capacitor CF is not a bulk
possibility of an infinite voltage generation over the
capacitor. Actually this is a small capacitor in the
lamp which could be good for a quickly lamp turn on.
range of nano Faradays.
On the other hand current would also rise to infinite
because the impedance of the circuit formed by L, Cs
and Cp is null just before the lamp is turned on. This
operation mode will result in the MOSFET’s and
driver’s destruction.
L
Cs
Ve
Cp
R
Fig. 2. Studied HPF Electronic Ballast.
Fig. 3. LCC Ballast.
III. BALLAST DESIGN CRITERIA
For the circuit showed in figure 3, considering the
To verify the performance of the proposed system a
voltage Ve a symmetrical wave (from Vpk sin (t)
LCC electronic ballast (figure 3) for a 250 W HPS
to - Vpk sin (t)V), a good simplification to study
lamp was designed. The nominal lamp voltage (Vlamp)
the system behavior comes from the frequency
was obtained from the lamp’s manufacturer datasheet
domain approach. To use this approach the first
and its value is 100 VRMS. To design the LCC ballast
harmonic component for this wave must be knew.
it was added 10 % to consider loses effect. The
Bum & Hee [1] presented the first harmonic peak
electronic ballast input power voltage comes from the
amplitude for a half bridge inverter considering an
output of an input bridge rectifier; consequently, this
ideal fixed DC bus voltage (E) the result for a full
input voltage is mains dependent. In the present
bridge is displayed in equation 2. In the present case,
design example the mains voltage adopted was Vmains=
the first harmonic peak amplitude was obtained using
220 VRMS. The switching frequency chosen was 68
the same expression 2 but the DC bus voltage (E) was
kHz. Assuming the resistive comportment of the
replaced by the mains RMS voltage (Vmains) resulting
lamp, we can estimate the value of its resistance (R)
in expression 3. The experimental results validate this
after ignition using equation 1.
procedure:
R
Vlamp 2
P
 40
(1)
Where P is the lamps power.
As it was indicated in [3], the best relationship
V1stRMS 
3 2 Vmains
3  1
(2)
V1stRMS 
6 2 Vmains
3  1
(3)
between the switching frequency and the resonance
In this study an expression was obtained to
frequency before the lamp turn on is ω0/ ωs = 3,
determine the peak voltage across the capacitor Cp.
guaranteeing the high voltage generation for the lamp
3
This expression, shown in equation 9, is valid before
signal over the lamp terminals, allowing the
the lamp start up.
determination of RESR using equation 4. This RESR was
obtained experimentally and its value was 6.5 Ω.
2E
Vcp 
1 e
(4)
 RESR
4 L F
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 3.8
kV. A typical RESR value is 6.5 Ω. Manipulating
equation (4) we can obtain the value of inductor L in
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
100 kΩ. If this resistance is taken to account a new
RESR = 5.7 Ω could be easily obtained.
The reference [2] and our experimental results
equation (5).
 RESR
4 F
L
 219.5 H

2E 
ln 1 


Vopk 

allow us to consider that after lamps ignition, the
(5)
lamp resistance is too low considering the Cp
reactance. Therefore, it can be deduced the equation
9:
The resonance frequency may be calculated using
1
// R  R
  CP
equation (6).
(6)
1
Fo 
2   L 
(9)
Consequently, after lamp ignition, the equivalent
circuit is showed in figure 4.
1
1
1

C p Cs
L
Cs
Ve
Considering the fact that the switching frequency is
R
estimated to be three times lesser then the resonance
frequency and, usually, capacitor Cp is, at least, 10
Fig. 4. – Ballast equivalent circuit after ignition.
times smaller then capacitor Cs, equation 6 may be
After lamp ignition the ballast must guaranty that
simplified into equation 7, because the effect of the
RMS voltage over the lamp do not overcome the
capacitance Cs is almost null.
nominal value. The RMS lamp voltage Vlamp can be
F
1
(7)
6   L  Cp
obtained using the well known voltage divider for the
circuit shown in figure 4, the equation 10 presents this
Manipulating equation (7), it can be obtained the
result:
value for the capacitor Cp as it is shown in equation
Vlamp 
(8).
Cp 
(10)
The modulus of the impedance of the circuit can be
1
6   F 
R
 Vm
Z
2
L
 2, 767nF
calculated with equation 11. To facilitate the design
(8)
To determinate the real value of the RESR, an
experimental circuit using a 220 μH inductor L and a
of the LCC filter the parameterized LCsR circuit
transfer function was obtained and the result is shown
in figure 13.
2,7 nF capacitor Cp was stimulated with a 60 V peakto-peak square wave signal, which generated a 660 V
4
Vlamp
Vm
(11)
1
  ,  
1



  2
2
electronic ballast with the following specification:
Where η is the capacitor relationship factor defined
as η = Cs/Cp, κ 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 time constant  
L
R 2C p
To validate the proposed system, a full-bridge
.
250 W HPS lamp, 220 VAC grid connected and
operation frequency of 68 kHz, was simulated using
the software PSIM® 6.0. Figure 6 shows the voltage
and current in the mains. The voltage and current in
lamp is showed in figure 7. The crest factor was
measured. Tests indicate that ballasts with higher
Figure 5 presents the relationship between the
RMS lamp voltage and the RMS first harmonic
voltage, Vlamp/V1stRMS, called as parameterized lamp
crest factors may result in depreciation of lumen
output or reduced lamp life. It was found a crest
factor
of
2
using
this
ballast.
HID
lamp
voltage V, for different values of η as design
recommendations suggest a maximum crest factor of
parameter. Using the graphic of figure 5, a η =180
1.8 for HPS lamps.
was adopted. This relationship will allow us to
achieve the desired V relationship in the startup
frequency, when the lamp is turned on.
1
1
V( 110   )
0.8
V( 80   )
V( 50   )
0.6
V( 30   )
V( 10   )
J( 1   )
0.4
i(  )
V( 180   )
0.2
0
0
0
2
4
6
8
10

0
10
Fig. 5. Transfer Function varying κ for different
Fig. 6. –Above, voltage in the lamp and voltage and
current in the mains below.
values of η.
With the η relationship, the value of Cs may be
obtained
using
equation
12
for
a
V=0.393
relationship.

Cs
 180  Cs    C p  498nF
Cp
(12)
IV. SIMULATION RESULTS
Fig. 7. –Voltage and current in the lamp.
5
V. CONCLUSION
This paper described single stage high power factor
electronic ballast for high pressure sodium lamps.
This ballast presents a very low cost because it avoids
an external PFP. The phenomenon of the acoustic
resonance was not observed. A very high power factor
was obtained. The crest factor found was not good
enough and must be improved. This could be solved
changing the capacitor Cs value. Increasing this
capacitor is possible to reduce the crest factor, on the
other hand, the power factor decreases.
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