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Transcript
ELECTRONIC BALLAST FOR METAL HALIDE LAMPS WITH
ACOUSTICAL RESONANCE AVOIDANCE
Marcelo Toss, Anderson S. Santos and Fernando Soares dos Reis
University Catholic of Rio Grande do Sul
PUCRS – PPGE – LEPUC
90619-900 – Porto Alegre – RS – Brazil – Fax +55.51.3320.3500
e-mail: [email protected]
Abstract-This paper presents the analyzed, design and implementation of some high
frequency electronic ballast for metal halide lamps. Extensive experiments using
resonant type electronic ballast have been conducted on 70W metal halide lamps to
investigate different control methods for avoiding the phenomenon known acoustic
resonance. Besides, a high frequency ballast to operate a different lamp markers for
test the methods is also presented.
I.
INTRODUCTION
Metal halide lamps have attracted much attention in recent years, because they offer
excellent color rendition, long life and compact volume, in contrast to fluorescent lamps
and incandescent lamps. Similarly to fluorescent lamps, the HID lamps present the negative
impedance and the device to limit the current should be used. The electromagnetic ballast
can be used. However, they have a high weight and size, poor regulation and sensibility to
voltage changes [3, 4].
In principle, the use of high frequency electronic ballast can reduce the size and the
weight of the ballast and improve the system efficacy. This feature is especially attractive
for low-wattage HID lamps because the overall lighting system is expected to be of small
size. However, the operation of high-pressure HID lamps with high-frequency current
waveforms is hampered by the occurrence of standing pressure waves called acoustical
resonance.
The phenomenon of acoustical resonance is characteristic of the HID lamps
operating at frequencies greater than 1kHz and they appear when the modulation of the
power in the lamp exceeds a threshold value. This phenomenon cause fluctuation of the
emitted light, variation of the color temperature, variation of lamp voltage and, in worst
case, rupture of the discharge tube[1].
Many ballast circuit topologies or control methods [3-5] have been proposed to
avoid instability caused by acoustic resonance. There are basically two proposed solutions
are the following:
1)
Operation inside a frequency range free of acoustic resonance. Typical ballast used
in this approach can be:
 Low frequency ballast: is based on the fact that there isn’t resonance acoustic in
frequency below 1kHz[6].The disadvantages of this method are the complicity of circuit
and low efficiency.
 Tuned high-frequency ballast: require predetermination of the free acoustic resonance
zone. However, it is very difficult to select the same window for all lamps marked because
the acoustical resonance is a function of tube geometry, gas density, and temperature[3]. It
also varies with manufacturing tolerance and by lamp age[4].
 Extra high-frequency ballast: its refers to the operation above the maximum resonance
frequency range. The disadvantages of this method are the high loss in the switching
components and EMI problems because the high frequency discharge arc is a very good
antenna radiating noise [5].
 Real-time autotracking system: is the same idea of tuned high-frequency, the difference
is the real-time autotracking system detect the resonance acoustic and change the
frequency. The main problem of this method are detecting a low intensity resonance
acoustical, because electrical parameters change are not enough strong to sensitize the
controller [6].
2)
Distribute the lamp power spectrum so that the lamp power at the acoustic
resonance frequency may not exceed the threshold value. Typical ballast used in this
approach can be:
 Modulation of the switching frequency ballast: the concept is change the frequency to
keep the lamp input energy distributed over a frequency range. Ideally this should be done
in a frequency range where acoustical resonance are not usually observed.
 Modulation of phase angle ballast: is based on the idea that constant phase variation
disturbs the excitation of acoustic resonance. The disadvantage of this method is the higher
level current at each jump phase[6].
 Non-sinusoidal voltage in the lamp ballast: the concept is used a high frequency squarewave operation for distribute power spectrum in a theoretically infinite number of
harmonics. The problem are the limitation of lower order harmonics and electromagnetic
interference (EMI) problems.
Comparing the advantages and disadvantages of the technical to eliminate the
resonance acoustic above, it can be said that the concept of tuned high frequency ballast
together with modulation of the switching frequency ballast is the best choice because de
ballast and control are simple and sheep.
This paper is organized as follows. Section II presents a description of the proposed
ballast. Section III show study about the free acoustic resonance zone for 70W halide lamps
from different manufactures. Section IV presents a modulation of the switching frequency
ballast used to eliminate the acoustic resonance phenomenon. Finally, the conclusions of
this work are presented in section V.
II.
INVERTER
The topology chosen is the half bridge inverter using a resonant LC series C
parallel, as can be seen on Figure 1. The LC series C parallel resonant converter has the
vantage that the output voltage can be regulated for applied high voltage in start up the HID
lamps. The resonant filter circuit design was made based on a method described in [7].
This calculation assumes that the lamp is a pure resistance, as stated previously [2].
S1
E
+
-
D1
Ls
DRIVE
Cs
S2
D2
Cs
Lamp
Figure 1 High frequency inverter with resonant circuit
Using the drive is possible to change the frequency of current lamp to check the free
acoustical resonance zone and testing the concept of modulation of the switching frequency
ballast.
III.
THE FREE ACOUSTICAL RESONANCE ZONE
According the reference [3] , the 70W metal halide, have a frequency range free of
acoustical resonance inside these frequency: 22-28kHz, 300-400kHz and >1 MHz. The
chose the first range, because the other ranges have problem with high loss in the switching
components and EMI.
The proposed inverter in Section II is used to determine the frequency range free of
acoustical resonance. For these, the control change the frequency of the ballast and the light
of the lamp is observed.
The Figure 2 show the result with lamps for different manufactures. The free
frequency windows are very narrow and your position depend on the lamps. For this, is
necessary to add other method to avoid the acoustical resonance.
Frequency Range Free of Acustical Resonance
Sylvânia
Metalarc HSI-TD
70W/NDL
Osram
PowerStart HQI-TS
70W/NDL
Philips
Powertone MHN-TD
70W
GE
MQI/70/T6/30
70W
Frequency kHz
Light Acoustical Resonance
The arc flicker
Heavy Acoustical Resonance
The arc extinguish
Free Zone
of Acoustical Resonance
Figure 2 The 70W metal halide frequency range free of acoustical resonance
IV.
MODULATION OF THE SWITCHING FREQUENCY
The frequency modulation was applied in the ballast drive to elimination de
acoustical resonance. In the test, the ballast is turn on and the frequency is adjusted for the
frequency with a light and heavy acoustical resonance. When the lamp is under light
acoustical resonance the modulation of the switching frequency eliminate all resonance.
However, when the lamp is under heavy acoustical resonance the modulation are not
enough for completely eliminate the resonance. For all lamp tested, the windows with light
and free acoustical resonance is large (18kHz to 25kHz). For this reason the modulation of
the switching frequency represent a solution to the problem of acoustic resonance.
V.
CONCLUSION
This paper presented a ballast circuit for HID lamps with acoustic resonance
avoidance. The methods for avoidance the resonance are studied and the low cost and
efficient method is select and implemented. A prototype is built to demonstrate the methods
proposed in this paper.
VI.
REFERENCES
[1] J. J. de Groot, J. M. van Vliet. “The high pressure sodium lamp”, Philips Technical
Library, Macmillan Education,  1986.
[2] T. J. Liang, K. H. Su and W. H. Fu. “High Frequency Electrical Circuit Model of Metal
Halide Lamp”. IEEE, pp1163-1165.
[3] Richard Redl and Jon D. P. “A New High Frequency and High Efficiency Ballast for
HID Lamps: Topology, Analysis, Design, and Experimental Results”. APEC 1999.
[4] J.Zhou, L. Ma, Z. Qian and K. Hong, “Acoustical Resonance in High Intensity
Discharge Lamps and its Possible Solutions”, ’97 International Symposium on Green
Lights in China, pp142-149, 1997.
[5] J. Zhou, F. Tao, F. C. Lee, N. Onishi and M. Okawa, “High Power Density Electronic
Ballast for HID Lamps” IEEE, pp1875-1880, 2002.
[6] A. S. André, A. J. Perin, C. C. Tavares and J. Moia, “Electronic Ballast for HighPressure Sodium Lamps with Acoustic Resonance Avoidance”. COPEB 2003.
[7]F. E. Bisogno, A. R. Seidel, R. Holsbach and R. N. do Prado, “Resonant Filter
Applications in Electronic Ballast”. IEEE, pp348-354, 2002.