Abstract: This paper presents the principle and advantages of electronic ballast (new green lighting products). Then introduces the electronic ballast developed by our company, indicates some problems needed paying attention in design process.And some practical problems must be resolved in future.

Key words: Green lighting, electronic ballast for HID lamp

I. Foreword

For electronic ballast has advantages of energy saving, small, light and high reliability, it is widely adopted to match with the compact fluorescence lamp, sunlight lamp and integrated lamp.It gained very good economy effect and social effect.Along with the developing of electronic technique continuously, the reliability of electronic component is also increased, and the cost decreased a great deal.Electronic ballast will be the important part of green lighting engineering.

HID lamp is high efficiency light-source and widely adopted in international market.Last year, had produced 14,800,000 lamps of MH & HPS only in China, further more, along with the increasing of foundation building, HID lamps needed yearly will also increase.Therefore, it is very important to design reasonable matching electrics-accessories for HID lamp, adopting electronic ballast is the best choice for its good ratio of performance/cost.This paper will introduce main technique characteristics and applications of electronic ballast, and discuss how to popularize the application of electronic ballast of HID lamps.

• Main advantages of electronic ballast

• Notable effect of energy saving:

※ Compare with traditional electromagnetic ballast under same condition and same illuminance, electronic ballast for HID lamp will decrease input power more then 10%, because of the electronic ballast uses current of high or low frequency and square wave to ignite the lamp, the system light efficacy is high.

※ Loss of electronic ballast produced by our company is low, the efficiency of 400 W electronic ballast can reach 93% or more.

• Power factor is high and can reach 0.99, and it will increase power supply capability and decrease loss of transmit electricity for a power plant.

• Because of electronic ballast has a stable out put power (variation of electronic ballast output power less then ±3%, while main voltage changes ±15%), under same condition the variation of traditional electromagnetic ballast output will be more then 10%.Therefore, in order to satisfy illuminance requirement within main voltage variation, we always based on the lower limit (-10%) of voltage variation to design the fixture.When the fixture is operated at normal voltage, the input voltage from main power will be 10% more then the rated fixture voltage, it will cause lamp overload ant shortened lamp life.But, the problem will not appear if it is matched with an electronic ballast, due to its stable output voltage, the input voltage from main power may be decreased more then 10%.

2. May save a lot of resource

It is well-known that traditional electromagnetic ballast needs a lot of silicon steel and enameled wire and consumes much from the limited resource of the Earth.Adopt electronic ballast will decrease the material expended.For example, 400 W CWA ballast for MH lamp needs copper 2.0 kg and silicon steel 4.0 kg, and that electronic ballast needs only 0.4 kg of copper.

3. Compare with traditional electromagnetic ballast, electronic ballast circuit has excellent ignition parameter

※ Input power to lamp is stable, variation of electronic ballast output power less then 3%, while main voltage changes from 120 to 265 V.It is useful for the application of a big fluctuation of main power.

The Fig below shows the output load character of electronic ballast for 150 W MH lamp.
 

From the Fig above, while the lamp is starting, lamp voltage increases and lamp current decreases gradually.Along with increasing of lamp voltage, the lamp power increases, and then maintains constant after it reaches its rate value.

Thanks to stable lamp power, we have two good effects:

• Stable lamp power causes lamp color is more constant.

• Based on the HID lamp characters, at the anaphase of HID lamp life, the lamp voltage difference within lamp tube will gradually increase.The output character of traditional electromagnetic ballast is constant-current, lamp current changes very small, it causes increasing of lamp power.Increasing of lamp power again increases lamp voltage difference within lamp tube, thus the lamp life will end quickly.But from Fig above, if adopt electronic ballast, while lamp voltage increases gradually, lamp current also decreases gradually, lamp power maintains constant.Therefore, lamp life is longer.

• PF>0.99, it will increase power supply efficiency and decreases total cost of transmit line design and installation.

※ Total harmonic disturbance of current wave (THD) ≤10% is less then that of traditional electromagnetic ballast (THD ≥15%), it can decrease pollute for main power.

※ Because of the electronic ballast adopts a high or low frequency wave current to ignite lamp, therefore lamp instantaneous output power is constant.There is no flicker, and it will improve the effect of lighting.

※ Igniting circuit of HID lamp usually uses high voltage to ignite lamp. Some lamps of bad starting performance or some lamps had been lighted for some times are difficult to start, especially at hot starting, traditional lighting circuit easily brought out a ‘shine draw-arc discharge’ and can not ignite lamp for a long time.It will damage the lamp electrode and decrease lamp life.Electronic ballast developed by our company can overcome this shortage.It adopts interval pulses to ignite lamp, and overcame the difficult of starting.At the same, when output circuit shorted or output circuit opened, or appearance of over-hot, the electronic ballast has auto-protection function.So it increases the reliability of lighting fixture with electronic ballast.

4. Electronic ballast can carry out many auto-controls easily, such as intelligent-control for light intensity, based on the lamp characteristics, the dimming range of sodium lamp is 40-100% and 50--100% of MH lamp.It is needed for many applications of lighting control energy saving.

There are many ways to realize HID lighting control

a. Test flesh-signal by infrared sensor, such as for supermarket, warehouse, gas station and parking lots etc.

b. Lamp power auto control uses light sensor, and activated by natural light or other light signal to realize auto control lamp power.It is applicable for the lightings of office, factory and mine, agriculture and so on.

c. Timing control for roadway lighting, it is configured with different programs to realize the variations of lumen output at different time period within one day (24 hours).It is capable to save much energy for lightings of road, street, tunnel and so on.

d. Dimming by hand: HPS or MH lamp can also be controlled over a wide range by adjust lamp input power by hand to achieve smooth and continuous regulation.

5. Small, light, and convenient installation

• The reliability research for electronic ballast

Along with the very fast speed of development of electronic technique, the quality of electronic components has increased continuously, so the reliability of electronic ballast had been essentially ensured.Therefore, most of the igniting circuits of sun-light lamp and energy-saving lamp are replaced with electronic ballast.In order to use electronic ballast for HID lamp, we must increase the reliability and ratio performance/price of electronic ballast.

Compare with sun-light lamp and energy-saving lamp, the HID lamp has more complex physical process, we must do our best to understand the HID lamp characteristic before design of a reliable circuit.Such as the problem of “Acoustic Resonance” of HID lamp, it causes unstable operation of lamp starting process, even to extinguish the lamp.We have considered the problems as follows:

1) Keep the stability of output power: Use a square wave current to ensure the stable character of output power, and delete the “Acoustic Resonance”.

2) The self-protection of abnormal operation of electronic ballast: When output circuit shorted or output circuit opened, or appearances of lamp failure or over-hot of circumstance, the electronic ballast has self-protection function.

3) Stability of output power means that: a) Ballast output power does not change while main power voltage changes; b) Along with the significant change of lamp input power in different period of whole HID lamp life time, ballast output power does not change.

4) Adopt zero voltage switch ZVS and zero current switch ZCS, decrease the voltage or current stress of power component significantly.

5) Control the temperature rise of product within prescribed limits.And design the electronic ballast inner thermal structure.We choice a kind of real hot-radiation material for hot dispelling of electronic ballast.

• The ratio of performance to cost and application foreground for HID lamp electronic ballast

Only after understanding the application worth, integrate economic index and the importance of increasing reliability of HID lamp, can we realize the popular of HID lamp.As an example, table below shows the compare of inductance ballast to electronic ballast for 400W sodium lamp.
 

From the mentioned above, may save 204.00 RMB every year, draw back 78% of cost at the same year.The colligated economy benefit is significant.

Now, there are 4 main ingredients of limiting popularization of HID lamp application.The first is the reliability: designer must overcome the phenomena of acoustic resonance existed in starting process absolutely.Compare with fluorescent lamp ballast circuit, the HID lamp ballast circuit is more complex, its quantity of component is much more then that of fluorescent lamp ballast circuit.Therefore, the failure probability of components is mush higher.In addition, there are many factories (or companies) manufacture HID lamp adopted different standard.It causes unmatchable lamp with electronic ballast and also decreases application effect.The manufacturer of electronic ballast must choice component strictly, increase product reliability.The second is operation condition of electronic ballast: it requires circumstance temperature less then 55 ℃ and its housing temperature less then 75℃, so as to ensure the electronic ballast life.Therefore, it needs to design good radiator for electronic ballast.The third is heat dissipation for high power electronic ballast: It is important factor to affect the electronic ballast life, and to wait for more perfect design of high power electronic ballast of utility type.The last is the price: Although the colligated economy benefit is significant, but the first investment is also high, it is difficult popularly received by all clients.And that along with increasing of reliability, the price will also increase.We believe that along with the very fast speed of development of electronic technique, the problems mentioned above will be resolved one by one, and HID lamp electronic ballast as a kind of green lighting product will popularly received by all clients.

V. Brief summary

HID lamp electronic ballast has advantages of good igniting parameter, high colligated economy benefit and decreasing pollute for main power net.It will push forward green lighting engineering greatly in China and it is an effective step to reach the goal of saving energy 10% as quick as possible.Therefore, we believe that same as the electronic ballast for energy saving lamp and sun light lamp, the electronic ballast for HID lamp will also be popularized with very fast speed.The application of HID lamp electronic ballast (developed by our company) of some highways lighting engineering in home or abroad market shows that electronic ballast not only has advantage of significant effect of energy saving, but also has advantage of long life.

References:

1. Electronic Ballast for HID Lamps with High Frequency Square Waveform to Avoid Acoustic Resonances

M. PonceAPEC 2001

2. < Pocket Guide to High Intensity Discharge Lamp Ballasts> ADVANCE