Electronic board for driving of HID and LED lamps with ... - IEEE Xplore

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Lecce, Italy paolo.visconti@unisalento.it giovanni[email protected]. D. Romanello, G. Cavalera. Cavalera Sistemi s.r.l.. Galatone, Lecce, Italy.
Electronic board for driving of HID and LED lamps with auxiliary power supply from solar panel and presence detector P. Visconti, G. Zizzari

D. Romanello, G. Cavalera

Department of Innovation Engineering University of Salento Lecce, Italy [email protected] [email protected]

Cavalera Sistemi s.r.l. Galatone, Lecce, Italy [email protected] [email protected]

Abstract— This paper describes an intelligent electronic system for the control of LED and SAP lamps for public lighting. The lighting system is designed to be applied in rural areas where there isn’t public voltage electricity. Each lighting point, in fact, has a system to convert solar energy into continuous voltage by photovoltaic panels. The communication between the electrical cabinet and the individual lighting point is through the power line. In order to ensure a high energy savings, in addition, the intensity of the luminous flux produced by the single lighting points is maintained at 50% of the nominal value. Instead, it is increased to 100% in case of vehicles in transit in the area illuminated by lighting point, vehicle or pedestrians detected using appropriate presence detector.

on/off, etc., then the designed electronic control system might be more interesting. In many rural areas that haven’t transmission line of public electrical power, the street lighting cannnot be installed; but it is very important and necessary for avoiding street accidents and assuring people life safety. For this reason we have also provided the opportunity to powered the individual lighting points through the solar energy produced by a photovoltaic panel.

Keywords-photovoltaic; HID; LED; ballast; lighting

I.

INTRODUCTION

Public lighting has some features that make it an ideal field in order to contribute in a practical way to save energy and to increase the environmental sustainability of our lifestyles. For this reason, public lighting systems need to be regulated by rules that are based on the observation of the principles of energy conservation, rational use of energy and lighting pollution. The future of public lighting will be the white LED based lamps. Essentially LED technology has got several advantages with respect to old HID technology. First of all the operational life of these lamps is about 100,000 hours, actually, more than six times the operational life of HID lamps (typically 15,000 hours). Another important aspect is the power consumption; in terms of efficiency (i.e. lumen/watt) the LED technology allows to get higher efficiency (> 80%). Last but not least, LED lamps ignite instantaneously and do not need a warm-up period. This technology is spreading in new yields and applications as well as in power-saving intelligent systems. Due to a very expensive installation cost, the old lighting systems should not be replaced but just retrofitted by adding the power saving intelligent systems. For these reasons an electronic board which can drive both HID and LED lamps will assume a crucial relevance in the public lighting systems. Moreover if the electronic board would provide also a remote control for dimming, power

Figure 1. Scheme of a street-lamp

II.

ELECTRONIC BALLAST BLOCK DIAGRAMS

The block diagram of electronic ballast capable of powering a discharge lamp or an LED module is shown in Figure 2. After the bridge rectifier that converts AC into DC voltage, a device called Power Factor Corrector (PFC) optimizes power consumption by the power line, avoiding unnecessary loss of power and provides a high voltage (Vbus). The output stage, consisting of an H-bridge, is driven by two half-bridge drivers and allows the HID lamp to be powered by an AC and low frequency (usually 50Hz) signal. The drivers are driven by a microcontroller. An ignition circuit is designed to “trigger” the HID lamp; it needs a high discharge voltage, provided by the so called “igniter”, in order to be started up. The igniter uses a high voltage transformer to generate the desired discharge voltage.

Intervention co-financed by the E.U. – O.P. Apulia Region 2007-2013 – Axis I - Line 1.1 "Aid for investment in research for SMEs" and supported by Cavalera Sistemi Srl – Galatone (LE)

978-1-4244-8782-0/11/$26.00 ©2011 IEEE

Figure 4. The diagram of the transceiver

Figure 2. HID or LED block diagram

The main feature of designed electronic ballast is the implementation of a reconfigurable output that is capable of driving, by user’s choice, a discharge lamp or a LED lamp. This is obtained through the use of switches whose purpouse is to exclude the ignition circuit if the lamp to be powered is the LED type. The system is also able to autolearn whether the load to be powered is a HID lamp or an LED lamp by measuring its electrical parameters. In this way, the microcontroller will only perform the routine of the firmware related to the lamp type recognized. The designed electronic board implements both power and communication control functions. This board allows to communicate, by the power line, with the electrical panel, for example in order to program the turning on or off of the lamps and their brightness. A. The transceiver The electronic board above described includes a communication module able to exchange data through the power line between lighting point and remote supervision electric cabinet.

Figure 3. The communication system that we have designed, applied to a lighting system: the Master will be placed in control panel and the Slaves will be installed in the individual light points.

A simplified electric scheme of the transceiver is illustrated in Figure 4. The bidirectional communication system consists of a Master and one or more Slaves, which can operate on 230Vac power supply line, without requiring therefore dedicated wiring cables.

The communication from Master to Slave can be accomplished by a proper amplitude modulation of voltage signal on the power line, while the communication from the Slave to the Master is obtained by a amplitude modulation of current signal. The system was designed, in particular, to be installed in public lighting in order to implement the communication between the control unit (Master) of the lamps and ballasts (Slave), in order to adjust the intensity of light produced by each lighting point, as specifically required by actual regulations regarding light pollution and energy saving for public lighting systems that have to implement the dimming of the luminous intensity of lamps. B. H Bridge driver In Figure 5 is shown the driver circuit of the H-bridge. The Rshunt resistance, on which the current flowing in the lamp is measured, the four H-bridge transistors (S1, S2, S3, S4), the L6385 half-bridge driver and the L100 inductor can be noticed. The main purpose of the inductor is to limit the ripple current flowing in the lamp. The C111 capacitor, instead, when a discharge lamp is used, has the task to avoid the phenomenon of acoustic resonance, while in the LED lamp case, it helps the inductor to limit ripple current.

Figure 5. The driving circuit of the H-bridge. In the case of LED module supply is necessary to connect the point 1 to point 3 and the point 5 to point 8 (in this way the igniter circuit is cut). If instead HID lamp is supplied, is necessary to connect the point 1 to point 2, the point 3 to point 4, the point 5 to point 6 and the point 7 to point 8.

C.

LED module driver circuit The attractive aspect of the designed board is the possibility to drive, with the same driver output, both HID and LED lamps. This is possible using some controlled switches in order to remove temporarily the igniter and using the same H-bridge to drive the LED lamp.

Figure 9. Control circuit implemented by SG3524

Figure 6. The driving circuit of the H-bridge for LED lamp

Figure 6 shows the circuit solution that allows driving the LED module through the H bridge. This is possible thanks to a bridge rectifier that allows to transform AC voltage output bridge in a positive voltage. The series of LED turn on with a frequency of 400 Hz (not perceptible by the human eye). The rectifier bridge has been directly installed on the LED module, so this solution does not require the use of any additional components on the designed power driving board. III.

PHOTOVOLTAIC STREETLIGHT FOR LOW POWER LAMP

The photovoltaic streetlight is a revolutionary system composed of photovoltaic modules which converts the sunlight into electric power. This energy is stored in a battery during the day and made available in night-time in order to power a sodium-vapour lamp or led moules. This is the ideal answer when there is the need of lighting squares, streets, crossings and no availability of electric power grid nearby.

In order to control the active switch device (MOSFET) as shown in Figure 8, a pulse signal with controllable duty ratio is required. Therefore, in order to avoid the complexity of a dedicated control circuit, the PWM integrated circuit (IC) number SG3524 was selected in order to generate the control signal. The designed and simulated control circuit is shown in figure 9. The VBUS voltage generated by the PFC, is provided as an input to the H-bridge, shown in Figure 5, which converts this continuos voltage into an AC voltage suitable for powering the HID lamp or the LED module with a bridge rectifier. This lighting system is used in places where isn’t required high intensity lighting, because the ballast is designed for lamps of low power rating. IV.

PHOTOVOLTAIC STREETLIGHT FOR HIGH POWER LAMP

Figure 10 shows the block diagram of a lighting system, with auxilary power supply, for driving of high power lamps.

Figure 7. Photovoltaic street lighting block diagram for low power

As shown in Figure 7, a switching device selects the power source for electronic ballast between the battery cherged from solar panel and 230Vac power line. If the selected source is the photovoltaic generator, the battery, recharged during the day, provides to the ballast a DC voltage of 12V.

Figure 8. Simplified schematic of the PFC in the case of solar panel power supply (VD = 12V DC provided from the battery)

The figure 8 shows the simplified block diagram of the PFC ballast in the case of power from solar panel through the battery. The transistor Q, driven by a suitable control circuit, charges the inductor L, using the voltage VD provided by the battery until it reaches the Vbus voltage.

Figure 10. Photovoltaic street lighting block diagram for high power

An electronic circuit called "step-up converter" has the purpose to raise the voltage provided from the battery to a voltage suitable for the ballast, so that it can supply a HID lamp or an LED module. The switching device has the task of selecting the power supply source of the lighting point from the public electricity or through the solar system. A. DC-DC Step Up converter The solar panel installed on every lighting point is able to produce 12Vdc voltage. The ballast needs a DC voltage (VBUS) of 400V to supply the high power lighting source. Therefore, it was designed a dc-dc step-up converter able to get 400V from 12V. The step-up DC-DC converter will step up

12V to 400V, using an isolated switch-mode push-pull DC-DC step up converter.

represents the presence sensor is added. This device communicates with the microcontroller installed on the control board of the ballast in order to adjust the lighting intensity produced from the lighting point. Without a in transit vehicle, the lighting point will provide a luminous flux of approximately 50% than the maximum (assuring energy saving). The percentage of reduced flux in the absence of vehicles can be set, while taking into account the minimum threshold established by existing laws on public lighting.

Figure 11. Push-Pull Converter

Figure 11 shows the schematic of the push-pull converter which utilizes a center-tapped transformer for both the primary and secondary windings. The primary winding is controlled by two transistors, which allows one of them to conduct during each half-cycle, so the output is receiving voltage directly through one of them at all times. The PWM control chip has the purpose to drive throught PWM signals, of appropriate frequency, the transistors Q1 and Q2, according to feedback signals (Vsense, Ilimit) detected on the powered load. The transfer function of the system is as follows: Vout

=

N N

s

× Vin × 2 × D

(1)

p

where “D” is the duty cycle of the signal given at Q1 and Q2. This lighting system is used in places where is not necessary to illuminate for many hours, because, in this case should be a high power photovoltaic generator (large size) in orderv to provide the needed energy. V.

STREETLIGHT WITH PRESENCE DETECTOR

The main objective to be achieved, is to get a highefficiency lighting system, which enables high energy savings but also to ensure a better quality of lighting. For this purpose, we have planned and realized a further technique that allows to achieve substantial energy savings. In particular, in each lighting point was added a presence detector designed in order to relieve the transit of vehicles or pedestrians in its area of illumination. The sensor by means of the control board ballast, lets the luminous flux to be increased from 50% of the total flow (in the absence of in transit vehicles) to the maximum value of 100% (in case of in transit vehicles).

Figure 13. Photovoltaic street lighting block diagram with presence detector

VI.

COMPARISON WITH STATE-OF-ART LIGHTING SYSTEMS

This paper describes an intelligent electronic system for the control of LED and HPS lamps for public lighting. Different commercial types of power supplies for LED lamps can create a fully programmable lighting system. The feature to drive both types of lamps is unique for the realized control board. This versatility is achieved through the implementation of a reconfigurable output capable of driving, by the user's choice, LED/HPS lamp. Through an appropriate routine implemented in the firmware of the control board, the system is capable of self-learning the type of lamp inserted in reconfigurable output. This feature allows to use the ballast in lighting systems that nowadays use the traditional discharge lamps and, primarily, will allow to keep the same ballast when discharge lamps will be replaced by the LED modules, in the near future in which the LED street lighting systems will be more affordable. The presented system allows communication through the power line with the electrical cabinet in order to program the turningon of the lamps and their brightness, allowing to avoid any additional wiring cost. The proposed solution is advantageous compared to communication devices currently on the market such as conveyed waves and Zig-bee, which have several disadvantages, such as the cost of components, high power consumption and excessive size. Finally the system with the presence detector and auxiliary power supply from solar panel provides high energy savings. ACKNOWLEDGMENT This work is supported by Cavalera Sistemi s.r.l - Galatone (Lecce) Italy, and University of Salento (Lecce) Italy. REFERENCES

Figure 12. Technique of the presence detector

The electronic system, as shown in figure 13, consists mainly of seven functional blocks. In addition to the blocks already described in previous paragraphs, the block that

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