lamps electronic ballast

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High Efficiency Single-Stage Multi-Fluorescent

Lamps Electronic Ballast

Hung-Ching Lu and Te-Lung Shih

Department of Electrical Engineering, Tatung University, Taiwan, R.O.C.

Abstract- A single-stage electronic ballast topology with the

properties of high efficiency and low stress is proposed in this

paper. The ballast consists of a voltage fed half-bridge

series-resonant series-parallel-load (SRSPL) inverter, playing the

role of lamp driver, and a voltage boost converter, which shares

low side switch device with half-bridge inverter and acts as

power-factor-correction (PFC). The inverter of the ballast is

loaded with resonant tanks which are designed and operated to be

capacitive and inductive to theoretically achieve both of

zero-voltage switching (ZVS) and zero-current switching (ZCS)

that eliminate the reactive current circulating through the switches

to prevent low switching and conduction losses. The boost

converter of the ballast provides sufficient high voltage to ignite the

lamp. In addition, prior to shaping the input current and reducing

harmonic currents to ignite the lamp, a power factor correction

stage is performed by the converter. The merit of a successive

ignition of the lamps can be attained with proposed operation

scheme so that current stress imposed on the switches can be

reduced. The simulation results and experimental measurements

are used to verify the theoretical prediction and analysis.

Index Terms:Single-Stage electronic ballast topology, Half-bridge

Series-resonant series-parallel-load (SRSPL) Inverter, Power Factor

Correction, Multi-Fluorescent Lamps Electronic Ballast

I. INTRODUCTIONIn recent years, electronic ballast has played a very important

role in lighting gears. In fluorescent lamp applications, the

electronic ballast is used widely because of its several

advantages. At high frequency operation, luminous efficacy of

fluorescent lamps is operated higher than 60Hz [1] and long

lamp life can be sustained. Most of the electronic ballast is

realized by resonant inverter operating at high frequency to

provide a sufficient high voltage to ignite the lamp and limit the

current. In conventional multiple fluorescent lamp lightingsystem, each lamp is equipped with its own LC network to

constitute a resonant tank. When all of the resonant tanks are

designed to operate at the same frequencies as the LC network,

the switching losses can be reduced; nevertheless, where

relatively large current will generated and flow through the

switches. This would also result in considerable conduction

losses and undesired current stress. In addition, a

power-factor-correction (PFC) circuit is attached to the ballast,

for the purpose of reducing the input line current harmonics.

The cost has increased when PFC stage cascade in front of

DC-AC inverter. In order to reduce the cost of the electronic

ballast, one single stage converter is used to perform both

function of the PFC and the DC-AC conversion simultaneously.

In this paper, a circuit operation scheme for multiple

fluorescent lamp lighting system is proposed. The scheme is to

operate all of the resonances for each resonant tank. By properly

selecting the component values of the overall tanks, an

equivalent resistive impedance of the overall tank can be derivedso as the switches can theoretically operate with both of

zero-voltage switching (ZVS) and zero-current-switching

(ZCS). Furthermore, conduction losses and current stress on the

switches can be reduced significantly since no reactive current

flows through switches. During startup transition, the lamps are

subsequently ignited because of switching frequency is

controlled to decrease monotonically. Hence, a small transition

peak current, as compared to that in the conventional ballast

system, will follow through switches during the glow-to-arc

transition.

The electronic ballast can be categorized systemically as dual

stage and single stage. The dual stage electronic ballastcompresses three switches and two controllers to consist of

AC-DC boost converter as PFC stage in front and DC-AC

half-bridge Inverter. However, dual stage electronic ballast has

better performance of power factor and current factor, where

cost increased by result of more complex circuitry. Therefore,

single stage electronic ballast was introduced to prevent the cost

drawback of dual stage electronic ballast, which has one switch

and one PFC controller of the boost converter can be omitted

[2-5]. Where the integrated boost converter and half-bridge

resonant inverter as shown in Fig. 1, in which boost converter is

operating in both of discontinue/continue modes with fixed

frequency and fixed duty cycle. The operating behavior is boostinductance current follow phase of input voltage to archive high

power factor [6, 7].

II. CIRCUIT OPERATIONIn this paper, work has been selected with four lamps in the

ballast; however, it could be three, five, six, etc. Next, the basic

multi-lamp requirements can be simply stated as follows:

(1) While a lamp is added; it should be ignited and kept in

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operation independently and should not disturb the operation of

other working lamps.

(2) While a lamp is removed from the light system; other

lamps should be kept in operation without interruption.

Fig 1. The proposed topology of Single-Stage Multi-Fluorescent Lamps

Electronic Ballast

With the above assumptions, that simplified electronic ballast,

explained as a half-bridge inverter, is used to supply the four

lamps, the connections between the lamps and the converter

have to be determined. But, before this discussion, it is

necessary to review the characteristics of the fluorescent lamp

firstly.

These lamps have a negative dynamic resistance behavior

which makes it necessary as the use of a ballast to limit the

current. A lamp modeling development which can predict the

fluorescent lamp electrical characteristics is necessary to do the

simulation of electronic ballasts due to the fluorescent lamp

nonlinear behavior. The lamp equivalent resistance of a

fluorescent can be expressed as

O SH

lamp S

O O H

V RVR R

I V V

= + =

(1)

where VOas well asIO are the rms lamp voltage and current,RS

and VHare defined as the parameters in the plasma model of

lamp.

The resonant tank design basin in [8] the method consists of

choosing the correct phase angle of the LCC resonant circuit that

will concern the lamp starting and the correct lamp power in

steady state. This analysis has just done for one of the lamps, and

the found values are repeated for all other ballast lamps.

Then, the phase angle is determined by

( ) ( )1 1 1 2 2 2 2 2tan 1lamp S P lamp lamp P R L C C R R C = +

(2)

where 2S

f = is the angular switching frequency, is

resonant tank impedance phase angle.

The half-bridge series-resonant series-parallel load resonant

circuits take account of resonant frequency operating characters

have both of capacitance and inductance, where parallel load

being capacitance are provided voltage gain and generated high

voltage with high equivalent lamp resistance to ignite the lamp.

However, the series load has well current regulation with

inductance characteristic, in which the voltage gain is reduced to

decrease the output voltage. When the lamp has beensuccessively ignited; the resonant frequency will be decreased

monotonically. Thus, the current stress imposed on the switches

can be reduced.

The voltage transfer function of the resonant circuit is given

as

2

( ) 1

( ) 1

1

11

1

lamp

lamp P lamp

lampin

S P lamp

PP

S lamp S lamp

R

V j j C R

RV jj L

j C j C R

C LLC j

C R C R

+

=

+ +

+

=

+ +

(3)

The series resonant frequency and CPmore then CSderived as

1S

SLC = (4)

The quality factor with (1) is

lamp

LCQR

= (5)

Take absolute value of (3) can be obtained as

22 2

2

( ) 1

( )

1

lamp

in

SP P

S S S S

V j

V jC C

QC C

=

+ +

(6)

During lamp igniting with character of series parallel resonant,

the lamp equivalent resistor can be considered as open circuit, (3)is used and the quality factor is close to zero, where ignite

voltage can be determined as

2

2 1

1

dc

strike

PP

S

VV

CLC

C

=

+

(7)

And the lamp stable voltage has been ignited can be derived

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as

,22

2

2 1

11

in

lamp rms

PP

S lamp S lamp

VV

C LLC

C R C R

=

+ +

(8)

Since operating frequency is 4 times of resonant frequency [5],

the resonant tank series inductorL and isolation capacitor CS

with operating frequency is expressed as

2S

S

fLC

= (9)

The capacitorCPon the resonant circuit is sustained the lamp

voltage during the lamp ignition,

1P

lamp

CR

= (10)

Therefore, with given stable lamp voltage Vlapm,rms, input DC

voltage Vdc and lamp equivalent resisterRlamp; the equations as

mention above can be solved to obtain resonator inductorL,

capacitorCSand ignition capacitorCP.

The ballast is obtained from the integration of the boost

converter design which considers output voltage is higher than

input voltage, which provides minimum ignition voltage and

operating voltage after lamp has ignited. The boost inductance

current into switch device on each switching cycle can be

obtained as of the boost converter and the half-bridge series

resonant parallel-loaded inverter. The operation of the boost

converter is in discontinued-current mode (DCM) providesunity power factor with constant frequency. In case of operating

partial lamps, a high power factor at the line input terminal will

be always retained. Thus, once the boost PFC stage is designed

to operate at DCM with fixed switching frequency, the input

current naturally follows the sinusoidal waveform of the ac line

source, that switching current of each cycle on the switch device

can be derived as

2

( ) sin(2 )2

m S

in

V D TI t ft

L= (11)

Furthermore, the input current and input voltage are operating

in same phase, which not only accomplish high input power

factor but also constraint total harmonic distortion of input

current, where the input power can be determined as

2

0

2 2

1sin(2 ) ( ) (2 )

2

4

in m in

m

P V ft I t d ft

V D

fL

=

=

(12)

With (11) the inductance of boost inductor can be derived as

2 2

4

m

in

V DL

fP L= (13)

III. SIMULATIONSome simulations have been done in order to verify the

multi-lamp arrangement behavior. To simulate, the fluorescent

lamp have been assumed same as the equivalent resistance

obtained from (1), the lamp as a resistor considered.

Additionally, the AC line voltage, rectifier bridge, and filter

capacitor have been used as a DC source, once that our aim is to

verify the multi-lamp arrangement behavior.

Simulation results are shown in Fig. 2, voltage in the lamps 1,

2, 3, and 4, in relation to Fig. 1. We can see that the lamp voltage

and switch voltage operation.

Fig 2. Thelamp voltage and one of switch voltage operation.

IV. EXPERIMENTAL RESULTSTo verify the predicted operation principles and theoretical

analysis of the proposed high efficiency single-stage ballast for

multiple fluorescent lamps, a laboratory electronic ballast of Fig.

1 is designed and built. The input voltage is 110Vat 60Hz, and

this circuit uses a dedicated integrated circuit TL494 to do the

high-frequency command, which switching frequency is fixed at

63kHz, and fixed duty 49.9%. Thus, the ballast can supply any

number of lamps and its frequency will not suffer variation. The

design parameters of circuit are shown in Table I.

Some experimental results have been done in order to verify

the experimental prototype behavior. The measured results are

presented the input voltage and current waveforms under

different operating conditions from single lamp, dual lamps and

triple lamps to quad lamps are shown in Fig. 3. Experimental

results are presented in Table. II. It is a prototype comparative

table to the different lamp numbers (4, 3, 2, and 1). where results

are illustrated of the input current is approximately sinusoidal

and operating same phase with input voltage, the power factor

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measured shown in Table II, and conclude it over 0.95 for all

lamps of experimental.

TABLE I. PARAMETER OF CIRCUIT

Designed Parameters

Design Reference Designed Value

1. Boost Inductor 1.1mH

2. Isolate CapacitorCS 60nF

3. Resonant CapacitorCP 3.5nF

4. Resonant Inductor 2.1mH

5. DC-link Capacitor 120uF

6 TL Lamp T5 28W

(a)

(b)

(c)

(d)

Vin50 V/divIin1 A/div time5 ms/div

Fig. 3. The waveform of Input voltage and current, Driving (a) single lamp,

(b)dual lamps, (c)triple lamps, and (d)quad lamps

TABLE II. EXPERMINTAL RESULTS

Number

of lamps

Single

lamp

Dual

lamps

Triple

lamps

Quad

lamps

Power

Factor0.953 0.961 0.968 0.973

The total ignition current ia for all lamps is 2.7A which is

shown in Fig. 4; with this current we can determine the

minimum rating of semiconductor switch device is 2.7A. In

order to prevent from destroying the device, the safe operation

rating of the MOSFET should be 5A or above. Next, Fig. 5

shows voltage over one lamp during its ignition process, which

maximum voltage is 827V. From these figures, it is possible to

verify the correct operation of the proposed electronic ballast,

during ignition and dimming control of the fluorescent lamps.Finally, Fig. 6.illustrates single lamp maximum start up current

is 390mA.

Iin1A/div time1 s/div

Fig. 4. Four Lamps ignited current waveform

0

0

Iin

Vin

Iin

0

Vin

Iin

Vin

0

Vin

Iin

0

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Vin200 V/div time5 ms/div

Fig 5. Lamp ignited voltage waveform

Iin100 mA/div time1 s/div

Fig 6. Single Lamp ignited current waveform

Fig. 7 shows the voltage and current waveforms through one

fluorescent lamp during operation at the maximum lighting

output condition. And Fig. 8 is shown the lamp 1, 2 and 3, 4 are

operating symmetrically and in 180o

opposite phase.

Fig. 9 is illustrates the voltage cross of the switches and

current waveform of boost inductor and resonant tanks which is

shown that the switching and conducting losses of the switches

in the proposed system are less than those in the conventional

system. In addition, the current stress imposed on the switches

in the proposed system is reduced significantly as compared to

that in the conventional one.

Vin100 V/div Iin200 mA/div time5 us/div

Fig 7. Lamp current and voltage are same phase driving

Vin100 V/div time5 us/div

Fig 8. Lamp current and voltage are same phase driving

Vin50 V/divIin200mA/div time2 us/div

Fig 9. Waveform driving signal and lamp current and boost inductor voltage

zero current switching and zero voltage switching

The solution to this problem is to determine an estimate of the

overall efficiency, measuring the input active power and the

active power of each lamp, one by one, using an oscilloscope. In

the maximum lighting condition, the total active power

processed through the lamps is approximately 112W, whereas

input active power is about 122W. Thus, the overall efficiency

of the proposed ballast is 91.8 0%, at the maximum lighting

condition.

V. CONCLUSIONA circuit operation scheme for a multiple fluorescent lamp

lighting system is proposed in this paper. The ballast is obtained

from the integration of a boost dc-to-dc converter and single

half-bridge series-resonant series-parallel loaded inverter. This

inverter circuit operation scheme is implemented with the

resonant tanks of the electronic ballast being capacitive andinductive, which can achieve lower switching losses, lower

conduction losses and lower current stresses over conventional

ballast with all inductive resonant tanks. The boost converter is

operated in discontinuous conduction mode and at constant

frequency providing an input power factor high enough to

satisfy present standard requirements. The operation of the

proposed ballast has also been investigated in detail in this paper.

A prototype of the ballast with proposed circuit operation

scheme for a four-lamp lighting system is implemented with

0

Vlamp1,2

Vlamp3,4

Vlamp

Ilamp

Low side switchHigh side switch

Lamp current ia

Boost inductor voltage

0

0

0

0

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practical considerations. In comparison with the conventional

electronic ballast for multiple fluorescent lamps, the proposed

electronic ballast for multiple fluorescent lamps presents a

significant reduction of cost. This reduction becomes even more

meaningful with larger number of lamps. The proposed

topology works as a good solution to implement low-cost

single-stage high efficiency electronic ballast for multiple

fluorescent lamps.

VI. ACKNOWLEDGMENTFinancial support of this research by the National Science

Council, Republic of China, under Grant NSC

97-2221-E-036-025 and Tatung University, Taipei, Taiwan,

under the grant B97-E04-040 is gratefully acknowledged.

VII. REFERENCES[1] E. E. Hammer and C. Ferreira, F40 fluorescent lamp considerations for

operation at high frequency, J. Illum. Eng. Soc., vol. 15, no. 1, 1985, pp.

63-74.

[2] L. Huber and M. M. Jovanovic, Single-Stage Single-SwitchInput-Current-Shaping Technique with Fast-Output-Voltage Regulation,IEEE Transactions on Power Electronics, Vol. 13, No. 3, May 1998, pp.

476-486.

[3] E. Deng, and S. Cuk, Single Stage, High Power Factor, Lamp Ballast,Proc IEEE Applied Power Electronics Conference, 1994, pp. 441-449.

[4] C. S. Moo, S. Y. Chan, and C. R. Lee, A Single-Stage High Power FactorElectronic Ballast with Duty-Ratio Controlled Series Resonant Inverter,

IEEE Transactions on Industrial Electronics, Vol. 46, No. 4, Aug. 1999, pp.

830-832.[5] J. A. Alves ,A. J. Perin, and I. Barbi,An electronic ballast with high power

factor for compact fluorescent lamps, Proc in Conf. Rec. IEEE-IAS Annu.Meeting, 1996, pp.2129-2135.

[6] M. A. Co, D. S. L. Simonetti and J. L. F. Vieira, High Power FactorElectronic Ballast Operating at Critical Conduction Mode, Proc PESC 96Record. Power Electronics Specialists Conference, 1996 27th Annual

IEEE, Vol. 2, June 1996, pp.962-968,.[7] J. Spangler and A. K. Behera, Power Factor Correction Techniques Used

For Fluorescent Lamp Ballast, Proc Conference Record of the 1991 IEEE

at Industry Applications Society Annual Meeting, Vol.2, , Oct. 1991, pp.1836-1841.

[8] R. N. Prado, A. R. Seidel, F. E. Bisogno, and R. K. Pavo, Self-OscillatingElectronic Ballast Design based on Point of View of Control System,

Thirty-Sixth IAS Annual Meeting. Conference Record of the 2001.

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lamps electronic ballast

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