3584 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 46, NO. 10, OCTOBER 2018

Design and Implementation of Novel Series TriggerCircuit for Xenon Flash Lamp Driver

Seung-Ho Song , Chan-Gi Cho, Su-Mi Park, Hyun-Il Park, and Hong-Je Ryoo , Member, IEEE

Abstract— This paper describes the design and implementationof novel trigger circuit (23 kV, 1.7 µs, and 0.66 J/pulse) forxenon flash lamp driver. The design is based on a modifiedflyback circuit in the discontinuous conduction mode to takeadvantage of both generating the high voltage from the resonancewith output capacitor and connecting the series with main pulsecircuit using the flyback transformer which can carry the fullcurrent of several kiloampere at high-voltage side. This designeliminates the requirement for additional high-voltage protectiondevices in a xenon flash lamp driver. In addition, the uniquehigh-voltage flyback transformer is designed with high turn ratioand low leakage inductance. The detailed design procedure forthe resonant circuit at the output side of the flyback circuitwith the permissible range of the parasitic component of thetransformer is described on the basis of simplified analysis ofresonant circuit. To verify the proposed design, computer simu-lation based on PSpice software and experiments for the proposedtriggering circuit with a main pulse circuit was performed.For the experiment, the trigger circuit is developed with thespecification of maximum 23-kV, 0.66-J/pulse output and testedwith a xenon flash lamp (Heraeus P4101) driver consisting ofa 1.5-kV, 36-kJ/s main pulse circuit and a 2.5-kW (500 V, 5 A)simmer circuit. The experiment is performed in both triggeringwithout the simmer mode and combining the simmer mode. Fromthe simulation and experimental results, it is verified that thetriggering circuit can be used effectively, as it exhibits reliableignition.

Index Terms— Flyback circuit, pulse generation, transformerwindings, trigger circuits, xenon flash lamp.

I. INTRODUCTION

XENON flash lamp systems are used for various appli-cations such as sterilization, polysilicon annealing, and

solid laser light sources, and recently they have also beenused as intense pulsed light sintering systems for printedelectronics [1]–[5]. Intense pulsed light sintering using a xenonflash lamp has the advantages of fast processing time, lowcost, ease of processing, etc., compared with the conventionaltechniques [6], [7]. Therefore, research on this topic is beingactively conducted [6]–[12].

Manuscript received January 2, 2018; accepted May 28, 2018. Dateof publication June 8, 2018; date of current version October 9, 2018.This work was supported in part by the National Research Foundationof Korea grant funded by the Korea Government (MSIP) under GrantNRF-2017R1A2B3004855 and in part by the Chung-Ang University GraduateResearch Scholarship in 2016. The review of this paper was arranged bySenior Editor W. Jiang. (Corresponding author: Hong-Je Ryoo.)

The authors are with the School of Energy Systems Engineering,Chung-Ang University, Seoul 06974, South Korea (e-mail: hjryoo@cau.ac.kr).

Color versions of one or more of the figures in this paper are availableonline at http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/TPS.2018.2842200

Fig. 1. Voltage characteristics of the xenon flash lamp driving processes.

The voltage characteristics of the xenon flash lamp drivingprocesses are shown in Fig. 1 [13]. For this process, a high-voltage trigger circuit for gas ionization and a high-powerpulse circuit for the main discharge operation are required.Moreover, in a xenon flash lamp with large capacity, a simmercircuit is generally used to increase the efficiency and lifecycleof the lamp by reducing its impedance [14]. Xenon flash lamptrigger circuits are generally divided into series and paralleldepending on the wiring method of the xenon flash lampdriver, which consists of a trigger circuit, simmer circuit, andmain pulse circuit [15].

In the case of a xenon flash lamp driver using a paralleltrigger circuit, the main pulse current of several kilo amperesdoes not flow to the secondary side of the triggering trans-former because all the circuits are connected in parallel. Sincethe transformer has a low current, there is an advantage thatthe transformer can be downsized. However, as a high-voltagetrigger pulse is applied to all the circuits in parallel, it isnecessary to protect the main pulse circuit and the simmercircuit from high voltage. A high-voltage diode can be usedin series to solve this problem [2], [15]. However, there isa limitation in using a diode as the high-voltage protectiondevice of the main pulse circuit because this device requireshigh voltage and large current rating equivalent to the triggerpulse voltage and the main pulse current [16]. Another optionis to use an isolation switch as a high-voltage protectiondevice for the main pulse discharge circuit. In the triggering

0093-3813 © 2018 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission.See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.

SONG et al.: DESIGN AND IMPLEMENTATION OF NOVEL SERIES TRIGGER CIRCUIT 3585

mode, the main pulse circuit is separated from high voltageby maintaining the switch in the OFF state, and the circuit isconnected by operating the switch during the simmer modeafter ignition [14].

In the case of a xenon flash lamp driver using a seriestrigger circuit, the trigger pulse voltage is not applied tothe simmer circuit because it is connected in series with thetrigger circuit. This is an advantage because series stackingdiodes that cause voltage drop and loss are not required inthe simmer circuit. However, the simmer current flows tothe secondary side of the triggering transformer because thetriggering circuit is connected in series with the simmer circuit.This is a disadvantage because a large transformer is requiredfor achieving the current capability at the secondary side ofthe triggering transformer. An isolation transformer in serieswith the trigger circuit is proposed to solve this problem [16].Xenon flash lamp drivers with the aforementioned conven-tional trigger circuit require an additional protection devicesuch as an isolation switch for separating the main pulse circuitfrom the trigger pulse voltage because the main pulse circuitis connected in parallel with the trigger circuit.

In this paper, a series trigger circuit design is proposedto solve the problem of protection of the main pulse circuitagainst trigger pulse voltage, via the series connection of themain pulse circuit with the trigger circuit. A xenon flashlamp driver using the proposed trigger circuit does not requirehigh-voltage protection devices in the main pulse circuit andthe simmer circuit because the trigger pulse is not applied toboth circuits. The simmer circuit connected in parallel withthe main pulse circuit can be configured using a single diodefor the main pulse voltage instead of a series stacking diodeat the output side. Furthermore, the design of the new triggertransformer is proposed in which the secondary winding cancarry the main pulse current, and all the primary windings areconnected in parallel. Owing to this winding design, it operateswith a high turn ratio and low leakage inductance for reliableignition. Finally, to demonstrate the effectiveness of the designproposed in this paper and to verify the isolated output ofthe trigger circuit, a simulation with the main pulse circuitis performed, and xenon flash lamp driving experiments areperformed using a xenon flash lamp driver consisting of theproposed trigger circuit, 36-kW main pulse circuit (1.5 kV,1.2 kA), and 2.5-kW simmer circuit (500 V, 5 A). The resultsare subsequently discussed.

II. ANALYSIS OF THE PROPOSED

SERIES TRIGGER CIRCUIT

Prior to the analysis of the circuit, a xenon flash lamp driverusing the proposed circuit will be described. The schematicof the xenon flash lamp driver using the proposed triggercircuit is shown in Fig. 2. In order to prevent high voltagefrom being applied to the main pulse circuit and the simmercircuit, the xenon flash lamp driver using the proposed circuitis connected to the lamp through the transformer of the triggercircuit. A bypass capacitor (Cb) provides the path for thetrigger pulse discharge between the simmer circuit and thetrigger circuit.

Fig. 2. Schematic of the xenon flash lamp driver using the proposed triggercircuit.

Fig. 3. Schematic of the proposed series trigger circuit.

The schematic of the proposed series trigger circuit is shownin Fig. 3. The magnitude and amplitude of the high-voltagetrigger pulse of the proposed series trigger circuit basedon a modified flyback circuit in discontinuous conductionmode (DCM) circuit are dependent on the optimal designof the resonant capacitor at the output side. This capacitorgenerates a pulse with the required voltage and width throughresonance with the inductance component of the transformer.

Some approximations are made to simplify the analysisof the circuit. The xenon flash lamp, which is the load ofthe trigger circuit, can approximate the open state becausexenon gas has an internal resistance of 10 M� or more inthe turn-OFF state. The bypass capacitor (Cb), which providesthe trigger pulse discharge path, is approximated by a shortbecause it is several tens of times larger than the resonantcapacitor (Cr ). Each operating mode is shown in Fig. 4.Voltage and current waveforms of the trigger circuit are shownin Fig. 5.

Mode 1 starts when the main switch S is turned ON. Duringthe ON time of switch S(tgate ON), the input current slope isproportional to the input voltage and inversely proportionalto the primary inductance component. This causes energy tobe stored in the primary side of the magnetizing inductance(Lmg) of the transformer. If the primary inductance of thetransformer is set to a constant value, the peak value of theprimary current in this section and the energy stored in themagnetizing inductance of the transformer can be expressedas follows:

Ipri peak = Vin

Lpri× tgate ON (1)

EL = 1

2× Lmg × I 2

pri peak. (2)

Mode 2 begins with resonance when the energy stored in themagnetizing inductance is discharged to the secondary side; at

3586 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 46, NO. 10, OCTOBER 2018

Fig. 4. Operation mode diagrams of the proposed trigger circuit.

the same time, the main switch S is turned OFF. In contrastto the conventional DCM flyback topology, which typicallyoutputs dc, the output appears as a half sine wave owing tothe inductance of the secondary side of the transformer (Lsec)and the resonance of the output side capacitor (Cr ). As thepulsewidth oscillates at the resonant frequency, it remainsconstant irrespective of the pulse energy and can be expressedas (3). The energy stored in the capacitor can be expressedas (4) for the output voltage and capacitance. If the energystored in Mode 1 is transferred without loss, the output voltagecan be expressed as (5). Mode 2 lasts until the end of the firsttrigger pulse, and the pulse energy is equal to the energy storedin the capacitor during this interval

Wpulse = 1

2× Tr = π × √

Lsec × Cr (3)

EC = 1

2× Cr × V 2

out peak (4)

Vout peak =√

2 × EL

Cr. (5)

Mode 3 refers to the period in which the inside of the xenonflash lamp is ionized by high voltage, and the resonance energyis reduced. When there is no lamp load, RLC resonance iscaused by the resistance component of the winding, and theenergy is gradually decreased.

III. DETAILED DESIGN PROCEDURE OF THE

PROPOSED TRIGGER CIRCUIT

The step-by-step design procedure and formula of theproposed trigger circuit based on a modified flyback circuitusing the specifications listed in Table I are as follows.

TABLE I

DESIGN SPECIFICATIONS FOR THE TRIGGER CIRCUIT

1) Calculation of transformer turn ratio (N)

N = Vout−peak

Vce − Vin. (6)

As shown in (5), the output voltage is not determinedby the number of transformer turns, but by the relationbetween the pulse energy and the value of the outputcapacitor. The turn ratio (N) of the transformer isexpressed in (6) as the relation between the breakdownvoltage of the primary side insulated gate bipolar tran-sistor (IGBT) (Vce), and the input and output voltages(Vin, Vout). According to the values listed in Table I,we obtain N = 21.3 and the number of primary sideturns is one; hence, the number of turns (n2) on thesecondary side of the transformer is calculated as 22.

2) Calculation of air-gap length (lgap) and magnetizinginductance of the secondary side (Lmg2)

lgap = 2 × μ0 × Emax

B2sat × Acore

(7)

Lmg2 = μ0 × n2 × Acore

lgap. (8)

The air-gap length (lgap) of the transformer core can beexpressed as (7) for the core specification and maximumoutput energy (Emax). The maximum output energy wasselected as 1.1 J to prevent saturation of the transformercore in pulse output. According to (7) and (8), the air-gap length (lgap) is 10 mm and the secondary side of themagnetization inductance (Lmg2) is calculated as 73 μH.

3) Calculating the capacitance of the resonant capaci-tor (Cr ) for the required output voltage (Vout peak)according to pulse energy (Epulse)

Cr = 2 × Epulse

V 2out peak

. (9)

Equation (4) can be expressed as (9) for the capacitanceof resonant capacitor (Cr ), and the result is calculatedas Cr 2.5 [nF].

4) Calculating the minimum leakage inductance of thesecondary side (L lk2 min) for the required minimum

SONG et al.: DESIGN AND IMPLEMENTATION OF NOVEL SERIES TRIGGER CIRCUIT 3587

Fig. 5. Operation waveform of the proposed trigger circuit.

Fig. 6. Photographs of developed 23-kV, 1.7-μs, and 0.66-J trigger circuit.

pulsewidth (Wpulse min)

L lk2 min = W 2pulse min

π2 × Cr− Lmg2. (10)

Equation (3) can be expressed as (10) for the minimumleakage inductance of the secondary side (L lk2 min), andthe result is calculated as L lk2 min18 [μH].

The higher the leakage inductance, the longer is thepulsewidth. In Mode 2, the energy stored in the leakageinductance on the primary side is discharged to the main IGBT,and the voltage across the switch is increased. Consequently,high leakage inductance can cause switch breakdown and thisvalue should be limited.

IV. DESIGN OF THE PROPOSED SERIES TRIGGER CIRCUIT

The proposed trigger circuit output pulses of 23 kV, 1.7 μs,and 0.66 J, and its specifications are presented in Fig. 6 andTable II. The process of designing the proposed trigger circuitis as follows.

A. Switch

The main switch is an IGBT FZ600R12KE4 from Infineonrated 1200 V/600 A for high-voltage rating and current-carrying capability. For reliable switching operation in the trig-ger circuit, a snubber circuit is required because the inductance

TABLE II

SPECIFICATIONS OF THE PROPOSED TRIGGER CIRCUIT

component of the circuit during the opening switch operationgenerates a spike voltage that can cause a breakdown of themain switch. However, as the use of the snubber circuit reducesthe energy of the pulse, the transformer and the PCB aredesigned such that the inductance component, which is thecause of the spike voltage, is minimized for the reliable switchoperation, and the breakdown of the IGBT is prevented withoutusing the snubber circuit.

B. Design of the High-Voltage Pulse Transformer

The design of the transformer used in the trigger circuitfor high-voltage pulses has considerations such as turn ratio,air-gap length, leakage inductance, high-voltage insulation,and the current-carrying capacity of the secondary windingto allow the main pulse current to flow. First, as the outputvoltage is represented by the value of the pulse energy andthe resonant capacitor regardless of the turn ratio accord-ing to (3), the turn ratio of the transformer is designed as22 according to (6). Subsequently, the core and air gap ofthe transformer are designed considering the energy of theoutput pulse. Furthermore, a 10-mm air gap was applied tothe output 0.66 J/pulse in the linear area of the B–H curve,and the maximum charge energy was 1.1 J/pulse. For thetransformer winding, the minimum value in (10) is satisfiedto ensure minimum pulsewidth and it must be designed tohave a low value in order to suppress the spike voltageformed in the main switch operation of the trigger circuit.For transformer windings, the minimum value in (10) mustbe satisfied to ensure minimum pulsewidth and it should bedesigned to have a low value to prevent the breakdown of themain switch in the trigger circuit. Accordingly, 18 primarywindings are connected in parallel between the secondarywindings of the 22 turns to minimize the length of thecurrent path and the space between the two windings inorder to minimize the inductance in the trigger circuit. Theleakage inductance of the fabricated transformer (L lk2 min)was measured as 40 μH. Finally, for insulation between two

3588 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 46, NO. 10, OCTOBER 2018

Fig. 7. Simulation model of the proposed trigger circuit with the main pulsecircuit.

windings, transformers with short winding distances shouldbe insulated using high-voltage insulation cables. However,as the secondary winding to which the high voltage is appliedmust satisfy the insulation and must be capable of flowingthe main pulse currents, there is a limitation in selectingthe secondary winding that satisfies this requirement. There-fore, the insulation between the two windings was achievedusing a high-voltage insulation cable as the primary winding,and the main pulse current-carrying capacity was achievedusing a wire with large cross-sectional area as the secondarywinding.

C. Resonant Capacitor

Resonant capacitors resonate with the inductance compo-nent of the transformer and output a half sine wave pulsewith constant peak voltage and width. In order to minimizethe energy lost by the resistance component during resonance,the resonant capacitor is placed close to the output side of thehigh-voltage pulse transformer. As this capacitor is chargedwith high voltage, four 8-kV/10-nF high-voltage capacitorsare connected in series.

V. SIMULATION AND EXPERIMENTAL RESULTS

In this paper, novel series trigger circuit that does not requirean additional high-voltage protection device is proposed for axenon flash lamp driver. Simulations and experiments wereperformed to verify the protection of the peripheral powersupply on the high-voltage trigger pulse and the formula forthe output voltage and pulsewidth according to the pulseenergy and resonant capacitor value. Fig. 7 shows the sim-ulation model of the proposed trigger circuit with the mainpulse circuit. A PSpice-based simulation circuit was used toverify the operation of the trigger circuit and the high-voltageprotection of the peripheral power supply, and it is configuredwith a main pulse circuit consisting of a capacitor bank andpulse discharge IGBT. The simulation was modeled basedon the parameters calculated according to the formula, andthe OFF-state ramp was modeled with a high-value resistorof 10 k�. As shown in Fig. 8, it was verified that the outputof the designed trigger circuit did not apply a high voltageto the main pulse circuit. The pulse voltage waveform of thetrigger circuit was measured using a Tektronix P6015A high-voltage probe.

Fig. 8. Simulation waveforms of the proposed trigger circuit.

Fig. 9. Experimental waveforms of the proposed trigger circuit.

Fig. 10. Experimental results of the proposed trigger circuit with the variationof the resonant capacitor value and pulse energy.

Finally, to verify the effect of high-voltage insulation, xenonlamp ignition tests with a xenon flash lamp driver were per-formed in the triggering mode without and with the simmeringoperation.

Fig. 9 shows the output waveform of the trigger circuitdesigned to the specifications of 23 kV and 1.7 μs accordingto the design procedure proposed in this paper. The outputvoltage and pulsewidth were 23 kV and 1.7 μs, respectively.It was confirmed that the designed specifications were sat-isfied. Fig. 10 shows the pulsewidth calculated by (3) andthe pulsewidth measured by the experiment according to thechange of the value of resonant capacitor and pulse energy.The calculated values were not significantly different from theexperimental results. Furthermore, Fig. 11 shows the outputof the pulse with the change in the pulse energy. It wasconfirmed from (3) and (5) that the pulsewidth was determined

SONG et al.: DESIGN AND IMPLEMENTATION OF NOVEL SERIES TRIGGER CIRCUIT 3589

Fig. 11. Experimental waveforms of the proposed trigger circuit with thevariation of pulse energy. (a) 0.4 J. (b) 0.75 J. (c) 0.9 J.

by the value of the output side resonant capacitor, not thepulse energy, and the output voltage had the same value asthat obtained using the formula. The validity of the equationsfor the output voltage and pulsewidth was verified by theseexperimental results.

Fig. 12 shows the result of the lamp (Heraeus P4101)operating experiment using the designed trigger circuit and thexenon flash lamp driver consisting of a 1.5 kV, 36 kJ/s mainpulse circuit and a 2.5-kW (500 V, 5 A) simmer circuit, andthe lamp operating experiment performed without the simmercircuit.

It is verified that high voltage is not applied to the mainpulse circuit during the triggering operation of the xenon flashlamp driver using the proposed trigger circuit.

Fig. 12. Experimental waveforms of xenon flash lamp ignition. (a) Withoutthe simmer mode. (b) With the simmer mode.

VI. CONCLUSION

In this paper, novel series trigger circuit was introduced forxenon flash lamp drivers to remove the high-voltage protectiondevice in the main pulse circuit through the isolated triggerpulse output. Moreover, the trigger transformer was suggestedto carry the several kiloampere at high-voltage side, it operatesas a small inductor during main pulse discharging. It is notnecessary to use high-current switch to bypass the triggercircuit.

A series trigger circuit based on a modified flyback circuitin DCM was designed to output pulses of 23 kV, 1.7 μs,and 0.66 J/pulse to ignite the lamp. Furthermore, the detaileddesign procedure including the operation mode analysis ofthe proposed trigger circuit, transformer design, and resonantcapacitor values has been described. In particular, consid-erations of the design of high-voltage pulse transformers,including winding configurations with high turn ratio andminimized leakage inductance, insulation between windings,and high current-carrying capability of the secondary winding,were provided for the series connection of the trigger circuit.A xenon flash lamp driver consisting of the proposed triggercircuit and the main pulse circuit was modeled using thePSpice-based simulation. It was confirmed via simulation ofthe trigger pulse and the main pulse output that the normaloperation of each circuit and the output of the trigger pulse

3590 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 46, NO. 10, OCTOBER 2018

do not apply a high voltage to the main pulse circuit. Basedon the trigger pulse output experiment of the designed triggercircuit, it was verified that the voltage and pulsewidth of theoutput pulse, according to the value of the output side resonantcapacitor and the pulse energy, satisfy the formula.

Finally, the xenon lamp driver consisting of the proposedtrigger circuit, 1.5-kV, 36-kJ/s main pulse circuit, and a 2.5-kW(500 V, 5 A) simmer circuit was tested with a xenon flash lampboth with and without simmering operation. Consequently,the simple design procedure and reliable operation of theproposed trigger circuit for use in xenon flash lamp driversare verified via the experimental results.

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Seung-Ho Song received the B.S. degree in electri-cal engineering from Kwangwoon University, Seoul,South Korea, in 2016. He is currently pursuing theM.S. and Ph.D. degrees with the Department ofEnergy Engineering, Chung-Ang University, Seoul.

His current research interests include soft-switchedresonant converter applications and high-voltagepulsed-power supply systems.

Chan-Gi Cho received the B.S. degree in infor-mation display engineering from Kyung Hee Uni-versity, Seoul, South Korea, in 2016, and the M.S.degree in energy system from Chung-Ang Univer-sity, Seoul, in 2018, where he is currently pursuingthe Ph.D. degree with the Department of EnergySystem Engineering.

His current research interests include resonantconverters and high-voltage pulsed-power system.

Su-Mi Park received the B.S. degree in energysystems engineering from Chung-Ang University,Seoul, South Korea, in 2017, where she is currentlypursuing the M.S. degree with the Department ofEnergy Engineering.

Hyun-Il Park received the B.S. degree in electri-cal engineering from Dankook University, Yongin,South Korea, in 2008. He is currently pursuingthe M.S. degree with the Department of EnergyEngineering, Chung-Ang University, Seoul, SouthKorea.

He is currently with Semisysco Co., Ltd.,Seoul. His current research interests includehigh-voltage pulsed-power supply systems includingthe soft-switched resonant converter applications forlight sintering system.

Hong-Je Ryoo (M’17) received the B.S., M.S.,and Ph.D. degrees in electrical engineering fromSungkyunkwan University, Seoul, South Korea,in 1991, 1995, and 2001, respectively.

From 1996 to 2015, he was a Principal ResearchEngineer with the Electric Propulsion Research Divi-sion, Korea Electrotechnology Research Institute,Changwon, South Korea, where he was a Leaderwith the Pulsed Power World Class Laboratory and aDirector of the Electric Propulsion Research Center.From 2004 to 2005, he was a Visiting Scholar

with the Wisconsin Electric Machines and Power Electronics Consortium,University of Wisconsin–Madison, Madison, WI, USA. From 2005 to 2015,he was a Professor with the Department of Energy Conversion Technology,University of Science and Technology, Deajeon, South Korea. In 2015,he joined the School of Energy Systems Engineering, Chung-Ang University,Seoul, where he is currently an Associate Professor. His current researchinterests include pulsed-power systems and their applications, as well as high-power and high-voltage conversions.

Prof. Ryoo is a member of the Korean Institute of Power Electronics,a Senior Member of the Korean Institute of Electrical Engineers, and a VicePresident of the Korean Institute of Illuminations and Electrical InstallationEngineers.