SUGISAKAMASANORI

Journal of Advances in Artificial Life Robotics
Vol. 1(2); September (2020), pp. 65–70
ON LINE ISSN 2435-8061; ISSN-L 2435-8061
https://alife-robotics.org/jallr.html

Research Article

Design of A Low Pulse High Current Series Topology for EDM
SystemYu-Kai Chen1, Min-Feng Lee1, Yung-Chun Wu1, Chau-Chung Songa1, Jui-Yang Chiu2
Department of Aeronautical Engineering, National Formosa University, Huwei, Yunlin, Taiwan
AcBel Polytech Inc. No.159, Sec. 3, Danjin Rd., Danshuei Dis., New Taipei City 251, Taiwan

12ARTICLE INFO
Article History
Received 05 December 2019
Accepted 21 July 2020
Keywords
Electric discharge machining (EDM)
LLCABSTRACT

The design of the LLC resonant converter is presented for use in Electric discharge machining(EDM) applications. The converter is designed to operate with a 3phase ac input voltage and will
output controlled dc voltages during the striking and arc conditions of EDM process. The methodof the LLC resonant converter can operate at zero voltage and zero current transitions, we change
the output current and control the current waveform of the EDM.

© 2022 The Author. Published by Sugisaka Masanori at ALife Robotics Corporation Ltd
This is an open access article distributed under the CC BY-NC 4.0 license(http://creativecommons.org/licenses/by-nc/4.0/

Resonant converter
Frequency control
Sic-MOSFET

1. Introduction

RIn this general, we have developed and improve thetechnology of performance equalization control ofElectric discharge machining (EDM) applications. Wechange the output current and control the current
waveform of the EDM. To control the current and the lossof the electrodes and increased the processing speed andthe processed object will not be too Rough, we havedesigned a smoothly rising current to let the electrodelossless; and to processing the super-hard alloy we havedesigned a low pulse high output current.

CWo rkp ie ce(a)

Wo rkp ie ce

RR
CONTORL
CIRCUIT(b)

Fig 1(a) Resistance Capacitance (RC) power;(b) transistor switching circuit

2. Developments in Power Configurations
The shapes of voltage and current pulses in the discharge
gap depend on the chosen power supply. There are twotypes of power supplies that have received most interest
amongst the scientific community. They are Resistance
Capacitance (RC) power supply, transistor switchingcircuit, Figure1 show the two type of power supply.

Those two type of EDM power supply topology applies
a square wave current as shown in Figure 2, thewaveform of a fixed current pulse width method is usedand control the pulse width of the discharge and keep
current certain width to maintain the surface of the work

Corresponding author’s E-mail: ykchen@nfu.edu.tw, lord159951@gmail.com URL: http://www.acbel.com

65Fig 2 Circuit diagram of the EDM power supply using a full-bridge LLC resonant converter.

piece smooth. However, to increase the processing speed,
the peak current Ip of the discharge current pulse willincrease, but the processing surface will become rough,and the electrode consumption ratio will also increase. In
order to reduce the electrode consumption, the discharge
current pulse width T can be increased. At this time, as
the discharge current pulse width T increases, thethickness of the work piece surface also becomes rough.

3. Full-bridge LLC resonate converter
experimental Prototype
The designed EDM impulse generator is a full-bridge
resonant converter whose switching frequency is far
higher than the machining frequency and we using Sic
MOSFET as switch. LLC resonant converters are able toachieve the required voltage for the dielectric breakdown
and, working above the resonant frequency current lags
voltage so this topology achieves zero voltage switching,
resulting in minimum switching losses.

IpCurrentTimeT3.1. Full-bridge LLC resonate converter overview
To achieved two different waveforms, so we set twoparallel LLC circuit to create base current and low plus
high peak current, these two converters are designed tooperate with three-phase three-line ac input voltage andoutput will be controlled two different dc voltages during
the EDM process, the method employed magnitude andfrequency control to enable the converter to operate atzero voltage and zero current transitions. During theEDM process will have two different output current firstis the base current, the base current is to reduce theelectrode the current will be smoothly rising to the basecurrent, when the base current has risen to the stable state,
the second LLC will be started output the low pulse highcurrent waveform shows in Figure 4, the output
waveform is controlled by MCU to change output thedifferent LLC.

Fig 3 output current waveform

Therefore, a new circuit topology is proposed, and theoutput waveform is as shown in Figure 3. It consists of aslowly rising base current square waveform t1 to t2 anda low pulse high peak current waveform t2 to t3. These
two waveforms are composed to find out whether thecharacteristics of the processed object can be maintained.
The homogenization, acceleration of processing speed,
reduction of electrode loss and improvement of thethickness of the machined surface. These characteristics
to the discharge current waveform and the realization of
the current waveform circuit finally proposed.
slowly rising Base current
square wave

t1-t2

low pulse highpeak current wave

t2-t3

3.2. LLC resonant inverter analysis and design

Current
t1

LLC resonant converter gain K is the product of thebridge switching gain, the resonance loop gain, and thetransformer's primary-side turns (NP) and secondary-sideturns (NS). The resonant tank circuit is composed of theelement resonant inductor Lr, resonant capacitor Cr, andexcitation inductance Lm. The resonant element is used

t2 t3

TimeFig 4 new design output waveform66

to achieve zero voltage or zero current switching of thepower switch, and the switching frequency is adjusted tochange the output voltage. The resonance loop gain canbe analyzed by analyzing the equivalent resonance The
circuit is shown in Figure 5. The equivalent circuit showsthat its resonance gain is shown in Equation (1).

The influence of design parameters on voltage regulationand efficiency performance, and the design of resonanttank parameters according to system specifications. The
ultimate design goal is to achieve the load to operate at
the best performance under any conditions. The detailed
design flowchart of the design method is shown in theFigure 6.

CR

VIN_ACLM

RAC

VO_ACStart

LR

Select QMAX ValueFig 5 LLC series-parallel resonant tank equivalent circuit
diagram=𝑲𝑲(𝑸𝑸, 𝒎𝒎, 𝑭𝑭𝒙𝒙 ) = �

𝑽𝑽𝑶𝑶𝑨𝑨𝑨𝑨 (𝒔𝒔)�𝑽𝑽𝑰𝑰𝑵𝑵𝑨𝑨𝑨𝑨 (𝒔𝒔)𝑭𝑭𝒙𝒙 𝟐𝟐 (𝒎𝒎 − 𝟏𝟏)𝟐𝟐

Select m Value𝟐𝟐

��𝒎𝒎 ∙ 𝑭𝑭𝒙𝒙 𝟐𝟐 − 𝟏𝟏� + 𝑭𝑭𝒙𝒙 𝟐𝟐 ∙ �𝑭𝑭𝒙𝒙 𝟐𝟐 − 𝟏𝟏� ∙ (𝒎𝒎 − 𝟏𝟏)𝟐𝟐 ∙ 𝑸𝑸𝟐𝟐

Design FxMIN

Increase m Value(1)

Reduce m Valuedesign gain KMAX

YESNOKmax <required gain?

NOCheck KMAX gain

3.3. Design the resonant tank

YES

The circuit parameter design The K value is obtained by
the above method, and its verification parameters are
already a better design of the circuit. Therefore, the Qvalue, Fx and fr can be used to solve the equation, andthe resonance can be obtained by equations (2) and (3)The resonance inductance and resonance capacitance ofthe tank are obtained by formula (6) to complete theparameter design of the resonance tank element, theformula is as follows.

Find the parameters of
the resonant tankEndFig 6 Resonant tank parameter design flow chart

4. Full-bridge LLC simulation results

Quality factor Q:
Q=

�L𝑅𝑅 /CR

(2)

1

(3)

RAC

Follow the step of the flow chart shown in Figure 6 todesign the LLC resonant converter. The base current
output voltage has design 60v and the low pulse highResonant frequency fr:𝑓𝑓𝑟𝑟 =2𝜋𝜋�𝐿𝐿𝑅𝑅 ∙𝐶𝐶𝑅𝑅

Table 1 Base current wave form Specifications

The reflected load resistance at full load:
8Rac = 2 ×π

Np 2
Ns 2×Ro

Ratio of switching frequency fs and resonancefrequency fr:
fFx = sfr

Base current waveform
Input voltage 3Φ3W
Output voltage(Vo1)
Output power(Po1)
Switching Frequency
Waveform time(t1t2)

(4)

(5)

Ratio of primary inductance to resonant inductance m:
L +L
m= r m(6)
Lr

67

Specifications
220V
60V
120W
100kHz300ms

current designs with 100v, the design data show inTabel1 and Table2.

output voltage; yellow is output current)

Table 2 Low plus high current peak waveform Specifications

Low plus highcurrent peak
waveform
Input voltage3Φ3W
Output voltage(Vo2)
Output power(Po2)
Switching Frequency
Waveform time(t2t3)

5. Experimental results
The simulation has approved that circuit can get theoutput that a smoothly rising current and a low pulse highpeak current and next we design a prototype to test theprototype shown in Figure 9 and and the output
waveform of Ton was controlled by MCU the output
waveform was shown in Figure 10.

Specifications
220V
100V
500W
100kHzSecond LLC for low
peak high current
peak100ms

MCU control board

Frist LLC for basecurrent

4.1. Full-bridge LLC simulation
In this section, the diagram of the EDM system with ac
to dc power supply and transistorized switching circuit aspulse generator designed in PSPICE and PSIM andschematic diagram is shown in Figure 7 there are two
LLC converter which private 60v and 100v and thesimulation output is shown in Figure 8.

Fig 9 Prototype power system

Fig 7 schematic diagram(a)(I4:500mA/ div、Time：2ms/ div)

60V 100V

300ms 100ms(b)(VO1:50V/ div、I4:500mA/ div、Time：100ms/ div)

Fig 8 Results of parallel LLC simulation (green is68

Authors Introduction
Yu-Kai Chen

He was born in Chiayi, Taiwan, in 1967.
He received the B.S. degree in electronicengineering from Feng Chia University,
Taichung, Taiwan, in 1990, the M.S.
degree in information and electronics
engineering from National Central
University, Chungli, Taiwan, 1994, andthe Ph.D. degree in electrical engineeringfrom National Chung Cheng University,Chiayi, in 1999. From 1994 to 1999, he was a Lecturer withthe Department of Electronic Engineering, Wu Feng Instituteof Technology, Chiayi. He was an Associate Professor withthe Department of Electrical Engineering, Chien kuo Instituteof Technology, Changhua, Taiwan, from 1999 to 2003. Since
2003, he has been with the Department of AeronauticalEngineering, National Formosa University, Huwei, Taiwan,
where he is currently a Distinguished Professor. In 2015 and2019, he received the outstanding industry collaboration
awards from National Formosa University. His researchinterests include modeling and control of power converters,
design of solar panel-supplied inverters for grid connection,and DSP- and microprocessor-based application systems withfuzzy and robust controls.

Low pulseHigh current(c)(VO1:50V/ div、I4:500mA/ div、Time：2m s/ div)
Fig 10 output waveform;(a)base current output 2A;(b)twoLLC output waveform(c) low pulse high peak current output

6. Conclusion
Design a parallel LLC circuit, and complete the basic
wave circuit and low pulse high peak current output, withfour Sic Mosfet. The output waveform still needs to becloser to the simulation output and connected to the EDM
machine to test for electricity consumption and theprocessing speed.

Min-Feng Lee
He received his Bachelor's degree from
theDepartmentofElectronics
engineering, Oriental Institute ofTechnology, Taiwan in 2017. He iscurrently a Master course student in
National Formosa University, Taiwan.

7. References
1. Y. K. Wang and B. Y. Song, “Research on HighlyEfficient EDM Pulse Power Supply and Its Experiments”
Trans Tech, Harbin, China, 2005
2. R. L. Steigerwald, “A comparison of half-bridge resonant
converter topologies”, IEEE Trans. Power Electron., vol.
3, pp. 174–182, Apr. 1988
3. M. Yan, Y. Liu, “Design, analysis and experimental studyof a high frequency power supply for finish cut of wireEDM”, International Journal of Machine Tools andManufacture, vol. 49, 2009) pp. 793–796.
4. Infineon, Improving Efficiency of Synchronous
Rectification by Analysis of the MOSFET Power Loss
Mechanism (Application Note, June 2009).
5. Infineon, Resonant LLC Converter: Operation and Design(Application Note, Step 2012).
6. A. Behrens, J. Ginzel, and F. L. Bruhns, “Arc detection inelectro-discharge machining,” ISEM XIII Conf. Proc.,
2001, pp. 283–294.

Yung-Chun Wu
He was born in Kaohsiung, Taiwan, in1971. He received the Ph.D. degree inelectrical engineering from National
Chung Cheng University, Chiayi, Taiwan,in 2000. From 2000 to 2001, he was anAssistant Professor with the Department ofElectrical Engineering, Chien kuo Instituteof Technology, Changhua, Taiwan. He was an AssistantProfessor with the Department of Electrical Engineering, IShou University, Kaohsiung, from 2001 to 2007. Since2007,
he has been with the Department of Aeronautical Engineering,
National Formosa University, Huwei, Taiwan, where he iscurrently an Assistant Professor. His research interests include
developing and designing converter topologies, LED drivers,electronic ballasts, and high-efficiency converter.

69

Chau-Chung SongHe is with the department ofAeronautical Engineering, NationalFormosa University, Taiwan. He
received the M.S. degree in Control
Engineering in 1994 and the Ph.D.
degree in Electrical and Control
Engineering from National Chiao Tung
University in 2001 at Taiwan. He is currently a professor in
Institute of Aeronautical and Electronic Technology, andDepartment of Aeronautical Engineering, National Formosa
University since 2006. His research interests include theanalysis and control of nonlinear systems, the powerelectronics and energy applications, the integration applicationof networking information system, the UAV technology andapplications, and the cloud network and Cyber-Physicalsystem (CPS).
Jui-Yang Chiu

He was born in Yunlin, Taiwan, in
1978. He received the B.E. degree inelectronic engineering from National
Yunlin University, Yunlin, Taiwan, in
2000, the M.S. degree in electricalengineering from National Chung
Cheng University, Chiayi, in 2002.
Since 2002, he has been with theDepartment of AcBel Polytech Inc. His research interests
include structure design and control of high-power
converters, design of high-power inverter for ElectricVehicle.

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