Modular Marx Topology for High Boost Ratio DC/DC Boost Converter
Asmarashin Ponniran*

Koji Orikawa*

Jun-ichi Itoh**Nagaoka University of Technology
1. Introduction
DC/DC converter with high boost ratio is required for someindustrial applications, such as for X-ray generation plasma
generation and others. In Marx circuits which are usually used forhigh voltage pulse generator, high conduction losses and copper
losses due to large input current are significant problems.
In this paper, a new Marx topology DC/DC boost converterwith charging choppers is proposed for a high boost ratio. In theproposed circuit, the parallel connection is applied at the input
side and the multistage connection is applied at the output side.
Therefore, a high efficiency boost converter can be achieved. For
the prototype development, only three-stage Marx topology
DC/DC boost converter is considered in order to confirm theconverter operation and the design method of the input inductors.

Fig. 1. Three-stage Marx topology boost converter.
Table 1. Stage capacitors operation.

2. Circuit topology
In a conventional DC/DC boost converter, the high boost ratio
can be achieved by connecting those converters in series or incascade connection [1]. However, this topology has low
efficiency due to the required number of the DC/DC converters.
Besides that generally DC/DC converters using high frequency
transformers are also can be considered in order to obtain a highboost ratio. However, this kind of converters usually suffers fromthe bulkiness, large losses and leakage current due to the parasitic
capacitance between the transformer windings. On the other hand,switched capacitor DC/DC converters also can achieve a highboost ratio. However, in this topology output voltage stress on theoutput capacitor is very high due to high output voltage [2,3].
Fig. 1 shows a circuit diagram of a Marx topology boost
converter (MTBC) of three-stage. Each stage of the MTBC
consists of a conventional boost DC/DC converter, a capacitor
and two additional switches. The converter is designed based ona principle of the Marx generator whereby a high-output voltage
is generated from a low-voltage DC source [4]. This principle canbe realized by charging a number of capacitors in parallel andthen suddenly connecting those capacitors in series. Therefore byarranging the combination of capacitors in the proposed converter,a high-output voltage can be generated. By piling stages, theMarx topology boost converter generates high voltage from alow-voltage DC power source. It is noted that 10 to 20 stages
might be required in order to reduce input currents stress,
switching devices voltage rating and stage capacitor voltages
stress in the actual application,.
The relationship between the input voltage Vin and the output
voltage Vout can be expressed as follows: D Vout = nVin ............................................................... (1)1− D where D is the duty ratio for the switches S1a, S1b, S2a, S2b, S3aand S3b and n is the number of stage. For the prototype, only
three-stage of the Marx topology boost converter is considered.
Fig. 2 shows the operation mode of the three-stage Marx
topology boost converter. Table 1 and Fig. 2(b) show that the(a) Switching pattern.
L3

D3

S3aC3

L2

D2

S2aC2S3bLout

L3

D3

S3aC3L2

D2

S2aC2S3c

L1VinS1aL3
S3a

Cout

Vout

L1
S1b

Vin

C1

S2a

S1c

Mode IS1a, S2a and S3a – ON
S1b, S2b and S3b – ON

Mode II
Dead-time Td condition
S1a, S2a and S3a – ON

C3

S3bLout

L3

D3

S3a

C3

C2

L1
S1a

S2b
Cout

Vout

L2

D2

S2a

C2Lout

L1
S1b

S2b
S2c

D1
C1

S3b
S3c

D2

S2c

Vin

S1b

S1c

D3

Vout

Cout

D1

S1a

S3c
L2

S2b
S2c

D1
C1

Lout

S3c

S2b
S2c

S3bVin

Cout

Vout

D1C1

S1a

S1b

S1c

S1c

Mode III
Additional delay-time Ta condition
S1a, S2a and S3a – ON
S1c, S2c and S3c – ON

Mode IV
S1c, S2c and S3c – ON(b) Equivalent circuit.
Fig. 2. Operation modes of the three-stage Marx topology boost.

stage capacitors C1, C2 and C3 are charged when those capacitors
are connected in parallel. Then those stage capacitors areTable 2. Specifications of the experimental prototype circuit.

connected in series during discharging condition. Thus from theseconditions, the output voltage can be boost-up by advantage of aseries connection of the stage capacitors. Therefore a high boost
ratio can be achieved. The voltage stresses on the switching
devices Sna (S1a, S1b and S1c), Snb (S2a, S2b and S2c) and Snc (S3a,S3b and S3c) are equal to the stage capacitor voltages VC1, VC2 andVC3, respectively. Meanwhile voltages stresses on the D1, D2 andD3 are equal to the VC1, 2VC2, and 3VC3, respectively.
In this paper, the inductor current of each stage in the MTBC
is designed to be operated in continuous current mode (CCM) inorder to minimize the peak input current. Thus the minimum
inductor current of each stage should be more than zero to ensure
a CCM condition is achieved. The minimum inductance of theinput inductor of each stage Lin(m) for CCM operation can be
expressed as follows:
2n (Vin ) D
Lin (m ) >................................................................. (2)2 Pout f sw
where n is the stage, Pout is the output power and fsw is theswitching frequency.
Meanwhile the inductor current ripple of each stage ∆ILin(m)can be expressed as follows:
V D∆I Lin(m ) = in................................................................ (3)f swLin(m )3. Experimental Results
Table 2 shows the specifications of the experimental
prototype circuit. The inductance of each stage of the input
inductor is designed by using (2). The designed inductance ofeach stage is 500 µH in this prototype. According to (3), thedesigned input inductor current ripple on each stage is 2.8 A.
Fig. 3 shows the experimental results of the input inductor
ripple currents of IL1 and IL2 are 2.8 A, respectively. In Fig. 3, theoutput power is 500 W and the average input current is 11.1 A.
Besides that, the experimental results of the inductor current
ripples of the IL1, IL2 and IL3 are according to the designed value
though IL3 is not shown in Fig. 3. As a result, both the designed
and the experimental results show a good agreement. In addition,in Fig. 3, the experimental results of the inductor currents of IL1(stage 1) and IL2 (stage 2) are shown. The average inductor
currents for the IL1 and IL1 are 3.7 A meanwhile the average
inductor current of IL3 (stage 3) is also 3.7 A because the input
current is divided by three due to three-stage arrangement in aparallel connection at the input side. Therefore if many stages are
considered, the input current will divided by the factor of thestage number and consequently the input current stress, theconduction loss and the copper loss will be reduced. On the other
hand, the stage capacitor voltage VC1 is 193 V and the stage
capacitor voltages of the VC2 and VC3 show good agreements withthe stage capacitor voltage VC1. Besides it is experimentallyconfirmed that the output voltage of 400 V is achieved.
Fig. 4 shows the efficiency of the Marx topology converter.
The input and output voltages are fixed at 48 V and 400 V,respectively. The measured maximum efficiency is 92.2 % at theoutput power of 500 W and 600 W. In addition, the efficiency isincreased when the output power is increased. From thischaracteristic, the conduction loss and copper loss which areincreased directly the squared of the current are not dominant in
the total power loss when the output power is high. On the otherFig. 3. Experimental waveforms of the output voltage, the capacitor
voltage (stage 1), the inductor current (stage 1) and the inductor current(stage 2).
93
9291
9089
8887
86
200300400500600Fig. 4. The converter efficiency characteristic.

hand, during low output power, the power loss are dominated by
the switching loss and the iron loss. As a result, the efficiency is
low during low output power.

4. Conclusion
This paper presented the high boost ratio of the Marx
topology converter whereby the parallel connection at the input
side and the multistage connection at the output side are applied.
Therefore the high efficiency converter is achieved. The
operation of the converter is confirmed by the three-stage Marx
topology converter prototype. The achieved maximum efficiency
is 92.2 % at the output power of 500 W and 600 W.
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