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Simulation studies of half-bridge isolated DC/DC boost converter

Krupa A.

Poznan University of Technology Academic Journals. Electrical Engineering

2014

No. 80

93--100

In order to utilize energy from low voltage power source it is necessary to use isolated DC/DC boost converter which will provide desirable input voltage step-up. To obtain a high voltage gain it is necessary to apply a magnetic device with the relevant turns ratio to the converter structure. This can be coupled inductor or transformer. The great advantage of the transformer is galvanic isolation between the subsequent power levels. Unfortunately, the high values of voltage gain is accompanied by significant currents on the primary transformer side. Large DC input currents cause an increase in power losses as the transistor conduction losses are proportional to square of current. The solution to this problem would be to divide a large input current into smaller currents through applying balancing transformers in converter structure. The input current in one stage exactly matches the current in the parallel branch, therefore there is no need for additional control to guarantee current balancing between power stages. This technique, together with the use of transistors with a small drain-source resistance and output SiC (silicon carbide) Schottky diodes enables converter to achieve necessary output voltage. This paper presents PSpice simulation results and mathematical analysis of half-bridge isolated DC/DC boost converter. In presented circuit high voltage gain and high conversion efficiency were achieved.

Simulation studies of flyback DC/DC converter with active clamp circuit

Krupa A.

Poznan University of Technology Academic Journals. Electrical Engineering

2014

No. 80

85--92

To yield energy from the low-voltage power source such as a photovoltaic panel or a fuel cell it is necessary to connect it with step-up DC/DC converter. Among many step-up topologies there are two basic types of converters: ones with and ones without galvanic isolation. Although both types provide voltage gain thanks to the turns ratio of transformer or coupled inductor, electrical isolation in some applications is essential. This paper presents an isolated DC/DC flyback converter using an active clamp and dual series resonance circuits. The converter operates as an isolated voltage amplifier with a voltage gain B dependent on duty cycle D and input voltage Vin. Through the use of transistors with low drain to source resistance RDS(on) conduction losses of main transistor switch can be reduced. The reverse recovery current of output rectifier can be omitted thanks to resonant tank consisted of transformer leakage inductance and voltage doubler capacitors. Active clamp circuit allows the energy transfer to the load in the two stages as in the forward converter. The 2-kW flyback converter simulation model was developed. Input voltage Vin varied from 12V to 48V and output voltage above 330V needed for 1-phase DC to AC conversion was achieved. Maximum converter efficiency was 92.3%.