This paper proposes current-fed resonant full-bridge boost DC/AC/DC converter with zero -current switching technique. The proposed converter is suitable for the high voltage applications. However, since it controls the secondary switch to build up the primary voltage during the very short period of time, the ZCS operation is easily achieved without any additional conduction losses of magnetizing current in the isolation transformer and resonant circuit. Furthermore, there are no additional circuits required for ZCS operation of power switches. Therefore, the proposed converter can achieve low EMI noise resulting from the soft switching without any additional conduction losses. The main of this paper is to simulate and hardware implementation of current fed resonant full-bridge boost DC/AC/DC converter. The performance of this converter is observed by using MATLAB simulation. The control circuit, power circuit and driver circuit are fabricated on general purpose PCB.Current-fed resonant full-Bridge boost DC/AC/DC Converter is implemented and the results observed by simulation are validated by the experimental results.
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Index Terms- Bridge, current-fed, dc/ac/dc converter, resonant.
A full bridge dc/ac/dc converter is widely used in high power dc/dc application. Power electronic converters are limited by high frequency application due to switching losses in power switching devices.
switching losses are reduced by Turn on/Turn off the switching devices either at Zero voltage switching (ZVS) and/or zero current switching (ZCS) instants.
The soft switching technique reduces the voltage /current stresses of main switches & achieve soft switching of the main switch's is a combination of the desirable features of conventional switch mode converter & resonant converter. MOSFET are increasingly preferred for high power & high frequency application because of low conduction loss, low cost & high frequency capability. It is located at the primary side of transformer. It also achieves soft commutation for output rectifier diodes. A proposed converter circuit consists of resonant inductor and resonant capacitor.
Block diagram and description will be presented in section II. The Proposed scheme converter circuit diagram and description presented in section III.Simulation result will be presented in section IV. Section V will explain the implementation of DC/AC/DC converter. Advantages of proposed circuit at the primary side of transformer are
Only one L and C circuit required for entire proposed scheme.
To achieve Zero Current Switching.
To achieve soft switching for output of single phase inverter.
Resonant inductor and resonant capacitor circuit helps to turn on/turn off the main switch softly.
Reverse recovery problem of rectifier is eliminated.
PROBLEM IDENTIFIED IN THE EXISTING SYSTEM
All-switched mode converters concerns transformer parasitic elements.
The transformer leakage inductance causes undesirable voltage spikes that may damage the circuit components.
The winding capacitance may result in current spikes.
A vital factor that determines the size and the cost of a converter is its operation frequency.
ADVANTAGES OF PROPOSED SYSTEM
It achieves ZCS for MOSFETs.
It achieves soft commutation for output rectifier diodes.
It provides simple structure.
It regulates the dc output voltage without over shoot, with reduced switching losses, compact size and high efficiency.
Reverse recovery problem of rectifier diodes is eliminated.
Battery chargers and dischargers.
Uninterruptible Power Systems (UPS).
Alternative energy systems.
Hybrid electric vehicles.
Medical X-ray imaging.
II. BLOCK DIAGRAM
Fig: 2. Block diagram
The input AC supply is given to rectifier to covert AC into DC.This DC is given to single phase full-Bridge inverter through filter to covert DC into AC.This AC is given to the isolation transformer. The isolation transformer output is given to the full-bridge uncontrolled rectifier to covert AC into DC.The output DC supply is given to the load. The load will be a DC motor Load. On/off process of MOSFET switch is controlled by pulse width modulation circuit (PWM).
III. PROPOSED SCHEME
Fig: 3. Proposed Converter Circuit
Vin - Input Voltage
iL - Inductor Current
ir - Resonant current
T1 to T4 - MOSFETs
Lin - Input Inductor
Always on Time
Marked to Standard
Io - Output Current
CT1 to CT4 - MOSFET parasitic
L - Inductor
C - Transformer Parasitic
Ll - Transformer Leakage
CF - Capacitive filter
IV. SIMULATION OUTPUTS
A. Simulation circuit
Fig: 4a. Simulation Circuit
B. Simulation output
Triggering pulses to MOSFET 1 &2
Fig : 4b. PWM pulse for T1 and T2
Triggering pulses to MOSFET 3 &4
Fig: 4b. PWM pulse for T3 and T4
Fig: 5. Current Vs Time
Fig: 6. Voltage Vs Time
Fig: 7. Enlarge output of Current VsTime
Fig: 8. Enlarge output of Voltage VsTime
This paper has presented a current -fed resonant full-bridge dc/ac/dc converter system with transformer isolation. The dc/ac converter is controlled by varying the control frequency and the constant MOSFET turn-off time. During the whole control range, the MOSFET current and voltage waveforms do not overlap, so the switching power dissipations do not occur. The ac/dc rectifier diodes operate in discontinuous range so their switching power dissipations are also minimized. Thus, high efficiency of the system can be obtained. Due to the fact that all of the parasitic capacitances and inductances are included in the resonant or filter circuits, the system does not generate parasitic oscillations and is devoid of uncontrolled high voltage and current spikes.
The proposed converter has very attractive features, such as ZCS for all active switches, no diode reverse recovery problems due to soft commutation of rectifier diodes, simple topology structure, and convenient control strategy. It seems more attractive in high power applications using MOSFET as main switches, and high efficiency can be achieved. Experimental results confirm the theoretical and simulation analysis.
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