Analysis and Simulation of Novel Soft Switching High Frequency Boost Converter

Analysis and Simulation of Novel Soft Switching High Frequency Boost Converter

Aparna Surendran

MTech Research Scholar Electrical and Electronics Engineering

Govt.Engineering College,Idukki Idukki, India

Ms. Frieda Mohan

Asst. Professor

Electrical and Electronics Engineering Govt.Engineering College,Idukki Idukki, India

Abstract- This paper presents the analysis and simulation of a new type of soft switching boost converter used for high frequency applications. It has an active snubber cell that provides main switch to turn ON with zero voltage transition and to turn OFF with zero current transition. The proposed converter can be operated at high frequencies. In this converter all semiconductor devices operating under soft switching. Also in this converter, there is no additional voltage stress across the main and auxiliary components. Also a modified soft switching converter is also given in this paper. That can be used for ac voltage applications and it can be extended to be used in LED lighting applications. The operation, design and analysis of this PWM boost converter and simulation of new topology is also given in this paper.

Index TermsBoost converter, soft switching, zero voltage switching(ZVS), zero current switching(ZCS), zero voltage transition(ZVT), zero current transition(ZCT)

I.INTRODUCTION

High frequency PWM DC-DC converters are generally used in renewable energy applications, battery charging, lighting applications and power factor correction due to their fast response and high power density. To achieve high power density and small converter size, it is required to operate converter at high switching frequency. But high frequency operation results in increased switching losses, high converter efficiency and higher electromagnetic interference. By using soft switching all these disadvantages can be minimized. Soft switched resonant dc-dc power converters are able to maintain high efficiency for increased switching frequency[1].

In this paper, a new type of boost converter with active snubber cell is proposed. In this converter, the main switch turn ON with ZVT and turn OFF with ZCT. Also, in this converter, all the semiconductor devices operate under soft switching. The proposed converter also have a simple structure and it is of low cost[2]. Following the introduction, the system configuration is given in section . Section describes the operation modes of the converter. In section IV, a deeper analysis of the converter is presented. Section V provides simulation results to validate the analysis. Finally, conclusions are given in section VI.

1. SYSTEM CONFIGURATION

   The system configuration of the soft switching high frequency boost converter is depicted in Fig.1.

   Fig.1.Circuit diagram of the proposed Converter

   In this circuit is the input voltage, is the main inductor, is the main switch, is the auxiliary switch, is the main diode, is the output filter capacitor, is the snubber capacitor, is the parasitic capacitor, is the snubber inductor and is the output voltage. The main

   switch consist of the main transistor (IGBT) and body diode . The auxiliary switch consist of transistor (MOSFET) and body diode . Here the parasitic capacitor

   is assumed to be the sum of the parasitic capacitor of and the other parasitic capacitors incorporating it.

   During one switching cycle, the following assumptions are made. The input and output voltages and input current are assumed to be constant and the reverse recovery time of is taken into account. The semiconductor devices and resonant circuit are assumed to be ideal for simplification.

2. OPERATION MODES

   Operation modes of the proposed soft switching boost converter. (a)mode 1; (b)mode 2; (c)mode 3; (d)mode 4;

   (e)mode 5; (f) mode 6; (g) mode 7; (h) mode 8; (i) mode 9; (j)

   mode 10; (k) mode 11

   Mode 1: At the beginning of this mode, the main transistor and auxiliary transistor are in the off state. The main diode

   is in the ON state and let the beginning of mode 1 be the OFF state of the conventional boost converter. Let the input current flows through the main diode. So in the beginning, =0; =0; =; and =.

   The mode 1 begins by applying a turn on signal to the gate of the auxiliary transistor . Now a resonance starts between the snubber inductance and the snubber capacitance . Due to the resonance, current rises and currents falls simultaneously. The rate of rise of the current is limited by the snubber inductance that connected in series with the auxiliary switch. So the turn on of the auxiliary switch provided with ZCS. At the end of this mode, the snubber capacitance voltage charged to .

   reaches and falls to zero. When reaches – ,

   is turned OFF and this stage finishes. So in mode 1, turns on with zero voltage switching and turned OFF with nearly zero voltage switching and zero current switching.

   Mode 2: At the beginning of this =0; = = + ; =0; = and =. The main diode and main transistor are in the OFF state. The auxiliary transistor is in the ON state and that conduct the sum of the input current and the reverse recovery current of .

   This mode begins with a resonance between the parasitic capacitor , snubber capacitance and the snubber inductance . This mode finishes with the parasitic capacitance voltage becomes 0.Thus the energy stored in the parasitic capacitor will be completely transferred to the resonance circuit. At the end of this mode, diode turns ON with nearly zero voltage switching. At the end of this mode,

   =.

   Mode 3: Just after the diode turned ON, i.e. at the beginning of this =0; = , =0, =0 and

   =.

   In this mode, the resonance between the snubber inductance and the snubber capacitance continuous. Here the diode is turned ON and that will conduct the excess of the snubber inductance current from the input current. This interval is called the ZVT duration of the main transistor. At the end of this mode, a control signal is applied to the gate of the main transistor . The diode is kept turned ON in order to provide ZVT turn On of .This mode ends with the snubber inductance current falls to input current and the diode turned OFF under ZCS.

   Mode 4: This mode begins when the diode is turned OFF. At the beginning of this =0, = =, =0,

   =0 and =.

   The main transistor turns ON with ZVT and its current starts to rise. The resonance between snubber inductance . and snubber capacitor continuous. At the end of this mode, the main transistor current reaches to Ii and

   becomes z0ero. this mode ends by removing the control signal of the auxiliary transistor.

   Mode 5: At the beginning of this mode, the auxiliary transistor is turned OFF under ZCT. And at the beginning, =, = =0, =, =0 and =0.

   This mode begins with the turn ON of the diode with zero current switching and its current starts to rise. The resonance between snubber inductance and snubber capacitance continuous in this mode. become negative and the current through the main transistor current becomes higher than the input current. At the end of this mode, the main transistor current decreases to input current level and becomes zero. Then becomes 0 and turned OFF under ZCS at the end of this mode.

   Mode 6: At the beginning of this mode, =, ===0, =0, = and =0.

   In this mode, the main transistor continuous to conduct the input current Ii and in this case, the snubber circuit is not active. This mode can be stated as the ON state of the conventional boost converter. The ON state duration can be controlle by the PWM control.

   Mode 7: At the beginning of this =, ==0, =0,= and =0.

   This mode begins by applying a control signal to the gate of the auxiliary transistor . Then a new resonance between snubber inductance and snubber capacitor starts. In this mode, the auxiliary transistor turned ON with ZCS. At the end of this mode, the current through the auxiliary transistor current reaches input current level and the main transistor current becomes zero.

   Mode 8: At the beginning of this mode, =0,==, =0, = and =0.

   This mode begins when current falls to zero so that turns ON with ZCS. can be turned OFF after the turn ON of so that can be turned OFF under ZCS and ZVS. The resonance between and continuous in this mode also. This mode ends by the turn OFF of .

   Mode 9: This mode begins after the turn OFF of under ZCS. At the beginning of this mode,

   =0,===, =0, == and =0.

   Now a resonance between parasitic capacitor , snubber inductance and snubber capacitor starts and falls to zero and the capacitor charged from 0 to . At the end of this mode, the control signal from the auxiliary transistor is removed. So that, is turned OFF under ZCS.

   Mode 10: At the beginning of this =0, ===0, =0, == and =.

   During this mode, the parasitic capacitor is charged linearly under the input current. At the end of this mode, voltage across reaches the output voltage and the main diode is turned ON under ZVS. This mode finishes.

   Mode 11: At the beginning of this =0, ==0,

   =, = and =.

   This mode can be stated as the OFF state of the conventional boost converter. During this mode, the main diode continuous to conduct the input current , and the snubber circuit is not active. The duration of this mode can be controlled by the PWM control. This is the end of one switching cycle. After this another switching cycle starts.

3. SIMULATUON RESULTS

First conventional hard switching boost converter simulation is performed with input voltage Vin = 12V, output voltage Vo = 28V, output power Po = 100W and switching frequency of main switch = 100 kHz .Fig 3. Shows the PSIM schematic layout of this hard switching boost converter.

Fig.3. Circuit layout of hard switching boost converter in PSIM

Fig.4. Input and Output voltages

Fig.5. Switching pulse of main Switch

Fig.6. Voltage and Current waveform across the main switch

From the results, we understood that the losses across the main switch is very high. So a new snubber circuit is introduced to reduce the switching losses by employing zero voltage and zero current transition across the main and auxiliary switches and the main diodes. So the switching losses can be reduced by reducing the overlap between the voltage and current waveforms across the switches.

The performance of the high frequency soft switching boost converter with zero voltage and zero current transition was evaluated and simulated a with following specification using PSIM software: input voltage Vin = 12V, constant output voltage of Vo = 28V, output power Po = 100W, switching frequency of main switch = 100 kHz and switching frequency of auxiliary switch = 100 kHz. Fig.3 shows the PSIM schematic layout of this converter. Simulation results are illustrated in Fig. 7 to Fig.10.

Fig.7. Circuit layout of soft switching boost converter in PSIM

Fig.8. Input and Output voltage waveforms

Fig.9. Gate signals of main and auxiliary transistors

Fig.10. Voltage and Current waveform across main switch

From the simulation results, we can see that the overlap between the voltage and current waveform is reduced. So the switching losses also reduced. So the efficiency is also increased in this converter. So zero voltage and zero current transition can reduces the switching losses.

A new topology is also introduced to work with ac voltage also. It is employed with soft switching to reduce switching losses across the main and auxiliary switches and other semiconductor devices also. It can be extended to use in the brightness control of LED lights.

Fig.14.Input and Output voltage waveforms

Fig.15. gate pulses of main and auxiliary switches.

Fig.12. Circuit layout of new topology in PSIM

Fig.13. input ac voltage waveform

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