CHAPTER 1

INTRODUCTION

1.1 POWER ELECTRONICS

Power electronics is the field of electrical engineering related to the use of

semiconductor devices to convert power from the form available from a source to
that required by a load. The load may be AC or DC, single-phase or three-phase,
and may or may not need isolation from the power source. The power source can
be a DC source or an AC source (single-phase or three-phase with line frequency
of 50 or 60 Hz), an electric battery, a solar panel, an electric generator or a
commercial power supply. A power converter takes the power provided by the
source and converts it to the form required by the load. The power converter can be
an AC-DC converter, a DC-DC converter, a DC-AC inverter or an AC-AC
converter depending on the application.

1.2 DC-DC CONVERTER

An dc to dc converter is an integral part of any power supply unit used in the

all electronic equipments. Also, it is used as an interface between utility and most
of the power electronic equipments. These electronic equipments form a major part
of load on the utility. Generally, to convert line frequency ac to dc, a line
frequency diode bridge rectifier is used. To reduce the ripple in the dc output
voltage, a large filter capacitor is used at the rectifier output. But due to this large
capacitor, the current drawn by this converter is peaky in nature. This input current
is rich in low order harmonics. Also, as power electronics equipments are
increasingly being used in power conversion, they inject low order harmonics into
the utility. Due to the presence of these harmonics, the total harmonic distortion is

1
high and the input power factor is poor. Due to problems associated with low
power factor and harmonics, utilities will enforce harmonic standards and
guidelines which will limit the amount of current distortion allowed into the utility
and thus the simple diode rectifiers may not in use. So, there is a need to achieve
rectification at close to unity power factor and low input current distortion.
Initially, power factor correction schemes have been implemented mainly for
heavy industrial loads like induction motors, induction heating furnaces etc., which
forms a major part of lagging power factor load. However, the trend is changing as
electronic equipments are increasingly being used in everyday life nowadays.
Hence, PFC is becoming an important aspect even for low power application
electronic equipments.

The CF-IBDCs mentioned above have low input current ripple and the high
voltage spike is reduced by using the clamp circuit, which however increases the
power losses and circuit complexity. In addition, these converters and their
control schemes cannot ensure all switches achieve ZVS over the full operating
range. However, all switches in the boost half-bridge CF-IBDC proposed in can
realize ZVS over the full operating range by the PWM plus phase shift control,
and the high voltage spike across the LV side switches is inexistent without
additional snubber circuits.

2
 CHAPTER 2

LITERATURE SURVEY

TITLE: Rotating Phase Shedding for Interleaved DC–DC Converter-Based

EVs Fast DC Chargers

AUTHOR: Abraham M. Alcaide

YEAR: 2020

DESCRIPTION:

Fast dc chargers are the key enablers for the massive rollout of electric vehicles
due to the reduced charging time. On the other hand, the rapid growth in battery
technology with different voltages and charging requirements has imposed
additional hurdles on the charger design to meet the efficiency requirements.
Multiphase interleaved converters with conventional phase-shedding control
improve the efficiency for a wide range of operations. However, they tend to
operate certain phases, resulting in uneven thermal stress among the converter
phases. This article proposes a rotating phase-shedding control to distribute the
switching activities among all phases, enhancing the system’s reliability while
retaining the efficiency improvement. The proposed technique selects the proper
number of active phases based on the required charging profile and periodically
swaps them with other phases to even out the stress. The thermal profile is
extracted to assess the thermal damage of the power switches. The performance of
the proposed approach is evaluated and compared with the conventional phase
shedding. The simulation and experimentally validated results confirm that the
proposed technique achieves a better even distribution of the thermal damage
between the phases compared with the conventional one. This will ultimately
extend the lifetime of the system.

3
TITLE: Isolated 3-Level DC–DC Converter With Complete ZVS Using
Magnetizing Inductors

AUTHOR: EHAB TARMOOM

YEAR:2018

DESCRIPTION:

An isolated dc–dc converter with dedicated 3-level modulation is proposed to

achieve a 4:1 output voltage range, and complete zero-voltage-switching (ZVS) of
all active switches using the magnetizing inductors. The single input 3-level
modulation scheme coordinates the phase-shift, duty cycle, and switching
frequency to ensure 1) the magnetizing currents are independent of load voltage
and current; 2) the output voltage is proportional to the modulation input. As a
result, the dual half- and full-bridge modes of the switching network are unified
and modeled as a voltagecontrolled voltage source, with the same control
parameters for both modes of operation. In addition, the magnetizing-to-series
inductance ratios of the leading and lagging transformers are increased to 100 and
25 times, respectively. Therefore, the circulating current is low, and the series
inductors can be integrated into the transformers. The proposed topology is
intended for high-power applications with a wide output voltage range but less
input voltage variation. A 30 kW prototype with a power density of 7.2 kW/L and
an output voltage of 165 V-680 V was built and tested to verify the characteristics
and feasibility of the proposed H8 topology plus modulation scheme.

4
TITLE: A HIGH POWER DENSITY WIDE RANGE DC – DC
CONVERTER FOR UNIVERSAL ELECTRIC VECHICLE CHARGING

AURHOR:SATYAKI MUKHERJEE

YEAR:2011

DESCRIPTION:

A straightforward way to extend the ZVS range is to proportionally increase the

magnetizing current as the phase-shift increases . Nonetheless, the magnetizing
inductor remains shorted during the lagging leg transition, and ZVS is lost at low
phase-shift and light load conditions during the passiveto-active transition. Another
approach is to add the constant magnetizing current of another converter to the
current of the series inductor to extend the ZVS range of the lagging leg . But in
the free-wheeling stage, since the two transformers on the secondary side are
connected in series, a circulating current will be generated. As a result, excessive
conduction loss is caused. The circulation problem is alleviated in , but the
circulation current still exists. The voltage stress on the secondary-side diodes is
much higher due to the small resetting capacitor. Additionally, single full-bridge
operation mode suffers from the same issue as traditional PSFBs. Another
approach is combining the ZVS principle of the LLC with a buck-type PSFB. The
idea is that the output is clamped and supported by a voltage source during the
transition to force theLm in series withLk and then charge/discharge Coss together.
The solution in and exploits this principle to achieve a full-range ZVS for the
leading leg. But the lagging leg can only achieve zero-current-switching (ZCS).

5
 CHAPTER 3

EXISTING SYSTEM

Efficient power conversion technologies are strategic to the

advancement of fuel cell vehicles (FCV). This paper presents an overview of
power conditioning system (PCS) architectures for FCV propulsion system. Two
new power conversion topologies to obtain variable ac from the fuel cell system
are proposed. The switching of the power devices are based on the proposed
hybrid modulation technique that minimizes the switching losses in the inverter.
The proposed converters do not use the dc link filter capacitors. Elimination of
dc-link capacitor not only reduces the size and volume, it also helps in retaining
the sine wave modulated information at the input of three-phase inverter.
Bidirectional converter topologies are proposed for interfacing low voltage battery
and fuel cell dc bus. Experimental results are presented for the proposed
topologies

This work presents an automated design procedure for series parallel

resonant converters (LCC) employed in electrostatic precipitator (ESP) power
supplies, which reduces the designer effort significantly. The requirements for the
power supplies in ESP applications andmeans to derive an accuratemathematical
model of the LCC converter, such as the power loss from commercial insulated-
gate bipolar transistors, are described in detail in this paper. The converter
parameters, such as resonant tank elements, are selected in order to improve the
overall efficiency of the system, when a typical ESP energization operation range
is considered. The analysis comprises two different control strategies: the
conventional variable frequency control and the dual control. Both control
strategies are analyzed by comparing semiconductor losses of five commercial

6
modules. Finally, the circuit operation and design are verified with a 60 kWLCC
resonant converter test setup.

3.1 Block diagram of existing system

AC Full bridge Isolation Rectifier Filter DC

Source Inverter transformer Load

Firing circuit

Controller DC supply

7
 Fig 3.1 Block diagram

3.2 Existing system circuit diagram

Fig 3.2: hybrid-type full-bridge dc/dc converter

3.3 PRINCIPLE OPERATION

The proposed converter on the primary side of the power transformer T, the
proposed converter has an FB circuit with one blocking diode DB and one clamp
capacitor Cc. On the secondary side, there is a voltage doublers rectifier. The
operation of the proposed converter can be classified into two cases. One is a PSFB
series-resonant converter mode and the other is an active-clamp step-up converter
mode.
To analyze the steady-state operation of the proposed converter, several
assumptions are made:
1) all switches S1 , S2 , S3 , and S4 are considered as ideal switches except for
their body diodes and output capacitors;

8
2) the clamp capacitor Cc and output capacitor C o are large enough, so the clamp
capacitor voltage Vc and output voltage Vo have no ripple voltage, respectively;
3) The transformer T is composed of an ideal transformer with the primary
winding turns Np, the secondary winding turns Ns , the magnetizing inductance
Lm, and the leakage inductance Llk ;
4) The capacitance of the resonant capacitors Cr1 and Cr2 is identical. Thus, Cr1 =
Cr2.

9
 CHAPTER 4

PROPOSED SYSTEM

4.1 Proposed System

 The proposed converter is simple circuit structure using with half bridge
series resonant converter.
 The half bridge converter act as a series resonant converter by applying soft
 switching and output voltage is accurate.

4.2 Block Diagram of proposed system

DC Micro Isolation Rectifier Filter AC

Source Inverter transformer Load

Firing circuit

Fig 4.2 Block Diagram of proposed system

Controller DC supply
The block diagram represents for the
dc-dc conversion the dc source is applied for the half bridge inverter, then the filter
section is filter for the noise and the isolation transformer is used to isolate for
primary and secondary side of the supplies.

Then bridge rectifier is rectified for the voltage and finally filter out the
unwanted noise, and then given to the output dc voltage in the R load.

4.3 Circuit Diagram of proposed system

10
 Fig 4.3 Circuit Diagram of proposed system

4.3.1 Operation of the converter

The operation of the converter input dc voltage applied to the half bridge
converter is convert the dc signal into ac signal then series filter is filter out the
unwanted noise in the circuit.

Then the isolating transformer is used to isolate the primary and secondary
side of the transformer; applies the signal is bridge rectifier, rectification of the
voltage and rectified supplies is sent to the filter.

Then output filter is filtered for the noises in the converter, finally the dc
signal is sent for the output. They have given to the dc voltage in R load.

Advantages

 Simple circuit structure.

 High power density.
 Reduction of conduction losses.
 High efficiency.

4.4 CONTROLLER

11
 Controllers are to perform a controlled operation and to obtain the desired
output. Mainly controllers have 3 modes they are P-Proportional, I-Integral, D-
derivative. One mode combines with another mode to create various controllers.
There are 3 main controllers used for controlling, they are

 P Controller

 PI Controller

 PID Controller

4.4.1 P Controller

In general it can be said that P controller cannot stabilize higher order

processes. For the 1st order processes, meaning the processes with one
energy storage, a large increase in gain can be tolerated. Proportional
controller can stabilize only 1st order unstable process. Changing controller
gain K can change closed loop dynamics. A large controller gain will result in
control system with:

a) Smaller steady state error, i.e. better reference following

b) Faster dynamics, i.e. broader signal frequency band of the closed

loop system and larger sensitivity with respect to measuring noise

c) Smaller amplitude and phase margin

When P controller is used, large gain is needed to improve steady

state error.

Stable systems do not have problems when large gain is used. Such systems are
system switch one energy storage (1st order capacitive systems).

12
4.4.2 PI Controller

PI controller will eliminate forced oscillations and steady state error

resulting in operation of on-off controller and P controller respectively.
Introducing integral mode has a negative effect on speed of the response
and overall stability of the system. Thus, PI controller will not increase the speed
of response. It can be expected since PI controller does not have means to predict
what will happen with the error in near future. This problem can be solved by
introducing derivative mode which has ability to predict what will happen with
the error in near future and thus to decrease a reaction time of the controller.

PI controllers are very often used in industry, especially when speed

of the response is not an issue. A control without D mode is used when:

a) Fast response of the system is not required

b) Large disturbances and noise are present during operation of the process

c) There is only one energy storage in process (capacitive or inductive)

d) There are large transport delays in the system

CHAPTER 5

HARDWARE REQUIREMENTS
13
5.1 POWER SUPPLY SECTION OF MICROCONTROLLER

5.1.1 Step down Transformer

When AC is applied to the primary winding of the power transformer it can

either be stepped down or up depending on the value of DC needed. In this circuit
the transformer of 230V/12-0-12V is used to perform the step down operation
where a 230V AC appears as 12V AC across the secondary winding. One
alteration of input causes the top of the transformer to be positive and the bottom
negative. The next alteration will temporarily cause the reverse. The current rating
of the transformer used in this project is 500mA. Apart from stepping down AC
voltages, it gives isolation between the power source and power supply circuits.

5.1.2 Diodes

Rectifier diodes are used in power supplies to convert alternating current

(AC) to direct current (DC), a process called rectification and it allows current in
only one direction. A bridge rectifier of four diodes (4*1N4007) is used to achieve
full wave rectification. Two diodes will conduct during the negative cycle and the
other two will conduct during the positive half cycle. The 1N4007 is suitable for
most low voltage circuits with a current of less than 1A.

5.1.3 Filtering Unit

Filter circuits, which usually capacitor is acting as a surge arrester, always,

follow the rectifier unit. This capacitor is also called as a decoupling capacitor or a
bypassing capacitor, is used not only to short the ripple with frequency of 130Hz to
ground but also to leave the frequency of the DC to appear at the output.

1000µF: for the reduction of ripples from the pulsating.

14
 100µF: for bypassing the high frequency disturbances

5.1.4 Voltage regulator

The voltage regulators play an important role in any power supply unit. The
primary purpose of a regulator is to aid the rectifier and filter circuit in providing a
constant DC voltage to the device. Power supplies without regulators have an
inherent problem of changing DC voltage values due to variation in the load or due
to fluctuations in the AC linear voltage. With a regulator connected to the DC
output, the voltage can be maintained within a close tolerant region of the desired
output.

5.1.5 Fixed voltage regulators:

a) Positive voltage regulator:

The 78xx series consists of three terminal positive voltage regulators with
seven voltage options. These ICs are designed as fixed voltage regulators and
with adequate heat sinking can relieve output currents in excess of 1 A.

We used 7812, 7815 & 7805 IC voltage regulators, they give output voltages
of +12v, +15 V and +5v respectively.

b) Negative voltage regulator:

The 79xx series of fixed output negative voltage regulators are

complements to the 78xx series devices. These regulators are also three
terminal devices. The three terminals are ground, input and output.

We used 7912 IC voltage regulator to give output voltage of –12v.Almost all

power supplies use some type of voltage regulator IC because voltage
regulators are simple to use, reliable, low in cost and available in a variety of
voltage and current ratings.

15
 These ICs are monolithic silicon chip and it is a fixed voltage regulator type,
which gives low cost, high reliability, reduction in size and excellent performance.
In this regulator, a capacitor is usually connected between the input terminal and
ground to cancel the inductive effects due to long distribution leads. The output
capacitor improves the transient response. Thus the filtered DC voltage is regulated
using 7805, 7812 and7912.

5.1.5 Resistor

Resistors are "Passive Devices", that is they contain no source of power or

amplification but only attenuate or reduce the voltage signal passing through them.
This attenuation results in electrical energy being lost in the form of heat as the
resistor resists the flow of electrons through it.
5.2 MICROCONTROLLER SECTION
5.2.1 PIC16F877A MICROCONTROLLER
It is a 40 pin 8-Bit CMOS FLASH microcontroller. The microcontrollers are
similar to microprocessors, but they are designed to work as a true single-chip
system by integrating all the devices needed for a system on a single-chip. The
timing and control unit will generate the necessary control signals for internal and
external operation of the microcontroller. Microcontrollers with internal ADC can
directly accept analog signals for processing.

The switching pulses required for inverter operation are generated using
PIC16F877A Microcontroller, thus reducing the overall system cost and
complexity. The Microcontroller generates a PWM pulse at Particular frequency
and switching pulses for the MOSFET switches.

16
 The crystal oscillator is used to generate the required clock for the
Microcontroller. Here we used Quartz Crustal oscillator. The maximum clock
frequency of quartz crystal that can be connected to Pic16f877a microcontroller is
20MHz. The internal clock frequency of microcontroller is same as crystal
frequency or externally supplied clock frequency. The Reset switch is used to reset
the microcontroller in order to bring the controller to a known state, for proper
reset the RST pin should be held low for at least 2 machine cycles.
5.2.1.1 General Features of “PIC”

 Power saving capability

 Easily programmable and executable devices
 Oscillator
 Oscillator start - up timer
 Real time clock

5.2.1.2 Micro Controller Core Features

 High performance RISC CPU
 Only 35 single word instructions to learn
 All single cycle instructions except for program branches which are two
cycles.
 Up to 8K x 14 words of flash memory
 Up to 368 x 8 bytes of data memory (RAM)
 Up to 265 x 8 bytes of EEPROM data memory
 Interrupt capability up to 14 sources
 Power-on Reset(POR)
 Power-up timer (PWRT) and Oscillator Start-up timer.
 Programmable code protection

17
  Power saving SLEEP mode

Fig 5.2.1 PIN DIAGRAM

Peripherals

The programmable peripheral device is designed to perform various

input/output functions. Every programmable device will have one (or) more
Instructions. The control word instruction which informs the peripheral about
various functions it has to perform.

Peripheral Features
 33 I/O pins; 5 I/O ports
18
  Timer0: 8-bit timer/counter with 8-bit prescaler
 Timer1: 16-bit timer/counter with prescaler
 Can be incremented during Sleep via external crystal/clock
 Timer2: 8-bit timer/counter with 8-bit period register, prescaler and
postscaler
 Two Capture, Compare, PWM modules
 16-bit Capture input; max resolution 12.5 ns
 16-bit Compare; max resolution 200 ns
 10-bit PWM
 Synchronous Serial Port with two modes:
 SPI Master
 I2C Master and Slave
 USART/SCI with 9-bit address detection
 Parallel Slave Port (PSP)
 8 bits wide with external RD, WR and CS controls
 Brown-out detection circuitry for Brown-Out Reset
 10-bit, 8-channel A/D Converter
 Analog Comparator module
 2 analog comparators
 Programmable on-chip voltage reference module
 Programmable input multiplexing from device inputs and
internal VREF
 Comparator outputs are externally accessible

Special Microcontroller Features

 Flash Memory: 14.3 Kbytes (8192 words)
 Data SRAM: 368 bytes
19
  Data EEPROM: 256 bytes
 Self-reprogrammable under software control
 In-Circuit Serial Programming via two pins (5V)
 Watchdog Timer with on-chip RC oscillator
 Programmable code protection
 Power-saving Sleep mode
 Selectable oscillator options
 In-Circuit Debug via two pins

Architectural Overview

PIC 16F877A Architecture has the program and data accessed from separate
memories. So the device has a program memory bus and a data memory bus
separating program and data memory further allows instruction to be sized
different than the 8 bit wide data word.

PIC 16F877A op codes are 14bit wide enabling a single word instruction. A
two stage pipeline overlaps fetch and execution of instruction consequently all
instruction in single cycle except program branches and conditions test.
ALU

The ALU is a general purpose arithmetic unit. It performs arithmetic and

Boolean function between data in the working register. The ALU is 8bit side and
capable of addition, subtraction, shift and logical operations.

Register

20
 It is an eight bit register. It is extensively used to store a Arithmetic Logic
units outputs most of the time, the result of arithmetic and logic operation in stored
in this register.
Program Counter
Program is a sequence of instruction set. In Micro controller instruction is
execute sequentially program counter stores the address of the next instruction to
be fetched.
Stack
Stack pointer is 8 level deep x 13bit wide hardware stack. Stack pointer is
used to hold the address of the most recent stack entry.
I/0 Ports
In PIC microcontroller 5 port is used. All ports can be used as input/output
function. Some special function also handles in this port like A/D converter,
parallel slave port, Interrupt control functions.
Status Register
The status register can be destination for any instruction as with any other
register. Depending on the instruction executed, the ALU may affect the value of
the carry ©, digit carry and zero (z) in the status register. The C and DC bits
operated as borrow and digit borrow out bit respectively in subtraction.
General Purpose Register File
The register file can be accessed either directly or indirectly through the File
Select Register (FSR).

Special Function Registers

21
 The Special Function Registers are registers used by the CPU and peripheral
modules for controlling the desired operation of the device. These registers are
implemented as static RAM. The Special Function Registers can be classified into
two sets: core (CPU) and peripheral.

I/O Ports
PORT A and the TRIS A Register
PORTA is a 6-bit wide, bi-directional port. The corresponding data direction
register is TRISA. Setting a TRISA bit (= 1) will make the corresponding PORTA
pin an input. Clearing a TRISA bit (= 0) will make the corresponding PORTA pin
an output. Pin RA4 is multiplexed with the Timer0 module clock input to become
the RA4/T0CKI pin.
PORT B and the TRIS B Register
PORTB is an 8-bit wide, bi-directional port. The corresponding data
direction register is TRISB. Setting a TRISB bit (= 1) will make the corresponding
PORTB pin an input. Clearing a TRISB bit (= 0) will make the corresponding
PORTB pin an output Three pins of PORTB are multiplexed with the Low Voltage
Programming function: RB3/PGM, RB6/PGC and RB7/PGD. Each of the PORTB
pins has a weak internal pull-up. A single control bit can turn on all the pull-ups.
This is performed by clearing bit (OPTION_REG<7>). The weak pull-up is
automatically turned off when the port pin is configured as an output. The pull-ups
are disabled on a Power-on Reset.

PORT C and the TRIS C Register

22
 PORTC is an 8-bit wide, bi-directional port. The corresponding data
direction register is TRISC. Setting a TRISC bit (= 1) will make the corresponding
PORTC pin an input. Clearing a TRISC bit (= 0) will make the corresponding
PORTC pin an output PORTC is multiplexed with several peripheral functions.
PORT D and TRIS D Registers
PORTD and TRISD are not implemented on the PIC16F873 or PIC16F876.
PORTD is an 8-bit port with Schmitt Trigger input buffers. Each pin is
individually configurable as an input or output. PORTD can be configured as an 8-
bit wide microprocessor port (parallel slave port) by setting control bit PSPMODE
(TRISE< 4 >).
PORT E and TRIS E Registers
PORTE has three pins (RE0/RD/AN5, RE1/WR/AN6, and RE2/CS/AN7)
which are individually configurable as inputs or outputs. These pins have Schmitt
Trigger input buffers. PORTE pins are multiplexed with analog inputs. When
selected for analog input, these pins will read as ’0’s. TRISE controls the direction
of the RE pins, even when they are being used as analog inputs. The user must
make sure to keep the pins configured as inputs when using them as analog inputs.

4.2.2 ANALOG –TO - DIGITAL CONVERTER (A/D)

The Analog-to-Digital (A/D) Converter has eight inputs. The analog input
charges a sample and hold capacitor. The output of the sample and hold capacitor
is the input into the converter. The converter then generates a digital result of this
analog level via successive approximation. The A/D conversion of the analog input
signal results in a corresponding 10-bit digital number. The A/D module has high
and low voltage reference input that is software selectable to some combination of
VDD, VSS, RA2, or RA3.

23
 The A/D converter has a unique feature of being able to operate while the
device is in SLEEP mode. To operate in SLEEP, the A/D clock must be derived
from the A/D’s internal RC oscillator.
The A/D module has four registers. These registers are:
• A/D Result High Register (ADRESH)
• A/D Result Low Register (ADRESL)
• A/D Control Register0 (ADCON0)
• A/D Control Register1 (ADCON1)

Memory Organisation

There are three memory blocks in PIC16F877A. The Program memory and
Data Memory block have separate buses so that concurrent access can occur. The
EEPROM data memory block is also used.

 Program Memory Organization

The PIC16F877A device has 13-bit program counter capable of

addressing an 8K x 14 program memory space. The RESET vector is at
0000h and the interrupt vector is at 0004h.

 Data Memory Organization

The data memory organization is portioned into multiple banks which

contain the General Purpose Registers and the Special function registers.
Bits RP1 and RP0 are the bank select bits.

24
Timer Modules

The timer0 module has the following features:

 8 bit timer/counter

 Readable and writable

 8 bit software programmable pre scalar

 Internal or external clock select

 Interrupt on overflow from FF to 00h

 Edge select for external clock.

Timer1 Module

The timer1 module is a 16-bit timer/counter consisting of two 8-bit registers

(TMR1H and TMR1L), which are readable and writable. The TMR! Register pair
increments from 0000h. The TMR1 Interrupt, if enabled, is generated on overflow,
which is latched in interrupt flag bit. This interrupt can be enabled/disabled by
setting/clearing TMR1 interrupt enabled bit. Timer1 can operate in one of the two
modes:

 As a counter.

 As a timer.

Timer2 Module

Timer2 is an 8-bit timer with a pre scalar and a post scalar. It can be used as
the PWM time base for the PWM mode of the CCP module. The timer2 register is

25
readable and writeable, and is cleared on any device RESET. Timer2 increments
from 00h until it match PR2 and then resets to 00h on the next increment cycle.
PR2 is a readable and writable register. The PR2 register is initialized to FF h upon
RESET.
5.3 INDUCTOR
An inductor is a passive two-terminal electrical component that stores
energy in its magnetic field. For comparison, capacitor stores energy in an electric
field and a resistor does not store energy but rather dissipates energy as heat.
When the current flowing through an inductor changes, creating a time-
varying magnetic field inside the coil, a voltage is induced, according to Faraday's
law of electromagnetic induction, which by Lenz's law opposes the change in
current that created it. Inductors are one of the basic components used in
electronics where current and voltage change with time, due to the ability of
inductors to delay and reshape alternating currents.

5.4. IRFP460 (MOSFET)

A metal-oxide semiconductor field-effect transistor (MOSFET) is a recent
device developed by combining the areas of field-effect concept and MOS
technology. The MOSFETs are used as controllable switches (i.e.) these devices
can be turned on and turned off by the application of control signals.
5.4.1 Symbol of MOSFET
D D rain

G ate

S S o u rce

Fig 5.4 MOSFET

26
5.4.2 MOSFET with Snubber Circuit

A snubber circuit consists of a series combination of resistance R s and

capacitance Cs in parallel with the MOSFET. The capacitor C s in parallel with the

device is sufficient to prevent unwanted dv/dt triggering of the device.

RS CS

S
D S

G
Load

Fig 5.4.1 MOSFET with Snubber Circuit

The common function of a diode is to allow an electric current to pass in one
direction,(called the diode’s forward direction) while blocking current in the
opposite direction(the reverse direction).This unidirectional behavior is called
rectification, and is used to convert alternating current to direct current.
These diodes are connected in order to prevent the reverse current flow and it
is also connected with auxiliary switch to accommodate the switching direction.
The diode IN5408 has the voltage range of 50 to 1000 volts and current range of
3.0A.

27
5.5 FIRING CIRCUIT
5.5.1 6N137
The 6N137, HCPL2601, HCPL2611 single-channel opt couplers consist of a
850 nm AlGaAS LED, optically coupled to a very high speed integrated photo-
detector logic gate with a strobable output. This output features an open collector,
thereby permitting wired OR outputs.
Pin Diagram

Fig 5.5 6N137 pin diagram

5.5.2 2N3904
The 2N3904 is Silicon NPN Epitaxial General Purpose Amplifier. It is used
for general purpose low-power amplifying or switching applications. The useful
dynamic range extends to 100 mA as a switch and to 100 MHz as an amplifier. It
has Low saturation voltage.
5.5.3 2N3906
The 2N3906 is a common PNP bipolar junction transistor used for general
purpose low-power amplifying or switching applications. Compared to the general
run of silicon transistors, it is designed for low current and power and medium
voltage, and can operate at moderately high speeds. This device is designed for

28
general purpose amplifier and switching applications at collector currents of 10μA
to 100 mA
5.6 DIODE RECTIFIER

 A rectifier is an electrical device that converts alternating current (AC),

which periodically reverses direction, to direct current (DC), which flows in
only one direction. The process is known as rectification.
 A bridge rectifier makes use of four diodes in a bridge arrangement to
achieve full-wave rectification. This is a widely used configuration, both
with individual diodes wired as shown and with single component bridges
where the diode bridge is wired internally.
5.7 SOFTWARE DEVELOPMENT
5.7.1Introduction to C Programming For Embedded Systems

 C used for embedded systems is slightly different compared to C used for

general purpose (under a PC platform)
 Programs for embedded systems are usually expected to monitor and control
external devices and directly manipulate and use the internal architecture of
the processor such as interrupt handling, timers, serial communications and
other available features.
 There are many factors to consider when selecting languages for embedded
systems
 Efficiency - Programs must be as short as possible and memory
must be used efficiently.
 Speed - Programs must run as fast as possible.
 Ease of implementation
 Maintainability
 Readability

29
  C compilers for embedded systems must provide ways to examine and
utilize various features of the microcontroller's internal and external
architecture; this includes:
 Interrupt Service Routines
 Reading from and writing to internal and external memories
 Bit manipulation
 Implementation of timers / counters
 Examination of internal registers

Standard C compiler communicates with the hardware components via the

operating system of the machine but the C compiler for the embedded system must
communicate directly with the processor and its components.
POWER CIRCUIT

D1
D3

Ls C0
Din Lp
Rload
T1
D2
D4

Cin
Vin

S1
Lr

Fig 5.7 POWER CIRCUIT

30
5.8 Firing circuit

Fig 5.8 Firing circuit

31
CODE

#include<pic.h>
#include<htc.h>
#define _XTAL_FREQ 20000000
#define TMR2PRESCALE 4
long freq;
define PWM1 RB6;
define PWM2 RB5;
define PWM3 RB4;
define PWM4 RB3;
int PWM_Max_Duty()
{
return(_XTAL_FREQ/(freq*TMR2PRESCALE);
}
PWM1_Init(long fre)
{
PR2 = (_XTAL_FREQ/(freq*4*TMR2PRESCALE)) - 1;
freq = fre;
}
PWM2_Init(long fre)
{
PR2 = (_XTAL_FREQ/(freq*4*TMR2PRESCALE)) - 1;
freq = fre;
}
PWM3_Init(long fre)
{
PR2 = (_XTAL_FREQ/(freq*4*TMR2PRESCALE)) - 1;
freq = fre;
}
PWM4_Init(long fre)
{
PR2 = (_XTAL_FREQ/(freq*4*TMR2PRESCALE)) - 1;
freq = fre;
}
PWM1_Duty(unsigned int duty)
{
if(duty<1024)
{
duty = ((float)duty/1023)*PWM_Max_Duty();
32
 CCP1X = duty & 2;
CCP1Y = duty & 1;
CCPR1L = duty>>2;
}
}
PWM2_Duty(unsigned int duty)
{
if(duty<1024)
{
duty = ((float)duty/1023)*PWM_Max_Duty();
CCP2X = duty & 2;
CCP2Y = duty & 1;
CCPR2L = duty>>2;
}
}
PWM3_Duty(unsigned int duty)
{
if(duty<1024)
{
duty = ((float)duty/1023)*PWM_Max_Duty();
CCP3X = duty & 2;
CCP3Y = duty & 1;
CCPR3L = duty>>2;
}
}
PWM4_Duty(unsigned int duty)
{
if(duty<1024)
{
duty = ((float)duty/1023)*PWM_Max_Duty();
CCP4X = duty & 2;
CCP4Y = duty & 1;
CCPR4L = duty>>2;
}
}

PWM1_Start()
{
CCP1M3 = 1;
CCP1M2 = 1;
33
 #if TMR2PRESCALE == 1
T2CKPS0 = 0;
T2CKPS1 = 0;
#elif TMR2PRESCALE == 4
T2CKPS0 = 1;
T2CKPS1 = 0;
#elif TMR2PRESCALE == 16
T2CKPS0 = 1;
T2CKPS1 = 1;
#endif
TMR2ON = 1;
TRISC2 = 0;
}
PWM1_Stop()
{
CCP1M3 = 0;
CCP1M2 = 0;
}
PWM2_Start()
{
CCP2M3 = 1;
CCP2M2 = 1;
#if TMR2PRESCALE == 1
T2CKPS0 = 0;
T2CKPS1 = 0;
#elif TMR2PRESCALE == 4
T2CKPS0 = 1;
T2CKPS1 = 0;
#elif TMR2PRESCALE == 16
T2CKPS0 = 1;
T2CKPS1 = 1;
#endif
TMR2ON = 1;
TRISC1 = 0;
}
PWM2_Stop()
{
CCP2M3 = 0;
CCP2M2 = 0;
}
34
PWM3_Start()
{
CCP3M3 = 1;
CCP3M2 = 1;
#if TMR2PRESCALE == 1
T2CKPS0 = 0;
T2CKPS1 = 0;
#elif TMR2PRESCALE == 4
T2CKPS0 = 1;
T2CKPS1 = 0;
#elif TMR2PRESCALE == 16
T2CKPS0 = 1;
T2CKPS1 = 1;
#endif
TMR2ON = 1;
TRISC2 = 0;
}
PWM3_Stop()
{
CCP3M3 = 0;
CCP3M2 = 0;
}
PWM4_Start()
{
CCP4M3 = 1;
CCP4M2 = 1;
#if TMR2PRESCALE == 1
T2CKPS0 = 0;
T2CKPS1 = 0;
#elif TMR2PRESCALE == 4
T2CKPS0 = 1;
T2CKPS1 = 0;
#elif TMR2PRESCALE == 16
T2CKPS0 = 1;
T2CKPS1 = 1;
#endif
TMR2ON = 1;
TRISC2 = 0;
}
void main()
35
{
unsigned int i=0,j=0;k=0;
PWM1_Init(5000);
PWM2_Init(5000);
PWM3_Int(5000);
PWM4_Int(5000);
TRISD = 0xFF;
TRISB = 0;
PWM1_Start();
PWM2_Start();
PWM3_Start();
PWM4_Start();
do
{
if(RD0 == 0 && i<1000)
i=i+10;
if(RD1 == 0 && i>0)
i=i-10;
if(RD2 == 0 && j<1000)
j=j+10;
if(RD3 == 0 && j>0)
j=j-10;
if(RD4 == 0 && k<1000)
k=k+10;
if(RD5 == 0 && k>0)
k=k-10;
if(RD6 == 0 && k<1000)
l=l+10;
if(RD7 == 0 && k>0)
l=l-10;
PWM1_Duty(i);
PWM2_Duty(j);
PWM3_Duty(k);
PWM3_Duty(l);

__delay_ms(50);
}while(1);
}

36
 CHAPTER 6

CONCLUSION

 In this paper, a single-phase single-stage ZCS current-fed full-bridge AC/DC

converter is proposed aiming to IGBT-based high power lower cost PFC
applications. The benefit of this topology include: no DC link capacitor is
required; soft-switching is realized with few components added; to design a
new type of FLYBACK dc/dc converter with high efficiency, simple circuit
structure, soft switching is used in the proposed system. The conduction loss
is comparable with traditional solutions; reverse recovery loss is pretty low
since most of the diodes are soft-switching or turned off under half of the
DC voltage; the control strategy is compatible with that is used for
traditional PFC converter. A 3kw prototype is built in the paper to verify the
proposed circuit. The results show that the converter can realize soft-
switching for all IGBTs, and the THD is 5.2% at the rated operation point.
The efficiency is estimated to be around 93% to 94%. The circuit has shown
its capability of high power applications because of the using of IGBT and
ZCS operation.

37
 REFERENCE
1.J. A. Sabat´e, V. Vlatkovic, R. B. Ridley, F. C. Lee, and B. H. Cho, “Design
considerations for high-voltage high-power full-bridge zero-voltageswitching
PWM converter,” in Proc. Appl. Power Electron. Conf., 1990, pp. 275–284.
2. I. O. Lee and G. W. Moon, “Phase-shifted PWM converter with a wide ZVS
range and reduced circulating current,” IEEE Trans. Power Electron., vol. 28, no.
2, pp. 908–919, Feb. 2013.
3. Y. S. Shin, S. S. Hong, D. J. Kim, D. S. Oh, and S. K. Han, “A new changeable
full bridge dc/dc converter for wide input voltage range,” in Proc. 8th Int. Conf.
Power Electron. ECCE Asia, May 2011, pp. 2328–2335.
4. P. K. Jain, W., Kang, H. Soin, and Y. Xi, “Analysis and design considerations of
a load and line independent zero voltage switching full bridge dc/dc converter
topology,” IEEE Trans. Power Electron., vol. 17, no. 5, pp. 649–657, Sep. 2002.
5. I. O. Lee and G. W. Moon, “Soft-switching DC/DC converter with a full ZVS
range and reduced output filter for high-voltage application,” IEEE Trans. Power
Electron., vol. 28, no. 1, pp. 112–122, Jan. 2013.
6. G. N. B. Yadav and N. L. Narasamma, “An active soft switched phaseshifted
full-bridge dc-dc converter:Analysis, modeling, design, and implementation,”
IEEE Trans. Power Electron., vol. 29, no. 9, pp. 4538–4550, Sep. 2014.
7. Y. Jang, M. M. Jovanovi´c, and Y.-M. Chang, “A new ZVS-PWM full-bridge
converter,” IEEE Trans. Power Electron., vol. 18, no. 5, pp. 1122–1129, Sep.
2003.

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