International Journal of Electrical and Electronics Engineering Research (IJEEER) ISSN 2250-155X Vol. 3, Issue 2, Jun 2013, 101-106 © TJPRC Pvt. Ltd.

FPGA TECHNOLOGY TO DEVELOP INVERTERS

K. KALPANA1 & M. MADHUMITHA2 1Assistant Professor, Department of Electrical and Electronics Engineering, Periyar Maniammai University, Vallam, Tanjore, Tamilnadu, India 2Final Year, ECE Student, Easwari Engineering College, Chennai, Tamilnadu, India

ABSTRACT

Today, inverters are playing vital role in the growing country. Such an equipment must be properly designed to protect it from ripples and other distortions. This paper shows that field-programmable gate arrays (FPGAs) are especially suited to fulfil these requirements;

FPGAs are very powerful, relatively inexpensive, and adaptable, since their configuration is specified in an abstract hardware description language.

KEYWORDS: Field-Programmable Gate Arrays (FPGAs), Hardware Description Language

INTRODUCTION

Power conditioning systems are often designed to supply an AC load from a DC source. An inverter should provide constant ripple free AC voltage to ensure the safety of the equipment. The design of such systems must achieve an output voltage behaviour as close as possible to the ideal AC voltage.

Fast transient response to load variations and low total harmonic distortion are needed. In recent years, many multi-level inverters[1,3,4] synthesizing larger number of levels have been developed for obtaining such an improved output waveform. In this work a cascaded type five-level inverter is chosen for study. The triggering pattern of this inverter is developed and presented.

OBJECTIVES OF THE PROJECT

 To fabricate a prototype of the cascade type single phase five level inverter.

 To design triggering pulses for the same

 To obtain the triggering pulses for the switching devices of the five level inverter using FPGA trainer and VHDL coding. [2,6]

 To test the fabricated five level in open loop with resistive load under supply and load disturbances and implement the same in real time.

FPGA

A Field-Programmable Gate Array is an FPD featuring a general structure that allows very high logic capacity. An FPGA is a silicon chip device.

It is made up of an array of regular pattern, of general purpose electronic circuit blocks. The blocks can be configured and connected together by using a hardware description language like VHDL. Thus an electronic circuit can be created, that performs a specific function or task in an electronic system. 102 K. Kalpana & M. Madhumitha

Figure 1: ARCHITECTURE OF FPGA

Fully fabricated FPGA chips contain thousands or even more of logic gates with programmable interconnects. A typical Field Programmable Gate Array (FPGA) chip consists of I/O buffers, and array of configurable Logic Blocks (CLBs) and programmable interconnect structures. This chip can be customized by the user for the specific application.

Features of FPGA

 Faster design and verification

 Reprogrammable nature

 More powerful architecture.

 More flexibility and amorphousness

 High reliability

 Low power consumption

 High sampling frequency

 System lovel design with memory

 Low NRE(Non Recurring Engineering) cost

Advantages of FPGA

With the above features FPGA combines the advantages of both the hardware and software.

Applications of FPGAs

FPGAs have gained rapid acceptance and growth over the past decade because they can be applied to a very wide range of applications. A list of typical applications includes: random logic, integrating multiple SPLDs, device controllers, communication encoding and filtering, small to medium sized systems with SRAM blocks, and many more. Other interesting applications of FPGAs are prototyping of designs later to be implemented in gate arrays, and also emulation of entire large hardware systems.

The former of these applications might be possible using only a single large FPGA (which corresponds to a small Gate Array in terms of capacity), and the latter would entail many FPGAs connected by some sort of interconnect; for emulation of hardware, QuickTurn [Wolff90] (and others) has developed products that comprise many FPGAs and the necessary software to partition and map circuits. Another promising area for FPGA application, which is only beginning to be developed, is the usage of FPGAs as custom computing machines. This involves using the programmable parts to “execute” software, rather than compiling the software for execution on a regular CPU. FPGA Technology to Develop Inverters 103

Various Configuration Modes in FPGA

 Master parallel mode

 Master serial mode

 Slave serial mode

 Peripheral mode

Design Entry

User can enter the design by written the description of any HDL hardware descripton language, which can be written in languages such as

 VHDL

 Verilog

Simulation

By simulation, user can verify the functionality of the design by applying various input signal combinations and observing the output results. MODELSM is the world‟s dominant VHDL and verilog simulator.

Implementation

Implementation is the process in which design is passed through various stages such as TRANSLATE, MAPPING, TIME ANALYSIS and BIT STREAM. For locking input and output signal to particular pins of the ddvices, user must write user constraint before implementation and guide the same file to implementation tool through the „set control files.‟ Output of implementation is bit file which has to be converted PROM file i.e., HEX file.

Programming

This is the process b which user can physically download the architecture from computer to the target device using programming cable.

Figure 2: Pictorial View of FPGA Design Flow 104 K. Kalpana & M. Madhumitha

Other Type of Programmable Switch used in FPGAs

Antifuses are originally open-circuits and take on low resistance only when programmed. Antifuses are suitable for FPGAs because they can be built using modified CMOS technology. As an Example, Actel‟s antifuse structure, known as PLICE [Ham88]The figure shows that an antifuse is positioned between two interconnect wires and physically consists of three sandwiched layers: the top and bottom layers are conductors, and the middle layer is an insulator. When unprogrammed, the insulator isolates the top and bottom layers, but when programmed the insulator changes to become a low-resistance link. PLICE uses Poly-Si and n+ diffusion as conductors

_SRAM

Logic Cell Logic Cell

Logic Cell Logic Cell

_SRAM

_SRAM

FPGA for Control Applications

Fpga chips are used widely for the control applications in the recent past. The chip used for this project is Spartan -11 E type from Xilinx Corporation and its specification is given below:

The FPGA chip used for chosen control application is mounted on a PCB and the software for controlling is downloaded from a PC.

Xilinx XC7000 CPLDs

Although Xilinx is mostly a manufacturer of FPGAs, they also offer a selection of PLDs, called XC7000, and have announced a new CPLD family called XC9500. There are two main families in the XC7000 offering: the 7200 series, originally marketed by Plus Logic as the Hiper EPLDs, and the 7300 series, developed by Xilinx. The 7200 series are moderately small devices, with about 600 to 1500 gates capacity, and they offer speed-performance of about 25 nsec pin- to-pin delays. Each chip consists of a collection of SPLD-like blocks that each have 9 macrocells. The macrocells in the 7200 series are different from those in other PLDs in that each macrocell includes two OR-gates and each of these OR- gates is input to a two-bit Arithmetic Logic Unit (ALU). The ALU can produce any functions of its two inputs, and its output feeds a configurable flip-flop. The Xilinx 7300 series is an enhanced version of the 7200, offering more capacity (up to 3000 gates when the entire family becomes available) and higher speed-performance.

Commercially Available FPGAs

As one of the largest growing segments of the semiconductor industry, the FPGA market-place is volatile. As such, the pool of companies involved changes rapidly and it is somewhat difficult to say which products will be the most significant when the industry reaches a stable state. For this reason, and to provide a more focused discussion, we will not FPGA Technology to Develop Inverters 105 mention all of the FPGA manufacturers that currently exist, but will instead focus on those companies whose products are in widespread use at this time. In describing each device we will list its capacity, nominally in 2-input NAND gates as given by the vendor. Gate count is an especially contentious issue in the FPGA industry, and so the numbers given in this paper for all manufacturers should not be taken too seriously. Wags have taken to calling them “dog” gates, in reference to the traditional ratio between human and dog years. There are two basic categories of FPGAs on the market today: 1. SRAM-based FPGAs and 2. antifuse-based FPGAs. In the first category, Xilinx and Altera are the leading manufacturers in terms of number of users, with the major competitor being AT&T. For antifuse-based products, Actel, Quicklogic and Cypress, and Xilinx offer competing products.

Hardware Implementation

The following figure shows the FPGA based firing pulses that are fed to the circuit.the optocoupler circuit provides isolation between the FPGA based control circuit and the power converter circuit. The optocoupler used in 6N 137 which is an optically coupled gate that combines a GaAsP light emitting diode and an integrated high gain photo detector. An enable input allows the detector to be strobed. The out to the detector IC inversion of the applied input.

Figure 3: Firing Diagram with FPGA

Mosfet Driver Circuit

The PWM signal form the FPGA controller os not capable of driving the MOSFET. In ordr to dtrenghten the pulses, a driver circuit is provided based on IC IR2110.

CONCLUSIONS

FPGA based control has been developed for inverter used in power conditioning systems. The above scheme incorporates a program that provides the output voltage of the five level inverter. The design and hardware realization aspects of the speed nature of the FPGA can be reached by other control techniques based on microcontroller and other techniques. 106 K. Kalpana & M. Madhumitha

REFERENCES

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