International Journal of Scientific & Engineering Research, Volume 5, Issue 4, April-2014 142 ISSN 2229-5518 IJSER © 2014 http://www.ijser.org Design and Implementation of Digital Controller for DC-DC Buck Boost Converter S.Chithra 1 ,V.Devi Maheswaran 2 Abstract - Several techniques are available for implementing DCDC converters using digital controllers. Some of them are dspace, DSP, FPGA etc. Among these FPGA (Field Programmable Gate Array based implementation provides various advantages in terms of speed, flexibility, low power usage, reduced equipment sizing and massive parallelism. The traditional methods allow fault diagnosis only after the final implementation which leads to extra cost and loss of design time. This paper proposes a smart method of FPGA based implementation of DC-DC Buck Boost converter control system using Matlab and ModelSim. The control algorithm and coding is done by means of VHDL code and implemented using Altera FPGA Board. The FPGA takes control of the entire system and decides whether to increase or decrease the voltage depending on the application. Load is applied and the efficiency is checked at variable load conditions. Also performance comparison is made between a DSP and FPGA to evaluate the effectiveness of both the systems at various operating conditions. Keywords – Converters, Field Programmable Gate Arrays, DSP. I INTRODUCTION All battery powered electronic devices have their voltage range that is in between the range of a fully charged to a semi charged battery. Since the required output may be greater or lesser than the supplied voltage, a buck and boost converter needs to be cascaded to be used for this purpose. Cascading of the two converters results in what is called as the buck-boost converter. the control of these converters has been traditionally implemented using analog methodologies. But due to recent advancements of digital technology, digital controllers haven begun to replace analogue controllers. Digital systems controlled using microcontrollers and Digital Signal Processor (DSP) is being replaced by a more suitable candidate, the Field Programmable Gate Array (FPGA) [2]. A Field Programmable Gate Array (FPGA) consists of a matrix of reconfigurable gate array logic circuitry that can be configured in a way depending on the user requirement. These logic blocks when configured and connected create a hardware implementation of a software application [4]. 1. Chithra.S, M.E Research scholar, Rajalakshmi Engineering College 2. Devi Maheswaran.V, Rajalakshmi Engineering College The behaviour of FPGA can be described using a Hardware Description Language (HDL) or a schematic. The FPGA technology is now considered by an increasing number of designers in various fields of application such as telecommunication, video, signal processing, embedded control systems and electrical control systems [9] . Therefore FPGA based controller is preferable because of the following advantages. • FPGA can process information faster. • Controller architecture can be optimized for space or speed. • Available in radiation tolerant package. • Implementation in HDL allows the targeting of a variety of commercially available device. • FPGA allows for implementation of parallel processing. Rest of the paper is organized as follows: Section II explains the system model of buck and boost converters and their working principle. Design specifications of the converter using FPGA is described in section III. Simulation results are given in section IV. Finally conclusions are presented in section V. II SYSTEM MODEL Fig.1 illustrates the model of the proposed buckboost converter. The proposed system can operate in buck, boost and buck-boost modes. Fig 1.Simplified block diagram of the converter implemented using digital controller. GATE PULSE AC SOURCE EMI FILTER RECTIFIER CONVERTER CIRCUIT OUTPUT DIGITAL CONTROLLER IJSER