06-08-2014, 12:52 PM
An Application of Direct Modulation to Generate SPWM Waveform Using VHDL for FPGA Interfaced H-Bridge Power Inverter
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Abstract
—In this paper, we propose a novel scheme to generate sinusoidal pulse width modulated (SPWM) switching pulses using Direct Modulation Strategy and its implementation has been done through software developed using VHDL code. In the given proposed scheme, the periodic PWM signals are generated, separated by positive and negative group of polarity control switching pulse and evoked at the output as a control signal for FPGA interfaced H Bridge circuit.
I. INTRODUCTION
Sinusoidal Pulse Width Modulation, abbreviated as SPWM, is a method of transmitting information on a series of pulses. In order to reduce the circuit complexity as well as memory consumption, a proper use of signal generator can be utilized. By varying pulse width in accordance with amplitude of sine wave, an approximated sine wave can be produced by averaging its output pulses [1]. In direct modulation scheme PWM pulses are generated directly and thus require less memory space as compared to conventional sine-triangular scheme [2]. This effectively simplifies the circuit and reduces the power consumption during the process of PWM signal generation without subtle loss or no loss at all. The proposed scheme is based on VHDL coded software developed with flexibility in its algorithm for generation of N number of control SPWM pulses in each cycle and easily be implemented to produce AC power using FPGA interfaced H bridge power inverter circuit
III. PROGRAMMING WITH VHDL
The programming in VHDL is done in two stages. The first stage is known as ‘entity’ declaration in which the whole circuit can be seen as a black box of which a set of input and outputs are defined. This portion of programming is done with an external view. The entity of the given programme is shown in Figure 2. In the second stage, the internal architecture is defined. The detailed connections and the circuit logic is defined in this section. The internal architecture of the circuit is shown in Figure 3.
VIII. CONCLUSION
Here direct modulaion scheme is used to generate Sinusoidal PWM pulses and has been carried out using VLSI technology on FPGA board. The scheme has been successfully implemented.