Closed Loop Control of an Interleaved Buck Converter with High Step-Down Conversion Ratio and Low Switch Voltage Stress

Abstract: Interleaving can be thought of as a method of paralleling converters but it has got additional benefits to offer in addition to those obtained from conventional approaches of paralleling converters. Interleaved converters due to its simple structure and low control complexity are widely used in applications where non-isolation and high output current with low ripples are required. They have got certain drawbacks such as high cost and high switching losses and require high voltage rated devices. These drawbacks can be rectified by means of a new interleaved DC-DC converter in which two input capacitors are series-charged by the input voltage and parallel discharged for providing a much higher step-down conversion ratio. This paper employs capacitive voltage division principle for increasing the step- down conversion ratio and reducing voltage stresses of active switches. Thus lower voltage rating switches can be used to reduce switching losses and the overall efficiency is improved. Moreover, due to the charge balance of the blocking capacitor, the converter features automatic uniform current sharing characteristic of the interleaved phases without adding extra circuitry or complex control methods. The closed loop control of the paper is carried out using MATLAB R2012a environment and results are obtained. The closed loop control is given using a PI controller. Finally, a prototype circuit is implemented with 110 V input voltage and 5.5 V output voltage.

Keywords: IBC, interleaving technique, step-down conversion ratio, low switch voltage stress.