The A MODE-SELECT CIRCUIT ANALYSIS BASED CONTROL OF A POSITIVE BUCK–BOOST CONVERTER

Abstract

The proposed work is to design a positive buck-boost converter with mode-select circuit and with wide
range of input voltages. Four switches produce more switching and conduction losses when the converter
operates in high frequency. In order to avoid those losses, we employ mode-select circuit in which the
converter can work in three different modes as buck, boost and buck-boost mode. With the mode-select
circuit the losses in switches are reduced and by the way the converter efficiency is improved. To lessen
the loss of switches as the positive buck-boost converter operates in wide range of supply voltages, it is
essential to avoid power converters operating in buck-boost mode. By implying feed-forward techniques,
the proposed converter can improve its transient response when the supply voltages are changed. It is
typically used to compensate for input variations and provide tighter control response of the output
voltage. With the above mentioned techniques the proposed converter can get better power efficiency and
extends the battery life. The proposed work was This paper describes a new method for minimizing the
transients in the output of a DC-DC converter required for small powered portable electronic applications.
The transient problem has been the most serious problem for power supplies needing the output voltage in
the mid-range of the input voltage. The maximum transient arises when the input voltage becomes almost
equal to the output voltage. Selecting the best approach involves a tradeoff among cost, efficiency, and
output noise or ripple. There are various techniques used to solve the problem of transients. However,
most of the methods have drawbacks such as comparatively higher transients or lower efficiency because
of the longer switching operations. This paper describes few methods already been used to solve the
transient problem and points out the demerits of those methods. In addition, a new combination method,
which combines buck and boost modes during the transition mode, is described in this paper to minimize
the transients at the output of the converters when the input voltage is near to the output voltage.
Mathematical equations have been put forward to support the proposed idea for the transient
minimization. Simulation results have been added to make a comparative analysis of transient response of
this method with respect to the other methods