A General Method to Study Multiple Discontinuous Conduction Modes in DC–DC Converters With One Transistor and Its Application to the Versatile Buck–Boost Converter

Abstract

The discontinuous conduction mode (DCM) is usually studied in single-diode and single-inductor converters, where only one DCM exists. However, multiple DCMs can appear in multidiode and multi-inductor topologies and the methodology to identify and characterize these multiple modes is not evident. In this article, a general method to study multiple DCMs is presented. The first step of the method consists in finding out the number n, which is the number of diodes conducting current passing exclusively through inductors when the transistor turns OFF. For a given n value, 2 n possible conduction modes are expected: 1 continuous mode and 2 n − 1 DCMs. The second step is to create an n-dimensional space called "k-space." In the k-space, the converter operation describes a straight line when the load changes. This straight line called "converter trajectory" passes through different n-dimensional enclosures. Each one of these enclosures represents a different conduction mode. The third step is to determine the borders between conduction modes which are subspaces of (n − 1) dimensions. This method must be followed for both control strategies (i.e., open-and closed-loop controls). The proposed method is applied to the versatile buck-boost converter. Experimental results verify the theoretical analysis for all the identified conduction modes.

A Systematic Method for Studying the Use of DC/DC Converters With Three Discontinuous Conduction Modes as Automatic PFCs

“…1. • Converters with two diodes that remain in inductive branches when the transistor is OFF (and therefore converters with three DCMs), working as conventional DC/DC converters [12] and [13] (i.e., as in the first case, constant output voltage, limited input voltage variation, and fast duty cycle variation characterize their operation).…”

“…Let us consider conventional DC/DC converters, but now with two diodes and two inductors (L 1 and L 2 ). If the two diodes remain in two inductive branches (made up of inductances L 1 and L 2 or a combination of the two) when its transistor is in OFF state, then the converter will have four conduction modes, one CCM and three DCMs [12], [13], [15], [16]. An example of the current passing through the converter diodes is shown in Fig.…”

“…To study the conduction modes, a plane is established from parameters k 1 and k 2 [12], which are defined as usual:…”

“…On the other hand, some DC/DC converters with several diodes can exhibit several DCMs. A general method for studying these converters was presented in [12]. That paper examined the use of a Versatile Buck-Boost converter.…”

Design of supply regulators for portable medical devices

“…There are two typical operation modes, continuous conduction mode (CCM) [56] and discontinuous conduction mode (DCM) [57]. As the current ripple in the inductor is same for both phases, it is derived that:…”