Active Input–Voltage and Load–Current Sharing in Input-Series and Output-Parallel Connected Modular DC–DC Converters Using Dynamic Input-Voltage Reference Scheme

Abstract

This paper explores a new configuration for modular dc-dc converters, namely, series connection at the input, and parallel connection at the output, such that the converters share the input voltage and load current equally. This is an important step toward realizing a truly modular power system architecture, where low-power, low-voltage, building block modules can be connected in any series/parallel combination at input or at output, to realize any given system specifications.A three-loop control scheme, consisting of a common output voltage loop, individual inner current loops, and individual input voltage loops, is proposed to achieve input voltage and load current sharing. The output voltage loop provides the basic reference for inner current loops, which is modified by the respective input voltage loops. The average of converter input voltages, which is dynamically varying, is chosen as the reference for input voltage loops. This choice of reference eliminates interaction among different control loops.The input-series and output-parallel (ISOP) configuration is analyzed using the incremental negative resistance model of dc-dc converters. Based on the analysis, design methods for input voltage controller are developed. Analysis and proposed design methods are verified through simulation, and experimentally, on an ISOP system consisting of two forward converters.

Input-Series Multiple-Output Auxiliary Power Supply Scheme Based on Transformer-Integration for High-Input-Voltage Applications

“…Fig. 1 shows the configuration of an ISOP DC/DC converter, which includes the following advantages: 1) ease of choice of devices due to the reduced voltage stress on each module, 2) increased efficiency due to the use of low voltage MOSFETs, and 3) ease of thermal design as a results of each module handling only a part of the total power [16]- [20]. The important issues of ISOP converters are ensuring the input voltage sharing (IVS) and the output current sharing (OCS) for each module [1], [18].…”

“…In [8], a two-module ISOP system has been implemented, using a charge control technique with input voltage feed forward. In [12], [15] and [16], three-loop control schemes have been used by sensing both the input voltage and the output current. In [19], a decoupled master/slave control for an ISOP converter was proposed to deal with low cost, high voltage auxiliary power supplies.…”

DSP Based Series-Parallel Connected Two Full-Bridge DC-DC Converter with Interleaving Output Current Sharing

“…However, input currents as well as input voltages have to been sensed. A three loop control scheme is implemented by sensing both the input voltages and the output currents [8], [9]. However, from the point view of power balance, achieving IVS can automatically realize OCS.…”

“…Sensorless current mode control is effective for an ISOP system [16], but component tolerances will lead to unbalanced voltage sharing among the modules. In practice, these schemes [3], [8]- [16] belong to voltage mode control instead of current mode control. For ISOP converters, direct OCS control results in run-away conditions due to equivalent negative resistance characteristics from each module's input terminals [8], [11].…”

“…In practice, these schemes [3], [8]- [16] belong to voltage mode control instead of current mode control. For ISOP converters, direct OCS control results in run-away conditions due to equivalent negative resistance characteristics from each module's input terminals [8], [11]. As a consequence, to achieve a power sharing balance, IVS control loops have to be used in order to achieve excellent power sharing for the ISOP modules.…”