Master-slave technique with direct variable frequency control for interleaved bidirectional boost converter

Multiphase interleaved synchronous boost converter is one of the most interesting topologies for non-isolated bidirectional applications due to its high efficiency, high reliability and low number of components. In order to increase the efficiency, this converter can work in Discontinuous Conduction Mode (DCM) but close to Boundary Conduction Mode (BCM), known as Quasi-Square Wave Zero Voltage Switching (QSW-ZVS) to achieve soft switching condition. Nevertheless, the main disadvantage of this particular mode is the complexity of the closed loop control. First, the control has to deal with the dead time necessary to get the soft switching condition defined by the resonance between the inductor and the transistor parasitic capacitance. Second, the control also has to manage the current balance between the interleaved phases in all the operating range. And third, the control has to regulate the voltage or current of the bidirectional conversion. These three issues lead to a variable frequency control which demands a large number of resources. This paper presents a very simple variable frequency control which does not need any highly complex mathematical operation. A master-slave scheme is also proposed in order to get a very simple approach for the interleaved multiphase implementation of this converter. Simulation and experimental results are obtained to validate the proposed control technique with a two phase bidirectional synchronous boost converter prototype of 1 kW.