Design of a parallel resonant converter as a constant current source with microcontroller-based output current regulation control

Parallel resonant converter (PRC) behaves as a constant current (CC) source when operated at its resonant frequency; however, its output current slightly depends on output load changes. In practical applications - e.g. in LED drivers - a precisely regulated output value should be requested, also over a wide load range. To fix this shortcoming, in this paper we present a PRC-CC with variable switching frequency control implemented on microcontroller (μc), to regulate output current against load variations. Optimal design considerations are introduced to allow the adoption of such kind of control strategy, without losing the CC circuit behavior and zero voltage switching (ZVS) transitions. A 100 W, 2 A PRC-CC prototype was realized. Experimental results demonstrate the CC behavior of the controller, as well as the effective output current regulation.