Finite element analysis of a variable inductor for an RSCC based LED lamp driver

This paper presents a finite element analysis (FEA) of a variable inductor (VI) used to control a resonant switched capacitor converter (RSCC) based LED Driver. As it is well known, resonant converters are generally preferred due to their easily achieved soft-switching as well as soft-starting. In the RSCC based LED driver, the average current flowing through the LEDs is controlled by means of a variable inductance placed in the resonant circuit. The VI is the device responsible for providing the required variable inductance. The RSCC operation with VI control, the operating principle of the VI and typical modelling techniques are briefly presented. In addition, a simplified design procedure for VIs, based on E, EF and EFD cores, is proposed. The FEA of the VI used in the LED lamp driver, based on a double gapped “EFD” core, is presented. The performed FEA simulations describe the behavior of the electromagnetic device and help understanding the non-linear characteristics of this element.