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PCB-embedded Integrated Coupled Inductor Design For Integrated VR in Smartphone Application

IVR structure
Fig. 1. Three-dimensional IVR structure.
  As the number of cores in microprocessors and power demand increase in mobile applications, power management is crucial to the whole system. Due to low-frequency operation of voltage regulators in today's smartphone products, passive components occupy lots of space on the motherboard. On the other hand, dynamic voltage and frequency scaling (DVFS) can help reduce power consumption of processors. However, traditional voltage regulators cannot support this function due to low- frequency operation and long power delivery path. In order to provide a compact and efficient power solution for high- performance processors, a three-dimensional integrated voltage regulator (IVR) operating at ultra-high frequency (>10 MHz) is proposed shown in Fig. 1. The multi-phase inductor is just underneath the processor to shorten the power delivery path. One of the most challenging parts of IVR design is integrated magnetic design with small volume and loss.
  In this paper, a novel, four-phase integrated coupled inductor structure is proposed shown in Fig. 2(a). Due to negative coupling, the dc flux in the core and inductor footprint are reduced. By integrating four inductors into one magnetic core, the inductor footprint is further reduced by flux cancellation without increasing inductor loss. By optimizing this new inductor structure with the help of a finite element tool, 70% inductor loss reduction and 40% footprint and thickness reduction are realized compared with previous inductor design. Furthermore, to demonstrate the feasibility of integrating active components with proposed inductor structure, the inductor samples are fabricated and embedded into PCB as shown in Fig. 2(b). By using PCB-compatible magnetic material, the inductor performance is not impacted by PCB integration. Finally, a very small footprint (<14 mm2) and low profile (0.6 mm) are achieved by this four-phase PCB-embedded, integrated coupled inductor.
coupled inductor
Fig. 2. Four-phase PCB-embedded integrated coupled inductor structure.

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