Investigation and Simulation Model Results of High Density Wireless Power Harvesting and Transfer Method

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1 Invesigaion and Simulaion Model Resuls of High Densiy Wireless Power Harvesing and Transfer Mehod Jaber A. Abu Qahouq, Senior Member, IEEE, and Zhigang Dang The Universiy of Alabama Deparmen of Elecrical and Compuer Engineering Tuscaloosa, Alabama 35487, USA Absrac The paper presens and provide simulaion model resuls of a mehod for wireless power ransfer by harvesing and/or ransferring he swiching ripple energy of he inducor curren in a swiching power converer. By placing a planar coil as a wireless power receiver (Rx) in he proximiy of a power inducor of a power converer, wireless power can be received by he Rx coil because of he oscillaing magneic field generaed by AC swiching ripple of he inducor curren. This yields a power converer wih a wireless power ransmier (Tx) in addiion o he original wired oupu of he power converer, herefore, eliminaing he need for Tx side in an inducive wireless power ransfer sysem. Using an example Buck-WPT sysem, which achieves sep down power conversion for a wired oupu and WPT a he same ime, his paper discusses he relaed operaion principle and provide simulaion model resuls. Index Terms Wireless Power Transfer, Buck Converer, Consumer Elecronics, Inducive Power Transfer, Maximum Power Transfer, Power Converer. I. INTRODUCTION Wireless Power Transfer (WPT) sysems are increasingly being adoped or considered in new applicaions such as consumer elecronics and elecric vehicle charging, among ohers [1-5]. A convenional inducive WPT sysem normally includes a ransmier (Tx) side circui, a Tx coil, a receiver (Rx) coil, and Rx side elecronics/load. In mos applicaions, a dedicaed DC-AC power circui is needed o drive he Tx coil in order o generae an oscillaing magneic field o ransmi wireless energy/power o Rx [2-5]. A convenional DC-DC swiching power converer, such as bu no limied o buck and boos converers, supplies regulaed volage/curren/power o a load from an energy source [6-9] hrough a wired (no wireless) connecion. The power inducor is a criical par of mos of hese converers, which carry a curren wih a DC componen and an AC swiching ripple componen [6-9]. This AC ripple/oscillaing magneic field is usually considered a disadvanage in erms of radiaed elecromagneic inerference (EMI) and conducion losses, bu is poenial for WPT has no been explored, unil his paper. This paper presen a mehod o uilize his elecromagneic field as a resul of he AC swiching ripple which is a par of he curren of he inducor in a swiching power converer and uilizes i for WPT. By doing so, he power converer-wpt sysem achieves DC-DC power conversion (wired power ransfer) and WPT funcion a he same ime, which helps o eliminae he Tx side circuiry and Tx coil of he convenional WPT sysem and achieves size and cos reducion of he oal sysem. Nex secion presens he operaion principle of he proposed mehod based on an example Buck-WPT sysem (achieves sep down DC-DC power conversion and WPT a he same ime). Secion III presens he simulaion model resuls. Secion IV gives he conclusion for he paper. II. OPERATION PRINCIPLE OF THE BUCK-WPT SYSTEM Using Buck-WPT sysem as an example, his secion presens he concep and operaion principle of Power converer-wpt sysem ha realizes DC-DC power conversion (wired power ransfer) and WPT operaion a he same ime. Fig. 1 illusraes he circui diagram of he Buck-WPT sysem. The sysem has one inpu V in and wo oupus: one for WPT, which is referred o as V o_wpt, and one for wired power ransfer, which is referred o as V o_wired. Fig. 2 illusraes he main operaion waveforms for Buck-WPT sysem. The curren of he inducor i 1 = I o + i ripple by superposiion consiss of he DC curren componen (I o) and he AC ripple curren componen (i ripple). V node is he volage a he phase node. In a Buck-WPT sysem, V o_wired and V o_wpt can operae simulaneously. The wired power pah has he same operaion as he convenional buck converer wihou WPT. The power inducor L 1 and oupu capacior C o are used o form he LC low pass filer leading o V o_wired. The WPT power pah does no have a sand-alone Tx side driving circui and Tx coil. Insead, i uilizes he buck converer power sage as he Tx side circui and uses power inducor L 1 as he Tx coil. The AC componen of he inducor curren is used o achieve WPT. This is because he AC ripple of he curren generaes oscillaing magneic field in he proximiy of he Tx coil wih L 1, which can be used for inducive WPT o a receiver Rx /17/$ IEEE 3095

2 Fig. 1. Illusraion diagrams of proposed Buck-WPT sysem V node i 1 i 1 = I o + i ripple I o i 2 0 DT T T+DT 2T Fig. 2. Illusraion for he main operaion waveforms for Buck-WPT sysem. When a planar receiver (Rx) coil wih L 2 is placed in he proximiy of he planar Tx coil, he Tx and Rx coils are coupled hrough a muual inducance M. As a resul, cerain amoun of power can be delivered o he WPT load (R WPT). The Buck- WPT sysem eliminaes Tx side circuiry and Tx coil compared wih he convenional WPT sysem, which helps o reduce he size and cos of he oal sysem. III. SIMULATION MODEL AND RESULTS An LTspice [10] model for Fig. 1 is developed wih he main specificaions shown in Table I. Fig. 3 hrough Fig. 5 show sample resuls waveforms as seleced coupling facor k value varies, which simulaes varying he disance beween Tx and Rx. Fig. 6 shows a plo of he received average power a Rx side as a funcion of k (for R WPT = 2 Ω). Fig. 7 shows a plo of he received Average power a Rx side as a funcion of R WPT (for k = 0.8). Table I. Simulaion model main parameer specificaions Parameer Value V in 12 V V o_wired 5 V R WPT nominal load 2 Ω Swiching frequency 200 khz L 1 3 µh L 2 9 µh k 0.6 ~

3 Vo-wired Io-wired i1 (WPT Tx) k = 0.8 RWPT = 2 Ω i2 (WPT Rx) Fig. 3. Sample waveforms when coupling facor k = 0.8. Vo-wired Io-wired i1 (WPT Tx) k = 0.7 RWPT = 2 Ω i2 (WPT Rx) Fig. 4. Sample waveforms when coupling facor k =

4 Fig. 5. Sample waveforms when coupling facor k = 0.6. Fig. 6. Average power a Rx side as a funcion of k (for R WPT = 2 Ω). Fig. 7. Average power a Rx side as a funcion of R WPT for k =

5 Fig. 8. Average power a Rx side as a funcion of R WPT for k = 0.6. Fig. 6 shows how he received power increases as he coupling facor k increases (one reason of coupling facor increase is reducion of disance beween Tx and Rx). This also can be observed as he curren rms value hrough R WPT = 2 increases when k increases ( = ). Fig. 7 indicaes ha he maximum wireless power received when k = 0.8 occurs when he value of is around 4 Ω. Fig. 8 indicaes ha he maximum wireless power received when k = 0.6 occurs when he value of is around 7.3 Ω. However, he maximum power received when k is lower is smaller, which is expeced. IV. CONCLUSION The simulaion model resuls presened in his paper demonsrae he operaion of a concep ha allows he uilizaion of a swiching power converer wih a power inducor as a wireless power ransmier while mainaining he original operaion of delivering a wired oupu. By aking a DC-DC buck converer as an example, he simulaion model shows how a wireless oupu and a wired oupu are realized while keeping he number of componens he same, i.e., wo swiches and a power magneic device. The simulaion model is uilized in his paper o sudy he effec of coupling facor and wireless power load on he operaion and received power. REFERENCES [1] N. Tesla, Sysem of ransmission of elecrical energy, U.S. Paen, No , Mar, 20, [2] Z. Dang, Y. Cao and J. A. Abu Qahouq, Reconfigurable Magneic Resonance-Coupled Wireless Power Transfer Sysem, IEEE Trans. Power Elecron., vol. 30, no. 11, pp , Nov [3] J. M. Miller, O. C. Onar, and M. Chinhavali, Primary-side power flow conrol of wireless power ransfer for elecric vehicle charging, IEEE J. Emerg. Sel. Topics Power Elecron., vol. 3, no. 1, pp , Mar [4] Y. Cao., Z. Dang, J. A. Abu Qahouq and E. Phillips, Dynamic efficiency racking conroller for reconfigurable four-coil wireless power ransfer sysem, IEEE Applied Power Elecronics Conference and Exposiion (APEC), pp , March, [5] D. Pail, M. Disworh, J. Pacheco, and W. Cai, A magneically enhanced wireless power ransfer sysem for compensaion of misalignmen in mobile charging plaforms, 2015 IEEE Energy Conversion Congress and Exposiion (ECCE), pp , [6] W. Huang, J. A. Abu Qahouq, and Z. Dang. CCM-DCM Power- Muliplexed Conrol Scheme for Single-Inducor Muliple-Oupu DC- DC Power Converer wih No Cross-Regulaion, IEEE Trans. Ind. Applicaions, vol. PP, issue 99, pp. 1-1, DOI: /TIA [7] Wangxin Huang and Jaber Abu Qahouq, "Inpu-Volage Ripple-Based Sensorless curren sharing auo-uning conroller for muliphase DC-DC converers," IEEE Transacions on Indusry Applicaions, Vol. 52, No. 5, Page(s): , Sep.-Oc, DOI: /TIA [8] Z. Dang and J. A. Abu Qahouq, Permanen magne coupled power inducor for muli-phase DC-DC power converers, IEEE Trans. Ind. Elecron., vol. 99, pp. 1-1, DOI: /TIE [9] Z. Dang and J. Abu Qahouq, "Evaluaion of High-Curren Toroid Power Inducor Wih NdFeB Magne for DC DC Power Converers," IEEE Trans. Ind. Elecron., vol. 62, no. 11, pp , Nov DOI: /TIE [10] Linear Technology, LTspice sofware, las accessed online November 15h 2016 a hp:// 3099