Available online at www.sciencedirect.com
ScienceDirect Procedia Engineering 168 (2016) 920 – 923
30th Eurosensors Conference, EUROSENSORS 2016
Primary side circuit design of a multi-coil inductive system for powering wireless sensors G. Bouattoura,b*, B. Kallela,b, O. Kanouna, N. Derbelb a
Chair for Measurement and Sensor Technology, Technische Universität Chemnitz, Reichenhainer Straße 70, 09126 Chemnitz, Germany b National Engineering School of Sfax, Road of Soukra km 3, 3038 Sfax, Tunisia
Abstract Circuit design of the primary side is decisive for the efficiency of inductive energy transmission. In order to maximise the transmitted energy to the load, primary side DC/AC inverter and system resonance topologies should be investigated. This paper presents an inverter for a multi-coil inductive system with different system resonance topologies for a low voltage and a relative high frequency of 1.2 MHz. A comparison between half-wave and full-wave inverters is carried out for both Series-Series (SS) and Parallel-Parallel (PP) topologies. Results show that the full-wave inverter with PP topology is adequate primary side circuit for multi-coil inductive system and reaches a sending power 10 times higher than a classical half wave inverter. © 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license © 2016 The Authors. Published by Elsevier Ltd. (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of the 30th Eurosensors Conference. Peer-review under responsibility of the organizing committee of the 30th Eurosensors Conference Keywords: Inductive power transmission, bridge inverter, half-wave inverter, Series-Series topology, Parallel-Parallel topology, DC/AC converter
Nomenclature Ls Lr Rs
inductance of the sending coil inductance of the receiving coil source resistance
* Corresponding author. Tel.: +21625262934. E-mail address:
[email protected]
1877-7058 © 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of the 30th Eurosensors Conference
doi:10.1016/j.proeng.2016.11.306
G. Bouattour et al. / Procedia Engineering 168 (2016) 920 – 923
RLs RLr PL RL
sending coil resistance receiving coil resistance load power load resistance
1. Introduction Charging wireless sensors with inductive power transmission shows many advantages such as flexibility to movable sensors even with a large air gap and with lateral misalignment between coils. The general structure of the portable inductive power transmission system is composed by a DC source which is connected to an inverter to produce an AC wave with a high frequency. The obtained signal is transferred by magnetic field from the sending side to the receiving side composed by one coil connected to the sensor that can be modeled by a resistive load. In a multi coil sending system different coils can be switched on corresponding to the position of the receiving coil. In this study, we consider four sending coils, which are positioned under the receiving coil [1]. To transmit a suitable level of power to the load, an appropriate design of the electronic part on the primary side has been studied. It is composed by an inverter and two compensation capacitances for systems resonance.
Fig 1: General structure of a multi-coil inductive system
Different circuit designs for inverters such as half-wave, and full-wave inverters, are studied in the literature. Each one offers specific features, performance, and specific requirements. For inductive power transmission systems, only a few studies are present for low input voltage and high frequency in the range of MHz [2-4]. These use generally a single MOSFET switch called also Class-E. It has the drawbacks of power stress through the switch and RLC filter who complicate the circuit design. The half bridge DC/AC converter is most balanced inverter in terms of cost, complexity and performance compared to the others inverters. Another type of inverters is the full bridge inverter characterized by high efficiency and higher complexity in implementation and control. It generally used on inductive power transmission for high power and low frequencies applications. For some applications high frequency is applied in the range of MHz, such as 1.5 MHz, 1 MHz [5-7]. The proposed resonant inverter has the big advantage of the full bridge is the modified sine wave output also the soft switching offers a high output quality, flexibility in controlling, higher output power and stability on the lateral misalignment variation [8] To transfer high power, a resonate LC circuit can be applied to the inductive power transmission system by adding a compensation capacitor in series or in parallel in the sending and receiving side to create four basic topologies called series sending - series receiving (SS), series sending parallel receiving (SP), parallel sending- series receiving (PS), parallel sending parallel receiving (PP) [9]. In this paper, a selection of the optimum DC/AC converter for high frequency and low power application because of the inverter systems complexity, dynamics and efficiency and the stability of the various system parameters like resonant frequency, air gap between coils and coil misalignment
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2. Inverter comparisons The most used DC/AC converters are the half wave who is composed by two series MOSFETs (fig.2. (a)) and the full wave is composed by two parallel pairs of series MOSFETs connected as a bridge (fig.2. (b)). These two inverters are characterized by their high output power and the flexibility in the way how to be controlled research.
(a)
(b) Fig. 2. (a) Full-wave inverter; (b) Half wave inverter.
The inverters MOSFETs are activated by a specific square wave signal with a voltage amplitude determined by the component characteristics. The synchronization of the different square wave voltage driver for the full bridge inverter can generate a modified sine wave output voltage that increases the output power and the efficiency of the inverter. For the half wave inverter, the square wave is generated by two complementary voltages with a 50% of duty which can dissipate energy due to the switches on/off delay. 3. Topologies comparison The different configuration of compensation capacitors has a big influence on the output power and efficiency. The basic topologies (SS, SP, PS and PP) are investigated in [9] with a comparison of output power and efficiency between different topologies with the use of a signal generator with a high source impedance. Table.1. presents different studied equations for the compensation capacitors, equivalent resistors and the load power. Table 1. Topologies, capacitances, resistances, and output power. Topologies Primary capacitance SS
ୱୱ ൌ
ଵ னమ ౩
Secondary capacitance ୰ୱ ൌ
ଵ னమ ౨
Primary resistance ଵ ൌ ୱ ౩
Secondary resistance ܴଶ ൌ ܴೝ ܴ
Output power ܲ ൌ ቀ
భǡೝೞ ଶ
ோಽ
ோೝ ାோభ
ோమ
ቁ ܴ
PP ౩ మ మ ౩ னሻ ାୖబ
ୱ୮ ൌ ሺ
With ൌ ୰ ౩ ܴ ൌ ሺ߱ܯሻଶΤܴଶ
୰୮ ൌ
ୖై మ ାඥୖୣሺ୮ሻ ଶ౩ ሺனୖై ሻమ
Zp= ସ െ ሺʹɘ ୱ ሻଶ
ଵ ൌ ୱ
ୖబ మ ାమ
ܴଶ ൌ ܴೝ
ோಽ ଵା൫ோಽ ೝ ఠ൯
మ
ܲ ൌ ሺͳ െ
ோಽೝ ோమ
ሻ
భǡೝೞమ ோೝ ோభ ሺோೝ ାோಽೞ ሻ
With ܣൌ ͳ െ ୱ ୱୱ ɘଶ ܤൌ ୱୱ ɘ ൌ ୰ ౩
Table 1 presents the different equations of inductive power transmission parameters such as the sending and the receiving sides compensation capacitors and resistor equations and also the output power equation for the SS and PP topology, the equations shows that SS topology is more insensitive to parameters variation such as load value and reflected resistance which depend of the mutual inductance variation due to movements of the receiving coil, variation of distance and lateral misalignment between coils in general. For the PP topology with a parallel
G. Bouattour et al. / Procedia Engineering 168 (2016) 920 – 923
compensation capacitor on both sides. In fact, the presence of the parallel compensation at the receiving side increases system sensitivity to load variation in the system and also presents a condition to the load value that should be more than the RL>2ȦLs the parallel compensation at the sending side increases system sensitivity to coil movements, who changes distance and lateral misalignment between coils and changes of the mutual inductance. 4. Results and discussion In this paper, the use of a portable wireless sensor by using inductive link alimented by a DC power supply and driven by an adequate DC/AC converter for the transmission of power. The comparison by simulation between these two inverters is made by the same circuit condition such as keeping the same MOSFET components and input voltage and it is presented in Table 2. Table 2. Comparison of load power for different inverter types and topologies
Inverter type
Full-wave Half-wave
Power at sending coil in mW SS
PP
12.71 0.78
18.3 4.1
The comparison of the inverters voltage shows that the full bridge is more efficient and gives an output voltage in the order of 8 V that represents two times more than the half wave inverter. The power at sending coil presented in Table 2 shows that the full bridge inverter is more than 6 times more powerful than the half wave inverter, but it costs more because of the use of more components and the use of PP topology gives higher power compared to the SS topology. Then the use of PP topology present 6 times higher sending coil power for the full wave inverter compared to the half wave inverter. References [1] B. Kallel, T. Keutel and O. Kanoun, "MISO configuration efficiency in inductive power transmission for supplying wireless sensors," Systems, Signals & Devices (SSD), 2014 11th International Multi-Conference on, Barcelona, 2014, pp. 1-5. [2] M. Liu; M. Fu; C. MA, "Low-Harmonic-Contents and High-Efficiency Class E Full-Wave Current-Driven Rectifier for Megahertz Wireless Power Transfer Systems," in IEEE Transactions on Power Electronics, vol.PP, no.99, pp.1-1 [3] Z. Wang, X. Wang and B. Zhang, "A magnetic coupled resonance WPT system design method of double-end impedance converter networks with Class-E amplifier," Industrial Electronics Society, IECON 2015 - 41st Annual Conference of the IEEE, Yokohama, 2015, pp. 003093003098 [4] M. K. Uddin, G. Ramasamy, S. Mekhilef, K. Ramar and Y. C. Lau, "A review on high frequency resonant inverter technologies for wireless power transfer using magnetic resonance coupling," Energy Conversion (CENCON), 2014 IEEE Conference on, Johor Bahru, 2014, pp. 412417 [5] D. Puyal, C. Bemal, J. M. Burdio, I. Millan and J. Acero, "Dual 1.5-MHz 3.5-kW versatile half-bridge series-resonant inverter module for inductive load characterization," APEC 07 - Twenty-Second Annual IEEE Applied Power Electronics Conference and Exposition, Anaheim, CA, USA, 2007, pp. 1133-1139. [6] Z. Ye, P. K. Jain and P. C. Sen, "A Full-Bridge Resonant Inverter With Modified Phase-Shift Modulation for High-Frequency AC Power Distribution Systems," in IEEE Transactions on Industrial Electronics, vol. 54, no. 5, pp. 2831-2845, Oct. 2007. [7] K. Yoshizawa, T. Tanaka, E. Hiraki and M. Okamoto, "MHz-class high-frequency soft-switching GaN-based inverter for wireless power transmission via electromagnetic resonance," 2014 International Power Electronics and Application Conference and Exposition, Shanghai, 2014, pp. 451-455. [8] "A High Efficiency High Frequency Resonant Inverter for High Frequency AC Power Distribution Architectures," Power Electronics Specialists Conference, 2006. PESC '06. 37th IEEE, Jeju, 2006, pp. 1-7 [9] G. Bouattour, B. Kallel, K. Sasmal, O. Kanoun and N. Derbel, "Comparative study of resonant circuit for power transmission via inductive link," Systems, Signals & Devices (SSD), 2015 12th International Multi-Conference on, Mahdia, 2015, pp. 1-6.
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