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The objective of this research is to design ultra-low power Hybrid Micro Energy Harvester (HMEH) circuit using hybrid inputs of radio frequency (RF), thermal and vibration for biomedical devices. In the HMEH architecture, three input sources (RF, thermal and vibration) are combined in parallel to solve the limitation issue of a single source energy harvester and to improve the system performance. Energy will be scavenged from the human body for thermal and vibration sources by converting directly temperature difference and human movement to electrical energy. The inputs are set to 0.02V and 0.5V for thermal and vibration respectively with the frequency of 1 kHz. Meanwhile, RF source is absorbed from radio wave propagation in our surrounding. For this work, the frequency is set to 915MHz and the output voltages for input ranges of-20dBm to 5dBm are recorded. The performance analysis of the HMEH is divided into two; thermal and vibration harvester circuit and RF harvester circuit. These proposed HMEH circuits are modeled, designed and simulated using PSPICE software. Vibration produces AC input and will be converted to DC using a rectifier. A comparator is used to compare the two sources (thermal and vibration) and boost converter is proposed to step-up these small input sources. Meanwhile, due to RF large frequency, the voltage multiplier is practical for both rectify and step up the input instead of the boost converter. LC resonant network is used to amplify low ambient input of RF passively before it goes to 4-stages voltage multiplier. The proposed HMEH able to achieve the output ranges of 2.0 to 4.0V with 1MΩ load. The results obtained in this research work shows that the proposed design able to produce sufficient voltage for biomedical application requirement which lies between 2.0-4.0 V from the ambient input of 0.02 to 0.5V for thermal and vibration while-9dBm for RF signal.

The deployment of energy harvester as a power supply attracts high attention especially for micro-scale devices. It is utilizingPermintaan ke atas peranti elektronik menjana kuasa sendiri semakin meningkat kebelakangan ini atas faktor kos yang rendah dan penyelenggaraan yang mudah. Antara sumber ambien yang berada di sekitar kita adalah tenaga haba, getaran, gelombang elektromagnet dan solar. Teknologi ini merupakan salah satu alternatif bagi menggantikan bateri terutamanya di kawasan luar bandar yang kadang kala memerlukan proses penyelenggaraan yang agak berisiko. Pembangunan sistem penuaian tenaga turut memberi sumbangan besar ke arah bidang bioperubatan dengan cara memanjangkan hayat bateri bagi peranti penderia pemantauan kesihatan. Tiga jenis sumber tenaga masukan yang dipilih bagi sistem penuai tenaga yang dicadangkan ialah RF, haba dan getaran. Gabungan tiga sumber masukan diilhamkan untuk menyelesaikan masalah kuasa yang dihasilkan oleh sumber masukan tunggal. Selain itu, ia digunakan sebagai sokongan antara satu sama lain bagi memastikan sumber tenaga dibekalkan secara berterusan untuk mencapai operasi autonomi. Misalnya, jika salah satu sumber masukan tidak wujud terutamanya sumber haba kerana masukannya yang terlalu rendah, penuai tenaga RF dan getaran akan digunakan. Bagi ketiga-tiga penuai tenaga ini, kelebihan dilihat pada penuai tenaga RF kerana ia sentiasa wujud di mana-mana dan boleh didapati sama ada siang atau malam. Penuai tenaga RF JK 29(1) 2017(6).indd 41 24/01/2018 3:40:55 PM

This research work presents an Ultra-Low-Power (ULP) Hybrid Micro Energy Harvester (HMEH) for biomedical application. This architecture uses the inputs of Thermoelectric Generator (TEG) and body vibration. TEG is based on temperature gradient between the ambient environment and human body. While vibration is based on the vibrate sources like motor that is able to generate an AC voltage. Having two sources overcome the issue of limitation caused by single source harvester but will result in impedance mismatching among the desired sources. The proposed of HMEH architecture consists of a control manager with Asynchronous Finite State Machine (AFSM) to grab the proper input value, a rectification to convert vibration input from AC to DC, a start-up to initialize the desired input, a Maximum Power Point Tracking (MPPT) to achieve maximum power extraction, a boost converter to boost up the input voltage, energy storage to keep the energy and voltage regulator to fix or produce the desired output voltage. A single power management circuit is used to reduce the number of components used and power losses. The HMEH will be modeled, designed and simulated using PSPICE software and then implement in 0.13 µm CMOS technology. Next, the developed HMEH will be coding using Verilog Hardware Description Language (VHDL) under mentor graphics and then download to Field Programmable Gate Array (FPGA) for real time implementation. The expectation from this ULP HMEH is to achieve 2.0-4.0 V of regulated voltage output from input sources range of 80-600 mV at start-up with an efficiency of 93%.

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