This paper presents a Charge-Pump-based SIMO (CPSIMO) buck-boost converter with three operation modes. By modifying the power stage topology of conventional SIMO buck-boost converters, the proposed converter exhibits faster transient response and higher efficiency. Moreover, an average- voltage-based mode selector is introduced to implement the smooth transition between three modes. The proposed converter is designed in TSMC 0.18 μm BCD process with a supply voltage of 2.7V-4.2V and has three outputs of 1.8V, 3.3V and 5V. Simulation results show that the proposed converter achieves a peak efficiency of 94.61% under output power of 2.8W and a load transient response time of 9μs with a 1.5W power step.

Flexible and stretchable dry active electrodes for multi bio-potentials sensing based on Ag flakes / polydimethylsiloxane (PDMS) electrically conductive composite (ECC) are developed and characterized. The proposed dry active electrode consists of soft substrate, electrode, and simple circuits with an amplifier and a capacitor. The soft substrate is made of silicone with a molding process, while the electrode is fabricated by bar coating the ECC on the patterned substrate. Furthermore, circuits interconnect, soldering of chip and other components, and connection with flexible PCB (FPC) are all implemented with ECC directly, which simplifies the fabrication process. A portable bio-potential sensing system is also designed and implemented to work with the proposed electrodes. Various experiments were carried out to verify the proposed electrodes as well as the whole sensing system. The connectivity and proper functionality of the electrodes and cables remain stable during the stretching test. The system and the sensors yield good signal quality for multiple bio-potentials. Compared with conventional Ag/AgCl wet passive electrodes in electrocardiogram (ECG) sensing, the proposed dry active electrodes showed comparable noise floor and less sensitivity to power line interferences and motion artifacts. In electroencephalogram (EEG) sensing, the observed alpha rhythm was 12.66 dB higher than the baseline in the eye-close state. The proposed sensors exhibited potential applications in wearable systems in the electromyogram (EMG) grip force measurement and classification test. Overall, the proposed sensors could provide better comforts during long-time wearing according to its better matching modulus with skin and can meet the requirements of high quality multi bio-potential sensing.

This paper presents a bipolar-input thermoelectric energy-harvesting interface based on boost/flyback hybrid converter (BFHC). Two-type ring oscillators are combined to form as a complementary group with bipolar-input voltage operating range for self-start. With the technique of combining the boost converter and flyback converter together, the system is able to convert the energy with bipolar-input voltages. The open-circuit voltage maximum power point tracking (MPPT) method is adopted in this harvester to extract as much energy as possible from the thermoelectric generator. By dynamically adjusting the switching frequency according to the input power, the system achieves a high conversion efficiency with a wide input range. Implemented in 180-nm CMOS process, the harvester achieves a peak conversion efficiency of 84% at $V_{{\text {TEG}}}=260$ mV and 79% at $V_{{\text {TEG}}}=-300$ mV. In addition, the harvester can self-startup with minimum voltages of 129 mV with a positive input voltage and −140 mV with a negative input voltage.

Recent advances in energy-harvesting techniques have allowed wearable and IoT devices to operate without batteries. A thermoelectric generator (TEG) is one energy source that can provide a bipolar voltage that is proportional to the temperature difference between its two sides. Most of the prior TEG-harvesting systems could handle the positive input voltage [1–3]; however, the TEG’s input voltage polarity may reverse due to environmental changes. Only a few prior publications provide a method to deal with the bipolar input voltage [4–6]. To harvest bipolar input energy, a switch-matrix-based boost converter is proposed in [4], but it cannot self-start and dynamically track the maximum power point. [5] and [6] provide methods for bipolar self-startup with an ultra-low input voltage, but both of them suffer from a low conversion efficiency. Hence, there is no complete system suitable for bipolar-input TEG energy harvesting. A solution must address three challenges: (1) the transfer of energy from a bipolar input voltage via a high-efficiency converter; (2) system self-start-up with a reasonably low bipolar input voltage; (3) a maximum power point tracking (MPPT) method for bipolar input voltage. This paper proposes a bipolar-input boost/flyback hybrid converter (BFHC) with an on-chip cold start-up for TEG energy harvesters.

A current-slope-based mode control method is proposed for a buck-boost DC-DC converter to realize automatic mode switching between buck and boost in one switching period without additional quiescent current (IQ). Implemented in 0.18μm CMOS, the converter realizes 95.3% peak efficiency and above 90% over a load range from 15μA to 200mA. Accurate current slope measurement is achieved with initial sampling and 135nA total IQ is achieved with a zero-IQ pull-up structure in the input monitor.

A hybrid single-inductor dual-input-triple-output (SIDITO) converter with an on-chip transformer-based starter for thermoelectric energy harvesting is presented. The on-chip transformer-based LC starter makes the system capable of self-startup at an open-circuit-voltage of 160 mV. With the proposed hybrid SIDITO architecture, additional inductor-sharing power switches are eliminated. An adaptive-on-time control scheme is also proposed to improve the efficiency at low input voltage levels. The chip is fabricated in a 0.18-mu m CMOS process. The measurement results show that the converter can provide an output current range from 1 mu A to 10 mA with a peak efficiency of 83.3%.

Based on 3.3 V, 0.35 μm, and single-poly CMOS digital process, a bandpass filter (BPF) with on-chip automatic tuning system used in bluetooth system is presented. The center frequency of the filter is 2 MHz. The bandwidth is 1.2 MHz and its power consumption is only 12 mW. The resonant condition of voltage controlled oscillator (VCO) in phase locked loops, which is used in auto-tuning circuit of integrated filter, is analyzed. The effect of operational transconductance amplifiers' parasitic parameters on VCO's resonant frequency is studied as well. By using a simple operational transconductance amplifier (OTA) as a negative impedance used in VCO, the problem of confining VCO's oscillation to a desired range is solved.