Chia-Ling Wei

In this letter, a temperature-sensing chip with a built-in photovoltaic (PV) energy harvesting circuit is proposed. The temperature-sensing circuit includes a bipolar-junction-transistor (BJT)-based sensing circuit, a gain stage, and a successive approximation register (SAR) analog-to-digital converter (ADC), while the energy harvesting circuit is a boost dc–dc converter with a perturbation-and-observation maximum power point tracking circuit. The main goal of this work is successful chip integration. To the best of our knowledge, this is the first chip that integrates a temperature sensor, an ADC, an energy harvesting circuit, a clock generator, and other related circuits into a single chip. While conventional temperature-sensing chips are typically powered by a stable power supply voltage (which may not be available in Internet of Things devices), the proposed chip is powered by the built-in boost converter, whose output voltage inevitably has ripples. Despite this, the performance of our temperature-sensing chip is excellent. In addition, the built-in clock generator can generate signals with a subhertz frequency, which is difficult to achieve with low-power requirements. The chip was fabricated using the TSMC 0.18-μm 1P6M mixed-signal process. The measured results indicate that the sensed temperature of the proposed chip ranges from –20 °C to 80 °C with 0.17 °C resolution. The error is within ±0.8 °C, and R ² representing linearity reaches 0.99988.

In this paper, a complete 3-D integrated sensing system intended for practical applications was presented on a PCB board, starting with lead-free piezoelectric films deposited using an RF sputtering system, a MEMS structure design/simulation, device fabrication, and a signal processing chip design including charge-to-voltage transformation, signal amplification, 60-Hz noise rejection, and low-power RF wireless transmission chip for remote monitoring. Both the signal processing chips and the RF wireless transmitter chips were manufactured using the TSMC CMOS process. The piezoelectric coefficient d33 was measured as 27.21pm/V of the proposed MLZO (ZnO: Li doped Mg) films. To meet the frequency specifications of industrial applications, the ring-structure devices with a 7730-Hz resonance frequency were designed using ANSYS simulation software. There was only a 0.39% deviation as compared to the simulation results with the actual experimental data. The measurement results of the proposed system showed that the acceleration detection range was approximately 137 mV/g(p-p). The voltage-controlled oscillator adopted in the wireless transmitter chip had a four-leaf clover structure inductor with two symmetrical axes resulting in better suppression of magnetic field radiation. Finally, this system was applied to industrial spindles, and the normal and abnormal operation information of spindles was successfully and wirelessly monitored.

A mixed-ripple adaptive on-time controlled non-inverting buck-boost dc-dc converter with novel adaptive-window-based mode selector is proposed, and no compensator is required in the control circuits. For achieving high conversion efficiency, the non-inverting buck-boost dc-dc converter only works in the buck or boost modes, not the buck-boost mode. Moreover, with the proposed mode selector, smooth transition between buck mode and boost mode can be achieved. Besides, it makes the efficiency reach its maximum when the input voltage approaches the output voltage. The proposed chip was implemented by using a $0.35~\mu \text{m}$ CMOS 2P4M 3.3V/5V mixed-signal polycide process. The input voltage may range from 2.5 to 5.0 V, and the output voltage is regulated at 3.3V. According to the measured results, the maximal conversion efficiency is 97.8%.

A photovoltaic (PV) energy harvesting chip with novel multiplier-based perturb and observe (P&O) maximum power point tracking (MPPT) circuit for Internet-of-Things applications is proposed, and it can be powered by only a small PV module. The proposed P&O MPPT circuit can accurately detect the maximum power point of the PV module without using a power-hungry microcontroller or inaccurate analog multiplier. Instead, a high-accuracy pulse-based multiplier is proposed. Its input signals are analog, while its output signal is digital. Moreover, a new MPPT controller based on the proposed multiplier is also presented. The chip was fabricated using a 0.18 μm 1P6M mixed-signal CMOS process. According to the measured results, the available power from the chosen PV module is 0.1-3 mW, the maximum tracking efficiency of the proposed MPPT circuit is 99.3%, and the maximum total efficiency of the proposed harvesting chip is 94.7%.

An admittance-to-digital-impedance converter (ADIC) for impedance measurement is proposed. The ADIC was integrated in a chip with a programmable sinusoidal frequency synthesizer, allowing an operating range from 0.1 Hz to 10 kHz. The frequency synthesizer generates sinusoidal voltage signals to a sample under test (SUT), and the resulting current signal from the SUT is sensed and sent to the ADIC for postprocessing. In fact, this sensed signal is proportional to the SUT admittance, rather than to its impedance. Hence, the proposed ADIC has two functions: taking the reciprocal of the sensed signal to make it proportional to impedance and converting it into a digital signal. Furthermore, two novel circuits are also proposed: a low-leakage magnitude detector that makes it possible to measure at sub-1-Hz frequencies and a stepped-pulse divider that performs an accurate dividing function. The chip was fabricated by using a 0.35- $\mu \text{m}$ 2P4M mixed-signal process. According to the measured results, the maximum errors in the magnitude and phase measurements were 1.6% and 1.8°, respectively, and the proposed system was verified by measuring the concentrations of albumin solutions.

In this study, we successfully deposited c-axis-oriented aluminum nitride piezoelectric films via low-temperature dc sputtering method. Based on the X-ray diffraction (XRD) and TEM analyses, deposited films with a c-axis monocrystal were identified. The effective d33,f value of the aluminum nitride (AlN) films is 5.92 pC/N, which is better than most of the reported data using dc sputtering processing. Using ANSYS software, we simulated and designed MEMS accelerometers based on AlN films. Furthermore, we successfully fabricated MEMS accelerometers. The sensitivity of the MEMS accelerometer is 1.49 mV/g, and the resonance frequency is 7.2 kHz. The MEMS accelerometer was combined with a sensing circuit constituting a module. The sensitivity of the module increases approximately tenfold. Finally, the vibration of spindles was successfully detected using the designed module.

In this work, a boost dc-dc converter with fully built-in startup circuits has been proposed as a thermoelectric energy harvester. The proposed chip was fabricated using a 0.18μm 1P6M mixed-signal standard CMOS process. Neither post-fabrication trimming nor additional external components are needed to startup the converter. Moreover, a new type of low-leakage logic gates is proposed for lowering the minimal startup voltage, and several low-voltage startup circuits are also proposed. According to the measured results, the minimal startup voltage is only 82 mV, and the input voltage range is 60-460 mV. The measured maximal input power is 2.7 mW, the measured quiescent power with 200-mV input voltage is 8.2 μW, and the measured peak efficiency is 78.55%.

A single-inductor dual-supply dc-dc converter with bidirectional energy flow is proposed for the Internet-of-Things applications. This paper combines two dc-dc converters into one by sharing a single inductor, and it is capable of storing energy and powering output load by using the bidirectional inductor current. Besides, the voltage of the energy storage element is continuously monitored in the proposed converter, which eliminates the possibility of overcharging. Furthermore, the variations on the output voltage are typically negligible when the input voltage changes. In addition, a novel two-step startup procedure that does not require any on-chip/off-chip startup auxiliary circuit is proposed, which can significantly reduce the chip area. The proposed converter is fabricated by a 0.18-μm CMOS mixed-signal process. The voltage range of the storing element is 1.2-1.4 V, and the maximal output power of the proposed converter is 18 mW with its output voltage setting at 1.8 V.

A photovoltaic (PV) energy harvester is proposed, and it adopts the fractional open-circuit voltage method to track the maximal power point of PV cells. The proposed harvester was designed and fabricated by using a 0.18-μm 1P6M mixed-signal process. The input voltage of the proposed harvester may range from 0.5 to 1.1 V, and its measured peak total efficiency is 93.4%. The proposed harvester is suitable for internet-of-things applications, and the maximal duty cycle it can afford for a device with a 5-mA load and 20-ms activation time is 50%.

A high-voltage (HV) lithium-ion battery charger control chip with sharp mode transition and partial current control technique is proposed in this paper. The proposed sharp mode transition eliminates the transition region between constant current (CC) and constant voltage (CV) stages in traditional CC-CV chargers. This technique reduces the charging time and simplifies the compensator design. Furthermore, by adopting the HV partial current control technique, the charging current at the CC stage can be regulated only by sensing part of inductor current. The charger is designed and fabricated using Taiwan Semiconductor Manufacturing Company 0.25-μm 1P3M bipolar-CMOS-DMOS HV process. With a 25-V input voltage, the output voltage (i.e., battery voltage) may range from 6 to 22 V and the maximum charging current is 2.5 A. The peak efficiency reaches 97%, occurring at 1-A charging current.