This article presents an ultra-fast adaptive on-time buck converter that utilizes a capacitor current sensing technique for superior transient performance. The design features an on-chip self-calibrated RC network that automatically matches the output capacitor impedance, enabling accurate real-time load current detection. This sensed current directly drives an optimal timing generator that computes and applies ideal switching patterns within a single cycle to counteract load transients. Consequently, the implemented architecture achieves time-optimal control with minimal voltage deviation. Fabricated in a 180 nm bipolar-CMOS-DMOS (BCD) process, the converter occupies 3.67 mm(2) and achieves 93.9% peak efficiency. Experimental results demonstrate consistent time-optimal response within one switching cycle across varying operating conditions, including different output voltages, output capacitors, and inductor values.

This article presents a time-domain-controlled (TDC) single-inductor triple-output (SITO) step-up converter for portable devices with a bipolar power supply. A time-domain controller is utilized in the proposed converter to achieve a minimized delay time and thus ensure a high-conversion ratio (CR) with a switching frequency of 2 MHz. The proposed power converter employs a time-domain energy distribution (ED) balance scheme to ensure the bipolar outputs are symmetrically regulated. In addition, with the assistance of the output offset correction circuits, the load regulation of the TDC-SITO converter is greatly improved. By using an analog-to-digital converter (ADC)-assisted fast-settling loop, the converter achieves an excellent load transient response with low undershoot/overshoot voltages. Powered by a lithium-ion battery, the TDC-SITO converter can generate a bipolar power supply of $\pm$ 12 V and a standard 5 V output voltage, indicating a maximum CR of 8.8×. Implemented in a 180 nm bipolar-CMOS-DMOS (BCD) process, the converter achieves a peak conversion efficiency of 91.6% at an output power of 2.25 W. With a load current step of 100 mA between two output voltages of $\pm$ 10 V, the output voltages recover their normal values within 100 $\mu$ s while the undershoot/overshoot voltages are below 160 mV. The maximum output power of the TDC-SITO converter is 9.6 W.

This article introduces a coupled-inductor hybrid step-up converter (CIHSUC) designed for low-ripple power supply applications in battery-operated devices. The CIHSUC combines the advantages of both a boost converter and a KY converter by proposing a novel hybrid converter topology that connects the input and output terminals of the converter in series with the coupled-inductor, resulting in a high conversion ratio (CR) and load-independent ultra-low output voltage ripple. By utilizing a coupled inductor instead of two discrete inductors, the CIHSUC further reduces inductor current ripple, output voltage ripple, and system size. Furthermore, (VIC)-I-2 adaptive off-time (AOT) control method is proposed to enhance the transient response and loop stability. Fabricated in a 0.18 mu m BCD process, the converter achieves a peak efficiency of 94.4% at V-IN = 5 V, V-O = 12 V and I-Load = 300 mA. Additionally, the measured output voltage ripple remains below 20 mV within the input range of 2-5 V and the output range of 5-15 V, representing up to a 6.6 x reduction compared to the theoretical optimum of a conventional boost converter.

Ripple based constant on-time (RBCOT) control has been widely used in dc–dc buck converters over past years. However, there has been no accurate loop gain model to link the property of RBCOT controlled buck converter to existing knowledge about basic feedback control principles like crossover frequency (Fc) and phase margin so far. The previously reported stability criterion for the output capacitor's equivalent series-resistor, i.e., Ton/(2C), is insufficient to avoid subharmonic oscillations over all duty cycle values. This article presents a new accurate loop gain model for the RBCOT control. Without simplification, the proposed model can accurately predict the system response even beyond the switching frequency. The proposed modeling approach has been extended to two types of external ramp compensation schemes (for solving the subharmonic oscillation issue) and optimum ranges of ramp compensation amplitudes have been derived accordingly. The modeling results are verified by the SIMPLIS simulations and experimental results.

This paper presents a time-domain-controlled (TDC) single-inductor triple-output (SITO) step-up converter with enhanced load transient response. The proposed converter can convert 2.7 to 5V input voltage into a pair of bipolar high output voltages ranging from ±7.5 to ±12V and a 5V positive output voltage with a maximum output power of 9.6W. By using the time-domain controller and an ADC-assisted fast settling loop, the converter exhibits a fast transient response with low undershoot/overshoot voltages. The proposed converter was fabricated in a 180nm BCD process. With a 2MHz switching frequency, the converter achieves a peak conversion efficiency of 91.6% at an output power of 2.25W.

An adaptive on-time (AOT) buck converter with constant switching frequency and fast transient response is presented. A frequency-locked loop (FLL) is used to achieve constant switching frequency. The on-time (TON) is adjusted by a TON extender to achieve fast transient response. The proposed AOT buck converter is implemented in 0.18µm CMOS process. The simulation results show that the switching frequency is fixed at IMHz under various load condition and the output voltage undershoot and settling time are only 50m V and 2.5µs, respectively during 4A load transient.

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%.

A 900-MHz RF (Radio Frequency) energy harvester implemented in TSMC 180-nm CMOS technology is presented. The RF energy harvester, which outputs an output voltage of 1.2V, incorporates a harvesting-efficiency tracking circuit to improve efficiency by changing the load of the rectifier automatically. By adopting dynamic comparator and duty-cycled operation a low power consumption is realized in the control circuit. For input RF power at -15dBm, the RF energy harvester achieves 30.1% efficiency.

A single-inductor dual-input-dual-output dc–dc converter with dual-mode and programmable-capacitor-array (PCA) maximum power point tracking (MPPT) control for thermoelectric energy harvesting is presented. With the proposed dual-mode control, the system can deliver a wide output power range from 180 $\boldsymbol {\mu }\text{W}$ to 21.6 mW. PCA-MPPT technique is proposed to harvest maximal power from thermoelectric generator with a peak tracking efficiency of 99.55%. The converter has been implemented in a 0.35 $\boldsymbol {\mu }\text{m}$ CMOS process and has a peak power conversion efficiency of 84.6%.

A 110nA quiescent current (IQ) buck converter for ultra-low power application is presented. A novel zero IQ pull-down structure, which consists in native NMOS and PJEF, is proposed to achieve zero-power supply monitor and save the total IQ. Implemented in 0.35um CMOS process, the converter realizes 78% efficiency in 1uA load and over 90% for load range from 5uA to 100mA. With adaptive-bias hysteresis comparator according to the load condition, near-constant output ripple is achieved in full load range without any efficiency deterioration.

A stable LDO using VCCS (voltage control current source) is presented. The LDO is designed and implemented on GF 2P4M 0.35 μm CMOS technology. Compared with a previous compensation scheme, VCCS can implement a real stable LDO with a small on-chip capacitor of 1 pF, whose stability is not affected by the variable ESR (equivalent series resistance) of the output capacitor. The unit gain frequency of the LDO loop can achieve 1.5 MHz, improving the transient response. The PSR of the LDO is larger than 45 dB within 0–40 kHz. The static current of the LDO at heavy load of 100 mA is 57 μA and the dropout voltage of the LDO is 150 mV. Experimental results show that a setting time of 10 μs is achieved, and the variation of output voltage is smaller than 35 mV for a 100 mA load step in transient response of the LDO.

Improving battery longevity in portable devices usually requires the use of different voltage levels with a wide range of load capability for various functional blocks. Since a single-inductor-multiple-output (SIMO) converter can support multiple output voltages while using only one inductor, it is an excellent candidate to minimize the component count and thus the production cost. However, the cross-regulation and power consumption are two main issues of the previously reported SIMO converters [1-5]. Although pseudo-continuous conduction-mode (PCCM) control with a freewheel period [1] tries to augment power density and eliminate cross-regulation, associated power dissipation of freewheel switch exacerbates its overall efficiency. The charge-control technique with energy recovery presented [2] decouples the output channels between each switching cycle, at the expense of additional switching loss and slow response. The comparator-based controlled SIMO converters are investigated in [3, 4] and the cross-regulation in most channels is improved due to the fast response of the comparator. However, since the channel that is last connected to inductor is inevitably regulated by the accumulative error of all channels to balance the overall inductor current, every load transition at other outputs will introduce serious cross-regulation [3] and load-regulation problem [4] in the channel. In addition, cross-regulation and slow response also limit the application of dynamic voltage scaling (DVS) technique, which is widely used in single-output converters to improve the system power efficiency by providing variable voltage with fast reference tracking.

A monolithic dual mode buck dc-dc converter is proposed in this paper. The converter operates in Peak-Current-Mode Pulse-Width-Modulation (PWM) with a 2 MHz switching frequency under the heavy load condition. And an Adaptive-On-Time Pulse-Frequency-Modulation (AOTPFM) is employed to suppress the output ripple voltage variations under the light load condition. The DC-DC converter has been implemented in a 0.35 μm CMOS process and measured. The peak efficiency reaches 93% and stay over 78% for load range from 10 mA to 2000 mA with the dual mode control.