This paper presents a low power boost converter for thermoelectric energy harvesting that demonstrates an efficiency that is 15% higher than the state-of-the-art for voltage conversion ratios above 20. This is achieved by utilizing a technique allowing synchronous rectification in the discontinuous conduction mode. A low-power method for input voltage monitoring is presented. The low input voltage requirements allow operation from a thermoelectric generator powered by body heat. The converter, fabricated in a 0.13 μm CMOS process, operates from input voltages ranging from 20 mV to 250 mV while supplying a regulated 1 V output. The converter consumes 1.6 (1.1) μW of quiescent power, delivers up to 25 (175) μW of output power, and is 46 (75)% efficient for a 20 mV and 100 mV input, respectively.

A 20 mV Input Boost Converter With Efficient Digital Control for Thermoelectric Energy Harvesting

Flexible thermoelectric materials and devices

Review of wearable thermoelectric energy harvesting: From body temperature to electronic systems

A wearable pyroelectric nanogenerator and self-powered breathing sensor

An integrated five-output single-inductor multiple-output dc-dc converter with ordered power-distributive control (OPDC) in a 0.5 mum Bi-CMOS process is presented. The converter has four main positive boost outputs programmable from +5 V to +12 V and one dependent negative output ranged from -12 V to -5 V. A maximum efficiency of 80.8% is achieved at a total output power of 450 mW, with a switching frequency of 700 kHz. The performance of the converter as a commercial product is successfully verified with a new control method and proposed circuits, including a full-waveform inductor-current sensing circuit, a variation-free frequency generator, and an in-rush-current-free soft-start method. With simplicity, flexibility, and reliability, the design enables shorter time-to-market in future extensions with more outputs and different operation requirements.

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A Single-Inductor Switching DC–DC Converter With Five Outputs and Ordered Power-Distributive Control

While the demand for micro-energy harvesters (μEHs) is increasing (for seamless energy source in applications such as wireless sensor node), two major problems still obstruct versatile use of them. The first problem is the self-startup capability. Because many wireless sensor nodes are likely to be located where human-maintenance is difficult, starting them up manually can be as difficult as replacing the battery. Its realization has been difficult because μEHs must be able to turn itself on without any stored energy. Some previous works have reported such a function: some needed high voltage [1] or vibration [2] and one used a transformer as a starter [3]. The other problem is the maximum power point tracking (MPPT) capability. Because it is known that MPPT algorithms usually require considerable power consumption [4], using them in μEHs is impractical. This paper suggests a new boost converter architecture and MPPT control method which can bring μEH into practical use.

A 40 mV Transformer-Reuse Self-Startup Boost Converter With MPPT Control for Thermoelectric Energy Harvesting

Several types of DC-DC converters for active-matrix organic LED (AMOLED) displays have been introduced to date [1–4]. Single-inductor multiple-output (SIMO) converters with current-mode control have many advantages including reduced PCB space and less cost for mass-production due to the use of only one off-chip inductor to provide many outputs [1,2]. However, a load-dependent stability issue has to be addressed which is due to the output capacitance and an internal integrator with an error amplifier. Recently, in efforts to overcome the stability issue of current-mode control, load-independent control converters have been developed. Although this concept works well, the inductor-current sensing and artificial ramp generation for stability still make the controller complicated [3,4]. In addition, the freewheeling current control converter requires an extra power switch for freewheeling current flow, thereby lowering power efficiency [3]. The vestigial current control converter, meanwhile, has weak points of requiring auxiliary output and an additional inductor, and thus consumes some additional power in the steady state [4]. Besides the controller issue, the previous converters when operating with a large step-up ratio, usually have heavy voltage stress applied to the inductor, resulting in a low efficiency [1,4]. To overcome these problems, the proposed SIMO converter employs emulated absolute current hysteretic control, which uses full current information and is characterized by intrinsic high stability. The energy sharing capacitor is also used for high output voltage to reduce the voltage swing of the switching node and the associated loss. In addition, to balance the total energy across the inductor, the energy balancing capacitor is adopted.

A high-stability emulated absolute current hysteretic control single-inductor 5-output switching DC-DC converter with energy sharing and balancing

A new integrated zero-inductor-current detection circuit suitable for step-up DC–DC converters is presented. The detection circuit can correctly detect zero-inductor-current with a novel method. The method helps overcome difficulties in measuring online current from on-resistance of output PMOS switches. With its simplicity and independence from output PMOS switches, this circuit promises wide application in either single-output step-up DC–DC converters or single inductor multiple output (SIMO) step-up DC–DC converters with different control theories, and especially in discontinuous-conduction-mode (DCM) operation.

Integrated zero-inductor-current detection circuit for step-up DC-DC converters

This paper presents fully integrated label-free DNA recognition circuit based on capacitance measurement. A CMOS-based DNA sensor is implemented for the electrical detection of DNA hybridization. The proposed architecture detects the difference of capacitance through the integration of current mismatch of capacitance between reference electrodes functionalized with only single-stranded DNA and sensing electrodes bound with complementary DNA strands specifically. In addition, to minimize the effects of parallel resistance between electrodes and DNA layers, the compensation technique of leakage current through the use of constant current charging and discharging is implemented in the proposed detection circuit. The chip was fabricated in 0.35um 4-metal 2-poly CMOS process, and 16×8 sensing electrode arrays were fabricated by post-processing steps.

Se-Won Wang

Papers

A 40 mV Transformer-Reuse Self-Startup Boost Converter With MPPT Control for Thermoelectric Energy Harvesting

A Single-Inductor Switching DC–DC Converter With Five Outputs and Ordered Power-Distributive Control

A high-stability emulated absolute current hysteretic control single-inductor 5-output switching DC-DC converter with energy sharing and balancing

Integrated zero-inductor-current detection circuit for step-up DC-DC converters

An electronic DNA sensor chip using integrated capacitive read-out circuit