Active rectification

Active rectification, or synchronous rectification, is a technique for improving the efficiency of rectification by replacing diodes with actively controlled switches, usually power MOSFETs or power bipolar junction transistors (BJT). Whereas normal semiconductor diodes have a roughly fixed voltage drop of around 0.5-1 volts, active rectifiers behave as resistances, and can have arbitrarily low voltage drop. Historically, vibrator driven switches or motor-driven commutators have also been used for mechanical rectifiers and synchronous rectification. Active rectification has many applications. It is frequently used for arrays of photovoltaic panels to avoid reverse current flow that can cause overheating with partial shading while giving minimum power loss. It is also used in switched-mode power supplies (SMPS). Motivation The constant voltage drop of a standard p-n junction diode is typically between 0.7 V and 1.7 V, caus

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High voltage power supply system for tethered drone part II

Clément Bongini

A high voltage power supply system for a tethered drone is presented. The project is a follow-up to a previous semester project and the purpose of this project is to review the implementation, improve the design and solve problems. The system consists of an inverter part, a transformer part and a rectifier part. The input voltage is 600 VDC and the output voltage is 12VDC for a maximum power of 1500W. The inverter part is composed of 4 transistors controlled by two gate drivers. On the other side of the transformer, we have a bridge rectifier which will be implemented in 3 different ways: a full-bridge diode and two new active rectification systems, including mosfets and controllers. We will first present the different systems chosen, review the previous part and make improvements, then we will implement these new systems, design the prototypes and make tests for each system. Finally, we will test the whole converter.

2021

An Efficient Piezoelectric Energy Harvesting Interface Circuit Using a Sense-and-Set Rectifier

Yimai Peng

Piezoelectric energy harvesters (PEHs) are widely deployed in many self-sustaining systems, and proper rectifier circuits can significantly improve the energy conversion efficiency and, thus, increase the harvested energy. Various active rectifiers have been proposed in the past decade, such as synchronized switch harvesting on inductor (SSHI) and synchronous electric charge extraction (SECE). This article presents a sense-andset (SaS) rectifier that achieves maximum-power-point-tracking (MPPT) of PEHs and maintains optimal energy extraction for different input excitation levels and output voltages. The proposed circuit is fabricated in the 0.18-μm CMOS process with a 0.47-mm 2 core area, a 230-nW active power, and a 7-nW leakage power. Measured with a commercial PEH device (Mide PPA-1022) at 85and 60-Hz vibration frequency, the proposed circuit shows 512% and 541% power extraction improvement [figure of merit (FoM)] compared with an ideal full-bridge rectifier (FBR) for ON-resonance and OFF-resonance vibrations, respectively, while maintaining high efficiency across different input levels and PEH parameters.

IEEE2019

Instability of p-i-n perovskite solar cells under reverse bias

Christophe Ballif, Laura Ding, Marion Solange Madeleine Dussouillez, Peter Joseph Fiala, Fan Fu, Daniel Anthony Jacobs, Quentin Thomas Jeangros, Sylvain Nicolay, Florent Sahli, Arnaud Walter, Chien-Jen Yang, Ricardo Augusto Zanotto Razera

Partial shading can trigger permanent damage in photovoltaic modules because the illuminated solar cells drive the shaded cells into reverse bias. Under reverse bias conditions, perovskite solar cells have been shown to degrade quickly due to processes that have so far remained elusive. Here, we combine optical, microstructural, and electrical characterization to address the mechanisms governing perovskite solar cell degradation under reverse bias. Three main processes are shown to occur in cesium/formamidinium lead iodide/bromide cells depending on the reverse voltage applied, the duration of the reverse bias treatment and the cell structure. The first and most severe involves the formation of highly conductive shunts, preferentially in regions covered by the metal electrode (with apparently equal propensity for various metals) and, at higher reverse voltages, within the perovskite active area. Second, we find that iodide is reversibly driven into the organic electron transport layer, causing an S-shape in the current-voltage curve and lowering power conversion efficiency. Finally, under heavy reverse biasing the perovskite absorber is shown to degrade into iodide- and bromide-rich sub-layers, an irreversible process associated with a shift in the effective band gap and changes to the perovskite microstructure. Criteria that must be met to pass partial shading tests defined by the International Electrotechnical Commission are also discussed in relation to these issues, indicating the urgent need for device structures far more robust than those usually reported.

2019

Rectifier

A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The reverse operation (c

Switched-mode power supply

A switched-mode power supply (switching-mode power supply, switch-mode power supply, switched power supply, SMPS, or switcher) is an electronic power supply that incorporates a switching regulator

Diode

A diode is a two-terminal electronic component that conducts current primarily in one direction (asymmetric conductance). It has low (ideally zero) resistance in one direction, and high (ideally i

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