Interleaved High Step-up DC-DC Converter with Diode-Capacitor Multiplier Cell and Ripple-Free Input Current

In this paper interleaving and switched-capacitor techniques are used to introduce a high step-up DC-DC converter for renewable energy systems application. The proposed converter delivers high voltage gain without utilizing transformer or excessive duty cycle and features ripple-free input current which results in lower conduction losses and decreased electromagnetic interference (EMI). Lower output capacitance is another advantage of proposed converter, leading to smaller size and lower cost. Furthermore lower voltage stress on switches allows the utilization of switches with low resistance. Simulation results verify the performance of suggested converter

Investigation of a GaN-Based Power Supply Topology Utilizing Solid State Transformer for Low Power Applications

Gallium nitride (GaN) power devices exhibit a much lower gate capacitance for a similar on-resistance than its silicon counterparts, making it highly desirable for high-frequency operation in switching converters, which leads to their significant benefits on power density, cost, and system volume. High-density switching converters are being realized with GaN power devices due to their high switching speeds that reduce the size of energy-storage circuit components. The purpose of this dissertation research is to investigate a new isolated GaN AC/DC switching converter based on solid-state transformer configuration with a totem-pole power factor corrector (PFC) front-end, a half-bridge series-resonant converter (SRC) for power conversion, and a current-doubler rectifier (CDR) at its output. A new equivalent circuit model for the converter is constructed consisting of a loss-free resistor model for the PFC rectifier with first harmonic approximation model for the SRC and the CDR. Then, state-space analysis is performed to derive the converter transfer function in order to design the controllers to yield sufficient phase margins. The converter offers the advantages of voltage regulation feature of the solid-state transformer, low harmonics and close-to-unity power factor of the PFC rectifier, soft-switching of the half-bridge SRC, reduced size of the high-frequency transformer, and smaller leakage inductance of the CDR which is used for low-voltage high-current applications as the CDR draws half of the load current in the transformer secondary side yielding less copper losses. A high-frequency nanocrystalline toroid transformer, based on a modified equation to determine its leakage inductance, is designed and fabricated to satisfy the performance specifications of the converter. A meticulously planned gate driving strategy together with a Kelvin-source return circuitry is used to mitigate Miller effects, minimize gate ringing, and minimize the parasitics of the pull-down and pull-up loops of the converter. A new programming method that combines MATLAB Simulink embedded coder with code composer studio for the TMS320F28335 digital signal processor (DSP) controller is developed and demonstrated. Finally, the GaN-based AC/DC converter is experimentally verified for a 120Vac to 48Vdc/60Vdc conversion operating at 100 kHz for various loadings

Interleaved High Step-up DC-DC Converter with Diode-Capacitor Multiplier Cell and Ripple-Free Input Current

In this paper interleaving and switched-capacitor techniques are used to introduce a high step-up DC-DC converter for renewable energy systems application. The proposed converter delivers high voltage gain without utilizing transformer or excessive duty cycle and features ripple-free input current which results in lower conduction losses and decreased electromagnetic interference (EMI). Lower output capacitance is another advantage of proposed converter, leading to smaller size and lower cost. Furthermore lower voltage stress on switches allows the utilization of switches with low resistance. Simulation results verify the performance of suggested converter

Power Management ICs for Internet of Things, Energy Harvesting and Biomedical Devices

This dissertation focuses on the power management unit (PMU) and integrated circuits (ICs) for the internet of things (IoT), energy harvesting and biomedical devices. Three monolithic power harvesting methods are studied for different challenges of smart nodes of IoT networks. Firstly, we propose that an impedance tuning approach is implemented with a capacitor value modulation to eliminate the quiescent power consumption. Secondly, we develop a hill-climbing MPPT mechanism that reuses and processes the information of the hysteresis controller in the time-domain and is free of power hungry analog circuits. Furthermore, the typical power-performance tradeoff of the hysteresis controller is solved by a self-triggered one-shot mechanism. Thus, the output regulation achieves high-performance and yet low-power operations as low as 12 µW. Thirdly, we introduce a reconfigurable charge pump to provide the hybrid conversion ratios (CRs) as 1⅓× up to 8× for minimizing the charge redistribution loss. The reconfigurable feature also dynamically tunes to maximum power point tracking (MPPT) with the frequency modulation, resulting in a two-dimensional MPPT. Therefore, the voltage conversion efficiency (VCE) and the power conversion efficiency (PCE) are enhanced and flattened across a wide harvesting range as 0.45 to 3 V. In a conclusion, we successfully develop an energy harvesting method for the IoT smart nodes with lower cost, smaller size, higher conversion efficiency, and better applicability. For the biomedical devices, this dissertation presents a novel cost-effective automatic resonance tracking method with maximum power transfer (MPT) for piezoelectric transducers (PT). The proposed tracking method is based on a band-pass filter (BPF) oscillator, exploiting the PT’s intrinsic resonance point through a sensing bridge. It guarantees automatic resonance tracking and maximum electrical power converted into mechanical motion regardless of process variations and environmental interferences. Thus, the proposed BPF oscillator-based scheme was designed for an ultrasonic vessel sealing and dissecting (UVSD) system. The sealing and dissecting functions were verified experimentally in chicken tissue and glycerin. Furthermore, a combined sensing scheme circuit allows multiple surgical tissue debulking, vessel sealer and dissector (VSD) technologies to operate from the same sensing scheme board. Its advantage is that a single driver controller could be used for both systems simplifying the complexity and design cost. In a conclusion, we successfully develop an ultrasonic scalpel to replace the other electrosurgical counterparts and the conventional scalpels with lower cost and better functionality

A 32 mV/69 mV input voltage booster based on a piezoelectric transformer for energy harvesting applications

This paper presents a novel method for battery-less circuit start-up from ultra-low voltage energy harvesting sources. The approach proposes for the first time the use of a Piezoelectric Transformer (PT) as the key component of a step-up oscillator. The proposed oscillator circuit is first modelled from a theoretical point of view and then validated experimentally with a commercial PT. The minimum achieved start-up voltage is about 69 mV, with no need for any external magnetic component. Hence, the presented system is compatible with the typical output voltages of thermoelectric generators (TEGs). Oscillation is achieved through a positive feedback coupling the PT with an inverter stage made up of JFETs. All the used components are in perspective compatible with microelectronic and MEMS technologies. In addition, in case the use of a ∼40 μH inductor is acceptable, the minimum start-up voltage becomes as low as about 32 mV

Interleaved coupled-inductor boost converter with multiplier cell and passive lossless clamp

As photovoltaic panels become a more dominant technology used to produce electrical power, more efficient and efficacious solutions are needed to convert this electrical power to a useable form. Solar microconverters, which are used to convert a single panel\u27s power, effectively overcome issues such as shading and panel-specific maximum power point tracking associated with traditional solar converters which use several panels in series. This thesis discusses a high gain DC-DC converter for incorporating single low-voltage solar panels to a distribution level voltage present in a DC microgrid. To do this, a converter was developed using coupled inductors and a capacitor-diode multiplying cell which is capable of high-gain power transmissions and continuous input current. This approach improves the efficiency of the system compared to cascaded converters typically used in this application. Challenges with this converter are discussed, a passive lossless clamp is introduced, and simulation results are presented. This converter has additional applications where high gain DC-DC conversion is required, including fuel cells and energy storage systems such as batteries and ultracapacitors --Abstract, page iii

High-power converters for space applications

Phase 1 was a concept definition effort to extend space-type dc/dc converter technology to the megawatt level with a weight of less than 0.1 kg/kW (220 lb./MW). Two system designs were evaluated in Phase 1. Each design operates from a 5 kV stacked fuel cell source and provides a voltage step-up to 100 kV at 10 A for charging capacitors (100 pps at a duty cycle of 17 min on, 17 min off). Both designs use an MCT-based, full-bridge inverter, gaseous hydrogen cooling, and crowbar fault protection. The GE-CRD system uses an advanced high-voltage transformer/rectifier filter is series with a resonant tank circuit, driven by an inverter operating at 20 to 50 kHz. Output voltage is controlled through frequency and phase shift control. Fast transient response and stability is ensured via optimal control. Super-resonant operation employing MCTs provides the advantages of lossless snubbing, no turn-on switching loss, use of medium-speed diodes, and intrinsic current limiting under load-fault conditions. Estimated weight of the GE-CRD system is 88 kg (1.5 cu ft.). Efficiency of 94.4 percent and total system loss is 55.711 kW operating at 1 MW load power. The Maxwell system is based on a resonance transformer approach using a cascade of five LC resonant sections at 100 kHz. The 5 kV bus is converted to a square wave, stepped-up to a 100 kV sine wave by the LC sections, rectified, and filtered. Output voltage is controlled with a special series regulator circuit. Estimated weight of the Maxwell system is 83.8 kg (4.0 cu ft.). Efficiency is 87.2 percent and total system loss is 146.411 kW operating at 1 MW load power

ANALYZING EFFICIENCY OF SWITCH-MODE WELDING POWER SUPPLY

esearches and studies have indicated that many of the welding quality issues are related to the weld schedule or power supply. During a weld, a certain amount of energy is lost which can be reduced to improve the efficiency of the power supply. This thesis presents a DC/DC buck converter power supply for small scale resistance spot welding (SSRSW), which can provide a testing platform for studies of different control modes, and at the end implement the results of the experiments and research done with this power supply. In this thesis, a model of the small scale resistance spot welding power supply has been implemented. The power supply uses pulse width modulation technique with MOSFETs to convert the power of a 12V battery to the weld current up to 1000A. Various measurements of voltage and current were taken at the respective terminals to calculate the energy losses. Capacitances were added with gradually increased values and again measurements were taken to calculate and analyze the energy losses in presence of the capacitances based on their numerical values. It was noted that the energy losses were reduced appreciably by this technique. So, the efficiency of the converters can be improved