A bidirectional charge equalization circuit based on a bidirectional flyback converter topology is proposed to achieve the balance charging and discharging in series-connected battery bank. The circuit comprises a multi-input transformer, in which the batteries bank are connected to the primary windings via associated active power switches. During discharging, the batteries transfer energy to the load by activating the primary power switches. On the contrary, the batteries are charged by activating the secondary power switch in which the load is replaced by a power source. In order to simplify the control circuit and provide a flexible modulation, a digital signal processor (DSP) with the associated sensors and interface circuits are used as the control kernel. It is used to monitor the variations of battery voltages, and to regulate the duty ratio of the converter to provide a balance charging or discharging among the batteries. A battery bank with four series connected lead-acid batteries is used for illustrating the operation of the bidirectional charge equalization circuit. The experimental results advocate the applicability of the proposed approach.

In the thesis, an LED driver circuit with Power Factor Correction (PFC) and constant output current is presented. For open-loop LED driver, an insulated switching Flyback power converter is designed, and the Flyback converter will be operated in Continuous Conduction Mode(CCM). One develops equivalent mathematical model for the drivers system. The main part of this thesis is about the design and the study of a closed loop PFC control circuit using inductor voltage sensing technology. In addition, one introduces another traditional inductor current sensing control technique is included to compare with the designed control circuit. Then, one confirms the designed circuits by simulation and the experiment. From the results, the power factor can reach to 0.97, and the expected constant output current control has also been achieved.

The power supply designers choose flyback topology due to its promising features of design simplicity, cost effectiveness and multiple outputs handling capability. The designed product based on flyback topology should be smaller in size, cost effective and energy efficient. Similarly, designers focus on reducing the circuit losses while operating at high frequencies that affect the converter efficiency and performance. Based on the above circumstances, an energy efficient open loop high frequency flyback converter is designed and operated in MHz frequency region using step down multilayer PCB planar transformer. The maximum efficiency of 84.75% is observed and maximum output power level reached is 22.8W. To overcome the switching losses, quasi-resonant soft switching technique is adopted and a high voltage CoolMOS power transistor is used.

Charge imbalance may happen to series-connected batteries during charging or discharging due to the discrepancies among batteries. The charge imbalance will cause some batteries being over-charged or over-discharged and is harmful to the battery cycle-life. Moreover, the storage capacity of the battery bank will not be effectively utilized. This thesis brings forth first the concept of charge equalization on discharging for battery banks. Various control strategies are implemented on a flyback converter with a multi-input transformer to provide the balance discharging function as well as output voltage regulation. Each battery of the battery bank is connected to a primary winding of the transformer via an active power switch. The batteries transfer their energy to load according to the residual energy in each battery. Meanwhile, by continually monitoring battery voltages, exhausted batteries can be disconnected to avoid being over-discharged. A battery bank with four series-connected lead-acid batteries is used as an example to illustrate the operation of the balance discharging circuit. The complicated calculations and precise control are accomplished by a digital signal processor (DSP). The experimental results advocate the applicability of the discharging circuit and control strategies.

In the thesis, an LED driver circuit that is applied in low power lighting LED with constant output current and Power Factor Correction (PFC) is presented. The insulated Flyback converter is used for the LED driver. Power Factor Correction is realized with both the method of Voltage Follower Approach Control under Discontinuous Conduction Mode and the method of Boundary Conduction Control under Boundary Conduction Mode. Compared with Voltage Follower Approach Control, Boundary Conduction Control needs only output current feedback. Moreover, it possesses lesser magnetize inductance current, lesser electrical stress of elements, more flexible choice of elements specification, smaller output current ripples, and higher power factor under light load. The circuit design is expounded, and verified by IsSpice simulation and experiment result.

This master’s thesis deals with design and construction of experimental flyback converter with utilization of novel lossless clamp circuit for switching transistor and with utilization of silicon carbide devices. The issue of flyback converter for higher power and possible control strategies are discussed. The thesis also describes power and control circuits design, design of PCB, construction of the converter and measured waveforms. End of the thesis contains technical documentation of designed board. Designed converter was successfully built and tested.

This thesis mainly presents the design and implementation of a flyback converter with single-stage power factor correction. In the beginning, we propose different power factor collection (PFC) techniques referring to the inductor current of converter under three kinds of operation modes. In the continuous mode, we adopt the nonlinear-carrier control (NLC). Then, in the discontinuous mode and boundary mode, voltage-follower control (VFC) and transition mode technique control (TM) are adopted respectively. As to the converter analysis, we derive and verify the results of a small-signal model and perform equivalent circuit analysis by state-space averaging method, loss-free resistor (LFR) model, averaging method for two-time-scale system (AM), and current injected equivalent circuit approach (CIECA). Results derived from the above-mentioned models are compared and verified to be accurate of the system model. Furthermore, the control function and element design are implemented by simulation. We perform a PI controller to achieve better power factor based on results of analysis of the time and frequency domains analysis. Finally, three sets of different hardware are fabricated and verified depending on measured result and theoretical simulation.

This thesis studies residential dc distribution system with primary focus on point-of-load (POL) converters. The growing number of inherently dc loads, increasing penetration of distributed energy resources (DERs) and advancements in power electronic converters are some of the reasons to reconsider the existing residential ac distribution system. A dc distribution system can achieve higher efficiency by eliminating the ac-dc rectifiers and power factor correction stages currently used in most domestic electronic appliances. In this thesis, 380V is identified as a suitable voltage level for the main dc bus. Safety issues are discussed and common domestic loads are characterized. Two common converter topologies – buck and flyback converters are suggested as POL converters for heating and LED lighting loads respectively. State-feedback control is designed and implemented for buck converter and current mode control of flyback converter is implemented. A 500W POL buck converter using state-feedback with integral control is designed and tested for heating load applications. Finally a small dc distribution system is simulated using the converter models. The response of the system is stable under load and line changes. / text

The thesis deals with the design and construction of a switching power supply with output voltage adjustable from 0 to 1200 V and rated power of 120 W, which will be used to replace the existing high voltage power supply for the irreversible electroporation (IRE) device developed at UVEE FEEC BUT. The thesis focuses on a basic description of the IRE device, a description of usable converter topologies and a selection of the best topology for the required purpose. The selection of the control circuit concept and its design are also integral parts of the thesis. The final part of the thesis contains the assembly of the power supply and the measurement verifying its function.

The aim of this thesis is to design a step-up DC/AC converter, an inverter from 12 V to 120 Vrms, with a sinus output signal. The converter should deliver a continuous performance of 300 W and a double peak power output of 600 W. The supposed usage of this inverter would be as a back-up power source for the circulatory pump of the central heating in the case of power outage. The inverter is consisting of a T-type power section.