An improved model for rosen type piezoelectric transformer for power converter

Piezoelectric transformer is attractive because of its small thickness. Rosen Type piezoelectric transformer has high step-up ratio which is advantageous for high voltage power converters. In most cases the load has a range of variable resistances that can greatly affect the output characteristic of a piezoelectric transformer. The conventional model is not sufficient to model the gain characteristics with a wide load range. In this paper a modified model is presented. A simple fictitious resistor is employed to modify the conventional model and it produces excellent match with measurements. Experimental measurements are given to show the merits of the proposed model.published_or_final_versio

Design and analysis of discontinuous mode series resonant converter

This paper aims at designing a low power, off-line, high efficiency, complex in size, twin-capacitors half-bridge series resonant converter. It gives steps by steps design procedures of the discontinuous mode series resonant converter starting from power stage circuit design to feedback loop control design. The small signal analysis is based on the injected-absorbed current method.published_or_final_versio

Comparison of three approaches on DSP based digital controlled 2-wheeler forward converter

This paper presents the design of digital controls of PWM DC-DC converters on a digital signal processor (DSP) based platform. Three digital control approaches are being investigated: discretisation of analog control, digital proportional-integral-derivative (PID) control, and deadbeat control. Simulation results of the three types of control are shown. Experimental results of a 25W 2-wheeler forward converter prototype are presented to verify the design.published_or_final_versio

Fast response Full Bridge Power Factor Corrector

A fast response Full Bridge Power Factor Corrector (FBPFC) is presented in this paper. The converter is combined by two interleaved boost cells and a conventional full bridge converter. As the interleaving technique is applied, the input ripple current of FBPFC are reduced. Experimental result shows that the maximum power factor is 0.98 even without input filter.published_or_final_versio

A novel soft switching crossing current resonant converter (XCRC)

Unlike other resonate or soft-switching converter, this novel topology employs only two switches and a very simply control method. The inherent constant power protection feature is another merit. No special resonate chip is needed to control the circuit. By adding two diode parallel with the dividing capacitors and selecting the capacitors for a small value that will fully charge and discharge in one cycle, one can obtain the zero voltage switching characteristic and control the output voltage regulation by frequency modulation. An industrial standard PWM chip can be easily modified to a VCO as the control element.published_or_final_versio

Leakage inductance calculation of complex transformer constructions based on a simple two-coil inductor model

The paper presents a set of systematic matrices operation derived from Kirchhoff s Node Law with the base of a simple two-coil inductor model to deduce leakage inductances of windings seen from the schematic point of view. This method provides a platform in calculating leakage inductances of complex transformer structures. Its robustness covers different kinds of concentric winding structures where by getting accurate values of mutual inductances between all combinations of winding elements in a pair-wise sense, accurate leakage inductances can be deduced through the matrices operation without any computational simulations. In essence, such operation reduces lots of difficult magnetic problems within a transformer into determination of mutual and self inductances of winding elements through a simple two-coil inductor model. The approach has been implemented on PowerESIM [5] [6], a web base server type power converter design program, for reader to test.published_or_final_versio

Interleaved boost power factor corrector operating in discontinuous-inductor-current mode

This paper presents the basic operation of the Discontinuous-Inductor-Current-Mode (DICM) boost PFC and the improvement achieved by interleaving technique. The PFC is constructed by at least two boost cells, each cell is kept running in DICM. Input current of the PFC is analyzed by numerical method and the optimum power factor is calculated in different modes of operation. The calculated result is verified by experiment and presented in graphical form with detailed discussion. The result shows that interleaving technique can alleviate the ripple current and improve the power factor. The improvement is obvious for the number of boost cells equal to 2 or 3 and the ripple alleviation is better when the PFC is operated in fixed frequency mode. The optimum power factor is improved up to 0.99 even without an input filter.published_or_final_versio

Inductance calculations of printed windings of power transformers using partial inductance method

The method of printed windings of transformer-windings are printed on a printed circuit board (PCB) and all windings are embedded in a stack of these PCBs is a promising way in controlling the windings' shape and air spacing in a fixed pattern; it eliminates the parameter variations in a great deal. The partial inductance method gives an easy and accurate approach to calculate loop inductance by the generalised partial inductance, which is derived from dividing the whole loop into finite length of elements. Self and mutual inductance are the summation of inductance contributed from individual elements. This is useful in predicting the leakage inductance which has been the most undesirable parameter in PWM converter. And this method can also be applied to transformers in resonant converters in which inductances have to be accurately controlled.published_or_final_versio

A microprocessor controlled piezoelectric power converter

Piezoelectric transformer (PT) for power conversion is receiving more and more attention because of its small thickness and high energy density. A major challenge of PT converter is the resonant characteristic of the PT that affects the performance of the whole converter. This paper presents a microprocessor controlled piezoelectric power converter system for Cold Cathode Fluorescent Lamp (CCFL) that can provide stable output around the resonant point of the PT. A micro-controller based control algorithm is introduced to provide frequency tracking. Experimental results are presented and illustrate that this system is suitable for such application.published_or_final_versio

Analysis of parallel connection of Rosen type piezoelectric transformers

Single layer Rosen type piezoelectric transformer is an attractive component for portable high voltage applications because of its small thickness and low cost. It is favorable for applications such as LCD backlight cold cathode fluorescent lamp converters where thickness is an important feature. In general piezoelectric transformer can produce low output power only and this is a major drawback in many applications where more power is needed. A promising solution is parallel connection of several transformers. In this paper parallel connection of piezoelectric transformers is investigated and discussed. A simple model is produced which allows representation of characteristics of parallel Rosen type piezoelectric transformers. Comparisons with experimental result verify the model. This model provides engineers with a simple and useful design tool.published_or_final_versio