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A new low-cost and efficient cold cathode fluorescent lamp (CCFL) inverter for liquid crystal display (LCD) application is suggested in this paper. The topology of the inverter is derived from modified class E-type resonant electronic ballasts and has a dc-like input current. In addition, a new sensing circuit for lamp current and transformer voltage is proposed. A simple RC-network measures the voltage of a ballasting capacitor in series with the lamp instead of the lamp current itself while the lamp is floated. Utilizing the printed circuit board capacitors for the sensing capacitors and integrating small-valued sensing resistors into a control integrated circuit make the inverter very simple, efficient, and cost-effective. The new sensing circuit can solve many problems that arise when a terminal of the lamp is grounded to sense the lamp current. The control circuits for the prototype experiments are also described in detail. The frequency control scheme with a fixed off-time and a varying on-time was chosen to maintain the operation of zero-voltage switching in the entire dimming range and to reduce the complexity of the control circuits. The control circuits have an analog dimming function using a current control loop, a low frequency pulsewidth modulation dimming, open-lamp protection and voltage regulation, and soft-on/off functions. Index Terms--Class E, cold-cathode fluorescent lamp (CCFL), current sensing, electronic ballasts, printed circuit board (PCB) capacitance, protection, resonant inverter, voltage sensing.

The layout of power multichip modules is one of the key points of a module design, especially for high power densities, where couplings are enlarged. This paper focuses on dynamic current imbalance between paralleled chips. It can be principally attributed to gate circuit dissymmetry, which modifies inductances and coupling, especially with the power circuit. This paper describes the analysis of an existing power module. An optimization process based on a modification of the gate circuit geometry allows balancing current during switching phases. This approach will be validated with experimental measurements and applied on an existing module. Index Terms--Direct bonding copper (DBC) tracks, power multichip modules, printed circuit board (PCB).

In the previous work, a way to improve packaging of power electronic converters by increasing integration level and using multifunctional construction parts is presented. The quantities intended to evaluate integration level and volumetric utilization in power converters are introduced. Based on these values, a number of methods to increase the integration level are presented. A design process in the form of a flow chart that implements these methods in concrete design problems is presented. In this paper, the design process is applied to a dc/dc 42/14-V converter for automotive applications. Utilizing commercially available technologies that lend themselves to mass production this design process results in three packaging concepts, namely lead frame converter, printed circuit board embedded converter, and heat conductor converter. These concepts are then compared to a benchmark converter implemented in the conventional, discrete packaging technology. It is shown that by smart use of parts in the converter construction, the high values of integration level and high power densities can be achieved. Index Terms--Heat conductor converter, lead frame converter, power electronic converters, printed circuit board (PCB).

This paper discusses the use of printed circuit board (PCB) integrated inductors for low power dc/dc buck converters. Coreless, magnetic plates and closed core structures are compared in terms of achievable inductance, power handling and efficiency in a footprint of 10 x 10 [mm.sup.2]. The magnetic layers consist of electroplated NiFe, so that the process is fully compatible with standard PCB process. Analytic and finite element method (FEM) methods are applied to predict inductor performance for typical current waveforms encountered in a buck converter. Conventional magnetic design procedures are applied to define optimum winding and core structures for typical inductor specifications. A 4.7 [micro]H PCB integrated inductor with dc current handling of up to 500 mA is presented. This inductor is employed in a 1.5 W buck converter using a commercial control integrated circuit (IC). The footprint of the entire converter measures 10 x 10 [mm.sup.2] and is built on top of the integrated inductor to demonstrate the concept of integrated passives in power electronic circuits to achieve ultra flat and compact converter solutions. Index Terms--Electroplating, embedded PCB magnetics, integrated magnetics, low power conversion, magnetic design study, ultra flat inductors.

Gate drive circuits for modern power electronic switches, such as MOSFET and insulated gate bipolar transistor (IGBT), often require electrical isolation. This paper describes the modeling and experimental results of some coreless printed circuit board (PCB)-based transformers that can be used for MOSFET and IGBT devices at high-frequency (500 kHz to 2 MHz) operation. PCB-based transformers do not require the manual winding procedure and thus simplify the manufacturing process of transformer-isolated gate drive circuits. With no core loss, coreless transformers are found to have favorable characteristics at high-frequency operations. This project demonstrates an important point that the size of the magnetic core can approach zero and become zero when the frequency is sufficiently high. Index Terms - Coreless PCB transformers, gate drive circuits, high-frequency magnetics.

Gate drive circuits for power MOSFET's and insulated gate bipolar transistors (IGBT's) often require electrical isolation. Coreless printed circuit board (PCB) transformers have been shown to have desirable characteristics from a few hundreds of hertz to a few megahertz and can be used for both power and signal transfer at low-power level. At low operating frequency, the magnetizing inductance has such low impedance that the driving power requirement could become excessive. This paper describes the use of a coreless PCB transformer for isolated gate drive circuits over a wide-frequency range. based on a resonance concept, the optimal operating condition that minimizes the power consumption of the gate drive circuits is developed and verified with experiments. The coreless PCB transformer demonstrated here confirms a fundamental concept that the size and volume of a magnetic core could approach zero and become zero if the operating frequency is sufficiently high. Coreless PCB transformers do not require the manual winding procedure and tires simplify the manufacturing process of transformer-isolated gate drive circuits and low-power converters. Their sizes can be much smaller than those of typical core-based pulse transformers. The electrical isolation of a PCB is much higher than that of an optocoupler. Index Terms - Coreless PCB transformers, gate drive circuits, high-frequency magnetics.

This paper describes the modeling and implementation of a coreless printed circuit board (PCB)-based transformer with 'multiple' secondary outputs. This new PCB transformer has been successfully applied in complementary gate drive circuits in a novel low-profile power converter with high-power density and a converter bridge. The PCB-based transformers do not require the manual winding procedure and thus simplify the manufacturing process of transformer-isolated gate drive circuits. The use of the multiple secondary outputs can in principle simplify the complementary gate drive circuits that are often required in many power electronics applications. Index Terms - Coreless PCB transformers, gate drives, magnetics.