Abstract - A brushless direct current (BLDC) fan motor driver system using sinusoidal PWM (SPWM) is introduced. The driver board is assembled in the motor to minimize the system size. Based on the signal from the hall position sensor on the board, the controller generates the SPWM input for the power module to drive the BLDC motor. Because it is a sinusoidal PWM instead of a square PWM, both vibration and noise are lower. Experimental results are presented to verify the stability of the driver system.

Abstract - Evaluations in surface mount board assembly are conducted for two advanced packages, the PQFN3x3 and PQFN5x6. These packages offer very low inductance for better circuit performance. This paper will provide practical guidance about PCB mounting and thermal management. It will evaluate processes such as stencil printing, component placement and reflow. Stencil design has shown to be the most critical. In the reflow process, exposure to temperature above its rating will result in reliability risks. Because of this risk, the thermocouple location must be considered in temperature profiling. Temperature cycle test, drop test, vibration and bending tests are conducted to determine reliability of the assembly process. Thermal simulation is conducted using ANSYS® software, showing the effect if voids are present in the solder between the package terminals and the land pad. Finally, recommendations are presented to ensure successful assembly.

Abstract - Among various kinds of soft-switching converters, the asymmetric PWM half-bridge converter has drawn considerable attention due to its simplicity, inherent zero voltage switching (ZVS) capability and fixed-frequency operation. This paper presents an analysis and reviews practical design considerations for the asymmetric half-bridge converter. It includes designing the transformer and selecting the components. The step-by-step design procedure explained with a design example will help engineers design the asymmetric half bridge converter.

Abstract - Auxiliary power supplies are required to have low standby power consumption at light load conditions. These power supplies also offer desirable features such as low cost, high efficiency and a Line Under Voltage Lockout (UVLO) function to detect the input voltage so the main power supply will not have to operate at low input voltage ranges. Fairchild’s FSQ510 has been specifically designed for low power consumption and valley switching control and is ideal for auxiliary power supplies. This paper will outline a design procedure for an auxiliary power supply using the FSQ510.

Abstract - The design of the main transformer is a critical part of designing a switch mode power supply. Understanding the process of making cores from powder into a final core shape, and understanding the effects of parameters like core loss, permeability and flux density, designers are better able to choose the right material to achieve the smallest size with lowest losses and reduced cost. With the additional understanding of AC losses and layer arrangements, designers can also optimize the windings to create a solid magnetic design with small size and high efficiency.

Abstract - Boundary conduction mode power factor converters are widely used in lower power off-line power supplies. Their application at higher power levels is less practical due to the high amplitude of the inductor ripple current that puts a burden on the EMI filter and can be a significant source of power dissipation in the boost inductor and power switch of the converter. Interleaving two of these boundary conduction mode converters mitigates the input filter problem and to a certain extent the issue of high RMS currents of the semiconductor devices. Interleaved BCM PFC circuits are becoming popular in the industry. This paper analyzes the advantages of such a solution, highlights critical design issues related to power factor correction in general, and addresses the specific requirements and potential solutions to control an interleaved boundary conduction mode power factor converter.

Abstract - The role of the Power MOSFET in achieving high efficiency converter design is the focus of this paper. It gives a brief overview of current low voltage MOSFET trench technologies, along with a discussion of on resistance versus gate charge tradeoffs for MOSFETs optimized for use as either control or synchronous switches. It also covers the importance of the integrated Schottky diode (SyncFET™) in synchronous rectification, and the necessity of packaging technologies with low parasitic inductance and resistance.

The MOSFET-to-circuit interaction will be discussed in detail with the aid of TCAD mixed-mode simulations. All relevant MOSFET switching events will be analyzed: common source inductance versus drain current rise and fall, body diode conduction and reverse recovery, external Schottky diode layout challenges versus SyncFET™ advantages, and elimination of shoot-through currents from gate bounce. The simulation of these MOSFET power losses is compared for different amounts of circuit inductance and used as background for discussing measured converter efficiency data. A review of popular MOSFET loss equations is also included.