Study On Smart Power Integrated Circuits

Smart power integrated circuits (SPIC) means power devices, signal processingsystem, interface circuits, protect circuits and detection circuits are integrated in amonolithic chip. SPICs are used everywhere, like consumer electronics, computer,domestic appliance, lightning, industrial control, aerospace, military area and so on.With the increase of the area which needs electricity and the focus on the environment,efficiency of processing electricity and cost are becoming the hot spot. SPIC hasbecome one of the most active areas of the whole semiconductor industry. The demandof decreasing of the energy cost and economic cost of the electronic products will boostthe development of SPIC.An off-line switched mode power supply (SMPS) chip CXB1101is studied in thedissertation. To design an off-line SMPS chip, the technology, the power devices andthe circuits need to be designed carefully together. The research of the dissertationfocuses on the following parts: design of the technology process, design of the highvoltage start-up current source, design of the control circuits and improvement of thepower devices.The author’s original main work is as follows.1. The technology process for the off-line SMPS chip is designed. The C1process,on which the chip is designed, is based on the OPT VLD technology proposed byProfessor Chen and is compatible with the main stream micron/submicron technologyprocess. The devices contain VDMOS and LDMOS which sustain800V breakdownvoltage, NMOS and PMOS which sustain50V breakdown voltage, NMOS and PMOSwhich sustain10V breakdown voltage and zener diodes, resistors, capacitors. Theimpurity distribution after multiple diffusion processes is analyzed and a simpleexpression for describing the distribution is given. The expression is helpful andinstructive to the design and fabrication of devices.2. The high voltage start-up current source needed in the SMPS chip is designed. Ahigh voltage start-up current source is always needed in a SMPS to provide start-up current for the control ICs. Usually external components or extra masks are used toform the current device. Based on Professor Chen’s patent “Method of producing alow-voltage power supply in a power integrated circuit”, two types of current source aredesigned. One of them provides output voltage about5V; the other provides outputvoltage larger than10V. The second one is used in the chip. Experimental results show,without using external components and extra mask, the high voltage start-up currentsource can start up and re-startup as designed. The current sources draw little current orno current from the line when shut down.3. The control ICs in the chip are designed. The power device in the chip needscontrol ICs to control its switch on and off, and to protect it. The regulator part,reference part, oscillator part and logic part are introduced in the dissertation. Thefabricated chip is tested. Experimental results show, the control ICs are able to functionas designed; the chip is able to start up and re-startup as designed; under a line voltageof100V, the chip is able to provide an amount of power as required. However, theelectrical characteristics are not fully accomplished and the chip needs to be altered.4. A novel LIGBT structure with a shorting PMOST driven by a p-island in the driftregion is presented. As the shorting PMOST turns on and off automatically during turnoff and on state, low on state voltage and fast switching capability are combined in onestructure. Simulated results show no increase of on state voltage and a drastic drop offall time for emitter current from120ns to12ns compared to the one with the shortingPMOST turned off all the time. A drop of turn off loss from2mJ/cm2to1.43mJ/cm2isobtained compared to the conventional LIGBT.