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Design of the Protection Circuit Applied in the BUCK DC-DC Converter

Author: LiuYuXing
Tutor: FengQuanYuan
School: Southwest Jiaotong University
Course: Microelectronics and Solid State Electronics
Keywords: DC-DC converter Protection circuit Undervoltage protection Overvoltage Protection
CLC: TM46
Type: Master's thesis
Year: 2009
Downloads: 566
Quote: 1
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Abstract

With the continuous development of electronic technology, electronic equipment functions are becoming more comprehensive and perfect, raised to the power requirements are also increasing. Because of their high level of integration, cost-effective and simple external circuit, high efficiency, etc., chip switching power supply has been widely used in many portable electronic products. This paper analyzes a widely used in distributed systems, network communications equipment, electrical equipment and laptops green buck (BUCK) direct current (DC-DC) switching converter, and focus on the analysis and design of one of the protection circuits section. Circuit protection circuit consists of two main modules: the undervoltage protection circuit and overvoltage protection circuits. The protective function of the chip is mainly reflected in the following two aspects: First, undervoltage protection circuit on the input voltage is too low, the control signal is given, the shutdown chip to prevent chip to operate normally, the input voltage fluctuations in a certain case, with certain hysteresis to prevent accidental turn-off occurs when the chip input voltage is too high, the internal voltage regulator function provides an interface circuit, to protect the internal control circuit to work; Second, the protection circuit monitors the output voltage , when the output voltage is too high, given the control signal, the output voltage promptly pulled down to protect the load, the output signal transmission path, the introduction of an appropriate response delay, which can effectively suppress voltage spikes caused by the false triggering. Chip uses 0.6umHV-BCD process is made applicable to a wide range of 4.75V-23V input, using the current control mode, the operating frequency of 340kHz. This article first BUCK-type DC-DC converter and the relevant principles commonly used chip switching power supply protection circuit are introduced. Based 0.6umHV-BCD technology, design and apply a buck dc switching power supply protection circuit protection circuit consists of two circuit sub-modules: undervoltage protection circuit, over-voltage protection circuit. Since switching applications in power input range, so in the circuit uses a new internal regulator interface circuit, conducted on the level of the appropriate conversion, so that it can meet both the internal pressure control module application needs, taking into account the protection of circuit design needs. In the overvoltage protection circuit, by setting the delay circuit, the output voltage of the solution obtained into voltage spikes caused by off-chip error problem. This is the circuit theory and practice of combining the results of the simulation. In the analysis circuit based on the principle, using HSPICE simulation software for each sub-circuit protection circuit module and the overall performance of the functions and performance parameters of the simulation, the simulation result is good.

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