本文選題：自適應(yīng)導(dǎo)通時(shí)間 + 降壓型變換器��； 參考：《西南交通大學(xué)》2017年碩士論文

【摘要】：近年來(lái),手機(jī)、平板電腦等電子產(chǎn)品更新?lián)Q代的速度越來(lái)越快,隨著其性能的不斷提升,它們對(duì)電源管理芯片在輸出電壓、功耗、安全性等諸多方面提出了更高的要求。在眾多的電源管理芯片中,AOT(自適應(yīng)導(dǎo)通時(shí)間)架構(gòu)的Buck變換器以其簡(jiǎn)潔穩(wěn)定的控制環(huán)路、快速的瞬態(tài)響應(yīng)和相對(duì)穩(wěn)定的工作頻率正成為降壓型電源管理芯片中的主流類型。電源管理芯片對(duì)電子產(chǎn)品中的電能進(jìn)行轉(zhuǎn)換,保證其安全性是至關(guān)重要。在所有電源管理芯片的故障中,發(fā)生過(guò)流、過(guò)溫是最主要的兩種情況,可能直接導(dǎo)致芯片被燒毀。為此,本文主要對(duì)AOT架構(gòu)的Buck變換器中的過(guò)流保護(hù)電路和過(guò)溫保護(hù)電路進(jìn)行了研究。本論文首先對(duì)電源管理芯片及其保護(hù)電路的研究背景、近年來(lái)國(guó)內(nèi)外的最新研究成果和發(fā)展趨勢(shì)進(jìn)行了簡(jiǎn)要的介紹,然后對(duì)電源管理芯片,尤其是AOT架構(gòu)Buck變換器的工作原理進(jìn)行了較為詳細(xì)的論述。隨后,本論文對(duì)適用于AOT架構(gòu)Buck變換器的過(guò)流保護(hù)電路進(jìn)行了深入研究,針對(duì)現(xiàn)有的過(guò)流保護(hù)電路中MOS管RDS電流檢測(cè)中存在的過(guò)流保護(hù)閾值隨溫度變化較大的問(wèn)題,本論文對(duì)傳統(tǒng)MOS管RDs電流檢測(cè)中過(guò)流比較器輸入端的參考電壓VREF進(jìn)行了改進(jìn),用一個(gè)PMOS管的漏源電壓VDS提供參考電壓給過(guò)流比較器,取代了通常使用的基準(zhǔn)電壓源。這樣使得溫度對(duì)載流子遷移率μ以及兩個(gè)MOS管的導(dǎo)通壓降的影響相互抵消,得到了一個(gè)基本不隨溫度變化的過(guò)流保護(hù)閾值,始終把電感電流限制在3.2A以下。為了盡可能減小過(guò)流保護(hù)過(guò)程中電路的功耗,本論文還在限流方式中引入了打嗝模式(Hiccup Mode),在短時(shí)間過(guò)流時(shí)采取恒定輸出電流的限流方式,一旦過(guò)流故障得到排除,輸出電流能迅速恢復(fù)正常;在長(zhǎng)時(shí)間過(guò)流時(shí)采取降低輸出電流的限流方式,每隔一段時(shí)間重復(fù)進(jìn)行一次軟啟動(dòng),大大降低了平均輸出電流,降低了功耗。在過(guò)溫保護(hù)電路的設(shè)計(jì)中,本論文用工作在亞閾值區(qū)的MOSFET取代通常使用的BJT來(lái)產(chǎn)生PTAT正溫度系數(shù)電壓和CTAT負(fù)溫度系數(shù)電壓,降低了保護(hù)電路的靜態(tài)功耗至5uA。同時(shí),在自偏置PTAT和CTAT電流源中對(duì)低壓寬擺幅共源共柵電流鏡進(jìn)行了改進(jìn),用兩個(gè)電阻為共源共柵電流鏡的MOSFET提供偏置,在提高PTAT、CTAT電流源精度的同時(shí)進(jìn)一步降低了所需的電源電壓,HSPICE仿真得出該過(guò)溫保護(hù)電路在1.5V-7V的電源電壓下都能正常工作,不同電源電壓下的過(guò)溫保護(hù)閾值容差僅0.1275℃C。
[Abstract]:In recent years, the speed of upgrading electronic products such as mobile phones, tablets and so on is getting faster and faster. With the continuous improvement of their performance, they put forward higher requirements on the output voltage, power consumption, security and other aspects of power management chips. In many power management chips, AOT (adaptive on-time) architecture Buck converter is becoming the mainstream type of the step-down power management chip with its simple and stable control loop, fast transient response and relatively stable operating frequency. It is very important for power management chip to convert electric energy in electronic products to ensure its safety. In all the faults of power management chips, overcurrent and overheating are the two most important cases, which may directly lead to the chip being destroyed. In this paper, the overcurrent protection circuit and the over-temperature protection circuit in the Buck converter with AOT architecture are studied in this paper. In this paper, the research background of power management chip and its protection circuit, the latest research results and development trend at home and abroad in recent years are briefly introduced, and then the power management chip is introduced. Especially, the working principle of AOT Buck converter is discussed in detail. Then, the overcurrent protection circuit suitable for Buck converter with AOT architecture is studied in this paper. Aiming at the problem of overcurrent protection threshold of RDS current detection of MOS transistor in the existing over-current protection circuit, the threshold value of overcurrent protection varies greatly with temperature. In this paper, the reference voltage VREF of the input of the over-current comparator in the traditional MOS tube RDs current detection is improved. The reference voltage is provided to the over-current comparator by the drain voltage VDS of a PMOS tube, which replaces the reference voltage source commonly used. In this way, the effect of temperature on carrier mobility 渭 and on voltage drop of two MOS transistors is counteracted, and an over-current protection threshold is obtained, which limits the inductance current below 3.2A. In order to reduce the power consumption of the circuit in the process of over-current protection as much as possible, this paper also introduces the hiccup mode in the current limiting mode, and adopts the constant output current limiting mode in the short time overcurrent, once the over-current fault is eliminated. The output current can be restored to normal rapidly, and the current limiting mode is adopted to reduce the output current for a long time, and the soft start is repeated every other time, which greatly reduces the average output current and reduces the power consumption. In the design of over-temperature protection circuit, the PTAT positive temperature coefficient voltage and the CTAT negative temperature coefficient voltage are generated by replacing the usual BJT with the MOSFET working in the sub-threshold region. The static power consumption of the protection circuit is reduced to 5 UA. At the same time, the low voltage wide swing cascode current mirror is improved in self-biased PTAT and CTAT current sources. Two resistors are used to provide bias for the MOSFET of the common gate current mirror. The simulation results show that the over-temperature protection circuit can work normally under the power supply voltage of 1.5V-7V, and the threshold tolerance of over-temperature protection is only 0.1275 鈩，

本文編號(hào)：1899937