本文關(guān)鍵詞：一款基于ACOT控制模式的降壓型變換器XD7252的設(shè)計　出處：《西安電子科技大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 開關(guān)電源 恒定導(dǎo)通時間 環(huán)路鎖頻 穩(wěn)定性

【摘要】：隨著互聯(lián)網(wǎng)技術(shù)的飛速發(fā)展,便攜式用電設(shè)備開始日益普及,電源作為這些電子產(chǎn)品不可缺少的關(guān)鍵部分,它的利用效率越來越受到人們關(guān)注。由于同一產(chǎn)品中的不同組件可能需要不同的供電電壓,所以開關(guān)電源芯片的應(yīng)用也越加普遍。同時隨著數(shù)字芯片、微處理器應(yīng)用日益普遍,對變換器而言,它們是一類在工作中非常容易發(fā)生變動的負(fù)載,負(fù)載電流的變化率較高,這就要求DC-DC變換器芯片能夠具有極快速的負(fù)載瞬態(tài)響應(yīng)速度。為了達(dá)到這些要求,人們開始研究和關(guān)注開關(guān)電源芯片的恒定導(dǎo)通控制模式,它具有極快速的瞬態(tài)響應(yīng)。本論文首先對開關(guān)電源芯片的背景知識做了簡單描述和介紹,接著對設(shè)計一款降壓型DC-DC變換器所必需的基本原理和關(guān)鍵技術(shù)進(jìn)行了詳細(xì)的論述。通過分析設(shè)計了XD7252的整體結(jié)構(gòu)和模塊劃分,制訂相關(guān)模塊的性能指標(biāo),接著對關(guān)鍵子模塊進(jìn)行了設(shè)計及仿真,最后對芯片的整體電路進(jìn)行了仿真分析。本論文中采用ACOT控制模式,這種模式具有極快速的負(fù)載瞬態(tài)響應(yīng),但其平均工作頻率還是受負(fù)載和輸入電壓的影響較大,故在芯片中設(shè)計了環(huán)路鎖頻模塊,該模塊通過檢測實際的工作頻率,將此頻率轉(zhuǎn)成電壓后與預(yù)設(shè)的電壓值相比較,利用比較的結(jié)果調(diào)整導(dǎo)通時間的長短,通過反饋回路使頻率穩(wěn)定在預(yù)設(shè)的范圍之內(nèi),該設(shè)計思想可以很好的應(yīng)用于其他恒定導(dǎo)通控制模式的芯片中。在恒定導(dǎo)通控制模式下使用陶瓷電容作為輸出濾波電容時,容易產(chǎn)生次諧波振蕩而引起系統(tǒng)的不穩(wěn)定,本論文提出一種產(chǎn)生虛擬電感電流紋波的新結(jié)構(gòu),補償了通常借助輸出電容ESR生成的輸出紋波電壓信號,這種結(jié)構(gòu)在不額外增加芯片引腳的情況下有效避免了次諧波振蕩,增強了系統(tǒng)穩(wěn)定性。本文設(shè)計的變換器XD7252采用0.18μm BCD工藝,利用Cadence軟件下的HspiceS工具對其進(jìn)行電路的設(shè)計和仿真驗證。仿真結(jié)果表明,芯片的各項指標(biāo)符合設(shè)計要求。
[Abstract]:With the rapid development of Internet technology, portable electrical equipment is becoming more and more popular. Power supply is an indispensable part of these electronic products. Because different components of the same product may need different power supply voltage, the application of switching power supply chip is more and more common. At the same time, with the digital chip. Microprocessor is becoming more and more popular. For converters, they are a kind of load which is easy to change in operation, and the change rate of load current is higher. This requires the DC-DC converter chip to have extremely fast load transient response speed. In order to achieve these requirements, people began to study and pay attention to the on-on-on-control mode of switching power supply chip. It has very fast transient response. Firstly, the background of switching power supply chip is briefly described and introduced in this paper. Then the basic principle and key technology of designing a step-down DC-DC converter are discussed in detail. The overall structure and module partition of XD7252 are designed and analyzed. Then the key sub-modules are designed and simulated. Finally, the whole circuit of the chip is simulated and analyzed. In this paper, the ACOT control mode is adopted. This mode has extremely fast load transient response, but its average operating frequency is still greatly affected by the load and input voltage, so the loop frequency locking module is designed in the chip. By detecting the actual working frequency, the module converts the frequency to the voltage and compares it with the preset voltage value, and adjusts the length of the conduction time by using the comparison results. The frequency is stabilized within the preset range by the feedback loop. The design idea can be well applied to other constant on-control mode chips. When the ceramic capacitor is used as the output filter capacitor in the constant on-on control mode. It is easy to produce sub-harmonic oscillation and cause the instability of the system. This paper proposes a new structure to generate virtual inductor current ripple, which compensates the output ripple voltage signal usually generated by output capacitance ESR. This structure can effectively avoid the sub-harmonic oscillation and enhance the stability of the system without adding additional chip pins. The converter XD7252 designed in this paper adopts 0.18 渭 m BCD technology. The circuit design and simulation are carried out by using the HspiceS tool of Cadence software. The simulation results show that each index of the chip meets the design requirements.
【學(xué)位授予單位】：西安電子科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TM46

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本文編號：1362575