發(fā)布時間：2018-10-21 08:40

【摘要】：LED是新一代綠色光源,它的優(yōu)勢在于發(fā)光效率極高、耗電量極少并且安全可靠、壽命長�，F(xiàn)在已經(jīng)普遍應用在顯示屏、汽車、背光源、家用照明等領域。LED的大量應用必將刺激與之相關的LED驅(qū)動電路的迅速發(fā)展。隨著研究的深入,LED驅(qū)動方式越來越多樣化,LED驅(qū)動電路的性能越來越優(yōu)良,功能越來越齊全。本文所敘述的線性恒流LED驅(qū)動電路,集成了功率LDMOS、控制電路和保護電路,具備PWM調(diào)光,線性調(diào)光和完善的保護措施。在220V交流條件下,芯片的輸出電流高達80mA并且可調(diào)。在全溫度范圍內(nèi),電流精度為6%。本文首先基于對各種LED驅(qū)動方式優(yōu)缺點的比較,確定了線性恒流驅(qū)動方式。然后介紹了芯片的整體結構和工作原理,并詳細敘述了芯片的部分電路模塊:括帶隙基準電路、電壓調(diào)整電路、誤差放大器和線性調(diào)光電路。帶隙基準電路用來產(chǎn)生一個穩(wěn)定可靠的帶隙基準電壓,提供給電壓調(diào)整電路。電壓調(diào)整電路的功能是基于低壓差線性穩(wěn)壓器的設計思想,將帶隙基準電壓通過電阻分壓網(wǎng)絡得到所需的基準電壓供芯片其他電路模塊使用。誤差放大器是整個芯片的關鍵模塊,它通過比較采樣電阻上電壓和基準電壓調(diào)節(jié)功率管的柵極,從而維持LED電流恒定。線性調(diào)光電路向LED電流回路注入或抽取電流。此電流隨線性調(diào)光電路的輸入電壓線性變化,流經(jīng)反饋電阻會造成采樣電阻上電壓也隨之線性變化,從而使得LED電流也發(fā)生線性變化。本文對以上四個電路模塊進行了詳細的闡述:從分析電路參數(shù)對電路性能的影響入手,制定了能滿足電路性能的指標要求;基于設定的指標,設計電路并敘述了設計思路;之后再對電路模塊進行仿真、驗證是否滿足指標要求。最后搭建整體電路,仿真、驗證整體電路的功能,并優(yōu)化整體電路的性能指標。
[Abstract]:LED is a new generation of green light source, which has the advantages of high luminous efficiency, low power consumption, safety and reliability, long life. Now it has been widely used in display, automobile, backlight, home lighting and so on. A large number of applications of LED will certainly stimulate the rapid development of related LED drive circuits. With the development of the research, the LED driver is becoming more and more diversified, and the performance of LED driver circuit is becoming more and more excellent and the function is more and more complete. The linear constant-current LED drive circuit described in this paper integrates the power LDMOS, control circuit and the protection circuit. It has PWM dimming, linear dimming and perfect protection measures. At 220 V AC, the output current of the chip is up to 80mA and adjustable. In the full temperature range, the current accuracy is 6. Firstly, based on the comparison of the advantages and disadvantages of various LED drivers, the linear constant-current drive mode is determined. Then the whole structure and working principle of the chip are introduced, and some circuit modules of the chip are described in detail, including bandgap reference circuit, voltage adjustment circuit, error amplifier and linear dimming circuit. The bandgap reference circuit is used to generate a stable and reliable bandgap reference voltage, which is provided to the voltage adjusting circuit. The function of the voltage adjusting circuit is based on the design idea of the low voltage difference linear regulator. The bandgap reference voltage is obtained through the resistive voltage divider network to be used by other circuit modules of the chip. The error amplifier is the key module of the whole chip. It adjusts the grid of the power transistor by comparing the voltage on the sample resistor with the reference voltage so as to maintain the LED current constant. The linear dimming circuit injects or extracts current into the LED current loop. The current changes linearly with the input voltage of the linear dimming circuit, and the voltage on the sample resistor changes linearly through the feedback resistor, which makes the LED current change linearly. In this paper, the above four circuit modules are described in detail: starting with the analysis of the influence of circuit parameters on the circuit performance, the paper formulates the index requirements that can meet the circuit performance, designs the circuit based on the set index, and describes the design ideas. Then the circuit module is simulated to verify whether it meets the requirements. Finally, the whole circuit is built, simulated, the function of the whole circuit is verified, and the performance index of the whole circuit is optimized.
【學位授予單位】：電子科技大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TM923.34

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