电源电压转换：什么是DCDC转换器

电源电压转换：什么是DCDC转换器 电源电压转换:什么是DC/DC转换器 2009-04-10 14:28 DC/DC转换器为转变输入电压后有效输出固定电压的电压转换器。DC/DC转换器分为三类:升压型DC/DC转换器、降压型DC/DC转换器以及升 降压型DC/DC转换器。根据需求可采用三类控制。PWM控制型效率高并具有良好的输出电压纹波和噪声。PFM控制型即使长时间使用，尤其小负载时具有耗 电小的优点。PWM/PFM转换型小负载时实行PFM控制，且在重负载时自动转换到PWM控制。目前DC-DC转换器广泛应用于手机、MP3、数码相机、 便携式媒体播放器等产品中。 什么是DC(Direct Current)呢,它示的是直流电源，诸如干电池或车载电池之类。家庭用的100V电源是交流电源(AC)。若通过一个转换器能将一个直流电压 (3.0V)转换成其他的直流电压(1.5V或5.0V)，我们称这个转换器为DC/DC转换器，或称之为开关电源或开关调整器。 A: DC/DC转换器一般由控制芯片，电感线圈，二极管，三极管，电容器构成。在讨论DC/DC转换器的性能时，如果单单针对控制芯片，是不能判断其优劣的。其外围电路的元器件特性，和基板的布线方式等，能改变电源电路的性能，因此，应进行综合判断。 B: 调制方式 1: PFM(脉冲频率调制方式) 开关脉冲宽度一定，通过改变脉冲输出的时间，使输出电压达到稳定。 2: PWM(脉冲宽度调制) 开关脉冲的频率一定，通过改变脉冲输出宽度，使输出电压达到稳定。 coefficient not greater than 1.3; High efficiency: control 1 hour travel time between any two points within the various groups within the area up to half an hour, 1-hour access to the airport, 45min reached the city's main traffic hub, external highway for half an hour with the main channels connecting bus 1.5 hours between any two groups of core areas; Intensive: 2030 transit share rate of around 35%, 2050 bus sharing rate of 45% per cent. 3rd chapter, Yibin city, traffic situation and General ... 3.1.1 city traffic status 1, external transport passenger and cargo traffic in Yibin city, traffic at the present main railway, highway, waterway and air four modes of passenger and freight transport, there C: 通常情况下，采用PFM和PWM这两种不同调制方式的DC/DC转换器的性能不同点如下。 ** PWM的频率，PFM的占空比的选择方法。 * PWM调制方式 在选用较高频率的情况下(如:500KHz) (1)小负载时，效率很低。 (2)输出电压的纹波较小。 在选用较低频率的情况下(如:100KHz) (1)小负载时,效率较高。 (2)输出电压的纹波较大。 因此，在小负载或待机时间较长的情况下，选用100KHz的频率，转换电路的效率较高，但若 考虑输出电压的纹波问题， 若选用500KHz的频率，纹波电压会较小。 参考数据 电感线圈相同，频率不同时纹波电压的比较。 * PFM调制方式 占空比较大的情况(如:Duty=75%) (1)小负载时,效率较低。 (2)可输出较大的电流。 coefficient not greater than 1.3; High efficiency: control 1 hour travel time between any two points within the various groups within the area up to half an hour, 1-hour access to the airport, 45min reached the city's main traffic hub, external highway for half an hour with the main channels connecting bus 1.5 hours between any two groups of core areas; Intensive: 2030 transit share rate of around 35%, 2050 bus sharing rate of 45% per cent. 3rd chapter, Yibin city, traffic situation and General ... 3.1.1 city traffic status 1, external transport passenger and cargo traffic in Yibin city, traffic at the present main railway, highway, waterway and air four modes of passenger and freight transport, there 占空比较小的情况(如:Duty=58%) (1)小负载时,效率较高。 (2)输出的电流较小。 因此，选用75%的占空比，可得到较大的输出电流。若在负载不是很大的情况下，选用58%的占空比，效率会较高。 参考数据 电感线圈相同，占空比不同时输出电压和效率的比较。 * 用MOSFET替换BJT晶体管作为外围电路的开关部件对效率的影响。 效率会相应提高。因为BJT管需要对其基极提供驱动电流，这增加了电路的电流消耗，而MOSFET是电压驱动，无需对其 栅极提供电流，也就不会增加电路的电流消耗。 但是，实际应用时请考虑MOSFET是否对周边元器件产生影响。 ** DC/DC转换器(开关调整器)的尖峰噪音。 DC/DC转换器(开关调整器)通过开关动作进行升压或降压，特别是晶体管或场效应管处于快速开关时，会产生尖峰 噪音，以及电磁干扰。 coefficient not greater than 1.3; High efficiency: control 1 hour travel time between any two points within the various groups within the area up to half an hour, 1-hour access to the airport, 45min reached the city's main traffic hub, external highway for half an hour with the main channels connecting bus 1.5 hours between any two groups of core areas; Intensive: 2030 transit share rate of around 35%, 2050 bus sharing rate of 45% per cent. 3rd chapter, Yibin city, traffic situation and General ... 3.1.1 city traffic status 1, external transport passenger and cargo traffic in Yibin city, traffic at the present main railway, highway, waterway and air four modes of passenger and freight transport, there