|
|
|
| | | | | | | | | ,这算盘估计打错了,你要仔细看规则哦,是做出来了,才报的。500w以下 |
|
|
|
| | | | | | | | | | | 呵呵,开始收集和查阅LLC资料了,希望顺利完成,拿到经费。 |
|
|
|
|
|
|
|
|
| | | | | 找资料时google到得第一份资料是来自弗吉尼亚大学博士论文,论文第四章详细的介绍LLC 转换器,后来才发现是大名鼎鼎的杨博士写的。
英文版的,比较难啃,先发上来分享下。
准备看完,如果有时间可以尝试翻译把它翻译到论坛上来,痛惜学习英文吧,顺便报考一个个英文考试。
LLC CONVERTER.pdf |
|
|
|
|
|
| | | | | | | 翻译之——4.1 introduction
双语,便于对照,若有错漏,请指正。英文也是纯手打,权当学习英语吧。
LLC resonant converter(LLC谐振转换器)
4.1 introduction(简介)
In previous chapter,the trends and technical challenges for front end DC/DC converter were discussed.
在前面的章节,已经讨论了前端DC-DC转换器的发展趋势和技术上所面临的挑战。
High power density,high efficiency and high power are the major driving force for this application。
高功率密度、高效率和大功率是它的主要驱动力。
Hold up time requirement poses big penalty to system performance. Two methods were proposed in chapter 2 to solve this problem and improve the efficiency.
保持时间的要求对于系统性能表现来说是一个大障碍。在第二章已经推荐了2种方法来解决这个问题和提高转换效率。
Range winding solution could improve the performance at high input voltage significantly, but with extra devices, winding and control circuit. Asymmetrical winding solution provides a simpler solution, but could only apply to asymmetrical half bridge topology.
在高压输入的情况下,平面(排)绕组方案可以显著提升转换器的性能,但它需要用到额外的器件、绕组和控制电路。非对称绕组方案相对更简单,但只能应用于“非对称半桥拓扑”中。
Also it introduced other problems like discontinuous output current and unbalanced stress.
第二章也介绍了诸如“非连续输出电流”和“不平衡应力”等问题。
To catch up with and move ahead of the trend, higher switching frequency, higher efficiency and advanced packaging are the paths we are taking now.
我们正在采用跟高的开关频率、更高的效率和更高先进的封装等方法,以达到紧跟和超越转移器的发展趋势的目的。
Within all these issues, a topology capable of higher switching frequency with higher efficiency is the key to achieve the goal.
在所有问题中,一个拓扑如何在高的开关频率情况下做到高效率是达到目的的关键。
With the techniques proposed in chapter 2, the performance at normal operation could be improved. But none of these methods dealt with the switching loss problem of PWM converter.
在普通的应用中第二章所推荐(或提及)的技术能提高转换器的性能。但它们不能解决脉宽调制(PWM)转换器开关损耗的问题。
Even with Zero Voltage Switching technique the turn on loss could be minimized; turn off loss still limits the capability of the converter to operate at higher switching frequency.
零电压转换技术虽然可以减少开关开通过程时的损耗,但它的关断过程的损耗依然限制其工作在更高的频率下。
Resonant converter, which were been investigated intensively in the 80’s, can achieve very low switching loss thus enable resonant topologies to operate at high switching frequency.
在八十年代期间曾被大量研究的谐振转换器可以做到很低开关损耗,因此它可以工作在更高的开关频率。
In resonant topologies, Series Resonant converter (SRC), Parallel Resonant Converter (PRC) and Series Parallel Resonant Converter (SPRC, also called LCC resonant converter) are the three most popular topologies.
在所有的谐振拓扑中,串联谐振转换器(SRC)、并联谐振转换器(PRC)和串并联谐振转换器(SPRC,也叫LCC谐振转换器)是最流行的。
The analysis and design of these topologies have been studies thoroughly. In next part, these three topologies will be investigated for front-end application.
它们的分析方法和设计方法已被充分研究。在本文下一部分我们将探讨(研究)它们在前端转换的应用情况。 |
|
|
|
| | | | | | | 4.2 Three traditional resonant topologies(三种传统谐振拓扑)
In this part, these topologies will be evaluated for front end DC/DC application. The major goal is to evaluate the performance of the converter with wide input range. For each topology, the switching frequency is designed at around 200 kHz.
这部分,我们将评估在宽电压输入前端DC-DC应用时这三种拓扑的性能。评估时开关频率都设计在200kHz左右。
4.2.1 Series resonant converter(串联谐振转换器)
The circuit diagram of a half bridge series resonant converter is shown in Figure4.1 [B8]-[B13]. The DC characteristic of SRC is shown in Figure 4.2.
图4.1是半桥式串联谐振转换器,它的直流特性见图4.2.
The resonant inductor Lr and resonant capacitor Cr are in series. They form a series resonant tank. The resonant tank will then in series with the load. From this configuration, the resonant tank and the load act as a voltage divider.
谐振电感Lr和谐振电容Cr串联,它们组成一个串联谐振回路,且与负载串联。这个电路结构中,谐振回路和负载组成一个分压器。
By changing the frequency of input voltage Va, the impedance of resonant tank will change. This impedance will divide the input voltage with load. Since it is a voltage divider, the DC gain of SRC is always lower than 1.
谐振回路的阻抗随着输入电压Va的频率改变而改变,而输入电压Va将被它的阻抗将与负载分压。由于SRC是一个分压器,所以SRC的直流增益总是小于1.
At resonant frequency, the impedance of series resonant tank will be very small; all the input voltage will drop on the load. So for series resonant converter, the maximum gain happens at resonant frequency.
谐振回路的阻抗在谐振频率点将非常小,所有的输入电压都降落负载上。因此串联谐振转换器的最大增益发生在谐振频点处。
For front-end DC/DC application, a SRC is designed to meet specifications with following parameters:
SRC前端DC-DC应用的设计参数如下:
Transformer turns ratio: 5:2 变压器变比: 5:2
Resonant inductance: 37uH 谐振电感量: 37uH
Resonant capacitance: 17nF 谐振电容量: 17nF
With above parameters, the range of Q is from 6 (full load) to 0 (No load).
上述参数,Q值的范围从6到0(则满载到空载)。
With above design, the operating region of converter is shown in figure 4.2 as shaded area. Simulation waveform is shown in figure 4.3. From the operation region graph and simulation waveforms, several things could be observed:
上述设计中,图4.2中的阴影面积表示转换器的工作范围(区域)。图4.3是它的仿真波形。从图中可以看出:
Operating region is on the right side of resonant frequency fr. This is because of zero voltage switching (ZVS) is preferred for this converter. When switching frequency is lower than resonant frequency, the converter will working under zero current switching (ZVC) condition.
工作区域在谐振频率fr的右边,因为零电压转换更适合于SRC。当开关频率小于谐振频率时,转换器将工作在零电流转换状态。
In fact, the rule is when DC gain slope is negative; the converter is working under zero voltage switching condition. When the DC gain slop is positive, the converter will work under zero current switching condition. For power MOSFET, zero voltage switching is preferred.
事实上,有这样的法则:当直流增益(曲线)变化斜率为负时,转换器工作在零电压状态;当直流增益(曲线)变化斜率为正时,转换器则工作在零电流状态。MOSFET功率管更适合工作在零电压状态。
It can be seen from the operating region that at light load, the switching frequency need to increase to very high to keep output voltage regulated. This is a big problem for SRC. To regulate the output voltage at light load, some other control method has to be added.
我们可以看到在轻载的时候,为了保证输出电压受控,开关频率需要升到很高,这是一个大问题。因而为了调整轻载时输出电压,需要添加其他的控制手段。
At 300V input, the converter is working close to resonant frequency. As input voltage increases, the converter is working at higher frequency away from resonant frequency. As frequency increases, the impedance of the resonant tank is increased. The means more and more energy is circulating in the resonant tank instead of transferred to output.
300V输入时,转换器工作在谐振频率附近。随着输入电压的增加,转换器的工作频率将比谐振频率更高。随着工作频率的递增,谐振回路的阻抗也随之递增,这就意味着越来越多啊的能量在谐振回路中循环流通,而不是传输到负载端。
From simulation waveforms, at 300V input the circulating energy is much smaller than 400V input situation. Here the circulating energy is defined as the energy send back to input source in each switching cycle, the higher the energy sending back to the source during each switching cycle, the higher the energy need to processed by the semiconductors, the higher the conduction loss.
从仿真波形可以直观看到,300V输入时谐振回路的“流通能量”比400V输入小很多。这里,“流通能量”定义为在每个开关周期内被传送回输入端的能量。“流通能量”越大,代表半导体器件处理的能量越多,则输出损耗就越高。
Also from the MOSFET current we can see that the turn off current is much smaller in 300V input. When input voltage increases to 400V, the turn off current is more than 10A, which is around the same level as PWM converter.
同样,从MOSFET的电流(波形图)我们可以看,在300V输入时关断电流相对更小。当输入电压增加到400V,关断电流超过10A,达到了PWM转换器的一样的(关断电流)水平。
With above analysis, we can see that SRC is not a good candidate for front-end DC/DC converter. The major problems are: light load regulation, high circulating energy and turn off current at high input voltage condition.
从上文分析可知,对于前端DC-DC转换器来说SRC并不是一个好的选择。主要问题在于:
轻载电压调节问题;
在高输入电压是存在(谐振回路)高流通能量和高关断电流等问题。 |
|
|
|
| | | | | | | | | 图4.2 中是否有问题?根据叙述Vin=400V和Vin=300V的表示位置反了。 |
|
|
|
|
|
|
|
|
|
|
|
| | | | | | | | | | | | | 谢谢您一如既往顶贴。最近几天繁杂事情特多。只能来刷刷新啦。 |
|
|
| | | | | 需要加速进程啦。
没玩过LLC,感觉有点像“老鼠拉龟无从下手”啦。
大家路过请推荐一下流行的芯片,回去啃啃芯片Datasheet。 |
|
|
| | | | | | | ST的LLC,具体的那颗芯片,你可以到他们网站上去找。要有学习能力和主动性。 |
|
|
|
|
|
|
|
| | | | | 楼主请问这个半桥LLC的AP值怎么算,找单相脉冲算呢,还是双向脉冲算呢?^B=2Bm还是Bm-Bs? |
|
|
| | | | | | | 你好,这个问题目前我回答不了。
对LLC完全不了解,学习中,杂事多啊。 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| | | | | LLC的资料外面,很多, 事例也很多的, 可以借鉴一下 |
|
|