LLC谐振转换器在轻载条件下增益失真的考虑事项

近来,尽管LLC谐振转换器设计颇为复杂,但由于具有某些出色的优势而得到很多关注。比如,可通过零电压开关（ZVS）实现高效率,在所有负载条件下工作频率变化范围很窄。LLC谐振转换器广泛用于家电、街灯充电器及其他各种电气设备。大家知道,LLC谐振转换器通过改变工作频率来调节输出电压。一般而言,电压转换比,也就是ZVS工作区域中的增益值,理论上随工作频率的增加而减小。

在下区域和上区域工作的LLC谐振转换器的设计

最近，带LED背光单元的LCD电视的市场开始大幅增长，众多制造商纷纷致力于研发更纤薄高效的解决方案。多种类型的LEDTV主功率级拓扑相继推出，比如非对称半桥转换器、双开关正激转换器和LLC谐振转换器。其中，LLC谐振转换器虽然相比其他转换器具有更多优势，但因为其设计复杂困难，所以在过去很少受到关注。不过，这几年间，ICN造商已开发出用于LLC谐振转换器的控制器，而且发表了许多相关技术说明和设计工具，让其设计变得更容易，并使得这种技术获得更多的关注。现在，LLC谐振转换器已经成为LEDTV最流行的主功率级拓扑。

Pyrogenicity of hyaluronic acid hydrogel crosslinked by divinyl sulfone for soft tissue augmentation

Hyaluronic acid hydrogels (HAHs) were synthesized by immersing the microbeads in phosphate buffered saline solution to assess short term biocompatibility of the gels by means of the rabbit pyrogen test and the bacterial endotoxin test. The rise in body temperature of 3 male New Zealand white rabbits weighing about 2~3 kg (12~16 weeks old) following intravenous injection of the test article (10 mL/kg) was mo nitored at 30 min intervals in 3 h to examine the pyrogenicity. No rabbits showed an individual rise in temperature of 0.5oC or more above its respective control temperature. The temperature rises of the rabbits after injection were 0.12oC, 0.13oC, and 0.18oC, respectively, sugge sting that HAH meets the requirements for the absence of pyrogens. The bacterial endotoxin test revealed that the concentration of endoto xins required to cause the lysate to clot under standard conditions was < 0.125 EU/mL. Comparing the HAHs that was synthesized in this experiment to the ones approved by FDA, the amount of < 0.125 EU/mL endotoxins is relatively safe and effective. The test solution did not contain any interfering factors under the ex perimental conditions used. It is conceivable that the HAHs are likely to be suitable injectable dermal filler for facial soft tissue augmentation due to the absence of

电芯平衡技术提升锂电池效能

与其它材料电池相比,锂离子电池具较高的额定电压（3.4～4.2伏特）和能量密度,因此通过串联连接数量较少的锂离子电池即可轻松实现高电压和高容量。但是,锂离子电池具有一些缺陷,例如在最坏情况下,由于过度充电、温度过高和外界影响而引起爆炸;或者由于锂电池过度放电而引起功能降低。

适用于锂离子电池应用的无源和有源电芯平衡技术

随着便携式设备的广泛使用，各种类型的紧凑和轻型电池，如铅酸电池、镍氢电池和LiB（锂离子电池）被开发出来。