【作者】 张睿；

【导师】 刘政林；

【作者基本信息】 华中科技大学 ， 微电子与与固体电子学， 2008， 硕士

【摘要】 LED常数电流驱动芯片是如今全球最热门的研究方向之一。LED常数电流驱动芯片性能的好坏很大程度上取决于其内置振荡器性能的好坏。在现有的产品中,其内置振荡器多采用具有低成本、低功耗、占空比严格保持50%等优点的张驰振荡器。同时,这种振荡器也具有温度系数较大、电压系数较大、其输出频率易受工艺偏差影响等缺点。本文以LED常数驱动和张驰振荡器的原理为基础,设计出了适用于LED常数电流驱动的高性能张驰振荡器。鉴于现有张驰振荡器存在的缺点,本文详细讨论了张驰振荡器的温度系数、电压系数的来源以及工艺偏差给输出频率带来的影响。提出了引入带隙基准和混合电阻以降低充、放电电流的温度系数的方法,提出了引入LDO以降低电流镜和电容充、放电偏置电压的电压系数的方法,提出了利用微电子与固体电子学原理和版图艺术对充、放电电流进行工艺偏差补偿的方法。在此基础上,介绍了本文设计的带隙基准和LDO,着重介绍了本文设计的混合电阻和工艺偏差补偿电路,并对版图中需要注意的匹配性问题给出了解决方案。最后对张驰振荡器进行整体仿真,仿真结果表明,本文设计的张驰振荡器其输出频率的温度系数不超过600ppm/℃、电压系数不超过0.08%/V、最大误差不超过20%,典型动态功耗仅为455μW。其性能达到设计目标并超过现有产品。更多还原

【Abstract】 Nowadays, LED constant current driver is one of the hottest globe research aspects. The performance of LED constant current driver is deadly determined by its oscillator on-chip. The relaxation oscillator that has advantages of low cost, low dissipation and which duty cycle that strictly maintains 50% is always selected for the oscillator on-chip in existing products. On the other hand, this oscillator also has disadvantages of high voltage dependency, high temperature dependency and high dependence of process error.In this dissertation, a design of high performance relaxation oscillator applied to LED constant current driver will be discussed based on their principles. This dissertation particularly points out the origin of voltage and temperature dependency and the effects brought by process error, whereas the disadvantages of existing products. New methods have been put forward that use bandgap and mixed resistance to reduce temperature dependency of charge current, use LDO to eliminate voltage dependency of charge bias voltage, use the principle of microelectronics and solid state electronics and art of layout to compensate charge current which has been affected by process error. Meanwhile the designs of the circuits concerned have been introduced, especially for mixed resistance and process error compensation circuit. And then the solution of match problems has been given.Finally the relaxation oscillator designed has been simulated, the results indicate temperature dependency has been reduced to 600ppm/℃and voltage dependency has been limited to 0.08%/V, maxim error is under 20%, the typical dynamic dissipation is only 455μW. The performance of relaxation oscillator designed achieves the target and exceeds existing products.更多还原