SIMPLE SWITCHER ® 稳压器概览--你所需要的资料都一一尽录National Semiconductor

简介：SIMPLE SWITCHER ® 稳压器概览--你所需要的资料都一一尽录

问：开关电源用在DSL产品中，对模拟（AFE）电路都有不同程度的干扰，有什么比较好的方法来避免吗？谢谢！
答： Dear Sir,

Switching noise alway is a issue on AFE application.
Good PCB grounding and low switcing noise are the solution.
A). Good PCB grounding, please refer as NSC application note  AN1197 and AN1229 which have details decribi

问：为降低EMI，如何选择电容和电感？LM集成电路内部有没有降低EMI的电路？
答： The EMI mainly come from the switching current in the PCB trace and external components, inductor. You can use shielded Inductor to reduce EMI.

问：教授，您好！
我是一位产品开发者。在我们产品中我们利用LM2575组合的恒流源作为电流驱动，但在实际的应用中我们发现LM2575发热过大，效率不高。因此我们选用LM2670，但是我们发现采用LM2670后，CPU经常复位，整够电路工作不起来，对此我们感到很困惑，请您给予解答，谢谢！
答： Dear Sir,

I would like you to meaure the voltage on CPU due to CPU is senseitive on switching noise and ripple. May be to have LC filter before connect to CPU Vcc is a right suggestion.

Best Regards,
Jacob

问：LM276X的效率能达94%，能介绍一下影响效率的设计要点和应用要点吗？
答： The efficiency is mainly depends on input voltage (higher Vin lower eff.), output voltage (lower Vout, lower eff.). Good Schotkky diode can improve the eff. a little bit. Higher inductor inductance also can improve eff. a little bit.

问：在补偿时如何防止电磁干扰到反馈回路？PCB布图有何要求？
答： Pls refer to our application note AN1229 Simple Switcher PCB layout guideline. You can download from our wedsite.

问：我用LM2674很好,但推荐的电感比较贵我用普通的相同电感量可以替代吗?
答： Possible. The key point is they have same parameter.

问：我们用2575HVT做60V输入、15输出，在工作时发现启动不稳定。设计时应注意哪些问题？
答： May be inrush current of LM2575HVT hit the current limit of the power source.

问：lm2596 在小电流工作时，如何提高效率
答： No, it is because LM2596 is fix frequency PWM. You will need PFM mode switching regulator to increase light load efficiency. NS have many of this kind of device. Pls check with our local office, distributors or visit our web site.

问：请问有没有-48V转成+3.3V或+5V的DC-DC，内部有没有做防电磁干扰，防电涌等电路？
答： In general, high voltage Simple Switcher can be using for it. However, the max. o/p current should be known before selecting the right part. Our products have soft-start function which can reduce in-rush current during start-up.

问：我不是专业的电源设计师，我想问一下，lm267x的adj和fix版本仅在于取样电阻的R1,R2的不同吗？（DMOS除外）
答： Yes, it is the only difference. However, because the feedback resistors are outside of the LM267x you can use them for stability adjustment/ optimisation