电路原理请教及求解
时间：10-02
整理：3721RD
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这是一个Buck电路，但是怎么计算流经LED的电流和整个电路的电流啊?
难道是按照下面说明书上的计算吗?不过那样算下来貌似不怎么对啊?求高手指教，谢谢！
The A6213 is a buck regulator designed for driving a high-current
LED string. It utilizes average current mode control to maintain
constant LED current and consistent brightness. The LED current
level is easily programmable by selection of an external sense
resistor, with a value determined as follows:
iLED = VCSREG / RSENSE
where VCSREG = 0.2 V typical.
难道是按照下面说明书上的计算吗?不过那样算下来貌似不怎么对啊?求高手指教，谢谢！
The A6213 is a buck regulator designed for driving a high-current
LED string. It utilizes average current mode control to maintain
constant LED current and consistent brightness. The LED current
level is easily programmable by selection of an external sense
resistor, with a value determined as follows:
iLED = VCSREG / RSENSE
where VCSREG = 0.2 V typical.
另外，R3的作用是什么?R3的取值应该怎么考虑?
datasheet 没有错，LED是恒电流工作，所以定电流设计。你再详细看下datasheet每一页，R3应该是限流或保护作用，作用不大，可以去掉。
补充内容 (2016-5-31 21:00):
C7、R4可以拿掉，这样你去算电流就差不多了，另外支路电流和回路总电流是不同的，你需要分清楚。
这个是恒流的，流经LED的电流为0.2V/0.56Ω≈357mA。因为这个电路是恒功率电路，输出功率可以很好的算出，但是因为效率不是一个定值，所以输入电流不能精准的计算?那么效率到底定为多少才是最合适的呢?