开关电源之“Layout of Boost Converter”

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 本文主要介绍Boost开关电源的PCB布局。


Boost Converter的布局布线原则如下：

  • The input capacitor should be placed as close as possible to the input pin for good input voltage filtering.

  • The inductor and diode should be placed as close as possible to the switch pin to minimize the noise coupling into other circuits.

  • Because the feedback pin and network is a high-impedance circuit, the feedback network should be routed away from the inductor. The feedback pin and feedback network should be shielded with a ground plane or trace to minimize noise coupling into this circuit.

  • To minimize the effects of ground noise, use wide and short traces for high current paths and for power ground tracks.

  • Use a common ground node for power ground and a different one for control/analog ground to minimize the effects of ground noise. Connect these ground nodes near the ground pins of the IC. Connect two ground nodes together at the load if possible. This allows the GND pin to be close to the output ground for good DC regulation. Any voltage difference between these two nodes would be gained up by feedback divider on the output.It is also beneficial to have the ground of the output capacitor close to PGND because there is a large current between them. To lay out signal ground, it is recommended to use short traces separated from power ground traces.

  • The most critical current path for all boost converters is from the switching FET, through the synchronous FET, the output capacitors, and back to the ground of the switching FET. Therefore, the output capacitors and their traces should be placed on the same board layer as the IC and as close as possible between the VOUT and PGND pins of the IC.（输出电容、同步FET、开关FET和PGND组成的回路面积最小！！！）

 


                           

为了最小化环路面积，当二极管没有集成在芯片内部时：二极管、电感尽量靠近IC的SW引脚，输出电容尽量靠近二极管和IC的GND引脚（接地过孔不要打在回流路径上）；当二极管集成在芯片内部时：电感尽量靠近IC的SW引脚，输出电容尽量靠近VOUT引脚。


下面是一些布局布线的实例，唯一的目的就是要保证电流瞬变部分走线的环路面积最小。





以上就是针对Boost电路的布局布线介绍，详细的可以参考相关芯片的datasheet、user guide、EVM参考设计等等。