Effect of inductor polarity on stability of feedback loop in buck converter

LIU Song; DING Yu; GAO Li; TENG Junqing

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Effect of inductor polarity on stability of feedback loop in buck converter
Vol. 48, Issue 12, Pages: 34-37(2018)
Published：2018
DOI：
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DOI：

LIU Song, DING Yu, GAO Li, et al. Effect of inductor polarity on stability of feedback loop in buck converter[J]. Eletric Welding Machine2018, 48(12): 34-37. DOI：

摘要

探讨电感的极性即电感绕组起始点不同的连接方式对电流模式的电源系统稳定性的影响。在小占空比工作状态下

系统工作在电流模式和电压模式的临界状态是系统不稳定的主要因素。电感绕组起始点不同的连接方式对于反馈环路产生不同方向的感应电流

在趋势上

增强电流反馈信号的连接方式

即电感的绕组起始点连接到LX管脚时

有利于稳定地工作在电流模式

不会再产生振荡。分析了不同连接方式下电感的磁场和反馈环路的感应电流磁场的方向。通过耦合电感模型

给出仿真波形和实际测试结果。

Abstract

The effect of different connection modes of inductor polarity

namely

the start point of inductor winding on the stability of the current mode power supply is discussed. The main reason of the system instability is that the system operates in the critical state of current mode and voltage mode at low duty cycle. The inductor will cause the space magnetic field

which will cause the inducted current in the system feedback loop. Connecting the start point of the inductor winding to LX of Buck IC can strengthen the current feedback signal according to the inducted current

so the system can consistently operate in current mode without the oscillation. Conversely

connecting the start point to Vo will cause oscillation in Buck converter from 12 V to 1.1 V. The simulation waveforms and actual test results are obtained through the couple inductor model.