Detailed explanation of starting surge current

duwang

Detailed explanation of starting surge current [Copy link]

This document describes the starting inrush current.

Since all switching power supplies have energy storage capacitors at the primary end according to different power levels,
there will be a large impact current at the moment of startup. This impact current has a large
interference on the power grid and power supply equipment, and has high requirements for the impact resistance and
reliability of the rectifier bridge, relay and other devices in the main power circuit of the power supply and module itself. For example: when the power supply is started, the current pulse flowing through the rectifier bridge is too large. If it exceeds
the nominal value, the rectifier bridge is easily damaged, especially when starting in a high temperature environment.

PowerAnts

If you are not familiar with circuits, simulation and calculation are all blind. The Q of the RLC series circuit is SQRT (L/C) / R, and R = 0.01R. It oscillates for dozens of cycles. How can it be regarded as an RC integral?

threetigher

PowerAnts posted on 2020-3-18 11:28 If you are not familiar with circuits, simulation and calculation are all blind. The RLC series circuit has Q=SQRT(L/C)/R, R=0.01R, and oscillates for dozens of cycles. How can it...

R=0.01Ω, L=25uH, C=22uF;

R=0.01Ω, L=250uH, C=220uF;

With pictures.

PowerAnts

threetigher published on 2020-3-18 22:36 R=0.01Ω，L=25uH，C=22uF； R=0.01Ω，L=250uH，C=220uF； With pictures.

For a circuit with a Q value of 100, will the voltage rise monotonically after power is turned on? Is it only capturing 1/4 cycle?