buck型开关电源，小占空比不稳定现象？

shuipihu

1.现在做buck型开关电源，斜波补偿在90%的占空比时，输出稳定，说明斜波补偿足够，但是在10%的占空比时候，输出却不稳定，出现了类似亚谐波震荡的电感电流波形，不知道什么原因？
2.在做电路整体仿真时，导致输出出现亚谐波震荡的除了斜波补偿模块，还有什么其他模块呢？

cjf723

波形先看一下啊

batelab

If you are using valley-current mode, only if duty ratio less than 50%, you need slope compensation; if you are using peak-current mode, only if duty ratio more than 50%, you need slope compensation. Since you sounds like you are using peak-current mode and got oscillations at duty ratio of 10%, that got nothing to do with slope compensation.

The best thing to do is tracing the waveforms.

Look at the error amplifier's output, see if it is oscillating like hell. Is your error amplifier working OK?

Does the relation between the current trip point and error amplifier output hold? If not, check your current comparator...

batelab

oh most important, is the output under regulation at all? the positive and negative inputs of error amplifier roughly equal or not?

cicixu

isense 的问题

icseubear

可能的原因：系统delay时间大于最小占空比时间// 将比较器的偏置电流加大仿真验证一下

jinjin0412

1,blanking time too small or you need to disable the PWM CMP during blanking time but not only disable the output of PWM CMP by nand or nor gates;
2, Your slope compensation has a set up time at every refresh duty, which leads to a reversed slope compensation at low duty  and cause sub-harmonic oscillation.

wangyanhustdk

学习！

tiger10whut

小占空比时是会有很多问题，本身片子的死区，不可避免的延时。可以看一下数据手册。

kjshen

good to learn.