[introduction] all sorts of electric equipment in our life, its power source should be experienced possibly everyday ” next report ” process, black out for instance, computer shuts machine, close TV, close air conditioning to wait. Power source needs to involve machine process steadily, namely power source will input voltage smoothly (V_IN) fall to 0V, what can prevent an accident so is too strong. And should judge power source ” next report ” stable, can fractionize becomes at 3 o’clock: Drab drop without time tick off, without had lost strong, without rebound, resemble such.

3 kinds of corresponding also this at 3 o’clock models are undee, name respectively for R, G, B, they comprised various strange weaveform.

R kind undee

Graph 1: R kind undee

This kind of weaveform is subdivisible into I model with II model:

R kind I cause, because output voltage to drop, when falling to carry voltage to laden belt, its electric current can be reduced suddenly, at this moment nowhere releases the redundant energy on the inductance of road of input end line of DC-DC, final meeting raises input tension, after exceeding DC-DC chip job to nod, DC-DC works afresh, bring about weaveform issueing report to appear time tick off, not drab. Should detect only SW end has Switch, can judge whether to belong to this kind.

Graph 2: R kind inductance of parasitism of road of I molded lines

This kind of weaveform compares good processing relatively, normally the book can be opposite the norms of DC-DC chip start and answer poor voltage to make a provision. For instance the MPM3683-7 of MPS company:

Graph 3: MPM3683-7 norms

So we can be passed the following two kinds of methods, allow car of skid of DC-DC firm quietly:

1.Reduce input voltage to rebound, optimize input filter wave for instance, reduce input inductance, choose bigger look value, the input capacitance of smaller ESR/L, let input capacitance to near end of power source chip as far as possible.

2.Input through cent falling to press resistor to make on reasonable setting EN drop to UVLO before, shut EN, give up thoroughly the thought that DC/DC switch Switching restarts.

R kind II

Because load is reduced suddenly,be, nowhere releases the redundant energy that DC-DC interior outputs inductance to perhaps output circuit inductance to store, final meeting will output the drive up when voltage is short.

Graph 4: R kind road of II molded lines

This kind does not have better solution, can be to rely on to optimize circuit only, reduce the inductance on circuit, increase load to carry capacitance to come depress rebounds.

G kind undee

Graph 5: G kind undee

It is subdivisible also for I model with II model:

G kind I

I because Buck circuit issues a canal to did not close when issueing report,be, inductance electric current causes reversely continuously, this kind of circumstance is relatively common when carry for nothing or carrying gently; To avoid this kind of problem, normally chip is closing had increased to detected at 0 o’clock when machine, the tube current below judgement passes reversely 0 when involve next valves actively, call ZCD point normally, this action can be prevented effectively close the generation when machine to lose to too strong.

Graph 6: Prevent G kind I had lost strong

G kind II

Cause, this kind of case appears more easily when burden perhaps outputs short circuit breakdown. Right now we reduce output circuitry inductance as far as possible with respect to need, increase load to carry capacitance, make its more stand by load to relieve a symptom.

Graph 7: Reduce G kind inductance of parasitism of road of II molded lines

B kind undee

Graph 8: The B below burden kind undee

This kind of weaveform often appears in burden to close when machine, often can be thought to follow R by accident so kind undee and similar, circuit inductance is caused. But, this rebounds occurrence time is very late, the influence of circuit inductance is Us class normally, and contrast inputs voltage weaveform this kind, you can discover first time closes machine hind, the rate that its rebound is very slow, reach Ms level, even a few Ms!

This kind of undee occurrence mechanism follows R kind, G kind it is completely different, its originate the absorption of dielectric effect. If input the discharge electric current of capacitance to begin very big, cut suddenly it is basically 0, the partial charge that the dielectric in capacitor admits before meeting general is again slow release, a machine voltage that obtains power source chip again when its when the dot, can cause output voltage to rebound.

This kind of circumstance also can issue report through EN, will raise those who input voltage to owe press protective feature and protection to answer sluggish, be like R kind I undee processing technique, make its rebound voltage is unapt pass high switch on the mobile phone to nod and be caused restart. Perhaps add load of a few static states to spend this share charge directly, can solve a problem.

Epilogue

Next electric wave form that the article analysed 3 kinds of in the point process below power source different types, and how to optimize these 3 kinds of weaveform to rise thereby stability and prevent to had been lost strong.

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