Author Topic: What a good AC characteristic for Linear psu means ?  (Read 1175 times)

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Offline namsterTopic starter

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What a good AC characteristic for Linear psu means ?
« on: July 23, 2020, 06:50:17 pm »
Hi All ,
i see in many linear PSU project the terms of AC characteristics bandwitch of the Power supply  :-//  but but this concept remains unclear for me could someone clarify this for me  :-DMM

 

Offline bdunham7

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Re: What a good AC characteristic for Linear psu means ?
« Reply #1 on: July 23, 2020, 07:35:07 pm »
Hi All ,
i see in many linear PSU project the terms of AC characteristics bandwitch of the Power supply  :-//  but but this concept remains unclear for me could someone clarify this for me  :-DMM

Can you provide a link to a project or description using those terms? 
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline namsterTopic starter

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Re: What a good AC characteristic for Linear psu means ?
« Reply #2 on: July 23, 2020, 09:20:11 pm »
Yes , for example this article https://www.analog.com/en/technical-articles/loop-gain-and-its-effect-on-analog-control-systems.html the point that I can't understand is the frequency in Bode diagram of an DC regulator , what determines the frequency of work ?
 

Offline bdunham7

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Re: What a good AC characteristic for Linear psu means ?
« Reply #3 on: July 23, 2020, 09:41:22 pm »
It's a complex subject and that article is about a fairly advanced characteristic of regulators and supplies, but if I understand your question, you are just asking what a discussion of frequency response is doing relative to DC power supplies, right?

So, the short quick answer is that it is a way of describing the ability of the regulator or supply to react to changes in either the input voltage or the load.  A regulator should filter out any variation in the supply voltage (ripple) and also keep the voltage constant even as the load current varies.  A standard regulator, like an LM7805, is good at suppressing 50/60Hz ripple, but if you feed it with a supply with high frequency ripple, say 1 MHz, it doesn't react quickly enough to filter that out.  Likewise, if you have a load that goes on or off too quickly, it won't react fast enough to prevent a dip or surge in the voltage.  Another way of looking at is to compare the regulator to an amplifier and say that it has a 'frequency response' curve.  A regulator with an extended frequency response will react more quickly to supply or load variations and then can filter out noise and ripple that occurs at higher frequencies.  Does that help?
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline namsterTopic starter

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Re: What a good AC characteristic for Linear psu means ?
« Reply #4 on: July 23, 2020, 10:28:10 pm »
So , the bandwitch is related to Transient response of the regulator , from what I understood the more is the bandwitch bigger , the more  quicky is the transient response is that correct ?
 

Offline bdunham7

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Re: What a good AC characteristic for Linear psu means ?
« Reply #5 on: July 23, 2020, 11:01:10 pm »
Yes, exactly.  And the faster it responds, the closer it can regulate.
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 
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Offline coppice

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Re: What a good AC characteristic for Linear psu means ?
« Reply #6 on: July 24, 2020, 12:11:51 am »
So , the bandwitch is related to Transient response of the regulator , from what I understood the more is the bandwitch bigger , the more  quicky is the transient response is that correct ?
Yes and no. Wide bandwidth is needed for rapid transient response. However, without good control of the frequency and phase response of this wide bandwidth control loop you can end up with horrible overshoots, and voltage spikes that might damage the load.
 


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