Comments on: Switching Regulators and Switching Noise http://chrisgammell.com/2009/03/16/switching-regulators-and-switching-noise/ Analog electronics and everything else between 1 and 0 Wed, 28 Jul 2010 16:00:36 +0000 hourly 1 http://wordpress.org/?v=3.0 By: saddy http://chrisgammell.com/2009/03/16/switching-regulators-and-switching-noise/comment-page-1/#comment-2201 saddy Fri, 16 Jul 2010 05:04:37 +0000 http://chrisgammell.com/?p=907#comment-2201 Hi, I am facing a problem ,i have used lm22680 for converting 12V to 5v and its getting heated up and voltage starts falling down as i connect my video transmit section to the supply.I am also using the %v o/p to generate -5V.can some one help me out. Hi,
I am facing a problem ,i have used lm22680 for converting 12V to 5v and its getting heated up and voltage starts falling down as i connect my video transmit section to the supply.I am also using the %v o/p to generate -5V.can some one help me out.

]]> By: Audrey http://chrisgammell.com/2009/03/16/switching-regulators-and-switching-noise/comment-page-1/#comment-1141 Audrey Tue, 25 Aug 2009 01:32:01 +0000 http://chrisgammell.com/?p=907#comment-1141 Hi, I have problem with switching noise. Every time MOSFET on and off, there is an overshoot wave of 1V. Now I am trying to step down 17V to 5V. My switching frequency is 133KHz. As I said, overshoot wave 1V synchronize with noises on 5V supply line on top of 100mV noise itself. This noise give problems to my circuit which using that 5V supply. So now according to your article my understanding is if I increase the switching frequency, that might solve the problem? I will try that. By the way I am using 390uH inductor. Hi,
I have problem with switching noise. Every time MOSFET on and off, there is an overshoot wave of 1V. Now I am trying to step down 17V to 5V. My switching frequency is 133KHz. As I said, overshoot wave 1V synchronize with noises on 5V supply line on top of 100mV noise itself. This noise give problems to my circuit which using that 5V supply. So now according to your article my understanding is if I increase the switching frequency, that might solve the problem? I will try that. By the way I am using 390uH inductor.

]]> By: wuifal http://chrisgammell.com/2009/03/16/switching-regulators-and-switching-noise/comment-page-1/#comment-965 wuifal Fri, 12 Jun 2009 20:23:34 +0000 http://chrisgammell.com/?p=907#comment-965 Hi, this article gives a good overview, i should have read it two years ago... Another thing that causes noise is the shape the MOSFET performs when switching the current. The faster the MOSFET switches the more harmonics it will cause, but the advance of switching fast ist to save power or the necessity of cooling your transistor. Switching the transistor fast may result in really severe radiation of high frequency noise at frequencies you might not expect (harmonics). Because the coupling path for higher harmonic might be better than for lower harmonics, it is possible that the higher harmonics (with less power) cause more radiation. The reason are the little antennas that are formed by your current path. So one of the most important things is your layout, keep it small and (!!!) keep the current loops small. regards wuifal Hi, this article gives a good overview, i should have read it two years ago…
Another thing that causes noise is the shape the MOSFET performs when
switching the current.

The faster the MOSFET switches the more harmonics it will cause, but the advance of switching fast ist to save power or the necessity of cooling your transistor.

Switching the transistor fast may result in really severe radiation of high frequency noise at frequencies you might not expect (harmonics). Because the coupling path for higher harmonic might be better than for lower harmonics, it is possible that the higher harmonics (with less power) cause more radiation. The reason are the little antennas that are formed by your current path.

So one of the most important things is your layout, keep it small and (!!!) keep
the current loops small.

regards

wuifal

]]> By: When To Use Analog Vs. Digital | Chris Gammell's Analog Life http://chrisgammell.com/2009/03/16/switching-regulators-and-switching-noise/comment-page-1/#comment-927 When To Use Analog Vs. Digital | Chris Gammell's Analog Life Wed, 20 May 2009 01:04:02 +0000 http://chrisgammell.com/?p=907#comment-927 [...] kinds of signals when working on just about any electronics these days. A simple example is in a switching regulator. These devices are meant to take input power from a wall plug or something providing a relatively [...] [...] kinds of signals when working on just about any electronics these days. A simple example is in a switching regulator. These devices are meant to take input power from a wall plug or something providing a relatively [...]

]]> By: Ketan http://chrisgammell.com/2009/03/16/switching-regulators-and-switching-noise/comment-page-1/#comment-917 Ketan Sun, 10 May 2009 17:38:06 +0000 http://chrisgammell.com/?p=907#comment-917 Hi, sorry to be anal but the voltage across an inductor is proportional to the change in current through it. So I don't know if it is really appropriate to say that current is being pulsed through the inductor (it can't change instantaneously). The switch instantaneously changes the voltage polarity across the inductor so it stores energy (switch on) or releases energy to the load (switch off). The chip determines how long the inductor needs to be "charging" appose delivering current to the load. Still though, this is more of a technical detail and I enjoyed the article. I have seen issues where EMI from the switcher has interfered with sensitive analog/RF components. Hi, sorry to be anal but the voltage across an inductor is proportional to the change in current through it. So I don’t know if it is really appropriate to say that current is being pulsed through the inductor (it can’t change instantaneously). The switch instantaneously changes the voltage polarity across the inductor so it stores energy (switch on) or releases energy to the load (switch off). The chip determines how long the inductor needs to be “charging” appose delivering current to the load. Still though, this is more of a technical detail and I enjoyed the article. I have seen issues where EMI from the switcher has interfered with sensitive analog/RF components.

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