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student-engineer
There is a nonlinear switch in every dc-dc converter.Is it the reason of harmonics in output voltage?
Yes,I am familiar with the function of switch.Inductor in the circuit maintains a continuous supply of current in the circuit,even when the switch is off.When switch is off,the inductor discharges energy.Because of the switch mode operation of semiconductor switch,the device has a duty cycle.By varying the duty cycle,the output voltage can be varied.jedishrfu said:Basically it seeks to keep the current levels constant even though devices connected to the converter may be switched on and off.
The reading material is much informative.Thank you for sharing.jedishrfu said:I think this describes its function here:
https://books.google.com/books?id=mZRsBgAAQBAJ&pg=SA9-PA60&lpg=SA9-PA60&dq=nonlinear+switch+in+every+dc-dc+converter+what+is+it+used+for&source=bl&ots=GgThrmPkF5&sig=t8AZur9nj5ztpn61vHdtQJ6qq2o&hl=en&sa=X&ved=0ahUKEwj1-6XU1qDXAhWs6YMKHY8xCYoQ6AEIXDAJ#v=onepage&q=nonlinear switch in every dc-dc converter what is it used for&f=false
https://www.omicsonline.org/open-ac...near-dynamics-2229-8711.1000166.php?aid=38311
Yes,I took it.I may not be remembering much about it.The square wave is composed of many harmonics.In power systems too the requirement is to have a perfect sinusoidal waveform.But in reality the wave is distorted due to harmonic components.Harmonics of a signal are analyzed in frequency domain.At fundamental frequency is the dc component.donpacino said:have you taken a signals and systems course yet?
have you studied what happens with switched signals?
as a hint... What is the frequency response of a square wave?
student-engineer said:Yes,I took it.I may not be remembering much about it.The square wave is composed of many harmonics.In power systems too the requirement is to have a perfect sinusoidal waveform.But in reality the wave is distorted due to harmonic components.Harmonics of a signal are analyzed in frequency domain.At fundamental frequency is the dc component.
Thank you.But also why does the switch produce a square wave,which is full of harmonics?The reason could might be that the switch used is a nonlinear electronic device.In nonlinear electronics,the current rise is not proportionate with voltage.One reason could might be variation of impedance in non-linear devices.Because of variation of impedance,the voltage is also varied,so the current also varies and this results in nonlinear V-I characteristics of such a device.donpacino said:Well you pointed out that a square wave is made of many harmonics. You also know that a on-off waveform is produced by the switches...
Yes,I know that a square wave is essentially composed of harmonics which become visible when Fourier transform of the square wave is taken i.e. the harmonics can be seen in frequency domain.The posts on this thread also clarified that the switch in the dc-dc converter produces the square wave voltage waveform when operated in switch mode and the square wave has harmonic content essentially and those harmonics are components of square wave i.e. the square wave is comprised of harmonics,and so the dc-dc converter is a non-linear circuit with harmonics.But why does the nonlinear switch device produce square wave i.e. harmonics?Averagesupernova said:It is not possible to have a square wave that is not composed of harmonics. It is part of what defines a square wave. A signals and systems course would explain this.
Switches don't necessarily create square waves. Square waves are a specific type of pulse waveform characterized by a 50% duty cycle - on half of the time; off half of the time. Switches can create pulses with other duty cycles, and pulse width (duty cycle) control is the idea behind PWM - Pulse Width Modulation.student-engineer said:But why does the nonlinear switch device produce square wave
student-engineer said:The reason that harmonics or square wave is produced by the switch could might be that the switch is a nonlinear device.In a nonlinear device, the impedance is not constant and it varies so a nonlinear characteristic v-i waveform is obtained. Thus harmonics occur in current waveform which cause harmonics in voltage waveform too.
http://www.mirusinternational.com/downloads/hmt_faq01.pdf
@student-engineer as @donpacino says, the switch transistor in a DC-DC converter is not necessarily a non-linear device. From your link:donpacino said:stop saying its because of the nonlinear device... its not.
the device produces square waves because that's how it functions
That is not describing the transistor action in a DC-DC converter...A load is considered non-linear if its impedance changes with the applied voltage.
Yes,but usually a semiconductor switch is used in such a converter.Semiconductor switches such as diode,mosfet,igbt are nonlinear.A dc-dc converter can also be load.In that pdf may be they were mentioning in general terms;I think that it means that a load or a device is nonlinear if its impedance changes.What else could be reason of nonlinearityberkeman said:@student-engineer as @donpacino says, the switch transistor in a DC-DC converter is not necessarily a non-linear device. From your link:
That is not describing the transistor action in a DC-DC converter...
The diode has a non-linear V-I characteristic, so it can be used as a "switch" in some applications. The transistor used in a Buck DC-DC converter is not non-linear. It is ON or OFF, at different times. Changing impedance at different times does not make a device non-linear.student-engineer said:diode,mosfet,igbt are nonlinear
Asymptotic said:Switches don't necessarily create square waves. Square waves are a specific type of pulse waveform characterized by a 50% duty cycle - on half of the time; off half of the time. Switches can create pulses with other duty cycles, and pulse width (duty cycle) control is the idea behind PWM - Pulse Width Modulation.
student-engineer said:Yes,but usually a semiconductor switch is used in such a converter.Semiconductor switches such as diode,mosfet,igbt are nonlinear.A dc-dc converter can also be load.In that pdf may be they were mentioning in general terms;I think that it means that a load or a device is nonlinear if its impedance changes.What else could be reason of nonlinearity
and yes, a non-linear load will impart harmonics onto the system, however like we said above, harmonics will exist with no load or completely linear loads as wellstudent-engineer said:The reason that harmonics or square wave is produced by the switch could might be that the switch is a nonlinear device.In a nonlinear device, the impedance is not constant and it varies so a nonlinear characteristic v-i waveform is obtained. Thus harmonics occur in current waveform which cause harmonics in voltage waveform too.
http://www.mirusinternational.com/downloads/hmt_faq01.pdf
Doesn't a switch produce a mathematical discontinuity ?student-engineer said:But why does the nonlinear switch device produce square wave i.e. harmonics?
Or, to put Jims explanation in slightly different words:jim hardy said:How does a DC to DC converter work ?
It 'chops' the incoming DC into an AC waveform
I mean page 93 in adobe acrobat.It makes page 164 of book.donpacino said:Page 93 is a bridge rectifier, it is not a dcdc converter
student-engineer said:But how does the dc waveform converts to ac in the circuit of such a converter.
jim hardy said:And the movie soundtrack never has the vibrator hum.
jim hardy said:I think one movie did , probably a Spielberg. He'd pay that kind of attention to detail. Perhaps "1942" ?
Averagesupernova said:The radio here: https://www.physicsforums.com/threa...rical-and-measuring-things-etc.755959/page-11
uses a vibrator that has commutator contacts. There is no rectifier diodes to obtain the B+. Was the first time I had ever heard of that but upon researching I found it was not uncommon.
Yes you do have to watch the polarity. But I can't take credit for the vid.jim hardy said:On those radios you have to pay attention to positive or negative ground.
Great video by the way.
Well you found it and were kind enough to share it.Averagesupernova said:But I can't take credit for the vid.