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kamalifard
Joined: 12 Aug 2008
Posts: 7
Helped: 1
Location: iran/tehran-yazd
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 15 Aug 2008 20:30 design a special switch mode power supply |
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i want to design a power supply by this characteristic in output:
variable output from 0 to 2kv
low ripple at output only + or - 10mv
positive and no constant currunt but little below 10mA
it not be linear type but cac have a linear stage
this supply from 220v AC 50Hz
tanks alot
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sunderwood
Joined: 08 Jan 2008
Posts: 64
Helped: 10
Location: US, CA
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| 15 Aug 2008 20:36 Re: design a special switch mode power supply |
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| Are you sure about that output ripple requirement ? This is going to be quite difficult to achieve. I'm curious how you'll get there. Good luck !
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FvM
Joined: 22 Jan 2008
Posts: 2635
Helped: 431
Location: Bochum, Germany
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| 15 Aug 2008 20:53 Re: design a special switch mode power supply |
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| A usual isolated flyback SMPS with a casacde rectifier should do. Add a passive filter or preferably a linear post-regulator to reduce ripple.
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barfi
Joined: 11 Dec 2006
Posts: 38
Location: tehran
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| 15 Aug 2008 21:43 Re: design a special switch mode power supply |
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Hi FvM
i believe it is not possible to use a linear 2Kv post regulator in output!
you should use a step up transformer and flyback configuration to generate
2KV in output , the ripple of the output depends on the current of the output and the capacity of the output capacitor and also switching frequency , the current ripple is dependent on ESR of the output capacitor, so you should use
a high quality type capacitor as polypropylene , only the problem is its high voltage
2KV that you should series some capacitors, for the designing of the transformer you should consider enough isolation between input and output....
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kamalifard
Joined: 12 Aug 2008
Posts: 7
Helped: 1
Location: iran/tehran-yazd
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| 16 Aug 2008 10:08 Re: design a special switch mode power supply |
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| why flyback are other type like :push-pull half-bridge fullbridge are not usefull?
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FvM
Joined: 22 Jan 2008
Posts: 2635
Helped: 431
Location: Bochum, Germany
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| 16 Aug 2008 10:24 Re: design a special switch mode power supply |
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| Quote: |
| i believe it is not possible to use a linear 2Kv post regulator in output! |
It's not a matter of believe, I think. It has been used before. Apart from reducing board space, dynamical specification may be a strong argument to use an active filtering respectively a linear post-regulator. If protected in a suitable way, it can be designed for a rather low voltage drop, e. g. some 10 volts.
For the said 20 W nominal power, flyback is the most economical solution, I think. As mentioned, it can be a standard off-mains SMPS with a modified transformer. But other topologies can be used as well.
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kamalifard
Joined: 12 Aug 2008
Posts: 7
Helped: 1
Location: iran/tehran-yazd
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| 18 Aug 2008 17:52 Re: design a special switch mode power supply |
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| whats capacitor ESR?
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insrusingh
Joined: 08 Jul 2008
Posts: 16
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| 19 Aug 2008 14:17 design a special switch mode power supply |
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| Capacitor ESR is calculated as sqroot R^2+(WL-1/WC)^2.
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sujojk
Joined: 22 Jun 2008
Posts: 13
Helped: 1
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| 10 Sep 2008 10:34 Re: design a special switch mode power supply |
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ESR means Effective Series Resistance. This is the resistance encountered by the current through the capacitor while charging/discharging (But not the lead resistance). It is caused by the difficulty offered by the dielectric to change from its current state of charge and depends upon the geometry, construction and type of dielectric used.
Electrolytic capacitors are having high value ESR (around 1ohm). That's why we are connecting ceramic capacitors (having low ESR) parallel to them in filters and other applications so that the total effective resistances will be paralelled and thus reduced.
Tantalum and Wet Tantalum capacitors are having good ESR performance than electrolytic capacitors.
ESR is a function of operating frequency also.
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barfi
Joined: 11 Dec 2006
Posts: 38
Location: tehran
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| 01 Oct 2008 4:20 Re: design a special switch mode power supply |
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Dear FvM
could you please explain more about the linear post regulation method in 2000v?
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senthilkumar
Joined: 24 Nov 2001
Posts: 631
Helped: 3
Location: india
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| 01 Oct 2008 4:42 design a special switch mode power supply |
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| any reference design for +15v/2A only.any link pls
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