design a special switch mode power supply

[kamalifard]

post filter switched mode

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

 

[sunderwood]

capacitor on output of switch mode

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 !

 

[FvM]

post regulation of switching power supply

A usual isolated flyback SMPS with a casacde rectifier should do. Add a passive filter or preferably a linear post-regulator to reduce ripple.

 

[barfi]

capacitor charging switching mode supply

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....

 

[kamalifard]

2kv switch mode

why flyback are other type like ush-pull half-bridge fullbridge are not usefull?

 

[FvM]

reducing ripple in switchmode

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.

 

[kamalifard]

whats capacitor ESR?

 

[insrusingh]

Capacitor ESR is calculated as sqroot R^2+(WL-1/WC)^2.

 

[sujojk]

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.

 

[barfi]

Dear FvM
could you please explain more about the linear post regulation method in 2000v?

 

[senthilkumar]

any reference design for +15v/2A only.any link pls