Power supply problem

[jep_pogi]

2.5A ung max na idadraw na current. so 3.125 A or pwede na pong 3A 

[jep_pogi]

sir, kailangan ko pa po pala ng current limiting circuit na iseseries sa 33.6ohms sabi ng prof ko. di ko pa po tlaga magets e.. sinabi nya kasi na kung motor, may times na parang short circuit xa. so kelangan ko daw ng current limiting na iseseries dun sa 33.6 ohms. pahelp po sana.. mtagal ko na po ginagawa at naghahanap pero di ko pdn malaman gagawin ko..

[jep_pogi]

hindi ko po alam kung current limiter o short circuit protection ba yung gusto nyang ilagay ko dun

[labgruppen]

check mo yung last reply ko sa bagong thread re current limiter.

[TinTopHack]

sir tingin nyo po ba dapat ako maging concerned sa intial spikes, pati sa steady state current spikes na 30A each? mga 4ms sila nag lalast each pulse.
pati naghahanap pa po ako ng pwedeng icorrect sa circuit kung may mali man. ayoko po kasi gawin agad ung supply sa board baka maging smoke machine lang e

The initial spike is due to the charging of your filter caps from 0V sa output ng rectifier. At this point your fiter caps appear as a short circuit to the source. The main concern with very high initial current spikes is that it can cause fuse or breakers to blow when you turn on your power supply.

The current spikes after that are due to the recharging of your filter caps during each half of the AC cycle and depend on your load - small load small spikes - big load big spikes. The high ESR caps will not be helpful here considering your input voltage is very high while ESR values of high ESR caps are still very very low. When you are using an ideal AC source you will see large spikes like that. But if you are using a transformer - a non-ideal AC source with all its internal impedance and inefficiences you will get smaller spikes. As mentioned somewhere in the thread, you can use a soft-start circuit if you are really concerned about the initial spike. The spikes that follow are dependent on your load so there is not much you can do UNLESS you use active power factor correction.

Active PFC forces the current waveform at the input of your circuit to follow the sine wave shape of the input voltage resulting not only in >0.9 power factor but also less current harmonic content - meaning less distortion of current waveform and cleaner power lines. (spikes are considered distortions) High end equipment usually employ active PFC to comply with EN/IEC61000 regulations.

[TinTopHack]

sirs,
eto po ung circuit na latest, pinagsama ko ung inductor na 10mH suggestion, pati ung 2 series capacitor with parallel resistors each:


tas eto po ung voltage response, ung RED ay sa node after ng inductor, so xa ung sa node din ng capacitors.
tapos ung GREEN ay for the output voltage na nilalabas nya.


tapos eto nmn sa current response, YELLOW ung across sa capacitor c1, tas red po yung output less than 3.5A


bumaba ung current spikes. is this better?
baka po may masuggest pa kayo.

and pwede po ba paexplain kung anu gnagawa nung inductor?

The inductor - inductance - prevents the current from changing immediately in response to a voltage change. It causes the current to ramp up instead of "spike up" Thus you see the spike reduced.

I think using a real world transformer will have a better effect of reducing the spike that te inductor you added. The inductance of a real world transformer is much higher than that of you inductor. You should see better results.

This is the limitation of simulation. Unless your models closely match the characteristics of real world devices your results will be quite far from reality.

[jep_pogi]

hello po and thank you sa mga nagrereply sa post ko
sorry po ngayon na lang ulit ako nakapag post, marami rin po kasing school work na ginawa.
pero nafabricate ko na yung power supply circuit ko sa PCB. nasolder ko na most of the parts.

eto na po yung latest na circuit schematic ko.


pinacheck ko na rin po yan, okey naman daw.
lagay nlng ako ng fuses, thermistor instead of inductor after ng diode bridge.
tapos current limiter sa output na gagamitin ko ay Thermistor na P-type Fuse.hindi ko pa sure kung pwede ba talaga yan.

and eto yung output nya sa simulation. current and voltage na yan magkapatong lang.


ang tanong ko naman po ngayon e anung mga jumper wires ang gagamitin ko papuntang power transistor ko na MJ15025?
nakahiwalay kasi sya sa PCB na finabricate ko and nasa 2A ung current na dadaan sa jumpers na yun. thanks.
pati po sana wat value ng fuse ang gagamitin ko, di ko sure kung san ko ba dapat ilagay ung fuse e. before the transformer ba o after.
please help po ulet. thanks po! sana po mabasa nyo pa to.