Making car amplifier SMPS with tl494 + DC Protection

Hello to every body.
I have made plenty car amplifiers + smps based on sg3525.I have read all this forums and any body have full schematic for making smps with tl494 + DC protection for loudspeaker than temperatur protection etc.:confused:

Here some pictures of my car amplifier + smps 1x100w.If there interesting I will put thr pcb on this site.The smps give +/-30V 5A.


  • 22.jpg
    25.6 KB · Views: 24,940
Re: Amplifier 1x100W - PCB

Risto80 said:
Ok that it. If you have any questions about making feritte toroid and basic calculating just ask.

Hi .

Well i have couple of questions about smps.

1) How many turns have u used for prim. and sec ?
2) Did you tryed to remove 4n35 and force duty cycle to 50% and then measure output voltage ?

I ask this because I have maded similar smps primary->4x4, secondary 11x11 . When I remove 4n35 and force sg3525 to duty 50% I got 60x60 volts .

About Feritte turns


1.The output voltage depens os turns on feritte core.The
calculating is this Ns/Np=Vo/8,8
Ns-Secondary voltage
Np-Primary turns usualy 4x4 turns
And you will get 13.6 turns better 2x14 turns

2. The 4n35 is a voltage regulator,You can not take off becous the schematic of smps is based on 4n35.You can use other schematic of smps and then you can not use 4n35 but the schematic about sg3525 is different.

I use this amplifier about 5 mounts for my subwoofer 300W and is sound very good,like my car amplifier Kenwood-719.No difference in sound ,just put input fuse about 15A and secondary fuses about 3 Amps.And some kind of speaker protection like dc-protection


  • fuy.jpg
    22 KB · Views: 14,169
Re: About Feritte turns


Can you tell me why have you separeted primary ground (battery ground) and secondary ground ?

Secoundary ground is connected to amplifier ground, and amplifier ground is connected to input audio cable ground, and input audio cable ground is conected to battery ground trough CD-player.

heh I hope you understand what I'm talking about .
You have : Sec.gnd->Audio.gnd->Batt.gnd .
So why not connecting them directly at PCB ??

Greetings from Croatia :)
Hi, nice work!

I have a question concerning the filter inductor. I got some ITL501 core to do the transformer somewhat similar to the one you've built, but I can't seem to find any good high current filters. What are the ones you use? To be able to get around 350W out of the power supply, the input filter inductor needs to be able to conduct a whoping 30 amps. For the output filter, the current is still high overing around 5A but way easier to find already made filters from the likes of Digi-Key.

On another note, in the schematic, the base of the transistor in the 4N25 isn't connected to anything, is this right? Shouldn't it be connected to ground?

ITL501 free samples

Hey guys...I visited the WILCO website and they are offering samples of the ITL-501 toroid...they will give you 5 samples (good isnt :D )

According Rod Elliots website, this core can be used for the SMPS trasnformer.

I ordered my samples today lets see if they send them.

Thanks for schematics, very simple :)

I have couple of questions .

1) How is this your amplifier good for normal speakers, not subwoofers .

2) I noticed that your schematics and pcb of smps are different in one inductor. You are using one separate inductor only for supply for sg3535 . Why is that ?

I ask that beacause whithout that inductor I'm having problems, one capacitor even exploded here and sg3525 got dead :) But that happened with heavy load on spms .

Also I have feeling that sg3525 is having problem with direct driving mosfets . I think Ill use transistors to drive mosfets in my new pcb.

Re Questions

1.This amplifier is good for any speacker.I used for subwoofer becouse the output tranzistors are very strong-150W.I you like to use with car speakers about 200W per speacker you can use smaller output tranzistors like tip35c/36c,the supply is the same.If you like to use this amplifier in bridged mode on 4ohm speacker the supply can be +/-25V.
2.Yes on schematic I hevent put the inductor for sg3525.This inductor is 100uH and is recomendet for suppluing the sg3525.With this inductor the whole smps is more stable.
3.If you use just two pairs of irfz44n or buzz1 you can use direct from driving from sg3525.But if you use more then 3 pairs you can use tranzistors.Download this smps pdf document and use that kind of tranzistors.
4.Grucho do you have any car amplifier schematic,or car amplifier service manuals about Kenwood.If you have please send me on my e-mail [email protected] I will send you lot of matirials for making car amplifier.

Sorry for my bad english


  • mono power supply
    40.6 KB · Views: 5,086