toroid for car amp smps

[metal]

Hi everybody

Can I use the big EE ferrite core in PC power supplies, I already have three of them, and its much simpler to wind.

[Alcaid]

Originally posted by metal
Hi everybody

Can I use the big EE ferrite core in PC power supplies, I already have three of them, and its much simpler to wind.

Read post #22 in this thread. There is your answer.

[Danyele82]

Originally posted by tennisballg
I am no super pro on this, and I assume you're going to use it for a car supply, I think the Drain to Source voltage is too low. in a 13.8 V car, you're going to see 27.6 volts from drain to source, plus a minor turn on overshoot.

And what do you think about THIS MOS IRL3713 (3 pair)!!

As for the toroid, if you really want 1000W RMS, two toroids will suit you best, use one for each primary.

Only one toroidal core is not sufficient???
The 44932 core can supply about 2600w at 50khz!!!
look here Datasheet at page 8...

Also, if you're doing an A/B with a bias of over 60%, you'll want to heatsink the mosfets separately from the amp, most car amps just use the same big heatsink(case) for all of them, but the heat produced from a highly biased A/B won't allow your MOSFETs to dissipate heat, especially in a car. You may even want to make the power supply its own separate module.

A bias (for rhe car amplifiers) is about 100mA...

[tennisballg]

Well, the toroid may be able to handle it, but the size of the toroid makes it tough to keep all of the windings exposed. there's more room to breathe if you use two smaller ones, and probably cheaper as well. For example, my red toroid from a page or two back is #44925 off of your mag-inc page, with a similar i.d. and o.d. to yours. I am using it for a single 500W supply (2x250@2 ohm, bridged makes 500W@ 4 ohm). So I am making 40V rails, I re-wound the secondaries to fit snugly in between the primaries rather than just winding over the top, and I almost had to start layering the windings, not good for heat dissipation. You're probably counting on 55-60V rails to put 500W into 2 ohms, so that's even more windings, and probably more parallel strands as well.

Those mosfets have great characteristics, but i'm still not too sure about such a low Vdss, because I know that there is always some overshoot when the MOSFET turns on. From my experiences, long story short, you could easily have 60V turn on spikes when or before you initially tweak the dead time settings, transformer windings, snubber circuits, etc. Having the Vdss so close to the operating voltage might a)blow a few sets while you're first building b) won't allow you to clearly see any turn on spikes with your scope...but hopefully someone will back me up on this because I am not so sure of my opinion. IMO, it's a good idea to have higher ratings rather than cutting it to the edge.

[Eva]

Nearly all Car-Audio amplifiers use 50-60V MOSFETs for push-pull power supply since this blocking capability is required for reability reasons

A coulpe of years ago, there was a manufacturer called Rödek using a pair of 40V MOSFETs per transformer and two transformers on their power supplies. Guess?. I had to repair a dozen or so of these amplifiers with blown 40V transistors. Blown output devices were also common since single TIP 35C/36C output devices used in CFP and powered by +-30V supplies driving 2 ohms of inductive [subwoofer] loads at high temperatures are not a reliable approach. After a year, these series of amplifiers were discontinued and replaced by a different more reliable design

[metal]

Alright, I read the reply, but how much power can I obtain from the main core in the PC power supply, and why should I take into account the number of turns that used for the 12 volt winding, and the operating frequency of the TL494.

Thanks

[djQUAN]

ok, where should I start?

anyone willing to "guesstimate" how much power each core could handle?

here are some measurements........

toroid #1 (grey)

inner dia:44mm
outer dia:69mm
thickness (height):15mm

toroid#2 (black, unpainted)

inner dia:38mm
outer dia:64mm
height:25mm

toroid#3 (green, red on one side)

inner dia:35mm
outer dia:57mm
height:14mm

toroid#4 (grey, probably useless for a car amp but still worth considering for a small SMPS)

inner dia:12mm
outer dia: 21mm
height: 7mm



I'm guessing
#1 could be good for about 600-800 watts,
#2 can be up to a kW if properly built/designed,
#3 could be up to around 400 watts or so, and
#4 can be for a preamp supply or up to an ampere or two of step down/step up supply.




and I do have twelve dual 16A 200V ultrafast diodes,

ten 80V 95A MOSFETs, (IFR1312)

and eleven 55V 110A MOSFETs. (IRF3205)


sounds like I could make monster SMPS's.





and I need a SMPS that can put out a regulated 15V, 2-3A max output from 10V to 15V input. it has to be very simple and can be made to fit in a board area of about 4-5 sq inches max. Isolated output is not required but a plus.

[Danyele82]

To reduce the spike i've found this: TOSHIBA





What do you think about this???

[tennisballg]

You should be able to get your supply from having spikes much above 30V by just playing with the ocillator timings and making sure that your transformer is wound properly. I think that if you NEED to use these, then there is a big problem with your SMPS, and they are just masking the problem, if you can even get these to work how you want. Trust me, I've done a lot of whining about MY spikes on the forums in the past, and after many hours at the bench I found that it's really not so hard to get it right, you just have to know what you're doing.

Even so, the beads in the top pic could be a good idea for optimization purposes, but get your power supply working correctly first, then the beads will only make it better.



Just go for the higher voltage rating, they'll last longer anyway. Imagine a dam that is constantly filled to the top, there's a lot more pressure and stress on it than one only half full. Well, your MOSFETs have to "dam" the voltage in the same way.

[Eva]

metal :

You need to know the number of 12V winding turns and the oscillator frequency to calculate the required number of turns for the voltage and frequency of your application

Te number of turns on each 12V winding is usually specefied for a 48V-pp square wave [+24V / -24V] operating at half the TLT494 oscillator frequency

For 12V car SMPS applications you will be appliying +-16V [32Vpp] to each winding of the transformer so you have to scale down the number of turns proportionally

Also, you may prefer to use a different oscillator frequency than the usual 70Khz found on PC SMPS [35Khz effective], so you have to scale up or down the number of turns knowing that decreasing frequency requires increasing proportionally the number of turns and vice-versa

12V secondary windings usually have 7 turns each. Scaling this for car-smps operation we get 4.666 turns. Scaling again for 40Khz operation [80Khz oscillator] we get 4 turns per winding

You have to do the calculations for your transformers since values may be different