Car Audio PSU Ideas

[fr0st]

I've been looking at this for a while now and still have no idea whick way to go.
Output ripple isn't really a large factor in the design since alternators give out a large amount anyway so ruling out linear reg's is a good idea, there power disapation also leads to alot of wasted money on heatsinks and whatnot.
Switching regs are the next option and probly the best. But all have similar effiency figures at high currents.
My question is which type is more suitable to the application (Buck, boost, half wave, full wave)?
Mains voltage switchers arn't really for the DIY'er so there ruled out.
I'm going to attemp to learn PIC programming so this might be a first project (with alot of practice).
Prefered stats - ~40amp , 9-16v

 

[dkemppai]

Hi,

Do you mean a power supply for in the car, or on the bench? If you're talking about building a switcher for in the car, your only realy option is push-pull. It's the only topology that will get enough power from the low (12v) input.

-Dan

 

[fr0st]

Do you mean a power supply for in the car, or on the bench?

Bench supply, for testing/home usage of car amps.
Probly a 25v supply but I havn't got any transformers yet

 

[dkemppai]

Bench supply, for testing/home usage of car amps.
Probly a 25v supply but I havn't got any transformers yet

fr0st,

I wouldn't bother trying to come up with an AC powered supply. Use a deep cycle battery, and small DC supply to float charge the battery when not in use.

In all honesty, I have both, a large (85 Amp) 12 volt supply, and a deep cycle battery. I prefer the battery. Current capacity is much higher than the supply. (about 10 times). Also, I have run into problems using the supply to power amplifiers. Sort of a zero beat problem between the two swithing frequencies (the supply, and the amp).

Oh, yeah, a battery will be much much cheaper...

-Dan

P.S. If you're still looking for large torroid cores, I may be willing to let one of mine go... ...in all reality I'm probably not going to use them all...

 

[jackinnj]

push pull is where you are headed

there are some switcher experts on these pages --

a 400 to 800 watt switching power supply is by no means a trivial excercise. with the push pull format you can design the windings of the transformer secondary to deliver the rail voltages you need. I highly recommend that you take a look at the ARRL Handbook section on switching supplies (or the equivalent RSGB book).

there really seems to be a demand for a high power switcher PCB! If no one else does it, I will design it, but will fix it for one of the chips I like,

 

[fr0st]

I've considered a battery I'd rather a power supply for the main reason that it would be used for alot fo other testing not just car audio.
The float charge for a battery is about 13-14v anyway so there still the posibility of scaling it down and use it as a charger.
Linear regs are a good option in elimitating beat frequency between power supplys but the inefficiency of it makes it an expensive option.

a 400 to 800 watt switching power supply is by no means a trivial excercise. with the push pull format you can design the windings of the transformer secondary to deliver the rail voltages you need.

A design like the ESP car SMPS is possible but you would be limited by core size. Parallel transformers is out for DIY as I've tried before it near impossible to get the voltage just right and for them to stay that way.
Is it possible to use chips like the tl494 and 3524/3525 in a switching regulator (buck)?
Although inductors arn't cheap many could be paralleled for higher current.

 

[dkemppai]

The float charge for a battery is about 13-14v anyway so there still the posibility of scaling it down and use it as a charger.
Linear regs are a good option in elimitating beat frequency between power supplys but the inefficiency of it makes it an expensive option.

Is it possible to use chips like the tl494 and 3524/3525 in a switching regulator (buck)?

I usually float charge my battey with 12.8 volt supply. I have an 8 amp supply doing that, with a constant 1 amp load (piece of equipment that always needs to run...) You don't want to float charge a battery with much more than it's normal terminal voltage, at least for long term.

As for linear regs... ...it can be done that way, but for the current you'd need, you'll need some really really big components. Even then, you'll probably have difficulty getting to the required current. I'm not saying that it can't be done... ...it can, but it may be more trouble than it's worth. What exactly are your requirements/design goals?

-Dan

P.S. There's a pic of a 2Kw DIY switcher.

 

[jackinnj]

note the liberal use of hot-melt adhesive!

do well all use Hot-Melt for keeping caps in their place -- I do too!

 

[RobM]

If you're talking about building a switcher for in the car, your only realy option is push-pull. It's the only topology that will get enough power from the low (12v) input.

H-bridge (aka full-bridge) is even better, especially from a reliability standpoint.

 

[dkemppai]

Re: note the liberal use of hot-melt adhesive!

do well all use Hot-Melt for keeping caps in their place -- I do too!

I have a friend who's said that "With a hot glue gun and a soldering iron, you can make anythying!" Sometimes I think he's right! It's great for prototypes!

H-bridge (aka full-bridge) is even better, especially from a reliability standpoint.

Problem with H-bridge is that you have two pairs of switching devices in series with each other, on each side of the transformer. Therefore conduction losses double, so it's not as efficient. H-Bridge is great at high input voltages, where currents are small, and conduction losses are minimal.

Push-pull can be as reilable as H-bridge... ...it's all in the design, not the topology...

-Dan

 

[fr0st]

I've got 5 of national's switching reg with sunc which could probly do about 20-25 amps but I'm not sure if that would be enough.
Theres a design here about adding a bipolar transister to boost a little switching reg up to 6 amps, If I replaced the 6 amp transister with a 35 amp one (2m max switching frequency, should be enough) and sync maybe 2 or 3 together would that fix my problem?

 

[N-Channel]

2kW Switcher

Hey dkemppai,

what controller chip did you ise? Toroid core? Switching frequency? output voltage(s)? (I like that big honkin' toroid!)

I built a 350W switcher based in Randy Vikan's car power supply fron 4/89 and 1/90 Audio Amateur. It's based on the SG3525AN PWM chip and uses IRF540s and MBR10100s. ll caps are the old Panasonic HF (superseded be theFC-series) or TSNA types. Outputs are +/-37V and +/- 45V (unloaded). Haven't loaded it down too much, but it will push an 8-ohm amp at 75W, so far......

 

[RobM]

Re: Re: note the liberal use of hot-melt adhesive!

Problem with H-bridge is that you have two pairs of switching devices in series with each other, on each side of the transformer. Therefore conduction losses double, so it's not as efficient. H-Bridge is great at high input voltages, where currents are small, and conduction losses are minimal.

It also depends upon what powers you're talking about. At 1kW+ I feel better with a bridge, even with a 12V input.

 

[dkemppai]

Re: 2kW Switcher

Hey dkemppai,

what controller chip did you ise? Toroid core? Switching frequency? output voltage(s)? (I like that big honkin' toroid!)

I built a 350W switcher based in Randy Vikan's car power supply fron 4/89 and 1/90 Audio Amateur. It's based on the SG3525AN PWM chip and uses IRF540s and MBR10100s. ll caps are the old Panasonic HF (superseded be theFC-series) or TSNA types. Outputs are +/-37V and +/- 45V (unloaded). Haven't loaded it down too much, but it will push an 8-ohm amp at 75W, so far......

LM3524D, +-65 VDC regulated outputs. Switching frequency About 45 Khz. Input caps are paralleled 3300uF FC series Panasonics, output are snap-cap type 8200uF 80 Volt TUP Pans also. Switching Fets are IRF1010N's with several in parallel.

The big toroid was a find. P Type Magnetics, I can get the exact part number later. I managed to get my hands on 18 of them in the last few years... ...normally not cheap (Ebay is great!) WaAc is massive. Second largest toroid they make.

At 1500 Everything runs ICE cold. No heat at all. If I were to do it again (and I probably will), I'd downsize a bunch of the components. It was my first attempt at a large PS, and I'll do a bunch of things differently the next time.

-Dan

 

[N-Channel]

2 kW

Dan,


No way, dude! Keep it cool! Since you're not putting it into mass-production, don't worry too much about down-sizing. Probably put it on a PC board with seriously beefed-up traces where appropriate, but don't downsize the MOSFETs. Those 100A FETs are just the ticket! Too bad ON doesn't make them anymore!

'73,

Steve

 

[fr0st]

Just a general switcher question... Should the ground on the secondary side of the transformer be connected to the primary ground?
I think this may have been the problem with alternator hum with my last car amp.

 

[jackinnj]

Just a general switcher question... Should the ground on the secondary side of the transformer be connected to the primary ground?
I think this may have been the problem with alternator hum with my last car amp.

No

The whine you are getting with the alternator can be eliminated with a filter. Remember that the leads from the battery to the switching power supply must be filtered (with a choke) , as well as the leads to the amplifier.

 

[fr0st]

No

The whine you are getting with the alternator can be eliminated with a filter. Remember that the leads from the battery to the switching power supply must be filtered (with a choke) , as well as the leads to the amplifier.

Another forum member surgested that having inputs chokes would be a bad idea since they increase transients and that the switcher should get rid of any alternator hum on its own.
opinions?

 

[JOE DIRT®]

If I may offer some advice on grounding in a automotive environment:

1/ Star ground all connections to a clean (bare metal) spot on the chassis

2/Make sure the alternator housing is grounded also {min 8Ga) the moter is on rubber mounts and the 10GA ground wire on the ourput connector does not cut it

3/Replace the Battery ground if it looks bad or is atleast 4GA or thicker

4/route power and signal wires on oppisite sides of the car if the amplifier is mounted in the back....if going through the firewall place a grommet in the hole (you`ll thank me later)

5/use atleast 8GA (I prefer 4GA) for all power and ground connections and make sure the battery is fused RIGHT at the battery, secondary fuses can be added to each indivual unit


thats a general rule of thumb that I have used building competition systems in the past and if the amplifier does not have a input filter then I suggest installing one right at the amplifier.

Cheers!!The DIRT®

 

[BenY]

Re: Re: 2kW Switcher

The big toroid was a find. P Type Magnetics, I can get the exact part number later. I managed to get my hands on 18 of them in the last few years... ...normally not cheap (Ebay is great!) WaAc is massive. Second largest toroid they make.

-Dan

Dan,
How do you select a toroid for 50Khz operation,What permiability should one select for optimal results?

Thanks.
Yuval.