Making car amplifier SMPS with tl494 + DC Protection

[Perry Babin]

The IC is using 5v as the reference on pin 2. If you lowered the value of the 47k, it would increase the rail voltage.

It's better to have both the positive and negative feed the regulator unless you're running a bridged amplifier or an amp that pulls from both rails at the same time.

[theAnonymous1]

Thanks Perry, I think we've got it.

17.5k gives me +/-40v with a 14.4v input. Before it was +/-47.5v.

The amp will either be bridged mono or at least stereo with one channel driven out of phase.

Now, do I need to add an output inductor to each rail since it is regulated now?

Thanks again and sorry if I was any hassle.

[Perry Babin]

I'd try it without the filter inductors. You're unlikely to see any improvement by using them. I know that some people will disagree but there are many manufacturers that don't use them and their amps work flawlessly.

[aliazhar]

Perry,

I have noticed that you are expert in SMPS and know it by heart...

I have a question (which i have tried to solve, but, since i am no expert...cant solve it without your help)

have a look at this inverter schematic....

there is a TL494 at the high frequency side...and another on at 50hz section...

both error amplifiers are either controlled by LM324 or 50hz TL494...

I need to remove both - LM324 and 50hz tl494...and use two error amplifiers as a voltage regulator and current regulator...

and there is no way i can do it....i have tried to reduce the voltages and i was successfull....but, removing 50hz tl494 just brings the voltages back to full...if both are there, then i can regulate the voltages on both side (high frequency and low frequency sides)


If you can help ....i will be really greatfull...

or if thats not possible to modify, then if you have another TL494 regulated smps circuit...?

one way or another, you are my best bet
i am pretty sure you can help.

Thanks again.

Regards

[aliazhar]

PDF file with a schematic.

[Perry Babin]

I'm no expert. The experts are on the power supply design forum.

Can you tell me precisely what you've done so far and the results?

You've been somewhat vague about what you're using this for. Can you provide more details?

[aliazhar]

well...the first thing i did was to reduce the output voltages at U2 to 44 volts - by changing resistance R29/R30 to lower values and increasing ground resistance R31....i was successfull

Then I reduce the voltages at the high-frequency side
by reducing resistance R42 and increasing resistance R39....
i was successfull in that too...and manage to get 44-volts.

but, since i dont need the low frequency stage, i want to get rid of it and get 44-volts output from U1....

I have also tried to totally remove U2 but, that brings the voltages back to 120v at U1 (power stage DC)

also, I have tried to remove R14 at U1 connected to pin 4...(dont know if it was a smart move) but, it did'nt work...

so, here i am...

[Perry Babin]

Did you try changing the 152v Zener before you changed the resistor values for the regulation?


Where does VCC connect in the inverter?


Can you post a photo of the insides? If you have a high res photo, email it to me:
babin_perry@yahoo.com


The transformer in this inverter probalby has a winding ratio that's too high to operate efficiently at 44v.

[aliazhar]

no...i never tried to change the zener....i did'nt even know that its a 152v zener....i only knew that its a zener...

here is another part of the schematic...

[aliazhar]

power stage schematic.