Fantastic Mr Quan 🙂 I'm glad to see that SMPS you did is basically identical to one I'm going to knock up for another project. Did you find any problems/drawbacks with that approach?
Just looking at that rectifier though, are you sure it's drawn correctly?
Just looking at that rectifier though, are you sure it's drawn correctly?
ooops. hehehe it's supposed to be a bridge arrangement. 
also, the one I used are schottky rectifiers in two legged TO220's since I already have those in hand.
R1 and R2 adjusts the freq and dead time for the fets.
R3 and R4 set the oscillating freq. with teh values shown, the oscillator runs at 50kHz
since I cannot find the components I used, I substituted ones from the eagle library that should also work.
what I used were: MPSA06 on all small transistors, IRFZ44 fets, and the schottky diodes.
the transformer was an unknown EE core wound with 18+18 turns primary, 28+28 turns secondary.
the supply is powering the amp and has a very small idle current of around 60-70mA without a load and with the entire EQ connected, the idle current is only around 500+mA. there is no heating (except for the onboard regulators of the EQ)
seems to work very well to me. 🙂
also, the one I used are schottky rectifiers in two legged TO220's since I already have those in hand.
R1 and R2 adjusts the freq and dead time for the fets.
R3 and R4 set the oscillating freq. with teh values shown, the oscillator runs at 50kHz
since I cannot find the components I used, I substituted ones from the eagle library that should also work.
what I used were: MPSA06 on all small transistors, IRFZ44 fets, and the schottky diodes.
the transformer was an unknown EE core wound with 18+18 turns primary, 28+28 turns secondary.
the supply is powering the amp and has a very small idle current of around 60-70mA without a load and with the entire EQ connected, the idle current is only around 500+mA. there is no heating (except for the onboard regulators of the EQ)
seems to work very well to me. 🙂
Did you play with R1 and R2 (560 R) to optimise the dead time? Or just calculate them somehow?
Would you consider a version driving a meatier transformer for maybe an amp?
Would you consider a version driving a meatier transformer for maybe an amp?
nope. I just took what I had on hand and built up the circuit. it does have a little too much dead time though. but still works well without anything heating up.
I'm planning on building a bigger version that can power a car amp but would have to figure out how to incorporate a soft start. other than that, everything else is solved.
planning it to power six channels of P3A, two a little overdriven to get 150x2 and 100x4
I'm planning on building a bigger version that can power a car amp but would have to figure out how to incorporate a soft start. other than that, everything else is solved.
planning it to power six channels of P3A, two a little overdriven to get 150x2 and 100x4
I'd be very interested to see how you get on.
Do you need soft start? Does the TL and SG chips have soft start?
Do you need soft start? Does the TL and SG chips have soft start?
the SG chips do have a separete pin just for the purpose, the TL chips can use the deadtime pin for that. my oscillator don't have any. 🙁
any ideas? I was thinking about powering the oscillator slowly so the SMPS does it in pulse amplitute modulation instead. so the gate voltage ramps up slowly......
any ideas? I was thinking about powering the oscillator slowly so the SMPS does it in pulse amplitute modulation instead. so the gate voltage ramps up slowly......
Yes if the remote pin was ramped it would do that. But it would also cause the MOSFETs to get hot during start up as not fully on, and maybe even not provide all that much soft start action anyway, as the gate voltage is very non-linear.
Ideally you need to start off with shorter pulses of normal amplitude. I think you could do this with a 555 timer, but then you lose the simplicity of the transistor setup.
Ideally you need to start off with shorter pulses of normal amplitude. I think you could do this with a 555 timer, but then you lose the simplicity of the transistor setup.
well, although it would get hot, it would only be for less than a second so it would be fully on before the sink gets hot.
or if I would use not too much secondary capacitance, I could no longer need soft start. 😉
or if I would use not too much secondary capacitance, I could no longer need soft start. 😉
I was thinking more in terms of the die temperature rocketing. Although it's probably a minor concern.
I think soft start is needed, you shouldn't have to skimp on capacitance.
I think soft start is needed, you shouldn't have to skimp on capacitance.
the last amp I fixed, an orion 225HCCA used PAM for powersupply regulation so I guess that soft start could be accomplished with ramping the gate voltage slowly.....if I increase the soft start delay a bit longer like say 2-3 secs, it might make the fets heat up much slower trather than heat up too quickly at start up.
Surely if you use PAM, increasing the soft-start period will only make the dies get even hotter? It's probably not an issue though. The other option is to add a traditional resistor/relay soft-start.
Interesting to know that a 'good make' amp used PAM for supply regulation, I really wouldn't expect that of a good design.
Interesting to know that a 'good make' amp used PAM for supply regulation, I really wouldn't expect that of a good design.
I don't like relays in the main power line. 😉 relay on the secondary side? hmmm but that would mean a lot of relays if I include the ones needed for speaker protection.
might as well build it using the schematic and the soft start with PAM. we'll see how it turns out. 🙂
also, I don't think I would need that much capacitance anyway since it will be driving midbass and up unlike subwoofers which need tons of capacitance.
might as well build it using the schematic and the soft start with PAM. we'll see how it turns out. 🙂
also, I don't think I would need that much capacitance anyway since it will be driving midbass and up unlike subwoofers which need tons of capacitance.
djQUAN said:
DJ,
See any of the DC-DC threads either here in the Car Audio forum, or in the Power Supply forum. SG3525 & TL494 are the easiest to implement and have all the functions you're looking for: Softstart, variable deadtime, output sensing, synchronization to an external clock (either slave or master), etc. etc. Plus, they're alot easier to lay out on the pc board than the free-running oscillator is.
Steve
N-Channel said:
I was trying to do that so I could have a fully discrete amp (no IC's!! 😀 ) but ended up using TL494 anyway.
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