150k
These must have more carats of gold in the front plate than the Goldmunds
What do these designers (company)
( used in the absence of a more appropriate smiley ) ??
Me tupid you smart, where is the answer?
And why you people so seeking low ripple. Good Ampi dun need ripple free supply and ripple will not reach speaker.
Looks like you people dun know how much ripple is tolerable.
Me inglish is too bad to read all that. As me understand its very simple and only me newcomer dun understand. So tell me in simple Inglish what much ripple do you want and why cause at me electronic level, ripple is not an issue for good profesional design ampi.
liching1952, that is just trolling. you are at least trilingual, and from what you've posted so far your english is more than sufficient for the task at hand - Ni Shuo Huai Hua. besides, with your MSc you should be able to follow the schematics and plots. that you have not and will not do so suggests you are either lazy or stupid. I'm assuming lazy.
As MagicBox points out, the thread is about transient response.
Why low ripple? stupid question. have you ever heard of PSRR? what about Early Voltage? cascoding?
As MagicBox points out, the thread is about transient response.
Why low ripple? stupid question. have you ever heard of PSRR? what about Early Voltage? cascoding?
I'm just playing with the xfmr-rectifier-cap setup. Toms model, one transformer driving a MBR20100 full bridge into a 5R load with N * 1.2mF 26mOhm caps in parallel.
and I didnt see quite what I expected to see - above about 10mF the conduction angle is constant. thats odd. so I started looking a bit harder. it looks like its the combined effect of ESR (xfmr + diodes + cap bank) & leakage inductance that prevents the conduction angle from narrowing further - IOW it limits the peak current.
The transformer winidng resistances are interesting. Its a forward-mode transformer so the RMS primary and secondary currents are closely related - Ip = Is/N + Imag (this aint necessarily so in a coupled inductor).
generally one designs Imag = small (this is why the huge ratio of Lmag to Lleak - Lmag must be >> Lbase and Lleak << Lbase) so Ip = Is/N. One normally assigns equal volume to equal power windings - so the primary winding area Aw_p should be roughly equal to the secondary winding area Aw_s. Filling this up with Cu then results in Rp = Rs*Np^2. and the resistive losses in each winding are therefore equal (casually ignoring skin & prox effect)
yet in this case Rp/N^2 = 157mOhm but Rs = 290mOhm - the secondary resistance is 1.85x what I would expect it to be. so ignoring magnetising current the secondary accounts for 1.85/2.85 = 65% of the total copper losses.
I might expect to see that in, say, a microwave oven transformer where the poor thing runs hard into saturation (some MOTs draw less current under load because the voltage droop across the primary leakage pulls the core out of saturation. it makes it hard to spot a dead transformer if you dont know this). But nobody in their right mind would do that to a transformer running continuously. and beside with Lmag = 52H the mag current is < 10mA.
It might be to do with the thermal behaviour - if the secondary is on the outside of a toroid it will cool better. I dont know, I havent designed any LF toroidal transformers, but it still seems like a poor idea - especially as it hurts regulation.
the high Lmag seems odd too - 6mA magnetising current is stupidly low* at 120VA thats 0.6% of load.
One would normally pick a number, say 10% full load and design Imag = that much. this reduces the number of turns, and the leakage goes down (and regulation improves). Maybe the manufacturer was trying to get stupidly low Bmax for some reason? who knows, but its certainly odd.
*I used to have a 100kW three-phase 400V:208V transformer with Imag = 200mA (about 0.1%), but that was designed to be switched on and off hundreds of times per day, so was not allowed to "boing" so it had a peak flux density of about 400mT IIRC.
that might be whats happening here - if this transformer were designed for minimum inrush (which is utterly pointless if it then drives a thumping great rectifier-capacitor load) it explains the low Imag and the high leakage.
this transformer might turn out to be a TERRIBLE choice for modelling power supply interactions
and I didnt see quite what I expected to see - above about 10mF the conduction angle is constant. thats odd. so I started looking a bit harder. it looks like its the combined effect of ESR (xfmr + diodes + cap bank) & leakage inductance that prevents the conduction angle from narrowing further - IOW it limits the peak current.
The transformer winidng resistances are interesting. Its a forward-mode transformer so the RMS primary and secondary currents are closely related - Ip = Is/N + Imag (this aint necessarily so in a coupled inductor).
generally one designs Imag = small (this is why the huge ratio of Lmag to Lleak - Lmag must be >> Lbase and Lleak << Lbase) so Ip = Is/N. One normally assigns equal volume to equal power windings - so the primary winding area Aw_p should be roughly equal to the secondary winding area Aw_s. Filling this up with Cu then results in Rp = Rs*Np^2. and the resistive losses in each winding are therefore equal (casually ignoring skin & prox effect)
yet in this case Rp/N^2 = 157mOhm but Rs = 290mOhm - the secondary resistance is 1.85x what I would expect it to be. so ignoring magnetising current the secondary accounts for 1.85/2.85 = 65% of the total copper losses.
I might expect to see that in, say, a microwave oven transformer where the poor thing runs hard into saturation (some MOTs draw less current under load because the voltage droop across the primary leakage pulls the core out of saturation. it makes it hard to spot a dead transformer if you dont know this). But nobody in their right mind would do that to a transformer running continuously. and beside with Lmag = 52H the mag current is < 10mA.
It might be to do with the thermal behaviour - if the secondary is on the outside of a toroid it will cool better. I dont know, I havent designed any LF toroidal transformers, but it still seems like a poor idea - especially as it hurts regulation.
the high Lmag seems odd too - 6mA magnetising current is stupidly low* at 120VA thats 0.6% of load.
One would normally pick a number, say 10% full load and design Imag = that much. this reduces the number of turns, and the leakage goes down (and regulation improves). Maybe the manufacturer was trying to get stupidly low Bmax for some reason? who knows, but its certainly odd.
*I used to have a 100kW three-phase 400V:208V transformer with Imag = 200mA (about 0.1%), but that was designed to be switched on and off hundreds of times per day, so was not allowed to "boing" so it had a peak flux density of about 400mT IIRC.
that might be whats happening here - if this transformer were designed for minimum inrush (which is utterly pointless if it then drives a thumping great rectifier-capacitor load) it explains the low Imag and the high leakage.
this transformer might turn out to be a TERRIBLE choice for modelling power supply interactions
It becomes more and more interesting, the whole scheme what you called a Cap multiplier is to minimize ripple now you mention transient. Explain, what which transient. No I dun know what PSRR or early voltage is, as said me Inglish is poor, so explain. And what has cascoding to do? I think that you want to make confusing because you recoq the stupidity but want to cover up. So explain instead calling for nonsence.
Yes its not nice to get critical critism from a low level trilingual new comer isnt it.
The big point with the cap multi is that you do NOT use a zener and keep the Vds/ce drop as low as possible since the goal is not to build a crude lineair regulator but to increase the virtual capacitance the output devices see.
Thats right you minimize the lost but thats not my question, why this effort to minimize ripple. A well designd amp doesnt need ripple free supply.
And, what you all dont see, the thir so called cap multiplr introduce a lot of other effects that lowered the overal performance of the amp thats why I called it nonsence but to be unpolite, its stupid.
To produce audio correctly and unaltered, a good amp has to work at and operate at frequencies up to 10 times the audio band. That's where transient response comes into play, most notable the "T=0" current as I call it. The initial current that needs to be drawn as a result of a change in the system. Propagation delay, parasitic inductance all limit the T=0 current resulting in a voltage sag that otherwise should not sag but deliver the associated, demanded current.
People here are not fighting ripple, PSRR does that like you say. We're past that. We're not analyzing ripple. We're analyzing T=0 current supply any moment the output demands it. And this does not apply to the 'slow' audio signal, but to the HF loop frequency of the circuit.
At regulatory frequences, the AC output impedance of a MOSFET / Transistor is rather low; any HF signal on the output transistors 'walks' right through the output device, severely destructing PSRR. Luckily the amp must be stable and as such will not have HF AC regulatory swing (if it does, it can't stable out) for audio signals. But to keep that audio signal in perfect shape, you no longer have to view an amp as an LF amp but as an MF/HF amp operating in the 100KHz - 1MHz area.
Edit: Basically the amp has to be fast enough to compensate for its inherent slowdowns in the circuit.
People here are not fighting ripple, PSRR does that like you say. We're past that. We're not analyzing ripple. We're analyzing T=0 current supply any moment the output demands it. And this does not apply to the 'slow' audio signal, but to the HF loop frequency of the circuit.
At regulatory frequences, the AC output impedance of a MOSFET / Transistor is rather low; any HF signal on the output transistors 'walks' right through the output device, severely destructing PSRR. Luckily the amp must be stable and as such will not have HF AC regulatory swing (if it does, it can't stable out) for audio signals. But to keep that audio signal in perfect shape, you no longer have to view an amp as an LF amp but as an MF/HF amp operating in the 100KHz - 1MHz area.
Edit: Basically the amp has to be fast enough to compensate for its inherent slowdowns in the circuit.
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No the amp dun see a bigger cap. There is less ripple but by no mean seeing a large cap. If you use a zener the ripple is zero. Do the amp sees an Infinity cap? Of course not. An infinit cap should supply the amp with current for invinit time which is certainly not the case. What the amps sees is only the small cap at the output. It even doesnt sees the rectifier cap since this blocked by the transistor.
Liching1952,
What does a cap multiplier have to do with this discussion anyway? You were the one that brought it up so why don't you answer your own question.
Terry,
do you say that the mag current from a rule of thumb should be a specific percentage of output current, or better still you have a rule of thumb for number of turns per volt? However number of turns will affect the inductance, so what is the starting point.
What does a cap multiplier have to do with this discussion anyway? You were the one that brought it up so why don't you answer your own question.
Terry,
do you say that the mag current from a rule of thumb should be a specific percentage of output current, or better still you have a rule of thumb for number of turns per volt? However number of turns will affect the inductance, so what is the starting point.
Another nonsense consensus. The energy content of music decreases rapidly after 6kHz or so. There is nothink above 15kHz and there are no transients fast enough to translate to more then 15kHz. As a rule of thumb, Transient x bandwidth = 0.35.
And assuming, there are fast transients, what has it to do with a cap multiplier? With a cap multiplier the amp sees only the small output cap, thus less cap then without the circuit.
Reading comprehension. We're not talking about the speaker terminal output. We're talking the collector/drain connection points of the output devices. The cap multi is a tool used locally close to the output device power terminals. It's called a "cap multiplier" for a reason. It prevents local sag with a much smaller cap, tapping into the stored current in the PSU buffer caps, though with the nastly L parasitic in between before it gets to your board. The CM transistor actually compensates for the T=0 current draw associated voltage sag.
You need to learn that what a circuit does is not always what a circuit wants to do. We're not talking audio signal transients. We're talking regulatory frequency transients caused by non-lineairities in devices. When all is good, the regulatory frequency is very high with minimal swing. When things are not so good you have an amp that's outright unstable and if it's on the edge, it'll be very tacky to listen to.
In the ideal situation there is no regulatory swing, it'll be Vpp=0. BUT as soon as a delta appears in the system, the regulatory swing will be back to adapt to the change in the system. The quicker and faster it can do that, the better the amp is.
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Wrong. When there is current demand from the amp, without CM, it will draw current from the big rectifier cap. With CM the amp can only draw current from the smaller C at the CM output. The supply will even drop more then without CM.
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