Amps that have regulated power supplys

[toaster 10+ year member]

http://www.bcae1.com/regunreg.htm

everyone read this before it gets too confusing.

 

[helotaxi 5,000+ posts]

HUH?? chopped DC is used @ the input to an amps transformer.... form there it is rectified thru diodes and filtered, where we get ac voltage.
the power supply takes dc voltage and inverts it to ac voltage. it does this @ a certain frequency, with d class amps actually switching into the audible higher freq range. thats why they only work well as sub amps, because @ higher freqs you can actually hear the switching noise as the voltage is being chopped up.

I know exactly how it works. Its typically pulsed DC created by a series of switching FETs run through a transformer. The fact is that the tranformer only works because of the pulsed nature of the current. It roughly approximates AC. If you hook straight DC up to a transformer, nothing happens except the transformer gets hot. As soon as you rectify the output of the transformer, it is no longer AC it is once a again straight DC. Both the input and the output of an amp power supply are DC. It is turned to AC by the output stage of the amp but that has nothing to do with the power supply. Pulsed DC through a transformer is the basis of an "unregulated" power supply. Because the switching frequency of the FETs is based on voltage, there is still some regulation of the power supply. This is the most simple of the basic amp supplies. Because there is a transformer involved, the output voltage of the transformer is a consant multiple of the input voltage.

In a fully regulated supply, the voltage increase in the power supply is generated by running pulsed DC into an inductor. The switching frequency determines the output voltage. The higher the switching freq, the higher he voltage. In this case the switching freq is controlled by the input voltage in an inverse function and monitored by a feedack circuit on the output. As the input voltage drops, it ups the switching freq to provide a realtively constant output voltage. The increase in switching freq effectively increases the duty cycle of the power supply and increases current consumption.

A Class D amp is little more than a power supply. The output voltage is regulated by the input signal and the output voltage is a stepped approximation of the signal input. The sampling frequency of the Class D is relatively low to keep the amp more efficient, but they are made for lower power operation with a higher switching freq for use in full range operations. These tend to be of lower power because of the loss of efficiency and the fact that you don't need as much power at higher freqs compared to sub bass.

 

[squeak9798 5,000+ posts]

thats why they only work well as sub amps, because @ higher freqs you can actually hear the switching noise as the voltage is being chopped up.

I find that comment extremely funny considering the multitude of full range Class D amplifiers used in both car audio and home audio that sound just as "good" as any other class of amplifier.

Is it possible there are some extremely poorly designed class D amps that suffer from what you describe? Yes. But that's because of their poor design, not the amplifier class as a whole.

 

[thch 10+ year member]

You should know well enough that there is no such thing as a DC transformer...
A transformer requires AC to work.

DC transformer is a concept and realizations have existed at least back to the 1920s. basically it is a switching supply. if you fix the pulse width and frequency of a forward, bridge, or push-pull topology, the output voltage becomes a function of the input voltage (and the transformer). and the input current is based upon the load current and the transformer. functionally, it is a DC transformer.

alternatively you allow the saturation of the transformer to turn off one device, and the flyback action to turn on another device. that's a royer converter.

not sure if its safe to use any high-power non-flyback, non-current fed design without output inductors.

i don't think frequency modulation is popular in non-resonant converters. i'd put my money on width modulation.

class D amps switching frequency is usually significantly higher then 20khz.

 

[CBRworm 10+ year member]

Right, the concept is of a DC transformer.

but a transformer is understood to be two or more sets of windings on an air or iron core. That doesn't do anything with DC except convert energy to heat, unless the DC is being modulated or chopped - effectively turning it into AC.

So we have a buck/boost switchmode power supply that takes the DC input, and modulates it at a variable or fixed rate effectively turning it into high frequency AC connected to an inductor of some sort and a series of diodes and capacitors to grab the positive voltage spike coming from the inductor, and clean it up into useable DC again usually with a feedback circuit that changes the pulse width or frequency on the input transistor to maintain a smooth requlated output at a selected voltage regardless of current draw.

The end result is what you would get with a transformer for DC if such a thing existed, but it doesn't.

 

[toaster 10+ year member]

thanks... what i was trying to say to start with, but alot better said