Zero Ohms

[DrV]

2 hours ago, richardash1981 said:

The weird thing with this patent is that it shows them in parallel with opposed polarities - which will more or less end up as a short circuit ...

Does it? Looks like they are the same way round to me, both the symbol and the polarity marking. Not the only weird thing either -

[quote] 

The first capacitor may have a capacitance that is larger than the capacitance of the capacitor of one channel of the power supply of the amplifier. 

 [/quote]

and

[quote] 

Without wishing to be bound to a particular theory, the applicant assumes that the first capacitor acts as a powers storage that ensures that all parallel connected loudspeakers are supplied with power.

[/quote]

I have opinions on both of these but decided to delete them as I don't know enough about the law to risk expressing them! Read, digest and form your own opinions.

[sunray]

 

8 hours ago, DrV said:

Indeed, but the usual arrangement is to put two in series with opposing polarities (obviously twice the required value).

However at school and college we were taught to use

4 hours ago, richardash1981 said:

 them in parallel with opposed polarities -

and treat the combination as the value of just one of them. 

Edited June 4, 2023 by sunray

[electronicsuk]

From the patent application:

 

Quote

FIGS. 3a to 3c show measurement results of the inventive passive loudspeaker multiplexer 1, 1′. The first column on the left side denotes the output voltage of the amplifier in V without load. The second column denotes the output voltage of the amplifier in V with load. The third column represents the output current of the passive loudspeaker multiplexer. The fourth column denotes the frequency output by the amplifier. The fifth column represents the internal impedance of the amplifier. The right column represents the impedance at the output of the passive  loudspeaker multiplexer.

They go on to say:

Quote

It can be seen from the tables that the internal impedance of the amplifier does not change although the impedance of the load changes significantly. Further, the current supplied by the amplifier changes significantly due to the load. However, the output voltage of the amplifier does not change, although the load changes significantly. Thereby, it can be prevented that the amplifier enters protection mode or switches off for any other reason.

The patent author(s) appear to state that because the amplifier's output voltage remains broadly the same when the lower impedance load is connected via their circuit, the amplifier can be prevented from going into protect. The tests are done at 1V nominal into a 0.47 Ohm load, so about 2.5W RMS. This doesn't represent the power levels typical of a large PA system.

Looking at the measurements, there are figures presented at 2 Ohms both with and without the circuit. It's a strange omission to only include the with-circuit measurements for the 0.47 Ohm load. I'd like to see how they compare to the same load without the circuit.

The patent application also seems to state that because the amplifier's internal impedance remains unchanged (I'm not sure how this is being measured), this negates any issues with the load impedance. I don't understand how this conclusion was drawn as I'd expect the amp's output impedance to remain relatively low, with respect to the design load impedance, regardless of what impedance is presented at the output terminals.

It'd be interesting to see how it scales up. The specs state power handling of up to 4K RMS. The test results in the patent application seem to suggest that the current at the output terminals remains largely unchanged, whether the load is connected directly or via the circuit. With a 0.47 Ohm load at 4K, that's a peak current of sqrt(4000/0.47) 92 Amps. The same 4K into a more typical 4 Ohm load would be about 32 Amps peak. That's a big difference as far as the output and protection circuitry of the amp is concerned. Unfortunately, as the current is being measured at the output terminals of the multiplexer and not the amplifier, you can only draw conclusions about the current at the amplifier's output terminals. 

Edited June 23, 2023 by electronicsuk
Typo