More vi limmiters

[sakis]

there has been an extensive discussion regarding VI limmiters and related applications in high power amplifiers .

one of the points was this idea of mine to use an smps pick up coil as a sensor from the output to drive transistors to limmit the drivers of the amp.

the idea was simple but very wery wrong since smps coils cannot be used for audio signals since the behaviour of the coil is not linear at all versus frequency

since i have so many smps pick up coils i thought about design of a circuit that will see how many amps are drawn from the power supply (at DC conditions ,what the coil was originally designed for and also monitoring bothrails ) and then limit the input or the drivers with this creteria

any opinion ???

[sakis]

bre anyone ????

nobody thinks that this is a possible idea ???

[jcx]

current transformers have a low frequency corner – maybe it would miss low frequency Audio or a DC fault

for "DC" apps you can get Hall effect or GMR sensors that measure the magnetic field around a conductor with very little effect on the signal

[sakis]

Originally Posted by jcx

current transformers have a low frequency corner – maybe it would miss low frequency Audio or a DC fault
for "DC" apps you can get Hall effect or GMR sensors that measure the magnetic field around a conductor with very little effect on the signal

neither low frequency corner nor low frequency audio will mater if your sensor is sensing how many amperes are passing by from the psu to the amplifier

dc fault is another story

[janneman]

Originally Posted by sakis

neither low frequency corner nor low frequency audio will mater if your sensor is sensing how many amperes are passing by from the psu to the amplifier

dc fault is another story

Remember that whatever passes from the supply is AC, not DC (except for the small DC bias). That xformer will catch, say 1kHz supply load, but not a 50Hz supply load.

But there is a more important issue. If you only look at the (Ic or Ids) current, your amp is not well protected. If you check up on 'Safe Area Operation' you will find that the allowed power before the output devices explode, varies with Vce (or Vds). So you musty check I, and V and find a (non-lineair) curve of what is allowed and what not. There's some info on that on my website.

jd