might be best explain with an example:
I have a relay protection circuit that uses a 7805 regulator to bring down the incoming DC to operating voltage. I am thinking of using a small AC-DC power supply (example: https://www.meanwell.com/productPdf.aspx?i=677#1).
Is there a requirement to tie the power supply grounds together in this situation? thanks
I have a relay protection circuit that uses a 7805 regulator to bring down the incoming DC to operating voltage. I am thinking of using a small AC-DC power supply (example: https://www.meanwell.com/productPdf.aspx?i=677#1).
Is there a requirement to tie the power supply grounds together in this situation? thanks
@Mister Audio I don't think this uses a transformer. Looks it's an SMPS which I believe does not use one?
I wouldn't use an SMPS to power up the speaker protection circuitry... The SMPS negative DC rail will have to sit at the same potential as the rest of the amplifier ground/common (so that the sensing circuitry can work), which is a bad idea from the noise injection point of view.
Even worse, that SMPS will spit HF rubbish back to the mains... to the same exact point from which you'll be sourcing the 240V AC for your amp.
If the amp rails are much higher than what that 7805 needs to see / can tolerate at its input, just use another smaller transformer and a bridge rectifier, to obtain a ball-park rail voltage of around 8-10V DC.
Of course, if the amp is already class D with an SMPS as a power source.... then everything is allowed and just ignore the above.
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