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-   -   Power unused circuits off: should power grounds be switched? (https://www.diyaudio.com/forums/power-supplies/345410-power-unused-circuits-power-grounds-switched.html)

zgtc 21st November 2019 05:49 AM

2 Attachment(s)
All the DC vs AC relays is super interesting, thank you.

I would like to come back to the finding in post 20 of AP22815BWT-7 power switch as a candidate replacement of a relay:
Quote:

Originally Posted by zgtc (https://www.diyaudio.com/forums/power-supplies/345410-power-unused-circuits-power-grounds-switched-post5981653.html#post5981653)
I might've found a way to avoid relays, using a power switch per each optional rail, at least for the 5V@3A. For instance, AP22815BWT-7. If I'm not mistaken this chip accepts a Input Voltage Range of 3.0V ~ 5.5V, and has an Enable input that acts as the switcher. It even has Overcurrent, Short-Circuit and Thermal Protection, Output Reverse-Voltage/Current Protection, Undervoltage Lockout etc. The EN feature is described as:

ON/OFF Input Operator
The EN input allows the output current to be switched on and off using a GPIO compatible input. The high signal (switch on) must be at least 1.2V and the low signal (switch off) no higher than 0.4V. This pin should not be left floating. It is advisable to hold the EN signal low when applying or removing power

Would anyone here please confirm this is a valid approach or I'm completely nuts? If this is valid, I'd need to find a similar product for +12V and for -12V rails.

Thank you so much

zgtc 21st November 2019 12:29 PM

1 Attachment(s)
Jean-Paul,

Quote:

Originally Posted by jean-paul
A drawing says way more than words.

Quote:

Originally Posted by zgtc (https://www.diyaudio.com/forums/power-supplies/345410-power-unused-circuits-power-grounds-switched-post5982012.html#post5982012)
I will try to do a basic scheme later tonight.

Here's the drawing. I don't think we need a super details proper schematics at this points.

Please see my previous message with a possible alternative to latching relays, using the AP22815BWT-7 power switch.

Thank you

Vovk Z 22nd November 2019 08:10 AM

Main "Isolated DC-DC" power unit will be on all time? So I dont see reason to use relay, but you can use just mosfet (for example - P-mosfet). May be there is some low-level (logic-level), I don't know exact popular part number right now. AO3401?

zgtc 22nd November 2019 08:30 AM

Quote:

Originally Posted by Vovk Z (https://www.diyaudio.com/forums/power-supplies/345410-power-unused-circuits-power-grounds-switched-post5984009.html#post5984009)
Main "Isolated DC-DC" power unit will be on all time? So I dont see reason to use relay, but you can use just mosfet (for example - P-mosfet). May be there is some low-level (logic-level), I don't know exact popular part number right now. AO3401?

Hi, yes, isolated DC-DC will be ON all the time. I will investigate on using mosfets, thank you. Any circuit you know I can look at?

Vovk Z 22nd November 2019 01:31 PM

I haven't exact circuit. When I needed recently something like that I googled "p-mosfet switch".

zgtc 22nd November 2019 02:36 PM

1 Attachment(s)
Hi again,

I'm just reading about using transistors. Apparently, the proper way to triggering a power circuit on/off through an Arduino signal is by using a P-Channel MOSFET as the switching transistor with a NPN transistor driver for that P-Channel. See NPN-PNP Driver Example section, from the baldengineer site, where I got the attachment capture from.

Also learnt from baldengineer that in theory there are off-the-shelf components called power switch or load switch, which basically would be ICs with the P-Channel MOSFET and a built-in NPN driver. Haven't found any in mouser though (or if I did, when reading the datasheet, I cannot find the explicit reference to the driver).

Also was having a look at this video Using PNP Bipolar Transistors with Arduino, from min 8:15 you'll see 3 circuits for the same purpose (one as the attachment, 2 a bit more complex, using Darlingtons).

I will keep reading.
Thank you again


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