The DC/DC converter can be tied directly to the AC power supplied without any diodes, they are already in them.
Set up the DC/DC to put out 20.3 volts or so and the AC supply the 20 volts.
If the DC drops the AC comes in automatically, and if not AC the DC takes over until cut-off time.
The trick is the 0.3 volts difference to do the switching.
No relays not special switching just ON-OFF switches
Nando
Thanks for the comments!
How can I be sure that I won't damage the power supplies by directly wiring the DC outputs together? I don't want to make smoke signals!
And note that I have this special feature that I don't want to draw any mains power at all while battery power is available, so I do need the 240V relay.
Rgds
Damon[ Parent ]
The DC/DC or the AC switching power converter if above its reference stop producing energy and in this case the DC/DC is the master and the AC is the slave,
The slave as a PWM supply will stop producing energy and goes dormant with a few milliwatts of power.
We have several PC connected this way for many years, in a close set up almost like yours.
Nando[ Parent ]
Damon [ Parent ]
The laptop mains adaptor is very good, and draws undetectably low power (I think << 2W) when it has no load.
Thus I am simplifying my design as you suggest and removing the mains transformer on the input side.
I am also connecting the OVs of the mains adaptor and 20V DC/DC converter supply together directly.
I am however still planning on switching between the mains adaptor and the DC/DC converter in the positive line with the relay. More details when I've built and tested...
