🚀 go-pugleaf

"Sylvia Else" <sylvia@not.at.this.address> wrote in message 
news:4964169c$0$25646$afc38c87@news.optusnet.com.au...
> This PS circuit seems rathed old fashioned. I opened a larged A/C unit 
> from the same manufacturer, and which was installed at the same time. It's 
> circuit board is only about half the size.
>
> Although this is a switch mode PS, it doesn't appear to use switch mode 
> regulation. As far as I can see, there is no feedback from the secondary 
> side back to the primary feedback circuit. Instead, there is a linear 
> regulator in the secondary side to set the voltage for the electronics.
>
> For what it does, the PS primary circuit seems rather complicated.
>
> Sylvia.

It's not at all uncommon to see switchers that are secondary-side 
linear-regulated only. I worked on a mixer / PA just a couple of weeks ago 
which had a full blown switcher in it. The main rails for the output stages 
had no regulation at all, and were completely dependant on the input line 
voltage. The low rails for the preamps had only simple linear regulators. At 
first, I thought this was a little odd, but of course, it is actually quite 
common for the main 'big' rails not to be regulated in this sort of kit, 
when it uses a conventional transformer-based supply. So what was the 
advantage of complicating things by using a switcher ? I can only assume 
that it's primarily because it's a portable item of band equipment, so it 
makes it much lighter to carry around. A lot of other kit uses switchers 
these days because of the energy efficiency, particularly when they are put 
into a 'sleep' mode, but an A/C unit ? It's beyond me why it would be worth 
the added complication of a switcher over a linear, given the energy-gulping 
nature of the appliance in the first place, and the potentially hostile 
environment that it has got to work in ...

Arfa