Can it get any simpler than this ?

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Jamie

Reply to
Maynard A. Philbrook Jr.
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Well, it could. Why does it need that third transformer winding and stuff? Why doesn't it just connect to the opto output?

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John Larkin         Highland Technology, Inc 

jlarkin att highlandtechnology dott com 
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Reply to
John Larkin

Input/Output Isolation? ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Reply to
Jim Thompson

if you want and isolated output you need an isolated supply for the control

-Lasse

Reply to
Lasse Langwadt Christensen

Don't see why. The IC has internal power, derived from the primary side. Why can't it pull up the phototransistor?

I think they are assuming that the phototransistor is always partly on, enough to actually power the chip internals. So that third winding really powers the chip after startup. But it doesn't have to.

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John Larkin         Highland Technology, Inc 

jlarkin att highlandtechnology dott com 
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Reply to
John Larkin

rol

yes looks like the control input powers the chip after startup, duty-cycle controlled by current shunted by the internal regulator I don't think you can use the internal supply except for startup, looks like it switches to the control input when the shunt regulator hits 5.7V and is in regulation

-Lasse

Reply to
Lasse Langwadt Christensen

OK, even simpler: get rid of the opto and do the sensing on the primary side. Then the regulator becomes a 2-terminal device.

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John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    
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Reply to
John Larkin

The document says the feedback current is its power source. Its internal regulator just does kickstarts.

A linear regulator off 600 V would probably require some not-simple cooling.

Reply to
Kevin McMurtrie

the datasheet says the range is 2-6mA so it is "only" ~3.6W

-Lasse

Reply to
Lasse Langwadt Christensen

Maybe they make/sell the transformers for extra income?

Reply to
Robert Baer

...but an iso-optulator already does that.

Reply to
Robert Baer

Check!

Reply to
Robert Baer

Then steal power from the TOPswitch,,

Reply to
Robert Baer

trol

afaict you'll need something like 12V at upto 6mA

-Lasse

Reply to
Lasse Langwadt Christensen

You could use a capacitor power supply to overcome this issue. Then, on the other hand the additional X-capacitor is both more bulky and more costly than the third winding. BTW, find it irritating that they correctly note C7 as Y1 class, but don't specify X1 for C6 (figure 8).

Klaus

Reply to
Klaus Bahner

Note the returns... and AC _common_ and output _common_. ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Reply to
Jim Thompson

Most people like to GND reference their power supplies, without the isolati on you would end up shorting the rectifier, then the input voltage on this is fairly huge so that even at a few milliamps loading there is fairly huge power savings by running the IC off a low voltage winding, then most cheap bastards run their transformer windings at the highest allowable current d ensities making the winding regulation with loading poor so the output leve l sensing needs to be done there. The stuff with zener and opto is pure una dulterated garbage, they should be using that TL431/opto combo thing, anyth ing else is a hope and a prayer.

Reply to
bloggs.fredbloggs.fred

On Fri, 25 Apr 2014 17:01:33 -0700, John Larkin Gave us:

You have never heard of feedback or control loops?

How did you ever make it in this industry?

Reply to
DecadentLinuxUserNumeroUno

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