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The picture below is a schematic of a power supply, this will be my mini tesla coils power supply, after changing secondary voltages. Which is where my question lies...How would I adjust the feedback to allow the +15v, and +9V I need? My guess would be to adjust R202 and R203, or maybe R204 and R205...not sure...
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
Regulation is achieved when the junction of R204 and R205 is at 2.5V in the example R204 = R205 so Vreg = 5V. You also need to change the number of secondary turns proportional to the required output voltage.
Registered Member #3900
Joined: Thu May 19 2011, 08:28PM
Location:
Posts: 600
as Sulaiman said about turns ratio: the 12v is preportional to the 5v and the 5v is the regulated output. so if you wanted 5v to be 9v, 12v would become 21.6v. or if you wanted 12v to become 15v, then 9v would have to be 6.25v. unless you rewound the xfmr, but if i understand you correctly then you just want to modify an existing psu and just want to swap the resistors.
Oh okay, so I just need to adjust the resistors to give 2.5V? Target voltages are +15V and +9V, so R204 and R205 should be 14.7K and 5.6K respectively for 9V out correct?
Yes I know I will have to wind extra turns, they use 8 turns for 12V so I will use 9 for 15V. Speaking of, how does this work exactly, cause with 8 turns that would be 37.7V...my guess would be low duty cycle probably?
EDIT: @ Ben, This is one I will build, therefore I will be winding my own transformer, I just planned on adding one extra turn to the given values, and then adjusting the feedback resistors to give 15V and 9V.
Registered Member #3900
Joined: Thu May 19 2011, 08:28PM
Location:
Posts: 600
Ok. The output voltage isnt what you should read, it's the energy built up in the inductor. A flyback supply is essentially just a boost converter, but isolated. The energy is transferred when the primary is "off"
And if you aren't looking for the output levels to be isolated from each other, why not just have one winding of ~9 turns for the 15v, then an off center tap for the 9v section. The. You can say for sure when the top voltage is >15, the 9v is also over 9. As opposed to seperate windings where more current from one output grows the other slightly off.
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Adjusting Power Supply Output?
