Timeline for Could someone answer my questions on a transformer with regulator circuit in LTspice?
Current License: CC BY-SA 4.0
15 events
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Oct 30, 2019 at 16:02 | vote | accept | kepsek | ||
Oct 28, 2019 at 17:21 | comment | added | Spehro 'speff' Pefhany | You're missing leakage inductance in the transformer model, which will (negatively) affect the transformer regulation. | |
Oct 28, 2019 at 16:57 | comment | added | kepsek | @jonk Those are very good points, I'll amend the design. thank you very much. | |
Oct 28, 2019 at 16:55 | comment | added | jonk | But you don't want the secondary to be \$20\:{\text{V}_{\!\text{AC}}}\$, instead a regulated output of \$20\:{\text{V}_{\!\text{DC}}}\$ which must take into account the voltage drop across the bridge rectifier and the input needs of the LM317. So maybe \$26\:{\text{V}_{\!\text{PK}}}\$ at the secondary. Divide by \$\sqrt{2}\$ to provide an RMS rating for the secondary of about \$18.4\:{\text{V}_{\!\text{AC}}}\$. Transformer regulation vagaries and I'd just accept the original \$20\:{\text{V}_{\!\text{AC}}}\$ I started with above. (Or choose transformer's value that's conveniently nearby.) | |
Oct 28, 2019 at 16:55 | comment | added | kepsek | @ThePhoton Ah sorry, Yes I've amended it now. | |
Oct 28, 2019 at 16:52 | comment | added | jonk | In LTspice (probably in most simulators, though the exact details of schematic editing and the features offered will probably vary), you do want to arrange things so that the inductance of the primary, relative to the secondary, has a squared relationship with respect to the desired voltage ratings. So, if your mains is \$230\:{\text{V}_{\!\text{AC}}}\$ and your desired secondary is \$20\:{\text{V}_{\!\text{AC}}}\$ then you do want \$L_1=\left(\frac{230\:{\text{V}_{\!\text{AC}}}}{20\:{\text{V}_{\!\text{AC}}}}\right)^2\cdot L_2=132.25\cdot L_2\$. Assuming coupling of 1, of course. | |
Oct 28, 2019 at 16:50 | history | edited | Voltage Spike♦ | CC BY-SA 4.0 |
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Oct 28, 2019 at 16:38 | answer | added | Voltage Spike♦ | timeline score: 2 | |
Oct 28, 2019 at 16:37 | answer | added | bobflux | timeline score: 2 | |
Oct 28, 2019 at 16:32 | history | edited | kepsek | CC BY-SA 4.0 |
added 104 characters in body
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Oct 28, 2019 at 16:26 | comment | added | The Photon | RE: "Are there better diodes to use as bridge rectifiers?", We can 't answer this if you don't tell us what diode you did use. | |
Oct 28, 2019 at 16:23 | comment | added | The Photon | The first obvious error I see is that neither terminal of L2 should be grounded. As drawn, diode D3 is shorted by ground connections on both sides. I don't know if this actually answers any of the questions you asked. | |
Oct 28, 2019 at 16:21 | comment | added | jonk | This isn't a long question. It's a series of open questions which have only one thing in common -- they are part of a power supply. These questions will resonate quite differently in different minds and the answers will likely vary quite widely. You also are making some wrong assumptions (your questions assume something not shown or demonstrated and then ask why, which can't really be answered without first fixing your wrong-minded question.) All of this makes it annoyingly difficult to give you a straight, direct answer. That said, some good in there too. | |
Oct 28, 2019 at 16:15 | review | First posts | |||
Oct 28, 2019 at 16:41 | |||||
Oct 28, 2019 at 16:11 | history | asked | kepsek | CC BY-SA 4.0 |