Slorrin Posted July 1, 2006 Report Share Posted July 1, 2006 I have a question. The bridge rectifier taking the 9VAC, converting it to DC... is then folowed by a 9VDC regulator.My question is this.. if you convert 9VAC to DC, is it boosted to a higher voltage? I don't know much about electronics.. so i'm, curious.Because wouldn't a 7809 require more than 9VDC to regulate DOWN to 9VDC? and also, why is the output of the 7809 marked on the diagram as 14VDC? isn't the function of a 7809 to create a constant voltage of 9VDC?please someone explain this to me. Quote Link to comment Share on other sites More sharing options...
Wilba Posted July 1, 2006 Report Share Posted July 1, 2006 This has been explained elsewhere on the forums, but cos I'm in a benevolent mood I'll explain it again ;DAn AC voltage rating of 9v means the actual voltage will be peaking higher than +9v and lower than -9v, 9v is measured as the RMS (root mean squared). Rectifiying will turn it into a series of peaks higher than +9v, then a capacitor will average it out to a slightly lumpy 12v DC, and then the 7809 will regulate it to a very flat 9v DC.So in general, 9v AC means it's equivalent power (i.e. you can convert it) to 9v DC.In the optimised PSU design, the 9v DC output of the 7809 is actually 9v above the 5v DC, observe the ground of the 7809 is on the +5v DC, so it will regulate to 9v above the 5v, thus 14v DC. This is then further regulated down to 12v or 9v by a regulator on the SID PCB (7809 or 7812 or 78L09 or 78L12). Quote Link to comment Share on other sites More sharing options...
Slorrin Posted July 1, 2006 Author Report Share Posted July 1, 2006 I love you, for 2 reasons.I can now construct a circuit to power a PSone screen from the 9vAC on my other commodore, assuming the power supply can withstand that many amps.. i will have to reasearch more (it needs 7.5 DC, 3 amps, bt i'm takling out the CCFLS and replacing them with very low amp LEDs instead, should reduce the current intensively)! Recitfy the 9vac and regulate down to 8v (unless i can find a 7.5 v regulator, i haven't seen them around). I have to check the specs of the video amp circuit, which is the only part in the psone that uses all 7.5, the rest is regulated down to 5.I have one more question.. I know when rectifying the AC, you add caps and often a load resistor, but how does one calculate the values of such things? And if you don't feel like answering, maybe you could point me in the direction of where i can find out about this.. Quote Link to comment Share on other sites More sharing options...
Wilba Posted July 2, 2006 Report Share Posted July 2, 2006 Everything I learned about power supplies comes from the net, or this forum, which had links to stuff on the net. Keywords: rectifier, regulator, filter capacitor Quote Link to comment Share on other sites More sharing options...
stryd_one Posted July 3, 2006 Report Share Posted July 3, 2006 Yeh I second that. This forum is a wealth of knowledge on power supplies, it was an enjoyable learning experience for me :) Quote Link to comment Share on other sites More sharing options...
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