EAGLE Central Forums
Where the EAGLE community meets. Sponsored by Stratford Digital.

Home » EAGLE Related Forums, Blogs, ... (Read-Only) » Element 14 :: EAGLE Related Posts » AC to DC Power Supply Design (Element 14 :: EAGLE Related Posts)
AC to DC Power Supply Design [message #170442] Fri, 12 May 2017 14:52 Go to next message
messages@element14.co
Messages: 565
Registered: March 2013
Senior Member
Afternoon all, Late on a Friday, I am clearly making some sort of simple error but I am blind to it. Please see the circuit below.  I have soldered it up and it isn't working.  I get 36VDC on what should be the regulated 12V rail and a little over 1VDC on the 5VDC rail. Any ideas, please?  I should add that if I remove the transformer and supply 18VDC from my bench PSU then everything works fine, even after the 36V spike which is over the LT3501 max so I *think* the regulator is fine. The number above the transformer is a UK Farnell product code.  It is a 2x 9V transformer with the secondaries wired in series to give 18V. Cheers, Simon PS: Context; it is a power supply for a rPi which is controlling, among other things, some 12V RGB LEDs.
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/222002?tstart=0#222002
Re: AC to DC Power Supply Design [message #170446 is a reply to message #170442] Fri, 12 May 2017 16:02 Go to previous messageGo to next message
messages@element14.co
Messages: 565
Registered: March 2013
Senior Member
You might try limiting your input current on your bench supply to see if you can duplicate the symptom with the transformer.250mA rating on the transformer may be too low for this circuit.
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/222004?tstart=0#222004
Re: AC to DC Power Supply Design [message #170451 is a reply to message #170442] Fri, 12 May 2017 20:30 Go to previous messageGo to next message
messages@element14.co
Messages: 565
Registered: March 2013
Senior Member
Value cap C9 is very low, so you get +18V with big ripple.Try to change it at least 1000uF.
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/222057?tstart=0#222057
Re: AC to DC Power Supply Design [message #170454 is a reply to message #170442] Sat, 13 May 2017 04:32 Go to previous messageGo to next message
messages@element14.co
Messages: 565
Registered: March 2013
Senior Member
Hi Simon,I assume you have check the Data sheet for some guidance but just in case here is a link to it: http://datasheet.octopart.com/LT3501EFE%23PBF-Linear-Technology-datasheet-17021123.pdf Some problem in the voltage dividers tied to FB-1 and FB-2 could have this effect but I have never worked with this circuit. Check out the sample circuit in the Data Sheet as it may be clearer than the schematic you have above though the resistor values may not be the same as they are showing a different set of regulated voltages. John
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/222049?tstart=0#222049
Re: AC to DC Power Supply Design [message #170455 is a reply to message #170442] Sat, 13 May 2017 05:16 Go to previous messageGo to next message
messages@element14.co
Messages: 565
Registered: March 2013
Senior Member
In the datasheet for the converter, the diodes across SW1 and SW2 are Schottky diodes https://www.vishay.com/docs/89071/b360a.pdf  In your circuit you have indicated they are 3A 40v 500mV, so the first question would be are they B360A or an equivalent. I agree with the previous two respondants that the current is too low to run a RPi, and the filter capacitor value too small.  mark
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/221977?tstart=0#221977
Re: AC to DC Power Supply Design [message #170459 is a reply to message #170442] Sat, 13 May 2017 09:47 Go to previous message
messages@element14.co
Messages: 565
Registered: March 2013
Senior Member
Definitely check those diodes and increase C9. Do you have a picture  - this part will be very fussy about layout. MK
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/222075?tstart=0#222075
Previous Topic: How to add Romex cable to this junction box.
Next Topic: Amega328p-au shorted pins ?
Goto Forum:
  


Current Time: Wed Oct 18 04:01:20 GMT 2017