I need to build a power supply that can give out ~13V DC at 10A. To do this I calculate that a 15V and near 400VA toroidal would be needed but finding a toroidal over 300VA that is 15V seems to be a bit of a problem in the UK.
It's not actually for an audio project as such this one, it's for an amateur radio transmitter but hopefully this is the best place for a good power supply design.
Can anyone suggest any kind of alternative design, or other methods of getting a fairly high current power supply at a lowish voltage?
Any help much appreciated.
Matt
It's not actually for an audio project as such this one, it's for an amateur radio transmitter but hopefully this is the best place for a good power supply design.
Can anyone suggest any kind of alternative design, or other methods of getting a fairly high current power supply at a lowish voltage?
Any help much appreciated.
Matt
.Maplin do a 225VA, 12v toroidal transformer, you can connect the secondaries in parallel for max current. It depends if you have a regulator that will drop volts requiring a 15v secondaries, cos they haven't got one of 15v as you say.
CPC have a much greater choice, order online like Maplin, they are owned by Farnell, but have a greater selection of audio - related stuff. Lookhere.
Just register with them and you can order with credit card etc. after a short while.
Hope this helps.
CPC have a much greater choice, order online like Maplin, they are owned by Farnell, but have a greater selection of audio - related stuff. Lookhere.
Just register with them and you can order with credit card etc. after a short while.
Hope this helps.
Thanks for the replies, similarly to audio amplifiers noise and incosistency on the power supply is a very important factor, and as with audio batteries are the best option, so this really gets rid of the SMPS option.
Current drawn is not steady at all, changing often between about 0.6A on Receive and upto 10A on transmit (i.e. when the RF power amplifier is in use).
I have made my calculations on the following formulae found for a full wave bridge rectifier circuit with capacitor.
VAC = 0.8 x ( VDC + 2 )
IAC = 1.8 x IDC
WATTS = VDC x IDC (output)
VA = 1.4 x ( WATTS + 2 IDC* )
So VAC = 0.8 x (13 + 2) = 12 (My apologies as I said 15V in the first post)
IAC = 1.8 x 10 = 18
WATTS = 13 x 10 = 130
so VA = 1.4 x (130 + (2 x 10)) = 210??
Having gone through the calculations again it seems I was a bit off when I rushed through them first time around!! My apologies, looks like a 300VA will be more than enough, could even get away with 225VA.
Feel really stupid now! but happy that the cost of the supply has dropped dramatically! Thanks for the replies that made me go through this again and find my mistakes!
Cheers,
Matt
Current drawn is not steady at all, changing often between about 0.6A on Receive and upto 10A on transmit (i.e. when the RF power amplifier is in use).
I have made my calculations on the following formulae found for a full wave bridge rectifier circuit with capacitor.
VAC = 0.8 x ( VDC + 2 )
IAC = 1.8 x IDC
WATTS = VDC x IDC (output)
VA = 1.4 x ( WATTS + 2 IDC* )
So VAC = 0.8 x (13 + 2) = 12 (My apologies as I said 15V in the first post)
IAC = 1.8 x 10 = 18
WATTS = 13 x 10 = 130
so VA = 1.4 x (130 + (2 x 10)) = 210??
Having gone through the calculations again it seems I was a bit off when I rushed through them first time around!! My apologies, looks like a 300VA will be more than enough, could even get away with 225VA.
Feel really stupid now! but happy that the cost of the supply has dropped dramatically! Thanks for the replies that made me go through this again and find my mistakes!
Cheers,
Matt
An old PC PSU would save money, space and again money on electric company bills
Old AT units are preferable over modern ATX ones since they are simpler and easier to understand and tweak
To turn on an ATX unit just short the pin 14 of the connector [usually green wire] to ground, see http://www.hardwarebook.net/connector/power/atxpower.html
Regulation may be tweaked to rely only on the 12V output and also to make it adjustable, otherwise +5V output should be loaded with >2A and some units require also load on +3.3V to properly regulate +12V output, however, negative outputs usually have its own regulation
Output rectification and filtering for +5V, +3.3V and negative outputs may be removed leaving enough space for enhancing +12V filtering [a pi filter and a common mode filter should be enough]
If EMI is a concern, just place the PSU some meters away from the RF equipment. Anyway, any PC PSU won't generate more EMI than any computer placed on the same room or even a TV set
The alternative to a 130W SMPS is a 130W linear regulator that sould be capable of dissipating up to 100W of heat in worst case conditions [providing enough input voltage margin, while PC PSUs already have excelent input voltage margin]
Old AT units are preferable over modern ATX ones since they are simpler and easier to understand and tweak
To turn on an ATX unit just short the pin 14 of the connector [usually green wire] to ground, see http://www.hardwarebook.net/connector/power/atxpower.html
Regulation may be tweaked to rely only on the 12V output and also to make it adjustable, otherwise +5V output should be loaded with >2A and some units require also load on +3.3V to properly regulate +12V output, however, negative outputs usually have its own regulation
Output rectification and filtering for +5V, +3.3V and negative outputs may be removed leaving enough space for enhancing +12V filtering [a pi filter and a common mode filter should be enough]
If EMI is a concern, just place the PSU some meters away from the RF equipment. Anyway, any PC PSU won't generate more EMI than any computer placed on the same room or even a TV set
The alternative to a 130W SMPS is a 130W linear regulator that sould be capable of dissipating up to 100W of heat in worst case conditions [providing enough input voltage margin, while PC PSUs already have excelent input voltage margin]
Are you familiar with the ARRL?
www.arrl.org
They have all manner of resources, and mobile radio gear is what they do. Their Radio Amateurs Handbook is the Bible to radio hobbyists. There are whole sections of it devoted to power supply.
I also though or getting an old battery charger and filtering the output
www.arrl.org
They have all manner of resources, and mobile radio gear is what they do. Their Radio Amateurs Handbook is the Bible to radio hobbyists. There are whole sections of it devoted to power supply.
I also though or getting an old battery charger and filtering the output
I rewound a Microwave oven transformer (MOT) for a high current 12V supply to use a couple car amplifiers in the house.
I just cut off the HV secondary,and rewound 2 windings of 10awg wire (about 10-15 turns,adjust for the correct voltage) and 2 bridge rectifiers (25A each) with the outputs paralelled to a large 0.15Farad bank of filter caps. Works great for my 400W sub amp.
I told my friend about it,and he built one for his 600W amp.
I just cut off the HV secondary,and rewound 2 windings of 10awg wire (about 10-15 turns,adjust for the correct voltage) and 2 bridge rectifiers (25A each) with the outputs paralelled to a large 0.15Farad bank of filter caps. Works great for my 400W sub amp.
I told my friend about it,and he built one for his 600W amp.
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