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1-7 of 7 messages
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Question for power supply guru's
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by KE6PKJ on February 3, 2004
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I need to quickly assemble a power supply package that can give me 28 volts dc @4 amps continuous from a 13.8 volt automobile. My thoughts are this, a walmart type $39.95 150 watt automotive AC inverter feeding into one of those Taiwanese universal switching power supplies available from Digikey, Mouser etc.(85-245 VAC 50/60 Hz in, 24 VDC 6 amps out). I can diddle the switching supply to give me 28 volts.
My concern is with the cheap automotive AC power inverters. Their outputs are usually modified sine wave and I don't know if that will present a problem (transients, spikes, noise etc.) feeding into the universal switching supply? I assume not, but I've no experience with cascading two switching power supplies. Any PS Guru's have any thoughts on this?
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RE: Question for power supply guru's
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by N3JWN on February 3, 2004
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Kirk sure sees like a big waste of money and power... not a bad Idea if your going to do this! Just double or tripple your desired specs.. Sounds like you need 100% duty ctcle !! and to get a 24vdc/120vac switcher and adj...1/6 of the total output is too far to be safe! and still regulate at the rated cuttent perhaps a 4 volt range. I suggest building or just purchacing the DC-DC convertor 12vdc to 28vdc 10 amps many companies make these for 28 volt dc equipment!! about $150-200.....12 to 110 then 110 to 28 volts is a big waist of power and with power comes heat.. and @150 watts thats 120vac @2 anps is 240 Watts if your going to do this go at least 1500-2000w 12V to 120vac and get a 28 volt switcher at 6-10 amps min for 100% duty cycle... you must double or tripple the expected current ...that way the units will be at 50% capacity at 100% duty cucle your going to need fans on both and what are you going to run...Also your Idea might be a little cheaper, 2 units to wire , mount, and cool verses 1 unit!!!! Need any help on building something please contact me Dick / n3jwn @rgbn3jwn@aol.com,,, Have fun but be safe P.S. fuse every line Pos.and Neg. especially right at the battery as close as posible to prevent fite or explosion!!
Kirk go to Google or ebay and type 12 volt to 28 volt 300watt convertors...........IE.
NEW COSEL 300 WATT 24 VDC POWER SUPPLY 14 AMP - ... you are bidding on a brand new, in the box, cosel power supply model lda300w-24. This open framed power supply provides a compact and lightweight design with unbeatable quality. This is a 300 watt, 24v power supply with a 14 amp dc output that retails for nearly 250. I have more power supplies. See my other auctions. Shipping and handling is 8.90 within the continental usa. I fully guarantee this power supply and gladly accept .... Current auctions from dockguys
RO POWER SUPPLY 1.5-6 VDC 5 AMP THERMO SHUTOF RO POWER SUPPLY 12-15 VDC 2.5 AMP THERMAL OFF
RO POWER SUPPLY 12-15 VDC 2.5 AMP THERMAL OFF AC/DC POWER ADAPTOR - 12 V - case of 100 pcs.
Laser Drive HeNe Power Supply 1250 VDC 4.0 m 28vDC Power Supply @ 1.8 Amps (LVS-45-28-B)
DC LASER POWER SUPPLY 4 PCS. ACME POWER SUPPLIES CPS-30-24/28
COMPAQ PROLIANT ML 350 350WATT power supply NEW Compaq Proliant PS4060 Power Supply 750W
RELIANCE COMM/TEC 300 VDC to 5 VDC Converter, RELIANCE COMM/TEC 300 VDC to 5 VDC Converter,
RELIANCE COMM/TEC 300 VDC to 12 VDC Converter RELIANCE COMM/TEC 300 VDC to 12 VDC Converter
Sola Power Supply SDN 10-24-100 NEW NEW LAMBDA POWER SUPPLY 24 VDC
SHANDON SOUTHERN INST. V500/150 POWER SUPPLY SHANDON INST. VOKAM 2000-300-150 POWER SUPPLY
ASTRON DC-DC Converters . . . .
ï HEAVY DUTY ï HIGH QUALITY ï RUGGED ï RELIABLE
Standard Features • Overvoltage Protection • Overcurrent Protection
• Short Circuit Protection • Terminal Block Connectors
• Extra Terminal provided to allow converters to be turned ON and OFF with the ignition switch.
Model N2412-12 N2412-24
Input Voltage 22-32 VDC 22-32 VDC
Output Voltage 13.8 VDC 13.8 VDC
Line/Load Regulation .03 VDC .04 VDC
Ripple 20mVrms 20mVrms
Continuous Current 10 Amps 20 Amps
Peak Current 12 Amps 24 Amps
Overvoltage Protection 16 VDC 16 VDC
Efficiency 88% 88%
Dimensions 2" x 6.2" x 6" 2" x 6.2" x 7"
Weight 1.5 Lbs 2 Lbs
MODEL 1212 & 1212-18 Switching Regulated Converter
Designed for FM transceivers and other applications requiring 12-volt power
source converted from 12-volt positive ground battery. Regulated with pulse
with modulation at 20 KHz.
Input - 12 V DC (Positive ground only). Functional from - 11 V DC - 16 V DC.
Output + 13.8 V DC (Negative ground only).
1212 1212-18
Output Voltage 13.8 V DC (±.2V DC) 13.8 V DC (±.2V DC)
Line/Load Regulation 200mV 200mV
Ripple Noise 50mV RMS 50mV RMS
Current Continuous 6 Amp 14 Amp
Current (ICS) 7 Amp 18 Amp
Current Limit 8 Amp 19 Amp
Case 2 3/4(H) x 6(W) x 6(D) 2 3/4(H) x 6(W) x 12(D)
Shipping Weight 2 lbs. 4 lbs.
MODEL 2412 & 2412-20, 4812 & 4812-20 Switching Regulated Converter
Designed for FM transceivers and other applications requiring 12-volt power
source converted from 24-volt positive ground battery. Regulated with pulse
with modulation at 20 KHz.
2412 2412-20 4812 4812-20
Input (Negative ground only) 22-32V DC 22-32V DC 30-56V DC 30-56V DC
Output Voltage (±.2V DC) 13.8V DC 13.8V DC 13.8V DC 13.8V DC
Line/Load Regulation 200mV 200mV 200mV 200mV
Ripple Noise 50mV RMS 50mV RMS 50mV RMS 50mV RMS
Current Continuous 9 Amp 16 Amp 9 Amp 16 Amp
Current Limit 12 Amp 20 Amp 12 Amp 20 Amp
2412/4812 Case Size 2 3/4(H) x 6(W) x 6(D)
2412-20/4812-20 Case Size 2 3/4(H) x 6(W) x 12(D)
Shipping Weight 2 lbs. 3 lbs. 2 lbs. 3 lbs.
--------------------------------------------------------------------------------
Home Switching Linear Custom Base Preset DC 28VDC DC-DC Conv. DC-AC Inverters Smart Chargers
9 Autry, Irvine, CA 92618
949-458-7277 ï FAX:949-458-0826
E-MAIL: eastron@astroncorp.com
--------------------------------------------------------------------------------
The location of this page: astroncorp.com
Copyright 1999 ~ 2001 all rights reserved
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RE: Question for power supply guru's
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by KA5N on February 3, 2004
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N3JWN's input pretty well covers it. Consider that 28 volts at 4 amps is 112 watts. A DC - DC convertor is maybe 70% efficient. This means that the car battery needs to supply 160 watts (13-14 amps). If you go the way you described the current drain would be maybe
18-20 amps. At this point I would stop and consider if what I was trying to do might be done a simpler or cheaper way.
Gud luck Allen
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RE: Question for power supply guru's
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by KT8K on February 3, 2004
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A single stage conversion will be MUCH more efficient, and correspondingly generate a lot less heat. A shorter chain has less links to be weak, less wiring/connectors and general fuss. My advice is, keep it simple and save yourself headaches.
Good luck es 73 de kt8k - Tim
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RE: Question for power supply guru's
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by K5LXP on February 3, 2004
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In the spirit of answering the question at hand, which was if a switching supply would be senstitive to the output of a square or modified sine inverter, the answer is usually no. In fact, I've found that most of these "universal" input (88-260V, 50-60Hz) supplies will run on just about anything, even DC. A lot of these supplies simply rectify the power input with a bridge and no matter what you feed it, AC or DC of either polarity, will work just fine. The only way to know if the supply you pick is truly compatible is to test it but by selecting one of these "universal" input units your odds are pretty good it's going to work for you.
Mark K5LXP
Albuquerque, NM
k5lxp@arrl.net
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RE: Question for power supply guru's
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by KE6PKJ on February 3, 2004
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Thanks for the response guy's, I'm designing my own switcher ps to go from 11-15 vdc in, to 28 vdc out. However time is of the essence, I need to kluge a power supply together to prove a transmitter during a field test. The actual current draw is about 3/4 of an amp 100% duty cycle at 28 volts, hence the 4 amp continuous rating to assure cool running and no stress.
I've searched the internet in the past for DC-DC converters to take me from 12 v to 26-28 v - but there is nothing available with any real current rating. Whatever is available above a few amps reqires an input of 18-36 volts. That's not really practical when the concept is to run off a vehicles 12 volt battery.
I was just hoping that the inefficient method of stepping up to 115 vac and then down to 28 vdc would work without any "bad" interactions between the two switchers.
73, Kirk
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RE: Question for power supply guru's
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by WB2WIK on February 3, 2004
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I agree with K5LXP that most switch mode power supplies or converters don't care much about input waveform. Using a DC:AC inverter followed by an AC:DC SMPS shouldn't be so inefficient, and basically represent the way a DC:DC converter normally works. Every DC:DC converter performs power conversion at AC and then rectifies and filters to create DC...you're just suggesting doing this in two boxes, rather than one.
You may have unknown RFI and EMC issues with what you suggest, but for an experiment, who cares?
WB2WIK/6
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