dc to dc

Discussion in 'General Electronics Chat' started by mlkcampion, Feb 2, 2007.

  1. mlkcampion

    Thread Starter Active Member

    Nov 16, 2006
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    Hey
    I have a AC/DC converter that converts the mains to 300vDC. This is connected to a DC/DC converter for 24Vdc 250W PSU. What i need to do is
    place the second brick into a shut down mode to prevent it from heating when the machine it is running is in standby. I also want to be able to do this
    with the same PLC that controls the machine therefore when i shut down the second brick i still need power to the PLC to monitor the status of inputs such as a keypad, whereby it would then switch back on the second power supply.
    My idea is to use the first brick (230vAC to 300vDC) to supply power to the PLC at all times. Shutting the PSU of completely woul be a last ditched effort and using a fan to keep it cool isn't an option. I have found alot of options for 1W to 2W DC/DC converters that will take input voltages up to 70vDC and give you anything from 5vDC to 24vDC, however i need something to reduce the 300vDC output first or a low power DC/DC converter that will take the 300vDC.
    Has anyone any ideas where i should look or how i can reduce the 300vDC to say 70vDC?

    Thanks
     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,140
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    Far and away the most effective way to do things is to get a transfomer that produces convenient AC voltages which are then converted to DC. This is far simpler than any DC/DC conversion scheme. If you have two DC/DC conversion schemes which are each 80% efficient then the result of two conversions is 64% which is just a bit better than a single linear regulator.
     
  3. mlkcampion

    Thread Starter Active Member

    Nov 16, 2006
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    Yea unfortunately the dc/dc scheme has one advantage at these power
    levels and it is it's compactness, its about an inch in height and that includes a water cooled heatsink. Its pretty compact in all other dimesions in comparison to other power supplies that use the transformer method. I have done a lot of looking for different power supplies and and its the same anywhere i look.
    At the moment the dc/dc internal circuits generate a lot of heat when the machine is in idle (i.e. the load on the power supply is only bout 200mA) but after 20 minutes with the water turned of you wouldn't place your hand on the heatsink. This is the problem i have, i solve it at the moment by doing a flush on the system every 15mins however due to certan demands this can't go on.
    I am actually not gone on the idea of havin to place a seperate power supply just to manage the problem, however if i could come up with a small enough module that would give me 12vDC and say 5w or less i would try it, and that brings us right back to the original problem!!!

    Any ideas

    Thanks
     
  4. Papabravo

    Expert

    Feb 24, 2006
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    There are no IC's that I know of that will accept a 300V input, and in the buck configuration, produce 70V output. There may be a discrete solution, but for all my years in the business I can't imagine what it would look like. Sometimes we just can't have what we want.
     
  5. mlkcampion

    Thread Starter Active Member

    Nov 16, 2006
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    0
    The DC/DC converter which i use at the moment takes the 300vDC and converts it to 24vDC (250Watt)??

    Maybe its only possible at these power levels?
     
  6. Papabravo

    Expert

    Feb 24, 2006
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    Read my last post again. I said I did not know of any integrated circuits that would do that function. A whole converter has has more parts and costs more. So go ask Vicor or one of the others for what you want. You'll pay an arm and a leg for it though.
     
  7. dragan733

    Senior Member

    Dec 12, 2004
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    mlkcampion, as I understood, you want a DC/DC converter where tne input signal is 300V and output signal 70VDC or lower. It is easy for the schematic. So the company Power Integrations, Inc produces such semiconductor components, as the TOP switch: TOP225. But the hard thing is to procure the ferrite transformer to convert the voltage. On Internet find the details for: TOP225
     
  8. Lindembruck

    Member

    Feb 28, 2016
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  9. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    FOUR posts and you still have not told us the manufacturer and part numbers of the bricks or posted a schematic. Vicor and SynQor have smaller 50 W and 100 W parts that might work, but it is literally impossible to say.

    Do any of the power conversion stages require galvanic isolation?

    ak
     
  10. Lindembruck

    Member

    Feb 28, 2016
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    Hi AnalogKid!
    Your answer to your problem is the TOP227 or the TOP225 as in the lines up and make the simple transformer using my link up or buy the PWM ready some where.
     
  11. Lindembruck

    Member

    Feb 28, 2016
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  12. Papabravo

    Expert

    Feb 24, 2006
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    You guys did notice this thread has been dead for more than a decade and the TS/OP was last active in 2011 -- right?
     
    Last edited: Feb 29, 2016
  13. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    He started it.

    ak
     
    Evanguy likes this.
  14. Lindembruck

    Member

    Feb 28, 2016
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    lol kkkkkkkk :D
     
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