Best way to convert 48v DC to 7.2 v DC

Discussion in 'General Electronics Chat' started by Kmoreau893, Jan 26, 2007.

  1. Kmoreau893

    Thread Starter New Member

    Jan 26, 2007
    1
    0
    I have been using a Sony Bluetooth Microphone and Receiver system

    (http://www.sonystyle.com/is-bin/INT...Name=acc_DIAccessories_DICamcorderMicrophones )

    with my Sony Camcorder with a proprietary connector that supplies power and audio inputs from the camcorder (called an Active Interface Shoe-AIS).

    I recently purchased a more professional Sony Camcorder with XLR audio (the Sony HVR-v1U) which doesn't have the Active Interface Shoe, but does have XLR inputs with 48v phantom power. I want to try to use the bluetooth receiver with my new Pro camcorder.

    The bluetooth receiver is powered by 7.2 volts. I've performed the custom wiring and I can get it to work well stand-alone with a 7.2v battery. I measured the current draw when operating the bluetooth receiver and it is 65 milliamps.

    With a simple voltage divider circuit using a 630 ohm and 110 ohm resistor I can get the 48v down to 7.2 volts to power the bluetooth receiver. However, I'm afraid I'm losing a lot of power with 3w of power dissipation and heat, which will drain the camcorder battery quite quickly.

    Is there a simple way for me to reduce this voltage without wasting precious camcorder battery power unncessarily?

    Thanks in advance for any advice.

    -Keith
     
  2. mrmeval

    Distinguished Member

    Jun 30, 2006
    833
    2
  3. Papabravo

    Expert

    Feb 24, 2006
    9,903
    1,723
    The power dissipated by the linear regulator will be
    Code ( (Unknown Language)):
    1.  
    2. (48 - 7.2) * Current
    3.  
    4. For 25 mA of current this is 1 Watt
    5. For 50 mA of current this is 2 Watts
    6.  
    You will need a substantial heatsink

    The only rational solution is a switching regulator in the buck configuration. The efficiency should be in the 80% to 90% range. Linear Technology has a simulation program that will give you canned designs from your input and output voltage and current requirements.
     
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