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
    I have been using a Sony Bluetooth Microphone and Receiver system

    ( )

    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.

  2. mrmeval

    AAC Fanatic!

    Jun 30, 2006
  3. Papabravo


    Feb 24, 2006
    The power dissipated by the linear regulator will be
    Code ( (Unknown Language)):
    2. (48 - 7.2) * Current
    4. For 25 mA of current this is 1 Watt
    5. For 50 mA of current this is 2 Watts
    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.