bridge definition

Discussion in 'General Electronics Chat' started by lokeycmos, Jul 17, 2010.

  1. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
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    can someone please explain to me what half bridge and full bridge drivers are and how they work? are they related to an H-bridge? TY
     
  2. tom66

    Senior Member

    May 9, 2009
    2,613
    214
    They are not related to a H-bridge.

    A few wikipedia articles ought to assist you:

    http://en.wikipedia.org/wiki/Bridge_rectifier
    http://en.wikipedia.org/wiki/Rectifier

    Essentially a full wave rectifier converts AC to DC with ripple.
    A half wave rectifier does the same, but it only conducts during the positive or negative half-cycle of the AC so you get DC with a LOT more ripple. You will only see half wave rectifiers in low power equipment.
     
  3. Potato Pudding

    Well-Known Member

    Jun 11, 2010
    684
    92
    For Drivers the Half Bridge using BJT is typically an NPN and PNP pair set up as a followers with the load like a speaker connected between their emitters and ground.

    For a Full Bridge the load is connected between two half bridges driven in opposite phases.

    So the Full Bridge can get more signal from a given power supply voltage.

    Half Bridge might go from +7 or -7 to ground when the Full Bridge is going from +7 to -7 and -7 to +7. 7 Volts output compared 14 volts.
     
  4. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
    432
    7
    sorry, i know what rectifiers are. what i meant was half and full bridge drivers, for example here:
    http://stevehv.4hv.org/FBD.htm
    he talks about a half bridge driver. ive also seen similar articles talking about full bridge. hope this clears things up. TY
     
  5. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
    432
    7
    i posted too soon. ty
     
  6. Potato Pudding

    Well-Known Member

    Jun 11, 2010
    684
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    H Bridge is driven in pulse mode where the normal bridges mentioned above are for analog voltage levels like audio.

    The H bridge would not use the transistors as followers. With BJT the transistors in an H bridge would switch positions from the regular bridge and have their emitters connected to the rails, and the load between their collectors.

    The H bridge is a more common way to control motors.

    The H bridge circuit topology is actually derived from normal reversing DC motor wiring for a DPDT switch or relay, and is still used with these controls.
     
  7. Potato Pudding

    Well-Known Member

    Jun 11, 2010
    684
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    You're welcome. :)
     
  8. Potato Pudding

    Well-Known Member

    Jun 11, 2010
    684
    92
    Flyback transformer circuits can be dangerous.
    The currents are normally low (1 amp at 30 Volts might transform to 1 ma at 30Kv) but beware of high voltage capacitors in the circuits.
     
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