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Whats different between these two circuits?

Discussion in 'Electronic Design' started by readeraz, Jul 24, 2008.

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  1. readeraz

    readeraz Guest

    Ringing choke circuit and blocking oscillator are different names of
    oscillator.
    Are they same meaning or they are different circuit in practice?
    How to distinctly identify them?
    thanks
     
  2. Tim Williams

    Tim Williams Guest

    Blocking oscillator blocks, LC oscillator rings. Pretty clear on the scope.

    The interesting ones are where you have both. . .

    Tim
     
  3. Both resemble variants of the Hartley oscillator, with the capacitor
    across the tapped inductor removed.

    A blocking oscillator has the oscillation feedback path through a
    resistor and capacitor in parallel. During the half-cycle where the
    transistor conducts, positive feedbck is through the capacitor. Once the
    capacitor has become excessively charged to maintain enough feedback to
    keep the transistor saturated, this half-cycle ends. This half-cycle is
    usually the shorter one. During the other half-cycle, the transistor is
    off until the capacitor is discharged sufficiently by its paralleled
    resistor to allow current to flow through the base of the transistor.

    In a ringing choke oscillator, the oscillation feedback (assuming a
    bipolar transistor) is through a resistor. The "transistor-on" half cycle
    is usually the longer one. That half-cycle ends when either the tapped
    inductor saturates or the transistor comes out of saturation. The
    transistor-off half cycle's onset reinforces itself with the feedback
    winding's voltage changing in a direction to reduce the transistor's
    collector current. In fact, once collector current starts decreasing, the
    transistor usually quickly slams off, and a high voltage pulse can occur.
    If a ringing choke oscillator is not carefully designed, the transistor
    may be destroyed by breakdown from high voltage pulses resulting from
    suddenly interrupting current flowing through the inductor.
    The transistor-off half cycle ends when the transistor's collector
    current has decreased to zero and has become steadily zero. There may be
    a delay for stray capacitance charged by the high voltage pulse to
    discharge before the feedback winding produces voltage in the forward bias
    direction, but that is usually short.

    - Don Klipstein ()
     
  4. readeraz

    readeraz Guest

    Thank you very much for your explain.
     
  5. readeraz

    readeraz Guest

    most of the rcc is working as negtive action so that when the
    trnsistor shut off, the energy is transported to load at second
    winding. and this avoid super higher voltage apply on the transistor.

    When the transistor become turen on from off, more circuit uses a
    capactor as an accelerator to force trnasistor on speedly. thats why I
    pulzzed their difference.

    That seems there is no too distinct between them.

    Hoever, thank you very much for your wonderful explain.
     
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