Whats different between these two circuits?

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

The interesting ones are where you have both. . .

Tim

-- Deep Friar: a very philosophical monk. Website:

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 ( snipped-for-privacy@misty.com)

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Thank you very much for your explain.

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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