DC to AC Converter: Understand Power Inverter Transistors & DC Source

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Discussion Overview

The discussion revolves around understanding the operation of a DC to AC converter, specifically focusing on the role of transistors and the DC source in generating alternating current through windings. The scope includes technical explanations and conceptual clarifications related to oscillators and inductance in power inverters.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about how the two transistors and the DC source work together to alternate current, suggesting that both transistors might be passing current constantly.
  • Another participant explains that the converter operates as a blocking or relaxation oscillator, utilizing energy storage in an inductor and providing a detailed description of the feedback mechanism involving transistors and coils.
  • A participant acknowledges their prior experience with DC and integrated circuits, indicating a transition to understanding analog systems.
  • There is a question about whether increasing inductance would decrease the frequency of the AC output, with a subsequent response affirming that it would, due to the longer time required for the current to reach steady state in the coil.

Areas of Agreement / Disagreement

The discussion contains both confusion and clarification regarding the operation of the converter. While there is an acknowledgment of the feedback mechanism, the initial misunderstanding about the transistors' operation indicates that multiple views exist on the topic.

Contextual Notes

The discussion does not resolve the initial confusion about the transistors' operation, and assumptions regarding the definitions of terms like "steady state" and "frequency" are not explicitly stated.

Who May Find This Useful

Individuals interested in power electronics, analog circuit design, and those seeking to understand the principles of oscillators and inductance in DC to AC conversion may find this discussion relevant.

Jammin_James
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I'm trying to understand the converter in this link:

http://en.wikipedia.org/wiki/Power_inverter

I don't see how the two transistors and the DC source cause the curretn to alternate through the windings. It seems that both transistors would be passing current constantly, not alternating between them.
 
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That's a blocking or a relaxation type of oscillator. It takes advantage of being able to store energy in an inductor, and releasing it. This is a mirror example of I'm not sure if you are familiar, a flip flop oscillator with two transistors and two capacitors.

Basically, when you turn it on, a rush of current through the collector coil will induce a voltage in the feedback coil that drives the base of the transistor, thus letting more current to run through the collector until it reaches a steady state. When the current reaches steady state, the main coil is no longer inducing voltage in the feedback base coil, thus the transistor begins to turn off. As the current than ran through the main coil collapses, it will induce oppose voltage in the feedback coil, thus turning off the transistor for good. When that reaches steady state, we are back to step one,
 
Durp!

I've been working with DC and ICs too much. This is the beginning of my journey to better know analog.

Thanks for the help!

Also, would increasing the inductance decrease the frequency of the AC?
 
Last edited:
Jammin_James said:
Also, would increasing the inductance decrease the frequency of the AC?

Yes, because it would take longer for the current to reach a steady state in the coil.
 

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