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Step 9So how does it operate?
Note: this is what I think is happening with this circuit, if someone with more knowledge could correct me in the comments I would be more than grateful to know!
When you first apply power to the circuit the transistor is off.
A small amount of current starts flowing through the voltage divider resistors and feedback coil and into the transistor base, as part of this current path is wound around the ferrite core (feedback coil) it stores some inductive energy in the core.
As current is now flowing through the base the transistor is now forward bias which turns it on.
Current then starts flowing through the primary coil and into the transistors collector and out of the emitter (conventional current flow BTW). The primary coil will also store energy in the core.
This takes the voltage of the feedback coil down to almost zero and the transistor turns off.
As the transistor turns off, the magnetic field in the feedback coil collapses which creates both a high voltage pulse in the secondary coil and a small voltage boost in the primary coil (this is why the transistor has to be a high voltage transistor).
As the induced current is in the oppersite direction to the supply current i am thinking this serves a current limiting action to the circuit, which might explain why it only seems to draw 2 amps max. If this was a non-inductive load then the transistor turning on would effectively be shorting the power supply right now.
As the transistor turns off the magnetic energy stored in the core from the primary coil rapidly collapses giving an even higher voltage pulse on the high voltage secondary coil.
The process repeats its self thousands of times per second.
Please correct me in the comments if I got any of this wrong!
When you first apply power to the circuit the transistor is off.
A small amount of current starts flowing through the voltage divider resistors and feedback coil and into the transistor base, as part of this current path is wound around the ferrite core (feedback coil) it stores some inductive energy in the core.
As current is now flowing through the base the transistor is now forward bias which turns it on.
Current then starts flowing through the primary coil and into the transistors collector and out of the emitter (conventional current flow BTW). The primary coil will also store energy in the core.
This takes the voltage of the feedback coil down to almost zero and the transistor turns off.
As the transistor turns off, the magnetic field in the feedback coil collapses which creates both a high voltage pulse in the secondary coil and a small voltage boost in the primary coil (this is why the transistor has to be a high voltage transistor).
As the induced current is in the oppersite direction to the supply current i am thinking this serves a current limiting action to the circuit, which might explain why it only seems to draw 2 amps max. If this was a non-inductive load then the transistor turning on would effectively be shorting the power supply right now.
As the transistor turns off the magnetic energy stored in the core from the primary coil rapidly collapses giving an even higher voltage pulse on the high voltage secondary coil.
The process repeats its self thousands of times per second.
Please correct me in the comments if I got any of this wrong!
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