is diode speed important for this circuit

crutschow

Joined Mar 14, 2008
25,660
What is the purpose of the diode in series with the inductor?
It's only apparent effect will be to reduce the inductor voltage by about 0.7V when the transistor is ON.
 

Papabravo

Joined Feb 24, 2006
14,684
This circuit is to generate high voltage such as for a step up transformer and the diode serves to prevent using the builtin diode in the MOSFET. This isn't a snubber diode.
As pointed out it doesn't do anything the way it is connected. What does the output of your simulation look like? The body diode of a MOSFET is seldom used anyway so what is the point?
Did you even run the simulation?
 
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Papabravo

Joined Feb 24, 2006
14,684
So what voltage are you trying to generate? Do you need to limit the maximum voltage in any way? Are you concerned about your own safety in working with such voltages and currents?
 

Papabravo

Joined Feb 24, 2006
14,684
Do you want to charge and discharge the capacitor or just charge it to a fixed voltage like 12-14 kV
Vn004 is the voltage on the capacitor. No diode in series with the inductor is required.
The capacitor does not limit the voltage.
 

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Papabravo

Joined Feb 24, 2006
14,684
This is for making high voltage with a transformer which might be made into high voltage dc with high voltage diodes.
The process still does not need the diode from your original circuit. Transformers don't generally work well with square waves and fast edges, and you didn't answer my question about the safety of such circuits. How high a voltage are we talking about? You are much better off using a mains transformer to get the high voltage DC you are looking for?
 

Papabravo

Joined Feb 24, 2006
14,684
Without diode transformer primary has square edge current which can damage it if its too rapid. Simulation showed without diode there is no high voltage on transformer secondary.
OK if you're happy with what you are doing, why do you bother to ask for advice? And you still haven't answered my questions.
 

crutschow

Joined Mar 14, 2008
25,660
It should ring making more high voltage peaks.
That doesn't answer my question. :rolleyes:
I already know you want to make a high voltage output but why do you want many peaks?
What is the use of the output?
If the voltage goes across a spark gap, the ringing will essentially stop after the first spark.
Is diode speed important?
Depends upon the resonant ringing speed of the actual circuit.
 

Thread Starter

pager48

Joined Nov 25, 2018
161
That doesn't answer my question. :rolleyes:
I already know you want to make a high voltage output but why do you want many peaks?
What is the use of the output?
If the voltage goes across a spark gap, the ringing will essentially stop after the first spark.
Depends upon the resonant ringing speed of the actual circuit.
Its going for tesla coil, charging leyden jar with HV diodes and other HV things. Whats the typical recovery time for that digikey P600 diode?

A safety gap would be on the output before HV diodes to prevent shorting secondary windings when charging leyden jar.
 
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crutschow

Joined Mar 14, 2008
25,660
Its going for tesla coil, charging leyden jar with HV diodes and other HV things.
Ringing won't increase the energy transferred to the leyden jar.
Once the magnetic energy is transferred after the single pulse without the diode, there is no more significant energy to transfer.
Thus the diode serves no purpose.
 

crutschow

Joined Mar 14, 2008
25,660
Without diode, L1 is shorted by body diode of transistor.
Only for the negative transition after the positive peak. But the output circuit should have extracted most of the energy from the inductor by then.
It's a standard flyback circuit.
They don't have or need the diode.
 
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