eem2am
Banned
Dear All,
Please may I ask yourselves about the waveforms in a flyback with a primary clamp to clamp the leakage spike.?
The primary clamp is just a diode and a voltage source.
(the voltage source represents a big capacitor)
This is a continuous mode flyback,
-and I am specifically referring to the circuit waveforms during those nanoseconds when the primary leakage inductance is discharging its flux through the clamp diode , ..that is, just after the Gate of the FET has been turned OFF.
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And also, to make it easier to understand , I am stipulating that this flyback has NO capacitance at the drain node of the Mosfet.
(…..because otherwise the turn-OFF waveforms are ‘soaked’ in resonant oscillations which make the basics difficult to highlight and grasp)
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Here is the spec. of the flyback:-
- - - - - - - - - - - - - - - - -
Vin = 320V
Vout = 30V
Ns / Np = 0.55
Ls = 1mH
Lp = 3.3Mh
Leakage Inductance has been referred to the Primary and is 30uH
Duty Cycle = 0.14
Switching Frequency = 102 KHz
- - - - - - - - - - - - - - - - -
Here is the Circuit Schematic:-
XXXXXXXXXXXXXXXXXXXXXXXXXX
-As you can see from above, there is a 100V DC source which acts to discharge the leakage flux.
Here are the circuit waveforms in the “gap” of time between the Mosfet starting to turn OFF (t1) and Output diode turning ON fully (t2).
My question is, when the Mosfet starts to turn OFF, the leakage inductor starts “discharging”. ……………..
-But what voltage is across the leakage inductance (in the above schematic) when it is “discharging” in the region between t1 and t2 of the waveform diagram above.?
(the region between t1 and t2 appears to involve the flyback "coupled inductors" actually acting as a proper transformer?)
Please may I ask yourselves about the waveforms in a flyback with a primary clamp to clamp the leakage spike.?
The primary clamp is just a diode and a voltage source.
(the voltage source represents a big capacitor)
This is a continuous mode flyback,
-and I am specifically referring to the circuit waveforms during those nanoseconds when the primary leakage inductance is discharging its flux through the clamp diode , ..that is, just after the Gate of the FET has been turned OFF.
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
And also, to make it easier to understand , I am stipulating that this flyback has NO capacitance at the drain node of the Mosfet.
(…..because otherwise the turn-OFF waveforms are ‘soaked’ in resonant oscillations which make the basics difficult to highlight and grasp)
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
Here is the spec. of the flyback:-
- - - - - - - - - - - - - - - - -
Vin = 320V
Vout = 30V
Ns / Np = 0.55
Ls = 1mH
Lp = 3.3Mh
Leakage Inductance has been referred to the Primary and is 30uH
Duty Cycle = 0.14
Switching Frequency = 102 KHz
- - - - - - - - - - - - - - - - -
Here is the Circuit Schematic:-
XXXXXXXXXXXXXXXXXXXXXXXXXX
-As you can see from above, there is a 100V DC source which acts to discharge the leakage flux.
Here are the circuit waveforms in the “gap” of time between the Mosfet starting to turn OFF (t1) and Output diode turning ON fully (t2).
My question is, when the Mosfet starts to turn OFF, the leakage inductor starts “discharging”. ……………..
-But what voltage is across the leakage inductance (in the above schematic) when it is “discharging” in the region between t1 and t2 of the waveform diagram above.?
(the region between t1 and t2 appears to involve the flyback "coupled inductors" actually acting as a proper transformer?)