FORWARD CONTROLLER DESIGN

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davidraj

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Voltage Regulation of Forward Converter in Voltage Mode Control

The converter was designed for the following conditions:
  • Enom = 48 V
  • Vo = 12V
  • n1:n2:n3 = 6:3:3
  • Emax = 60V
  • Emin = 40V
  • Manetizing inductance of transformer seen from primary = 50µH
  • E L = 10µH
  • C = 400µF
  • rC = 0,001Ω (Also called Capacitor ESR)
  • Pmax = 150W
  • Pmin = 15W
The PWM ramp has amplitude of 3V The Reference voltage for the regulator is 2.5V
All the diodes have the reference RB238NS100 Fsw = 100 kHz 1 The transistor is a MOSFET reference IPB107N20N3. I have implemented the control loop and I could also see that my capacitor and resistor values are wrong but my problem is that the simulation is so slow and I do not understand by. Please help me.

 

* Your schematic has inductors/ transformers neighboring diodes (or PN junctions). In simulations I've seen these combinations generate high-frequency oscillations. My hunch is that the inductor produces a current spike (turns On) starting current again in the diode just after it shut Off.

* At this early stage of development your schematic is overly complicated. Try deleting the right half. Substitute a dirt-simple PWM signal which controls the mosfet at left. Experiment by adjusting all parameters of your PWM: frequency, peak voltage trough voltage, duty cycle, etc. Later you can add the second half.

* Delete unnecessary wires or else you force the simulator to calculate Amperes through wires needlessly. Example, where a component joins other components going to ground, give each a ground icon: to L3 D1 C1 R2. Delete current source I1.
 

Thanks for your response but do you think, or can we assume that my circuit is fine for now at least the build and connections(schematic) for the given specifications?
 
Last edited:

I don't know how to say much about a forward converter. Someone more expert would have better advice. My own reply focussed on bottlenecks that I've seen cause a simulation to take ages to reach convergence for a single frame.
 

putting RC snubbers across the power diodes and the mosfet - will greatly increase speed of simulation
 

Hi,

My - well meant - recommendation: please learn to draw clean schematics, especially when you want others to read them.
some issues:
* bottom left: why two GND symbols are joined? Why it needs 8 pieces of 90° bends to do so
* abandoned V2
* several unnecessary junction dots
* two GND nodes at U1
* text overlapping symbols
* text/labels overlapping signal lines
* unnecessary signal split using labels
* signal lables like "OPAMP" ... don´t tell much.
* and so on.

I understand it was made for your own usage ... But if you look at the schematic after years ... it will be more easy to read a clean schematic.
It avoids confusion and eventual mis-interpreation.

Then: not a single power supply decoupling capacitor. (and the RC snubber EasyPeasy mentiones)
I know they are not necessary for simulation ... but often the simulation schematic is used to design the PCB/real circuit .. und then often these essential capacitors are missing. Your real circuit won´t work reliably without these capacitors.
It won´t hurt to add them here .. to have a complete schematic. (as a reference for your PCB .. and for later)

Klaus
 

Thank you klaus, I clearly understand that my circuit is a mess I could clean it once it started working just like code. What can I say except apologies I am Genz.
 

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