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Everything posted by indulis

  1. And during the dead time... how is the secondary current circulating? Now, if that current were to flow through the secondary winding (changing flux), how would it reflect to the primary?
  2. You have to consider what the anode voltage will be when the diode is not conducting (when it swings negative). Also any spikes that may be there.
  3. In a multi output forward converter, calculate the inductance needed for the "higher" power output. Then, for the coupled filter inductor, the turns ratio between the transformer secondaries has to match the inductors turns ratio.
  4. Where is the schematic? What is the output voltage & current? Where are you measuring the input current... directly across the I sense resistor? Do you have a RC fiter on it before the PWM Try to make it run without the active clamp first (just use RC or DRC snubbers).
  5. Do a search for Llyod Dixon-Unitrode Seminars-Transformer Design
  6. Any diode will work as a zener (PVI) but not very well. What makes zeners different is the “doping” levels in the N & P materials. By controlling the levels, the “zener voltage” (breakdown) can be "more" accurately controlled.
  7. Think about it this way... first remove the current limit stuff (Q3, R4, P1). Then what to do with Q1... the collector-base looks like a diode... that "kinda works". I don't see how making Q1 a n-p-n will work at all. Then add the current limit function back in.
  8. Simplify the circuit... remove the OVP (over voltage protection) circuit... then it runs fast If you want to simulate the OVP function, do that by itself.
  9. You say it's an over voltage protection circuit, yet you ask if it can "drive a 3A load". I think your real question is can this circuit handle 3A... the IRFZ44 is rated for 36A at 100°C, so the answer is yes.
  10. Try http://www.circuitcalculator.com/wordpress/2006/01/31/pcb-trace-width-calculator/
  11. Where did you tie the "Adj" pin of the LM236-5 (D2)? It should be ties to the cathode if you wanted a 5V reference. Are you relying on "T1 & R2" to make it constant current? Don't!
  12. You have a couple of problems... first, if the the supply voltage to the LM358 is 12V, the base of the BDX33C needs to be at least a Vbe drop above the emitter voltage to get 12V at Vout... you can't get there with what you have. Second, put a feedback cap on the LM358, say .1
  13. What makes you think the kit is defective? Does the parts list agree with the PCB? Do the parts in the kit agree with the parts list?
  14. If true, it's probably from a "off-line switch mode power supply", in which case you can not connect it directly to mains AC voltage. Transformers/coupled inductors (if it was a flyback) of that type are meant to run at much higher frequencies.
  15. Try it with a sine wave instead... With a square wave you're just looking at the charge/discharge of the cap
  16. There are no articles "like this" there, and some of what is there is highly questionable.
  17. Google VRM (voltage regulator module ).
  18. The voltage rating on a capacitor is dictated by its dielectric. Thats the stuff between the "plates".
  19. Your schematic shows that the Vcc pin is only connected to a diode anode, the Vcc pin also needs to be connected to a voltage (i.e. input voltage to the buck converter). If you don't connect Vcc to a voltage of course your not going to have a output!
  20. How about applying the converters input voltage to the Vcc pin of the driver.
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