lynxlynx
A rumbling soft motor
Thanks Lynx,
Finally I got an Oscilloscope and starting over again.
Currently I wound 4 turns to my ferrite torroid and noticed measured Inductance 60uH. That gives approx Al value of 3.75. I rewired the ferrite with 8 turns primar and 4 turns secondary. No more core heating .But output current still does not go beyond5 amps.
Couple of Observations I would like to highlight.
1. While switching,i.e 56khz, drain voltage is almost 30volt peak.
2.While playing around with error correction with pin 1 of sgs3525 I noticed out put voltage raise upto 30 volt meanwhile out put diode MBR3045 conked.
3.Does SG3525 needs a constant voltage supply with 12-15 volt zenner diode to maintain its output voltage limited as I noticed when PWM is varied towards narrow pulse PWM amplitude increases upto 5volt+.As right now I have put a 2.2ohm RC filter only on Vcc of 3525. My power supply is now 16 volt 200 Va transformer with 10000uf capacitor .
4. Once Mosfet blew up while I removed the Gate resistor.Now I am Maintaining a 12 volt zenner clamp on gate. What is the right method of calculating optimum gate resistor ?
Thanks in Advance.
I
1. It is normal for push-pull to have drain go far beyond your supply voltage, it's how it works. Be sure only to have FETs rated at least for 40V when running in 10-16V battery range. To beginners I even recommend 55V ones - IRF3205 are nice fets to use.
2. It seems that you still have excessive secondary. I usually wind my transformers and test them on a little 2xIR2110 full bridge with frequency controls provided by TL494 both for heat testing, idle current and output voltage monitoring. If I need to test a HV one I connect it to a step-up one and lower amplitude and see what is going on then. Regarding your core I suggest you to see what is going on on secondary - disconnect it from diodes and place a 12V 60W lamp on it directly then connect a scope across. What is picture?
3. No it takes voltage it puts voltage minus some 1-2V on output transistors if you talking about FETs gate voltage. If you talking about output voltage, then you use SG3525 internal 5.1V reference for that and that 5.1V reference is always identical, so your voltage divider at output is always running fine unless you have a noise somewhere...
4. You really should place Rgs back again. Charging gate without it could get a spikes you see in your next post. Calculation is unnecessary however (in most cases!), I usually take what I have: 10R or 2R2. Wattage does not matter.