Silvio
Well-known member
Hi mituadas, the waves look ok to me it is only the little oscillation you have on the switch off at the bottom of the wave form. This can be corrected by putting a 4.7k resistor from gate to source. The resistor will help the mosfet to stay off between each cycle and any stray inductance and capacitance will not false trigger them. A snubber across the primary will also tame down the spikes. Do not be fooled as the more load you add to the output the spikes will get larger. you will correct this when the smps is stable.
I see you have an owon scope and this can work on battery. It is important that during the test you work on battery power so that it will be galvanically isolated from the mains. If your scope can handle 300v in the input you can directly connect the probe across the transformer primary with these set to X10. If not you can make a resistive divider across the primary of the transformer to limit the voltage for the scope. The resistive divider can be made with a 100k and 10k resistors in series. These will divide the voltage seen by the scope by 10.
Important that your scope probes will be put across the 10k resistor. Use only one probe and ground
Now you can measure the wave form across the primary of the transformer and see the real result,
It is important that you put a 100w lamp in series with the mains supply as a current limiter. Do not try to operate directly from the mains without a current limiter lamp. if something is not right you will blow the mosfets again.
You will only remove the 100w lamp if the smps is stable after 5 minutes of operation and nothing gets hot.
See how it goes from here and we talk later on your findings
Silvio
I see you have an owon scope and this can work on battery. It is important that during the test you work on battery power so that it will be galvanically isolated from the mains. If your scope can handle 300v in the input you can directly connect the probe across the transformer primary with these set to X10. If not you can make a resistive divider across the primary of the transformer to limit the voltage for the scope. The resistive divider can be made with a 100k and 10k resistors in series. These will divide the voltage seen by the scope by 10.
Important that your scope probes will be put across the 10k resistor. Use only one probe and ground
Now you can measure the wave form across the primary of the transformer and see the real result,
It is important that you put a 100w lamp in series with the mains supply as a current limiter. Do not try to operate directly from the mains without a current limiter lamp. if something is not right you will blow the mosfets again.
You will only remove the 100w lamp if the smps is stable after 5 minutes of operation and nothing gets hot.
See how it goes from here and we talk later on your findings
Silvio