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How to reduce current spike at inductor during start up ?

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Hello everyone, how do we normally reduce the current spike of the flyback converter during start-up as shown in the figure below? Where V(n006) and I(R6) are the output voltage and current. Thank you for the help in advance.

Simple: don't use voltage-mode control!

Look into current-mode control, particularly peak and average modes.


You are asking about the high currents in the coupled inductors/transformer?

Most power supply controllers will have some form of a softstart feature.  This limits the duty cycle until the output voltage reaches its target.  The newer types may have more elaborate control schemes for startup and response to faults and overloads but even the older ones from 30yrs ago usually had a softstart feature.

Install current sensor resistor between M1 Source and GND and limit the current.


--- Quote ---Install current sensor resistor between M1 Source and GND and limit the current.
--- End quote ---

Yes, this is the modern approach.  Inner control loop on current with outer control loop on the voltage.

For the OP, they can add a peak current detector that will end the ON time of the primary switch when the peak current is reached.  Once past the inrush period, current will be less and then the outer voltage control takes over.

This also helps to prevent damaging the circuit when there is a overload or shorted load fault.


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