switching power supply reacting to spikes

[planet69]

Does a simple switching power supply designed using LM2576 suppresses incoming spikes or transients effectively without the need to add extra protection like TVS or MOV.

 

[BuckySparks]

the MOV and TVS devices are typically used to limit the transient input voltages to less than the absolute maximum a device can tolerate.
The LM2576 has an absolute maximum voltage rating of 40V, so choose a device to limit the voltage to less than 40V to prevent a failure.

The line regulation graph in the datasheet gives output voltage variation from the input voltage change. The LM2576 uses a voltage mode control with a fixed gain feedback compensation. This method has a wider output tolerance vs load current and input voltage compare to a current mode control device with high gain frequency compensation.

 

[planet69]

Ok. I think i know where you are heading here.
LM2576 reacts quickly to changes in the input and maintains regulation at specified output.
in that sense, how do we explain temporary power interruption to an embedded system running on low voltages such as 3.3V-5VDC as a direct result of a transients at the input. how do we reconcile this to the above.

rgds.

 

[BuckySparks]

Things I would try to troubleshoot the issue.

How much is the output changing during the event?
if not much, make sure the decoupling capacitors are close to the devices being powered.
if output changing by 5% to 10%, then add more capacitance on the output, this could reduce the transient on the output.

What is the input voltage changing from? Is the switching regulator bumping in the maximum duty cycle limitations.

More capacitance or a filter on the input, this could reduce the effect of transient on the device.
if the maximum duty cycle is the culprit, then keep the input voltage above to stay away from the maximum duty cycle limit

 

[planet69]

You do agree if adequate filtering capacitors were in place and the use of MOV or TVS at the input as well at the output does not give absolute protection against voltage spikes.
Low voltage rail on the the circuit board do get effected and sometimes damages the MCU and perhaps other semicon. as well.