E-Load transient test in Resistance mode?

[cupoftea]

Hi,
Customer sent us a 37V single stage PFC'd Flyback of 230W (6.2Aout) Peak. 150W (4.1Aout) average.
37Vout.

We sent it no_load_to_full_load transients of time length 13.5ms. (using SDL1030X E-load in resistance mode, but pulsed)

The eload was 10k for 5.013 seconds, then 6.5R (5.6A) for 13.5ms, repeatedly.

Every 7th , or so, pulse, the Flyback dropped out and went below 8Vout for 8 seconds, then recovered.....for all the other load transients, the vout just dipped down to ~28V and back up to 37V (in 17ms).

Do you think the eload struggles to "get into regulation" at the start of the transient pulse?.....ie, it might have been a lot less than 6.5R when it was first applied, and would have drawn a much_higher_than 5.6A current?

SDL1030X ELOAD used...

https://siglent.co.uk/jg/wp-content/uploads/2021/08/Siglent-SDL1000X-Electronic-Load-Datasheet.pdf

P.S. (or did we just catch it at the mains zero crossing)

 

[dick_freebird]

I don't like e-loads for load transients, and "constant R" least of all as it has two quantities to handle, real time. Have seen the DC-DC control loop "argue" with the e-load cotrol loop making unstable / "rogue wave" behavior.

I like switching a load resistor (or N) if you want a pulsed resistive load.

 

[cupoftea]

Thanks, from what you say, i do suspect that the resistance presented by the eload, may have actually been well below 6.5R?....at least, at the very start of the load pulse.