Triangular waveform shown by DSO for DC output. Is this usual?
From the text at upper-left, it looks like the 'scope is meant to show that the output ripple is 50 mV peak-peak. (I can't read the Chinese, I'm just guessing from the units). 

That's a fairly small ac signal, which might be acceptable in many digital applications, or which could be further filtered by the user.