Hell team,
Could you tell me which term tssdelay and tss are. I would like to know the meaning of them. Is below figure correct about the term of tss and tssdelay?
Best regards,
Ochi
Hi Ochi, Ryo:
tss = soft start time
tssdelay = soft start delay
These are defined in Section 6.6 of the part datasheet here, and I have inserted an image of it here for convenience:
The test conditions are described in the third column above, so it will be similar to the circuit shown below , but specifically with Cload = 40uF and RL = 5ohms at the secondary side of the transformer.
Under these conditions, the part will do a smooth , current controlled start-up on the secondary side, smoothly charging the output capacitor, per the waveform you shared. From a D1/D2 point of view, the swing will steadily increase and ramp-up and stabilize, fully indicative of the load seen by the secondary side. All this time, the secondary side will be multiplying this proportionately (per the transformer turns ration N) all the time and reflecting it on the output, minus the drop from the Schottky diodes. (Please note that you need this swing from the primary side on the D1/D2 pins to be able to transfer it across the transformer )
Hope this helps.
Best regards, Abhi
Hi Ochi-san, RYO,
For completeness, below are waveform captures of D2 after EN goes high and through the soft start delay:
D2 and D1 waveforms are complementary, thus identical with a 180 degree phase shift. If we zoom in on the D2 waveform, we can see that as the SN6505 powers up with soft start, the amplitude of D1 / D2 increases as they switch to drive the transformer and Vout.
Thank you,
Manuel Chavez
