Innoswitch desigm does not startup correctly

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I have done a design based on the Innoswitch3, INN3676C.
Primary side does strat up. BPP is 5.73V. There is one switch cycle on the primary side. Which looks OK, rather short ~200ns.
Nothing more.
After some time, 2-3s, a new start attempt
This repeats

Shouldn't there be a burst of switching cycle until the secondary starts up and take control
Datasheet mentions a time Tar in which the secondary side must start up. Typically 82 ms.

What could cause the controller to inhibit startup after only 1 switching cycle ?


Hi unneback,
Can you share with me your design such as schematic, transformer, and waveform that you got so that I can check? During start-up, to prevent 2s auto-restart, this scenarios should not occur: 1) no Frequency overload; 2) BPP UV (which was ok based on your measurement); 3) There should be handshake; 3) no 2 consecutive SRS pulses.