My guess is it's a mixture of analog and digital stuff. On the analog side, there's probably a bandgap voltage reference, temperature and current sensing, soft-

My guess is it's a mixture of analog and digital stuff. On the analog side, there's probably a bandgap voltage reference, temperature and current sensing, soft-start circuitry. It needs to detect the primary's clock and lock on it (probably with a PLL), and adjust the phase as necessary. Then there will be drivers for the power transistors. The digital side is probably fairly simple logic to stop the chip if there's a fault and restart it if the fault goes away. From the datasheet, there are various different overload states it can go into, limiting power, changing to passive rectification, and then shutting down entirely. So the logic would need to manage these states. There's always the possibility that they threw a microcontroller in to handle this, but it seems like overkill. Also, I didn't see anything that looked like ROM. So I think the control is hard-wired.