Hello,
What is the expected regulation tolerance of the UCC28730 NOT using the UCC24650?
Is there a plan to release a UCC28730 “zero power” flyback controller with an integrated FET like UCC289xx?
Thank you, Keith
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Hello Keith,
The PSR controller's are generally +/-5% in accuracy. The UCC24650 wakeup chip will reduce the output capacitance required by a factor of 6.5 due to the faster transient response. I think this is bigger selling feature compared to the 0 power.
If you don't use the wakeup chip you have to size your output capacitor to handle a transient response based on 32 Hz. I would not recommend using this PSR controller without the wakeup chip.
You could use the UCC28910/1 devices that have integrated FETs, that don't require the wakeup chip.
At this time I don't believe the product line plans on developing a version of the UCC28730 with an integrated FET.
However, I will mention it to the product line.
Regards,
Mike
Hey Keith,
1. The VS pin does a whole lot more than just regulate the output voltage. Its top priority is to monitor the scaled down version of the DRAIN waveform to determine the demagnetization point of the transformer, so tying this pin directly to the regulated output voltage wouldn't work well, an auxilliary winding is needed so that the signal on VS looks like what is shown in Figure 14 of the UCC28730 data sheeet.
2. and 3. are sort of related; No concern with using a DC supply as long as HV can supply enough current for the internal current source to charge VDD. The minimum voltage to start charging is around 20V on HV but the current needed is up to 500uA (max) for start up until VDD ramps up to UVLO.