Other Parts Discussed in Thread: UCC27524
Hi, team.
My customers are designing PFC circuits using UCC28070.
Please tell the customer that there is a doubt about this device.
<Question>
1.How to determine the C value of the CT reset circuit
Please tell me about the method of determining "Crr" constant in Fig. 1 of document No. JAJA216.
※There is description of calculation method of Rr, but Crr calculation method can not be found
(Crr = 4.7 pF in Figure 1, please tell me how to derive this 4.7 pF)
2.On connection of Rta resistor and GDA terminal
In Figure 1 of Document No. JAJA216 there is a point connecting the Rta resistor and the GDA terminal to add DC offset to the current sense signal.
The customer has the circuit configuration UCC28070_GDA terminal ⇒ driver IC (UCC27524) ⇒ power MOSFET.
Which is recommended for connecting the Rta resistor, GDA pin of UCC28070 or Output side of Driver IC?
And, please also tell me why (reason)?
3.About minimum pulse width
How many is the minimum pulse width of the GDA signal?
※Is it possible to output even with a pulse width of 0.1 us?
There are cases where the input voltage and the output voltage of the PFC circuit are equal,
and we are worried about the possibility that the switching ON time theoretically becomes 0.1 μs.
Best regards,
Masumi Sekiguchi