
Figure 3.
LLC operation at f
SW
< f
RES
Looking at
is it possible to see that, when working below resonance, the time shift duration and the half
period become quite similar. As a limit case, when working on the boundary between inductive and capacitive
regions, the time shift is exactly half of the switching cycle.
The above information can be used to estimate a first value for the maximum time shift
Equation 14
fSWmin ≅
1
2 ∙ TSmax + ZCDdelay
(14)
Where TS
max
is the maximum time shift value and ZCD
delay
is the delay given by the ZCD comparator and digital
filtering
Equation 15
ZCDdelay = ZCD_c "LLC ZCD comp digital filtering"
(15)
ZCD_comp
del
is the comparator delay, estimated in 150 ns. “LLC ZCD comp digital filtering” is the digital filtering
of the ZCD comparator.
This formula can be used to start the design and the value can be fine-tuned at the bench,running the real
application prototype.
Remember that the STNRG011A provides anti capacitive protection (ACP), so, even if the user puts a large value
there is no risk of damaging the board components.
3.4.8
LLC OLP threshold
Size: 4 bits
Sets the threshold of the LLC OC1 comparator on LLC_CS pin for OLP functionality.
Available values are:
•
23.87 mV
•
55.61 mV
•
87.35 mV
•
119.1 mV
•
150.84 mV
•
182.58 mV
•
214.32 mV
•
246.06 mV
•
277.81 mV
•
309.55 mV
•
341.29 mV
UM3002
LLC parameters
UM3002
-
Rev 1
page 23/42