Application Note
15
2011-07-06
2.3.8
VINS pin setting
The minimum operation input voltage needs to be specified for LLC resonant converter with the Vins pin.
The typical circuit of mains input voltage sense and process is shown Figure 6.
Figure 6
Mains input voltage sense
The mains input voltage is divided by
INSH
R
and
INSL
R
. With the internal current source
hys
I
is
connected between VINS and Ground, an adjustable hysteresis between the on and off input voltage can
be created as
[24]
Assuming the turn-on bus voltage
INon
V
is 380V typically and the turn-off bus voltage
INoff
V
is 320V
typically.The
INSH
R
and
INSL
R
can be calculated as:
[25]
[26]
A standard resistor value for
INSL
R
is 24k
Ω
.
The blanking time for leaving brown-out is around 500
μ
s and for entering brown-out is around 50
μ
s.
Please note that the calculation above is based on typical specification values of the IC.
2.3.9
Latch off function and burst mode selection
Internally, the EnA pin has a pull-up current source of 100
μ
A. By connecting a resistor outside from this
pin to ground, certain voltage level is set up on this pin. If the voltage level on this pin is pulled down
below certain level during operation, IC is latched. If the external resistor has a negative temperature
coefficient, this pin can be used to implement over- temperature protection (OTP). In this design,
EnA
R
is
selected at 1M
Ω
to set the pin voltage to be 2V level and no OTP is designed.
Ω
=
−
=
−
=
−
M
I
V
V
R
INS
INoff
INon
INSH
6
10
*
10
320
380
6
INSH
hys
hys
R
I
V
*
=
Ω
=
−
=
−
=
k
V
V
R
V
R
th
inoff
INSH
th
INSL
5
.
23
25
.
1
320
10
*
6
*
25
.
1
6