Design Guide
19 of 48
V 1.0
2018-06-06
XDPL8218 design guide
For high power factor flyback converter with constant voltage output
Input voltage levels for start-up and protection
11
Input voltage levels for start-up and protection
EN
OVP,In
parameter refers to the enable switch for maximum input voltage start-up check and input OVP, based
on V
in,start,max
and V
inOV
levels, respectively. EN
OVP,In
= Enabled is selected in this design example.
EN
UVP,In
parameter refers to the enable switch for minimum input voltage start-up check and input UVP, based
on V
in,start,min
and V
inUV
levels, respectively. EN
UVP,In
= Enabled is selected in this design example.
Note:
The estimated input voltage V
in
used for start-up check and protection is in rms value, which is
assumed as 0.707 of estimated peak input voltage V
in,peak
regardless of whether actual input
voltage is AC or DC. As the input voltage is estimated based on ZCD pin and CS pin switching
signals, proper ZCD resistor selection (see
Section
) and R
in
parameter fine-tuning (see
Section
) are needed.
V
in,start,max
parameter refers to the maximum input voltage level setting for start-up, which is recommended to be
configured as V
in,high
. Hence, V
in,start,max
= 326 V
rms
is selected in this design example. V
inOV
parameter refers to the
input OVP level setting, which is recommended to be:
𝑉
𝑖𝑛𝑂𝑉
≥ 𝑉
𝑖𝑛,𝑠𝑡𝑎𝑟𝑡,𝑚𝑎𝑥
∙ 107% = 349 𝑉
𝑟𝑚𝑠
(30)
V
in,start,min
parameter refers to the minimum input voltage level setting for start-up, which is recommended to be
configured as V
in,low
. Hence, V
in,start,min
= 82 V
rms
is selected in this design example. V
inUV
parameter refers to the
input UV (brown-out) protection level setting, which is recommended as:
𝑉
𝑖𝑛𝑈𝑉
≤ 𝑉
𝑖𝑛,𝑠𝑡𝑎𝑟𝑡,𝑚𝑖𝑛
∙ 93% = 76 𝑉
𝑟𝑚𝑠
(31)
Based on the above, V
inOV
= 350 V
rms
and V
inUV
= 70 V
rms
are selected in this design example.
EN
VIN,ABM
refers to the enable switch for input voltage protections (based on V
inOV
and V
inUV
) in ABM.
If EN
VIN,ABM
is enabled, the enable switches for V
inOV
and V
inUV
protections in ABM are respectively based on EN
OVP,In
and EN
UVP,In
. If EN
VIN,ABM
is disabled, both V
inOV
and V
inUV
protections are inactive in ABM.
In this design example, EN
VIN,ABM
= Enabled is selected.
Note:
The reaction of V
inOV
and V
inUV
protections is auto-restart. A typical blanking time of either 10 half
sine wave periods or 10 burst periods applies on V
inOV
and V
inUV
protections triggering.
V
in
t
V
inOV
V
in,start,max
V
inUV
V
in,start,min
Startup
Startup
Startup
Protection
triggered
Protection
triggered
Figure 14
Input voltage levels for start-up and protection
