AC
voltage monitoring and zero-voltage
synchronization
UM2076
30/43
DocID029457 Rev 1
7
AC voltage monitoring and zero-voltage
synchronization
7.1
Zero voltage and AC line voltage sensor circuits
The AC line voltage (V
AC
) must be measured to detect the RMS AC line voltage level and
to manage the AC line dips (as described in
Section 8: "Mains voltage dips and
). As the MCU is connected after the diode bridge, a differential measurement
must be performed to measure the AC line voltage (V
AC
). The V
AC
measurement is based
on the line voltage (V
L
) and the neutral voltage (V
N
) measurement (V
AC
= V
L
- V
N
).
The resistor divider bridge in the following figure id used to sense V
L
and V
N.
Figure 21: AC line voltage measurement principle
Given V
L
and V
N
images, the MCU is able to deduce V
AC
from Equation 1, where V
AC_IM
is
the image of the AC line voltage and K is the proportional coefficient between V
AC
and
V
AC_IM
defined by the resistors divider bridge.
Equation 1
𝑉
𝐴𝐶
= (𝑉
𝐿
− 𝑉
𝑁
) = 𝐾 × (𝑉
𝐿_𝐼𝑀
− 𝑉
𝑁_𝐼𝑀
) = 𝐾 × 𝑉
𝐴𝐶_𝐼𝑀
Equation 2 shows how to calculate resistance R
D
from chosen resistance R
U
, where
V
AC_RMS_Max
is the maximum RMS AC line voltage which can be applied in the application
and V
AC_IM_Max
is the maximum AC line voltage image voltage applied at the MCU ADC
input.
Equation 2
𝑅
𝐷
= 𝑅
𝑈
{(
𝑉
𝐴𝐶_𝐼𝑀_𝑀𝑎𝑥
(√2 × 𝑉
𝐴𝐶_𝑅𝑀𝑆_𝑀𝑎𝑥
) − 𝑉
𝐴𝐶_𝐼𝑀_𝑀𝑎𝑥
)}
Equation 3 gives the proportional coefficient between V
AC
and V
AC_IM
Equation 3
𝐾 = (
(𝑅
𝑈
× 𝑅
𝐷
)
𝑅
𝐷
)
Содержание STEVAL-ISF003V1
Страница 3: ...UM2076 Contents DocID029457 Rev 1 3 43 13 Conclusion 41 14 Revision history 42 ...
Страница 18: ...Schematic diagrams UM2076 18 43 DocID029457 Rev 1 Figure 12 STEVAL ISF003V1 control circuit schematic ...
Страница 19: ...UM2076 Schematic diagrams DocID029457 Rev 1 19 43 Figure 13 STEVAL ISF003V1 flyback SMPS schematic ...
