ade7953 Analog Devices, Inc., ade7953 Datasheet - Page 25

• Manufacturer Part Number: ade7953
• Description: Single Phase, Multifunction Metering Ic With Neutral Current Measurement Ade7953
• Manufacturer: Analog Devices, Inc.

Active Energy Line Cycle Accumulation Mode
In active energy line cycle accumulation mode, the energy
accumulation of the ADE7953 is synchronized to the voltage
channel zero crossing so that the active energy can be accumu-
lated over an integral number of half line cycles. This feature is
available for both Current Channel A and Current Channel B
active energy. The advantage of summing the active energy over
an integral number of half line cycles is that the sinusoidal
component of the active energy is reduced to 0 (see Equation 12
to Equation 15). This eliminates any ripple in the energy calcula-
tion. Energy is calculated more accurately and in a shorter time
because the integration period can be shortened. The line cycle
accumulation mode can be used for fast calibration and also to
obtain the average power over a specified time period. Using
Equation 6, the following description of the energy accumulation
can be derived:
where:
n is an integer.
T is the line cycle period.
Because the sinusoidal component is integrated over an integer
number of line cycles, its value is always 0. Therefore,
Line cycle accumulation mode is disabled by default and can be
enabled on Current Channel A and Current Channel B by setting
the ALWATT and BLWATT bits to 1 in the LCYCMODE register
(Address 0x004). The accumulation time should be written to
the LINECYC register (Address 0x101) in the unit of number of
half line cycles. The ADE7953 can accumulate energy for up to
65,535 half line cycles. This equates to an accumulation period
of approximately 655 sec with 50 Hz inputs and 546 sec with
60 Hz inputs.
P(t) = VI – [ LPF ] × cos(2ω t)
E = VInt
E
E(t)
) (
t
=
=
nT
nT
∫
0
∫
0
VIdt
VIdt
−
+
[
0
LPF
VOLTAGE CHANNEL
]
×
OUTPUT FROM
OUTPUT FROM
nT
∫
0
cos(
2
LPF2
ADC
ωt
)
dt
LPF1
Figure 48. Active Energy Line Cycle Accumulation
xWGAIN
ZERO-CROSSING
DETECTION
(12)
(13)
(14)
(15)
Rev. 0 | Page 25 of 68
xWATTOS
+
+
15
48
FIXED INTERNAL
ACCUMULATION
CALIBRATION
The number of half line cycles written to the LINECYC register
is used for both the Current Channel A and Current Channel B
accumulation periods. At the end of a line cycle accumulation
cycle, the AENERGYA and AENERGYB registers are updated,
and the CYCEND flag is set in the IRQSTATA register (Address
0x22D and Address 0x32D). If the CYCEND bit in the IRQENA
register is set, an external interrupt is issued on the IRQ pin. In
this way, the IRQ pin can also be used to signal the completion of
the line cycle accumulation. Another accumulation cycle begins
immediately as long as the ALWATT and BLWATT bits in the
LCYCMODE register remain set.
The contents of the AENERGYA and AENERGYB registers are
updated synchronous to the CYCEND flag. The AENERGYA and
AENERGYB registers hold their current values until the end of
the next line cycle period, when the contents are replaced with
the new reading. If the read-with-reset bit (RSTREAD) in the
LCYCMODE register (Address 0x004) is set, the contents of the
AENERGYA and AENERGYB registers are cleared after a read
and remain at 0 until the end of the next line cycle period.
If a new value is written to the LINECYC register (Address 0x101)
midway through a line cycle accumulation, the new value is not
internally loaded until the end of a line cycle period. When the
LINECYC register is updated mid-reading, the current energy
accumulation cycle is completed, and the new value is then
programmed, ready for the next cycle. This prevents any invalid
readings due to changes to the LINECYC register (see Figure 47).
THRESHOLD
AENERGYx REGISTER
INTERNAL
LINECYC
CONTROL
LINECYC REGISTER
CYCEND IRQ
0
0
VALUE PROGRAMMED
Figure 47. Changing the LINECYC Register
NEW LINE CYCLE
23
AENERGYx
0
INTERNAL LINE CYCLE
UPDATED
ADE7953