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ADE7761BARS 参数 Datasheet PDF下载

ADE7761BARS图片预览
型号: ADE7761BARS
PDF下载: 下载PDF文件 查看货源
内容描述: 电能计量IC ,带有片上故障和中性丢失检测 [Energy Metering IC with On-Chip Fault and Missing Neutral Detection]
分类和应用: 模拟IC信号电路光电二极管
文件页数/大小: 24 页 / 528 K
品牌: ADI [ ADI ]
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ADE7761B  
APPLICATIONS INFORMATION  
INTERFACING TO A MICROCONTROLLER FOR  
ENERGY MEASUREMENT  
SELECTING A FREQUENCY FOR AN ENERGY  
METER APPLICATION  
The easiest way to interface the ADE7761B to a microcontroller  
is to use the CF high frequency output with the output frequency  
scaling set to 2048 × F1, F2. This is done by setting SCF = 0  
and S0 = S1 = 1 (see Table 8). With full-scale ac signals on the  
analog inputs, the output frequency on CF is approximately  
5.5 kHz. Figure 35 illustrates one scheme that could be used to  
digitize the output frequency and carry out the necessary  
averaging mentioned in the Frequency Output CF section.  
As shown in Table 6, the user can select one of four frequencies.  
This frequency selection determines the maximum frequency  
on F1 and F2. These outputs are intended to be used to drive  
the energy register (electromechanical or other). Because only  
four different output frequencies can be selected, the available  
frequency selection was optimized for a meter constant of  
100 impulses/kWh with a maximum current of between 10 A  
and 120 A. Table 9 shows the output frequency for several  
maximum currents (IMAX) with a line voltage of 240 V. In all  
cases, the meter constant is 100 impulses/kWh.  
CF  
FREQUENCY  
RIPPLE  
Table 9. F1 and F2 Frequency at 100 Impulses/kWh  
AVERAGE  
FREQUENCY  
±10%  
IMAX (A)  
12.ꢀ  
2ꢀ  
F1 and F2 (Hz)  
0.083  
0.166  
0.266  
0.4  
40  
TIME  
60  
MCU  
80  
0.ꢀ33  
0.8  
ADE7761B  
COUNTER  
120  
CF  
1
The f1–4 frequencies allow complete coverage of this range of  
output frequencies on F1 and F2. When designing an energy  
meter, the nominal design voltage on Channel V2 (voltage)  
should be set to half-scale to allow for calibration of the meter  
constant. The current channel should also be no more than half-  
scale when the meter sees maximum load, which accommodates  
overcurrent signals and signals with high crest factors. Table 10  
shows the output frequency on F1 and F2 when both analog  
inputs are half-scale. The frequencies listed in Table 10 align  
well with those listed in Table 9 for maximum load.  
UP/DOWN  
REVP  
2
FAULT  
LOGIC  
1
REVP MUST BE USED IF THE METER IS BIDIRECTIONAL OR  
DIRECTION OF ENERGY FLOW IS NEEDED.  
FAULT MUST BE USED TO RECORD ENERGY IN FAULT CONDITION.  
2
Figure 35. Interfacing the ADE7761B to an MCU  
As shown in Figure 35, the frequency output CF is connected to  
an MCU counter or port that counts the number of pulses in a  
given integration time, determined by an MCU internal timer.  
The average power, proportional to the average frequency, is  
Table 10. F1 and F2 Frequency with Half-Scale AC Inputs  
Frequency on F1 and F2, Channel V1 and  
S0 S1 f1–4 (Hz) Channel V2, Half-Scale AC Inputs (Hz)  
Counter  
Average Frequency = Average Active Power =  
Timer  
The energy consumed during an integration period is  
Counter  
0
0
1
1
0
1
0
1
1.72  
3.44  
6.86  
13.ꢀ  
0.092  
0.183  
0.337  
0.734  
Energy = Average Power ×Time =  
×Time = Counter  
Time  
When selecting a suitable f1–4 frequency for a meter design, the  
frequency output at IMAX (maximum load) with a meter constant  
of 100 impulses/kWh should be compared with Column 4 of  
Table 10. The frequency that is closest in Table 10 determines  
the best choice of frequency (f1-4). For example, if a meter with  
a maximum current of 40 A is being designed, the output  
frequency on F1 and F2 with a meter constant of 100 impulses  
per kWh is 0.266 Hz at 40 A and 240 V (see Table 9).  
For the purpose of calibration, this integration time could be  
10 sec to 20 sec to accumulate enough pulses to ensure correct  
averaging of the frequency. In normal operation, the integration  
time could be reduced to 1 sec or 2 sec, depending on, for  
example, the required update rate of a display. With shorter  
integration times on the MCU, the amount of energy in each  
update may still have a small amount of ripple, even under  
steady load conditions. However, over a minute or more, the  
measured energy has no ripple.  
Looking at Table 10, the closest frequency to 0.266 Hz  
in Column 4 is 0.183 Hz. Therefore, F2 (3.4 Hz; see Table 6)  
is selected for this design.  
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