BL0921

BL0921

BL0921

BL0921

http://www.belling.com.cn

- 9 -

3/15/2007

Total 13 Pages

Single Phase Energy Meter IC

Single Phase Energy Meter IC

Single Phase Energy Meter IC

Single Phase Energy Meter IC

with Integrated Oscillator

with Integrated Oscillator

with Integrated Oscillator

with Integrated Oscillator

AGND

VAP

VN

+

-

CF

AGND

CF

RF

RF

CT

±660mV

AGND

AGND

VAP

VN

+

-

CF

AGND

CF

Ra

RF

±660mV

AGND

AGND

Rb

Rv

AGND

Ra >> RF

Rb+Rv=RF

Phase Neutral

Phase Neutral

Figure 5.

Typical Connections for Voltage Channels

Current Channel Input

The voltage outputs from the current transducers are connected to the BL0921 here. As Figure6

shows that channel V1 has two voltage inputs, namely V1A and V1B. These inputs are fully

differential with respect to V1N. However, at any one time, only one is selected to perform the

power calculation.

V1

V2

+660mV

-660mV

V1

V2

AGND

V2P

V2N

+

-

Maximun input differential voltage

±660mV

Maximun input common-mode voltage

±100mV

Figure 6.

Current Channels

The analog inputs V1A, V1B and V1N have same maximum signal level restrictions as V2P and

V2N. However, Channel 1 has a programmable gain amplifier (PGA) with user-selectable gains of

1 or 16. These gains facilitate easy transducer interfacing. Figure illustrates the maximum signal

levels on V1A, V1B, and V1N. The maximum differential voltage is ±660 mV divided by the

gain selection. Again, the differential voltage signal on the inputs must be referenced to a common

mode, e.g., GND. The maximum common-mode signal is ±100 mV.

Figure7 shows a typical connection diagram for Channel V1. Here the analog inputs are being

used to monitor both the phase and neutral currents. Because of the large potential difference

between the phase and neutral, two CTs (current transformers) must be used to provide the

isolation. The CT turns ratio and burden resistor (Rb) are selected to give a peak differential

voltage of ±660 mV/gain.