BL6533
Single Phase Energy Meter IC with LCD Driver
The average active power is related to the cosine value of the phase difference between the voltage
signal and the current signal. This cosine value is called as Power Factor (PF) of the two channel signals.
Figure1.
The Effect of phase
When the signal phase difference between the voltage and current channels is more than 90°, the
average active power is negative. It indicates the user is using the electrical energy reversely.
Operation Process
In BL6533, the two ADCs digitize the voltage signals from the current and voltage transducers. These
ADCs are 16-bit second order sigma-delta with an oversampling rate of 900 kHz. This analog input
structure greatly simplifies transducer interfacing by providing a wide dynamic range for direct
connection to the transducer and also simplifying the antialiasing filter design. A programmable gain
stage in the current channel further facilitates easy transducer interfacing. A high pass filter in the
current channel removes any dc component from the current signal. This eliminates any inaccuracies in
the real power calculation due to offsets in the voltage or current signals.
The real power calculation is derived from the instantaneous power signal. The instantaneous power
signal is generated by a direct multiplication of the current and voltage signals. In order to extract the
real power component (i.e., the dc component), the instantaneous power signal is low-pass filtered.
Figure 2 illustrates the instantaneous real power signal and shows how the real power information can be
extracted by low-pass filtering the instantaneous power signal. This scheme correctly calculates real
power for nonsinusoidal current and voltage waveforms at all power factors. All signal processing is
carried out in the digital domain for superior stability over temperature and time.
http://www.belling.com.cn
-7-
Total
10 Pages
9/9/2009
BELLING [ SHANGHAI BELLING CO., LTD. ]
