AN2317 Datasheet, PDF (6/27 Pages) STMicroelectronics – Energy Metering IC External Circuits

External Circuit Design
AN2317 - Application
1.1
1.1.1
Current Sensing Circuit
The STPM01 has two external current sensing circuits (see Figure 1 on page 5):
1. Primary channel, and
2. Secondary channel.
Primary Current Sensing
The primary channel uses a current transformer to couple the mains current (see Figure 2).
The Burden resistor is used to produce a voltage between V_IN1 and V_IP1. The Low-pass
filter (LPF) is used to filter out the high frequency interference and has little influence on the
voltage drop between V_IN1 and V_IP1.
Figure 2. Primary Current Sensing Circuit
I1
I2
Burden Resistor
1
1
LPF
1 ^R2 2
1.0k
2
2 ₁ R1 ₂
1.0k
VIN1
1
+
U0
2
–
VIP1
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