ljy4468
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- The first one senses the motor current, the second one the H-bridge input current. That's an important difference referring to the voltage and current conversion capability of the H-bridge. During some states, motor current will be e.g. circulated through the upper or lower switches and doesnt't contribute to the current seen in circuit 2.
- As a practical problem, the first circuit requires a common mode range equal to the bus voltage.
it seems that there'll be no difference, but anyone can tell me about those circuit.
View attachment 70790
Using the second method you don't actually need a differential amplifier, only optional voltage divider + zener diode to protect the ADC. This is because differential voltage equals voltage on the upper side of the resistor minus voltage on the lower side of it, and the lower side is connected to GND. Hence potential of the upper side or resistor referenced to common gnd equals to differential voltage drop across this resistor.