Today, current sensing technology has become increasingly sophisticated thanks to industrial development. However, traditional solutions are not necessarily unusable; they still have their place in various application environments. Current sensing is typically used to perform two basic functions: measuring the "size" of the current and determining the action to be taken when the current is "too large."
(1) Shunt resistor
All of these topologies carry certain risks. Low-end detection circuits are prone to interfering with the ground line; high-end detection requires high precision in the selection of resistors and operational amplifiers.
Detecting resistance is the simplest method for measuring current, and it can be used to measure both alternating current and direct current. The biggest drawback of this method is that a resistor is connected to the circuit under test, resulting in energy consumption (I^2*R).
(2) TRACE resistor
Ohm's law states that the voltage across a conductor is directly proportional to the current flowing through it. For resistive materials, this law can be extended to: J = σ(E + v × B).
In the formula, J is the current density, E is the electric field strength, v is the charge flow velocity, B is the magnetic flux density acting on the charge, and σ is the conductivity of the material. The above formula can then be simplified to: J = σE
This method, which uses the inherent resistance of the conductor in the circuit instead of the shunt resistor to measure current, is also an alternative current measurement method.
If a TRACE resistor is used, a high-gain amplifier is required to amplify the voltage signal, but the bandwidth performance of the amplifier has been a bottleneck that has not yet been overcome.
Numerous experts and scholars have conducted extensive research on the current testing performance of TRACE resistors. The results show that metallic copper has typical thermal drift characteristics, therefore this measurement method is not suitable for high-precision application environments.
(3) Inductance and DC resistance
The inductor DC resistance measurement circuit is a type of non-destructive sampling circuit. This circuit requires precise calibration before sampling; currently, it is only suitable for rough current measurement. It is typically used in non-destructive current measurement of switching power supplies and low-voltage (less than 1.5V ) current measurement applications.
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