Although circuit and PCB designers are familiar with current clamps, they want something more portable and useful systems. There are relatively few current sensing techniques that can be useful as tiny circuits in a professional zero phase current transformer, regardless of whether you need to detect extremely large AC currents or very low DC currents. Let’s examine these techniques and see how well they may combine to get precise current readings.
Existing Sense Techniques for Systems
In power electronics, current sensing techniques are often applied in three basic ways. Normally, the current is not measured directly. Alternatively, it may be transformed into a voltage, and then the voltage could be detected by contrasting it with a consistent reference value (as in an ADC). Put differently, current sensing is really voltage sensing under a different garb, and it converts current to voltage by lowering the current over a precise resistance.
Resistors for current sensing
Current-to-voltage conversion is achievable using a current-sensing resistor, which is most commonly useful in current-mode-regulated power regulators. Usually, current sense resistor components come with very low voltage and great accuracy. The theory is that the voltage created across the current sensing resistor is V = IR and that the current does not lose power across it too much.
The voltage may be too high to send into an ADC or regulator feedback pin when the current is high. If so, it is possible to create a lower voltage by stepping down the voltage across the current sensing resistor. This lower voltage may then readable using an ADC, comparator, amplifier, etc.
Transformers for current
One kind of transformer designed particularly for large currents is the current transformer. This is because their usual purpose is to reduce the amount of an AC, particularly at a harmonic frequency. They are frequently useful to monitor currents on circuits that depend on AC mains power or to measure currents on AC main lines.
The peak of the AC waveform can be determined after the current is stepped down (or up). Using Schottky rectifier diodes to rectify the current and then dropping it over a precision resistor is the simplest method for doing this. After that, an amplifier or ADC may be useful to measure the voltage across the resistor.
Sense Amplifiers for Current Systems
A current sense amplifier is a pre-packaged product by mini PCB current transformer manufacturers that can measure currents rapidly and precisely. By simply cutting the current through a precision resistor and comparing the result to a reference voltage. These may take place using discrete components. On the other hand, a wide variety of currents may be useful with pre-packaged current sensing amplifier integrated circuits (ICs).
In essence, Systems current sense amplifiers transform current into voltage. With an output voltage that is proportionate to the current entering the circuit. These parts use precise resistors to transform a current into a low voltage. Which is then amplified and sent to a different area of the system. The output, for instance, can be useful directly to a measurement in an ADC.