An alternative low-cost current-sensing scheme for high-current power electronics circuits

A lightweight, low-cost current sensor for application in high-current, high-frequency power inverters and power converters is described. The current sensor consists of three elements. The first is a Rogowski coil, also known as a Maxwell worm, which is a nonmagnetic toroid wound like an inductor. The output voltage at the open terminals of the winding is proportional to the time derivative of the current flowing in a conductor passing through the toroid. The second element of the sensor is an op-amp integrator, which has as its input the output of the Rogowski coil. The third element of the sensor is a circuit to reset the integrator to zero when the current through the Rogowski coil is zero, to prevent the integration of the op-amp's offset voltages and biases from accumulating. For the case of a semiconductor switch, the current through the switch is zero when the switch is gated off. >