A fail-safe thin-film current sensor using a flux saturable ring core

We have developed a fail-safe thin-film current sensor using a flux saturable ring core. The sensor consists of a transformer unit composed of a saturable core, primary and secondary coils, and a load coil which surrounds the transformer unit. The sensor is suitable for the purpose of a fail-safe system. The chip size is 4 mm/spl times/4 mm. A transmission efficiency of 60% was obtained when the carrier signal was 3 Vpp-1 MHz sine wave. The secondary voltage of the sensor successfully dropped by 90% when a 100 mA load current was applied to 20-turn load coil.