A power line filter comprises a filter circuit in the form of an impedor assembly (30) that filters a network supply voltage to be applied to a load. A voltage sensor means (34) monitors a characteristic of the supply that is representative of the interference content of the supply voltage. A microprocessor (36) compares the monitored characteristic with data that is stored in a memory (38) and is representative of a desired supply characteristic. By way of control means (32), the microprocessor (36) cause variation of a filtration characteristic of the impedor assembly (30) in a sense to minimize any divergence between the two above-mentioned characteristics, thereby to better suppress the interference.
The system for suppressing an ambient noise signal which comtaminates a desired signal includes a noise pickup detector for detecting the ambient noise signal. A noise discriminator processes the detected noise signal into noise data. A reference noise generator converts the noise data into a reference noise signal. The noise generator automatically adjusts the reference noise signal to correspond with changes in the noise signal as it is being detected. A filter filters the reference noise signal into an error signal which is adapted to remove the noise signal from the contaminated signal. A cross-correlator cross-correlates the contaminated signal with the reference noise signal and adjusts the filter to produce the required error signal.
An apparatus and method for reducing distortion currents present in an alternating current power system supplying power to a load which includes a passive filter and an active filter. In a first embodiment, the passive filter is operably connected to the power system across the load by a switching device. An active filter is then connected across the switching device and operated to draw a current equal to the current through the passive filter. The active filter and the passive filter are thereby connected in series across the load. The active filter is controlled to draw a fundamental frequency component and to provide distortion currents required by the load. In a second embodiment, the active filter is connected in parallel with a first circuit, the parallel combination of which is connected in series with a second circuit across the load. Besides providing distortion currents required by the load, the active filter is controlled to draw a current substantially in phase with the voltage across it in order to provide damping.
A filter for a switching power supply. The filter includes a common mode inductor with coil configurations allowing differential mode current from a dc source to pass through but attenuating common mode noise from the power supply so that the noise does not reach the dc source. The invention also includes the use of feed through capacitors at the switching power supply input terminals to provide further high-frequency noise attenuation.
A method for recovery from overstress conditions, comprising the steps of (A) detecting an overstress event, (B) storing an occurrence of the overstress event and (C) taking appropriate action in response to the stored occurrence of the overstress event.
