Noise Test Circuit for Line-Operated Electronic Apparatus

Abstract

A new noise superimposer is proposed for noise tests of line-operated electronic apparatus. Currently, the commercial ac voltage is tainted by the noise generated in a large proportion of electronic equipment. The frequencies of the noise have a wider range than the audio frequency. Therefore, noise superimposers are needed for use in this frequency range. In the experimental circuit, the frequency response for noise signals was beyond 10 Hz∼100 kHz except near the frequency of commercial ac, and a normal low-frequency power amplifier can be used as the noise signal source. The commercial ac current hardly flows into the noise signal source, because of the principle of the transformer bridge. Appropriate selections of two impedance circuits for this bridge enable the noise signal to be sent to the load. The operating characteristics for the commercial ac power supply and the noise signal are analyzed.