Hitachi, Ltd.

Kazuo Katou

Takashi Sase

Ikuho Horinaka

Yasuji Kamata

Yoshiyuki Nihashi

Syuichi Senda

A time division multiplexing amplifier having a differential amplifier, such as a dynamic bridge amplifier, which has a predetermined gain accurately provided by means of operational network resistors. The differential amplifier is used to amplify differential signals containing a common-mode voltage. Prior to amplification of the differential signals, a common-mode voltage is applied in common to two input terminals of the differential amplifier, and then the differential amplifier is adjusted to provide a zero offset voltage. After that, the differential signals are applied to the differential amplifier, so that the differential signals can be amplified without having any adverse effect of a common-mode voltage.

Time division multiplexing amplifier

In measuring analog input voltages through isolation transformers, an analog input voltage V.sub.in is applied across a primary winding of the isolation transformer, voltages V.sub.A and V.sub.B developing across the secondary winding of lapses of time T.sub.A and T.sub.B (T.sub.A &lt; T.sub.B) from application of the analog input voltage are detected, and by using measured times T.sub.A and T.sub.B and secondary winding voltages V.sub.A and V.sub.B, the analog input voltage V.sub.in is calculated in accordance with an expression ##EQU1## whereby influence of sag due to the isolation transformer is compensated for.

Method of measuring analog input voltages through isolation transformers

A DC-to-DC converter for providing a DC output voltage proportional to a DC voltage applied to the primary winding of a transformer by turning on and off the applied DC voltage by means of a switching element connected in series with the primary winding. The voltage developed across the secondary winding of the transformer upon the turning on and off of the applied DC voltage is rectified and smoothed by means of a circuit including a rectifying diode, a choke coil and a capacitor. The transformer has a core which exhibits a rectangular hysteresis characteristic. When the switching element is turned off, the current flowing through the choke coil when the switching element is conductive is caused to flow as a reset current through a part of the secondary winding of the transformer so that the level of the magnetic flux of the core of the transformer may be restored to its initial value.

Growing community of inventors

Ibaraki, Japan

Kazuo Katou