JPS553665A - Solenoid drive system - Google Patents

Abstract

PURPOSE: To inhibit crashing sounds and mechanical vibration in case of functioning, by limiting currents at a moment when a solenoid starts its action, and by letting overcurrents flow after delay time.

CONSTITUTION: Currents are differentiated by means of a differentiation circuit A₁ at a moment when an input terminal T becomes to high voltage, polarity is inverted and a transistor TrQ₁ is conducted only for a fixed time. A TrQ₂ is under a conductive condition during the time when the input terminal T is in high voltage. Meanwhile, a TrQ₃ does not become to a conductive condition owing to a retardation element A₂ for a while after the T reaches high voltage. Thus, currents from power sources +B₁, +B₂ pass through a solenoid SOL and flow through the TrQ₂, but the currents do not flow up to the maximum value of overcurrents because they are limited by means of a resistance R4. When the output of the retardation element A₂ also reaches high voltage, currents flowing through the SOL also flows through the TrQ₃ because the TrQ₃ also becomes to a conductive condition. Consequently, the maximum currents of overcurrents from the power source +B₁ flow through the SOL, and the SOL positively functions.

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