Electromagnetic device driving apparatus

Abstract

A driving apparatus for an electromagnetic valve comprises a conduction control circuit and a current-limit-value setting circuit. The conduction control circuit turns on and off an FET so that a conduction current flowing through the electromagnetic valve has a magnitude equal to a predetermined current limit value while a microcomputer is outputting a driving signal to the conduction control circuit. The predetermined current limit value is set at a first current limit value during a first predetermined period starting at a point of time the microcomputer outputs the driving signal. When the predetermined first period has lapsed, the predetermined current limit value is switched to a second current limit value for a second period. The second limit value is smaller than the first current limit value. A first off-time of the FET for attaining the first current limit value is set to be shorter than a second off-time of the FET for attaining the second current limit value. Alternatively, a first on-time of the FET for attaining the first current limit value is set to be shorter than a second on-time of the FET for attaining the second current limit value in the second period.

Dependencies are inferred from the claim text.