| 摘要 |
PURPOSE:To protect a drive circuit upon short-circuit of a fuel injection valve, by delivering a signal voltage given to the drive circuit and a voltage imposed to the fuel injection valve, to a logic circuit so that the energization of the fuel injection valve is ceased during the operation of a timer circuit. CONSTITUTION:An AND circuit receives a signal voltage Vi, a voltage which is obtained by inverting a voltage Vo imposed to a fuel injection valve through, a NOT circuit, and a voltage which is obtained by inverting the output of a monostable multivibrator OSM through a NOT circuit. Upon short-circuit of the fuel injection valve the output of the AND gate is turned into H-level from L-level, and therefore, the monostable multivibrator OSM is triggered so that the output thereof is turned into H from Q for a predetermined time. Accordingly, a transistor Tr 4 is turned on while a transistor Tr 2 is turned off so that the injection valve is deenergized. With this arrangement, no power transistors are failured, and as well no heart is generated in association with protection against short-circuit, thereby the device may be miniaturized with an enhanced reliability. |
