Ignition device and method of controlling the same

Abstract

An ignition device includes a semiconductor switching element, a constant-current circuit, and a control section. The semiconductor switching element has a gate, a collector and an emitter, and is coupled with a primary winding of an ignition coil. The semiconductor switching element is configured to control a gate voltage and an electric current flowing between the collector and the emitter so as to control a coil current flowing in the primary winding, a voltage at two ends of a secondary winding, and an electric discharge at a plug coupled with the secondary winding. The constant-current circuit is coupled with the gate for supplying a constant current to the gate. The control section is configured to switch the semiconductor switching element by switching a supply or non-supply of the constant current to the gate based on an ignition signal.

1 . An ignition device for controlling an ignition with a plug coupled with an ignition coil that includes a primary winding and a secondary winding, the ignition device comprising:
 a semiconductor switching element that has a metal-oxide semiconductor structure having a gate, a collector and an emitter, and that is coupled with the primary winding, the semiconductor switching element being configured to control a gate voltage and an electric current flowing between the collector and the emitter so as to control a coil current flowing in the primary winding, a voltage at two ends of the secondary winding, and an electric discharge at the plug;   a constant-current circuit coupled with the gate of the semiconductor switching element for supplying a constant current to the gate, so that an electric charge is accumulated at the gate and the gate voltage increases; and   a control section configured to switch the semiconductor switching element by switching a supply or non-supply of the constant current generated at the constant-current circuit to the gate of the semiconductor switching element based on an ignition signal.   
   
   
       2 . The ignition device according to  claim 1 , wherein:
 the gate voltage of the semiconductor switching element increases approximately linearly to a threshold voltage of the semiconductor switching element by a predetermined gradient, then is maintained at the threshold voltage for a predetermined time, and further increases from the threshold voltage approximately linearly by the predetermined gradient, when the constant current is supplied to the gate.   
   
   
       3 . The ignition device according to  claim 2 , wherein:
 the predetermined time is about in a range from 5 μs to 200 μs.   
   
   
       4 . The ignition device according to  claim 1 , wherein:
 the constant current has a current value about in a range from 10 μA to 200 μA.   
   
   
       5 . A method of controlling an ignition device that includes a semiconductor switching element and a constant-current circuit, the method comprising:
 generating a constant current at the constant-current circuit;   supplying the constant current to a gate of the semiconductor switching element in accordance with an ignition signal; and   controlling a gate voltage of the semiconductor switching element and an electric current flowing between a collector and an emitter of the semiconductor switching element so as to control a coil current flowing in a primary winding of an ignition coil, a voltage at two ends of a secondary winding of the ignition coil, and an electric discharge at a plug coupled with the secondary winding.   
   
   
       6 . The method according to  claim 5 , wherein:
 the gate voltage of the semiconductor switching element increases approximately linearly to a threshold voltage of the semiconductor switching element by a predetermined gradient, then is maintained at the threshold voltage for a predetermined time, and further increases from the threshold voltage approximately linearly by the predetermined gradient, when the constant current is supplied to the gate.   
   
   
       7 . The method according to  claim 6 , wherein:
 the predetermined time is about in a range from 5 μs to 200 μs.   
   
   
       8 . The method according to  claim 5 , wherein:
 the constant current has a current value about in a range from 10 μA to 200 μA.