Ignition device

An ignition device for use in an internal combustion engine that uses a fuel including at least hydrogen, comprising:

• an ignition coil formed by electromagnetic coupling of a primary coil and a secondary coil;
• a power supply device configured to apply a direct-current voltage to one end of the primary coil via a power supply line;
• a switching element interposed between the other end of the primary coil and a ground point, the switching element being capable of performing switching between passage and interruption of a primary current flowing through the primary coil from the power supply device;
• a spark plug configured to ignite the fuel by occurrence of discharge at a gap, based on a high voltage induced at one end of the secondary coil;
• and
• a limiting diode including a Zener diode or an avalanche diode that is interposed in a first connecting wire connecting directly or indirectly the other end of the secondary coil and the power supply device or the ground point, or a second connecting wire connecting the one end of the secondary coil and the spark plug, and is forward-biased when the diode is oriented in a direction from the one end of the secondary coil to the other end of the secondary coil, wherein
• a breakdown voltage of the limiting diode is higher than a maximum value of an ON-state voltage obtained by multiplication of a voltage value of the direct-current voltage applied to the one end of the primary coil by the power supply device, by a ratio of the number of turns of the secondary coil to the number of turns of the primary coil.