Patent ID: 7631633

Claim:
A capacitor discharge ignition device for an engine comprising: an exciter coil provided in a magneto generator driven by the engine; a voltage increasing circuit that increases an output voltage of one half cycle of said exciter coil; an ignition capacitor charged by an output voltage of said voltage increasing circuit; a capacitor discharge switch that which becomes an on-state when receiving an ignition signal and discharges charges in said capacitor through a primary coil of an ignition coil; and an ignition control portion that provides an ignition signal to said capacitor discharge switch at ignition timing of said engine, wherein said voltage increasing circuit includes: a voltage increasing switch that is comprised of a switch element that can be an on-state while receiving a drive signal, is connected in parallel with said exciter coil, and is turned on to pass a short-circuit current through said exciter coil when said exciter coil generates said output voltage of one half cycle; a voltage increasing switch drive circuit that provides said drive signal to said voltage increasing switch; a first shunt resistor for current detection connected in series with said voltage increasing switch; an interruption control switch that is provided so as to allow said drive signal to be provided to said voltage increasing switch when the interruption control switch is in an off-state and bypass said drive signal from said voltage increasing switch to interrupt said voltage increasing switch when the interruption control switch is in an on-state, and receives a trigger signal and is turned on when a voltage across said first shunt resistor reaches a set trigger level; a second shunt resistor connected in parallel across said first shunt resistor through a resistance value changeover switch; and a switch control portion that controls said resistance value changeover switch so as to maintain said resistance value changeover switch in an on-state when a rotational speed of said engine is a set value or less, and maintain said resistance value changeover switch in an off-state when said rotational speed exceeds said set value.