Patent ID: 7119502

Claim:
A power supply portion for a flash discharge tube comprising: a charge and discharge capacitor, electrically connected to a DC constant power supply source and the positive electrode and negative electrode of a flash discharge tube, accumulating charges supplied from the DC constant power supply and supplying the charges to the negative electrode of the flash discharge tube to make the flash discharge tube emit light; charging monitoring means for monitoring a time required for charging and a charging voltage during a charging operation to the charge and discharge capacitor, the charging monitoring means including a charge and discharge circuit as a time measuring means which is charged linked with the charging of the charge and discharge capacitor and which is discharged upon the stopping of the charging of the charge and discharge capacitor; and charging stopping control means for stopping the charging operation to the charge and discharge capacitor with reference to the monitoring result of the charging monitoring means, the charging stopping control means including a latch circuit as a signal generating means for generating a charge stop signal when the voltage of the charge and discharge circuit reaches a predetermined latch voltage, wherein the charge and discharge circuit includes a charge time measuring capacitor and the charge and discharge circuit charges this charge time measuring capacitor at a slower rate than the charging of the charge and discharge capacitor; and a charging circuit for charging the charge and discharge capacitor, the charging circuit including a current detecting circuit, wherein the charge and discharge circuit charges the charge time measuring capacitor via the current detecting circuit.