Flashing discharge tube-use power supply and control method therefor
A voltage for light emission is applied to the positive electrode 11 and negative electrode 13 of a flash discharge tube 3 (xenon flash lamp) by a charge and discharge capacitor 17 . When the voltage of the charge and discharge capacitor 17 does not reach a predetermined value, for example a voltage normally required for light emission operation of the flash discharge tube until a predetermined, for example, a time normally required to charge the charge and discharge capacitor 17 , a timer circuit 39 generates a charging stop signal S 3 . A control circuit 35 controls to turn off the switch of a power supply 33 with reference to the signal S 3 to stop the charging to the charge and discharge capacitor 17.
1. 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.
2. The flash discharge tube power supply portion according to claim 1 , further comprising a transformer disposed between the DC constant power supply source and the charge and discharge capacitor and controlled by the charging stop control means.
3. A method of controlling a power supply portion for a flash discharge tube by monitoring a charge time and a charging voltage during a charging operation of a charge and discharge capacitor for supplying charges to make the flash discharge tube carry out arc light emission, and stopping the charging operation to the charge and discharge capacitor with reference to the monitoring result, the method including:
charging the charge and discharge capacitor via a charging circuit including a current detecting circuit;
charging a charge and discharge circuit by charging a charge time measuring capacitor included in the charge and discharge circuit, which is provided as a time measuring circuit, wherein the charging of the charge time measuring capacitor is linked with the charging of the charge and discharge capacitor,
wherein the charge time measuring capacitor is charged at a slower rate than the charging of the charge and discharge capacitor, and
wherein the charge and discharge circuit charges the charge time measuring capacitor via the current detecting circuit;
discharging the charge and discharge circuit upon the stopping of the charging of the charge and discharge capacitor; and
generating a charge stop signal when the voltage of the charge and discharge circuit reaches a predetermined latch voltage.