Abstract The present invention concerns with the flash device in which the output of an electric power source is boosted by a DC-DC converter, and a main capacitor is charged by the output of the DC-DC converter. In the above-described flash device, to detect the charging state of the main capacitor, a voltage detecting circuit such as voltage dividing resistors is connected in parallel to the main capacitor. For this reason, when the DC-DC converter is rendered inoperative, a problem arises that the electric charges on the main capacitor discharge through the voltage detecting circuit. In the present invention, to eliminate this problem, the flash device is provided with a unilateral conducting element such as diode connected in between the main capacitor and the voltage detecting circuit.
A flash device having a DC-DC converter for boosting an output of an electric power source, a capacitor for storage of energy for flash light to be charged by an output of said DC-DC converter, and a charge voltage detecting circuit for detecting a charge voltage of said capacitor, comprising: (a) a latch circuit for latching a charge completion signal output from said charge voltage detecting circuit; (b) switch means for determining whether a charging operation of said flash device is rendered operative or inoperative; (c) a timer circuit arranged to start operating when said flash device is rendered inoperative by said switch means; and (d) a control circuit which causes said flash device to be operative while maintaining the latching state of said latch circuit when the charging operation of said flash device is made operative by said switch means within the time period set by said timer circuit, and releases the latching of said latch circuit when said flash device is not made operative upon the expiration of the time period.
Claim 2
Dependent Claim
173 words
A flash device having a DC-DC converter for boosting an output of an electric power source, a capacitor for storage of energy for flash light to be charged by an output of said DC-DC converter, and a charge voltage detecting circuit for detecting a charge voltage of said capacitor, comprising: (a) a latch circuit for latching a charge completion signal output from said charge voltage detecting circuit; (b) switch means for determining whether a charging operation of said flash device is rendered operative or inoperative; (c) a timer circuit arranged to start operating when said flash device is rendered inoperative by said switch means; and (d) a control circuit which causes said flash device to be operative while maintaining the latching state of said latch circuit when the charging operation of said flash device is made operative by said switch means within the time period set by said timer circuit, and releases the latching of said latch circuit when said flash device is not made operative upon the expiration of the time period.
Claim 3
Dependent Claim
21 words
A flash device according to claim 1 wherein said switch means determines whether said DC-DC converter is rendered operative or inoperative.