| 摘要 |
PROBLEM TO BE SOLVED: To provide a flash charging circuit constantly controlling a capacitor charging time without influenced by a change in surrounding temperature. SOLUTION: The flash charging circuit includes a step-up transformer, a capacitor, a constant voltage circuit, a current limiter section and a control section. A DC voltage is supplied to the primary side of the step-up transformer to generate a step-up voltage on the secondary side. The capacitor accumulates electric energy for flash light emission with a current supplied from the secondary side. The constant voltage circuit converts the DC voltage to a predetermined voltage. The current limiter section is connected to the constant voltage circuit and includes a temperature sensitive element whose resistance value is varied according to the surrounding temperature to determine the upper limit value of a current supplied to the primary side according to the change of the resistance value. The control section is connected to the constant voltage circuit to switch current supply to the primary side and shut-off and to shut-off the current supply when the current on the primary side reaches the upper limit value. COPYRIGHT: (C)2010,JPO&INPIT |
