| 摘要 |
PROBLEM TO BE SOLVED: To provide a step-up circuit, in which charging time of a backup capacitor is short and noise is not likely to be generated, when a transistor is turned on/off, and to provide a crew protection system comprising it. SOLUTION: The step-up circuit comprises a DC-DC converter 20, and a backup circuit 60. The DC-DC converter comprises a step-up coil 23 for receiving energy from a DC power supply, a step-up switching transistor 55 being turned on/off in order to store energy in the step-up coil, a threshold alteration means 30 for detecting transistor current, having an alterable threshold and turning the step-up switching transistor off, when the transistor current reaches the threshold, and an off time determining circuit 45 for starting when the step-up switching transistor is turned off, and steps up the voltage of the DC power supply. Threshold of the transistor current is altered, depending on the magnitude of difference between a predetermined voltage and the output voltage. COPYRIGHT: (C)2005,JPO&NCIPI
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