| 摘要 |
PROBLEM TO BE SOLVED: To provide an abnormal-current preventive circuit for a DC-DC converter having a small circuit scale, reducing a delay and having a small effect of element dispersion on characteristics. SOLUTION: The voltage of a detecting resistor 12 is a negative voltage in a normal case but a positive voltage appears when a reverse current is generated in an abnormal case. A current comparator 30 monitors the voltage of the detecting resistor 12, and a high power is transmitted to an AND circuit 20 to transmit an output signal of a driver 10 to switching elements 14 and 19 on the low side for a time period when the voltage of the detecting resistor 12 is the negative voltage. When the voltage of the detecting resistor 12 reaches the positive voltage, an output voltage of the current comparator 30 goes low, and the switching elements 14 and 19 on the low side are turned off forcibly. The current comparator 30 can make an output-current value larger than a voltage comparator in the prior art, so a delay does not arise in determining the generation of an abnormal current a speed increases extremely, and a large change width can be taken. COPYRIGHT: (C)2010,JPO&INPIT
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