| 摘要 |
PROBLEM TO BE SOLVED: To extend the degree of freedom in design by setting the low input voltage detection level and the over input voltage detection level of a switching power supply independently with a small number of external components. SOLUTION: In the switching power supply, DC power applied to the primary winding of a transformer 8 is switched by the switching element 5 of a semiconductor device 4 where an oscillation circuit 10, an input voltage detection circuit 40, and the switching element 5, e.g. a power MOSFET, are integrated on a semiconductor chip substrate. A first detection resistor 51 and a second detection resistor 52 are connected in series between the input voltage detection terminal 1 of the semiconductor device 4 and a DC voltage line Vin, and a Zener diode 53 is connected in parallel with the detection resistor 51 or 52. A low input voltage detection level and an over input voltage detection level can be set independently by the combination of the first detection resistor 51, the second detection resistor 52 and the Zener diode 53. COPYRIGHT: (C)2005,JPO&NCIPI
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