| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To prevent an excessive current from flowing to a part of a circuit and heating to high temperature from occurring by the overvoltage within an electronic apparatus. <P>SOLUTION: When the power voltage within the electronic apparatus comes to overvoltage and reaches the Zener voltage of a Zener diode ZD3, the base current of a transistor Q15 flows and it goes into ON state, and a transistor Q14 is switched off, since the collector current of the transistor Q15 flows to the base and goes into ON state, and the collector current of the transistor Q14 flows. Even if the power voltage within the electronic apparatus falls under the Zener voltage of the Zener diode ZD3, the ON state of the transistor Q15 is kept. When the collector current of the transistor Q14 flows, the base current of a transistor Q12 is interrupted, and an external control terminal R becomes high impedance, and DC voltage of approximately 1.4V being remote off voltage is outputted between the Vout terminal and the GND terminal of a constant-voltage switching power circuit. <P>COPYRIGHT: (C)2005,JPO&NCIPI</p> |
