| 摘要 |
PURPOSE:To make it possible to interrupt power supply to equipment without any influence of ambient temperature when a cooling fan motor comes to a standstill, by detecting variations in the collector voltage of a switching transistor through a power supply control circuit, and thereby interrupting the output of a power circuit. CONSTITUTION:When the rotation of a fan motor 2 comes to a stop, an L (low) level signal is output. Thus a transistor 3 is turned off, and the voltage at point A is increased. A Zener diode 6 of such a rating as allows Zener current to pass at this time, is selected and employed. When Zener current passes through the Zener diode 6, the switching transistor R is biased and turned on. Then collector current passes, and the collector voltage of the transistor 8 drops. A voltage control circuit 9 detects the stop of the cooling fan motor 2 rotation through variations in the collector voltage of the transistor 8. A power supply control circuit 9 inputs control signals to a power circuit 1, and interrupts the secondary output from the power circuit 1. |
