| 摘要 |
PURPOSE: To perform detection by unloaded operation by making connection to a reference voltage source at one input terminal and including a comparator at the other input terminal. CONSTITUTION: A reference voltage U2 that is equivalent to a voltage drop at a resistor 5 is given to an input terminal 9. The voltage U2 is constant since a current source 6 that is connected in series with the resistor 5 takes one constant current regardless of the height of a supply voltage VBB. Also, the voltage U2 is selected to be absolutely smaller than the voltage U1 that drops to the level of a MOSFET 1 when no load 2 is broken. On the other hand, when the load 2 is broken, the voltage U2 is set absolutely larger than the voltage UN that drops to the level of FET 1 when the load 2 is broken. Then, both voltages that drop to the FET 1 differ and are evaluated as a criterion of load loss. In this manner, the load loss generates one voltage jump at an output terminal 14 of a comparator 10, and the load is evaluated as an indicator for the unloaded operation of the load 2. |
