| 摘要 |
PURPOSE:To stabilize a circuit with simple constitution, by turning off a controlling transistor TR to prevent the breakdown of circuit elements due to the overload when the load is short-circuited and resetting the controlling TR automatically when the abnormality in the load side is released. CONSTITUTION:An operational amplifier 2 amplifies the difference between a reference voltage VZ and a divided voltage Vd and adjusts the base current of an output voltage controlling TR1 through a resistance 6 to secure a constant voltage V against the variance of the load. Even if the voltage Vd drops toward 0 because of the short-circuit of the load, the amplifier 2 reaches a shift voltage VA just before Vd=0. Since the voltage VA is lower than the voltage VZ, the output is inverted to the H level quickly to turn off the TR1 quickly. The voltage Vd becomes 0 thereafter, but the TR1 is kept in the turning-off state because the amplifier 3 is driven to a displacement area, and thus, the breakdown of elements is prevented. |
