| 摘要 |
PROBLEM TO BE SOLVED: To reduce the number of components and simplify the construction by a method wherein the constant voltage control and a minus power supply for the current detection are eliminated. SOLUTION: A coil 8, an N-MOS 3 and a resistor 14 are connected in series to each other between both the plus and minus power supply lines. A resistor 11 is connected between the plus power supply line and the gate of the N-MOS 3. An N-P-N 5 which is turned on and off in accordance with the voltage of the resistor 14 and turns off the N-MOS 3 if the voltage of the resistor 14 reaches a predetermined value is provided. A resistor 10 and a capacitor 15 are connected in series to each other between the base of an N-P-N 4 whose emitter is grounded to the minus power supply line and the drain of the N-MOS and a diode 7 is connected in reverse-parallel to the emitter junction of the N-P-N 4. A comparator which complicates the construction can be eliminated. |
