| 摘要 |
PROBLEM TO BE SOLVED: To protect a DC power supply circuit using a coaxial cable and a load from the overcurrent of the DC power supply circuit. SOLUTION: An electric current from a DC power supply circuit 1 becomes a reference voltage through a Zener diode 11 and flows to a power transistor 4 and a monitor resistor 7 monitors the quantity of the emitter current of the transistor 4. When the emitter current increases and an overcurrent flows, the both-terminal voltage of the resistor 7 increases and a switching transistor 6 is turned on. In addition, an electric current flows to a resistor 8 and a counter 15 starts to operate. When the count value of the counter 15 becomes a certain value, a decoder 16 outputs a signal and a thyristor 5 is turned on. Consequently, the base current of the transistor 4 is broken and the transistor 4 is completely turned off. Therefore, the transistor 4 operates as a protective circuit which protects the DC power supply circuit 1 and a load 2 from an overcurrent. |
