| 摘要 |
PROBLEM TO BE SOLVED: To prevent the application of a voltage higher than the maximum rating of a driven load across the driven load by connecting a Zener diode having a breakdown voltage lower than the maximum rating of the load in parallel with the load. SOLUTION: When the voltage applied across the load 1 is lower than the breakdown voltage of a Zener diode 6, a constant current is supplied to the load 1 by controlling the applied voltage Vy so that a voltage Vx can become constant. When the resistance of the load 1 abnormally becomes higher, the voltage Vz applied across the diode 6 becomes higher than the breakdown voltage of the diode 6 and a large current flows to the diode 6. Then the voltage Vx becomes higher and a constant-current drive driver 3 lowers the applied voltage Vy upon receiving an H-level signal from a comparator 4. Therefore, the application of a higher voltage than the breakdown voltage of the diode 6 across the load 1 is eliminated and the application of a higher voltage than the maximum rating of the load 1 is prevented. |
