| 摘要 |
PURPOSE:To supply a stable voltage to a laser tube, by keeping relay contacts at a closed state, when an output voltage from a judging circuit, into which output signals from upper and lower input-voltage-limit detector circuits are inputted, and when its input voltage lies between the upper limit value and the lower limit value. CONSTITUTION:When an input voltage to a gas laser power source 1 is lower than an upper limit value, an upper input-voltage-limit detector 6 outputs a high level signal. When the input voltage is higher than a lower limit value, a lower input-voltage detector 7 outputs a high level signal. When the input voltage is within a specified range, the high level signals from both detectors are inputted into an AND circuit, and a high level signal is outputted to a relay driving circuit 9. A relay 5 is energized and normally opened relay contacts 5a and 5b are kept closed. AC voltage is supplied to a converter circuit 2 and a voltage required for the gas laser tube is applied. When the input voltage becomes out of the specified range, one of the inputs to the AND circuit 8 becomes a low level. The relay driving circuit 9 deenergizes the relay 5, and the normally opened relay contacts 5a and 5b are returned to opened state. Thus the input of the voltage outside the specified range is prevented. |
