Coherent light generators – Particular pumping means – Electrical
Patent
1988-10-27
1989-10-03
Sikes, William L.
Coherent light generators
Particular pumping means
Electrical
372 81, H01S 3097
Patent
active
048721786
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention is directed to an output voltage detecting device in a laser oscillator, and more particularly to an output voltage detecting device in a laser oscillator which is operable at a low voltage and manufactured at an inexpensive cost.
A laser tube has an electrical impedance which varies depending upon an confined gas status in the interior of the laser tube. As a consequence, a voltage supplied to the laser tube varies. For example, in a laser oscillator having a current feedback loop with which a current is fedback to the laser tube, the variation in the electrical impedance of the laser tube causes the supply voltage to vary, since the current is being controlled to be a constant. If this condition is left as it stands, semiconductor elements, the laser tube or other elements which form an inverter in a high frequency power supply are damaged. Furthermore, the output voltage needs to be monitored to ascertain if the supply voltage is stable.
In view of the foregoing, it is conventional practice to detect the voltage supplied to the laser tube, and when the resultant voltage is above a reference voltage, an alarm is generated. When the detected voltage is above a danger-level voltage, the driving is stopped. In addition, it has been necessary to detect and monitor the output voltage in order to control the output voltage to a constant. Accordingly, it can be appreciated that in the laser oscillator, monitoring of the voltage supplied to the laser tube and measurement thereof are important measuring items. Conventionally, such measurements have been carried out using a transformer or voltage-division capacitors.
However, the transformer is required to have a considerably high voltage insulation resistivity. The transformer is further required to have a high frequency characteristic attendant to the high frequency power supply unit. For such reasons, the transformers which are extremely expensive have to be employed.
A method in which the voltage is divided by capacitors is involved with a problem such that a power supply line led to the laser tube cannot be isolated from a ground connection of a control apparatus, so that noise is liable to be introduced into a control circuit.
SUMMARY OF THE INVENTION
It is an object of the present invention to resolve the above-mentioned problems and to provide an output voltage detecting device in a laser oscillator, which is operable at a low voltage and inexpensive to manufacture.
In order to resolve the above-mentioned problems, the present invention provides an output voltage detecting device in a laser oscillator, including a matching circuit connected between a high frequency power supply unit and a laser tube, the matching circuit having reactance elements connected in parallel to a load of the matching circuit, the laser oscillator also comprising a current transformer for detecting a current flowing in a ground terminal of one of the reactance elements connected to an output terminal of the matching a voltage applied to the laser tube is detected on the basis of the current detected by the current transformer.
Since the current transformer is coupled to the ground terminal of the reactance element, the voltage induced in the current transformer is extremely low. In addition, the output voltage is given by the product of the current detected by the current transformer and the impedance of the parallel-connected reactance.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a block diagram showing one embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
One embodiment of the invention will be described with reference to a drawing.
FIG. 1 is a block diagram of one embodiment according to the present invention. In the figure, a high frequency power supply unit 1 supplies a high frequency voltage upon rectifying a current from a commercial power supply to provide a D.C. current and then converts it to the high frequency voltage using a high frequency inverter. A booster transformer 2 boosts the
REFERENCES:
patent: 4748634 (1988-05-01), Hesterman
WO-A-8 806 810 (Fanuc), Claim 7; FIG. 4 (PCT/JP88/00182).
Epps Georgia Y.
Fanuc Ltd
Sikes William L.
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