JPH04208583A - Controlling method for high frequency power source of laser - Google Patents

Abstract

PURPOSE:To widely set a laser processing condition and to perform an excellent processing by controlling ON, OFF a pulse oscillation by a high frequency inverter, and controlling a feedback by dividing to the times of ON and OFF of pulse oscillations by a switching circuit. CONSTITUTION:Since a feedback switching circuit 17 and an output pair voltage comparator 19 are provided in an output controller 7, when a command pulse is ON, an error signal between a command current compared by a comparator and an output current is passed through an electronic switch S3 to control a switching transistor Tr1 of a converter 3 through a PWM circuit. When the pulse is OFF, an error signal of an output voltage E2 of a converter compared by the comparator 19 is passed through an electronic switch S4 to similarly control the transistor Tr1. Thus, even if the ON, OFF of the pulse are controlled by the inverter, a feedback loop is normally operated. In this manner, a pulse of a rectangular wave having no unsharpness up to several kHz can be output, and hence a processing condition can be widely set to perform an excellent processing.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a method of controlling a high frequency power source for a laser.

(Prior Art) An example of a circuit of a conventional high frequency power source for a laser is shown in FIG. As shown in the figure, the conventional circuit includes a rectifier section 1, a converter section 3, a high frequency inverter section 5, an output control section 7, an output transformer T, a current sensor 9, a current signal generation section 11, and the like. The rectifier 1 rectifies and smoothes a commercial three-phase AC (200V) using a diode group D1 and a smoothing capacitor C1, and outputs a DC voltage E+ (approximately 250V).

The converter unit 3 converts the DC voltage E1 into a DC voltage E2 (0 to 200V pulse or continuous waveform) corresponding to the command current.
The switching transistor T22,
Feedback diode D2, choke coil, capacitor 0
It consists of 2nd class.

The switching transistors T, 1 are controlled by the output control section 7.
The switching frequency fs is generally between 10 KHz and 100 KHz.

The high frequency inverter section 5 converts the DC voltage E2 into a high frequency AC E3.
(Frequency fc is 100 KHz ~ 30 MH
2), and is composed of four switching transistors Tt2 to T79, a high frequency drive section 13, a high frequency oscillator 15, etc. The output of the high frequency inverter is connected to a load via an output transformer T.

The output current is detected by the current sensor 9 and converted into a feedback signal by the current signal generator 11. This signal is compared with the command current by a comparator in the output control section 7, and the error signal drives the PWM circuit, controls the switching transistor Tl+ of the converter section, and makes the output current match the command current.

(Problem to be solved by the invention) When drilling or cutting in laser processing,
Usually a pulsed laser is used. This is because pulsed lasers can heat up a narrow area more quickly than continuous lasers.

This pulse frequency fp is usually several tens to several KHz, and its duty ratio is also appropriately selected depending on the processing conditions.

When pulse oscillation is performed using the conventional high-frequency power supply circuit for a laser, the output voltage E2 of the converter section becomes as shown in Fig. 4(b) in response to a command current as shown in Fig. 4(a), and the output The current is as shown in figure (c). That is, the output current has a response delay with respect to the command current, and the waveform becomes irregular. If the waveform becomes dull, the effect of pulse processing will be reduced. The cause of this is due to the influence of the choke coil L and capacitor C2 of the converter section 3, and the response delay is several tens of thousands.
It becomes μs to 1ms.

On the other hand, the pulse frequency fp is several tens to several KHz as mentioned above.
For example, in the case of IKHz, the period is 1-m
s, which is comparable to the response delay described above. In reality, f
In a power source of c-2MHzS f 5 = 150KH2, if fp exceeds 500Hz, the waveform becomes rounded or large, and if fp exceeds IKHz, pulse oscillation becomes practically impossible.

This invention was created with attention to these points, and by making it possible to output square wave pulses without rounding up to several KHz, laser processing conditions can be set over a wide range.
It is an object of the present invention to provide a method of controlling a high frequency power source for a laser, which enables good processing.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, a method for controlling a high frequency power source for a laser according to the present invention provides a method for controlling a high frequency power source for a laser, which includes a converter section for output control and a high frequency inverter section. In the power supply, ON and OFF control of pulse oscillation is performed by a high-frequency inverter section, and feedback control is performed by a switching circuit that separates the ON and OFF states of the pulse oscillation. Sometimes, the output voltage of the converter section is controlled by comparing it with a predetermined predetermined voltage for the command current.

(Function) Since ON/OFF control of pulse oscillation is performed by the high frequency inverter section, there is almost no rounding in the waveform of the high frequency pulse of the output current. Feedback is pulse oscillation ON
When the pulse oscillation is ON, the output current is controlled to be the command current as in the past, and when the pulse oscillation is OFF, the output voltage of the converter section is controlled in advance to the command current in preparation for the next pulse ON. The current is controlled to a predetermined voltage.

(Example) Next, an example of the present invention will be described based on the drawings. FIG. 1 is a circuit diagram implementing the present invention. Rectifier part 1
, the converter section 3, the high frequency inverter section 5, and other main circuits are the same as the conventional circuit shown in FIG. The difference is that the output current and pulse commands are separated, but this is because the circuit for achieving the purpose of the invention becomes simpler. The next major difference is that in conventional circuits, the pulse output was controlled by the converter section, whereas in this circuit, the pulse output is controlled by the high frequency inverter section.

Next, control of this pulse output will be explained in detail. Frequency fc of high frequency oscillator 15 (100KHz to 30MHz
2) The carrier signal is sent to buffer B1 and inverted buffer B2.
The signal is divided into two-phase signals, which are supplied to the high-frequency drive section 13 through electronic switches s, , s2, respectively. The high-frequency drive section 13 drives the switching transistors T, 2 to Tr of the inverter circuit with this two-phase signal, and converts the DC voltage E2 supplied from the converter section 3 into a high-frequency AC signal with a frequency fc.

Electronic switches S1 and S2 are enabled only when a command pulse (which may be continuous) is ON, allowing two-phase signals to pass through. When the command pulse is OFF, no signal is sent to the high frequency drive unit 13, so all switching transistors in the inverter circuit are OFF and do not operate. Therefore, when the pulse command is ON, it operates as a normal inverter, and when the pulse command is OFF, it does not output, thereby enabling pulse control.

Next, the difference from the conventional circuit is that the output control section 7 is provided with a feedback switching circuit 17 and an output-to-voltage comparison circuit 19. The reason for this is that when the command current and the output current are compared with a comparator and the feedback control is performed using the error signal, it is good when ON, but when the output current is 0 when OFF, the error signal becomes large, and the output of converter section 3 Voltage E2 increases more than necessary. Therefore, in this circuit, the feedback is the output current and the converter output voltage.
System, switch by ON/OFF of pulse, O
The output voltage E2 of the converter section 3 is controlled to an appropriate value even during FF operation.

The electronic switch S3 of the feedback switching circuit 17 is enabled when the command pulse is ON, and the electronic switch S4 is enabled and allows the signal to pass when the command pulse is OFF. One output-to-voltage comparison circuit stores a predetermined appropriate output voltage (predetermined voltage) of the converter for a specified current, and compares this with the converter output voltage E2 detected by the voltage detector. It compares and outputs the error signal.

Therefore, when the command pulse force is ON, the error signal between the command current and the output current, which are compared by the comparator, passes through the electronic switch S3 and the switching transistor TI of the converter section 3 via the PWM circuit. Control. Further, when the command pulse is OFF, an error signal of the output voltage E2 of the converter compared by the output-to-voltage comparison circuit 19 passes through the electronic switch S4, and similarly controls the switching transistor TI. In this way, the feedback loop operates normally even if the pulse is controlled on and off using an inverter.

The pulse waveform of the output current from this circuit is shown in Figure 2 (b).
The result is as follows, and there is very little waveform distortion. this is,
This is because the response delay caused by transistors, electronic switches, etc. in the high frequency inverter section is so small that it can be ignored with respect to the pulse frequency fp.

[Effects of the Invention] As can be understood from the above description, since the present invention has the configuration described in the claims, it is possible to output square wave pulses with no rounding up to several KHz. therefore,
It is possible to provide a method of controlling a high frequency power source for a laser, which allows a wide range of processing conditions to be set and allows for good processing.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram implementing the present invention, Figure 2 (a) is the command pulse waveform (including continuous waveforms), Figure 2 (b) is the output current waveform from the circuit in Figure 1, and Figure 3 is the conventional 4(a) is the command current waveform, FIG. 4(b) is the waveform of the converter output voltage E2 from the circuit of FIG. 3, and FIG. 4(c) is the same as the output current waveform. It is a waveform. Agent Patent Attorney Hidekazu Miyoshi

Claims (1)

[Claims] Turns pulse oscillation on and off in a laser power supply equipped with a converter section for output control and a high frequency inverter section.
Control is performed by a high-frequency inverter section, and feedback control is performed by dividing the pulse oscillation into ON and OFF times using a switching circuit. When ON, the output current is compared with the command current, and when OFF, the output voltage of the converter section is controlled by comparing it with the command current. A method for controlling a high frequency power source for a laser, characterized in that control is performed by comparing the voltage with a predetermined voltage.