JP2017028235A - Short pulse laser light-emitting drive circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the following problem: a conventional short pulse laser light-emitting drive circuit generates series resonance and varies a voltage charged into a capacitor after a polarity of a charging current changes from a positive current to a negative current and varies an output current depending on a starting time of a control signal for lighting laser and hence variances occur in optical power of laser, improvements of which have been highly demanded.SOLUTION: A short pulse laser light-emitting drive circuit, capable of achieving a solution to the problem using a system of storing and discharging charges in/from a capacitor, includes a wiring portion constructed by connecting a circuit portion formed with an inductance and a resistor connected in parallel, in series to a diode and by connecting the capacitor with the circuit portion or the diode.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a current drive circuit of a short pulse laser light emitting device.

  In a distance measuring device and a laser processing machine using a laser, a semiconductor laser beam having a high output and a short duration is used. This short pulse laser beam requires a current drive circuit with a large current and a short pulse. The current drive circuit can generate a short pulse by turning on a semiconductor switch in a current path for a short time.

  However, it takes time to turn on and turn off a semiconductor switch that conducts a large current from an OFF state, and it is difficult to generate a desired short pulse. Therefore, a method has been devised in which the charge stored in the capacitor is started by turning on the semiconductor switch to start light emission of the laser diode or LED, and the light emission is stopped by eliminating the charge of the capacitor for high-speed discharge. . As a result, it is not necessary to turn off the semiconductor switch at high speed, and a pulse having a large current and a short width can be produced. This is disclosed in Patent Document 1 (Special Table 2009-554422).

  The circuit shown in FIG. 1 is a conventional circuit disclosed in Patent Document 1, and a resistor (7) is used in a circuit for charging a fast discharge capacitor (6). This is an example in which it is inefficient to store energy in the capacitor by receiving energy from a high voltage. The current / voltage waveforms at this time are shown in FIG. The dark hatched portion in FIG. 4 is a period in which the semiconductor switch is turned on in order to pass a current to the laser diode or LED (3), but it does not function at all to store electric charge in the capacitor. The power of the product of the current flowing over time generates resistance (7) and wastes power, and the resistance generates heat, so that it can be applied only to a circuit for low power. (In each drawing, the same number means the same thing.)

  Therefore, FIG. 2 shows that a current backflow prevention diode (9) and an inductor (8) are placed in place of the resistor (7), which is disclosed in Patent Document 1. If the current backflow prevention diode (9) is an ideal diode and the junction capacitance is sufficiently small, the current stops immediately after the polarity of the current flowing through the diode (9) changes, and the voltage applied to the semiconductor switch (4) is constant. become. The current voltage waveform in this case is shown in FIG. In FIG. 5, since the semiconductor switches of 100 nS to 150 nS and 500 nS to 550 nS on the time axis are in the ON state, the current linearly increases in the inductor (8) and the charge backflow prevention diode (9). Go. The dark hatched portion in FIG. 5 corresponds to that. The current flowing during this time is accumulated in the inductor (8). After the semiconductor switch is turned off, the inductor (8) and the high-speed discharge capacitor (6) perform series resonance, but when the current flowing through the charge backflow prevention diode (9) becomes negative, the current stops there. The thin hatched portion in FIG. 5 corresponds to this.

  However, when the junction capacitance of the current backflow prevention diode (9) becomes finite, series resonance occurs between the junction capacitance and the series combined capacitance of the high-speed discharge capacitor (6) and the inductor (8). The negative current due to the current fluctuation caused by the resonance does not flow to the charging diode (5) but flows to the laser (3), and there is a possibility that the laser emits light in an unintended manner. Further, this current fluctuation becomes a voltage fluctuation charged in the capacitor (6), and this voltage fluctuation induces a fluctuation of the current pulse according to the timing of the control signal for the next light emission. The current voltage waveform in this case is shown in FIG. The hatched portion shows the current fluctuation generated due to the junction capacitance of the charge backflow prevention diode.

  As an improvement measure, by inserting a resonance suppression resistor (10) in parallel with the inductor (8), the series resonance is suppressed while exhibiting the effect of adding the inductor (8) and the backflow prevention diode (9), and the charging current is reduced. It is possible to give a stable charging voltage to the high-speed discharge capacitor (6). FIG. 3 is a basic circuit diagram of the present invention.

  Special table 2009-554422

  As described above, the problem to be solved by the present invention is a circuit capable of flowing a large current (first problem), capable of generating a short pulse (second problem), and having a polarity of a charging current. After the change from positive to negative, that is, after the energy stored in the inductor (8) becomes zero, the series resonance occurs and the voltage charged to the capacitor becomes unstable (third problem) Is to prevent. Moreover, it is intended to prevent the possibility (fourth problem) that the laser (3) emits light at an unintended timing.

  As described above, the present invention uses the circuit of FIG. 3 as an example. By inserting the resonance suppression resistor (10) in parallel with the inductor (8), the series resonance is suppressed while the effect of adding the inductor (8) and the backflow prevention diode (10) is exhibited, thereby suppressing the fluctuation of the charging current. A stable charging voltage can be applied to the high-speed discharge capacitor (8). This is FIG. In general, for series resonance, a resistor is inserted in series and damped. That is, the series resonance suppression resistor (11) shown in FIG. However, in this case, as in the general case, if a damping resistor is inserted in series, the efficiency of charging the high-speed discharge capacitor (6) in the period from 150 nS to 250 nS in FIG. Although the voltage cannot be boosted, the present invention has an effect of not causing such a problem.

  The present invention is a short pulse laser emission driving circuit of a system for accumulating / discharging electric charges in a capacitor, wherein a circuit part in which an inductor and a resistor are arranged in parallel is connected in series with a diode, and the circuit part or the diode is connected with the circuit part. The present invention provides a short pulse light emission driving circuit including a wiring portion to which a capacitor is connected. For each of the connections, a direct connection or an indirect connection can be selected depending on the purpose and effect. For example, other components may be provided such as via a resistor for adjustment.

  Furthermore, the present invention provides the short pulse laser characterized in that the circuit part is connected directly or indirectly behind the diode and the capacitor is connected indirectly or directly behind the circuit part. A light emission driving circuit is provided.

  Further, the present invention provides the short pulse laser emission driving circuit, characterized in that one is directly or indirectly connected to a laser diode or LED and a power source is directly or indirectly connected to the other. The present invention provides a short pulse laser emission device including the short pulse laser emission drive circuit.

  In the present invention, the components used in the circuit can be those that are generally available, and appropriate components can be selected from the required performance. Further, the connection of each component may be a direct connection or an indirect connection via another component as described above unless otherwise specified, but it is possible to change within the scope of the object of the present invention. Is possible. In addition, each component to be used has an inductor (8) of 0.2 microhenry or more, and the resonance suppression resistor (10) is suitably in the range of 0.5 to 2 times the impedance of the inductor (8) at the resonance frequency. However, depending on the degree to which the fluctuation of the laser output is allowed, it can be set to be twice or more.

  As described above, the effect of the present invention is that, as described above, first, the voltage fluctuation is reduced and the fluctuation of the laser current due to the difference in the interval of the light emission timing is reduced. This has the effect of greatly improving the accuracy of the laser processing machine.

  Second, it prevents current from flowing through the laser when the charging current becomes negative. This means that the laser does not emit light at an unintended time. Light emission at an unintended time significantly degrades the accuracy of the laser processing machine and the distance measurement using the laser. The present invention can improve this.

  Third, since the voltage applied to the semiconductor switch (4) becomes constant, the semiconductor switch having a low withstand voltage can be used. That is, even if the same parts are used, a larger current can be passed through the laser. The breakdown voltage of the semiconductor switch (4) must be designed to be greater than or equal to the maximum value of the fluctuating voltage, but this restriction can be relaxed by the present invention.

  Fourthly, unnecessary radiation can be reduced. FIG. 9 shows the current voltage of each part of the circuit when a circuit having no resonance suppression resistor and having a low junction capacitance is selected as the charge backflow prevention diode. Although the voltage applied to the semiconductor switch is relatively constant, a high voltage high frequency is generated at the anode of the backflow prevention diode. The resistor connected in parallel to the inductor (8) in the present invention suppresses this unnecessary radiation.

  Therefore, the present invention can improve the drawbacks of the conventional circuit with a large current and short pulse emission, and can provide a circuit to which the various effects described above are added. That is, a high current pulse exceeding a switching speed exceeding GHz and exceeding 1 A is possible, and a preferable short pulse can be obtained.

  In addition to the above-described effects, the present invention has good charging efficiency, can reduce the amount of heat generation, and can reduce the voltage of the voltage source to be supplied. In addition, since the charging radio wave waveform is a waveform close to a half cycle of a sine wave, the charging current waveform of the conventional method has a shorter charging time than the exponential function waveform, and it is possible to increase the discharge repetition frequency. . Depending on the width of the control signal, the height of the pulse can also be adjusted.

FIG. 1 shows an example of a conventional basic circuit of Patent Document 1. FIG. 2 relates to the improvement of the conventional circuit in Patent Document 1. FIG. 3 is an example of a basic circuit of the present invention. FIG. 4 is a time waveform of the current voltage of the main part of FIG. FIG. 5 is a time waveform of the current voltage of the main part when the current backflow prevention diode in FIG. 2 is an ideal one. FIG. 6 is a time waveform of the current voltage of the main part when the current backflow prevention diode in FIG. 2 has a realistic junction capacitance. FIG. 7 is a time waveform of the current voltage of the main part of the circuit according to the present invention. FIG. 8 is a circuit diagram of Embodiment 2 of the present invention. FIG. 9 is a time waveform of the current voltage of the main part when the junction capacitance of the current backflow prevention diode in FIG. 2 is smaller than the actual junction capacitance.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 3 shows one embodiment of the present invention. The circuit has been described above.

  In this circuit, there is no problem even if the order of the pair of the charge backflow prevention diode (9), the inductor (8) and the resonance suppression resistor (10) arranged in parallel is reversed.

  The embodiment of FIG. 8 is a circuit example in which the laser or LED (3) is connected so as not to be included in the charging circuit, and the charging diode (5) of FIG. 3 is unnecessary. A resistor connected in parallel to the inductor of this circuit also exhibits the same effect as FIG.

  The present invention is used in industries for manufacturing short pulse laser light emitting devices.

2 Discharge current limiting resistor 3 Laser diode or LED
4 Semiconductor Switch 5 Charging Diode 6 High Speed Discharge Capacitor 7 Charging Current Limiting Resistor 8 Inductor 9 Charge Backflow Prevention Diode 10 Resonance Suppressing Resistor 11 Series Resonance Suppressing Resistor 12 Discharge Substrate Determining Resistor

Claims (5)

  A short pulse light emission driving circuit for storing and discharging electric charge in a capacitor, wherein a circuit part in which an inductance and a resistor are arranged in parallel is connected in series with a diode, and the capacitor is connected to the circuit part or the diode A short pulse laser emission driving circuit including a portion.   2. The short pulse laser emission drive circuit according to claim 1, wherein the circuit portion is directly connected to the rear of the diode, and the capacitor is connected to the rear of the circuit portion indirectly or directly.   3. The short pulse laser emission drive circuit according to claim 1 or 2, wherein one is connected to a laser diode or LED and the other is connected to a power source.   4. The short pulse laser emission driving circuit according to claim 1, wherein the laser diode or LED is directly connected to the capacitor, and the power source is directly connected.   A short pulse laser emission device comprising the short pulse laser emission drive circuit according to claim 4.

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