JP2011199079A - Excitation light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excitation light source device capable of determining whether a laser diode fails in a short-circuit mode or an open mode by a simple configuration.SOLUTION: An excitation light source device 1 comprises an excitation light source circuit 20 in which a plurality of laser diodes LD1 to LDn are connected in series and the laser diodes LD1 to LDn are connected in parallel with the bypass circuits BP1 to BPn, respectively, whose drop voltages are larger than those of the laser diodes LD1 to LDn, a constant voltage source 10 connected to one side of the excitation light source circuit 20, a constant current circuit 30 connected to the other side of the excitation light source circuit 20, and a fault detection circuit 40 that detects a fault of the laser diode based on a change in the drop voltage of the excitation light source circuit 20 as a whole.

Description

  The present invention relates to an excitation light source device.

  A fiber laser device is known as one of laser devices used in the fields of processing machines, medical equipment, measuring instruments, and the like. In a fiber laser device, seed light with relatively low power output from an oscillator or the like is generally amplified by pumping light output from a pumping light source and output as output light. And in the fiber laser apparatus used for a processing machine, a medical device, a measuring instrument, etc., in order to obtain output light with strong power, excitation light with strong power is often required. In order to obtain excitation light having such strong power, excitation light is generally output from a plurality of laser diodes.

  Several methods for detecting this laser diode failure have been proposed. In the failure detection method for a laser diode described in Patent Document 1 below, the voltage between the anode and cathode of the laser diode is detected on the assumption that the failure of the laser diode is a failure due to the short mode. And when this voltage falls below a predetermined voltage, it is assumed that the laser diode has failed due to the short mode. Further, in the laser diode failure detection method described in Patent Document 2, a bypass circuit is connected in parallel to each of the plurality of laser diodes connected in series, and further, between the anode and cathode of each laser diode. Detect voltage. Based on the detected voltage, when each laser diode fails in the open mode, the failure is detected.

Japanese Patent Laid-Open No. 2001-168552 JP 2005-57036 A

  However, in the laser diode failure detection methods described in Patent Documents 1 and 2, only the failure detection in the short mode or the failure detection in the open mode is performed, and further, the voltage of each laser diode is detected. It was necessary and the configuration was complicated.

  Therefore, an object of the present invention is to provide an excitation light source device that can detect a failure with a simple configuration, regardless of whether the laser diode fails in the short mode or in the open mode.

  In the excitation light source device of the present invention, a plurality of laser diodes are connected in series, and each of the laser diodes is connected in parallel with a bypass circuit having a larger voltage drop than the laser diode, A constant voltage source connected to one side of the excitation light source circuit, a constant current circuit connected to the other side of the excitation light source circuit, and the laser diode based on a change in the voltage drop across the excitation light source circuit. And a failure detection circuit for detecting a failure.

  According to such an excitation light source device, a constant voltage is applied to the excitation light source circuit by the constant voltage source, and a constant current flows through the constant current circuit. Therefore, when one of the laser diodes fails due to the short mode, the voltage drop across the entire excitation light source circuit is reduced. On the other hand, when one of the laser diodes fails due to the open mode, the voltage drop across the excitation light source increases due to the resistance of the bypass circuit connected in parallel with the failed laser diode. Therefore, the failure detection circuit detects the failure of the laser diode based on the change in the voltage drop across the excitation light source circuit, so that it is not necessary to provide a failure detection circuit for each laser diode, and with a simple configuration, Even when the laser diode fails in the short mode or in the open mode, the failure can be detected.

  In the excitation light source device, the constant current circuit includes a current control element connected in series with the excitation light source circuit, and the failure detection circuit detects the voltage of the current control element, thereby It is preferable to detect a failure of the laser diode based on a change in the voltage drop across the entire excitation light source circuit.

  According to such an excitation light source device, it is not necessary to directly detect the voltage drop across the entire excitation light source circuit, and it is possible to easily detect a failure of the laser diode based on the change in the voltage drop across the excitation light source circuit. .

  The excitation light source device further includes a determination circuit that determines whether the laser diode has failed in an open mode or a short mode based on a change in a voltage drop across the entire excitation light source circuit. Is preferred.

  According to such an excitation light source device, it is possible to easily know whether the laser diode has failed in the open mode or the short mode, based on the result of the determination circuit.

  In the excitation light source device, a difference between a forward voltage drop of the laser diode and a voltage drop of a bypass circuit connected in parallel with the laser diode is determined by the laser diode and the bypass circuit connected in parallel to each other. Preferably, the determination circuit identifies a failed laser diode based on a change in the voltage drop across the entire excitation light source circuit when the failure mode is an open mode. .

  According to such an excitation light source device, when the laser diode fails in the open mode, the drop voltage of the entire excitation light source circuit varies depending on the location of the failed laser diode. Therefore, when a laser diode fails in the open mode, it is easy to know which laser diode has failed in the open mode based on the result of the decision circuit based on the change in the voltage drop across the entire excitation light source circuit. Can do.

  In the excitation light source device, each of the bypass circuits includes a diode and a resistor connected in series with each other, and each of the diodes has the same forward voltage drop, and It is preferable that the forward drop voltage is higher than that of the laser diode connected in parallel with the diode, and that each of the resistors has a different resistance value for each of the bypass circuits.

  According to such an excitation light source device, since the diode having a higher forward voltage drop than the laser diode does not flow current to the bypass circuit unless the laser diode fails in the open mode, is the excitation light source circuit normal? It is possible to determine whether a failure has occurred. In addition, when a failure occurs in the open mode, it is possible to specify which laser diode has failed by the voltage drop of the bypass circuit, so it is possible to identify the laser diode that has failed in the open mode with a simple configuration. it can.

  In the excitation light source device, the laser diodes may have the same forward voltage drop.

  As described above, according to the present invention, there is provided an excitation light source device that can detect a failure with a simple configuration even when the laser diode fails in the short mode or in the open mode.

It is a figure which shows the excitation light source device which concerns on this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of an excitation light source device according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing an excitation light source device of the present invention. As shown in FIG. 1, the excitation light source device 1 includes an excitation light source circuit 20, a constant voltage source 10 connected to one side of the excitation light source device 20, and a constant current circuit connected to the other side of the excitation light source device 20. 30 and a failure detection circuit 40 for detecting a failure of the excitation light source circuit 20 as main components.

  The constant voltage source 10 is composed of a DC-DC converter, for example, and outputs a constant voltage Vcc.

  The excitation light source circuit 20 has a plurality of excitation light output laser diodes LD1 to LDn, and the laser diodes LD1 to LDn are connected in series. The number of laser diodes is, for example, six. The laser diodes LD1 to LDn have the same configuration and the same forward voltage drop.

  A bypass circuit BP1 including a diode D1 and a resistor R1 is connected in parallel to the laser diode LD1. In this bypass circuit BP1, the cathode of the diode D1 and the resistor R1 are connected, the anode of the diode D1 is connected to the anode of the laser diode LD1, and the side opposite to the side connected to the diode D1 of the resistor R1 is the laser. It is connected to the cathode of the diode LD1. A similar bypass circuit is connected in parallel to the laser diodes LD2 to LDn, and a bypass circuit BPn including a diode Dn and a resistor Rn is connected in parallel to the laser diode LDn. In this bypass circuit BPn, the cathode of the diode Dn and the resistor Rn are connected, the anode of the diode Dn is connected to the anode of the laser diode LDn, and the side opposite to the side connected to the diode Dn of the resistor Rn is the laser. It is connected to the cathode of the diode LDn.

  Note that the diodes D1 to Dn in the respective bypass circuits have the same forward voltage drop and higher forward voltages than the laser diodes LD1 to LDn. Further, the resistors R1 to Rn have different resistance values. Therefore, each of the bypass circuits BP1 to BPn has a different drop voltage. In this way, the respective laser diodes LD1 to LDn have the same forward voltage drop, and the respective bypass circuits BP1 to BPn have different voltage drops, so that the forward voltage drops of the laser diodes LD1 to LDn. And the voltage drop of the bypass circuits BP1 to BPn connected in parallel to the laser diodes LD1 to LDn have different values for each combination of the laser diode and the bypass circuit connected in parallel to each other. .

  The constant current circuit 30 includes a current control element Tr, a resistor Rs connected to the current control element Tr, a comparison circuit Op connected to the current control element Tr and the resistor Rs, and a predetermined reference voltage Vth to the comparison circuit Op. A reference voltage source 31 to be applied is provided as a main configuration.

  The current control element Tr is configured by an active element having a switching function, such as a bipolar transistor or a field effect transistor (FET). When the current control element Tr is a bipolar transistor, the collector of the current control element Tr is connected to the excitation light source circuit 20, and when the current control element Tr is an FET, the drain of the current control element Tr is excited. Connected to the light source circuit 20.

  One side of the resistor Rs is connected to the side opposite to the side connected to the excitation light source circuit 20 of the current control element Tr. Therefore, when the current control element Tr is a bipolar transistor, one side of the resistor Rs is connected to the emitter, and when the current control element Tr is an FET, it is connected to the source. The other side of the resistor Rs is connected to the ground.

  The comparison circuit Op has a set of input terminals and an output terminal. One input terminal is connected in parallel to the resistor Rs with respect to the current control element Tr, and the other input terminal is connected to the reference voltage. Connected to the source 31. The output terminal is connected to the current control element Tr so that the current control element Tr can be controlled. Therefore, the output terminal is connected to the base when the current control element Tr is a bipolar transistor, and is connected to the gate when the current control element Tr is an FET. As such a comparison circuit Op, for example, an operational amplifier can be used.

  The failure detection circuit 40 includes a voltage detection circuit 41 and a determination circuit 42 as main components. The voltage detection circuit 41 is connected in parallel to the current control element Tr of the constant current circuit 30, and detects the voltage (inter-terminal voltage) Vtr of the current control element Tr. When the current control element Tr is a bipolar transistor, the voltage detection circuit 41 is connected to the collector and the emitter, and detects the collector-emitter voltage of the current control element Tr. Further, when the current control element Tr is an FET, the voltage detection circuit 41 is connected to the drain and the source, and detects the drain-source voltage of the current control element Tr.

  The voltage detection circuit 41 outputs a signal corresponding to the detected inter-terminal voltage Vtr to the determination circuit 42. The determination circuit 42 is composed of, for example, a memory and a microcomputer. The memory stores information based on the voltage Vtr between the terminals of the current control element Tr when the excitation light source circuit 20 is in a normal state, and current control when any laser diode of the excitation light source circuit 20 fails in the short mode. Information based on the inter-terminal voltage Vtr of the element Tr and the current when each laser diode fails for each of the laser diodes LD1 to LDn when any laser diode of the pumping light source circuit 20 fails in the open mode. Information based on the inter-terminal voltage Vtr of the control element Tr is stored. And based on the signal output from the voltage detection circuit 41, the state of the excitation light source circuit 20 is determined, and the determination result is output.

  Next, the operation of the excitation light source device 1 will be described.

  When a predetermined voltage Vcc is applied from the constant voltage source 10 to the excitation light source circuit 20, when the excitation light source circuit 20 is in a normal state, the respective laser diodes LD1 to LDn of the excitation light source circuit 20 emit light and the excitation light. Is output. Then, voltage drops due to the respective laser diodes LD1 to LDn, the current control element Tr, and the resistor Rs are generated, and finally grounded. At this time, the comparison circuit Op compares the potential between the current control element Tr and the resistor Rs with the reference voltage Vth applied from the reference voltage source 31 so that the current flowing through the current control element Tr becomes constant. The current control element Tr is controlled. Thus, a constant current Ild flows through the pumping light source circuit 20 connected in series with the constant current circuit 30, and each of the laser diodes LD1 to LDn outputs a predetermined optical power.

Further, the voltage detection circuit 41 of the failure detection circuit 40 detects the inter-terminal voltage Vtr of the current control element Tr. In the normal state of the excitation light source circuit 20 as described above, when the forward voltage drop of each laser diode is Vld, the voltage Vtr between the terminals of the current control element Tr is as follows.

  As described above, since the forward voltage drop of each laser diode LD1 to LDn is the same, the voltage drop of each laser diode can be set to the same value Vld. Then, the voltage detection circuit 41 outputs a signal corresponding to the detected inter-terminal voltage Vtr of the current control element Tr to the determination circuit 42. The determination circuit 42 refers to the table included in the determination circuit 42, determines that the excitation light source circuit 20 is normal if Vtr is a normal voltage, and outputs the determination result.

When any of the laser diodes LD1 to LDn fails in the short mode, the forward drop voltage of the failed laser diode becomes almost zero. Accordingly, the inter-terminal voltage Vtr of the current control element Tr in this case is as follows.

  In this case, the inter-terminal voltage Vtr is higher by Vld than when the excitation light source circuit 20 is normal. Then, the voltage detection circuit 41 outputs a signal corresponding to the detected inter-terminal voltage Vtr of the current control element Tr to the determination circuit 42. At this time, the determination circuit 42 refers to the table included in the determination circuit 42 and the inter-terminal voltage Vtr is higher than the normal voltage, so that the excitation light source circuit 20 has failed in the short mode. This determination result is output.

When any of the laser diodes LD1 to LDn fails in the open mode, no current flows through the failed laser diode. For this reason, a current flows through a bypass circuit connected in parallel with the failed laser diode. For example, when the laser diode LDn fails in the open mode, a current flows through the bypass circuit BPn. At this time, when the forward voltage drop of the diode Dn in the bypass circuit BPn is Vd and the resistance value of the resistor Rn is Rn, the voltage drop of the bypass circuit BPn is as follows.

Accordingly, the inter-terminal voltage Vtr of the current control element Tr in this case is as follows.

As described above, since the forward voltage drop of each of the diodes D1 to Dn is the same, the voltage drop caused by the diode can be set to the same value Vd when any laser diode fails. Further, the value of the inter-terminal voltage Vtr varies depending on the resistance value Rn of the resistor Rn. That is, the difference between the forward drop voltage Vld of the failed laser diode LDn and the drop voltage of the bypass circuit BPn connected in parallel to the failed laser diode LDn is as follows among the expressions representing the inter-terminal voltage Vtr: become.

  This value is different for each combination of the laser diode and the bypass circuit connected in parallel to each other because the resistance values of the resistors R1 to Rn are different. Accordingly, the voltage Vtr between the terminals of the current control element Tr varies depending on the location of the laser diode that has failed in the open mode. Then, the voltage detection circuit 41 outputs a signal corresponding to the detected inter-terminal voltage Vtr of the current control element Tr to the determination circuit 42. At this time, the determination circuit 42 refers to the table included in the determination circuit 42 to determine that the excitation light source circuit 20 has failed in the open mode, and that the laser diode LDn has failed. Make a decision and output the decision result.

  In this way, the failure detection circuit 40 detects the failure of the laser diodes LD1 to LDn based on the change in the voltage drop across the excitation light source circuit 20 by detecting the voltage Vtr between the terminals of the current control element Tr. .

  As described above, according to the excitation light source device 1 according to the present embodiment, the constant voltage source 10 applies the constant voltage Vcc to the excitation light source circuit 20, and the constant current circuit 30 generates the constant current Vld. Flowing. Therefore, when any of the laser diodes LD1 to LDn fails in the short mode, the voltage drop across the pumping light source circuit 20 is reduced. On the other hand, when one of the laser diodes LD1 to LDn fails in the open mode, the voltage drop across the excitation light source circuit 20 increases due to the voltage drop in the bypass circuit connected in parallel with the failed laser diode. Therefore, the failure detection circuit 40 detects the failure of the laser diode based on the change in the voltage drop across the entire excitation light source circuit 20, so that it is not necessary to provide a failure detection circuit for each of the laser diodes LD1 to LDn. With a simple configuration, it is possible to detect a failure even when the laser diode fails in the short mode or in the open mode.

  Further, the failure detection circuit 40 does not need to directly detect the voltage of the entire excitation light source circuit 20 by detecting the voltage Vtr between the terminals of the current control element Tr, and can easily reduce the voltage drop across the excitation light source circuit 20. A laser diode failure can be detected based on the change.

  Further, the user of the excitation light source device 1 can easily know from the result of the determination circuit 42 whether the laser diode has failed in the open mode or the short mode.

  Further, the difference between the forward voltage drop of the laser diodes LD1 to LDn and the voltage drop of the bypass circuits BP1 to BPn connected in parallel to the laser diodes LD1 to LDn is the laser diode LD1 to LD1 connected in parallel to each other. Since each of the combinations of the LDn and the bypass circuits BP1 to BPn has a different value, when any laser diode fails in the open mode, the entire pumping light source circuit 20 drops depending on the location of the failed laser diode. The voltage changes. Therefore, when any laser diode fails in the open mode, which laser diode fails in the open mode according to the result of the determination circuit 42 based on the change in the voltage drop across the excitation light source circuit 20. Can be easily known.

  Further, due to the diodes D1 to Dn having higher forward drop voltages than the laser diodes LD1 to LDn, no current flows through the bypass circuits BP1 to BPn unless the laser diodes LD1 to LDn fail in the open mode. Therefore, it can be determined whether the excitation light source circuit 20 is normal or has failed. In addition, when a failure occurs in the open mode, it is possible to identify which laser diode has failed due to the resistance of the bypass circuit, so it is possible to identify the failed laser diode in the open mode with a simple configuration. .

  As mentioned above, although this invention was demonstrated to the example for embodiment, this invention is not limited to these.

  For example, in the above-described embodiment, the failure of the laser diode is detected based on the change in the voltage drop across the excitation light source circuit 20 by detecting the voltage of the current control element Tr. May be detected directly, and a failure of the laser diode may be detected based on a change in the voltage drop across the pumping light source circuit 20 as a whole.

  In the above embodiment, the failure mode of the laser diodes LD1 to LDn is determined by the determination circuit 42. Further, when any laser diode fails in the open mode, the determination circuit 42 determines which laser. It was judged whether the diode failed. However, the determination circuit 42 is not necessarily essential, and the failure detection circuit 40 may be configured to output only a failure based on the output result of the voltage detection circuit 41. In this case, the user of the excitation light source device may determine the failure mode based on the output result of the voltage detection circuit 41 or specify the failed laser diode when the laser diode fails in the open mode. In this case, the configuration can be simplified because the determination circuit 42 is not provided.

  Further, the diodes D1 to Dn of the bypass circuits BP1 to BPn may be Zener diodes, the anode of the Zener diode and the resistor are connected, and the cathode of the Zener diode may be connected to the anode of the laser diode. . In this case, a Zener break may be generated when the laser diode fails in the open mode.

  Alternatively, the diodes D1 to Dn of the respective bypass circuits BP1 to BPn may have different forward drop voltages, and the resistors R1 to Rn of the respective bypass circuits BP1 to BPn may be omitted.

  In the above embodiment, the forward drop voltages of the laser diodes LD1 to LDn are the same. However, the forward drop voltages of the laser diodes LD1 to LDn may be different from each other. In this case, the difference between the drop voltage of the laser diodes LD1 to LDn and the drop voltage of the bypass circuits BP1 to BPn connected in parallel with the laser diodes LD1 to LDn is the difference between the laser diodes LD1 to LDn connected in parallel with each other. It is preferable to set a different value for each combination with the bypass circuits BP1 to BPn. By doing so, even if the forward voltage drop of each of the laser diodes LD1 to LDn is different from each other, if any of the laser diodes LD1 to LDn is broken in the open mode, it depends on the location of the broken laser diode. The magnitude of the change in the voltage drop across the excitation light source circuit 20 changes. Therefore, it is possible to identify which laser diode is broken based on the change in the voltage drop across the excitation light source circuit 20.

  According to the present invention, there is provided an excitation light source device that can detect a failure with a simple configuration, regardless of whether the laser diode fails in the short mode or in the open mode.

DESCRIPTION OF SYMBOLS 1 ... Excitation light source device 10 ... Constant voltage source 20 ... Excitation light source circuit 30 ... Constant current circuit 31 ... Reference voltage source 40 ... Fault detection circuit 41 ... Voltage detection circuit 42 ... Judgment circuit BP1 to BPn ... Bypass circuit D1 to Dn ... Diode LD1 to LDn ... Laser diode Op ... Comparison circuit R1 to Rn, Rs ... Resistor Tr ... Current control element

Claims (6)

A plurality of laser diodes are connected in series, and each of the laser diodes is connected in parallel with a bypass circuit having a larger voltage drop than the laser diode;
A constant voltage source connected to one side of the excitation light source circuit;
A constant current circuit connected to the other side of the excitation light source circuit;
A failure detection circuit for detecting a failure of the laser diode based on a change in the voltage drop across the excitation light source circuit;
An excitation light source device comprising: The constant current circuit has a current control element connected in series with the excitation light source circuit,
The failure detection circuit detects a failure of the laser diode based on a change in a voltage drop across the excitation light source circuit by detecting a voltage of the current control element. Excitation light source device.   The determination circuit according to claim 1, further comprising: a determination circuit configured to determine whether the laser diode has failed in an open mode or a short mode based on a change in a voltage drop across the excitation light source circuit. 2. The excitation light source device according to 2. The difference between the forward voltage drop of the laser diode and the voltage drop of the bypass circuit connected in parallel with the laser diode is different for each combination of the laser diode and the bypass circuit connected in parallel with each other. ,
4. The excitation according to claim 3, wherein when the failure mode is an open mode, the determination circuit identifies a failed laser diode based on a change in a voltage drop across the excitation light source circuit. Light source device. Each of the bypass circuits is composed of a diode and a resistor connected in series with each other,
Each of the diodes has the same forward drop voltage as each other, and a higher forward drop voltage than the laser diode connected in parallel with each of the diodes,
The excitation light source device according to claim 4, wherein each of the resistors has a different resistance value for each of the bypass circuits.   6. The excitation light source device according to claim 1, wherein each of the laser diodes has the same forward voltage drop. 6.

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