JP7197422B2 - power supply - Google Patents

Description

The present invention relates to a power supply for a laser diode for supplying a commanded current to the laser diode.

As described in Patent Document 1, in a power supply device for a laser diode, a plurality of step-down converter circuits (hereinafter referred to as step-down circuits) having switching elements are connected in parallel, and the current output from each step-down circuit is There is a configuration in which the signals are combined and supplied to the laser diode. In such a configuration, a current having a value of (1/the number of step-down circuits) generated by each step-down circuit is output by shifting the timing at which the switching element turns on by (switching period/the number of step-down circuits). This makes it possible to reduce the ripple current and allow a constant current to flow through the laser diode.

JP-A-2001-286059

However, the above-described prior art could not sufficiently reduce the ripple current.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a power supply device capable of reducing the ripple current of the current flowing through a laser diode.

An aspect of the present invention is a power supply device for a laser diode for supplying current to the laser diode, comprising N current generation circuits connected in parallel and provided with switching elements, for converting an input DC voltage into an output DC voltage. A command output voltage is determined from a command current value using a conversion circuit that converts the current into a current and supplies the output DC current to the laser diode, and a current-voltage characteristic that indicates the relationship between the current and voltage of the laser diode. a command output voltage determination unit; an on-duty storage unit storing an on-duty dependent on the N of the switching element capable of suppressing the ripple current flowing through the laser diode to a predetermined value or less; the on-duty; a command input voltage determination unit that determines a command input voltage based on the command output voltage; and an input voltage that generates the input DC voltage by converting an AC voltage supplied from an AC power supply into a DC voltage of the command input voltage. and an adjustment circuit.

According to the present invention, it is possible to reduce the ripple current of the current flowing through the laser diode.

1 is a schematic configuration diagram of a power supply device according to a first embodiment; FIG. 3 is a diagram showing a circuit configuration of a current generating circuit; FIG. FIG. 4 is a diagram showing signal patterns of respective parts of the current generating circuit; 7 is a graph showing the relationship between on-duty for each N and ripple current; 4 is a table showing an input DC voltage (Vin) corresponding to an on-duty for each N and an output DC voltage (Vout); 4 is a flowchart for explaining control of the power supply device according to the first embodiment; 2 is a schematic configuration diagram of a power supply device in a second embodiment; FIG. 9 is a flowchart for explaining control of the power supply device according to the second embodiment; FIG. 11 is a schematic configuration diagram of a power supply device according to a third embodiment; 10 is a flowchart for explaining control of the power supply device according to the third embodiment;

BEST MODE FOR CARRYING OUT THE INVENTION A power supply device according to the present invention will be described in detail below with preferred embodiments and with reference to the accompanying drawings.

[First embodiment]
FIG. 1 is a schematic configuration diagram of a power supply device 10 according to the first embodiment. The power supply 10 is a laser diode power supply for supplying a current to the laser diode 14 according to a command current value given from an external controller (not shown) based on the power supplied from the AC power supply 12 . be.

The power supply device 10 includes a capacitor 16, a conversion circuit 18, a command output voltage determination unit 20, a command input voltage determination unit 22, an input voltage adjustment circuit 24, an on-duty storage unit 26, and a current-voltage characteristic storage unit. 28 , a current detection unit 30 and a control unit 34 .

The input voltage adjustment circuit 24 converts the AC voltage supplied from the AC power supply 12 into the DC voltage of the command input voltage (Vin') determined by the command input voltage determination unit 22 as described later, and converts the input DC voltage (Vin ). An input DC voltage (Vin) output from the input voltage adjustment circuit 24 is smoothed by the capacitor 16 and input to the conversion circuit 18 .

The conversion circuit 18 has N current generation circuits 40 connected in parallel and provided with switching elements. N is an integer of 2 or more. The conversion circuit 18 converts the input DC voltage (Vin) into an output DC current and supplies the laser diode 14 with the output DC current. An output DC voltage (Vout) is generated across the laser diode 14 by supplying the output DC current to the laser diode 14 .

The control unit 34 is a control circuit that controls the N current generation circuits 40 so that the difference between the command current value given from the external controller and the current detection value detected by the current detection unit 30 becomes small. Specifically, the control unit 34 sets a value obtained by correcting (command current value/N) as the target current value so that the difference between the command current value and the current detection value detected by the current detection unit 30 becomes small. output to the current generating circuits 40. In addition, the control unit 34 generates N currents so that the timings (phases) at which the switching elements of the N current generation circuits 40 are turned on are shifted by a value (T/N) equal to the switching period T divided by N. Control circuit 40;

FIG. 2 is a diagram showing the circuit configuration of the current generating circuit 40. As shown in FIG. The current generation circuit 40 has an input terminal X1 connected to the positive terminal of the input voltage adjustment circuit 24, an input terminal X2 connected to the negative terminal of the input voltage adjustment circuit 24, and an output terminal Y1 connected to both ends of the laser diode 14. , Y2, switching elements SW1 and SW2, a coil L, an individual current detector 42, and a controller 46. The input terminal X2 and the output terminal Y2 are short-circuited.

A switching element SW1 is connected between the input terminal X1 and the terminal X, and a switching element SW2 is connected between the terminal X and the input terminal X2 (output terminal Y2). Furthermore, a coil L and an individual current detector 42 are connected in series between the terminal X and the output terminal Y1. The switching elements SW1 and SW2 are controlled to be on or off at a constant period T by the controller 46. FIG. The switching elements SW1 and SW2 are switched so that ON and OFF are opposite to each other. When the switching element SW1 is on (switching element SW2 is off), current flows along the current path 48a, and when the switching element SW1 is off (switching element SW2 is on), current flows along the current path 48b. flow.

FIG. 3 is a diagram showing signal patterns of each part of the current generation circuit 40. As shown in FIG. All horizontal axes are time. As described above, the ON/OFF operations of the switching elements SW1 and SW2 are opposite to each other, as shown in "state of SW1" and "state of SW2". Assuming that the ON time of the switching element SW1 in the period T is ton, the individual on-duty Don1 of the switching element SW1 is defined by ton/T. Therefore, the individual on-duty Don2 of the switching element SW2 is 1-Don1. The relationship between the input DC voltage (Vin), which is the voltage between the input terminals X1 and X2, and the output DC voltage (Vout), which is the voltage between the output terminals Y1 and Y2, is Vout=Don1×Vin. .

The controller 46 of the current generation circuit 40 controls the values of the individual on-duties Don1 and Don2 so that the output current supplied by the current generation circuit 40 to the laser diode 14 becomes the target current value commanded by the control unit 34. do.

As shown in FIG. 3, "voltage of terminal X" indicates time change of voltage of terminal X, "current of SW1" indicates time change of current flowing through switching element SW1, and "current of SW2" indicates switching element SW1. FIG. 4 shows temporal changes in the current flowing through the element SW2. As a result, the current flowing through the coil L varies with time as indicated by "L current". Here, I0 is the average value of the current flowing through the coil L. The current flowing through the coil L is the output current that one current generation circuit 40 supplies to the laser diode 14 .

Further, the controller 46 of the current generating circuit 40 is controlled by the control unit 34 to control the timing of turning on the switching element SW1 (turning off the switching element SW2). The control unit 34 controls the controllers 46 of the current generation circuits 40 so that the switching elements SW1 of the N current generation circuits 40 are turned on (the switching elements SW2 are turned off) at different timings separated by T/N. to control. Therefore, the output direct current flowing through the laser diode 14 is N currents in which the phases of the "L current" waveform in FIG. 3 are shifted by T/N.

The current-voltage characteristic storage unit 28 stores previously acquired current-voltage characteristics indicating the relationship between the current and voltage of the laser diode 14 . The current-voltage characteristics stored in the current-voltage characteristics storage unit 28 are characteristics measured in advance for the laser diode 14, but may be average characteristics obtained from a plurality of laser diodes.

The command output voltage determination unit 20 obtains a voltage value corresponding to the command current value given from the external controller in the current-voltage characteristics stored in the current-voltage characteristics storage unit 28, and converts the voltage value into the command output voltage ( Vout').

The on-duty storage unit 26 stores an on-duty Don0 that serves as a reference value for the individual on-duty Don1 of the switching element SW1 of the current generation circuit 40 . The on-duty Don0 is a value that depends on the number N of current generation circuits 40 . The on-duty Don0 is a value that can suppress the ripple current flowing through the laser diode 14 to a predetermined value or less, and can be expressed as on-duty Don0=M/N (M is a natural number less than N). That is, for a given N, one value selected in advance from a plurality of values 1/N, 2/N, . A value of on-duty Don0 is stored in the on-duty storage unit 26 .

FIG. 4 is a graph showing the relationship between the on-duty for each N and the ripple current. The horizontal axis is on-duty and the vertical axis is ripple current. For example, when N=3, by selecting one of a plurality of values of 33.3 . can be suppressed.

FIG. 5 is a table showing the input DC voltage (Vin) corresponding to the on-duty for each N and the output DC voltage (Vout). For example, when N=3 and Vout=100V, when Vin=300V, ON-duty Don0=33.3..% is selected and stored in the ON-duty storage unit 26. When Vin=150V, On-duty Don0=66.6 . In the case of N=3 and Vout=200V, if Vin=600V, on-duty Don0=33.3..% is selected and stored in the on-duty storage unit 26. If Vin=300V, On-duty Don0=66.6 .

The command input voltage determination unit 22 determines the command input voltage (Vin' ). Specifically, the command input voltage determination unit 22 determines the command input voltage (Vin') according to the relational expression Vin'=Vout'/Don0.

The current detector 30 is provided between the output terminal Y2 and the negative electrode of the laser diode 14 and detects the current flowing through the laser diode 14 . The current detector 30 may be provided between the output terminal Y1 and the positive electrode of the laser diode 14 .

FIG. 6 is a flow chart illustrating control of the power supply device 10 in the first embodiment.

First, the command output voltage determination unit 20 obtains the voltage value that becomes the command current value in the current-voltage characteristics stored in the current-voltage characteristics storage unit 28, and determines the voltage value as the command output voltage (Vout'). (step S1).

Next, the command input voltage determination unit 22 determines the command input voltage (Vin' ) is determined (step S2).

Next, the input voltage adjustment circuit 24 converts the AC voltage supplied from the AC power supply 12 into the DC voltage of the command input voltage (Vin') determined in step S2 to generate the input DC voltage (Vin). (Step S3). After step S3, the process returns to step S1.

As described above, according to the power supply device 10 of the first embodiment, the ripple current can be suppressed to a predetermined value or less by the on-duty depending on the given number N of the current generation circuits 40 .

The on-duty storage unit 26 may store a plurality of on-duty values that satisfy Don0=M/N (M is a natural number less than N), and the user can select from a plurality of on-duty values. It can be like this. Also, the command input voltage determination unit 22 may automatically select from among a plurality of on-duty values.

[Second embodiment]
FIG. 7 is a schematic configuration diagram of a power supply device 10A according to the second embodiment. The power supply device 10A has a configuration in which a ripple current measurement circuit 52, a voltage detection unit 54, and a correction amount storage unit 20a are added to the configuration of the power supply device 10 of the first embodiment, and an instruction to reduce the ripple current is provided. Correct the output voltage (Vout'). The following description focuses on points that differ from the first embodiment.

The ripple current measurement circuit 52 measures ripple current from the current detection value detected by the current detection section 30 . A voltage detector 54 detects an output DC voltage (Vout), which is the voltage across the laser diode 14 . The correction amount storage unit 20a is provided in the command output voltage determination unit 20, and stores the correction amount for the command output voltage (Vout').

The command output voltage determination unit 20 of the second embodiment obtains the voltage value that becomes the command current value given from the external controller in the current-voltage characteristics stored in the current-voltage characteristics storage unit 28 . Then, the command output voltage determination unit 20 determines a voltage value obtained by correcting the voltage value with the correction amount stored in the correction amount storage unit 20a as the command output voltage (Vout').

Furthermore, when the value of the ripple current exceeds a predetermined threshold, the command output voltage determination unit 20 determines the difference between the output DC voltage (Vout) detected by the voltage detection unit 54 and the command output voltage (Vout'). (Vout-Vout') is calculated as a new correction amount and stored in the correction amount storage unit 20a. However, when the value of the ripple current is equal to or less than the threshold, the command output voltage determination section 20 does not change the correction amount stored in the correction amount storage section 20a.

FIG. 8 is a flow chart for explaining control of the power supply device 10A in the second embodiment. At the start of this flowchart, the correction amount for the command output voltage (Vout') stored in the correction amount storage unit 20a is 0V.

First, the command output voltage determination unit 20 obtains the voltage value that becomes the command current value in the current-voltage characteristics stored in the current-voltage characteristics storage unit 28 . Then, the command output voltage determination unit 20 determines the command output voltage (Vout') by adding the correction amount stored in the correction amount storage unit 20a to the determined voltage value and correcting the value (step S11). .

The following steps S12 and S13 are the same as steps S2 and S3 in the first embodiment, so description thereof will be omitted.

After step S13, the command output voltage determination unit 20 determines whether or not the ripple current exceeds the threshold (step S14).

If the ripple current exceeds the threshold (step S14: YES), the command output voltage determining unit 20 obtains the difference between the output DC voltage (Vout) and the command output voltage (Vout') as a correction amount (step S15). , the calculated correction amount is stored in the correction amount storage unit 20a. After step S15, the process returns to step S11.

If the ripple current does not exceed the threshold (step S14: NO), the process returns to step S11.

As described above, according to the power supply device 10A of the second embodiment, by correcting the command output voltage (Vout') based on the ripple current, in addition to the effect obtained in the first embodiment, It becomes possible to further reduce the ripple current.

[Third Embodiment]
FIG. 9 is a schematic configuration diagram of a power supply device 10B according to the third embodiment. The power supply device 10B has the configuration of the power supply device 10 of the first embodiment, a configuration in which the value of the individual on-duty Don1 is sent from each of the N current generation circuits 40 to the command input voltage determination unit 22, and a correction amount A storage unit 22b is added. The correction amount storage unit 22b is provided in the command input voltage determination unit 22 and stores the correction amount for the command input voltage (Vin'). Then, the power supply device 10B corrects the command input voltage (Vin') so as to reduce the ripple current. The following description will focus on the differences from the first embodiment.

The command input voltage determination unit 22 of the third embodiment responds to the command input voltage (Vin') based on the N individual on-duties Don1 given from the controllers 46 of the N current generation circuits 40. A correction amount is determined and stored in the correction amount storage unit 22b. Then, the command input voltage determination unit 22 corrects the command input voltage (Vin') obtained based on the on-duty Don0 and the command output voltage (Vout') with the correction amount, and corrects the command input voltage ( Vin') is determined.

Specifically, the command input voltage determination unit 22 first determines the on-duty difference Don_err, which is the difference between the average value Don_ave of the N individual on-duties Don1 and the on-duty Don0 stored in the on-duty storage unit 26. Obtain (=Don_ave-Don0).

Next, the command input voltage determination unit 22 determines the addition value to the correction amount stored in the correction amount storage unit 22b. Specifically, when the on-duty difference Don_err is a positive value, the command input voltage determining unit 22 determines a predetermined positive fixed value or a positive fluctuation value whose absolute value increases as the absolute value of Don_err increases. A value is determined as an addition value to the correction amount. Further, when the on-duty difference Don_err is a negative value, the command input voltage determination unit 22 sets a predetermined negative fixed value or a negative fluctuation value whose absolute value increases as the absolute value of Don_err increases. Determined as an additional value to the correction amount. When the variation value is the added value, the added value may be set to a value proportional to Don_err regardless of whether the added value is positive or negative.

Then, the command input voltage determination unit 22 obtains a value obtained by adding the addition value determined as described above to the correction amount stored in the correction amount storage unit 22b as a new correction amount, and stores the new correction amount in the correction amount storage. It is stored in the section 22b.

The command input voltage determination unit 22 determines the correction amount stored in the correction amount storage unit 22b as described above, based on the command input voltage (Vin') obtained based on the on-duty Don0 and the command output voltage (Vout'). to determine the corrected command input voltage (Vin').

The above correction increases the voltage value of the command input voltage (Vin') when the on-duty difference Don_err is a positive value, and increases the voltage value of the command input voltage (Vin') when the on-duty difference Don_err is a negative value. is corrected to reduce

FIG. 10 is a flowchart for explaining control of the power supply device 10B in the third embodiment. At the start of this flowchart, the correction amount for the command input voltage (Vin') stored in the correction amount storage unit 22b is 0V.

First, since step S21 is the same as step S1 in the first embodiment, the explanation is omitted.

After step S21, the command input voltage determination unit 22 determines the command input voltage ( Vin'). Then, the correction amount stored in the correction amount storage unit 22b is added to this to determine the corrected command input voltage (Vin') (step S22).

The next step S23 is the same as step S3 in the first embodiment, so the description is omitted.

After step S23, the command input voltage determination unit 22 obtains the on-duty difference Don_err (step S24).

Next, the command input voltage determination unit 22 determines the addition value to the correction amount as described above based on the value of the on-duty difference Don_err obtained in step S24. The command input voltage determination unit 22 obtains a value obtained by adding the determined addition value to the correction amount stored in the correction amount storage unit 22b as a new correction amount for the command input voltage (Vin') (step S25). The correction amount is stored in the correction amount storage unit 22b. After step S25, the process returns to step S21.

In step S22, instead of correcting the command input voltage (Vin') by adding the correction amount as described above, the command input voltage determination unit 22 determines the on-duty value Don0 based on the on-duty difference Don_err. By correcting , the command input voltage (Vin') may be corrected.

As described above, according to the power supply device 10B of the third embodiment, the command input voltage (Vin') is corrected based on the difference between the average value Don_ave of the N individual on-duties Don1 and the on-duty Don0. By doing so, in addition to the effect obtained in the first embodiment, it is possible to further reduce the ripple current.

[Invention obtained from the embodiment]
Inventions that can be understood from the above embodiments will be described below.

The power supply (10, 10A, 10B) is a laser diode power supply for supplying current to the laser diode (14). The power supply device (10, 10A, 10B) has N current generation circuits (40) connected in parallel and equipped with switching elements (SW1, SW2), converts an input DC voltage into an output DC current, A command output voltage is determined from a command current value using a conversion circuit (18) that supplies an output direct current to a diode (14) and a current-voltage characteristic that indicates the relationship between the current and voltage of the laser diode (14). A command output voltage determination unit (20) and an on-duty storage unit that stores an on-duty dependent on the N of the switching elements (SW1, SW2) capable of suppressing the ripple current flowing through the laser diode (14) to a predetermined value or less. (26), a command input voltage determination unit (22) that determines the command input voltage based on the on-duty and the command output voltage, an input voltage adjustment circuit (24) that converts to voltage and generates an input DC voltage.

As a result, the ripple current flowing through the laser diode (14) can be reduced.

A power supply (10, 10A, 10B) includes a current detection section (30) that detects current flowing through a laser diode (14), and a difference between a command current value and a current detection value detected by the current detection section (30). A control section (34) may be provided that outputs a target current value obtained by correcting a value of 1/N of the command current value to be smaller, to the current generating circuit (40). Each of the N current generation circuits (40) controls the individual on-duty of its own switching elements (SW1, SW2) so that the output current supplied to the laser diode (14) becomes a target current value. may have a controller (46) that Thereby, the values of the individual on-duties Don1 and Don2 can be controlled.

The power supply (10A) may include a ripple current measurement circuit (52) that measures ripple current from the current detection value. The command output voltage determining section (20) may determine the command output voltage by correcting it based on the ripple current. This makes it possible to further reduce the ripple current.

A command output voltage determination unit (20) determines an output DC voltage generated across a laser diode (14) by being supplied with an output DC current when the ripple current exceeds a predetermined threshold, and a command output voltage. may be added as a correction amount to determine the command output voltage after correction. This makes it possible to further reduce the ripple current.

The command input voltage determining section (22) may determine the command input voltage by performing correction based on the N individual on-duties. This makes it possible to further reduce the ripple current.

A command input voltage determination unit (22) corrects the command input voltage to increase the voltage value when the difference between the average value of the N individual on-duties and the on-duty is a positive value, and corrects the command input voltage to increase the voltage value when the difference is a negative value. may correct the command input voltage so that the voltage value decreases. This makes it possible to further reduce the ripple current.

The on-duty value may be M/N (M is a natural number less than N). Thereby, the ripple current can be suppressed to a predetermined value or less.

DESCRIPTION OF SYMBOLS 10, 10A, 10B... Power supply device 12... AC power supply 14... Laser diode 16... Capacitor 18... Conversion circuit 20... Command output voltage determination part 20a, 22b... Correction amount storage part 22... Command input voltage determination part 24... Input voltage adjustment Circuit 26... On-duty storage unit 28... Voltage characteristic storage unit 30... Current detection unit 34... Control unit 40... Current generation circuit 42... Individual current detection unit 46... Controllers 48a, 48b... Current path 52... Ripple current measurement circuit 54... Voltage detection part SW1, SW2... Switching element X... Terminal X1, X2... Input terminal Y1, Y2... Output terminal

Claims (7)

A power supply for a laser diode for supplying current to the laser diode, comprising:
a conversion circuit having N current generation circuits connected in parallel and provided with switching elements, converting an input DC voltage into an output DC current, and supplying the output DC current to the laser diode;
a command output voltage determination unit that determines a command output voltage from a command current value using a current-voltage characteristic that indicates the relationship between the current and voltage of the laser diode;
an on-duty storage unit storing an on-duty dependent on the N of the switching element capable of suppressing a ripple current flowing through the laser diode to a predetermined value or less;
a command input voltage determination unit that determines a command input voltage based on the on-duty and the command output voltage;
an input voltage adjustment circuit that converts an AC voltage supplied from an AC power supply into a DC voltage of the command input voltage to generate the input DC voltage;
A power supply. The power supply device according to claim 1,
a current detection unit that detects a current flowing through the laser diode;
A control unit that outputs to the current generation circuit a target current value obtained by correcting 1/N of the command current value so that the difference between the command current value and the current detection value detected by the current detection unit is small. with
Each of the N current generation circuits has a controller for controlling the individual on-duty of the switching element provided therein so that the output current supplied to the laser diode becomes the target current value. . The power supply device according to claim 2,
A ripple current measurement circuit that measures the ripple current from the current detection value,
The power supply device, wherein the command output voltage determination unit determines the command output voltage by correcting based on the ripple current. The power supply device according to claim 3,
When the ripple current exceeds a predetermined threshold, the command output voltage determination unit determines the output DC voltage generated across the laser diode by the supply of the output DC current and the command output voltage. and determining the command output voltage after correction by adding the difference between the above as a correction amount. The power supply device according to claim 2,
The power supply device, wherein the command input voltage determination unit determines the command input voltage by performing correction based on the N individual on-duties. The power supply device according to claim 5,
The command input voltage determination unit corrects the command input voltage to increase the voltage value when the difference between the average value of the N individual on-duties and the on-duty is a positive value, and corrects the command input voltage to a negative value. In the case of , the power supply device corrects the command input voltage so that the voltage value decreases. The power supply device according to any one of claims 1 to 6,
The power supply device, wherein the on-duty value is M/N (M is a natural number less than N).

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