JP2018018782A - Power supply unit for led strobe light emission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply unit for LED strobe light emission, capable of operating with an electric current corresponding to a capacity of a connected LED.SOLUTION: The power supply unit includes: a continuous current source 3; a power storage element 4 which is connected with the continuous current source 3 and an LED 11 to supply an electric current to the LED 11 at strobe light emission and to charge electrical charges from the continuous current source 3 during an idle period; and a current control unit 7 which variably controls a charge current into the power storage element 4 during the idle period.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a power supply device for LED strobe light emission used for surface inspection or the like.

  The LED can emit light with high brightness by flowing a current several times the rated value in a short time and when a considerable rest period is available (for example, when the duty ratio is 1/10 or less at 10 ms or less). When an LED is used in a strobe light emitting device as shown in Patent Document 1, since this characteristic is used, a power supply device that supplies current to the strobe light emitting device is required to have a function capable of instantaneously supplying a large current during strobe light emission. The

  Therefore, since it is difficult to supply all of this from a continuous current source such as a DC-DC converter built in the power supply device, this type of power supply device is provided with a large-capacity capacitor and the like, During the light-off period, the capacitor is charged from a continuous current source, and a large current is emitted from the capacitor to the LED during light emission.

  More specifically, for example, when an LED with a strobe emission rating (overdrive rating) of 48V and 10A is caused to emit strobe with a duty ratio of 1/10, the power supply device theoretically assumes 48V if the efficiency is ignored. A current that can be output and that can be continuously supplied is 1 A, that is, a current that can output 48 W is used (in reality, there is no 100% efficiency, so the capacity is a little larger).

  During the idle period, a current of 1 A is charged from the continuous current source to the capacitor. During light emission, in addition to 1 A from the continuous current source, 9 A is discharged from the charged capacitor, and 10 A is the LED strobe. It is supplied to the light emitting device. Note that FIG. 3 (large capacity) shows changes in the current waveform and charge amount of the capacitor at this time.

  Naturally, the power supply device described above can also be used for LED strobe light emitting devices with lower rated power.

  However, for example, the user uses an LED strobe light emitting device having a small capacity (low power) (for example, a device in which strobe light emission is performed at 48 V, 5 A and operated at a duty ratio of 1/10). However, when trying to use the power supply device for this, the following problems may occur.

  The average current required for the LED strobe light emitting device is 0.5 A. Therefore, it is assumed that the external power supply equipment of the user can supply a current of 0.5 A or slightly larger accordingly.

  Since the conventional power supply device cannot control the charge current to the capacitor, it tries to charge the capacitor with 1A in the power supply device during the idle period. FIG. 3 (small capacity) shows changes in the current waveform and charge amount of the capacitor at this time.

However, since the external power supply cannot supply the current of 1A, as a result, the voltage of the external power supply may be reduced, or the operation of the power supply may be stopped due to an error.
That is, although the power consumption of the LED strobe light emitting device is sufficiently large enough to cover the power consumption, there is a problem that the power supply device interposed between the LED strobe light emitting device may hinder the operation.

JP2013-156305

  The present invention has been made in view of such problems, and does not require an excessively large current from the outside, and operates with an LED strobe light-emitting power supply that operates with a current according to the capacity of the connected LED. Is intended to provide.

  That is, the power supply device for LED strobe light emission according to the present invention supplies a current to a connected LED with at least a predetermined rest period to cause the LED to strobe light, and includes a continuous current source, A storage element connected to the continuous current source and connected to the LED to supply current to the LED when the LED emits strobe light, and to be charged with electric charge from the continuous current source in the pause period, and in the pause period And a current control unit that variably controls the charge current to the power storage element.

  More specifically, the current control unit determines a charge current to the power storage element based on a charge amount of the power storage element discharged by the strobe light emission. Most preferably, the current control unit The charge current may be a value obtained by dividing the charge amount of the storage element discharged by the strobe light emission by the rest period.

If it is such, if the electric current sent at the time of strobe light emission of connected LED is small, according to it, the charging current to the electrical storage element in an idle period can also be made small.
Therefore, an excessively large current is not required for the external power supply equipment, and the present invention can be applied without difficulty to LEDs having various capacities.

The schematic diagram of the power supply device in one Embodiment of this invention. The graph which shows the time change of the electric current waveform of a capacitor | condenser and the amount of electric charges in a strobe light emission period and a rest period when strobe light emission is repeated with the power supply device in the embodiment. The graph which shows the time change of the electric current waveform of a capacitor | condenser and the amount of electric charge in a strobe light emission period when a strobe light emission is repeated with the conventional power supply device.

  An embodiment of the present invention will be described with reference to the drawings.

  The LED illumination system 100 in this embodiment is used for surface inspection of a workpiece, and as shown in FIG. 1, an LED strobe light emitting device 1 (hereinafter also simply referred to as a light emitting device 1) and this light emission. An LED strobe light-emitting power supply device 2 (hereinafter also simply referred to as a power supply device 2) that supplies power to the device 1 is provided.

  The light emitting device 1 includes LEDs 11 arranged in series or in parallel. These LEDs 11 are those that can emit strobe light by overdrive. In addition, this light-emitting device 1 can also make LED11 light-emit continuously other than strobe light emission.

  The power supply device 2 is continuously supplied with electric power from an external power supply facility PS (for example, a DC power supply facility installed in a factory, an AC-DC converter, etc.), converted into direct current, and supplied to the light emitting device 1. A current source 3, a capacitor 4 that is connected to the continuous current source 3 and that additionally supplies current to the light emitting device 1 during strobe light emission, and a control circuit 5 that controls the strobe light emission timing are provided. Yes.

The continuous current source 3 is, for example, a DC / DC converter, and an external power supply facility PS provided on the user side is connected to an input terminal thereof, and an output terminal thereof is connected to the light emitting device 1 via an electric cable. It is connected to the anode of the LED 11 provided.
As the continuous current source 3, a CVCC type capable of variably adjusting the voltage / current is used here, but an adjustment circuit for variably adjusting the voltage / current is provided separately from the DC / DC converter. May be.

  The capacitor 4 has a large capacity such as a film capacitor or an aluminum electrolytic capacitor. As described above, one end of the capacitor 4 is connected to the output terminal of the continuous current source 3, and the other end is connected to the ground. It is comprised so that an electric charge can be supplied to LED11.

  The control circuit 5 causes the LED 11 to emit strobe light with a predetermined light emission time and a predetermined duty ratio. In this embodiment, the control circuit 5 includes a switch element 52 provided on the current line of the LED 11 and an information processing device 51. It is configured.

  Here, the switch element 52 is, for example, a MOSFET, but a bipolar transistor or the like may be used.

  The information processing apparatus 51 is, for example, an analog / digital mixed circuit including a CPU, a memory, an AD converter, a DA converter, an amplifier, and the like (not shown). The CPU and its peripheral devices cooperate in accordance with a predetermined program stored in the memory. By operating, the switch element 52 generates a control signal to turn it on / off, and the LED lighting control unit 7 for controlling the blinking timing of the LED 11 and the current command signal and the voltage command signal to the continuous current source 3. And functions as a current control unit 8 or the like that operates the continuous current source 3 with an output current and an output voltage corresponding to the values.

Next, the operation of the power supply device 2 having such a configuration will be described.
As a premise, the output voltage and output current of the continuous current source 3, the duty ratio of the strobe light emission, and one strobe light emission time are set by initial setting or subsequent setting by user input or communication from other devices. And the value is stored in a predetermined area of the memory.

Therefore, when receiving an operation start command from the user, the information processing apparatus 51 operates the continuous current source 3 with the LED 11 turned off to fully charge the capacitor 4.
Next, the information processing device 51 (LED lighting control unit 7) issues an ON control signal to the switch element 52 to make the LED 11 strobe light only once in a test.

During the test strobe emission, the information processing device 51 (current control unit 8) calculates the charge discharged from the capacitor 4.
That is, the information processing device 51 detects the current flowing through the LED during strobe light emission, and calculates the discharge charge amount by performing time integration. Then, a minimum current for charging the discharge amount in one pause period, that is, a time during which no strobe light is emitted in one duty cycle is calculated. For this purpose, the information processing apparatus 51 sets the minimum charge current as a value obtained by dividing the calculated discharge charge amount by the pause period.
Finally, the minimum charge current calculated in this way, or a current slightly larger than that obtained by multiplying (or adding) a predetermined safety factor is set as the output current of the continuous current source 3.

  In this embodiment, a current detection circuit 6 is provided to detect the current flowing through the LED 11. The current detection circuit 6 has a function of a resistance element having one end connected to the switch element 52 and the other end connected to the ground. One end of the resistance element becomes an output end, and the voltage becomes a current index value indicating the current flowing through the LED 11. The information processing device 51 acquires the output voltage of the current detection circuit 6 and calculates a current from the value.

  When the output current of the continuous current source 3 is set in this way, a normal strobe light emission operation is performed thereafter.

If this is the case, as shown in FIG. 2, if the current that flows when the strobe light is emitted to the connected LED 11 is small, the charge current to the capacitor 4 during the idle period also decreases accordingly.
Therefore, the power supply device 2 can be applied to the LEDs 11 having various capacities without excessively demanding an excessively large current for the external power supply facility PS.

The present invention is not limited to the above embodiment.
For example, the discharge amount may be calculated from the output terminal voltage of the capacitor, for example. Specifically, the discharge amount can be calculated by integrating the value obtained by multiplying the capacitance of the capacitor and the output terminal voltage by the strobe light emission time.

  Further, for example, the type of the LED strobe light emitting device and the minimum charge current during the rest period required in advance are stored in pairs in a memory, and the type of the connected LED strobe light emitting device is determined by the user. This may be recognized by input or automatic identification, and the current control unit may refer to the table and set the minimum charge current, that is, the operating current of the continuous current source.

  The test flash emission may be performed a plurality of times before the operation starts. In that case, an average charge current or a maximum charge current obtained by the test strobe emission may be set as the operating current.

  Test strobe light emission may be performed only at the time of installation, or may be performed before the start of each operation to update the operating current each time.

  The LED strobe light emitting device is not only used for the work surface inspection as in the above embodiment, but also can be applied to, for example, exposure, spectrometer, and other general illumination.

  In addition, it goes without saying that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

2 ... LED strobe light source 11 ... LED
3. Continuous current source (DC-DC converter)
4 ... Storage element (capacitor)
7 ... Current controller

Claims (4)

A current is supplied to the connected LED at least after a predetermined pause period, and the LED is stroboscopically emitted.
A continuous current source;
A storage element connected to the continuous current source and connected to the LED, supplying current to the LED during the strobe light emission, and being charged with charge from the continuous current source during the rest period;
A power supply device for LED strobe light emission, comprising: a current control unit that variably controls a charge current to the power storage element during the pause period.   The power supply device for LED strobe light emission according to claim 1, wherein the current control unit determines a charge current to the power storage element based on a charge amount of the power storage element discharged by the strobe light emission.   3. The LED strobe light-emitting power supply device according to claim 2, wherein the current control unit sets the charge current to a value obtained by dividing the charge amount of the storage element discharged by the strobe light emission by the rest period. A current is supplied to the connected LED with at least a predetermined rest period, and the LED is stroboscopically emitted. The continuous current source is connected to the continuous current source and to the LED. A power supply device for LED strobe emission that includes a power storage element that supplies current to the LED at the time of strobe light emission of the LED and is charged with charge from the continuous current source during the rest period,
A program for a power supply device, which causes a function as a current control unit for determining a charge current to the power storage element during the rest period based on a charge amount of the power storage element discharged by the strobe light emission.