JP4700417B2 - LED power supply device and control method thereof - Google Patents

Description

  The present invention relates to an LED power supply device and a control method thereof, and more particularly to a constant voltage power supply device and a control method thereof.

  Conventionally, as shown in Patent Document 1, a constant current power supply voltage is mainly used for LEDs. In this constant current system power supply device, the relationship between the luminance of the LED and the current flowing through the LED is directly proportional, and therefore the luminance of the LED can be controlled easily and accurately.

  However, for example, when a plurality of LEDs are connected in parallel, when a problem occurs in a certain LED, a constant current is flowing, so that the current consumed by the defective LED flows to the other LEDs, A change occurs in the current flowing through the LED. As a result, there is a problem that a failure of one LED affects other LEDs and causes a problem such as a change in brightness, deterioration, or damage.

  On the other hand, there is one that controls the brightness of an LED using a constant voltage power supply. For example, even if a plurality of LEDs are connected in parallel, a constant voltage is applied to the LEDs connected in parallel, and a certain LED is damaged. However, there is an advantage that other LEDs are not affected.

However, since the relationship between the voltage applied to the LED and the luminance of the LED is not linear, there is a problem that it is very difficult to control the luminance as compared with a constant current type power supply device.
JP 2004-039290 A

  Therefore, the present invention has been made for the purpose of solving the above problems all at once. That is, the main purpose of the present invention is to provide a power supply device that can easily and accurately control the luminance of the LED using a constant voltage power supply device.

That is, the power supply device for LED according to the present invention receives a voltage instruction signal, applies a voltage according to the value to the LED, emits light, and measures the current flowing through the LED, and according to the measured value. A current measurement unit that outputs a measurement signal of the value, and changes the value of the voltage instruction signal in a predetermined range, obtains the value of the measurement signal that changes in accordance with the value, and determines the value of the voltage instruction signal and the value of the measurement signal A relational data generation unit for generating relational data indicating the relation between the LED and a dimming signal for making the LED have a desired luminance, and a value of an initial measurement signal corresponding to a current value to be passed through the LED is determined from the value together, determined based on a voltage instruction signal value corresponding to the initial measurement signal value to said relational data comprises a conversion unit for outputting a voltage command signal of that value to the variable voltage power source, and the relationship data Forming portion, the voltage intermittently pulsed outputs an instruction signal value, and characterized in that to obtain the value of the measurement signal during the output.

  If this is the case, the relationship between the voltage applied to the LED and the current flowing through the LED is obtained in advance under the assumption that the luminance of the LED and the current flowing through the LED are directly proportional to each other. Since the brightness of the LED is controlled using the relationship, it is possible to provide a power supply apparatus that can easily and accurately control the brightness of the LED in the constant voltage system power supply apparatus.

  When the temperature of the LED changes, the current flowing through the LED changes, and the brightness of the LED changes. In order to suitably prevent this, the conversion unit receives the measurement signal from the current measurement unit, compares the value with the initial measurement signal value, and the measurement signal value from the current measurement unit is It is desirable to perform feedback control in which the voltage instruction signal value is changed so as to be the initial measurement signal value, and the voltage instruction signal of that value is output to the variable voltage power source.

  In addition, when the current value changes suddenly due to LED damage or the like, in order to notify the user or the like and prevent other LEDs from being damaged, a measurement signal from the current measurement unit is used. It is preferable to further include a notifying unit for notifying when the value of is changed by a predetermined value or more.

  Further, when obtaining a measurement signal for creating relational data, the relational data generation unit intermittently outputs the voltage instruction signal in order to suppress heat generation from the LED and to prevent thermal runaway of the LED. However, it is desirable to acquire the value of the measurement signal at the time of output.

  According to the present invention configured as described above, the relationship between the voltage applied to the LED and the current flowing through the LED is preliminarily determined on the assumption that the brightness of the LED and the current flowing through the LED have a direct proportional relationship. Thus, since the brightness of the LED is controlled using the relationship, a power supply apparatus that can easily and accurately control the brightness of the LED using a constant voltage power supply apparatus can be provided.

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

  The LED power supply device 1 according to the present embodiment is a constant-voltage power supply device that applies a DC voltage to the LED illumination unit 2, and receives a voltage instruction signal as shown in FIG. A variable voltage power source 3 that applies voltage to the LED illumination unit 2 to emit light; a current measurement unit 4 that measures a current flowing through the LED illumination unit 2 and outputs a measurement signal having a value corresponding to the measured value; and a current measurement unit 4 and a control device 5 for controlling the variable voltage power supply 3 based on the measurement signal.

  As shown in FIG. 2, the LED illuminator 2 uses a plurality of LEDs 21 connected in parallel. However, one LED 21 may be used, or a plurality of LEDs 21 are connected in series as shown in FIG. A plurality of connected devices may be connected in parallel. Here, the LED 21 can flow a current of 200 mA or more (for example, 200 mA to 2 A is preferable) continuously for a predetermined time, and emits light with a much larger light amount than a conventional one. To do.

  The variable voltage power source 3 is controlled by a control device 5 described later, and has a function of supplying a constant voltage to the LED illumination unit 2.

  The current measuring unit 4 uses a resistor or a Hall sensor, measures the current flowing through the LED lighting unit 2, that is, the current flowing through the circuit 6 including the LED lighting unit 2, and according to the measured value. A value measurement signal is output to the control device 5 described later.

  As shown in FIG. 4, the control device 5 is a general purpose or dedicated computer having a CPU 501, a memory 502, an input / output interface 503, an AD converter 504, etc., and is stored in a predetermined area of the memory 502. By causing the CPU 501 and peripheral devices to cooperate in accordance with the predetermined program, the functions as the relational data generation unit 51, the relational data storage part D1, the conversion part 52, the notification part 53, etc. are exhibited as shown in FIG. To do.

  Below, each part 51-53 and D1 are demonstrated.

  As shown in FIG. 5, the relationship data generation unit 51 generates a relationship indicating the VI characteristics of the current with respect to the voltage of the LED illumination unit 2 connected to the LED power supply device 1. In the generation method, the voltage applied to the LED illumination unit 2 is changed by changing the value of the voltage instruction signal within a predetermined range, and the value of the measurement signal measured by the current measurement unit 4 that changes in accordance with the voltage is changed. Obtaining and generating relation data indicating the relation between the value of the voltage instruction signal and the value of the measurement signal. Here, the predetermined range is a range that covers the use rated range of the LED 21, and is from zero to the maximum rated current value of the LED 21.

  As a more detailed generation method, as shown in FIG. 6, after a certain voltage is applied to the LED illumination unit 2 for a certain period of time, the voltage is intermittently changed. In this embodiment, the voltage is changed to gradually increase. If the voltage is continuously increased, the LED 21 may cause thermal runaway in the generation data generation stage. However, if the voltage is gradually increased, if it is applied intermittently for a certain time, Thermal runaway of the LED 21 can be prevented. Further, the application of the voltage in the pulse form in this way can be performed much more easily than the constant current control because of the constant voltage control.

  The relationship data storage unit D1 is for storing the relationship data generated by the relationship data generation unit 51.

  The conversion unit 52 receives a dimming signal input from a user, for example, in order to cause the LED illumination unit 2 to emit light with a desired luminance. Then, from the luminance value indicated by the dimming signal, an initial measurement signal of the current value that must flow to the LED illumination unit 2 is determined, and a voltage instruction signal corresponding to the initial measurement signal value is determined based on the related data. The voltage instruction signal of that value is output to the variable voltage power source 3.

  When a constant voltage is applied to the LED illumination unit 2, the temperature of the LED illumination unit 2 rises and the current flowing through the LED illumination unit 2 increases, so that the current flowing through the LED illumination unit 2 is converted to feedback control. The unit 52 receives the measurement signal from the current measurement unit 4 and compares the value with the initial measurement signal value, so that the measurement signal value from the current measurement unit 4 is equal to the initial measurement signal value. The value is changed, and a voltage instruction signal having the value is output to the variable voltage power source 3.

  The conversion unit 52 receives the measurement signal from the current measurement unit 4 and, if the variation in the value is within a predetermined range, updates the voltage instruction signal as described above to keep the brightness of the LED illumination unit 2 constant. However, when the variation of the measurement signal value exceeds a predetermined range, the conversion unit 52 outputs a notification signal to the notification unit 53 described later.

  The notification unit 53 notifies a user or the like when the current flowing through the LED illumination unit 2 fluctuates beyond a predetermined range. For example, the notification unit 53 generates a sound by a notification signal from the conversion unit 52. It is done.

  Next, the operation of the thus configured LED power supply device 1 will be described below. In describing the operation of the LED power supply device 1, it is assumed that a connector (not shown) that connects the LED power supply device 1 and the LED illumination unit 2 is not removed during the operation.

  The operation of the LED power supply device 1 of the present embodiment mainly includes an initial setting operation and a feedback control operation.

  First, the initial setting operation will be described with reference to FIG.

  The LED illumination unit 2 is connected to the LED power supply device 1. When a main switch or a reset switch (not shown) is turned on (step Sa1), the relational data generation unit 51 determines whether or not generation of relational data has been completed by executing a series of initial setting operations a predetermined number of times ( Step Sa2). If the generation of the relationship data is not completed, the relationship data generation unit 51 outputs a voltage instruction signal to the variable voltage power source 3 (step Sa3). Based on the voltage instruction signal, the variable voltage power supply 3 applies a voltage to the LED illumination unit 2, and the current measurement unit 4 measures the current flowing at that time, and outputs the measurement signal to the relational data generation unit 51. (Step Sa4). Thereafter, the relationship data generation unit 51 stores the value of the voltage instruction signal and the value of the measurement signal in a pair in the relationship data storage unit D1 (step Sa5). When the series of operations is executed a predetermined number of times and the generation of the relationship data is completed, the relationship data generation unit 51 ends the initial setting operation. Here, one out of the predetermined number of times is one pulse of the voltage instruction signal value that the relational data generation unit 51 outputs intermittently.

  Next, the feedback control operation will be described with reference to FIG.

  First, the conversion unit 52 receives a dimming signal from the user (step Sb1). The conversion unit 53 that has received the dimming signal determines an initial measurement signal value of an initial current value that should flow to the LED illumination unit 2 from the direct proportional relationship between the current and the luminance (step Sb2), and the relationship is determined from the initial measurement signal value. A voltage instruction signal value is determined based on the data, and the voltage instruction signal is output to the variable voltage power source 3 (step Sb3).

  While applying a voltage to the LED illumination unit 2, the conversion unit 52 receives a measurement signal from the current measurement unit 4 (step Sb4), and the value of the measurement signal is determined by the dimming signal. Is determined (step Sb5). If the measurement signal from the current measurement unit 4 is the value of the measurement signal determined by the dimming signal, the conversion unit 52 outputs a constant voltage instruction signal to the variable voltage power source 3 as it is. On the other hand, if the measurement signal value from the current measurement unit 4 is different from the value of the initial measurement signal, it is determined whether or not the difference is equal to or greater than a predetermined value (step Sb6). If it is less than the predetermined value, the converter 52 changes the value of the voltage instruction signal so that the current flowing through the LED measuring unit 2 becomes a desired value, and outputs the voltage instruction signal of that value to the variable voltage power source 3 (step). Sb7). Moreover, if it is more than a predetermined value, the conversion part 52 will output an alerting | reporting signal to the alerting | reporting part 53 (step Sb8).

  As described above, according to the LED power supply device 1 according to this embodiment, the voltage applied to the LED illumination unit 2 and the voltage applied to the LED illumination unit 2 are based on the assumption that the luminance of the LED 21 and the current flowing through the LED 21 are directly proportional. Since the relationship with the current flowing through the LED illumination unit 2 is obtained in advance and the luminance of the LED illumination unit 2 is controlled using the relationship, the luminance of the LED illumination unit 2 is controlled in the constant voltage power supply device 1. A power supply device 1 that can be controlled easily and accurately can be provided.

  In addition, since the conversion unit 52 feedback-controls the value of the voltage instruction signal based on the value of the measurement signal from the current measurement unit 4 and the related data, the luminance change caused by the temperature change of the LED illumination unit 2 can be detected. It can prevent suitably.

  Furthermore, when the current flowing through the LED illumination unit 2 fluctuates beyond a predetermined range, the notification unit 53 that notifies the user or the like is provided, so that the current value changes suddenly due to the LED 21 being damaged or the like. In addition, this can be notified to the user, and other LEDs 21 can be prevented from being damaged.

  When the relation data generation unit 51 changes the value of the voltage instruction signal in a predetermined range, the value is intermittently changed after being applied for a certain time, so when obtaining a measurement signal for creating relation data, Heat generation from the LED illumination unit 2 and further thermal runaway of the LED 21 can be suppressed.

  The present invention is not limited to the above embodiment.

  For example, in the above-described embodiment, the relational data creating unit intermittently outputs the voltage instruction signal for a certain period of time when creating the relational data. However, the present invention is not limited to this. You may make it output a voltage instruction | indication signal to a variable voltage power supply so that it may change continuously.

  In addition, depending on the object to be irradiated, there may be a case where a more accurate adjustment is necessary within a predetermined range of luminance. In this case, the relationship is set so that fine control can be performed within the predetermined range of luminance. Data should be created.

  Further, in the embodiment, the voltage instruction signal is changed when the measurement signal value and the initial measurement signal value are different. However, the difference between the measurement signal value and the initial measurement signal value is equal to or greater than a predetermined value. In this case, the voltage instruction signal may be changed for the first time.

  In addition, while it is assumed that the connector is not removed during the operation of the embodiment, a predetermined operation may be performed when the connector is removed. That is, when a certain voltage is applied, if the measurement signal value is zero, it may be determined that the connector has been removed and the initial setting operation may be returned.

  Specifically, if the initial setting operation is in progress, a certain voltage instruction signal is output at a timing other than the pulse output of the voltage instruction signal. If it is determined that it has been removed, the initial setting operation is started again and related data is generated.If the feedback control operation is in progress, the measured signal value becomes zero even though the predetermined voltage is generated. It is determined that the connector has been removed, and the initial setting operation is started again to generate relation data.

  In addition, a part or all of the above-described embodiments and modified embodiments may be combined as appropriate, and the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit thereof. Needless to say.

The schematic block diagram of the power supply device for LED in one Embodiment of this invention. The circuit block diagram of the LED illumination part in the embodiment. The circuit block diagram of the LED illumination part in other embodiment. The equipment block diagram of the control apparatus in one Embodiment of this invention. The figure which shows the relationship of the VI characteristic of LED. The voltage application method at the time of relation data creation in the same embodiment. The flowchart which shows the initial setting operation | movement of the power supply device for LED in the embodiment. The flowchart which shows the feedback control operation | movement of the power supply device for LED in the embodiment.

Explanation of symbols

1 ... LED power supply 21 ... LED
3... Variable voltage power source 4... Current measurement unit 51... Relation data generation unit 52.

Claims (5)

A variable voltage power source that receives a voltage instruction signal and applies a voltage according to the value to the LED to emit light;
A current measuring unit that measures a current flowing through the LED and outputs a measurement signal having a value corresponding to the measured value;
Relational data generation that changes the value of the voltage instruction signal within a predetermined range, obtains the value of the measurement signal that changes in accordance with the value, and generates relational data indicating the relationship between the value of the voltage instruction signal and the value of the measurement signal And
A dimming signal for setting the LED to a desired luminance is received, and an initial measurement signal value corresponding to the current value to be passed through the LED is determined from the value, and a voltage instruction signal value corresponding to the initial measurement signal value is determined. A conversion unit that is determined based on the relational data and outputs a voltage instruction signal of that value to the variable voltage power supply ,
The LED power supply device, wherein the relational data generation unit intermittently outputs a pulse of the voltage instruction signal value and acquires a value of a measurement signal at the time of output .   The converter receives a measurement signal from the current measurement unit, compares the value with the initial measurement signal value, and the measurement signal value from the current measurement unit becomes the initial measurement signal value, 2. The LED power supply device according to claim 1, wherein the voltage instruction signal value is changed, and a voltage instruction signal having the value is output to the variable voltage power supply.   The LED power supply device according to claim 1, further comprising a notification unit that notifies when a value of a measurement signal from the current measurement unit changes by a predetermined value or more. A variable voltage power source that receives a voltage instruction signal and applies a voltage according to the value to the LED to emit light; a current measuring unit that measures a current flowing through the LED and outputs a measurement signal having a value according to the measured value; A method for controlling an LED power supply device comprising:
A generation step of changing the value of the voltage instruction signal in a predetermined range, acquiring a value of the measurement signal that changes in accordance with the value, and generating relational data indicating a relationship between the value of the voltage instruction signal and the value of the measurement signal; ,
A dimming signal for setting the LED to a desired luminance is received, and an initial measurement signal value corresponding to the current value to be passed through the LED is determined from the value, and a voltage instruction signal value corresponding to the initial measurement signal value is determined. determined based on the relationship data, Ri Do and a conversion step for outputting a voltage command signal of that value to the variable voltage power source,
The method for controlling a power supply device for an LED , wherein the generating step intermittently outputs the voltage instruction signal value in a pulse and obtains a value of a measurement signal at the time of output . The voltage instruction signal value is received so that the measurement signal is received from the current measurement unit, and the value is compared with the initial measurement signal value so that the measurement signal value from the current measurement unit becomes the initial measurement signal value. The LED power supply device control method according to claim 4 , further comprising an update step of changing the voltage and outputting a voltage instruction signal having the value to the variable voltage power supply.