JP2019194992A - Led device and control method for the same - Google Patents

Abstract

To provide an LED device in which a plurality of LED elements are connected in parallel, the LED device being able to restrict the maximum current of a power source that supplies power to the LED elements even in a condition that respective on-periods of switching elements connected to the LED elements are made different from each other.SOLUTION: An LED device comprises: a load module unit 4 having a plurality of LED elements 11-1 to 11-N connected in parallel and a plurality of load switching elements 12-1 to 12-N respectively connected to the plurality of LED elements in series; and a control unit 15 that on/off controls the plurality of load switching elements. The control unit determines an on-period such that each load switching element is on-controlled in correspondence with the timing of off-control of the other load switching elements.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an LED device configured to connect a plurality of LED (Light Emitting Diode) elements in parallel and apply the same power supply voltage, and a control method thereof.

  In recent years, the use of LEDs (light emitting diodes) for various light sources has been accelerated from the viewpoint of energy saving. For example, a light source using a plurality of LEDs is also used for an automobile headlight. Not only is the LED efficient, but the light source is small and the lighting area can be limited. Therefore, an ADB (Adaptive Driving Beam) that lights only a necessary area using a plurality of LEDs is mounted. The ADB assigns LEDs for each irradiation range, and when an oncoming vehicle or the like is detected, the LED corresponding to the detection portion is turned on / off / dimmed.

  As an LED device used in such an ADB, there is an LED device in which a plurality of LED groups composed of a plurality of LED elements connected in series are connected in parallel and connected to an LED driving power source (for example, Patent Document 1). reference). In the LED device disclosed in Patent Document 1, switching elements are connected for each LED group, and the driving timing of each switching element is determined by a period obtained by dividing one period of pulse energization by the number of LED groups, that is, LED When five groups are connected in parallel, control is performed by shifting by 1/5 period. By setting it as such a structure, the sudden rise of the power supply which supplies an electric current to each LED can be prevented, and generation | occurrence | production of noise can be suppressed.

JP 2008-91311 A

  Patent Document 1 discloses an LED device in which pulse energization is performed with the same pulse width for each LED group. However, with the recent advancement of control of LED devices, LED lighting pulse widths of LED groups are different. It is assumed that the control will be performed. For example, in the case of the LED device used in the above-mentioned ADB, it is assumed that the LED device is lit along a road curve, and the lighting pulse width of each LED group is changed so as to actively illuminate the direction in which the road continues. There is a case. Applying the condition that the on-time width of the LED lighting pulse of each LED group is different to the method of controlling the timing by shifting one period of pulse energization divided by the number of LED groups as shown in Patent Document 1 In this case, there is a problem that the maximum current of the power source that supplies current to the LED may increase.

  For example, it is assumed that there are 5 LED groups in parallel, the current flow period for each LED group is 90%, 70%, 50%, 30%, 10%, respectively, and 1 A is passed to each LED group. In this case, if the lighting pulse width is determined by shifting the drive start timing, which is a feature of Patent Document 1, by 1/5 period, the output current of the power supply changes from 0 A to 5 A. When the maximum current of the power supply to the LED element increases as in this example, there is a problem that not only the generation of noise increases, but also the loss of the power supply for supplying current to the LED element increases.

  The present invention has been made to solve the above problems, and in an LED device in which a plurality of LED elements are connected in parallel, at least one switching element among the switching elements connected in series to each LED element. LED device capable of suppressing the maximum current of the power supply for supplying power to the LED element even when the ON period length of the switching element is different from the ON period length of the other switching elements, and its control method The purpose is to obtain.

  An LED device according to the present invention includes a load module unit having a plurality of LED elements each connected in parallel, and a plurality of load switching elements connected in series to each of the plurality of LED elements, and an input from a power source A power conversion unit that converts power into power and outputs it to the load module unit, and a plurality of switching elements that are turned on based on a lighting control command value that indicates a ratio of a period during which a current flows through the LED element in a control cycle of the load switching element. A control unit that determines a period and controls a plurality of load switching elements to be turned on or off, wherein the control unit is configured to turn on at least one load switching element among the plurality of load switching elements. Are divided into a plurality of ON periods within the control cycle, and at least one of the divided ON periods is set to a different negative value. The switching element determines the ON period to start so as to correspond to the timing of the off, characterized by.

  The LED device control method according to the present invention includes a plurality of LED elements connected in parallel, a load module unit having a plurality of load switching elements connected in series to each of the plurality of LED elements, and a power source. A power converter that converts the input power from the power and outputs the power to the load module unit, and a control unit that controls the on periods of the plurality of load switching elements by controlling the plurality of load switching elements to be on or off. A control method for an LED device comprising: a first step of taking a lighting control command value indicating a ratio of a period during which a current of a plurality of LED elements flows in each control cycle; A second step for setting the order of determining the ON period for the load switching element, and a negative value set by the control unit as a starting point in the second step. A third step of determining the ON period of the switching element from the start timing of the control period to the ON period by the lighting control command value corresponding to the load switching element, and the control unit other than the load switching element set as the starting point And a fourth step of determining an on period of the load switching element so as to control the load switching element to be turned on in accordance with a timing of controlling the load switching element whose on period is determined to be off before the load switching element. Features.

  According to the present invention, in the LED device in which a plurality of LED elements are connected in parallel, the length of the on period of at least one switching element among the switching elements connected in series to each LED element is the length of the on period of the other switching elements. Even when the conditions are different from each other, the maximum current of the power supply that supplies power to the LED elements can be suppressed, and the loss of the power supply can be reduced.

It is a block diagram which shows the basic composition of the LED apparatus which concerns on Embodiment 1 of this invention. It is a block diagram which shows the structure of the control part of the LED apparatus which concerns on Embodiment 1 of this invention. It is a block diagram which shows the structure of explanatory drawing of the lighting pattern production | generation method of the LED apparatus which concerns on Embodiment 1 of this invention. It is a flowchart explaining the control method of the LED apparatus which concerns on Embodiment 1 of this invention. It is explanatory drawing of the lighting pattern production | generation method of the LED apparatus which concerns on Embodiment 2 of this invention.

Embodiment 1 FIG.
The LED device according to Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the LED device according to Embodiment 1 of the present invention. In the drawings or the following description, the same or similar components are denoted by the same reference numerals. Further, when there are a plurality of identical or similar components such as load switching elements, “−” and numbers / symbols are added and distinguished as load switching elements 12-1 to 12 -N. In addition, when not distinguishing or generically referring to a plurality of identical or similar components, a description will be given by omitting “-” and numerals / symbols, for example, like the load switching element 12. .

  The LED device shown in Embodiment 1 of the present invention includes a power supply main circuit unit 1, a power supply control unit 2 that controls the power supply main circuit unit 1, and a DC power supply 5 that supplies power to the power supply main circuit unit 1. Yes. The power source main circuit unit 1 includes a DC / DC converter 3 as a power conversion unit and a load module unit 4 having a plurality of LED elements, and a DC power source 5 is connected to one terminal (here, the DC / DC converter 3). The load module unit 4 is connected to the other terminal of the DC / DC converter 3 (here, an output terminal for convenience).

  The DC / DC converter 3 is a power conversion unit, which converts the input power from the DC power supply 5 and outputs it to the load module unit 4. The DC / DC converter 3 includes a switching element 6, a diode 7, a reactor 8, and a capacitor 9. The switching element 6 is, for example, a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). In the example shown in FIG. 1, a switching element 6 and a reactor 8 are provided on the positive bus connected to the positive input terminal of the DC / DC converter 3. The diode 7 has a cathode connected to a connection point between the switching element and the reactor, and an anode connected to a negative bus connected to the negative input terminal of the DC / DC converter 3. Capacitor 9 has one terminal connected to the positive bus between reactor 8 and the positive output terminal, and the other terminal of capacitor 9 connected to the negative bus. The DC / DC converter 3 adjusts the amount of current supplied to the load module unit 4 to a desired value by controlling on / off of the switching element 6 according to the control signal output from the power supply control unit 2, and Electric power is supplied to the load module unit 4 including a certain LED element. Needless to say, the DC / DC converter 3 is not limited to the configuration shown in FIG. 1, and may be any circuit as long as it performs power conversion and outputs a desired amount of current. For example, a step-up chopper circuit, a flyback converter, an H-type buck-boost converter, or a SEPIC (Single-Ended Primary-Inductance Converter) may be used.

  In the load module unit 4, a plurality of LED elements 11 are connected in parallel. In the example shown in FIG. 1, the LED device includes N LED elements 11-1 to N (N is an integer of 2 or more). 1 to Nth LED element). Each LED element 11 is described as having a plurality of LED elements connected in series, but the number of LED elements is not necessarily a plurality, and the present invention can be applied even in a single case. In addition, each LED element 11 has a load switching element 12 connected in series to each LED element 11. In the example shown in FIG. 1, each of the LED elements 11-1 to N has a load switching element. 12-1 to N (first to Nth load switching elements) are connected in series. Here, the load switching element 12 may be any type, but, for example, a MOSFET can be used.

  Here, the LED element 11 and the load switching element 12 connected to the LED element 11 are collectively referred to as an LED drive string. That is, the load module unit 4 has a configuration in which a plurality of LED drive strings are connected in parallel. In the LED drive string, the load switching elements 12-1 to 12-N are controlled to be turned on or off according to the load switch signals 13-1 to 13-N output from the power supply control unit 2. When the load switching element 12 is on, the corresponding LED elements 11-1 to 11-N are electrically connected and supplied with power, and when the load switching element 12-1 to N is off, the load module unit 4 The LED elements 11-1 to 11-N corresponding to the load switching elements 12-1 to 12-N become electrically non-conductive and the power supply is stopped.

  The power supply main circuit unit 1 includes a current detection unit 10 that detects a circuit current flowing through the reactor 8, the load module unit 4, and the like. For example, the circuit current is detected as a voltage value using a resistor, an operational amplifier, or the like. . In the example shown in FIG. 1, the current detection unit 10 is provided inside the load module unit 4, and the current detection unit 10 is connected to the negative output terminal of the DC / DC converter 3.

  The DC power source 5 is a power source that outputs DC power, and is, for example, a battery. Needless to say, any power source that outputs DC power may be used.

  The power supply control unit 2 includes a current control unit 18 and a command value generation unit 19. The power supply main circuit is based on the detection result of the current detection unit 10 of the power supply main circuit unit 1 and the lighting control command 14 input from the outside. Control of unit 1 is performed. That is, the load switch signal 13 and the switch signal 17 are output to the switching element 6 and the load switching element 12, and the switching element 6 and the load switching element 12 are controlled to be turned on or off. Take control. Moreover, the control part 15 is a microcomputer, for example, according to the control method mentioned later, the load switch signals 13-1 to N for controlling the load switching elements 12-1 to N, and the switching elements of the DC / DC converter 3 6 is calculated.

  In the LED device according to Embodiment 1, the lighting control command 14 is input from the outside as described above. Here, the lighting control command 14 includes a lighting control command value corresponding to each LED element 11. The lighting control command value indicates a ratio of a period during which each load switching element 12 is turned on in the control period, that is, a ratio of a period during which a current is supplied to each LED element 11 within the control period. The lighting control command value is set for each load switching element 12 and for each control cycle. Any method of setting the lighting control command value may be used. For example, in the case where the lighting control command value is used for a headlight of an automobile, the automobile is brightly illuminated in the direction in which the road follows the road curve. A setting method that increases the proportion of the period during which the current of the corresponding LED element is allowed to flow can be performed.

An operation of the LED device according to the first embodiment will be described. First, the operation of the entire LED device will be described.
The DC power output from the DC power supply 5 is input to the DC / DC converter 3. In the DC / DC converter 3 to which DC power is input, the amount of current supplied to the load module unit 4 is desired by controlling on / off of the switching element 6 in accordance with the switch signal 17 output from the power supply control unit 2. The power is supplied to the load module unit 4 constituted by the LED elements 11-1 to N and the load switching elements 12-1 to N. In the load module unit 4, the load switching element 12 is on / off controlled based on the load switch signal 13 from the command value generation unit 19. The load module unit 4 supplied with power is supplied with power to the LED element 11 connected to the load switching element 12 set to ON, and the LED element 11 supplied with power is turned on.

  Next, the control operation in the DC / DC converter 3 will be described with reference to FIG. The DC / DC converter 3 controls on / off of the switching element 6 according to the switch signal 17 generated by the control unit 15 and controls the current amount to a desired value. In the control unit 15, the target command value of the output current of the DC / DC converter 3 calculated in the command value generation unit 19 is used as the ON number of each load switching element 12-1 to N set in the command value generation unit 19 described later. And based on the value of the current passed through the LED elements 11-1 to 11-N. That is, the command value generation unit 19 outputs the target command of the output current from the multiplication value of the number of load switching elements 12 set to ON among the load switching elements 12-1 to 12 -N and the current value passed through the LED element 11. Generate a value. For example, when the ON number of the load switching element 12 is 3 and the current flowing through each LED element 11 is 1A, the target command value of the output current of the DC / DC converter 3 is 3A by multiplying the ON number 3 and 1A. Set to. The command value generation unit 19 outputs the set target command value to the current control unit 18.

  The current control unit 18 calculates an error by performing subtraction between the target command value set by the command value generation unit 19 and the current detection signal 16 detected by the current detection unit 10 of the power supply main circuit unit 1. The error is output to the PI control unit 20. The PI control unit 20 calculates the control amount so as to reduce the error by performing PI calculation or the like. The calculated control amount is compared with the carrier frequency output from the carrier frequency output unit 21 to generate the switch signal 17 of the switching element 6 of the DC / DC converter 3 and output it to the DC / DC converter 3. The DC / DC converter 3 to which the switch signal 17 is input from the power supply control unit 2 turns on and off the switching element 6 based on this signal, and adjusts the amount of current output to the load module unit 4.

  Here, in the above description, the digital arithmetic processing such as a microcomputer has been described. However, it is needless to say that the present invention is not limited to this and can be executed by analog control. Further, although the PI calculation has been described as an example of the method for calculating the control amount, any control may be used as long as it is control for convergence to the target value, for example, PID control or H∞ control.

  Next, the control operation of the load switching element 12 of the load module unit 4 will be described. The load switching elements 12-1 to 12 -N turn on and off each load switching element based on the load switch signal 13 generated in the command value generation unit 19, and turn on the LED elements of the LED elements 11 in a desired pattern.

  A method for generating the load switch signal 13 in the command value generation unit 19 will be described with reference to FIG. FIG. 3 is an explanatory diagram of a lighting pattern generation method for the LED device according to Embodiment 1 of the present invention. FIG. 3 shows a lighting pattern generation method when five LED elements 11 are arranged in parallel, that is, when N is 5 in FIG. Needless to say, the present invention is not limited to the case where the LED elements 11 are 5 in parallel, and the lighting pattern is similarly applied even when the number of LED elements 11 is less than 5 or more than 5 parallel. Can be generated.

In FIG. 3, the percentage (%) shown on the left side indicates the lighting control command values (I _{LED1 to} I _LED5 ) of the LED elements 11-1 to N, that is, currents to the LED elements 11-1 to N in the control cycle. The ratio of the period which flows is shown. For example, the LED element 11-3 whose lighting control command value is set to 50% indicates that the load switching element 12-3 is set to ON only during a period of 50% in one control cycle and current is supplied. In FIG. 3, the numerical value on the left side of the arrow (⇒) is the lighting control command value, and the numerical value on the right side of the arrow (⇒) is the load switch signal 13 for driving the load switching element 12 in the command value generation unit 19. The value after generating the lighting pattern is shown. Like the load switching element 12-3, the load switching element 12 in which two ratios of 40% + 10% are described indicates that the ON period is divided into two times in one control cycle. In the example illustrated in FIG. 3, the load switching element 12-3 is controlled to be turned on simultaneously with the control cycle start timing, continues the on period for 10% of one control period, and is one before the on period is set. The load switching element 12 in this order (in the example shown in FIG. 3, the load switching element 12-2) is controlled to be turned on simultaneously with the timing for controlling the load switching element 12-2 to be turned on for a period of 40% of one control cycle. Show.

  In the LED device according to Embodiment 1 of the present invention, the control cycle of the load switching element 12 is determined in advance, and the control unit 15 sets the ON period of each load switching element 12 for each control cycle. Further, the control unit 15 is set to determine the on period of the load switching elements 12-1 to 12 -N in this order. First, the on period of the load switching element 12-1 is set, and the load switching element 12 is set. The ON period is determined so that the timing for controlling -1 to be ON is turned on simultaneously with the start timing of the control cycle. Here, the on period refers to a period from the timing when the on control is performed to the timing when the next off control is performed, and is set based on a lighting control command value input from the outside.

  Next, the ON period of the load switching element 12-2 is determined. The control unit 15 controls the load switching element 12 to be turned on in accordance with the timing at which the different load switching elements 12 are turned off within the control cycle. That is, the on period is set so that the load switching element 12-2 is turned on simultaneously with the timing when the load switching element 12-1 is controlled to be turned off. The setting of the ON period is repeated in order for each load switching element 12, and the ON period of the load switching element 12-N is determined and the process ends. That is, when n is an integer from 1 to N-1, the control unit 15 switches the load switching element 12- (n + 1) to the switching element corresponding to the timing at which the load switching element 12-n is turned off. Control on.

Moreover, although the timing which controls the load switching element 12-2 to OFF is determined based on the load control command value of the load switching element 12-2, it is controlled from the timing which controls the load switching element 12-2 to ON. When the period until the end timing of the cycle is equal to or less than the lighting control command value related to the load switching element 12-2, the ON period of the load switching element 12-2 is divided into two times. One of the two timings to turn on is controlled to correspond to the start timing of the control cycle, and one time is switched to correspond to the timing when the other load switching element 12-1 is turned off. Control the element on.
Details of the control method will be described below.

The details of the control method of the LED device according to the first embodiment will be described using the example shown in FIG. In the example shown in FIG. 3, the lighting control command values (I _{LED1 to} I _LED5 ) of the LED elements 11-1 to 11-5 are 90%, 70%, 50%, 30%, and 10%, respectively. The LED element 11-1 is 90% during one control period, the LED element 11-2 is 70% during one control period, the LED element 11-3 is 50% during one control period, and the LED element 11-4. Indicates that current is supplied by 30% during one control period, and LED element 11-5 is supplied by 10% during one control period. The right side of FIG. 3 shows time on the horizontal axis and load switch signals 13-1 to 13-5 that are actually given to the load switching elements 12-1 to 5 up to the fifth stage from the top. The figures after the fifth stage are target command values of the output current set in the current controller 18 when 1 A is assumed to flow through each LED. As a result of the control, the output current of the DC / DC converter 3 and Become.

FIG. 4 shows a flowchart for explaining a lighting pattern generation method. A lighting pattern command generation method in the command value generation unit 19 will be described with reference to FIG.
(1) The lighting control command value of the lighting control command 14 input from the outside at a predetermined timing is taken in (step S101). Here, as many lighting control commands as the number of LED elements 11 connected in parallel are required.
(2) The load switching element 12 that is the starting point among the arbitrary load switching elements 12 is set, and the order of the load switching elements 12 that determines the ON period is set (step S102). Note that the order of setting the load switching element 12 as the starting point and the ON period may be set in advance.
(3) The ON period of the load switching element 12 set as the starting point, that is, the lighting pattern of the LED element 11 connected to the load switching element 12 set as the starting point is determined according to the lighting control command value from the start timing of the control cycle. (Step S103).
(4) When n is an integer of 1 to N-1 and the on period of the load switching element 12- (n + 1) is set, 100% and the lighting control command value (I _LEDn ) of each load switching element 12-n And a difference value (I _subn ) is calculated (step S104).
(5) the difference value _{(I subn)} found when the lighting is larger than the control command value _{(I LEDn + 1)} of the load switching element 12-(n + 1) is (step S105: Yes), the load from the off timing of the load switching element 12-n The ON setting for the lighting control command value (I _{LEDn + 1} ) of the switching element 12- (n + 1) is performed. Further, the lighting control command value (I _{LEDn + 1} ) of the load switching element 12- (n + 1) is changed to the numerical value of I _{LEDn + 1} + I _LEDn to prepare for the next setting of the ON period of the load switching element 12 (step S106).
(6) the difference value _{(I subn)} found when the lighting control command value of the load switching element _{12- (n + 1) (I} LEDn + 1) smaller than (Step S105: No), the control from the off timing of the load switching element 12-n performs setting of the on-period to the end timing of the _period, performing on setting the start timing of the amount corresponding control period of a value obtained by subtracting the _{I subn} from _{I LEDn + 1 (I LEDn +} 1 -I sub). _Further, by changing the _{I LEDn + 1} to a number of _I LEDn + _{1 -I sub} prepared for the next LED lighting pattern generation (step S107).
The above steps S104 to S107 are executed N-1 times to set ON periods of all the load switching elements 12.

Here, description will be made by taking the condition of the lighting control command value in FIG. 3 as an example.
(1) At predetermined timing, 90%, 70%, 50%, 30%, and 10% are taken in as the lighting control command values _{ILED1 to ILED5} of the lighting control command 14 (step S101).
(2) The load switching element 12-1 is set as a starting point (step S102). Further, the load switching elements 12-1 to 12-5 are set so as to determine the ON period in this order.
(3) The ON period of the load switching element 12-1 is determined as 90% of the lighting control command value from the start timing of the control cycle (step S103).
(4) The ON period of the load switching element 12-2 is determined. 100% and the difference value _{I sub1} taken the difference between _{I LED1} 10% next (step _{S104), I sub1} because less than 70% is _{I LED2,} respectively divides the ON period two to set. The first ON period is set from the OFF timing of the load switching element 12-1 to the end timing of the control cycle. In the second ON period, the ON period is set from the start timing of the control cycle by a value I _LED2 −I _sub1 = 70% −10% = 60% _obtained by subtracting I _sub1 from I _LED2 . _Further, by changing the _{I LED2} to _I LED2 _-I sub1 = 60% provided to determine the ON period of the next load switching element 12 (step S107).
(5) The ON period of the load switching element 12-3 is determined. The value I _{sub2 obtained} by taking the difference between 100% and I _LED2 is 40% (step S104). Since I _sub2 is smaller than I _{LED3, the} on setting is set from the off timing of the load switching element 12-2 to the end of the control cycle. The value _obtained by subtracting I _sub2 from I _{LED3 is} set to ON from the beginning of the control period by the amount of I _LED3 −I _sub1 = 50% −40% = 10%, and I _LED3 is set to I _LED3 −I _sub2 = 10% It changes and prepares for determination of the ON period of the next load switching element 12 (step S107).
(6) The ON period of the load switching element 12-4 is determined. 100% and the difference value _{I sub3} taken the difference between _{I LED 3} is becomes _{90%, I sub3} is to become larger than _{I LED 4,} set the off timing of the load switching element 12-3 to 30% of the on period of the _{I LED 4} It was carried out, by changing the value of I _{LED 4} to _{I LED4 + I LED3 = 30%} + 10% = 40% provided to determine the oN period of the next load switching element 12 (step S106).
(7) The ON period of the load switching element 12-5 is determined. 100% and the difference value _{I sub4} taken the difference between _{I LED 4} is becomes _{60%, I sub4} since larger than _{I LED 5,} for 10% of the on-set of _{I LED 5} from the OFF timing of the load switching element 12-4 (Step S106).
Since the number of LED elements in parallel is five, the setting of the on period ends here.

  By determining the ON period of the load switching element 12 as described above, the output current of the DC / DC converter 3 is controlled at 3 A or 2 A, and there is no large current fluctuation, and the maximum current can be suppressed. I understand that.

  Here, the predetermined timing at which the command value of the lighting control command 14 is taken is set to a time required for generating the lighting pattern from the lighting control command with respect to the control cycle of the LED. desirable. In the above example, the lighting control command is indicated by a numerical value as a percentage, but an analog signal or the like may be used. In the above example, the load switching element 12-1 is used as a starting point, but it goes without saying that the same effect can be obtained regardless of the starting pattern, regardless of the order in which the lighting pattern is formed. Yes.

  Although the case where the on timing of the load switching element 12 is set simultaneously with the off timing of other load switching elements has been described here, the present invention is not limited to this. For example, when the on-timing of the load switching element overlaps due to variations in the peripheral circuit of the load switching element, it is necessary to flow a large current instantaneously. In order to prevent this, a dead time may be provided in consideration of an error in timing for controlling on and off. That is, the control unit 15 may control the load switching element 12- (n + 1) to be turned on after a predetermined period has elapsed from the timing at which the load switching element 12-n is turned off. Thus, by providing the dead time, the on-timing of the load switching element can be reliably shifted.

  Thus, according to the LED device according to Embodiment 1, in the LED device in which a plurality of LED elements are connected in parallel and the load switching element connected in series with the plurality of LED elements is controlled, input from the outside is performed. On the basis of the lighting control command to be started, the on period of the load switching element that is the starting point is started from the start timing of the control cycle, and the on period of the load switching element other than the starting point is turned off of the load switching element in the previous order Whether or not to divide the lighting pattern into two is determined from the relationship between the timing and the end timing of the control cycle. If not divided, the ON setting is made for the lighting control from the OFF timing of the load switching element in the previous order, and if divided, from the OFF timing of the load switching element in the previous order to the end timing of the control cycle And is set to continue for the remaining ON period from the start timing of the control cycle.

Thereby, whatever the lighting control command is, the maximum current of the DC / DC converter can be suppressed, and the loss of the DC / DC converter can be suppressed. In the first embodiment, the DC / DC converter 3 is a step-down chopper circuit. However, the present invention is not limited to this as long as a desired current is supplied to the LED, and a step-up chopper circuit or a flyback converter may be used.
In the first embodiment, when generating the lighting pattern, the control unit 15 generates the lighting control command 14 from the outside. However, the present invention is not limited to this. For example, the lighting pattern is predetermined in the control device. A lighting pattern may be generated based on the lighting control command.

Embodiment 2. FIG.
In the LED device and the control method thereof shown in the first embodiment, the case where the control cycle is considered only for one cycle is shown. In the second embodiment, a method for reducing switching loss of switching elements connected in series to LED elements in a plurality of consecutive control cycles will be described. The configuration of the LED device according to Embodiment 2 is the same as that shown in FIG. In the LED device according to Embodiment 2, the ON period is determined for the first to Nth load switching elements in this order in the first period among a plurality of consecutive control periods, and the first period and thereafter are 1 The load switching element that is turned on at the end timing of the control cycle in the previous control cycle is set as the starting point, and the on period is set in order from the load switching element that is set as the starting point. The details will be described below.

FIG. 4 shows a lighting pattern when the method for determining the on period of each load switching element 12 of the LED device according to Embodiment 2 is used. FIG. 4 is a diagram in which a control cycle 2 is newly added with the control cycle of the ON period of the load switching element 12 shown in FIG. Moreover, the lighting control command value of the control cycle 2 is shown in the right column on the left side of FIG. 4, and the lighting control command values (I _{LED1 to} I _LED5 of the load switching elements 12-1 to 5 in the control cycle 2 are each 30%. , 30%, 40%, 40%, 50%.

  A feature of the LED device according to the second embodiment is a method for setting an ON period of the load switching element 12 as a starting point. Control cycle 1 determines the on period of each load switching element 12 starting from load switching element 12-1 as in the case of the first embodiment. On the other hand, in the control cycle 2, the load switching element 12 that is turned on at the end timing of the control cycle 1 is set as a starting point. In the example shown in FIG. 4, the load switching element 12-3 is shown as the starting point of the control cycle 2. The method for setting the on period of the load switching element 12-3 is the same as the method for setting the on period of the load switching element 12-1 shown in the first embodiment, and a description thereof will be omitted. The order in which the on periods are set is the order of the load switching elements 12-3, 4, 5, 1, and 2. The method for setting the on period other than the load switching element 12-3 is the same as that in the first embodiment. By setting the load switching element 12 that is set to ON at the end timing of the previous control cycle as a starting point, the number of ON and OFF times in the load switching element 12 can be reduced, and the switching loss of the load switching element 12 is reduced. can do.

  As described above, according to the LED device and the control method thereof according to the second embodiment, the control method in the case where there are a plurality of control cycles is shown, and the ON setting is performed at the end timing in the previous control cycle. By setting the load switching element that is the starting point and applying the lighting pattern generation method in the first embodiment, the number of on / off times of the lighting control command that is the starting point can be reduced, and the LED is connected in series It is possible to reduce the switching loss of the switching element. As in the first embodiment, the maximum current of the DC / DC converter can always be suppressed regardless of the on-period, and the effect of suppressing the loss of the DCDC converter can be obtained. Become.

  DESCRIPTION OF SYMBOLS 1 Power supply main circuit part, 2 Power supply control part, 3 DC / DC converter, 4 Load module part 4, 5 DC power supply, 6 Switching element, 7 Diode, 8 Reactor, 9 Capacitor, 10 Current detection part, 11 LED element, 12 Load switching element, 13 Load switch signal, 14 Lighting control command, 15 Control unit, 16 Current detection signal, 17 Switch signal, 18 Current control unit, 19 Command value generation unit, 20 PI control unit, 21 Carrier frequency output unit

Claims (9)

A load module unit having a plurality of LED elements each connected in parallel, and a plurality of load switching elements connected in series to each of the plurality of LED elements;
A power conversion unit that converts input power from a power source and outputs the power to the load module unit; and
An ON period of the plurality of load switching elements is determined based on a lighting control command value indicating a ratio of a period during which a current flows to the LED element in a control cycle of the load switching element, and the plurality of load switching elements are turned on. Or a control unit that controls off,
An LED device comprising:
The control unit divides an ON period of at least one load switching element among the plurality of load switching elements into a plurality of ON periods within the control cycle, and differs at least once among the plurality of divided ON periods. Determining an on period to start in response to a timing at which the load switching element is turned off;
LED device characterized by the above. The control unit determines an on period to start one of the plurality of on periods in correspondence with a start timing of the control period;
The LED device according to claim 1. When N is an integer of 2 or more and n is an integer of 1 to N-1,
The load module section includes first to Nth LED elements and first to Nth load switching elements, and the first to Nth LED elements and the first to Nth load switching elements are Each is connected in series,
The controller is
The on period of the first to Nth load switching elements is determined in this order,
The ON period of the first load switching element is started in correspondence with the start timing of the control cycle, and the ON period is continued for the lighting control command value corresponding to the first load switching element. Decide
The timing for starting the on period of the (n + 1) th load switching element is determined in correspondence with the timing for controlling the nth load switching element to be turned off, and the determined on period of the (n + 1) th load switching element is started. When the period from the start timing to the end timing of the control cycle is less than or equal to the lighting control command value for the n + 1th load switching element, the ON period of the n + 1th load switching element is divided into a plurality of times within the control cycle Then, one of the plurality of on periods is made to correspond to the start timing of the control cycle, and the on period is started, and the other one is made to correspond to the timing when the nth load switching element is turned off. Determining that the on-period begins,
The LED device according to any one of claims 1 and 2. The controller determines that the ON period of the (n + 1) th load switching element starts at the same time as turning off the nth load switching element;
The LED device according to claim 3. The controller determines that the ON period of the (n + 1) th load switching element starts after a predetermined period from the timing of turning off the nth load switching element;
The LED device according to claim 3. In the case where the control unit determines the ON period of the load switching element in a plurality of consecutive control cycles,
In the first period, the on period of the first to Nth load switching elements is determined in this order,
In the second and subsequent cycles, the load switching element that is turned on at the end timing of the control cycle in the previous control cycle is set as the starting point, and the on period is set in order from the load switching element set as the starting point. To do,
The LED device according to claim 3. The power conversion unit includes a boost chopper circuit, a flyback converter, an H-type buck-boost converter, and a SEPIC.
The LED device according to any one of claims 1 to 6. A load module unit having a plurality of LED elements each connected in parallel and a plurality of load switching elements connected in series to each of the plurality of LED elements;
A power conversion unit that converts input power from a power source and outputs the power to the load module unit; and
A control unit that controls on periods of the plurality of load switching elements by controlling the plurality of load switching elements to be on or off; and
A method for controlling an LED device comprising:
A first step in which the control unit captures a lighting control command value indicating a ratio of a period during which a current of the plurality of LED elements flows in each control cycle;
A second step in which the control unit sets an order of determining an on period for the plurality of load switching elements;
The control unit determines an on period of the load switching element set as the starting point in the second step as an on period from the start timing of the control period by an amount corresponding to the lighting control command value corresponding to the load switching element. Steps,
The control unit turns on an on period of a load switching element other than the load switching element set as the starting point in correspondence with a timing at which the load switching element whose on period is determined before the load switching element is turned off. A fourth step of deciding to control
A method for controlling an LED device, comprising: When N is an integer of 2 or more and n is an integer of 1 to N-1,
The load module section includes first to Nth LED elements and first to Nth load switching elements, and the first to Nth LED elements and the first to Nth load switching elements are respectively Connected in series,
In the second step, the control unit determines an ON period for the first to Nth load switching elements in this order,
In the third step, the control unit determines an ON period of the first load switching element,
In the fourth step, the control unit determines a timing at which an on period of the n + 1th load switching element starts to correspond to a timing at which the nth load switching element is controlled to be turned off. When the period from the start timing of the ON period of the (n + 1) th load switching element to the end timing of the control cycle is equal to or less than the lighting control command value for the (n + 1) th load switching element, An on-period is divided into a plurality of times within the control cycle, one of the plurality of on-periods is made to correspond to the start timing of the control cycle, and the other one is made the n-th load Determining that the on period starts in response to the timing when the switching element is turned off;
The method for controlling an LED device according to claim 8.

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