WO2019003498A1

WO2019003498A1 - Led device and control method therefor

Info

Publication number: WO2019003498A1
Application number: PCT/JP2018/008359
Authority: WO
Inventors: 友一坂下; 義章石黒; 章太渡辺
Original assignee: 三菱電機株式会社
Priority date: 2017-06-27
Filing date: 2018-03-05
Publication date: 2019-01-03
Also published as: JP2019194992A; JPWO2019003498A1; JP6726283B2

Abstract

The purpose of the present invention is to obtain an LED device capable of limiting the maximum current from a power source that supplies power to an LED element. This is achieved by an LED device comprising a load module unit having a plurality of LED elements connected in parallel and a plurality of load-switching elements connected in series to each of the plurality of LED elements, and a control unit for controlling the plurality of load-switching elements to turn on or off, wherein the control unit divides the on-period of at least one load-switching element among the plurality of load-switching elements into a plurality of on-periods in the control cycle, and sets on-periods so that at least one of the plurality of on-periods resulting from the division begins when a different load-switching element is timed to turn off.

Description

LED device and control method thereof

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

In recent years, adoption of LEDs (light emitting diodes) has been accelerated for various light sources from the viewpoint of energy saving. For example, a light source using a plurality of LEDs is also used for automobile headlights. The LEDs not only have high efficiency, but also have a small light source and can limit the lighting area. Therefore, an ADB (Adaptive Driving Beam) is mounted to light only the necessary area using a plurality of LEDs. The ADB assigns an LED to each irradiation range, and when an oncoming vehicle or the like is detected, turns on / off / light-controls the LED corresponding to the detection portion.

As an LED device used for such an ADB, there is an LED device connected in parallel to a plurality of LED groups consisting of a plurality of LED elements connected in series and connected to an LED-driven power supply (for example, Patent Document 1) reference). In the LED device shown in Patent Document 1, a switching element is connected to each LED group, and the driving timing of each switching element is divided into one cycle of pulse energization divided by the number of LED groups, that is, LED When five groups are connected in parallel, it is characterized in that control is performed by being shifted by 1⁄5 cycle. With such a configuration, it is possible to prevent the rapid rise of the power supply that supplies current to each LED, and to suppress the generation of noise.

JP, 2008-91311, A

Patent Document 1 discloses an LED device that performs pulse energization with the same pulse width for each LED group, but as the control of the LED device is advanced in recent years, the LED lighting pulse width of the LED group may be different. Control is expected to be performed. For example, in the case of the LED device used in the above-described ADB, it is assumed that lighting is performed along a curve of the road, and the lighting pulse width of each LED group is changed to positively illuminate the direction in which the road continues There is a case. In the method shown in Patent Document 1 in which one cycle of pulse energization is fixed at timing shifted by each cycle divided by the number of LED groups and controlled, the condition that the ON time width of LED lighting pulse of each LED group is different is applied In this case, there is a problem that the maximum current of the power supply for supplying the current to the LED may be increased.

For example, assuming that the LED groups are 5 parallel and the current flows in each LED group within 90%, 70%, 50%, 30%, and 10%, respectively, 1A flows in 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 cycle, the output current of the power supply will change from 0A to 5A. When the maximum current of the power supply supplied to the LED element is increased as in this example, not only the generation of noise increases but also the loss of the power source for supplying the current to the LED element increases.

The present invention has been made to solve the problems as described above, and in an LED device in which a plurality of LED elements are connected in parallel, at least one switching element among switching elements connected in series to each LED element The LED device capable of suppressing the maximum current of the power supply that supplies power to the LED element even when the length of the on period of the switch is different from the length of the on period of the other switching elements The aim is to get

An LED device according to the present invention includes: a load module unit including a plurality of LED elements connected in parallel and a plurality of load switching elements connected in series to each of the plurality of LED elements; Turning on the plurality of switching elements based on a lighting control command value indicating a ratio of a period during which current flows to the LED element in the control period of the power conversion unit that converts the power into power and outputs it to the load module unit A control unit that determines a period and controls a plurality of load switching devices to turn on or off, the control unit including an on period of at least one of the plurality of load switching devices; Is divided into a plurality of on periods within the control period, and at least one of the divided plurality of on periods is different The load switching element determines the ON period to start so as to correspond to the timing of the off, characterized by.

Further, according to a control method of an LED device according to the present invention, a load module unit including a plurality of LED elements 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 the input power from the power supply and outputs the power to the load module unit; and a control unit that controls the on periods of the plurality of load switching devices by controlling the plurality of load switching devices on or off. A control method of an LED device, comprising: a first step of taking in a lighting control command value indicating a ratio of a period during which current of a plurality of LED elements flows in each control cycle; and a plurality of control units The second step of setting the order in which the on period is determined for the load switching element, and the control unit sets the starting point in the second step The third step of determining the on period of the load switching element as the on period by the lighting control command value corresponding to the load switching element from the start timing of the control period, and the load switching element other than the load switching element set as the starting point And a fourth step of determining the on period of the load switching device to be controlled to be on corresponding to the timing of controlling the load switching device whose on period has been determined before the load switching device to turn off. It is characterized by

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 of the switching elements connected in series to each LED element is the length of the on period of the other switching elements Even under different conditions, the maximum current of the power supply that supplies power to the LED element 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
An 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 a 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. In addition, when there are a plurality of identical or similar components as load switching elements, they are distinguished by adding "-" and numerals / symbols like load switching elements 12-1 to 12-N. In addition, when not distinguishing each component of the same or similar component which exists in multiple numbers, or collectively naming, it abbreviate | omits "-" and a number and a symbol like the load switching element 12, for example, and demonstrates. .

The LED device shown in the first embodiment of the present invention comprises a power supply main circuit unit 1, a power supply control unit 2 for controlling the power supply main circuit unit 1, and a DC power supply 5 for supplying power to the power supply main circuit unit 1. There is. The power supply 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 the DC power supply 5 has one terminal of the DC / DC converter 3 (here, The load module unit 4 is connected to the other input terminal of the DC / DC converter 3 (here, it is referred to as an output terminal for convenience).

The DC / DC converter 3 is a power conversion unit, converts the power input from the DC power supply 5 and outputs the power to the load module unit 4. The DC / DC converter 3 is configured of 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, the switching element 6 and the reactor 8 are provided on the positive side bus connected to the positive side input terminal of the DC / DC converter 3. The diode 7 is connected on the cathode side to the connection point between the switching element and the reactor, and on the anode side to the negative bus connected to the negative input terminal of the DC / DC converter 3. In addition, one terminal of the capacitor 9 is connected to the positive busbar between the reactor 8 and the positive output terminal, and the other terminal of the capacitor 9 is connected to the negative busbar. The DC / DC converter 3 adjusts the amount of current supplied to the load module unit 4 to a desired value by controlling the on / off of the switching element 6 according to the control signal output from the power supply control unit 2, Power is supplied to a load module unit 4 provided with a certain LED element. It goes without saying that the DC / DC converter 3 is not limited to the configuration shown in FIG. 1 and may be any circuit as long as it is a circuit that 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 single-ended primary-inductance converter (SEPIC) may be used.

The load module unit 4 has a plurality of LED elements 11 connected in parallel, and in the example shown in FIG. 1, the LED device includes N (N is an integer of 2 or more) LED elements 11-1 to N The first to Nth LED elements are provided. Although each LED element 11 is described as a plurality of LED elements connected in series, the number of LED elements does not have to be plural, and the present invention can be applied even in the case of one. In each LED element 11, a load switching element 12 is connected in series to each LED element 11. In the example shown in FIG. 1, the load switching elements are connected to each of the LED elements 11-1 to N. 12-1 to 12 N (first to Nth load switching elements) are connected in series. Here, although the load switching element 12 may be any type, 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 on or off in accordance with 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 N are electrically conducted and power is supplied, and when the load switching elements 12-1 to N are off, the inside of the load module unit 4 The LED elements 11-1 to N corresponding to the respective load switching elements 12-1 to N become electrically nonconductive and the power supply is stopped.

The power supply main circuit unit 1 further includes a current detection unit 10 that detects a circuit current flowing through the reactor 8, the load module unit 4, etc. For example, the circuit current is detected as a voltage value using a resistor, an operational amplifier, etc. . 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 supply 5 is a power supply that outputs DC power, and is, for example, a battery. It is needless to say that any power supply can be used as long as it can output DC power.

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

In the LED device according to the first embodiment, as described above, the lighting control command 14 is input from the outside. Here, the lighting control command 14 includes a lighting control command value corresponding to each LED element 11. The lighting control command value indicates the ratio of the period in which each load switching element 12 is turned on in the control period, that is, the ratio of the period in which 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. The method of setting the lighting control command value may be any method, for example, in the case of being used as a headlight of a car, so that the car brightly illuminates the direction in which the road continues along the curve of the road. The setting method can be performed to increase the ratio of the period in which the current of the corresponding LED element flows.

The 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 the on / off of the switching element 6 according to the switch signal 17 output from the power supply control unit 2 The electric 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. The load module unit 4 performs on / off control of the load switching element 12 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 powered LED element 11 is lit.

Next, the control operation of the DC / DC converter 3 will be described with reference to FIG. The DC / DC converter 3 controls the on / off of the switching element 6 in accordance with the switch signal 17 generated in the control unit 15 to control the amount of current 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 the number of ONs of the load switching elements 12-1 to N set in the command value generation unit 19 described later. And the current value flowing to the LED elements 11-1 to N. That is, the command value generation unit 19 determines the target command of the output current from the product of the number of load switching elements 12 set to ON among the load switching elements 12-1 to N and the current value supplied to the LED element 11. Generate a value For example, when the number of ONs of the load switching element 12 is 3 and the current supplied to each LED element 11 is 1 A, the target command value of the output current of the DC / DC converter 3 is 3A by multiplication of 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 subtracting 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 resulting error is output to the PI control unit 20. The PI control unit 20 performs PI calculation and the like to calculate the control amount so as to reduce the error. 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 the switching element 6 on and off based on this signal, and adjusts the amount of current output to the load module unit 4.

Here, in the above, the description has been made of digital arithmetic processing of a microcomputer or the like, but it is needless to say that the present invention is not limited to this and analog control can also be executed. Also, as a method of calculating the control amount, PI calculation has been described as an example, but any control may be used as long as it is control for causing the target value to converge, 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 / 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 element of the LED element 11 in a desired pattern.

The method of 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 method of generating a lighting pattern of the LED device according to Embodiment 1 of the present invention. FIG. 3 shows a lighting pattern generation method in the case where the LED elements 11 are 5 parallel, that is, N is 5 in FIG. Needless to say, the present invention is not limited to the case where the LED elements 11 are arranged in 5 parallels, and the lighting pattern is similarly set even when the LED elements 11 are smaller than 5 parallels or more than 5 parallels. Can be generated.

In FIG. 3, the percentage (%) shown on the left is the lighting control command value (I _LED1 to I _LED5 ) of each of the LED elements 11-1 to N, that is, the current of each LED element 11-1 to N within the control period. Indicates the percentage of the period during which For example, the LED element 11-3 for which the lighting control command value is set to 50% indicates that the load switching element 12-3 is set to ON only for a 50% period in one control cycle, and the current flows. Further, in FIG. 3, the numerical value on the left of the arrow (⇒) is the lighting control command value, and the numerical value on the right of the arrow (⇒) is the load switch signal 13 for driving the load switching element 12 in the command value generation unit 19. Shows the value after the lighting pattern is generated. Like the load switching element 12-3, the load switching element 12 in which the ratio of 40% + 10% is described indicates that the on period is divided into two in one control cycle. In the example shown in FIG. 3, the load switching element 12-3 is controlled to be on at the same time as the control cycle start timing, continues the on period for a period of 10% of one control period, and one period before the on period is set. At the same time when the load switching element 12 (in the example shown in FIG. 3, the load switching element 12-2 in the example shown in FIG. Show.

In the LED device according to the first embodiment 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. In addition, the control unit 15 is set to determine the on period of the load switching elements 12-1 to 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 of controlling to turn on by -1 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 control is on to the timing when the control is off next, and is set based on the 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 response to the timing at which the different load switching elements 12 are turned off within the control period. That is, the on period is set to turn on the load switching device 12-2 simultaneously with the timing at which the load switching device 12-1 is controlled to be off. The setting of the on period is repeated sequentially for each load switching element 12, 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 causes the load switching element 12-n to turn off in response to the timing at which the load switching element 12- (n + 1) switches. Control on.

Further, the timing at which the load switching element 12-2 is controlled to be turned off is determined based on the load control command value of the load switching element 12-2, but from the timing at which the load switching element 12-2 is controlled to be controlled When the period until the end timing of the cycle is equal to or less than the lighting control command value for the load switching device 12-2, the on period of the load switching device 12-2 is divided into two. One of the two ON control timings is controlled to be ON corresponding to the start timing of the control cycle, and one switching is performed corresponding to the timing when the other load switching element 12-1 is OFF. Control the element on.
The details of the control method will be described below.

Details of a control method of the LED device according to the first embodiment will be described using an example shown in FIG. In the example shown in FIG. 3, the lighting control command values (I _LED1 to I _LED5 ) of the respective LED elements 11-1 to 5 are 90%, 70%, 50%, 30%, and 10%, respectively. This means that 90% of the LED element 11-1 in one control period, 70% of the LED element 11-2 in one control period, 50% of the LED element 11-3 in one control period, the LED element 11-4 And 30% during one control period, and 10% of the LED element 11-5 during one control period. The right side of FIG. 3 shows time on the horizontal axis, and load switch signals 13-1 to 5 actually applied to the load switching elements 12-1 to 5 from the top to the fifth stage. The fifth and subsequent figures show target command values of the output current set in the current control unit 18 when it is assumed that 1A flows to each LED, and as a result of control, the output current of the DC / DC converter 3 and Become.

FIG. 4 is a flowchart illustrating the 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 is taken in at a predetermined timing (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, which is the starting point of the optional load switching elements 12, is set, and the order of the load switching elements 12 for determining the on period is set (step S102). 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, ie, the lighting pattern of the LED element 11 connected to the load switching element 12 set as the starting point, is determined from the start timing of the control cycle according to the lighting control command value (Step S103).
(4) When n is an integer from 1 to N-1 and the on period of the load switching element 12- (n + 1) is set, the lighting control command value (I _LEDn ) of each load switching element 12-n is 100%. And the 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 of 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 value of I _{LEDn + 1} + I _LEDn to prepare for setting of the next 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, I _{LEDn + 1} is changed to a value of I _{LEDn + 1} -I _sub to prepare for the next LED lighting pattern generation (step S107).
The above steps S104 to S107 are executed N-1 times to set the on periods of all the load switching elements 12.

Here, the conditions of the lighting control command value of FIG. 3 will be described as an example.
(1) At predetermined timings, 90%, 70%, 50%, 30%, and 10% are taken in as the lighting control command values I _LED1 to I _LED ₅ of the lighting control command 14 (step S101).
(2) The load switching element 12-1 is set as the starting point (step S102). Further, the load switching elements 12-1 to 5 are set 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) Determine the on period of the load switching element 12-2. The difference value I _{sub1 obtained} by subtracting the difference between 100% and I _LED1 is 10% (step S104), and I _sub1 is smaller than 70% of I _LED2. _Therefore , the on period is divided into two and setting is performed. In the first on period, the 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) Determine the on period of the load switching element 12-3. The value I _{sub2 obtained} by subtracting the difference between 100% and I _LED2 is 40% (step S104), and I _sub2 is smaller than I _LED3. _Therefore , the on setting is set from the off timing of the load switching element 12-2 to the end of the control period And set I _LED3 to I _LED3 -I _sub2 = 10% from the beginning of the control cycle by a value _obtained by subtracting I _sub2 from I _LED3 by I _LED3 -I _sub1 = 50% -40% = 10%. It changes and prepares for determination of the ON period of the next load switching element 12 (Step S107).
(6) Determine the on period of the load switching element 12-4. The difference value I _{sub3 obtained} by subtracting the difference between 100% and I _LED3 is 90%, and I _sub3 is larger than I _{LED 4} so that the ON period of 30% of I _{LED 4} is set from the off timing of the load switching element 12-3. And change the value of I _LED4 to I _LED4 + I _LED3 = 30% + 10% = 40% to prepare for the determination of the on period of the next load switching element 12 (step S106).
(7) Determine the on period of the load switching element 12-5. 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 parallel LED elements 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, there is no large current fluctuation, and the maximum current can be suppressed. I understand that.

Here, the predetermined timing for capturing the command value of the lighting control command 14 described above may be set earlier than the control cycle of the LED by the time necessary to perform the lighting pattern generation from the lighting control command. desirable. In the above example, the lighting control command is indicated by a percentage value, but may be an analog signal or the like. In the above example, the load switching element 12-1 is used as the starting point, but it goes without saying that the same effect can be obtained even if the lighting pattern is formed in any order regardless of which point is the starting point. Yes.

Although the case where the setting of the on timing of the load switching element 12 is made simultaneous with the off timing of the other load switching elements has been described here, the present invention is not limited to this. For example, when the on timings of the load switching elements overlap due to the variation of the load switching element peripheral circuit, 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 of controlling on and off. That is, the control unit 15 may turn on the load switching element 12- (n + 1) after a predetermined period has elapsed from the timing of turning off the load switching element 12-n. By thus providing the dead time, it is possible to reliably shift the on timing of the load switching element.

As described above, according to the LED device according to the first embodiment, a plurality of LED elements are connected in parallel, and the LED device that controls the load switching element connected in series with the plurality of LED elements is externally input The on period of the load switching element as the starting point is started from the start timing of the control cycle based on the lighting control command to be turned on, and the on period of the load switching elements other than the starting point is the off of the load switching element of the previous order. From the relationship between the timing and the end timing of the control cycle, it is determined whether to divide the lighting pattern into two. When not dividing, the ON setting is performed for the lighting control from the OFF timing of the load switching element of the previous order, and when dividing, from the OFF timing of the load switching element of the previous order to the end timing of the control cycle And, it is set to continue for the remaining on period from the start timing of the control cycle.

Thereby, the maximum current of the DC / DC converter can be suppressed and the loss of the DC / DC converter can be suppressed regardless of the lighting control command. 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.
Further, in the first embodiment, when the lighting pattern is generated, the lighting control command 14 from the outside is taken into the control unit 15 and generated. However, the present invention is not limited to this. A lighting pattern may be generated based on the lighting control command.

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

The lighting pattern at the time of using the determination method of the ON period of each load switching element 12 of the LED apparatus which concerns on FIG. 4 at Embodiment 2 is shown. FIG. 4 newly adds a control cycle 2 with the control cycle of the on period of the load switching element 12 shown in FIG. 3 as the control cycle 1. The lighting control command values for control cycle 2 are shown in the right column on the left side of FIG. 4, and the lighting control command values for load switching elements 12-1 to 5 in control cycle 2 (30% for I _LED1 to I _LED5 respectively) , 30%, 40%, 40%, 50%.

The feature of the LED device according to the second embodiment lies in the method of setting the on period of the load switching element 12 as the starting point. The control period 1 determines the on period of each load switching element 12 from the 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 which is set to ON at the end timing of the control cycle 1 is set as a starting point. The example shown in FIG. 4 shows the case where the load switching element 12-3 is the starting point of the control cycle 2. The method of setting the on period of the load switching element 12-3 is the same as the method of setting the on period of the load switching element 12-1 shown in the first embodiment, and the description thereof will be omitted. Further, the order of setting the on period is the order of the load switching elements 12-3, 4, 5, 1, 2. The method of setting the on period other than the load switching element 12-3 is the same as that of the first embodiment. By setting the load switching element 12 that is turned on at the end timing of the previous control cycle as the starting point, the number of times of on and off 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. By setting the load switching element as a starting point and applying the lighting pattern generation method according to the first embodiment, it is possible to reduce the number of ON / OFF of the lighting control command used as the starting point, and connect in series with the LED. It is possible to reduce the switching loss of the switching element. Further, as in the first embodiment, it is possible to always suppress the maximum current of the DC / DC converter regardless of the on period, and to obtain the effect of suppressing the loss of the DCDC converter. Become.

DESCRIPTION OF SYMBOLS 1 power supply main circuit unit, 2 power supply control unit, 3 DC / DC converter, 4

load module unit

4, 5 DC power supply, 6 switching element, 7 diode, 8 reactor, 9 capacitor, 10 current detection unit, 11 LED element, 12 Load switching elements, 13 load switch signals, 14 lighting control commands, 15 control units, 16 current detection signals, 17 switch signals, 18 current control units, 19 command value generation units, 20 PI control units, 21 carrier frequency output units

Claims

A load module unit having a plurality of LED elements 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 supply and outputs the power to the load module unit;
The on period of the plurality of load switching devices is determined based on the lighting control command value indicating the ratio of the period during which current flows to the LED element in the control period of the load switching device, and the plurality of load switching devices 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 in the control cycle, and at least one of the divided on periods is different. Determining an on period to start corresponding to the timing at which the load switching element is turned off;
LED device characterized by
The control unit may determine the on period so as to start one of the plurality of on periods in correspondence with the start timing of the control cycle.
The LED device according to claim 1, characterized in that
When N is an integer of 2 or more and n is an integer of 1 to N-1,
The load module portion has 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 control unit
Determining the on period of the first to Nth load switching elements in this order;
The ON period of the first load switching element is started corresponding to the start timing of the control cycle, and the ON period is continued by the lighting control command value corresponding to the first load switching element. Decide
The start timing of the on period of the (n + 1) th load switching device is determined according to the timing of controlling the nth load switching device to be off, and the determined on period of the (n + 1) th load switching device is started When the period from the timing 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, the on period of the (n + 1) th load switching element is divided into plural in the control cycle. And one of the plurality of on periods is made to correspond to the start timing of the control cycle to start the on period, 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 starts
The LED device according to claim 1 or 2, characterized in that
The control unit may determine the on period of the (n + 1) th load switching device to start simultaneously with the timing at which the nth load switching device is turned off.
The LED device according to claim 3, characterized in that
The control unit may determine the on period of the (n + 1) th load switching device to start after a predetermined period has elapsed from the timing of turning off the nth load switching device;
The LED device according to claim 3, characterized in that
In the case where the control unit determines the on period of the load switching element in a plurality of continuous control cycles,
In the first cycle, the first to Nth load switching elements are determined in this order in the on period,
In the second and subsequent cycles, the load switching element which is turned on at the end timing of the control cycle in the control cycle immediately before 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, characterized in that
The power conversion unit is configured by a boost chopper circuit, a flyback converter, an H-type buck-boost converter, and SEPIC.
The LED device according to any one of claims 1 to 6, characterized in that
A load module unit having a plurality of LED elements connected in parallel and a plurality of load switching elements connected in series with each of the plurality of LED elements;
A power conversion unit that converts input power from a power supply and outputs the power to the load module unit;
A control unit configured to control an on period of the plurality of load switching devices by controlling the plurality of load switching devices to be on or off;
A control method of an LED device provided with
A first step of taking in a lighting control command value indicating a ratio of a period in which the current of the plurality of LED elements flows in each control cycle;
A second step of setting an order in which the control unit determines an on period for the plurality of load switching elements;
The control unit determines the on period of the load switching element set as the starting point in the second step to the on period by the lighting control command value corresponding to the load switching element from the start timing of the control period. Step and
The control unit turns on an on period of a load switching device other than the load switching device set as the starting point in accordance with a timing at which the load switching device whose on period is determined before the load switching device is controlled to be off. A fourth step to decide to control
A method of 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 portion has 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 the on period of 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 the timing at which the on period of the (n + 1) th load switching device starts to correspond to the timing at which the nth load switching device is controlled to be off, and is determined When the period from the start of the on period of the (n + 1) th load switching device 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 device, the (n + 1) th load switching device The on period is divided into a plurality of portions in the control period, one of the plurality of on periods is made to correspond to the start timing of the control period to start the on period, and the other one is the nth load Determining that the on period starts corresponding to the timing at which the switching element is turned off;
The control method of the LED apparatus of Claim 8 characterized by the above-mentioned.