JP7147656B2 - load driver - Google Patents

Description

The present invention relates to a load driving device for driving an LED load such as an LED lighting composed of light emitting diodes (hereinafter referred to as LEDs).

Conventionally, Patent Document 1 discloses a load drive circuit that drives a load using a filament type lamp as a load. This load drive circuit drives the lamp with a duty ratio calculated from the power supply voltage applied to the lamp, thereby keeping the illuminance of the lamp within a certain range and preventing flickering of the lamp.

On the other hand, Patent Document 2 proposes a technology for preventing flickering by driving an LED with a duty ratio calculated from a power supply voltage in the same manner as Patent Document 1 in a drive device that drives an LED load. In this driving device, the voltage drop width in the forward direction of the LED is Vf [V], the power supply voltage is VB [V], the duty ratio is 100%, and the LED is driven at the target voltage Vx [V]. A duty ratio Ti is set based on the following equation. Note that the voltage drop width Vf [V] in the forward direction of the LED is a fixed value stored in advance in a memory or the like.

(Number 1)
Ti=(Vx-Vf)/(VB-Vf)

JP 2011-119236 A JP 2018-6187 A

However, in the case of LEDs, since they are affected by diode characteristics, even if the duty ratio is calculated simply based on the power supply voltage applied to the LEDs as in Patent Document 1, flicker cannot be prevented accurately.

Further, even if the duty ratio is set only by the power supply voltage VB [V] and the voltage drop width Vf [V] stored in advance as a fixed value as in Patent Document 2, the voltage drop at the LED is actually has dependency on the number of LED stages and voltage temperature, it is impossible to set an appropriate duty ratio. For this reason, when an LED lamp with a plurality of LEDs having different numbers of stages is used as a load, the illuminance cannot be kept constant.

In view of the above points, the present invention provides a load driving device for driving an LED load composed of LEDs, capable of suppressing flickering even when the LED load is composed of a plurality of LEDs having different numbers of stages. for the purpose.

In order to achieve the above object, the invention according to claim 1 provides light emitting diodes (61a, 62b) having limiting resistors (61b, 62b) and a predetermined number of stages based on a power supply voltage when a drive instruction signal is input. is used to drive a load (60) connected in series with a voltage detector (23) for detecting the power supply voltage, and a memory storing data on the voltage dependency of the voltage drop width of the LED a control unit (25) for calculating, when the drive instruction signal is input, the duty ratio of the drive signal based on the voltage detection result of the voltage detection unit and the voltage dependency data stored in the storage unit; (21), a load drive output unit (22) that outputs a drive signal with the duty ratio calculated by the control unit, and on/off drive according to the duty ratio based on the drive signal, so that the power supply voltage is applied to the load. and a driving device (50) for applying voltage to the LED so as to cause illumination by the LED, and the storage unit stores Vf as the voltage drop width of the LED, ΔVfv as the voltage dependence, and ΔVfv as the voltage dependence data. A target voltage Vx for setting the LED to a constant illuminance is stored, and the control unit is characterized in that the power supply voltage is VB and the duty ratio Ti is calculated by Equation 3 described later.

In this way, the load driving device stores the characteristics of the LED load to be driven, and calculates the duty ratio Ti by taking into account the amount of change in the voltage drop width corresponding to the fluctuation of the power supply voltage. As a result, flickering can be suppressed even if a plurality of LED loads have different numbers of LED stages.

In the invention according to claim 2, the storage unit stores, as voltage dependency data, the voltage drop width of the LED Vf, the voltage dependency ΔVfv, the target voltage when the LED has a constant illuminance Vx, the LED The number of stages is stored as n, and the control unit is characterized in that the power supply voltage is VB and the duty ratio Ti is calculated by Equation 4 described later.

In this way, flickering can be further suppressed by calculating the duty ratio Ti in consideration of the number of stages of the LEDs in addition to the amount of change in the voltage drop width corresponding to the fluctuation of the power supply voltage VB.

The invention according to claim 3 has a temperature detection unit (24) for detecting the ambient temperature, the storage unit also stores temperature dependency data of the LED, and the control unit receives a drive instruction signal. Then, the duty ratio of the driving signal is calculated based on the temperature dependence data in addition to the voltage detection result of the voltage detection unit and the voltage dependence data stored in the storage unit. A value obtained by subtracting ΔVft ( Ta−Tx ) from the denominator in the formula for calculating the duty ratio, where ΔVft is the property, Tx is the ambient temperature, and Ta is the target temperature when the LED is at a constant illuminance. , the duty ratio Ti is calculated.

In this way, the duty ratio Ti can be calculated by taking into consideration the amount of change in the voltage drop width corresponding to the temperature change, in addition to the power supply voltage change and the number of stages of the LEDs. By doing so, it is possible to further suppress flickering.

The load driving devices described in claims 1 to 3 can be provided, for example, as described in claim 4, one for each load.

Further, the load driving devices described in claims 1 to 3 may be used in common for driving a plurality of loads composed of LEDs with different numbers of stages as described in claims 5 and 6. good.

In that case, as shown in claim 5, the number of drive devices corresponding to each of the plurality of loads is provided, the storage section stores data for each of the plurality of loads, and the control section stores data for each of the plurality of loads. A duty ratio Ti is calculated, a plurality of loads and the calculated duty ratios Ti are linked, and output to the load drive output unit, and the linked duty ratios are output to the load drive output unit for each of the plurality of loads. By outputting the drive signal at Ti, the corresponding drive device can be turned on and off.

Further, as shown in claim 6, the number of load drive output units and drive devices corresponding to each of the plurality of loads is provided, the storage unit stores data for each of the plurality of loads, and the control unit stores a plurality of duty ratio Ti is calculated for each of the loads, and the duty ratio Ti corresponding to the load is output to the load drive output unit used to drive the corresponding load among the plurality of loads, and the load drive output unit outputs , and the duty ratio Ti, the corresponding drive device can be turned on and off.

It should be noted that the reference numerals in parentheses attached to each component etc. indicate an example of the correspondence relationship between the component etc. and specific components etc. described in the embodiments described later.

It is the figure which showed the block structure of the load drive device concerning 1st Embodiment. It is a circuit diagram of an LED load in the case of one stage of LEDs. FIG. 3 is a circuit diagram of an LED load when LEDs are arranged in three stages; FIG. 10 is a diagram showing the results of examining the relationship between the amount of change in current and the variation in power supply voltage while changing the number of stages of LEDs forming an LED load. FIG. 5 is a diagram showing the results of investigating the relationship between the amount of change in current and the variation in ambient temperature by changing the number of stages of LEDs that constitute the LED load. It is the figure which showed the block structure of the load drive device concerning 2nd Embodiment. It is the figure which showed the block structure of the load drive device concerning 3rd Embodiment.

An embodiment of the present invention will be described below with reference to the drawings. In addition, in each of the following embodiments, portions that are the same or equivalent to each other will be described with the same reference numerals.

(First embodiment)
A load driving device according to a first embodiment of the present invention will be described. FIG. 1 is a diagram showing a block configuration of the load driving device 10. As shown in FIG. First, the configuration of the load driving device 10 will be described with reference to this figure. In addition, in this embodiment, a form in which the load driving device 10 is provided for each LED load will be described. Although FIG. 1 shows only the load driving device 10 provided for one of the LED loads, each load driving device 10 has the same configuration.

A load driving device 10 shown in FIG. 1 is provided for each of a plurality of LED loads 60, and includes a control integrated circuit (hereinafter referred to as a control IC) 20, a voltage detection circuit 30, a temperature detection circuit 40, and a driving device 50. It is considered to be a configuration.

The control IC 20 is composed of, for example, a microcomputer having a CPU, ROM, RAM, I/O, etc., and is driven by a predetermined voltage (eg, 5V). In this embodiment, the control IC 20 has a control section 21, a load drive output section 22, a voltage detection section 23, a temperature detection section 24, a non-volatile memory 25, etc., and drives the LED load 60 based on the drive instruction signal. do.

The control unit 21 calculates the duty ratio based on, for example, a drive instruction signal from the vehicle, and outputs a control signal indicating the calculated duty ratio to the load drive output unit 22 in order to drive the LED load. . Specifically, the control unit 21 adjusts the duty ratio based on the voltage detection result of the voltage detection unit 23, the temperature detection result of the temperature detection unit 24, and various data stored in the nonvolatile memory 25. have set. The details of the calculation method of this duty ratio will be described later.

The load drive output unit 22 drives the LED load 60 by outputting a drive signal for turning on/off the drive device 50 according to the duty ratio calculated by the control unit 21 . As will be described later, since the driving device 50 is configured by switching elements, the load drive output unit 22 drives a voltage or current having a predetermined duty ratio for driving the switching elements that constitute the driving device 50. output as a signal.

The voltage detection unit 23 detects the power supply voltage VB by converting the monitor voltage Vs corresponding to the power supply voltage VB detected by the voltage detection circuit 30 into a digital value, and is configured by an AD conversion circuit or the like. . Since the allowable input voltage of the control IC 20 is 5V or less, the voltage detection circuit 30 described above divides the power supply voltage VB to 5V or less to generate the monitor voltage Vs. The voltage detection section 23 converts the monitor voltage Vs indicated by the analog value generated by the voltage detection circuit 30 into a digital value and inputs it to the control section 21 .

The temperature detection unit 24 receives a temperature detection signal according to the ambient temperature transmitted from the temperature detection circuit 40 and converts it into a digital value, and is configured by an AD conversion circuit or the like.

The nonvolatile memory 25 corresponds to a storage unit, and is a non-transitional tangible recording medium such as a flash memory that constitutes a ROM or the like built in the control IC 20, and stores various data so that the control unit 21 can read the data. It's becoming Specifically, the nonvolatile memory 25 stores Vf [V], Vx [V], Tx [°C], ΔVfv [V/V], and ΔVft [V/°C] as the characteristics of the LED load 60. there is Vf is the voltage drop width in the forward direction of the LED. Vx is a target voltage when the illuminance of the LED load 60 is kept constant, and it is assumed that the illuminance is kept constant when driven at the target voltage Vx with a duty ratio of 100%. Tx is a target temperature at which the illuminance of the LED load 60 is kept constant, and it is assumed that the illuminance is constant when driven at the target temperature Tx with a duty ratio of 100%. ΔVfv is the voltage dependency of Vf, that is, the amount of change in Vf when the power supply voltage fluctuates by 1V. ΔVft is the temperature dependence of Vf, that is, the amount of change in Vf when the ambient temperature fluctuates by 1°C.

In this embodiment, the characteristics of the LED load 60 stored in the nonvolatile memory 25 are those of the LED load 60 to be driven by the load driving device 10 . Therefore, the characteristics corresponding to the LED loads 60 to be driven are separately stored in the nonvolatile memory 25 of each load driving device 10 .

The voltage detection circuit 30 converts the power supply voltage VB into a monitor voltage Vs corresponding to the power supply voltage VB and inputs it to the voltage detection section 23 . For example, the voltage detection circuit 30 is composed of voltage dividing resistors, and divides the power supply voltage VB by the voltage dividing resistors to generate the monitor voltage Vs. The monitor voltage Vs generated by the voltage detection circuit 30 is set to an allowable input voltage to the control IC 20, for example, 5 V or less.

The temperature detection circuit 40 is composed of a temperature sensor or the like, and inputs a temperature detection signal corresponding to the ambient temperature to the temperature detection section 24 . The ambient temperature here is the temperature around the LED load 60 that correlates with the temperature of the LED load 60 to be driven. Although it is preferable to directly measure the temperature of the LED load 60 , it is difficult to measure directly. Of course, instead of using the ambient temperature as the temperature of the LED load 60 as it is, for example, the ambient temperature is corrected by multiplying the temperature by a predetermined coefficient, or the ambient temperature and the LED load corresponding to the ambient temperature are determined using a correlation diagram that has been investigated in advance by experiments. The temperature of the LED load 60 may be obtained more accurately by obtaining the temperature of the LED load 60 . For example, the temperature sensor is composed of diodes arranged in multiple stages, and outputs a temperature detection signal corresponding to the ambient temperature based on the change in forward voltage drop width Vf of the diodes due to temperature characteristics.

The drive device 50 supplies drive current for driving the LED load 60 based on the drive signal from the load drive output section 22 . For example, the driving device 50 is composed of a MOSFET, a transistor, an IPD (intelligent power device), or the like. By duty-driving the drive device 50 based on the drive signal, the average current value of the drive current supplied to the LED load 60 is controlled to a value that keeps the illuminance of the LED load 60 constant. there is

The LED load 60 performs LED lighting by driving the driving device 50 with duty. Specifically, the LED load 60 performs LED lighting by applying the power supply voltage VB when the driving device 50 is turned on. The illuminance of the LED lighting changes according to the average current value supplied to the LED load 60, that is, the magnitude of the current value per unit time, and the greater the average current value, the higher the illuminance. Since the average current value is variable according to the duty ratio of the drive current of the drive device 50, the illuminance of the LED load 60 is adjusted based on the duty ratio set by the controller 21. there is

Although only one LED load 60 is shown in FIG. 1, a plurality of LED loads 60 having different numbers of stages are actually provided. driven by 2A shows a configuration including a first load 61 as the LED load 60, and FIG. 2B illustrates a configuration including a second load 62 as the LED load 60. FIG. The first load 61 and the second load 62 are different in the number of stages of the LEDs 61a and the number of stages of the LEDs 62a. In the first load 61, a limiting resistor 61b is connected in series with the LED 61a, and in the second load 62, a limiting resistor 62b is connected in series with the LED 62a. Therefore, the current is limited so that an excessive current does not flow through each of the LEDs 61a and 62a.

The load driving device 10 according to the present embodiment is configured as described above. Next, the operation of the load driving device 10 of this embodiment will be described.

The load driving device 10 shown in FIG. 1 is driven, for example, based on a driving instruction signal from the vehicle. For example, when a user switches a lighting switch provided in the vehicle from off to on, a driving instruction signal for driving the LED load 60 and lighting the LED lighting is input to the load driving device 10 accordingly. . As a result, in the control unit 21, the duty ratio is set based on the voltage detection result of the voltage detection unit 23, the temperature detection result of the temperature detection unit 24, and various data stored in the nonvolatile memory 25, thereby driving the load. The output section 22 outputs a voltage or current driving signal having the duty ratio. As a result, the drive device 50 is duty-driven based on the drive signal, the LED load 60 is driven, and the LED lighting is turned on.

Here, the details of the calculation method of the duty ratio by the control unit 21 will be described.

As described above, the control unit 21 determines the duty ratio from the following equation based on the voltage detection result of the voltage detection unit 23, the temperature detection result of the temperature detection unit 24, and various data stored in the nonvolatile memory 25. Ti is calculated.

(Number 2)
Ti=(Vx−nVf)/
{VB-nVf-ΔVfv(VB-Vx)-ΔVft(Ta-Tx)}
In the LED load 60, even if the power supply voltage VB is the same voltage value, the value of the current flowing through the LEDs changes depending on the number of stages of LEDs configured. As shown in FIG. 2, FIG. 3 shows the measurement of the amount of current change when the power supply voltage VB is changed for each of the first load 61 having one stage of LEDs 61a and the second load 62 having three stages of LEDs 62a. The results are shown. Here, the power supply voltage VB of 13 V is used as a reference, and the amount of current change from that point is shown. Further, FIG. 4 shows the result of measuring the amount of current change when the ambient temperature Ta is changed for each of the first load 61 having one LED 61a and the second load 62 having three LEDs 62a. . Here, the ambient temperature Ta is assumed to be -30° C. to 80° C. as the operating environment of the vehicle, and the amount of current change from -30° C. is shown.

As shown in these figures, the inclination of the amount of current change with respect to the change in the power supply voltage VB and the change in the ambient temperature Ta differs between the one-stage LED 61a and the three-stage LED 62a. As described above, when the power supply voltage VB or the ambient temperature Ta fluctuates, the amount of current change changes. It is not possible to deal with variations in the number of stages, the power supply voltage VB, and the ambient temperature Ta.

For this reason, in the present embodiment, the duty ratio Ti is calculated based on Equation 2 above, taking into consideration the number of stages of the LEDs, the power supply voltage VB, and the ambient temperature Ta.

Specifically, by multiplying Vf in each term by the number of stages n, the voltage drop width is determined according to the number of stages. Further, by multiplying the difference between the power supply voltage VB and the target voltage Vx by ΔVfv, when there is a voltage difference between the power supply voltage VB and the target voltage Vx, the voltage drop width corresponding to the voltage difference can be obtained. The amount of change is obtained. Similarly, by multiplying the difference between the ambient temperature Ta and the target temperature Tx by ΔVft, if there is a temperature difference between the ambient temperature Ta and the target temperature Tx, the voltage drop width corresponding to the temperature difference is obtained. Therefore, the voltage drop width Vf corresponding to the number of stages of LEDs is subtracted from the target voltage Vx, and the voltage drop width Vf corresponding to the number of stages of LEDs is subtracted from the power supply voltage VB. The duty ratio Ti is calculated by dividing by the value obtained by subtracting .

Note that the duty ratio Ti is calculated for each of the first load 61 and the second load 62, and the target voltage Vx is the same voltage. For example, the law stipulates that the LED should be driven at a voltage of 13.5 V and a duty ratio of 100%, with the upper limit being 13.5 V, in consideration of the life of the LED. . Therefore, for example, 13.0 V, which is lower than that, is set as the target voltage Vx. Then, if the power supply voltage VB is higher than the target voltage Vx, the voltage difference VB-Vx is obtained, and by multiplying it by the amount of change in the voltage drop width corresponding to the voltage difference, the third term in the denominator of Equation 2 is is required.

As described above, the characteristics of the LED load 60 to be driven are stored in the load driving device 10, and each load driving device 10 calculates the duty ratio Ti in consideration of the characteristics. Therefore, even if the LED loads 60 have different numbers of stages of LEDs, flickering can be suppressed.

(Second embodiment)
A second embodiment will be described. This embodiment differs from the first embodiment in that a plurality of LED loads 60 are driven by a common load driving device 10, and the rest is the same as in the first embodiment. , only the portions different from the first embodiment will be described.

As shown in FIG. 5, the load driving device 10 of this embodiment includes driving devices 50 corresponding in number to the LED loads 60, and a driving signal is output from the load driving output unit 22 to each driving device 50. It is designed to be

In such a form, all the characteristics of each LED load 60 are stored in the non-volatile memory 25, and the duty ratio Ti according to the characteristics of each LED load 60 is calculated separately by the controller 21. FIG. Then, the calculation result for each LED load 60 is linked so that the duty ratio Ti of which LED load 60 is shown and transmitted to the load drive output unit 22, and the load drive output unit 22 corresponds to the LED load 60 A driving signal corresponding to the calculated duty ratio Ti is output to the driving device 50 .

By doing so, when the plurality of LED loads 60 are driven by the common load driving device 10, flickering can be suppressed even if the plurality of LED loads 60 have different numbers of LED stages. It becomes possible.

(Third Embodiment)
A third embodiment will be described. This embodiment also differs from the first embodiment in that a plurality of LED loads 60 are driven by a common load driving device 10, and other aspects are the same as in the first embodiment. , only the portions different from the first embodiment will be described.

As shown in FIG. 6, the load driving device 10 of this embodiment also includes driving devices 50 corresponding in number to the LED loads 60 as in the second embodiment. A number corresponding to the load 60 is provided. In the case of this embodiment, by providing a plurality of load drive output units 22 as external components independent from the control IC 20, it is easy to match the number of the LED loads 60. You can prepare.

In this manner, the number of load drive output units 22 and drive devices 50 corresponding to the number of LED loads 60 may be provided. Also in this case, as in the second embodiment, all the characteristics of each LED load 60 are stored in the nonvolatile memory 25, and the duty ratio Ti according to the characteristics of each LED load 60 is set separately by the controller 21. Calculate to Then, the calculation result for each LED load 60 is transmitted to the load drive output unit 22 used for driving the LED load 60, and the load drive output unit 22 outputs a drive signal corresponding to the calculated duty ratio Ti to the corresponding drive device 50. to output Even in this way, the same effect as in the second embodiment can be obtained.

(Other embodiments)
The present invention is not limited to the above-described embodiments, and can be appropriately modified within the scope of the claims.

For example, in the above embodiment, the first load 61 and the second load 62 were used as the LED loads 60, but the number of the LED loads 60 is arbitrary, and the number of stages of LEDs constituting each LED load 60 is arbitrary. is also arbitrary.

Further, in the above-described embodiment, an example is shown in which it is possible to cope with all variations in the number of stages of LEDs constituting the LED load 60, the power supply voltage VB, and the ambient temperature Ta. However, even if it is not possible to deal with all of them, it is sufficient if the duty ratio Ti can be set in consideration of at least the amount of change in the voltage drop width corresponding to the fluctuation of the power supply voltage VB.

For example, when the duty ratio Ti is set by considering only the amount of change in the voltage drop width corresponding to the fluctuation of the power supply voltage VB, the duty ratio Ti can be calculated by Equation (3). If the number of stages of LEDs is taken into account in addition to the amount of change in the voltage drop width corresponding to the fluctuation of the power supply voltage VB, the duty ratio Ti can be calculated by Equation 4. Furthermore, if the amount of change in voltage drop width corresponding to temperature fluctuations is taken into consideration in addition to the amount of change in voltage drop width corresponding to fluctuations in power supply voltage VB, the duty ratio Ti can be calculated by equation (5).

(Number 3)
Ti=(Vx−Vf)/{VB−Vf−ΔVfv(VB−Vx)}

(Number 4)
Ti=(Vx−nVf)/{VB−nVf−ΔVfv(VB−Vx)}

(Number 5)
Ti=(Vx−Vf)/{VB−Vf−ΔVfv(VB−Vx)−ΔVft(Ta−Tx)}

DESCRIPTION OF SYMBOLS 10... Load drive device 20... Control IC 21... Control part 22... Load drive output part 23... Voltage detection part 24... Temperature detection part 25... Non-volatile memory 30... Voltage detection circuit 40... Temperature Detection circuit 50 Drive device 60 LED load 61 First load 61a LED 61b Limiting resistance 62 Second load 62a LED 62b Limiting resistance

Claims (6)

When the drive instruction signal is input, the load drive drives the load (60) in which the limiting resistors (61b, 62b) and the light emitting diodes (61a, 62b) having a predetermined number of stages are connected in series based on the power supply voltage. a device,
a voltage detection unit (23) for detecting the power supply voltage;
a storage unit (25) storing voltage dependency data of the voltage drop width of the light emitting diode;
When the drive instruction signal is input, the control unit (21 )When,
a load drive output unit (22) that outputs the drive signal at the duty ratio calculated by the control unit;
a driving device (50) that applies the power supply voltage to the load by performing on/off driving according to the duty ratio based on the driving signal, so that illumination is performed by the light emitting diode; have
The storage unit stores Vf as the voltage drop width of the light emitting diode, ΔVfv as the voltage dependency, and Vx as the target voltage when the light emitting diode has a constant illuminance as the voltage dependency data. ,
The control unit sets the power supply voltage to VB and sets the duty ratio Ti to
Ti=(Vx−Vf)/{VB−Vf−ΔVfv(VB−Vx)}
A load driving device characterized in that it is calculated by a mathematical expression represented by: When the drive instruction signal is input, the load drive drives the load (60) in which the limiting resistors (61b, 62b) and the light emitting diodes (61a, 62b) having a predetermined number of stages are connected in series based on the power supply voltage. a device,
a voltage detection unit (23) for detecting the power supply voltage;
a storage unit (25) storing voltage dependency data of the voltage drop width of the light emitting diode;
When the drive instruction signal is input, the control unit (21 )When,
a load drive output section (22) that outputs the drive signal at the duty ratio calculated by the control section;
a driving device (50) that applies the power supply voltage to the load by performing on/off driving according to the duty ratio based on the driving signal, so that illumination is performed by the light emitting diode; have
The storage unit stores, as the voltage dependency data, the voltage drop width of the light emitting diode Vf, the voltage dependency ΔVfv, the target voltage when the light emitting diode has a constant illuminance Vx, and the light emitting diode The number of stages is stored as n,
The control unit sets the power supply voltage to VB and sets the duty ratio Ti to
Ti=(Vx−nVf)/{VB−nVf−ΔVfv(VB−Vx)}
A load driving device characterized in that it is calculated by a mathematical expression represented by: having a temperature detection unit (24) for detecting ambient temperature,
The storage unit also stores temperature dependency data of the light emitting diode,
The control unit
When the drive instruction signal is input, the drive signal is generated based on the temperature dependency data in addition to the voltage detection result of the voltage detection unit and the voltage dependency data stored in the storage unit. The duty ratio of is calculated,
Assuming that the temperature dependence is ΔVft, the ambient temperature is Tx, and the target temperature is Ta when the light emitting diode has a constant illuminance,
3. The duty ratio Ti according to claim 1, wherein the duty ratio Ti is calculated by subtracting ΔVf t ( Ta−Tx ) from the denominator of the formula for calculating the duty ratio. load drive. 4. The load driving device according to any one of claims 1 to 3, wherein one load driving device is provided corresponding to each of the loads. used to drive a plurality of the loads composed of the light-emitting diodes in different stages;
The driving devices are provided in a number corresponding to each of the plurality of loads,
The storage unit stores the data for each of the plurality of loads,
The control unit calculates the duty ratio Ti for each of the plurality of loads, associates the plurality of loads with the calculated duty ratio Ti, and outputs the calculated duty ratio Ti to the load drive output unit;
1. The load drive output unit outputs the drive signal with the associated duty ratio Ti for each of the plurality of loads, thereby turning on and off the corresponding drive device. 4. The load driving device according to any one of 3. used to drive a plurality of the loads composed of the light-emitting diodes in different stages;
The load drive output units and the drive devices are provided in numbers corresponding to each of the plurality of loads,
The storage unit stores the data for each of the plurality of loads,
The control section calculates the duty ratio Ti for each of the plurality of loads, and outputs the duty ratio Ti corresponding to the load to the load drive output section used to drive the corresponding load among the plurality of loads. output Ti,
4. The load drive according to any one of claims 1 to 3, wherein the load drive output unit outputs the drive signal with the duty ratio Ti to turn on/off the corresponding drive device. Device.

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