JP7016284B2 - LED module and backlight device - Google Patents

Description

The present invention relates to an LED module and a backlight device including the LED module.

In recent years, since the luminous efficiency of LEDs (Light Emitting Diodes) has improved, LEDs are often used as backlights for liquid crystals and the like.

Although LEDs are current-driven devices, the voltage (VF) across the LEDs required to maintain a specified current level varies considerably due to manufacturing variations between the LEDs. Therefore, when a plurality of LED rows are driven by the same power supply voltage, the row having the maximum VF is detected from the LED rows and the power supply voltage is optimally adjusted (Patent Document 1). reference).

Further, after detecting the optimum power supply voltage in the above, in order to optimize the VF other than the column having the maximum VF, the current flowing through the load resistance is changed to reduce the brightness shift caused by the change of the current. Correction is performed by PWM_Duty drive that adjusts by the on / off time of the LED (see Patent Document 1).

When a plurality of LEDs are driven in parallel using the anode of the LED as a common power source, the VF of the LED varies, so that the voltage applied to the LED driver for driving each LED varies. In particular, when LEDs are connected in series, the variations of the LEDs are superimposed and the voltage difference of the variations becomes large.

An LED driver with a large applied voltage has a large power loss, so that it generates a large amount of heat, and it is necessary to design heat dissipation under that condition, so that the cost increases as a heat dissipation measure.

Therefore, in order to simplify the heat dissipation design and reduce the cost of the system, by adjusting the LED current and aligning the VFs, the heat generation of the LED driver should be made uniform and the variation in power loss in the LED driver should be reduced. Is being done.

Japanese Unexamined Patent Publication No. 2012-195291 (published on October 11, 2012)

As in Patent Document 1, in order to optimize the VF of each LED, a means for gradually increasing the LED current until a cathode voltage that allows sufficient LED current to flow remains, and an LED on / off period according to the increased current. There is a need for a means of adjusting (PWM_Duty) to control the brightness so that it does not change.

For example, FIG. 17 shows a correction factor of PWM_Duty when the current flowing through the load resistance is changed by an adjustment ratio in units of 2% up to an increase of 30%. It is necessary to take the correspondence between the current adjustment ratio and the PWM_Duty correction factor, but as can be seen from the figure, the PWM_Duty correction factor is not constant and has no regularity.

Therefore, it is necessary to take measures such as storing the PWM_Duty setting value in the table. Further, in order to adjust the product of the LED current adjustment ratio and the PWM_Duty correction factor to be constant, complicated arithmetic processing is required.

Therefore, an external processing device is required to control the optimum value of the current amount of the LED driver and to control the set value of PWM_Duty, and the control is performed between the LED driver and the external processing device. It becomes necessary to communicate the signal.

Further, as described above, when the control signal is communicated between the LED driver and the external processing device, the number of LED area divisions increases, and when the number of LED drivers increases, the number of wirings increases and the load of the processing device increases. There is a problem that becomes large.

One aspect of the present invention has been made in view of the above problems, and an object thereof is to realize an LED module or the like that can reduce the cost by reducing the number of wirings and the number of terminals of the driver. To do.

In order to solve the above problems, the LED module according to one aspect of the present invention includes a plurality of LEDs or LED rows, a plurality of drivers for driving each of the plurality of LEDs or the LED rows, and the plurality of drivers. An LED module including a controller for controlling drive, and each of the plurality of drivers and the controller transmit an enable signal indicating a timing for receiving a data signal output from the controller. The driver is cascaded via the above, and the driver is configured to transmit an error signal indicating an error state of the driver to the controller via the enable signal line.

Further, in order to solve the above-mentioned problems, the LED module according to one aspect of the present invention includes a plurality of LEDs or LED rows, a plurality of drivers for driving each of the plurality of LEDs or LED rows, and the plurality of drivers. An LED module including a controller for controlling the drive of a driver, and each of the plurality of drivers and the controller are a data line for transmitting a data signal including at least brightness information output from the controller. The driver is connected in parallel via the data line, and the driver transmits an error signal indicating an error state of the driver to the controller via the data line.

According to one aspect of the present invention, it is possible to reduce the cost by reducing the number of wirings and the number of terminals of the driver.

It is a circuit diagram which shows the outline structure of the backlight apparatus which concerns on Embodiment 1 of this invention. This is the first half of the timing chart showing the operation of the backlight device. This is the latter half of the timing chart showing the operation of the backlight device. It is a circuit diagram which shows the structure of the LED driver provided in the said backlight apparatus. It is a figure which shows the relationship between the adjustment ratio of the current value of the current flowing through LED, and the correction factor of PWM_Duty. It is a circuit diagram which shows the outline structure of the backlight apparatus which concerns on Embodiment 2 of this invention. It is a circuit diagram which shows the structure of the LED driver provided in the said backlight apparatus. It is a circuit diagram which shows the outline structure of the backlight apparatus which concerns on Embodiment 3 of this invention. It is a state transition diagram which shows the operation flow of the LED driver provided in the said backlight apparatus. It is a timing chart which shows the operation of the backlight apparatus which concerns on Embodiment 4 of this invention. It is a figure for demonstrating the writing procedure of address data and luminance data. It is a timing chart which shows the operation of the said backlight apparatus. It is a state transition diagram which shows the operation flow of the LED driver provided in the said backlight apparatus. It is a timing chart which shows the operation of the said backlight apparatus. It is a timing chart which shows the operation of the backlight apparatus which concerns on Embodiment 5 of this invention. It is a timing chart which shows the operation of the backlight apparatus which concerns on Embodiment 6 of this invention. It is a figure which shows the relationship between the adjustment ratio of the current value of the current flowing through LED and the correction factor of PWM_Duty in the prior art.

[Embodiment 1]
As shown in FIG. 1, the backlight device (LED module) 1 includes a backlight panel 40, a controller 70, and a power supply 80. The backlight panel 40 is provided with an LED driver (driver) 60 for driving the three LEDs 50. The backlight panel 40 irradiates the display panel with light from behind the display panel (not shown). The LED driver 60 controls the lighting brightness of the LED 50 based on the control information.

The controller 70 controls a plurality of LED drivers 60. The LED driver 60 drives three LEDs 50 based on the luminance data DATA and the control signal from the controller 70. The number of LEDs 50 driven by the LED driver 60 is not limited to three. Further, the LED driver 60 may drive a single LED row or a plurality of LED rows in which a plurality of LEDs 50 are arranged in an array.

An enable signal line (ENABLE) for transmitting an enable signal indicating a timing for receiving a data signal output from the controller 70 is connected to the controller 70. Further, the enable signal line is cascaded to each of the plurality of LED drivers 60.

A data line (DATA) that outputs a data signal including at least luminance data DATA (luminance information) is connected to the controller 70. Further, the data line is connected in parallel to a plurality of LED drivers 60.

A clock signal line (CLK) that outputs a clock signal is connected to the controller 70. Further, the clock signal line is connected in parallel to a plurality of LED drivers 60.

Next, based on FIGS. 2 to 4, the first-stage LED driver 60A (the first-stage driver among the plurality of LED drivers 60 is referred to as the LED driver 60A) and the second-stage LED driver 60B (the next-stage driver of the LED driver 60A). Is referred to as an LED driver 60B).

As shown in FIG. 2, the luminance data DATA, the clock CLK, and the start pulse SP (SP1) are transmitted synchronously from the controller. First, in the LED driver 60A, the SP counter 62 outputs the start pulse SP1 as the enable signal ENB because the count value obtained by counting the input start pulse SP1 becomes the set value “1”.

Next, when the data latch circuit 63 receives the enable signal ENB (start pulse SP1), it starts sampling the brightness data DATA and samples the input serial brightness data DATA (d0 to d11) bit by bit. And convert it to parallel bit data D01 to D111.

The data latch circuit 63 shifts the start pulse SP1 by a 12-bit shift register at the timing of the clock CLK to generate latch pulses D0 (Lat1) to D11 (Lat1). The data latch circuit 63 sequentially captures and holds bit data D01 to D111 bit by bit in synchronization with the latch pulses D0 (Lat1) to D11 (Lat1).

Next, as shown in FIG. 3, the SP counter 62 outputs the start pulse SPout (SP2) at the next timing when the latch pulse D11 (Lat1) is output. The output of the start pulse SPout informs the LED driver 60B of the next stage of the end of data sampling in the LED driver 60A.

In the LED driver 60B of the next stage, when the start pulse SPout is input as the start pulse SP2, the SP counter 62 counts the start pulse SP2 by one set by the set value, so that the start pulse SP2 is used as the enable signal ENB. Output.

When the data latch circuit 63 receives the enable signal ENB (start pulse SP2), the input serial brightness data DATA (d0 to d11) is sampled bit by bit and converted into parallel bit data D02 to D112. The data latch circuit 63 sequentially captures and holds bit data D02 to D112 bit by bit in synchronization with the latch pulses D0 (Lat2) to D11 (Lat2) generated based on the start pulse SP2.

As described above, by sequentially transmitting the start pulse SP between the cascade-connected LED drivers 60 (60A, 60B ...), each LED driver 60 can sequentially capture the serial luminance data DATA. .. Therefore, in the backlight panel 40 in which a large number of LED drivers 60 are arranged, if the LED driver 60 is applied as the LED driver, the wiring formed on the backlight panel 40 can be reduced.

As shown in FIGS. 2 and 3, the start pulse SPout is output between the final bit value d11 of the luminance data DATA and the first bit value d0 of the next luminance data DATA for one clock. It is necessary to provide an interval between.

In addition to the data representing the gradation, the brightness data DATA includes data for adjusting the overall brightness from the ambient brightness, data showing the current consumption priority, and the like. In this embodiment, a 12-bit configuration is described for convenience.

Next, the configuration of the LED driver 60 will be described with reference to FIG. As shown in the figure, the LED driver 60 includes an SP counter 62, a data latch circuit 63, a data processing unit 65, a PWM signal generation unit 66, a counter & selector 67, a voltage determination unit 68, and a current setting unit 69.

The SP counter 62 is a counter that counts the start pulse SP. When the SP counter 62 counts the start pulse SP up to a predetermined set value, the SP counter 62 outputs an enable signal ENB from the enable terminal EN. The enable signal is a signal required for the data latch circuit 63 to start data acquisition.

The SP counter 62 delays the input start pulse SP to the timing at the end of the serial luminance data DATA and outputs the start pulse SP out. The SP counter 62 may have, for example, a shift register that shifts the start pulse SP in synchronization with the clock CLK in order to delay the start pulse SP.

The data latch circuit 63 is a circuit that samples the input serial luminance data DATA and converts it in parallel, and latches the converted parallel luminance data DATA. The data latch circuit 63 has an enable terminal EN, and when the enable signal ENB supplied from the SP counter 62 is received at the enable terminal EN, sampling of luminance data DATA is started. For example, if the brightness data DATA is composed of 8 bits, the data latch circuit 63 acquires 8-bit brightness data DATA by performing sampling 8 times.

The data processing unit 65 sets the PWM_Duty value and gives it to the PWM signal generation unit 66. Further, the data processing unit 65 sets a set current value and gives it to the counter & selector 67.

The PWM signal generation unit 66 generates a PWM signal based on the PWM_Duty value supplied from the data processing unit 65. More specifically, the PWM signal generation unit 66 changes the PWM_Duty (duty ratio) at a constant rate every time one bit changes. The duty ratio is the ratio of the period during which the LED 50 is turned on in a fixed cycle with respect to the on / off period of the LED 50 shown in FIG. Further, the constant cycle is an integral multiple of the cycle of the clock shown in FIG. 2, and the constant cycle is, for example, 4096 clocks.

The counter & selector 67 controls the operation of the current setting unit 69 based on the set current value supplied from the data processing unit 65. Specifically, control for selecting switches SW1 to SWn of the current setting unit 69 is performed.

The voltage determination unit 68 compares the cathode voltage (point a voltage) of the LED 50 with the reference voltage VREF in order to confirm the operation of the LED 50.

The current setting unit 69 sets the LED drive current to be increased or decreased stepwise.

More specifically, when the cathode voltage of the LED 50 is higher than the reference voltage VREF, the voltage determination unit 68 uses an LED driver to allow the VF of the LED to be smaller than the VF of another LED, that is, to pass a constant current. It is judged that the power lost is larger than the others.

The current setting unit 69 corrects so that a large amount of LED current flows, lowers the cathode voltage of the LED 50, makes it equivalent to the VF of other LEDs, and reduces the power lost by the LED driver 60. The PWM signal generation unit 66 corrects PWM_Duty so that the brightness does not change even if the LED current is corrected.

As a result, although the adjustment ratio of the current value is not constant, the correction factor of PWM_Duty is constant. Further, the arithmetic processing for adjusting so that the product of the adjustment ratio of the current value of the LED current and the correction factor of PWM_Duty becomes constant becomes simple. Therefore, the scale of the arithmetic circuit that corrects the PWM_Duty can be reduced.

Further, the current setting unit 69 adjusts the size of the transistor by selecting switches SW1 to SWn. In FIG. 4, numerical values such as W = 100 μm and W = 1.6 μm described in the range of the current setting unit 69 indicate the size of the transistor.

The reference current Iref of the current setting unit 69 is set from the brightness data DATA acquired by the data processing unit 65, and the PWM signal generation unit 66 generates a PWM signal that regulates the on / off of the LED 50. The gradation of the LED 50 is defined by the reference current Iref.

Here, the luminance data DATA is composed of an "LED current value" and a "PWM_Duty value". The reference current Iref is determined by this LED current value.

When the LED current value is set to 100 mA, all the SWs are turned off, and 100 mA flows while the LED current is flowing only by the transistor of W = 100 μm. When the LED current value is set to 50 mA, if the Ireff is halved, the LED current becomes 50 mA with only the transistor of W = 100 μm connected.

The act of connecting SW1 to SWn leads to adjusting the LED current. When SW1 is turned on, the LED current increases by 1.6% (101.6mA when the LED current setting is 100mA and 50.8mA when the LED current setting is 50mA).

The PWM_Duty value adjusts the overall LED brightness. For example, if the PWM_Duty value is 50%, the LED 50 is repeatedly turned on and off at the same time to halve the brightness and reduce the brightness to half. The luminance data DATA is used to express the gradation. The PWM_Duty value is also a part of the luminance data. The basic brightness adjustment adjusts the brightness by changing the PWM_Duty value without changing the LED current.

Next, a method of optimizing the VF (voltage across the LED 50) of the LED 50 driven by the LED driver 60 will be described.

If point a is higher than a constant voltage (depending on the value of the reference current Iref), the LED current can flow according to the set current, but if point a falls below a constant voltage, the LED current cannot flow gradually. To go. Keep a constant voltage (0.5V in the case of the following explanation) or higher so that the current flows according to the set current.

In order to confirm the operation of the LED 50, the voltage determination unit 68 compares the cathode voltage (point a voltage) of the LED 50 with the reference voltage VREF.

When the reference voltage VREF exceeds the VF of the LED 50 and the LED current according to the set current cannot flow, the output of the voltage determination unit 68 is set to a fixed voltage of, for example, 0.5 V so as to be LOW. The reference voltage VREF may be variably set according to the reference current Iref.

When the output of the voltage determination unit 68 is High, the drive current of the LED 50 is increased, and the increase in luminance due to the increase in the current is reduced by adjusting the on / off period (PWM_Duty) of the LED 50. When the output of the voltage determination unit 68 becomes LOW, the drive current of the LED 50 is reduced and the luminance reduction due to the current reduction is increased by adjusting the on / off period of the LED 50. By this control, the VF can be optimized and the LED 50 can emit light.

Next, a method of increasing / decreasing the drive current of the LED 50 and adjusting the on / off period of the LED 50 will be described. In the current setting unit 69, the reference current Iref is used as the current of the constant current source and transmitted by the current mirror circuit to be the LED drive current.

If the transistor size on the reference current side and the LED drive current side of the current mirror is the same, the LED drive current is lit with the gradation defined by the brightness data, but in the circuit of this embodiment, the LED drive current side is lit. Change the transistor to change the drive current. That is, the current flowing through the LED 50 is adjusted by changing the transistor size.

This is to suppress extra power consumption by lowering the voltage at point a (reducing the power consumed by the LED driver).

Since the anode of the LED is supplied in common to all the LEDs, it is necessary to raise the anode voltage to a voltage at which the voltage at point a can be secured even for an LED having a large VF. In order to lower the voltage at point a of an LED with a small VF, it is realized by increasing the LED current only for that LED and increasing the VF.

As shown in FIG. 4, a transistor can be added to the transistor on the LED drive current side by the switch SW1 to SWn. The size of the transistor to be added is set so that the PWM_Duty value, which is reduced in order to offset the increase in luminance generated by the increase in drive current, is constantly reduced.

In this embodiment, as shown in FIG. 5, the PWM_Duty value is reduced by 1.56%. A resolution of 12 bits (4096) is required to control the PWM_Duty value with an accuracy of about 0.02%, but the change region is set so that only 4 bits out of 12 bits change. As a result, the counter & selector 67 for selecting SWn from the switch SW1 for selecting the transistor to be added can be configured with 4 bits.

As a result, the PWM_Duty correction table can be simplified, and since the correction table can be simplified, the arithmetic circuit for multiplying the current value adjustment ratio and the PWM_Duty correction factor can be simplified.

For example, if 4 bits are "1110", a transistor whose current increases by 1.6% is added. Further, for example, if the transistor size of the current mirror is 100, a transistor having a size of 1.6 may be added. Multiply the PWM_Duty value set in the luminance data DATA by 98.44% so as to add a transistor and reduce the PWM_Duty value by 1.56%. Further, for example, if the setting is 50%, the on / off period of the LED 50 is controlled by multiplying by 98.44% and a PWM_Duty value of 49.22%.

The decrease value of the PWM_Duty value can also be set corresponding to the 4 bits of the counter & selector 67. When 4 bits are "1101", a transistor whose current increases by 3.2% is added. You may add a 3.2 size transistor, or you can add a 1.6 size transistor and a 1.6 size transistor to be selected in the case of "1110" to make a 3.2 size transistor. be. At this time as well, the PWM_Duty value is set to 96.87%.

As described above, the increase in current due to the addition of the transistor and the adjustment of the PWM_Duty value are set with a 4-bit value, the drive current is increased or decreased, and the on / off period of the LED 50 is adjusted.

In the conventional technique, the LED current is gradually increased until the cathode voltage at which the LED current can flow sufficiently remains. The PWM_Duty value is shortened according to the increased current, and the brightness is controlled so as not to change.

The rate at which the PWM_Duty value is shortened according to the increase in the LED current is expressed in binary. When the PWM_Duty value is set in 12 bits, the notation of the ratio for shortening the PWM_Duty value is also required to be about 12 bits in binary.

The table when the PWM_Duty value is adjusted so that the product of the adjustment ratio of the current value of the LED current and the correction factor of the PWM_Duty becomes constant when the LED current is increased by 30% at regular intervals is shown in FIG. become. Of the 12 bits, the lower 10 bits change data irregularly, so the PWM_Duty setting value needs to be stored in the table.

In the present embodiment, as shown in FIG. 5, the PWM_Duty value (duty ratio) is set to decrease at a constant rate instead of increasing the LED current value at a constant rate.

As shown in FIG. 5, the correction table that adjusts the duty ratio at a ratio of 1/26 is a simple table in which the ^6th bit is decremented by 1 from the MSB (Most Significant Bit). Further, if the table is adjusted at a ratio of 1/25, it will be a simple table in which the ^5th bit is decremented by 1 from the MSB.

Simplify the correction table to simplify the duty ratio correction calculation circuit. For that purpose, the correction ratio is simplified by 2 bit notation. For that purpose, it should be corrected in 1/2 ⁿ increments.

As a result, it is necessary to correct the LED current in order to keep the brightness constant even if the duty ratio is corrected, but since the LED current does not change at a constant rate, a non-linear LED current correction circuit is intentionally used.

In the present embodiment, when n is a natural number, the PWM signal generation unit 66 changes the duty ratio by 1/2 ⁿ . That is, in the present embodiment, by setting the rate at which the PWM_Duty decreases to 1/2 ⁿ , the table for reducing the PWM_Duty value changes regularly, so that it is only necessary to count up / down by 1/2 ⁿ .

As shown in the embodiment, it is not necessary to change the 12 ^- bit data by 1/26, but it may be changed by 1/25 ⁽ the current adjustment step becomes larger), and ^1/27 . You may change it one by one.

By making the LED current step non-linear (the circuit that increases the LED current becomes complicated), the PWM_Duty correction circuit is simplified, the circuit is incorporated in the LED driver side, and the LED current correction state is fed back to the controller side. Simplify the system by eliminating the need.

Since the adjustment value of PWM_Duty also changes by only 4 bits, the circuit scale at the time of calculation can be reduced. The increase value of the LED current will not be at regular intervals, but if the circuit is such that transistors matching the current value for which the size of the transistor to be added to the output transistor is to be increased are added one after another, the circuit will not increase significantly.

While the adjustment value of PWM_Duty changes with a width of 10 bits, when only the width of 4 bits changes, the circuit for calculating PWM_Duty also becomes small. Further, in the calculation of PWM_Duty, the value to be reduced is calculated, and then the value is subtracted from the original set value. Since the calculation of the value to be reduced is performed by the data of the 12-bit width × the adjustment value width (10-bit / 4-bit), the adjustment value changes only in the 4-bit width, so that the arithmetic circuit becomes smaller.

According to the above method, the arithmetic circuit for correcting the PWM_Duty value is simplified and the chip size is reduced.

As the number of LED area divisions increases, the number of LED drivers 60 increases accordingly, and when information on whether the LED current can sufficiently flow is fed back to the controller 70, the load on the controller 70 increases.

Therefore, inside the LED driver 60, it is possible to detect whether the LED current can be sufficiently flowed, increase the LED current from the detection result, and complete the feedback that shortens the PWM_Duty accordingly. By doing so, it is not necessary to feed back the information as to whether the LED current can be sufficiently passed to the controller 70, so that the system becomes simple.

When the LEDs 50 are connected in parallel, the residual voltage of the cathode varies due to the forward variation of the LEDs 50. When the remaining voltage of the cathode is higher than the minimum required voltage, the forward voltage can be increased and the remaining voltage can be reduced by increasing the LED current.

Since the brightness of the LED increases when the LED current is increased, it is advisable to shorten the PWM_Duty value in order not to change the average brightness.

As described above, if the adjustment for shortening the PWM_Duty value is performed by the LED driver 60 itself, it is not necessary to return the information for adjusting the LED current to the controller 70, so that the system becomes simple and the cost of the system is reduced.

[Embodiment 2]
Next, the backlight device (LED module) 2 according to the second embodiment of the present invention will be described with reference to FIGS. 6 and 7.

The backlight device 2 of the present embodiment is different from the backlight device 1 described above in that a function of returning an error signal XEROR from the LED driver 60a to the controller 70 is added. Specifically, each of the LED drivers 60a is provided with an XERR terminal, and each XERR terminal is connected to the controller 70 in parallel.

As shown in FIG. 7, the LED driver 60a of the present embodiment is different from the LED driver 60 described above in that the data processing unit 65a outputs an error signal XERROR. The XERROR signal shown in the figure is output when the anode voltage of the LED 50 decreases and the LED 50 cannot be turned on.

The above function is used when adjusting the anode voltage commonly given to the entire LED driver 60a. The method of adjusting the anode voltage will be described below.

First, the set current value is set. The set current value is set by the constant current source of the current setting unit 69 installed in each LED driver 60a shown in FIG. 7 (for example, Iref = 40 mA). The power supply 80 is adjusted, the anode voltage is gradually lowered, and the LED driver 60a that cannot flow the reference set current is detected. The detection is performed by the voltage determination unit 68 of each LED driver 60a shown in FIG. 7, as described in the first embodiment.

At this time, the output of the voltage determination unit 68 becomes LOW, and as described in the first embodiment, the function of reducing the LED current works, but since the anode voltage is low, the VF that can turn on the LED 50 cannot be set. Therefore, the output of the voltage determination unit 68 remains LOW. When the output of the voltage determination unit 68 is in the LOW state for a certain period of time in this way, the data processing unit 65a outputs the error signal XERROR. In the example shown in FIG. 6, LOW is output.

In FIG. 6, the XERROR terminal of each LED driver 60a is commonly connected and pulled up. If the XERROR terminal of one LED driver 60a becomes LOW, the input XERR of the controller 70 becomes LOW, and the controller 70 determines that there is an LED driver 60a that cannot flow the set current.

Next, the controller 70 adjusts the power supply, gradually raises the anode voltage, and stops changing the anode voltage when XERR becomes High again to determine the anode voltage. As described above, the controller 70 changes the anode voltage of the LED 50, and when the LED driver 60a determines that the cathode voltage of the LED 50 is equal to or higher than a predetermined voltage at the changed anode voltage, the controller 70 is notified of the anode voltage. If the current voltage is maintained and the cathode voltage is determined to be less than the predetermined voltage, the controller 70 may raise the anode voltage from the current voltage. By the above operation, the minimum anode voltage required for the entire LED driver 60a can be set, so that the power consumption can be reduced.

[Embodiment 3]
Next, the backlight device (LED module) 3 according to the second embodiment of the present invention will be described with reference to FIGS. 8 and 9.

In the second embodiment described above, the terminal XERROR is provided so that the LED driver 60a, which cannot flow the set current, outputs a signal. However, in the present embodiment, the LED driver 60 transmits an error signal indicating its own error state via an enable signal line that transmits an enable signal indicating the timing of receiving the data signal output from the controller 70. It is different in that it is. The enable signal line is cascade-connected to each of the plurality of LED drivers 60.

According to the above configuration, since the signal line for transmitting the error signal can be shared by the enable signal line, it is not necessary to separately provide the signal line for transmitting the error signal and its terminal. Therefore, the cost can be reduced by reducing the number of wirings and the number of terminals of the LED driver 60.

The SP (ENABLE_IN) is provided with a function in which the timing for capturing the luminance data DATA is input, the timing for capturing the luminance data DATA in the next stage is created by the SP counter 62, and the timing is output from SPOUT (ENABLE_OUT) to the next stage.

Next, with reference to FIG. 9, a method having both a function of capturing the luminance data DATA and a function of returning an error signal to the controller 70 will be described.

FIG. 9A shows a standby state. Both SP (ENABLE_IN) and SPOUT (ENABLE_OUT) are waiting in the input state.

FIG. 9B shows a state in which the luminance data DATA is captured. By inputting SP (ENABLE_IN), the luminance data DATA serially input as described with reference to FIGS. 2 and 3 is captured in parallel.

FIG. 9C shows a state after the luminance data DATA is captured. The enable signal of the next stage is output to SPOUT (ENABLE_OUT), and if an error is determined, the error signal is returned from SP (ENABLE_IN) to the LED driver 60 of the previous stage.

FIG. 9D shows a state after the enable signal of the next stage is output to SPOUT (ENABLE_OUT). Connect from SPOUT (ENABLE_OUT) to SP (ENABLE_IN). As a result, the LED driver 60 in the next and subsequent stages can relay the error signal returned to the SP (ENABLE_IN), and the error signal is returned to the controller 70.

Next, as shown in FIG. 10, since an error signal is returned at the timing when the enable signal to the next stage is output by each LED driver 60, the controller 70 determines which LED driver 60 returned the error signal. Can be grasped.

That is, the controller 70 determines which of the plurality of LED drivers 60 is in the error state based on the timing of receiving the error signal. Thereby, it is possible to recognize which of the plurality of LED drivers 60 is in the error state.

In the present embodiment, the mode in which the operation of the second embodiment is performed and the anode voltage of the LED 50 is adjusted has been described, but the error signal XERROR can be used in addition to the second embodiment. For example, a temperature sensor is provided in the LED driver 60, and when the temperature reaches a certain level or higher, an error signal XERROR is output to start the operation of the cooling circuit. In addition, various usage methods such as notifying the occurrence of a circuit failure can be considered.

[Embodiment 4]
In the data transfer method (see FIGS. 2 and 3) shown in the first embodiment described above, when the luminance data DATA is transmitted, the relay of the enable signal is inserted in the middle, so that it is necessary to insert a wait time in the middle of the data. ..

In the data acquisition method of the present embodiment described below, as shown in FIG. 12, when the luminance data DATA is sent, the relay of the enable signal is not inserted in the middle, so that it is not necessary to insert a wait time in the middle of the data. .. For this reason, data communication is simplified, and the data transfer speed can be increased.

As shown in FIGS. 11A and 11B, the data lines connected in parallel are used as enable signals, and the address data is written to all the LED drivers 60 using the address data lines connected in cascade.

Since the address data is in the order of recognizing the luminance data DATA, the address 1, the address 2, ... Are set in order from the LED driver 60 in front of the cascade connection.

When the enable signal connected in parallel after sending the address data is set to Low, the written address data is latched and the address data setting mode is terminated.

When the address data setting mode ends, the enable signal is input to all the LED drivers 60 as it is when the controller 70 sets the enable signal to the cascade-connected signal line as the enable signal and the parallel-connected signal as the luminance data line. Will be done.

When the controller 70 sends the luminance data DATA one after another, each LED driver 60 recognizes the data sent in the order of the addresses set in the address data.

Next, a method of returning an error to the controller by the above data transfer method will be described. In the initial state shown in FIG. 13 (a), both ENABLE_IN and ENABLE_OUT are waiting in the input state.

In the state shown in FIG. 13 (b), when HIGH is input to ENABLE_IN, the LED driver 60 captures the luminance data DATA sent in the order of its own address data.

When the data transfer is completed and LOW is input to ENABLE_IN, the input of ENABLE_OUT is output from ENABLE_IN, and if an error is determined, the error signal is returned to the front LED driver 60.

As shown in FIG. 13 (c), even if an error is not determined, when an error signal is returned from the next LED driver 60, the error signal is relayed to the LED driver 60 in front of the LED driver 60. Next, by inputting a clock signal, it returns to the initial state.

FIG. 14 shows the overall timing. As shown in the figure, when the enable signal is set to LOW, LOW is transmitted to all LED drivers (drivers A to D). If there is an LED driver that has determined an error, the error signal returns to the controller 70 with the driver as the start.

[Embodiment 5]
In the above-described fourth embodiment, after inputting LOW to ENABLE_IN, the controller 70 can recognize which LED driver has an error in the delay time until the error signal returns.

However, it is not necessary to know which LED driver has the error, and if you want to know the presence or absence of the error quickly, the error signal is acquired as shown in FIG. 15 (see the broken line square).

After setting ENABLE_IN to HIGH, the error signal from the LED driver is acquired using the data line. That is, the LED driver may transmit an error signal indicating its own error state to the controller 70 via the data line. A data line for transmitting a data signal including at least luminance data DATA (luminance information) output from the controller 70 is connected to the plurality of LED drivers.

That is, in the present embodiment, an error is returned to the controller 70 by setting the data line to HIGH when the enable signal becomes HIGH. As a result, it is not possible to know which LED driver has the error, but the time for returning the error is short.

According to the above configuration, since the signal line for transmitting the error signal can be shared by the data line, it is not necessary to separately provide the signal line for transmitting the error signal and its terminal. Therefore, the cost can be reduced by reducing the number of wirings and the number of terminals of the driver.

In the case of the method shown in FIG. 15, the LED driver having an error sets the data line to HIGH. The controller 70 recognizes that an error has occurred when the data line becomes HIGH.

Next, by inputting the clock signal (CLK) to the LED driver, the LED driver is in the data acquisition state, and data transfer can be started from the next clock.

[Embodiment 6]
Next, in order to return an error signal on the data line as in the fifth embodiment and further recognize which LED driver (drivers A to D) has caused the error, acquisition of the error signal is performed as shown in FIG. Do (see dashed square).

After sending the luminance data DATA corresponding to one LED driver, the controller 70 stops the clock and acquires the signal from the LED driver using the data line. As shown in FIG. 16, the LED driver to which the luminance data DATA is transferred sets the data line to HIGH if there is an error, and notifies that there is an error.

That is, in the present embodiment, if each LED driver determines an error when receiving its own data, the error is returned to the controller 70 by setting the data line to HIGH. This allows you to know which LED driver is in error.

After the controller 70 acquires the signal from the driver, the clock signal is output, so that the LED driver that has output the error signal stops the output, and the data transfer of the next driver is possible.

〔summary〕
The LED module according to the first aspect of the present invention drives a plurality of LEDs or LED rows, a plurality of drivers (LED drivers 60, 60a) for driving each of the plurality of LEDs or LED rows, and the plurality of drivers. An LED module including a controlling controller (controllers 70, 70a), and each of the plurality of drivers and the controller transmit an enable signal indicating a timing for receiving a data signal output from the controller. Cascaded via the enable signal line to
The driver is configured to transmit an error signal indicating an error state of the driver to the controller via the enable signal line.

According to the above configuration, since the signal line for transmitting the error signal can be shared by the enable signal line, it is not necessary to separately provide the signal line for transmitting the error signal and its terminal. Therefore, the cost can be reduced by reducing the number of wirings and the number of terminals of the driver.

The LED module according to the second aspect of the present invention drives a plurality of LEDs or LED rows, a plurality of drivers (LED drivers 60, 60a) for driving each of the plurality of LEDs or LED rows, and the plurality of drivers. An LED module including a controller (controllers 70, 70a) to be controlled, and each of the plurality of drivers and the controller are data output from the controller and transmitting a data signal including at least brightness information. The driver is connected in parallel via a line, and the driver is configured to transmit an error signal indicating an error state of the driver to the controller via the data line.

According to the above configuration, since the signal line for transmitting the error signal can be shared by the data line, it is not necessary to separately provide the signal line for transmitting the error signal and its terminal. Therefore, the cost can be reduced by reducing the number of wirings and the number of terminals of the driver.

In the LED module according to the third aspect of the present invention, in the first or second aspect, the controller may determine which of the plurality of drivers is in the error state according to the timing of receiving the error signal. preferable. According to the above configuration, it is possible to recognize which of the plurality of drivers is in the error state.

In the LED module according to the fourth aspect of the present invention, in any one of the first to third aspects, the controller changes the anode voltage of the LED or the LED row, and the driver changes the anode voltage of the LED or the LED or the LED at the changed anode voltage. When it is determined that the cathode voltage of the LED row is equal to or higher than a predetermined voltage, the controller is made to maintain the current voltage of the anode voltage, and when it is determined that the cathode voltage is less than the predetermined voltage, the controller is made to maintain the current anode voltage. The voltage may be increased from the current voltage. According to the above configuration, the minimum anode voltage required for the entire driver can be set, and low power consumption can be realized.

The backlight device according to the fifth aspect of the present invention preferably includes the LED module according to any one of the above aspects 1 to 4. According to the above configuration, the same effect as that of the above aspect 1 or 2 can be obtained.

[Additional notes]
The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and the embodiments obtained by appropriately combining the technical means disclosed in the different embodiments. Is also included in the technical scope of the present invention. Further, by combining the technical means disclosed in each embodiment, new technical features can be formed.

1-3 Backlight device (LED module)
60,60a LED driver (driver)
70,70a controller

Claims (5)

An LED module including a plurality of LEDs or LED rows, a plurality of drivers for driving each of the plurality of LEDs or LED rows, and a controller for controlling the driving of the plurality of drivers.
Each of the plurality of drivers and the controller are cascaded via an enable signal line that transmits an enable signal indicating the timing of receiving the data signal output from the controller.
The driver is an LED module characterized by transmitting an error signal indicating an error state of the driver to the controller via the enable signal line. An LED module including a plurality of LEDs or LED rows, a plurality of drivers for driving each of the plurality of LEDs or LED rows, and a controller for controlling the driving of the plurality of drivers.
Each of the plurality of drivers and the controller are connected in parallel via a data line that transmits a data signal including at least luminance information output from the controller.
The driver is an LED module characterized by transmitting an error signal indicating an error state of the driver to the controller via the data line. The LED module according to claim 1 or 2, wherein the controller determines which of the plurality of drivers is in an error state based on the timing of receiving the error signal. The controller changes the anode voltage of the LED or LED row.
When the driver determines that the cathode voltage of the LED or the LED row is equal to or higher than the predetermined voltage at the changed anode voltage, the driver causes the controller to maintain the current voltage of the anode voltage, and the cathode voltage is the predetermined voltage. The LED module according to any one of claims 1 to 3, wherein the controller raises the anode voltage from the current voltage when it is determined to be less than the voltage. A backlight device comprising the LED module according to any one of claims 1 to 4.

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