JP2011243825A - Power supply controller having automatic reset function and image display device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reset each individual channel of a constant current power supply having a plurality of channels automatically when transition is made to the state of normal connection after protective operation is actuated by abnormal circuit connection during normal operation.SOLUTION: In the constant current power supply having a plurality of channels, a constant current control unit 125 switches the amount of current to be drawn by each channel to become small for a set current value through an operation control unit 123 based on a decision made at an operation decision unit 124 which detects operation of each channel, and interrupts connection with an error amplifier. Consequently, each channel stopping in abnormal connection state can be reset independently and automatically when a transition is made subsequently to normal connection state.

Description

  The present invention relates to a power supply control device having an automatic return function and a video display device using the same, and particularly when a protective operation is activated due to an unexpected abnormal connection and then returns to a normal connection state, it automatically returns to normal operation. The present invention relates to a power supply control device having an automatic return function and a video display device using the same.

  A typical video display device is a video display device using a liquid crystal display or the like. In such a video display device, an LED (Light Emitting Diode) is often used as a light source of a backlight for a liquid crystal display. Generally, a constant current power source capable of outputting a constant current is used as a power supply device for the LED. Used.

  The constant current power supply incorporates a power supply device (or circuit) for protecting the power supply so as to cope with unpredictable conditions.

  As a conventional constant current source for LED, when PWM control is used for dimming control of LED, LED is open so that other LEDs will not be affected even if LED is open The protection circuit that short-circuits the LED unit by the operation of the protection circuit, the voltage generation circuit that generates the operating voltage that turns on the corresponding protection circuit when the LED of the LED unit is opened, and the protection circuit are on. An LED lighting device and a lighting device system including a charging circuit that generates a voltage for maintaining the on-operation of a protection circuit based on the on-current when the PWM control is off are known. (For example, refer to Patent Document 1).

  Moreover, as a conventional power supply control device, when the output voltage of the switching power supply becomes an overcurrent state due to a short circuit or the like, the overcurrent detection unit lowers the output voltage of the soft start circuit to 0 V, and the PWM comparator Is not output (see, for example, Patent Document 2).

  Patent Document 2 describes that the output of the comparison means is not input to the switching means until the output of the soft start means reaches a predetermined voltage, and prevents the operation of the switching means during the non-protection period of overcurrent protection. Therefore, the output peak current value for each voltage return of the soft start means can be reduced, the adverse effect on the element connected to the output can be reduced, and the GND fluctuation to other elements such as an IC due to the output peak current can be reduced. Etc. can be reduced.

JP 2008-204866 A JP 2006-115596 A

  However, although the thing of the said patent document 1 can maintain lighting operation with another LED unit when a plurality of LED units are used connected in series, lighting operation cannot be maintained in the following cases.

That is, when a single LED element or a plurality of LED elements connected in series (however, each having the same forward direction) is referred to as an LED array, two or more LED arrays are connected in parallel (LED group). ) In a state where each anode is connected to a power source in common, the voltage for each LED column cannot be detected, so that power control for each column cannot be performed, and each LED element When the one described in Patent Document 1 is applied individually, there is a problem that the scale of the apparatus increases and the cost increases.

  Furthermore, the switching power supply described in Patent Document 2 stops the operation of the switch elements in all rows when the overcurrent protection is activated when the above LED group is connected as a load. The power supply to the LEDs operating in the normal state will be stopped.

  For example, when an LED group is used as a light source for a backlight of a liquid crystal display, a power supply device that drives the LED has a plurality of connection terminals (channels) between the cathode of the LED group and a constant current power source, and a plurality of columns When the anode and cathode of the LED row are short-circuited only in one row, the reset operation is performed when returning, so the LEDs in all rows are temporarily turned off, so a black image must be sandwiched. It is conceivable that the user feels uncomfortable.

  An object of the present invention is to solve the above-described conventional problem, and when an LED group having a plurality of LED strings is connected as a load to a power supply, the specific problem is caused by an unexpected unexpected overcurrent or overvoltage. Power supply control that allows normal operation to be restored for each column connected in parallel without affecting the load on other columns connected in parallel, even when a protection operation is activated for the column load An apparatus and an image display device are provided.

  In order to achieve the above object, the power supply control device of the present invention is a power supply control in which a single LED element or a plurality of LED elements connected in series with the same forward direction of a plurality of LED elements are connected in parallel. In the apparatus, the cathodes of the LED rows in the plurality of rows are connected, current values flowing in the LED rows in the plurality of rows are detected, and the detected current values become preset current values. The constant current control unit to be controlled, the operation determination unit for determining the connection state of each of the LED strings, and the constant current control unit to change a current value to be passed through the LED string based on a result of the operation determination unit An operation control unit for controlling, and when the operation determination unit determines that any of the plurality of LED columns is in an abnormal connection state, the constant current control unit It has a configuration that limits the amount of current flowing into the LED arrays is the abnormal connection state based your on.

  Furthermore, the video display device of the present invention is an LED array in which a screen displaying video and a single LED element or a plurality of LED elements emitting light toward the screen are connected in series with the same forward direction. Are connected in parallel with each other, and the cathodes of the LED rows of the plurality of rows are connected to each other so that the current flowing through each of the LED rows of the plurality of rows becomes a preset current value. A constant current control unit for controlling, an operation determination unit for determining a connection state of each of the LED rows, and an operation control unit for controlling the constant current control unit so as to switch a current value based on a result of the operation determination unit. And the operation determining unit determines that any of the plurality of LEDs is in an abnormal connection state, the constant current control unit is configured to control the abnormality based on the control of the operation control unit. In this configuration, the amount of current that flows through the LED array in a connected state is limited.

According to the present invention, when an LED group having a plurality of LED strings is connected as a load of a power supply, a protection operation is performed for a load of a specific string due to an unexpected unexpected overcurrent or overvoltage. Even in this case, it is possible to provide a power supply control device that can restore normal operation for each channel connected in parallel without affecting the load of other columns. There is an advantage that it is possible to provide a video display device that does not unnecessarily give the user a sense of incongruity.

1 is a block diagram showing a system including a power supply control device, a video device, and peripheral configurations thereof in an embodiment of the present invention The block diagram which shows the whole structure of the power supply control apparatus in embodiment of this invention Block diagram for explaining operation until a protection operation of the power supply control device according to the first embodiment of the present invention is detected and restored.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an overall block diagram of a system including a power supply control device having an automatic return function and a video display device using the same according to an embodiment of the present invention.

  This system includes a video display device 1 and a video source 2 connected to the video display device 1. The power control device having the automatic return function corresponds to the LED control LSI 12 described later in detail, and in this embodiment, the LED control LSI 12 is provided inside the video display device 1.

  First, the video source 2 will be described. The video source 2 is connected to the video display device 1 and transmits a video signal A to the video display device 1.

  FIG. 1 shows a DVD player 2A and a tuner 2B as examples of the video source 2. The DVD player 2 </ b> A transmits the video A read and reproduced from the DVD (Digital Versatile Disc) to the video display device 1. The tuner 2B receives, for example, terrestrial digital broadcasting and transmits the video B constituting the reproduced program to the video display device 1. Note that the DVD player 2A and the tuner 2B transmit audio as well as video.

  Next, the video display apparatus 1 in this Embodiment is demonstrated. The video display device 1 includes at least a video processing LSI 11, an LED control LSI 12, a display 13, and a CPU 14.

  When divided into functional blocks, the CPU 12 includes a video processing control unit 141 and a backlight control unit 142. The display 13 includes a screen 131 and an LED group 132 as a backlight.

  As described above, when the video source 2 transmits a video signal to the video display device 1, the video signal is input to the video processing LSI 11, and a signal is output from the video processing control unit 141 in the CPU 14 based on the input video signal data. Then, the video processing control unit 141 transmits the video signal after the signal processing to the screen 131 in the display 13.

  Here, as the screen 131, a display that does not emit light such as a liquid crystal panel generally used in the present embodiment is used. In a display that does not emit light such as a liquid crystal panel, the LED group 132 is used as a backlight for emitting light toward the screen 131.

When the LED group 132 refers to a single LED element or a plurality of LED elements connected in series (where the forward direction is the same), the LED string is 2
It is a configuration in which more than one row is connected in parallel.

  The LED group 132 is controlled by the LED control LSI 12, and the LED control LSI 12 has a function of adjusting the luminance of the liquid crystal panel under the control of the backlight control unit 142 in the CPU 14.

  Next, an LED control circuit applied to the system configured as described above will be described with reference to FIG.

  FIG. 2 is a block diagram showing the LED control circuit 15 showing the overall circuit configuration of the LED control LSI 12 and peripheral component configurations according to the embodiment of the present invention.

  The LED control circuit 15 includes an LED control LSI 12, an input capacitor C1, an inductor L1, a diode D1, and an output capacitor C2. The LED control LSI 12 includes at least a switch unit 121, an error amplifier 122, an operation control unit 123, an operation determination unit 124, and a constant current control unit 125.

  The LED control circuit 15 is for controlling the LED group 132 as a backlight. In the present embodiment, as shown in FIG. 2, the LED group 132 is configured such that the anodes of the three LED arrays and the diodes D <b> 1 are connected, and the cathodes of the LED arrays are independent for each LED. The constant current controller 125 in the control LSI 12 is connected.

  However, the number of LED rows and the number of LED elements per row are not limited to this number.

  The switch unit 121 is connected to the diode D1 and the inductor L1. The input capacitor C1 and the output capacitor C2 are connected to the power supply line of the LED control circuit 15 as a bypass capacitor.

  As will be described in detail later, the error amplifier 122 constantly compares the amount of current flowing through the LED array with a preset amount of current (current value), and based on the error, switches the switch unit 121 (turns on the switch). A function of controlling a so-called on / off operation).

  Here, the “predetermined amount of current” means, for example, a current to be passed through the LED array in order to maintain a luminance suitable for viewing a video displayed on the display 13 when the LED group is used as a backlight. It is an amount, and refers to an amount (value) that is set in advance by the video display device 1 or by the user of the video display device 1.

  The constant current control unit 125 detects a current value flowing from the cathode of each column of the LED group 132 to the constant current control unit 125 and operates so that the detected current value becomes a preset current value. When any column of the LED group 132 is in an abnormal connection state, a current that flows from the cathode of the column in the abnormal connection state of the LED group 132 to the constant current control unit 125 in response to a control signal from the operation control unit 123. Has the ability to change the amount. However, “changing the current amount” includes the intention of “stopping the current amount”.

  When any column of the LED group 132 is in an abnormal connection state, the operation determination unit 124 detects that the LED group 132 is in an abnormal state, and which LED column in the LED group 132 is in an abnormal connection state. And has a function of notifying the operation control unit 123 of the determination result.

  The operation control unit 123 performs control so as to stop the current flowing from the cathode of the abnormally connected row of the LED group 132 to the constant current control unit 125, and the LED row and the error amplifier that are abnormally connected to the LED group 132. 122 has a function of blocking the connection with 122.

  Next, the operation of the LED control circuit 15 will be described. As will be described in detail below, the LED control circuit 15 is a circuit that controls the constant current control unit 125 to flow a preset current to each column of the LED group 132.

  First, the operation in the normal state is as follows. The LED control LSI 12 turns on the switch unit 121 to pass a current from the battery to the inductor L1 and the switch unit 121, and accumulates electric charge in the inductor L1.

  Next, the LED control LSI 12 turns off the switch unit 121, rectifies the electric charge stored in the inductor L <b> 1 by the diode D <b> 1, and applies a voltage to the anode of the LED group 132 to cause the LED group 132 to emit light.

  The constant current control unit 125 sets the amount of current by the FET 35 in the constant current control unit, which will be described later, so that the current from the cathode of the LED group 132, that is, the current flowing in each column of the LED group 132 becomes a preset current value. adjust.

  Here, if the current flowing in each column of the LED group 132 is different from a preset current value, the LED control LSI 12 controls the switch operation of the switch unit 121 and adjusts the output voltage by the operation of the error amplifier 122.

  That is, when the current flowing through the constant current control unit 125 is larger than the preset current value, the error amplifier 122 stops the switch operation of the switch unit 121 and decreases the output voltage. When the current flowing through the current control unit 125 is smaller than a preset current value, the switch unit 121 performs a switch operation to increase the output voltage.

  In this manner, the error amplifier 122 compares the amount of current flowing through the LED group 132 with a preset current value, and controls the switch unit 121 according to the amount of current.

  Next, the operation in the abnormal state will be described below. When the LED group 132 and the LED control circuit 15 are in an abnormal connection state during operation, an overcurrent or overvoltage is applied to the LED control LSI 12, which may destroy the LED control LSI 12. The LED control LSI 12 has a function for protecting.

The protection operation in the LED control LSI 12 of this embodiment will be described with reference to FIG.
As in the case of the normal operation described above, a configuration in which an LED group 132 including three LED rows 132A, 132B, and 132C is connected to the LED control circuit 15 will be described as an example.

  If the LED connection 132 is short-circuited or opened due to dust or the like around the LED group 132 and an overcurrent flows or an overvoltage occurs in the LED control LSI 12, the LED control LSI 12 may be destroyed. Therefore, the LED control LSI 12 has a function of protecting the LED control LSI 12 from overcurrent and overvoltage.

  As an example of such a situation, consider a case where only the LED row 132A of the LED group 132 is in an abnormal connection state during a normal lighting operation.

  The following four cases are considered as abnormal states in the connection of the LED row 132A. The first is when the anode and the cathode of the LED string 132A are short-circuited, the second is when the LED string 132A is opened, and the third is when the cathode of the LED string 132A is grounded. The fourth is considered when several LEDs connected in series in the LED row 132A are short-circuited.

  Hereinafter, the operation of the LED control circuit 12 at the time of abnormal connection in which the anode and the cathode of the LED row 132A are short-circuited will be described.

  When the anode and the cathode of the LED string 132A are short-circuited, an overcurrent is generated from the LED string 132A to the constant current control unit 125 of the LED control circuit 12. Although the configuration and operation of the constant current control unit 125 will be described in detail later, if the current flowing from the cathode of the LED array 132A to the constant current control unit 125 is significantly different from a preset current value, an abnormality is detected in the operation determination unit 124. A connection state is detected, and it is determined that the connection state of the LED row 132A is abnormal.

  When the operation determination unit 124 determines that the LED row 132A is in an abnormal connection state, the operation determination unit 124 notifies the operation control unit 123 that the LED row 132A is in an abnormal state. The control unit 125 is controlled to stop the current flowing from the cathode of the LED row 132A to the constant current control unit 125, and the connection between the errored LED row and the error amplifier 122 is cut off.

  That is, the LED group 132A is controlled so that the current from the LED cathode does not flow to the constant current control unit 125, and the abnormal current does not flow to the LSI, so that the LED control LSI 12 is protected.

  In addition, in the other three abnormal connection states described above, the LED control LSI 12 also determines that the current from the LED group 132A is different from a preset current value and that the anode voltage VOUT of the LED group 132 is an abnormal voltage value. And the LED control LSI 12 is protected by the same operation.

  The above is an explanation of the operation of protecting the LED control LSI 12 when an overcurrent or overvoltage occurs in the LED control LSI 12 due to an unexpected LED connection between the LED group 132 and the LED control circuit 15.

  Next, the return operation when the LED group 132 and the LED control circuit 15 according to the embodiment of the present invention return from the abnormal connection state to the normal connection state will be described with reference to FIG.

  The LED control LSI 12 includes an error amplifier 122, an operation control unit 123, an operation determination unit 124, and a constant current control unit 125, as shown in FIG.

  Furthermore, the constant current control unit 125 includes a resistor R1, a comparator 33, a current mirror circuit 31, a resistor R2, a comparator 34, an FET 35, a resistor R4, a mirror circuit 32, a resistor R3, and an AND circuit. 36 and FET 37.

  The cathode of the LED row 132A is connected to the drain of the FET 35. In addition, the gate of the FET 35 and the operation determination unit 124 are connected. The operation determination unit 124 is connected to the operation control unit 123. The operation control unit 123 is connected to the FET 37 and the AND circuit 36.

  However, although not shown in FIG. 3, the FET 37 and the AND circuit 36 are provided for each channel, and are configured to perform an operation according to the connection state of each LED row.

  The operation of the LED control LSI 12 configured as described above will be described below when a current set in the LED array 132A flows. The current flowing through each of the LED array 132A, the LED array 132B, and the LED array 132C is preset by the resistance value of R1.

  The constant current control unit 125 compares the current flowing from the cathode of the LED group 132 to the constant current control unit 125 using the current flowing through the resistor R1 as a reference value, and the current value flowing from the cathode of the LED group 132 to the constant current control unit 125 And the reference value are set to the same value. The detailed operation will be described below.

  The previously set current value is determined by the constant of the resistor R1. Since the voltage applied to the resistor R1 is controlled by the comparator 33 to be a predetermined value VREF1, the current flowing through the resistor R1 is also a constant value.

  Then, the current flowing through the resistor R1 is amplified by the mirror circuit 31 and converted from current to voltage by the resistor R2, and the voltage Va is referred to by the comparator 34.

  The cathode of the LED string 132A is connected to the drain of the FET 35, and current flows from the cathode of the LED string 132A to the resistor 4. The voltage applied to the resistor R4 is referred to by the comparator 34, and the FET 35 is turned on / off so that the preset voltage value Va is equal to the voltage value applied to the resistor R4. The amount of current flowing is controlled.

  That is, when the voltage of the resistor R4 is smaller than the reference voltage Va, the comparator 34 turns on the FET 35, and current flows from the cathode of the LED array 132A to the resistor R4. On the other hand, when the voltage of R4 is higher than the reference voltage Va, the comparator 34 turns off the FET 35 and does not pass a current from the cathode of the LED string 132A to the resistor R4.

  As described above, the amount of all the current flowing through the LED row 132A, the LED row 132B, and the LED row 132C is determined by the constant of the resistor R1.

  When the LED row 132A is in a normal connection state, a current set in advance as described above flows through the resistor R4. However, when the LED row 132A is in an abnormal connection state, for example, the LED row 132A of the above example When the anode and cathode are short-circuited, the operation is as follows.

  When the anode and cathode of the LED string 132A are short-circuited, the current flowing through R4 becomes very large and the gate voltage of the FET 35 also becomes large.

  In this case, since the gate of the FET 35 and the operation determination unit 124 are connected, the gate voltage of the FET is referred to by the operation determination unit 124, and the operation determination unit 124 has a gate voltage of the FET 35 that is much higher than the preset current. If it is larger, the connection between the LED array 132A and the LED control LSI 12 is detected to be abnormal.

Then, the operation determination unit 124 determines that the connection between the LED array 132A and the LED control LSI 12 is in an abnormal connection state, and notifies the operation control unit 123 of the abnormality. The operation control unit 123 turns off the FET 37, disconnects the abnormally connected LED string 132A and the error amplifier 122, turns off the output of the AND circuit 36, and stops the operation of the comparator 34.

  As a result, the FET 35 is turned off and no current flows from the LED string 132A to the resistor R4, so that the LED control LSI 12 is protected.

  As described later in detail, the operation determination unit 124 that constantly monitors the connection state when the contaminants such as dust are removed and the normal connection state is restored, the current flowing from the LED row 132A to the constant current control unit 125 is described later. When the current amount set in advance for returning the operation is determined to be a normal connection state, the error amplifier 122 that has been disconnected due to the abnormal connection of the LED row 132A is connected to return to the normal operation.

  The disconnection between the LED array in the abnormal connection state and the error amplifier 122 will be described in detail later, but the switch unit 121 that operates to have a preset current value and the LED in the abnormal connection state will be described later. Since the linkage with the column can be eliminated, it is convenient for the following reasons.

  That is, when the connection between the LED string in an abnormal connection state and the error amplifier 122 is not disconnected, if a current is passed from the LED string 132A to the constant current control unit 125, the LED string is in an abnormal connection state. Therefore, the current flowing through the LED array does not have a preset current value, but the switch unit 122 is controlled to have a preset current value from the error amplifier 122, and thus is in a normal connection state. The current values of the LED row 132B and the LED row 132C become unstable, the luminance of the video displayed on the display 13 changes, and it appears as flicker to the user.

  Therefore, it is desirable that the connection between the LED string and the error amplifier 122 is cut only in the line determined to be abnormal connection so as not to affect other LED strings.

Hereinafter, an operation when the LED array 132A and the LED control LSI 12 transition from the abnormal connection state to the normal connection state will be described.
The operation control unit 123 prepares for returning the LED string 132A to normal as described below in preparation for the case where the connection of the LED string 132A returns to normal.

  The operation control unit 123 switches the reference voltage of the comparator 34 from Va to the reference voltage Vb for returning the operation with, for example, a switch.

The reference voltage Vb is set so that the current flowing from the drain to the source of the FET 35 that is stopped is a minute current with respect to a preset current.
If the reference voltage Vb is not sufficiently small, the LED row 132A may be abnormally lit when detecting the connection state.

  The reference voltage Vb is generated by the mirror circuit 32 and the resistor R3 from the current of the resistor R1. The reference voltage Vb is set so that the reference voltage Vb becomes smaller than the reference voltage Va by reducing the amplification factor of the mirror circuit 32 or by making the resistance value of R3 smaller than R2.

  The operation control unit 123 switches the reference voltage of the comparator 34 to a small value, then turns on the output of the AND circuit 36 and turns on the switching operation of the FET 35. A very small current flows through the resistor R4 because the reference voltage is switched to Vb.

  When the LED row 132A returns to the normal connection state, the operation determination unit 124 returns to the normal connection state between the LED row 132A and the LED control LSI 12 because the gate voltage of the FET is stabilized in the state of Vb. It is determined that

  The operation determination unit 124 notifies the operation control unit 123 that the LED array 132A and the LED control LSI 12 have returned to the normal connection state, and the operation control unit 123 turns off the output of the AND circuit 36 and the comparator 34. Is stopped.

  The operation control unit 123 switches the reference voltage referred to by the comparator 34 from the reference voltage Vb to the reference voltage Va with a switch or the like. After switching the reference voltage of the comparator 34, the operation control unit 123 turns on the output of the AND circuit 36 and operates the comparator 34. Further, the operation control unit 123 turns on the FET 37, and the LED 132A and the error amplifier 122 are connected. Therefore, the operation control unit 123 returns the operation so that the LED string 132A has a preset current.

  As described above, a condition in which the current from the cathode can be switched so as to be small during the protection operation, and the reference voltage Vb is made smaller than the reference voltage Va, so that there is almost no influence on other columns. The operation can be determined with.

  Furthermore, in order to disconnect the abnormally connected LED string from the error amplifier 122, the switch operation of the switch unit 21 is not affected by the LED string in the abnormal state, and the LED string 132B and the LED in the normal connected state are not affected. Column 132C continues to operate normally. For this reason, flickering of the display can be prevented even when the connection of the LED is abnormal by applying the LED as a light source for backlight of the video display device 1.

  As described above, according to the present embodiment, since the current flowing through the resistor R4 is reduced during the protection operation, the resistor R4 is provided with the mirror circuit 32 and the resistor R3 that switch the reference voltage of the comparator 34. It is possible to reliably detect whether or not the connection state has returned to normal by reducing the amount of flowing current.

  Further, by configuring the mirror circuit for detecting the connection state of the circuit to have a sufficiently small current with respect to the set value, detection in the power saving state is possible.

  In the power supply control circuit of the present invention, the LED element is inadvertently connected abnormally, an overcurrent and an overvoltage are generated, and the LED control LSI is protected. The LED control LSI is useful as a function that normally restores the operation of the LED control LSI when the connection with the LED element transitions from the protected state to the normal connection state.

1 video display device 11 video processing LSI
12 LED control LSI
121 switch unit 122 error amplifier 123 operation control unit 124 operation determination unit 125 constant current control unit 13 display 131 screen 132 LED group 132A LED column 132B LED column 132C LED column 14 CPU
141 Video processing control unit 142 Backlight control unit 2 Video source 2A DVD player 2B tuner
31, 32 Current mirror circuit 33, 34 Comparator 35, 37 MOSFET
36 AND circuit C1 Input capacitor L1 Inductor D1 Diode C2 Output capacitor R1, R2, R3, R4 Resistance

Claims (5)

A power supply control device in which a plurality of LED rows connected in series with a single LED element or a plurality of LED elements connected in series with the same forward direction are connected in parallel,
Constant current control for connecting the cathodes of the LED rows of the plurality of rows, detecting a current value flowing through each of the LED rows of the plurality of rows, and controlling the detected current value to be a preset current value And
An operation determination unit for determining each connection state of the LED rows;
An operation control unit for controlling the constant current control unit so as to change a current value flowing through the LED array based on a result of the operation determination unit;
When the operation determination unit determines that any one of the LED rows in the plurality of rows is in an abnormal connection state, the constant current control unit is an LED in the abnormal connection state based on the control of the operation control unit. A power supply control device that limits the amount of current that flows in a row.   A switch unit that performs an on / off operation on a current flowing from the power source to the cathodes of the plurality of LED columns, a current value that flows through the LED column detected by the constant current control unit, and the preset current value The power supply control device according to claim 1, further comprising: an error amplifier that controls an on / off operation of the switch unit based on a difference between the switch unit and the switch unit.   The operation control unit disconnects the constant current control unit and the error amplifier when the operation determination unit determines that any one of the plurality of LED columns is in an abnormal connection state. The power supply control device according to claim 2.   When the operation determination unit determines that any one of the plurality of LED columns is in an abnormal connection state, the constant current control unit is in the abnormal connection state based on the control of the operation control unit. 2. The power supply according to claim 1, wherein an operation of passing a current through a certain LED row is temporarily stopped, and then a current having a current value smaller than the preset current value is caused to flow through the LED row in the abnormal connection state. Control device. A screen for displaying images,
A backlight in which a single LED element that emits light toward the screen or a plurality of LED elements connected in series with the same forward direction of a plurality of LED elements is connected in parallel, and the plurality of columns A constant current control unit that is connected to each cathode of the LED rows and controls the current flowing in each of the plurality of LED rows to a preset current value; and a connection state of each of the LED rows An operation control unit that controls the constant current control unit so as to switch a current value based on a result of the operation determination unit and the operation determination unit;
When the operation determination unit determines that any one of the plurality of LEDs is in an abnormal connection state, the constant current control unit converts the LED row in the abnormal connection state based on the control of the operation control unit. An image display device characterized by limiting an amount of current to flow.