JP2007305929A - Led display device and led illumination device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an LED device capable of coping even with the LED of a large power/high luminance. <P>SOLUTION: As it is recognized from the repetition unit of a configuration indicated by a code 1, FETs 5 are inserted in parallel to all the LEDs 3. Since the FET 5 is turned on when the LED 3 fails and detected as disconnected due to defects, a current is made to flow as bypassing the failed LED. Also, for the fault detection of the LED 3, when the LED 3 fails and becomes open, since the current does not flow to a resistor R inserted between the cathode of the LED 3 and the GND, it drops to an "L" level. The level is detected, and when it lowers to a voltage equal to or below a certain fixed value (set value), "1"/"0" is judged by a comparator 27 for which input is connected to one end on the opposite side of the GND of the resistor R, and non-lighting of the LED (LED Error 31) is confirmed. An FET 7 is provided in order to adjust (shift the level of) the voltage supplied from a CPU 41 with the FETs 5 for switching the LEDs 3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an LED display device and an LED lighting device.

  Display devices and lighting devices using LEDs are actively used in various fields.

Japanese Patent Application Laid-Open No. 2005-49239, “Vehicle Instrument Lighting Device” JP 2005-310998 A, “Constant Current Drive Device, Backlight Light Source Device, and Color Liquid Crystal Display Device” Japanese Patent Application Laid-Open No. 2005-310999, “Constant Current Drive Device, Backlight Light Source Device, and Color Liquid Crystal Display Device”

  In the case of an illuminating device using an LED, it is common to use a multi-lamp in which LEDs are connected in series. However, as described in the above-mentioned patent document, the LED fails and becomes an OPEN state. If this happens, no light will be emitted.

  In the above-mentioned Patent Document 1, an attempt is made to solve the problem of non-lighting by using the leakage current of the Zener. However, in recent years, the driving current (some LEDs exceed max 10 A) is greatly increased along with the increasing tendency of the light emission amount of the LED. It is increasing. In the case of such a large current, switching at the Zener voltage is virtually impossible.

  Further, the above-mentioned Patent Document 2 is premised on pulse dimming, and there is a problem that the light is not turned on when pulse dimming is not used. Although the above-mentioned patent document 3 solves this weak point, since the minimum current between the anode and the cathode must be kept flowing, the LED drive current flows slightly, and the LED is lit. That is, since it cannot be completely turned off, there is a problem that it cannot be used for a field sequential display device.

    An object of this invention is to provide the LED apparatus which can respond also to high power / high-intensity type LED.

  In the present invention, a SW is provided to prevent unlighting of the LED. By devising the SW circuit configuration as shown in FIG. 1 to be described later, it can be applied to a field sequential display device.

  That is, according to one aspect of the present invention, in an LED lighting device having a light-emitting diode (LED) row (hereinafter referred to as “LED row”) in which a plurality of LEDs are connected in series, the LEDs constituting the LED row. There is provided an LED lighting device characterized by having a short-circuit portion that short-circuits each of the above. A failure can be determined using the drive current when the LED fails. Note that even when the microcomputer port is insufficient, the control by the DC expands to “H” / “L”, so that the control by the expander can be easily performed.

  The short-circuit unit is a switch connected in parallel to the LED, and the switch includes a p-channel field effect transistor or a pnp bipolar transistor. By configuring the control circuit as P-CH_MOSFET / PNP-TR, a failed LED can be bypass-controlled in either mode of light emission of PWM drive or light emission of steady drive. (Note that FIG. 1 to be described later is a diagram showing a configuration example of the MOSFET.)

  There is a resistance for current detection between the cathode of the LED and the ground (current-voltage conversion and feedback is performed to keep the voltage constant), and the potential at both ends of the resistance is input to the comparator. By doing so, it is possible to confirm that the LED is not lit. It is also possible to provide a light sensor in the vicinity of the LED row and to confirm that the LED row is not lit based on the reading value of the light sensor. Furthermore, by having a storage unit for storing the short-circuited switch among the switches, failure information is stored for the LED determined to have failed using a storage device such as an EEPROM, and this information is reflected in the next operation based on this information. Can do. It can also have a notification part which notifies failure information, when the un-lighting of the said LED row is detected. As a result, it is possible to notify the user that the vehicle is operating in the emergency mode.

  In addition, in the LED row described above, the unlit LED due to opening is identified by sequentially short-circuiting the LEDs from 1 to n-1 among n (n is an integer of 2 or more) LEDs. There is provided a method for detecting a defect of an LED lighting device, comprising the step of: The LED string can be repaired by continuing the short circuit of the defective LED identified by this method.

  In the present invention, since the zener leakage current is not used as a means for bypassing (short-circuiting) the LED, the voltage can be reduced, and a high power / high luminance type LED can be handled. Further, since the circuit for bypassing the LED is configured to be turned ON / OFF by DC, it can be used for applications other than pulsed light emission. Furthermore, since the unlit LED in the LED array can be specified, there is an effect in terms of user interface and service.

  In recent years, as the brightness of LEDs has rapidly increased, devices for increasing the brightness by applying large power have also appeared. Along with this, not only the conventional small liquid crystal backlight, but also a case where it is used for the backlight of a large liquid crystal panel, the light source of a projector, the illumination of an automobile, etc. has come out. The technology according to the present embodiment can seek improvement in safety / long-term reliability in these LED products.

  FIG. 1 is a diagram showing a configuration example of a circuit block of an LED display device according to an embodiment of the present invention. In the circuit block A shown in FIG. 1, first, as a power supply circuit (VCC) 37 used for driving the LED 3 or the like, a resistor R is inserted between the cathode and the GND of the LED 3 because the LED 3 or the like needs to be driven at a constant current. In general, a method of controlling the constant current by looking at the voltage generated by the current flowing through the resistor R is used, and the circuit type 35 is a step-up / step-down switching regulator. Alternatively, a series regulator may be used.

  Further, the circuit block A according to the present embodiment is characterized in that the SW circuit 11 is added between the output of the regulator 35 and the LED 3. By adding the SW circuit 11, dimming by pulse emission can be performed by turning on / off the SW circuit 11, and the current can be completely cut off during the off period, so that the light source corresponding to the field sequential can be used. Also has the advantage that it can be used.

  In FIG. 1, as can be seen from the repeating unit having the configuration indicated by reference numeral 1, FETs 5 are inserted in parallel for all the LEDs 3... When the FET 5 is turned on, a current can be passed by bypassing the failed LED. The failure detection of the LED 3 falls to the “L” level because when the LED 3 fails and becomes open, no current flows through the resistor R inserted between the cathode of the LED 3 and GND. In this embodiment, when this level is detected and lowered to a voltage below a certain level (set value), the comparator 27 whose input is connected to one end of the resistor R on the opposite side to GND is set to “1” / It is possible to determine “0” and confirm that the LED is not lit (LED Error 31). The FET 7 is provided to adjust (level shift) the voltage supplied from the CPU 41 and the CPU 41 that switches the LED 3. Reference numerals 17, 21, 23, and 25 represent polarities of supplied voltages.

  As for the failure detection operation here, when a display is assumed, there are not a few cases where a color sensor / illuminance sensor, etc. are mounted, and even if a switching feedback voltage check mechanism is not provided, It is also possible to confirm whether or not an unlit LED has occurred in the reading.

  The switching feedback voltage check mechanism is a control signal for non-lighting determination after the comparator. By using a color / illuminance sensor and passing through a comparator, the feedback voltage during switching is the same as the result of passing through the comparator.

  An example of a specific structure of the circuit shown in FIG. 1 will be described below. FIG. 4 is a cross-sectional view showing a configuration example of the LED array according to the present embodiment. FIG. 5 is a cross-sectional view showing a configuration example of a switch using a bipolar transistor formed on the same substrate as the LED array of FIG. FIG. 6 is a cross-sectional view showing a configuration example of a switch using an FET formed on the same substrate as the LED array of FIG.

  As shown in FIG. 4, an LED array X1 is formed on a p-type Si substrate 10 to which a p-type impurity is added. In the figure, three LEDs 3 are shown, but this is an example. The LED 3 is formed by an n-type Si layer 3b formed in the p-type Si 3c and a p-type Si layer 3a formed in the n-type Si layer 3b. A first terminal T1 is formed for the p-type Si layer 3a, and a second terminal T2 is formed for the n-type Si layer 3b. Light emission is obtained from the p-type Si layer 3a (actually, a depletion layer between the n-type Si layer 3b) by applying a high positive bias to the second terminal with respect to the first terminal T1. . In order to configure the LED array X1, the T1 terminal and the T2 terminal of the adjacent LEDs 3 may be connected in series. FIG. 5 is a structural sectional view of a switch using a pnp bipolar transistor and FIG. 6 is a structural sectional view of a switch using an n-channel MOSFET on the same p-type Si substrate 10 as FIG.

  As shown in FIG. 5, an n-type Si well layer 6d is formed on a p-type Si substrate 10 to which a p-type impurity is added. In this well layer 6d, a collector layer 6c made of p-type Si, a base layer 6b made of n-type Si, and an emitter layer 6a made of p-type Si are formed to constitute a pnp-type bipolar transistor. . A terminal T5 is formed for the collector layer 6c, a terminal T4 is formed for the base layer 6b, and a terminal T3 is formed for the emitter layer 6a. Then, wiring for connecting the transistor (FET) 5 and the LED 3 as shown in FIG. 1 is formed, and the configuration shown in FIG. 1 is formed monolithically.

  Alternatively, as shown in FIG. 6, a well layer 12b made of p-type Si is formed on a p-type Si substrate 10 to which a p-type impurity is added, and a source 12a and a drain 12a made of n-type Si are formed therein. The channel layer and the gate electrode formed thereon are formed between them, forming an n-type MOSFET. A terminal T8 is formed for the source 12a, a terminal T7 is formed for the gate, and a terminal T6 is formed for the drain 12c.

  7 shows a circuit diagram shown in FIG. 1 in which one LED 3 and two pnp bipolar transistors 6 (reference numeral 5 in FIG. 1) and 6 (reference numeral 7 in FIG. 1) are placed in the same substrate (chip) 10. By forming and wiring the terminals T1 to T5 along FIG. 1, the integrated circuit 1 indicated by the broken line in FIG. 1 (a resistance layer is not shown, but a p-type or n-type semiconductor layer or A resistive metal can be formed on the chip). One chip formed in this manner can be mounted on a chip carrier to form a hybrid integrated circuit shown in FIG.

  Alternatively, wiring for connecting the transistor 5 and the LED 3 (which may include a resistor) as shown in FIG. 1 is formed according to the design, and the possible configuration shown in FIG. 1 is formed monolithically. Is also possible. At this time, it is also possible to form an LED array including a desired number of LEDs in one chip by changing the wiring according to the number of LED arrays required by the user.

  As described above, the configured control circuit is configured by P-CH_FET / PNP-TR, and the malfunctioned LED is bypass-controlled in either mode of light emission of PWM drive or light emission of steady drive. .

  Next, an operation algorithm according to the present embodiment will be described with reference to FIGS. FIG. 2 is a flowchart showing a flow of LED display check processing according to the embodiment of the present invention. First, in step S1, the power is turned on, and in step S2, the EEPROM 33 is checked immediately after the power is turned on. This is a process of checking whether the LEDs 3... Are faulty and which LEDs are faulty. If the confirmation result in the EEPROM 33 is NG, a message is output and the process is terminated (step S3). When the failure location of the LEDs 3 is found, the FET 5 connected in parallel to the LEDs is operated (step S4), and then the LED driver is started (step S5). In parallel with this processing, a notification that a failure has occurred is also sent.

  The LED error check is repeated periodically to check whether the LED is turned off. At this time, when the light emission uses pulse light emission, the LED is turned off during the light emission ON period (step S6).

  If it is confirmed that the LED 3 is turned off, the FETs connected in parallel to the LED are sequentially turned on (step S7 to step S17) to check whether the LED lighting is restored. If the lighting of the LED is not confirmed in all combinations shown in FIG. 3 to be described later, a notification that the repair is impossible is sent (step S18). When the lighting of the LED is confirmed and the repair is confirmed, the LED is informed that it has failed (step S19).

  The power-off process (step S9) is started by the user's power-off command (step S10) (step S8). At this time, if the LED failure status increases from the state currently stored in the EEPROM. Further, it is stored in the EEPROM (step S11).

  An example of a check method will be described with reference to FIG. 3 and Tables 1 and 2. As shown in FIG. 3, as an example, in the case of an LED array configuration in which eight LEDs are connected in series, when the LED array is not lit, each LED is given a serial number 1 to 8 for explanation. . The left end of FIG. 3 is the anode power supply side, and the right end is the feedback side. In the priority order of the check shown in Table 1 when the LED string is not lit, in 1), each of the LED strings 1 to 8 is separately short-circuited by the FET 5 (FIG. 1), and the other seven LEDs Check if the column is lit. If the LED row is lit only by short-circuiting one LED, it can be estimated that the short-circuited LED is disconnected. Thus, when only one LED is disconnected, the LED array can be lit by short-circuiting the disconnected LED. It should be noted that the unlighted LED can be confirmed by determining “1” / “0” by the comparator 27 as described above.

  The method of priority 2) is a method of checking whether or not the LED string is lit by shorting two LEDs, and is executed when the LED string is not lit in the method of priority 1). In the following, the method of priority 3) checks 3 LEDs, the method of priority 4) 4 LEDs, the priority 5) method 5 LEDs, the priority 6) method 6 LEDs, and so on. Will continue. Thereby, the LED row which became unlit can be recovered somewhere in the above procedure. However, shorting all eight LEDs is meaningless and is not implemented.

  As described above, in the present invention, the leakage current of the Zener is not used for bypassing the LED, so that it is possible to cope with a recent high power / high brightness type LED. In addition, since the circuit for bypassing the LED is on / off with DC, it can be used for applications other than pulsed light emission. Further, since the unlit LED can be specified, the effect can be exhibited in terms of user interface and service. That is, by identifying the unlit part, it is possible to notify the user that there is a malfunction and that the user is operating in an emergency evacuation. Further, since the unlit part has already been specified for the service, there is an advantage that the LED to be repaired and replaced is clear, and it is not necessary to perform a task such as searching for a troubled part as in the prior art.

  When a storage device such as the above-described EEPROM is used, failure information can be stored for the LED determined to be failed. Based on this information, it can be reflected in the next operation. Further, failure information may be notified to the user. As a result, it is possible to notify that the vehicle is operating in the emergency mode.

  In the above embodiment, an example in which an FET or a bipolar transistor is used as a switch connected in parallel to the LED has been described. However, the present invention is not limited to this, and other switches may be used.

  The present invention can be used for LED display devices, LED lighting devices, and the like.

It is a figure which shows one structural example of the circuit block of the LED display apparatus by one embodiment of this invention. It is a flowchart figure which shows the flow of the check process of LED display by one embodiment of this invention. It is a figure which shows the structural example of the LED row | line | column by which LED 8 light is connected in series. It is sectional drawing which shows one structural example of LED row | line | column. FIG. 5 is a cross-sectional view illustrating a configuration example of a switch using a bipolar transistor formed on the same substrate as the LED array of FIG. 4. FIG. 5 is a cross-sectional view illustrating a configuration example of a switch using an FET formed on the same substrate as the LED row in FIG. 4. It is sectional drawing which shows the example of a position structure which formed the circuit element shown by the code | symbol 1 of FIG. 1 in 1 chip | tip.

Explanation of symbols

A ... LED display device, 1 ... repeating unit, 3 ... LED, 5, 7 ... FET, 11 ... switch circuit (for PWM dimming), 27 ... comparator, 33 ... EEPROM, 35 ... regulator, 37 ... power supply, 41 ... CPU.

Claims (12)

In an LED lighting device having a light emitting diode (LED) row (hereinafter referred to as “LED row”) in which a plurality of LEDs are connected in series,
An LED lighting device, comprising: a short-circuit unit that independently short-circuits each of the LEDs constituting the LED array.   The LED lighting device according to claim 1, wherein the short-circuit unit is a switch connected in parallel to the LED.   The LED lighting device according to claim 2, wherein the switch is a p-channel transistor or a pnp transistor.   4. A non-lighting of the LED is confirmed by a resistor provided between a cathode of the LED and a ground, and a comparator having a voltage between the resistor and the cathode as an input. The LED lighting device according to any one of the above.   The pn junction that forms the LED is formed monolithically on the same substrate or chip as the p-channel transistor or pnp transistor that forms the switch. LED lighting device.   6. A level shift transistor for level shift for adjusting a voltage level applied to a charge limiting electrode on a control electrode of a p-channel transistor or a pnp transistor forming the switch. The LED lighting device according to claim 1.   The LED lighting device according to claim 5, wherein the level shift transistor is formed on the same substrate or chip as the LED and the switch.   The LED lighting device according to claim 1, further comprising a storage unit that stores a short-circuited switch among the switches. An optical sensor is provided in the vicinity of the LED row,
The LED lighting device according to any one of claims 1 to 8, wherein non-lighting of the LED array is detected based on a reading value of the light sensor.   The LED illumination device according to claim 9, further comprising: a notification unit that notifies failure information when detecting the non-lighting of the LED row.   In the LED row | line | column of any one of Claim 1-7, By short-circuiting LED of 1 to n-1 among n (n is an integer greater than or equal to 2) LED in order. A method for detecting a defect in an LED lighting device, comprising the step of identifying an unlit LED due to opening.   The repair method of the LED lighting apparatus characterized by repairing the said LED row | line | column by continuing the short circuit of the unlit LED specified by the method of Claim 11.

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