JP2003208993A - LED lighting device - Google Patents

Abstract

(57) [Summary] In an LED lighting device, a plurality of LEDs are connected in series, and even if one of them is disconnected, another LED is connected.
The ED should not be turned off, reduce the number of wires, minimize the amount of heat generated by the circuit, and make the LED brightness uniform. SOLUTION: An LED unit 3 has four LEs.
D6 are all connected in series, and a current alternative path switch 7 and a disconnection detection circuit 8 are connected to each LED 6 in parallel. The disconnection detection circuit 8 monitors the voltage between both ends of the LED 6 to determine disconnection. When a disconnection occurs, the current alternative path switch 7 is turned on instantaneously so that the current continues to flow. Each of the disconnection detection circuits 8 outputs a disconnection detection signal when a disconnection occurs, and the control unit 2
When even one of the four LEDs 6 is disconnected, a disconnection signal is output to the control unit 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LED lighting device in which a plurality of light emitting diodes are connected in series and used as a light source.

In the present specification, the LED chip itself or the entire package including an optical device such as a package resin or a lens system on which the LED chip is mounted is referred to as a "light emitting diode" or "LED".

[0003]

2. Description of the Related Art A conventional LED lighting device will be described with reference to FIGS. FIG. 3 is a circuit diagram showing a circuit of a conventional LED lighting device in which a plurality of light emitting diodes are connected in series and turned on. FIG. 4 is a circuit diagram showing a circuit of an LED lighting device having a function of detecting a disconnection of an individual LED by connecting and lighting a plurality of conventional light emitting diodes in parallel.

As shown in FIG. 3, the light emitting diode 2
LED lighting device 2 for connecting and lighting a plurality of 3 in series
0, power supply 21, switch 22, LED23,
Since the current adjusting resistors 24 are all connected in series,
When any one of the LEDs 23 is disconnected, all the other LEDs 23 are also turned off. Further, when it is necessary to detect the disconnection of each LED, the series connection as shown in FIG. 3 cannot be applied, so the LE shown in FIG.
Like the D illumination device 30, all the individual LEDs 35 are connected in parallel, and the disconnection detection circuit 37 is attached to each. Since the disconnection detection signal is input to the OR circuit 38 and is output to the outside, if any one of the LEDs 35 is disconnected, it can be immediately determined from the outside.

[0005]

However, the LED
When the unit 32 and the control unit 31 are separately installed, wiring of the number of power supply lines + the number of parallel circuits is required,
There is a problem in that it takes time and cost for wiring. Further, each LED 35 requires a current limiting resistor 36, and when the number of LEDs 35 increases, the number of current limiting resistors 36 also increases, and the amount of heat generated by the LEDs 35 cannot be ignored.
Also, if there is a variation in the forward voltage of each LED 35,
The flowing current varies, and the brightness of the LED 35 also varies.

Therefore, according to the present invention, a plurality of LEDs are connected in series, and even if any one of them is disconnected, another LED is connected.
It is an object of the present invention to provide an LED lighting device in which the number of wirings is reduced, the amount of heat generated in the circuit is minimized, and the brightness of the light emitting diode is made uniform by not turning off.

[0007]

According to a first aspect of the present invention, there is provided an LED lighting device in which a plurality of light emitting diodes are connected in series for lighting, and any one of the plurality of light emitting diodes is disconnected. Even if the light is turned off, an alternative path through which an electric current flows instantly is formed to prevent other normal light emitting diodes from being turned off.

Thus, even if any one of the plurality of LEDs connected in series is disconnected, the other LEDs are not turned off. Further, since all the LEDs are connected in series, only one current adjusting resistor is required, and the heat generation amount of the circuit can be minimized.

In this way, by connecting all the LEDs in series and preventing the other LEDs from turning off even if one of them is broken, the number of wirings is reduced and the heat generation amount of the circuit is minimized. Thus, the LED lighting device can have uniform brightness of the light emitting diode.

According to a second aspect of the present invention, in the LED lighting device according to the first aspect, a circuit for detecting disconnection is provided in each of the plurality of light emitting diodes connected in series.

As a result, when any one of the plurality of LEDs connected in series is disconnected, the disconnection is immediately detected and transmitted to the outside. Therefore, the operator replaces the disconnected LED with a new one. It is possible to take necessary measures, such as to prevent the LED from being left open.

In this way, when one of the LEDs is broken, the other LEDs are turned on, and an appropriate treatment can be immediately applied to the broken LED.

According to a third aspect of the present invention, in the LED lighting device according to the first or second aspect, the alternative path is formed in a state in which a voltage is applied to both ends without completely connecting the disconnection portion. It is a thing.

In this LED lighting device, when the LED is broken, an alternative path is instantly formed to prevent the other LEDs from being turned off. However, even if the LED is not broken due to a malfunction, the alternative path is If the LED portion is completely connected by the alternative path, it is not possible to detect that the alternative path is formed due to a malfunction, so the LED remains off even though it is normal. Become. Therefore, in order to prevent this, the disconnection portion is not completely connected and the voltage is left at both ends of the alternative path. By this, by measuring the voltage across the alternative path, it is possible to detect whether or not the LED is actually broken.

In this way, even if the LED is not broken due to a malfunction and an alternative path is formed, the LED lighting device can detect the LED and normally light the LED. .

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a circuit diagram showing an outline of a circuit of an LED lighting device according to an embodiment of the present invention. FIG. 2 shows an LED according to the embodiment of the present invention.
It is a circuit diagram which shows the more detailed circuit of an illuminating device.

As shown in FIG. 1, the L of this embodiment is
The ED lighting device 1 includes a control unit 2 and a light emitting diode unit 3. This LED unit 3
In FIG. 4, all four LEDs 6 are connected in series, and a switch 7 for a current alternative path and a disconnection detection circuit 8 are connected in parallel to each LED 6. As described above, the actual alternative path is not such a switch 7 but a semiconductor switch circuit such as a transistor that leaves a voltage at both ends, but here it is shown as a switch 7 for simplicity. . The disconnection detection circuit 8 judges the disconnection by monitoring the voltage across the LED 6. When a disconnection occurs, the current alternate path switch 7 is instantly turned on so that the current continues to flow. Each of the disconnection detection circuits 8 outputs a disconnection detection signal when a disconnection occurs and is connected to the control unit 2 via the OR circuit 9. Therefore, if any one of the four LEDs 6 is disconnected, the control unit 2 A disconnection signal is output to.

A constant current circuit 10 is provided in the control unit in order to stabilize the brightness of the LEDs 6, but this constant current circuit 10 corresponds to a current adjusting resistor, and all the LEDs 6 are connected in series. Constant current circuit 1
Only one 0 is required, and the heat generation amount of the circuit can be minimized.

In this way, even if any one of the four LEDs 6 connected in series is disconnected, the other LEDs 6 are not turned off. Then, when the disconnection occurs, the disconnection detection circuit immediately outputs the disconnection signal to disconnect the LE.
Appropriate measures such as replacement of D6 can be taken. Also,
Since the four LEDs 6 are connected in series, even if the control unit 2 and the LED unit 3 are installed separately, the wiring connecting them is a total of three power supply lines and one disconnection signal line. Because it is only, it does not require wiring work and cost is not high. This situation is the same regardless of how many LEDs 6 are provided.

Next, a more detailed circuit and its operation will be described with reference to FIG. To show specific values, the power supply voltage = 12V, the voltage V1 = 2.0V, the resistance R1
= 27 kΩ, R2 = 68 kΩ, Q reference voltage = 2.5 V
As described below.

First, when the light emitting diode 6 is normally turned on, a current flows through the light emitting diode 6 through the path. The voltage V1 is 2.0 V, and the voltage V2 is divided by resistors R1 and R2 that divide the voltage across the light emitting diode 6, resulting in V2 = 2.0 × 68 / (27 + 68) = 1.43 V. At this time, the Tr1 driving shunt regulator (hereinafter, also simply referred to as “shunt regulator”) Q acts to set the voltage V2 to the reference voltage of 2.5 V, raises the voltage V3, and the voltage V3 is the value of the voltage V1. Is almost equal to. Therefore, since the base current for turning on the current alternative path transistor Tr1 does not flow (path of), it remains off, and no current flows through the path of. Since no current flows to the disconnection signal output transistor Tr2, the disconnection signal output transistor Tr2 remains OFF, and the disconnection signal is not output.

On the other hand, when the light emitting diode 6 is broken, the current stops flowing in the path of, and the current tries to flow in the path of. Since the voltage dividing resistors R1 and R2 have large resistance values, the value of the voltage V1 suddenly increases and tries to rise to a value close to the power supply voltage value. At the same time, the voltage V2 also rises. At this time, the shunt regulator Q acts to suppress the voltage V2 to the reference voltage of 2.5V, and lowers the voltage V3. Then, the base current of the current alternative path transistor Tr1 flows through the path, and the current alternative path transistor Tr1 is turned on. Therefore, a current alternative path is formed by the current alternative path transistor Tr1. As described above, even if the path due to the disconnection of the light emitting diode 6 is cut off, the current continues to flow through the instant path, and the other light emitting diodes are continuously turned on without being turned off. After that, the voltage V1 is controlled by the shunt regulator 3.
Stabilizes around 5V.

Then, as described above, the current flows through the path at the time of disconnection. Part of this current flows to the disconnection signal output transistor Tr2 via the backflow prevention diode D3 for outputting the disconnection signal and the base resistance R4 of the disconnection signal output transistor Tr2. Therefore, the disconnection signal output transistor Tr2 is turned on and is output to the outside as a disconnection signal. Since the disconnection detection signals of the other LEDs 6 connected in series are also connected to the disconnection signal output transistor Tr2, the disconnection signal output transistor Tr2 is turned on regardless of which light emitting diode is disconnected.

Note that R3 is a resistor that limits the current flowing to the shunt regulator Q, and D2 is a backflow prevention diode for outputting a disconnection signal, like D3.

Here, although the LED 6 is not broken, the transistor Tr for the current alternate path is erroneously operated due to malfunction.
When the current flows through the path in which 1 is ON, the LED 6 is not broken, so that the voltage V1 between both ends does not reach around 3.5V, and the forward voltage of the LED 6 is 2.
It becomes 0V. As a result, since it is known that a malfunction has occurred, the current alternate path transistor Tr1 can be turned off to restore the normal state, and the LED 6 can be normally turned on.

As described above, the current alternative path transistor T
By combining the r1 and the Tr1 driving shunt regulator Q, when the LED 6 is broken, the shunt regulator Q instantly turns on the current alternative path transistor Tr1 to form an alternative path through which current flows. This prevents the other LEDs 6 connected in series from being extinguished. At the same time, the disconnection signal output transistor Tr2 is turned on to notify the outside that any of the LEDs 6 is disconnected. As a result, appropriate measures can be taken immediately without the LED 6 being left open.

In the present embodiment, the shunt regulator and the transistor are used for detecting the disconnection and forming the alternative path for the current. However, in addition to this, a circuit using a thyristor,
A circuit in which transistors are combined is conceivable, and any method may be used.

The configuration, shape, quantity, material, size, connection relationship, etc. of the other parts of the LED lighting device are not limited to those in this embodiment.

[0029]

As described above, the LED lighting device according to the invention of claim 1 is an LED lighting device in which a plurality of light emitting diodes are connected in series for lighting, and any one of the plurality of light emitting diodes is used. Even if the LED is disconnected and turned off, an alternative path through which an electric current instantaneously flows is formed to prevent other normal light emitting diodes from being turned off.

Thus, even if any one of the plurality of LEDs connected in series is disconnected, the other LEDs are not turned off. Further, since all the LEDs are connected in series, only one current adjusting resistor is required, and the heat generation amount of the circuit can be minimized.

By thus connecting all the LEDs in series and preventing the other LEDs from being turned off even if one of them is broken, the number of wirings is reduced and the heat generation amount of the circuit is minimized. Thus, the LED lighting device can have uniform brightness of the light emitting diode.

According to a second aspect of the present invention, in the LED lighting device according to the first aspect, a circuit for detecting disconnection is provided in each of the plurality of light emitting diodes connected in series.

As a result, in addition to the effect described in claim 1, when any one of the plurality of LEDs connected in series is disconnected, the disconnection is immediately detected and transmitted to the outside. The operator can take necessary measures such as replacing the broken LED with a new one, and the LED will not be left in a broken state.

In this way, when one of the LEDs is broken, the other LED is turned on, and the LED which has been broken immediately can be appropriately treated.

According to a third aspect of the present invention, in the LED lighting device according to the first or second aspect, the alternative path is formed in a state in which a voltage is applied to both ends without completely connecting the disconnection portion. It is a thing.

In this LED lighting device, when an LED is broken, an alternative path is instantly formed to prevent the other LEDs from being turned off. However, even if the LED is not broken due to a malfunction, the alternative path is If the LED portion is completely connected by the alternative path, it is not possible to detect that the alternative path is formed due to a malfunction, so the LED remains off even though it is normal. Become. Therefore, in addition to the effect described in claim 1 or claim 2, in order to prevent this, the disconnection portion is not completely connected and a voltage is left at both ends of the alternative path. By this, by measuring the voltage across the alternative path, it is possible to detect whether or not the LED is actually broken.

In this way, even if the LED is not broken due to a malfunction and an alternative path is formed, the LED lighting device can detect the alternative path and normally light the LED. .

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an outline of a circuit of an LED lighting device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a more detailed circuit of the LED lighting device according to the embodiment of the present invention.

FIG. 3 is a circuit diagram showing a circuit of an LED lighting device in which a plurality of conventional light emitting diodes are connected in series and turned on.

FIG. 4 is a circuit diagram showing a circuit of an LED lighting device having a function of detecting a disconnection of an individual LED by connecting and lighting a plurality of conventional light emitting diodes in parallel.

[Explanation of symbols]

1 LED lighting device 6 Light emitting diode (LED) 7, Tr1 alternative road 8, D3, R4, Tr2 Circuit to detect disconnection

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 3K073 AA13 AA22 AA43 AA55 AA94                       AB03 CF02 CG23 CJ17                 5F041 AA25 BB03 BB06 BB22 BB25                       BB26 BB27 FF11

Claims (3)

[Claims] 1. An LED lighting device in which a plurality of light emitting diodes are connected in series and turned on, and an alternative path through which an electric current instantaneously flows is formed even if any of the plurality of light emitting diodes is broken and turned off. And an LED lighting device having a function of preventing other normal light emitting diodes from being turned off. 2. The LED lighting device according to claim 1, further comprising a circuit for detecting disconnection in each of the plurality of light emitting diodes connected in series. 3. The LED lighting device according to claim 1, wherein the alternative path is formed in a state where voltage is still applied to both ends without completely connecting the disconnection portion.