JP2009255679A - Lighting control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent large current from flowing to a lighting control unit when a signal line is grounded. <P>SOLUTION: This lighting control device detects disconnection of a LED 3a. A driver module 2 has a disconnection signal interface 2c for outputting potential corresponding to a disconnection state to a flasher relay 1. The disconnection signal interface 2c has a clamping part 2i for clamping current flowing when a disconnection detection signal line is grounded to constant current. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a lighting control device that controls lighting of a semiconductor light source composed of a semiconductor light emitting element, and more particularly to a lighting control device that has a disconnection detection function and is miniaturized.

  Conventionally, for example, a vehicular lamp has been developed that employs a semiconductor light emitting element such as an LED (Light Emitting Diode) as a light source. And in this vehicle lamp etc., the lighting control apparatus which controls lighting of this LED is generally used.

  A lighting system generally includes a flasher relay, a driver module as a lighting control device, and an LED unit, and detection of disconnection of a light source such as an LED is performed on the flash chalet side. That is, the flasher relay is connected to the driver module via a disconnection detection line, and determines whether the lighting is normally performed or a disconnection occurs based on the voltage of the disconnection detection terminal.

  Here, as this type of technology, Patent Document 1 includes a disconnection detection unit that detects disconnection of a light source and notifies the outside of the lamp body, and at least one of a plurality of light sources connected in parallel is disconnected. Further, there is disclosed a vehicle lamp in which the disconnection detecting unit detects disconnection.

  On the other hand, in the lighting control circuit according to the prior art, as shown in FIG. 3, in the driver module 101, the emitter of the transistor Tr11 is connected to the power supply terminal, and the collector of the transistor Tr11 is connected to the disconnection detection terminal via the output resistor R11. It is connected to the. The disconnection detection terminal is connected to one end of an input resistor R12 inside the flasher relay via a disconnection detection terminal on the flasher relay 100 side.

  Nowadays, it is required that the flasher relay 101 makes a normal determination when the battery voltage is 8 V or higher when the lamp is normally lit.

JP 2004-122913 A

  However, in the configuration of FIG. 3 described above, in order to satisfy the above requirement, when the impedance of the input resistor R12 of the flasher relay 100 is low, it is necessary to considerably reduce the impedance of the output resistor R11 on the driver module 101 side. is there.

For example, if the input impedance of the input resistor R12 is 1.2 kΩ and the threshold value of the normal lighting determination voltage is 7 V or more, the output impedance of the output resistor R11 is
1.2kΩ / (1.2kΩ + R11)) · 8V > 7V
And R11 < 170Ω.

  That is, for example, when the power supply voltage is 8 V, in order to output a voltage of 7 V or more to the disconnection detection terminal on the flasher relay 100 side during normal lighting, the output impedance of the output resistor R11 on the driver module 101 side must be 170 Ω or less. Don't be.

  If the output impedance of the output resistor R11 is set to 170Ω, and the disconnection signal line is grounded as shown in FIG. 3 during normal operation, the output voltage is 16V (ie, the worst condition). A current of 100 mA flows through the resistor R11. For this reason, it is necessary to employ a rated 2 W class resistor as the output resistor R11, which leads to an increase in the size of the circuit itself.

  Therefore, the present invention improves safety by limiting the current that flows to the blinking control unit or the like in the event of a ground fault of the disconnection signal line, further downsizing the output resistance of the lighting control unit, and thus downsizing and reducing the device itself. The task is to reduce costs.

  A lighting control device according to one aspect of the present invention is a lighting control device including a lighting control unit having a disconnection detecting unit that detects disconnection of a semiconductor light emitting element. The disconnection detecting means is connected to a blinking control unit that blinks the semiconductor light emitting element with a single signal line, and has a disconnection signal output means for outputting a potential corresponding to the disconnection state to the blinking control unit. The disconnection signal output unit includes a clamp unit that clamps the current flowing through the disconnection signal output unit to a constant current when one signal line is grounded.

  Therefore, the current flowing through the disconnection signal output means is clamped to a constant current by the clamp unit.

  In this lighting control device, the disconnection signal output means may include a switch unit, a load unit, and a Zener diode. The switch unit is a transistor, and the Zener diode may be connected between the base and emitter of the transistor. The disconnection signal output means may include a switch unit, a load unit, and a differential amplifier.

  According to the first aspect of the present invention, safety is improved by limiting the current flowing to the blinking control unit or the like in the event of a ground fault of the disconnection signal line, the output resistance of the lighting control unit is further reduced, and consequently the size of the device itself is reduced. And cost reduction.

  According to the invention of claim 2, the Zener diode functions as a clamp part, the current flowing through the blinking control unit or the like is a constant current, and safety is improved.

  According to the invention of claim 3, the current that flows to the blinking control unit or the like is made constant by the emitter follower, and safety is improved.

  The best mode for carrying out the present invention (hereinafter simply referred to as an embodiment) will be described below in detail with reference to the drawings.

  FIG. 1 shows and describes the configuration of a lighting system that employs a lighting control device according to an embodiment of the present invention. As shown in FIG. 1, the lighting system includes a flasher relay 1 as a blinking control unit, a driver module 2 as a lighting control device, and an LED unit 3. In addition, although the example which employ | adopted LED as a semiconductor light emitting element is shown here, it is not limited to this.

  The flasher relay 1 includes a power supply terminal 1a, and the power supply terminal 1a is connected to an output-side power supply terminal 1c via a switch 1b. Further, a disconnection detection terminal 1d is provided, and the disconnection detection terminal 1d is connected to the ground terminal 1e via an input resistor Rin.

  The driver module 2 includes a lighting circuit 2a, a disconnection detection circuit 2b as disconnection detection means, and a disconnection signal interface 2c as disconnection signal output means. The power terminal 1c of the flasher relay 1 is connected to the power terminal 2d on the driver module 2 side. One end of the lighting circuit 2a is connected to a power supply line extending from the power supply terminal 2d, and the other end is connected to a ground line extending between the ground terminals 2f to 2g. The output terminal of the lighting circuit 2a is also connected to the disconnection detection circuit 2b. One end of the disconnection detection circuit 2b is connected to the power supply terminal 2e, and the other end is extended to the ground terminals 2f to 2g. Connected to the line. Of these components, the disconnection detection circuit 2b and the disconnection signal interface 2c constitute a lighting control unit.

  The disconnection output terminal of the disconnection detection circuit 2b is connected to the disconnection signal interface 2c. That is, the disconnection output terminal is connected to the base of the switching element Tr1 via the resistor R4. In this example, an NPN transistor is employed as the switching element Tr1. The emitter of the switching element Tr1 is connected to the ground line, and the collector is connected to the base of the switching element Tr2 via the resistor R2. In this example, a PNP transistor is employed as the switching element Tr2. The connection end of the resistor R4 and the base of the switching element Tr1 is connected to the ground line via the resistor R5. The emitter of the switching element Tr2 is connected to the power supply line via the output resistor R1, and the collector is connected to the disconnection detection terminal 2h.

  A Zener diode ZD1 as a clamp part 2i is provided between the base and emitter of the switching element Tr2. More specifically, the cathode of the Zener diode ZD1 is connected to the power supply line, and the anode of the Zener diode ZD1 is connected to the connection end of the resistor R2 and the base of the switching element Tr2. This Zener diode ZD1 has a current-voltage characteristic and a forward characteristic substantially the same as a normal rectifying diode. However, in the reverse bias state, when breakdown occurs, the voltage becomes constant without depending on the current. To function as a constant voltage source. The connection end of the resistor R1 and the switching element Tr2 and the anode of the Zener diode ZD1 are connected via the resistor R3.

  On the other hand, the LED unit 3 has a configuration in which LEDs 3a as a plurality of semiconductor light emitting elements are connected in series, and one end of this LED group is connected to a power supply terminal 2e on the driver module 2 side via a power supply terminal 3b. The other end is connected to a ground terminal 2f on the driver module 2 side via a ground terminal 3c.

  In such a configuration, in the lighting control device, the LED unit 3 is connected to a power source (battery or the like) (not shown) via the flasher relay 1 and the driver module 2, and the determination of the disconnection of the LED is performed by the flasher relay 1. On the side. Specifically, the flasher relay 1 determines that the disconnection detection terminal 1d is normal when the potential of the disconnection detection terminal 1d is equal to or higher than a predetermined threshold (7 V in this example), and is disconnected when the potential is equal to or lower than the predetermined threshold (2 V in this example). .

  That is, during normal lighting, the disconnection output signal of the disconnection detection circuit of the driver module 2 becomes high level (Hi), the switching element Tr1 is turned on, the switching Tr2 is turned on, and a + B voltage is applied to the disconnection detection terminal 1d. The voltage divided by the output resistance R1 of 2 and the input resistance Rin of the flasher relay 1 is generated.

  If this voltage is 7V or more, it is determined that the flasher relay 1 is normally lit. On the other hand, at the time of disconnection, the disconnection output signal of the disconnection detection circuit 2b of the driver module 2 becomes low level (Lo), the switching element Tr1 is turned off, the switching Tr2 is turned off, and the potential of the disconnection detection terminal 1d becomes 0V. The flasher relay 1 is determined to be disconnected.

  In the lighting control device according to this embodiment, in particular, the output resistor R1 is connected to the emitter side of the switching element Tr2, and the Zener diode ZD1 is connected between the base and emitter of the switching element Tr2, so that the current flowing through the output resistor R1 Is clamped to a predetermined current value. Therefore, even if the disconnection signal line is grounded, no overcurrent flows through the output resistor R1, so the rating of the output resistor R1 is lower than that of the conventional circuit, and the size is reduced.

For example, if the voltage VZD1 of the Zener diode ZD1 is 2.7 V and the base-emitter voltage Vbe1 of the switching element Tr2 is 0.6 V, the current to be clamped is
(VZD1-Vbe1) / R1 = (2.7V-0.6V) / 170Ω = 12 mA
It becomes.

  Therefore, the relationship between the power supply voltage + B and the current flowing through the output resistor R1 is as shown in FIG. As can be seen from the figure, since the switching element Tr2 is completely turned on when the disconnection signal line is normal, 7V is output to the disconnection detection terminal 1d when the power supply voltage + B is 8V. It becomes possible. When the disconnection signal line is grounded, the + B voltage is clamped from about 2.5V, and the current ground flowing through the resistor R1 is constant at 12 mA.

  As described above, according to one embodiment of the present invention, when the lighting is normally performed, the power supply voltage is set to 8V and 7V or more can be output to the disconnecting terminal, and then the current flows when the disconnecting signal line is grounded. The current can be limited and the output resistance of the driver module can be reduced.

  The embodiment of the present invention has been described above, but the present invention is not limited to this, and it is needless to say that various improvements and changes can be made without departing from the spirit of the present invention.

  For example, in the above-described embodiment, an example in which the Zener diode ZD1 is employed for the clamp portion 2i has been described. However, the present invention is not limited to this, and a differential amplifier or the like may be employed. Further, an FET may be employed as the switching element Tr2, and in this case, the clamp unit 2i realizes a source follower.

The block diagram of the lighting system which employ | adopted the lighting control apparatus of one embodiment of this invention. The figure which shows the voltage-current characteristic at the time of the ground fault of a disconnection detection signal, and normal. The partial block diagram of the lighting control apparatus which concerns on a prior art.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Flasher relay, 2 ... Driver module, 2a ... Lighting circuit, 2b ... Disconnection detection circuit, 2c ... Disconnection signal interface, 2i ... Clamp part, 3 ... LED unit, 3a ... LED, 4 ... Disconnection detection signal line, R1 ... Output resistance, Rin ... Input resistance, ZD1 ... Zener diode

Claims (3)

A lighting control device comprising a lighting control unit having a disconnection detecting means for detecting disconnection of a semiconductor light emitting element,
The disconnection detecting means includes
It is connected to a blinking control unit that blinks the semiconductor light emitting element by a single signal line, and has a disconnection signal output means for outputting a potential corresponding to the disconnection state to the blinking control unit,
The disconnection signal output means includes
A lighting control device comprising: a clamp unit that clamps a current flowing through the disconnection signal output means to a constant current when the one signal line is grounded. The lighting control device according to claim 1, wherein the disconnection signal output unit includes a switch unit, a load unit, and a Zener diode. The lighting control device according to claim 2, wherein the switch unit is a transistor, and the Zener diode is connected between a base and an emitter of the transistor.

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