JP4714701B2 - LED vehicle lighting control circuit - Google Patents

Description

  The present invention relates to a lighting control circuit for an LED vehicle lamp, and more specifically, in an LED vehicle lamp including a low beam light source and a high beam light source, when either one of the light sources is not disconnected, The present invention relates to a lighting control circuit for an LED vehicle lamp that automatically ensures lighting of the other light source.

  In a vehicular lamp that uses a plurality of LEDs as a light source and controls the LEDs to be turned on simultaneously, the LEDs are connected in series in consideration of variations in individual current-voltage characteristics. The series connection is an effective connection method also from the viewpoint of connection of the protection circuit of the LED and correspondence of one lighting disconnection.

  Similarly, an LED unit composed of a plurality of LEDs connected in series is driven at a constant current in order to suppress variation in brightness between the LED units due to variation in current-voltage characteristics of individual LEDs.

  For the above reasons, in vehicle lamps using LEDs as light sources, many proposals have been made regarding drive circuits and drive methods for LED units in which a plurality of LEDs constituting the lamps are connected in series.

  For example, as shown in the circuit configuration of FIG. 2, a light source block 58a composed of a plurality of LEDs connected in series or a light source block 58a composed of a plurality of light source units connected in series to each other in parallel. Similarly, a high-beam head is configured by a light beam block 58b that includes a plurality of LEDs connected in series or a light source block 58b that includes a plurality of light source units connected in series. Configure the lamp.

  The light source block 58 a and the light source block 58 b are connected in series with each other, and both ends of the light source blocks 58 a and 58 b connected in series are connected to the output side of the switching regulator 114.

When the high beam switch 202a is turned off and the low beam switch 202b is turned on, the transistor 206 is turned on and the switch 204 is turned on, both ends of the light source block 58b are short-circuited, and only the light source block 58a is lit. When the high beam switch 202a is turned on and the low beam switch 202b is turned off, the transistor 206 is turned off and the switch 204 is turned off, both ends of the light source block 58b are opened, and both the light source block 58a and the light source block 58b are lit. To do. (For example, refer to Patent Document 1).
JP 2004-136719 A

  When the high beam switch 202a is ON, the lighting control circuit for the LED vehicular lamp having the above configuration has an abnormality in at least one of the light source block 58a and the light source block 58b that are turned on at the same time, resulting in disconnection. In the normal light source block, the current path is cut off and the power supply is stopped.

  For example, when the high beam switch 202a is ON, if the light source block 58b constituting the high beam headlamp is disconnected and is not lit, the light source block 58a constituting the low beam headlamp is also not lit at the same time. End up.

  For this reason, the lamp does not function as a vehicular lamp, which is extremely undesirable for ensuring the safety of the driver.

  Accordingly, the present invention was devised in view of the above problems, and the object of the present invention is to cut off any one of the light sources in an LED vehicle lamp equipped with a low beam light source and a high beam light source. In such a case, a lighting control circuit that automatically ensures lighting of the other light source is provided.

  In order to solve the above-mentioned problems, an invention described in claim 1 of the present invention is a lighting control circuit for an LED vehicle lamp in which a first LED light source and a second LED light source are connected in series. The first LED light source is provided with first disconnection detecting means for detecting disconnection of the first LED light source, and both ends of the first LED light source are electrically short-circuited or opened. First switch means for switching to a state is connected, and the second LED light source is provided with second disconnection detection means for detecting disconnection of the second LED light source, and both ends of the second LED light source are connected to each other. Second switch means for electrically switching to either the short / open state is connected, and the first LED light source is connected to the second disconnection detection result of the disconnection detection result of the first disconnection detection means. Wire break inspection ON / OFF is switched by the first switch means controlled by the result and the switching state of the external changeover switch, and the second LED light source has the disconnection detection result of the first disconnection detection means, The lighting / extinguishing is switched by the second switch means controlled by the disconnection detection result of the second disconnection detecting means and the switching state of the external changeover switch.

  The invention described in claim 2 of the present invention is characterized in that, in claim 1, the first switch means and the second switch means are both FETs or bipolar transistors. is there.

  According to a third aspect of the present invention, in the first or second aspect, the first disconnection detecting means and the second disconnection detecting means constitute a photocoupler. This is due to the lighting / non-lighting of the LED.

  Further, in the invention described in claim 4 of the present invention, in any one of claims 1 to 3, each of the first LED light source and the second LED light source is one LED or in series. It consists of several LED connected to this.

  The dimming circuit for the LED vehicle lamp according to the present invention includes a switch means for switching on / off of each LED light source and a disconnection of each light source for each of the first LED light source and the second LED light source connected in series. A disconnection detection means for detecting is provided, and each switch means is controlled to switch on / off of each LED light source according to the switching state of the external changeover switch and the detection result of both disconnection detection means.

  As a result, when one of the first light source and the second light source is not disconnected, the other light source can be automatically turned on.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIG. 1 (the same reference numerals are given to the same portions). In addition, since the Example described below is a suitable specific example of this invention, various technically preferable restrictions are attached | subjected, The range of this invention limits this invention especially in the following description. As long as there is no description of that, it is not restricted to these Examples.

  FIG. 1 is a configuration diagram of a lighting control circuit for an LED vehicle lamp according to the present invention. The common contact 2C of the high beam / low beam switching SW2 is connected to the (+) terminal of the battery 1, and the anodes of the reverse connection prevention diode D1 and the reverse connection prevention diode D2 are connected to the low beam contact terminal 2L and the high beam contact terminal 2H, respectively. The cathodes of D1 and D2 are connected to each other and connected to the input of the constant current control DC / DC converter 3.

  The output of the constant current control DC / DC converter 3 is connected to the anode side of an LED unit LL formed by connecting a plurality of LEDs 1 to n in series via a current detection resistor R1, and the cathode side is similarly connected to a plurality of LEDs. The LED unit LH formed by connecting the LEDs 1 to n in series is connected to the anode side, and the cathode side is connected to the same potential portion (hereinafter referred to as GND) of the (−) side potential of the battery 1.

  In this case, the LED unit LL constitutes a low beam light source unit, and the LED unit LH constitutes a high beam light source unit.

  The LED unit LL is connected in parallel with a Zener diode ZDL connected in series, a resistor R2 and a light emitting element (LED) of a photocoupler PCL, and a source S and a drain D of a MOSFET QL2 are connected to both ends of the LED unit LL. Has been.

  Similarly, a Zener diode ZDH connected in series, a resistor R3, and a light emitting element (LED) of a photocoupler PCH are connected in parallel to the LED unit LH, and the source S and drain of the MOSFET QH2 are connected to both ends of the LED unit LH. D is connected.

  The cathode side connection point P1 of each of the diodes D1 and D2 is connected to the gate G of the MOSFET QH2, the collector C of the transistor QH1, the anode A of the thyristor THYLB, and one terminal of each of the Zener diode ZD and the resistor R through the resistor R4. The emitter E of the transistor QH1, the cathode C of the thyristor THYLB, and the other terminals of the Zener diode ZD and the resistor R are connected to GND.

  The high beam contact terminal 2H of the high beam / low beam switching SW2 is connected to the base B of the transistor QH1 and the anode A of the thyristor THYH via the reverse connection prevention diode D3 and the resistor 5, and the cathode C of the thyristor THYH is connected to GND.

  The gate G of the thyristor THYH is connected to the emitter E of the light receiving element (phototransistor PT) of the photocoupler PCH and one terminal of each of the resistor R and the capacitor C, and the other terminal of each of the resistor R and the capacitor C is GND. The collector C of the light receiving element (phototransistor PT) of the photocoupler PCH is connected to the resistor R1 via the resistor R6.

  The light receiving element (phototransistor PT) of the photocoupler PCL has a collector C connected to the base B of the transistor QL1 via a resistor R8 and a resistor R7, and an emitter E connected to GND.

  In the transistor QL1, the emitter E is connected to the resistor R1, the base B is connected to the connection point P2 between the resistors R7 and R8, the collector C is connected to the gate G of the thyristor THYLB via R9, and the resistor R10 is connected. To the gate G of the thyristor THYLA.

  The gate G of the thyristor THYLB and the gate G of the thyristor THYLA are both connected to one terminal of each of the resistor R and the capacitor C, and the other terminal of each of the resistor R and the capacitor C is connected to GND. The cathode C of the thyristor THYLA is connected to GND.

  The gate G of the MOSFET QL2 is connected to the anode A of the thyristor THYLA through the resistor R11, and is connected to one terminal of each of the Zener diode ZD and the resistor R. The other terminal of each of the Zener diode ZD and the resistor R is It is connected to the source S of the MOSFET QL2.

  Therefore, in the lighting control circuit having the above-described configuration, first, a circuit operation in a case where there is no disconnection in both the LED unit LL and the LED unit LH will be described.

  When the common contact 2C of the high beam / low beam switching SW2 is connected to the low beam contact terminal 2L, the voltage of the battery 1 is input to the constant current control DC / DC converter through the reverse connection prevention diode D1, and is applied to the gate G of the MOSFET QH2 to be applied to the MOSFET QH2. Is turned on. Then, the drain D and the source S of the MOSFET QH2 are conducted, and both ends of the LED unit LH are electrically short-circuited.

  At this time, the transistor QH1 is in an OFF state since the current supply to the base B is blocked by the reverse connection prevention diode D2.

Therefore, when the relationship between the total forward voltage V _{LL of} the LEDs 1 to n constituting the LED unit LL and the Zener voltage V _ZDL of the Zener diode ZDL becomes V _LL <V _ZDL , no current is supplied to the LED of the photocoupler PCL. The phototransistor PT of the photocoupler PCL is turned off, and accordingly, the transistor QL1 and the MOSFET QL2 are turned off.

  Then, the drain D and the source S of the MOSFET QL2 are electrically opened (opened), and the current supplied from the output of the constant current control DC / DC converter is the current detection resistor R1, the LED unit LL, and the MOSFET QH2. It reaches GND via a path between the drain D and the source S.

  Therefore, the LED unit LL is turned on, the LED unit LH is turned off, and light is emitted only from the low beam light source unit.

  On the other hand, when the common contact 2C of the high beam / low beam switching SW2 is connected to the high beam contact terminal 2H, the voltage of the battery 1 is input to the constant current control DC / DC converter through the reverse connection prevention diode D2, and the current is applied to the base B of the transistor QH1. Is supplied to turn on the transistor QH1.

  Then, the collector C and the emitter E of the transistor QH1 become conductive, the voltage of the gate G of the MOSFET QH2 drops to near the GND level, the MOSFET QH2 is turned OFF, and the drain D and the source S of the MOSFET QH2 are opened.

At this time, since the drain D and the source S of the MOSFET QL2 are also in an open state, the relationship between the total forward voltage V _LH of the LEDs 1 to n constituting the LED unit LH and the Zener voltage V _ZDH of the Zener diode ZDH is V _{When LH} < _VZDH , no current is supplied to the LED of the photocoupler PCL, and the current supplied from the output of the constant current control DC / DC converter is the current detection resistor R1, LED unit LL, and LED unit LH. It reaches GND via the route of.

  Accordingly, both the LED unit LL and the LED unit LH are turned on, and light is emitted from both the low beam light source unit and the high beam light source unit.

Next, a circuit protection method and a lighting maintenance method when the LED unit is disconnected will be described. First, when the common contact 2C of the high beam / low beam switching SW2 is connected to the low beam contact terminal 2L, that is, when the LED unit LL constituting the low beam light source unit is lit and the LED unit LH constituting the high beam light source unit is turned on. When the LED unit LL that is only lit is disconnected in the light-off state, the constant current control DC / DC converter 3 increases the output voltage V _O in an attempt to maintain the supply of the current I that is controlled by the constant current.

LED emits light current flows Zener diode ZDL becomes conductive when the output voltage _{V O} rises exceeding the Zener voltage _{V ZDL} of the Zener diode ZDL the LED of the photocoupler PCL, photocoupler PCL which receives the light The phototransistor PT is turned on.

  Then, a current flows through the resistor R7, the resistor R8 and the path between the collector C and the emitter E of the phototransistor PT to the GND, the base B voltage of the transistor QL1 is lowered, and the transistor QL1 is turned on.

  When the transistor QL1 is turned ON, the gate G of the thyristor THYLA is triggered and becomes conductive, the gate G voltage of the MOSFET QL2 decreases, the MOSFET QL2 becomes NO, and the drain D and the source S are conductive and disconnected. To protect the circuit.

  At the same time, when the transistor QL1 is turned on, the gate G of the thyristor THYLB is also triggered to become conductive, the gate G voltage of the MOSFET QH2 is lowered to near the GND level, the MOSFET QH2 is turned off, and drains connected to both ends of the LED unit LH. The space between D and the source S is opened, current is supplied to the LED unit LH, and the LED unit LH is lit.

  That is, when only the LED unit LL constituting the low beam light source unit is lit, when the LED unit LL is disconnected, both ends of the disconnected LED unit LL are short-circuited to protect the circuit, and the LED unit The LED unit LH constituting the high beam light source unit that has been turned off until then is turned on instead of LL. This makes it possible to ensure safety during vehicle travel.

  If the LED unit LH is in a lighted state and the LED unit LH is in a light-off state, if the LED unit LH in the light-off state is disconnected, there is no problem because both ends of the unit LH are already short-circuited by the MOSFET QH2. .

On the other hand, when the common contact 2C of the high beam / low beam switching SW2 is connected to the high beam contact terminal 2H, that is, the LED unit LL constituting the low beam light source unit and the LED unit LH constituting the high beam light source unit are both lit. At this time, when the disconnection occurs in the LED unit LH, the constant current control DC / DC converter 3 increases the output voltage V _O in an attempt to maintain the supply of the current I controlled by the constant current.

When the output voltage V _O rises and exceeds the Zener voltage V _ZDH of the Zener diode ZDH, the Zener diode ZDH is turned on, a current flows through the LED of the photocoupler PCH, the LED emits light, and the photocoupler PCH that receives the light The phototransistor PT is turned on.

Then, when the phototransistor PT of the photocoupler PCH is turned on, the gate G of the thyristor THYLH is triggered to become conductive, the base B voltage of the transistor QH1 is lowered to near the GND level, the transistor QH1 is turned off, and the gate G of the MOSFET QH2 is turned on. The battery voltage V _I is applied to the via the diode D2. Then, the MOSFET QH2 is turned on, the drain D and the source S are conducted, and both ends of the disconnected LED unit LH are short-circuited to protect the circuit.

  At this time, the current I output from the constant current control DC / DC converter 1 reaches GND via the path between the LED unit LL and the drain D and source S of the MOSFET QH2.

  That is, when the LED unit LL constituting the low-beam light source unit and the LED unit LH constituting the high-beam light source unit are both lit, when the LED unit LH is disconnected, both ends of the disconnected LED unit LH are short-circuited. Thus, the circuit can be protected and the LED unit LL can be kept on, and safety during vehicle travel can be ensured.

  Note that when the MOSFET QL2 and the MOSFET QH2 work to protect the circuit of the disconnected LED unit LL and the LED unit LH and secure the current flow path, the operation of the photocoupler PCL and the photocoupler PCH stops, but in this state, the thyristor THYLA Since both the thyristor THYLB and the thyristor THYH are latched, the circuit protection and the securing of the current flow path by the MOSFET QL2 and the MOSFET QH2 are maintained as they are.

  MOSFET QL2 and MOSFET QH2 may each be a bipolar transistor.

  The Zener diode ZD provided between the gate G and the source S of the MOSFET QL2 and MOSFET QH2 is generally used for protecting the gate of the MOSFET and is not related to the present invention.

FIG. 1 is a configuration diagram of a lighting control circuit for an LED vehicle lamp according to the present invention. It is a block diagram of a prior art example.

Explanation of symbols

1 Battery 2 High beam / Low beam switching SW
3 Constant current control DC / DC converter

Claims (4)

  A lighting control circuit for an LED vehicular lamp in which a first LED light source and a second LED light source are connected in series, wherein the first LED light source detects a disconnection of the first LED light source. First disconnection detection means is provided, and first switch means for electrically switching both ends of the first LED light source to either the short / open state is connected, and the second LED light source is connected to the second LED light source. Second disconnection detecting means for detecting disconnection of the second LED light source is provided, and second switch means for electrically switching both ends of the second LED light source to either the short circuit / open state is connected. Before the first LED light source is controlled by the disconnection detection result of the first disconnection detection means, the disconnection detection result of the second disconnection detection means, and the switching state of the external selector switch. ON / OFF is switched by the first switch means, and the second LED light source is connected to the disconnection detection result of the first disconnection detection means, the disconnection detection result of the second disconnection detection means, and the external switching. A lighting control circuit for an LED vehicular lamp, wherein lighting / extinguishing is switched by the second switch means controlled by a switching state of the switch.   2. The lighting control circuit for an LED vehicle lamp according to claim 1, wherein each of the first switch means and the second switch means is an FET or a bipolar transistor.   The first disconnection detecting means and the second disconnection detecting means are based on lighting / non-lighting of an LED constituting a photocoupler. LED lighting control circuit for the vehicle.   The first LED light source and the second LED light source are each composed of one LED or a plurality of LEDs connected in series. LED lighting control circuit for the vehicle.

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