JP5187756B2 - Light emitting device for vehicle lamp - Google Patents

Description

  The present invention relates to a light emitting device for a vehicular lamp, and relates to a light emitting device for a vehicular lamp that controls light emission of a semiconductor light source for a headlamp and a semiconductor light source for other functions.

  2. Description of the Related Art Conventionally, as a vehicular lamp, one using a semiconductor light emitting element such as a light emitting diode (LED) as a semiconductor light source is known, and this type of vehicular lamp controls light emission of an LED. The light emitting device is mounted.

  Some of the light emitting devices include a single switching regulator, a plurality of current driving units, and a control unit (see, for example, Patent Document 1).

  Each current driver includes a shunt resistor that detects an LED drive current, a comparison amplifier, an NMOS (Negative Channel Metal Oxide Semiconductor) transistor, and a PMOS (Positive Channel Metal Oxide Semiconductor) transistor. The positive input of the comparison amplifier receives a first instruction signal instructing to turn on / off each LED and a second instruction signal instructing dimming of each LED. The second semiconductor element that is turned on / off is connected.

  Hereinafter, the operation of the above-described conventional light emitting device when the first semiconductor element is a PNP transistor and the second semiconductor element is an NPN transistor will be described.

  When a high level signal is sent as a first instruction signal from the control unit to the PNP transistor of the current driver connected to the LED for the headlamp, for example, the low beam LED, the PNP transistor is turned off and the comparison amplifier Off signal is sent out and the low beam LED is turned off. When a low level signal is sent to the PNP transistor as the first instruction signal, the PNP transistor is turned on, an on signal is sent from the comparison amplifier, and the low beam LED is lit.

  The collector of the NPN transistor is connected to the comparison amplifier via a connection node of two resistors. When a high level signal is sent as the second instruction signal from the control unit to the NPN transistor of the current driver connected to the low beam LED, the NPN transistor is turned on and the positive input voltage of the comparison amplifier is lowered, and the low beam LED The current flowing through the LED becomes lower and the light emission of the low beam LED is weakened. When a low level signal is sent to the NPN transistor as the second instruction signal, the NPN transistor is turned off, the positive input voltage of the comparison amplifier is increased, the current flowing through the low beam LED is increased, and the light emission of the low beam LED is intensified.

JP 2006-103477 A

  By the way, when the CPU built in the control unit becomes an abnormal state due to, for example, a circuit failure or a change in the external environment due to heat, the input / output impedance of the CPU becomes a high impedance state. That is, the PNP transistor is turned off and the NPN transistor is also turned off. When the PNP transistor and the NPN transistor are turned off, the low beam LED is turned off. Therefore, if the control unit becomes abnormal while the headlamp is turned on, the low beam LED is turned off, which causes a problem that the safety during driving of the vehicle is lowered.

  Therefore, a light emitting device for a vehicle lamp according to the present invention aims to improve the safety during driving of the vehicle by maintaining the lighting state of the headlamp even when the control unit has an abnormality. .

  A light emitting device for a vehicle lamp according to a first aspect of the present invention includes a plurality of switch means respectively connected to a plurality of semiconductor light sources configured by a semiconductor light source for headlamps and a semiconductor light source for other functions. A headlight current driving means and other function current driving means for supplying a driving current to the headlight semiconductor light source and the other function semiconductor light source, respectively, and at least turning off and turning off each of the semiconductor light sources. And a control means for transmitting a first instruction signal for instructing, wherein the headlamp current driving means and the other functional current driving means receive the first instruction signal, respectively. And when the first instruction signal is not sent from the control means to the first semiconductor element of the current drive means for the headlamp, Semiconductor The first semiconductor element of the headlamp current driving means is controlled so as to maintain the lighting state of the light source, and the other functional current driving is performed so as to maintain the light-off state of the other function semiconductor light source. The first semiconductor element of the means is controlled.

  Therefore, in the light emitting device for a vehicle lamp, when the first instruction signal is not sent to the first semiconductor element of the current driving means for the headlamp, the driving to the semiconductor light source for the headlamp is performed. The operation is performed so that the supply of current is maintained and the supply of drive current to the semiconductor light sources for other functions is stopped.

  A light emitting device for a vehicle lamp according to the present invention includes a plurality of switch means respectively connected to a plurality of semiconductor light sources configured by a semiconductor light source for headlamps and a semiconductor light source for other functions. A headlamp current driving means and other functional current driving means for supplying a driving current to the semiconductor light source and the semiconductor light source for other functions, respectively, and a first instruction for instructing at least turning on and off each of the semiconductor light sources In the light emitting device for a vehicular lamp having a control means for transmitting a signal, the headlight current driving means and the other functional current driving means each receive a first instruction signal and turn on and off. When the first instruction signal is not sent from the control means to the first semiconductor element of the current drive means for headlamps, the lighting state of the semiconductor light source for the headlamps is changed. The first semiconductor element of the current driving means for the headlamp is controlled so as to hold, and the first light source of the other functional current driving means is maintained so as to keep the semiconductor light source for the other function off. The semiconductor element is controlled.

  Therefore, according to the present invention, even when the control means is abnormal and the first instruction signal is not sent, the lighting state of the headlamp is maintained and the light-off state of the semiconductor light source for other functions is maintained. Therefore, it is possible to improve safety during driving of the vehicle.

  According to a second aspect of the present invention, the control means has a second instruction signal for instructing dimming of the semiconductor light sources, and the headlamp current driving means and the other functional currents. Each of the driving means has a second semiconductor element that turns on and off in response to the second instruction signal sent from the control means, and from the control means to the first semiconductor element of the headlamp current driving means When the first semiconductor element of the current driving means for the headlamp is controlled to maintain the lighting state of the semiconductor light source for the headlamp without sending the first instruction signal, The second semiconductor element of the current driving means for the headlamp is controlled so as to weaken the light emission of the semiconductor light source for the headlamp.

  Therefore, the lighting state of the semiconductor light source for headlamps can be maintained without intensifying the light emission of the semiconductor light source for headlamps, so that it is possible to further improve safety while driving the vehicle and Can suppress the influence on the semiconductor light source.

  In the invention described in claim 3, the first semiconductor element of the current driving means for the headlamp is a PNP transistor, and the second semiconductor element of the current driving means for the headlamp is an NPN transistor. A pull-down resistor is provided between the base of the PNP transistor and the control means, and a pull-up resistor is provided between the base of the NPN transistor and the control means.

  Therefore, in the light emitting device in which the lighting and dimming of the headlamp are controlled by the PNP transistor and the NPN transistor of the current driving means for the headlamp, the control means has an abnormality and the first instruction signal is sent out. Even if not, the lighting state of the semiconductor light source for the headlamp is maintained by the pull-down of the pull-down resistor, and the light emission of the semiconductor light source for the headlamp is maintained weak by the pull-up of the pull-up resistor. As a result, it is possible to improve the safety during the operation of the motor and to suppress the influence of the heat on the semiconductor light source.

  Below, the light-emitting device of the vehicle lamp which concerns on embodiment of this invention is demonstrated with reference to FIG. FIG. 1 is a diagram showing a configuration of a light emitting device for a vehicle lamp according to the present invention.

  The light emitting device 1 for a vehicle lamp includes a single switching regulator 10, an LED 40-1 as a semiconductor light source for headlamps, an LED 40-2 as a semiconductor light source for other functions, and current drive for headlamps. A current drive unit 30-1 as a means, a current drive unit 30-2 as another function current drive means, and a control circuit 25 as a control means are provided.

  In this embodiment, the case where there is one LED 40-2 as a semiconductor light source for other functions is taken as an example, but a plurality of LEDs 40-2 may be provided. In addition, as a lamp using a semiconductor light source for other functions, for example, a clearance lamp that functions as a vehicle width light, a turn signal lamp that functions as a direction indicator, and lights up in a time zone other than nighttime to exhibit a sign function There is a daytime running lamp to do.

The switching regulator 10 includes capacitors C1 and C2, a transformer T, a diode D1, an NMOS transistor 11, and a switching regulator control circuit 18. Both ends of the capacitor C1 are connected to power input terminals 15 and 16, respectively, and both ends of the capacitor C2 are connected to output terminals 19 and 20, respectively. The power input terminal 15 is connected to the plus terminal of the in-vehicle battery 13, and the power input terminal 16 is connected to the minus terminal of the in-vehicle battery 13. The output terminal 19 is connected to the anode side of each LED 40-1 and 40-2 through a shunt resistor R _SH and a PMOS transistor 33. The output terminal 20 is connected to the cathode side of each LED 40-1 and 40-2.

  The switching regulator 10 supplies an LED drive voltage to the LEDs 40-1 and 40-2 as a flyback type switching regulator.

  In the switching regulator 10, the NMOS transistor 11 is turned on / off by a switching signal output from the switching regulator control circuit 18, for example, a switching signal having a frequency of several tens of kHz to several hundreds of kHz. In order to use the DC voltage input between the power input terminals 15 and 16 as the light emission energy of the LEDs 40-1 and 40-2, the DC voltage is converted into an AC voltage. The AC voltage is rectified on the secondary side of the transformer T.

  The input DC voltage is converted into an AC voltage on the primary side of the transformer T. The AC voltage is rectified using the diode D1 provided on the secondary side as a rectifying element, and the rectified current is smoothed by the capacitor C2. The DC voltage smoothed in this way is supplied to the LEDs 40-1 and 40-2.

  The control circuit 25 includes a CPU 22, a RAM (Random Access Memory: not shown), and a ROM (Read Only Memory: not shown).

  The current driving units 30-1 and 30-2 are respectively a comparison amplifier 31, an NMOS transistor 32 and a PMOS transistor 33 that function as switching means, a PNP transistor 36 as a first semiconductor element, and an NPN transistor as a second semiconductor element. The LED drive current is supplied to the LEDs 40-1 and 40-2. Note that an NPN bipolar transistor and a PNP bipolar transistor may be used in place of the NMOS transistor 32 and the PMOS transistor 33, respectively. In place of the PNP transistor 36 and the NPN transistor 37, a PMOS transistor and an NMOS transistor may be used, respectively.

A shunt resistor R _SH that functions as a current detection unit is connected to the anode side of each of the LEDs 40-1 and 40-2. Differential amplifier 62 is connected in parallel to the shunt resistor R _SH. The detection voltage at the shunt resistor R _SH is applied to the negative input terminal of the comparison amplifier 31 via the differential amplifier 62.

  The positive input terminal of the comparison amplifier 31 is connected to the collector of a PNP transistor 36 as a first semiconductor element via a resistor R7, and is connected to the output terminal 20 via a resistor R8. The base of the PNP transistor 36 is connected to a signal output terminal of a CPU (Central Processing Unit) 22 built in the control circuit 25 via a resistor R11. A pull-down resistor R20 is connected to one end of the resistor R11 of the current driver 30-1.

  The NPN transistor 37 has a function of controlling dimming of the LEDs 40-1 and 40-2. The collector of the NPN transistor 37 is connected to the positive input terminal of the comparison amplifier 31 via the resistor R9, and the base is connected to the signal output terminal of the CPU 22 via the resistor R13. A pull-up resistor R30 is connected to one end of the resistor R13 of the current driver 30-1.

  A PMOS transistor 33 is connected to the anode side of each of the LEDs 40-1 and 40-2.

  Below, operation | movement of the light-emitting device 1 which concerns on this Embodiment is demonstrated.

  When a low level signal is input as the first instruction signal from the CPU 22 to the base of the PNP transistor 36 of the current driver 30-1, the PNP transistor 36 is turned on in response to the low level signal, and the positive input terminal of the comparison amplifier 31. A resistance partial pressure of a reference voltage is applied to. Therefore, an analog control signal for controlling the NMOS transistor 32 to be turned on is sent from the comparison amplifier 31 to the gate of the NMOS transistor 32. The NMOS transistor 32 is turned on in response to the analog control signal, and the PMOS transistor 33 is also turned on. Therefore, the LED drive current is supplied to the LED 40-1, and the LED 40-1 is lit.

  When a high level signal is input as the first instruction signal from the CPU 22 to the base of the PNP transistor 36 of the current driver 30-1, the PNP transistor 36 is turned off in response to the high level signal. Therefore, an analog control signal for controlling the NMOS transistor 32 to be turned off is sent from the comparison amplifier 31 to the gate of the NMOS transistor 32. The NMOS transistor 32 is turned off in response to the analog control signal, and the PMOS transistor 33 is also turned off. Accordingly, the supply of the LED drive current to the LED 40-1 is stopped, and the LED 40-1 is turned off.

  When a high level signal is input as the second instruction signal from the CPU 22 to the base of the NPN transistor 37 of the current driving unit 30-1, the NPN transistor 37 is turned on, and the positive input voltage of the comparison amplifier 31 is lowered to the LED 40-1. The flowing current decreases. When the current flowing through the LED 40-1 decreases, the light emission of the LED 40-1 is weakened.

  When a low level signal is input as the second instruction signal from the CPU 22 to the base of the NPN transistor 37 of the current driver 30-1, the NPN transistor 37 is turned off, and the positive input voltage of the comparison amplifier 31 becomes high, and the LED 40-1 The current flowing through becomes higher. When the current flowing through the LED 40-1 increases, the light emission of the LED 40-1 increases.

  Regarding the control of turning on / off and dimming of the LED 40-2, as in the case of the LED 40-1, the PNP transistor 36 and the NPN transistor 37 of the current driver 30-2 are respectively connected to the first instruction signal and the second This is done by sending an instruction signal. The operations of the PNP transistor 36 and the NPN transistor 37 that have received the first instruction signal and the second instruction signal, respectively, are the same as the above-described control of turning on / off the light and controlling the dimming of the LED 40-1. Omitted.

  In the light emitting device 1 that operates as described above, if the CPU 22 is in an abnormal state when the LED 40-1 is lit, the input / output impedance of the CPU 22 is in a high impedance state. Therefore, the first instruction signal and the second instruction signal are not sent from the CPU 22 to the PNP transistor 36 and the NPN transistor 37 of the current driver 30-1, respectively.

  At this time, a current flows from the emitter to the base of the PNP transistor 36 due to the pull-down of the pull-down resistor R20, the base voltage of the PNP transistor 36 becomes low level, and the PNP transistor 36 is turned on. Accordingly, since the NMOS transistor 32 is turned on and the PMOS transistor 33 is also turned on, the supply of the LED driving current to the LED 40-1 is maintained, and the lighting of the LED 40-1 is maintained.

  When the LED 40-2 is on and the CPU 22 is in an abnormal state, the CPU 22 does not send the first instruction signal and the second instruction signal to the PNP transistor 36 and the NPN transistor 37 of the current driver 30-2, respectively. Therefore, the PNP transistor 36 and the NPN transistor 37 are turned off. For this reason, the LED drive current is not supplied to the LED 40-2, and the LED 40-2 is turned off.

  Therefore, even when the control unit 25 enters an abnormal state when the headlamp that uses the LED 40-1 as the light source is lit, the headlamp remains on, and other than the headlamp that uses the LED 40-2 as the light source. Since the lamp is turned off, it is possible to improve safety during driving of the vehicle.

  Next, an operation in the case where the PNP transistor 36 is turned on and the LED 40-1 is kept on and the second instruction signal is not sent from the CPU 22 to the NPN transistor 37 when the CPU 22 is abnormal will be described.

  Since the pull-up resistor R30 is provided between the base of the NPN transistor 37 and the CPU 22, when the second instruction signal is not sent from the CPU 22 to the NPN transistor 37, the pull-up resistor is connected from the base of the NPN transistor 37 to the emitter. A current flows due to the pull-up of R30, the base voltage of the NPN transistor 37 becomes high level, and the NPN transistor 37 is turned on. Therefore, the positive input voltage of the comparison amplifier 31 is lowered, the current flowing through the LED 40-1 is reduced, and the state where the light emission of the LED 40-1 is weakened is maintained. Accordingly, it is possible to further improve safety during driving of the vehicle and to suppress failure of the LEDs 40-1 and 40-2 due to heat.

  Each of the above-described embodiments is merely an example of a preferred embodiment of the present invention, and the present invention can be implemented with various modifications without departing from the gist thereof.

It is the figure which showed the structure of the light-emitting device of the vehicle lamp which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Light-emitting device, 22 ... CPU, 25 ... Control circuit, 30-1, 30-2 ... Current drive part, 32 ... NMOS transistor, 33 ... PMOS transistor, 36 ... PNP transistor, 37 ... NPN transistor, 40-1, 40-2 ... LED

Claims (3)

The semiconductor light source for headlamps and the semiconductor for other functions including a plurality of switch means respectively connected to a plurality of semiconductor light sources constituted by a semiconductor light source for headlamps and a semiconductor light source for other functions Vehicle having headlamp current drive means and other function current drive means for supplying drive current to the light sources, and control means for sending at least a first instruction signal for turning on / off each of the semiconductor light sources. In the light emitting device of the lighting equipment,
The headlamp current driving means and the other functional current driving means each include a first semiconductor element that turns on and off in response to the first instruction signal,
When the first instruction signal is not sent from the control means to the first semiconductor element of the current driving means for the headlamp, the lighting state of the semiconductor light source for the headlamp is maintained. The first semiconductor element of the current driving means for headlamps is controlled, and the first semiconductor element of the other current driving means for other functions is controlled so as to maintain the extinction state of the semiconductor light source for other functions. A light emitting device for a vehicular lamp characterized by the above. The control means has a second instruction signal for instructing dimming of each semiconductor light source,
The headlamp current driving means and the other functional current driving means each have a second semiconductor element that turns on and off in response to the second instruction signal sent from the control means,
The first instruction signal is not sent from the control means to the first semiconductor element of the headlight current driving means, and the first semiconductor element of the headlight current driving means is When the semiconductor light source for the headlamp is controlled to maintain the lighting state, the second semiconductor element of the current drive means for the headlamp is controlled so as to weaken the light emission of the semiconductor light source for the headlamp. The light-emitting device of the vehicular lamp according to claim 1. The first semiconductor element of the current driving means for the headlamp is a PNP transistor, and the second semiconductor element of the current driving means for the headlamp is an NPN transistor,
A pull-down resistor is provided between the base of the PNP transistor and the control means;
The light-emitting device for a vehicle lamp according to claim 2, wherein a pull-up resistor is provided between a base of the NPN transistor and the control means.

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