JP7147246B2 - vehicle lamp - Google Patents

Description

The present invention relates to a vehicle lamp.

2. Description of the Related Art In recent years, a lamp unit using a light emitting element such as an LED (Light Emitting Diode) as a light source has been adopted as a vehicle lamp (for example, see Patent Documents 1 and 2).

JP 2014-213663 A JP 2015-110357 A

However, in the prior arts such as those described in Patent Documents 1 and 2, when the input voltage repeatedly fluctuates in a state lower than normal, the light emitting element alternately repeats the ON state and the OFF state. Therefore, the light emitting element may flicker.

The present disclosure has been made in view of such circumstances, and aims to prevent flickering of a light emitting element.

A vehicle lamp, which is one aspect of the present disclosure, includes a plurality of light emitting elements connected in series, a power supply unit that supplies an input current to the plurality of light emitting elements, and at least some of the plurality of light emitting elements. a bypass circuit that is connected in parallel and forms a bypass path for the input current; and a flicker prevention circuit that controls the bypass path formed by the bypass circuit according to the input voltage applied by the power supply unit. When the input voltage transitions from a transient state to a stable state, the flicker prevention circuit controls the bypass path from an on state to an off state, and is connected in parallel with the bypass circuit among the plurality of light emitting elements. an open detection circuit for detecting whether or not the light-emitting element is in an open state; a bypass stop circuit for controlling the bypass path to be in an off state when the open detection circuit detects that the light emitting element is in the open state; further provide .

Further, in the vehicle lamp according to one aspect of the present disclosure, the flicker prevention circuit sets the detection result of the open detection circuit to the open state when the input voltage transitions from a transient state to a stable state. is preferred.

According to one aspect of the present disclosure, flickering of a light emitting element can be prevented.

1 is a block diagram of a vehicle lamp according to an embodiment to which the present disclosure is applied; FIG. 1 is a circuit diagram of a vehicle lamp according to an embodiment to which the present disclosure is applied; FIG. 4 is a timing chart of voltage waveforms according to an embodiment to which the present disclosure is applied;

Hereinafter, embodiments of a vehicle lamp to which the present disclosure is applied will be described in detail based on the drawings. Note that the present disclosure is not limited by this embodiment.

(Outline configuration)
FIG. 1 is a block diagram of a vehicle lamp according to an embodiment to which the present disclosure is applied. A vehicle lamp is, for example, a headlamp, and headlamp units are mounted on both left and right ends of a front portion of a vehicle. The vehicle lamp includes a bypass circuit 21, a bypass stop circuit 22, an open detection circuit 23, a current control circuit 24, a flicker prevention circuit 25, and light emitting elements 31A-31C. 1 also shows a diode D1, a power supply unit 11, a lighting switch 2, an in-vehicle battery 1, a control unit 3, and an ECU 4. As shown in FIG. Further, the light-emitting elements 31A to 31C are referred to as the light-emitting element 31 when there is no particular need to distinguish between them. The light-emitting element 31 is, for example, a self-luminous semiconductor light source such as an OLED (organic light-emitting diode) using an LED or an OEL (organic EL).

In the vehicle lamp, LEDs are connected in series as the light emitting elements 31 . In the vehicle lamp, when the lighting switch 2 is turned on, the power supply unit 11 uses the DC voltage supplied from the vehicle battery 1 to supply the input current I_in to the light emitting element 31, causing the light emitting element 31 to emit light. The power supply unit 11 is configured by a DC-DC converter, for example, as a switching regulator (not shown). The power supply unit 11 performs switching control of the switching regulator when the converter operates according to an on/off control signal supplied from the control unit 3 . Note that the control unit 3 operates according to control commands from the ECU 4 . The input side of the power supply unit 11 is connected to the positive and negative electrodes (ground) of the vehicle battery 1 via terminals 11a and 11b. The output side of the power source section 11 is connected to the light emitting elements 31A to 31C constituting the light source via terminals 11c and 11d. That is, the power supply unit 11 steps up or steps down the DC voltage between the terminals 11a and 11b to generate the input voltage V_in for driving the light emitting elements 31A to 31C, and outputs the input voltage V_in to the terminals 11c and 11d. Therefore, the power supply unit 11 supplies the input current I_in to the plurality of light emitting elements 31 .

The bypass circuit 21 is connected in parallel to at least some of the plurality of light emitting elements 31 to form a bypass path for the input current I_in. In one example of FIG. 1, the bypass circuit 21 is connected in parallel to the light emitting element 31A among the plurality of light emitting elements 31. In FIG. That is, the bypass circuit 21 is connected in series with the light emitting elements 31B and 31C. The flicker prevention circuit 25 controls the bypass path formed by the bypass circuit 21 according to the input voltage V_in applied to the light emitting elements 31A to 31C by the power supply section 11. FIG. Although the details will be described later, the flicker prevention circuit 25 controls the bypass path from the ON state to the OFF state when the input voltage V_in transitions from the transient state to the stable state.

The open detection circuit 23 detects whether or not the light emitting element 31A connected in parallel with the bypass circuit 21 among the plurality of light emitting elements 31 is in the open state. The light-emitting element 31 is in an abnormal state when it is in a short-circuited state or an open-circuited state. Therefore, the open detection circuit 23 performs failure detection of the light emitting element 31A by detecting whether or not the light emitting element 31A is in the open state. When the open detection circuit 23 detects that the light emitting element 31A is in the open state, the bypass stop circuit 22 controls the bypass path to the off state. The current control circuit 24 limits and controls the direct current.

By the way, when turning on the vehicle lamp, the vehicle side monitors the input current I_in, and if it is determined that the input current I_in is equal to or less than a preset threshold current, the driver is notified of the failure. As shown in FIG. 1, when three light emitting elements 31 are connected in series and a drive circuit (not shown) controls the power supply unit 11 by constant current driving, the input current I_in is equal to It greatly depends on the forward voltage Vf of the element 31 . If the ambient temperature is a normal temperature, the forward voltage Vf of the light emitting element 31 used in the vehicle lamp is about 3.0V. However, if the ambient temperature is low, the forward voltage Vf of the light emitting element 31 is about 3.3V. Therefore, when three light emitting elements 31 are connected in series, almost no input current I_in flows even if the input voltage V_in exceeds 10 V, which is within the operating voltage range for failure detection. Therefore, fault detection malfunctions.

Therefore, when the input voltage V_in is low, the circuit configuration bypasses one or more light emitting elements 31 so that the number of light emitting elements 31 connected in series is two or less. With such a connection configuration, the total forward voltage Vf of the light emitting element 31 can be lowered, so that the input current I_in can exceed the preset threshold current even at the minimum operating voltage for failure detection. . Therefore, it is possible to avoid a situation in which failure detection malfunctions.

If the circuit configuration is not bypassed, when any one of the plurality of light emitting elements 31 has an open failure, the serially connected light emitting elements 31 are open, so that the input current I_in does not flow. Therefore, it is determined that the input current I_in is equal to or less than the preset threshold current, and the failure is detected. However, in the bypass circuit configuration, when any one of the plurality of light emitting elements 31 has an open failure, the input current I_in flows through the bypass circuit configuration until the input voltage V_in reaches the bypass switching voltage. As a result, even if the input voltage V_in is within the operating voltage range for failure detection, the input current I_in does not become equal to or less than the preset threshold current. do not have. Therefore, fault detection may not work. Therefore, when the light emitting element 31 connected in parallel with the circuit configuration to be bypassed has an open failure, the circuit configuration to be bypassed is cancelled. Such control ensures that the input current I_in falls below the preset threshold current even when the light emitting element 31 has an open failure. Specifically, when the input voltage V_in transitions from the transient state to the stable state, the flicker prevention circuit 25 sets the detection result of the open detection circuit 23 to the open state.

(circuit configuration)
FIG. 2 is a circuit diagram of a vehicle lamp according to an embodiment to which the present disclosure is applied. The current supplied from the power supply unit 11 is unidirectionally controlled by the diode D1 whose anode side is connected to the terminal 11c, and is harmonically controlled by the capacitors C1 and C2 connected in parallel between the terminals 11c and 11d. and other noise components are removed. An input current I_in flowing through the light emitting elements 31A to 31C has its noise component removed by a capacitor C3 connected in parallel with the light emitting elements 31A to 31C. A transient voltage suppression diode TVS1 is connected in parallel between the terminals 11c and 11d to protect various elements of the vehicle lamp. The flicker prevention circuit 25 includes a capacitor C4, resistors R11 and R12, and switching elements Q16 and Q17. The switching elements Q16 and Q17 are NPN transistors. One side of the capacitor C4 is connected to the terminal 11c side, and the other side of the capacitor C4 is connected in series with the resistor R12. A series circuit composed of a capacitor C4 and a resistor R12 is connected to the base side of the switching element Q16. One end of the resistor R11 is connected to the terminal 11c side, and the other end is connected to the collector side of the switching element Q16. A connection point between the resistor R11 and the collector side of the switching element Q16 is connected to the base side of the switching element Q17. The emitter sides of the switching elements Q16 and Q17 are connected to the ground.

The bypass circuit 21 has a switching element Q4. The switching element Q4 is a PNP transistor. The switching element Q4 has a collector side connected to a connection point between the cathode side of the light emitting element 31A and the anode side of the light emitting element 31B, and an emitter side connected to the terminal 11c side. That is, a path including the switching element Q4 and connected in parallel with the light emitting element 31A becomes a bypass path.

The open detection circuit 23 has a switching element Q5 and resistors R8 and R10. The switching element Q5 is an NPN transistor. The switching element Q5 has a collector side connected to a connection point between the base side of the switching element Q6 and one of the resistors R9, an emitter side connected to the ground, and a base side connected to a connection point between one side of the resistor R8 and one side of the resistor R10. It is The base side of the switching element Q5 is also connected to the collector side of the switching element Q17. The other end of the resistor R8 is connected between the cathode side of the light emitting element 31A and the anode side of the light emitting element 31B. The other end of the resistor R10 is connected to the ground.

The bypass stop circuit 22 includes switching elements Q3, Q6, resistors R6, R7, R9, and a Zener diode ZD1. The switching element Q3 is a PNP transistor. The switching element Q6 is an NPN transistor. The switching element Q3 has a collector connected to a connection point between the base of the switching element Q4 and one of the resistors R7, an emitter connected to the terminal 11c, and a base connected to one of the resistors R6. The other end of resistor R6 is connected to the connection point between the cathode side of Zener diode ZD1 and the collector side of switching element Q6. A Zener diode ZD1 having a Zener voltage Vz higher than the forward voltage Vf of the light emitting element 31A is used. The switching element Q6 has a base connected to a connection point between the collector side of the switching element Q5 and one of the resistors R9. The other end of the resistor R9 is connected to the terminal 11c side. The anode side of the Zener diode ZD1, the emitter side of the switching element Q6, and the other side of the resistor R7 are connected to the ground.

The current control circuit 24 includes resistors R1 to R5 and switching elements Q1 and Q2. The switching element Q1 is an NPN transistor. The switching element Q2 is an N-channel MOS-FET (Metal Oxide Semiconductor-Field Effect Transistor). The switching element Q1 has a collector side connected to one side of the resistor R1, an emitter side connected to the ground, and a base side connected to the source side of the switching element Q2. The other end of the resistor R1 is connected to the terminal 11c side. The switching element Q2 has a gate side connected to the collector side of the switching element Q1, a drain side connected to the cathode side of the light emitting element 31C, and a source side connected to the base side of the switching element Q1 and one of the resistors R3 to R5. The resistors R3 to R5 are connected in parallel, one of which is connected to the source side of the switching element Q2 and the other of which is grounded. One end of the resistor R2 is connected to the gate side of the switching element Q2, and the other end is connected to the ground.

(circuit operation)
FIG. 3 is a timing chart of voltage waveforms according to an embodiment to which the present disclosure is applied. When the input voltage V_in is in a transient state and is in the rising process, a current flows through the capacitor C4 of the flicker prevention circuit 25, thereby opening the switching element Q16 and closing the switching element Q17. The flicker prevention circuit 25 does not affect the detection result of the open detection circuit 23 while the input voltage V_in is in a transient state and rising process. Therefore, as usual, the light emitting element 31A is bypassed by the switching element Q4 until the bypass switching voltage is reached.

In addition, if the light emitting element 31A is in an open state, the switching element Q5 is in a closed state. If the switching element Q5 is in the closed state, the switching element Q6 will be in the open state. If the switching element Q6 is in an open state, the switching element Q3 will be in a closed state. If the switching element Q3 is in the closed state, the switching element Q4 will be in the open state and the bypass path will be in the OFF state. On the other hand, if the light emitting element 31A is in the closed state, the switching element Q5 will be in the open state. If the switching element Q5 is open, the switching element Q6 is closed. If the switching element Q6 is in the closed state, the switching element Q3 will be in the open state. If the switching element Q3 is open, the switching element Q4 is closed and the bypass path is turned on.

When the input voltage V_in reaches the bypass switching voltage, the light emitting element 31A is also lit, so the number of light emitting elements 31 to be lit is switched from two to three. After that, the input voltage V_in once rises to the rated voltage. The rated voltage is 13.5V, for example. When the input voltage V_in rises to the rated voltage, no current flows through the capacitor C4. Therefore, since the switching element Q16 is closed, the switching element Q17 is open. If the switching element Q17 is in the open state, the switching element Q5 is in the closed state, which is the same as the light emitting element 31A is always in the open state as described above. Therefore, the bypass path is turned off by the bypass stop circuit 22, and the light emitting element 31A is not switched. In other words, once the input voltage V_in stabilizes, the bypass path formed by the bypass circuit 21 is turned off. Therefore, even if the input voltage V_in of the in-vehicle battery 1, the lighting switch 2, the control unit 3, or the ECU 4 or the wire harness connecting them drops to the bypass switching voltage due to some condition, the light emitting element 31A is not bypassed, and flickering is not caused. Causative actions can be prevented.

As described above, in the present embodiment, when the input voltage V_in transitions from the transient state to the stable state, the bypass path is controlled from the ON state to the OFF state. Therefore, even if the input voltage V_in drops to the bypass switching voltage under some conditions, the input current I_in flowing through the light emitting element 31 is not bypassed. Therefore, flickering of the light emitting element 31 can be prevented.

Further, in this embodiment, when the light emitting element 31 connected in parallel with the bypass circuit 21 is detected to be in an open state, the bypass path is controlled to be in an off state. Therefore, when the light emitting element 31 has an open failure, the bypass circuit 21 stops. Therefore, when the light-emitting element 31 has an open failure, the input current I_in reliably falls below the failure threshold, so failure detection can be reliably activated.

Further, in this embodiment, when the input voltage V_in transitions from the transient state to the stable state, the detection result of the open detection circuit 23 is set to the open state. Therefore, even if the input voltage V_in drops to the bypass switching voltage under some conditions after the input voltage V_in is stabilized and the bypass path is turned off, the detection result of the open detection circuit 23 is set to the open state. Therefore, the bypass path is controlled to be off. Therefore, the flickering of the light emitting element 31 can be prevented particularly remarkably.

As described above, the vehicle lamp to which the present disclosure is applied has been described based on the embodiment, but the present disclosure is not limited to this, and modifications may be made without departing from the gist of the present disclosure.

For example, although the open detection circuit 23 has been described as an example of a circuit configuration in which a transistor functions as a bypass switch, it is not particularly limited to this. For example, the open detection circuit 23 may have a circuit configuration in which a MOS-FET functions as a bypass switch.

Also, for example, an example in which a vehicle lamp is incorporated as a headlamp has been described, but the present invention is not particularly limited to this. For example, a vehicle lamp may be incorporated as a taillight.

Also, for example, although an example in which the light-emitting element 31 is an LED has been described, the present invention is not particularly limited to this. For example, the light emitting element 31 may be composed of a semiconductor laser. In this case, the headlamp unit is provided with, for example, a blue laser diode and a yellow phosphor in order to form a pseudo-white color, and the blue light and the yellow light are condensed by a convex lens and condensed. The light should be diffused by a concave lens and emitted.

Further, for example, an example in which three light emitting elements 31 are connected in series and the bypass circuit 21 is connected in parallel to the light emitting element 31A of the three light emitting elements 31 has been described, but the present invention is particularly limited to this. not a thing For example, four or more light emitting elements 31 may be connected in series, and the bypass circuit 21 may be connected in parallel to two of the four or more light emitting elements 31 . In other words, the bypass circuit 21 may be connected in parallel to at least some of the plurality of light emitting elements 31 .

1 vehicle battery 2 lighting switch 3 control section 4 ECU
11 power supply unit 11a-11d terminal 21 bypass circuit 22 bypass stop circuit 23 open detection circuit 24 current control circuit 25 flicker prevention circuit 31, 31A-31C light emitting element I_in input current V_in input voltage Vf forward voltage Vz zener voltage D1 diode TVS1 transient Voltage suppression diode ZD1 Zener diode Q1~Q6, Q16, Q17 Switching element C1~C4 Capacitor R1~R12 Resistor

Claims (2)

a plurality of light emitting elements connected in series;
a power supply unit that supplies an input current to the plurality of light emitting elements;
a bypass circuit connected in parallel to at least some of the plurality of light emitting elements and forming a bypass path for the input current;
a flicker prevention circuit that controls the bypass path formed by the bypass circuit according to the input voltage applied by the power supply;
with
The flicker prevention circuit is
controlling the bypass path from an ON state to an OFF state when the input voltage transitions from a transient state to a stable state;
an open detection circuit for detecting whether or not a light emitting element connected in parallel with the bypass circuit among the plurality of light emitting elements is in an open state;
a bypass stop circuit that controls the bypass path to an off state when the open state is detected by the open detection circuit;
further comprising
Vehicle lighting. The flicker prevention circuit is
setting the detection result of the open detection circuit to the open state when the input voltage transitions from a transient state to a stable state;
The vehicle lamp according to claim 1 .

Images