JP2012028184A - Led lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an LED lighting device capable of, as to lighting of LEDs in which the plural LEDs of a lighting fixture performing arbitrary emission of light by providing a short circuit and an open circuit between terminals of a part of the LEDs are connected in series to light them, suppressing over current to the LEDs which are lit on which arises in providing the short circuit between the terminals of the part of LEDs and reducing deterioration of the LEDs, and capable of preventing the LEDs which are lit on from being turned out by reducing decrease of current in providing the open circuit.SOLUTION: In the lighting device, an operation of switching which switches switching elements Q1 and Q2 providing a short circuit between terminals of LEDs from an open circuit to the short circuit and an operation of switching them from the short circuit to the open circuit are performed slower than a response operation of output power by a DC/DC converter 3.

Description

  The present invention relates to an LED lighting device for lighting an LED (light emitting diode) used as a light source such as an in-vehicle headlamp, a position lamp, and a tail lamp.

Instead of conventional tungsten light bulbs, LEDs (light emitting diodes) that have a long life and do not require maintenance are widely used as in-vehicle light sources. The LED has a long life and can secure the necessary brightness with a small amount of power, and can emit a stable brightness by a simple control for supplying a constant current, which is suitable as an in-vehicle light source. is there.
When a plurality of LEDs are connected to form an in-vehicle light source, it is a conventional means to provide a lighting device for lighting LEDs for each LED.
However, in vehicle equipment, it is desired to reduce the number of mounted devices as much as possible. For this reason, when using a light source for in-vehicle use in which a plurality of LEDs are connected in series, a lighting device is not provided for each LED, and the terminals of the LEDs that do not need to be turned on are short-circuited and turned off. There has been proposed a configuration in which power is supplied and lighted without short-circuiting between terminals of LEDs.

  For example, in Patent Document 1, when a part of a plurality of LEDs connected in series is short-circuited and turned off, the part of the LEDs is short-circuited and the output voltage of the lighting device decreases. Discloses a technique for preventing the electric charge stored in the smoothing capacitor of the DC / DC converter from flowing out without being restricted and being energized as an excessive current to the remaining LEDs. ing. In this device, an integrator is incorporated in a circuit that short-circuits the LED, and the voltage applied to the LED by the integrator is lowered with a slope in a slightly decreasing direction to reduce the energization current. Thereby, damage to the LED due to an excessive energization current is avoided, and the occurrence of a malfunction in which the protection circuit erroneously determines the excessive energization current as an overcurrent due to a short circuit of the LED can be suppressed.

JP 2008-126958 A

In a conventional device represented by Patent Document 1, a smoothing capacitor of a DC / DC converter is used at a timing when a part of a plurality of LEDs connected in series is short-circuited and extinguished and then the short-circuit of the LED is opened. It is not considered whether or not a sufficient charge is accumulated.
That is, when a short circuit of a part of a plurality of LEDs connected in series is short-circuited and the remaining LEDs are lit, the voltage of the smoothing capacitor of the DC / DC converter is released. So that the output current of the DC / DC converter flows into the smoothing capacitor. At this time, no current is output to the LED until the voltage of the smoothing capacitor reaches the forward voltage of the LED connected to the smoothing capacitor. That is, the LED is turned off until a sufficient charge is accumulated in the smoothing capacitor. Such turning off of the LED manifests as flickering, and there is a problem that the quality of the light for the lamp is lowered.

  The present invention has been made in order to solve the above-described problems, and an excessive current to the LED generated when the terminals of the LED of the LED light source in which a plurality of LEDs are connected in series is short-circuited and opened. It aims at obtaining the LED lighting device which can prevent electricity supply or LED extinction.

  The LED lighting device according to the present invention includes an LED light source composed of a plurality of LEDs connected in series, and among the plurality of LEDs of the LED light source, the terminals of the LEDs that do not need to be lighted are short-circuited to turn off, and the remaining In an LED lighting device that lights an LED of a lamp that emits light arbitrarily by turning on the LED, a short circuit is established between the power supply unit that receives power and supplies a predetermined power for LED lighting to the LED light source and the LED terminal. And an operation for switching from opening to short-circuiting between the terminals of the LED by the switching element and an operation for switching from short-circuiting to opening are made slower than the response operation of the output power by the power supply unit.

  According to the present invention, the operation of switching from open to short circuit between the terminals of the LED by the switching element and the operation of switching from short circuit to open are slower than the response operation of the output power by the power supply unit, so a plurality of LEDs are connected in series. Thus, there is an effect that it is possible to prevent excessive current from flowing to the LED or turning off the LED which is generated when the LED terminals of the LED light source are short-circuited and opened.

It is a circuit diagram which shows the structure of the LED lighting device by Embodiment 1 of this invention. It is a figure explaining the behavior (there is no delay circuit) of the switching element which short-circuits an LED block. It is a figure explaining the behavior (with a delay circuit) of the switching element which short-circuits an LED block. FIG. 6 is a circuit diagram illustrating another configuration (No. 1) of the LED lighting device according to the first embodiment. It is a circuit diagram which shows the other structure (the 2) of the LED lighting device by Embodiment 1. FIG. 6 is a circuit diagram illustrating another configuration (No. 3) of the LED lighting device according to the first embodiment. FIG. 10 is a diagram for explaining the operation of the LED lighting device according to the second embodiment.

Embodiment 1 FIG.
The DC / DC converter with a constant current output used in the LED lighting device uses a smoothing capacitor that stabilizes the voltage. Therefore, if the output voltage decreases by short-circuiting some of the LEDs connected in series, the smoothing The capacitor charge flows out to the LED side. In this case, the control circuit of the LED lighting device feeds back the discharge current of the smoothing capacitor, reduces the output current of the DC / DC converter, and operates the switching element so that the output current becomes constant.
However, when the current flowing out from the smoothing capacitor exceeds the original output current value, even if the output current of the DC / DC converter is stopped, excessive current flows out to the LED side. In other words, if a part of a plurality of LEDs connected in series is short-circuited and turned off, the remaining LEDs that are lit are energized with an excessive amount of charge stored in the smoothing capacitor. Become. Such an excessive energizing current causes problems such as breakage of the LED. In addition, the protection circuit may erroneously determine that an excessive current energized on the LED side is an overcurrent generated by a short circuit of the LED and malfunction. In this case, in order to prevent malfunction, it is necessary to set a large preset current for the protection circuit in consideration of an excessive current value.

In the conventional LED lighting device represented by Patent Document 1, in order to eliminate the above-described problems, an integrator is incorporated in a circuit that short-circuits the LEDs, and when a part of a plurality of LEDs connected in series is short-circuited, By the integrator, the voltage applied to the remaining LEDs that are lit is lowered from the specified value with a gradient in a slightly decreasing direction. As a result, the current supplied to the remaining LEDs is reduced, the LED damage due to the excessive current supply is avoided, and a malfunction that erroneously determines the excessive current supply as an overcurrent due to a short circuit of the LED is also caused. Suppressed.
As described above, in the conventional LED lighting device represented by Patent Document 1, when a part of a plurality of LEDs connected in series is short-circuited, excessive current is not supplied to the remaining LEDs. Only to be considered. For this reason, in the said LED lighting device, the following malfunctions generate | occur | produce by the difference in the time constant of the charge side of the smoothing capacitor of a DC / DC converter, and the discharge side.

For example, in Patent Document 1, a short circuit for short-circuiting a part of a plurality of LEDs connected in series includes a first resistor having one end connected to an input terminal and a capacitor having one end connected to the other end of the first resistor. And a second resistor connected in parallel with the capacitor, the other end of the capacitor is grounded, the end of the capacitor and the second resistor not grounded, and the first resistor The other end of the LED is connected to the gate of a switching element in which some of the plurality of LEDs connected in series are connected between the source and drain terminals (see FIG. 1 of Patent Document 1).
In the short circuit, the time constant for charging the capacitor is faster on the discharge side in which the first resistor and the second resistor are connected in parallel than on the charge side of the first resistor.

Another short circuit described in Patent Document 1 includes an NPN transistor connected between an input terminal and a base terminal, a capacitor connected between the emitter and collector of the NPN transistor, and a first connected in parallel with the capacitor. A second resistor and a first resistor connected to one end of the second resistor connected to the collector terminal of the NPN transistor, and an end of the capacitor and the second resistor connected to the emitter terminal of the NPN transistor. The first and second resistors are connected to the gate of the switching element in which a part of the plurality of LEDs connected in series is connected between the source and drain terminals. The other end of the resistor is connected to the source terminal (see FIG. 3 of Patent Document 1).
Even in the short circuit, an NPN transistor is used for discharging while using the first resistor for charging, and the time constant on the discharging side is faster than that on the charging side.

  Since the short circuit described in Patent Document 1 is configured as described above, a part of a plurality of LEDs connected in series is short-circuited, and a switching element is turned on from the state where the remaining LEDs are lit. When the shorted LED is turned off and the short-circuited LED is opened, the voltage applied to the LEDs (the total number of LEDs connected in series) is the forward voltage at which current flows (the forward voltage of the LEDs connected in series). In addition, the output current of the DC / DC converter all flows into the smoothing capacitor so as to increase the voltage of the smoothing capacitor. Thereafter, no current is output to the LED until the voltage of the smoothing capacitor reaches the forward voltage of the LED connected to the smoothing capacitor. That is, the LED is turned off until a sufficient charge is accumulated in the smoothing capacitor.

  According to the present invention, when switching a part of a plurality of LEDs connected in series from a short circuit to an open circuit, the switching element is operated slowly, that is, the equivalent resistance of a path for short-circuiting a part of the LED is slowly increased. Thus, the voltage applied to the LED is brought into an open state with a slope in a slightly increasing direction from the specified value. Thus, when a part of the plurality of LEDs connected in series is released from the short-circuit state, the problem that all the LEDs are extinguished until a sufficient charge is accumulated in the smoothing capacitor is solved.

  1 is a circuit diagram showing a configuration of an LED lighting device according to Embodiment 1 of the present invention. In FIG. 1, an LED lighting device 1 is a device that lights an LED light source 4 using a DC voltage of a DC power supply 2 in accordance with an instruction from a lighting LED instruction device 10, and includes a DC / DC converter 3 and a control power supply unit 5. , A control unit 6, a delay circuit 7, a constant current circuit 8, and an input I / F 9. The DC power supply 2 is a power supply that supplies a DC voltage to the DC / DC converter 3, and the DC voltage to the DC / DC converter 3 is supplied or cut off by the power switch 2a.

  The DC / DC converter (power supply unit) 3 includes a transformer 3a, a switching element Qa composed of a MOS field effect transistor, a rectifying diode D0, and a smoothing capacitor C0. In the DC / DC converter 3, the switching element Qa is subjected to switching control with an output signal from the control unit 6, the magnetic energy is stored in the transformer 3 a, and this is discharged, so that the voltage generated in the transformer 3 a is rectified. Rectification is performed by the diode D0, and smoothing is performed by the smoothing capacitor C0 to generate a DC voltage. The smoothing capacitor C0 of the DC / DC converter 3 is connected to the LED block 4a of the LED light source 4 via the resistor R0, and the end on the rectifying diode D0 side is connected to the LED block 4b of the LED light source 4.

  The LED light source 4 is configured by connecting LEDs 4a-1 to 4a-n and 4b-1 to 4b-m in series. In addition, this Embodiment 1 has shown the case where the LED light source 4 is applied to a vehicle-mounted headlamp, and it is an LED block 4a in which LEDs 4a-1 to 4a-n are connected in series. The LED block 4b in which the LEDs 4b-1 to 4b-m are connected in series constitutes a traveling light (high beam; hereinafter, appropriately described as the H side). The LED block 4a is short-circuited when the switching element Q1 is turned on, and is opened when the switching element Q1 is turned off. Further, the LED block 4b is short-circuited when the switching element Q2 is turned on, and is opened when the switching element Q2 is turned off. As the switching elements Q1 and Q2, various transistors such as IGBT (Insulated Gate Bipolar Transistor) can be used in addition to the field effect transistor (FET) shown in FIG.

  The control power supply unit 5 supplies control power to the control unit 6. The control unit 6 supplies a predetermined value of current to obtain the light emission amount necessary for the light source for the headlamp to the LED light source 4, so that the output current to the LED light source 4 detected by the resistor R0 is constant. A PWM control output is supplied to the switching element Qa of the DC / DC converter 3. Moreover, the control part 6 inputs the output voltage output to the LED light source 4, and performs failure detection of LED, for example from the change of output voltage. Further, the control unit 6 outputs an L-side short-circuit output or an H-side short-circuit output based on a control signal input from the lighting LED instruction device 10 via the input I / F 9, and the LED block in the LED light source 4. 4a or LED block 4b is short-circuited and turned off.

The delay circuit 7 slows changes in the voltage applied to the base terminals of the transistors Q3 and Q4 of the constant current circuit 8 connected to the switching element Q1 that short-circuits the LED block 4a and the switching element Q2 that short-circuits the LED block 4b. Thus, the gate voltage of the switching elements Q1, Q2 is slowly increased or decreased.
As the configuration, one end is connected to the terminal of the L side short-circuit output of the control unit 6, the other end of the resistor Ra and the base terminal of the transistor Q 3 of the constant current circuit 8, and the other end is grounded. One end is connected to the terminal of the L side delay part which has the capacitor C1, and the H side short circuit output of the control part 6, the other end of the resistor Rb, and the transistor Q4 of the constant current circuit 8 is one end. An H-side delay unit having a capacitor C2 connected and grounded at the other end is provided.

  For example, when a high-level voltage is output to the L-side short-circuit output terminal of the control unit 6 in the L-side delay unit, the charge current a flows into the capacitor C1 via the resistor Ra and charges are accumulated, and the terminal voltage of the capacitor C1 Gradually rises. When the L-side short-circuit output terminal outputs a low level voltage, the electric charge accumulated in the capacitor C1 is discharged as a discharge current b through the resistor Ra, and the terminal voltage of the capacitor C1 gradually decreases. In the delay circuit 7, the time constants on the charging side and discharging side of the capacitors C1 and C2 are approximately the same.

The constant current circuit 8 is a circuit that causes a constant current to flow through the gate resistors R3 and R4 of the switching elements Q1 and Q2 that short-circuit the current flowing through the LED blocks 4a and 4b. As its configuration, the L-side delay portion of the delay circuit 7 is connected to the base terminal of the transistor Q3, and has a resistor R1 having one end connected to the emitter terminal and the other end connected to the power source.
Similarly, the L-side delay portion of the delay circuit 7 has a resistor R2 connected to the base terminal of the transistor Q4, one end connected to the emitter terminal, and the other end connected to the power source.

  For example, in the L side circuit portion, when the L side short-circuit output circuit becomes high level, the output of the L side delay portion of the delay circuit 7 rises slowly and slowly, and the slow voltage is applied to the base terminal of the transistor Q3. Thus, the emitter voltage of the transistor Q3 rises slowly corresponding to the voltage. As a result, the current flowing through the resistor R1 decreases slowly. A constant current generated by the emitter voltage and the resistor R1 is supplied to the gate resistor R3 of the switching element Q1, and the voltage generated at the gate resistor R3 slowly decreases. The voltage generated in the gate resistor R3 is applied to the switching element Q1, and the switching element Q1 slowly changes from on (short-circuiting of the LED terminal block 4a) to off (same open).

  The lighting LED instruction device 10 is a device that generates a lighting instruction signal that causes one of the LED blocks 4a and 4b to be short-circuited to be extinguished and lighted without short-circuiting the other. The input I / F 9 is an interface between the control unit 6 and the lighting LED instruction device 10, and outputs a lighting instruction signal to the control unit 6 via the input I / F 9.

Next, the operation will be described.
As described above, the LED lighting device 1 is provided with the delay circuit 7 including a resistor and a capacitor in the signal transmission circuit between the output of the control unit 6 that short-circuits the LED blocks 4a and 4b and the constant current circuit 8. When the LED blocks 4a and 4b are switched from short-circuit to open-circuit by slowing the change in voltage applied to the base terminals of the transistors Q3 and Q4 of the current circuit 8, the operation of the switching elements Q1 and Q2 is changed to the DC / DC converter 3 The response is slower.

  FIG. 2 is a diagram for explaining the behavior of the switching element that short-circuits the LED block and the output current. In FIG. 1, the delay circuit 7 is not provided in the signal transmission circuit between the control unit 6 and the constant current circuit 8. Shows the case. FIG. 2A shows the operation of the switching elements Q1 and Q2. Here, the operation of the switching elements Q1 and Q2 is a switching operation of turning on (short-circuiting both terminals of the LED block) and turning off (opening both terminals of the LED block) in the switching element. When there is no delay circuit, as shown in FIG. 2A, the operation time of the switching element is very short, and the LED block is short-circuited and opened instantaneously.

  FIG. 2B is a diagram illustrating an output voltage of the LED lighting device that does not include the delay circuit 7. When the switching element Q2 is turned on and the LED block 4b is short-circuited in FIG. 2A, the output voltage of the LED lighting device is only the forward voltage of the LED block 4a on the L side during the ON period of the switching element Q2. Become. When the switching element Q2 is turned off from on, the total forward voltage of the L-side LED block 4a and the H-side LED block 4b is output during this off period.

FIG. 2C shows the output current of the DC / DC converter and the charge / discharge current of the smoothing capacitor. When the LED block 4a is short-circuited and extinguished from the state in which both the LED blocks 4a and 4b are turned on, in response to this, the control unit 6 reduces the output current of the DC / DC converter 3 so that the output current becomes constant. The switching element Qa is operated.
However, the voltage applied to the series circuit of the LED blocks 4a and 4b so far from the difference between the time during which the switching element Q1 operates from OFF to ON and the response time of the output voltage control of the DC / DC converter 3 is It is applied only to the LED block 4b that is lit for a moment. The electric charge stored in the smoothing capacitor C0 by this overvoltage flows out to the LED block 4b as a discharge current.

On the other hand, when the LED block 4a is opened from the short-circuited state, in response to this, the control unit 6 operates the switching element Qa so that the output current of the DC / DC converter 3 becomes constant. Here, in the same manner as described above, only the forward voltage of the LED block 4b so far is derived from the difference between the time during which the switching element Q1 operates from on to off and the response time of the output voltage control of the DC / DC converter 3. A voltage is applied to the series circuit of the LED block 4a and the LED block 4b.
At this time, the DC / DC converter 3 supplies a charging current so as to increase the voltage of the smoothing capacitor C0, but until the voltage of the smoothing capacitor reaches the forward voltage of the series circuit of the LED blocks 4a and 4b. Current cannot be supplied to both LED blocks.

  FIG. 2D is a diagram showing the output current of the LED lighting device not provided with the delay circuit 7, and it is assumed that the indicated value of the output current is constant. As shown in FIG. 2D, when the LED block 4a is short-circuited and extinguished from the state in which both the LED blocks 4a and 4b are lit, the voltage applied to the series circuit of the LED blocks 4a and 4b is instantaneously The overvoltage is applied to the LED block 4b. Due to this overvoltage, the LED block 4b is energized as an excessive discharge current from the smoothing capacitor C0.

  When the LED block 4a is opened from the shorted state, the output current of the DC / DC converter 3 flows into the smoothing capacitor C0 as shown in FIG. 2 (d). For this reason, current is not output to the LED blocks 4a and 4b until the voltage of the smoothing capacitor C0 reaches the total voltage of the forward voltages of the LED block 4a and the LED block 4b. That is, the LED blocks 4a and 4b are turned off simultaneously until a sufficient charge is accumulated in the smoothing capacitor C0.

  FIG. 3 is a diagram for explaining the behavior of the switching element that short-circuits the LED block and the output current, and shows the case of the configuration of FIG. 1 in which the delay circuit 7 is provided between the control unit 6 and the constant current circuit 8. Yes. FIG. 3A shows the operation of the switching elements Q1 and Q2. When the delay circuit 7 slows down the change in the voltage applied to the base terminals of the transistors Q3 and Q4 of the constant current circuit 8, the switching elements Q1 and Q2 are turned on / off accordingly, as shown in FIG. Operation is slow.

  FIG. 3B is a diagram showing an output voltage of the LED lighting device 1 provided with the delay circuit 7. When the on / off switching operation of the switching elements Q1 and Q2 becomes slow, as shown in FIG. 3B, the LED lighting device when any of the LED blocks 4a and 4b is short-circuited from the open state or opened from the short-circuit state. 1 changes gradually.

  FIG. 3C shows the output current of the DC / DC converter and the charge / discharge current of the smoothing capacitor. For example, when both of the LED blocks 4a and 4b are turned on and the LED block 4a is short-circuited and turned off, the delay circuit 7 gradually increases the gate voltage of the switching element Q1 so that the equivalent between the both ends of the LED block 4a is obtained. By gradually decreasing the resistance, the LED block 4a is short-circuited over time while limiting the discharge current flowing out of the smoothing capacitor C0.

  Even when the LED block 4a is opened from a short circuit, the delay circuit 7 gradually decreases the gate voltage of the switching element Q1 to gradually increase the equivalent resistance between both ends of the LED block 4a, thereby smoothing the LED block 4a. The LED block 4a is opened from the short circuit over time while limiting the charging current flowing into the capacitor C0.

FIG. 3D is a diagram showing the output current of the LED lighting device 1 provided with the delay circuit 7, and the indicated value of the output current is assumed to be constant. As shown in FIG. 3 (d), the LED circuit 4b is gradually short-circuited from the state in which both of the LED blocks 4a and 4b are turned on by the delay circuit 7, so that the LED block 4b is energized. Without constant, a constant current is passed through the LED block 4b.
Further, the delay circuit 7 extends the time for switching the LED block 4a from short circuit (switching element Q1 is on) to open (switching element Q1 is off), and limits the charging current to the smoothing capacitor C0. A constant current is applied to the blocks 4a and 4b without interruption of the current.

  As described above, by slowing down the operation of the switching elements Q1 and Q2 by the delay circuit 7, it is possible to prevent the LED block from being turned off when the short circuit of the LED block 4a or the LED block 4b is opened.

In addition, although the LED lighting device 1 provided with the delay circuit 7 and the constant current circuit 8 was demonstrated so far, the following structures may be sufficient, for example.
FIG. 4 is a circuit diagram showing another configuration of the LED lighting device according to the first embodiment. In FIG. 4, the LED lighting device 1 </ b> A includes a delay circuit 7 </ b> A using a constant current circuit between the control unit 6 and the switching elements Q <b> 1 and Q <b> 2 instead of the delay circuit 7 and the constant current circuit 8 shown in FIG. 1. Prepare. The delay circuit 7A includes an L-side delay unit having a transistor Q3 and a capacitor C3, and an H-side delay unit having a transistor Q4 and a capacitor C4.

  The transistor Q3 has a base terminal connected to the L-side short-circuit output terminal of the control unit 6 via a resistor Ra, an emitter terminal connected to a power source via a resistor R1, and a collector terminal connected to the gate terminal of the switching element Q1 and a capacitor C3. The capacitor C3 and the gate resistor R3 are connected in parallel between the gate terminal and the source terminal of the switching element Q1.

  Similarly, the transistor Q4 has a base terminal connected to the H-side short-circuit output terminal of the control unit 6 via a resistor Rb, an emitter terminal connected to a power source via a resistor R2, and a collector terminal connected to the gate terminal of the switching element Q2. And the capacitor C4 and the gate resistor R4, and the resistor R4 and the capacitor C4 are connected in parallel between the gate and source terminals of the switching element Q2. In the delay circuit 7A, the time constants on the circuit side for charging the capacitors C3 and C4 and the circuit side for discharging can be arbitrarily set, and can be set to the same level.

  For example, in the H side delay unit, when a high level voltage is output to the H side short circuit output terminal of the control unit 6, the base voltage of the transistor Q4 becomes high level via the resistor Rb, and the emitter voltage of the transistor Q4 becomes high level. It becomes. As a result, the predetermined current a flowing through the resistor R2 is interrupted, the electric charge of the capacitor C4 is gradually discharged (current b) by R4, and the voltage between the gate and source terminals of the switching element Q2 gradually decreases, and the switching element Turn off Q2 slowly.

  On the other hand, when the switching element Q2 is turned on, when a low level voltage is output to the H side short-circuit output terminal of the control unit 6 and the transistor Q4 is turned on, a predetermined current a is supplied to the gate resistor R4 and the capacitor C4 is charged. Are gradually stored, the gate-source terminal voltage of the switching element Q2 gradually increases, and the switching element Q2 is slowly turned on.

  FIG. 5 is a circuit diagram showing another configuration of the LED lighting device according to the first embodiment. In FIG. 5, an LED lighting device 1B uses switching elements Q1 and Q2 as constituent elements instead of the delay circuit 7 and the constant current circuit 8 shown in FIG. 1, and a capacitor C5 and a capacitor C6 as capacitors for negative feedback operation. As a delay circuit 7B.

  The transistor Q3 has a base terminal connected to the L-side short-circuit output terminal of the control unit 6 via a resistor Ra, a power source and an emitter terminal connected via a resistor R1, and a collector terminal connected to the gate terminal of the switching element Q1. . Capacitor C5 has one end connected to the gate terminal of switching element Q1, and the other end connected to the drain terminal of switching element Q1. That is, the capacitor C5 is provided between the gate and drain terminals of the switching element Q1. The resistor R3 is connected between the gate and source terminals of the switching element Q1.

  Similarly, the transistor Q4 has a base terminal connected to the H side short-circuit output terminal of the control unit 6 via a resistor Rb, a power source and an emitter terminal connected via a resistor R2, and a collector terminal connected to the gate terminal of the switching element Q2. Connect to. Capacitor C6 is provided between the gate and drain terminals of switching element Q2, and resistor R4 is connected between the gate and source terminals of switching element Q2. In the delay circuit 7B, the time constants on the circuit side for charging the capacitors C5 and C6 and the circuit side for discharging can be arbitrarily set, and can be set to the same level.

As described above, the delay circuit 7B shown in FIG. 5 forms an integration circuit that performs a negative feedback operation that feeds back the drain voltage to the gate terminal of the switching element via the capacitor, and slowly increases the gate voltage of the switching element. Lower.
For example, in the H side delay unit, when a high level voltage is output to the H side short-circuit output terminal of the control unit 6, the base voltage of the transistor Q4 becomes high level via the resistor Rb, and the transistor Q4 is turned off. As a result, the predetermined current a flowing through the resistor R2 is interrupted, and the switching element Q2 is turned off by lowering the gate voltage. At this time, the capacitor 6 between the gate and drain terminals of the switching element Q2 in the on state until just before is first discharged by the resistor R4 by the resistor R4, with the charges accumulated at the terminal voltages on the high potential gate side and the low potential drain side, Next, the battery is charged in the reverse direction (current b), but in the charging process in the reverse direction to the discharge of the capacitor 6, the gate terminal voltage rises due to the drain terminal voltage rising when the switching element Q2 is turned off. Therefore, the voltage at the gate terminal gradually decreases without suddenly dropping, and the switching element Q2 is slowly turned off.
Note that when a low level voltage is output to the H side short-circuit output terminal of the control unit 6 and the transistor Q4 is turned on, a predetermined current a flows to raise the gate voltage and turn on the switching element Q2. At this time, the capacitor 6 between the gate and drain terminals of the switching element Q2 in the OFF state until just before discharges the charges accumulated at the terminal voltages on the low potential gate side and the high potential drain side first, and then in the reverse direction. In the charging process in the opposite direction to the discharge of the capacitor 6, the negative voltage is caused by the gate terminal voltage being lowered due to the drain terminal voltage being lowered when the switching element Q2 is turned on. Since the feedback operation works, the voltage at the gate terminal gradually increases without rapidly increasing, and the switching element Q2 is slowly turned on.

1, 4, and 5 described above, the lighting voltage of the LED light source 4 output from the DC / DC converter 3 is a negative voltage, and the switching elements Q <b> 1 and 1 that short-circuit the LED blocks 4 a and 4 b, respectively. Q2 is driven through a level shift circuit using a constant current circuit composed of resistors R1 and R2 and transistors Q3 and Q4. As described above, a constant current circuit using a resistor and a transistor is provided on the high voltage (plus voltage) side, and a predetermined current output from the constant current circuit is provided on the low voltage (minus voltage) side. , R4 is energized to generate a constant voltage drop and apply the voltage generated in the resistor to the gate terminals of the switching elements Q1, Q2. By doing in this way, the switching element which short-circuits LED with a simple circuit structure can be driven.
In general, the configuration of a circuit that transmits an operation signal to the switching element arranged at a negative potential from the control unit of the positive potential or the configuration of a circuit that transmits a signal between circuits having different potentials is level. This is called a shift circuit.

Moreover, you may comprise so that the switching element which short-circuits between the terminals of LED may be driven via a bootstrap circuit by making the voltage for LED lighting output from the DC / DC converter 3 into a plus voltage.
FIG. 6 is a circuit diagram showing another configuration of the LED lighting device according to the first embodiment. In FIG. 6, the LED lighting device 1 </ b> C uses the LED lighting voltage output from the DC / DC converter 3 as a positive voltage, and instead of the delay circuit 7 and the constant current circuit 8 of FIG. 1, the control unit 6 and the switching element Q <b> 1. , Q2 are provided with a delay circuit 7C and a bootstrap circuit 11.

  The delay circuit 7C includes an L side delay unit and an H side delay unit. The L-side delay unit includes a resistor Ra having one end connected to the L-side short-circuit output terminal of the control unit 6, a capacitor C8 having one end connected to the other end of the resistor Ra and the base terminal of the transistor Q3, and the other end grounded. The H-side delay unit has a resistor Rb having one end connected to the H-side short-circuit output terminal of the control unit 6, one end connected to the other end of the resistor Rb and the base terminal of the transistor Q4, and the other end grounded. And a capacitor C9.

  The bootstrap circuit 11 includes a diode D2, a capacitor C7, resistors R7 and R8, and a transistor Q3. The diode D2 has an anode terminal connected to the power supply and a cathode terminal connected to the capacitor C7 and the resistor R7. Capacitor C7 has one end connected to the drain terminal of switching element Q2, and the other end connected to the connection point of diode D2 and resistor R7. The resistor R7 has one end connected to the connection point between the diode D2 and the capacitor C7, and the other end connected to the collector terminal of the transistor Q3 and the gate terminal of the switching element Q1. Further, a Zener diode Z1 having an anode terminal connected to the source terminal is provided between the gate and source terminals of the switching element Q1.

For example, in the L-side short-circuit portion, when a high level voltage is output to the L-side short-circuit output terminal of the control unit 6, charges are accumulated in the capacitor C8 via the resistor Ra, and the base terminal voltage of the transistor Q3 gradually increases. . As a result, the emitter terminal voltage of the transistor Q3 gradually increases, and the current flowing through the resistor R8 gradually increases. The current flowing from the power supply gradually increases via the diode D2 and the resistor R7, and the voltage drop of the resistor R7 gradually increases. When the voltage drop of the resistor R7 is gradually increased, the gate voltage of the switching element Q1 is gradually decreased, so that the switching element is gradually turned off.
When the switching element Q1 is turned off, the voltage at the source terminal is lowered, and a current flows from the power source through the diode D2 to the capacitor C7 to be charged.
When a low level voltage is output to the L-side short-circuit output terminal of the control unit 6, the charge of the capacitor C8 is discharged through the resistor Ra, and the base terminal voltage of the transistor Q3 gradually decreases to a low level. As a result, the emitter terminal voltage of the transistor Q3 gradually decreases, and the current flowing through the resistor R8 gradually decreases. The current flowing from the power supply through the diode D2 and the resistor R7 gradually decreases, and the voltage drop of the resistor R7 gradually decreases. When the voltage drop of the resistor R7 gradually decreases, the gate voltage of the switching element Q1 gradually increases, so that the switching element is gradually turned on.
When the switching element Q1 is turned on, the voltage at the source terminal rises. However, electric charge is stored in the capacitor C7, and the potential on the diode D2 side of the resistor R7 is applied to the source terminal of the switching element Q1 by the charging voltage of the capacitor C7. On the other hand, the voltage can be kept high, and the switching element Q1 can be kept on.

In addition, as an in-vehicle lamp configured by combining a plurality of lamps to which the LED lighting devices 1 and 1A to 1C according to the first embodiment are applied, the following may be mentioned. Each of these lamps can use a plurality of LEDs connected in series as a light source.
(1) Head lamp A traveling light (high beam), a passing light (low beam), and a fog lamp (fog lamp).
(2) A vehicle width lamp (position lamp) and a direction indicator lamp (blinker).
(3) Tail lamp Stop lamp (stop lamp), reverse lamp (backup lamp), rear fog lamp (rear fog lamp).
In the present invention, when the shorted LED is opened to turn on the LED that has been turned off, the LED to be turned on, including the LED that has been turned on at that time, does not turn off, ensuring the quality as a light source. can do.

  As described above, according to the first embodiment, the switching operation between the terminals of the LEDs by the switching elements Q1 and Q2 and the switching operation from the short circuit to the open circuit are performed by the DC / DC converter 3. Since it is slower than the response operation of electric power, it is possible to prevent excessive current from being applied to the LED or turning off the LED that occurs when the terminals of the LED of the LED light source 4 are short-circuited and opened. In addition, with the configuration shown in FIGS. 1, 4, 5, and 6, a delay circuit can be realized with a simple circuit configuration, and the quality as a light source can be ensured.

Embodiment 2. FIG.
In the second embodiment, the operations of switching from opening to shorting and switching from shorting to opening between the terminals of the LEDs by the switching elements Q1 and Q2 and switching from the shorting to the opening are performed by the DC / DC converter 3. Change the view of "slower than the response operation of the LED", and change the response operation of the output power by the DC / DC converter 3 from switching between the open terminals of the LEDs by the switching elements Q1, Q2 to short circuit and from short circuit to open circuit It is possible to obtain an equivalent effect by making each operation of the switching operation more agile, and before driving the switching element that short-circuits between the LED terminals of the lamp, the controller controls the output power of the DC / DC converter. Thus, a configuration in which the operation of the power supply unit is agile with respect to the operation of the switching element that short-circuits the LED terminals of the lamp is described
The LED lighting device of the second embodiment has a circuit configuration in which the delay function is eliminated by removing the capacitors C1 and C2 in the configuration described with reference to FIG. 1 in the first embodiment. The L-side short-circuit output terminal and the base terminal of the transistor Q3 are connected via a resistor Ra, and the H-side short-circuit output terminal of the control unit 6 and the base terminal of the transistor Q4 are connected via a resistor Rb. If the capacitors C3 and C4 in FIG. 4, the capacitors C5 and C6 in FIG. 5, and the capacitors C8 and C9 in FIG. 6 are deleted, the configuration is the same as the above configuration. Therefore, the following description of the configuration of the LED lighting device of the second embodiment will typically refer to FIG.

Next, the operation will be described.
FIG. 7 is a diagram for explaining the operation of the LED lighting device according to the second embodiment of the present invention. FIG. 7 (a) shows the indicated value of the output current generated by the control unit 6, and FIG. (B) shows the operation of the switching element, FIG. 7 (c) shows the output voltage of the LED lighting device, and FIG. 7 (d) shows the charge / discharge current of the smoothing capacitor and the DC / DC. The output current of the converter is shown, and FIG. 7 (e) shows the output current of the LED lighting device.

(A) When switching the switching element from OFF to ON As shown in FIG. 7A, the control unit 6 instructs in advance to temporarily reduce the output current of the DC / DC converter 3 (temporarily output current). To reduce the output value of the DC / DC converter 3 to a small output. After this operation, the control unit 6 controls the short-circuit output, and switches the switching element that short-circuits between the terminals of the LED block from open (off) to short-circuit (on), as shown in FIG. At this time, the output voltage of the LED lighting device is as shown in FIG.

In this way, before the LED is short-circuited, the charge stored in the smoothing capacitor C0 of the DC / DC converter 3 is reduced in advance, and the LED as shown in FIGS. 7 (d) and 7 (e). The overcurrent flowing through the block can be reduced.
That is, the control unit 6 controls the DC / DC converter 3 so as to reduce the overcurrent flowing through the LED block, so that the smoothing capacitor C0 is included rather than the operation time of the switching element shown in FIG. The apparent response time of the DC / DC converter 3 is increased.

(B) When switching the switching element from ON to OFF As shown in FIG. 7A, the control unit 6 instructs in advance to temporarily increase the output current of the DC / DC converter 3 (temporarily output current). To increase the output value of the DC / DC converter 3 to a large output. After this operation, the control unit 6 controls the short-circuit output, and switches the switching element that short-circuits between the terminals of the LED blocks from short-circuit (ON) to open (OFF) as shown in FIG. 7B. At this time, the output voltage of the LED lighting device is as shown in FIG.

In this way, before the LED is short-circuited, the charge stored in the smoothing capacitor C0 of the DC / DC converter 3 is increased in advance, and the LED as shown in FIGS. 7 (d) and 7 (e). It is possible to reduce the interruption of the current flowing through the block.
That is, the control unit 6 controls the DC / DC converter 3 so as to reduce the LED block from being extinguished due to a shortage of current, so that the smoothing capacitor is longer than the operation time of the switching element shown in FIG. The apparent response time of the DC / DC converter 3 including C0 is shortened.

As described above, according to the second embodiment, the control unit 6 switches to the LED light source 4 by the DC / DC converter 3 in advance before switching from opening to short circuit between the terminals of the LEDs by the switching elements Q1 and Q2. The output current to the LED light source 4 by the DC / DC converter 3 is temporarily changed in advance before switching from short-circuiting between the terminals of the LEDs by the switching elements Q1 and Q2 to opening. Control to become larger.
In this way, by operating the output of the control unit 6 in advance before operating the switching elements Q1 and Q2, it is possible to reduce LED stress and suppress LED degradation without changing the circuit configuration. A lighting device that does not turn off can be configured.

  In the first and second embodiments, the control unit 6 controls the DC / DC converter 3 to intermittently supply the output current to the LED light source 4 in a comb shape, thereby reducing the LED light source 4. You may make it light. For example, a DRL (Daytime Running Lamp) power source is configured using a headlamp running light (high beam). Since it is necessary to make the DRL darker than the normal high beam emission, the energization current (average current) of the high beam LED is reduced by PWM control of the control unit 6 to reduce the brightness. Further, when a lamp that is used as both a tail lamp stop lamp and a vehicle width lamp is configured, the lamp can be lit brightly when the stop lamp is lit while being lit dark when traveling.

  It is possible to reduce the current supplied to the LED light source 4 in a DC manner. However, if the current supplied is reduced, the emission color changes, so that the quality of the light source of the headlamp and tail lamp is reduced. Become. For this reason, the LED light source 4 is turned on by a comb-like intermittent current having an off period with the energization current being the same as the current during steady lighting.

  In the above configuration, the comb-like intermittent current supplied to the LED light source 4 is generated by repeating the operation and stop of the DC / DC converter 3. For example, the operation of the DC / DC converter 3 is repeatedly turned on and off for 1 ms each (turns on at 500 Hz) to supply a comb-like current, and the LED light source 4 is turned on darker than the original brightness. By doing so, the DRL can be configured with a simple circuit configuration.

Further, in the first and second embodiments, the control unit 6 has a function of feeding back the output voltage of the LED lighting device and outputting a predetermined voltage, and the LED block 4a or 4b of the LED light source 4 is used for DRL. When lighting (dimming) darker than the original brightness, for example, when the LED block 4b is dimmed and turned on for DRL, the output voltage is higher than the forward voltage of the LED block 4b, and the LED block 4a It sets so that it may become lower than the total value of the forward voltage of LED block 4b, and the following operation | movement is repeated so that the electric current supplied to LED block 4b may become a comb-tooth-like intermittent current.
At the timing of lighting the LEDs in the intermittent current, the terminals of the LED blocks 4a that are not lit are short-circuited, and the control unit 6 controls the DC / DC converter 3 to supply a predetermined current to the LED blocks 4b. Lights up.
In addition, at the timing of turning off the LEDs in the intermittent current, the control unit 6 controls the DC / DC converter 3 to output the predetermined voltage and open the terminals of the LED blocks 4a that are not turned on. To turn off the LED.

  In addition, although the example which lights up the H side LED block 4b by energization of the comb-like intermittent electric current and lights up darker than original brightness was shown above, the structure which lights up the L side LED block 4a by the same method is also shown. I do not care.

  As described above, a part of the LED light source 4 is lit intermittently, so that when the output current flows, the terminals of the LEDs that are not lit are short-circuited, the DC / DC converter 3 is controlled at a constant current, and the output current is stopped. When this is done, the terminals of the LEDs that are not lit are opened, and the DC / DC converter 3 is controlled at a constant voltage. At this time, the output voltage set by the constant voltage control is lower than the total voltage of the forward voltages of all the LEDs constituting the LED light source 4 and higher than the total voltage of the forward voltages of the LEDs to be lit.

  At the timing when the control unit 6 opens (turns off) all the LED short-circuiting switching elements, the output voltage of the DC / DC converter 3 controlled by constant voltage is the forward direction of all the LEDs constituting the LED light source 4. Since the voltage is lower than the total voltage, no current flows through all the LEDs constituting the LED light source 4, so that the LED is turned off.

On the other hand, since the output voltage of the DC / DC converter 3 is higher than the forward voltage of the LED to be lit at the timing when a part of the LED light source is short-circuited and the remaining LEDs are lit, a current flows through the LED to be lit. The LED can be turned on. At this timing, the control unit 6 switches the DC / DC converter 3 from constant voltage control to constant current control and outputs a constant current to the LED.
In this manner, the DC / DC converter is operated and stopped simply by repeatedly turning it off and on, so that the current supplied to the LED rises and falls from the method in which the comb-like intermittent current is supplied to the LED. The falling edge becomes steep (close to an ideal rectangular wave), and a DRL with good emission characteristics can be configured.

Further, in the first and second embodiments, when a disconnection failure occurs in the LED that is short-circuited by the switching element and the wiring connected to the LED, the switching element may be short-circuited.
For example, when the headlamp running light (high beam) LED is disconnected, the low beam LED is turned on by turning off the switching element that short-circuits the high beam LED after turning on the low light (low beam). Will also go out at the same time.

At this time, the control unit 6 continues the low-beam lighting operation and maintains at least the low-beam lighting even if a high-beam lighting signal is input to the LED lighting device.
That is, in order not to turn off the remaining LEDs even if some of the plurality of LEDs connected in series are disconnected, the control unit 6 detects the energization current to the LED light source 4 and if the energization current stops, It is determined that a disconnection has occurred in a part of the circuit including the LED in the LED light source 4, and the short-circuiting (ON) of the switching element that short-circuits the disconnected part is continued.
By doing in this way, even if some of the plurality of LEDs connected in series are disconnected, the remaining LEDs can be turned on, and a safe headlamp that secures at least some brightness can be configured. .

  Further, in the first and second embodiments, when the current supplied to the LED is interrupted and then the LED is supplied again by the above determination, the power output operation of the DC / DC converter 3 is first stopped. Then, after the necessary switching elements are operated, the power output operation of the DC / DC converter 3 is performed.

For example, as described above, when the energizing current is interrupted when the switching element for short-circuiting the high-beam LED is opened (off), the DC / DC converter 3 becomes in an unloaded state and charges the smoothing capacitor C0. While increasing the output voltage.
In this state, when it is determined that a disconnection has occurred in the circuit including the high-beam LED, and the low-beam switching element is turned on to turn on the low-beam LED that has not been disconnected, smoothing is performed. Due to the charge stored in the capacitor C0, a larger overcurrent flows than in the normal on / off switching operation.

Therefore, when the LED for the low beam is turned on, first, the DC / DC converter 3 is temporarily stopped to reduce the charge accumulated in the smoothing capacitor C0, the output voltage is lowered, and then the high beam side switching is performed. The element is short-circuited (turned on), and then the DC / DC converter 3 is operated again to turn on the low beam LED.
By doing in this way, generation | occurrence | production of the overcurrent which flows into LED reliably can be suppressed. That is, when some of the plurality of LEDs connected in series are disconnected, even if the remaining LEDs are turned on, the stress applied to the remaining LEDs can be reduced, so that deterioration of the LEDs can be suppressed. .

  In addition, the series of operations after the energization current is interrupted is the operation when the energization is restored by further contact (disconnection is repaired) after separation (disconnection) occurs in a part of the wiring connecting the LEDs. Is also effective. The above-described operation can be easily realized by incorporating a CPU in the control unit 6.

  1, 1A, 1B, 1C LED lighting device, 2 DC power supply (power supply), 2a power switch, 3 DC / DC converter (power supply unit), 3a transformer, 4 LED light source, 4a, 4b LED block, 4a-1 to 4a -N, 4b-1 to 4b-m LED, 5 control power supply unit, 6 control unit, 7, 7A, 7B, 7C delay circuit, 8 constant current circuit, 9 input I / F, 10 lighting LED indicating device, 11 boot Strap circuit, C0 smoothing capacitor, C1-C9 capacitor, D0, D1 rectifying diode, D2 diode, Qa, Q1, Q2 switching element, Q3-Q4 transistor, Ra, Rb, R0-R8 resistor.

Claims (11)

In a LED lighting device that lights a plurality of LEDs connected in series as a light source, the LED provided in a lamp that emits light arbitrarily by short-circuiting between the terminals of some of the LEDs of the light source,
A power supply unit that receives power and supplies predetermined power for LED lighting to the LED;
A switching element for short-circuiting and opening between the terminals of the LED,
The LED lighting device characterized in that the operation of switching from open to short circuit between the terminals of the LED by the switching element and the operation of switching from short circuit to open are made slower than the response operation of the output power by the power supply unit.   The LED lighting device according to claim 1, further comprising a delay circuit that delays a signal for operating the switching element. A control unit for controlling the power supply operation by the power supply unit and the operation of short-circuiting and opening the terminals of the LED by the switching element;
The controller controls the output current to the LED to be temporarily reduced before the operation to switch from open to short circuit between the LED terminals by the switching element, and between the LED terminals by the switching element. 2. The LED lighting device according to claim 1, wherein the LED lighting device is controlled to temporarily increase an output current to the LED before an operation of switching from a short circuit to an open circuit. 3. The power supply unit is configured to supply a negative voltage to the LED as a voltage for lighting the LED, the switching element is disposed on the negative potential side,
A control unit for controlling the power supply operation by the power supply unit and the operation for short-circuiting and opening the terminals of the LEDs by the switching element; and a level shift circuit for operating the switching element from a positive potential to a negative potential of the control unit; The LED lighting device according to claim 1, further comprising: The power supply unit is configured to supply a positive voltage to the LED as a voltage for lighting the LED, the switching element is disposed on the positive potential side,
The control unit for controlling the power supply operation by the power supply unit and the operation for short-circuiting and opening the terminals of the LEDs by the switching element, and a bootstrap circuit for operating the switching element. The LED lighting device according to 1. A control unit for controlling the power supply operation by the power supply unit and the operation of short-circuiting and opening the terminals of the LED by the switching element;
2. The LED lighting device according to claim 1, wherein the control unit controls the power source unit to supply a comb-toothed intermittent current to the LED, thereby dimming the LED. 3.   The LED lighting device according to claim 6, wherein the comb-like intermittent current supplied to the LED is generated by repeatedly operating and stopping the power supply unit. The controller is
Provided with a function of outputting a predetermined voltage by feeding back an output voltage output to the LED,
When generating the comb-like intermittent current to be supplied to the LED, at the timing of lighting the LED while the current is intermittent, the terminals of the LEDs that are not lit are short-circuited by the switching element, and a predetermined current Output
At the timing of turning off the LED, the switching element is opened and a voltage lower than the total forward voltage of all the LEDs connected in series is higher than the total forward voltage of the LEDs to be lit. The LED lighting device according to claim 6, wherein the LED lighting device is output.   The LED lighting device according to claim 1, wherein the lamp using the LED as a light source is a headlamp in which an LED for a traveling lamp and an LED for a passing lamp are connected in series.   When the disconnection failure occurs in a part of the LED and a part of the wiring connected to the LED, the control unit short-circuits between the LED including the disconnection failure or the terminal including the disconnection failure wiring by the switching element. The LED lighting device according to claim 1, wherein:   When the disconnection failure occurs in the LED and its wiring and the disconnection failure part is short-circuited by the switching element, the control unit first stops the power supply by the power supply unit and then the terminal of the LED by the switching element. The LED lighting device according to claim 10, wherein the power supply unit is operated to supply power to the LED after short-circuiting between them.

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