JP2012133939A - Light-emitting diode lighting device, and luminaire using the light-emitting diode lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting diode lighting device which is less prone to abnormally generate heat, and a luminaire using the light-emitting diode lighting device.SOLUTION: A light-emitting diode lighting device 1 comprises: a lighting circuit 4 which includes a buck converter and decreases the voltage of an input DC power and inputs the resultant power to the light-emitting diode array 3; a fuse 5 inserted in a power-supply path to the lighting circuit 4, and is fused and cut when output terminals of the lighting circuit 4 are short-circuited at least in the condition that a switching element of the lighting circuit 4 is not turned off; and a protection circuit 6 which short-circuits the output terminals of the lighting circuit 4 when the output voltage of the lighting circuit 4 exceeds a prescribed short circuit threshold voltage. In response to the occurrence of a short circuit in the switching element of the lighting circuit 4, the protection circuit 6 short-circuits the output terminals of the lighting circuit 4, whereby the fuse 5 is fused and cut without fail and the power supply to the lighting circuit 4 is stopped. Therefore, the light-emitting diode lighting device is less prone to cause an abnormal heat generation in comparison to the case where the protection circuit 6 is not provided.

Description

  The present invention relates to a light emitting diode lighting device and a lighting device using the light emitting diode lighting device.

  Conventionally, a light-emitting diode lighting device for lighting a light-emitting diode has been provided (see, for example, Patent Document 1).

  This type of light emitting diode lighting device converts input DC power or AC power into DC power suitable for lighting of the light emitting diode and outputs the converted DC power.

  As this type of light-emitting diode lighting device, there is a light-emitting diode lighting device 1 including a lighting circuit 4 that steps down DC power input from a DC power supply 2 and outputs it to the light-emitting diode array 3 as shown in FIG.

  The lighting circuit 4 includes a known so-called buck converter (step-down chopper circuit). That is, the lighting circuit 4 is connected between the diode D1 whose cathode is connected to the output terminal on the high voltage side of the DC power supply 2 and the anode of the diode D1 and the output terminal on the low voltage side of the DC power supply 2. Switch device 40, capacitor C1 having one end connected to the cathode of diode D1, and inductor L1 having one end connected to the other end of the capacitor and the other end connected to a connection point between diode D1 and switch device 40 And both ends of the capacitor C1 are connected to the light emitting diode array 3 as output ends.

  The switch device 40 includes, for example, a switching element connected between the output terminal on the low voltage side of the DC power supply 2 and the anode of the diode D1, and a driving unit that periodically drives the switching element on and off. It is composed of an integrated circuit integrated. For example, a field effect transistor (FET) can be used as the switching element. In this case, the source is connected to the output terminal on the low voltage side of the DC power supply 2, and the drain is connected to the anode of the diode D1. . Further, the driving unit changes the on-duty of the on-off driving as needed so as to keep the output current of the lighting circuit 4 constant. Since such a switch device 40 is well known and commercially available, detailed illustration and description thereof will be omitted.

  Further, in the example of FIG. 5, the fuse 5 serving as a circuit interrupting means for stopping the input of DC power to the lighting circuit 4 by fusing with Joule heat when a certain amount of current flows flows from the DC power supply 2 to the lighting circuit. 4 is inserted in the power feeding path to 4.

JP 2007-189004 A

  Here, a fuse that is blown when the output terminals of the lighting circuit 4 are short-circuited in a state where at least the switching element of the switch device 40 is not turned off is used as the fuse 5. It should be noted that the “state where the switching element is not turned off” here is not only a state where the switching element remains turned on, but is sufficiently high even if an OFF control is input to the switching element (that is, circuit design). Also included are situations where the impedance (as required above) is not achieved. Accordingly, when the output voltage of the lighting circuit 4 becomes abnormally high due to some failure, the light emitting diode array 3 is destroyed, the output terminals of the lighting circuit 4 are short-circuited, and the switching device 40 is switched in the lighting circuit 4. If the output current is not suppressed by turning off the element, the fuse 5 is blown to protect each circuit component of the lighting circuit 4 from electrical stress. As a failure in which the output voltage of the lighting circuit 4 becomes abnormally high as described above, for example, a short circuit of the switch device 40 can be considered. In this case, the output voltage of the lighting circuit 4 is approximately the same as the output voltage of the DC power supply 2. Become.

  However, even when the output voltage of the lighting circuit 4 becomes abnormally high as described above, the light emitting diode array 3 is not destroyed as described above, and the fuse 5 is not blown. When excessive voltage is applied to each circuit component of the lighting circuit 4 and the light emitting diode array 3, abnormal heat generation may occur.

  The present invention has been made in view of the above-described reasons, and an object thereof is to provide a light-emitting diode lighting device that hardly generates abnormal heat and a lighting device using the light-emitting diode lighting device.

  The light-emitting diode lighting device of the present invention is inserted into a lighting circuit composed of a buck converter for lighting the light-emitting diode by stepping down the input DC power and outputting it to the light-emitting diode, and a power supply path to the lighting circuit. A circuit shut-off means for stopping the input of DC power to the lighting circuit when at least an output terminal of the lighting circuit is short-circuited in a state where the switching element of the lighting circuit is not turned off; and an output voltage of the lighting circuit is a predetermined value And a protection circuit that short-circuits between the output terminals of the lighting circuit when the voltage becomes equal to or higher than a short-circuit threshold voltage.

  The light-emitting diode lighting device includes a power factor correction circuit including at least one switching element and connected to a preceding stage of the lighting circuit, and the power factor correction circuit is provided between output terminals of the lighting circuit by at least the protection circuit. It is desirable to stop the operation when is short-circuited.

  In this light emitting diode lighting device, it is preferable that the lighting circuit stops operating before the protection circuit short-circuits between the output terminals of the lighting circuit.

  The illumination device of the present invention includes any one of the above-described light-emitting diode lighting devices and at least one light-emitting diode that is turned on by an output of the lighting circuit.

  According to the present invention, when the output voltage of the lighting circuit rises abnormally, the output circuit of the lighting circuit is short-circuited by the protection circuit, so that the power supply to the lighting circuit is surely stopped by the circuit interruption means. Therefore, abnormal heat generation is less likely to occur than when no protection circuit is provided.

1 is a circuit block diagram showing a first embodiment. 6 is a circuit block unit showing a second embodiment. It is a circuit block part which shows the example of a change same as the above. It is a circuit block part which shows another example of a change same as the above. It is a circuit block diagram which shows a prior art example.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

(Embodiment 1)
The basic configuration of this embodiment is the same as that of the conventional example described with reference to FIG.

  As shown in FIG. 1, in the light-emitting diode lighting device 1 of the present embodiment, the output voltage of the lighting circuit 4 (that is, the voltage across the capacitor C1) exceeds a predetermined voltage (hereinafter referred to as “short-circuit threshold voltage”). A protective circuit 6 for short-circuiting the output terminals of the lighting circuit 4 when the lighting circuit 4 is connected.

  The protection circuit 6 includes a thyristor Q1 having an anode connected to the output terminal on the high voltage side of the lighting circuit 4 and a cathode connected to the output terminal on the low voltage side of the lighting circuit 4, and the gate of the thyristor Q1 and the lighting circuit. 4 and a Zener diode ZD having an anode connected to the thyristor Q1 side between the output terminals on the high voltage side. More specifically, the Zener diode ZD has an anode directly connected to the gate of the thyristor Q1, and a cathode connected to the output terminal on the high voltage side of the lighting circuit 4 via the resistor R1. The gate of the thyristor Q1 is connected to the output terminal on the low voltage side of the lighting circuit 4 through a parallel circuit of a resistor R2 and a capacitor C2.

  That is, when the output voltage of the lighting circuit 4 becomes equal to or higher than the short-circuit threshold voltage, the thyristor Q1 is turned on, so that the output terminals of the lighting circuit 4 are short-circuited via the thyristor Q1. In other words, in the protection circuit 6, the circuit elements other than the thyristor Q1 constitute a thyristor driving unit that turns on the thyristor Q1 when the output voltage of the lighting circuit 4 becomes equal to or higher than the short-circuit threshold voltage. The short-circuit threshold voltage is a voltage obtained by adding the Zener voltage of the Zener diode ZD to the voltage obtained by multiplying the gate trigger voltage of the thyristor Q1 by the reciprocal (R1 + R2) / R2 of the voltage dividing ratio by the resistors R1 and R2 of the protection circuit 6. . The short-circuit threshold voltage is lower than the output voltage of the DC power supply 2 and higher than the output voltage during normal operation of the lighting circuit 4 (that is, the forward voltage drop of the connected light-emitting diode array 3).

  According to the above configuration, even when an abnormality such as a short circuit between the drain and source of the switching device 40 occurs in the lighting circuit 4 and the output voltage becomes abnormally high, the output of the lighting circuit 4 is output by the protection circuit 6. The ends are short-circuited. As the fuse 5, a fuse that blows when the output terminals of the lighting circuit 4 are short-circuited in a state where at least the switching element of the switch device 40 is not turned off is used. As already explained, the “state where the switching element is not turned off” here is not only a state where the switching element remains on, but is sufficiently high even if an OFF control is input to the switching element. A state where impedance is not achieved (that is, as required in circuit design) is also included. Therefore, when an abnormality such as a short circuit in which the switching element is not turned off occurs in the lighting circuit 4, the fuse 5 is surely blown by the short circuit by the protection circuit 6 as described above, and is connected to the lighting circuit 4. Power supply is stopped. As described above, abnormal heat generation is less likely to occur than when the protection circuit 6 is not provided.

  Further, if the short-circuit threshold voltage is set to a voltage that is sufficiently low that the light-emitting diode array 3 does not break down, the light-emitting diode array 3 can be prevented from being broken due to the short circuit by the protection circuit 6.

(Embodiment 2)
Since the basic configuration of the present embodiment is the same as that of the first embodiment, description of the common parts is omitted.

  In the present embodiment, the switch device 40 includes a switching element Q2 and a drive unit 41 that drives the switching element Q2 on and off, and the stop control terminal 411 is provided in the drive unit 41. The switching element Q2 is composed of, for example, an FET whose drain is connected to the anode of the diode D1 and whose source is connected to the output terminal on the low voltage side of the DC power supply 2 via the resistor R3. As the switching element Q2, in addition to the FET as described above, other well-known switching elements such as IGBTs may be used. The drive unit 41 is composed of, for example, a one-chip integrated circuit, and repeatedly drives the switching element Q2 on and off. The on-duty of the on / off drive is controlled by feedback control that maintains the output current of the lighting circuit 4 constant. Change from time to time. More specifically, for example, the drive unit 41 turns on the switching element Q2 when the output current to the capacitor C1 becomes 0, and then the voltage across the resistor R3 reaches an off voltage described later. Sometimes the switching element Q2 is turned off. The off voltage is increased when the output current of the lighting circuit 4 is lower than a predetermined target current, and is decreased when the output current of the lighting circuit 4 is higher than the target current. It will be changed as needed. Since the drive unit 41 as described above can be realized by a known technique, detailed illustration and description thereof are omitted.

  Further, in the present embodiment, when the output voltage of the lighting circuit 4 becomes equal to or higher than a predetermined voltage (hereinafter referred to as “output stop voltage”), the lighting circuit 4 stops its operation, that is, the lighting circuit 4 Switching element Q2 is maintained in the off state.

  Specifically, as shown in FIG. 2, the switching device 40 of the lighting circuit 4 is connected to the ground (that is, the same potential as the output terminal on the low voltage side of the DC power supply 2) via the output terminal of the photocoupler 8a. A stop control terminal 411 that stops operation when the stop control terminal 411 is connected to the ground is used. Further, the input terminal of the photocoupler 8a is connected between the gate of the thyristor Q1 and the Zener diode ZD in the protection circuit 6. That is, the output stop voltage is an output voltage of the lighting circuit 4 when a current flows through the Zener diode ZD and the photocoupler 8a is turned on. The short-circuit threshold voltage in the present embodiment is a voltage obtained by adding the forward drop voltage of the light emitting diode of the photocoupler 8a to the short-circuit threshold voltage in the first embodiment.

  Furthermore, the timing at which the lighting circuit 4 is stopped is before the timing at which the short circuit by the protection circuit 6 is performed. As a method for realizing such an operation, for example, a method in which the gate trigger voltage is sufficiently high as the thyristor Q1 and the output stop voltage is made lower than the short-circuit threshold voltage, or the capacitance of the capacitor C2 of the protection circuit 6 is used. A method of increasing the size sufficiently is conceivable.

  In this embodiment, the same effect as that of the first embodiment can be obtained.

  Here, a case where the light emitting diode array 3 is removed during the operation of the lighting circuit 4 is considered. Then, the output voltage of the lighting circuit 4 gradually increases due to the feedback operation for maintaining the output current constant, although the switch device 40 of the lighting circuit 4 does not cause a short circuit.

  In the first embodiment, the thyristor Q1 is turned on in the protection circuit 6 in the above case, and the output terminals of the lighting circuit 4 are short-circuited. Even if the output circuit of the lighting circuit 4 is short-circuited by the protection circuit 6, if the output current is suppressed by appropriately turning off the switching element in the lighting circuit 4, the operation of the circuit breaking means (in the case of the fuse 5, fusing) ) Is avoided. However, since the protection circuit 6 operates (that is, the output terminals of the lighting circuit 4 are short-circuited), it is necessary to restore the protection circuit 6 at the time of recovery. Specifically, since the thyristor Q1, which is an element that short-circuits between the output terminals of the lighting circuit 4 in the protection circuit 6, does not have a self-extinguishing capability, the protection circuit 6 is restored at the time of recovery (that is, In order to turn off the thyristor Q1, it is necessary to temporarily stop the current supplied to the thyristor Q1 (eg, to turn off the power).

  On the other hand, in this embodiment, when the lighting circuit 4 itself is normal as described above, the lighting circuit 4 is stopped before the short circuit by the protection circuit 6 is performed, and therefore the protection circuit 6 does not operate. Therefore, the work of returning the protection circuit 6 at the time of restoration becomes unnecessary.

  Furthermore, after the stop as described above, when the output voltage of the lighting circuit 4 drops below a predetermined voltage (hereinafter referred to as “operation restart voltage”), the lighting circuit 4 automatically restarts operation. By doing so, it is possible to recover by simply reconnecting the light emitting diode array 3. For example, in the example of FIG. 2, if the lighting circuit 4 resumes operation when the photodiode 8a is turned off, the operation resumption voltage is equal to the output stop voltage. That is, in the state where the light emitting diode array 3 is not connected, when the output voltage of the lighting circuit 4 drops below the operation restart voltage after the lighting circuit 4 is stopped, the operation of the lighting circuit 4 is restarted. The intermittent operation that the lighting circuit 4 is stopped when the voltage exceeds the output stop voltage again is repeated. However, when the light emitting diode array 3 is connected, the output voltage of the lighting circuit 4 is stabilized below the output stop voltage. As a result, the lighting circuit 4 returns to continuous operation.

  Here, when the protection circuit 6 is not provided, the output voltage of the lighting circuit 4 becomes excessively high (for example, up to about the output voltage of the DC power supply 2) after the light emitting diode array 3 is removed. When the light emitting diode array 3 is connected to 4, excessive electrical stress is applied to the light emitting diode array 3. On the other hand, in the present embodiment, the output voltage of the lighting circuit 4 with the light emitting diode array 3 removed is about the output stop voltage, which is at least lower than the output voltage of the DC power supply 2. Sometimes electrical stress applied to the light emitting diode array 3 is suppressed.

  In each of the first and second embodiments, the light emitting diode array 3 is a single series circuit composed of a plurality of light emitting diodes in FIGS. Such a series circuit or a plurality of light emitting diodes connected in parallel may be used. Further, instead of the light emitting diode array 3, only one light emitting diode may be connected between the output terminals of the lighting circuit 4.

  In each of the first and second embodiments, a known battery can be used as the DC power source 2 connected to the input terminal of the lighting circuit 4, but the present invention is not limited to this, and a known DC power source circuit is not limited thereto. May be used. For example, as the DC power source 2, as shown in FIG. 3, a rectifying / smoothing circuit that rectifies and smoothes AC power input from an external AC power source 7 can be used. In the example of FIG. 3, the DC power supply 2 includes a diode bridge 21 that performs full-wave rectification of AC power input from the AC power supply 7, and a smoothing capacitor C0 that smoothes the output of the diode bridge 21. It is connected to one AC input end of the bridge 21. As the smoothing capacitor C0, for example, an electrolytic capacitor can be used. In the example of FIG. 3, the fuse 5 is connected between the diode bridge 21 and the AC power supply 7. Further, in the example of FIG. 3, resistors R4 and R5 are connected between the capacitor C1 and the protection circuit 6 of the lighting circuit 4 and between the diode bridge 21 and the smoothing capacitor C0 of the DC power supply 2, respectively. . A resistor R5 connected between the diode bridge 21 of the DC power supply 2 and the smoothing capacitor C0 suppresses an inrush current to the smoothing capacitor C0 when the power is turned on. In FIG. Although connected to the voltage side, it may be connected to the high voltage side. Further, the resistor R4 between the lighting circuit 4 and the protection circuit 6 is connected to the low voltage side of the output of the lighting circuit 4 in FIG. 3, but may be connected to the high voltage side. Here, in the example of FIG. 3, the smoothing capacitor C0 may be omitted, and the DC power supply 2 may be configured by only the diode bridge 21, that is, the rectifier circuit.

  Further, as shown in FIG. 4, as the DC power source 2, a power factor correction circuit 22 having at least one switching element (not shown) connected to the subsequent stage of the diode bridge 21 may be used. Good. As the power factor correction circuit 22 as described above, for example, a known boost converter (boost chopper circuit) can be used.

  In the example of FIG. 4, the power factor correction circuit 22 has a stop control terminal 221 connected to the ground via the output terminal of the photocoupler 8b, and when this stop control terminal 221 is connected to the ground. The operation (that is, the on / off driving of the switching element) is stopped. The input terminal of the photocoupler 8b is connected between the gate of the thyristor Q1 and the Zener diode ZD in the protection circuit 6. That is, when the output voltage of the lighting circuit 4 reaches a predetermined voltage (hereinafter referred to as “pre-stage stop voltage”), a current flows through the Zener diode ZD and the photocouplers 8a and 8b are turned on. The power factor correction circuit 22 and the lighting circuit 4 are stopped. The short-circuit threshold voltage in the example of FIG. 4 is a voltage obtained by adding the sum of the forward drop voltages of the light emitting diodes of the two photocouplers 8a and 8b to the short-circuit threshold voltage in the first embodiment. Further, in the example of FIG. 4, the pre-stage stop voltage is equal to the output stop voltage, but these may be different from each other.

  Here, since the input current per unit time to the DC power supply 2 is reduced during the operation of the power factor correction circuit 22 than when the power factor improvement circuit 22 is stopped, the fuse 5 Fusing may take time. Therefore, in the example of FIG. 4, the power factor is improved when at least the protective circuit 6 is short-circuited between the output terminals of the lighting circuit 4 so that the fuse 5 can be blown immediately (that is, the operation of the circuit breaker). By stopping the circuit 22, the input current to the lighting circuit 4 is increased. The timing at which the power factor correction circuit 22 is stopped may be before the timing at which the short circuit by the protection circuit 6 is performed, or at the same time as the timing at which the short circuit by the protection circuit 6 is performed. In FIG. 4, the photocouplers 8a and 8b are provided for both the power factor correction circuit 22 and the lighting circuit 4, but the photocouplers 8a and 8b are provided for one or both of the power factor correction circuit 22 and the lighting circuit 4. May be omitted.

  Furthermore, in the various light emitting diode lighting devices 1, as the resistors R <b> 3 to R <b> 5 on the upstream side of the protection circuit 6, one that shuts off the circuit when a certain amount of current flows may be used. In particular, when the resistors R3 and R5 constituting the power supply path to the lighting circuit 4 are to shut off the circuit before the fuse 5, the resistors R3 and R5 serve as a circuit breaking means.

  The various light emitting diode lighting devices 1 can constitute a lighting device together with the light emitting diode array 3 (or one light emitting diode) that is turned on by the output of the lighting circuit 4.

DESCRIPTION OF SYMBOLS 1 Light emitting diode lighting device 3 Light emitting diode array 4 Lighting circuit 5 Fuse (circuit interruption | blocking means)
6 Protection circuit 22 Power factor correction circuit Q2 Switching element

Claims (4)

A lighting circuit composed of a buck converter for lighting the light emitting diode by stepping down the input DC power and outputting it to the light emitting diode;
Circuit interrupting means for stopping the input of DC power to the lighting circuit when the output terminal of the lighting circuit is short-circuited in a state where at least the switching element of the lighting circuit is not turned off by being inserted into the power supply path to the lighting circuit When,
A light emitting diode lighting device comprising: a protection circuit for short-circuiting between output terminals of the lighting circuit when the output voltage of the lighting circuit becomes equal to or higher than a predetermined short-circuit threshold voltage. Including a power factor correction circuit including at least one switching element and connected to a preceding stage of the lighting circuit;
2. The light emitting diode lighting device according to claim 1, wherein the power factor correction circuit stops its operation when at least the output circuit of the lighting circuit is short-circuited by the protection circuit.   3. The light emitting diode lighting device according to claim 1, wherein the lighting circuit stops operating before the protection circuit short-circuits between output terminals of the lighting circuit. 4. The light-emitting diode lighting device according to any one of claims 1 to 3,
An illumination device comprising: at least one light emitting diode that is turned on by an output of the lighting circuit.

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