JP2016152087A - Led lighting device and luminaire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an LED lighting device and a luminaire that can suppress excessive output voltage and rush current.SOLUTION: A power supply circuit 4 supplies output current to make an LED 2 emit light, and adjusts the current value of the output current through the switching operation of a switching element Q1. A control circuit 9 controls the switching operation of the switching element Q1. An output current detector 5 detects the output current. An output voltage detector 6 detects an output voltage to be applied to LED 2. An output current comparator 7 outputs a comparison result between a first reference value and the output current detected by the output current detector 5 as a second reference value. An output voltage comparator 8 compares the output voltage detected by the output voltage detector 6 with the second reference value. A control circuit 9 controls the switching element Q1 so that the output voltage is equal to the second reference value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an LED lighting device and a lighting fixture that can suppress excessive output voltage and rush current.

  In recent years, LEDs have become the mainstream in place of conventional incandescent bulbs and fluorescent lamps as light sources for lighting fixtures. LEDs have the characteristics of low power consumption and long life. Research and development of LED lighting devices that turn on LEDs are being carried out by various companies. In the LED lighting device, in order to make the luminous flux constant, constant current control is mainly used in which the current flowing to the LED as a load is made constant. As an example of constant current control, the voltage generated in the current detection resistor connected in series with the LED is detected, the on-time of the switching element is adjusted by feedback control, and the voltage of the current detection resistor is made constant, so that the LED Is controlled so that a constant current flows.

  If there is no path for the current flowing from the LED lighting device to the LED due to removal of the LED or the like, the current does not flow to the current detection resistor. Since no current flows through the current detection resistor, no voltage is generated in the current detection resistor. However, since the constant current control operates so as to make the voltage of the current detection resistor constant, an excessive output voltage is generated.

  Further, when the output voltage becomes high due to removal of the LED or the like, the rated voltage of components used in the LED lighting device may be exceeded. Alternatively, a rush current may flow through the LED when the connector is connected by connecting / disconnecting the output connector for a short time. This damages the LED and the lighting device. Thus, in order to suppress an excessive output voltage, it is common to provide a protection circuit (see, for example, Patent Documents 1 and 2).

Japanese Patent No. 5486388 JP 2012-204317 A

  In order to suppress the rush current of the LED when the output connector is connected / disconnected for a short time, the protection circuit is required to operate at a voltage as low as possible with respect to the output voltage in the lighting state. On the other hand, if the operating voltage of the protection circuit is set low, the protection circuit may operate unnecessarily due to malfunctions such as power-on, instantaneous power failure, and noise. Further, when the LED is removed, the output voltage increases instantaneously, so that a protective operation must be performed in a short time.

  The present invention has been made to solve the above-described problems, and an object thereof is to obtain an LED lighting device and a lighting fixture capable of suppressing an excessive output voltage and rush current.

  An LED lighting device according to the present invention supplies an output current to an LED to light it, and adjusts the current value of the output current by switching operation of the switching element, and a control circuit that controls the switching operation of the switching element The output current detector for detecting the output current, the output voltage detector for detecting the output voltage applied to the LED, and the output current detected by the output current detector and the first reference value were compared. An output current comparator that outputs a result as a second reference value; and an output voltage comparator that compares the output voltage detected by the output voltage detector with the second reference value. The switching operation of the switching element is controlled so that the output voltage becomes the same as the second reference value.

  In the present invention, the result of comparing the detected output current and the first reference value is used as the second reference value, and the switching operation of the switching element is controlled so that the detected output voltage is the same as the second reference value. . Thereby, an excessive output voltage and a rush current can be suppressed.

It is a figure which shows the lighting fixture which concerns on Embodiment 1 of this invention. It is a time chart which shows the operation | movement at the time of removal of LED in the lighting fixture which concerns on a comparative example. It is a time chart which shows the operation | movement of insertion / extraction of the output connector in the lighting fixture which concerns on a comparative example. It is a time chart which shows operation | movement of the lighting fixture which concerns on Embodiment 1 of this invention. It is a figure which shows the lighting fixture which concerns on Embodiment 2 of this invention.

  An LED lighting device and a lighting fixture according to an embodiment of the present invention will be described with reference to the drawings. The same or corresponding components are denoted by the same reference numerals, and repeated description may be omitted.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a lighting fixture according to Embodiment 1 of the present invention. In FIG. 1, components other than the commercial AC power source 1 and the LED 2 are components of the LED lighting device. The LED lighting device is a device that turns on the LED 2 by receiving power from the commercial AC power source 1.

  The LED lighting device includes a rectifier circuit 3, a smoothing capacitor C1, a power supply circuit 4, an output current detector 5, an output voltage detector 6, an output current comparison unit 7, an output voltage comparison unit 8, and a control circuit. 9 and connectors 11a and 11b for connecting the LED 2 are provided.

  The rectifier circuit 3 performs full-wave rectification on the AC voltage supplied from the commercial AC power supply 1. The smoothing capacitor C <b> 1 smoothes the pulsating voltage that has been full-wave rectified by the rectifier circuit 3. The rectifier circuit 3 forms, for example, a diode bridge and is a capacitor input type rectifier circuit here, but may be any circuit configuration that generates a DC voltage in the smoothing capacitor C1. For example, when performing power factor improvement, a step-up chopper circuit (power factor correction circuit) may be inserted between the rectifier circuit 3 and the smoothing capacitor C1.

  The power supply circuit 4 is a step-down chopper circuit having a switching element Q1, a drive circuit 12, a freewheeling diode D1, an inductor L1, and a capacitor C2. The switching element Q1 is, for example, a MOSFET. The drive circuit 12 supplies a gate signal for ON / OFF control of the switching element Q1 to the gate of the switching element Q1. The on / off controlled current is stepped down by the inductor L1, smoothed by the capacitor C2, and flows through the LED2. The free-wheeling diode D1 becomes a current path for the inductor L1 when the switching element Q1 is turned off. In this way, the power supply circuit 4 adjusts the current value of the output current by the switching operation of the switching element Q1, and supplies the output current to the LED 2 to light it.

  The output current detector 5 has a resistor R1 connected in series with the LED2. The output voltage detector 6 includes resistors R2 and R3 connected in series between the connector 11a and a ground point. The output voltage V1 is divided by resistors R2 and R3, and the voltage is reduced by the resistance ratio, and is output from the connection point between the resistors R2 and R3. Thereby, the output current detector 5 detects the output current I1, and the output voltage detector 6 detects the output voltage V1 applied to the LED 2.

  The output current comparator 7 outputs the result of comparing the output current detected by the output current detector 5 with the first reference value as the second reference value. Specifically, the output voltage of the output current detector 5 is compared with the reference voltage ref, and the output voltage of the output current comparison unit 7 is changed according to the difference. Note that the reference voltage ref may be variable in accordance with a signal from the outside such as a dimmer so that dimming can be performed.

  The output voltage comparison unit 8 compares the output voltage detected by the output voltage detector 6 with the second reference value. Note that the voltage output from the output current comparison unit 7 to the output voltage comparison unit 8 may be gradually set to a target value with a fade.

  The control circuit 9 sends a drive signal to the drive circuit 12 based on the output of the output voltage comparator 8, and the drive circuit 12 supplies a gate signal for on / off control of the switching element Q1 to the gate of the switching element Q1. .

  Here, the drive signal from the control circuit 9 is input to the gate of the switching element Q1, but in this embodiment, since the switching element Q1 is provided on the high voltage side, the drive signal is electrically transmitted by the drive circuit 12. Communicated. Generally, a transformer, a photocoupler, or the like is used as the drive circuit 12. The drive signal is a rectangular wave, and the on-duty ratio of the rectangular wave is changed based on the output of the output voltage comparison unit 8. The switching element Q1 is turned on / off according to the on-duty ratio. When the on-duty ratio increases, the current of the LED 2 increases, and when the on-duty ratio decreases, the current of the LED 2 decreases.

  In the present embodiment, the control circuit 9 controls the switching operation of the switching element Q1 so that the output voltage becomes the same as the second reference value. By controlling the output voltage to be the same as the second reference value in this way, the output current that generates the second reference voltage is controlled to be the same as the first reference value. As a result, the output current is controlled to be constant.

  Subsequently, the effect of the present embodiment will be described in comparison with a comparative example. In the comparative example, there is no output voltage detector 6 or output voltage comparison unit 8, and the control circuit 9 performs constant current control so that the output of the output current comparison unit 7 is constant.

  FIG. 2 is a time chart showing an operation at the time of LED removal in the lighting fixture according to the comparative example. A in the figure represents the timing at which the LED 2 is removed. B in the figure represents the timing when the operation of the power supply circuit 4 is stopped. ΔV represents the difference from the voltage in the stable state.

  When the LED 2 is removed at A, the current path flowing through the LED 2 disappears and the output current I1 becomes zero. The output voltage V1 increases steeply when an electric current is passed through the LED 2 from A to B. In B, when the protection level for detecting an overvoltage of the preset output voltage is reached, the control circuit 9 outputs a control signal for stopping the operation of the switching element Q1. As a result, the power supply circuit 4 stops operating. Specifically, since the gate signal is not input to the gate of the switching element Q1 from the drive circuit 12 controlled by the power supply circuit 4, the gate voltage V2 of the switching element Q1 becomes 0 (stopped). Thereafter, the electric charge accumulated in the capacitor C2 is discharged through the resistors R2 and R3, and the output voltage V1 gradually decreases.

  FIG. 3 is a time chart showing the operation of inserting / removing the output connector in the lighting fixture according to the comparative example. C in the drawing represents the timing when the LED 2 is removed and then attached again. Since the operations from A to B are the same as those in FIG. After stopping the operation at B, the voltage V1 gradually decreases, but the LED 2 is attached at C on the way. This timing assumes that the output connector is inserted and removed in a short time when the voltage V1 when the LED 2 is attached is equal to or higher than the voltage in the stable state.

  Since the output voltage V1 is equal to or higher than the stable voltage at C, the charge stored in the capacitor C2 flows as a transient rush current (output current I1 at C) to the attached LED2. The rush current increases as the voltage difference ΔV increases. Accordingly, as the time from when the LED 2 is removed to when it is attached is shorter, the LED 2 is attached with the voltage V1 being higher, so the rush current becomes larger. Since the rush current is larger than the current that flows through the LED 2 at normal times, the LED 2 is stressed, and in the worst case, the LED 2 may fail. Since the rush current also flows through the resistor R1 of the output current detector 5, the LED lighting device is also stressed.

  FIG. 4 is a time chart showing the operation of the lighting apparatus according to Embodiment 1 of the present invention. Compared with the comparative example, the output voltage V1 rises gradually after the LED 2 is removed at A until the operation is stopped at B. Further, ΔV when the operation of the power supply circuit 4 is stopped at B is suppressed as compared with the comparative example. For this reason, even when the LED 2 is attached again after B, the rush current flowing through the LED 2 can be reduced.

  As described above, in the present embodiment, the result of comparing the detected output current and the first reference value is used as the second reference value, and switching is performed so that the detected output voltage is the same as the second reference value. The switching operation of the element Q1 is controlled. In the conventional constant current control, when the LED 2 is removed during lighting, an attempt is made to flow current through the LED 2 and the output voltage rises sharply. On the other hand, since the output voltage is controlled in the embodiment, the output voltage does not rise sharply when the LED 2 is removed. As described above, if the output voltage of the output current comparator 7 is faded, the operation gradually increases the output voltage. This is the operation from A to B in FIG. Since the output voltage gradually rises, the overvoltage protection operation of the output voltage can be performed at a low voltage even when the time delay of the protection operation is taken into consideration. Therefore, according to the present embodiment, it is possible to suppress the rush current of the LED 2 when the output connector is inserted or removed while suppressing the excessive output voltage when the LED 2 is removed or the like.

  The control circuit 9 is realized by a processing circuit such as a CPU or a system LSI that executes a program stored in a memory. In addition, a plurality of processing circuits may cooperate to execute the above function. Further, the output current comparison unit 7 and the output voltage comparison unit 8 may be configured by a microcomputer, but may be configured by an electronic component such as an operational amplifier.

  Further, as a feature of the LED 2, even if the flowing current is changed, a substantially constant voltage characteristic is exhibited. For this reason, even when the current flowing through the LED 2 is largely changed, the change in the voltage of the LED 2 may be small, so that the output voltage may be gradually changed a little.

Embodiment 2. FIG.
FIG. 5 is a diagram showing a lighting fixture according to Embodiment 2 of the present invention. In this embodiment, an output state determination unit 13 and an output control unit 14 are added to the configuration of the first embodiment. The output state determination unit 13 determines the output state based on the output current detected by the output current detector 5 and the output voltage detected by the output voltage detector 6. Specifically, it is determined that the LED 2 is normally lit when an output voltage and an output current are detected. On the other hand, when the output voltage increases and the output current decreases to 0 or decreases, it is determined that the LED 2 is removed.

  The output control unit 14 controls output based on the determination result of the output state determination unit 13. Specifically, when it is determined that the LED 2 is normally lit, the output control unit 14 transmits the output of the output voltage comparison unit 8 to the control circuit 9 as it is. On the other hand, when the output state determination unit 13 determines that the LED 2 has been removed, the output control unit 14 notifies the control circuit 9 to stop the operation of the switching element Q1. Therefore, the control circuit 9 stops the switching operation of the switching element Q1 when the output state determination unit 13 determines that the LED 2 has been removed.

  In addition, when the determination that the LED 2 has been removed is continuously output from the output state determination unit 13 for 100 ms, the output control unit 14 preferably notifies the control circuit 9 to stop the operation of the switching element Q1. As a result, even when the LEDs 2 having different output voltages are used, the operation can be stopped with a slight increase in voltage from the stable output voltage. However, it is not limited to 100 ms, and may be increased or decreased in consideration of an increase in output voltage. In terms of preventing malfunction, it is preferable to make a determination with a certain amount of continuous time. The period from A to B in FIG. 4 corresponds to this. Thereby, ΔV when the gate voltage V2 stops at the timing B can be suppressed to a small value.

2 LED, 4 power supply circuit, 5 output current detector, 6 output voltage detector, 7 output current comparison unit, 8 output voltage comparison unit, 9 control circuit, 13 output state determination unit, Q1 switching element

Claims (3)

A power supply circuit for supplying an output current to the LED and lighting the LED, and adjusting a current value of the output current by a switching operation of the switching element;
A control circuit for controlling the switching operation of the switching element;
An output current detector for detecting the output current;
An output voltage detector for detecting an output voltage applied to the LED;
An output current comparator that outputs a result of comparing the output current detected by the output current detector with a first reference value as a second reference value;
An output voltage comparator that compares the output voltage detected by the output voltage detector with the second reference value;
The LED lighting device, wherein the control circuit controls a switching operation of the switching element so that the output voltage becomes the same as the second reference value. When the output voltage detected by the output voltage detector is increased and the output current detected by the output current detector is decreased, an output state determination unit that determines that the LED has been removed is further provided,
The LED lighting device according to claim 1, wherein the control circuit stops the switching operation of the switching element when the output state determination unit determines that the LED is removed.   A lighting fixture comprising the LED lighting device according to claim 1.

Images