JP2023127103A - Lighting device, illumination instrument and illumination control system - Google Patents

Abstract

To provide a lighting device capable of reducing flickering of a light source, an illumination instrument and an illumination control system.SOLUTION: A lighting device according to the present disclosure comprises: a switching element which is connected in series with a light source; a power supply circuit for turning on the light source by supplying power to both ends of a series circuit including the light source and the switching element; and a control circuit for changing impedance of the switching element in such a manner that a light source current is matched with a predetermined target value while performing constant voltage feedback control on the power supply circuit in a ripple suppressed mode, and for performing constant current feedback control on the power supply circuit in such a manner that the light source current is matched with a predetermined target value while fixing the impedance of the switching element in a ripple non-suppressed mode. In a predetermined period after the ripple suppressed mode and the ripple non-suppressed mode are switched, the control circuit makes a feedback cycle of the power supply circuit shorter than the other period.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a lighting device, a lighting fixture, and a lighting control system.

Patent Document 1 discloses an LED driving device that converts AC input power into desired DC output power and supplies it to an LED load. This LED driving device includes a switching element that is controlled to be turned on and off, a ripple current reduction section that is connected in series to the LED load and reduces current ripple flowing through the LED load, and a control circuit. The control circuit controls the DC output power to a predetermined value by controlling the switching element on and off based on the feedback voltage at the connection point between the LED load and the ripple current reduction section. The ripple current reduction section has a feedback type constant current control circuit that variably controls impedance.

Patent No. 5110197

In the LED driving device shown in Patent Document 1, light source current ripple can be suppressed by adding a ripple current reduction section. On the other hand, the addition of the ripple current reduction section generates a loss corresponding to the product of the ripple voltage and the current flowing through the light source. For this reason, there is a possibility that circuit efficiency will decrease. Furthermore, if the LED drive device is installed in an environment in which a ripple suppression function is included in advance, the ripple current reduction unit may become unnecessary.

Therefore, it is desirable to use either ripple current reduction operation or high efficiency operation depending on the usage environment. In other words, it is desirable that the ripple suppression function of the ripple current reduction section be switchable. Here, from the perspective of the switching power supply circuit in the preceding stage of the ripple current reduction section, switching the ripple suppression function is equivalent to changing the load. When load fluctuation occurs, overshoot or undershoot may occur in the light source current due to the feedback cycle of the switching power supply circuit. As a result, flickering may occur in the light source.

The present disclosure has been made to solve the above-mentioned problems, and aims to provide a lighting device, a lighting fixture, and a lighting control system that can reduce flickering of a light source.

A lighting device according to the present disclosure includes: a switching element connected in series with a light source; a power supply circuit that supplies power to both ends of a series circuit including the light source and the switching element to light the light source; In the suppression mode, the impedance of the switching element is changed while controlling the power supply circuit with constant voltage feedback so that the light source current flowing through the light source matches a predetermined target value; a control circuit that fixes the impedance of a switching element and performs constant current feedback control of the power supply circuit so that the light source current matches a predetermined target value, the control circuit controlling the ripple suppression mode. In a predetermined period after switching between the mode and the ripple suppression non-mode, the feedback cycle of the power supply circuit is made shorter than other periods.

In the lighting device according to the present disclosure, the feedback cycle of the power supply circuit is a predetermined period after switching between the ripple suppression mode and the ripple suppression non-mode, and is shorter than other periods. Therefore, overshoot or undershoot of the light source current can be suppressed in a short period of time, and flickering of the light source can be reduced.

1 is a circuit block diagram of a lighting fixture according to Embodiment 1. FIG. FIG. 7 is a diagram showing a light source current waveform when switching control modes. 1 is a diagram showing a lighting control system according to Embodiment 1. FIG. FIG. 3 is a diagram illustrating a control mode switching method in the lighting control system according to the first embodiment. FIG. 3 is a diagram showing a light source current waveform at the time of control mode switching in the lighting control system according to the first embodiment. 7 is a diagram illustrating a control mode switching method in the lighting control system according to Embodiment 2. FIG. 7 is a diagram showing a light source current waveform at the time of control mode switching in the lighting control system according to Embodiment 2. FIG.

A lighting device, a lighting fixture, and a lighting control system according to each embodiment will be described with reference to the drawings. Identical or corresponding components may be given the same reference numerals and repeated descriptions may be omitted.

Embodiment 1.
FIG. 1 is a circuit block diagram of a lighting fixture 100 according to the first embodiment. The lighting fixture 100 includes a lighting device 50 and a light source 80. The light source 80 includes a plurality of LEDs connected in series as light emitting elements.

In the lighting device 50, a smoothing capacitor C1 and a buck converter circuit 10 are connected to the output side of the diode bridge DB1. The alternating current voltage from the alternating current power supply AC is rectified by the diode bridge DB1, and converted into a direct current voltage accompanied by a pulsating voltage by the smoothing capacitor C1. The converted voltage is input to the buck converter circuit 10.

Buck converter circuit 10 includes a switching element Q1, a diode D1, an inductor L1, and a smoothing capacitor C2. The switching element Q1 is, for example, a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). The switching element Q1 includes a drain, a source, and a gate.

A light source 80 and a regulator circuit 20 are connected in series to the output of the buck converter circuit 10. Regulator circuit 20 includes a switching element Q2 and a current detection resistor R1 connected in series with switching element Q2. The switching element Q2 is, for example, a MOSFET. The buck converter circuit 10 is a power supply circuit that supplies power to both ends of a series circuit formed by the light source 80, the switching element Q2, and the current detection resistor R1 to turn on the light source 80.

The control circuit 30 is, for example, a composite IC including a microcomputer and a driver. The control circuit 30 has a Q1DRV terminal and a Q2DRV terminal for driving switching elements Q1 and Q2. The Q1DRV terminal and the Q2DRV terminal are connected to the gates of switching elements Q1 and Q2, respectively. Further, the control circuit 30 has a Vin terminal for detecting the voltage value input to the lighting fixture 100. A series circuit of resistors R2 and R3 is connected in parallel with smoothing capacitor C1. A connection point between resistors R2 and R3 is connected to the Vin terminal.

The control circuit 30 has a VOUT terminal for detecting the voltage generated in the switching element Q2 and an IFB terminal for detecting the light source current flowing through the light source 80. The VOUT terminal is connected to the drain of switching element Q2. The IFB terminal is connected to a connection point between switching element Q2 and current detection resistor R1.

Further, the control circuit 30 has a VB terminal that serves as a power source for a driver that drives the switching elements Q1 and Q2, and a VDD terminal that serves as a power source for a microcomputer. The output voltage V1 of the control power supply circuit 40 is input to the VB terminal. The output voltage of the step-down circuit 42 is input to the VDD terminal.

Control power supply circuit 40 is, for example, a buck converter circuit. The input voltage Vin is stepped down to a predetermined voltage by the control power supply circuit 40. The stepped down voltage is smoothed by electrolytic capacitor C3 to generate power supply voltage V1. The power supply voltage V1 is, for example, 13V. The control power supply circuit 40 may be any other circuit such as a flyback circuit as long as a desired voltage can be obtained. The step-down circuit 42 generates a power supply voltage VDD for the control circuit 30 from the power supply voltage V1. The step-down circuit 42 is, for example, a regulator circuit. The power supply voltage VDD is, for example, 3.3V.

The control signal 60 is, for example, a serial signal. The control circuit 30 includes a connection terminal Rx for connecting to an external device. The control circuit 30 operates according to a control signal 60 input from an external device via the connection terminal Rx. The control circuit 30 can switch the dimming state or control mode by receiving a dimming state or a control mode switching signal, which will be described later, as the control signal 60.

The lighting device 50 has a ripple suppression mode and a ripple suppression non-suppression mode as control modes. First, the operation in the ripple suppression mode will be explained. When input voltage Vin is applied from alternating current power supply AC, control power supply circuit 40 and step-down circuit 42 operate to generate power supply voltages V1 and VDD. When the power supply voltage VDD rises to a voltage at which the control circuit 30 can operate, the control circuit 30 is activated. Control circuit 30 detects input voltage Vin, and operates buck converter circuit 10 and regulator circuit 20 when the detected voltage is a predetermined voltage.

In the ripple suppression mode, the control circuit 30 performs constant voltage feedback control on the buck converter circuit 10 so that the voltage VQ2 generated in the switching element Q2 matches a predetermined target voltage. Specifically, the control circuit 30 detects the drain voltage of the switching element Q2 at the VOUT terminal as the voltage VQ2. The control circuit 30 compares the voltage VQ2 with a target voltage previously stored in the control circuit 30, and adjusts a PWM (Pulse Width Modulation) signal output from the Q1DRV terminal based on the comparison result. Thereby, the buck converter circuit 10 performs a constant voltage operation so that the cathode voltage of the light source 80, that is, the drain voltage of the switching element Q2 is kept constant.

The feedback period at this time is set to be below the commercial frequency in order to improve the power factor. At this time, a voltage accompanied by a ripple voltage of the commercial component is generated at the output of the buck converter circuit 10. Specifically, a ripple with a frequency twice that of the AC power supply AC is superimposed on the output voltage of the buck converter circuit 10. Note that the ripple voltage changes depending on the capacitance of the smoothing capacitor C2. In order to reduce the ripple voltage to zero, a large-capacity smoothing capacitor C2 is required, and the ripple voltage cannot be completely removed with a common-sense capacitance.

The regulator circuit 20 performs constant current operation so that the light source current is constant. Specifically, the control circuit 30 detects the voltage VR1 generated in the current detection resistor R1 connected in series with the light source 80 at the IFB terminal. The control circuit 30 compares the voltage VR1 with a target value previously stored in the control circuit 30, and adjusts the level of the output voltage from the Q2DRV terminal based on the comparison result. That is, the control circuit 30 adjusts the impedance of the switching element Q2 so that the voltage VR1 matches the target value.

In this way, in the ripple suppression mode, the control circuit 30 changes the impedance of the switching element Q2 while controlling the buck converter circuit 10 with constant voltage feedback so that the light source current matches the predetermined target value. At this time, the voltage applied to the light source 80 is controlled to be constant because the impedance of the switching element Q2 takes charge of the ripple voltage. That is, ripples in the light source current are suppressed and the light source current is controlled to be constant.

Next, the operation in the non-ripple suppression mode will be explained. Here, mainly the differences from the ripple suppression mode will be explained. In the non-ripple suppression mode, the impedance of the switching element Q2 is fixed. The control circuit 30 does not adjust the impedance of the switching element Q2, but fixes it to the minimum impedance, for example. Further, the control circuit 30 performs constant current feedback control on the buck converter circuit 10 so that the light source current matches a predetermined target value. That is, the control circuit 30 detects the voltage generated in the current detection resistor R1 at the IFB terminal, and adjusts the PWM signal output from the Q1DRV terminal so that the detected value is constant. In this way, the buck converter circuit 10 is controlled with constant current.

As in the ripple suppression mode, the buck converter circuit 10 performs a power factor correction operation. Therefore, a ripple with a frequency twice that of the AC power supply AC is superimposed on the output voltage of the buck converter circuit 10. Further, in the non-ripple suppression mode, the impedance of the switching element Q2 is fixed. Therefore, a ripple with a frequency twice that of the AC power source is superimposed on the light source current as well.

However, in the non-ripple suppression mode, the loss due to the voltage drop of the switching element Q2 is suppressed compared to the ripple suppression mode. Therefore, the circuit loss of the lighting device 50 is reduced, and the efficiency is higher than that in the ripple suppression mode.

As described above, in the mode with ripple suppression and the mode without ripple suppression, there is a trade-off relationship between circuit loss and ripple of the light source. For this reason, it is desirable to use different control modes depending on the usage environment. Next, switching of control modes will be explained. FIG. 2 is a diagram showing a light source current waveform when switching control modes.

First, as a comparative example of this embodiment, a case where the control mode is simply switched will be described. For example, when switching from the non-ripple suppression mode to the ripple suppression mode, when viewed from the buck converter circuit 10, in addition to the light source 80, the impedance of the switching element Q2 is added, increasing the load. Therefore, immediately after switching, the supplied power becomes insufficient for the load. Therefore, undershoot of the light source current occurs. On the other hand, when switching from the ripple suppression mode to the no ripple suppression mode, the load on the switching element Q2 is reduced from the perspective of the buck converter circuit 10. Therefore, the load is light relative to the supplied power, and overshoot of the light source current occurs.

In normal operation, the feedback cycle of the buck converter circuit 10 is set to be equal to or less than the commercial cycle. For this reason, it takes time to make the light source current match the target value through feedback control after overshoot or undershoot occurs. If this overshoot or undershoot is detected by the human eye, there is a possibility that the user may see it as flickering.

In contrast, in this embodiment, the responsiveness of the feedback control of the buck converter circuit 10 is temporarily improved when switching the control mode. In other words, the control circuit 30 makes the feedback period of the buck converter circuit 10 shorter in a predetermined fixed period after switching between the ripple suppression mode and the ripple suppression non-mode, compared to other periods. Thereby, overshoot or undershoot of the light source current can be suppressed in a short period of time, and flickering of the light source 80 can be reduced.

The feedback period for a certain period after switching the control mode is set so that, for example, overshoot or undershoot of the light source current that occurs when switching between the ripple suppression mode and the ripple suppression mode cannot be detected by the human eye. That's good. Specifically, as shown in FIG. 2, the feedback cycle in this period is preferably set so that overshoot or undershoot is 10 ms or less. That is, it is preferable that overshoot or undershoot be stabilized at a frequency of 100 Hz or higher. Generally, if the frequency is 100 Hz or more, it cannot be detected by the human eye, so it is possible to suppress the user's recognition of flickering when switching control modes.

For example, the control circuit 30 returns the feedback period to the original commercial period or less after a certain period of time has elapsed since the control mode was switched. After switching the control mode, the control circuit 30 may return the feedback cycle to the original cycle when the overshoot or undershoot converges and the light source current matches the target value. Further, the control circuit 30 may switch the control mode after shortening the feedback cycle. Note that the trigger for switching the feedback period is, for example, the control signal 60.

Next, a lighting control system 101 including the lighting fixture 100 of this embodiment will be described. FIG. 3 is a diagram showing the lighting control system 101 according to the first embodiment. The lighting control system 101 includes a plurality of lighting fixtures 100, 200, 300, and a controller 500 that switches the control mode of the plurality of lighting fixtures 100, 200, 300 between a ripple suppression mode and a ripple suppression non-mode. . The configurations of lighting fixtures 200 and 300 are similar to the configuration of lighting fixture 100. The lighting control system 101 may include a plurality of lighting fixtures.

If even one of the multiple lighting fixtures illuminating the floor has a superimposed ripple current, it will appear on camera as flicker. Therefore, it is preferable that ripple be suppressed for all lighting equipment on the floor where images are to be taken with a camera or the like. Therefore, switching the control mode of the lighting fixtures 100 on the same floor is preferably performed by an upstream system. The upstream system includes a controller 500, for example.

A user uses a mobile terminal to transmit a control mode switching command to controller 500. In response to the control mode switching command, the controller 500 transmits a control mode switching signal to the connected lighting fixtures 100, 200, and 300. This control mode switching signal corresponds to a control signal. Each lighting device 100, 200, 300 changes its own control mode in response to a control signal from the control system while improving feedback responsiveness as described above.

Here, in the single lighting fixture 100 of this embodiment, flickering can be suppressed due to the aforementioned improvement in feedback responsiveness. However, if the brightness of a plurality of lighting fixtures on a floor fluctuates continuously, the period of fluctuation in the brightness of the entire floor becomes long, and users may notice flickering. In this way, if lighting fixtures on the same floor switch control modes at random timing, problems may arise.

FIG. 4 is a diagram illustrating a control mode switching method in the lighting control system 101 according to the first embodiment. FIG. 5 is a diagram showing a light source current waveform when switching control modes in the lighting control system 101 according to the first embodiment. In this embodiment, controller 500 simultaneously switches the control modes of multiple lighting devices 100, 200, and 300. Thereby, the lighting fixtures 100, 200, and 300 in the lighting control system 101 collectively change the control mode at the same timing. Thereby, it is possible to suppress an increase in the brightness fluctuation period of the entire lighting control system 101, and it is possible to suppress flickering.

Furthermore, in this embodiment, the output timing of control signals from the lighting control system 101 to the plurality of lighting fixtures 100, 200, and 300 can be made the same. Therefore, the lighting control system 101 can be easily constructed.

As a modification of this embodiment, the buck converter circuit 10 may be another type of power supply circuit. Further, the light emitting element constituting the light source 80 may be an organic EL. Furthermore, the control circuit 30 is not limited to a composite IC, and any circuit capable of feedback control and driving of switching elements can be employed. The control circuit 30 may be realized by hardware such as an independent A/D converter, logic circuit, gate array, or D/A converter.

Further, although the control signal is a serial signal, other methods may be used as long as the present embodiment can be satisfied. The dimming command and control mode switching command from the user are not limited to the mobile terminal, and may be transmitted from a stationary terminal such as a PC or a device installed on a wall or the like. Further, communication between the mobile terminal and the controller 500 and communication between the controller 500 and the lighting fixtures 100, 200, and 300 may be performed by a wireless method or a wired method.

These modifications can be applied as appropriate to the lighting devices, lighting fixtures, and lighting control systems according to the following embodiments. Note that the lighting device, lighting fixture, and lighting control system according to the following embodiments have many features in common with Embodiment 1, so the description will focus on the differences from Embodiment 1.

Embodiment 2.
FIG. 6 is a diagram illustrating a control mode switching method in the lighting control system 101 according to the second embodiment. FIG. 7 is a diagram showing a light source current waveform when switching control modes in the lighting control system 101 according to the second embodiment. In the first embodiment, since the control mode is changed all at once, there is a possibility that the disturbance in the input current becomes large temporarily. In contrast, in the present embodiment, controller 500 first switches the control mode of lighting fixture 100 among the plurality of lighting fixtures 100, 200, and 300. Next, the controller 500 switches the control mode of the lighting fixture 200 after the overshoot or undershoot of the light source current in the lighting fixture 100 has converged. Similarly, the controller 500 switches the control mode of the lighting fixture 300 after the overshoot or undershoot of the light source current in the lighting fixture 200 has converged.

In this embodiment, the controller 500 changes the control mode of each lighting fixture one by one at sufficient intervals. This makes it possible to reduce disturbances in the input current. On the other hand, in this embodiment, system construction may be more complicated than in the first embodiment.

The present disclosure is not limited to the embodiments described above. Unless departing from the gist of the present disclosure, various changes made to each embodiment and other forms constructed by combining some of the components of each embodiment are within the scope of the present disclosure. included.

10 buck converter circuit, 20 regulator circuit, 30 control circuit, 40 control power supply circuit, 42 step-down circuit, 50 lighting device, 60 control signal, 80 light source, 100 lighting fixture, 101 lighting control system, 200, 300 lighting fixture, 500 controller , AC AC power supply, C1, C2 smoothing capacitor, C3 electrolytic capacitor, D1 diode, DB1 diode bridge, L1 inductor, Q1, Q2 switching element, R1 current detection resistor, R2, R3 resistor, Rx connection terminal

Claims (10)

a switching element connected in series with the light source;
a power supply circuit that supplies power to both ends of a series circuit including the light source and the switching element to turn on the light source;
In the ripple suppression mode, while controlling the power supply circuit with constant voltage feedback, the impedance of the switching element is changed so that the light source current flowing through the light source matches a predetermined target value, and in the non-ripple suppression mode, a control circuit that fixes the impedance of the switching element and performs constant current feedback control of the power supply circuit so that the light source current matches a predetermined target value;
Equipped with
The lighting device is characterized in that the control circuit shortens the feedback period of the power supply circuit in a predetermined period after switching between the ripple suppression mode and the ripple suppression non-mode, compared to other periods. . The feedback cycle in the period is set so that overshoot or undershoot of the light source current that occurs when switching between the ripple suppression mode and the ripple suppression non-mode is undetectable to the human eye. The lighting device according to claim 1. The feedback cycle in the period is set such that an overshoot or undershoot of the light source current that occurs when switching between the ripple suppression mode and the ripple suppression non-mode is 10 ms or less. The lighting device according to claim 1 or 2. In the ripple suppression mode, the control circuit performs constant voltage feedback control on the power supply circuit so that the voltage generated in the switching element matches a predetermined target voltage. The lighting device according to any one of the above. The power supply circuit is supplied with AC power,
5. The lighting device according to claim 1, wherein a ripple having a frequency twice that of the AC power source is superimposed on the output voltage of the power supply circuit. The power supply circuit is supplied with AC power,
6. The lighting device according to claim 1, wherein in the ripple suppression non-ripple mode, a ripple having a frequency twice that of the AC power source is superimposed on the light source current. The lighting device according to any one of claims 1 to 6,
the light source;
A lighting fixture comprising: A plurality of lighting devices according to claim 7 are provided,
A lighting control system comprising: a controller that switches a control mode of the plurality of lighting fixtures between the ripple suppression mode and the ripple suppression non-mode. The lighting control system according to claim 8, wherein the controller simultaneously switches control modes of the plurality of lighting fixtures. The controller switches the control mode of a first lighting fixture among the plurality of lighting fixtures, and controls the light source current generated when the first lighting fixture switches between the ripple suppression mode and the ripple suppression non-mode. 9. The lighting control system according to claim 8, wherein the control mode of a second lighting fixture among the plurality of lighting fixtures is switched after overshoot or undershoot converges.

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