Lighting devices and lighting fixtures

Abstract

The objective is to obtain a lighting device and lighting fixture that can suppress repeated dimming. [Solution] The lighting device according to the present disclosure comprises a lighting circuit for lighting a light source, a control circuit for controlling the lighting circuit, and a temperature-sensitive element for detecting the temperature of the light source or the lighting device. The control circuit, when the detected temperature detected by the temperature-sensitive element is higher than a predetermined first temperature in a predetermined first period, reduces the brightness of the light source to a level lower than the brightness in the first period in a predetermined second period following the first period.

Description

Technical Field

[0001] The present disclosure relates to a lighting device and a lighting fixture.

Background Art

[0002] Patent Document 1 discloses a power supply device. In this power supply device, a bridge circuit converts a DC voltage into an AC voltage by turning on and off switching elements. A transformer includes a primary winding connected to the bridge circuit and a secondary winding magnetically coupled to the primary winding. A rectifying and smoothing circuit converts the AC voltage output from the secondary winding into a DC output voltage and supplies it to a DC load. A driver has a frequency setting terminal and adjusts the output voltage by controlling the on and off of the switching elements at a switching frequency corresponding to the current flowing through the frequency setting terminal. A temperature-sensitive element is connected to the frequency setting terminal and changes the current flowing through the frequency setting terminal in response to an increase in temperature.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1, in a lighting device, protection against abnormal temperature rise is performed using a temperature-sensitive element. Here, from the viewpoint of protection against sudden abnormal heat generation, it is desirable to quickly control the brightness of the light source in conjunction with the temperature. However, if dimming is repeated according to the temperature, there is a risk of giving discomfort to the user.

[0005] An object of the present disclosure is to obtain a lighting device and a lighting fixture that can suppress repeated dimming.

Means for Solving the Problems

[0006] The lighting device according to this disclosure comprises a lighting circuit for lighting a light source, a control circuit for controlling the lighting circuit, and a temperature-sensing element for detecting the temperature of the light source or the lighting device, wherein the control circuit, when the detected temperature detected by the temperature-sensing element is higher than a predetermined first temperature in a predetermined first period, reduces the brightness of the light source to a level lower than the brightness in the first period in a predetermined second period following the first period. [Effects of the Invention]

[0007] In the lighting device according to this disclosure, when the detected temperature is higher than a predetermined first temperature in a predetermined first period, the brightness of the light source is reduced to a level lower than the brightness in the first period in a predetermined second period following the first period. This suppresses repeated dimming. [Brief explanation of the drawing]

[0008] [Figure 1] This is a block diagram illustrating the configuration of the lighting fixture according to Embodiment 1. [Figure 2A] This is a flowchart illustrating the operation of the lighting fixture according to Embodiment 1. [Figure 2B] This is a flowchart illustrating the operation of the lighting fixture according to Embodiment 1. [Figure 3] This figure illustrates the change in dimming rate of the lighting fixture according to Embodiment 1. [Figure 4] This figure illustrates the change in dimming rate of the lighting fixture according to Embodiment 1. [Figure 5] This figure illustrates the change in dimming rate of the lighting fixture according to Embodiment 2. [Figure 6] This figure illustrates the change in dimming rate of the lighting fixture according to Embodiment 2. [Modes for carrying out the invention]

[0009] The lighting devices according to each embodiment will be described with reference to the drawings. The same or corresponding components are denoted by the same reference numerals, and repetition of the description may be omitted.

[0010] Embodiment 1. Figure 1 is a block diagram illustrating the configuration of a lighting fixture 100 according to Embodiment 1. The lighting fixture 100 comprises an input unit 12, a rectifier 14, a lighting device 10, and a light source 40. Commercial AC power is input to the rectifier 14 via the input unit 12. The rectifier 14 has a rectifier DB that rectifies the commercial AC power. Note that the input unit 12 and the rectifier 14 may be part of the lighting device 10.

[0011] The lighting device 10 is equipped with a so-called boost chopper circuit that converts the pulsating voltage, which has been full-wave rectified by the rectifier 14, to charge a predetermined DC high voltage to the capacitor C2. The boost chopper circuit consists of a coil L1, a switching element Q1, and a diode D1. The switching element Q1 is, for example, a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). The voltage charged to the capacitor C2 is input to the P1 terminal of the control IC 30 via a resistive voltage divider using resistors R3 and R4. This allows the control IC 30 to detect a voltage proportional to the voltage across the capacitor C2. Let V1 be the DC voltage charged to the capacitor C2. The control IC 30 corresponds to the control circuit.

[0012] The control IC 30 controls the voltage charged to capacitor C2 to a predetermined DC voltage. That is, the control IC 30 performs feedback control to keep the voltage at terminal P1 constant and outputs a switching signal from terminal Vg1 to control the switching element Q1. The control IC 30 is, for example, a microcontroller. Generally, the operating power supply voltage of a microcontroller is lower than the drive voltage of a MOSFET. Therefore, the control IC 30 first inputs the switching signal from terminal Vg1 to the MOSFET driver 18. The MOSFET driver 18 can output a voltage higher than that of the lighting control IC 30. Therefore, the switching element Q1 can be switched stably.

[0013] A resistor R6 is connected to the source terminal of the switching element Q1. The voltage across resistor R6 is input to the P4 terminal of control IC 30. By converting the current that flows when the switching element Q1 is turned on into a voltage using resistor R4, the control IC 30 can detect the current value flowing through the switching element Q1.

[0014] The boost chopper circuit performs power factor correction circuit operation to increase the power factor of the power output from the commercial AC power supply. In power factor correction circuit operation, the switching control is performed by keeping the ON width of the switching element Q1 constant over the period of the commercial AC power supply, so that the average value of the switching current is controlled to be proportional to the phase of the commercial AC power supply. Since it is necessary to perform the above feedback control while keeping the ON width of the switching element Q1 constant, the feedback period must be longer than the period of full-wave rectification of the commercial AC power supply.

[0015] Furthermore, the voltage fully rectified by the rectifier DB is smoothed by capacitor C1, becoming the power supply for the boost chopper circuit. Therefore, the full-wave rectified voltage is applied to capacitor C1 as a result of the boost chopper circuit operating.

[0016] A buck converter circuit is connected to a capacitor C2 that has been charged with a predetermined DC voltage. The buck converter circuit consists of a switching element Q2, a coil L2, and a diode D2. A light source 40 is connected to the buck converter circuit. By smoothing the high-frequency voltage output by the buck converter circuit with a capacitor C3 connected in parallel with the light source 40, a DC voltage can be supplied to the light source 40 to light it up. The buck converter circuit, or the boost chopper circuit and the buck converter circuit, constitute the lighting circuit that lights up the light source 40. The lighting circuit can also be said to be an AC-DC conversion circuit. The light source 40 is, for example, an LED light source. The light source 40 has a plurality of light-emitting elements 41, such as LEDs.

[0017] A resistor R7 is connected to the capacitor C3 and the light source 40. A switching current output by the buck converter circuit flows through the resistor R7. The current flowing through the resistor R7 is converted into a voltage and input to the P2 terminal of the control IC30. The current flowing through the resistor R7 is the buck converter current, and its average value is equal to the LED current flowing through the light source 40. The control IC30 outputs a switching signal for controlling the switching element Q2 from the Vg2 terminal so that the voltage generated in the resistor R7 becomes constant. Therefore, the light source 40 lights up under constant current control. The switching signal from the Vg2 terminal is input to the switching element Q2 via the MOSFET driver 18, similar to the boost chopper circuit. Thereby, the switching element Q2 can be stably switched.

[0018] The control power supply of the MOSFET driver 18 is supplied by generating a voltage from the charge stored in the capacitor C2 in the control power supply circuit section 16 and smoothing it with the capacitor C4. Let the voltage of the control power supply be V2. For example, the voltage V2 is 15V. Further, the voltage V2 is input to the VDD terminal of the control IC30 via the step-down circuit section 20 and serves as the control power supply of the control IC30. The voltage of the VDD terminal is, for example, 5V. The control power supply circuit section 16 may be a step-down converter circuit such as a buck converter circuit or a buck-boost converter such as a flyback circuit.

[0019] Resistors R1 and R2 are connected between both ends of the capacitor C1. The voltage divided by the resistors R1 and R2 is input to the P3 terminal of the control IC30. Thereby, the control IC30 can detect a voltage proportional to the voltage obtained by full-wave rectifying the commercial power supply AC from the P3 terminal and reflect it in the control.

[0020] Resistors R5 and R6 are connected to the step-down circuit section 20 and the VDD terminal. The voltage divided by the resistors R5 and R6 is input to the P4 terminal of the control IC30. A temperature-sensitive element may be used for either of the resistors R5 and R6. The resistance value of the temperature-sensitive element changes with temperature. Therefore, the control IC30 can detect the temperature by detecting the voltage input to the P4 terminal. The temperature-sensitive element is, for example, a thermistor.

[0021] Figures 2A and 2B are flowcharts for explaining the operation of the lighting fixture according to Embodiment 1. Using FIG. 2, the operation of the lighting fixture 100 when the temperature is detected at the P4 terminal will be described. First, the power supply of the lighting fixture 100 is turned on (step 1). Next, the control IC 30 lights the light source 40 at a preset dimming rate (step 2). Here, for example, the light source 40 is lit at a dimming rate of 100%. Next, the control IC 30 detects the temperature with the temperature-sensitive element for a preset first period T1 (step 3). The first period T1 is, for example, 10 minutes. The control IC 30 has a function of detecting time and can measure a period such as the first period.

[0022] When the detected temperature detected by the temperature-sensitive element in the first period T1 is equal to or higher than the first temperature (YES in step 3), when the control IC 30 shifts to the next preset second period T2 of the first period T1, the dimming rate is decreased by a preset dimming rate (step 5). The second period T2 is, for example, 10 minutes. The preset dimming rate is, for example, 10%. Note that step 4 will be described later.

[0023] Also, when the detected temperature does not exceed the first temperature in the first period T1 (No in step 3), the process proceeds to step 7. When the detected temperature detected by the temperature-sensitive element in the first period T1 is lower than a preset second temperature (YES in step 7), when the control IC 30 shifts to the second period T2, the dimming rate is increased by a preset dimming rate (step 9). The preset dimming rate is, for example, 10%. Note that step 8 will be described later.

[0024] When the detected temperature does not exceed the first temperature and does not fall below the second temperature in the first period T1 (No in step 7), the control IC 30 maintains the preset dimming rate (step 11). That is, the current dimming rate of 100% is also maintained in the second period T2.

[0025] In this way, when the temperature detected by the temperature sensing element in a predetermined first period T1 is higher than a predetermined first temperature, the control IC 30 reduces the brightness of the light source 40 to the brightness in the first period in the predetermined second period T2 following the first period T1. By setting a fixed judgment period as the first period T1 and the second period T2 in this way, repeated dimming in a short period of time can be suppressed. This reduces user discomfort. It also prevents the user from mistakenly perceiving the protective action as a malfunction. Furthermore, by setting a fixed judgment period and reducing the amount or rate of change of the dimming rate in steps 5 and 9, abrupt changes in brightness can be suppressed. This further enhances the user's sense of security while protecting the lighting fixture 100 from abnormal heat generation.

[0026] Furthermore, when the detected temperature in the first period T1 is lower than a predetermined second temperature, the control IC 30 increases the brightness of the light source 40 in the second period T2 to a level higher than the brightness in the first period T1. This allows the dimming rate to be restored when the temperature drops. Also, the first temperature is set higher than the second temperature. This allows the dimming rate to be maintained when the temperature stabilizes between the first and second temperatures. Therefore, unnecessary repeated dimming can be prevented.

[0027] If the detected temperature in the second period T2 is higher than the first temperature (YES in step 12), the control IC 30 reduces the brightness of the light source 40 in the predetermined third period T3 following the second period T2 to the brightness in the second period T2 (step 14). Also, if the detected temperature in the second period T2 is lower than the second temperature (YES in step 16), the control IC 30 increases the brightness of the light source 40 in the third period T3 to the brightness in the second period T2 (step 18). In other words, steps 12 to 20 of the second period T2 repeat the same process as steps 3 to 11 of the first period T1. Similarly, steps 21 to 29 of the third period T3 repeat the same process as steps 12 to 20 of the second period T2. The process for subsequent nth periods Tn is the same.

[0028] This allows for further reduction of the dimming rate to enhance protection if abnormal heat generation is progressing. Furthermore, the dimming rate can be gradually reduced once the heat generation subsides. Therefore, the lighting device 10 can be operated within an appropriate operating temperature range. Additionally, because the brightness is changed by a predetermined dimming rate at each judgment period, abrupt changes in brightness can be suppressed.

[0029] Furthermore, if the detected temperature is higher than the first temperature in the first period T1 (YES in step 3), the control IC 30 may reduce the brightness of the light source 40 in the second period T2 (step 5), provided that it does not fall below a predetermined lower limit (NO in step 4). If the brightness of the light source 40 has reached the lower limit (YES in step 4), the brightness of the light source 40 is maintained (step 6).

[0030] Furthermore, if the detected temperature in the first period T1 is lower than the second temperature (YES in step 7), the control IC 30 may increase the brightness of the light source 40 in the second period T2 to a higher level than the brightness in the first period T1 (step 9), provided that it does not exceed a predetermined upper limit (NO in step 8). Also, if the brightness of the light source 40 has reached the upper limit (YES in step 8), the brightness of the light source 40 is maintained (step 10).

[0031] In this way, upper and lower limits can be set for the dimming rate. This prevents the light source 40 from turning off or creating a dangerous situation where sufficient illumination cannot be maintained. It also protects against the light source 40 turning on beyond the upper limit.

[0032] Figures 3 and 4 illustrate the change in dimming rate of the lighting fixture 100 according to Embodiment 1. When changing the dimming rate, a predetermined fade time is provided until the target dimming rate is reached. The fade begins at the start of the second period. The control IC 30 may change the brightness over a longer fade time in the second period T2 if the change in brightness between the first period T1 and the second period T2 is large. In the example in Figure 3, the change in dimming rate is 10%. In the example in Figure 4, the change in dimming rate is 50%. In the case of Figure 3, the fade time is shorter than in the case of Figure 4.

[0033] When the dimming rate changes significantly, the change in brightness is also large. In this case, by increasing the fade time, the brightness can be changed gradually, reducing user discomfort. Furthermore, user safety can be ensured, and protective actions can be performed.

[0034] In this embodiment, examples of changes in dimming rate for each judgment period of 10% and 50% are shown, but the change in dimming rate for each judgment period can be any value. Furthermore, the change in dimming rate may differ depending on the judgment period.

[0035] Furthermore, while the judgment periods for the first and second periods were set to 10 minutes, any length of time is acceptable. The judgment periods are preferably of a certain length, for example, 1 minute or longer. The length of each judgment period may differ. Also, the timing and number of temperature detections within each judgment period are not limited.

[0036] Furthermore, the first temperature may be the same as the second temperature. In this case, the dimming ratio will not be maintained, but the fade control described above can suppress abrupt changes in brightness, thereby reducing user discomfort.

[0037] The temperature-sensing element does not have to be a thermistor. The temperature-sensing element only needs to be able to detect the temperature of the lighting fixture 100, light source 40, or lighting device 10. Note that temperature detection includes directly or indirectly detecting the temperature of the lighting fixture 100, light source 40, or lighting device 10, as well as detecting the ambient temperature around the lighting fixture 100, light source 40, or lighting device 10.

[0038] The control IC 30 can be composed of, for example, one or more processors 31 and one or more memories 32. The memory 32 stores a program that causes the processor 31 to execute the control of the control IC 30 described above. Alternatively, the lighting circuit may be controlled by another IC located outside the lighting device 10 or lighting fixture 100 as a control circuit.

[0039] These modifications can be appropriately applied to the lighting device according to the following embodiment. Since the lighting device according to the following embodiment has many similarities with Embodiment 1, the explanation will focus on the differences from Embodiment 1.

[0040] Embodiment 2. Figures 5 and 6 illustrate the change in dimming rate of the lighting fixture 100 according to Embodiment 2. The control IC 30 increases the rate of change in brightness when changing the brightness of the light source 40 based on the detected temperature in the second period T2, as the change in detected temperature over a predetermined period increases. Furthermore, the control IC 30 may increase the fade time as the change in detected temperature increases. In other words, the temperature rise value of the temperature sensing element is detected, and the dimming rate and fade time are determined according to the temperature rise value.

[0041] In the example in Figure 5, the temperature rise during the first period T1 is smaller than in the example in Figure 6. In this case, the rate of change in the dimming rate during the second period T2 is smaller and the fade time is set shorter in the example in Figure 5 than in the example in Figure 6. As a result, when the temperature rise is large, as in the example in Figure 6, the dimming rate can be significantly reduced by a large rate of change and a long fade time. This allows for a rapid and significant reduction in the dimming rate in dangerous high-temperature conditions, enabling safe protective operation.

[0042] Similarly, when the temperature decrease in the first period T1 is large, the dimming rate may be significantly increased in the second period T2 by using a large rate of change and a long fade time. This allows for a rapid recovery of the dimming rate.

[0043] Furthermore, the greater the change in detected temperature, the greater the rate of change in brightness, and the less the fade time needs to be increased. Also, the rate of change in brightness in the second period T2 is set based on the change in detected temperature over a predetermined period, but this predetermined period may be the first period T1 or any other period. The predetermined period may also be a part of the first period. In addition, the greater the change in detected temperature over the predetermined period, the greater the change in the brightness of the light source 40 in the second period T2 compared to the brightness in the first period may be.

[0044] Embodiment 3. As described above, the lighting circuit of the lighting device 10 receives an AC voltage from the commercial power supply and outputs power to light up the light source 40. In this embodiment, the first temperature and the second temperature are set higher as the AC voltage decreases. Table 1 shows an example of the relationship between the AC voltage and the first and second temperatures.

[0045] [Table 1]

[0046] When constant power control is performed, the steady-state temperature differs depending on the input AC voltage. The lower the input AC voltage, the greater the heat generated by the lighting device 10. For example, if the first temperature is high when the input AC voltage is high, the temperature difference between the first temperature and the steady state is large, which may cause the lighting device 10 to fail due to abnormal heat generation before protective action can be taken.

[0047] In contrast, in this embodiment, the first or second temperature is set higher when the input AC voltage is low. This makes it possible to maintain a similar temperature difference between the first or second temperature and the steady-state temperature regardless of the AC voltage. Therefore, appropriate protection can be provided.

[0048] The technical features described in each embodiment may be used in combination as appropriate.

[0049] The various aspects of this disclosure are summarized below as an appendix. (Note 1) A lighting circuit that turns on the light source, A control circuit for controlling the aforementioned lighting circuit, A temperature-sensing element for detecting the temperature of the light source or lighting device, Equipped with, The control circuit is characterized in that, when the detected temperature detected by the temperature sensing element is higher than a predetermined first temperature in a predetermined first period, it reduces the brightness of the light source in a predetermined second period following the first period to a brightness lower than the brightness in the first period. (Note 2) The lighting device according to Appendix 1, characterized in that when the detected temperature is lower than a predetermined second temperature in the first period, the control circuit increases the brightness of the light source in the second period to a level higher than the brightness in the first period. (Note 3) The lighting device according to Appendix 1 or Appendix 2, characterized in that when the detected temperature is higher than the first temperature in the second period, the control circuit reduces the brightness of the light source to a level lower than the brightness in the second period in a predetermined third period following the second period. (Note 4) The lighting device according to any one of Appendix 1 to Appendix 3, characterized in that when the detected temperature is lower than a predetermined second temperature in the second period, the brightness of the light source is increased to a higher level in a predetermined third period following the second period than the brightness in the second period. (Note 5) The lighting device according to any one of Appendix 1 to Appendix 4, characterized in that the control circuit changes the brightness over a longer period of time in the second period as the change in brightness between the first period and the second period is greater. (Note 6) The lighting device according to any one of Appendix 1 to Appendix 5, characterized in that the control circuit increases the rate of change of brightness when changing the brightness of the light source in the second period, as the change in the detected temperature in a predetermined period increases. (Note 7) The aforementioned lighting circuit receives an AC voltage and outputs power to light the light source, The lighting device according to any one of Appendix 1 to Appendix 6, characterized in that the first temperature is set higher as the AC voltage decreases. (Note 8) The aforementioned lighting circuit receives an AC voltage and outputs power to light the light source, The lighting device according to Appendix 2, characterized in that the second temperature is set higher as the AC voltage decreases. (Note 9) The lighting device according to any one of Appendix 1 to Appendix 8, characterized in that the control circuit reduces the brightness of the light source in the second period to the brightness in the first period if the detected temperature is higher than the first temperature in the first period and does not fall below a predetermined lower limit. (Note 10) The lighting device according to Appendix 2, characterized in that, when the detected temperature is lower than the second temperature in the first period, the control circuit increases the brightness of the light source in the second period to a higher level than the brightness in the first period, provided that the detected temperature does not exceed a predetermined upper limit. (Note 11) The lighting device according to Appendix 2, characterized in that the first temperature is higher than the second temperature. (Note 12) The lighting device according to Appendix 2, characterized in that the first temperature is the same as the second temperature. (Note 13) A lighting device as described in any one of the appendices 1 to 12, The aforementioned light source, A lighting fixture characterized by having the following features. [Explanation of symbols]

[0050] 10 Lighting device, 12 Input section, 14 Rectifier, 16 Control power supply circuit section, 18 Driver, 20 Step-down circuit section, 30 Control IC, 31 Processor, 32 Memory, 40 Light source, 41 Light-emitting element, 100 Lighting fixture

Claims

1. A lighting circuit that turns on the light source, A control circuit for controlling the aforementioned lighting circuit, A temperature-sensing element for detecting the temperature of the light source or lighting device, Equipped with, The control circuit is characterized in that, when the detected temperature detected by the temperature sensing element is higher than a predetermined first temperature in a predetermined first period, it reduces the brightness of the light source in a predetermined second period following the first period to a brightness lower than the brightness in the first period.

2. The lighting device according to claim 1, wherein the control circuit increases the brightness of the light source during the second period to a level higher than the brightness during the first period when the detected temperature is lower than a predetermined second temperature during the first period.

3. The lighting device according to claim 1 or 2, characterized in that when the detected temperature is higher than the first temperature in the second period, the control circuit reduces the brightness of the light source to a level lower than the brightness in the second period in a predetermined third period following the second period.

4. The lighting device according to claim 1 or 2, characterized in that when the detected temperature is lower than a predetermined second temperature in the second period, the control circuit increases the brightness of the light source to a higher level than the brightness in the second period in a predetermined third period following the second period.

5. The lighting device according to claim 1 or 2, characterized in that the control circuit changes the brightness over a longer period of time in the second period as the change in brightness between the first period and the second period is greater.

6. The lighting device according to claim 1 or 2, characterized in that the control circuit increases the rate of change of brightness when changing the brightness of the light source during the second period, as the change in the detected temperature during a predetermined period increases.

7. The aforementioned lighting circuit receives an AC voltage and outputs power to light the light source, The lighting device according to claim 1 or 2, characterized in that the first temperature is set to be higher as the AC voltage decreases.

8. The aforementioned lighting circuit receives an AC voltage and outputs power to light the light source, The lighting device according to claim 2, characterized in that the second temperature is set to be higher as the AC voltage decreases.

9. The lighting device according to claim 1 or 2, characterized in that the control circuit reduces the brightness of the light source in the second period to a level lower than the brightness in the first period, provided that the detected temperature is higher than the first temperature in the first period and does not fall below a predetermined lower limit.

10. The lighting device according to claim 2, characterized in that the control circuit increases the brightness of the light source during the second period to a level higher than the brightness during the first period, provided that the detected temperature is lower than the second temperature during the first period and does not exceed a predetermined upper limit.

11. The lighting device according to claim 2, characterized in that the first temperature is higher than the second temperature.

12. The lighting device according to claim 2, characterized in that the first temperature is the same as the second temperature.

13. A lighting device according to claim 1 or 2, The aforementioned light source, A lighting fixture characterized by having the following features.

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