JP2015219953A - Lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighting device capable of quickly performing a protection operation at circuit failures.SOLUTION: A lighting device 1 comprises a step-up chopper circuit 2, a buck converter circuit 3, and a control device 40. A detection resistor 24 is provided in the buck converter circuit 3 and used for detecting an LED current. A detection voltage from the detection resistor 24 is inputted to the control device 40. The control device 40 on/off-controls a switching element Q2 of the buck converter circuit 3 on the basis of the detection voltage so that a current flowing in the LED module 27 becomes constant. The control device 40 performs a protection operation respectively in a case where an off state of the switching element Q2 continues for "a predetermined time period Tofferr" and in a case where an operation that the switching element Q2 is switched at a preliminarily defined maximum on-duty continues for "a predetermined time period Tonerr".

Description

  The present invention relates to a lighting device.

  Conventionally, for example, as disclosed in Japanese Patent No. 5401939, there is known a lighting device having a circuit configuration for coping with a short-circuit mode failure in a step-down chopper circuit. When an LED is connected to the output of the step-down chopper circuit and the switching element of the step-down chopper circuit fails in the short-circuit mode, the DC output voltage of the step-up chopper circuit connected to the previous stage of the step-down chopper circuit is applied to the LED. . In such a short-circuit mode failure, in the prior art, the DC output voltage of the boost chopper circuit is set high so that at least some of the plurality of LEDs are destroyed in the open mode. Thereby, the circuit on the load side can be opened.

Japanese Patent No. 5401939 JP 2012-135095 A

  However, in the above conventional technique, the protection is completed by opening the circuit on the load side when the failure in the step-down chopper circuit has progressed considerably and at least some of the plurality of LEDs are broken in the open mode. . It is preferable that the protection operation is performed immediately when an abnormality occurs in the circuit. In this respect, the conventional technique still leaves room for improvement.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a lighting device capable of promptly performing a protection operation when a circuit failure occurs.

  A lighting device according to the present invention includes a converter circuit having a switching element, a detection unit that detects an LED current supplied to an LED by the converter circuit, and an on-state of the switching element based on the LED current detected by the detection unit. A control device for adjusting time, wherein the control device performs a second predetermined time when the switching element is turned off for a first predetermined time and when the switching element is switched at a predetermined predetermined on-duty. In at least one of the following cases, the protection operation is performed.

  According to the present invention, since the protection operation is performed based on the state of the ON time or the OFF time of the switching element, the protection operation can be quickly performed when a switching abnormality occurs due to a circuit failure.

It is a circuit diagram which shows the lighting device concerning embodiment of this invention. It is a time chart which shows operation | movement of the lighting device concerning embodiment of this invention. It is a time chart which shows operation | movement of the lighting device concerning embodiment of this invention. It is a figure which shows the failure mode of the lighting device concerning embodiment of this invention. It is a figure which shows the failure mode of the lighting device concerning embodiment of this invention. It is a figure which shows the failure mode of the lighting device concerning embodiment of this invention.

  FIG. 1 is a circuit diagram showing a lighting device 1 according to an embodiment of the present invention. The luminaire 100 includes an LED module 27 including a plurality of LEDs 26, a lighting device 1, a dimmer 28, and a dimming signal interface (I / F) circuit 4. The lighting device 1 includes a step-up chopper circuit 2, a buck converter circuit 3, and a control device 40.

  The step-up chopper circuit 2 is a power factor correction circuit, a rectifier circuit 8, a capacitor 9, a voltage dividing circuit in which resistors 31 and 32 are connected in series, an inductor 10, a switching element Q1, a diode 14, and a capacitor 17 And a voltage dividing circuit in which resistors 15 and 16 are connected in series. The rectifier circuit 8 is connected to the AC power source 7. The capacitor 9 is connected in parallel to the output terminal of the rectifier circuit 8. A voltage dividing circuit in which resistors 31 and 32 are connected in series is connected in parallel to the capacitor 9. The voltage across the capacitor 9 is divided by resistors 31 and 32 and input to the control device 40. One end of the inductor 10 is connected to the high potential side of the rectifier circuit 8. The switching element Q1 is a MOSFET in this embodiment, and a control terminal (this book) for switching between the first terminal (drain in this embodiment), the second terminal (source in this embodiment), and the first and second terminals. In the embodiment, the first terminal is connected to the other end of the inductor 10. The anode of the diode 14 is connected to the connection point between the first terminal of the switching element Q1 and the other end of the inductor 10. The capacitor 17 is composed of an electrolytic capacitor having a positive electrode connected to the cathode of the diode 14 and a negative electrode connected to the low potential side of the rectifier circuit 8. A voltage dividing circuit in which resistors 15 and 16 are connected in series is connected in parallel to the capacitor 17. The voltage across the capacitor 17 is divided by the resistors 15 and 16 and input to the control device 40.

  The buck converter circuit 3 includes a switching element Q2, a diode 21, an inductor (choke coil) 22, a capacitor 23, and a detection resistor 24. A series circuit composed of the switching element Q2 and the diode 21 is connected in parallel with the capacitor 17 of the step-up chopper circuit 2. The switching element Q2 is a MOSFET in this embodiment, and a control terminal (this book) for switching between the first terminal (drain in this embodiment), the second terminal (source in this embodiment), and the first and second terminals. In the embodiment, a gate is provided. The first terminal is connected to one end (positive electrode) of the capacitor 17, and the second terminal is connected to the cathode of the diode 21. The inductor 22, the capacitor 23, and the detection resistor 24 are connected in this order to form a series circuit, and this series circuit is connected in parallel to the diode 21.

  The detection resistor 24 is provided in the buck converter circuit 3 and is used to detect the LED current flowing through the LED module 27. The detection voltage from the detection resistor 24 is input to the control device 40, and the control device 40 turns on and off the switching element Q2 of the buck converter circuit 3 based on this detection voltage so that the current flowing through the LED module 27 becomes a constant current. .

  Since various microcomputers provided as digital power supply control devices are already known, these known microcomputers can be used as appropriate for the control device 40. As an example in the present embodiment, the control device 40 shown in FIG. 1 includes control circuits 41 and 42, a storage unit 43, an A / D conversion circuit 44, and a processing device 45 that are connected to each other via an internal bus. . The control circuits 41 and 42 output PWM signals that switch the switching elements Q1 and Q2, respectively. The storage unit 43 includes, for example, a nonvolatile memory, and stores a calculation program to be executed by the processing device 45 and various data used for the calculation. Data is written to and read from the storage unit 43 from the outside. The processing device 45 calculates an on-time or the like in the switching control of the switching elements Q1 and Q2. The control device 40 receives a voltage divided by the resistors 15 and 16, a voltage divided by the resistors 31 and 32, and a voltage corresponding to the LED current detected by the detection resistor 24. These voltage values are converted into digital values by the A / D conversion circuit 44, and arithmetic processing is performed by the processing device 45 using the digital values. A dimming command value from the dimmer 28 is input to the control device 40 via the dimming signal I / F circuit 4. The control device 40 adjusts the ON time of the switching element Q2 based on the LED current detected by the detection resistor 24 so that the LED current matches the target current determined based on the dimming command value. Current control is performed.

  As will be described later, the control device 40 operates when the switching element Q2 is turned off for “predetermined time Tofferr” and when the switching element Q2 is switched at a predetermined maximum on-duty for “predetermined time Toner”. Each of them performs a protection operation. The predetermined time Tofferr and the predetermined time Toner are predetermined and stored in the storage unit 43 of the control device 40, and are used in the determination process. The predetermined time Tofferr and the predetermined time Toner may be different from each other (that is, one may be longer than the other) or the same value. Specifically, the protection operation is to stop switching element Q2 on / off and switching element Q1 on / off.

  FIG. 2 is a time chart showing the operation of the lighting device 1 according to the embodiment of the present invention. An operation in which the control device 40 performs the protection operation when the switching element Q2 is turned off for a “predetermined time Tofferr” will be specifically described. First, in a circuit configuration including the step-up chopper circuit 2 and the buck converter circuit 3, there may occur a failure in which the switching element Q2 made of the MOSFET of the buck converter circuit 3 is short-circuited or a circuit failure that is in an ohmic short state occurs. 4 and 5 are diagrams showing failure modes of the lighting device 1 according to the embodiment of the present invention. FIG. 4 shows a state in which the first and second terminals of the switching element Q2 are electrically connected via the virtual resistor 101 due to the ohmic short state. FIG. 5 shows a state in which the first and second terminals of the switching element Q2 are electrically connected via the virtual wiring 102 due to a short circuit failure.

  When a current exceeding a constant current flows through the LED 26, the control device 40 executes a control for narrowing (that is, reducing) the ON time of the switching element Q <b> 2 of the buck converter circuit 3. If the current flowing through the LED 26 does not decrease to the target value even when the on-time is reduced by a certain value, the on-time is further reduced. That is, the on-time is narrowed as in the on-time ton11 → ton12 → ton13 in the time chart of FIG. If a current exceeding the constant current target value continues to flow, the control device 40 sets the ON time of the switching element Q2 to zero, that is, stops the ON control. As a result, the control signal of the switching element Q2 is kept off as in the lowermost stage in the time chart of FIG. Further, when the on-control is stopped, that is, the off-state is maintained for a predetermined “predetermined time Tofferr” or more, it is determined that the buck converter circuit 3 is abnormal, and the switching of the boost chopper circuit 2 and the buck converter circuit 3 is stopped. To do. The predetermined time Tofferr may be set to several seconds, specifically 5 seconds, for example.

  FIG. 3 is a time chart showing the operation of the lighting device 1 according to the embodiment of the present invention. The operation in which the control device 40 performs the protective operation when the operation in which the switching element Q2 is switched at the predetermined maximum on-duty continues for “predetermined time Toner” will be specifically described. A detection voltage from the detection resistor 24 for detecting the LED current is input to the control device 40, and the control device 40 switches the switching element Q2 of the buck converter circuit 3 based on this detection voltage so that the current flowing through the LED 26 becomes a constant current. ON / OFF control.

  FIG. 6 is a diagram showing a failure mode of the lighting device 1 according to the embodiment of the present invention. FIG. 6 shows a state in which one end and the other end of the detection resistor 24 are electrically connected via the virtual wiring 103 due to a short circuit failure. When a circuit failure occurs in which the detection resistor 24 that detects the LED current is in a short circuit state, the detection voltage input to the control device 40 decreases, and thus the control device 40 performs control to increase the ON time of the switching element Q2. If the detection voltage of the detection resistor 24 for detecting the LED current does not reach a predetermined voltage value even when a current exceeding a constant current flows through the LED 26, the control device 40 performs control to increase the ON time of the switching element Q2 of the buck converter circuit 3. It becomes. This state is shown in the time chart of FIG. 3, and the on-time is expanded as the on-time ton21 → ton22.

  If the detection voltage of the detection resistor 24 still does not reach the predetermined voltage value, the switching element Q2 is switched to the maximum on-time, that is, the maximum on-duty. As shown in the lowermost stage in the time chart of FIG. 3, the on-time ton23 reaches the maximum on-time ton_max, and the on-duty at this time is the maximum on-duty Duty_max. The maximum on time ton_max and the maximum on duty Duty_max are respectively upper limit values set in advance. During normal operation of the lighting device 1, the on-time of the switching element Q2 is adjusted within a range not reaching this maximum on-duty. If switching at the maximum on-duty continues for a predetermined “predetermined time Toner” or longer, it is determined that the buck converter circuit 3 is abnormal, and the control device 40 stops switching the boost chopper circuit 2 and the buck converter circuit 3. To do.

  According to the present embodiment described above, it is possible to quickly perform a protective operation on control when a switching abnormality due to a circuit failure occurs. In addition, whether the cause of the switching abnormality is a short circuit or ohmic short of the switching element Q2 or a short circuit of the detection resistor 24 can be distinguished based on the on-time value of the switching element Q2.

  In the above-described embodiment, the on / off operation of the switching element Q2 is compared with both the predetermined time Tofferr and the predetermined time Tonerr to perform protection operation against two types of abnormalities. However, the present invention is not limited to this. It is not something that can be done. The protection operation may be performed by comparing on / off of the switching element Q2 with only one of the predetermined time Tofferr and the predetermined time Toner.

  Note that the control device 40 may determine whether or not the buck converter circuit 3 and the lighting device 1 have failed according to the number of times the abnormality has occurred in the switching element Q2. Specifically, for example, the control device 40 determines that an on-abnormality has occurred once when the operation switched at the maximum on-duty continues for a predetermined time Toner, and by accumulating the number of on-abnormalities, May be counted. When the number of ON abnormalities reaches a predetermined number, the switching elements Q1 and Q2 may be prohibited from being turned on when the lighting device 1 is restarted.

  Alternatively, the control device 40 may count the “number of times of off-abnormality” by accumulating the number of times of off-abnormality, assuming that the off-abnormality occurs once when the switching element Q2 continues to be turned off for a predetermined time Tofferr. When the number of abnormalities of OFF reaches a predetermined number of times, the switching elements Q1 and Q2 may be prohibited from being turned on when the lighting device 1 is restarted.

  Alternatively, the “total number of abnormalities” that is the total value of the number of on abnormalities and the number of abnormalities in off is calculated, and when the total number of abnormalities reaches a predetermined number of times, switching is performed when the lighting device 1 is restarted. The elements Q1 and Q2 may be turned off.

  The “predetermined number of times” can be appropriately set to an integer of 2 or more, but may be set once. In addition, the predetermined number of times compared with the number of abnormalities of ON, the predetermined number of times of comparison with the number of abnormalities of OFF, and the predetermined number of times compared with the total number of abnormalities may be the same value, or may be different from each other (that is One may be larger than the other).

  As an example of the actual control process, first, the above-described process of counting the number of on-abnormalities, the number of off-abnormalities, or the total number of abnormalities is executed and stored in the storage unit 43 of the controller 40. The value stored in the storage unit 43 may be held while the lighting device 1 is turned off, may be accumulated throughout the cumulative operation period of the lighting device 1, or may be reset at regular intervals. When the lighting device 1 is restarted, a determination process is performed to determine whether or not the number of abnormality detections stored in the storage unit 43 exceeds a predetermined number. If it exceeds, the failure of the buck converter circuit 3 is determined. Switching of the boost chopper circuit 2 and the buck converter circuit 3 is not started (that is, switching is prohibited).

1 lighting device, 2 step-up chopper circuit, 3 buck converter circuit, 4 dimming signal I / F circuit, 7 AC power supply, 8 rectifier circuit, 9, 17, 23 capacitor, 10, 22 inductor, 14, 21 diode, 15, 16, 31, 32 resistance, 24 detection resistance, 26 LED, 27 LED module, 28 dimmer, 40 control device, 41, 42 control circuit, 43 storage unit, 44 A / D conversion circuit, 45 processing device, 100 illumination Appliance, 101 Virtual resistance, 102, 103 Virtual wiring, Q1, Q2 Switching element

Claims (3)

A converter circuit having a switching element;
Detecting means for detecting an LED current supplied to the LED by the converter circuit;
A control device for adjusting the on-time of the switching element based on the LED current detected by the detection means;
With
The control device protects at least one of the case where the switching element is turned off for a first predetermined time and the case where the switching element is switched at a predetermined on-duty for a second predetermined time. A lighting device that operates.   The control device counts the number of times of abnormal on, which is the number of times that the switching element is switched at the predetermined on-duty for the second predetermined time, and when the number of on-abnormality reaches a predetermined number of times. The lighting device according to claim 1, wherein switching of the switching element is prohibited.   The control device counts the number of times of abnormal off, which is the number of times the switching element has been turned off for the first predetermined time, and prohibits switching of the switching element when the number of off abnormalities reaches a predetermined number of times. The lighting device according to claim 1 or 2.

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