JP6685018B2 - Lighting device and lighting equipment - Google Patents

Description

  The present invention generally relates to a lighting device and a lighting fixture, and more particularly to a lighting device and a lighting fixture including a step-down chopper circuit.

  Conventionally, various lighting devices such as an LED power supply device have been proposed. For example, Patent Document 1 discloses an LED power supply device that lights an LED (light source) with electric power from an AC power supply (power supply). The LED power supply device of Patent Document 1 includes a switch element, and includes an output power supply adjustment circuit (step-down chopper circuit) that operates so as to extract desired power from the LED, and a drive circuit that drives the switch element.

JP2012-244737A

  In the LED power supply device of Patent Document 1, a switch element (step-down switching element) of the step-down chopper circuit may be short-circuited. When the step-down switching element is short-circuited, the voltage of the AC power supply is applied to the LED, and an overcurrent may flow in the LED. The LED power supply device of Patent Document 1 cannot detect a short circuit of the step-down switching element.

  An object of the present invention is to provide a lighting device and a lighting fixture capable of protecting a light source when a step-down switching element of a step-down chopper circuit is short-circuited.

  A lighting device according to one aspect of the present invention includes a power conversion circuit, a control circuit, and a determination circuit. The power conversion circuit has a pair of input terminals, a pair of high-voltage side and low-voltage side output terminals, a rectifier circuit, and a step-down chopper circuit. The pair of input terminals are connected to an AC power supply that outputs an AC voltage having a first frequency. The pair of high voltage side and low voltage side output terminals are connected to a light source. The rectifier circuit has a pair of high-voltage side and low-voltage side terminals, rectifies the AC voltage applied between the pair of input terminals to form a direct current between the pair of high-voltage side and low-voltage side terminals. It is configured to generate a voltage. The step-down chopper circuit has a step-down switching element electrically connected between the high-voltage side terminal and the high-voltage side output terminal. The control circuit is configured to perform a lighting operation. The lighting operation is an operation of controlling the power conversion circuit to generate a DC output voltage between the pair of high-voltage side and low-voltage side output terminals based on the AC voltage. The determination circuit is configured to determine whether a specific component having a second frequency has increased in the power supplied to the light source from the pair of high-voltage side and low-voltage side output terminals. The control circuit is configured to start a protection operation for limiting a current supplied to the light source when the determination circuit determines that the specific component has increased. The second frequency is twice the first frequency.

  A lighting fixture according to one aspect of the present invention includes the lighting device according to the above aspect, and the light source.

  The lighting device and the lighting fixture according to the aspect of the present invention have an effect of protecting the light source when the step-down switching element of the step-down chopper circuit is short-circuited.

FIG. 1 is a circuit diagram of a lighting device according to an embodiment of the present invention. FIG. 2A is an example of a filter of the lighting device. FIG. 2B is another example of the filter of the lighting device. FIG. 3 is a rear perspective view of a lighting fixture including the lighting device.

1. Embodiment FIG. 1 shows a lighting device 10 according to an embodiment of the present invention. The lighting device 10 is configured to light the light source 60 with electric power supplied from the AC power supply 50.

  The light source 60 is, for example, a DC light source that operates with DC power (DC voltage). The light source 60 is a series circuit of a plurality of light emitting elements 61. The light emitting element 61 is, for example, a solid state light emitting element (for example, an LED (light emitting diode), an organic electroluminescence element, a laser diode).

  The AC power supply 50 is, for example, a power supply that outputs AC power (AC voltage) having a predetermined frequency (first frequency). The AC power supply 50 is, for example, a commercial AC power supply having an effective value of 200V. The first frequency is, for example, 50 Hz or 60 Hz.

  The lighting device 10 includes a power conversion circuit 20, a control circuit 30, and a determination circuit 40.

  The power conversion circuit 20 includes a pair of input terminals 211 and 212 connected to the AC power supply 50, and a pair of output terminals (high voltage side and low voltage side output terminals) 221 and 222 connected to the light source 60. . The power conversion circuit 20 also includes a rectifier circuit 23, a step-up chopper circuit 24, a step-down chopper circuit 25, a filter circuit 26, and a protection circuit 27.

  The rectifier circuit 23 has a pair of input terminals 231 and 232 and a pair of output terminals (high voltage side and low voltage side terminals) 233 and 234. The rectifier circuit 23 is configured to full-wave rectify the voltage applied between the pair of input terminals 231 and 232 to generate a DC voltage at the pair of high-voltage side and low-voltage side terminals 233 and 234. The pair of input terminals 231 and 232 are electrically connected to the pair of input terminals 211 and 212, respectively. Therefore, the rectifier circuit 23 full-wave rectifies the AC voltage applied between the pair of input terminals 211 and 212 to generate a DC voltage (sine wave AC voltage between the pair of high-voltage side and low-voltage side terminals 233, 234). In the case of, pulsating voltage) is generated. The DC voltage generated between the pair of high-voltage side and low-voltage side terminals 233 and 234 has twice the frequency of the AC voltage applied between the pair of input terminals 211 and 212. The rectifier circuit 23 is, for example, a diode bridge.

  The boost chopper circuit 24 is configured to increase and output the voltage between the pair of high-voltage side and low-voltage side terminals 233 and 234 of the rectifier circuit 23. The boost chopper circuit 24 is also used as a power factor correction circuit. The boost chopper circuit 24 has, for example, a series circuit of an inductor L1 and a diode D1 which are electrically connected to the high voltage side terminal 233. The step-up chopper circuit 24 also has a switching element (step-up switching element) Q1 connected between the connection point of the inductor L1 and the diode D1 and the low-voltage side terminal 234. More specifically, the boost chopper circuit 24 includes an inductor L1, a diode D1, a switching element Q1, a resistor R1, and a capacitor C1. The inductor L1 has a first end electrically connected to the high voltage side terminal 233 of the rectifier circuit 23, and a second end electrically connected to the anode of the diode D1. The second end of the inductor L1 is electrically connected to the low voltage side terminal 234 via the series circuit of the switching element Q1 and the resistor R1. The switching element Q1 is, for example, a semiconductor switching element such as a field effect transistor (FET). The capacitor C1 is electrically connected between the cathode of the diode D1 and the output terminal 234. The voltage across the capacitor C1 becomes the output voltage of the boost chopper circuit 24. Due to the switching operation of the switching element Q1, the step-up chopper circuit 24 applies a DC voltage higher than the input voltage (voltage between the pair of high-voltage side and low-voltage side terminals 233 and 234 of the rectifier circuit 23) across the capacitor C1. Cause to. Since the configuration of the boost chopper circuit 24 is well known, detailed description will be omitted.

  The step-down chopper circuit 25 is configured to reduce and output the output voltage of the step-up chopper circuit 24. The step-down chopper circuit 25 has, for example, a switching element (step-down switching element) Q2 electrically connected between the high-voltage side terminal 233 and the high-voltage side output terminal 221. More specifically, the step-down chopper circuit 25 includes a switching element Q2, an inductor L2, a diode D2, and a capacitor C2. The switching element Q2 is, for example, a semiconductor switching element such as a field effect transistor (FET). The cathode of the diode D2 is electrically connected to the cathode of the diode D1 via the switching element Q2, and the anode thereof is electrically connected to the output terminal 234. The inductor L2 has a first end electrically connected to a connection point between the switching element Q2 and the diode D2, and a second end electrically connected to the output terminal 234 via the capacitor C2. Both ends of the capacitor C2 are electrically connected to the pair of output terminals 221 and 222, respectively. The voltage across the capacitor C2 becomes the output voltage of the step-down chopper circuit 25, which is applied to the light source 60 via the pair of output terminals 221 and 222. The step-down chopper circuit 25 produces a DC voltage lower than the input voltage (output voltage of the step-up chopper circuit 24) across the capacitor C2 by the switching operation of the switching element Q2. Since the configuration of the step-down chopper circuit 25 is well known, detailed description will be omitted.

  The filter circuit 26 is configured to remove high frequency components from the AC voltage from the AC power supply 50, for example. The filter circuit 26 includes, for example, a pair of low-pass filters inserted between the input terminal 211 and the input terminal 231, and between the input terminal 212 and the input terminal 232. The filter circuit 26 is not essential.

  The protection circuit 27 has a function of limiting the current supplied to the light source 60. The protection circuit 27 includes, for example, a switch TH1, a positive temperature coefficient thermistor (PTC thermistor) PH1, resistors R2 and R3, and an auxiliary inductor L3. The switch TH1 is electrically connected between the high voltage side terminal 233 and the inductor L1. The switch TH1 is, for example, a thyristor (three-terminal thyristor), the anode of which is electrically connected to the high-voltage side terminal 233, the cathode of which is electrically connected to the inductor L1 and the first end of the series circuit of the resistors R2 and R3. There is. The PTC thermistor PH1 is connected in parallel to the switch TH1. The auxiliary inductor L3 is magnetically coupled to the inductor L1. The auxiliary inductor L3 has a first end electrically connected to the first end of the inductor L1 and a second end electrically connected to the second end of the series circuit of the resistors R2 and R3. The gate of the switch TH1 is electrically connected to the connection point of the resistors R2 and R3. Therefore, the induced voltage of the auxiliary inductor L3 is applied to the gate of the switch TH1. Therefore, when the induced voltage of the auxiliary inductor L3 becomes equal to or higher than the predetermined voltage (breakover voltage of the switch TH1), the switch TH1 is turned on.

  Thus, the protection circuit 27 has the switch TH1 connected in series to the switching element Q2 between the high voltage side terminal 233 and the high voltage side output terminal 221. Further, the protection circuit 27 has an auxiliary inductor L3 magnetically coupled to the inductor L1, and a positive temperature coefficient thermistor PH1 connected in parallel to the switch TH1. The switch TH1 is configured to turn on when the induced voltage of the auxiliary inductor L3 becomes equal to or higher than a predetermined voltage.

  In the protection circuit 27, a current flows from the rectifier circuit 23 to the boost chopper circuit 24 through the switch TH1 while the switch TH1 is on. On the other hand, when the switch TH1 is turned off, current starts to flow from the rectifier circuit 23 to the boost chopper circuit 24 through the PTC thermistor PH1. Here, if the current continues to flow through the PTC thermistor PH1, the temperature of the PTC thermistor PH1 rises. When the temperature of the PTC thermistor PH1 exceeds the point C (Curie point), the resistance of the PTC thermistor PH1 rapidly increases. As a result, the PTC thermistor PH1 will not conduct current. When the current stops flowing through the PTC thermistor PH1, the temperature of the PTC thermistor PH1 decreases, the resistance of the PTC thermistor PH1 decreases, and the current again flows through the PTC thermistor PH1. However, the temperature of the PTC thermistor PH1 again reaches the Curie point, and the PTC thermistor PH1 stops passing current. In this way, the protection circuit 27 allows the light source 60 to be supplied with current intermittently. As a result, the protection circuit 27 limits the current supplied to the light source 60.

  With such a protection circuit 27, the current supplied to the light source 60 can be limited with a relatively simple circuit configuration. Further, the control circuit 30 can turn off the switch TH1 by using the boosting switching element Q1. Therefore, the number of parts can be reduced as compared with the case where the control circuit 30 newly provides a circuit for controlling the switch TH1.

  The control circuit 30 is configured to control the switching element Q1 of the step-up chopper circuit 24 and the switching element Q2 of the step-down chopper circuit 25. The control circuit 30 is, for example, a microcomputer, and executes an operation described later by executing a program stored in the memory.

  The control circuit 30 is configured to perform, for example, a lighting operation and a protection operation.

  The lighting operation is performed by controlling the power conversion circuit 20 and based on the voltage between the pair of high-voltage side and low-voltage side terminals 233 and 234 (that is, the AC voltage of the AC power supply 50). This is an operation of generating a DC output voltage between the output terminals 221 and 222. In particular, in the lighting operation, the control circuit 30 executes constant current control in which a constant current is supplied to the light source 60. For example, the control circuit 30 adjusts the DC output voltage so that a current having a target value flows through the light source 60. For example, the control circuit 30 has a function of detecting a current flowing through the light source 60, and adjusts the DC output voltage so that the value of the current flowing through the light source 60 becomes a target value. The target value is determined by, for example, an external signal given to the control circuit 30. The external signal is, for example, a dimming signal indicating the dimming level of the light source 60. The control circuit 30 determines the target value of the constant current according to the dimming level. The dimming level is represented by, for example, a percentage with respect to an upper limit value of a preset light output range (referred to as a usage range) of the light source 60. The current and voltage corresponding to the upper limit of the operating range are called rated current and rated voltage (or steady voltage). The control circuit 30 is configured to perform switching control of at least the step-down switching element Q2 at a predetermined switching frequency in the lighting operation. The predetermined switching frequency is selected from a predetermined frequency range according to the dimming level, for example. More specifically, the control circuit 30 is configured to control the power conversion circuit 20 by switching control of the step-up switching element Q1 and the step-down switching element Q2 in the lighting operation. That is, the control circuit 30 supplies the constant current according to the dimming level to the light source 60 by performing PWM control of the switching element Q1 and the switching element Q2 according to the dimming level.

  The protection operation is an operation of limiting the current flowing through the light source 60. In the protection operation, the control circuit 30 is configured to turn off the switch TH1. Specifically, in the protection operation, the control circuit 30 is configured to turn off the switching element Q1 so that the induced voltage of the auxiliary inductor L3 becomes less than the predetermined voltage. In this state, when current stops flowing in the switch TH1, the switch TH1 is turned off. The control circuit 30 is configured to end the protection operation when a predetermined time has elapsed after starting the protection operation. That is, the control circuit 30 ends the protection operation and restarts the lighting operation when a predetermined time has elapsed after starting the protection operation. The predetermined time is preferably a relatively short time. However, the predetermined time is set longer than the time required for the temperature of the PTC thermistor PH1 to reach the Curie point. That is, the predetermined time is set so that at least once there is a period during which no current flows in the light source 60. The predetermined time is, for example, 0.5 to 1.0 seconds. Further, the control circuit 30 is configured such that after the protection operation is executed a predetermined number of times within a specified time, the protection operation is not ended even if a predetermined time has elapsed after the protection operation was started. The predetermined number of times is preferably twice or more, for example, three times. The stipulated time is appropriately set in consideration of the predetermined number of times and the predetermined time.

  The determination circuit 40 is a circuit for determining whether or not a short circuit has occurred in the step-down switching element Q2 of the step-down chopper circuit 25. When the switching element Q2 of the step-down chopper circuit 25 is short-circuited, the step-down chopper circuit 25 does not function. As a result, it has been confirmed that the specific component appears in the electric power (voltage or current) supplied to the light source 60 from the pair of high-voltage side and low-voltage side output terminals 221 and 222. The specific component is a component (ripple component) having a frequency (second frequency) that is twice the frequency (first frequency) of the AC voltage of the AC power supply 50. It is considered that such a ripple component is caused by the DC voltage generated by the rectifier circuit 23. Therefore, the determination circuit 40 is configured to determine whether the specific component having the second frequency has increased in the power supplied to the light source 60 from the pair of high-voltage side and low-voltage side output terminals 221 and 222. It The second frequency is twice the first frequency. In the present embodiment, since the first frequency is 50 Hz or 60 Hz, the second frequency is considered to be included in the range of 100 Hz to 120 Hz, for example. In particular, the determination circuit 40 is configured to determine that the specific component has increased when the maximum value (peak value) of the specific component is equal to or greater than the threshold value. The threshold value is determined, for example, based on the maximum value (peak value) of the AC voltage of the AC power supply 50 and the DC voltage (voltage across the capacitor C1) of the boost chopper circuit 24.

  As shown in FIG. 1, the determination circuit 40 includes a filter 41 and a comparison circuit 42.

  The filter 41 is configured to pass a specific component of the electric power supplied to the light source 60. The filter 41 does not have to be configured to pass only the specific component in the strict sense. The filter 41 is a bandpass filter and has a low cutoff frequency and a high cutoff frequency. The low cutoff frequency is set to be higher than the first frequency and lower than the second frequency. Since the second frequency is considered to be included in the range of 100 Hz to 120 Hz, the low cutoff frequency is preferably lower than the lower limit value of the range of the second frequency. For example, the low cutoff frequency is set to 80 Hz or less. The high cutoff frequency is set to be higher than the second frequency and lower than the predetermined switching frequency of the step-down switching element Q2. Further, the high cutoff frequency is preferably higher than the upper limit value of the range of the second frequency. Further, the high cutoff frequency is preferably lower than the lower limit value of the predetermined switching frequency (lower limit value of the predetermined frequency range). For example, the high cutoff frequency is set to 500 Hz to 20 kHz. It suffices that the high cutoff frequency has a value capable of removing noise caused by switching control of the step-down switching element Q2. Accordingly, when the step-down switching element Q2 is not short-circuited, it is possible to suppress erroneous determination due to noise caused by the switching control of the step-down switching element Q2.

  2A and 2B show an example of the filter 41. FIG. 2A is an RLC bandpass filter. The RLC bandpass filter has an input terminal 411, an output terminal 412, an inductor L411, a capacitor C411, and a resistor R411. The inductor L411 and the capacitor C411 form a series circuit and are electrically connected between the input terminal 411 and the output terminal 412. The resistor R411 is electrically connected between the output terminal 412 and the ground. The input terminal 411 is connected between the connection point between the inductor L2 and the capacitor C2 and the high voltage side output terminal 221. The output terminal 412 is connected to the comparison circuit 42. Since the configuration of the RLC bandpass filter is well known, detailed description will be omitted. FIG. 2B shows an active bandpass filter. The active bandpass filter includes an input terminal 411, an output terminal 412, an operational amplifier 413, capacitors C412 and C413, and resistors R412 and R413. The input terminal 411 is electrically connected to the non-inverting input terminal of the operational amplifier 413. The capacitor C412 and the resistor R412 form a series circuit, and are electrically connected between the ground and the inverting input terminal of the operational amplifier 413. The capacitor C413 and the resistor R413 form a parallel circuit, and are electrically connected between the inverting input terminal and the output terminal of the operational amplifier 413. The output terminal 412 is electrically connected to the output terminal of the operational amplifier 413. Since the structure of the active bandpass filter is well known, detailed description thereof will be omitted.

  The comparison circuit 42 is configured to compare the maximum value (peak value) of the component that has passed through the filter 41 with a threshold value and output the comparison result to the control circuit 30. The component that has passed through the filter 41 includes the specific component. Therefore, the comparison circuit 42 compares the peak value of the specific component with the threshold value. In the present embodiment, the comparison circuit 42 is configured to compare the maximum value of the voltage value of the component that has passed through the filter 41 with the threshold value. The comparison circuit 42 includes, for example, a voltage detection circuit and a comparator. The voltage detection circuit is, for example, a voltage dividing circuit configured by a series circuit of resistors, and is electrically connected between the output terminal 412 of the filter 41 and the ground. The non-inverting input terminal of the comparator is electrically connected to the output terminal of the voltage detection circuit, and the inverting input terminal receives the voltage corresponding to the threshold value. The output terminal of the comparator is electrically connected to the control circuit 30. The voltage of the output terminal of the comparator (output voltage of the comparison circuit 42) is at a high level if the voltage of the non-inverting input terminal (corresponding to the peak value of the specific component) is equal to or higher than the voltage of the inverting input terminal (corresponding to the threshold value). When the voltage at the non-inverting input terminal is less than the voltage at the inverting input terminal, the level becomes low. That is, the high level of the output voltage of the comparison circuit 42 means that the determination circuit 40 has determined that the specific component has increased.

  In this way, the determination circuit 40 is configured to determine that the specific component has increased if the peak value of the component that has passed through the filter 41 is equal to or greater than the threshold value.

  When the determination circuit 40 determines that the specific component has increased, the control circuit 30 starts the protection operation. That is, the control circuit 30 performs the lighting operation when the output voltage of the comparison circuit 42 is low level, and the protection operation when the output voltage of the comparison circuit 42 is high level.

  The operation of the lighting device 10 will be described below.

  In the initial state, the output voltage of the comparison circuit 42 is low level. Therefore, the control circuit 30 starts the lighting operation. In the lighting operation, the control circuit 30 controls the switching of the switching elements Q1 and Q2 so that the current flowing through the light source 60 reaches the target value. In the initial state, the switch TH1 of the protection circuit 27 is off, but current is supplied from the rectifier circuit 23 to the boost chopper circuit 24 through the PTC thermistor PH1. Since the control circuit 30 controls the switching of the switching element Q1, electric power is stored in the inductor L1 while the switching element Q1 is on, whereby an induced voltage is generated in the auxiliary inductor L3 and the switch TH1 is turned on. After that, a current is supplied from the rectifier circuit 23 to the boost chopper circuit 24 through the switch TH1. In this way, the control circuit 30 executes the lighting operation, and lights the light source 60 with the power from the AC power supply 50. In this case, the electric power supplied to the light source 60 from the pair of high-voltage side and low-voltage side output terminals 221 and 222 contains almost no specific component, and the peak value of the specific component does not exceed the threshold value. Therefore, the output voltage of the comparison circuit 42 does not become high level, and the control circuit 30 does not execute the protection operation.

  Next, the operation of the lighting device 10 when an abnormality occurs will be described. For example, assume that the switching element Q2 of the step-down chopper circuit 25 is short-circuited. In this case, the power supplied from the pair of high-voltage side and low-voltage side output terminals 221 and 222 to the light source 60 contains the specific component. As a result, the peak value of the component that has passed through the filter 41 becomes greater than or equal to the threshold value. As a result, in the determination circuit 40, the output voltage of the comparison circuit 42 becomes high level. Therefore, the control circuit 30 ends the lighting operation and starts the protection operation. That is, the control circuit 30 ends the switching control of the switching element Q1 of the boost chopper circuit 24 and turns off the switching element Q1. As a result, the induced voltage of the auxiliary inductor L3 becomes less than the predetermined voltage. As a result, the voltage of the gate of the switch TH1 becomes less than the breakover voltage. Then, when the voltage at the high-voltage side and low-voltage side terminals 233 of the rectifying circuit 23 becomes zero, no current flows through the switch TH1, so the switch TH1 is turned off. After that, a current flows from the rectifier circuit 23 to the boost chopper circuit 24 through the PTC thermistor PH1. As a result, as described above, the current flows through the light source 60 intermittently, and the current supplied to the light source 60 is limited. Therefore, in the lighting device 10, the light source 60 can be protected when the step-down switching element Q2 of the step-down chopper circuit 25 is short-circuited.

  The control circuit 30 ends the protection operation and restarts the lighting operation when a predetermined time has elapsed after starting the protection operation. As a result, the switch TH1 is turned on, and the step-up chopper circuit 24 supplies the output voltage to the step-down chopper circuit 25. However, since the switching element Q2 is short-circuited, the peak value of the component that has passed through the filter 41 eventually becomes the threshold value or more. Therefore, the control circuit 30 ends the lighting operation and restarts the protection operation. Then, the control circuit 30 does not end the protection operation after the protection operation has been executed a predetermined number of times within a specified time, even if a predetermined time has elapsed since the start of the protection operation. This keeps the current supplied to the light source 60 limited. Therefore, the lighting operation is not repeated when an abnormality occurs, and the light source 60 can be reliably protected.

  Next, the operation of the lighting device 10 when the peak value of the component that has temporarily passed through the filter 41 due to noise or the like becomes equal to or greater than the threshold value will be described. Also in this case, the control circuit 30 ends the lighting operation and starts the protection operation. Then, the control circuit 30 ends the protection operation and restarts the lighting operation when a predetermined time has elapsed after starting the protection operation. In this case, since the switching element Q2 is not short-circuited, the step-down chopper circuit 25 functions normally, and the peak value of the component passing through the filter 41 remains below the threshold value. As a result, in the determination circuit 40, the output voltage of the comparison circuit 42 does not become high level. Therefore, the control circuit 30 continues the lighting operation. Therefore, when the peak value of the component that has passed through the filter 41 temporarily exceeds the threshold value due to noise or the like instead of abnormality, it is possible to return from the protection operation to the lighting operation.

  In this way, the lighting device 10 of the present embodiment can protect the light source 60 when the step-down switching element Q2 of the step-down chopper circuit 25 is short-circuited.

  The lighting device 10 described above is used, for example, in the lighting fixture shown in FIG. The lighting fixture of FIG. 3 includes a lighting device 10 and a light source 60 connected between a pair of high-voltage side and low-voltage side output terminals 221 and 222 of the lighting device 10. The lighting fixture of FIG. 3 is, for example, a floodlight. The lighting device 10 may be used for a lighting device other than the floodlight (for example, a base light, a spotlight, a downlight, a horizontal light). According to such a lighting fixture, the light source 60 can be protected when the step-down switching element Q2 of the step-down chopper circuit 25 is short-circuited.

2. Modifications Embodiments of the present invention are not limited to the above embodiments. The above-described embodiment can be variously modified according to the design and the like as long as the object of the present invention can be achieved.

  For example, in the above embodiment, the protection circuit 27 limits the current by intermittently supplying the current to the light source 60. In a modified example, the protection circuit 27 may be configured to stop the supply of current to the light source 60, or reduce the current supplied to the light source 60 to such a level that the light source 60 is not adversely affected. It may be configured as follows.

  For example, in the above embodiment, the switch TH1 of the protection circuit 27 is a thyristor. In a modification, the switch TH1 may be a switching element such as a field effect transistor (FET).

  For example, in the above embodiment, the control circuit 30 controls the switch TH1 using the switching element Q1 of the boost chopper circuit 24. In a modification, the control circuit 30 may be configured to directly control the switch TH1.

  For example, in the above embodiment, the control circuit 30 ends the protection operation and restarts the lighting operation when a predetermined time has elapsed after the protection operation was started. In a modification, once the control circuit 30 starts the protection operation, the control circuit 30 may continue the protection operation regardless of the predetermined time.

  For example, in the above embodiment, the determination circuit 40 is configured to determine that the specific component has increased when the peak value of the component that has passed through the filter 41 is equal to or greater than the threshold value. In a modification, the determination circuit 40 may be configured to determine that the specific component has increased when the amplitude of the component that has passed through the filter 41 is equal to or larger than a predetermined value. In this case, the comparison circuit 42 may compare the amplitude of the component passed through the filter 41 with the threshold value. For example, the comparison circuit 42 compares the maximum value of the component passed through the filter 41 with a threshold value (first threshold value), and the minimum value of the component passed through the filter 41 and a threshold value (smaller than the first threshold value by a predetermined value). 2 threshold value). In this case, the comparison circuit 42 may set the output voltage to a high level when the maximum value is the first threshold value or more and the minimum value is the second threshold value or less. The predetermined value, the first threshold value, and the second threshold value are appropriately set based on the amplitude of the specific component. For example, the predetermined value is a value corresponding to 5 to 200% of the voltage normally applied to the light source 60, preferably a value corresponding to 10%.

  For example, the filter 41 is not limited to a bandpass filter. In a modification, the filter 41 may be a high pass filter. In this case, the high pass filter is designed to have a cutoff frequency that is higher than the first frequency and lower than the second frequency. The high-pass filter is effective when noise caused by the switching control of the step-down switching element Q2 is relatively small.

  In the above embodiment, the comparison circuit 42 is configured to compare the maximum value of the voltage value of the component that has passed through the filter 41 with the threshold value. In a modification, the comparison circuit 42 may be configured to compare the maximum value of the current value of the component that has passed through the filter 41 with the threshold value. In this case, the comparison circuit 42 may include a current detection circuit instead of the voltage detection circuit. Also in this case, the determination circuit 40 may be configured to determine that the specific component has increased when the amplitude of the component that has passed through the filter 41 is equal to or larger than the predetermined value. For example, the predetermined value is a value corresponding to 5 to 500% of the current that normally flows through the light source 60, preferably a value corresponding to 20%.

  In a modified example, the light source 60 may be a parallel circuit of a plurality of light emitting elements 61. Further, the light source 60 may be composed of one light emitting element 61. That is, the light source 60 may include at least one light emitting element 61.

3. Mode As is apparent from the above-described embodiment and modification, the lighting device (10) according to the first mode of the present invention includes a power conversion circuit (20), a control circuit (30), and a determination circuit (40). , Is provided. The power conversion circuit (20) includes a pair of input terminals (211, 212), a pair of high-voltage side and low-voltage side output terminals (221, 222), a rectifier circuit (23), and a step-down chopper circuit (25). ), And have. The pair of input terminals (211 and 212) are connected to an AC power supply (50) that outputs an AC voltage having a first frequency. The pair of high-voltage side and low-voltage side output terminals (221, 222) are connected to a light source (60). The rectifier circuit (23) has a pair of high voltage side and low voltage side terminals (233, 234). The rectifier circuit (23) performs full-wave rectification on the AC voltage applied between the pair of input terminals (211 and 212) and between the pair of high-voltage side and low-voltage side terminals (233, 234). It is configured to generate a DC voltage. The step-down chopper circuit (25) has a step-down switching element (Q2) electrically connected between the high-voltage side terminal (233) and the high-voltage side output terminal (221). The control circuit (30) is configured to perform a lighting operation. The lighting operation is an operation of controlling the power conversion circuit (20) to generate a DC output voltage between the pair of high-voltage side and low-voltage side output terminals (221, 222) based on the AC voltage. . The determination circuit (40) determines whether a specific component having a second frequency has increased in the power supplied from the pair of high-voltage side and low-voltage side output terminals (221, 222) to the light source (60). Is configured to determine. The control circuit (30) is configured to start a protection operation for limiting the current supplied to the light source (60) when the determination circuit (40) determines that the specific component has increased. The second frequency is twice the first frequency. According to the first aspect, the light source (60) can be protected when the step-down switching element (Q2) of the step-down chopper circuit (25) is short-circuited.

  The lighting device (10) of the second aspect according to the present invention can be realized in combination with the first aspect. In the second aspect, the determination circuit (40) includes a filter (41) and a comparison circuit (42). The filter (41) is connected to the high voltage side output terminal (221). The comparison circuit (42) is configured to compare the peak value or amplitude of the component passed through the filter (41) with a threshold value. The determination circuit (40) is configured to determine that the specific component has increased if the peak value or the amplitude of the component that has passed through the filter (41) is equal to or greater than the threshold value. The filter (41) has a low cutoff frequency higher than the first frequency and lower than the second frequency. According to the second aspect, the specific component can be extracted with a simple configuration.

  The lighting device (10) of the third aspect according to the present invention can be realized in combination with the second aspect. In the third aspect, the control circuit (30) is configured to perform switching control of at least the step-down switching element (Q2) at a predetermined switching frequency in the lighting operation. The filter (41) has a high cutoff frequency that is higher than the second frequency and lower than the predetermined switching frequency. According to the third aspect, erroneous determination due to noise caused by switching control of the step-down switching element (Q2) can be suppressed when the step-down switching element (Q2) is not short-circuited.

  The lighting device (10) of the fourth aspect according to the present invention can be realized by a combination with any one of the first to third aspects. In a fourth aspect, the control circuit (30) is configured to end the protection operation when a predetermined time has elapsed after starting the protection operation. According to the fourth aspect, when it is erroneously determined that the specific component increases due to noise or the like instead of abnormality, it is possible to return from the protection operation to the lighting operation.

  The lighting device (10) of the fifth aspect according to the present invention can be realized in combination with the fourth aspect. In a fifth aspect, the control circuit (30) terminates the protection operation even after the predetermined time elapses after the protection operation is started after the protection operation is performed a predetermined number of times within a specified time. Configured not to. According to the fifth aspect, the lighting operation is not repeated when an abnormality occurs, and the light source (60) can be reliably protected.

  The lighting device (10) of the sixth aspect according to the present invention can be realized by a combination with any one of the first to fifth aspects. In the sixth aspect, the power conversion circuit (20) further includes a protection circuit (27). The protection circuit (27) has a switch (TH1) connected in series with the step-down switching element (Q2) between the high voltage side terminal (233) and the high voltage side output terminal (221). . The control circuit (30) is configured to turn on the switch (TH1) in the lighting operation and turn off the switch (TH1) in the protection operation. According to the sixth aspect, the current supplied to the light source (60) can be limited with a relatively simple configuration.

  The lighting device (10) of the seventh aspect according to the present invention can be realized in combination with the sixth aspect. In the seventh aspect, the power conversion circuit (20) further includes a boost chopper circuit (24). The boost chopper circuit (24) has a series circuit of an inductor (L1) and a diode (D1) electrically connected to the high voltage side terminal (233). The step-up chopper circuit (24) includes a step-up switching element (Q1) connected between a connection point between the inductor (L1) and the diode (D1) and the low-voltage side terminal (234). Have. The step-down switching element (Q2) is electrically connected to the high voltage side terminal (233) through the series circuit of the inductor (L1) and the diode (D1). The protection circuit (27) includes an auxiliary inductor (L3) magnetically coupled to the inductor (L1), and a positive temperature coefficient thermistor (PH1) connected in parallel to the switch (TH1). The switch (TH1) is configured to be turned on when the induced voltage of the auxiliary inductor (L3) becomes equal to or higher than a predetermined voltage. In the lighting operation, the control circuit (30) is configured to control the power conversion circuit (20) by switching control of the step-up switching element (Q1) and the step-down switching element (Q2). In the protection operation, the control circuit (30) is configured to turn off the boosting switching element (Q1) so that the induced voltage becomes less than the predetermined voltage. According to the seventh aspect, the switch (TH1) can be turned off by using the boosting switching element (Q1). Therefore, the number of parts can be reduced as compared with the case where the control circuit (30) newly provides a circuit for controlling the switch (TH1).

  An illuminator according to an eighth aspect of the present invention includes the lighting device (10) according to any one of the first to seventh aspects, and the light source (60). According to the eighth aspect, the light source (60) can be protected when the step-down switching element (Q2) of the step-down chopper circuit (25) is short-circuited.

10 Lighting device 20 Power conversion circuit 23 Rectifier circuit 24 Step-up chopper circuit 25 Step-down chopper circuit 27 Protection circuit 30 Control circuit 40 Judgment circuit 41 Filter 42 Comparison circuit 50 AC power supply 60 Light source 211, 212 Input terminal 221 High voltage side output terminal 222 Low Voltage side output terminal 233 High voltage side terminal 234 Low voltage side terminal L1 Inductor L3 Auxiliary inductor PH1 Positive characteristic thermistor Q1 Step-up switching element Q2 Step-down switching element TH1 switch

Claims (8)

A pair of input terminals connected to an AC power source that outputs an AC voltage of the first frequency, a pair of high-voltage side and low-voltage side output terminals connected to the light source, and a pair of high-voltage side and low-voltage side terminals. A rectifying circuit that full-wave rectifies the AC voltage applied between the pair of input terminals to generate a DC voltage between the pair of high-voltage side and low-voltage side terminals, the high-voltage side terminal, and the A step-down chopper circuit having a step-down switching element electrically connected between the high-voltage side output terminal, and a power conversion circuit having:
A control circuit that controls the power conversion circuit to perform a lighting operation that generates a DC output voltage between the pair of high-voltage side and low-voltage side output terminals based on the AC voltage;
A determination circuit that determines whether or not a specific component having a second frequency has increased in the power supplied to the light source from the pair of high-voltage side and low-voltage side output terminals;
Equipped with
When the determination circuit determines that the specific component has increased, the control circuit is configured to start a protection operation that limits a current supplied to the light source,
The second frequency is twice the first frequency,
Lighting device. The determination circuit is
A filter connected to the high voltage side output terminal,
A comparison circuit that compares the peak value or amplitude of the component that has passed through the filter with a threshold value;
Equipped with
If the peak value or the amplitude of the component passed through the filter is equal to or more than the threshold value, it is configured to determine that the specific component has increased,
The filter has a low cutoff frequency higher than the first frequency and lower than the second frequency,
The lighting device according to claim 1. The control circuit is configured to perform switching control of at least the step-down switching element at a predetermined switching frequency in the lighting operation,
The filter has a high cutoff frequency that is higher than the second frequency and lower than the predetermined switching frequency,
The lighting device according to claim 2. The control circuit is configured to end the protection operation when a predetermined time has elapsed after starting the protection operation.
The lighting device according to claim 1. The control circuit is configured such that after performing the protection operation a predetermined number of times within a prescribed time, the protection operation is not terminated even if the predetermined time has elapsed after starting the protection operation,
The lighting device according to claim 4. The power conversion circuit further includes a protection circuit,
The protection circuit has a switch connected in series to the step-down switching element between the high-voltage side terminal and the high-voltage side output terminal,
The control circuit is configured to turn on the switch in the lighting operation and turn off the switch in the protection operation.
The lighting device according to any one of claims 1 to 5. The power conversion circuit further has a boost chopper circuit,
The boost chopper circuit is connected between a series circuit of an inductor and a diode electrically connected to the high-voltage side terminal, a connection point of the inductor and the diode, and the low-voltage side terminal. And a switching element for boosting
The step-down switching element is electrically connected to the high-voltage side terminal via the series circuit of the inductor and the diode,
The protection circuit includes an auxiliary inductor magnetically coupled to the inductor, and a positive temperature coefficient thermistor connected in parallel to the switch,
The switch is configured to be turned on when the induced voltage of the auxiliary inductor becomes equal to or higher than a predetermined voltage,
In the lighting operation, the control circuit is configured to control the power conversion circuit by switching control of the step-up switching element and the step-down switching element,
In the protection operation, the control circuit is configured to set the induced voltage to be less than the predetermined voltage by turning off the boost switching element.
The lighting device according to claim 6. A lighting device according to any one of claims 1 to 7,
The light source,
With
lighting equipment.

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