JP2012014879A - Lighting device for semiconductor light emitting element, and luminaire using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stop operation or suppress an output of a power factor improving circuit 1 which becomes unnecessary or harmful when a semiconductor light emitting element 4 has abnormality such as an open circuit and a short circuit, in a lighting device which supplies current from an AC power source to the semiconductor light emitting element 4 through a power factor improving circuit 1 like a step-up chopper circuit 1a and a power conversion circuit 2 like a step-down chopper circuit.SOLUTION: The lighting device for the semiconductor light emitting element includes the power factor improving circuit 1 connected to the AC power source Vs, the power conversion circuit 2 which power-converts the output of the power factor improving circuit 1 to supply the current to the semiconductor light emitting element 4, an abnormality detection circuit 7 which detects abnormality of the semiconductor light emitting element 4, and a control circuit 8 which stops the operation of the power factor improving circuit 1 or suppresses the output when the abnormality detection circuit 7 detects the abnormality.

Description

  The present invention relates to a lighting device for a semiconductor light-emitting element for lighting a semiconductor light-emitting element such as a light-emitting diode with a commercial power source at a high power factor, and a lighting fixture using the same.

  Conventionally, as shown in FIG. 9, a commercial AC power supply Vs is converted into a DC voltage by a rectifying / smoothing circuit including a full-wave rectifier DB and a smoothing capacitor C1, and the DC voltage is stepped down by a step-down chopper circuit 2a to light an LED. An LED lighting device is known. Conventionally, many LED lighting devices of this type have a relatively small input current. Therefore, even if a capacitor input type rectifying and smoothing circuit as shown in FIG. There was no. However, in recent years, LED lighting devices tend to be used for main lighting, and input current per appliance tends to increase. Moreover, when all the lights in the building are replaced with LED lighting, a large number of appliances are connected to the commercial power line in parallel. Therefore, if a capacitor input type rectifying and smoothing circuit is used, the input power factor is reduced. It becomes a problem.

  Therefore, as shown in FIG. 10, the commercial AC power source Vs is converted into a DC voltage boosted by the boost chopper circuit 1a, and the boosted DC voltage is stepped down by the step-down chopper circuit 2a to turn on the LED. Devices have come to be used (Patent Document 1). The step-up chopper circuit 1a has a power factor improving function, and the input current waveform can be made substantially proportional to the input voltage waveform if a high-frequency component due to switching is appropriately removed by a filter circuit.

  In addition, since LED lighting is a power-saving, environmentally conscious lighting, it is necessary to spread it at low cost all over the world. For this purpose, it is desired to use a circuit that can be commonly used in countries with different power supply voltages. In the capacitor input type rectifying and smoothing circuit as shown in FIG. 9, when the commercial AC power supply has a different voltage, for example, 100V to 220V, the DC voltage after the rectifying and smoothing also differs. On the other hand, in the configuration shown in FIG. 10, if the output voltage of the step-up chopper circuit 1a is set to, for example, 300V to 400V, even if the voltage of the commercial AC power supply is different, a common circuit can be used.

  As described above, the LED lighting device having the step-up chopper circuit at the front stage of the LED lighting step-down chopper circuit has a high input power factor as viewed from the commercial AC power source and has high resistance to fluctuations in the power source voltage. Opportunities for hiring will increase.

JP 2010-40878 A

  However, when the LED lighting step-down chopper circuit has a constant current control function, if the LED is broken, the output voltage of the step-down chopper circuit rises to the output voltage of the step-up chopper circuit. There is. As shown in FIG. 10, the step-down chopper circuit 2a is generally provided with a smoothing capacitor C2 in the output section, but the withstand voltage of the smoothing capacitor C2 is equivalent to that of the output capacitor C1 of the step-up chopper circuit 1a. If it has, it becomes a factor of a cost increase.

  Accordingly, it is considered that when the LED is disconnected, if the step-up chopper circuit itself is stopped, an increase in the output voltage of the step-down chopper circuit when the LED is disconnected can be suppressed. In that case, the input power factor improvement function stops, but improvement of the input power factor is necessary in the first place when the input current is large. However, when the LED is disconnected and the current consumption becomes substantially zero, the input power factor is improved. The rate improvement function is no longer needed.

  Further, if the LED lighting step-down chopper circuit does not have a constant current control function, an excessive current will flow if the LED is short-circuited. In such a case, the step-down chopper circuit should be stopped promptly. However, if the output voltage of the step-up chopper circuit is also reduced at the same time, it is considered that safety is further improved.

  The present invention has been made based on such knowledge, and supplies current to a semiconductor light emitting element from an AC power source via a power factor correction circuit such as a step-up chopper circuit and a power conversion circuit such as a step-down chopper circuit. An object of the present invention is to make it possible to stop or suppress the output of a power factor correction circuit that is useless or harmful when a semiconductor light emitting element such as a disconnection or a short circuit is abnormal.

  In order to solve the above problem, the invention of claim 1 is a semiconductor which converts power factor improving circuit 1 connected to AC power source Vs and output of power factor improving circuit 1 to power as shown in FIG. The power conversion circuit 2 that supplies current to the light emitting element 4, the abnormality detection circuit 7 that detects an abnormality of the semiconductor light emitting element 4, and the operation of the power factor correction circuit 1 is stopped when an abnormality is detected by the abnormality detection circuit 7. Or it has the control circuit 8 which suppresses an output, It is characterized by the above-mentioned.

  According to a second aspect of the present invention, in the lighting device for a semiconductor light emitting element according to the first aspect, the abnormality detection circuit 7 detects the opening of the semiconductor light emitting element 4 or the opening of the wiring from the power conversion circuit 2 to the semiconductor light emitting element 4 as an abnormality. It is characterized by doing.

  According to a third aspect of the present invention, in the lighting device for a semiconductor light emitting element according to the first aspect, the abnormality detection circuit 7 detects a short circuit of the semiconductor light emitting element 4 or a short circuit of the wiring from the power conversion circuit 2 to the semiconductor light emitting element 4 as an abnormality. It is characterized by doing.

  The invention of claim 4 is a lighting apparatus comprising the semiconductor light emitting element lighting device according to any one of claims 1 to 3 and the semiconductor light emitting element supplied with a current from the lighting device (FIG. 8).

  According to the present invention, in a lighting device for supplying a current from an AC power source to a semiconductor light emitting element via a power factor correction circuit and a power conversion circuit, the power conversion circuit can be used when an abnormality occurs such as when the semiconductor light emitting element is open or shorted. Since the operation of the power factor correction circuit in the previous stage is stopped or the output is suppressed, useless power consumption does not occur. Further, when the power factor correction circuit has a boosting function, there is an advantage that the input voltage of the power conversion circuit can be reduced at the time of abnormality.

It is a circuit diagram of Embodiment 1 of the present invention. It is a circuit diagram which shows the specific example of the power converter circuit used for Embodiment 1 of this invention. It is a circuit diagram of Embodiment 2 of the present invention. It is a circuit diagram of Embodiment 3 of the present invention. It is a circuit diagram of Embodiment 4 of the present invention. It is a circuit diagram of Embodiment 5 of the present invention. It is a circuit diagram of Embodiment 6 of the present invention. It is sectional drawing which shows schematic structure of the lighting fixture of Embodiment 7 of this invention. FIG. 6 is a circuit diagram of Conventional Example 1. FIG. 10 is a circuit diagram of Conventional Example 2.

(Embodiment 1)
FIG. 1 is a circuit diagram of a lighting device according to Embodiment 1 of the present invention. A step-up chopper circuit 1a is connected as a power factor correction circuit 1 to a DC output terminal of a rectifier DB for full-wave rectification of the commercial AC power supply Vs. The input terminal AB of the power conversion circuit 2 is connected to the output terminal of the boost chopper circuit 1a. A semiconductor light emitting element 4 is connected between output terminals CD of the power conversion circuit 2 via an output connector 5.

  Here, the semiconductor light emitting element 4 may be an LED module in which a plurality of LEDs (light emitting diodes) are connected in series, in parallel, or in series-parallel. When the forward voltage per LED is Vf and the number of LEDs in series is n, the voltage across the semiconductor light emitting element 4 is n × Vf. If the semiconductor light emitting element 4 is properly connected to the output connector 5, the voltage across the output terminals CD of the power conversion circuit 2 is clamped to n × Vf.

  The output connector 5 and the semiconductor light emitting element 4 are connected by a lead wire or the like. When the lead wire is disconnected, the contact failure of the output connector 5 or the LED is disconnected inside the semiconductor light emitting element 4, the output connector 5 is opened. At this time, the both-ends voltage between the output terminals C-D of the power conversion circuit 2 is not clamped to n × Vf, and becomes a no-load voltage higher than normal. In particular, when the power conversion circuit 2 has a constant current control function, the no-load voltage rises to an abnormally high level compared to the normal time. Therefore, in order to detect such a load opening abnormality, a voltage detection unit 6 and an abnormality detection circuit 7 are provided.

  The voltage detection unit 6 includes a resistance voltage dividing circuit and the like, detects a voltage across the output terminals C-D of the power conversion circuit 2, and inputs the detected voltage to the abnormality detection circuit 7. The abnormality detection circuit 7 is composed of a voltage comparator or the like, and when the detection voltage by the voltage detection unit 6 becomes abnormally higher than normal, it is determined that a load opening abnormality has occurred, and an abnormality detection signal is output to the stop control circuit 8 To do. The stop control circuit 8 is formed of a latch circuit such as a flip-flop whose output is inverted upon receiving an abnormality detection signal, and stops the operation of the power factor correction circuit 1 by the output held in the latch circuit.

  The abnormality detection circuit 7 is not limited to detecting a load opening abnormality, and may be configured to detect a load short circuit abnormality. For example, when the terminals of the output connector 5 are short-circuited, the lead wire between the output connector 5 and the semiconductor light-emitting element 4 is short-circuited, or a short-circuit occurs inside the semiconductor light-emitting element 4, the output terminal of the power conversion circuit 2 The voltage across C-D is abnormally low compared to normal. In such a case, the abnormality detection circuit 7 determines that a load short-circuit abnormality has occurred, and outputs an abnormality detection signal to the stop control circuit 8. The stop control circuit 8 receives the abnormality detection signal and stops the operation of the power factor correction circuit 1.

  In the present embodiment, the power factor correction circuit 1 is composed of a boost chopper circuit 1a. The configuration and operation of the step-up chopper circuit 1a are well known, and the switching element Q1 is turned on and off at a sufficiently high frequency (for example, several tens of kHz) compared to the frequency (50/60 Hz) of the commercial AC power supply Vs. A high-frequency current is drawn from the AC power source Vs through the filter circuit 9, and the input power factor is improved. Specifically, when the switching element Q1 is turned on, the input current flows through the path of the commercial AC power supply Vs → filter circuit 9 → full wave rectifier DB → inductor L1 → switching element Q1 → full wave rectifier DB → filter circuit 9 → commercial AC power supply Vs. . When the switching element Q1 is turned off, the counter electromotive voltage generated across the inductor L1 is superimposed on the output voltage of the full-wave rectifier DB, and the commercial AC power supply Vs → filter circuit 9 → full-wave rectifier DB → inductor L1 → diode D1 → The input current flows through the path of the smoothing capacitor C1, the full-wave rectifier DB, the filter circuit 9, and the commercial AC power source Vs. As a result, a high-frequency input current can be passed at the peak (near the peak) or the valley (near the zero cross) of the commercial AC power supply Vs, and the input current pause period can be eliminated.

  The filter circuit 9 is a low-pass filter circuit that removes a high-frequency component due to the switching operation of the switching element Q1 and allows a commercial frequency current to pass therethrough. By removing the high-frequency component of the input current by the filter circuit 9, the input current waveform viewed from the commercial AC power supply Vs can be a sine wave that is substantially proportional to the input voltage waveform, thereby increasing the input power factor, A power supply device with less input current harmonic distortion can be obtained.

  The high frequency switching operation of the switching element Q1 is controlled by the PFC control circuit 3a. Here, PFC (Power Factor Correction) control, in a narrow sense, means that the input current from the power supply is controlled to be a sine wave having substantially the same phase as the input voltage. If it has a function to improve the input power factor as compared with the capacitor input type rectifying and smoothing circuit (conventional example of FIG. 9) by shortening the pause period, it is included in the PFC control.

  The PFC control circuit 3a may be self-excited or separately-excited, but in the configuration example of FIG. 1, it is assumed that start / stop can be controlled by an external signal. When the load detection or the load short circuit is detected by the abnormality detection circuit 7, the stop control circuit 8 gives a stop signal to the PFC control circuit 3a to stop the control signal from the PFC control circuit 3a to the switching element Q1, The switching operation of the switching element Q1 is stopped. Then, the operation is the same as that of a normal rectifying / smoothing circuit (see FIG. 9), the input current flows only near the peak value of the pulsating voltage output from the full-wave rectifier DB, and the input power factor decreases. Further, when the commercial AC power supply Vs is 100V (effective value), when the step-up chopper operation is stopped, the charging voltage of the capacitor C1 is about 140V. On the other hand, since the charging voltage of the capacitor C1 is about 300 to 400 V during the boost chopper operation, the voltage applied to the power conversion circuit 2 can be significantly reduced by stopping the boost chopper operation.

  The specific configuration for stopping the operation of the power factor correction circuit 1 by the stop control circuit 8 is not limited. In the configuration example of FIG. 1, the stop operation of the PFC control circuit 3a is stopped by giving a stop signal from the stop control circuit 8 to the PFC control circuit 3a, but the oscillation operation of the PFC control circuit 3a is continued. The control signal of the switching element Q1 may be cut off. For example, a semiconductor switch element that can be turned on by a stop signal from the stop control circuit 8 is connected in parallel between the control electrode of the switching element Q1 and the ground, and the semiconductor switch element is turned on to bring the control electrode of the switching element Q1 to the ground level. It is also possible to use a means for interrupting the control signal by short-circuiting the control signal.

  The specific configuration of the power conversion circuit 2 is not limited. In addition to the step-down chopper circuits 2a and 2b as shown in FIG. 2A or 2B, a flyback converter as shown in FIG. A circuit 2c, a forward converter circuit 2d as shown in FIG. In any configuration, when the switching element Q2 is turned on / off at a high frequency, the input DC voltage is converted into a voltage and a DC output voltage is generated in the output capacitor C2.

  Further, when the semiconductor light emitting element 4 has a configuration capable of AC input, for example, when it has a configuration in which a pair of LED series circuits are connected in reverse parallel, or when the input section is provided with a diode bridge for nonpolarization Alternatively, the power conversion circuit 2 may be an orthogonal conversion circuit (inverter circuit).

(Embodiment 2)
FIG. 3 is a circuit diagram of the lighting device according to the second embodiment of the present invention. In the present embodiment, a specific configuration example of the abnormality detection circuit 10 for detecting a load opening abnormality or a load short-circuit abnormality will be described. A case will be described in which the power factor correction circuit 1 operates to suppress the output when a load abnormality is detected.

  The abnormality detection circuit 10 includes a Zener diode ZD1 for detecting a load release and a Zener diode ZD2 for detecting a load short circuit. When the load release abnormality occurs, the Zener diode ZD1 becomes conductive, a current flows through the resistors R6 and R7, the light emitting element of the photocoupler PC1 generates an optical signal, and the light receiving element of the photocoupler PC1 becomes conductive. When a load short circuit abnormality occurs, the Zener diode ZD2 is turned on, a current flows through the resistors R8 and R9, the light emitting element of the photocoupler PC2 generates an optical signal, and the light receiving element of the photocoupler PC2 is turned on. .

  A boost chopper circuit 1a is connected as a power factor correction circuit 1 to a DC output terminal of a full-wave rectifier DB that rectifies the commercial AC power supply Vs. The output voltage is divided by resistors R1 and R2 and input to the PFC control circuit 3a. The PFC control circuit 3a controls the on-pulse width of the switching element Q1 so that the voltage divided by the resistors R1 and R2 becomes a constant voltage. A parallel circuit of light receiving elements of the photocouplers PC1 and PC2 and a series circuit of the resistor R0 are connected in parallel to the resistor R1. As described above, the photocoupler PC1 is for load release detection, and the photocoupler PC2 is for load short-circuit detection, and operates to increase the voltage dividing ratio of the resistors R1 and R2 when the Zener diodes ZD1 and ZD2 are turned on, respectively. To do.

  When normal, that is, when there is no load opening abnormality or load short-circuit abnormality, the Zener voltage is set so that the Zener diodes ZD1 and ZD2 do not conduct. For this reason, during normal operation, the output voltage Vc1 of the capacitor C1 is controlled to be a constant value (for example, 300 V) by the voltage dividing ratio of the resistors R1 and R2.

  The semiconductor light emitting element 4 is composed of a series circuit of a plurality of LEDs. If the forward voltage of one LED is 3.5V and the number n in series is 30, the total voltage is n × Vf = 105V. The Zener voltage Vzd1 of the Zener diode ZD1 is set slightly higher than this n × Vf. Therefore, if there is no load release abnormality, the Zener diode ZD1 does not conduct, and the light emitting element of the photocoupler PC1 does not generate an optical signal.

  Further, when the voltage of the semiconductor light emitting element 4 in a normal state is 105V and the output voltage Vc1 of the capacitor C1 is 300V, the difference voltage: 300−105 = 195V is applied between the negative electrode of the capacitor C2 and the negative electrode of the capacitor C1. Will be. The Zener voltage Vzd2 of the Zener diode ZD2 for detecting a load short circuit is set slightly higher than this voltage. Therefore, if there is no load short circuit abnormality, the Zener diode ZD2 is not conducted, and the light emitting element of the photocoupler PC2 does not generate an optical signal.

  On the other hand, when a load release abnormality occurs, the voltage across the capacitor C2 rises and the Zener diode ZD1 becomes conductive. As a result, the light emitting element of the photocoupler PC1 generates an optical signal and the light receiving element of the photocoupler PC1 is turned on, so that the resistor R0 is connected in parallel to the resistor R1, and the voltage dividing ratio is increased. Further, when a load short circuit abnormality occurs, the voltage applied between the negative electrode of the capacitor C2 and the negative electrode of the capacitor C1 rises, so that the Zener diode ZD2 becomes conductive. As a result, the light emitting element of the photocoupler PC2 generates an optical signal and the light receiving element of the photocoupler PC2 is turned on, so that the resistor R0 is connected in parallel to the resistor R1, and the voltage dividing ratio is increased. Then, the PFC control circuit 3a determines that the voltage Vc1 of the capacitor C1 has increased, and controls the direction in which the output voltage Vc1 is decreased by narrowing the on-pulse width of the switching element Q1. That is, the power factor correction circuit 1 operates so as to suppress the output when a load abnormality such as a load release or a load short circuit is detected.

  Note that the Zener diodes ZD1 and ZD2 for detecting a load opening abnormality or a load short-circuit abnormality may be a plurality of Zener diodes connected in series or other constant voltage elements. Further, the voltage after being divided by the resistance voltage dividing circuit may be detected.

  In the present embodiment, the step-down chopper circuit 2b shown in FIG. 2B is connected to the output terminal of the power factor correction circuit 1 as a power conversion circuit. A current detection resistor R3 is connected in series to the switching element Q2 of the step-down chopper circuit 2b, and a control signal is supplied to the control electrode of the switching element Q2 from the output control circuit 3b.

  The output control circuit 3b outputs a signal for performing on / off control of the switching element Q2 at a high frequency. When the switching element Q2 is on, current flows through a path of the capacitor C1, the capacitor C2, the inductor L2, the switching element Q2, the current detection resistor R3, and the capacitor C1, and energy is accumulated in the inductor L2. When the switching element Q2 is turned off, the regenerative current flows through the path of the inductor L2, the diode D2, the capacitor C2, and the inductor L2 due to the energy stored in the inductor L2. As a result, a DC voltage obtained by stepping down the voltage of the capacitor C1 is charged in the capacitor C2.

  The output control circuit 3b detects the current flowing through the switching element Q2 by the current detection resistor R3. When the detected value reaches a predetermined value, the output control circuit 3b turns off the switching element Q2. That is, the off-timing control of the switching element Q2 is peak current control. Control when turning on the switching element Q2 again after turning it off, that is, on-timing control of the switching element Q2 may be either the continuous mode or the discontinuous mode described below, but is preferably the critical mode.

  Here, the continuous mode is a control mode in which the switching element Q2 is turned on while the regenerative current is flowing through the diode D2, and an instantaneous large current flows through the switching element Q2 during the reverse recovery time of the diode D2. As a result, the switching loss increases.

  The discontinuous mode is a control mode in which the switching element Q2 is turned on through a predetermined current quiescent period after the regenerative current of the diode D2 has finished flowing, and the current peak value is high due to the occurrence of the current quiescent period. However, the current average value is low, and the efficiency is poor.

  The critical mode is a control mode in which the switching element Q2 is turned on when it is detected that the regenerative current of the diode D2 has finished flowing, and the switching element Q2 is turned on when the reverse recovery time of the diode D2 has elapsed. , Switching loss is reduced. If the inductor L2 is used in a range where magnetic saturation does not occur, 1/2 of the current peak value becomes the current average value. Therefore, the current average value is controlled to be constant only by controlling the current peak value to be constant. It is suitable for constant current control. The critical mode is sometimes called a boundary mode or zero-cross mode.

  In order to realize the control in the critical mode, it is necessary to detect the timing when the regenerative current of the diode D2 has finished flowing. For example, a rise in the voltage across the diode D2 may be detected, or a drop in the drain voltage of the switching element Q2 may be detected. However, a secondary winding is provided in the inductor L2, and the timing of disappearance of the secondary winding output is detected. Is the simplest to detect.

  In the present embodiment, when the switching element Q2 is controlled to be switched in the critical mode, the switching operation of the high frequency (tens of kHz to several tens of kHz) is performed according to the low frequency (several hundred Hz to several kHz) PWM signal. The light control operation is realized by stopping the operation intermittently. The low-frequency PWM signal is a rectangular wave voltage signal of 1 kHz, for example, and is in an oscillation stop state when it is at the H level and in an oscillation permission state when it is at the L level. Even if the PWM signal always becomes L level due to disconnection of the dimming signal line or other failure, it can be used in a fully lit state.

  Note that other methods may be used as the dimming control method. For example, the load current may be constant-current controlled by converting a low-frequency PWM signal into a DC voltage by a CR integration circuit and using the converted DC voltage as a target value for current feedback control.

  In any case, when the step-down chopper circuit 2b performs constant current control and an abnormal load release occurs, the output voltage rises to increase the current. In the worst case, the voltage of the capacitor C2 rises to a voltage equivalent to the voltage of the capacitor C1. Therefore, if there is an abnormal load release, the abnormality detection circuit 10 detects it and suppresses the output of the power factor correction circuit 1. As a result, the voltage of the capacitor C1 is lowered, so that the voltage increase of the capacitor C2 can be suppressed. As a result, an element with a low withstand voltage can be used as the capacitor C2, and the cost of the lighting device can be reduced.

  In addition, when there is a load short-circuit abnormality, when the step-down chopper circuit 2b performs constant current control, there is no fear that an excessive current flows, but if the voltage of the capacitor C1 remains high, the step-down chopper circuit Extra stress is added to 2b. Accordingly, in this case as well, the stress of the step-down chopper circuit 2b can be reduced by detecting by the abnormality detection circuit 10 and suppressing the output of the power factor correction circuit 1.

(Embodiment 3)
FIG. 4 is a circuit diagram of a lighting device according to Embodiment 3 of the present invention. In the second embodiment described above, the disconnection of the semiconductor light emitting element 4 is detected by increasing the output voltage of the step-down chopper circuit. In this embodiment, however, the disconnection of the semiconductor light emitting element 4 is detected by cutting off the output current of the step-down chopper circuit. The point of detection is different. In the second embodiment, the switching element Q2 of the step-down chopper circuit 2b is provided on the low potential side. In the present embodiment, the switching element Q2 of the step-down chopper circuit 2a is provided on the high potential side. . Further, in the present embodiment, details of an external circuit of the PFC control circuit 3a will be described. 3 and 4, the filter circuit 9 is not shown.

  The PFC control circuit 3a that controls the switching element Q1 of the step-up chopper circuit 1a detects the pulsating voltage output from the full-wave rectifier DB by dividing it with the resistors R11 and R12, and the peak value of the chopper current flowing through the switching element Q1. The envelope is controlled so as to be approximately proportional to the pulsating voltage waveform. For this purpose, the source current of the switching element Q1 is detected by voltage conversion by the resistor R13, and when the detected voltage reaches a target value that is substantially proportional to the pulsating voltage, the switching element Q1 is controlled to be turned off. Further, when the charging voltage of the smoothing capacitor C1 is detected by dividing by the resistors R1 and R2, and the charging voltage of the smoothing capacitor C1 is low, the target value is set high in order to increase the ON time width of the switching element Q1. On the contrary, when the charging voltage of the smoothing capacitor C1 is high, the target value is set low in order to shorten the ON time width of the switching element Q1. Further, the disappearance (zero crossing) of the regenerative current flowing through the inductor L1 is detected based on the presence or absence of the secondary winding voltage of the inductor L1, and the switching element Q1 is controlled to be turned on again when the regenerative current disappears. Such a PFC control circuit 3a can be constructed at low cost using a general-purpose integrated circuit (for example, L6562 manufactured by STMicroelectronics).

  In this embodiment, the control power supply voltage Vcc of the PFC control circuit 3a is supplied from the secondary winding of the inductor L2 connected in series with the semiconductor light emitting element 4, and when the semiconductor light emitting element 4 is disconnected, the inductor L2 The PFC control circuit 3a is configured to automatically stop when the secondary winding output disappears.

  When the power is turned on, since the PFC control circuit 3a is not supplied with the control power supply voltage Vcc, the boost chopper circuit 1a is not operating. Therefore, the smoothing capacitor C1 is charged via the inductor L1 and the diode D1 by the pulsating voltage output from the full-wave rectifier DB, and becomes a voltage of about 140 V near the peak value of the pulsating voltage. Compared with this voltage, the voltage drop (the above-mentioned n × Vf) of the semiconductor light emitting element 4 is set low. For this reason, a weak starting current flows through the path of the smoothing capacitor C1, the current limiting resistor R10, the diode D5, the power supply capacitor C4, the inductor L2, and the semiconductor light emitting element 4, and the voltage of the power supply capacitor C4 rises. When the voltage of the power supply capacitor C4 rises to the operable voltage of the output control circuit 3b, the on / off operation of the switching element Q2 is started.

  When the switching element Q2 is turned on, current flows through the path of the smoothing capacitor C1, the switching element Q2, the current detection resistor R3, the inductor L2, and the semiconductor light emitting element 4, and energy is accumulated in the inductor L2. The current flowing through the switching element Q2 is monitored as a voltage value of the current detection resistor R3 by the output control circuit 3b, and when it reaches a predetermined peak value, the switching element Q2 is turned off.

  When the switching element Q2 is turned off, the regenerative current flows through the path of the inductor L2, the semiconductor light emitting element 4, and the regenerative diode D2 due to the energy stored in the inductor L2, and the energy of the inductor L2 is released. The output control circuit 3b monitors the secondary winding voltage of the inductor L2, and when the secondary winding voltage disappears, the switching element Q2 is turned on again, assuming that the energy emission of the inductor L2 is completed.

  As a result, since a high-frequency triangular wave current flows through the inductor L2, the power supply capacitor C3 on the low potential side is charged via the diode D3 by the secondary winding output. The conduction polarity of the diode D3 is generally on the flyback side (when the diode D2 is on), but may be on the forward side (when the switching element Q2 is on). The voltage of the capacitor C3 is regulated by the Zener diode ZD3 and is supplied to the PFC control circuit 3a as the control power supply voltage Vcc. When the power supply voltage Vcc of the PFC control circuit 3a reaches the operable voltage, the switching element Q1 starts to be turned on and off, and the boost chopper circuit 1a operates, so that the voltage of the smoothing capacitor C1 is a boosted voltage (for example, 300V to 400V). )

  Further, the power supply capacitor C4 on the high potential side is charged via the diode D4 by another secondary winding output. The conduction polarity of the diode D4 is generally on the flyback side (when the diode D2 is conductive), but may be on the forward side (when the switching element Q2 is conductive). Further, the conduction polarity of the diode D3 and the conduction polarity of the diode D4 may be reversed or the same polarity. The voltage of the capacitor C4 is regulated by the Zener diode ZD4 and supplied to the output control circuit 3b as the control power supply voltage HVcc on the high potential side. For this reason, the current limiting resistor R10 only needs to be able to supply a weak DC current for starting, and an element having a high resistance value can be used. The diode D5 is inserted so that the charge of the capacitor C4 is not wasted when the switching element Q2 is turned on, but may be omitted if the resistor R10 has a sufficiently high resistance.

  Here, when the semiconductor light-emitting element 4 is disconnected, no current flows through the inductor L2, so that the voltage of the power supply capacitor C3 charged by the secondary winding output decreases. When the voltage Vcc of the power supply capacitor C3 becomes lower than the operable voltage of the PFC control circuit 3a, the PFC control circuit 3a stops the control signal to the switching element Q1, so that the boost chopper circuit 1a stops its operation. Then, the voltage of the capacitor C1 drops to near the peak value (about 140V) of the pulsating voltage of the full-wave rectifier DB.

  At the same time, the power supply capacitor C4 on the high potential side charged by the other secondary winding output of the inductor L2 also loses the charging current, and the charging voltage HVcc is lowered. Moreover, since the semiconductor light emitting element 4 is disconnected, the charging path via the resistor R10 and the diode D5 is also cut off, so that the voltage of the power supply capacitor C4 continues to decrease. When the voltage of the power supply capacitor C4 becomes lower than the operable voltage of the output control circuit 3b, the output control circuit 3b stops the control signal to the switching element Q2, so that the step-down chopper circuit 2a also stops operating.

  As described above, in the present embodiment, when the semiconductor light emitting element 4 is disconnected, neither the PFC control circuit 3a nor the output control circuit 3b operates, so that the boost chopper circuit 1a as the power factor correction circuit and the power conversion circuit are used. Both step-down chopper circuits 2a are maintained in a stopped state.

(Embodiment 4)
FIG. 5 is a circuit diagram of a lighting device according to Embodiment 4 of the present invention. In the present embodiment, a DC-DC conversion circuit that rectifies and smoothes the high-frequency AC output of the two-stone inverter circuit is adopted as the power conversion circuit 2e, and one of the switching elements Q1 is also used as the switching element of the boost chopper circuit. The reverse diode of the other switching element Q2 is also used as a diode of the boost chopper circuit. Further, the presence or absence of a current flowing through the semiconductor light emitting element 4 is detected by the transistor Tr1, and on / off of the control power cutoff transistor Tr2 is controlled according to the detection result.

  The two switching elements Q1 and Q2 are controlled so as to be alternately turned on and off at a high frequency by the control circuit 3c. However, since the control power supply voltage Vcc is not supplied immediately after the power is turned on, the switching elements Q1 and Q2 are both turned off. It is. In this state, due to the pulsating voltage output from the full-wave rectifier DB, a charging current flows through the path of the inductor L1 → the reverse diode of the switching element Q2 → the smoothing capacitor C1, and the capacitor C1 is charged. Since switching element Q2 in FIG. 5 is a MOSFET, a reverse diode is built in. However, in the case of a bipolar transistor, the diode needs to be connected in reverse parallel.

  In the initial state, the charging voltage of the capacitor C1 is about 140 V near the peak value of the pulsating voltage. Compared to this voltage, the forward voltage (the above-mentioned n × Vf) of the semiconductor light emitting element 4 is set low. For this reason, a weak current flows through the path of the smoothing capacitor C1 → the resistors R21, R22 → the output connector 5 → the semiconductor light emitting element 4 → the output connector 5 → the current detection resistor R3 → the smoothing capacitor C1, and the current flows through the resistor R21. As a result, the base-emitter of the transistor Tr1 is forward-biased, the transistor Tr1 is turned on, and a starting current flows through the path of the smoothing capacitor C1, the transistor Tr1, the resistor R23, the resistor R24, the power supply capacitor C3, and the smoothing capacitor C1. The voltage of the power supply capacitor C3 rises. When the voltage of the power supply capacitor C3 rises to the operable voltage of the control circuit 3c, the on / off operation of the switching elements Q1, Q2 is started.

  The step-up chopper circuit as a power factor correction circuit includes an inductor L1, a switching element Q1, a reverse diode of the switching element Q2, and a smoothing capacitor C1, and the switching elements Q1 and Q2 are alternately turned on and off at a high frequency. Thus, the boosted DC voltage is charged in the smoothing capacitor C1.

  As a result, the current flowing through the resistor R24 increases, and the transistor Tr2 forward-biased by the resistor R24 is completely turned on. Since the transistor Tr2 is on, the capacitor C3 is charged via the diode D3 by the secondary winding output of the inductor L1. The voltage of the capacitor C3 is regulated by the Zener diode ZD3 and supplied to the control circuit 3c as the control power supply voltage Vcc.

  When the switching element Q1 is turned on, the connection point b of the switching elements Q1 and Q2 drops to the ground potential. At this time, the power supply capacitor C4 on the high potential side is charged with the control power supply voltage Vcc on the low potential side via the diode D4. To do. The voltage HVcc of the power supply capacitor C4 on the high potential side is used for driving the gate electrode a of the switching element Q2 on the high potential side by the control circuit 3c.

  When the switching elements Q1 and Q2 are alternately turned on and off at high frequencies, the potential at the connection point b of the switching elements Q1 and Q2 becomes a rectangular wave voltage that is switched between the potential of the smoothing capacitor C1 and the ground potential. A high-frequency AC voltage is applied to the primary winding n1 of the step-down transformer T1 via An AC voltage obtained by stepping down this in accordance with the turn ratio n2 / n1 is generated in the secondary winding n2. The middle point of the secondary winding n2 is connected to the ground potential, the voltage across the secondary winding n2 is full-wave rectified by the diodes D2 and D6, and the DC voltage is charged in the smoothing capacitor C2. Thereby, the converter circuit 2e operates as a step-down converter circuit that steps down the DC voltage between the terminals A and B and outputs the voltage between the terminals CD.

  The semiconductor light emitting element 4 is connected between the terminals C and D via the diode D7, the output connector 5, and the current detection resistor R3. The voltage across the current detection resistor R3 is detected by the control circuit 3c, and the ON time width of the switching elements Q1 and Q2 is controlled so that the detected current is constant.

  Here, when the semiconductor light emitting element 4 is disconnected, the weak current flowing through the resistors R21 and R22 is cut off, so that the transistor Tr1 is turned off. Then, the base-emitter voltage of the transistor Tr2 that has been forward-biased by the current flowing through the resistor R24 via the transistor Tr1 disappears, and the transistor Tr2 is turned off. As a result, the path for charging the power supply capacitor C3 from the secondary winding output of the inductor L1 via the diode D3 is cut off, and the supply of the control power supply voltage Vcc is cut off. Then, the control circuit 3c stops operating, and the switching elements Q1 and Q2 are both turned off.

  Thereafter, the charging voltage of the capacitor C1 is maintained at about 140 V near the peak value of the pulsating voltage output from the full-wave rectifier DB. The charging voltage of the output capacitor C2 of the converter circuit 2e is discharged by the discharge resistor R25 and becomes substantially zero. Note that the presence of the diode D7 for preventing reverse current between the terminals E and C prevents the transistor Tr1 from being turned on by the current through the discharge resistor R25.

  As described above, in the present embodiment, the presence / absence of current through the semiconductor light emitting element 4 is detected by the transistor Tr1, and the start / stop of the power factor correction circuit is controlled according to the detection result. The power factor correction circuit does not operate when the element 4 is disconnected, and no wasteful power consumption occurs. Further, since the voltage of the smoothing capacitor C1 is lowered while the operation of the power factor correction circuit is stopped, the circuit stress can be reduced.

(Embodiment 5)
FIG. 6 is a circuit diagram of a lighting device according to Embodiment 5 of the present invention. In this embodiment, the step-up / step-down chopper circuit 1b is used as the power factor correction circuit. The configuration and operation of the step-up / step-down chopper circuit 1b are well known. A series circuit of an inductor L1 and a switching element Q1 is connected to the DC output terminal of the full-wave rectifier DB, and a smoothing capacitor C1 is connected to both ends of the inductor L1 via a diode D1. Connected. When the switching element Q1 is turned on, an input current is drawn from the AC power supply Vs via the full-wave rectifier DB and the inductor L1. When the switching element Q1 is turned off, the energy stored in the inductor L1 is released to the smoothing capacitor C1 through the regenerative diode D1. Since the polarity of the DC voltage obtained in the smoothing capacitor C1 is opposite to that of the input voltage, it is also called a polarity inversion type chopper circuit.

  One advantage of using the step-up / step-down chopper circuit 1b as the power factor correction circuit is that the inrush current at power-on can be reduced. That is, when the power is turned on, there is no path through which current flows directly to the smoothing capacitor C1 when viewed from the commercial AC power supply Vs. Therefore, an excessive inrush current flows without providing an inrush current prevention circuit. Absent. On the other hand, in the step-up chopper circuit 1a as shown in FIG. 10, a charging current flows through the smoothing capacitor C1 through the inductor L1 and the diode D1 when the power is turned on, so that an inrush current becomes a problem. Even if the inrush current per lighting fixture is small, if all the lighting fixtures that are simultaneously turned on and off by the same power switch are replaced with LED lighting, the inrush current flows through the lighting fixtures simultaneously. As a result, the breaker may fall, and measures to prevent inrush current are required.

  In order to avoid this problem, when the step-up chopper circuit 1a is used as the power factor correction circuit, an inrush current prevention circuit is generally inserted between the full-wave rectifier DB and the inductor L1. The inrush current prevention circuit is composed of, for example, a parallel circuit of a current limiting resistor and an SCR (reverse blocking three-terminal thyristor), and a voltage obtained by rectifying and smoothing the secondary winding output of the inductor L1 is applied between the gate and the cathode of the SCR. It is comprised so that. When the power is turned on, the inrush current is relaxed by the current limiting resistor, and after the switching operation of the boost chopper circuit 1a is started, the SCR is turned on by the secondary winding output of the inductor L1, and the current limiting resistor is short-circuited. It has become.

  As described above, when the step-up chopper circuit 1a is used as the power factor correction circuit, it is necessary to take measures to prevent the inrush current to the smoothing capacitor C1 when the power is turned on. However, as in this embodiment, the power factor improvement is performed. When the step-up / step-down chopper circuit 1b is used as a circuit, there is an advantage that the circuit itself becomes a countermeasure against inrush current.

  As another advantage, if the operation of the step-up / step-down chopper circuit 1b is stopped when a load abnormality is detected, the voltage of the smoothing capacitor C1 can be eliminated, so that the stress of the subsequent circuit can be further alleviated. In the case of the step-up chopper circuit 1a, the voltage (about 140V) remains in the smoothing capacitor C1 even if the switching operation is stopped, so that a configuration for stopping the subsequent power conversion circuit is required. On the other hand, when the step-up / step-down chopper circuit 1b is used as a power factor correction circuit, the voltage of the smoothing capacitor C1 disappears due to the stop of the switching operation, and therefore the configuration for stopping the subsequent power conversion circuit is omitted. You can also. Therefore, even when a self-excited power conversion circuit is used instead of the separately-excited power conversion circuit, the switching operation of the subsequent-stage power conversion circuit is stopped by stopping the switching operation of the preceding step-up / step-down chopper circuit 1b. Will automatically stop.

  In the configuration example of FIG. 6, the separately excited step-down chopper circuit 2b is used as the power conversion circuit, and the output of the step-down chopper circuit 2b is output via the diode D4 by the secondary winding output of the inductor L1 of the step-up / step-down chopper circuit 1b. The power supply capacitor C4 of the control circuit 3b is charged. Therefore, when the step-up / step-down chopper circuit 1b stops the switching operation, the step-down chopper circuit 2b also quickly stops the switching operation. However, the power supply capacitor C4 is temporarily charged from the smoothing capacitor C1 through the step-down resistor. Even in this case, the voltage HVcc of the power supply capacitor C4 can be reduced by eliminating the voltage of the smoothing capacitor C1. In addition, since the voltage of the smoothing capacitor C1 serving as the main power source of the step-down chopper circuit 2b is eliminated, the step-down chopper circuit 2b cannot continue to operate, and therefore will eventually stop even if the control power source is not shut off. .

  Next, the operation when the power is turned on will be described. Immediately after the power is turned on, the smoothing capacitor C1 is not charged. The peak value of the pulsating voltage output from the full-wave rectifier DB is about 140 V, and the forward voltage (the above-mentioned n × Vf) of the semiconductor light emitting element 4 is set lower than this. Due to the pulsating voltage output from this full-wave rectifier DB, the path of current detection resistor R3 → reverse diode of switching element Q2 → regenerative diode D2 → semiconductor light emitting element 4 → diode D5 → resistor R23 → resistor R24 → power supply capacitor C3 As a result, a pulsating (100/120 Hz) starting current intermittently flows, and the voltage of the power supply capacitor C3 rises.

  When the voltage of the power supply capacitor C3 rises above the operable voltage of the PFC control circuit 3a, the switching element Q1 starts an on / off operation, and a DC voltage is obtained at the smoothing capacitor C1. Then, the DC voltage of the smoothing capacitor C1 is superimposed on the pulsating voltage output from the full wave rectifier DB, and the full wave rectifier DB → smoothing capacitor C1 → semiconductor light emitting element 4 → diode D5 → resistor R23 → resistor R24 → power supply capacitor. A continuous pulsating current flows through the path C3. As a result, the transistor Tr2 is always turned on. The bias resistors R23 and R24 of the transistor Tr2 can be set so that the transistor Tr2 is saturated only with the DC voltage of the smoothing capacitor C1 even when the output voltage of the full-wave rectifier DB becomes zero. It ’s fine.

  As described above, when the step-up / step-down chopper circuit 1b starts the switching operation, the DC voltage of the smoothing capacitor C1 rises, so that the transistor Tr2 is always turned on, and the power is supplied via the diode D3 by the secondary winding output of the inductor L1. Capacitor C3 is charged. The upper limit of the voltage Vcc of the power supply capacitor C3 is defined by the Zener diode ZD3.

  Further, the power supply capacitor C4 is charged through the diode D4 by the secondary winding output of the inductor L1. The upper limit of voltage HVcc of power supply capacitor C4 is defined by Zener diode ZD4. When the voltage HVcc of the capacitor C4 rises above the operable voltage of the output control circuit 3b, the switching element Q2 starts an on / off operation.

  When the switching element Q2 is turned on, current flows through the path of the smoothing capacitor C1, the output capacitor C2, the inductor L2, the switching element Q2, and the current detection resistor R3, and energy is accumulated in the inductor L2. When the voltage of the current detection resistor R3 reaches the target value, the switching element Q2 is turned off by the output control circuit 3b. Then, the regenerative current due to the energy stored in the inductor L2 is discharged to the output capacitor C2 via the diode D2. When the energy release of the inductor L2 is completed, the disappearance of the secondary winding output of the inductor L2 is detected, and the output control circuit 3b turns on the switching element Q2 again. Thereafter, the same operation is repeated to charge the output capacitor C2.

  When the voltage of the output capacitor C2 reaches the forward voltage (n × Vf) of the semiconductor light emitting element 4, a main current flows to the semiconductor light emitting element 4 via the diode D7, and then the voltage of the output capacitor C2 is Clamped to n × Vf + Vd7.

  At this time, the Zener diode ZD5 for overvoltage protection does not conduct. The Zener voltage Vzd5 of the Zener diode ZD5 is set higher than the above-mentioned n × Vf + Vd7. Vd7 is a forward voltage of the diode D7.

  Next, an operation when the semiconductor light emitting element 4 is disconnected will be described. When the semiconductor light emitting element 4 is disconnected, the voltage of the output capacitor C2 increases. However, since the Zener diode ZD5 for overvoltage protection is turned on, no overvoltage exceeding the withstand voltage of the output capacitor C2 is applied. Since the current flowing through the Zener diode ZD5 is blocked by the backflow prevention diode D7, it does not flow through the diode D5. Therefore, when the semiconductor light emitting element 4 is disconnected, the current through the diode D5 is cut off and no current flows through the resistors R23 and R24, so that the transistor Tr2 is turned off. Then, since the path for charging the power supply capacitor C3 from the secondary winding output of the inductor L1 through the diode D3 is cut, the control power supply voltage Vcc is lowered and becomes lower than the operable voltage of the PFC control circuit 3a. The PFC control circuit 3a stops operating. Thereby, the step-up / step-down chopper circuit 1b as the power factor correction circuit stops the switching operation.

  Then, since the secondary winding output of the inductor L1 is lost, the power supply capacitor C4 cannot be charged via the diode D4, and when the control power supply voltage HVcc, which is the charging voltage, becomes lower than the operable voltage of the output control circuit 3b, The output control circuit 3b stops the switching operation of the switching element Q2. Thereby, when the semiconductor light emitting element 4 is disconnected, the switching operation of the step-up / step-down chopper circuit 1b as the power factor correction circuit is stopped, and the switching operation of the subsequent step-down chopper circuit 2b is also stopped.

  Further, when the semiconductor light emitting element 4 is disconnected from the beginning when the power is turned on, since the starting current of the power supply capacitor C3 does not flow in the first place, no circuit current flows, and the circuit is completely stopped.

  Note that, as illustrated in the fourth embodiment (FIG. 5), in the switching power supply device in which there is a timing when the negative electrode of the high-potential-side power supply capacitor C4 has substantially the same potential as the negative electrode of the low-potential-side power supply capacitor C3. By providing a path through which a current flows from the positive electrode of the low-potential power supply capacitor C3 to the positive electrode of the high-potential power supply capacitor C4 through the anode and cathode of the diode D4, the high-potential power supply capacitor C4 is intermittently connected. Charging is possible. In the same way of thinking, also in the present embodiment (configuration of FIG. 6), the high-potential-side power supply is supplied during the period when the switching element Q1 is turned on at the timing when the pulsating voltage output from the full-wave rectifier DB becomes substantially zero. Since the negative electrode of the capacitor C4 has substantially the same potential as the negative electrode of the power supply capacitor C3 on the low potential side, if the anode of the diode D4 is connected to the positive electrode of the capacitor C3, the secondary winding output of the inductor L1 can be used. However, the capacitor C4 can be charged. Similarly, also in the third embodiment (configuration of FIG. 4), at the timing when the regenerative diode D2 is turned on, the negative electrode of the high-potential side power supply capacitor C4 has substantially the same potential as the negative electrode of the low-potential side power supply capacitor C3. If the anode of the diode D4 is connected to the positive electrode of the capacitor C3, the capacitor C4 can be charged without using the secondary winding output of the inductor L2.

(Embodiment 6)
FIG. 7 is a circuit diagram of a lighting device according to Embodiment 6 of the present invention. In the present embodiment, a flyback converter circuit 1c is used as the power factor correction circuit. The configuration and operation of the flyback converter circuit 1c are well known. A series circuit of the primary winding of the transformer T1 and the switching element Q1 is connected to the DC output terminal of the full-wave rectifier DB, and both ends of the secondary winding of the transformer T1. Is connected to a smoothing capacitor C1 through a diode D1. The polarity of the diode D1 is connected in a direction to block current when the switching element Q1 is turned on.

  When the switching element Q1 is turned on, an input current is drawn from the AC power supply Vs via the full-wave rectifier DB and the primary winding of the transformer T1. At this time, since the diode D1 is in a non-conductive state, the transformer T1 functions as an inductor, and energy is stored in the transformer T1. When the switching element Q1 is turned off, the energy stored in the transformer T1 is released to the smoothing capacitor C1 through the diode D1. The DC voltage obtained at the smoothing capacitor C1 is insulated from the input side. In order to transmit the detection voltage obtained by dividing the voltage of the smoothing capacitor C1 by the resistors R1 and R2 to the PFC control circuit 3a, it is preferable to use a photocoupler PC3.

  Further, when the disconnection or short circuit of the semiconductor light emitting element 4 is detected by the voltage detector 6, the detection signal is transmitted to the PFC control circuit 3a via the photocoupler PC4, and the operation of the power factor correction circuit is stopped or the output is suppressed. To control. Note that the photocouplers PC3 and PC4 are used to maintain insulation between the primary side and the secondary side of the transformer T1, and separate elements are used in FIG. 7, but they may be used together. For example, if the output of the voltage detector 6 is input to the photocoupler PC3, only one photocoupler is required. Other configurations and operations are the same as those of the above-described embodiment.

  The PFC control circuit 3a that controls the switching element Q1 of the flyback converter circuit 1c detects the pulsating voltage output from the full-wave rectifier DB by dividing it with the resistors R11 and R12, and detects 1 of the transformer T1 flowing through the switching element Q1. The envelope of the peak value of the next winding current is controlled so as to be substantially proportional to the pulsating voltage waveform. For this purpose, the source current of the switching element Q1 is detected by voltage conversion by the resistor R13, and when the detected voltage reaches a target value that is substantially proportional to the pulsating voltage, the switching element Q1 is controlled to be turned off. Further, the charging voltage of the smoothing capacitor C1 is divided and detected by the resistors R1 and R2, and transmitted to the PFC control circuit 3a via the photocoupler PC3. When the charging voltage of the smoothing capacitor C1 is low, the switching element Q1 In order to increase the ON time width, the target value is set high. Conversely, when the charging voltage of the smoothing capacitor C1 is high, the target value is set low to shorten the ON time width of the switching element Q1. . Further, an auxiliary winding for detecting a regenerative current is provided in the transformer T1, and the disappearance (zero cross) of the regenerative current discharged from the transformer T1 is detected by the presence or absence of the winding voltage, and when the regenerative current disappears, the switching element Control is performed to turn on Q1 again.

  Although the illustration of the configuration for obtaining the control power supply voltage of the PFC control circuit 3a is omitted, for example, the power supply capacitor is charged from the output terminal of the full-wave rectifier DB through the current limiting resistor, and the PFC is generated by the charge voltage. After the operation of the control circuit 3a is started, a configuration in which the power supply capacitor is charged from the regenerative current detection winding of the transformer T1 via a rectifying diode can be used.

  The flyback converter circuit 1c may be considered as a circuit obtained by modifying the step-up / step-down chopper circuit 1b of the fifth embodiment (FIG. 6) to an input / output insulation type. Therefore, there is an effect similar to that of the fifth embodiment. When the power factor correction circuit at the front stage is stopped, the power conversion circuit at the rear stage is automatically stopped. In the configuration of FIG. 7, since the power supply capacitor C4 of the output control circuit 3b is charged from the voltage of the smoothing capacitor C1 through the step-down resistor R10, the flyback converter circuit 1c is stopped and the voltage of the smoothing capacitor C1 is reduced. When it disappears, the voltage of the power supply capacitor C4 also disappears, and the output control circuit 3b automatically stops. In any case, since the voltage of the smoothing capacitor C1 disappears, the step-down chopper circuit 2b as the power conversion circuit is cut off from the main power supply, and automatically stops operating. Therefore, the step-down chopper circuit 2b may be self-excited.

In each of the above-described embodiments, the case where the Zener diodes ZD3 and ZD4 are used as the means for stabilizing the voltage of the power supply capacitors C3 and C4 is exemplified. However, the voltage of the three-terminal regulator IC or IPD (intelligent power device) is used. Stabilization means may be employed as appropriate.
Further, the above-described embodiments may be implemented in combination as appropriate.

(Embodiment 7)
FIG. 8 shows a schematic configuration of an LED lighting fixture with a separate power source using the LED lighting device of the present invention. In this separate power supply type LED lighting apparatus, the power supply unit 12 is built in a case different from the casing 42 of the LED module 40. By doing so, the LED module 40 can be thinned, and the separately mounted power supply unit 12 can be installed regardless of the location.

  The instrument housing 42 is made of a metal cylinder that is open at the lower end, and the lower end open portion is covered with a light diffusion plate 43. The LED module 40 is disposed so as to face the light diffusion plate 43. Reference numeral 41 denotes an LED mounting board on which the LEDs 4a to 4d of the LED module 40 are mounted. The instrument housing 42 is embedded in the ceiling 20, and is wired from the power supply unit 12 disposed on the back of the ceiling via the lead wire 50 and the connector 5.

  The power unit 12 houses the power factor correction circuit 1, the power conversion circuit 2, the full-wave rectifier DB, the filter circuit 9, and the like. A series circuit (LED module 40) of the LEDs 4a to 4d corresponds to the semiconductor light emitting element 4 described above.

  In the separate-type LED lighting fixture shown in FIG. 8, the fixture housing 42 in which the LED module 40 is housed and the power supply unit 12 that provides output to emit light from the LEDs 4 a to 4 d are separately arranged. Requires attaching the power supply unit 12 at the site, attaching the instrument housing 42, and connecting them with the lead wire 50 and the connector 5.

  If there is a connection failure or forget to connect the connector 5 or the lead wire 50 is disconnected, the power conversion circuit 2 built in the power supply unit 12 stops its operation, and the power factor improvement circuit 1 in the preceding stage also stops its operation. .

  In the present embodiment, the power supply unit type LED lighting fixture is illustrated in which the power supply unit is housed in a separate housing from the LED module. However, the power supply integrated LED lighting device in which the power supply unit is housed in the same housing as the LED module is illustrated. Alternatively, the lighting device of the present invention may be used.

  The lighting device of the present invention is not limited to a lighting fixture, and may be used as various light sources, for example, a backlight of a liquid crystal display, a light source of a copying machine, a scanner, a projector, or the like.

  In the description of each embodiment described above, a light emitting diode is exemplified as the semiconductor light emitting element 4, but the present invention is not limited to this, and may be, for example, an organic EL element or a semiconductor laser element.

DESCRIPTION OF SYMBOLS 1 Power factor improvement circuit 2 Power conversion circuit 3a PFC control circuit 4 Semiconductor light emitting element 5 Output connector 6 Voltage detection circuit 7 Abnormality detection circuit 8 Stop control circuit

Claims (4)

A power factor correction circuit connected to an AC power source, a power conversion circuit that converts the output of the power factor correction circuit to power and supplies current to the semiconductor light emitting element, an abnormality detection circuit that detects an abnormality of the semiconductor light emitting element, And a control circuit for stopping the operation of the power factor correction circuit or suppressing the output when an abnormality is detected by the detection circuit. 2. The lighting device for a semiconductor light emitting element according to claim 1, wherein the abnormality detection circuit detects an opening of the semiconductor light emitting element or an opening of the wiring from the power conversion circuit to the semiconductor light emitting element as an abnormality. 2. The lighting device for a semiconductor light emitting element according to claim 1, wherein the abnormality detection circuit detects a short circuit of the semiconductor light emitting element or a short circuit of the wiring from the power conversion circuit to the semiconductor light emitting element as an abnormality. The lighting device which comprises the lighting device of the semiconductor light-emitting element in any one of Claims 1-3, and the semiconductor light-emitting element supplied with an electric current from this lighting device.

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