JP2017022039A - LED lighting circuit and LED lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply stably control power to an automatic flasher or the like during lighting-off without increasing a loss during lighting-on in an LED lighting circuit comprising the automatic flasher.SOLUTION: An LED lighting circuit (1) comprises: a DC/DC converter (20) which supplies DC power to an LED (2); an automatic flasher (30) which switches a turn-on signal and a turn-off signal; a control circuit (40) which performs PWM drive of a switching element (21) in such a manner that an output voltage is maintained at a limiter setting that is lower than a forward voltage, when the turn-off signal is outputted; an auxiliary power supply circuit (50) by which a control voltage is generated from a voltage generated in an auxiliary winding of a transformer (22) and supplied to the automatic flasher and the control circuit; a regulator circuit (60) by which a control voltage is generated from the output voltage and supplied to at least the automatic flasher; and an operation switching circuit (65) which makes the regulator circuit inactive if the output voltage is higher than the limiter setting, and makes the regulator circuit active while the output voltage is maintained at the limiter setting.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an LED lighting circuit with an automatic flasher and an LED lighting device.

  Patent document 1 discloses the illuminating device which has an illuminance sensor. The lighting device includes a power supply voltage conversion unit that converts an external power supply voltage and supplies the converted LED to an LED, a sensor control unit that controls the power supply voltage conversion unit based on detection of an illuminance sensor, an external power supply input unit, and a power supply voltage conversion unit And a sensor power supply unit that supplies a voltage lower than the external power supply voltage to the illuminance sensor and the sensor control unit. The power supply voltage conversion unit and the illuminance sensor are provided on a common substrate. In the control circuit, when the illuminance detected by the illuminance sensor is higher than the reference value, the sensor control unit controls the driver of the power supply voltage conversion unit to stop the supply of the DC voltage to the LED and turn off the LED. Thus, an LED lighting circuit with an automatic blinker having an illuminance sensor is known.

  By the way, in a converter circuit composed of a switching power supply for supplying predetermined DC power to an LED, for example, an isolated flyback converter, a reference potential for the switching operation on the primary side of the converter circuit and a detection on the secondary side In addition, the reference potential for the control operation may be different. The secondary side includes an automatic flasher and a lighting control circuit. As a configuration for generating such a control power supply for the secondary circuit, for example, a configuration in which a voltage generated in an auxiliary winding of a transformer of a converter circuit is rectified and smoothed (for example, see Patent Document 2) and a converter There is a configuration in which the output voltage of the circuit is stepped down and used (for example, see Patent Document 3).

JP 2012-216464 A JP-A-2015-103336 JP 2011-200117 A

  However, in the configuration in which the control power supply is generated by rectifying and smoothing the voltage of the transformer auxiliary winding of the converter circuit, the drive of the converter circuit is reduced in the light load state when the LED is turned off, and thus obtained from the auxiliary winding. The control power supply that is available can also be reduced. For this reason, when the light is turned off, there is a possibility that the automatic flasher included in the LED lighting circuit and the control power supply of the control circuit are not sufficiently secured. On the other hand, in the configuration in which the output voltage of the converter circuit is stepped down to generate the control power supply, the output voltage from the output voltage to the control voltage is increased due to the output voltage of the converter circuit being equal to or higher than the forward voltage of the LED when the LED is lit. Loss increases in the step-down configuration. Therefore, the circuit efficiency at the time of LED lighting will fall.

  Therefore, the present invention provides an LED lighting circuit with an automatic flasher and an LED lighting device using the same, and supplies a stable control power to the automatic flasher or the like when the LED is turned off without increasing the loss when the LED is turned on. It is an object of the present invention to provide a configuration that enables the above.

  The LED lighting circuit of the present invention includes a switching element and a transformer, a DC / DC converter that supplies DC power to the LED by PWM driving of the switching element, an automatic flasher that switches between a lighting signal and a light-off signal, and outputs When the lighting signal is output, the output voltage of the DC / DC converter is maintained to be equal to or higher than the forward voltage of the LED, and when the turn-off signal is output, the output voltage is maintained at a limiter set value less than the forward voltage. A control circuit for PWM driving the switching element, an auxiliary power supply circuit for generating a control voltage from a voltage generated in an auxiliary winding provided in the transformer and feeding the automatic flasher and the control circuit, and a control voltage from the output voltage Regulator circuit configured to generate and supply power to the automatic flasher or automatic flasher and control circuit, and output voltage limiter setting A regulator circuit with non-operation is higher than, and a operation switching circuit for operating the regulator circuit when the output voltage is maintained at a limiter setting.

  According to the LED lighting circuit described above, when the PWM drive amount of the switching element is large and the potential difference between the output voltage and the control voltage is large, a control voltage is generated from the transformer auxiliary winding by the auxiliary power supply circuit and the automatic flasher is supplied with power. At the same time, the regulator circuit is deactivated. On the other hand, when the switching element PWM drive amount is small and the potential difference between the output voltage and the control voltage is small, the regulator circuit generates a control voltage from the output voltage and powers the automatic flasher and the like. As a result, in an LED lighting circuit with an automatic flasher, it is possible to supply a stable control power to the automatic flasher or the like when the LED is turned off without increasing the loss when the LED is turned on.

  Here, the operation switching circuit has an operation switching transistor, and for the operation switching setting value higher than the limiter setting value and less than the forward voltage, the operation switching transistor is turned on when the output voltage exceeds the operation switching setting value. When the output voltage is less than or equal to the operation switching set value, it is turned off, and the regulator circuit is configured to be inactive when the operation switching transistor is on and to operate when the operation switching transistor is off. Is preferred. Thus, the non-operation / operation of the regulator circuit is determined by the output voltage, and the operation switching setting value of the output voltage that determines the boundary of the non-operation / operation is set higher than the limiter setting value and less than the forward voltage. Therefore, the regulator circuit is surely inactivated when turned on and is reliably operated when turned off.

  An output voltage limiter circuit having a limiter transistor that is turned off when the lighting signal is output, and is turned on when the extinguishing signal is output and the output voltage is equal to or higher than a limiter set value; A PWM control circuit configured to reduce the PWM drive on-width when the limiter transistor is on or to stop the PWM drive and to increase the PWM drive on-width when the limiter transistor is off; It is preferable to provide. Thereby, the constant voltage control by the limiter set value is realized with a simple configuration.

  Still further, when the control circuit includes a current detection resistor for detecting the LED current flowing in the LED and a lighting signal is output, the PWM control circuit matches the LED current detected by the current detection resistor with the target value. Thus, it is preferable that the on-width of the PWM drive is determined. Thereby, the structure for performing the constant current control when the LED is turned on and the structure for performing the constant voltage control and the generation of the control voltage when the LED is turned off are appropriately combined.

  As one form, the DC / DC converter (20) has a high potential side output line (L1) and a low potential side output line (L0), and the control circuit (40) has a high potential side output line and a low potential side output. A high-potential side first resistor (451) and a low-potential side second resistor (453) connected in series between the lines, and a low anode terminal between the high-potential side output line and the second resistor A first Zener diode (452) connected in series to the first resistor toward the potential side, and a limiter transistor whose control terminal is fed from the high potential side output line via the first resistor and the first Zener diode (455) and an output voltage limiter circuit (45) having a blinking control transistor (450) that turns off the limiter transistor when a lighting signal is output, and PWM drive on when the limiter transistor is on. Or the PWM control circuit (41) configured to increase the on width of the PWM drive when the limiter transistor is in the off state, and the operation switching circuit (65), A third resistor (651) on the high potential side and a fourth resistor (653) on the low potential side connected in series between the high potential side output line and the low potential side output line, the high potential side output line and the first resistor The second Zener diode (652) connected in series with the third resistor with the anode terminal facing the low potential side between the four resistors and the control terminal from the high potential side output line to the third resistor and the second resistor An operation switching transistor (650) fed through the Zener diode, the Zener voltage (ZV1) of the first Zener diode is set to the limiter set value (V1), and the Zener diode of the second Zener diode is set When the voltage (ZV2) is set to the operation switching setting value (V2) that is higher than the limiter setting value and less than the forward voltage (Vf), the regulator circuit becomes inoperative when the operation switching transistor is in the ON state. Configured to operate when is in an off state. According to this configuration, it is possible to adjust the setting value of the limiter when the light is turned off and the operation switching setting value that determines the non-operation / operation of the regulator circuit by setting the Zener voltage of the first and second Zener diodes. Thus, the ease of design increases. In particular, since the Zener voltage of the second Zener diode is higher than the Zener voltage of the first Zener diode, the regulator circuit operates reliably when extinguished.

  The limiter set value is preferably 45 V or less. This ensures sufficient user safety even when the LED is replaced when the LED is turned off.

  The LED lighting device of the present invention includes the above LED lighting circuit and LEDs. Thereby, in the LED lighting device provided with the automatic blinker as a part of the LED lighting circuit, it is possible to achieve both a low-loss lighting operation and a stable extinguishing operation.

1 is a circuit diagram of an LED lighting circuit and an LED lighting device according to an embodiment of the present invention. It is a figure which shows a part of LED lighting circuit by one modification of this invention. It is a figure which shows a part of LED lighting circuit by the other modification of this invention. It is a figure which shows a part of LED lighting circuit by the other modification of this invention.

  FIG. 1 shows a circuit diagram of an LED lighting circuit 1 according to an embodiment of the present invention and an LED lighting device 3 using the same. An LED lighting device 3 is configured by the LED lighting circuit 1 and the LED 2. The LED lighting circuit 1 is a switching power supply, and converts an AC voltage input from an AC power supply AC (for example, a commercial power supply) into a predetermined DC power and supplies it to the LED 2. The LED lighting circuit 1 has an automatic flasher 30 described later, and the LED 2 is turned on and off by the operation of the automatic flasher 30.

  The LED lighting circuit 1 includes a rectifier circuit 10, a DC / DC converter 20, an automatic flasher 30, a control circuit 40, an auxiliary power circuit 50, a regulator circuit 60, and an operation switching circuit 65. It should be noted that it is for convenience of explanation which element the LED lighting circuit 1 belongs to. Each transistor described as a bipolar transistor may be appropriately replaced with a MOSFET, a built-in resistor type transistor, or the like. The base terminal and the gate terminal are collectively referred to as a control terminal.

  The rectifier circuit 10 includes a diode bridge 11 and an input capacitor 12. The AC input voltage is full-wave rectified by the diode bridge 11, and a pulsating voltage appears at the input capacitor 12. If necessary, current fuses F1 and F2 and a noise filter (not shown) are connected to the previous stage of the diode bridge 11. Note that the rectifier circuit 10 is not required when a DC voltage from a DC power source is input to the LED lighting circuit 1.

  The DC / DC converter 20 includes a switching element 21 (MOSFET), a transformer 22, a diode 23, and an output capacitor 24, and supplies DC power to the LED 2 by PWM driving of the switching element 21. In the present embodiment, the DC / DC converter 20 is an insulating flyback converter, and constitutes a so-called one-converter flyback circuit having a power factor improving function.

  Energy is accumulated by the primary winding of the transformer 22 during the ON period of the switching element 21, and the energy is charged to the output capacitor 24 from the secondary winding side of the transformer 22 via the diode 23 during the OFF period of the switching element 21. . The output power of the DC / DC converter 20 is determined by the on-duty (duty ratio) in the PWM control of the switching element 21, the turn ratio of the secondary winding to the primary winding, and the like. The switching element 21 is driven by a control IC 410 for switching control described later.

  In the following description, the output voltage of the DC / DC converter 20 is simply referred to as “output voltage”, and the output current of the DC / DC converter 20 is simply referred to as “output current”. Further, the low potential side output wiring of the DC / DC converter 20 is referred to as a low potential side output line L0, and the high potential side output wiring is referred to as a high potential side output line L1. Further, the primary side reference potential (that is, the potential of the low potential electrode of the input capacitor 12) of the DC / DC converter 20 is referred to as a primary side ground, and the secondary side reference potential (ie, the low potential side output line L0). Also called secondary ground.

  The automatic flasher 30 includes an illuminance sensor 31 and a flashing signal generation unit 32, and is configured as a part of the LED lighting circuit 1 in this embodiment. However, even when the automatic flasher 30 is not connected (for example, not mounted), the LED lighting circuit 1 functions as a normal lighting circuit for lighting the LED 2. The automatic flasher 30 is operated by a control power source generated inside the LED lighting circuit 1 with the low potential side output line L0 as a reference potential. The illuminance sensor 31 is, for example, installed at a position and orientation above the LED lighting device 3 where the light of the LED 2 is not incident, and detects the ambient illuminance around the LED lighting device 3. The blinking signal generation unit 32 generates a blinking control signal S for lighting / extinguishing control based on the environmental illuminance detected by the illuminance sensor 31, and supplies this to the control circuit 40 (an output voltage limiter circuit 45 described later). . Therefore, the automatic flasher 30 outputs a lighting signal as the flashing control signal S at night when the environmental illuminance is low, and outputs a turn-off signal as the flashing control signal S during the day when the environmental illuminance is high. In the present specification, the logic high blinking control signal S is a lighting signal, and the logic low blinking control signal S is an extinguishing signal.

  The automatic flasher 30 may include a clock or a timer instead of the illuminance sensor 31. In this case, the lighting signal and the extinguishing signal are switched at a predetermined time or every predetermined time. Or the automatic flasher 30 may be provided with the human sensor which consists of an infrared sensor instead of the illumination intensity sensor 31, for example. In this case, when the human sensor detects the presence of a person in the detection area, a lighting signal is output, and in other cases, a turn-off signal is output. That is, in any case, the automatic flasher 30 switches between the lighting signal and the extinguishing signal and outputs them when a predetermined condition is satisfied.

  The control circuit 40 includes a PWM control circuit 41, a current detection resistor 42, and an output voltage limiter circuit 45, and controls the output operation of the DC / DC converter 20, that is, the PWM drive of the switching element 21. In general, the control circuit 40 turns on the LED 2 when a lighting signal is output from the automatic flasher 30 and turns off the LED 2 when a turn-off signal is output, and the output voltage is less than the forward voltage Vf. The operating state of the switching element 21 is controlled so as to maintain the set value V1.

  The current detection resistor 42 is composed of a low resistance element, and is inserted and connected to the current path (low potential side output line L0) of the LED2. The voltage generated in the current detection resistor 42 is input to the PWM control circuit 41 of the control circuit 40 described later as a current detection value of the LED current.

The PWM control circuit 41 includes a primary side control circuit that uses the primary side ground as a reference potential and a secondary side control circuit that uses the secondary side ground (low potential side output line L0) as a reference potential.
The primary side control circuit includes a control IC 410 and its peripheral circuits (not shown) and a phototransistor 416 t of the photocoupler 416. The control IC 410 is composed of a general LED driver IC, generates a PWM drive signal having a pulse width corresponding to the output state of the phototransistor 416t, and outputs it as the gate voltage of the switching element 21. Further, the control IC 410 is supplied with power from the high-potential side wiring (common cathode end of the diode bridge 11) of the primary side circuit via a starting resistor (not shown) before the control power is supplied from the auxiliary power supply circuit 50. Can be started or maintained. In this embodiment, the control IC 410 and its peripheral circuits are configured such that the PWM drive on-width decreases or the PWM drive stops as the photodiode current and phototransistor current of the photocoupler 416 increase. And

  The secondary side control circuit includes, for example, an operational amplifier 411, resistors 412 and 413, a diode 414, a resistor 415, and a photodiode 416d of a photocoupler 416, and forms an error amplification circuit as a whole. Note that a resistor may be connected instead of the diode 414. The operational amplifier 411 is supplied with power from the control power supply Vcc. The current detection value from the current detection resistor 42 is input to the negative input terminal (−) of the operational amplifier 411, and the reference voltage corresponding to the target value of the LED current is input to the positive input terminal (+) of the operational amplifier 411. The This reference voltage corresponds to the target value of the output current, and is determined by the divided value by the resistors 412 and 413 of the control power supply Vcc. A feedback element (not shown) (a resistor, a capacitor, or a series circuit or a parallel circuit thereof) is connected between the negative input terminal and the output terminal of the operational amplifier 411, and an error between the negative input terminal voltage and the positive input terminal voltage is detected at the output terminal. Is output. The output of the operational amplifier 411 is connected to the cathode of the photodiode 416d through the diode 414, and the anode of the photodiode 416d is connected to the control power supply Vcc through the resistor 415.

  In the photocoupler 416, the output state of the output phototransistor 416t is determined according to the current flowing through the photodiode 416d, that is, according to the voltage at the cathode terminal of the photodiode 416d, and the output of the phototransistor 416t is used as an input signal as the control IC 410. Is input. Thereby, at the time of lighting when a transistor 455 described later is turned off, the operational amplifier 411 increases the ON width in the PWM control of the switching element 21 so that the output current (current detection value) matches the target value (reference voltage). Will be determined. In other words, the secondary side control circuit of the PWM control circuit 41 operates so as to perform constant current control of the LED current at the time of lighting.

  The output voltage limiter circuit 45 includes a transistor 450, a resistor 451, a Zener diode 452, a resistor 453, a transistor 455, and a resistor 456. The collector terminal of the transistor 450 is connected to the base terminal of the transistor 455, and the emitter terminal of the transistor 450 is connected to the low potential side output line L0. The resistors 451 and 453 are connected in series between the high-potential side output line L1 and the low-potential side output line L0, and the Zener diode 452 is connected between the high-potential side output line L1 and the resistor 453 so that the anode terminal is on the low potential side. The resistor 451 is connected in series. The base terminal of the transistor 455 is supplied with power from the high-potential side output line L1 through the resistor 451 and the Zener diode 452. A blinking signal generation unit 32 is connected to the base terminal of the transistor 450 and the blinking control signal S is input. The collector terminal of the transistor 455 is connected to the cathode terminal of the photodiode 416d, and the emitter terminal is connected to the secondary side ground (low potential side output line L0). The resistor 456 is a resistor for keeping the transistor 450 on and not operating the output voltage limiter circuit 45 when the automatic flasher 30 is not connected. When the automatic flasher 30 is connected as in the present embodiment, the resistor 456 pulls up the potential of the base terminal of the transistor 450, but the flashing control signal S (particularly the lighting signal) from the automatic flasher 30. ) May be omitted when the transistor 450 can be driven.

  Here, the Zener voltage ZV1 of the Zener diode 452 is set to a value less than the forward voltage Vf of the LED2. Thereby, the transistor 455 is turned on when the output voltage exceeds the Zener voltage ZV1 (assuming that the transistor 450 is turned off), and is turned off when the output voltage becomes equal to or lower than the Zener voltage ZV1.

The operation of the output voltage limiter circuit 45 is as follows.
When the blinking control signal S is logic high, that is, when a lighting signal is output, the transistor 450 is turned on and the transistor 455 is maintained in the off state. Therefore, the output voltage limiter circuit 45 does not affect the constant current control operation of the PWM control circuit 41 during lighting.

On the other hand, when the blinking control signal S is a logic low, that is, when a turn-off signal is output,
(1) First, the transistor 450 is turned off. At this time, since the output voltage is equal to or higher than the forward voltage Vf, the transistor 455 is supplied with power from the high potential side output line L1 through the resistor 451 and the Zener diode 452, and is turned on.
(2) As a result, the photodiode current and the phototransistor current of the photocoupler 416 are maximized, and the on-width of the PWM drive of the switching element 21 is minimized by the primary side control circuit (control IC 410 or the like) or the PWM control is stopped. Is done.
(3) Thereafter, when the output voltage decreases and falls below the forward voltage Vf of the LED 2, the LED 2 is turned off.
(4) When the output voltage becomes equal to or lower than the zener voltage ZV1, the transistor 455 is turned off. In this state, since the current detection value is zero with respect to the current target value in the secondary control circuit (such as the operational amplifier 411), an operation for increasing the output current by the operation of the operational amplifier 411, that is, the photodiode 416d An operation for increasing the potential at the cathode end is performed. As a result, the photodiode current and the phototransistor current become minimum (for example, zero), the on-width of the PWM drive of the switching element 21 is maximized by the primary side control circuit, and the output voltage rises.
(5) When the output voltage exceeds the Zener voltage ZV1, the transistor 455 is turned on again, the photodiode current and the phototransistor current are maximized, and the on-width of the PWM drive of the switching element 21 is minimized by the primary side control circuit, Alternatively, the PWM drive is stopped.

  Thereafter, the above operations (4) and (5) are repeated until the lighting signal is output. Since the operations (4) and (5) are executed with a relatively fast response, constant voltage control is executed such that the output voltage is constant at substantially the same value as the Zener voltage ZV1. Further, when the PWM drive is stopped in the operation (5), the switching element 21 is in an intermittent oscillation state as a result of the operations (4) and (5).

  The set value of the output voltage at the time of constant voltage control by the output voltage limiter circuit 45 (in this embodiment, substantially the same value as the Zener voltage ZV1) is referred to as a limiter set value V1. The limiter set value V1 is set to 45 V or less, which is a safety extra low voltage (SELV) in the Electrical Appliance and Material Safety Law (J60598-1 (H14)), on the assumption that the forward voltage Vf of the LED 2 is lower. It is preferable. Thereby, even when the replacement work of the LED 2 is performed in a state in which the operation of turning off the LED lighting circuit 1 is maintained, the safety of the worker is sufficiently ensured. In other words, even if the main power supply (that is, AC power supply AC) of the LED lighting device 3 is not turned off, the safe replacement work of the LED 2 when the LED is turned off is executed.

  As described above, in the control circuit 40, the transistor 455 of the output voltage limiter circuit 45 is turned on when the turn-off signal is output and the output voltage is equal to or higher than the limiter set value V1. When the transistor 455 is on, the PWM control circuit 41 drives or stops the switching element 21 with the minimum on-width when the transistor 455 is on, and stops the switching element 21 when the transistor 455 is off. PWM drive with maximum ON width. Thereby, the constant voltage control by the limiter set value V1 is realized with a simple configuration. Further, when a lighting signal is output, the PWM control circuit 41 is configured to determine the on-width of the PWM drive so that the LED current detected by the current detection resistor 42 matches the target value. Thereby, the configuration for constant voltage control when the LED is turned off and the configuration for constant current control when the LED is turned on are appropriately coupled.

  The auxiliary power supply circuit 50 includes a primary side auxiliary winding s1, a diode 501 and a capacitor 502 as a primary side circuit having a primary side ground as a reference potential. The auxiliary power circuit 50 includes a secondary side auxiliary winding s2 of the transformer 22, a diode 503, a capacitor 504, a constant voltage circuit 505, and a capacitor 506 as a secondary side circuit having the secondary side ground as a reference potential. The auxiliary power supply circuit 50 generates control power for the automatic flasher 30 and the control circuit 40 based on the switching operation of the switching element 21.

  Specifically, in the primary side circuit, the voltage generated in the primary side auxiliary winding s1 is rectified and smoothed by the diode 501 and the capacitor 502, and the smoothed voltage is supplied to the primary side control circuit of the PWM control circuit 41 as a control power source. Supplied as In the secondary side circuit, the voltage generated in the secondary side auxiliary winding s2 is rectified and smoothed by the diode 503 and the capacitor 504, and is made constant by the constant voltage circuit 505. Stabilized by capacitor 506. The constant voltage circuit 505 is a three-terminal regulator, a series regulator, a Zener diode, or the like. As a result, a control power supply Vcc (also referred to as “control voltage Vcc”) is generated, and power is supplied to the automatic flasher 30, the secondary control circuit of the PWM control circuit 41, and the like.

  The regulator circuit 60 includes a transistor 600, a resistor 601, a Zener diode 602, and a diode 603, and constitutes a series regulator. The collector terminal of the transistor 600 is connected to the high potential side output line L 1, and the emitter terminal is connected to the anode of the diode 603. The resistor 601 is connected between the collector terminal and the base terminal of the transistor 600. The base terminal of the transistor 600 is connected to the cathode of the Zener diode 602, and the anode of the Zener diode 602 is connected to the low potential side output line L0. The cathode of the diode 603 is connected to the positive electrode of the capacitor 506.

  As will be described later, the transistor 600 is maintained in the off state when the lighting signal is output and the transistor 650 of the operation switching circuit 65 is in the on state, and when the extinction signal is output and the transistor 650 is in the off state. It becomes possible to operate. That is, the regulator circuit 60 reduces the output voltage to the Zener voltage ZV3 of the Zener diode 602 and generates the control power supply Vcc only when the light is turned off. As a result, the regulator circuit 60 can supply power to the automatic flasher 30 and the control circuit 40 in place of the auxiliary power supply circuit 50 having reduced voltage generation capability when the light is turned off.

  The operation switching circuit 65 includes a transistor 650, a resistor 651, a Zener diode 652, a resistor 653, and a base resistor 654. The resistors 651 and 653 are connected in series between the high-potential side output line L1 and the low-potential side output line L0, and the Zener diode 652 is connected between the high-potential side output line L1 and the resistor 653 so that the anode terminal is on the low potential side. The resistor 651 is connected in series. The base terminal of the transistor 650 is supplied with power from the high potential side output line L1 through the resistor 651 and the Zener diode 652. The collector terminal of the transistor 650 is connected to the base terminal of the transistor 600 of the regulator circuit 60, and the emitter terminal of the transistor 650 is connected to the low potential side output line L0.

  The Zener voltage ZV2 of the Zener diode 652 is set to a value higher than the Zener voltage ZV1 of the Zener diode 452 and less than the forward voltage Vf of the LED2. The transistor 650 is turned on when the output voltage exceeds the Zener voltage ZV2, and turned off when the output voltage is equal to or lower than the Zener voltage ZV2. However, the output voltage is not less than the forward voltage Vf higher than the Zener voltage ZV2 at the time of lighting and near the limiter set value V1 lower than the Zener voltage ZV2 at the time of turning off, so that the output voltage does not stay near the Zener voltage ZV2. . Here, assuming that an output voltage (substantially the same value as the Zener voltage ZV2 in this embodiment) serving as an on / off switching boundary of the transistor 650 is an operation switching set value V2, the limiter setting value V1 <the operation switching setting value V2. <The forward voltage Vf.

  When the lighting signal is output, that is, when the LED 2 is lit, the output voltage exceeds the operation switching set value V2 and the forward voltage Vf, so that the Zener diode 652 and the transistor 650 are turned on. As a result, the transistor 600 is turned off and the regulator circuit 60 is deactivated.

  On the other hand, when the turn-off signal is output, that is, when the LED 2 is turned off, the output voltage is maintained at the limiter setting value V1 (<operation switching setting value V2) by the operation of the output voltage limiter circuit 45. Zener diode 652 and transistor 650 are turned off. As a result, the transistor 600 becomes operable and the regulator circuit 60 operates.

  Thus, the transistor 650 of the operation switching circuit 65 is turned on when the output voltage exceeds the operation switching set value V2 when the limiter set value V1 <the operation switching set value V2 <the forward voltage Vf. Is in the off state when is less than or equal to the operation switching set value V2. The regulator circuit 60 is configured to be inactive when the transistor 650 is in an on state and to operate when the transistor 650 is in an off state. That is, the regulator circuit 60 is activated when the potential difference between the output voltage and the control power supply is small, and is deactivated when the potential difference between the output voltage and the control power supply is large. Therefore, loss in the transistor 600 is reduced. Further, the non-operation / operation of the regulator circuit 60 is determined by the output voltage, and the operation switching setting value V2 of the output voltage that determines the boundary between the non-operation / operation is set higher than the limiter setting value V1 and lower than the forward voltage Vf. Therefore, the regulator circuit 60 is surely deactivated when turned on and operates reliably when turned off.

  Furthermore, the setting of the Zener voltages ZV1 and ZV2 makes it possible to adjust the setting of the limiter setting value V1 at the time of extinction and the operation switching setting value V2 that determines the operating state of the regulator circuit 60, thereby improving design ease. . In particular, since the Zener voltage ZV2 is higher than the Zener voltage ZV1, the regulator circuit 60 operates reliably when extinguished.

The operation of the LED lighting circuit 1 particularly regarding the control power supply is summarized as follows.
When a lighting signal (a logic high blinking control signal S) is output from the automatic blinker 30, the transistor 455 of the output voltage limiter circuit 45 is turned off, and the LED2 is under the constant current control of the LED current by the PWM control circuit 41. Lights up. At this time, since the output voltage is higher than the operation switching set value V2, the transistor 650 of the operation switching circuit 65 is turned on, and the regulator circuit 60 is not operated. Therefore, the voltage generated by the auxiliary power supply circuit 50 is supplied as the control voltage Vcc to the automatic flasher 30 and the control circuit 40 (in particular, the secondary control circuit of the PWM control circuit 41).

  When a turn-off signal (logic low blink control signal S) is output from the automatic blinker 30, the LED 2 is turned off, the transistor 455 of the output voltage limiter circuit 45 can be turned on and off, and the constant voltage at the limiter set value V1. Control is executed. At this time, since the output voltage is lower than the operation switching set value V2, the transistor 650 of the operation switching circuit 65 is turned off, and the regulator circuit 60 operates. Therefore, the regulator circuit 60 generates a control voltage instead of the auxiliary power supply circuit 50 having a reduced voltage generation capability in a light load state due to the LED being turned off, and the automatic flasher 30 and the control circuit 40 (particularly, the PWM control circuit 41). The control voltage Vcc is supplied to the secondary control circuit.

  As described above, the LED lighting circuit 1 according to the present embodiment switches the switching element 21 so that the output voltage is maintained at the limiter set value V1 less than the forward voltage Vf when the extinguishing signal is output from the automatic flasher 30. A control circuit 40 for PWM driving, an auxiliary power supply circuit 50 for generating a control voltage Vcc1 from the voltage generated in the auxiliary winding s2 and supplying power to the automatic flasher 30 and the control circuit 40, and a control voltage Vcc2 from the output voltage The regulator circuit 60 configured to supply power to the automatic flasher 30 and the control circuit 40, and when the output voltage is higher than the limiter set value V1, the regulator circuit 60 is deactivated, and the output voltage is set to the limiter set value V1. The operation switching circuit 65 is provided for operating the regulator circuit 60 when the voltage is maintained. As described above, when the switching element 21 has a large PWM driving amount and a large potential difference between the output voltage and the control voltage, the auxiliary power supply circuit 50 generates the control voltage from the transformer auxiliary winding s2, and the automatic flasher 30 or the like supplies power. At the same time, the regulator circuit 60 is deactivated. On the other hand, when the PWM drive amount of the switching element 21 is small and the potential difference between the output voltage and the control voltage is small, the regulator circuit 60 generates a control voltage from the output voltage and powers the automatic flasher 30 and the like. Therefore, in the LED lighting circuit 1 with the automatic flasher 30, it is possible to supply a stable control voltage Vcc to the automatic flasher 30 and the control circuit 40 when the LED is turned off without increasing the loss when the LED is turned on.

  The LED lighting device 3 includes the LED lighting circuit 1 and the LED 2 described above. Therefore, in the LED lighting device 3 including the automatic flasher 30 as a part of the LED lighting circuit 1, a low-loss lighting operation and a stable light-off operation are compatible.

<Modification>
Although preferred embodiments of the present invention have been described above, the present invention can be modified into various modes as shown below, for example.

(1) Modification of Operation Switching Circuit 65 In the above embodiment, the configuration in which the transistor 650 is turned off in response to a decrease in the output voltage in the operation switching circuit 65 is shown. However, the transistor 650 is turned off by a turn-off signal. Also good. FIG. 2 shows a part of the LED lighting circuit 1 according to this modification. In the present modification, the same components as those in the above embodiment are denoted by the same reference numerals, or illustrations thereof are omitted, and duplicate descriptions are omitted.

  As shown in FIG. 2, the blinking signal generation unit 32 of the automatic blinker 30 is connected to the base terminal of the transistor 650 and the blinking control signal S is input. At the time of lighting, by inputting a logic high flashing control signal S (lighting signal) to the base terminal of the transistor 650, the transistor 650 is turned on, and the regulator circuit 60 is not operated. When the light is turned off, the logic low blinking control signal S (light-off signal) is input to the base terminal of the transistor 650, whereby the transistor 650 is turned off and the regulator circuit 60 operates. Therefore, in this modification, there is no concept of the operation switching set value V2 with respect to the operation switching circuit 65.

(2) Modification of output voltage limiter circuit 45 and operation switching circuit 65 In the above embodiment, the voltage detection configuration (resistor 451, Zener diode 452 and resistor 453) of output voltage limiter circuit 45 and the voltage detection configuration of operation switching circuit 65 ( Although the resistor 651, the Zener diode 652, and the resistor 653) are configured as individual circuits, some of them may be shared. FIG. 3 shows a part of the LED lighting circuit 1 according to this modification. In the present modification, the same components as those in the above embodiment are denoted by the same reference numerals, or illustrations thereof are omitted, and duplicate descriptions are omitted.

  As shown in FIG. 3, the output voltage limiter circuit 45 includes transistors 450 and 455, a Zener diode 454, a resistor 456, and voltage dividing resistors 457 and 458, and the operation switching circuit 65 includes a transistor 650 and a Zener diode 655. A series circuit of voltage dividing resistors 457 and 458 is connected in series between the high potential side output line L1 and the low potential side output line L0. The cathodes of the Zener diodes 454 and 655 are connected to a connection point between the voltage dividing resistors 457 and 458 (hereinafter referred to as “voltage dividing point”). The anode of the Zener diode 454 is connected to the base terminal of the transistor 455, and the anode of the Zener diode 655 is connected to the base terminal of the transistor 650. Similar to the above embodiment, the collector terminal of the transistor 450 is connected to the base terminal of the transistor 455.

  The limiter setting value V1 is determined by the voltage dividing ratio of the voltage dividing resistors 457 and 458 and the Zener voltage ZV4 of the Zener diode 454. The operation switching setting value V2 is determined by the voltage dividing ratio of the voltage dividing resistors 457 and 458 and the Zener voltage ZV5 of the Zener diode 655. It is determined. Also in this modified example, the Zener voltage ZV4 <the Zener voltage ZV5 is set so that the limiter set value V1 <the operation switching set value V2. Further, the voltage dividing resistors 457 and 458 and the Zener voltage ZV5 are set so that the operation switching set value V2 is less than the forward voltage Vf.

  According to this configuration, at the time of lighting, the transistor 450 is turned on and the transistor 455 is turned off by the logic high flashing control signal S (lighting signal). Thereby, constant current control of the LED current is executed by the PWM control circuit 41, and an output voltage equal to or higher than the forward voltage Vf of the LED 2 is applied to the voltage dividing resistors 457 and 458. Therefore, the Zener diode 655 and the transistor 650 are turned on, and the regulator circuit 60 is not operated.

  When the light is turned off, the transistor 450 is turned off by the logic low blinking control signal S (light-off signal), and the transistor 455 can be turned on and off. When the voltage at the voltage dividing point of the voltage dividing resistors 457 and 458 exceeds the zener voltage ZV4, the transistor 455 is turned on, the PWM drive on width of the switching element 21 is reduced or the PWM drive is stopped, and the voltage at the voltage dividing point is reduced. When the voltage becomes lower than the zener voltage ZV4, the transistor 455 is turned off and the driving of the switching element 21 is maximized. By repeating this, an output voltage substantially equal to the limiter set value V1 is applied to the voltage dividing resistors 457 and 458. Since the Zener voltage ZV5 is higher than the Zener voltage ZV4, the Zener diode 655 is turned off when the output voltage is maintained at the limiter set value V1. Accordingly, the transistor 650 is turned off and the regulator circuit 60 operates.

(3) Modification Regarding Power Supply Destination of Regulator Circuit 60 In the embodiment described above, the configuration in which the control voltage from the regulator circuit 60 is supplied to the automatic flasher 30 and the control circuit 40 when the light is turned off has been described. On the other hand, when only the operation of the control circuit 40 is secured by the control voltage from the auxiliary power supply circuit 50 when the light is turned off, the control voltage from the auxiliary power supply circuit 50 is supplied to the control circuit 40 and the control from the regulator circuit 60 is performed. The voltage may be supplied to the automatic flasher 30. FIG. 4 shows an LED lighting circuit 1 according to this modification. In the present modification, the same components as those in the above embodiment are denoted by the same reference numerals, or illustrations thereof are omitted, and duplicate descriptions are omitted.

  As shown in FIG. 4, the regulator circuit 60 includes diodes 603 and 604 and a capacitor 605 on the output side. The anode of the diode 603 is connected to the collector terminal of the transistor 600, and the cathode is connected to the capacitor 605 and the control power supply unit of the automatic flasher 30. The anode of the diode 604 is connected to the output part of the auxiliary power supply circuit 50, that is, the control power supply Vcc of the control circuit 40, and the cathode is connected to the control power supply part of the automatic flasher 30.

  According to this configuration, at the time of lighting, the control voltage from the auxiliary power supply circuit 50 is supplied to the control circuit 40 and also supplied to the automatic flasher 30 via the diode 604. When the light is turned off, the control voltage from the auxiliary power supply circuit 50 is supplied to the control circuit 40 and the control voltage from the regulator circuit 60 is supplied to the automatic flasher 30 via the diode 603.

1 LED lighting circuit 2 LED
3 LED lighting device 20 DC / DC converter 30 Automatic flasher 40 Control circuit 41 PWM control circuit 42 Current detection resistor 45 Output voltage limiter circuit 50 Auxiliary power supply circuit 60 Regulator circuit 65 Operation switching circuit 450 Transistor (flashing control transistor)
455 transistor (limiter transistor)
650 transistor (operation switching transistor)

Claims (7)

An LED lighting circuit,
A DC / DC converter having a switching element and a transformer, and supplying DC power to the LED by PWM driving of the switching element;
An automatic flasher that switches between the output signal and the turn-off signal, and
When the lighting signal is output, the output voltage of the DC / DC converter is maintained at or above the forward voltage of the LED, and when the extinguishing signal is output, the output voltage is less than the forward voltage. A control circuit for PWM driving the switching element to maintain the limiter set value;
An auxiliary power supply circuit that generates a first control voltage from a voltage generated in an auxiliary winding provided in the transformer and supplies power to the automatic flasher and the control circuit;
A regulator circuit configured to generate a second control voltage from the output voltage to power the automatic flasher or the automatic flasher and the control circuit;
An LED comprising: an operation switching circuit that deactivates the regulator circuit when the output voltage is higher than the limiter set value, and operates the regulator circuit when the output voltage is maintained at the limiter set value; Lighting circuit. In the LED lighting circuit according to claim 1,
The operation switching circuit has an operation switching transistor, and the operation switching transistor is turned on when the output voltage exceeds the operation switching setting value for the operation switching setting value higher than the limiter setting value and less than the forward voltage. When the output voltage is less than or equal to the operation switching set value, it is turned off,
An LED lighting circuit configured such that the regulator circuit is inoperative when the operation switching transistor is in an on state and operates when the operation switching transistor is in an off state. In the LED lighting circuit according to claim 1 or 2,
The control circuit comprises:
An output voltage limiter circuit having a limiter transistor that is turned off when the lighting signal is output, and is turned on when the extinguishing signal is output and the output voltage is equal to or higher than the limiter set value;
When the limiter transistor is in an on state, the PWM drive on width is decreased or the PWM drive is stopped, and when the limiter transistor is in an off state, the PWM drive on width is increased. LED lighting circuit comprising a PWM control circuit. The LED lighting circuit according to claim 3,
The control circuit further comprises a current detection resistor for detecting an LED current flowing through the LED,
When the lighting signal is output, the PWM control circuit is configured to determine an ON width of the PWM drive so that an LED current detected by the current detection resistor matches a target value. Lighting circuit. The LED lighting circuit according to claim 1, wherein the DC / DC converter has a high potential side output line and a low potential side output line,
The control circuit comprises:
A high potential side first resistor and a low potential side second resistor connected in series between the high potential side output line and the low potential side output line, the high potential side output line and the second potential A first Zener diode connected in series with the first resistor with an anode terminal facing the low potential side between the resistors, and a control terminal from the high potential side output line to the first resistor and the first Zener An output voltage limiter circuit having a limiter transistor fed via a diode, and a blinking control transistor that turns off the limiter transistor when the lighting signal is output;
When the limiter transistor is in an on state, the PWM drive on width is decreased or the PWM drive is stopped, and when the limiter transistor is in an off state, the PWM drive on width is increased. PWM control circuit
The operation switching circuit is
A third resistor on the high potential side and a fourth resistor on the low potential side connected in series between the high potential side output line and the low potential side output line, the high potential side output line and the fourth resistor A second Zener diode connected in series with the third resistor with the anode terminal facing the low potential side between the resistors, and a control terminal from the high potential side output line to the third resistor and the second resistor Having an operation switching transistor fed through a Zener diode;
The Zener voltage of the first Zener diode is set to the limiter set value, the Zener voltage of the second Zener diode is set to an operation switching set value that is higher than the limiter set value and less than the forward voltage,
An LED lighting circuit configured such that the regulator circuit is inoperative when the operation switching transistor is in an on state and operates when the operation switching transistor is in an off state.   The LED lighting circuit according to any one of claims 1 to 5, wherein the limiter set value is 45V or less.   The LED lighting apparatus provided with the LED lighting circuit as described in any one of Claim 1 to 6, and the said LED.

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