JP6249167B2 - LED lighting device and LED lighting device - Google Patents

Description

  The present invention relates to an LED lighting device and an LED lighting device using the LED lighting device.

  Patent Document 1 discloses a power supply device including an insulating switching power supply circuit and overload protection means. This power supply device includes an overload state of a load such as a conversion unit that converts alternating current into direct current, a switching element that switches direct current supplied from the conversion unit to the primary side of the transformer, and an LED provided on the secondary side of the transformer And an overload protection unit that stops the operation of the switching element and maintains the stopped state when an overload state is detected by the overload detection unit. The power supply device operates with a regulator unit that generates a DC voltage using a voltage supplied from the auxiliary winding of the transformer, a DC current generated by the regulator unit, and feedbacks according to the LED current and voltage. A constant current constant voltage control unit for controlling the control signal is provided. When the overload protection unit detects an overload state such as an LED overvoltage based on a signal from the constant current constant voltage control unit, the overload protection unit stops the operation of the switching element and latches the state.

JP 2010-57331 A

  In the configuration of Patent Document 1, since a latch-type protection circuit is employed, output stop to the LED is maintained in the protection operation at the time of overload. In such a configuration, since the lighting of the LED does not automatically return when the overload is eliminated, the AC power supply (commercial power) needs to be turned on again by the user for the relighting after the overload is eliminated. However, it is desirable that the light projecting function, which is the original function of the lighting device, be secured immediately when the overload condition is resolved. Therefore, in order to automatically return to the lighting state when the overload is eliminated, it is preferable not to latch the stop state of the output operation of the apparatus in the protection state but to continue the output operation intermittently.

  Incidentally, as in the same document, in an insulated power supply circuit, a voltage supplied from an auxiliary winding of a transformer is generally used to generate a control voltage of a secondary circuit having a reference potential different from that of the primary circuit. The In such a control power supply circuit, when the transformer primary side switching element is intermittently driven in a no-load state in which the LED is disconnected or removed, the power generated in the transformer auxiliary winding decreases, and the control unit of the secondary side circuit A state in which a sufficient control voltage is not supplied to the (constant current constant voltage control unit) may occur. Then, an unstable control state is brought about due to this insufficient control voltage, and the secondary output voltage of the transformer that should be maintained at the upper limit set value by the function of constant voltage control is the upper limit setting. May rise above the value. Such a state causes a failure of circuit parts constituting the device, and the reliability of the device is lowered.

  Therefore, the present invention provides an LED lighting device having an insulation type DC power supply circuit, and even when the switching element of the DC power supply circuit is intermittently driven at a light load such as no load, the secondary side circuit is stably provided. It is an object of the present invention to provide a configuration capable of obtaining the control voltage.

  The LED lighting device of the present invention has an insulation type DC power supply circuit that drives the switching element of the primary side circuit and applies the output voltage of the secondary side circuit to the LED, and the same reference potential as the secondary side circuit, A detection circuit that detects the output state of the secondary circuit, and a secondary circuit that has the same reference potential as the secondary circuit and determines the driving state of the switching element based on the detection value detected by the detection circuit The control circuit and the secondary side circuit have the same reference potential, generate a first voltage from a voltage generated in response to driving of the switching element, and use the first voltage as a control voltage for the secondary side control circuit. A secondary auxiliary power supply circuit to be supplied and a voltage supplement circuit configured to generate a second voltage from the output voltage of the secondary circuit and superimpose the second voltage on the control voltage are provided.

  According to the LED lighting device of the present invention, the voltage supplementing circuit generates the second voltage from the output voltage of the secondary side circuit and superimposes it on the control voltage of the secondary side control circuit. Even when the switching element of the primary side circuit of the isolated DC power supply circuit is in an intermittent drive state at a light load such as, the control voltage of the secondary side control circuit can be stably obtained.

  Here, the voltage supplement circuit includes a resistance element connected to the high potential side output terminal of the secondary circuit, and a Zener diode connected in series to the resistance element and having an anode connected to the reference potential terminal of the secondary circuit. And a diode whose anode is connected to the cathode of the Zener diode and whose cathode is connected to the positive terminal of the secondary side auxiliary power supply circuit. As a result, a voltage supplement circuit that can reliably supply power even at light loads such as no load is configured with a small number of parts, and the LED lighting device can be reduced in size and cost.

  Furthermore, the voltage supplement circuit is inserted between the voltage detection unit for detecting the voltage between the high potential side output terminal and the positive terminal of the secondary side auxiliary power supply circuit, and the resistance element, the cathode of the Zener diode, and the anode of the diode. The switch element may be further configured so that the switch element is turned on when the voltage detected by the voltage detection unit exceeds a predetermined value. As a result, an energization path from the output voltage of the secondary side circuit to the voltage supplement circuit is formed only during a light load such as no load, so that the loss in the voltage supplement circuit is reduced.

  In addition, the DC power supply circuit is composed of a flyback converter having a transformer, the primary side circuit is connected to the primary main winding of the transformer, the secondary side circuit is connected to the secondary main winding of the transformer, and the auxiliary winding of the transformer. The secondary side auxiliary power supply circuit can be connected to the power source. Thereby, the LED lighting device is formed with a simple configuration, and the size and cost thereof can be reduced.

  The LED lighting device of the present invention includes the LED lighting device and the LED. Since the LED lighting device having the above effects is mounted, the reliability of the LED lighting device can be improved, and the size and cost can be reduced.

It is a circuit block diagram of the LED lighting apparatus containing the LED lighting device by the 1st Embodiment of this invention. It is a figure explaining operation | movement of the LED lighting device by a comparative example. It is a figure explaining an example of operation of the LED lighting device by a 1st embodiment. It is a figure explaining the other example of operation | movement of the LED lighting device by 1st Embodiment. It is a circuit block diagram which shows the voltage supplementary circuit of the LED lighting device by the 2nd Embodiment of this invention.

Embodiment 1. FIG.
FIG. 1 shows a circuit configuration diagram of an LED lighting device 100 and an LED lighting device 150 using the LED lighting device 100 according to the first embodiment of the present invention. The LED lighting device 150 includes an LED lighting device 100 and an LED module 50. An input voltage from the AC power supply AC is input to the input terminals T1 and T2 of the LED lighting device 100, and a DC output from the output terminals T3 and T4 of the LED lighting device 100 is supplied to the terminal T5 of the LED module 50 via the wirings W1 and W2. And T6.

  The LED module 50 includes an LED array including a plurality of LEDs connected in series between the terminal T5 and the terminal T6. The anode end of the LED array is connected to the high potential side output terminal T3 of the LED lighting device 100 via the input terminal T5 and the wiring W1, and the anode end of the LED array is connected to the low potential side output terminal via the input terminal T6 and the wiring W2. Connected to T4. In addition, the LED lighting device 100 and the LED module 50 may be integrated in one housing, or may be configured separately in two housings.

  The LED lighting device 100 includes an input circuit 200, a DC power supply circuit 300, a detection circuit 400, a primary side auxiliary power supply circuit 500, a secondary side auxiliary power supply circuit 600, a primary side control circuit 700, a secondary side control circuit 800, and a voltage supplement. A circuit 900 is provided. In the description in this specification, it is convenient for each circuit element to belong to which circuit, and the present invention is not bound thereto.

  The input circuit 200 includes current fuses 1 and 2, a diode bridge 3, a capacitor 4, and a noise filter as necessary. An AC voltage from an AC power supply AC (for example, commercial power supply) is input to the input circuit 200, and a full-wave rectified output from the diode bridge 3 is input to the DC power supply circuit 300. When the input power source is a DC power source, the diode bridge 3 is not necessary.

  The DC power supply circuit 300 is an isolated flyback converter, and constitutes a so-called one-converter flyback step-down circuit having a power factor improving function. The DC power supply circuit 300 includes a switching element 5, a transformer 6, a resistor 7, a diode 8, and an electrolytic capacitor 9. The positive electrode terminal of the electrolytic capacitor 9 becomes the high potential side output terminal of the DC power supply circuit 300, and the negative electrode terminal becomes the reference potential terminal, that is, the ground. In the DC power supply circuit 300, the switching element 5, the primary main winding 6a of the transformer 6 and the resistor 7 constitute a primary side circuit, and the secondary main winding 6b, the diode 8 and the electrolytic capacitor 9 of the transformer 6 are the secondary side circuit. Configure.

  In the DC power supply circuit 300, energy is accumulated by the primary main winding 6a of the transformer 6 during the ON period of the switching element 5, and the energy is transmitted from the secondary main winding 6b side of the transformer 6 to the diode 8 during the OFF period of the switching element 5. The electrolytic capacitor 9 is charged via The step-down ratio is determined by the turn ratio of the secondary main winding 6b to the primary main winding 6a, and the output current is determined by the on-duty (ON width) in the PWM control of the switching element 5. The switching element 5 is driven by the switching control IC 10, and the switching control IC 10 appropriately adjusts the driving state with reference to the current of the switching element 6 detected by the resistor 7. In the following description, the output voltage of the DC power supply circuit 300 is referred to as “output voltage VL”, and the output current of the DC power supply circuit 300 is referred to as “output current IL”.

  The detection circuit 400 includes a voltage detection circuit including voltage dividing resistors 11, 12 and 13 and a current detection circuit including a current detection resistor 14. The detection circuit 400 has the same reference potential as the secondary side circuit of the DC power supply circuit 300. The voltage dividing resistors 11, 12 and 13 are formed of a voltage dividing resistor circuit connected in parallel to the electrolytic capacitor 9 of the DC power supply circuit 300, and a voltage proportional to the output voltage VL is generated in the voltage dividing resistor 13. The current detection resistor 14 is composed of a low resistance element inserted between the ground and the low potential side output terminal T4, and a voltage proportional to the output current IL is generated in the current detection resistor 14.

  The primary side auxiliary power supply circuit 500 includes a primary side auxiliary winding 6 c of the transformer 6, a diode 15, a capacitor 16, a transistor 17, a resistor 18, a Zener diode 19, and a capacitor 20. The reference potential of the primary side auxiliary power supply circuit 500 is the same as the reference potential of the primary side circuit of the DC power supply circuit 300 (the potential at the common anode end of the diode bridge 3). The winding direction of the primary side auxiliary winding 6c is the same as the winding direction of the secondary main winding 6b, and the voltage corresponding to the turn ratio of the primary side auxiliary winding 6c with respect to the secondary main winding 6b is the primary side auxiliary winding. Occurs in 6c. The voltage generated in the primary side auxiliary winding 6 c is rectified and smoothed by the diode 15 and the capacitor 16, and this smoothed voltage is stepped down by a series regulator constituted by the transistor 17, the resistor 18 and the Zener diode 19. The stepped down voltage is smoothed by the capacitor 20 and becomes the output voltage of the primary side auxiliary power supply circuit 500. Thus, the primary side auxiliary power supply circuit 500 smoothes the voltage generated for each drive pulse of the switching element 5 and supplies the control voltage to the switching control IC 10.

  The secondary side auxiliary power supply circuit 600 includes a secondary side auxiliary winding 6 d of the transformer 6, a diode 21, a capacitor 22, a transistor 23, a resistor 24, a Zener diode 25, a diode 26, and a capacitor 27. The secondary side auxiliary power supply circuit 600 has the same reference potential as the secondary side circuit of the DC power supply circuit 300. The winding direction of the secondary side auxiliary winding 6d is the same as the winding direction of the primary main winding 6a, and the voltage corresponding to the turn ratio of the secondary side auxiliary winding 6d with respect to the primary main winding 6a is the secondary side auxiliary winding. Occurs on line 6d. The voltage generated in the secondary side auxiliary winding 6d is rectified and smoothed by the diode 21 and the capacitor 22, and the smoothed voltage is stepped down by a series regulator constituted by the transistor 23, the resistor 24 and the Zener diode 25. The stepped down voltage (hereinafter referred to as “driving system auxiliary voltage”) is smoothed by the capacitor 27 via the diode 26 and output from the secondary side auxiliary power supply circuit 600 (hereinafter referred to as “secondary side control voltage Vcc”). It becomes.

  The primary side control circuit 700 includes a switching control IC 10 and a photocoupler 28 (phototransistor portion). The primary side control circuit 700 has the same reference potential as the primary side circuit of the DC power supply circuit 300. The switching control IC 10 performs PWM control of the switching element 5 with an ON width based on the output state of the phototransistor of the photocoupler 28. The output state of the photocoupler 28 is determined by the secondary side control circuit 800. Note that peripheral circuit components may be connected to the switching control IC 10 as necessary.

  The secondary side control circuit 800 includes operational amplifiers 29 and 30, a resistor 31, a shunt regulator 32, resistors 33, 34, 35 and 36, diodes 37 and 38, resistors 39 and 40, and a photocoupler 28 (a photodiode portion). Including. The secondary side control circuit 800 has the same reference potential as the secondary side circuit of the DC power supply circuit 300. In general, the operational amplifier 29 is a constant voltage control operational amplifier having a function of stabilizing the output voltage VL, and the operational amplifier 30 is a constant current control operational amplifier having a function of stabilizing the output current IL. Then, according to the output state of the DC power supply circuit 300, one of constant voltage control and constant current control is selected by the diode OR circuit composed of the diodes 37 and 38, and the input state of the photocoupler 28 is determined. That is, the switching element 5 is PWM-controlled by the primary side control circuit 700 so as to perform either constant current control or constant voltage control by the secondary side control circuit 800.

  The constant voltage control operational amplifier 29 operates by feeding the secondary control voltage Vcc. The voltage detection value detected by the voltage detection circuit is input to the negative input terminal (−) of the operational amplifier 29, and the voltage reference value Vref1 corresponding to the target value of the output voltage VL is input to the positive input terminal (+). . The voltage reference value Vref1 is a voltage obtained by dividing the voltage stabilized by the shunt regulator 32 by the resistors 33 and 34. Note that 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 29. The operational amplifier 29 amplifies and outputs an error between the voltage detection value input to the negative input terminal and the voltage reference value Vref1 input to the positive input terminal. In other words, when the diode 37 is turned on and constant voltage control is selected, the operational amplifier 29 determines the ON width in the PWM control so that the voltage detection value matches the voltage reference value Vref1.

  The constant current control operational amplifier 30 is also operated by feeding the secondary side control voltage Vcc. The operational amplifiers 29 and 30 can be composed of operational amplifiers built in the same IC. The current detection value detected by the current detection circuit is input to the negative input terminal (−) of the operational amplifier 30, and the current reference value Vref2 corresponding to the target value of the output current IL is input to the positive input terminal (+). . The current reference value Vref2 is a voltage value obtained by dividing the voltage stabilized by the shunt regulator 32 by the resistors 35 and 36. Note that a feedback element (not shown) is also connected between the negative input terminal and the output terminal of the operational amplifier 30. The operational amplifier 30 amplifies and outputs an error between the current detection value input to the negative input terminal and the current reference value Vref2 input to the positive input terminal. In other words, when the diode 38 is turned on and constant current control is selected, the operational amplifier 30 determines the ON width in PWM control so that the current detection value matches the current reference value Vref2.

  The diode OR circuit composed of the diodes 37 and 38 is turned on with respect to the lower one of the output terminal voltage of the constant current control operational amplifier 29 and the output terminal voltage of the constant voltage control operational amplifier 30. The common anode of the diode OR circuit is connected to the cathode side of the photodiode of the photocoupler 28. The anode of the photodiode of the photocoupler 28 is connected to the output of the shunt regulator 32 via a resistor 39, and the resistor 40 is connected in parallel to the photodiode. The resistor 39 may be inserted on the cathode side of the photodiode. An output current corresponding to the current (light emission) flowing through the photodiode flows through the phototransistor of the photocoupler 28. As described above, the switching control IC 10 generates a PWM drive signal having a pulse width corresponding to the output state of the phototransistor of the photocoupler 28, and outputs it as the gate voltage of the switching element 5.

  Here, an operation when the LED module 50 is normal (hereinafter referred to as “normal operation”) will be described. In normal operation, basically, the operation of the operational amplifier 30 is selected by the diode OR circuit and constant current control is performed. In this embodiment, when the current detection value is smaller than the current reference value Vref2, the output terminal voltage of the operational amplifier 30 swings to the high side, the current flowing through the photodiode of the photocoupler 28 decreases, and the output current from the phototransistor. Also decreases. On the other hand, when the current detection value is larger than the current reference value Vref2, the output terminal voltage of the operational amplifier 30 swings to the low side, the current flowing through the photodiode of the photocoupler 28 increases and the output current from the phototransistor also increases. It is assumed that the switching control IC 10 is configured to increase the pulse width of the PWM control with respect to the decrease in the output current of the phototransistor.

  Therefore, when the detected current value is smaller than the current reference value Vref2, the operational amplifier 30 acts in the direction of increasing the PWM control pulse width of the switching element 5, that is, in the direction of increasing the output current IL. On the contrary, when the current detection value is larger than the current reference value Vref2, the operational amplifier 30 acts in the direction of decreasing the pulse width of the PWM control of the switching element 5, that is, the direction of decreasing the output current IL. Thus, constant current control is performed by feedback of the output current IL during normal lighting operation.

  The operation when the LED module 50 is removed or the LED elements constituting the LED module 50 are disconnected and the LED lighting device 100 is in a no-load state will be described. When there is no load, no current flows through the current detection resistor 14. Therefore, if the above-described constant current control is performed as it is, the PWM width of the switching element 5 is maximized and the output voltage VL is greatly increased by the action of the operational amplifier 30 for constant current control. Therefore, when no load is applied, the operation of the constant voltage control operational amplifier 29 is selected by the diode OR circuit, and the constant voltage control is performed so that the output voltage VL becomes constant at the limiter voltage (corresponding to the voltage reference value Vref1). .

  In the present embodiment, when the voltage detection value is smaller than the voltage reference value Vref1, the output terminal voltage of the operational amplifier 29 swings to the high side, the current flowing through the photodiode of the photocoupler 28 decreases, and the output current from the phototransistor also increases. Decrease. On the other hand, when the voltage detection value is larger than the voltage reference value Vref1, the output terminal voltage of the operational amplifier 29 swings to the low side, the current flowing through the photodiode of the photocoupler 28 increases and the output current from the phototransistor also increases.

  Therefore, as in the case of the constant current control, when the voltage detection value is smaller than the voltage reference value Vref1, the operational amplifier 29 increases the pulse width of the PWM control of the switching element 5, that is, increases the output voltage VL. Works. On the contrary, when the voltage detection value is larger than the voltage reference value Vref1, the operational amplifier 29 acts in the direction of decreasing the pulse width of the PWM control of the switching element 5, that is, the direction of decreasing the output voltage VL. Thus, constant voltage control is performed by feedback of the output voltage VL when there is no load, and the operational amplifier 29 functions as a limiter of the output voltage VL in a no-load state (in some cases, a normal operation state).

  The voltage supplement circuit 900 includes resistors 41 and 42, a Zener diode 43, and a diode 44. The resistors 41 and 42 are connected to the high potential side output terminal of the DC power supply circuit 300. The Zener diode 43 is connected in series to the resistors 41 and 42, the cathode is connected to the resistor 42, and the anode is connected to the ground. The diode 44 has its anode connected to the cathode of the Zener diode 43 and its cathode connected to the positive terminal of the secondary auxiliary power circuit 600 (the connection point between the cathode of the diode 26 and the capacitor 27). As will be described in detail later, the voltage supplement circuit 900 includes a secondary side control circuit that superimposes a voltage obtained through the resistors 41 and 42 (hereinafter referred to as “output system auxiliary voltage”) on the secondary side control voltage Vcc. 800 is configured to supply.

  Here, the operation at the time of a light load such as the above-mentioned no load will be examined again. The function as an output voltage limiter by the operational amplifier 29 in the above-described no-load state is naturally when the secondary side control voltage Vcc is higher than the operation stop voltage of the operational amplifiers 29 and 30, that is, when the operational amplifiers 29 and 30 are operating. To be demonstrated. Furthermore, the resistors 35 to 38, 39 and 40 and the photocoupler 28 need to be appropriately supplied with power through the shunt regulator 32. By the way, when the switching element 5 is in an intermittent drive state, the power supplied from the secondary side auxiliary winding 6d of the transformer 6 to the secondary side auxiliary power supply circuit 600 is reduced, thereby reducing the drive system auxiliary voltage. The secondary control voltage Vcc decreases. The reduction of the secondary side control voltage Vcc is caused by the power consumption by the operational amplifiers 29 and 30, the photocoupler 28, the resistors 33, 34, 35 and 36, the resistors 39 and 40 through the shunt regulator 32, and the like. Further, when a circuit for dealing with external dimming, a microcomputer for additional functions, etc. are provided and these are powered from the secondary side control voltage Vcc, the secondary side control voltage Vcc is reduced. It gets even faster. Therefore, even in the state where the switching element 5 is intermittently driven, it is necessary that the secondary control voltage Vcc is secured and each circuit in the secondary control circuit 800 operates normally.

  FIG. 2 shows the secondary control voltage Vcc and the output voltage VL when a no-load state occurs in the circuit configuration (comparative example) in which the voltage supplement circuit 900 is removed from the LED lighting device 100. The horizontal axis is time, and the vertical axis is voltage. As a general rule, a no-load state occurs at the point A, and then the secondary control voltage Vcc repeatedly rises and falls (in this example, one cycle of this repetition is about 100 ms), and according to this repetition As a result, the output voltage VL gradually increases.

  Specifically, when a no-load state occurs at the point A, the output voltage VL reaches the limiter voltage by the action of the secondary side control circuit 800 and the primary side control circuit 700 described above, and the driving of the switching element 5 is stopped. The When the switching element 5 is stopped, the generation of the drive system auxiliary voltage is stopped, the secondary side control voltage Vcc is lowered, and the output voltage VL is slightly reduced.

  When the secondary control voltage Vcc becomes equal to or lower than the operation stop voltage of the operational amplifiers 29 and 30 at the point B, the operational amplifiers 29 and 30 stop operating and open their output terminals. As a result, the current flowing through the photodiode of the photocoupler 28 and the current output from the phototransistor decrease, so the primary side control circuit 700 re-drives the switching element 5 with the maximum on-duty, that is, the output voltage VL is maximized. Acts to increase with output. In addition, the switching element 5 “drives” means that the switching element 5 is repeatedly turned on and off. As a result, the output voltage VL rises at the point B, and the drive system auxiliary voltage is obtained, and the secondary side control voltage Vcc rises instantaneously. When the secondary side control voltage Vcc exceeds the operation stop voltage of the operational amplifiers 29 and 30, the operational amplifiers 29 and 30 are restarted, and the constant voltage control of the secondary side control circuit 800 is resumed. Will not continue.

  Since the voltage detection value is already higher than the voltage reference value Vref1 in the operational amplifier 29 at the time point C immediately after the point B, it corresponds to the constant voltage control of the secondary side control circuit 800 that maintains the output voltage VL at the limiter voltage. Thus, the primary side control circuit 700 stops driving the switching element 5 again. In other words, since the switching element 5 is driven from the point B to the point C, the output voltage VL rises from the voltage at the point B. On the other hand, after the point C, the secondary control voltage Vcc drops in the same manner as the points A to B. Thereafter, an operation similar to that at point B occurs at point D. As described above, by repeating the operations indicated by points B to D, the output voltage VL increases during the no-load period.

  FIG. 3 shows an example of an operation at the time of no load in the LED lighting device 100 of the present embodiment provided with the voltage supplement circuit 900. As in FIG. 2, the horizontal axis is time, and the vertical axis is voltage. As a general rule, a no-load state occurs at the point A, and then the secondary side control voltage Vcc repeatedly increases and decreases (in this example, one cycle is about 50 ms), but the output voltage VL is Maintained constant.

  Specifically, when a no-load state occurs at the point A, the output voltage VL reaches the limiter voltage by the action of the secondary side control circuit 800 and the primary side control circuit 700 described above, and the driving of the switching element 5 is stopped. The When the switching element 5 is stopped, the generation of the drive system auxiliary voltage is stopped, the secondary control voltage Vcc is lowered, and the output voltage VL is reduced.

  At the point B, since the secondary control voltage Vcc, which is the sum of the drive system auxiliary voltage and the output system auxiliary voltage, exceeds the operation stop voltage of the operational amplifiers 29 and 30, the operational amplifiers 29 and 30 continue to operate. Yes. Here, the operational amplifier 29 operates to drive the switching element 5 again in order to return the voltage detection value (output voltage VL) to the voltage reference value Vref1. As described above, the intermittent drive of the switching element 5 is continued thereafter, but the secondary control voltage Vcc stops the operation of the operational amplifiers 29 and 30 by intermittently decreasing the drive system auxiliary voltage due to the intermittent drive. It will never go below the voltage. Therefore, the constant voltage control of the secondary side control circuit 800 is enabled throughout the period, and the output voltage VL is maintained substantially constant at the limiter voltage. Thereafter, an operation similar to that at point B occurs at point D. Thus, by repeating the operations indicated by points B to D, the output voltage VL is maintained substantially constant during the no-load period.

  FIG. 4 shows another example of the operation at the time of no load in the LED lighting device 100 of this embodiment provided with the voltage supplement circuit 900. Similar to FIG. 3, the horizontal axis is time, and the vertical axis is voltage. The difference between the operation shown in FIG. 3 and the operation shown in FIG. 4 is caused by a difference in circuit constants. As a general rule, a no-load state occurs at the point A, and then the secondary side control voltage Vcc repeatedly rises and falls (in this example, one repeated cycle is about 5 s), but the output voltage VL is Maintained constant.

  Specifically, when a no-load state occurs at the point A, the output voltage VL reaches the limiter voltage by the action of the secondary side control circuit 800 and the primary side control circuit 700 described above, and the driving of the switching element 5 is stopped. The When the switching element 5 is stopped, the generation of the drive system auxiliary voltage is stopped, the secondary side control voltage Vcc is lowered, and the output voltage VL is gradually reduced.

  At the point B, the drive system auxiliary voltage is exhausted, but since the output system auxiliary voltage exceeds the operation stop voltage of the operational amplifiers 29 and 30, the operational amplifiers 29 and 30 continue to operate and the switching element 5 is intermittent. Driving continues thereafter. Therefore, the secondary side control voltage Vcc does not become lower than the operation stop voltage of the operational amplifiers 29 and 30 even during the period when the switching element 5 is not driven thereafter (the period from the point B to the point C). Therefore, the constant voltage control of the secondary side control circuit 800 is enabled throughout the period, and the output voltage VL is maintained substantially constant at the limiter voltage. At the point D immediately after the point C, the secondary control voltage Vcc is clamped by the breakdown voltage of the Zener diode 24 or the Zener diode 43. Thereafter, an operation similar to that at point B occurs at point E. Thus, by repeating the operations indicated by points B to E, the output voltage VL is maintained substantially constant during the no-load period.

  The resistors 41 and 42 are preferably adjusted or set to resistance values that can supply a minimum current that allows the secondary-side control circuit 800 to operate at no load. This reduces the loss during normal operation. On the contrary, if the loss during normal operation is not a problem, the resistance values of the resistors 41 and 42 can be reduced to further stabilize the secondary control voltage Vcc.

  For example, the output voltage VL during normal operation is 100 V, the output voltage VL (limiter voltage) during no load is 120 V, the secondary control voltage Vcc during normal operation is 12 V, and the operational amplifiers 29 and 30 When the operation stop voltage is 3 V, the total resistance value of the resistors 41 and 42 may be about several kΩ to 100 kΩ, and preferably about 10 kΩ to 60 kΩ. In this case, the breakdown voltage of the Zener diode 43 may be 12 V, which is the same as the secondary side control voltage Vcc.

  As described above, according to the LED lighting device 100 according to the present embodiment, the secondary side auxiliary power supply circuit 600 generates the drive system auxiliary voltage from the voltage generated according to the driving of the switching element 5, Is supplied to the secondary control circuit 800 as the side control voltage Vcc, and the voltage supplement circuit 900 generates an output system auxiliary voltage from the output voltage VL and superimposes it on the secondary control voltage Vcc. Thereby, even when the switching element 5 is in the intermittent drive state at a light load such as no load, the secondary side control voltage Vcc is stably obtained, and the stable operation of the secondary side control circuit 800 is realized. . And since the output voltage VL does not exceed a limiter voltage, the reliability of the LED lighting device 100 and the LED lighting device 150 is ensured.

Embodiment 2. FIG.
In the first embodiment, the voltage replenishment circuit 900 is always energized. However, in this embodiment, the voltage replenishment circuit 900 is not energized during normal operation of the DC power supply circuit 300 (non-load state). The configuration is shown. That is, in the present embodiment, when the switching element 5 is continuously driven, the voltage supplement circuit 900 is energized because the supply capability of the secondary control voltage Vcc by the drive system auxiliary voltage is sufficient. Stop and avoid losses.

  FIG. 5 shows a voltage supplement circuit 900 in the LED lighting device 100 of the present embodiment. In addition, the same code | symbol is attached | subjected to the same element as 1st Embodiment, and the detailed description is abbreviate | omitted. The voltage supplement circuit 900 includes resistors 41 and 42, a Zener diode 43, a diode 44, resistors 45, 46 and 47, and a switch element 48. The resistors 45, 46, and 47 are connected in series between the high potential side output terminal of the DC power supply circuit 300 and the cathode of the Zener diode 43, and constitute a voltage detection unit that detects a voltage therebetween. The switch element 48 is inserted between the resistor 42 and the cathode of the Zener diode 43 and the anode of the diode 44. Specifically, the input terminal of the switch element 48 is connected to the resistor 42, the output terminal is connected to the cathode of the Zener diode 43, and the control terminal is connected to the connection point between the resistor 46 and the resistor 47. The input terminal, the output terminal, and the control terminal are a collector terminal, an emitter terminal, and a base terminal, respectively, when the switch element 48 is formed of a bipolar transistor, and are each a drain terminal, when the switch element 48 is formed of an FET. Source terminal and gate terminal.

  In the above configuration, when the output voltage VL increases and the cathode voltage of the Zener diode 43 decreases and the voltage across the resistors 41 and 42 increases, the voltage detected by the voltage detector (that is, generated in the resistor 47). When the voltage) exceeds the operating threshold of the switch element 48, the switch element 48 becomes conductive. In other words, the resistance values of the resistors 45, 46, and 47 are such that the voltage generated at the resistor 47 when the output voltage VL is near the limiter voltage and the secondary control voltage Vcc is lowered is the operating threshold value of the switch element 48. It is set to exceed. The above-described state in which the output voltage VL increases and the secondary control voltage Vcc decreases can occur at light loads such as no load when the switching element 5 is intermittently driven. Therefore, the generation of the output system auxiliary voltage by the voltage supplement circuit 900 can be validated by turning on the switch element 48 only during a light load such as no load. On the other hand, the state in which both the output voltage VL and the secondary side control voltage Vcc are relatively high, or the state in which both the output voltage VL and the secondary side control voltage Vcc are relatively low is during normal operation in which the switching element 5 is continuously driven ( This can happen when there is a load. Therefore, during the normal operation in which the drive system auxiliary voltage can be sufficiently obtained, the switch element 48 is turned off, so that the voltage supplement circuit 900 is not energized, and losses in the resistors 41 and 42 are avoided.

  The voltage detection unit can directly or indirectly detect the voltage between the high potential output terminal and the positive terminal of the secondary side auxiliary power circuit 600, that is, the potential difference between the output voltage VL and the secondary control voltage Vcc. Any other configuration circuit may be used. For example, the resistor 47 of the detection unit may be connected to the cathode (that is, the positive terminal of the secondary side auxiliary power supply circuit 600) instead of the anode of the diode 44.

  As described above, in the LED lighting device 100 according to the present embodiment, the energization path of the voltage supplement circuit 900 is formed at a light load such as a no load in which the switching element 5 is intermittently driven. Therefore, during the normal operation in which the switching element 5 is continuously driven, the energization path of the voltage supplement circuit 900 is opened, and the loss in the resistors 41 and 42 is reduced.

<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 DC Power Supply Circuit 300 In each of the above embodiments, a so-called one-converter type isolated flyback converter has been shown as the DC power supply circuit 300. However, the DC power supply circuit 300 is a switching circuit composed of a converter of another type. A power supply circuit may be used. For example, the DC power supply circuit 300 may be a forward converter, or a circuit including a power factor correction circuit and a flyback converter.

(2) Modification of Secondary Auxiliary Power Supply Circuit 600 In each of the above embodiments, the DC power supply circuit 300 is configured by a flyback converter, and the drive system auxiliary voltage is generated from the auxiliary winding of the transformer of the flyback converter. Although the configuration is shown, the configuration in which the drive system auxiliary voltage is generated is not limited to this. For example, when the DC power supply circuit 300 is composed of a forward type converter, the drive system auxiliary voltage may be generated from an auxiliary winding provided in a choke coil connected in series to the transformer secondary winding. it can. When the DC power supply circuit 300 includes a power factor correction circuit and a flyback converter, the drive system auxiliary voltage is generated from an auxiliary winding provided in a coil constituting the power factor correction circuit. You can also. In either configuration, the drive system auxiliary voltage can be generated by smoothing the voltage generated for each drive pulse of the switching elements constituting each circuit.

5 Switching element 6 Transformer 41, 42 Resistance (resistance element)
43 Zener diode 44 Diode 45, 46, 47 Resistance (voltage detection unit)
48 Switch element 50 LED module (LED)
100 LED lighting device 150 LED lighting device 300 DC power supply circuit 600 Secondary side auxiliary power supply circuit 800 Secondary side control circuit 900 Voltage supplement circuit

Claims (5)

An LED lighting device,
An insulation type DC power supply circuit that drives the switching element of the primary circuit and applies the output voltage of the secondary circuit to the LED;
A detection circuit having the same reference potential as the secondary side circuit and detecting an output state of the secondary side circuit;
A secondary side control circuit having the same reference potential as the secondary side circuit, and for determining a driving state of the switching element based on a detection value detected by the detection circuit;
A first voltage is generated from a voltage that has the same reference potential as that of the secondary side circuit and is generated according to driving of the switching element, and the first voltage is used as a control voltage for the secondary side control circuit. A secondary side auxiliary power circuit to supply;
An LED lighting device comprising: a voltage supplement circuit configured to generate a second voltage from the output voltage of the secondary side circuit and to superimpose the second voltage on the control voltage.   2. The LED lighting device according to claim 1, wherein the voltage supplement circuit is connected in series to the resistance element connected to a high-potential side output terminal of the secondary side circuit, and an anode is connected to the secondary side. LED lighting device comprising: a Zener diode connected to a reference potential end of a side circuit; and a diode having an anode connected to a cathode of the Zener diode and a cathode connected to a positive end of the secondary side auxiliary power supply circuit .   3. The LED lighting device according to claim 2, wherein the voltage supplement circuit detects a voltage between the high potential side output terminal and a positive terminal of the secondary side auxiliary power circuit, and the resistance element. A switching element inserted between a cathode of the Zener diode and an anode of the diode, and is configured to conduct the switching element when a voltage detected by the voltage detection unit exceeds a predetermined value. LED lighting device.   4. The LED lighting device according to claim 1, wherein the DC power supply circuit includes a flyback converter having a transformer, and the primary side circuit is connected to a primary main winding of the transformer. The secondary side circuit is connected to the secondary main winding of the LED, and the secondary side auxiliary power circuit is connected to the auxiliary winding of the transformer. The LED lighting apparatus provided with the LED lighting device as described in any one of Claim 1 to 4, and the said LED.

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