JP5357553B2 - Power supply device and lighting apparatus using the same - Google Patents

Description

  The present invention relates to a power supply device having a full bridge circuit and a lighting fixture using the same.

  It is known that an organic EL element has an effect of restoring a lifetime by applying a reverse voltage (Patent Document 1). Therefore, conventionally, as in the circuit of FIG. 5, during the normal lighting period, the voltage supplied to the organic EL element 3 from the DC power source Vdc via the resistor R is supplied to the capacitor C via the normally closed contact of the switch circuit SW. In the recovery period, the switch circuit SW is switched to the normally-open contact side so that a reverse voltage can be applied to the organic EL element 3.

  However, in the conventional example of FIG. 5, it is difficult to arbitrarily control the time for applying the reverse voltage to the organic EL element 3, the applied voltage, and the current, so that excessive stress is applied to the organic EL element 3. There is a problem that the characteristics cannot be sufficiently recovered.

  Therefore, Patent Document 2 discloses a configuration in which a full-bridge circuit is used to apply a forward voltage to the organic EL element during a normal lighting period and to apply a reverse voltage by switching the polarity of the full-bridge circuit during a recovery period. Yes. As an improvement technique, in Patent Document 3, a forward voltage is applied to the organic EL element using a step-down chopper operation during a normal lighting period, and a reverse voltage is directly applied from a power source without using a step-down chopper operation during a recovery period. It has been proposed to apply.

Japanese Patent No. 2663648 Japanese Patent Laying-Open No. 2005-078828 JP 2007-149463 A

  However, in the techniques of Patent Documents 2 and 3, it is difficult to appropriately set the reverse voltage and the reverse current applied to the organic EL element during the recovery period. For this reason, there is a possibility that an excessive stress is applied to the organic EL element during the recovery period, and there is a possibility that the maximum lifetime improvement effect cannot always be expected.

  The present invention has been made in view of the above points, and a power supply apparatus that can maximize the life improvement effect of an organic EL element by applying an appropriate voltage and current to the organic EL element in a reverse direction over an appropriate time. It is an issue to provide.

In order to solve the above-mentioned problem, the invention of claim 1 connects the organic EL element 3 to a DC power source through a full bridge circuit as shown in FIG. Among the elements Q1 to Q4, a constant voltage element for setting a reverse voltage applied to the organic EL element 3 in series with at least one of the two switching elements Q1 and Q4 that are in opposite directions with respect to the organic EL element 3 This is characterized in that ZD is connected. According to the first aspect of the present invention, the organic EL element 3 is connected to the output of the full bridge circuit via the inductor L, and at least one of the two switching elements Q1 and Q4 in the opposite direction to the organic EL element 3 is used. The diode D for energizing the regenerative current is connected in reverse parallel with the energy, and the energy stored in the inductor L of the two switching elements Q2 and Q3 in the forward direction with respect to the organic EL element 3 flows during a normal lighting period. Forming the path with the diode D and the organic EL element 3 is turned on, the other is turned on and off at high frequency, and the two switching elements Q1 and Q4 that are opposite to the organic EL element 3 are turned on during the recovery period. The control part 1 to be provided is provided.

In order to solve the above-described problem, another invention of the present application connects the organic EL element 3 to a DC power source via a full bridge circuit as shown in FIG. Of the elements Q1 to Q4, a current limiting element for setting a reverse current applied to the organic EL element 3 in series with at least one of the two switching elements Q1 and Q4 opposite to the organic EL element 3 R2 is connected.

The invention of claim 2 is characterized in that the function of the constant voltage element ZD of claim 1 is combined with at least one of the two switching elements Q1 and Q4 in the opposite direction to the organic EL element 3.

The invention of claim 3 is an illumination instrument comprising the power supply device according to claim 1 or claim 2 Symbol placement.

  According to the present invention, since an arbitrary voltage and current can be applied to an organic EL element in an opposite direction for an arbitrary time, the life and performance of the organic EL element can be optimally recovered with a simple circuit.

It is a circuit diagram of Embodiment 1 of the present invention. It is operation | movement explanatory drawing of Embodiment 1 of this invention. It is a circuit diagram of Embodiment 2 of the present invention. It is a circuit diagram of Embodiment 3 of the present invention. It is a circuit diagram of a conventional example.

(Embodiment 1)
FIG. 1 is a circuit diagram of Embodiment 1 of the present invention. The commercial AC power supply Vs is full-wave rectified by the diode bridge circuit DB, and the DC voltage is charged in the smoothing capacitor C. To the positive electrode of the capacitor C, the emitters of switching elements Q1, Q3 made of PNP transistors are connected. A collector of the switching element Q2 made of an NPN transistor is connected to the collector of the switching element Q1. The emitter of the switching element Q2 is connected to the ground via a resistor R1. The negative electrode of the capacitor C is connected to the ground.

  A series circuit of an inductor L and an organic EL element 3 is connected between the collector of the switching element Q1 and the collector of the switching element Q3. Further, a regenerative current conducting diode D is connected in reverse parallel to both ends of the switching element Q1. The switching element Q3, the inductor L, and the diode D constitute a buck converter (step-down chopper circuit).

  The collector of the switching element Q3 is connected to the collector of the switching element Q4 made of an NPN transistor via a Zener diode ZD. The emitter of the switching element Q4 is connected to the ground via a resistor R2.

  The resistor R1 is a current detection resistor for allowing an optimum current to flow through the organic EL element 3 during the lighting period. The resistor R2 functions as a current limiting resistor during a recovery period in which a reverse voltage is applied to the organic EL element 3, and is a resistor for monitoring the current flowing through the switching element Q4. The voltages at the non-ground side terminals of the resistors R1 and R2 are input to the control unit 1 and monitored.

  A full bridge circuit is configured by the switching elements Q1 to Q4. A base terminal which is a control electrode of each of the switching elements Q1 to Q4 is connected to an output of the control unit 1, and an on / off state thereof can be switched by the control unit 1. The operating power supply for the control unit 1 is supplied from a capacitor C.

  FIG. 2 is a waveform diagram for explaining the operation of the first embodiment. The load current flowing through the organic EL element 3, the current of the switching element Q2, the current of the diode D, and the ON / OFF states of the switching elements Q1 to Q4 are shown.

  During the lighting period, the switching element Q3 is always ON, and a high-frequency PWM signal is applied to the switching element Q2. When the switching element Q2 is ON, a current flows through a path of the capacitor C → the switching element Q3 → the organic EL element 3 → the inductor L → the switching element Q2 → the current detection resistor R1 → the ground. Further, when the switching element Q2 is OFF, the energy stored in the inductor L flows through the path of the inductor L → the diode D → the switching element Q3 → the organic EL element 3 → the inductor L. In this case, it operates as a normal switching converter.

  Next, the reverse voltage application operation at the time of characteristic recovery is performed by turning off the switching elements Q2 and Q3 and turning on the switching elements Q1 and Q4. At this time, the current flows through a path of the capacitor C → the switching element Q1 → the inductor L → the organic EL element 3 → the zener diode ZD → the switching element Q4 → the current limiting resistor R2 → the ground.

  The application time of the reverse voltage can be adjusted by the ON time of the switching element Q4 or Q1. At this time, an optimal reverse voltage can be applied to the organic EL element 3 by appropriately selecting the Zener voltage of the Zener diode ZD arranged in series. Further, a circuit in which the Zener diode ZD is omitted and the switching element Q4 has the function of the Zener diode ZD may be used. That is, by adjusting the control voltage / control current supplied from the control unit 1 to the control electrode of the switching element Q4, the magnitude of the voltage drop caused by the switching element Q4 can be appropriately adjusted. By using it in the unsaturated region, the function of the Zener diode ZD can be shared.

  Furthermore, an optimum reverse current can be passed through the organic EL element 3 by selecting the resistance value of the resistor R2 connected in series with the switching element Q4. Further, the resistor R2 may be omitted, and a circuit in which the switching element Q4 has the role of the resistor R2 may be used. That is, by detecting the voltage across the resistor R2 by the control unit 1 and adjusting the control voltage / control current supplied from the control unit 1 to the control electrode of the switching element Q4 so that the detected value becomes an appropriate value. The reverse current flowing through the organic EL element 3 can be adjusted appropriately. That is, the function of the resistor R2 can be shared by using the switching element Q4 in the unsaturated region.

  In addition, since the reverse current flowing through the organic EL element 3 during the recovery period is not a large current compared with the lighting period, it can be said that no large power loss occurs even when the switching element Q4 is used in the unsaturated region.

  In the circuit configuration as shown in FIG. 1, by issuing a reverse voltage application signal from the control unit 1, an arbitrary voltage and an arbitrary current can be applied to the organic EL element 3 in an opposite direction over an arbitrary time. The lifetime characteristics of the organic EL element 3 can be sufficiently recovered without applying stress.

(Embodiment 2)
FIG. 3 is a circuit diagram of Embodiment 2 of the present invention. In this embodiment, the diode D connected in antiparallel with the switching element Q1 is omitted in the circuit of FIG. 1, and instead the diode D is connected in antiparallel with the series circuit of the Zener diode ZD, switching element Q4, and resistor R2. doing.

  The reverse voltage application operation at the time of characteristic recovery is the same as that of the first embodiment. In the normal lighting period, in the first embodiment, the switching element Q3 is always ON, and a high-frequency PWM signal is supplied to the switching element Q2. However, in the present embodiment, in the normal lighting period, the switching element Q3 is switched on. The difference is that Q2 is always ON and a high-frequency PWM signal is supplied to the switching element Q3.

  When the switching element Q3 is ON, a current flows through a path of the capacitor C → the switching element Q3 → the organic EL element 3 → the inductor L → the switching element Q2 → the current detection resistor R1 → the ground. This operation is the same as in the first embodiment. In addition, when the switching element Q3 is OFF, the energy accumulated in the inductor L flows through the path of the inductor L → the switching element Q2 → the current detection resistor R1 → the diode D → the organic EL element 3 → the inductor L. Therefore, in the second embodiment, the load current flowing through the organic EL element 3 can always be detected by the resistor R1, so that the load current can be controlled with higher accuracy than in the first embodiment.

(Embodiment 3)
FIG. 4 is a circuit diagram of Embodiment 3 of the present invention. In the present embodiment, the diode D1 is connected in antiparallel with the switching element Q1, and the diode D2 is connected in antiparallel with the series circuit of the Zener diode ZD, the switching element Q4, and the resistor R2.

  The reverse voltage application operation at the time of characteristic recovery is the same as that of the first embodiment. In the normal lighting period, in the first and second embodiments, one of the switching elements Q2 and Q3 is always ON, and a high-frequency PWM signal is supplied to the other. However, in this embodiment, the switching elements Q2 and Q3 are supplied. The difference is that a high-frequency PWM signal is supplied to Q3.

  When the switching elements Q2 and Q3 are ON, a current flows through a path of the capacitor C → the switching element Q3 → the organic EL element 3 → the inductor L → the switching element Q2 → the current detection resistor R1 → the ground. This operation is the same as in the first and second embodiments. Further, when the switching elements Q2 and Q3 are OFF, the energy accumulated in the inductor L flows through the path of inductor L → diode D1 → capacitor C → diode D2 → organic EL element 3 → inductor L. In this case, since a part of the energy stored in the inductor L is regenerated in the smoothing capacitor C, the decay rate of the regenerative current can be increased even when the load voltage of the organic EL element 3 is low, The OFF period of switching elements Q2 and Q3 can be shortened.

(Embodiment 4)
The circuit configuration of the present embodiment is the same as that of FIG. 4 except that the control of the switching elements Q2 and Q3 during a normal lighting period is appropriately combined with the first and second embodiments and the third embodiment. For example, from the first state in which the switching elements Q2 and Q3 are simultaneously ON, to the third state in which both are OFF through the second state in which one is ON and the other is OFF. Repeat the operation to switch. In this case, the load current flowing in the organic EL element 3 rises rapidly in the first state, attenuates slowly in the second state, and rapidly attenuates in the third state.

  The order of the second state (where one is ON and the other is OFF) and the third state (both are OFF) in which the regenerative current flows may be switched. In that case, the load current flowing through the organic EL element 3 rises rapidly in the first state, rapidly attenuates in the third state, and slowly attenuates in the second state.

  As described above, the average value of the load current can be freely changed by changing the time ratio and the order of the second state and the third state in which the regenerative current flows as a control element other than the ON time width of the switching elements Q2 and Q3. Can be controlled. Thereby, the load current flowing through the organic EL element 3 via the inductor L can be optimally controlled regardless of the power supply voltage or the load voltage.

  For example, in order to improve the input power factor from the commercial power source Vs, when the capacitance of the capacitor C is intentionally set small and a DC voltage that is not completely smoothed is used as the power source, the switching element Q2 is changed by the fluctuation of the power source voltage. , The rate of increase of the load current when Q3 is on varies. In such a case, since it is necessary to shorten the ON period of the switching elements Q2 and Q3 during a period when the power supply voltage is high, the regenerative current is slowly attenuated by using the regenerative operation of the first and second embodiments. Further, since it is necessary to lengthen the ON period of the switching elements Q2 and Q3 during the period when the power supply voltage is low, the regenerative current is rapidly attenuated by using the regenerative operation of the third embodiment. By controlling in this way, the load current can be optimally controlled with respect to fluctuations in the power supply voltage without changing the switching frequency. The fact that there is no need to change the switching frequency is advantageous in terms of noise countermeasures.

  In the configuration of FIG. 4, if the operation of the first embodiment in which the regenerative current flows through the diode D1 and the operation of the second embodiment in which the regenerative current flows through the diode D2, the regenerative current flowing through the diodes D1 and D2 are changed. Since it can be halved, heat generation of the diodes D1 and D2 can be suppressed.

(Other variations)
In each of the above embodiments, the switching elements Q1 and Q3 are realized by PNP transistors and the switching elements Q2 and Q4 are realized by NPN transistors. However, the former may be replaced by a p-channel MOSFET and the latter by an n-channel MOSFET. Further, if the high-potential side switching elements Q1 and Q3 are also driven through a transformer or a high-side driver, they can be replaced with inexpensive n-channel MOSFETs.

  Further, a light emitting diode may be connected in series or in parallel with the organic EL element 3. For example, if a series circuit of light emitting diodes is connected in antiparallel to both ends of the organic EL element 3, the light emitting diode can be turned on as an indicator during the recovery period of the organic EL element 3, and it is in the recovery period. Can be displayed. In addition, the minimum light can be secured even during the recovery period. Furthermore, the reverse voltage applied to the organic EL element 3 can be optimally set by adjusting the number of light emitting diodes in series.

  Further, instead of the Zener diode ZD as the constant voltage element, one or a plurality of diodes or light emitting diodes or a series circuit thereof may be connected. These constant voltage elements may be mixed and connected in series.

  Further, the Zener diode ZD as the constant voltage element is connected in series with the low-potential side switching element Q4, but may be connected in series with the high-potential side switching element Q1, or the switching elements Q1 and Q4 A constant voltage element may be connected in series to both. The same applies to the current limiting element R2.

  In addition, although the commercial AC power supply Vs was rectified by full-wave rectification by the diode bridge circuit DB as the DC power supply and smoothed by the smoothing capacitor C, the configuration is not limited thereto. For example, a PFC circuit (power factor correction circuit) may be inserted between the diode bridge circuit DB and the smoothing capacitor C. Further, instead of a rectified and smoothed DC power supply as a commercial power supply, a battery power supply such as a storage battery or a DC power supply obtained by converting the output thereof may be used.

(Embodiment of lighting apparatus)
In the lighting fixture using the power supply device of the present invention, the use of the organic EL element makes it possible to reduce the thickness and weight of the fixture. In addition, since an appropriate voltage and current can be applied to the organic EL element in the reverse direction over an appropriate time during the recovery period, a long-life lighting device can be obtained.

DESCRIPTION OF SYMBOLS 1 Control part 3 Organic EL element Q1-Q4 Switching element L Inductor (inductive element)
D Diode C Capacitor (DC power supply)
R1, R2 resistance ZD Zener diode (constant voltage element)

Claims (3)

An organic EL element is connected to a direct current power source via a full bridge circuit, and at least two of the switching elements that are opposite to the organic EL element among the four switching elements constituting the full bridge circuit. A constant voltage element for setting a reverse voltage applied to the organic EL element is connected in series with one side, the organic EL element is connected to the output of the full bridge circuit via an inductor, and the organic EL element is connected to the organic EL element. In contrast, at least one of the two switching elements that are in the reverse direction is connected in reverse parallel with a diode for energizing a regenerative current, and in the normal lighting period, the two of the two that are in the forward direction with respect to the organic EL element. Oh the other hand to form a path energy stored in the inductor of the switching element flows together with the diode and the organic EL device Power supply, and turned on and off and the other at a high frequency, the recovery period, characterized in that it comprises a control unit for turning on the two of the switching element to be a direction opposite to the organic EL element. 2. The power supply apparatus according to claim 1, wherein the function of the constant voltage element of claim 1 is combined with at least one of the two switching elements that are in opposite directions with respect to the organic EL element. A lighting fixture comprising the power supply device according to claim 1.

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