JP2007266088A - Lighting system and illuminator for organic el - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting system capable of properly detecting a current without complicating a circuit configuration and controlling a lighting capable of lengthening a lifetime, and to provide an illuminator. <P>SOLUTION: The lighting system for the organic EL has a rectifier 51 being connected to an AC power supply PS and outputting a DC voltage, a step-down converter 52 varying an output voltage from the rectifier 51 and a full-bridge inverter 53 being connected to the step-down converter 52 and configuring a full bridge by four switching elements Q1 to Q4. The lighting system for the organic EL further has a current detector 54 being connected between an output from the step-down converter 52 and the full-bridge inverter 53 and having a resistor R detecting the current of the full-bridge inverter 53, a control circuit 55 supplying the full-bridge inverter 53 with control signals S1 to S4 and an organic EL element 10 as a light-emitting element. The relationship of a forward-voltage applying period Ton and an opposite voltage applying period Toff at the maximum output value of the organic EL element 10 reaching the period Ton/(the period Ton+the period Toff)<1 is controlled by the control circuit 55. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pulse width modulation type organic EL lighting device and lighting device.

  In recent years, it has been proposed to use an organic electroluminescence element (hereinafter referred to as an organic EL element) which is a carrier injection type solid state light emitting element in a lighting device. An organic EL element has a structure in which an organic thin film is sandwiched between electrodes, and carriers injected from the electrode recombine in the organic thin film, and organic molecules excited by the recombination energy return to the ground state. It uses light emitted from

  For at least one of the electrodes sandwiching the organic thin film, a transparent material is used to extract light. The organic EL element can constitute a thin and lightweight light emitting element. In addition, the organic EL element can be driven at a low voltage of several V to several tens of V, and the driving voltage is lower than that of a discharge lamp as a mainstream lighting means so far, so that the lighting device is inexpensive. It can be configured and expected to be applied to thin and lightweight lighting fixtures.

  By the way, in using an illuminating device, dimming of the illuminating device is generally performed from the viewpoint of power saving and lighting performance, and is described in Patent Document 1 as an illuminating device using a conventional organic EL element. There is something.

  As shown in FIG. 8, this conventional example includes converter means 20 for converting AC power supplied from an AC power source PS into DC power, and an organic EL element by turning on / off the DC current supplied from the converter means 20. Switching means 30 for intermittently supplying a forward current to 10 and control for switching on / off of the switching means 30 at a switching frequency higher than that of the AC input power supply PS and controlling the on-duty ratio of the switching means 30 The on-duty ratio is controlled by the control means 40 so that a desired brightness value is obtained by an external dimming mechanism that can be adjusted to a desired brightness by a dial or the like. The organic EL element 10 is caused to blink by turning on / off the switching means 30 according to the on-duty ratio. It is made to.

  Here, since the switching means 30 performs switching at a frequency higher than that of the AC power supply PS, the flickering of luminance is prevented and the light emission life is improved. In addition, the control means 40 can variably control the on-duty ratio to obtain a desired luminance.

  In the conventional lighting device shown in FIG. 8, the resistor Ri for detecting the current of the switching means 30 is in the forward current loop, and strictly the same voltage as the reverse voltage is not applied. That is, in principle, the forward voltage is smaller than the reverse voltage.

  The reason why the reverse voltage becomes higher than the forward voltage is that the resistance Ri is not on the loop in the reverse direction, so that a voltage drop of the current detection resistor Ri occurs only in the forward direction. If the voltage drop at the current detection resistor Ri is not sufficiently small compared to the forward voltage of the organic EL element 10, it is disadvantageous in terms of efficiency, but the forward voltage of the organic EL element 10 is relatively low. Therefore, if the value is sufficiently smaller than this voltage, the voltage becomes very small, which is disadvantageous in terms of detection accuracy. Therefore, the resistance value needs to be increased to some extent, and it is considered that the voltage drop also increases.

  If the output voltage of the step-down converter is the same in the forward direction and in the reverse direction when the resistance value is large to some extent, the voltage applied to the organic EL element in the reverse direction is larger than that in the forward direction. More elements to do.

That is, if the resistance value is small, there is a problem in detection accuracy, but if the resistance value is large, the problem of studying the circuit configuration increases, and it becomes difficult to obtain an appropriate resistance value.
JP-A-2005-78828

  The present invention has been made in view of the above-described conventional circumstances, and provides an organic EL lighting device and an illuminating device that can appropriately detect a current without complicating a circuit configuration and can have a long lifetime. It is intended to provide.

  The organic EL lighting device of the present invention includes a period Ton for applying a forward voltage to the organic EL element and a period Toff for applying a reverse voltage to the organic EL element, and changing a ratio of the period Ton and the period Toff. The organic EL lighting device performs dimming, and the forward voltage and the reverse voltage are substantially equal, and the relationship between the period Ton and the period Toff at the maximum output value of the organic EL element is the period Ton / Control is performed such that (period Ton + period Toff) <1.

  According to the above configuration, the dimming control is performed so that the relationship between the period Ton and the period Toff in the maximum output value of the organic EL element is the period Ton / (period Ton + period Toff) <1, thereby reliably applying the reverse voltage. It is possible to perform lighting control that can secure a period and extend the life.

  Further, the organic EL lighting device of the present invention includes converter means for outputting predetermined DC power, switching means for converting DC power supplied from the converter means into AC power, and supplying the AC power to the organic EL element, It is connected between the said converter means and the said switching means, The detection means which detects the electric current which flows into the said organic EL element is provided.

  According to the above configuration, by connecting the detection means between the converter means and the switching means, the forward voltage applied to the organic EL element becomes substantially equal to the reverse voltage, and the detection means for detecting the current is small. An electric current can be appropriately detected using a resistor having a resistance value, and an efficient organic EL lighting device can be provided.

  Further, the organic EL lighting device of the present invention is characterized in that the sum of the period Ton and the period Toff is constant. The organic EL lighting device of the present invention is characterized in that the period Toff is constant. Moreover, the lighting device of the present invention uses the lighting device for organic EL of the present invention.

  According to the above configuration, since the on-duty at the maximum output of the organic EL element is less than 100%, there is always a time for applying a reverse voltage to the organic EL element, and the organic EL element is refreshed by the refresh effect. It is possible to promote the extension of the lifetime of the element.

  According to the present invention, in an organic EL lighting circuit for lighting an organic EL element with a rectangular wave voltage including a reverse voltage application period, a dimming method using pulse width modulation is adopted, and the maximum duty of the pulse width is less than 100%. By doing so, it is possible to realize an organic EL dimming method that ensures a reverse voltage application period, can appropriately detect a current without complicating the circuit configuration, and can extend the lifetime.

  FIG. 1 is a view for explaining an organic EL lighting device 50 according to an embodiment of the present invention. The organic EL lighting device 50 according to the present embodiment is connected to an AC power source PS to output a DC voltage, a step-down converter 52 that varies the output voltage of the rectifier 51, and a step-down converter 52. A full-bridge inverter 53 that forms a full bridge with the switching elements Q1 to Q4, and a current detection circuit 54 that is connected between the output of the step-down converter 52 and the full-bridge inverter 53 and detects a current of the full-bridge inverter 53. And a control circuit 55 that supplies control signals S1 to S4 to the full bridge inverter 53, and an organic EL element 10 that is a light emitting element.

  The step-down converter 52 includes a capacitor C1 charged by the output of the rectifier 51, a switching element Q5 for chopping the voltage charged in the capacitor C1, a diode D1, a choke coil L for smoothing the chopped voltage, and And a smoothing capacitor C2.

  In the organic EL lighting device 50 of the present embodiment, a forward voltage applied to the organic EL element 10 is connected by connecting a resistor R that detects the current of the full bridge inverter 53 between the step-down converter 52 and the full bridge inverter 53. And make the reverse voltage almost equal.

In the control circuit 55, the relationship between the period Ton for applying the forward voltage to the organic EL element 10 and the period Toff for applying the reverse voltage at the maximum output value of the organic EL element 10 is as follows.
Period Ton / (period Ton + period Toff) <1 (Formula 1)
The drive signals S1 to S4 of the switching elements Q1 to Q4 constituting the full bridge inverter 53 are generated so that

  In the conventional lighting device shown in FIG. 8, the resistor Ri for detecting the current of the switching means 30 is in the forward current loop, and strictly the same voltage as the reverse voltage is not applied. That is, in principle, the forward voltage is smaller than the reverse voltage.

  The reason why the reverse voltage becomes higher than the forward voltage is that the resistance Ri is not on the loop in the reverse direction, so that a voltage drop of the current detection resistor Ri occurs only in the forward direction. If the voltage drop at the current detection resistor Ri is not sufficiently small compared to the forward voltage of the organic EL element 10, it is disadvantageous in terms of efficiency, but the forward voltage of the organic EL element 10 is relatively low. Therefore, if the value is sufficiently smaller than this voltage, the voltage becomes very small, which is disadvantageous in terms of detection accuracy. Therefore, the resistance value needs to be increased to some extent, and it is considered that the voltage drop also increases.

  In the organic EL lighting device 50 of the present embodiment, a forward voltage applied to the organic EL element 10 is connected by connecting a resistor R that detects the current of the full bridge inverter 53 between the step-down converter 52 and the full bridge inverter 53. Is approximately equal to the reverse voltage. Thereby, the current can be appropriately detected by using the resistor R having a small resistance value in the current detection circuit 54. In addition, the organic EL lighting device 50 of the present embodiment can be applied to a lighting device.

  FIG. 2 shows the relationship between the applied voltage V corresponding to each light output to the organic EL element 10 and the flowing current I in the organic EL lighting device 50 according to the embodiment of the present invention. As shown in the figure, a rectangular wave voltage V having a constant period is applied to the organic EL element 10. When the applied voltage V is a forward voltage, the organic EL element 10 is turned on. When the applied voltage V is a reverse voltage, the ionized electrode is refreshed when the forward voltage is applied.

  FIG. 3 shows the relationship between the ratio (on duty) to the period of the period in which the forward voltage is applied and the light output. As shown in the figure, in the organic EL lighting device 50 of the present embodiment, the maximum on-duty dmax is set to less than 100%. Since the on-duty at the maximum output is less than 100%, there is always a time for applying a reverse voltage to the organic EL element 10, and in order to extend the life of the organic EL element 10 by the refresh effect. Become advantageous.

  In FIG. 3, the relationship between the on-duty and the light output is a linear relationship, but it is not necessary to limit the relationship to a linear relationship as long as it is a monotonically increasing relationship. Further, although the light output is set to 0% when the on-duty is 0%, the light output may be set to 0% at the time of several%. In short, it is only necessary that the reverse voltage exists within one cycle.

  FIG. 4 is a diagram for explaining a schematic configuration of the illumination device 100 according to the embodiment of the present invention. The illuminating device 100 of this embodiment inputs the dimming signal of the dimming controller 2 used for a fluorescent lamp into the dimming means 3, and inverts it with the dimming means 3, and controls the voltage application time of an organic EL element. Light control. That is, the on-duty of the pulse width modulation signal of the dimming controller 2 and the lighting time of the organic EL element are controlled to be reversed.

  As shown in FIG. 4, the illuminating device 100 of this embodiment is based on the solid light emitting element 1 used as a light source, and the light control signal from the light control controller 2 used for light control of a fluorescent lamp lighting fixture. And a dimming means 3 for dimming the solid state light emitting device 1 by turning on and off the application of a DC voltage to 1.

  The solid-state light emitting element 1 emits light when a direct current voltage is applied in a specified direction like an organic EL element, for example, and is driven by a direct current voltage supplied from a direct current power source. The dimming is performed by changing the light emission time per unit time by turning on and off the application of the DC voltage. In addition to the organic EL element, other solid light emitting elements such as a light emitting diode may be used.

  An operation unit 2a and a power switch 2b are provided on the front surface of the dimming controller 2. The operation unit 2a is a lever, which changes the resistance value of the variable resistor built in the dimming controller 2 by sliding in the vertical direction in the figure and modulates the pulse width according to the dimming ratio corresponding to the resistance value. The adjusted dimming signal is output. With the dimming signal, the dimming ratios of the fluorescent lamp lighting fixture and the lighting device using the solid light emitting element 1 can be adjusted simultaneously. Here, the dimming signal is a pulse width modulation signal composed of binary values of Hi and Lo, and the dimming signal output from the dimming controller 2 has a dimming ratio and an on-duty ratio in an inversely proportional relationship. When the light knob 2a is slid in the upper direction, that is, the direction in which the dimming ratio is increased, the on-duty ratio is decreased, and when the light knob 2a is slid in the lower direction, that is, in the direction in which the dimming ratio is decreased, the on-duty ratio is increased. It has become. The power switch 2b turns on / off AC power supplied from an AC power source that is a power source of the dimming controller 2.

  The dimming means 3 is connected in series to the inverting circuit 3a that inverts the dimming signal consisting of binary values of Hi and Lo and outputs it to the control terminal of the switching element, and is input to the control terminal. The switching element 3b is turned on when the signal is at the Hi level, supplies a DC voltage to the solid state light emitting element 1, and is turned off when the signal is at the Lo level. Since the dimming signal generally has a voltage of 10 V and a frequency of 1 kHz, if the switching element 3b is a MOSFET that can be driven even at a low voltage, it can be directly driven by the dimming signal. When the switching element 3b is not directly driven, a dimming signal may be used as a control signal for the switching element 3b and a buffer circuit may be provided for driving.

  Hereinafter, operation | movement of the illuminating device 100 of this embodiment is demonstrated. The solid-state light emitting element 1 is connected in series with a DC power source and the light control means 3, and flashes and emits light by turning on / off the DC voltage by switching on / off the switching element 3 b of the light control means 3. The switching element 3b is driven by a pulse width modulation signal obtained by inverting the dimming signal output from the dimming controller 2 by the inverting circuit 3a, and the switch is turned on when the pulse width modulation signal is Hi so that the solid state light emitting element DC voltage is supplied to 1 and the switch is turned off when Lo.

  For example, when compared with the brightness of the dimming signal having an on-duty ratio of 50% shown in FIG. 5B, as shown in FIG. 5A, in the case of the dimming signal having an on-duty ratio of 25%, the inverting circuit 3a Since the on-duty ratio is converted to a pulse width modulation signal with 75% and the switching element 3b is driven by this signal, the voltage application time per unit time becomes longer, and the brightness of the solid state light emitting element 1 has an on-duty ratio of 50%. It becomes brighter than the case of. In the case of a dimming signal with an on-duty ratio of 75%, as shown in FIG. 5C, the inverter circuit 3a converts it to a pulse width modulation signal with an on-duty ratio of 25%, and this signal drives the switching element 3b. Therefore, the voltage application time per unit time is shortened, and the brightness of the solid state light emitting device 1 becomes darker than that when the on-duty ratio is 50%. As described above, the dimming of the lighting device and the fluorescent lamp illuminating device is unified by using the dimming signal output from the dimming controller 2 in the lighting device by inverting it.

  Further, in the illumination device 100 of the present embodiment, the minimum time of the reverse voltage application time can be ensured by controlling the minimum ON width of the pulse width modulation signal of the dimming controller 2 to correspond to the reverse direction application time. Configure as follows. If the minimum ON width of the pulse width modulation signal of the dimming controller 2 is reduced to 0% or smaller than the reverse voltage application time, the dimming means 3 ensures the minimum time of the reverse voltage application time. It needs to be configured so that it can.

  FIG. 6 shows the relationship between the applied voltage V corresponding to each light output to the organic EL element 10 and the flowing current I in the organic EL lighting device 50 according to Example 3 of the present invention. The time Toff for applying the reverse voltage to the organic EL element 10 is fixed, and the light output of the organic EL element 10 is changed by changing the time Ton for applying the forward voltage.

Assuming that the time Tonmax during which the forward voltage is applied at the time of maximum illumination output, the lighting cycle T is
T = Tonmax + Toff (Formula 2)
Therefore, the maximum on-duty value dmax is
dmax = Tonmax / (Tonmax + Toff) <1 (Formula 3)
It becomes.

  The relationship between the light output and the on-duty is schematically as shown in FIG. In FIG. 7, the relationship between the on-duty and the light output is a linear relationship, but it is not necessary to limit the relationship to a linear relationship as long as it is a monotonically increasing relationship. Further, although the light output is set to 0% when the on-duty is 0%, the light output may be set to 0% at the time of several%. In short, it is only necessary that the reverse voltage exists within one cycle.

  According to the organic EL lighting device 50 of the present embodiment, since the on-duty at the maximum output of the organic EL element 10 is less than 100%, there is always time to apply a reverse voltage to the organic EL element 10. Therefore, the lifetime of the organic EL element 10 can be promoted by the refresh effect.

  As described above, according to the organic EL lighting device and the lighting device according to the present embodiment, in the organic EL lighting circuit for lighting the organic EL element with the rectangular wave voltage including the reverse voltage application period, the adjustment by pulse width modulation is performed. By adopting the optical method and making the maximum duty of the pulse width less than 100%, the reverse voltage application period for extending the lifetime of the organic EL element is ensured, and the long-life organic EL dimming method Can be realized. In addition, by making the forward voltage applied to the organic EL element substantially equal to the reverse voltage, the current can be appropriately detected by using the resistor R having a small resistance value in the current detection circuit.

  INDUSTRIAL APPLICABILITY The present invention has an effect that current can be appropriately detected without complicating a circuit configuration and that the lifetime can be extended, and is useful for a pulse width modulation type organic EL lighting device and lighting device. .

The figure for demonstrating the lighting device 50 for organic EL concerning embodiment of this invention. FIG. 6 is a diagram (1) showing a relationship between an applied voltage V corresponding to each light output to the organic EL element 10 and a flowing current I in the organic EL lighting device 50 according to the embodiment of the present invention. The figure which shows the ratio (on duty) with respect to the period of the period which applies a forward voltage, and a light output (1) The figure for demonstrating schematic structure of the illuminating device 100 concerning embodiment of this invention. The figure for demonstrating schematic operation | movement of the illuminating device 100 concerning embodiment of this invention. FIG. 2 is a diagram (2) showing a relationship between an applied voltage V corresponding to each light output to the organic EL element 10 and a flowing current I in the organic EL lighting device 50 according to the embodiment of the present invention. Figure (2) showing the relationship between the ratio (on duty) to the period of the period in which the forward voltage is applied (on duty) and the light output The figure for demonstrating schematic structure of the conventional illuminating device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Solid state light emitting element 2 Dimming controller 2a Operation part 2b Power switch 3 Dimming means 3a Inversion circuit 3b Switching element 10 Organic EL element 20 Converter means 30 Switching means 40 Control means 50 Organic EL lighting device 51 Rectifier 52 Step-down converter 53 Full Bridge inverter 54 Current detection circuit 55 Control circuit 100 Lighting device 101 Electrode (anode)
102 Electrode (cathode)
DESCRIPTION OF SYMBOLS 103 Organic light emitting layer 104 Pattern resistance 105 Transparent substrate 106 Light reflection part 112 Hole transport layer 113 Electron transport layer 115 Terminal A
116 Terminal B
117 Terminal C

Claims (5)

An organic EL lighting device that provides a period Ton for applying a forward voltage to the organic EL element and a period Toff for applying a reverse voltage to the organic EL element, and performs dimming by changing the ratio of the period Ton and the period Toff Because
The forward voltage and the reverse voltage are substantially equal;
The relationship between the period Ton and the period Toff in the maximum output value of the organic EL element,
Period Ton / (Period Ton + Period Toff) <1
An organic EL lighting device that is controlled to be The organic EL lighting device according to claim 1,
Converter means for outputting predetermined DC power;
Switching means for converting the DC power supplied from the converter means into AC power and supplying the converted power to the organic EL element;
Detecting means connected between the converter means and the switching means for detecting a current flowing in the organic EL element;
A lighting device for organic EL, comprising: A lighting device for organic EL according to claim 1 or 2,
The organic EL lighting device, wherein a sum of the period Ton and the period Toff is constant. A lighting device for organic EL according to claim 1 or 2,
The organic EL lighting device, wherein the period Toff is constant.   The illuminating device using the lighting apparatus for organic EL as described in any one of Claims 1 thru | or 4.

Images