CN201504346U - Drive controller of OLED illuminating lamp or backlight source - Google Patents

Abstract

A drive controller of an OLED illuminating lamp or backlight relates to an OLED drive control circuit. The circuit comprises a constant current source control circuit, a constant voltage source control circuit, a forward constant current source circuit, a reverse constant voltage source circuit and a selection circuit; the output ends of the constant current source control circuit and the constant voltage source control circuit are respectively connected with the input end of the constant current source circuit, the input end of the constant voltage source circuit and the input end of the selection circuit, and the constant current source circuit and the constant voltage source circuit are respectively controlled by the constant current source control circuit and the constant voltage source control circuit; the output end of the constant current source circuit and the output end of the constant voltage source circuit are connected with the input end of the selection circuit so as to switch the constant current source circuit and the constant voltage source circuit; the output end of the selection circuit is connected with the load OLED illuminating lamp or the backlight source, and the circuit has the advantages that the service life of the OLED can be prolonged by more than 10 times compared with a common driving circuit through a large number of comprehensive experiments; and the display uniformity and stability can be improved.

Description

A driving controller for OLED lighting or backlight

technical field

The utility model relates to an OLED drive control circuit, in particular to a drive circuit capable of improving the service life and stability of OLED lighting and backlight display screens, and can also independently control a constant current or constant voltage drive controller.

Background technique

OLED, that is, organic light-emitting diode, is also called organic electroluminescence display (OELD). Because of its thinness, high contrast ratio, wide viewing angle, fast response, good display color, power saving, OLED’s adaptability to temperature is much stronger than that of LED, and it is very suitable for severe cold environments. These features are slowly becoming familiar to everyone, and full-color OLEDs have been widely used in MP3, MP4, mobile phones, digital cameras and other products.

The use of OLED for lighting and as a backlight is also slowly being applied and paid attention to. Its planar light emission is more promising and meaningful than LED's point light emission. OLED lighting products are more than three times more efficient than incandescent lamps, more than 10 times more efficient than light bulbs, and have a longer service life, do not contain mercury, and are environmentally friendly. Manufacturers from Europe, America and Japan have entered the field of OLED lighting one after another, hoping to replace the current fluorescent lamp market after 2010. At present, OLED is mainly used in lighting: including automotive lighting, LCD backlight, general lighting, medical and industrial lighting, billboard lighting and advertising special effects, etc. It can be seen that OLED has a bright future as lighting and has huge market potential.

However, due to factors such as organic materials, device structures, electrode materials, process conditions, and driving modes, the stability of OLEDs requires further efforts, especially the life of the display screen is particularly prominent. With the improvement of the stability and efficiency of organic materials and the optimization of process parameters, the lifetime of OLED devices can be improved, but in practical applications, a driving circuit with an ideal driving mode is also essential.

OLED's planar light emitting form is more suitable for the lighting industry than LED's point-shaped light emitting, because it does not need to use a flat light source composed of multiple LEDs and light diffusion treatment. Most LED drive power supplies use constant current mode, which can overcome changes in LED current caused by changes in the forward voltage of LED devices (specific voltage changes caused by temperature or manufacturing changes). Constant current mode produces constant LED brightness regardless of changes in forward voltage.

The same is true for OLED. Due to the OLED manufacturing process, all OLED pixels on a display cannot have the same optical threshold voltage; and changes in the electrode IT0 material and process will cause different voltage drops. In this way, the luminance distribution of the display pixels will be uneven when driven by a simple constant voltage. According to the OLED life test experiment, the half-life life of the AC drive signal is more than 10 times higher than that of the DC drive.

Utility model content

The main purpose of the utility model is to provide a driving controller for OLED lighting or backlight, which is driven in an ideal AC driving mode, thereby improving the life and stability of the OLED lighting display.

In order to achieve the above object, the utility model has designed the following technical solutions:

A driving controller for an OLED illuminating lamp or a backlight source, its circuit includes a constant current source control circuit, a constant voltage source control circuit, a forward constant current source circuit, a reverse constant voltage source circuit and a selection circuit; The output end of the source control circuit is connected to the input end of the constant current source circuit, the output end of the constant voltage source control circuit is connected to the input end of the constant voltage source circuit, the constant current source control circuit, the constant voltage source control circuit Control the constant current source circuit and the constant voltage source circuit respectively; the output end of the constant current source circuit and the output end of the constant voltage source circuit are connected to the selection circuit, so as to control the constant current source circuit and the constant voltage source circuit. The constant voltage source circuit is switched; the output terminal of the selection circuit is connected with the load OLED lighting lamp or the backlight source.

A drive controller for OLED lighting or backlight source of the utility model, its driving method is to add forward constant current and reverse constant voltage at both ends of the OLED pixel to provide an AC drive signal with a certain duty ratio and frequency ; At the same time, the driving circuit provided by the present invention adopts a high-efficiency step-down mode considering that it is suitable for large-size, high-power OLED lighting panels. Under flexible configuration, this driver can also be used as a high-power LED driver or a constant voltage source circuit alone.

The constant current source control circuit and the constant voltage source control circuit include a pulse width modulation circuit PWM that converts direct current into a high-frequency square wave current through repeated on/off switching; the constant current source control circuit and the The constant voltage source control circuit also includes an adjustment circuit that outputs the duty ratio frequency of the AC pulse square wave signal; the constant current source control circuit and the constant voltage source control circuit also include a circuit that closes and opens the constant current source and closes Turn on the circuit of the constant voltage source.

The constant current source circuit adopts a step-down mode, which includes a terminal Isense, a current comparator, a pulse width modulation comparator, an oscillation circuit and a D flip-flop for detecting the output current, and the input of the terminal Isense and the current comparator The output terminal of the current comparator is connected with the pulse width modulation comparator, one end of the pulse width modulation comparator is connected with the oscillation circuit, and the other end is connected with one end of the oscillation circuit to the D flip-flop; the constant current source circuit is provided with a The control pin IENB connected with the constant current circuit for closing and opening.

The constant voltage source circuit is also provided with a control pin VENB connected to turn off and on the constant voltage source circuit, and the constant voltage source circuit is also provided with a feedback terminal FB.

The selection circuit uses a power high-speed switch NMOSFET-PMOSFET as a high-speed switch switching circuit to quickly switch the constant current source circuit and the constant voltage source circuit. The power high-speed switch NMOSFET-PMOSFET includes an N-type field effect transistor NMOSFET and a P-type field effect transistor. Tube PMOSFET, the selection circuit also includes the first control interface CON1 and the second control interface CON2.

The output terminal Iout of the constant current source circuit is connected to the feedback resistor Rsense and the terminal Isense, and the other end of the feedback resistor Rsense is connected to the external power supply input terminal VIN.

The constant current source control circuit (IENB) is also connected with a non-gate, and the other end of the non-gate is connected with a field effect transistor MOSFET.

The field effect transistor MOSFET further controls the SW terminal in the step-down regulation circuit to charge and discharge with the inductor in the step-down regulation circuit.

The constant current source circuit and the constant voltage source circuit can be designed independently. According to the requirement that the driving waveforms given to the OLED are constant current in the forward direction and constant voltage in the reverse direction, the two sets of power sources can be designed without interfering with each other. . All circuits are integrated in the IC, which simplifies circuit design, simplifies the number of purchased components, and brings users an excellent development environment.

Considering the continuous expansion of the display size, the power will increase, and the present invention will use a DC step-down method to deal with it; and give a reverse voltage source during the non-conduction period of the OLED.

Compared with the prior art, the beneficial effect of the utility model is that: a large number of comprehensive experiments prove that the circuit of the utility model can improve the service life of the OLED, which is more than 10 times higher than that of the ordinary driving circuit; it can also improve the display uniformity, stability.

In order to further illustrate the features and technical content of the utility model, please refer to the following drawings and descriptions related to the utility model.

Description of drawings

Fig. 1: the drive circuit block diagram of the utility model;

Fig. 2: The circuit diagram of the constant current source of the present utility model;

Fig. 3: the constant voltage source circuit diagram of the utility model;

Fig. 4: The equivalent circuit diagram when the selection circuit of the present invention selects the constant current source unit;

Figure 5: The equivalent circuit diagram when the selection circuit of the present invention selects the constant voltage source unit;

Figure 6: The overall interface diagram of the utility model;

Figure 7: Timing diagram of forward constant current and reverse constant voltage control output.

Detailed ways

The OLED lighting display device of the specific embodiment of the utility model adopts 3.5" white light OLED (WOLED) and 3.5" yellow light OLED (YOLED) as loads for driving and a lot of experiments. As shown in Figure 1 is a block diagram of the driving principle of the present invention, the control circuit controls the constant current source circuit, constant voltage source circuit, and selection circuit, so as to achieve forward constant current and reverse constant voltage.

Figure 2 is a constant current source drive circuit, which is provided with a pair of terminals Isense for detecting the output current, which are used to detect the output current, and connected to this terminal through a current feedback resistor Rsense. The basic principle of the constant current circuit is: the OLED lighting load is connected between the output terminal Iout and the negative pole K1 of the output terminal in Figure 2, the output terminal Iout is connected to the positive pole A of the lighting load, and the negative pole K1 of the output terminal is connected to the negative pole K of the load. When the current flows through the OLED load, a load current will be generated. This current will pass through the feedback resistor Rsense synchronously. This current will be detected by the terminal ISENSE that detects the output current, and the detected current value will be input to the internal current comparator. This comparator will always monitor the change of the OLED load and adjust the negative voltage of the output OLED load by means of PWM. The output terminal of the current comparator is connected to the pulse width modulation comparator, and one end of the pulse width modulation comparator is connected to the oscillator. Connected, the other end and one end of the oscillator are connected to the D flip-flop. By closing and opening the circuit of the constant current source to control the MOSFET switch tube and then control the SW terminal in the step-down adjustment circuit and the inductance in the step-down adjustment circuit to charge and discharge, so as to control the negative voltage of the load to achieve the purpose of constant current.

Fig. 3 is a block diagram of the constant voltage source circuit. The constant voltage source circuit is also provided with a circuit for closing and opening the constant voltage source, and the switching enable of the entire circuit of the constant voltage source is controlled by closing and opening the constant voltage source circuit. The constant voltage source circuit can be completely independent of the constant current source circuit, and the switching between them is carried out by the selection circuit.

As shown in Figure 4 and Figure 5, the internal equivalent circuit diagram of the selection circuit is provided. There are two control interface I/O, respectively, the first control interface CON1 and the second control interface CON2, which are used to select the forward direction and the reverse direction. The circuit connection of these two control interfaces I/O cooperates with the PWM of the constant current source and the control circuit of the constant voltage source to set the forward and reverse frequency and the size of the duty cycle according to a certain timing.

Figure 6 is the interface control diagram of the entire controller drive circuit, which is simple and easy to control after the entire integration.

Figure 7 is a timing diagram for outputting an ideal driving signal. As can be seen from the figure, the driving signal output to the OLED display is a forward constant current and a reverse constant voltage.

In summary, the present invention provides a drive circuit with forward constant current and reverse constant voltage functions. All its functional circuits can be designed independently or integrated in an IC, but no matter which method is included in the content of the present invention.

Claims (9)

1. A drive controller for an OLED illuminating lamp or a backlight source, characterized in that: its circuit includes a constant current source control circuit, a constant voltage source control circuit, a forward constant current source circuit, and a reverse constant voltage source circuit and selection circuit; the output end of the constant current source control circuit is connected to the input end of the constant current source circuit, the output end of the constant voltage source control circuit is connected to the input end of the constant voltage source circuit, and the constant current source control circuit The constant voltage source control circuit controls the constant current source circuit and the constant voltage source circuit respectively; the output end of the constant current source circuit and the output end of the constant voltage source circuit are connected with the selection circuit to control the The constant current source circuit and the constant voltage source circuit are switched; the output end of the selection circuit is connected to a load OLED lighting lamp or a backlight source. 2. A drive controller for an OLED illuminating lamp or backlight according to claim 1, characterized in that: the constant current source control circuit and the constant voltage source control circuit include repeated on/off switch mode The DC current is converted into a pulse width modulation circuit (PWM) of a high-frequency square wave current; the constant current source control circuit and the constant voltage source control circuit also include an adjustment circuit that outputs the duty cycle frequency of the AC pulse square wave signal; The constant current source control circuit and the constant voltage source control circuit also include a circuit for closing and opening the constant current source. 3. The driving controller of a lighting lamp or a backlight source of an OLED according to claim 1, wherein the constant current source circuit adopts a step-down mode, and includes a terminal (ISENSE) for detecting the output current , current comparator, pulse width modulation comparator, oscillation circuit and D flip-flop, the terminal (ISENSE) to detect the output current is connected to the input terminal of the current comparator, and the output terminal of the current comparator is connected to the pulse width modulation comparator One end of the pulse width modulation comparator is connected to the oscillating circuit, and the other end is connected to the D flip-flop together with one end of the oscillating circuit; the constant current source circuit is also provided with a control pin (IENB) connected to the closed and open constant current source circuit. 4. The drive controller of a lighting lamp or a backlight source of a kind of OLED according to claim 1, characterized in that: the constant voltage source circuit is also provided with a control pin (VENB) connected with closing and opening the constant voltage source circuit, The constant voltage source circuit also has a feedback terminal (FB). 5. The driving controller of a lighting lamp or a backlight source of an OLED according to claim 1, wherein the selection circuit adopts a power high-speed switch (NMOSFET-PMOSFET) as a high-speed switching circuit to control the constant current source circuit Switch quickly with the constant voltage source circuit, the power high-speed switch (NMOSFET-PMOSFET) includes N-type field effect transistor (NMOSFET) and P-type field effect transistor (PMOSFET), and the selection circuit also includes No. 1 control interface (CON1) and No. 2 control interface interface (CON2). 6. the drive controller of the illuminating lamp of a kind of OLED according to claim 1 or backlight source, it is characterized in that: the output end (Iout) of constant current source circuit is connected with feedback resistance (Rsense) and terminal (Isense), The other end of the feedback resistor (Rsense) is connected to the external power supply input terminal (VIN). 7. The driving controller of a lighting lamp or a backlight source of a kind of OLED according to claim 1, wherein the constant current source control circuit is also connected with a NOT gate, and the other end of the NOT gate is connected with a field effect transistor (MOSFET) . 8. The drive controller of a lighting lamp or a backlight source of an OLED according to claim 7, characterized in that: a field effect transistor (MOSFET) further controls the SW end in the step-down regulation circuit and the step-down regulation circuit The inductor in the charging and discharging. 9. A drive controller for an OLED illuminating lamp or a backlight source according to claim 1, characterized in that: a constant current source control circuit, a constant voltage source control circuit, a constant current source circuit, a constant voltage source circuit, a selection The circuits can be designed separately or integrated in an IC.

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