JP2007095560A - Large capacitative el panel driving circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an EL driving circuit capable of smoothly driving large capacitative EL panels of A0-A2 sizes without using a cooling device at high luminance and high stability. <P>SOLUTION: This large capacitative EL panel driving circuit 17 is equipped with a main circuit composed of a step-up transformer 11, a converter 12 connected to the step-up transformer 11, and an inverter 13 connected to the converter 12, and a control circuit composed of a load current detecting circuit 15 to detect a load current flowing in the large capacitative EL panel 17, a CPU 91 connected to the the load current detecting circuit 15, and a PWM control circuit 92 connected to the CPU 91. The output of the PWM control circuit 92 is connected to the inverter 13, and a reactor 14 is connected to the output side of the inverter 13 in this driving circuit. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a large-capacity EL panel driving circuit.

Various drive circuits for capacitive EL elements have been proposed so far (see, for example, Patent Document 1).
As many EL drive inverters have larger EL sizes (areas), improvements in inverter conversion efficiency and compact power supplies are strongly demanded. In particular, recently, large EL display elements of A0 size (841 × 1189 mm) to A2 size (420 × 594 mm) have been developed. Such a large-capacity large EL panel can be replaced with a conventional self-excited blocking oscillation method, When driven using a series resonance passive inverter type drive circuit, a large current flows, so there is a lot of heat generation and it is necessary to cool with a liquid cooling device, so that it is difficult to put it to practical use.
JP 2003-333849 A

  The present invention has been made to solve these problems, and can drive a large-capacity EL display element such as A0 size to A2 size with high brightness, high stability and no failure without using a cooling device. An object of the present invention is to provide an EL drive circuit that can cope with a decrease in capacitance due to deterioration of an EL display element.

In order to achieve the above object, a first aspect of the present invention relates to a large-capacity EL panel driving circuit, and comprises a step-up transformer, a converter connected to the step-up transformer, and an inverter connected to the converter. Circuit,
A control circuit comprising a load current detection circuit for detecting a load current flowing through a large-capacity EL panel as a load, a CPU connected to the load current detection circuit, and a PWM control circuit connected to the CPU; A large-capacity EL panel drive circuit comprising: an output of the PWM control circuit connected to the inverter;
A reactor is connected to the output side of the inverter 13.
According to a second aspect of the present invention, in the large-capacity EL panel driving circuit according to the first aspect, a filter circuit is connected before or after the reactor.

  With such a configuration, a high-capacity EL panel drive circuit that can be driven without failure without using a cooling device can be obtained, and it can cope with a decrease in capacity due to deterioration of the EL display element. You can also do it.

In the present invention, a drive circuit for a large-capacity EL display element is obtained by stopping a conventional series resonance passive inverter drive circuit and using a PWM control inverter drive circuit.
PWM control itself is a well-known technique used for conventional motor control. FIG. 2 shows an example of a circuit in which PWM control itself is used for motor control. In the figure, a step-up transformer 21, a converter 22, an inverter 23, and an induction motor 24 constitute a main circuit of the motor.

The control of this is as follows.
When the operator gives an operation condition to the CPU 91 from the input / output device and starts operation, the CPU 91 calculates a command from the operation condition according to the control program, and gives this to the PWM control circuit 92. The PWM control circuit 92 gives an ON / OFF control signal according to the PWM control from the command to the switching element of the DC / AC inverter 23. Thereby, the motor 24 is controlled according to the PWM control.
The rotation speed of the motor 24 is detected by an attached encoder, and the detected value is feedback-controlled by the CPU and reflected in the next command.
As a result, the motor drive circuit can be increased in frequency, so that the size and weight can be reduced.

  Here, the pulse width modulation control handled by the present invention will be described. FIG. 3 shows a main circuit configuration diagram of the three-phase current source inverter. The current source inverter has a high impedance by inserting a reactor L in a DC circuit, and operates as a current source when viewed from the AC output side. A capacitor C is connected to the AC side, and absorbs a surge voltage accompanying a sudden change in output current.

FIG. 4 shows a basic operation of the PWM control current source inverter in the case of outputting a sine wave current synchronized with a load voltage (for example, a counter electromotive force of an AC motor). In the current source inverter, it is necessary to always secure the current path of the reactor L, and the PWM control operation is slightly different from that of the voltage source inverter.
The electrical angle of the fundamental frequency is divided every 60 °, one element of the phase with the largest modulation rate is turned on during the 60 ° period, the other two-phase elements are PWM controlled, and the sine wave output current is Trying to get. For example, in the 60 ° period from a to b, the element S1 is turned on, and S5 and S6 are PWM-controlled to control the V-phase and W-phase currents. At this time, a period in which both S5 and S6 are off occurs. During that period, an ON signal is given to the element S4, the U-phase upper and lower arms are short-circuited, and the current path of the reactor is secured. As a result, the U-phase current iu is as shown in the figure, and a sine wave current synchronized with the load voltage vu is obtained as an average value thereof.

FIG. 5 is a circuit example in which the PWM control used for the motor control is applied to the large-capacity EL panel targeted by the present invention.
In the figure, a step-up transformer 11, a converter 12, an inverter 13, and a large-capacity EL panel 17 as a load constitute a main circuit, and a current / voltage detection circuit 15 is replaced with an inverter 13 and a load instead of an encoder provided in a motor. The large-capacity EL panel 17 is inserted.
In this control, when an operator gives an operating condition from the input / output device to the CPU and starts operation, the CPU calculates a command from the operating condition according to the control program, and gives this to the PWM control circuit. The PWM control circuit gives an on / off control signal according to the PWM control from the command to the switching element of the DC / AC inverter.
As a result, the large-capacity EL panel should be controlled according to the PWM control. However, when the inverter was driven with an inverter using a large capacity EL panel panel instead of the motor, the inverter 13 suddenly failed and was not put into practical use.

  Therefore, the present applicant sought the cause and found that an excessive inrush current that did not occur in the case of the motor flows in the large-capacity EL panel panel. The present invention improves the drawback of FIG. 5 and, as a result, prevents an excessive inrush current from flowing through the large-capacity EL panel.

FIG. 1 shows a large capacity EL panel driving circuit according to the present invention, which is a successful example of applying PWM control to a large capacity EL panel.
In the figure, a step-up transformer 11, a converter 12, an inverter 13, and a large-capacity EL panel 17 as a load constitute a main circuit, and a current / voltage detection circuit 15 is replaced with an inverter 13 and a load instead of an encoder provided in a motor. 5 is the same as in FIG. 5 until it is inserted between the inverter 13 and the current / voltage detection circuit 15, but differs in that a reactor is inserted. .
The load current detection circuit 15 detects the load current flowing through the large-capacity EL panel as a load and transmits it to the CPU 91. The output of the CPU 91 is sent to the converter 12 and the PWM control circuit 92, and the output of the PWM control circuit 92 is sent to the inverter 13.

  In this control, when an operator gives an operation condition to the CPU 91 from the input / output device and starts operation, the CPU 91 calculates a command from the operation condition according to the control program and gives this to the PWM control circuit 92. The PWM control circuit 92 gives an on / off control signal according to the PWM control from the command to the switching element of the DC / AC inverter 13.

The feedback system 15 functions as follows.
If the luminance of the large-capacity EL panel deteriorates and the luminance decreases, the current flowing through the large-capacity EL panel 17 also decreases. This can be detected by the current detection circuit 15 with a small detection value. A small detection value commensurate with this value is entered, and the difference from the reference value increases, and the CPU 91 gives a command to the DC / AC inverter 13 in a direction to reduce this difference, thereby increasing the luminance of the large-capacity EL panel. It becomes.
As a result, the large-capacity EL panel 17 is smoothly controlled according to the PWM control, and no problem occurs.
It can be inferred that this is because the reactor 14 functions to prevent a large inrush current flowing into the large-capacity EL panel 17.

  Further, although the reactor is inserted between the inverter 13 and the current / voltage detection circuit 15, it may be inserted between the current / voltage detection circuit 15 and the load 17 (or filter circuit).

  Furthermore, by providing the filter circuit 16 between the reactor 14 and the large-capacity EL panel panel 17, the large-capacity EL panel is finally obtained by absorbing spike noise that may be caused by inserting the reactor 14. It has been put to practical use as 17 drive circuits.

As described above, according to the present invention, a main circuit including a step-up transformer, a converter connected to the step-up transformer, and an inverter connected to the converter,
A control circuit comprising a load current detection circuit for detecting a load current flowing through a large-capacity EL panel as a load, a CPU connected to the load current detection circuit, and a PWM control circuit connected to the CPU; In the large-capacity EL panel drive circuit in which the output of the PWM control circuit is connected to the inverter, a large capacity such as A0 size to A2 size is obtained by connecting a reactor to the output side of the inverter 13. An EL drive circuit that can drive an EL display element with high brightness and high stability without using a cooling device without failure and can cope with a decrease in capacitance due to deterioration of the EL display element is obtained.

FIG. 3 is a circuit configuration diagram of a large-capacity EL panel driving circuit according to the present invention. The circuit example in which PWM control itself is used for motor control is shown. It is a figure which shows an example of the main circuit structure of a three-phase current source inverter. It is a figure which shows the basic operation | movement of the PWM control current source inverter in the case of outputting the sine wave current synchronized with the load voltage. This is a circuit example in which PWM control of motor control is applied to a large-capacity EL panel.

Explanation of symbols

11 Step-up transformer 12 Converter 13 Inverter 14 Reactor 15 Load current detection circuit 16 Filter circuit 17 Large-capacity EL panel 91 CPU
92 PWM control circuit

Claims (2)

A main circuit comprising a step-up transformer, a converter connected to the step-up transformer, and an inverter connected to the converter;
A control circuit comprising a load current detection circuit for detecting a load current flowing through a large-capacity EL panel as a load, a CPU connected to the load current detection circuit, and a PWM control circuit connected to the CPU; A large-capacity EL panel drive circuit comprising: an output of the PWM control circuit connected to the inverter;
A large-capacity EL panel drive circuit, wherein a reactor is connected to the output side of the inverter 13.   2. The large-capacity EL panel driving circuit according to claim 1, wherein a filter circuit is connected before or after the reactor.

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