JPH0447697A - Driving device for el lamp - Google Patents

Abstract

PURPOSE:To control the luminance of an EL lamp at will and keep the luminance constant by lighting the EL lamp at the optimum drive frequency based on the count of the accumulated operation time and the result from measuring the luminance of the EL lamp. CONSTITUTION:A CPU 1 reads a frequency setting data and the operation time data of an EL lamp 8 out of a backup SRAM 3, and sets the read frequency setting data in a frequency setting circuit 6. The data of the accumulated operation time in the past of the EL lamp 8 is set into a timer circuit 5 to start the operation of a driving device for EL lamp. The lapse of the driving time of the EL lamp 8 is monitored to determine whether or not the value is larger than a predetermined time. If the result is ON, the driving time is counted up and the value is stored in the SRAM 3. However, if the value is larger, the frequency setting data in the SRAM 3 is updated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an EL clamp driving device for driving an EL clamp used as a backlight for a liquid crystal display (hereinafter referred to as LCD).

[Prior Art] Conventionally, EL clamps have been widely used as backlights for LCDs, and the EL clamps are mainly driven by self-study inverter circuits. The deterioration in brightness is corrected by increasing the self-oscillation frequency.

[Problems to be Solved by the Invention] However, in the above conventional example, the frequency change due to EL clamp deterioration is about 50%, and although there is a slight brightness correction effect by increasing the automatic oscillation frequency, the brightness is always adjusted. The disadvantage is that it is difficult to maintain a constant EL clamping motion.

Further, there is a drawback that the self-oscillation frequency changes by about 10 to 20% due to variations in elements such as the EL clamp EL transformer, and this greatly affects variations in the EL clamp brightness.

[Means for Solving the Problems] The present invention has been made for the purpose of solving the above-mentioned problems, and includes the following configuration as one means for solving the above-mentioned problems.

That is, storage means for storing the EL clamp drive frequency;
A driving means for driving the EL clamp at a driving frequency stored in the storage means, a recognition means for recognizing a change in EL clamp brightness, and a determining means for determining an EL clamp driving frequency based on a recognition result by the recognition means; and means for storing the EL clamp drive frequency determined by the determining means in the storing means, the storing means being constituted by a non-volatile memory.

[For Notes] In the above configuration, the EL clamp drive frequency can be optimized and the brightness can be kept constant.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows one of the preferred embodiments of the present invention, EL
FIG. 2 is a block diagram showing the configuration of a clamp motion device.

In FIG. 1, the CPUI controls the entire EL lamp driving device via a bus 2 consisting of an address bus, a data bus, and a control bus. The bus 2 includes a backup SRAM 3 that stores frequency setting data and EL clamp operation time data, which will be described later, backed up by a backup power supply 4, a timer circuit 5 for measuring the elapsed operation time of the EL clamp, and data from the backup SRAM. A frequency setting circuit 6 is connected to the frequency setting circuit 6, which can set the frequency based on the frequency.

In addition, the frequency setting data and E
L clamp operation time data is provided via the input circuit 12.

The inverter power supply 7 is used to separately excite the drive power supply of the EL clamp, and the frequency fo is set by the frequency setting circuit 6.
The sine wave output voltage of ACloov is converted to the EL clamp's driving frequency by DC-AC conversion.
Output to clamp.

FIG. 2 is a flowchart showing the control procedure of the EL clamp motion device according to this embodiment.

When the power of the EL clamp operating device is turned on in step S1 of FIG. 2, the CPU 1 retrieves the pre-registered frequency setting data and EL clamp operating time data (set to 1+) from the backup SRAM 3 in step S2. Read out. Then, in step S3, the read frequency setting data is set in the frequency setting circuit 6. In the following step S4, data t1, which is the past cumulative operation time of the EL clamp, is set in the timer circuit 5, and the operation of the EL clamp moving device is started.

In step S5, the elapse of the driving time t of the EL clamp is monitored, and it is determined whether or not it is a value larger than a preset time α. If the result is No, the process advances to step S6, where the driving time t is counted up and the value is stored in the backup SRAM 3.

However, in the determination in step S5, the drive time t is the time α
If the value is larger, the process advances to step S7, and the value of the frequency setting data in the backup SRAM is updated. Then, in the next step S8, the updated frequency setting data value is reset to the frequency setting circuit 6. Continued step S9
Then, operate the timer circuit 5 to clear the drive time t (1
=O) and returns to step S5 again.

The above control is repeated until the power to the EL clamp motion device is turned off.

As explained above, according to this embodiment, the reduction in EL clamp brightness can be suppressed by constantly monitoring the accumulation of elapsed EL clamp operation time and updating the drive frequency based on the results. There is.

In addition, by changing the setting data, you can change the EL clamp stepwise brightness, or change the setting frequency data to 0.
By doing so, there is an effect that the EL clamp light emission can be turned off.

In the above-described embodiment, the frequency setting data and the EL clamp operation time data are stored in the backup SRAM 3, but they may be replaced with an EEFROM, which is a backup SRAM.

This eliminates the need for, for example, a battery as the backup power source 4, and eliminates the hassle of battery replacement.

<Other Examples> Next, other embodiments according to the present invention will be described.

FIG. 3 is a block diagram showing the configuration of an EL clamp motion device according to another embodiment. In the figure, E shown in Figure 1
Components that are the same as the L-clamp motion device are given the same numbers,
A detailed explanation thereof will be omitted.

In Fig. 3, the setting of the driving frequency of the EL clamp is as follows.
For example, the information is input into the EEFROM 9 in advance using an input circuit 12 consisting of a keyboard or the like. Then, the brightness of the EL clamp is measured by a photosensor 10 installed near the EL lamp 8, and the analog output of the photosensor 10 is
A D converter 11 converts it into digital data.

The CPUI is set to EEFROM9.
The brightness of the L clamp is compared with the digital data from the A/D converter 11, and the set value of the frequency setting circuit 6 is changed so that the brightness of the EL clamp becomes the same as the set value.

As explained above, in this embodiment, by measuring the actual brightness of the EL clamp and controlling the driving frequency so that the value matches the set value, it is possible to always maintain a constant brightness of the EL clamp. effective.

Furthermore, since the driving frequency is controlled based on the actual brightness of the EL clamp, there is an effect that variations in the elements constituting the EL clamp driving device can be canceled out.

[Effects of the Invention] As explained above, according to the present invention, the EL clamp can be lit at the optimal drive frequency based on the measurement of the cumulative usage time of the EL clamp and the results of the brightness measurement, so the brightness of the EL clamp can be adjusted arbitrarily. This has the effect of making it possible to keep the brightness constant.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an EL clamp motion device which is one of the preferred embodiments of the present invention, FIG. 2 is a flowchart showing the control procedure of the EL clamp motion device according to the embodiment, and FIG. 3 FIG. 2 is a block diagram of an EL clamp motion device according to another embodiment. In the figure, 1... CPU, 2... Bus, 3... Backup SRAM, 4... Backup power supply, 5...
Timer circuit, 6... Frequency setting circuit, 7... Inverter power supply, 8... EL clamp 9... EEPRO
M. 10... Photo sensor, 11... A/D converter,
12... Input circuit.

Claims (2)

[Claims] (1) An EL lamp driving device that externally excites an EL lamp, comprising: storage means for storing the driving frequency of the EL lamp; driving means for driving the EL lamp at the driving frequency stored in the storage means; and an EL lamp. recognition means for recognizing a change in brightness of the EL lamp; determining means for determining a driving frequency of the EL lamp based on the recognition result of the recognition means; and storing the driving frequency of the EL lamp determined by the determining means in the storage means. An EL lamp driving device characterized by having means for. (2) The EL lamp driving device according to claim 1, wherein the storage means is constituted by a nonvolatile memory.