JPH07161475A - Electroluminescence driving device - Google Patents

Abstract

PURPOSE:To obtain an efficient electroluminescence driving device using a small inductor without using a large transformer. CONSTITUTION:Transistors Tr1, Tr4 mutually repeat turn-on/off at a first frequency. A transistor Tr2 is turned on/off at a second frequency faster then the first frequency during the turn-o of the transistor Tr1. The energy stored in an inductor L1 during the turn-on of the transistor Tr2 works as the electromotive force at an instant when the transistor Tr2 is turned off, and an EL element is charged with positive voltage through a diode D2. Similarly, during the turn-on of the transistor Tr4, the transistor Tr3 is turned on/off at a third frequency faster than the first frequency, and the energy stored in an inductor L2 works as the electromotive force, and the EL element is charged with negative voltage through a diode D3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, a backlight for displaying a message on a camera or a pocket computer,
Alternatively, the present invention relates to an electroluminescence drive device used for a display backlight of a liquid crystal display in a sewing machine.

[0002]

2. Description of the Related Art This type of electroluminescence (E
2. Description of the Related Art As a drive device known in the related art, there is a drive device that supplies a voltage by using a step-up transformer or an inductance for resonance.

These are adapted to resonate by matching the secondary side inductance of the step-up transformer and the resonance inductance to the capacitance of the EL element. by the way,
Driving the EL element with a low frequency high voltage of about 400 to 3000 Hz and about 100 V is the most efficient in terms of the life of the EL element and the brightness balance.

However, in the conventional EL drive device using the above step-up transformer and the resonance inductance, a large inductance value is required because of the low frequency in order to perform the above-mentioned efficient resonance. As a result, there is a drawback that the transformer and the inductance become large.

As a conventional technique, for example, Japanese Patent Application Laid-Open No. 5-36477 discloses the following EL drive device which requires only a small inductance and does not require a large transformer.

FIG. 24 is a schematic configuration diagram of the above-mentioned EL drive device as a conventional technique. Between the DC power source 1 and the output terminal 3 connected to EL2, a boost chopper circuit 4 for inducing a high voltage with a first polarity at the output terminal 3, and a high voltage with a second polarity at the output terminal 3. A polarity reversal boost chopper circuit 5 for inducing is generated is connected.

Further, the detection circuit 6 for detecting the output voltage of the output terminal 3 and the ON / OFF control of both boost chopper circuits 4 and 5 by outputting a pulse signal,
CPU that generates an AC output of a constant frequency at the output terminal 3
In order to keep the output voltage detected by the frequency control circuit 7 in 10 and the detection circuit 6 at a constant value, the pulse signal is controlled to control the power supply time from the DC power supply to both boost chopper circuits 4 and 5. And a voltage control circuit 8 in the CPU 10 for operating the DC power supply 1
It shares the inductance 9 fed from. And
The inductance 9 can be reduced by increasing the speed of the boost chopper circuits 4 and 5.

[0008]

However, since there is a bipolar transistor (hereinafter abbreviated as a transistor) in the boosting path of both chopper circuits, a part of boosting energy flows as a base current of this transistor, so that part of the energy is boosted. Boosting efficiency drops.

Further, the efficiency is lowered due to the parasitic capacitance between the collector and the emitter of this transistor. Typically,
In a device using a battery as a power source, it is necessary to have a low current consumption, and there is a problem that it is difficult to use a booster circuit having poor efficiency.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an efficient electroluminescence driving device using a small inductor without using a large transformer.

[0011]

In order to achieve the above object, the electroluminescence driving device of the present invention has a first structure.
A first step-up circuit that outputs a positive step-up voltage by intermittently energizing the first coil.
A second booster circuit including a second coil, which outputs a negative boosted voltage by intermittently energizing the second coil, and is connected to the output points of the first and second booster circuits. For operating the electroluminescent element and the first booster circuit for a first predetermined time, and for operating the second booster circuit for a second predetermined time following the first predetermined time. And a timing signal generating means for outputting a timing signal, wherein the positive boosted voltage output from the first booster circuit and the negative boosted voltage output from the second booster circuit are used for the electroluminescence. It is characterized in that the voltage is alternately applied to the elements.

[0012]

In the electroluminescence driving device of the present invention, the first coil which includes the first coil and outputs the positive boosted voltage by intermittently energizing the first coil is provided.
Second booster circuit including a second booster circuit and a second coil, which outputs a negative boosted voltage by intermittently energizing the second coil, and outputs of the first and second booster circuits. It has an electroluminescent element connected to the point. After energizing the first coil for a first predetermined time to activate the first booster circuit, a second predetermined time following the first predetermined time from the timing signal generating means. During the time, the timing signal for operating the second booster circuit by intermittently energizing the second coil is output. Then, the positive boosted voltage output from the first booster circuit and the negative boosted voltage output from the second booster circuit are alternately applied to the electroluminescent element.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. 1A and 1B show a first embodiment of an EL drive device of the present invention.

This EL drive device has a positive boosting inductor L1 and a negative boosting inductor L2. One of the inductors L1 is connected to the plus side of a DC power source E via a transistor Tr1 and the other. Is connected to the anode of the diode D1 and the anode of the diode D2.

The cathode of the diode D1 is connected to the negative side of the DC power source E via the transistor Tr2,
The cathode of the diode D2 is connected to one of the EL elements and the anode of the diode D3.

One of the inductors L2 is connected to the negative side of the DC power source E via the transistor Tr4, and the other is connected to the cathode of the diode D4 and the diode D3.
Connected to the cathode of.

The anode of the diode D4 is connected to the plus side of the DC power source E via the transistor Tr3.
The other side of the EL element is connected to the negative side of the DC power source E.

The operation of the EL drive device configured as described above will be described. FIG. 2 is a time chart showing how the EL element is charged in the first embodiment.

The transistors Tr1 and Tr4 are alternately turned on and off repeatedly at the first frequency. Transistor Tr
2 turns on and off at a second frequency higher than the first frequency at least when the transistor Tr1 is on. The energy stored in the inductor L1 while the transistor Tr2 is on becomes an electromotive force when the transistor Tr2 is turned off at the next moment, and charges the EL element with a positive voltage through the diode D2.

Here, as shown in FIG.
It is considered that the element equivalently has a capacitor and a resistor connected in parallel, and a positive charge is stored in this equivalent capacitor.

Similarly, the transistor Tr3 turns on and off at a third frequency higher than the first frequency at least when the transistor Tr4 is on. The energy stored in the inductor L2 while the transistor Tr3 is on is changed to the transistor Tr2 at the next moment.
When 3 is turned off, an electromotive force is generated and diode D3
To charge the EL element with a negative voltage.

When the EL element is positively boosted by turning on and off the transistor Tr2, the transistor Tr4 is off and the diode D2 prevents the current from flowing through the transistor Tr3.

Similarly, when the EL element is negatively boosted by turning on / off the transistor Tr3, the transistor T3 is turned on.
Since r1 is off and the diode D2 is present, no current flows through the transistor Tr2.

Although the other of the EL elements is connected to the negative side of the DC power source E here, it may be the positive side of the DC power source E. FIG. 3 shows a second embodiment of the EL drive device of the present invention.

FIG. 4 is a time chart showing how the EL element is charged in the second embodiment. The transistor Tr8 supplies power to the entire EL drive circuit, and the transistor Tr8 is controlled by the CEN terminal signal of the CPU.

Transistor Tr1 and transistor T
r4 turns on and off the positive booster and the negative booster, respectively. Since the transistor Tr1 is a PNP transistor and the transistor Tr4 is an NPN transistor, the transistor Tr1 is on when the CK1 terminal signal of the CPU is “L”, and the transistor T1 is “H”.
r4 is turned off, and oscillation is performed at several 100 Hz to several KHz.

The resistor R8 and the collector of the transistor Tr5 are connected to the base of the transistor Tr2, and the base of the transistor Tr5 is connected to the CK2 terminal of the CPU via the resistor R7. Therefore, the transistor Tr1
Each time the CK2 terminal signal is changed from "H" to "L" or "L" to "H" when is on, the transistor T
r2 also turns on and off repeatedly.

When the transistor Tr2 is on, a current flows through the inductor L1, while when the transistor Tr2 is off, the electromotive force of the inductor L1 positively charges the capacitor C2 and the EL element via the diode D2. .

At this time, since the transistor Tr4 is off and the diodes D2 and D4 are present, the capacitor C
2 and the voltage stored in the EL element drops almost only by the resistance of the EL element itself.

When the EL element is left and used, the EL element deteriorates and the resistance component increases, but the capacitor C2
The effect can be reduced by making the capacitance of 1 larger than the equivalent capacitance of the EL element.

The CK2 terminal signal of the CPU is set to several hundred KHZ.
Therefore, the inductance required to boost the voltage of the EL element to about 100 V can be reduced by setting it to several MHZ. Therefore, an inductor having a small size can be used.

The same applies to negative boosting, which will be described below. The resistor R13 and the collector of the transistor Tr7 are connected to the base of the transistor Tr3, and the base of the transistor Tr7 is connected to the CK2 terminal of the CPU via the resistor R10. Therefore, the transistor Tr4
Is on (when Tr1 is off), the transistor Tr3 is repeatedly turned on and off each time the CK2 terminal signal is changed from "H" to "L" or "L" to "H".

When the transistor Tr3 is on, a current flows in the inductor L2, and when the transistor Tr3 is off, the electromotive force of the inductor L2 causes a diode D2.
Negative charging is performed on the capacitor C2 and the EL element via the capacitor 3.

At this time, since the transistor Tr1 is off and the diodes D1 and D3 are present, the capacitor C
2 and the voltage stored in the EL element drops almost only by the resistance of the EL element itself.

Although the transistors Tr2 and Tr3 are controlled only by the CK2 terminal signal, the inductor L
When the characteristics of 1 and L2 are different, control may be performed with pulses of different frequencies.

In any case, since boosting can be performed at a high frequency, a small inductor having a small inductance value can be used. Two inductors are required, but since a very small inductor can be used, it is possible to make the size significantly smaller than using one large transformer.

In the above embodiment, the transistor Tr is used for switching on and off the power supply of the entire EL drive device.
However, it is needless to say that a constant voltage source may be used instead of the transistor Tr8 to perform on / off switching.

FIG. 5 is a graph showing the voltage and luminance characteristics of the EL element. As shown in FIG. 5, the higher the voltage applied to the EL element, the higher the brightness, and the higher the frequency, the higher the brightness.

FIG. 6 is a graph showing the deterioration characteristic of the luminance characteristic of the EL element. As shown in FIG. 6, the deterioration of the brightness due to the lighting of the EL element is
The higher the humidity, the more intense it becomes.

Although it deteriorates even if it is left unlit, it is much smaller than when it is lit. Figure 7
It is a figure which shows the countermeasure method to the deterioration of the brightness of an EL element.

FIG. 7A shows charging of the EL element before deterioration, and FIG. 7B shows charging of the EL element after deterioration. As shown in FIG. 7A, before deterioration, CK1
The EL element is boosted by oscillating the terminal signal at 2 KHz and the CK2 terminal signal at 500 KHz.

As shown in FIG. 7B, after deterioration, the equivalent capacitance and equivalent resistance of the EL element increase, so E
The L element boosts up to 70 V at 2 KHz. Therefore, the frequency of the CK1 terminal signal is lowered and the boosting time is extended once to boost the voltage to 100V. As a result, the frequency becomes low but the voltage becomes high, so that even a deteriorated EL element can obtain a brightness similar to the brightness before the deterioration.

Here, it is difficult to finely adjust the high frequency CK2 terminal signal, but it is easy to change the frequency of the low frequency CK1 terminal signal. Further, FIG. 8 is a diagram showing a means for reducing the required energy in the above-mentioned method of coping with the deterioration.

The control of the transistors Tr1 and Tr2 by the CK1 terminal signal and the CK2 terminal signal in FIG. 7 is the same as shown in FIG. The energy required to output the brightness can be reduced.

FIG. 9 shows a third embodiment of the EL drive device of the present invention. Instead of the bipolar transistor in the second embodiment, a field effect transistor (Field Ef) is used.
fect Ttansistor (FET).

The operation is the same as in the second embodiment, and only the differences from the second embodiment will be described below. In the third embodiment, a field effect transistor is used instead of the bipolar transistor, and the field effect transistor FET is used.
Zener diodes ZD1, ZD2, ZD3 and Z for gate protection on the gates of FET1, FET2, FET3 and FET4
D4 is connected.

Field effect transistors FET1 and FET3
Is a P-channel enhanced field effect transistor, and the field effect transistors FET2 and FET4 are N
It is a channel-enhanced field effect transistor.

In the case of the bipolar transistor of the second embodiment, the transistor Tr8 is required to turn off the whole because the current flows through the base resistor. However, in the case of the field effect transistor of the third embodiment,
When no current flows through the gate, and when the CK1 terminal signal is set to "H" and the CK2 terminal signal is set to "L", the field effect transistors FET2 and FET3 are turned on, but no current flows due to the diodes D2 and D3.

As a result, the current of the booster circuit can be turned off, so that the entire switching element such as the transistor Tr8 becomes unnecessary. Next, as a fourth embodiment of the present invention,
A camera to which the EL drive device is applied will be described.

10 (a) and 10 (b) show the appearance of an example of a camera to which the present invention is applied. Figure 10 (a)
FIG. 3 is a view of the camera viewed from above, in which a liquid crystal display device (hereinafter abbreviated as LCD) is provided in the center, and an EL element is used as a backlight of the LCD.

FIG. 10B is a front view of the camera, and the camera is a barrier type. FIG. 11 is a block diagram of a camera using the present invention. The CPU 20 includes a first release button switch (R1SW) 35, a second release button switch (R2SW) 36, a mode switch (mode SW) 37, a date display switch (clock SW) 38, and a barrier switch (barrier SW). 39 and feeding motor drive circuit 21, photometry unit 22, lens motor drive circuit 23, shutter control circuit 24, battery check circuit 25, charging circuit 26, strobe light emission control circuit 2
7. Distance measuring unit 28, LCD for displaying camera mode and number of frames
29, the EL control circuit 30 is connected. Furthermore, CPU
A date LCD 31 for imprinting the date and an EL control circuit 32 for lighting the date are also connected to 20.

Two oscillators 33 and 34 of 32 KHz and 2 MHz are connected to the CPU 20,
A one-second timer that generates an interrupt every one second from a clock of 32 KHz is internally connected, and a normal instruction is executed by a clock of 2 MHz.

The interrupt for every one second is for displaying the date and time and for imprinting the date, and is not necessary for a model without a date. Therefore, the 32 KHz oscillator 33 is not necessary. The EL control circuit 30 is the same as the EL drive device described as the first embodiment of the present invention, and has a CEN terminal for ON / OFF and a C for outputting a positive / negative switching signal for boosting.
K1 terminal and CK that outputs a high-speed boosting clock signal
It has two terminals.

12 and 13 are flowcharts showing the main processing of the camera to which the present invention is applied. First, when the battery is loaded, it is determined in step S1 whether or not the model has a date. If the model has no date, the process proceeds to step S6. If the model has a date, the process proceeds to step S2. Whether or not the model has a date may be determined by checking the state of the port or by storing the presence or absence of the date in an EEPROM (not shown) in the CPU 20.

In step S6, the watch timer interrupt is prohibited, and the process proceeds to step S8. On the other hand, step S2
Then, from the above EEPROM, date data DATE2
To lead.

In step S3, DATE2 and CP
Date data DAT on RAM (not shown) in U20
E1 is compared, and if they are equal, the process proceeds to step S7,
If they are not equal, the process proceeds to step S4.

Here, in DATE1 and DATE2,
It contains year, month, and week data, and will be described later, but once a week
It is assumed that DATE1 is stored in the EEPROM as DATE2.

When DATE1 and DATE2 are equal, the data in the RAM in the CPU 20 is not abnormal. That is, the battery is simply removed for a short time so that the RAM in the CPU 20 does not become abnormal, and at that time, DATE1 is used as it is.

In step S4, a predetermined value, which is data of year, month, and week, is stored in DATE1, and the DAT is stored.
Store E1 in DATE2. Subsequently, in step S5, DATE2 is stored in the EEPROM, and the process proceeds to step S7.

In step S7, the watch timer interrupt is enabled, and the process proceeds to step S8. In step S8,
The subroutine "SNK" is executed. Here, the subroutine "SNK" is a process of retracting the lens if it is not retracted.

After that, the processing is the same as the processing by changing the barrier. First, in step S9, the deterioration amount T _EL of the EL element is read from the EEPROM, and in step S10, the temperature is measured.

In step S11, it is determined whether or not the barrier is open. If the barrier is open, the process proceeds to step S12, and if it is closed, the process proceeds to step S13.

In step S12, the subroutine "WI"
The lens is set to the initial position in D ", and the process proceeds to step S14. In step 13, the subroutine" SNK "is set.
To retract the lens.

Here, the initial position is the position where the lens is extended, and when it is already at the initial position, nothing is done in the subroutine "WID". Step S14
Then, the timer for the display time of 4 minutes of the LCD 29 and the lighting time of the EL element of 30 seconds is started, and the process proceeds to step S15.

In step S15, it is determined whether or not the barrier is open. If the barrier is open, the process proceeds to step S16, and if it is closed, the process proceeds to step S17. In step S16, it is determined whether or not 4 minutes, which is the display time of the LCD 29, has elapsed. When it has elapsed, the process proceeds to step S17, and when it has not elapsed, the process proceeds to step S22.

That is, in step S22 when the barrier is open and less than 4 minutes have passed, the LCD
The display of 29 is turned on, and in the next step S23, if 30 seconds have not elapsed since the timer was started, the process proceeds to step S24, and if 30 seconds have elapsed, the process proceeds to step S25.

In step S24, the EL control circuit 30 is turned on (that is, the CEN terminal signal is set to "L", CK
The oscillation of the 1-terminal signal and the CK2 terminal signal is started), and the process proceeds to step S26.

A step S25 turns off the EL control circuit 30 (that is, sets the CEN terminal signal to "H", and CK
The oscillation of the 1-terminal signal and the CK2 terminal signal is stopped), and the process proceeds to step S26.

Further, the lighting time of the EL element may be set to 4 minutes so that the EL element is always turned on during the display on the LCD 29, or the lighting may be started by a specific switch.

In step S26, charging is performed. If already charged, do nothing. In step S27, it is determined whether or not the rear cover is opened and then closed. If the rear cover is closed, the process proceeds to step S31, and if not closed, the process proceeds to step S28.

In step S31, the lens is retracted, and in step S32, the lens is fed in the idle state, and then in step S14.
Return to. In step S28, it is determined whether or not the rear lid is opened from the closed state, and when it is opened, the step S28 is performed.
29, and if not opened, the process proceeds to step S33.

In step S29, the lens is retracted. In step S31, RWEDF is set to "0", and the process returns to step S14. Here, RWEDF is a flag that becomes "1" at the end of rewind.

In step S33, RWEDF is "1".
If it is "1", the process proceeds to step S46, and if it is "0", the process proceeds to step S34. That is, when RWEDF is "1", the determination of R1SW35, rewind SW, and mode SW37 is not performed, and the process jumps to step S46.

In step S34, it is determined whether the R1SW 35 is on or off. If it is on, the process proceeds to step S35, and if it is off, the process proceeds to step S37. In step S35, a subroutine "WID" is called, in step S36, a subroutine "R1" which is a half-pressed process is called, and the process proceeds to step S38. The release process is performed in this subroutine "R1".

In step S38, it is determined whether or not the film is over, and if the film is over, step S39.
If the film is not finished, the process proceeds to step S14.
Return to.

In step S37, it is determined whether the rewind SW is off or on. If it is on, the process proceeds to step S39, and if it is off, the process proceeds to step S42. In step S39, the lens is retracted, rewinding is performed in step S40, RWEDF is set to "1" in step S41, and then the process returns to step S14.

In step S42, it is determined whether the mode SW 37 is off or on. If it is on, the process proceeds to step S43, and if it is off, the process proceeds to step S45. In step S43, the mode is changed, in step S44, the subroutine "WID" is called, and then in step S1.
Return to 4.

In step S45, it is determined whether or not the clock SW38 has been operated, and when it is operated, step S4 is performed.
6, the process proceeds to step S49 when no operation is performed.

In step S46, year, month, week, day,
Change the time, such as hours and minutes. In step S47,
The year, month, and week data DATE1 is stored as DATE2, which is stored in the EEPROM in step S48, and the process proceeds to step S49.

Here, when the year, month and week are not changed, it is not necessary to write in the EEPROM. In step S49, it is determined whether or not 1 second has elapsed. When 1 second has elapsed, the process proceeds to the next step S50, and when 1 second has not elapsed, the process returns to step S15.

In step S50, it is determined whether or not the EL control circuit 30 is turned on. If it is turned on, the process proceeds to step S51, and if it is not turned on, step S1 is performed.
Return to 5.

In step S51, the deterioration amount of the EL element due to lighting for 1 second is set to ΔT _EL . Step S5
In 2, we obtain a new total deterioration amount T _EL plus [Delta] T _EL total deterioration amount T _EL. Then, it returns to step S15.

If it is determined in step S15 that the barrier is closed or that 4 minutes have elapsed in step S16, the process proceeds to step S17. This step S
In 17 the lens is retracted, and in step S18 the LCD2
Turn off the display of 9.

In step S19, the EL oscillation circuit including the CPU 20 and the EL control circuit 30 is turned off, the total deterioration amount T _EL is stored in the EEPROM in step S20, and the HALT state is set in step S21.

After that, when the HALT is released by opening / closing the barrier, loading the battery, operating various SWs, etc., step S
Return to 14. Here, HALT is a state in which the 2 MHz clock is stopped and the instruction execution of the CPU is stopped.
The 2 KHz clock is operational.

If the model does not have a date and does not have a 32 KHz clock, it will be in a completely stopped state. FIG. 14A is a flowchart showing the processing of the release processing R1.

First, in step S54, the EL oscillation circuit is turned off, and in the next step S55, distance measurement and photometry are performed. In step S56, the EL oscillation circuit is turned on again. This is to prevent the accuracy of distance measurement and photometry from being deteriorated by noise caused by the oscillation of the EL oscillation circuit.

In step S57, the amount of extension is calculated, and in the next step S58, the exposure is calculated. In steps S59 and S64, it waits for the R2SW 36 to turn on.

If the R1SW 35 is turned off during that time, the process returns. When the R2SW 36 is turned on, step S60
In step S61, the lens is extended and the focus is adjusted. In step S61, shutter control is performed.
2. Imprint the date.

In the next step S63, one frame is wound up, and in the next step S64, the lens is retracted. This is the end of the release sequence. FIG. 14 (b) shows
It is a flowchart which shows the process of date imprinting.

First, in step S70, it is determined whether or not the model has a date, and if it has a date, step S7.
Go to 1 and return if there is no date. In step S71, the date LCD 31 is turned on, and then in step S72, the date EL control circuit 32 is turned on.

Next, in step S73, a time corresponding to the film sensitivity is waited, and then in step S74, the date E is set.
The L control circuit 32 is turned off, and the date L is set in step S75.
Turn off CD31. Then return.

Regarding the film sensitivity, the LCD 31 for the date and the EL control circuit 32 for the date are turned on for a long time at a low ISO, and the L for the date is low for a short time at a high ISO.
By turning on the CD 31 and the EL control circuit 32 for date, proper printing is performed.

FIGS. 15A and 15B are external views showing the structure of the imprinting unit for imprinting the date. Figure 15
As shown in (a), the film 40 is a film retainer 4
Pressing with 1 keeps the flatness. A hole is formed in a part of the film retainer 41 so that the date is imprinted on the film 40. Specifically, an LCD for imprinting is provided by the fixing member 42 to the film retainer.
43, the EL element 44 for imprinting, and the flexible printed wiring board 45 are fixed.

For example, although the date as shown in FIG. 15 (b) is imprinted, the LCD 43 is a non-transparent LCD when it is off and a character and a number are transparent when it is on.
The LCD 43 is connected to the flexible printed wiring board 45 by the conductive rubber 46, and the EL element 44 is connected to the soldering portion 4
It is connected to the flexible printed wiring board 45 by 7.

FIG. 16 is a flow chart showing the clock interrupt processing every one second. First, in step S80, the time such as year, month, week, day, hour, minute, second, etc. is updated. Here, the year, month, and week data DATE1 is updated.

In step S81, it is determined whether the day of the week is Tuesday to Wednesday, and if it is Wednesday, step S82.
Move to and return if it is not Wednesday. In step S82, the temperature is measured and the next step S83
Then, the ΔP for one week is calculated.

Here, the deterioration amount of the EL element is obtained according to the temperature. The amount of deterioration is determined by temperature and humidity, but in this example, it is calculated only by temperature. In step S84, EEP
The total amount P of deterioration due to leaving is read from the ROM.

In the next step S85, the deterioration amount ΔP corresponding to this week is added to the total amount P of deterioration, and step S86
To store in EEPROM. Then return. The amount of deterioration for one week was calculated from Tuesday to Wednesday because the camera is usually stored in the same place.
This is because it is determined that deterioration should be obtained every week.

However, in a model without a date, since the clock interrupt does not occur, the deterioration amount P due to being left alone cannot be obtained. FIG. 17 is a diagram showing the relationship between the deterioration amount ΔP of the EL element after being left for one week and the deterioration amount ΔT _EL due to lighting for one second with respect to the temperature.

It is the amount of deterioration due to average humidity at each temperature. FIG. 18 shows the total deterioration amount T _EL + P of the EL element to E.
This is the frequency of the L element.

The luminance in the initial state also fluctuates due to variations in EL elements and circuits, and also fluctuates depending on the battery voltage. Therefore, it is classified into four types and each frequency has a table.

When the camera is manufactured, the EL circuit is driven at a predetermined frequency and the brightness is measured to determine whether the EL circuit is of the high brightness type or the low brightness type, and the result is stored in the EEPROM. Further, FIG. 19 is classified into four types according to the type of EL element and the battery voltage. Here, the battery voltage is detected by the battery check circuit 25 shown in FIG.

FIG. 20 is a diagram showing the configuration of an EL oscillation circuit including an EL control circuit and a CPU used in the fourth embodiment of the present invention. 500K inside the CPU 50
The Hz clock 51 and the CK2 latch 52 are connected to the AND circuit 53, and the output thereof is CK2 of the EL control circuit 54.
Input to the terminal.

Comparison data 55 corresponding to the frequency for CK1
And the counter 56 match, the flip-flop 5
The signal inverted by 7 and the CK1 latch 58 are connected to the AND circuit 59, and the output thereof is CK of the EL control circuit 54.
Input to one terminal.

The EL control circuit 54 is similar to that shown in FIG.
The CEN terminal signal from the PU controls the overall on / off. FIG. 21 is a flowchart showing a process when turning on the EL oscillation circuit.

First, in step S90, 500 KHz
Is turned on, and in the next step S91, CK2
The latch signal for is set to "H", and the clock is output from the CK2 terminal.

In step S92, the counter 36 is started, and in the next step S93, the brightness type of the EL circuit is read from the EEPROM (not shown) in the CPU 50. In step S94, the battery voltage is measured, and in the next step S95, it is determined which of the four types of EL elements, according to FIG.

In step S96, CK is generated according to FIG.
The frequency for 1 is selected and the corresponding comparison data is set, and in the next step S97, the CK1 latch signal is set to "H" and a pulse is output from the CK1 terminal.

In step S98, the CEN terminal signal is set to "L" to start lighting the EL. FIG. 22 is a flowchart showing a process when turning off the EL oscillation circuit.

First, in step S100, the CEN terminal signal is set to "H", and in the next step S101, 500K.
Turn off the Hz clock. In step S102, CK
The latch signal for 2 is set to "L", and the next step S103
Then, stop the counter.

In step S104, the CK1 latch signal is set to "L" to turn off the EL control circuit 54. From the above, even if the EL element deteriorates, the EL with the same brightness as in the initial stage
Can be turned on, and a camera with good operability can be realized even in the dark.

23 (a) to 23 (c) are views showing the mounting state of the EL element, FIG. 23 (a) is the overall configuration diagram, and FIG. 23 (b) is the broken line in the overall configuration diagram. Perspective view of the part,
FIG. 23C is an enlarged view of a broken line portion in the overall configuration diagram.

As shown in FIG. 23A, a transparent transmission part 61 is provided in a part of the exterior 60 of the camera, a transflective LCD 62 is provided under the transparent transmission part 61, an EL element 63 is provided under the LCD 62, and a flexible printed wiring is provided. The plate 64 and the fixing frame 65 are configured in this order.

The LCD 62 is connected to the pattern of the flexible printed wiring board 64 by the conductive rubber 66. E
The L element 63 includes a nylon film 70, a conductive layer 67, a light emitting layer (dielectric + phosphor) 68, and an aluminum foil 69. The nylon film 70 and the conductive layer 67 are shown in FIG.
As shown in FIGS. 0 (b) and (c), the length is made longer than the light emitting layer 68 and the aluminum foil 69, and the fixing frame 65 presses the flexible printed wiring board 64.

At the portion where the fixing frame 65 of the flexible printed wiring board 64 is crimped to the aluminum foil 69, a land on the negative side of the battery shown in FIG. 3 is formed and crimped to conduct electricity.

Similarly, the flexible printed wiring board 64
A land at point A shown in FIG. 3 is formed in a portion crimped to the conductive layer 67 by the fixing frame 65, and is made to conduct by crimping.

In the present invention, one side of the EL element 63 is always at the same potential as the negative side of the battery (in this case, aluminum foil),
Even if there is an electric circuit under the fixing frame 65, there is no need for shielding. Further, the EL element 63 may be entirely surrounded by a moisture-proof film so that only part of the aluminum foil 69 and part of the conductive layer 67 are exposed.

[0119]

As described above, according to the present invention, an efficient electroluminescence driving device using a small inductor can be realized without using a large transformer.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of an electroluminescence driving device of the present invention.

FIG. 2 is a time chart showing how the electroluminescence element is charged in the first embodiment.

FIG. 3 is a diagram showing a second embodiment of the electroluminescence driving device of the present invention.

FIG. 4 is a time chart showing how an electroluminescent element is charged in a second example.

FIG. 5 is a graph showing voltage and luminance characteristics of an electroluminescence element.

FIG. 6 is a graph showing the property of deterioration of the luminance characteristic of the electroluminescent element.

FIG. 7 is a diagram showing a method of coping with deterioration of luminance of an electroluminescence element.

FIG. 8 is a diagram showing a means for reducing required energy in a method of coping with deterioration of luminance of an electroluminescence element.

FIG. 9 is a third embodiment of the present invention and is a diagram showing an electroluminescence driving device using a field effect transistor FET in place of the bipolar transistor in the second embodiment.

10A and 10B are external views showing an example of a camera to which an electroluminescence driving device is applied as a fourth embodiment of the present invention, and FIG. 10A is a top view of the camera. FIG. 4B is a front view of the camera.

FIG. 11 is a block configuration diagram of a camera as a fourth embodiment of the present invention.

FIG. 12 is a flowchart showing main processing of a camera as a fourth embodiment of the present invention.

FIG. 13 is a flowchart showing main processing of a camera as a fourth embodiment of the present invention.

FIG. 14A is a flowchart showing a release processing R1 process in a flowchart showing a main process of a camera as a fourth embodiment of the present invention. (B) is
It is a flowchart which shows the process of date imprinting.

FIG. 15 is an external view showing a configuration of a date imprinting unit for imprinting a date on a camera as a fourth embodiment of the present invention.

FIG. 16 is a flowchart showing clock interrupt processing every 1 second in the flowchart showing main processing of the camera as the fourth embodiment of the present invention.

FIG. 17 is a diagram showing the relationship between the deterioration amount ΔP of the electroluminescent element left for one week and the deterioration amount ΔT _{EL of} one second of lighting with respect to temperature.

FIG. 18: Total deterioration amount T of electroluminescent element
It is the figure which calculated | required the frequency of the electroluminescent element from _EL + P.

FIG. 19 is a diagram in which electroluminescent elements are classified into four types according to the type of electroluminescent element and the battery voltage.

FIG. 20 is a diagram showing a configuration of an electroluminescence oscillation circuit used in a fourth embodiment of the present invention.

FIG. 21 is a flowchart showing a process when turning on the electroluminescence oscillation circuit of FIG. 20.

22 is a flowchart showing a process when turning off the electroluminescence oscillation circuit of FIG. 20. FIG.

23 (a) to 23 (c) are diagrams showing a mounting state of an electroluminescence element, FIG. 23 (a) is an overall configuration diagram, and FIG. 23 (b) is a dashed line portion in the overall configuration diagram. FIG. 23C is a perspective view showing an enlarged view of a broken line portion in the overall configuration diagram.

FIG. 24 is a schematic configuration diagram of an electroluminescence driving device as a conventional technique.

[Explanation of symbols]

20 ... CPU, 21 ... Feed motor drive circuit, 22 ... Photometric unit, 23 ... Lens motor drive circuit, 24 ... Shutter control circuit, 25 ... Battery check circuit, 26 ... Charging circuit, 27 ... Strobe light emission control circuit, 28 ... Distance measuring unit, 29
Liquid crystal display device (LCD), 30 ... Electroluminescence (EL) control circuit, 31 ... Date liquid crystal display device (LCD), 32 ... Date electroluminescence (EL) control circuit.

Claims (1)

[Claims] 1. A first booster circuit including a first coil, which outputs a positive boosted voltage by intermittently energizing the first coil, and a second coil. A second booster circuit that outputs a negative boosted voltage by intermittently energizing the coil, an electroluminescent element connected to the output points of the first and second booster circuits, and a first predetermined time period. While operating the first booster circuit,
Timing signal generating means for outputting a timing signal for operating the second boosting circuit for a second predetermined time following the first predetermined time, and the timing signal generating means outputs the timing signal. The electroluminescent driving device, wherein the positive boosted voltage and the negative boosted voltage output from the second booster circuit are alternately applied to the electroluminescent element.