JP2969992B2 - Lighting circuit for electroluminescent lamps - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an electroluminescent lamp (hereinafter referred to as EL).
) Lighting circuit.

[0002]

2. Description of the Related Art An EL has a capacitor structure in which a light emitter is sandwiched between two electrodes. When an AC voltage is applied between the two electrodes, an AC electric field is applied to a fluorescent substance of the light emitter to emit light.
Also, since EL has a property that the luminance increases in proportion to the magnitude and frequency of the applied voltage, rather than applying a commercial AC power supply voltage, a dry cell, a storage battery or a DC voltage obtained by rectifying the commercial AC voltage is used for EL. In many cases, the light is converted into a high-frequency and high-voltage AC voltage through a lighting circuit (inverter), and the lighting is performed. An example of this is shown below with reference to FIG. The lighting circuit (DA ₁ ) is a blocking oscillation type inverter.
L connected to L (1) Lance (T) and input terminal (V
i ₁ ) (Vi ₂ ) and a switching circuit (S ₁ ) provided between the transformer (T). Then, the input terminal (V
i ₁ ) (Vi ₂ ) The applied DC voltage Vcc is applied to the ON-0F of the transistor (Q ₁ ) of the switching circuit (S ₁ ).
Is converted into an AC voltage by F operation is applied to the primary side of the transformer (T), obtained by multiplying the turn ratio N ₂ / N ₁ of the primary winding and the secondary winding of the transformer (T) to the primary voltage The secondary-side output voltage is applied to EL (1). (Japanese Patent Publication No. 62-15032)

The blocking oscillation type inverter (DA ₁ ) is mainly used for EL lighting. In recent years, the DC-DC shown in FIG.
An inverter (DA ₂ ) that uses a DC voltage boosted by a DC converter (2) is also used. It has become. The inverter (DA ₂ ) has a function of increasing the input voltage Vcc. And C-DC converter (2), respectively with connecting collector-emitter between the terminals of the EL (1) and the DC-DC converter (2), resistance (R ₁₎ each via a (R ₂₎ based (Q ₂ ) connected to a DC-DC converter ( ₂ ) Diodes (D ₁ ) and (D ₂ ) between (Q ₃ ) and each terminal of EL (1) and ground. The switching transistors (Q ₄ ) and (Q ₅ ), whose collectors and emitters are connected via the gates, and the bases of the transistors (Q ₄ ) and (Q ₅ ) are input / output via resistors (R ₃ ) and (R ₄ ). Po)
(Pi) and an inversion circuit (IC ₁ ).

In the above configuration, first, an inverting circuit (I
Switching time is applied to the input (Pi) of C ₁ ). Road (not shown)
Input a higher signal. Then, the transistor (Q ₄ ) A low signal is input to the base from the inverting circuit (IC ₁ ) to cut off and A high signal is directly input to the base of the transistor (Q ₅ ) to conduct. Therefore,
Tiger The transistor (Q ₂ ) conducts, the transistor (Q ₃ ) shuts off, and the DC-DC converter (2) is charged in one direction of the EL (1) through the transistor (Q ₂ ).
The current then flows from EL (1) to ground via diode (D ₂ ) and transistor (Q ₅ ).

Next, the input (Pi) of the inverting circuit (IC ₁ )
Signal from the above switching circuit. Enter the issue. Then, a high signal is input to the base of the transistor (Q ₄ ) from the inverting circuit (IC ₁ ), and the transistor becomes conductive.
Straight to the base of the transistor (Q ₅₎ Contact, a row signal is input and cut off. Then, the transistor (Q ₂ ) is turned off. At the same time, the transistor (Q ₃ ) conducts, and the DC-D
Tiger from C converter (2) E through the transistor (Q ₃ )
The charging current flows in the other direction of L (1), and EL (1)
Flows through the diode (D ₁ ) and the transistor (Q ₄ ) to the ground. At this time, E passes through the transistor (Q ₃ ).
When charging L (1), cancel the previous residual charge In addition, the reverse charging is further performed. In this way,
Inverting circuit (IC ₁ ) A high signal and a low signal are alternately input from the switching circuit to an input (Pi), and a DC voltage is converted into a high-frequency AC voltage and applied to EL (1).

[0006]

The first problem to be solved is a blocking oscillation type inverter (DA ₁ ).
In the case of (1), the power factor is low and the loss is large because the EL (1) is capacitive, the conversion efficiency (the ratio of the power consumed by the EL to the input power) is low (about 50%), and the transformer (T)
There is a point that the equipment becomes large due to this. In the case of an inverter (DA ₂ ), When charging by the DC-DC converter (2), each time the charging direction changes, the previous residual charge must be canceled to perform further reverse charging, and DC-DC
Since the converter (2) is always operating, the conversion efficiency is low, and a DC output is required.
The rectifier circuit (rectifier diode and high-voltage smoothing capacitor) is required inside the DC converter (2) in addition to the booster circuit.

[0007]

SUMMARY OF THE INVENTION The present invention provides a DC-DC converter for boosting an input voltage and unidirectionally charging an electroluminescent lamp via a diode, and a reactor and a discharger connected to a charging input of the electroluminescent lamp. A discharging circuit in which transistors for reverse discharge are connected in parallel in the reverse direction to the transistors, a timing signal for controlling the DC-DC converter to operate only during the charging period, and conduction of the discharging transistors. And a timing signal circuit for transmitting a timing signal to be controlled. The transistor is turned on to discharge the electroluminescent lamp under the control of the timing signal circuit, and is charged in another direction by the transient characteristics of the reactor, and further discharged in reverse. Re-discharges through the diode for use, and the transient characteristics of the Characterized in that it re-charging.

[0008]

When the DC-DC converter is operated only during the period of charging the EL capacitance and a voltage is applied to the EL, the EL emits light by the charging current, but stops emitting when the charging is completed and the current becomes zero. . However, the charged charge remains in the capacitance of the EL, which is generally called a residual charge.

In a discharge circuit including a reverse discharge diode connected between the collector and the emitter terminal of the transistor in a direction opposite to the conduction direction of the EL and the reactor and the transistor, the transistor is made conductive to discharge the residual charge of the EL to the reactor and the transistor. And the transient characteristics due to the capacitance of the EL and the inductance of the reactor, the EL is temporarily charged with a voltage in a direction opposite to the residual charge.
l. 43 No. 10 p. 25-29 (1990.1
0, 30) etc.
Emits light again by this current.

The electric charge of the EL charged to the opposite polarity flows through the reverse discharging diode and the reactor connected between the collector and the emitter of the discharging transistor, and a current flows in the reverse direction to the discharging. Is recharged. By setting the discharging transistor to a non-conducting state during an arbitrary period during which a current flows through the reverse discharging diode, the discharging operation can be stopped in a state where the EL has been recharged in one direction.

[0011] The polarity of the recharging voltage is the same as the polarity of the charging voltage to the EL by the DC-DC converter, and then, when the DC-DC converter is operated again, only the voltage lost by the discharging operation or the light emission becomes DC-DC. The remaining charge of the EL, which is replenished from the converter, is effectively used in the next light emission cycle.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. First, in FIG. 1, (3) is a DC-DC converter, (4) is a timing signal circuit, and (5) is a discharge circuit. The DC-DC converter (3) is a DC-DC converter.
This boosts the input voltage (Vcc) and charges the EL (1) in one direction via the diode (D ₃ ). ,
The diode (D ₃ ) is a rectifier diode, EL (1) is a smoothing capacitor, No rectifier circuit is required in the converter. Timing signal circuit (4), together with controls to operate the DC-DC converter (3) only EL charging period, as described later, the discharge transistor of the discharge circuit (5) (Q ₆₎ is also controlled. Discharge circuit (5) is E
The reactor (Rc) and the discharging transistor (Q ₆ ) are connected in series to the charging terminal of L (1), and a reverse discharging diode (D ₄ ) is connected between the collector and the emitter of the transistor (Q ₆ ). ₆ ) The transistor (Q ₆ ) is connected in parallel in the direction opposite to the conduction direction of the transistor (Q ₆ ) under the control of the timing signal circuit (4). It conducts and discharges EL (1), and then, due to the transient characteristics due to the EL capacitance and the inductance of the reactor (Rc), the EL (1) is discharged.
Charge (1) in the other direction. Then, the diode (D
₄ ) After re-discharge by flowing through EL) (1) To one side.

The operation of the present invention based on the above configuration will be described below. First, as shown in FIG. 2, the DC-DC converter control signal (Sd) is transmitted by the timing signal circuit (4) to operate the DC-DC converter (3), and the transistor (Q) is transmitted by the discharge control signal (Sq). ₆ )
Is cut off, and the DC input voltage (Vcc) is boosted to Eau through (D ₃₎ to charge the EL (1) in one direction. Then, EL (1 ) Rises, and when charging reaches the saturation voltage (Veo) while applying the DC output voltage (Vd) for a fixed time (Td), the output of the DC-DC converter is stopped after the elapse of the time. Even so, the terminal voltage of EL is maintained at the charging voltage (Veo). Next, when a discharge control signal (Sq) is sent out by the timing signal circuit (4) to turn on the transistor (Q ₆ ), the charge (residual charge) of the charged EL (1) is obtained. Load) is discharged through the reactor (Rc), the EL voltage (Ve) starts to drop, and the EL current (Ie) is discharged (Ie).
eq). Here, even after the terminal voltage (Ve) of the EL becomes 0 V due to the transient characteristics due to the capacitance of the EL and the inductance of the reactor (Rc), the discharge current (Ieq) continues to flow while attenuating, and the electrostatic capacitance of the EL continues. The capacitor is charged with a voltage (Vqm) having a polarity opposite to that of the residual charge (ie, in the other direction). When the discharge current (Ieq) reaches 0, the re-discharge current (Idm) starts flowing through the reverse discharge diode (D ₆ ) and the reactor (Rc). The reverse-polarity voltage (Vqm) charged to the capacitance of the EL by this re-discharge current (Ied) discharges to 0 V soon, but the re-discharge current (Idm) continues to flow while attenuating for the same reason as described above. This time, the voltage (Vdm) is charged to the capacitance of the EL in the opposite reverse polarity, that is, in one direction.

On the other hand, the conduction state of the transistor (Q ₆ ) by the discharge control signal (Sq) from the timing signal circuit (4) is not activated during an arbitrary period during which the re-discharge current (Idm) flows. When the conductive state is maintained, the current (Ie) flowing to the EL becomes zero at the timing when the re-discharge current (Idm) becomes zero. At this time, the EL terminal voltage has a characteristic that the recharge voltage (Vdm) substantially reaches the maximum due to transient characteristics.

Therefore, after that, when the timing signal circuit (4) is controlled at a predetermined time (Tb) and the DC-DC converter (3) is operated again to charge the EL (1),
It suffices to supply only the difference voltage (ΔV) between the charging voltage (Veo) and the recharging voltage (Vdm), and the use efficiency of the DC-DC converter (3) is good. Thereafter, the same operation may be repeated. At this time, the cycle of the control signal sent from the timing signal circuit (4) becomes the cycle (T) of the control signal (Sd) sent to the DC-DC converter (3), and the lighting frequency of the EL depends on the cycle (T). Can be determined.

[Example 2] NEC Technical Report Vol. 43
No. 10 p. 25-29 (1990.10.30)
DC-D used in the inverter for EL
Among the C converters, the one having a constant power characteristic is excellent in the life compensation characteristic of the EL.

It is clear that the same effect can be obtained in the present EL inverter. In addition, the DC-DC converter is operated from the recharge voltage (Vdm) in one direction to set a constant voltage when charging the difference voltage (ΔV). By controlling the operation time (Td) of the power DC-DC converter, the power supply to the EL can be adjusted. This means that constant power DC
-The luminance of the EL can be adjusted only by controlling the operation time while the operation conditions of the DC converter are kept optimal, and the conversion efficiency can be further increased.

[0018]

According to the present invention, since the DC-DC converter is operated only during the period of charging the EL, wasteful power consumption is eliminated, the conversion efficiency is improved, and the EL capacity can be directly charged. Eliminates the need for capacitors, reduces the number of converter components, reduces size,
By making the power of the DC-DC converter constant, there is an effect that the brightness of the EL can be adjusted while maintaining the optimum operation of the DC-DC converter depending on the operation time.

[Brief description of the drawings]

FIG. It is a circuit diagram showing an example of a lighting circuit for an electroluminescent lamp according to the present invention.

FIG. 2 FIG. 3 is a waveform diagram of a control signal of a timing signal circuit, a DC-DC converter output, and a voltage and a current of an electroluminescent lamp, showing the lighting circuit operation of FIG. 1.

FIG. 3 FIG. 9 is a circuit diagram showing a specific example of a conventional lighting circuit for an electroluminescent lamp.

FIG. 4 FIG. 9 is a circuit diagram showing a specific example of a conventional lighting circuit for an electroluminescent lamp.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 electroluminescent lamp 3 DC-DC converter 4 timing signal circuit 5 discharge circuit Rc reactor D ₃ diode D ₄ reverse discharge diode Q ₆ reverse discharge transistor

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁶ , DB name) H05B 33/08 G09F 13/22

Claims (2)

(57) [Claims] (1) A DC-DC converter that boosts the input voltage and charges the electroluminescent lamp in one direction via a diode; and connects a reactor and a discharging transistor in series to the charging input of the electroluminescent lamp, and reversely discharges the transistor to the transistor. A discharge circuit in which diodes are connected in parallel in the reverse direction,
A timing signal circuit for transmitting a timing signal for controlling the DC-DC converter to operate only during a charging period and a timing signal for controlling conduction of the discharge transistor; and controlling the transistor by controlling the timing signal circuit. Discharge the electroluminescent lamp and charge it in the other direction by the transient characteristics of the reactor, re-discharge through the diode for reverse discharge, and recharge the electroluminescent lamp in one direction by the transient characteristics of the reactor A lighting circuit for an electroluminescent lamp. (2) 2. The lighting circuit for an electroluminescent lamp according to claim 1, wherein the DC-DC converter is of a constant power output type with respect to a load change.