JPH03235674A - El driving circuit - Google Patents

Abstract

PURPOSE:To improve a switching efficiency by a method wherein respective switching devices provided on the primary side of an output transformer are controlled by the outputs of feedback circuits which are provided on the primary side of the output transformer and have feedback windings to which currents having a directions opposite the each other are applied. CONSTITUTION:Feedback circuits 6a and 6b which have respective feedback windings L1 and L2 to which currents having directions opposite to each other are applied are provided on the primary side of the output transformer 5 of an inverter 4. The change of the flux of an output winding L3 is fed back by the primary side feedback windings L1 and L2 and switching transistors T1 and T2 are controlled by the respective feedback circuits 6a and 6b in accordance with the fed back signals. At that time, the feedback windings L1 and L2 are composed of bifilar windings and the timings of the feedback circuits 6a and 6b are opposite to each other, so that balanced control of the switching transistors T1 and T2 can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an EL drive circuit equipped with an inverter that drives an EL (electroluminescent element) with high frequency power of about 400H2.

[Conventional technology]

FIG. 5 is a block diagram of a conventional EL drive circuit equipped with this type of inverter. In the figure, 1 is an AClooV commercial AC power supply, 3 is a power supply unit that converts the AC input from the AC power supply 1 into DC, and a diode Dl that half-wave rectifies the input AC.

D2, smoothing capacitors C1, C2 and resistors R2, R
3, forming a voltage doubler rectifier circuit. 4 is a switching transistor Tl, T2 for direct current from the power supply section 3.
5 is an output transformer of this inverter 4, -
Feedback winding fiL1 with pie filer wound on the next side. L2,
It is equipped with feedback circuits 6a and 6b having capacitors C5 and C6 and resistors R4 and R5.
The output of the switching transistors TI, T2
is controlled. 7 is an EL connected as a load to the output winding L3 on the secondary side of the output transformer 5, and the output winding L3 and L
C resonates. Note that R6 and R7 are bias resistors.

In the circuit with the above configuration, A input from the AC power supply 1
The AC of C100V is voltage doubled and rectified in the power supply section 3.

This rectified direct current is switched by the switching transistors TI and T2 of the inverter 4, which causes the inverter 4 to oscillate and generate high frequency power on the secondary side of the output transformer 5. And this high frequency power is EL
7 and EL7 lights up. At this time, an LC resonance circuit is formed by the capacitance of EL7 and the inductance of the output winding L3, and the inverter 4 oscillates due to the LC resonance. And the feedback winding Ll.

Transistor T with the signal fed back by L2
The timing of switching (ON, OFF) of I and T2 is determined, the above-mentioned oscillation is performed continuously, and EL7 is lit continuously.

[Problem to be solved by the invention]

However, in the conventional EL drive circuit as described above, the power supply section is a voltage doubler circuit with half-wave rectification, so a voltage of approximately ±141V (100V x J2) is applied to each element, and each element is It is necessary to use a device with a high withstand voltage, making it expensive, and there are problems such as poor switching efficiency and large heat generation.In addition, the output to the EL should be adjusted to the preferable value of 100 V/400 Hz. In this case, since the high voltage of ±141v is half-switched, the load on the switching element becomes large.
The problem was that it generated a lot of heat.

This invention was made by focusing on these problems, and it is possible to lower the withstand voltage of each element, reduce the cost, have good switching efficiency, and generate less heat, and even if the output to the EL is adjusted to a desired value, no heat is generated. I/) for the purpose of obtaining a small 1EL drive circuit.

[Means to solve the problem]

The EL active circuit of the present invention includes a full-wave rectifier that performs full-wave rectification of alternating current from an alternating current power supply, and an inverter that performs switching control to convert the full-wave rectified direct current into high-frequency alternating current, and the inverter includes two E connected to the next output winding
has an output transformer in which L and the secondary winding resonate with LC,
The inverter has feedback circuits each having a feedback winding in which current flows in opposite directions on the primary side of the output transformer, and the output of the feedback circuit causes each switching element provided on the primary side of the output transformer of the inverter to be activated. In addition, a capacitor is connected to the control line of the switching element, and a resistor is connected to the output line of the full-wave rectifier.

[Effect]

In the ELffi dynamic circuit of the present invention, the input AC is full-wave rectified in the power supply section, so the withstand voltage of each element is lowered, switching efficiency is good, and heat generation is lower than in the case of half-wave rectification. Furthermore, when attempting to adjust the output to the EL to a desired value, the degree of switching becomes close to full and less heat is generated.

〔Example〕

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
The same reference numerals as in the figures indicate the same components.

In the figure, 1 is AClooV (50/60)12)
2 is a full-wave rectifier that performs full-wave rectification of the alternating current from this AC power supply 1, 3 is a power supply unit equipped with this full-wave rectifier 2, and an inrush unit connected to the output line of the full-wave rectifier 2. Resistor R1 for current suppression, capacitors C1 and C2 for smoothing
and discharge resistors R2, R3, etc., forming a voltage doubler rectifier circuit. 4 is a switching transistor T1. T2 is an inverter that performs switching control and converts it into high-frequency alternating current; 5 is an output transformer of this inverter 4;
b is a feedback circuit provided on the primary side of the output transformer 5 and having feedback wires Ll and L2 flowing in mutually opposite directions, with capacitors C5 and C6 connected to the feedback windings Ll and L2. A series circuit of resistors R4 and R5 connects the bases of the switching transistors TI and T2 and the feedback winding L.
l.

Bias resistors R6 and R5 are connected between the capacitor C5 and C6 and the resistors R4 and R5.
7 is connected. Further, capacitors C3 and C4 forming a filter circuit are connected to the control lines (base lines) of the switching transistors TI and T2. 7 is an EL connected to the output winding L3 on the secondary side of the output transformer 5, and the capacitance of this EL7 and the output winding L3 are
An LC resonant circuit is formed with the inductance. Note that the discharging resistors R2 and R3 of the power supply section 3 are connected to the inverter 4.
This can be omitted depending on the bias values of the bias resistors R6 and R7.

Next, the operation will be explained.

The AClooV alternating current from the AC power supply 1 is full-wave rectified by the full-wave rectifier 2 of the power supply section 3 and converted into direct current. This direct current passes through the resistor R1, which has a very large rate of change in resistance in the positive direction with respect to temperature, and is charged to the capacitors CI and C2.
The inrush current is suppressed, and each element of the full-wave rectifier 2 is also protected from the inrush current. Therefore, the capacity of the full-wave rectifier 2 can be reduced, and fuses and the like can be omitted. At this time, if the surge current is 17, the voltage is vl, and the value of the resistor R1 is R1, then V, =
The relationship is R,·11.

The DC input from the power supply section 3 to the inverter 4 is switched by the switching transistors TI and T2, thereby generating high frequency power in the output transformer 5, and this high frequency power is supplied to the EL7. At that time, the switching frequency f is determined by the LC resonance of the output winding L3 and EL7, and the inductance of the output winding L3 is set to
If the capacitance of L, E L7 is C8, then this frequency f
is f=1/2π, rth row. Then, this change in the magnetic flux of the output winding L3 is fed back by the feedback winding L1L2 on the primary side, and each feedback circuit 6
Switching transistors TI and T2 are controlled by a and 6b. At this time, feedback winding L1. L2 has a pie filer winding, and the timings of the feedback circuits 6a and 6b are opposite to each other, so that the switching transistors TI and T2 are controlled in a balanced manner. Moreover, the switching transistor T1. Capacitor C is on the baseline of T2.
3. Since C4 is connected, the bases of switching transistors TI and T2 are stabilized by its filter effect, preventing abnormal oscillations, etc., allowing maximum matching adjustment, and making it easier to scale up EL7. .

Here, since full-wave rectification is performed in the power supply section 3, the above-mentioned switching is performed at approximately ±70V, and the withstand voltage of each element may be low. Therefore, there is a wide range of element types, delivery dates, etc., and the cost can be reduced. At the same time, the switching efficiency in the switching transistors TI and T2 is improved, and the heat generation is reduced to about 1/2 of that in the case of half-wave rectification.

Furthermore, when the output to EL7 is adjusted to a preferable value of 100V/400H, the degree of switching becomes close to full, and heat generation becomes extremely small.

Note that, as shown in FIG. 2, noise can be reduced by interposing a gap material 8C in the form of double-sided tape between the I-type core 8a and the E-type core 8b of the output transformer 5. Furthermore, as shown in FIG. 3, by wrapping the bobbin core of the output transformer 5 with a copper foil tape 9, leakage of magnetic flux can be reduced and efficiency can be increased.

Furthermore, as shown in FIG. 4, noise can be further reduced by wrapping the periphery of the core 8 with a double-sided tape 8d made of the same material as the gap material 8C.

〔Effect of the invention〕

As described above, according to the present invention, a full-wave rectifier is provided in the power supply section and the full-wave rectified direct current is switched. Therefore, the voltage resistance of each element is reduced, and the switching efficiency is also improved. This has the effect of reducing heat generation, and also has the effect of reducing heat generation when the output to the EL is adjusted to a preferable value. Furthermore, oscillation can be stabilized by connecting a capacitor to the control line of the switching element, and rush current can be suppressed by connecting a resistor to the output line of the full-wave rectifier.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, FIGS. 2, 3, and 4 are perspective views showing the specific configuration of the output transformer shown in FIG. 1, and FIG. 5 is a conventional EL drive. It is a block diagram of a circuit. 1...Commercial AC power supply 2...Full wave rectifier 3...Power supply section 4...Inverter 5...Output transformer 7... -EL 6a, 6b...Feedback circuit TI, T2=-...Switching transistor L1
, L 2---Feedback winding L3---Output winding C3, C4---Capacitor R1------Resistance

Claims (3)

[Claims] (1) A full-wave rectifier that performs full-wave rectification of AC from an AC power source, and an inverter that performs switching control to convert the full-wave rectified DC into high-frequency AC, the inverter comprising:
EL connected to the output winding on the secondary side and the secondary winding
Each feedback circuit has an output transformer having C resonance and a feedback winding in which current flows in opposite directions to the primary side of the output transformer, and the output of the feedback circuit causes the primary side of the output transformer of the inverter to An EL drive circuit characterized by controlling each switching element provided on the side. (2) The EL drive circuit according to claim 1, further comprising a capacitor connected to the control line of the switching element. (3) The EL drive circuit according to claim 1 or 2, characterized in that a resistor is connected to the output line of the full-wave rectifier.