JPH066478Y2 - Inverter for lighting EL lamp - Google Patents

Description

[Detailed description of the device]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter for lighting an EL lamp.

[Prior art]

EL lamps are usually tens to hundreds of volts, hundreds to several KHz.
It is lit by alternating current of the frequency. Further, the inverter for the lamp is generally driven by a commercial power source of 100V, 60Hz or a direct current of several volts. Therefore, the inverter for lighting the EL lamp needs to convert the supplied power into a voltage and a frequency that can light the EL lamp. An inverter that realizes this is composed of a booster circuit that boosts the supply voltage to a predetermined voltage and a DC-AC converter circuit that converts the boosted direct current into alternating current. This inverter has an EL on the output side of the DC-AC conversion circuit.
Connect the lamp. The DC-AC conversion circuit preferably supplies a sine wave to the EL lamp. This is because the sine wave can efficiently emit light from the EL lamp as compared with the rectangular wave. However, DC whose output waveform is a sine wave
The -AC conversion circuit has drawbacks that the power efficiency of the output stage is low, the amount of heat generated in the output stage is large, and the output power per supplied power is low. This is because the output stage cannot be turned on and off because the output waveform is a sine wave. The DC-AC conversion circuit that can control the output stage on and off is
The power conversion efficiency can be increased. However, this inverter has a drawback that the luminous efficiency of the EL lamp is lowered. In order to solve this drawback, an inverter has been developed in which a reactor is connected to an EL lamp in series, the reactor and the capacitance of the EL lamp cause series resonance, and the EL lamp is excited by a sine wave. This inverter is shown in FIG. This inverter has the features of high power efficiency and efficient light emission from the EL lamp. The inverter shown in FIG. 4 is a DC-AC.
The output side of the converter circuit, and a pair of switching elements Q ₇ to Q ₈ connected in series. A series resonance circuit of the reactor L ₃ and the EL lamp is connected as a load to the midpoint of the switching elements Q ₇ and Q ₈ connected in series. Switching elements Q ₇ and Q ₈ connected in series
Switches on and off alternately. However, this inverter generates a reverse voltage when the reactor L _{3 of} the load and the EL lamp resonate, and this drives the switching elements Q ₇ and Q ₈ in the reverse direction. Therefore, as shown in FIG. 5, the current waveform flowing through the point A crosses zero and the current flows in the opposite direction. Therefore, when the switching elements Q ₇ and Q ₈ are switched from off to on, it is necessary to inject this reverse current as well.
A current that short-circuits both switching elements Q ₇ and Q ₈ for a moment flows, which causes heat generation of the switching elements Q ₇ and Q ₈ and causes a decrease in efficiency. The large current flowing through the switching element causes the switching element to be temporarily overloaded. Therefore, it is necessary to use a transistor or the like that can withstand a large current as the switching element. In order to solve this drawback, a circuit for inputting rectangular waves of different waveforms to switching elements connected in series has been proposed (Japanese Patent Publication No. 58-28591). The inverter described in this publication is shown in FIG. This inverter uses transistors Q ₉ and Q ₁₀ as switching elements. The two transistors Q ₉ and Q ₁₀ are connected in series. As shown in FIG. 7, rectangular waves with shifted phases are input to the bases of both transistors Q ₉ and Q ₁₀ . The rectangular wave input to the base has such a waveform that both transistors Q ₉ and Q ₁₀ are not turned on at the same time. That is, a rectangular wave for turning on the other transistors Q ₁₀ and Q ₉ is input after a lapse of a certain time after one of the transistors Q ₉ and Q ₁₀ is turned off.

[Problems to be solved by the device]

However, the inverter having this circuit configuration requires an extremely complicated oscillation circuit as an oscillation circuit for inputting a rectangular wave to the switching element. An oscillation circuit that inputs a rectangular wave of a single waveform to both switching elements can be realized by a set of multivibrators. However, as shown in FIG. 7, in order to input two rectangular waves out of phase to the two switching elements, a plurality of sets of multivibrators that operate in synchronization with each other are required. For this reason, the inverter that inputs a rectangular wave shifted in time to the switching element has a drawback that the circuit configuration becomes complicated. In addition, this inverter includes transistors Q ₉ , Q ₁₀
The diodes D ₅ and D ₆ are connected in series in the forward direction, and both transistors Q ₉ and Q ₁₀ are temporarily turned off. The diodes D ₅ and D ₆ block the current flowing in the reverse direction in the transistors Q ₉ and Q ₁₀ . Therefore, the inverter having this circuit configuration forcibly controls both the transistors Q ₉ and Q ₁₀ to be in the off state in the state where energy is stored in the load. The load that is turned off in this state generates a high voltage across the load due to the accumulated energy. Therefore, in this inverter, it is necessary to use transistors Q ₉ and Q ₁₀ having a high breakdown voltage. Furthermore, the inverter that forcibly turns off the two transistors Q ₉ and Q ₁₀ connected in series for a certain period of time supplies power from the power supply when both transistors Q ₉ and Q ₁₀ are turned off. There is a drawback that cannot be done. That is, as shown in FIG. 6, a conventional inverter that temporarily controls a pair of transistors connected in series to be in an off state has a load that stores energy so that both transistors are not turned on at the same time. There is a drawback in that the power supply from the power supply is limited by opening the switch to generate a high voltage at both ends. The present invention was developed for the purpose of solving these drawbacks of conventional inverters for EL lamps.
The important purpose of this device is to have a very simple circuit configuration.
It is an object of the present invention to provide an inverter capable of effectively supplying electric power to an L lamp and using a switching element having a low withstand voltage so that the EL lamp can efficiently emit light. Another important object of the present invention is to provide an inverter for an EL lamp that can efficiently supply electric power to the EL lamp.

[Means for solving problems]

An inverter for lighting an EL lamp according to the present invention has the following configuration in order to achieve the above-mentioned object. (a) An inverter is a DC-DC booster circuit that boosts an input voltage to a voltage capable of lighting an EL lamp and converts it into a direct current;
A DC-AC conversion circuit for exchanging the output of the C-DC booster circuit to AC is provided. (b) The DC-AC conversion circuit includes an EL lamp lighting oscillation circuit and an output circuit that power-amplifies the output of the EL lamp lighting oscillation circuit. (c) The EL lamp lighting oscillation circuit is a rectangular wave oscillation circuit, and the oscillation frequency is specified in the range of 400 to 5000 Hz. (d) The output circuit has a pair of switching elements that are turned on and off. (e) The switching elements are connected in series with each other via a diode. (f) The switching elements connected in series are input with rectangular waves of the same phase, and are alternately controlled to be turned on and off. By the way, in this specification, the "rectangular wave having the same phase" means a state in which the rising time and the falling time of the two rectangular waves are the same. Therefore, the phase shift is 1
The 80 degree state is also defined as the same phase. (g) The series resonance circuit of the reactor and EL lamp is connected to the output side of the output circuit as a load. (h) The series resonance circuit of the reactor and the EL lamp is connected to the middle point of the switching elements connected in series via the diode. (i) The diode connected in series with the switching element is connected in the forward direction with respect to the switching element.

[Operation effect]

The invention of the inverter shown in FIG. 1 is a pair of switching elements Q _7, Q _8, to input a rectangular wave of the same phase, the V ₂ points of the first figure, a sign of a half cycle shown in Figure 2 Wave current can flow. It is a diode D ₃ , D connected in series with the switching elements Q ₇ , Q _{8.
This is because 4} blocks the reverse current flow. For this reason, the inverter of the present invention can prevent unnecessary current from flowing through the switching elements Q ₇ and Q ₈ of the output circuit by inputting rectangular waves of the same phase to the pair of switching elements Q ₇ and Q _8. There is. In addition, the inverter of this invention is designed for reactor L ₃ and E
The load connected in series with the L lamp is not opened in the energy storage state. Therefore, there is a feature that high voltage is not generated in a state where the load is open due to the energy accumulated in the load. That is, as shown in FIG.
A pair of switching elements Q ₇ and Q connected in series
_8, enter the rectangular wave of the same phase, both switching elements Q
_The reason for this is to alternately control ₇ and Q ₈ in the on and off states. That is, in a pair of switching elements to which rectangular waves of the same phase are input, when one switching element is switched from on to off, the other switching element is switched from off to on, so that energy is stored in the load. Do not open the state. The inverter shown in FIG. 1 turns on the transistor Q ₈ .
With the transistor Q ₇ turned off, current flows from the power supply into the reactor L ₃ and the EL lamp to store energy. The energy stored in the reactor L ₃ in the energized state increases in proportion to the inductance of the reactor L ₃ and the square of the current. When energy is stored in the load and opened, energy cannot be consumed and high voltage is generated at both ends. This principle is widely used as a simple high-voltage generating circuit. However, the inverter of this invention uses the transistor Q ₈
The instant the transistor turns off, the transistor Q ₇ turns on and does not open with current flowing through the load. This is because the same phase rectangular wave is input to both transistors. Both the rise of the square wave to be input to the transistor is a vertical, on the two transistors, assuming zero off-time, after the transistor Q ₈ is turned off, the transistor Q ₇ without any time delay is turned on. However,
In reality, the rising edge of the rectangular wave is not completely vertical, and the on / off time of the transistor is not zero. Therefore, after the transistor Q ₈ is turned off, the transistor Q ₇ is turned on with a delay of some time. However, since rectangular waves of the same phase are input to both transistors, the time delay thereof is extremely short compared to the cycle of turning on / off the switching element. Therefore, the inverter of this invention is the one of the switching elements Q ₈ is turned on to, a current flows from the power source to the load, then switched to on another switching element Q ₇ from off, the energy stored in the load Discharge the
This operation is alternately repeated at a constant cycle to energize the load with alternating current. In this operation, the inverter of the present invention has an extremely short switching time from the state of supplying current to the load to the state of discharging, and both switching elements can be switched with almost no time delay. AC is energized in an ideal state without opening. Further, since a high voltage is not generated across the load when switching between on and off, it is not necessary to use a switching element having a high breakdown voltage. Furthermore, since the inverter of this invention does not need to turn off both of the pair of switching elements, it can extend the time for supplying power from the power supply to the load, and can efficiently supply power to the load to illuminate brightly. There is also. Furthermore, since rectangular waves of the same phase are input to both switching elements, the rectangular wave oscillation circuit can be simplified and the cost can be reduced.

[Preferred embodiment]

An embodiment of the present invention will be described below with reference to the drawings. However, the embodiments described below exemplify an inverter for embodying the technical idea of the present invention, and the inverter of the present invention does not specify the circuit configuration as follows. The inverter of this invention is subject to various modifications within the scope of the claims for utility model registration. The EL lamp lighting inverter shown in FIGS. 1 and 3 includes a DC-DC booster circuit 1 that boosts an input voltage to an EL lamp lighting voltage and converts it into direct current. DC-DC step-up circuit 1 has a transistor _Q 1, _{Q 2,} transformer _{T 1,} diodes _D 1, _{D 2,} reactor _L 1, L
₂ , a Royer circuit including a resistor R ₁ and a capacitor C ₃ is used. The DC-DC booster circuit 1 may use another known circuit capable of boosting the input voltage to the EL lamp lighting voltage. The alternating current boosted by the transformer T ₁ is double-wave rectified by the diodes D ₁ and D ₂ connected to the secondary side of the transformer. The rectified pulsating flow is converted into a smooth direct current by the reactor L ₂ and the capacitor C ₃ . The direct current converted into the voltage for lighting the EL lamp is DC-A
It is supplied to the EL lamp via the C conversion circuit 2. DC-
The AC conversion circuit 2 includes an oscillating circuit 3 that determines a cycle of converting direct current into alternating current, and an output circuit 4 that amplifies the oscillated rectangular wave by power. The oscillation circuit 3 for lighting the EL lamp includes a transistor Q ₃ ,
It is composed of a multi-vabrator composed of Q ₄ , resistors R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , and capacitors C ₄ , C ₅ . The multivibrator includes resistors R ₄ and R ₅ and a capacitor C.
₄ and C ₅ determine the free-running oscillation frequency. This frequency specifies the frequency of the power supplied to the EL lamp. This frequency is adjusted in the range of 400-5000 Hz. The multivibrator oscillates a rectangular wave. As the oscillator circuit 3, another known circuit that oscillates a rectangular wave may be used. The output circuit 4 includes transistors Q ₅ , Q ₆ , Q ₇ , and Q ₈ as switching elements. This circuit, in addition to transistors, resistors _{R 8, R 9, R 10} , R 11
And diodes D ₃ and D ₄ . The transistors Q ₇ and Q ₈ are connected in series with each other. The emitter side of the transistors Q ₇ and Q ₈ connected in series is connected to the power supply. Therefore, the transistor Q ₈ is of the npn type, and the transistor Q ₇ is of the pnp type. Transistor Q ₇ has its emitter on the positive side of the power supply, and transistor Q _7
8 has its emitter connected to the negative side of the power supply. The collector sides of the transistors Q ₇ and Q ₈ are connected to each other through series-connected diodes D ₃ and D ₄ . The diodes D ₃ and D ₄ are connected in the forward direction with respect to the transistors Q ₇ and Q ₈ . The output circuit 4 is a rectangular wave input from the oscillation circuit 3, and the transistors Q ₅ and Q ₆ are alternately turned on and off repeatedly, and further the resistors R ₈ , R ₉ , R ₁₀ , and R _{11 are used to form the} transistor Q. _7, on the _{Q 8} alternately, turned off. A reactor L ₃ is connected to a connection point of the diodes D ₃ and D ₄ , and an EL lamp is connected to the output circuit via the reactor L ₃ . That is, EL lamp and reactor L
₃ and ₃ are connected in series, and this is connected as a load of the output circuit. The transistors Q ₇ and Q ₈ of the output circuit are alternately turned on,
Repeat off. When the transistor Q ₇ is off and the transistor Q ₈ is on, the load supplies current to the load. Conversely, when transistor Q ₇ is on and transistor Q ₈ is off, current flows in the reverse direction through the load. Therefore,
The output circuit supplies a rectangular wave output to the series resonant circuit of the EL lamp and the reactor L ₃ . The rectangular wave pulse voltage supplied from the transistors Q ₇ and Q ₈ to the load resonates in the capacitive EL lamp and the reactor L ₃ , and supplies a high voltage to the EL lamp. Transistors Q _7, Q ₈ connected in series with a diode D ₃ which is a switching _element, D ₄ is a series resonant load, when the voltage of the power supply point is deflected in the opposite direction, to cut it, the transistor Q _7, along with preventing the unnecessary current flows in opposite directions Q _8, on, smoothly switching off, preventing the heat generation of the switching element. In the inverter of FIG. 3, feedback is applied to the oscillation circuit 3 in order to pull the oscillation frequency of the oscillation circuit 3 into the resonance frequency of the series resonance circuit from the voltage generation point of the resonance circuit of the EL lamp and the reactor L _3. ing. This inverter feeds back to the oscillation circuit 3 from the connection point of the reactor L ₃ and the EL lamp via the resistor R ₁₂ and the capacitor C ₆ . The feedback amount from the resonance circuit of the EL lamp and the reactor L ₃ can be adjusted by the resistor R ₁₂ . When the resistance R ₁₂ is small, the feedback becomes strong, and the oscillation frequency of the oscillation circuit 3 is more strongly pulled to the resonance frequency. On the contrary, if the resistance R ₁₂ is large, the EL lamp and the reactor L
_The amount of feedback from the resonance circuit with ₃ decreases,
Retraction from the resonance circuit is small, and the resonance circuit 3 oscillates at a frequency close to the free running oscillation frequency. The resistor R ₁₂ is adjusted to adjust the amount of feedback from the resonant circuit of the EL lamp and the reactor L ₃ to the oscillation circuit, the resonance frequency determined by the resonant circuit of the EL lamp and the reactor L _3, the actual oscillator circuit By adjusting the deviation of the oscillation frequency, the optimum frequency is always applied to the EL lamp. When the EL lamp deteriorates and changes with time, the capacitance component decreases, and along with the change, the resonance frequency increases and moves to a new optimum point. Therefore, the frequency and voltage of the EL lamp gradually increase, and the decrease in brightness can be reduced over a long period of time. Further, in the inverter of FIG. ₃ , feedback is also applied to the input side of the output circuit 4 from the voltage generation point of the resonance circuit of the EL lamp and the reactor L ₃ . The output circuit 4 is fed back by the resistor R ₁₂ and the capacitor C ₇ . The EL lamp and the reactor L ₃ are connected via the resistor ₁₂ and the capacitor C ₇ which are connected in series.
From the connection point with the transistor Q on the input side of the output circuit 4
_5, based on the feedback of _{Q 6} is over. The resistor ₁₂ and the capacitor C ₇ feed back a part of the sine wave from the resonance circuit of the EL lamp and the reactor L ₃ to the bases of the transistors Q ₅ and Q ₆ of the output circuit. This feedback applies to the transistors Q ₇ and Q _8.
The timing of alternately turning on and off is adjusted, and a rectangular wave with a duty of 50% is supplied to the load of the resonance circuit including the reactor L ₃ and the EL lamp. A rectangular wave with a duty approaching 50% was supplied.
The resonance circuit of the L lamp and the reactor L ₃ is energized by a sine wave with less distortion, enhances the resonance effect, and causes the EL lamp to efficiently emit light. Since the inverter shown in FIG. 3 controls the switching elements on and off by the single oscillator circuit 3, it has a feature that the oscillation frequency of the oscillator circuit can be controlled by a simple feedback circuit and the EL lamp can efficiently emit light for a long period of time. .

[Brief description of drawings]

1 and 3 are circuit diagrams of an inverter showing an embodiment of the present invention, and FIG. 2 is a DC of the inverter shown in FIG.
-AC conversion circuit V is a graph showing a current waveform at a point ₂ , FIG. 4 is a circuit diagram showing an output circuit of a conventional inverter, FIG. 5 is a graph showing a current waveform at a point A of the output circuit shown in FIG. 4,
FIG. 6 is a circuit diagram of a conventional inverter, and FIG. 7 is a graph showing a rectangular wave input to the transistor of the inverter shown in FIG. 1 ... DC-DC booster circuit, 2 ... DC-AC conversion circuit, 3 ... oscillation circuit, 4 ... output circuit.

Claims (1)

[Scope of utility model registration request] 1. An inverter for lighting an EL lamp having the following structure: (a) a DC-DC booster circuit for boosting an input voltage to a voltage capable of lighting an EL lamp and converting it to a direct current; and an output of the DC-DC booster circuit is an alternating current. It is equipped with a DC-AC conversion circuit for exchanging. (b) The DC-AC conversion circuit includes an EL lamp lighting oscillation circuit and an output circuit that amplifies the output of the EL lamp lighting oscillation circuit. (c) The EL lamp lighting oscillation circuit is a rectangular wave oscillation circuit, and the oscillation frequency is specified in the range of 400 to 5000 Hz. (d) The output circuit has a pair of switching elements that are turned on and off. (e) The switching elements are connected in series with each other via a diode. (f) In the pair of switching elements connected in series,
A rectangular wave of the same phase is input, and the rectangular wave of the same phase is alternately turned on and off. (g) The series resonance circuit of the reactor and EL lamp is connected to the output side of the output circuit as a load. (h) The series resonance circuit of the reactor and the EL lamp is connected to the middle point of the switching elements connected in series via the diode. (i) The diode connected in series with the switching element is connected in the forward direction with respect to the switching element.