JPH10191653A - Inverter circuit, and illumination device using the circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop a mobile inverter push-pull circuit, to apply the circuit to an illumination device, and to manually or automatically dim the illumination device. SOLUTION: Coils L1 and L2 of a transformer TR1 and variable resistors VR1 and VR2 are connected to a positive terminal of a power source E, and emitters of transistors Q1 and Q2 and resistors R1 and R2 are connected to a negative terminal. Another terminals of L1 and L2 are respectively connected to collectors of Q1 and Q2 and variable capacitors VC1 and VC2, another terminal of VC1 is connected to a base of Q2 and another terminals of VR1 and R2, and another terminal of VC2 is connected to a base of Q1 and another terminals of VR2 and R1. A coil L3 of TR1 is connected to an electric-discharge LMP through the capacitor C1 to constitute an illumination device using a mobile inverter push-pull circuit. The repeat period and the duty ratio are fluctuated by the change in characteristics of VR1, VR2, VC1, VC2, and the illumination device can be manually or automatically dimmed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-propelled inverter / push-pull circuit and a lighting device for lighting a discharge tube using the circuit. Although the circuit of the present invention uses a cold cathode discharge tube as a load for explanation, it can be applied to a hot cathode discharge tube by adding a high-pressure mercury lamp or a filament circuit, and can be applied to other than a discharge tube such as a switching regulator power supply. It can also be applied to the load of.

[0002]

2. Description of the Related Art The illuminance required by a lighting device is not always constant, and varies depending on the surrounding illuminance, an object to be visually recognized, and the like. In addition, the brightness of the discharge tube during lighting varies depending on the ambient temperature. For example, if the ambient temperature becomes about -30 degrees Celsius, it becomes about 10% of that at room temperature. Therefore, in home lighting devices and backlight lighting devices for liquid crystal display devices using an inverter circuit, a circuit that manually adjusts light in accordance with the ambient temperature and illuminance is used. As an inverter circuit used for a lighting device, an inverter, a one-piece circuit, an inverter push-pull circuit, or an inverter series circuit is widely used. A self-excited inverter / push-pull circuit or a self-excited inverter / series circuit has a smaller number of components than a separately-excited inverter / push-pull circuit or a separately-excited inverter / series circuit, and can be designed to be smaller, but uses a transformer for feedback. Therefore, the frequency is determined by the magnetic circuit, so that it was not possible to change the frequency and change the impedance of the inductor or capacitor, which is a load current control element (ballast), to perform dimming. . Inverter / one-stone circuit and inverter /
In the operation of the push-pull circuit, a voltage twice as much as the power supply voltage is applied to the transistor in both the self-excited inverter circuit and the separately-excited inverter circuit, and therefore, the push-pull circuit is often used for a lighting device using a power supply voltage equal to or lower than the medium voltage. . However, inverters and series circuits, in principle, do not apply a voltage higher than the power supply voltage to the transistor in self-excited inverter circuits or separately-excited inverter circuits, so lighting devices using relatively high power supply voltages may be used. Many.

FIG. 3 shows a conventional self-excited inverter / push-pull circuit, and FIG. 4 is a block diagram showing a circuit in which the circuit has a dimming function. The time chart is shown in FIG. The self-excited inverter push-pull circuit shown in FIG. 3 will be described. In this circuit, two transistors Q3 and Q4 are NPN bipolar transistors, and the collector of Q3 is one of transformer TR2 using a saturable iron core.
Connect to the non-spot side terminal of the coil L4 which is the next winding,
4 is connected to another primary winding of TR2, the coil L5.
The other terminals of L4 and L5 are connected to the positive terminal of the DC power supply E. The emitters of the two transistors Q3 and Q4 are connected to the negative terminal of the DC power supply E. The terminal on the black point side of the coil L6 which is one feedback winding of the transformer TR2 is connected to the base of the transistor Q3 via the resistor R3, and the terminal on the non-black point side of the coil L7 which is another feedback winding is a resistor. Connected to the base of transistor Q4 via R4, the other terminals of L6 and L7 are connected to the cathode of diode D, and the anode of D is connected to the emitters of Q3 and Q4 and the negative terminal of DC source E. . A coil L8 as a secondary winding of the transformer TR2 is connected to a discharge tube LMP as a load via a capacitor C2 as a load current control element. Note that a startup resistor R5 is connected between the positive terminal of the DC power supply E and the base of the transistor Q3.

The operation of FIG. 3 will be described. Starting resistor R
5 causes a current to flow between the base and the emitter of one of the transistors Q3 and Q4, but if a current flows between the base and the emitter of the transistor Q3 due to a slight difference in characteristics, the current from the power source will be equal to the power source E -Resistor R5-base-emitter of transistor Q3-power supply E;
The transistor Q3 is turned on by this current, but Q4
Remains off because no base current flows. By turning on the transistor Q3, the current from the power supply becomes equal to the power supply E-
It flows with the coil L4-transistor Q3-power supply E. On the other hand, the voltage induced on the feedback winding of TR2 by the current of coil L4, which is the primary winding of transformer TR2, becomes positive on the black point side. The current flows through the resistor R3, the base-emitter of the transistor Q3, the diode D, and the coil L6, and acts to deeply turn on the transistor Q3 to further increase the collector current. The discharge tube LMP is driven by the coil L8, which is the secondary winding of the transformer TR2, and the capacitor C by the current of the coil L4, which is the collector current of the transistor Q3.
Lights via 2. Since the base current of the transistor Q4 does not flow with the voltage induced in the coil L7, which is another feedback winding of the transformer TR2, Q4 remains off. The current flowing through the coil L4, which is the primary winding of the transformer TR2, increases with time, and the magnetic flux of TR2 using a saturable iron core also increases with time. When the magnetic flux reaches the saturation magnetic flux, the magnetic flux does not increase, so that the voltage induced in the coil L6 becomes zero, and the base current and the collector current of the transistor Q3 become zero. Then the coils L4 to L
7, a reverse voltage is generated, and the transistor Q4 is turned on because the base current flows, but the transistor Q3 is turned off because the base current does not flow. At this time, the current from the power supply flows through the power supply E, the coil L5, the transistor Q4, and the power supply E.

On the other hand, the voltage induced on the feedback winding of TR2 by the current of coil L5, which is the primary winding of transformer TR2, becomes positive on the non-spot side, so that the current of coil L7, which is one of the feedback windings, , The coil L7, the resistor R4, the base-emitter of the transistor Q4, the diode D, and the coil L7, and the transistor Q4 is turned on deeply to increase the collector current. Transistor Q
The discharge tube LMP is driven by a coil L8, which is a secondary winding of the
Then, a current flows in the opposite direction via the capacitor C2 and the light is turned on. Since the base current of the transistor Q3 does not flow with the voltage induced in the coil L6, which is another feedback winding of the transformer TR2, Q3 remains off. Transformer T
The current flowing through the coil L5, which is the primary winding of R2, increases with time, and the magnetic flux of TR2 using a saturable iron core also increases with time. When the magnetic flux reaches the saturation magnetic flux, the magnetic flux does not increase, so that the voltage induced in the coil L7 becomes zero, and the base current and the collector current of the transistor Q4 become zero. Thereafter, the transistors Q3 and Q4 alternately turn on and off, self-oscillate, and the discharge tube LMP lights up. This circuit is called the Loyer circuit, but it becomes large because it uses a transformer with a saturable iron core.
Further, since the area surrounded by the BH curve representing the magnetic characteristics is large, the loss is large, and the higher the frequency is, the more the loss is. Further, since the oscillation frequency is determined by the magnetic circuit, the oscillation frequency is varied. This is a circuit that cannot perform dimming by changing the impedance of an inductor or a capacitor, which is a load current control element.

Therefore, when dimming is performed by a lighting device using a self-excited inverter / push-pull circuit, the duty ratio of the control frequency is changed without changing the operating frequency, and the dimming is performed by the pulse width control circuit. There were many things. FIG. 4 shows a block diagram of a circuit for dimming by the pulse width control circuit. This circuit includes a sawtooth pulse voltage oscillation circuit NOS
A sawtooth pulse voltage P1 oscillated at step S1 and a reference voltage VS obtained by dividing the voltage of the DC power supply E by a variable resistor VR3 are applied to both inputs of a comparator CMP, and a rectangular wave pulse voltage P2 output from the CMP is inverted. This is a circuit that is applied to the control unit of the circuit INV to control the pulse width of the oscillation of the inverter circuit INV. FIG. 5 is a time chart of the waveform of the main part shown in FIG.

The operation of FIG. 4 will be described. This circuit oscillates a sawtooth pulse voltage P1 in a sawtooth pulse voltage oscillating circuit NOS, but uses a variable resistor V
The reference voltage VS and P1 divided by R3 are compared with the comparator CM.
P is applied to both inputs of P, the sawtooth pulse voltage P1 is clipped by the reference voltage VS, and the output of the comparator CMP is switched from high to low at the boundary of the clip point, and the rectangular pulse voltage P2 is output. To the inverter circuit INV
And the inverter circuit INV oscillates with a pulse width of either high or low of P2. FIG. 5 shows the sawtooth pulse voltage P1 and the reference voltage VS.
Is the relationship of the square wave pulse voltage P2, and P3 is P2
6 is a time chart showing a current flowing through the discharge tube LMP when the inverter circuit INV oscillates when is high. FIG.
As can be seen from the above, if the repetition period of the rectangular wave pulse voltage P2 output from the comparator CMP is T1, and the inverter circuit INV oscillates with the high pulse width T4 of P2, the pulse width of light emission is T4 and T4 / T1 becomes the light emission duty ratio, and the light control of the discharge tube LMP can be performed by the fluctuation of the duty ratio. In general, the dimming operation is generally performed by manually operating the variable resistor VR3 to change the reference voltage VS to perform dimming. In addition to the inverter push-pull circuit, the inverter circuit INV shown in FIG. 4 can be an inverter / single-circuit circuit or an inverter / series circuit, and may be either a self-excited inverter circuit or a separately-excited inverter circuit. .

[0008]

As a self-excited inverter push-pull circuit conventionally used, a Loyer circuit using a saturable iron core shown in FIG. 3 and a Jensen circuit which is an improved circuit thereof are well known. However, each circuit uses a transformer with a saturable iron core, so that the circuit is large and expensive, and the oscillation circuit is formed using magnetic saturation, so that the area surrounded by the BH curve is large. Therefore, since the oscillation frequency is determined by the magnetic circuit, the oscillation frequency cannot be changed and the dimming cannot be performed. Therefore, a complicated circuit as shown in the block diagram of FIG. The dimming is performed by the width control circuit, and there is a problem that it is large, expensive, and heavy. If a separately-excited inverter / push-pull circuit is adopted, it is easy to change the oscillation frequency and use the fluctuation in the impedance of the load current control element to perform dimming.
Since the oscillating circuit is a separate circuit, it is larger than a self-excited inverter / push-pull circuit, and is also expensive and heavy. In addition, although the conventional dimming control methods are all manual, for example, in the case of an instrument panel in the interior of a car, the illuminance constantly fluctuates as the vehicle travels, and over time due to air conditioning, self-heating of the inverter circuit, and the like. Since the wall temperature of the discharge tube also changes, it is necessary to adjust the brightness, but in reality, it was not possible to sufficiently control the light due to the complexity. Therefore, the emergence of a self-excited inverter / push-pull circuit whose oscillation frequency fluctuates with a simple circuit with low loss, and the emergence of a lighting device that uses a self-excited inverter / push-pull circuit whose frequency fluctuates, and There has been a demand for a lighting device using a self-excited inverter / push-pull circuit capable of automatically adjusting the light in response to a change in temperature and / or a change in illuminance. The present invention solves such a problem, and operates in the same manner as a self-excited inverter push-pull circuit, and furthermore, two transistors connected substantially in parallel to a power supply are connected to a resistor and a capacitor. Self-propelled inverter push-pull circuit that is turned on and off by positive feedback, a lighting device based on the self-propelled inverter push-pull circuit, and at least one of the resistance of two resistors and the capacitance of two capacitors It is an object of the present invention to provide a small, light, and inexpensive lighting device that uses a self-propelled inverter / push-pull circuit that adjusts light by changing one of them. Note that elements that do not need to change their characteristics even if they are described as variable resistors or variable capacitors in the drawings may be ordinary resistors or capacitors.

[0009]

In order to achieve the above object, the first step of the present invention is to develop a self-running inverter / push-pull circuit, which comprises two transistors substantially connected in parallel to a DC power supply. Is turned on and off alternately by a positive feedback circuit combining two resistors and two capacitors, and two primary windings of a transformer are connected to loads of two transistors like a push-pull circuit, respectively. hand,
If a load is connected to the secondary winding of the transformer, it becomes a self-propelled inverter push-pull circuit. Next, as a second stage of the present invention, in order to achieve the above object, the development of a lighting device for lighting a discharge tube by a self-propelled inverter / push-pull circuit is described.・
If a discharge tube and a load current control element are connected in series to the secondary winding of the transformer of the push-pull circuit, a lighting device using a self-propelled inverter / push-pull circuit is obtained. further,
A third step of the present invention for achieving the above object is to dimming a discharge tube of a lighting device that is turned on by a self-propelled inverter / push-pull circuit, but is used as a positive feedback circuit described in the second step. If at least one of the resistance of the two resistors and the capacitance of the two capacitors is changed, the impedance of the load current control element fluctuates due to the fluctuation of the repetition period, or the square wave generated by the fluctuation of the pulse width Interaction of the duty ratio of the operating waveform of the pulse voltage with the capacitor that is the load current control element, or the operation of the square wave pulse voltage due to the change in the impedance of the load current control element and the pulse width due to the change in the repetition period. The self-propelled discharge tube can be dimmed by the interaction between the duty ratio of the waveform and the capacitor that is the load current control element. It will lighting apparatus using an inverter push pull circuit. There is a method of manually and automatically changing the resistance of the resistor and the capacitance of the capacitor. To manually change the resistance of the resistor and the capacitance of the capacitor, a variable resistor or a variable capacitor may be used. External conditions that need to automatically change the resistance of the resistor and the capacitance of the capacitor are temperature and illuminance. The temperature sensor as a specific element is a porcelain capacitor with temperature characteristics, a thermistor,
Positive characteristic thermistors, metal resistance temperature sensors, etc., and illuminance sensors are CdS, photodiodes, phototransistors, PbS, etc. For example, instead of a variable resistor, C
If dS is replaced by a porcelain capacitor having a temperature characteristic in place of the variable capacitor, a lighting device capable of dimming with temperature and illuminance can be obtained. The self-running inverter push-pull circuit is a positive feedback circuit using two resistors and two capacitors, and two transistors are turned on alternately.
This is a pulse generation circuit that uses a self-running multivibrator that is turned off, but is expressed as an oscillation circuit when expressed as a frequency. When converting the pulse width to frequency,
The reciprocal of the repetition period is the frequency. The semiconductor element to be used can be changed to an enhancement type MOSFET with a slight change in the circuit in addition to the bipolar transistor shown in the embodiment. Bipolar transistor and FET
Is represented as a transistor. FE
T absorbs a surge voltage at the time of switching because a parasitic diode exists between the drain and the source. However, a bipolar transistor does not have a parasitic diode, so that a diode may be connected as necessary. As the circuit, a circuit that speeds up or slows down the switching speed by using auxiliary driving transistors or capacitors, a circuit that prevents two transistors from turning on at the same time, or the like can be appropriately used.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. A lighting device using a self-propelled inverter push-pull circuit uses two NPN bipolar transistors, two variable resistors, and two variable capacitors. The positive terminal of the DC power supply connects to one terminal of the two primary windings of the transformer, and the other terminal of the two primary windings connects to the collectors of two NPN transistors each. The negative terminal of the DC power supply is 2
Connected to the emitters of two transistors. Two sets of a series circuit of a variable resistor and a resistor are configured, the two variable resistor side terminals are connected to the positive terminal of the power supply, the resistor side terminal is connected to the negative terminal of the power supply, and the variable resistor and the resistor are connected. The connection points of the devices are each connected to the base of the transistor. A variable capacitor is connected between the base of each transistor and the collector of another transistor. The secondary winding of the transformer is connected to a discharge tube as a load via a capacitor as a load current control element. This circuit is a circuit for lighting a discharge tube by a self-propelled inverter push-pull circuit. The circuit has a time constant of 2 by a combination of the resistance of two variable resistors and a variable capacitor connected to one end of the variable resistor. Since the on / off pulse width of the two transistors is determined, at least one of the resistances of the two variable resistors and the capacitance of the two variable capacitors changes, so that the impedance of the load current control element fluctuates due to the fluctuation of the repetition period. To do,
Or, the fluctuation of the duty ratio of the operating waveform of the rectangular wave pulse voltage due to the fluctuation of the pulse width and the interaction with the capacitor as the load current control element, or the fluctuation of the impedance of the load current control element and the pulse width due to the fluctuation of the repetition period. Lighting device using a self-running inverter / push-pull circuit capable of dimming the discharge tube due to the interaction between the duty ratio of the operating waveform of the square-wave pulse voltage due to the fluctuation of the pulse voltage and the capacitor that is the load current control element become. When the lighting device is capable of automatically adjusting light due to a change in temperature and / or a change in illuminance, at least one of two variable resistors and two variable capacitors is used.
If one is replaced with an element whose resistance or capacitance changes depending on temperature or illuminance, a self-running inverter push-pull circuit that can automatically adjust dimming due to temperature change and / or illuminance change It is also the lighting device used. Since this circuit does not use magnetic saturation, it is a circuit with little loss.

[0011]

Embodiment 1 FIG. 1 shows an embodiment according to claims 1 to 3 of the present invention, in which the invention is applied to a self-running inverter push-pull circuit using bipolar transistors.
In this circuit, the positive terminal of the DC power supply E is connected to the black point side terminal of the coil L1, which is the primary winding of the transformer TR1, the non-black point side terminal of the coil L2, and one terminal of the variable resistors VR1 and VR2. The negative terminal of the power supply E is an NPN transistor Q
1 and Q2 and to one terminal of resistors R1 and R2. The non-black point side terminal of the coil L1 is connected to the collector of the transistor Q1 and one terminal of the variable capacitor VC1, and the black point side terminal of the coil L2 is connected to the collector of the transistor Q2 and one terminal of the variable capacitor VC2. Another terminal of the variable capacitor VC1 is connected to the base of the transistor Q2 and another terminal of the variable resistor VR1 and the resistor R2, and another terminal of the variable capacitor VC2 is connected to the base of the transistor Q1 and the variable resistor VR.
2 and another terminal of the resistor R1. Transformer T
A coil L3, which is a secondary winding of R1, is connected to a discharge tube LMP via a capacitor C1, which is a load current control element, to provide a lighting device using a self-propelled inverter push-pull circuit.

The operation of FIG. 1 will be described. When the DC power supply E is connected, a current flows between the base and the emitter of one of the transistors Q1 and Q2, but if a current flows between the base and the emitter of the transistor Q1 due to a slight difference in characteristics, the power supply is Is supplied to the power supply E-variable resistor VR2
The current flows between the base and the emitter of the transistor Q1 and the power supply E to turn on Q1, but keep Q2 off. When the transistor Q1 is turned on, the collector voltage of the transistor Q1 drops to a voltage close to the negative terminal voltage of the power source E. Therefore, the base voltage of the transistor Q2 becomes a voltage close to the negative terminal voltage of the power source E via the variable capacitor VC1, Remains off. When the transistor Q1 is turned on, a current flowing through the coil L1, which is one of the primary windings, flows through the power supply E, the coil L1, the transistor Q1, and the power supply E. Coil L
With the current of 1, the discharge tube LMP is turned on via the coil L3 and the capacitor C1. At this time, the coil L1
Is the voltage of the positive terminal of the DC power source E,
Since the non-spot side terminal 1 has a voltage close to the negative terminal of the DC power supply E, the black point side terminal of the coil L2, which is another primary winding, has a voltage close to twice the power supply voltage. . The base terminal of the transistor Q1 of the variable capacitor VC2 is about 0.7 V, and the collector terminal of the transistor Q2 has a voltage almost twice the power supply voltage. Capacitor VC2-
The current flows between the base and emitter of the transistor Q1, the power supply E, and the coil L2, and positively charges the coil L2 side of VC2. On the other hand, when the transistor Q1 is turned on, the variable resistor V
Since the current flowing through R1 flows through the power supply E, the variable resistor VR1, the variable capacitor VC1, the transistor Q1, and the power supply E, the VR1 side of VC1 is positively charged. The base voltage of the transistor Q2 gradually increases with the charging of the variable capacitor VC1, but if the voltage becomes a voltage at which the base current of the transistor Q2 flows, the variable resistor VR1
Flows through the power supply E, the variable resistor VR1, the base-emitter of the transistor Q2, and the power supply E to turn on the transistor Q2. When the transistor Q2 is turned on, the collector voltage of the transistor Q2 decreases to a voltage close to the negative terminal voltage of the DC power supply E. Therefore, the voltage charged in the variable capacitor VC2 makes the base voltage of the transistor Q1 negative, and the transistor Q1 is turned off. Become. At this time, the current passing through the coil L2 flows through the power supply E-coil L2-transistor Q2-power supply E. By the current of the coil L2,
The discharge tube LMP is lit by a current flowing in the opposite direction via the coil L3 and the capacitor C1. At this time, the non-black point side terminal of the coil L2 is the voltage of the positive terminal of the DC power supply E, but the black point side terminal of the coil L2 has a voltage close to the negative terminal of the DC power supply E. The terminal on the non-black point side has a voltage close to twice the power supply voltage. The terminal on the base side of the transistor Q2 of the variable capacitor VC1 is about 0.7
V, and the collector terminal of the transistor Q1 is at a voltage close to twice the power supply voltage. Therefore, the current of the coil L1 is: coil L1-variable capacitor VC1-base-emitter of transistor Q2-power supply E-coil L1 flows, and the coil L1 side of VC1 is positively charged. On the other hand, the current flowing through the variable resistor VR2 when the transistor Q2 is turned on is expressed by a power source E-variable resistor VR2-variable capacitor V2.
C2-transistor Q2-power supply E flows, so VC2
VR2 side is charged positively. With the charging of the variable capacitor VC2, the base voltage of the transistor Q1 gradually increases. If the voltage becomes a voltage at which the base current of the transistor Q1 starts flowing, the current passing through the variable resistor VR2 is changed to the power supply E-variable resistor. VR2 flows between the base and the emitter of the transistor Q1 and the power supply E to turn on the transistor Q1. Thereafter, the transistors Q1 and Q2 are alternately turned on and off, and the discharge tube LMP is turned on.

The operation at the time of dimming will be described with reference to FIG.
FIG. 2 shows the case where the on / off pulse widths T2 and T3 of the transistors Q1 and Q2 are the same, and the duty ratio with the repetition period T1 is 50 (1/2). 2, the transistors Q1 and Q2 when the duty ratio with the repetition period T1 is 33 (1/3)
2 is a time chart in which the relationship between the voltage (collector-emitter voltage) and the current (collector current) is idealized. In the circuit of FIG. 1, since the transformer TR1 and the capacitor C1 are connected, an actual waveform does not form such a clean rectangular wave pulse, but the concept is shown. Figure 2
A is the resistance of the variable resistor VR1 and the variable capacitor VC1
The pulse width T2 based on the time constant based on the capacity of the variable resistor VR2 and the pulse width T3 based on the time constant based on the capacity of the variable capacitor VC2 are the same.
The on-off duty ratio of Q1 and Q2 is 50, and the on-off of Q1 and Q2 is 1/2. The sum of the currents of the transistors Q1 and Q2 at this time is 1.
FIG. 2B shows the resistance of the variable resistor VR2 and the variable capacitor VC2 without changing the pulse width T2 based on the time constant of the resistance of the variable resistor VR1 and the capacitance of the variable capacitor VC1.
FIG. 2 shows only the pulse width T3 based on the time constant due to the capacitance of FIG.
The duty ratio becomes 33 when it is set to の of −A. At this time, the ON time of the transistor Q2 is as shown in FIG.
The current due to Q2 is halved since it is の of A, but since the charging current and discharging current of the capacitor C1 are the same, the current of the transistor Q1 is also halved as a result.
At this time, the sum of the currents of the transistors Q1 and Q2 is 0.6.
7 (2/3). That is, if the current when the pulse widths T2 and T3 are the same is 1, and the shorter pulse width of T2 and T3 when one of the pulse widths is varied is T3, the repetition period T1 = T2 + T3. The current at that time is
2 (T3 / T1). The above is the dimming due to the interaction between the variation of the duty ratio due to the variation of the one pulse width and the interaction of the capacitor which is the load current control element due to the variation of the one time constant. Next, the influence of the operating frequency which is the reciprocal of the repetition period T1 = T2 + T3 is obtained. If an inductor or a capacitor is used as the load current control element, the impedance of the load current control element varies depending on the operation frequency. Changing at least one of the resistors VR1 and VR2 and the capacitance of the variable capacitors VC1 and VC2 changes the repetition period T1, so that dimming is possible. The above two dimming methods are based on the case where only the time constant related to T3 is changed, but the time constant of T2 may be changed simultaneously. If a time constant is selected, it is possible to perform dimming by one of the above two dimming methods, or to perform dimming by both. As described above, in this circuit, a rectangular wave pulse voltage is generated by positive feedback, so that the pulse width T2 based on the time constant of the resistance of the variable resistor VR1 and the capacitance of the variable capacitor VC1 shown in FIG. The pulse width T3 based on the time constant based on the resistance of the resistor VR2 and the capacitance of the variable capacitor VC2 determines the on-off pulse width of the transistors Q1 and Q2, so that the resistance of the variable resistors VR1 and VR2 and the capacitance of the variable capacitors VC1 and VC2. At least one of
By changing one of them, a self-propelled inverter / push-pull circuit capable of dimming the discharge tube is obtained. When the lighting device is capable of automatically adjusting the light by a change in temperature and / or a change in illuminance, at least one of the two variable resistors VR1 and VR2 and the two variable capacitors VC1 and VC2 is A self-propelled inverter / push-pull circuit that can automatically adjust the discharge tube according to changes in temperature and / or illuminance, if the resistance or capacitance changes with temperature or illuminance. . Since this circuit does not use magnetic saturation, it is a circuit with little loss. The pulse waveform in this circuit is basically a rectangular pulse, and is a highly efficient waveform for lighting the discharge tube. This circuit is a self-running inverter / constant voltage push-pull circuit, but can also be applied to a self-running inverter / constant current push-pull circuit in which an inductor is connected in series with the DC power supply E. In this circuit, when the transistor is switched from on to off, a reverse voltage is applied between the base and the emitter of the transistor. When the voltage is high and adversely affects the transistor, it may be blocked with a diode.

The relationship between the circuit and the claims is as follows. This circuit is substantially a DC power supply according to claim 1,
2 connected in parallel via the two primary windings of the transformer
In a push-pull inverter circuit in which two transistors are alternately turned on and off, two transistors are alternately turned on and off by a positive feedback circuit combining a resistor and a capacitor.
It is a self-running inverter push-pull circuit that is turned off. In this circuit, two transistors connected in parallel to the DC power supply through two primary windings of a transformer are alternately turned on by a positive feedback circuit combining a resistor and a capacitor. A lighting device using a self-propelled inverter push-pull circuit in which a discharge tube is connected to the secondary side of a transformer in a push-pull inverter circuit that is turned off. This circuit comprises two transistors connected in parallel to a substantially direct-current power supply via two primary windings of a transformer alternately by a positive feedback circuit combining a resistor and a capacitor. In a lighting device for lighting a discharge tube by a push-pull inverter circuit that turns on and off, by changing at least one of the resistance of the resistor and the capacitance of a capacitor,
This is a lighting device using a self-propelled inverter / push-pull circuit for dimming by one of the following groups. a. Utilization of fluctuation of load current control element impedance due to fluctuating oscillation frequency b. Use of the interaction between the duty ratio of the fluctuating operating waveform and the capacitor connected in series with the discharge tube c. Use of the fluctuation of the impedance of the load current control element due to the changing oscillation frequency, and use of the interaction between the duty ratio of the changing operation waveform and the capacitor connected in series with the discharge tube

[0015]

As described above, according to the present invention, two transistors connected in parallel via two primary windings of a transformer are alternately turned on and off to a DC power supply. In the pull inverter circuit, a self-running inverter push-pull circuit in which two transistors are alternately turned on and off by a positive feedback circuit combining a resistor and a capacitor can be provided. Further, a push-pull inverter circuit in which two transistors connected in parallel to the DC power supply via two primary windings of a transformer are alternately turned on and off by a positive feedback circuit combining a resistor and a capacitor. In this case, a lighting device using a self-propelled inverter / push-pull circuit in which a discharge tube is connected to the secondary side of a transformer can be provided. further,
A push-pull inverter circuit in which two transistors connected in parallel to the DC power supply through two primary windings of a transformer are alternately turned on and off by a positive feedback circuit combining a resistor and a capacitor. In a lighting device for lighting a discharge tube, by changing at least one of a resistance of a resistor and a capacitance of a capacitor,
A lighting device using a self-propelled inverter / push-pull circuit that can be manually or automatically dimmed can be provided.
The self-running inverter / push-pull circuit does not require a separate oscillation circuit like a separately-excited inverter circuit, and does not require a feedback transformer like a self-excited inverter circuit. A lighting device using a self-propelled inverter / push-pull circuit which is an inexpensive inverter circuit has the effect of providing a circuit which can manually or automatically adjust light by a simple method.

[Brief description of the drawings]

FIG. 1 is a circuit diagram to which an embodiment 1 of the present invention is applied;
This is an illumination device that uses a self-propelled inverter / push-pull circuit that uses a bipolar transistor and has a variable pulse width and dimming.

FIG. 2 is a time chart of a voltage waveform and a current waveform of two transistors when dimming is performed by changing a duty ratio due to a change in one pulse width in the circuit of FIG. 1;

FIG. 3 is a circuit diagram according to the related art, and is a lighting device using a self-excited inverter / push-pull circuit of a fixed oscillation frequency using an NPN bipolar transistor.

FIG. 4 is a circuit diagram according to the related art, and is a block diagram of an illumination device that uses a sawtooth pulse voltage oscillation circuit and a comparator to control light using a pulse width control circuit.

FIG. 5 is a time chart of voltage and current of a main part of the circuit shown in the block diagram of FIG. 4;

[Explanation of symbols]

E DC power supply R1 to R5 Resistor C1 to C2 Capacitor VR1 to VR3 Variable resistor VC1 to VC2 Variable capacitor Q1 to Q4 NPN bipolar transistor D Diode TR1 to TR2 Transformer L1 to L8 Transformer coil INV Inverter circuit NOS sawtooth pulse voltage oscillation Circuit CMP Comparator P1 to P3 Voltage waveform and current waveform of main part T1 Pulse repetition period T2 Pulse width T3 Shorter pulse width T4 Width of inverter circuit operating in pulse width control circuit LMP Discharge tube

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Harumi Suzuki 7-29-3 Kita-Terao, Tsurumi-ku, Yokohama, Kanagawa

Claims (3)

[Claims] 1. A push-pull inverter circuit in which two transistors connected in parallel via two primary windings of a transformer to a DC power supply are alternately turned on and off. Self-propelled inverter push-pull circuit that is turned on and off alternately by a positive feedback circuit combining a capacitor and a capacitor. 2. A push switch in which two transistors connected in parallel through two primary windings of a transformer are alternately turned on and off by a positive feedback circuit combining a resistor and a capacitor. A lighting device using a self-propelled inverter push-pull circuit in which a discharge tube is connected to a secondary side of a transformer in a pull inverter circuit. 3. Two transistors connected in parallel to a substantially DC power supply via two primary windings of a transformer are alternately turned on and off by a positive feedback circuit combining a resistor and a capacitor. In a lighting device for lighting a discharge tube by a push-pull inverter circuit, a self-propelled inverter that dims light by one of the following groups by changing at least one of the resistance of the resistor and the capacitance of a capacitor. -An illumination device using a push-pull circuit. a. Utilization of fluctuation of load current control element impedance due to fluctuating oscillation frequency b. Use of the interaction between the duty ratio of the fluctuating operating waveform and the capacitor connected in series with the discharge tube c. Use of the fluctuation of the impedance of the load current control element due to the changing oscillation frequency, and use of the interaction between the duty ratio of the changing operation waveform and the capacitor connected in series with the discharge tube