JPH1070888A - Inverter device, discharge lamp lighting device and illumination device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stop inverter operation when a load is removed even if there is any parasitic capacitance that cannot be disregarded in the wiring path to the load, in an inverter device provided with a current feedback circuit, wherein its feedback loop is virtually interrupted when a load is removed. SOLUTION: A switching means 3 is connected so that switched voltage will be applied to the primary winding of an output transformer 4. The primary winding of a current transformer is inserted in series with a load connected to the secondary winding of the output transformer 4, and its secondary winding is connected to the control terminal on the switching beans 3 to from a reversed- polarity feedback means 7 that makes the switching means 3 self-oscillate by current feedback and is capable of offsetting the amount of feedback produced by a parasitic capacitance Cs in the wiring path when the load is removed. When the load is removed, the current feedback circuit 6 is virtually interrupted. If current feedback is performed by the parasitic capacitance Cs, however, it is offset by the reversed-polarity feedback means 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an inverter device, a discharge lamp lighting device, and a lighting device.

[0002]

2. Description of the Related Art FIG. 7 is a circuit diagram showing a conventional current feedback type self-excited oscillation type inverter device.

In the figure, 71 is an AC power supply, 72 is a DC power supply, 73 is a switching means, 74 is an insulated output transformer, 75 is a load, for example, a discharge lamp, and 76 is a current feedback circuit.

[0004] The DC power supply 72 includes a rectifier circuit, and outputs rectified DC from the AC power supply 71.

The switching means 73 includes an output transformer 7
4 are connected so as to apply the switched voltage to the primary winding.

In the current feedback circuit 76, a primary winding is inserted in series with a circuit of a load 75 connected between secondary windings of an output transformer 74, and a secondary winding is connected to a control terminal of a switching means. And a positive feedback to the switching means 73.

[0007]

In the prior art shown in FIG. 7, when there is a non-negligible stray capacitance between the wiring paths leading to the load 75, the weak feedback is performed in a state where the load is removed. A current is generated, which can cause oscillation to continue. The oscillation at this time is an abnormal oscillation because the feedback current is small and the driving of the switching means 73 of the inverter device is insufficient. That is, since the drive is small during abnormal oscillation, the voltage drop of the switching means is large, so that the switching loss increases, the temperature rise of the switching means becomes excessive, and sometimes the switching means is destroyed.

Also, depending on the value of the floating capacitance, the inverter device operates near the resonance point between the floating capacitance and the secondary inductance of the output transformer, and the secondary open-circuit voltage becomes extremely high. There is a problem that electric shock is given to the human body when the lamp is replaced, or the life of the output transformer is shortened.

Further, there is a problem that the switching characteristics from startup to stable operation when the lamp is removed are not good.

The present invention relates to an inverter device having a current feedback circuit in which a feedback loop is substantially disconnected when a load is removed. Another object of the present invention is to provide an inverter device, a discharge lamp lighting device, and a lighting device that reliably stop the inverter operation when the load is removed.

[0011]

According to the first aspect of the present invention, there is provided an inverter device which is arranged to switch a direct current and to supply an alternating current to a load; A current feedback circuit that oscillates but substantially breaks a feedback loop when a load connected via a wiring path is removed; and a feedback amount that can be caused by stray capacitance between the wiring paths when the load is removed. And reverse polarity feedback means capable of canceling each other.

In the present invention and each of the following inventions, definitions and technical meanings of terms are as follows unless otherwise specified.

The load may be any load, but a discharge lamp, particularly a fluorescent lamp, is suitable as the load.

The switching means permits all kinds of switching means used in the inverter device, such as a field effect transistor which can use a built-in parasitic diode for reverse current flow. When the safety means is made to respond to a change in the next open circuit voltage, a bipolar transistor is particularly suitable as the switching means. When a bipolar transistor is used, a diode can be reversely connected between the collector and the emitter of the transistor in order to allow a reverse current to flow.

In configuring the inverter main circuit using the switching means, all commonly used inverter circuits are allowed. That is, a half-bridge circuit, a single-circuit circuit, a parallel circuit, or the like can be used. As a modification of the half-bridge type circuit, a circuit described in Japanese Patent Application Laid-Open No. 8-98555, which is filed by the same applicant, can also be used. According to this circuit configuration, the input voltage is smoothed to reduce the pulsation of the output voltage,
By increasing the input power factor, harmonics of the input current can be reduced.

The control circuit may have any circuit configuration as long as it turns on and off the switching means. The ON and OFF frequencies are higher than the frequency of the AC power supply, and are several KHz or more, preferably 20 KHz or more.

The reverse polarity feedback means may supply a current of a reverse polarity to the current feedback circuit, which cancels a current that can flow through the current feedback circuit due to a floating capacitance between the wiring paths when the load is removed. The circuit configuration may be any. It should be noted that canceling does not mean only complete canceling, but it is permissible that some feedback due to stray capacitance remains as long as the switching means does not perform undesired switching. Further, even if the amount of reverse polarity feedback by the reverse polarity feedback means is larger than the amount of feedback by the stray capacitance, the switching means does not perform undesired switching, so that it can be accepted.

If the wiring path is allowed to be up to 10 m in design, in the case of a vinyl electric wire, the floating capacitance between the wiring paths is about 300 pF. When the load is a fluorescent lamp for illumination purposes, the floating capacitance between the wiring paths is usually about several pF to several hundred pF. However, the present invention is not subject to any restrictions on the length of the wiring path and the type of electric wire, and it is possible to arbitrarily set a desired wiring length and use a desired electric wire. Therefore, the stray capacitance between the wiring paths also changes depending on the wiring path length and the type of electric wire.

Thus, according to the present invention, when the load is removed, even if there is a non-negligible floating capacitance between the wiring paths, the floating capacitance is generated by the reverse polarity feedback by the reverse polarity feedback means. , The unwanted feedback current does not flow through the current transformer. That is, since no current feedback is performed, the inverter device surely stops its inverter operation.

According to a second aspect of the present invention, there is provided an inverter device having an insulation type output transformer capable of connecting a load to a secondary side via a wiring path; and applying a switched voltage to a primary winding of the output transformer. Switching means arranged so that the primary winding is inserted into the secondary circuit of the output transformer, and the secondary winding controls the switching means so that the switching means performs a current feedback type self-excited oscillation operation. A current feedback circuit including a current transformer connected to a terminal; and a reverse polarity feedback means capable of canceling a feedback amount that can be caused by a stray capacitance between wiring lines when a load is removed. It is characterized by having.

The output transformer may be provided with a leakage inductance to perform a current limiting function when the load is a discharge lamp, or may be provided with a current limiting impedance before or in the output transformer without actively providing a leakage impedance. An external device may be provided at a later stage.

According to a third aspect of the present invention, in the inverter device according to the second aspect, the reverse polarity feedback means includes a series circuit of a tertiary winding and a capacitor having opposite polarities to the secondary winding of the output transformer. And connected in parallel to the primary winding of the current transformer.

According to the present invention, as described above, the reverse polarity feedback current supplied from the low voltage generated by the tertiary winding of the output transformer is supplied to the primary winding of the current transformer. . Therefore, the feedback current is canceled on the primary side of the current transformer.

The tertiary winding may be further used for filament heating. In this case, both ends of the capacitor may be connected to both ends of the filament to be heated. The filament heating may be performed by providing a quaternary winding separately if necessary.

According to a fourth aspect of the present invention, in the inverter device of the first or second aspect, the reverse polarity feedback means is constituted by an inductor connected between output terminals.

A lag-phase current flows through the inductor.
On the other hand, the current flowing due to the floating capacitance is in the leading phase, so that both currents are canceled. Therefore, if the value of the inductor is appropriately selected, positive feedback to the switching means can be substantially eliminated.

According to a fifth aspect of the present invention, there is provided an inverter apparatus comprising: a switching means arranged to switch a direct current and supply an alternating current to a load; and perform a positive feedback to cause the switching means to self-oscillate. A current feedback circuit in which a feedback loop is substantially disconnected when a load connected via the load is removed; and acts to provide current feedback at a frequency when the load is mounted in relation to a frequency change when the load is removed. Frequency response means.

In the self-excited oscillation type inverter device, when the load is removed, the response frequency of the circuit changes, so that the oscillation frequency is affected and changes. In particular, if the load is a fluorescent lamp and the circuit type has a preheating capacitor connected between the non-power supply terminals of each filament electrode,
Since the preheating capacitor is opened when the fluorescent lamp is removed, a remarkable frequency change occurs.

The frequency response means operates in response to the frequency change so that current feedback is performed only when a load is mounted. For example, when the frequency at the time when the load is removed is reached, if a circuit is configured to short-circuit or open the current feedback open circuit, no current feedback is performed.
Further, the circuit may be configured to pass the current feedback only for the frequency when the load is mounted. In this way, current feedback is blocked at the frequency at which the load was removed.

Thus, the present invention allows current feedback only when the load is mounted in response to the frequency change accompanying the attachment and detachment of the load, so that the inverter device does not oscillate when the load is removed.

According to a sixth aspect of the present invention, there is provided an inverter device having an insulation type output transformer capable of connecting a load to a secondary side via a wiring path; and applying a switched voltage to a primary winding of the output transformer. Switching means arranged so that the primary winding is inserted into the secondary circuit of the output transformer, and the secondary winding controls the switching means so that the switching means performs a current feedback type self-excited oscillation operation. A current feedback circuit including a current transformer connected to the terminal; and a frequency response means operable to perform current feedback at a frequency when the load is mounted in relation to a frequency change when the load is removed. It is characterized by having.

The output transformer is as described in claim 2, and the frequency response means is as described in claim 5.

According to a seventh aspect of the present invention, in the inverter device according to the fifth or sixth aspect, the frequency response means has a trap frequency corresponding to a frequency when the load is removed, and the trap inserted in the current feedback circuit. It is characterized by being constituted by means.

In the present invention, the frequency response means is constituted by using the trap means. However, when a series resonance type is used, the impedance becomes zero at the trap frequency, so that the current feedback circuit is short-circuited. What is necessary is just to connect. When using a parallel resonance type,
Since the impedance becomes infinite at the trap frequency, the current feedback circuit may be connected so as to be opened.

In this way, the current feedback circuit is substantially eliminated by performing a trapping operation in response to the oscillation frequency when the load is removed and disabling the current feedback circuit.

According to an eighth aspect of the present invention, in the inverter device according to the fifth or sixth aspect, the frequency response means has a characteristic of selectively passing a frequency when a load is mounted, and is inserted into the current feedback circuit. Characterized by a filter means.

In the present invention, the frequency response means is constituted by using the filter means. Since only the oscillating frequency when the load is mounted is passed, even if the current feedback is performed when the load is removed, the filter means is not blocked. Therefore, current feedback is not substantially performed.

According to a ninth aspect of the present invention, there is provided a discharge lamp lighting device,
An inverter device according to any one of claims 1 to 8, and a discharge lamp energized by an output of the inverter device.

The present invention is a discharge lamp lighting device having the functions and features of claims 1 to 8.

According to a tenth aspect of the present invention, there is provided a lighting device, comprising: a lighting device main body; and a discharge lamp lighting device according to the ninth aspect, which is disposed in the lighting device main body.

According to the present invention, there is provided a lighting apparatus such as a lighting apparatus having the functions and features of the first to eighth aspects.

[0042]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing a first embodiment of the inverter device and the discharge lamp lighting device of the present invention.

In the drawing, 1 is an AC power supply, 2 is a DC power supply, 3 is a switching means, 4 is an output transformer, 5 is a load, for example, a discharge lamp, 6 is a current feedback circuit, and 7 is a reverse polarity feedback means.

The DC power supply 2 is of a type obtained by rectifying AC.

The switching means 3 is composed of, for example, a single bipolar transistor. The switching means 3 is connected in series with the primary winding 4a of the output transformer between DC power supplies, and outputs a voltage switched with respect to the primary winding 4a. Apply.

The output transformer 4 includes a secondary winding 4b and a secondary winding 4b.
A tertiary winding 4c whose polarity is opposite to that of the secondary winding 4b is provided. The secondary winding 4b is provided with a leakage impedance, and is configured to perform a current limiting action when a discharge lamp such as a fluorescent lamp is connected as the load 5 between the secondary windings 4b. Capacitor C ₁ for resonance is connected in parallel with the primary winding 4a.

The load 5 of the fluorescent lamp is connected a capacitor C ₂ of the filament preheating between non-power terminal.

The current feedback circuit 6 includes a current transformer 6a having a primary winding 6a1 connected in series with the load 5. The base of the switching means 3 to the secondary winding 6a2 of the current transformer 6a via a capacitor C _3, constitute a current feedback circuit 6 connected between the emitter.

The reverse polarity feedback means 7 is connected to the output transformer 4.
3 windings 4c and made a series circuit of a capacitor C ₄ of, and connected in parallel with the primary winding 6a1 of the current transformer 6a. The tertiary winding 4c is given an opposite polarity to the secondary winding 4b.

[0051] 8 a so-called reset circuit consists of a series circuit of a diode 8a and resistor 8b, discharge-based switching means 3, and are connected between the emitter, the electric charge of the capacitor C ₃ to the OFF state of the switching means 3 It has a function to make it work.

C _S is the stray capacitance between the wiring paths.

If the load 5 is removed while the inverter device is oscillating, a weaker feedback current flows through the secondary winding 6a2 of the current transformer 6a due to the stray capacitance as compared to when the load is mounted. At the same time, since the reverse polarity feedback means 7 supplies a current in a direction to cancel the feedback current, the feedback current is canceled out, and the feedback current to the switching means 3 does not substantially flow. As described above, since the current feedback is substantially eliminated, the inverter operation of the inverter main circuit 3 stops. Therefore, no abnormal oscillation occurs. Incidentally, when the time of the load attached to the capacitor C ₂ for preheating is 0.01μF example, a voltage of several V is induced in the secondary winding 6a2 of the current transformer 6a, a reverse polarity feedback means according to the invention In the case where there is no current and the current due to the stray capacitance C _S is fed back, a smaller voltage than the above is induced, which causes abnormal switching.

Next, specific numerical examples will be described.

The voltage V _{L of the} secondary winding 4b of the output transformer 4
Is 100 V, the voltage V _{4 of the} tertiary winding 4 c is 3 V, and the stray capacitance C _S is 300 pF, the capacitor C ₄ can be obtained by the following equation.

C ₄ = V _L · C _S / V ₄ = 10 × 10 ⁻⁹ = 10 nF FIG. 2 is a circuit diagram showing a second embodiment of the inverter device and the discharge lamp lighting device of the present invention.

The same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

This embodiment differs from the first embodiment in the reverse polarity feedback means. That is, an inductor L ₁ connected between the output terminal of the inverter device.

Thus, the current fed back by the floating capacitance C _S is a leading current, whereas the inductor L
_Since the current flowing by ₁ is a lagging current, the two are canceled out and substantially no current feedback is performed in the current feedback circuit.

Next, specific numerical examples will be described.

Since the impedance of the stray capacitance and the impedance of the inductor need only be made equal, the value of the inductor L ₁ is obtained by the following equation. Note that the floating capacitance C _S is 300 pF.

1 / 2πfC _S = 2πfL ₁ L ₁ = 4π ² f ² C _S = 33.8 mH FIG. 3 is a circuit diagram showing a third embodiment of the inverter device and the discharge lamp lighting device of the present invention.

The same parts as those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted.

This embodiment is characterized in that a frequency response means 9 is provided. The frequency responsive means 9 includes a load 5
It works so that current feedback can be performed at the frequency when the load is attached in relation to the frequency change when the load is removed. There are several possible configurations. In FIG. 3, the trap frequency is set to the frequency when the load is removed. The trap means is used. That is, the trap means therefore frequency responsive means comprises a series circuit of the inductor L ₂ and capacitor C _5, are connected in parallel with the primary winding 6a1 of the current transformer 6a.

Then, when the load 5 is removed, the frequency changes to the trap frequency, and the impedance of the trap means becomes substantially zero. Therefore, the trap means traps the feedback current and sends it to the current transformer 6a. Do not let it flow. Therefore, since no current feedback is performed, the inverter device stops the inverter operation.

A specific numerical example will be described.

The frequency when the load 5 is mounted is 50 KHz,
When the frequency of detaching the load 5 and 200 KHz, the inductor L ₂ 2.9μH, a capacitor C ₅ 0.
What is necessary is just 22 μF.

FIG. 4 is a circuit diagram showing a fourth embodiment of the inverter device and the discharge lamp lighting device of the present invention.

The same parts as those in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted.

This embodiment differs from the embodiment of FIG. 3 in the configuration of the frequency response means 9 '. That is, the trap means including a parallel circuit of an inductor L ₃ and capacitor C ₆ of the current feedback circuit is inserted in series.

When the load 5 is removed in this manner, a frequency change occurs to reach the trap frequency. Since the trap means has a very large impedance due to parallel resonance,
It acts as a trap to prevent current feedback. Therefore, the inverter device stops.

A specific numerical example will be described.

If the frequency at the time of load attachment and the frequency at the time of load removal are the same as in FIG. 3, the trap frequency is the same as that of FIG. 3, and therefore, the circuit constant can be the same.

FIG. 5 is a circuit diagram showing a fifth embodiment of the inverter device and the discharge lamp lighting device of the present invention.

The same parts as those in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted.

This embodiment differs from the embodiment of FIG. 4 in that the frequency responsive means 9 "uses a filter means.
₄ and a filter means comprising a series circuit of a capacitor C _7, are inserted in series into the current feedback circuit 6.
The filter means uses the frequency when the load is mounted as the pass frequency.

When the load 5 is mounted, the frequency response means 9 "passes the current feedback.
The inverter device performs current feedback type self-sustained pulsation at the desired frequency. However, when the load 5 is removed, the frequency changes. Therefore, the frequency response means 9 "performs a blocking operation, so that the current feedback circuit is opened. Therefore, the current feedback operation cannot be performed, and the inverter device stops.

A specific numerical example will be described.

[0079] When the frequency at the frequency and load removal at the load attachment the same as those of FIG. 3, for example, may be the L ₄ 10.1μH, a C ₇ to 1 .mu.F.

FIG. 6 is a perspective view of a lighting fixture showing one embodiment of the lighting device of the present invention.

In the figure, reference numeral 10 denotes a lighting fixture main body;
Is a fluorescent lamp.

The lighting fixture body 10 supports the fluorescent lamp 11 and has a built-in inverter device (not shown) of the present invention.

[0083]

According to the first to eighth aspects of the present invention, in an inverter device having a current feedback open circuit in which a feedback loop is substantially cut off when a load is removed, it can be ignored between wiring lines leading to the load. It is possible to provide an inverter device that reliably stops the inverter operation when the load is removed even if there is no floating capacitance. Therefore, it is possible to prevent problems such as abnormal heat generation and destruction of the switching means due to undesired abnormal switching.

According to the first to fourth aspects of the present invention, in addition to the above, the current feedback due to the stray capacitance is canceled by the feedback of the opposite polarity by the reverse polarity feedback means, so that the feedback is substantially reduced when the load is removed. Therefore, the inverter operation can be reliably stopped.

According to each of the fifth to eighth aspects of the present invention, in addition to the fact that the frequency response device maintains the current feedback at the frequency when the load is mounted and prevents the current feedback at the frequency when the load is removed, the inverter responds. An inverter device that reliably stops operation can be provided.

According to the ninth aspect of the present invention, a discharge lamp lighting device having the effects of the first to eighth aspects can be provided.

According to the tenth aspect, it is possible to provide a lighting device having the effects of the first to eighth aspects.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of an inverter device and a discharge lamp lighting device of the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of the inverter device and the discharge lamp lighting device of the present invention.

FIG. 3 is a circuit diagram showing a third embodiment of the inverter device and the discharge lamp lighting device of the present invention.

FIG. 4 is a circuit diagram showing a fourth embodiment of the inverter device and the discharge lamp lighting device of the present invention.

FIG. 5 is a circuit diagram showing a fifth embodiment of the inverter device and the discharge lamp lighting device of the present invention.

FIG. 6 is a perspective view of a lighting fixture showing one embodiment of the lighting device of the present invention.

FIG. 7 is a circuit diagram showing a conventional current feedback type self-excited oscillation type inverter device.

[Explanation of symbols]

1 ... AC power source 2 ... DC power supply 3 ... switching means 4 ... output transformer 5 ... load 6 ... current feedback circuit 7 ... opposite polarity feedback means C _S ... stray capacitance

Claims (10)

[Claims] 1. Switching means arranged to switch a direct current to supply an alternating current to a load; and perform positive feedback to cause the switching means to self-oscillate but remove a load connected via a wiring path. A current feedback circuit in which a feedback loop is substantially disconnected when the load is removed; and a reverse polarity feedback means capable of canceling a feedback amount that may be caused by a stray capacitance between wiring lines when a load is removed. An inverter device characterized in that: 2. An output transformer of an insulation type capable of connecting a load to a secondary side via a wiring path;
Switching means arranged to apply a switched voltage to the secondary winding; a primary winding inserted into a secondary circuit of the output transformer, wherein the secondary winding has a switching means of a current feedback type; A current feedback circuit including a current transformer connected to a control terminal of the switching means for performing an excitation oscillation operation; a feedback amount which can be generated by a floating capacitance between wiring lines when a load is removed; And a reverse polarity feedback means. The reverse polarity feedback means includes a series circuit of a tertiary winding and a capacitor of opposite polarity to the secondary winding of the output transformer, and is connected in parallel to the primary winding of the current transformer. The inverter device according to claim 2, wherein the inverter device is configured as follows. 4. The inverter device according to claim 1, wherein the reverse polarity feedback means comprises an inductor connected between the output terminals. 5. Switching means arranged to switch a direct current to supply an alternating current to a load; and perform positive feedback to cause the switching means to self-oscillate but remove a load connected via a wiring path. A current feedback circuit that substantially cuts off the feedback loop when the load is removed; and a frequency response means operable to perform current feedback at a frequency when the load is mounted in relation to a frequency change when the load is removed. An inverter device characterized in that: 6. An insulated output transformer capable of connecting a load to a secondary side via a wiring path;
Switching means arranged to apply a switched voltage to the secondary winding; a primary winding inserted into a secondary circuit of the output transformer, wherein the secondary winding has a switching means of a current feedback type; A current feedback circuit including a current transformer connected to a control terminal of the switching means so as to perform the excitation oscillation operation; and acting to perform current feedback at a frequency when the load is mounted in relation to a frequency change when the load is removed. And a frequency responsive means. 7. The inverter according to claim 5, wherein the frequency response means has a trap frequency corresponding to the frequency at the time of load removal, and is constituted by a trap means inserted in the current feedback circuit. apparatus. 8. The frequency response means according to claim 5, wherein the frequency response means has a characteristic of selectively passing a frequency when a load is mounted, and is constituted by filter means inserted in a current feedback circuit. Inverter device. 9. A discharge lamp lighting device comprising: the inverter device according to claim 1; and a discharge lamp energized by an output of the inverter device. 10. A lighting device comprising: a lighting device main body; and the discharge lamp lighting device according to claim 9 disposed in the lighting device main body.