JPH0487567A - Inverter device - Google Patents

Abstract

PURPOSE:To improve the input power factor by providing a power-factor improving capacitor which is charged from a commercial power source through a rectifying circuit and an inverter and whose polarity is reversed by the resonance action of the inverter. CONSTITUTION:A power-factor improving capacitor C3 is connected in parallel to the series circuit of a diode D5 with an inductor L1, and the inductor L1 and capacitor C3 constitute a resonance circuit. A resistor R1, a capacitor C4, and a diode AC switch (diac) DA1 constitute a starting circuit, and a capacitor C4 is charged through the resistor R1. When its charged voltage reaches the breakdown voltage of the diode AC switch DA1, the diode AC switch DA1 is turned on, base current is supplied to a transistor Tr1 from a capacitor C4, and an inverter INV begins to oscillate. The polarity of the capacitor C3 is reversed by utilizing the resonance action of the inverter INV, and its electric charges are returned to the input current. This reduces the higher harmonic components of the input current, and improves the input power factor.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applied to an inverter device that receives a commercial AC voltage as an input and drives a load at a high frequency. For example, it is used for lighting a discharge lamp at a high frequency. It is something that is used.

[Prior Art] Conventionally, a discharge lamp lighting device has been widely used in which a DC voltage obtained by rectifying and smoothing an AC voltage of a commercial power source is converted into a high frequency by an inverter and supplied to a discharge lamp, thereby lighting the discharge lamp at a high frequency. In this type of lighting device, the rectified output of the commercial AC voltage is smoothed by ensuring that the envelope of the high-frequency current supplied to the discharge lamp does not fluctuate with the cycle of the commercial AC voltage. Improves luminous efficiency, reduces device power consumption, and eliminates flickering of light.
This is to improve the performance of the lighting device.

However, when the commercial AC voltage is rectified and smoothed, the current flowing from the commercial power supply to the smoothing capacitor will only flow near the peak value of the commercial AC voltage, and the current flowing into the smoothing capacitor from the commercial power supply will only flow around the peak value of the commercial AC voltage. Since it is an input current, the input power factor is poor and it also contains many high-order harmonic components relative to the AC fundamental frequency, which may cause high-frequency noise to be mixed into other equipment connected to the same AC power distribution system. There was a negative impact. Therefore, various proposals have been made as described below in order to increase the power factor of the input current, reduce harmonic components, and supply as flat a DC smoothed voltage as possible to the inverter.

Ryotaka n Figure 13 shows the circuit shown in Japanese Patent Application No. 160163/1986, in which the AC voltage of the commercial power supply AC is rectified by the rectifier circuit DB, and the inductor L0 and the first smoothing capacitor C
In a device for lighting a discharge lamp La with the high frequency output of the inverter INV, the current returned from a part of the inverter INV charges the second smoothing capacitor C0, and the switching element Q0 The voltage of the second smoothing capacitor C6 is intermittently applied to the inductor L0 via the inductor L0. During the ON period of the transistor Q0, the voltage of the second capacitor C0 is the same as that of the inductor L.

In addition to this, energy is stored in inductor L0,
Transistor Q. In the off period of the inductor. The self-induced voltage is superimposed on the full-wave rectified output, and the first smoothing capacitor C1 is charged.

The self-induced voltage of the inductor L0 is effectively superimposed during the period when the instantaneous voltage value of the commercial power supply AC is low, and the input current Iin from the commercial power supply AC can flow to the first smoothing capacitor C1. The idle period of the input current Iin is eliminated, the current ■La flowing through the discharge lamp La is stabilized, the input power factor is increased, and harmonic components of the input current are reduced. However, this conventional example requires a second smoothing capacitor Co and its charging means, and also uses an inductor to create a voltage source to be superimposed on the full-wave rectified output of the rectifier circuit DB. This method requires a switching element Q0 and a switching element Q0, which has the drawback of increasing the cost of the device.

[1] Figure 14 is a circuit shown in Japanese Patent Application No. 1-252175, in which the AC voltage of the commercial power supply AC is rectified by the rectifier circuit DB, and smoothed through a series circuit of an inductor L0 and a diode D0. Applied to capacitor C1. Smoothing capacitor C3 has an inductor, and capacitor C9
A switching transistor Q is connected through a parallel resonant circuit. A discharge lamp La is connected to the parallel resonant circuit via an inductor L8, and a capacitor C2 is connected between the non-power supply side terminals of the discharge lamp La. A switching signal with a frequency of several tens of kilohertz is input to the base of the transistor Q.

This constitutes a -stone inverter circuit. Furthermore, by turning on and off the transistor Q1, the high frequency voltage generated at the collector is applied to the inductor L0 and the diode D via the capacitor Cm. is applied to the connection point. As a result, the diode D0 repeatedly turns on and off at a frequency higher than the frequency of the input commercial power supply AC, and the AC input current has a conduction period even when the instantaneous value of the input AC voltage is low. In other words, during the period when transistor Q1 is on,
From the rectifier circuit DB through the inductor L0 to the capacitor C3
Current flows through and charges this capacitor C@. Capacitor C8 is gradually charged and the anode voltage of diode D0 rises, and when it exceeds the voltage of smoothing capacitor C3, diode D0 is turned on, inductor L0 acts as a boost element, and current flows from rectifier circuit DB through inductor L0. flows and charges the smoothing capacitor C1.

In this system, inductor L6 and diode D0
Since the potential at the connection point of is not changed directly by a switching element, but is changed indirectly via the capacitor Cs, the voltage across the smoothing capacitor C2 does not increase much, and as shown in FIG. As shown in a),
The envelope of the input current Iin can be made proportional to the input voltage Vin, and when compared with the comparative example shown in FIG. 15(b), it is possible to reduce the harmonic components of the input current Iin and improve the input power factor. It has the advantage of being possible. However, in this case, some kind of impedance element is required between the rectifier circuit DB and the diode D0 in order to change the anode potential of the diode D0. Moreover, in order to charge the smoothing capacitor C1, improve input current distortion, and achieve complete smoothing, it is necessary to generate a voltage that exceeds the voltage across the smoothing capacitor C1 even when the actual voltage is low. A pressor effect is required. Therefore, an inductor L1 acting as a boost chopper is required between the rectifier circuit DB and the diode D0, which has the disadvantage of increasing the device cost.

[Problem to be solved by the invention] The present invention has been made in view of the above points,
The purpose of this is to add an inexpensive capacitor without using an expensive inductor that acts as a boost chopper, reverse the polarity of this capacitor using the inverter's resonance, and feed the charge back into the input current. An object of the present invention is to provide an inverter device that reduces harmonic components of input current and improves input power factor.

[Means for Solving the Problems] In the present invention, in order to solve the above problems, the first
As shown in the figure, there is a rectifier circuit DB that rectifies the alternating current voltage of the commercial power supply AC, a smoothing capacitor CI that smoothes the rectified voltage, and a smoothing capacitor C3 that converts the voltage of the smoothing capacitor C3 to a high frequency and supplies it to the load (discharge lamp La). In a device equipped with an inverter INV that applies voltage, the device is charged from a commercial power supply AC via the rectifier circuit DB and the inverter INV, and the inverter INV
The present invention is characterized in that it includes a power factor improving capacitor C1 whose polarity is reversed by the resonance action of the power factor.

[Function] As described above, the present invention includes the power factor correction capacitor C8, which is charged from the commercial power supply AC through the rectifier circuit DB and the inverter INV, and whose polarity is reversed by the resonance action of the inverter. Therefore, simply by providing the relatively inexpensive capacitor C1, it is possible to substantially lengthen the period during which the input current is flowing from the commercial power supply AC, reduce the harmonic components of the input current, and reduce the input power factor. can be improved.

More detailed configuration and operation of the present invention will become clearer in the following description of the embodiments.

[Embodiment 1] Figure 1 is a circuit diagram of an embodiment of the present invention. In this embodiment, input AC voltage from a commercial power supply AC is connected to a diode D,
~ Rectified by bridge circuit DB of D4, diode D
5 and is smoothed by capacitor C1. The voltage obtained across the smoothing capacitor C1 is applied to a series circuit consisting of an inductor and a transistor T, and a discharge lamp La is connected to both ends of the transistor Tr via an inductor L2. A capacitor C2 is connected in parallel between the non-power supply side terminals of La.The secondary winding of the inductor L2 is connected between the base and emitter of the transistor Trl via a base resistor R2.A diode D , and an inductor L1, a capacitor C1 is connected in parallel, and this is a characteristic configuration of the present invention.

The inductor L1 and the capacitor C1 constitute an LC resonance circuit, the inductor L2 is a current-limiting parasitic inductor, and the capacitor C2 is for preheating the filament of the discharge lamp La.

Resistor R1, capacitor C4, and diac D A + constitute a starting circuit. Capacitor C via resistor R1
4 is charged and when its voltage reaches the breakdown voltage of the diac DAl, the diac DA,h: conducts and supplies the base current of the transistor Tr+ from the capacitor C4,
Start oscillation of inverter INV. Inverter IN
The oscillation operation of V is maintained by feeding back the load current flowing through the inductor L2 between the base and emitter of the transistor Tr through the secondary winding L3. After the inverter INV starts the automatic oscillation operation, the collector potential of the transistor Trl decreases periodically, so that the charge of the capacitor C4 is discharged through the diode D6, and the above-mentioned starting circuit stops operating.

A diode Dt is connected in antiparallel to the transistor Tr1. This diode D is the inverter INV
It is provided to conduct a current due to the resonance energy of.

The operation of this embodiment will be explained below. First, when the transistor Tr+ is ON, as shown in the second W(a),
A current (
) and the inductor L from the smoothing capacitor CI.
,, the current flowing back to the capacitor C1 via the transistor Tr+ (see the solid line ■) flows through the transistor Tr+.
When l is turned off, as shown in Figure 2(b), a current (see broken line ■) flows through inductor C3, capacitor C1, and diode D5 due to the stored energy in inductor L and the stored charge in capacitor C3. As a result, the polarity of capacitor C5 is reversed. The charges stored in the capacitor C3, whose polarity has been reversed, are transferred to the inductor L2, the discharge lamp La, and the diode D shown in FIG.

Or, it is discharged at the red path of the AC power source AC, the diode D2 or Dl, and the capacitor C. Therefore, in the end,
The polarity of the charge stored in the capacitor C1 is reversed by resonance with the inductor L1, and the discharge of the charge can be fed back to the input power source by the diode D5.

Figure 3 shows the operating waveform of this embodiment.The input current waveform is a combination of the high frequency feedback current to the commercial power supply AC by the capacitor C and the low frequency charging current to the smoothing capacitor C1. . In this way, in this embodiment, current flows through the input even when the input voltage is not at its peak, and the input power factor is significantly improved.

[Embodiment 2] In the embodiment shown in FIG. 4, an inductor L4 is inserted in series on the output side of the rectifier circuit DB to fill in the valleys of the high frequency current and smooth the input current. In this embodiment, the voltage of the capacitor C3 is boosted by the presence of the inductor L4, so that the low frequency charging current from the commercial power supply AC to the smoothing capacitor C3 is eliminated. Therefore, the input current waveform is as shown in the fifth (2I).

[Embodiment 3] The embodiment shown in FIG. 6 is a circuit in which an inductor L4 is inserted in series on the input side of the rectifier circuit DB, and its operating waveform is shown in FIG. A high frequency feedback current (see FIG. 7(b)) from the inductor L4 is fed back to the alternating current power source AC as a current having a low frequency sinusoidal envelope (see FIG. 7(d)),
The remaining current (see FIG. 7(c)) is fed back to the capacitor C1 through the diodes D3, D or D4, D2 constituting the rectifier circuit DB. Furthermore, the current fed back to the commercial power supply AC (see 71M(d)) is filled in by the action of the inductor and becomes a low-frequency sinusoidal current (see FIG. 7(e)). In this case, the smoothing capacitor C1 is charged with the valley-filling current due to the action of the inductor L4, and its voltage is increased.

[Embodiment 4] In the embodiment shown in FIG. 8, inductors L = and Ls are inserted on the input side and output side of the rectifier circuit DB, respectively. Similarly, the input current has a sinusoidal current waveform with no rest period.

[Example 5] In the example shown in FIG. 9, two transistors T r ,
.

A half-bridge type inverter INV is used in which inductor 2 and capacitors C9 and C6 perform resonant operation by alternately turning on and off Tr2. The AC voltage of the commercial power supply AC is inductor L.

is rectified by a rectifier circuit DB via a diode D,
A DC voltage is charged to the capacitor CI via the capacitor CI. The voltage of the capacitor CI is the voltage of the transistor Tr1゜Tr2
applied to the series circuit. Each transistor T' + t
Diodes D, , D, are connected in antiparallel to T r 2, respectively. At both ends of the transistor Tr2,
A series circuit of an inductor L2 and a capacitor C1 is connected, and a discharge lamp La is connected to both ends of the capacitor C9 via a capacitor C7. A capacitor C2 is connected in parallel between the non-power supply side terminals of the discharge lamp La. The connection point between the inductor L2 and the capacitor C5 is connected to the connection point between the diode D and the rectifier circuit DB via the capacitor C6.

The operation of this embodiment will be explained below. First, transistor T r + is turned on and transistor Tr2 is turned off.
At this time, a resonant current flows through the capacitor C6 through the path of the smoothing capacitor CI, the transistor Tr+, the inductor 2, and the capacitor C6 (see the solid line in Figure 10).The capacitor C6 has the AC power supply AC, the transistor Tr,...
A resonant current flows through the path between the inductor L2 and the capacitor C6 (see the broken line in FIG. 10).

Next, the transistor Tr+ is turned off, and the transistor Tr+ is turned off.
2 is ON, capacitor C5, inductor L2
, a resonant current flows through the path of the transistor Tr2, and the polarity of the capacitor C5 is reversed (see the solid line in Figure 11).
In addition, a resonant current flows in the path of capacitor C6, inductor L2, transistor Trz, and diode D,
The polarity of capacitor C6 is also reversed (see the dashed line in Figure 11), so in this circuit as well, capacitor C6
Since the resonant current is fed back to the input power supply side, by filling in the valleys with an inductor 4 or the like, it is possible to make the input current without a rest period or a sinusoidal current with few harmonic components.

[Embodiment 6] In the embodiment shown in FIG. 12, the inductor L4 is connected to the rectifier circuit D.
It is placed on the output side of B. Further, the capacitor C1 and the diode D are arranged in the opposite way to those in the fifth embodiment. Furthermore, the load circuit of the inverter INV includes a transistor Tr.
Connected in parallel to the + side. In this embodiment as well, the same operation as in the fifth embodiment described above can be realized.

[Effects of the Invention] As described above, the present invention includes a rectifying means for rectifying AC voltage of a commercial power supply, a smoothing capacitor for smoothing the rectified voltage, and a smoothing capacitor for converting the voltage of the smoothing capacitor into a high frequency. In a device comprising an inverter that applies to a load,
It is charged from a commercial power source via a rectifier and an inverter,
Since it is equipped with a power factor correction capacitor whose polarity is reversed by the resonance effect of the inverter, there is no need to use an inductor that acts as a boost chopper, just add a relatively inexpensive capacitor that acts as a resonance element. This has the effect of reducing harmonic components of the input current from the commercial power source and improving the input power factor.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of the first embodiment of the present invention, FIG. 2 is a circuit diagram for explaining the operation of the same, and FIG. 3 is an operation waveform diagram of the same.
FIG. 4 is a circuit diagram of a second embodiment of the present invention, FIG. 5 is an operating waveform diagram of the same as above, FIG. 6 is a circuit diagram of a third embodiment of the present invention, and FIG. 7 is an operating waveform diagram of the same as above. FIG. 8 is a circuit diagram of a fourth embodiment of the present invention, FIG. 9 is a circuit diagram of a fifth embodiment of the present invention, and FIG.
0 and 11 are circuit diagrams for explaining the operation of the same as above, FIG. 12 is a circuit diagram of the sixth embodiment of the present invention, FIG. 13 is a circuit diagram of a conventional example, and FIG. 14 is another conventional example. The circuit diagram of FIG. 15 is a waveform diagram for explaining the operation of the same. AC is a commercial power supply, DB is a rectifier circuit, C1 is a smoothing capacitor, C1 is a capacitor for power factor correction, INV is an inverter, and La is a discharge lamp.

Claims (1)

[Claims] (1) In a device equipped with a rectifying means for rectifying AC voltage from a commercial power supply, a smoothing capacitor for smoothing the rectified voltage, and an inverter for converting the voltage of the smoothing capacitor into a high frequency and applying it to a load, An inverter device comprising a power factor improving capacitor that is charged via a rectifier and an inverter and whose polarity is reversed by the resonance action of the inverter.