JPH0487568A - Inverter device - Google Patents

Abstract

PURPOSE:To improve the input power factor by providing the second resonance circuit which shares switching elements with the first resonance circuit and returns switching current by the on/off action of the switching elements to a commercial power source. CONSTITUTION:Switching elements Q1, Q2 are shared by the first and second resonance circuits 1, 2. The first resonance current is caused to flow in the first resonance circuit 1. by the on/off action of the switching elements Q1, Q2 and power is supplied to an electric-discharge lamp La. Simultaneously the second resonance current is caused to flow in the second resonance circuit 2, and the switching current is returned to a commercial power source AC. This reduces the higher harmonic components of the input current from the commercial power source AC, and improves the input power factor.

Description

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

[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.

Fig. 6 is a circuit shown in Japanese Patent Application No. 63-160163, 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 C1
In a device for lighting a discharge lamp La with the high frequency output of the inverter rNV, the second smoothing capacitor C0 is charged by the current returned from a part of the inverter INV, and the switching element Q0 is The voltage of the second smoothing capacitor C8 is intermittently applied to the inductor L0 through 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 and transistor Q. In the off period of the inductor.

The self-induced voltage of is superimposed on the full-wave rectified output, and the first smoothing capacitor C2 is charged. Inductor. The self-induced voltage of the commercial power supply AC is effectively superimposed during the period when the instantaneous voltage value of the commercial power supply AC is low, and the self-induced voltage of the commercial power supply A
Since the input current fin from C can be passed, there is no pause period for the input current Iin from the commercial power supply AC,
The current ILa 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 the second smoothing capacitor C6 and its charging means, and also requires the inductor L0 and the switching element Q to create a voltage source to be superimposed on the full-wave rectified output of the rectifier circuit DB. , and the device cost is high.

1 prong λ1 Fig. 7 is a circuit shown in Japanese Patent Application No. 1-252175, in which the alternating current voltage of the commercial power supply AC is rectified by a rectifier circuit DB, an inductor L0 and a diode D. is applied to the smoothing capacitor C1 through a series circuit of. A switching transistor T is connected to the smoothing capacitor CI via a parallel resonant circuit of an inductor L9 and a capacitor C1.
r is connected. A discharge lamp La is connected to the parallel resonant circuit through an inductor Ls, and the discharge lamp L
A capacitor C1 is connected between the non-power supply side terminals of a. A switching signal with a frequency of several tens of kilohertz is input to the base of the transistor Tr.

This constitutes a -stone inverter circuit. Furthermore, the high frequency voltage generated at the collector by turning on and off the transistor Tr is applied to the connection point between the inductor L0 and the diode D0 via the capacitor C8. 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 the transistor Tr is on, the capacitor C passes from the rectifier circuit DB through the inductor L0.
A current flows through a, charging this capacitor C1. Capacitor C is gradually charged and diode D. When the anode voltage of increases and becomes equal to or higher than the voltage of the smoothing capacitor C1, the diode Do turns on, and the inductor L0 acts as a boosting element, causing the inductor L0 to flow from the rectifier circuit DB.
A current flows through and charges the smoothing capacitor CI.

In this method, inductor L0 and diode D0
The potential at the connection point of the capacitor C is not directly changed by a switching element.

Since the voltage is changed indirectly through the smoothing capacitor C1, the voltage across the smoothing capacitor C1 does not rise much.
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. 8(b), the harmonic components of the input IE current fin can be reduced. , waiting for the advantage of being able to improve the input power factor. However, in this case the diode D
In order to change the anode potential of 0, some kind of impedance element is required between the rectifier circuit DB and the diode D0. Furthermore, 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 C even when the input voltage is low. In other words, a pressurizing action is necessary. Therefore, between the rectifier circuit DB and the diode D0 there is an inductor L that acts as a boost chopper.
1 is required, which has the drawback 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 a second resonant circuit separate from the first resonant circuit of the inverter, without using an expensive inductor that acts as a step-up chopper, and to share the switching elements of the inverter with the second resonant circuit. An object of the present invention is to provide an inverter device that reduces harmonic components of an input current and improves the input power factor by passing a switching current through a resonant circuit and feeding the switching current back to the input current.

[Means for Solving the Problems] In the present invention, in order to solve the above problems, the first
As shown in the figure, a rectifier circuit DB rectifies the AC voltage of the commercial power supply AC, a smoothing capacitor C3 smoothes the rectified voltage, and the voltage of the smoothing capacitor C7 is used as a power source to turn switching elements Q1 and Q2 on and off. In an inverter device that has a first resonant circuit 1 that generates a high-frequency output, and supplies power to a load (discharge lamp La) with this high-frequency output, the first resonant circuit 1 and a switching element Q, It is characterized in that a second resonant circuit 2 is provided which shares Q2 and feeds back the switching current caused by the on/off of the switching element QQ2 to the commercial power supply AC.

[Function] In this way, in the present invention, the first resonant circuit 1 and the switching elements Q, Q2 are shared, and the switching current caused by the on/off of the switching elements Q, Q2 is fed back to the commercial power supply AC. Therefore, by simply adding the relatively inexpensive second resonant circuit 2, it is possible to substantially lengthen the period during which the input current is flowing from the commercial AC power source. This makes it possible to reduce harmonic components of the input current and improve the input power factor.

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.6 In this embodiment, input AC voltage from a commercial power supply AC is rectified by a rectifier circuit DB, and is then rectified by a capacitor C1 via a diode D1. It's smooth. The voltage obtained across the smoothing capacitor C4 is applied to a series circuit of switching elements Q, Q2. A discharge lamp La is connected to both ends of the switching element Q2 on one side via an inductor L1 and a capacitor C1. A capacitor C4 is connected in parallel between the non-power supply side terminals of the discharge lamp La. The secondary winding of the inductor L1 is a switching element Q, which is a bipolar transistor, and a resistor R2 between the base and emitter of Q2, respectively.
Connected via R3. Switching element Q1
．． The connection point of Q2 is inductor L2 and capacitor C
The rectifier path DB and the diode D,
connected to the connection point.

Switching element Q 1. Q2 is the first resonant circuit 1
and the second resonant circuit 2. The resonant elements of the first resonant circuit 1 are mainly an inductor L1 and a capacitor C4, and the capacitor C1 is a coupling capacitor for cutting a DC component. The resonant current flowing through the inductor L1 is fed back through the secondary winding between the bases and emitters of the switching elements Q, Q2, which are bipolar transistors, to perform self-oscillation operation.

A starting circuit 3 is provided to start this automatic oscillation operation. In the starting circuit 3, the capacitor c6 is charged via the resistor R, and when the voltage reaches the breakdown voltage of the voltage responsive element Q, the voltage responsive element Q becomes conductive and the base of the switching element Q2 consisting of a bipolar transistor is connected. Start-up current is supplied to start automatic oscillation operation. After the self-excited vibration operation starts, the switching element.

Since the collector potential of the capacitor c6 periodically decreases, the charge of the capacitor c6 is discharged via the diode D2, and the starting circuit 3 stops operating.

FIG. 2 shows the operation when switching element Q is on and switching element Q2 is off. First, the first resonant circuit 1 includes a capacitor C, a switching element Q, an inductor L, and a coupling capacitor C3.
, a resonant current ■ flows through the parallel circuit of the discharge lamp La and the capacitor C1, and returns to the capacitor CI (see the solid line in Figure 2). Rectifier circuit DB, switching element Q2, inductor L2, capacitor C2, rectifier circuit DB, commercial power supply A
A common S current ■ flows in the path C (see the broken line in FIG. 2).

FIG. 3 shows the operation when switching element Q is off and switching element Q2 is on.

First, the first resonant circuit 1 is connected to the inductor L, the switching element Q2, the discharge lamp La, and the resonant capacitor C1 due to the vibration energy of the inductor L and the capacitor C4.
A resonant current ■ flows through the parallel circuit of the coupling capacitor C7 (see the solid line in Figure 3).Next, in the second resonant circuit 2, due to the vibration energy of the inductor L2 and the capacitor C2, the capacitor C2, Inductor L2,
Switching element Q2, diode D1, capacitor C
A resonant current ■ flows in the closed circuit of 2 (see the broken line in Figure 3).
.

As a result, the charge in the resonant capacitor C2 is discharged.

In this way, the first resonant current ■,
■ is supplied to the discharge lamp La, and at the same time, the second resonant currents ■ and ■ are supplied to the second resonant circuit 2 to supply power to the commercial power source A.
The switching current is fed back to C.

Figure 4 shows the waveform of the input current from the commercial power supply AC in this embodiment. In addition, the second resonant circuit 2 is charged with the voltage shown in FIG.
) flows a switching current having a sinusoidal envelope of a commercial frequency of 60 Hz (or 50 Hz). This current waveform is processed by a filter circuit (not shown).
The input current is shaped into a sinusoidal waveform. For this reason, the fourth
The current waveform shown in FIG. 4(e), which is a composite of the two input currents shown in FIGS. 4(a) and 4(b), is the input current waveform of this embodiment. In this way, since the input current flows in the entire section, the input current has a high input power factor and has few high-order harmonic components relative to the AC fundamental frequency.

[Example 2] FIG. 5 is a circuit diagram of another embodiment of the present invention.

In this embodiment, the switching element Q2 of the above-mentioned embodiment 1 is
Instead of capacitor C7 and inductor.

The first resonant circuit 1 includes a switching element Q1 made of a bipolar transistor.
, inductor 1, capacitor C1, inductor L1,
It is an automatic oscillation circuit that is composed of a parallel circuit of a coupling capacitor C, a discharge lamp La, and a capacitor C1, and oscillates using the charge of the electrolytic capacitor C1 as a power source. The circuit operation is also almost the same as in Example 1, and after starting the switching element Q by the current flowing through the starting resistor R3,
By feeding back the resonant current flowing through the inductor L1 to the base of the switching element Q through the secondary winding, the switching element Q1 is turned on/off and high-frequency power is supplied to the discharge lamp La. The second resonant circuit 2 includes an inductor L2 and a capacitor C2, and as in the first embodiment, returns a switching current to the commercial power supply AC by turning on/off the switching element Q1. The input current waveform is almost the same as that shown in Figure 4, and with a high input power factor,
An input current waveform with few high-order harmonic components can be obtained.

In the above description of the embodiment, an automatic type circuit was exemplified, but a separately excited type circuit may also be used.In short, the switching element is shared with the first resonant circuit, and the switching current is fed back to the commercial power supply. The circuit system is not limited as long as the second resonant circuit is provided.

[Effects of the Invention] As described above, the present invention includes a rectifying means for rectifying AC voltage of a commercial power source, a smoothing capacitor for smoothing the rectified voltage, and a switching element using the voltage of the smoothing capacitor as a power source. In an inverter device that includes a first resonant circuit that generates a high-frequency output by turning on/off the high-frequency output, and supplies power to a load using the high-frequency output, the first resonant circuit and the switching element are shared, and the switching element Since the second resonant circuit is provided to feed back the switching current caused by the on/off of the converter to the commercial power supply, a relatively inexpensive second resonant circuit can be added without using an inductor that acts as a step-up chopper. This has the effect of reducing harmonic components of the input current from the commercial power supply 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.
The figure is a circuit diagram for explaining the operation of the same as above, FIG. 4 is an operation waveform diagram of the same as above, FIG. 5 is a circuit diagram of the second embodiment of the present invention, and FIG.
FIG. 7 is a circuit diagram of a conventional example, FIG. 7 is a circuit diagram of another conventional example, and FIG. 8 is a waveform diagram for explaining the operation of the same. 1 is the first resonant circuit, 2 is the second resonant circuit, AC is the commercial power supply, DB is the rectifier circuit, C1 is the smoothing capacitor, C2,
C4 is a resonant capacitor, L, L2 is a resonant inductor, La is a discharge lamp, and Q, C2 is a switching element.

Claims (1)

[Claims] (1) A rectifier that rectifies the AC voltage of the commercial power supply, a smoothing capacitor that smoothes the rectified voltage, and a first circuit that uses the voltage of the smoothing capacitor as a power source to generate a high-frequency output by turning on/off a switching element. In an inverter device that has a resonant circuit and supplies power to a load using this high-frequency output, the first resonant circuit and the switching element are shared, and the switching current generated by turning on and off the switching element is returned to the commercial power source. An inverter device characterized in that two resonance circuits are provided.