JP3235366B2 - Inverter device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device having a DC power supply for supplying a high-frequency output to an AC load. The present invention relates to an inverter device for promoting power factor improvement.

[0002]

2. Description of the Related Art In the conventional inverter device shown in FIG.
The voltage applied between the DC input terminals of the inverter is shown in FIG.
(A), and the capacitor 4 of the smoothing circuit is
The battery is charged from time A to time B by the output voltage of the full-wave rectifier circuit 2, and the voltage of the capacitor 4 rises to the peak voltage value of the AC power supply 1. Further, during the period from time B to time A, since the voltage of the capacitor 4 is higher than the voltage of the AC power supply 1, no current is supplied from the AC power supply 1 and the capacitor 4
Is discharged to the inverter.

[0003]

Therefore, the charging current from the AC power supply 1 to the capacitor 4 and the supply current to the inverter flow from time A to time B in FIG. , The supply current from the AC power supply 1 stops.
Accordingly, the output of the rectifier circuit has a waveform with a high peak value having a pause period as shown in FIG. 4B, and the power factor is extremely deteriorated. An object of the present invention is to provide an inverter device with an improved power factor.

[0004]

In order to achieve the above object, the present invention provides an inverter having an operating characteristic in which a DC input current is intermittently inserted, in which an auxiliary inductor is inserted in series with the DC input terminal to interrupt the input current of the inverter. An auxiliary capacitor that is sometimes charged with a voltage generated in the auxiliary inductor, further prevents the charge of the auxiliary capacitor from discharging through the auxiliary inductor and the smoothing circuit, and discharges through a rectifier circuit. A rectifier for selective discharge is provided at a position where the rectification is allowed.

[0005]

The inverter has an intermittent characteristic of the input current during its operation, accumulates energy in the auxiliary inductor while the input current is flowing, and supplies the auxiliary capacitor with a voltage generated in the auxiliary inductor when the input current is cut off. Charge. Since the charge of the auxiliary capacitor is discharged only through the rectifier circuit by the rectifier for selective discharge, the output of the rectifier circuit from the viewpoint of the inverter is obtained by adding the voltage of the auxiliary capacitor to the AC power supply voltage. Therefore, even when the AC power supply voltage is lower than the discharge voltage of the smoothing capacitor of the smoothing circuit, the output of the rectifier circuit is promoted, so that the power factor can be improved.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The apparatus of the present invention shown in FIG. 1 will be described. The AC power supply 1 is a full-wave rectifier circuit 2 composed of a diode bridge.
, And a filter capacitor 3 is connected between the output terminals of the rectifier circuit 2. One terminal of a smoothing capacitor is connected to ten terminals of the rectifier circuit 2, and the other end is connected to one terminal of the rectifier circuit 2 via the anode and cathode of the rectifier 21 for selective discharge. At both ends of the smoothing capacitor 4, a parallel circuit of a capacitor 5 and an inductor 6 and a parallel circuit of a transistor 7 and a rectifier 8 constituting an inverter are connected in series via an auxiliary inductor, and an emitter of the transistor 7 and a rectifier 21 for selective discharge are connected. A rectifier 22 and an auxiliary capacitor 23 are connected in parallel between the cathodes.
An AC load 10 is connected to both ends of the inductor 6, and a control circuit 9 is connected to a base of the transistor 7. The inverter device in FIG. 1 supplies high-frequency power to an AC load 10 by turning on and off a transistor 7 by a control circuit 9. With. 1 will be described with reference to the waveform diagram of FIG. FIG. 2A shows the voltage waveform of the smoothing capacitor 4 of the smoothing circuit. During the period from time A to time B, the smoothing capacitor 4 is charged by the output of the rectifier circuit to the peak value of the AC power supply voltage via the rectifier 21 for selective discharge. You. At the same time, the rectifier circuit output supplies current to the inverter via rectifier 22. Therefore, no current flows through the auxiliary inductor 20, and the auxiliary capacitor 23 is not wastefully charged by the auxiliary inductor 20. Next, after the time point b, the voltage of the smoothing capacitor 4 is higher than the rectified output of the AC power supply 1 voltage, so that the charge of the smoothing capacitor 4 is discharged to the inverter via the auxiliary inductor 20. At this time, energy is stored in the auxiliary inductor 20 when the transistor 7 is turned on,
When the transistor 7 is turned off, the auxiliary capacitor 23 is charged by the voltage generated in the auxiliary inductor 20 via the rectifier 21 for selective discharge. The charge of the auxiliary capacitor 23 is not discharged by the selective discharge rectifier 21 through the smoothing capacitor 4 and the auxiliary inductor 20, but is discharged only through the rectifier circuit 2 and the AC power supply 1. For this reason,
When the auxiliary capacitor 23 is charged, the voltage applied to the inverter becomes a value obtained by adding the charging voltage of the auxiliary capacitor 23 to the voltage of the AC power supply 1. When the added voltage becomes higher than the voltage of the smoothing capacitor 4, 4
Is stopped and the auxiliary capacitor 23 discharges the electric charge, so that the output of the rectifier circuit supplies a current to the inverter. When the auxiliary capacitor 23 discharges the electric charge, a current is again supplied to the inverter by discharging the smoothing capacitor 4, and this operation is repeated until time a. For this reason, the current waveform of the output of the rectifier circuit has a short rest period in which the high-frequency current flows between time A and time B as shown in FIG. 2B, and the power factor is improved. The smoothing circuit including the smoothing capacitor 4 in FIG. 1 may be a so-called partial smoothing circuit. A typical example of the partial smoothing circuit is a circuit including a pair of capacitors, one charging rectifier, and two discharging rectifiers. The pair of capacitors is charged in series via the charging rectifier, and the charge of each capacitor is It is discharged in parallel with each other via each rectifier.

[0007]

According to the present invention, the electric charge charged in the auxiliary capacitor is discharged through the rectifier circuit, so that the output of the rectifier circuit is maintained even during the period when the AC power supply voltage is lower than the discharge voltage of the smoothing capacitor of the smoothing circuit. And the power factor can be improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of the device of the present invention.

FIG. 2 is a waveform chart for explaining the operation of the apparatus in FIG. 1;

FIG. 3 is a circuit diagram of a conventional device.

FIG. 4 is a waveform chart for explaining the operation of the apparatus in FIG. 3;

[Explanation of symbols]

1: AC power supply, 2: Rectifier circuit, 3: Filter capacitor, 4: Smoothing capacitor, 5.12: Capacitor, 6.
11: inductor, 7: transistor, 8.22: rectifier, 9: control circuit, 10: AC load, 13: discharge lamp, 2
0: auxiliary inductor, 21: rectifier for selective discharge, 23:
Auxiliary capacitor.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02M 7/48 H02M 7/06 H02M 3/07

Claims (1)

(57) [Claims] A rectifier circuit for rectifying an AC power supply voltage;
A smoothing circuit for smoothing a rectified output voltage of the rectifying circuit, and an inverter connected between output terminals of the rectifying circuit and between output terminals of the smoothing circuit;
The smoothing circuit includes at least one smoothing capacitor, the inverter has an input interrupting characteristic in which a DC input current flowing between its DC input terminals is interrupted when the inverter operates, and supplies a high-frequency output of the inverter to an AC load. In an inverter device with a DC power supply unit, an auxiliary inductor is inserted in series with the DC input terminal of the inverter, and an auxiliary capacitor that is charged with a voltage generated in the auxiliary inductor when the DC input current is interrupted is provided. An inverter device, wherein a rectifier for selective discharge is provided at a position where the discharge of the charge through the auxiliary inductor and the smoothing circuit is prevented and the discharge through the rectifier circuit is allowed.