JPH04222469A - Inverter device - Google Patents

Abstract

PURPOSE:To improve the input power factor and to reduce higher harmonic components of the input current in an inverter device which converts the DC voltage obtained by rectifying and smoothing a source of an AC into a high frequency and then provides it to the load. CONSTITUTION:A source of an AC Vs is rectified by a rectifier DB and is smoothed by a capacitor C1 through an inductor L2. A load circuit is connected through a capacitor C3 between a junction of first and second switching elements Q1 and Q2 which are connected in parallel to the capacitor C1 and a junction of the output terminal of the rectifier DB and the inductor L2. Since the inductor L2 takes partial charge of the voltage difference between the rectifier DB and the capacitor C1, the rectifier DB conducts and input current flows even when the input voltage Vin from the source of an AC Vs is lower than the voltage of the capacitor C1. And, what's more, higher harmonic components of the input current is held down and thereby the input power factor is improved. A rush current is also alleviated by the inductor L2.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device that converts a DC voltage obtained by rectifying and smoothing an AC power source into a high frequency signal and supplies the same to a load.

0002

[Prior art] Conventional inverter device
8496) is shown in FIG. 12. A commercial AC power supply Vs is connected to an AC input terminal of a full-wave rectifier DB. A diode D3 is connected to the DC output terminal of the full-wave rectifier DB.
A smoothing capacitor C1 is connected through the capacitor C1. This capacitor C1 includes switching elements Q1,
A series circuit of Q2 is connected. Each switching element Q1, Q2 has a diode D1, D, respectively.
2 are connected in antiparallel. Furthermore, a series circuit of capacitors C3 and C4 is connected to the DC output terminal of the full-wave rectifier DB. A series circuit of a load 1 and an inductor L1 is connected between the connection point of the capacitors C3 and C4 and the connection point of the switching elements Q1 and Q2.

The operation of the circuit shown in FIG. 12 will be explained below. The commercial AC power supply Vs is full-wave rectified by a full-wave rectifier DB, and smoothed by a capacitor C1 via a diode D3. The switching elements Q1 and Q2 are alternately turned on and off at high frequency. Switching element Q
1 is ON, a path returns from capacitor C1 to capacitor C1 via switching element Q1, inductor L1, load 1, and capacitor C4, and from capacitor C3 to diode D3, switching element Q1, inductor L1, and load 1. A current flows through the capacitor C3 and back to the capacitor C3. When switching element Q2 is ON, load 1 is transferred from capacitor C4.
, inductor L1, switching element Q2, and returns to capacitor C4, a current flows through load 1 in the opposite direction to the above, and as a result, a high frequency current flows through load 1.

[0004] In this circuit, capacitors C3 and C4
When the capacitance of Q2 is selected appropriately, switching element Q2 is turned on.
When , full-wave rectifier DB, capacitor C3, load 1
, the inductor L1, the switching element Q2, and the full-wave rectifier DB. Therefore, the input current can constantly flow. When the switching element Q2 is ON, the current flowing from the full-wave rectifier DB to the load 1 via the capacitor C3 is approximately proportional to the magnitude of the power supply voltage of the AC power supply Vs, and the higher the power supply voltage, the more current flows. . Therefore, the input current becomes an in-phase current that is almost proportional to the power supply voltage and has no rest period, resulting in a high input power factor.

[0005]

In the circuit of FIG. 12, the diode D3 connects the full-wave rectifier DB to the capacitor C1.
It is characterized in that it is inserted in the direction toward
During a period that is sufficiently lower than dc, the input current flows through load 1 in the above loop, but when the power supply voltage Vin becomes Vin≧Vdc near the peak value, the input current flows in addition to load 1 through diode D3. A large current flows through the Therefore, in the input current waveform, a pulse-like rush waveform appears near the peak value of the power supply voltage Vin, and although the input power factor is high, the input current contains many harmonic components. Furthermore, there is a limit to the input power factor due to the inrush current.

The present invention has been made in view of the above points, and its purpose is to reduce the harmonic components of the input current due to rush current from the AC power supply in an inverter device, and to reduce the input power factor. The aim is to raise the level even higher.

[0007]

[Means for Solving the Problems] In order to solve the above problems, in the inverter device of the present invention, as shown in FIG. a first capacitor C1 for smoothing through the first capacitor C1, a series circuit of first and second switching elements Q1 and Q2 connected in parallel to the first capacitor C1 and turned ON/OFF alternately, and the output of the rectifier DB. The connection point between the end and the inductor L2 and the first
and a load circuit connected via a second capacitor C3 between the connection point of the second switching elements Q1 and Q2.

[0008]

[Operation] In the circuit of FIG. 1, the diode D3
By using the inductor L2 instead, the difference in voltage between the output voltage of the rectifier DB and the capacitor C1 can be shared by the inductor L2, and even during periods when the input voltage from the AC power supply Vs is lower than the voltage of the capacitor C1. The input current can be passed, and harmonic distortion of the input current can be reduced. Further, since the magnitude of this input current is proportional to the magnitude of the input voltage, the input current waveform can be made similar to the input voltage, and the input power factor can be increased. Furthermore, the inrush current near the peak value of the voltage of the AC power source Vs is also reduced due to the inductor L2, and harmonic components of the input current can be reduced. More detailed configuration and operation of the present invention will be explained in detail in the description of the embodiments described below.

[0009]

Embodiment A first embodiment of the present invention is shown in FIG. In this embodiment, an inductor L2 is connected in place of the diode D3 in the conventional example shown in FIG. This inductor L2 is inserted into a part of the current loop of the inverter, and this inductor L2 suppresses the rush current from the AC power supply Vs. Switching elements Q1, Q2
is alternately turned on and off at high frequency to supply high frequency power to load 1.

The operation of this embodiment will be explained below. When switching element Q1 is ON, capacitor C
1, switching element Q1, inductor L1
, load 1, capacitor C4, capacitor C1
and from capacitor C3 to inductor L
2, a current flows through the switching element Q1, the inductor L1, the load 1, and returns to the capacitor C3. When switching element Q2 is ON, there is a path from capacitor C4, through load 1, inductor L1, and switching element Q2, and back to capacitor C4, and from capacitor C1, inductor L2, capacitor C3, load 1, inductor L1, and switching element. A current flows through Q2 and back to the capacitor C1 in the opposite direction to the load 1, thereby supplying the load 1 with high frequency power.

Here, when the switching element Q2 is ON and current flows from the capacitor C1 through the loop of the inductor L2, the capacitor C3, the load 1, the inductor L1, the switching element Q2, and the capacitor C1, the inductor L2 has a A voltage is generated in the direction of arrow V2 inside. This voltage V2 is the capacitor C
If the capacitance of 4 is made appropriately small, it can be set to the difference between the output voltage of the full-wave rectifier DB and the voltage of the capacitor C1. As a result, the full-wave rectifier DB can conduct even if the input voltage Vin is low, and the full-wave rectifier DB and the capacitor C
3, load 1, inductor L1, switching element Q
2. Current flows in the loop of the full-wave rectifier DB. Also,
If the input voltage Vin is sufficiently high, in addition to the above loop, when switching element Q1 is turned on, full-wave rectifier D
A current flows through the path of B, inductor L2, switching element Q1, inductor L1, load 1, capacitor C4, and full-wave rectifier DB, and the path of full-wave rectifier DB, inductor L2, capacitor C1, and full-wave rectifier DB. The magnitude of the input current Iin in this embodiment is the power supply voltage Vi
The current is approximately proportional to n and has the same phase, resulting in a high input power factor.

Furthermore, the inrush current near the peak value of the power supply voltage Vin is also reduced due to the inductor L2, and the harmonic components of the input current Iin can be reduced, and the input power factor is further increased accordingly. Furthermore, in this embodiment, the inductor L2
The circuit configuration is simple, as only one is added.

Note that the filter circuit 2 inserted between the AC power supply Vs and the full-wave rectifier DB is for removing high frequency components of the input current Iin. Moreover, the same operation and effect can be obtained even if the capacitor C4 is omitted. Input voltage Vin and input current Ii in this embodiment
The waveform of n is shown in FIG.

FIG. 3 is a circuit diagram of a second embodiment of the present invention. In this embodiment, the inductor L2 is connected to the negative electrode side of the full-wave rectifier DB, and the capacitor C3 is omitted. In this configuration, when the switching element Q1 is turned on, a voltage is generated in the inductor L2 in the direction of V2 in the figure, and the voltage difference between the full-wave rectifier DB and the capacitor C1 is shared. In this embodiment, a discharge lamp is used as the load 1. A capacitor C2 connected in parallel between the non-power supply side terminals of the filament of the discharge lamp is for resonance with the inductor L1, and a sinusoidal current flows through the discharge lamp 1 due to its resonance action. The effect of reducing input current harmonics is similar to that of the embodiment shown in FIG.

FIG. 4 is a circuit diagram of a third embodiment of the present invention. In this embodiment, two inductors L2 and L3 are connected to the positive and negative sides of the full-wave rectifier DB, respectively. The effect is similar to that of the embodiment shown in FIG.

FIG. 5 is a circuit diagram of a fourth embodiment of the present invention. In this embodiment, in the embodiment of FIG.
4 is omitted. In this case, inductor L3
The function of inductor L3 in the embodiment of FIG. 4 is different from that of inductor L3 in the embodiment of FIG. First, when switching element Q2 is turned on,
A voltage is generated in the inductor L2, which shares the voltage difference between the full-wave rectifier DB and the capacitor C1, and the full-wave rectifier DB becomes conductive. Then, the input current flows through the full-wave rectifier DB and the capacitor C3.
, discharge lamp 1, inductor L1, switching element Q
2, flows in the loop of inductor L3. At this time,
Inductor L3 does not share the voltage difference like inductor L2. However, the switching element Q
2 is turned off, an induced voltage is generated in the inductor L3, and the loop of the full-wave rectifier DB, the capacitor C3, the discharge lamp 1, the inductor L1, the diode D1, the capacitor C1, and the inductor L3 causes the capacitor C1 to be turned off.
to charge. That is, inductor L3 functions as a chopper. This embodiment also has the function of eliminating inrush current of the input current, and the harmonics of the input current are reduced compared to the conventional example.

FIG. 6 is a circuit diagram of a fifth embodiment of the present invention. In this embodiment, the inductor L3 in the embodiment of FIG.
is connected to the positive side of the full-wave rectifier DB, and the capacitor C4
is added. The operation is the same as the embodiment of FIG. Moreover, the effect is also similar to that of the embodiment shown in FIG.

FIG. 7 is a circuit diagram of a sixth embodiment of the present invention. In this embodiment, a smoothing capacitor C1 is connected to the output end of the full-wave rectifier DB via an inductor L3 and a diode D3, and the diode D3 is included in the current loop of the inverter. The switching elements Q1 and Q2 are alternately turned on and off at high frequency to supply high frequency power to the load 1. Switching element Q1
When is ON, a path returns from capacitor C1 to capacitor C1 via switching element Q1, inductor L1, discharge lamp 1, and capacitor C4, and from capacitor C3 to diode D3 and switching element Q.
1, the inductor L1, and the discharge lamp 1, a current flows in a path returning to the capacitor C3. When the switching element Q2 is ON, a current flows from the capacitor C4 through the discharge lamp 1, the inductor L1, the switching element Q2, and back to the capacitor C4 in the opposite direction to the above, and high-frequency power is supplied to the discharge lamp 1. Supplied. In this circuit, capacitor C4 is essential. because,
This is because without capacitor C4, there would be no loop for discharging the current from capacitor C1. Diode D3 prevents current from being discharged from capacitor C1 when switching element Q2 is turned on, and shares the difference between the voltage of capacitor C1 and the output voltage of full-wave rectifier DB. Therefore, an input current flows from the full-wave rectifier DB through a loop including the inductor L3, the capacitor C3, the discharge lamp 1, the inductor L1, the switching element Q2, and the full-wave rectifier DB. Furthermore, the switching element Q
2 turns off, the induced electromotive force of inductor L3 turns on diode D3, which functions as a chopper to charge capacitor C1. In addition, the inrush current near the peak value of the power supply voltage is also suppressed by the inductor L3. Other than that, the effect of reducing harmonics of the input current is the same as in each of the above embodiments.

FIG. 8 is a circuit diagram of a seventh embodiment of the present invention. In this circuit, the positions of the switching elements Q1 and Q2 in the embodiment of FIG. 7 and the positions of the capacitors C3 and C4 are exchanged. In this embodiment, the inductor L3 prevents inrush current and functions as a chopper, as in the embodiment of FIG. 7.

FIG. 9 is a circuit diagram of an eighth embodiment of the present invention. This circuit is based on the position of switching elements Q1 and Q2 and the capacitors C3 and C4 in the embodiment of FIG.
The positions of the two have been swapped. In this embodiment, inductor L2 prevents inrush current, and full-wave rectifier D
Sharing the voltage difference between B and capacitor C1 is shown in Figure 1.
This is similar to the embodiment.

FIG. 10 is a circuit diagram of a ninth embodiment of the present invention. This circuit, in the embodiment of FIG.
2 is connected to the negative electrode side of the rectifier DB, and the switching elements Q1 and Q2 are MOSFETs. Therefore, the anti-parallel diodes D1 and D2 can be replaced with built-in diodes of the MOSFET shown by broken lines in the figure. Further, in this embodiment, a closed loop is formed in the inductor L2 by the diode D4 and the capacitor C5, and a current discharge loop from the inductor L2 is configured. When switching element Q2 is turned on, the voltage from capacitor C1 to capacitor C3 to inductor L1
, the discharge lamp 1, and the switching element Q2. After switching element Q2 is turned off, inductor L2 charges capacitor C5 via diode D4. As a result, switching element Q2
The stress on the circuit elements due to current discharge from the inductor L2 after the inductor L2 is turned off is reduced. This capacitor C
The voltage of 5 can be used as a control power source for the switching element Q2.

FIG. 11 is a circuit diagram of a tenth embodiment of the present invention. This circuit is the same as the inductor L in the circuit of FIG.
2, connect capacitor C5 in series with inductor L
2. A diode D3 is connected in parallel with a series circuit of a capacitor C5. The inductor L3 on the negative electrode side of the full-wave rectifier DB is omitted. In this configuration, an inrush current flows near the peak value of the power supply voltage due to the diode D3, similar to the conventional example. However, diode D3
A current flows through the impedance component connected in parallel with the inductor L2 due to the vibration of the inverter load circuit.
There is a period in which a voltage is generated across the capacitor C5 such that the diode D3 is reverse biased. During this period, current flows through inductor L2 and capacitor C5, so due to this impedance component,
Inrush current from AC power supply Vs is reduced.

[0023]

[Effects of the Invention] According to the present invention, since a smoothing capacitor is connected to the output end of the rectifier via an inductor, inrush current near the peak value of the power supply voltage can be reduced, and therefore harmonic components of the input current can be reduced. In addition, the inductor can share the voltage difference between the output voltage of the rectifier and the smoothing capacitor, allowing the input current to flow even during periods when the input voltage from the AC power supply is lower than the voltage of the smoothing capacitor. can reduce harmonic distortion of the input current,
Input power factor can be increased

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a first embodiment of the present invention.

FIG. 2 is an operation waveform diagram of the first embodiment of the present invention.

FIG. 3 is a circuit diagram of a second embodiment of the present invention.

FIG. 4 is a circuit diagram of a third embodiment of the present invention.

FIG. 5 is a circuit diagram of a fourth embodiment of the present invention.

FIG. 6 is a circuit diagram of a fifth embodiment of the present invention.

FIG. 7 is a circuit diagram of a sixth embodiment of the present invention.

FIG. 8 is a circuit diagram of a seventh embodiment of the present invention.

FIG. 9 is a circuit diagram of an eighth embodiment of the present invention.

FIG. 10 is a circuit diagram of a ninth embodiment of the present invention.

FIG. 11 is a circuit diagram of a tenth embodiment of the present invention.

FIG. 12 is a circuit diagram of a conventional example.

[Explanation of symbols]

Vs Commercial AC power supply DB Full wave rectifier C1 Smoothing capacitor C2 Resonance capacitor C3 Capacitor C4 Capacitor D1 Diode D2 Diode L1 Inductor L2 Inductor Q1 Switching element Q2 Switching element 1 Load

Claims (4)

[Claims] Claim 1: A rectifier that rectifies AC power; a first capacitor that smoothes the output of the rectifier via an inductor;
A second capacitor is connected between a series circuit of first and second switching elements to be FF, a connection point between the output end of the rectifier and the inductor, and a connection point between the first and second switching elements. An inverter device comprising a load circuit connected thereto. 2. A rectifier that rectifies an AC power source, a first capacitor that smoothes the output of the rectifier via an inductor, and a first capacitor that is connected in parallel to the first capacitor and that is turned on and off alternately.
A series circuit of first and second switching elements that are FF, a series circuit of second and third capacitors connected in parallel to the first capacitor, a connection point between the second and third capacitors, and a first and a load circuit connected between the connection point of the second switching element. 3. A rectifier that rectifies an AC power source, a first capacitor that smoothes the output of the rectifier via a series circuit of an inductor and a diode, and a first capacitor that is connected in parallel to the first capacitor and is turned on and off alternately. and a load circuit connected via a second capacitor between a connection point between the inductor and the diode and a connection point between the first and second switching elements. An inverter device featuring: 4. A rectifier for rectifying AC power; a first capacitor for smoothing the output of the rectifier via a series circuit of an inductor and a diode; a series circuit of first and second switching elements connected in parallel to the first capacitor; a series circuit of second and third capacitors connected in parallel to the first capacitor; and a connection point between the second and third capacitors and the first and third capacitors. and a load circuit connected between the connection points of the second switching element.