JP2000232793A - Inverter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an inverter in which the number of switching elements can be decreased. SOLUTION: An AC voltage corresponding to the voltage of a DC power supply and the turn ratio of a transformer 4 is generated in the secondary winding 4c thereof by turning switching elements 2, 3 on/off alternately. The voltage generated in the secondary winding 4c of the transformer 4 is fed through a diode 6 to a capacitor 8 when the polarity is in the directed shown by an arrow of solid line and fed through a diode 5 to a capacitor 7 when the polarity is in the directed shown by an arrow of dot line. Under that state, switching elements 9, 10 are turned on/off alternately at a specified interval. When the switching element 9 is turned on, charging voltage of the capacitor 7 is outputted from the output terminals 11a, 11b and when the switching element 10 is turned on, charging voltage of the capacitor 8 is outputted from the output terminals 11a, 11b. Consequently, an AC voltage of specified frequency is outputted from the output terminals 11a, 11b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter, and more particularly, to an inverter having a reduced number of switching elements.

[0002]

2. Description of the Related Art Conventionally, an inverter having a configuration as shown in FIG. 2 is known. The inverter shown in FIG. 2 includes a DC power supply 31 such as a battery, a transformer 34, a full-wave rectifier circuit 35, a capacitor 36, and switching elements 32, 33, 37 to 4
0 or the like. Switching element 37-4
0 forms a bridge type inverter. The primary windings 34a and 34b of the transformer 34 and the secondary winding 3
4c are connected as shown by the arrows.

The inverter having the configuration shown in FIG. 2 operates as follows. When the switching element 32 is on and the switching element 33 is off, the DC power supply 31
The excitation current flows through the primary winding 34a in the direction indicated by the solid line arrow shown in FIG. Thereby, the secondary winding 3 of the transformer 34
At 4c, a voltage having a polarity in the direction of the solid arrow shown in FIG. 2 is generated. On the other hand, when the switching element 32 is off and the switching element 33 is on, an exciting current flows from the DC power supply 31 to the primary winding 34b of the transformer 34 in the direction of the dotted arrow shown in FIG. As a result, a voltage having a polarity in the direction of the dotted arrow shown in FIG. 2 is generated in the secondary winding 34c of the transformer 34. By alternately turning on and off the switching elements 32 and 33 in this manner, the transformer 34
In the secondary winding 34c, a voltage having a polarity in the directions of the solid arrow and the dotted arrow is generated alternately. The voltage generated in the secondary winding 4c of the transformer 4 is converted into a DC voltage by the rectifier circuit 35, and then supplied to the capacitor 36. This allows
The capacitor 36 is charged to the polarity shown. In this state,
When the switching elements 37 and 40 are turned on and the switching elements 38 and 39 are turned off, the charging voltage of the capacitor 36 is output to the output terminals 41a and 41b via the switching elements 37 and 40. At this time, the output terminal 41
A voltage is output such that the a side is positive and the output terminal 41b side is negative. On the other hand, when the switching elements 37 and 40 are turned off and the switching elements 38 and 39 are turned on, the charging voltage of the capacitor 36 is output to the output terminals 41a and 41b via the switching elements 38 and 39. At this time, a negative voltage is output on the output terminal 41a side and a positive voltage is output on the output terminal 41b side. Thus, the switching elements 37 and 40
And the combination of the switching elements 38 and 39 are turned on and off alternately, so that the output terminal 41
a and 41b output an AC voltage. Output terminal 41
The frequency of the AC voltage output from a and 41b can be changed by adjusting the ON / OFF cycle of the switching elements 37 to 40.

[0004]

Such a conventional inverter has four switching elements 3 as switching elements for converting the charging voltage of the capacitor 36 into an AC voltage.
Requires 7-40. When the number of switching elements is large, the cost increases and the configuration of a control circuit that controls the switching elements becomes complicated. The present invention has been made in view of such a point, and it is an object of the present invention to provide an inverter that can reduce the number of switching elements.

[0005]

According to a first aspect of the present invention, there is provided an inverter according to the present invention. When the inverter according to the first aspect is used, the number of switching elements can be reduced, so that the cost is reduced and the configuration of a control circuit for controlling the switching elements is simplified. A second aspect of the present invention is an inverter according to the second aspect.
When the inverter according to claim 2 is used, the first and second inverters can be used.
Since the DC power supply circuit can be constituted by a capacitor, it is inexpensive and can be constituted by a simple circuit. According to a third aspect of the present invention, there is provided an inverter according to the third aspect. If the inverter according to claim 3 is used, the number of diodes constituting the charging means for charging the first capacitor and the second capacitor can be reduced, so that the cost is reduced and the circuit is configured with a simple circuit. be able to.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an embodiment of the inverter according to the present invention. The inverter shown in FIG. 1 includes a DC power supply 1 such as a battery, a transformer 4, diodes 5, 6, capacitors 7, 8, switching elements 2, 3,
9, 10, and the like. The switching elements 2, 3, 9, 10 are transistors or MOS transistors.
Various switching elements such as a semiconductor switching element such as an FET and a mechanical switching element can be used. Although not shown, the switching element 2,
A control circuit for controlling 3, 9, 10 is provided.

The transformer 4 includes divided primary windings 4a and 4b and a secondary winding 4c. And
The series circuit of the DC power supply 1 and the switching element 2 is connected to the terminals A and B of the primary winding 4a, and the series circuit of the DC power supply 1 and the switching element 3 is connected to the terminals B and C of the primary winding 4b. ing. The DC power supply 1, the switching elements 2, 3, and the transformer 4 constitute a DC-AC (DC-AC) conversion circuit. A series circuit of a diode 5 and a capacitor 7 and a series circuit of a diode 6 and a capacitor 8 are connected to terminals D and E of the secondary winding 4c of the transformer 4. The diode 5 has an anode connected to the terminal D and a cathode connected to a terminal P connected to one terminal of the capacitor 7. The diode 6 has a terminal N whose anode is connected to the other terminal of the capacitor 8.
, And the cathode is connected to the terminal D. The other terminal of the capacitor 7 and one terminal of the capacitor 8 are connected to a terminal G connected to the terminal E. Thus, the capacitor 7 is charged so that the terminal connected to the terminal P has a positive polarity and the terminal connected to the terminal G has a negative polarity, and the capacitor 8 is connected to the terminal G. The terminal connected to the terminal N has a positive polarity, and the terminal connected to the terminal N has a negative polarity. Capacitor 7
A DC power supply circuit is constituted by the capacitor 8 and the DC power supply 1, the switching elements 2, 3, the transformer 4, and the diodes 5, 6 constitute a charging circuit. In this specification, the terminals of the positive and negative capacitors 7 and 8 are referred to as a terminal having one polarity and a terminal having the other polarity, respectively. The switching element 9 is connected between the terminal P and the output terminal 11a, and the switching element 10 is connected between the terminal N and the output terminal 11a. Also, terminal G
Is connected to the output terminal 11b. DC-AC (DC-A)
C) A conversion circuit is configured.

Next, the operation of the inverter shown in FIG. 1 will be described. The switching element 2 and the switching element 3 are alternately turned on and off by the control circuit. The switching elements 2 and 3 are turned on and off at a cycle of, for example, 50 KHz. When the switching element 2 is on, the exciting current flows through the primary winding 4a of the transformer 4 in the direction of the solid arrow shown in FIG. 1, and the secondary winding 4c has the polarity in the direction of the solid arrow shown in FIG. Voltage is generated. The value of the voltage generated in the secondary winding 4c is determined by the voltage of the DC power supply 1 and the turns ratio between the primary winding 4a and the secondary winding 4c of the transformer 4. At this time, since the diode 6 becomes conductive, the voltage generated in the secondary winding 4c is supplied to the capacitor 8, and the capacitor 8 is charged. Since the diode 5 is in a non-conductive state, the capacitor 7 is not charged. On the other hand, when the switching element 3 is turned on, the exciting current flows through the primary winding 4b of the transformer 4 in the direction of the dotted arrow shown in FIG. 1, and flows through the secondary winding 4c in the direction of the dotted arrow shown in FIG. A voltage of the polarity is generated. The value of the voltage generated in the secondary winding 4c is determined by the voltage of the DC power supply 1 and the turn ratio between the primary winding 4b and the secondary winding 4c of the transformer 4. At this time, since the diode 5 becomes conductive, the voltage generated in the secondary winding 4c is supplied to the capacitor 7, and the capacitor 7 is charged. The diode 6
Is non-conductive, the capacitor 8 is not charged. By alternately turning on and off the switching elements 2 and 3 in this manner, the capacitor 7 is connected to the terminal G on the side connected to the terminal G so that the terminal connected to the terminal P has a positive polarity. The terminal is charged so as to have a positive polarity.

In this state, the switching element 9 and the switching element 10 are alternately turned on and off by the control circuit. The ON / OFF cycle of the switching elements 9 and 10 is determined by the frequency of the AC voltage output from the output terminals 11a and 11b. When the switching element 9 is turned on and the switching element 10 is turned off, the charged voltage of the capacitor 7 is changed to the output terminals 11a and 11a.
b. At this time, since the capacitor 7 is charged so that the terminal connected to the terminal P has a positive polarity, the output voltage has a positive polarity on the output terminal 11a side and a negative polarity on the output terminal 11b side. On the other hand, when the switching element 9 is off and the switching element 10 is on, the charging voltage of the capacitor 8 is output from the output terminals 11a and 11b. At this time, since the capacitor 8 is charged so that the terminal to which the terminal G is connected has a positive polarity, the output voltage is negative on the output terminal 11a side and the output terminal 1
The 1b side has a positive polarity. As described above, by alternately turning on and off the switching elements 9 and 10 at a predetermined cycle, an AC voltage having a predetermined frequency is output between the output terminals 11a and 11b. The peak value of the AC voltage output between the output terminals 11a and 11b is determined by the voltage value of the DC power supply 1 and the turns ratio between the primary winding and the secondary winding of the transformer 4.

As described above, in the present embodiment, since the inverter can be constituted by the two switching elements 9 and 10, the number of switching elements can be reduced as compared with the conventional inverter. This allows
The cost is reduced, and the configuration of the control circuit for controlling the switching element is simplified. Also, capacitors 7 and 8
Can be constituted by the two diodes 5 and 6, the cost is reduced and the circuit configuration is simplified.

In the above embodiment, the DC power supply circuit includes the DC power supply 1, the switching elements 2, 3, the transformer 4,
Although the capacitors 7 and 8 that are charged by the charging circuit constituted by the diodes 5 and 6 are used, the DC power supply circuit is not limited to the capacitor, and various power supply circuits can be used. Further, the charging circuit is configured by a half-wave rectifier circuit, but may be configured by a full-wave rectifier circuit or the like. Further, although the AC power supply circuit is constituted by the DC power supply and the DC-AC conversion circuit, the AC power supply circuit is not limited to this, and various power supply circuits can be used. Further, the ON / OFF cycle of the switching elements 2 and 3 and the ON / OFF cycle of the switching elements 9 and 10 can be appropriately changed.

[0012]

As described above, the number of switching elements can be reduced by using the inverters according to the first to third aspects.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of an inverter according to the present invention.

FIG. 2 is a schematic configuration diagram of a conventional inverter.

[Explanation of symbols]

 4 Transformer 5, 6 Diode 7, 8 Capacitor 2, 3, 9, 10 Switching element

Claims (3)

[Claims] A first DC power supply circuit; a second DC power supply circuit; a first switching element; a second switching element; and a pair of output terminals. A terminal of one polarity is connected to one output terminal via the first switching element, a terminal of the other polarity is connected to the other output terminal, and the second DC power supply circuit A polarity terminal is connected to one output terminal via a second switching element, one polarity terminal is connected to the other output terminal, and the first switching element and the second switching element alternate. An inverter that is turned on and off. 2. The inverter according to claim 1, wherein:
An inverter in which a first DC power supply circuit and a second DC power supply circuit are respectively constituted by a first capacitor and a second capacitor, and further comprising a charging means for charging the first capacitor and the second capacitor. 3. The inverter according to claim 2, wherein:
The charging means includes an AC power source, a first diode connected between the AC power source and a terminal of one polarity of the first capacitor, and a first diode connected between the AC power source and a terminal of the other polarity of the second capacitor. Having a second diode connected to the inverter.