JP2573229B2 - Variable voltage and variable frequency power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a variable voltage / variable frequency power supply device used for speed control of a small single-phase induction motor, a computer, and the like, and particularly to an improvement in the input current waveform and output power waveform. It is about.

[Prior Art] An example of a conventional variable voltage / variable frequency power supply device will be described with reference to FIG.

In the figure, (1) is a diode, and a converter circuit (F) is formed by four diodes (1). (2) is a capacitor, which smoothes the DC voltage rectified by the smoothing circuit (G).
(3) is a switching element composed of a combination of a flywheel diode (3d) and a transistor (3t). An inverter circuit (H) is formed by combining the four switching elements (3).

Such a conventional variable voltage / variable frequency power supply,
It works as follows.

The single-phase AC input voltage is applied to the converter circuit (F) via a protection circuit (not shown) such as an insulating transformer, a surge killer, and a noise filter.

Then, the single-phase AC input voltage is rectified and converted into a DC voltage by the bridge-type converter circuit (F) including the four diodes (1).

That is, in this figure, the upper side is the positive voltage side and the lower side is the negative voltage side.

The waveform of the DC voltage obtained by the converter circuit (F) in this way includes a large ripple. For this reason, this is smoothed by the capacitor (2) of the smoothing circuit to obtain a DC voltage in which the ripple is reduced to several percent. Then, this DC voltage is input to the inverter circuit (H).

The switching element (3) of the inverter circuit (H) is switching-controlled by a control circuit (not shown), and converts an input DC voltage into AC power having a constant voltage and a constant frequency.

Here, the switching control is performed by the transistor (3
t) is controlled by PAM (pulse amplitude modulation) or PWM (pulse width modulation) control.

[Problems to be Solved by the Invention] Since the conventional variable voltage / variable frequency power supply device is configured as described above, only four diodes, one smoothing capacitor of required capacity, and a transistor are required in the basic circuit alone. There was a problem that the number of necessary parts was large, four, and the cost was high.

In addition, since the inverter circuit (H) is switched at a high frequency, noise such as radio noise is generated, and between the power input unit (a in FIG. 5) and the power output unit (b in FIG. 5). In addition, there is a problem that a step-like voltage change occurs, noise cannot be removed unless a transformer, a good filter, and the like are used, and the efficiency is deteriorated. In addition, there is a problem that power cannot be regenerated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and it has been made possible to reduce the number of components, simplify the circuit, reduce the loss, improve the input power waveform control power factor, reduce the generated noise, and simplify the filter. It is an object of the present invention to obtain a variable voltage / variable frequency power supply device capable of realizing power regeneration.

[Means for Solving the Problems] A variable voltage / variable frequency power supply device according to the present invention is connected to a converter circuit for converting AC power to DC power by the converter circuit and a smoothing circuit, and is converted by the converter circuit. And an inverter circuit that converts the converted DC power into AC power, and a variable voltage / variable frequency power supply device that outputs AC power obtained by converting the voltage or frequency of the AC power input from the input terminal pair from the output terminal pair. The converter circuit has a configuration in which two switching means in which a switching element and a flywheel diode are connected in parallel are connected in series, and the inverter circuit includes a switching means in which a switching element and a flywheel diode are connected in parallel. One of the input terminal pairs having a configuration in which two are connected in series; A terminal is connected to an intermediate connection point between two switching means constituting the converter circuit, and one terminal of the output terminal pair is connected to an intermediate connection point between the two switching means constituting the inverter circuit; The other terminal of the input terminal pair is
Connected to the other terminal of the output terminal pair, the smoothing circuit has a configuration in which two capacitors are connected in series, and an intermediate connection point between the two capacitors is connected to the other terminal of the input terminal pair. And a variable voltage / variable frequency power supply device connected to the other terminal of the output terminal pair.

Further, a variable voltage / variable frequency power supply device, wherein an intermediate connection point of the two capacitors, and the other terminal of the input terminal pair and the other terminal of the output terminal pair are connected via a switch. It is.

Further, in a power supply device having an AC power input, a converter circuit for converting the DC power into DC power, a smoothing circuit for smoothing the DC power, and an inverter circuit for converting the DC power into a predetermined AC power, The circuit is formed by connecting two rectifying elements in series, the inverter circuit is formed by connecting two switching elements consisting of a flywheel diode and a transistor in series, and the smoothing circuit is formed by connecting two capacitors. One of a pair of AC power input sections is connected to an intermediate section connecting two rectifying elements of the converter circuit, and one of a pair of AC power output sections is connected to two of the inverter circuit. A switching element connected to an intermediate portion, and the other of the pair of AC power input portions and the pair of AC The other of the output terminals is connected, and an intermediate connection point of the two capacitors is connected to the other terminal of the input terminal pair and the other terminal of the output terminal pair via a switch. It is a variable voltage / variable frequency power supply device.

[Operation] The variable voltage / variable frequency power supply device according to the present invention includes:
Only one terminal of the input pair of AC power is connected to the converter circuit, and the other terminal is directly connected to the output terminal. Therefore, conversion is performed on only one terminal by the converter circuit, and smoothing and conversion by the inverter circuit are performed.

As a result, both the converter circuit and the inverter circuit can be constituted by a so-called half-bridge circuit, and the number of components can be reduced.

In addition, since the inverter circuit and the converter circuit have the same configuration, the input / output relationship is a target configuration. Therefore, when power is supplied from the output terminal, power can be input from the output terminal, and power can be output from the terminal that has been the input terminal. That is, so-called power regeneration is possible.

Further, since the intermediate connection point of the capacitor and the other terminal of the input terminal pair and the other terminal of the output terminal pair are connected via a switch, by turning off this switch, the input unit and the output unit are turned off. And can be directly connected.

Embodiment of the Invention A variable voltage / variable frequency power supply device according to a first embodiment of the present invention will be described with reference to FIG.

In the figure, (A) is a converter circuit, which is formed by connecting the diodes (1) in series.

(B) is a smoothing circuit connected in parallel to the converter circuit (A). This smoothing circuit (B) is formed by two capacitors connected in series.

(C) is an inverter circuit connected to the smoothing circuit (B). The inverter circuit (C) comprises two switching elements (3) connected in series.

This switching element (3) is a transistor (3t)
And a flywheel diode (3d) connecting between the collector and the emitter.

One of the single-phase AC voltage power input units (5)
It is connected to the two diodes (1) and the intermediate part of the converter circuit (A).

One of the power output units (6) is connected to an intermediate portion between two switching elements of the inverter circuit (C).

The other of the power input unit (5) and the power output unit (6)
Are connected by one connection line. This connection line is grounded and through a switch (4),
It is connected to an intermediate portion between two capacitors (2) of the smoothing circuit (B).

 Next, the operation of the first embodiment will be described.

The single-phase AC voltage is input from the power input unit (5),
One of the power input portions (5) is connected to one of the power output portions (6) by one connection line. Since this connection line is grounded, it is maintained at a predetermined potential.

The other end of the power input section (5) is connected by a connection line to an intermediate portion between two diodes of the converter circuit (A).

Since the diodes (1) are connected in series in the same direction, current flows only upward in the figure and is rectified. The DC voltage including the large ripple component obtained in this manner is supplied to the smoothing circuit (B).
Is smoothed. This gives a few percent ripple
The following DC voltage is obtained.

This DC voltage is converted into AC power of a predetermined voltage and frequency by the inverter circuit (C). Switching in the inverter circuit (C) is performed by, for example, the following PWM control. This PWM control obtains AC power of a predetermined voltage and frequency by modulating and controlling the width of a pulse applied to the base of the transistor (3t).

The upper shaded portion in FIG. 3 indicates the conduction state of the upper switching element (3) in FIG. 1, and the lower shaded portion in FIG. 3 indicates the lower switching element in FIG. (3) shows the conduction state. By such switching control, an output power having a waveform as shown by a curve (7) in FIG. 3 is obtained.

Here, the DC voltage output from the smoothing circuit (B) is Ed
From 2 to -Ed. When the switch (4) is turned on, the potential at the intermediate point of the smoothing circuit (B) becomes 0 V, which is exactly intermediate between Ed and -Ed. In addition,
The switch (4) is turned off, and the inverter circuit (C)
When the two switching elements are turned on, the power input unit (5) can be connected to a power supply, and the power output unit (6) can be connected to a load such as a motor.

Thus, in the first embodiment, the converter (A) has two diodes (1) and the inverter (C) has two switching elements (3).

That is, this circuit is a half-bridge circuit composed of half of the conventional circuit. Therefore, the number of parts can be reduced.

In this circuit, one of the input unit and the output unit is connected by one connection line. Therefore, there is no voltage change here, and it is possible to prevent the output from being affected by noise. Further, since this connection line is grounded, a step-like change in the potential between the input and output does not appear, and the generation of noise is reliably prevented.

Further, a sinusoidal voltage fundamental wave as shown in FIG. 3 can be generated by the above-described PWM control, and a sinusoidal wave variable voltage / variable frequency output voltage can be obtained.

Next, a variable voltage / variable frequency power supply device according to a second embodiment of the present invention will be described.

In this embodiment, a converter (D) is used instead of the converter (A) in FIG.

This converter D is composed of two switching elements (3). For this reason, the circuit in this example has exactly the same configuration as viewed from both the input side and the output side. Also, since the switching element is bidirectional with respect to the current, it can be both an inverter and a converter. Therefore, a power supply (8) is connected to the input side, and a load (9) is connected to the output side.
When the power supply (8) is connected to the power supply (8), power regeneration can be performed.

When the switch (4) is turned on, the smoothing circuit (B)
When the capacitor is charged, the inverter (E) side is subjected to PWM control, so that a waveform of a shaded portion as shown in FIG. 3 is generated at the output (6), and an inverter (E) not shown , A sinusoidal voltage fundamental wave is obtained. (In this case, the inverter (E)
Acts as an inverter that converts DC voltage to AC voltage. Also, when energy is regenerated from the load on the output side, when the switch (4) is turned on, the smoothing circuit (B)
Are charged, and the converter (D) side is subjected to PWM control, so that a shaded waveform as shown in FIG. 3 is generated at the input (5), and the input side of the converter (D) not shown. A sinusoidal voltage fundamental wave is obtained by the filter described above, and by controlling the current to flow to the input side, a so-called regenerative operation in which power flows backward from the output (6) to the input (5) is possible.

Further, a switch (4) is added, the switch (4) is turned off, and the switching element (3t) of the upper arm of each of the converter circuit (D) and the inverter circuit (E) is turned on, and the switching of the lower arm is performed. By turning off (blocking) the element (3t) or by turning off the switching element (3t) of each upper arm and turning on the switching element (3t) of each lower arm, or of the converter (D). By turning off the two switching elements and turning on the two switching elements of the inverter circuit (E), the input section can be directly connected to the output section. Therefore, the input power can be output without conversion. Furthermore, by switching the switching elements (3t) of the converter circuit and the inverter circuit, which are turned on, at a frequency higher than the input frequency, the average output voltage can be varied, and the power supply to the load can be varied.

In the above embodiment, a bipolar transistor is shown as a transistor with a flywheel diode. However, a MOSFET transistor may be used.

[Effect of the Invention] As described above, according to the variable voltage / variable frequency power supply device of the present invention, the converter circuit and the inverter circuit
Since it has the same configuration, the input / output direction of power can be arbitrarily selected. Therefore, when the power flows backward from the output side, a so-called regenerative operation can be performed, and as a result, a power supply device with higher efficiency can be obtained.

Further, when a capacitor is used in the smoothing circuit, a power supply device capable of easily reducing a DC ripple can be obtained.

Further, according to the variable voltage / variable frequency power supply device of the present invention, the converter circuit and the inverter circuit (voltage and frequency adjustment circuit) can be constituted by four switching elements or two diodes and two switching elements. For this reason, the number of parts is small and the apparatus can be inexpensive. Furthermore, noise generated is reduced, the filter is simplified, and a highly accurate power supply device is obtained.

Further, when the switch connecting the intermediate connection point of the capacitor and the other terminal of the input terminal pair and the other terminal of the output terminal pair is turned off, the input unit and the output unit are directly connected, and the voltage of the input unit is changed. Can be directly output to the output unit.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a basic circuit of a variable voltage / frequency power supply device according to one embodiment of the present invention, FIG. 2 is a circuit diagram of a basic circuit showing another embodiment of the present invention, and FIG. FIG. 4 is a circuit diagram showing a basic circuit of a conventional variable voltage / variable frequency power supply device. (1) is a diode, (2) is a capacitor, (3) is a switching element, (4) is a switch, (A), (D),
(F) is a converter circuit, (B) is a smoothing circuit, (C),
(E) and (H) are inverter circuits. In the drawings, the same reference numerals indicate the same or corresponding parts.

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-51-72742 (JP, A)

Claims (3)

(57) [Claims] 1. A converter circuit for converting AC power into DC power, and an inverter circuit connected to the converter circuit by a smoothing circuit and converting DC power converted by the converter circuit into AC power. In a variable voltage / variable frequency power supply device for outputting AC power obtained by converting the voltage or frequency of AC power input from a terminal pair from an output terminal pair, the converter circuit includes a switching element and a flywheel diode connected in parallel. The inverter circuit has a configuration in which two switching means in which a switching element and a flywheel diode are connected in parallel are connected in series, and the smoothing circuit has two components. Of the input terminal pair. A terminal connected to an intermediate connection point between two switching means constituting the converter circuit; one terminal of the output terminal pair is connected to an intermediate connection point between the two switching means constituting the inverter circuit; An intermediate connection point between the two capacitors is connected to the other terminal of the input terminal pair and the other terminal of the output terminal pair, and the other terminal of the input terminal pair is connected to the other terminal of the output terminal pair. A variable voltage / variable frequency power supply device. 2. The variable voltage / variable frequency power supply device according to claim 1, wherein an intermediate connection point between said two capacitors, and the other terminal of said input terminal pair and said other terminal of said output terminal pair. The variable voltage / variable frequency power supply device is connected through a switch. 3. A power supply apparatus having an AC power input, a converter circuit for converting the DC power into DC power, a smoothing circuit for smoothing the DC power, and an inverter circuit for converting the DC power into a predetermined AC power. The converter circuit is formed by connecting two rectifying elements in series, the inverter circuit is formed by connecting two switching elements each including a flywheel diode and a transistor in series, and the smoothing circuit is formed by two Are connected in series, and one of the pair of AC power input units is connected to the
And one of a pair of AC power output sections is connected to the intermediate section connecting the two rectifier elements.
The other of the pair of AC power input sections and the other of the pair of AC power output sections, and an intermediate connection point between the two capacitors and the input terminal pair. And the other terminal of the output terminal pair is connected via a switch.