JP2003079151A - Ac voltage converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of a conventional AC voltage converter being poor in efficiency and requiring complicated circuit constitution, since it requires a number of circuit elements and switching elements such that it needs a circuit for determining the signal of the cycle of inverting the polarity of commercial AC voltage so as to bridge-rectify the commercial AC voltage once, to convert it into bridge-rectified voltage and to convert it again into AC in the final stage of the circuit or in its middle stage and a control circuit for driving a switch element so as to invert the polarity. SOLUTION: The AC input voltage represented by commercial AC input voltage is applied to both ends of two pairs of AC switching elements connected in series, and the point of intersection of the two pairs of AC switches and the one open end of the reactor of a filter circuit, composed of a reactor and a capacitor connected in series, are connected with each other; the one open end of the capacitor is connected to one side of AC input voltage, and the section between both ends of the capacitor or the junction between the reactor and the capacitor and the one end of AC input voltage which is not connected to the capacitor in question is constituted as the output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit system of an AC voltage converter for reducing an AC voltage.

[0002]

2. Description of the Related Art Conventionally, in order to step down an AC voltage, a circuit as shown in FIG. 1- (a) or a circuit as shown in FIG. 1- (b) has been used.

In the circuit of FIG. 1- (a), a bridge rectified voltage obtained by rectifying an AC input voltage Vac represented by a commercial AC voltage by a bridge rectifier DB is output voltage Vout.
PWM or PFM control is performed according to the increase / decrease in the feedback amount of the signal, and the switching elements Q1 and Q2 with built-in diodes are alternately turned on / off to pass through the filter circuit including the reactor L and the capacitor C, thereby stepping down the voltage. No bridge rectified voltage,
The full-bridge circuit composed of Q3, Q4, Q5 and Q6 is polarity-reversed at appropriate times in accordance with the cycle of the original commercial AC voltage, thereby obtaining an AC output of a constant voltage which is synchronized with the AC input voltage and stepped down.

In the circuit of FIG. 1- (b), the circuit of FIG.
In principle, it is the same as (a), but the switching elements Q5,
Q6 takes charge of PWM or PFM control, and constitutes a filter circuit by the reactor L and the capacitor C. The switch elements Q1, Q2, Q3 and Q4 have a role of reversing the polarity according to the cycle of the original AC input voltage. It is a circuit that also has the function of a bridge rectifier.

[0005]

As described above, in the conventional circuit, the AC input voltage is once bridge rectified,
A circuit that determines the signal of the polarity reversal cycle of the AC input voltage to convert it to a bridge rectified voltage and at the final stage or intermediate stage of the circuit to make it alternating current, and further drives the switch element to perform polarity reversal. A large number of circuit elements and switch elements such as a control circuit are required, and a complicated circuit configuration is required.

Further, in these circuits, a large amount of power loss occurs because the current passes through many switching elements and rectifying elements.

An object of the present invention is to realize an inefficient AC voltage converter by such a complicated control method and an AC voltage converter of high efficiency by a simple control method with a simple circuit.

[0008]

In order to achieve the above object, however, the present invention applies an AC input voltage represented by a commercial AC input voltage to both ends of two pairs of AC switch elements connected in series, and Connect the intersection of two pairs of AC switches and the open end of the reactor of the filter circuit consisting of a reactor and a capacitor connected in series, connect the open end of the capacitor to one side of the AC input voltage, and connect both ends of the capacitor. Configure as output.

The two pairs of AC switch elements are PWM,
According to the modulation method typified by PFM, the output voltage across the capacitor is compared with the AC reference voltage synchronized with the input voltage, and the result is compared with two pairs of AC by the modulation method typified by PWM or PFM. Switch ON / OFF alternately
The output can be obtained across the capacitor as a stepped down stabilized AC voltage synchronized with the AC input voltage by the filter circuit including the reactor and the capacitor which is turned off. Alternatively, it can be output between the connection point of the reactor and the capacitor and one end of the AC input voltage that is not connected to the capacitor.

It is also possible to obtain a stepped up or stepped down output by connecting an autotransformer or an insulation transformer to the output.

The above-mentioned AC reference voltage can be provided by making the AC voltage obtained by dividing the AC input voltage constant by comparing the average value, which is an effective value, with a preset DC reference voltage. Alternatively, an externally generated sinusoidal AC reference voltage synchronized with the AC input voltage can be provided as the reference voltage.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is an example of the embodiment of the present invention.

Q1, Q2, Q3 and Q4 are IGBs each having a built-in diode as a typical DC switch element.
A description will be given using T as an example.

Further, FIG. 3 illustrates the PWM modulation method as an example.

Q1 and Q2, and Q3 and Q4 in FIG. 2 are respectively connected to the emitter and gate of the IGBT in common, and are constructed as two pairs of AC switch elements.

A PWM waveform modulated as shown by AB in FIG. 3 is applied between the gate and the emitter of the AC switch composed of Q1 and Q2, and the AC switch composed of Q3 and Q4. Between the gate and emitter is E- in FIG.
An inverted PWM waveform of A-B is added as indicated by F.

Therefore, the voltage of the PWM-modulated waveform of the input AC voltage Vac shown by Vo in FIG. 3 appears in Vo in FIG. 2, and the voltage is changed by the filter circuit including the reactor L and the capacitor C provided later. The stabilized AC output of which the input AC voltage Vac represented by Vout of 3 is stepped down is output.

Further, by connecting an autotransformer or an insulation transformer, it is possible to obtain a stepped-up or stepped-down output. An example of the case where the input AC voltage is stepped down by the autotransformer is shown in FIG. a) and FIG. 5- (b).

Further, in the circuit diagram of FIG. 2, the reactor L,
Instead of using the filter circuit of the capacitor C, the PWM waveform appearing at Vo is directly supplied as a load to an inductance utilizing component such as a motor, so that an AC current is caused to flow by the smoothing action of this inductance utilizing component, similar to the above filter circuit. Can also play a role.

Further, the filter circuit composed of the reactor L and the capacitor C may have various configurations as shown in FIGS. 4 (a) and 4 (b).

[0021]

The present invention has the following effects because each part is configured as described above.

An AC output voltage can be obtained by simply turning ON / OFF two pairs of AC switch elements by a modulation method typified by PWM, PFM, etc., and rectifies the input AC voltage as seen in conventional circuits. , And a high-efficiency alternating current that does not require a control circuit, switch element, or rectifying element that synchronizes with the input alternating voltage and returns to alternating current output, and the circuit itself is simple and does not cause unnecessary switch or rectifying element circuit loss. A voltage converter can be realized.

Further, in the circuit of FIG. 2, a pair of DC switch elements, for example, an emitter and a gate of an IGBT can be connected to each other to form an AC switch element in combination with a diode built in the IGBT. PWM composed of a similar AC switch element,
The AC voltage conversion device can be realized by a very simple circuit in which the control circuit of the modulation circuit typified by PFM or the like only sends the modulation signal to the gates connected to each of the two pairs of AC switch elements.

In the circuit of FIG. 2, by combining a transformer with the output, an AC constant voltage power supply, a motor control power supply,
This is an industrially very useful invention in which a voltage conversion device, a power saving device, etc. can be realized with a very simple and highly efficient circuit.

[Brief description of drawings] [Explanation of symbols]

Vac AC input voltage Q1 DC switch element Q2 DC switch element Q3 DC switch element Q4 DC switch element Q5 DC switch element Q6 DC switch element Vout Stable AC output Vo Input AC voltage Vac PWM modulated waveform voltage L Reactor C capacitor DB Bridge rectifier A-B Input end E-F Input end T Autotransformer

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[Procedure amendment]

[Submission date] November 21, 2001 (2001.11.
21)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is an example of a conventional circuit.

FIG. 2 shows an example of an embodiment of the present invention.

FIG. 3 is a waveform of each part.

FIG. 4 shows an example of a filter circuit.

FIG. 5 is an example of a circuit that steps down an input AC voltage with an autotransformer.

[Explanation of Codes] Vac AC input voltage Q1 DC switching element Q2 DC switching element Q3 DC switching element Q4 DC switching element Q5 DC switching element Q6 DC switching element Vout Stable AC output Vo Input of PWM modulated waveform of input AC voltage Vac Voltage L Reactor C Capacitor DB Bridge rectifier AB Input end EF Input end T Autotransformer

Claims (5)

[Claims] 1. An AC input voltage typified by a commercial AC input voltage is applied to both ends of two pairs of AC switch elements connected in series, the intersection of the two pairs of AC switches, and a reactor and a capacitor connected in series. Connect the open end of the reactor of the filter circuit consisting of, connect the open end of the capacitor to one side of the AC input voltage, and connect both ends of the capacitor or the connection point between the reactor and the capacitor and the AC that is not connected to the capacitor. An AC voltage conversion device configured as an output between one end of an input voltage and the output. 2. The two pairs of AC switching elements described in claim 1 are compared with an output voltage across the capacitor and an AC reference voltage synchronized with the input voltage according to a modulation system represented by PWM, PFM or the like. As a result, the two pairs of AC switches are alternately turned ON / OFF by the modulation method typified by PWM, PFM, etc., and the voltage is stabilized in a step-down manner synchronized with the AC input voltage by the filter circuit including the reactor and the capacitor. An AC voltage converter that can obtain an output across a capacitor as an AC voltage. 3. An AC voltage conversion device realized by connecting a gate and an emitter of a pair of IGBTs to each other, when the AC switch element is an IGBT of a typical DC switch element. 4. An AC input voltage is applied to both ends of two pairs of AC switch elements connected in series to bridge-rectify the AC input voltage to convert it into a bridge rectified voltage, and at the final stage or an intermediate stage of the circuit. An AC voltage converter that does not require a circuit to convert it to AC again. 5. A transformer is connected to the output described in claim 1,
An AC voltage converter configured to step up or step down a voltage.