JPS6295979A - Constant voltage and constant frequency power source device - Google Patents

Abstract

PURPOSE:To securely prevent a transformer and the like set on the output side of a constant voltage and constant frequency output(CVCF)circuit from being damaged owing to DC excitation, by reducing and correcting the DC deviation of the output voltage of the CVCF circuit always and automatically. CONSTITUTION:The input of the output voltage of a CVCF circuit 3 to a low pass filter 71 is provided, and DC component only is taken out, and the DC component is inputted to an amplifying circuit 73 via an insulation amplifying circuit 72. By the amplifying circuit 73, the specified correction quantity of DC deviation is determined, and the correction quantity is added to a reference sine wave by an adder 74. As a result, the DC component of the reference sine wave is corrected and controlled by DC deviation, and is fed to a PWM pulse control circuit 62. By the output of control signal generated from the PWM pulse control circuit 62, the inverter of the CVCF circuit is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a constant voltage constant frequency power supply device that supplies a constant voltage constant frequency output to a load.

[Conventional technology]

FIG. 5 is a block diagram showing an outline of a conventional constant voltage constant frequency power supply device. In the figure, 1 is an AC power supply, 2 is a transformer that transforms the output voltage of the AC power supply 1, and 3 is a transformer 2.
A constant voltage constant frequency output circuit (hereinafter abbreviated as CVCF circuit) that obtains a constant voltage constant frequency output based on the blade of the blade. 4 is a transformer that transforms the constant voltage constant frequency output from the CVCF circuit 3 and supplies it to the load 5.

The upper dpi CVCF circuit 3 is a converter 3 that converts the AC power from the AC power supplied via the transformer 2 into DC.
1, an inverter 32 that converts the output of this converter 31 into alternating current, and an alternating current filter 33.
The inverter 32 is controlled by a control circuit 6.

[Problem that the invention seeks to solve]

Conventional constant voltage constant frequency power supplies are configured as described above, so the cutting voltage is a sine wave, but due to changes in control drift, changes in the reference sine wave command, etc., a DC component is applied to the output, resulting in a DC voltage. Produces biased magnetism. When this DC bias magnetization occurs, there is a problem that the transformer provided on the output side of the CVCF circuit is not excited by DC current, and the DC ML current flows to the next side and is heated, causing the transformer to burn out.

This invention was made to solve the above problems.
The object of the present invention is to obtain a constant voltage, constant frequency power supply device that can automatically correct direct current biased magnetism.

[Means for solving problems]

The constant voltage constant frequency power supply device according to the present invention extracts a DC component from an output voltage, amplifies this DC component to obtain a DC bias correction amount, and adds the DC bias correction amount and a reference sine wave. It has a correction circuit that corrects and controls the direct current component of the direct multiple sine wave using direct current bias magnetism.

[Effect]

The correction circuit in this invention automatically corrects the DC bias of the output voltage by correcting the DC component of the reference sine wave with the DC bias of the output voltage of the CVCF circuit. To ensure that inconveniences are prevented.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 7 is a correction circuit that detects the amount of DC bias in the output voltage of the CVCF circuit 3 and corrects the amount of DC bias.

FIG. 2 is a block diagram showing an example of the control circuit 6 and correction circuit 7. The control circuit 6 is composed of a reference sine wave generation circuit 61 and a PWM pulse control circuit 62.

On the other hand, the correction circuit 7 includes a low-pass filter 71 that extracts only the DC component from the 60 Hz output voltage of the CVCF circuit 3;
The DC voltage obtained by this low-pass filter 71 is
An insulated amplifier circuit 72 that insulates the F circuit side and the control circuit side and sends the signal to the control circuit side, an amplifier circuit 73 that obtains a predetermined correction amount of DC bias magnetism, and a DC bias feedback correction from this amplifier circuit 73. The adder 74 adds the reference sine wave from the reference sine wave generation circuit 61 and corrects and controls the DC component of the reference sine wave using DC bias magnetism.

Figure 3 shows the output voltage of the CVCF circuit 3, (a
) is a normal output voltage without DC bias, (b) is an output voltage with DC bias in the positive direction, and (C) is an output voltage with DC bias in the negative direction.

FIG. 4 is a diagram showing the relationship between the amount of DC biased magnetism and the correction amount, where the horizontal axis is the amount of DC biased magnetism, and the vertical axis is the amount of correction. In the figure, a%C point is the amount of direct current biased magnetism shown corresponding to FIGS. 3(a) to (C).

Next, the operation will be explained. The output voltage of the CVCF circuit 3 is input to a low-pass filter 71 to extract only the DC component, and this DC component is input to the amplifier circuit 73 via the insulated amplifier circuit 72. This amplifier circuit 73 determines a predetermined correction amount for DC bias magnetization, and this correction amount is applied to an adder 74.
Add to reference sine wave. As a result, the DC component of the reference sine wave is corrected and controlled by DC polarization, and the PWM pulse control circuit 6
2.

Therefore, even if the initial setting of the reference sine wave has temperature drift or other changes over time, the PWM pulse control circuit 6
2, the inverter 32 of the CvCF circuit 3 is controlled by the control signal output from the CVCF circuit 3.
．． A DC polarization output voltage within 1 to 0.5% can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, since the DC bias of the output voltage of the CVCF circuit is automatically reduced and corrected at all times, damage caused by DC excitation of the transformer etc. provided on the output side of the CVCF circuit is prevented. This has the effect of being able to reliably prevent this.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a constant voltage constant frequency power supply device according to an embodiment of the present invention, Fig. 2 is a block diagram of a control circuit having a DC bias correction circuit, and Fig. 3 is a waveform of the output voltage of the CVCF circuit. FIG. 4 is a diagram showing the relationship between the amount of direct current biased magnetism and the amount of correction, and FIG. 5 is a block diagram showing a conventional constant voltage constant frequency power supply device. 1 is an AC power supply, 5 is a load, 6 is a control circuit, 31 is a converter, 32 is an inverter, 71 is a filter, 73 is an amplifier circuit, and 74 is an adder. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] A constant voltage constant frequency output circuit includes a converter that converts the output from an AC power supply to DC, and an inverter that converts the output of the converter to AC and supplies it to a load; A constant voltage constant frequency power supply device comprising: a filter that extracts only a DC component from the output of the inverter; an amplifier circuit that obtains a DC bias correction amount based on the output of the filter; A constant-voltage, constant-frequency power supply device comprising a correction circuit that adds a biased magnetization correction amount to the reference sine wave and corrects and controls a DC component of the reference sine wave using DC bias.