JPH0261180B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a low frequency alternating current generating device in a transmission communication device or the like.

Conventional low-frequency AC generating circuits used for signal power sources in transmission and communication equipment include, for example, magnetically coupled oscillation circuits called Royer circuits, but when the oscillation frequency is as low as 16Hz to 25Hz, , because the transformer is inevitably large and heavy,
It had the drawback of not being able to keep up with the progress in making other circuit devices smaller and lighter.

Furthermore, in order to obtain a stable low frequency, a low frequency generation circuit is disclosed in which the high frequency current from the high frequency generation circuit is generated in a rectifier circuit into half waves of opposite polarity, and the opening and closing of these two rectifications are controlled by a thyristor. (Special Publication No. 42-7727).

However, in such a circuit, the influence of the low frequency current controlling the two rectifications sometimes appears on the output low frequency.

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks, it is an object of the present invention to provide a low frequency generator that is miniaturized and is capable of extracting low frequency alternating current that is blocked from the earth's atmosphere.

The present invention operates with a single DC power supply to generate high-frequency current, converts it to an appropriate voltage via a high-frequency transformer, and then generates two DC currents with positive and negative polarities using two sets of rectifier circuits. An optically coupled semiconductor element is interposed in each of the positive and negative DC circuits and connected to the output terminal, and the output of a separately provided control low frequency oscillator is controlled to alternately conduct the optically coupled semiconductor elements, and the output terminal is connected to the output terminal. It is characterized by a configuration that generates low-frequency alternating current.

Next, details of the present invention will be described with reference to embodiments with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. The high frequency oscillation circuit 1 oscillates at, for example, 18 KHz to 25 KHz in response to a direct current power supply (not shown). The high frequency transformer 2 receiving the high frequency output converts voltage and also functions as an isolation transformer.

The input and output waveforms of high frequency transformer 2 are the first
At points A, B, and C in the figure, Fig. 2 A, respectively.
Represented by B and C.

The output of the high frequency transformer 2 is connected to two rectifier circuits 3,
4 and are converted into direct current of equal absolute value with positive and negative polarity, respectively, and the voltage situation is as follows:
It will look like Figure DE.

The DC outputs of these two rectifiers 3 and 4 are guided to optically coupled semiconductor elements 5 and 6, respectively, where they are alternately subjected to opening and closing control for conduction and interruption. Therefore, at the output terminal 7, an alternating current with a period determined by the control of the optically coupled semiconductor elements 5 and 6 is obtained.

Control inputs for the optically coupled semiconductor elements 5, 6 are supplied from a low frequency alternating current generator 8, whose waveforms are shown in FIG.
It is given by alternating voltages as shown in G. The light-emitting part of the optically coupled semiconductor element emits light for the (+) voltage application time shown in the figure, and the input DC is alternately opened and closed between (+) polarity and (-) polarity by optical coupling control, so that the output A low frequency alternating current as shown in FIG. 4H is generated at the terminal 7. The rectifier circuits 3 and 4 are insulated from the supply DC input terminals 10 and 11 by the high frequency transformer 2, and the controlled opening/closing parts of the optical coupling elements 5 and 6 are optically coupled and electrically isolated from the control input. Therefore, the supply DC power input terminal 10,1
1, a low frequency alternating current that is completely independent in potential can be output to the output terminals 7 and 9, and can be supplied to the load.

As explained above, the present invention is a low-frequency AC generator in which the functions of voltage conversion and isolation transformer are performed by a high-frequency transformer in a method of converting direct current to high frequency. This eliminates the need for large low-frequency transformers,
A low frequency AC generator is provided which is significantly smaller and lighter than conventional ones. When the present invention is applied to a transmission communication device or the like, there is an excellent effect that a device can be obtained in which other parts are made smaller and lighter in coordination.

Furthermore, it is possible to extract low-frequency alternating current that is blocked from the ground air. This low-frequency alternating current is useful as a power source for a current that is isolated from the earth, such as a signal power source for a communication device, such as a ringing current for a telephone sent to a pair of wires.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention. Second
The figure is a waveform diagram of points A, B, and C in Fig. 1. Third
The figure is a waveform diagram of points D and E in Figure 1. FIG. 4 is a waveform diagram of points F, G, and H in FIG. 1. DESCRIPTION OF SYMBOLS 1... High frequency oscillation circuit, 2... High frequency transformer, 3, 4... Rectifier circuit, 5, 6... Optical coupling semiconductor element, 7... Output terminal, 8... Low frequency alternating current generator.

Claims (1)

[Claims] 1. A means for generating a high-frequency current, a high-frequency transformer that receives the high-frequency current as input and outputs a high-frequency signal cut off from the earth's air, and a means for receiving the output of this high-frequency transformer from the earth's air of opposite polarity. A rectifier circuit that generates the two blocked DC currents, two optically coupled semiconductor elements that alternately conduct and cut off the two DC currents, and two optically coupled semiconductor elements that alternately connect the optically coupled semiconductor elements so that alternating voltages can be taken out from the optically coupled semiconductor elements. A low frequency alternating current generator comprising a low frequency alternating current generator for generating a control signal to interrupt conduction.