JPS6041333A - Transmitter for power line carrier - Google Patents

Abstract

PURPOSE:To improve the injection efficiency and to reduce the size of a commercial frequency cutting capacitor to make the whole of a device small in size, by connecting a series resonance circuit, which resonates to a prescribed frequency between a power line and the output of a transmitter which superposes a carrier signal having the specified frequency onto the power line and transmits it. CONSTITUTION:The output signal of an oscillator 6 which generates the carrier signal having the prescribed frequency is amplified by an amplifier 7, and this carrier signal is superposed onto a power line 12 having a commercial frequency by an output transformer 8. A series resonance circuit 11 which resonates to the prescribed frequency is connected between the secondary side of the output transformer 8 and the power line 12, and the resonance circuit 11 consists of a coil 9 and a capacitor 10. The impedance of the resonance circuit 11 is made smaller than the output impedance in the secondary side of the output transformer 8, and the overall output impedance is made equal to the impedance of the power line 12, thus improving the injection efficiency to the power line 12 and making the capacitor 10 small in size.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a power line carrier transmitter that performs communication by superimposing a carrier signal of a predetermined frequency on a power line.

Configuration of the conventional example and its problems In the conventional power line carrier transmitter, as shown in FIG. Matching is performed, and the commercial frequency is cut using capacitor 6.
A carrier signal was superimposed on the power line 4. Generally, the high frequency impedance of the power line 4 is several ohms (in the worst case, 1
Ω or less), so unless the output impedance of the transmitter is lowered, the transmission efficiency will decrease. However, no matter how much you adjust the output transformer 3 to lower the impedance, the capacitor 5 remains between the output transformer 3 and the power line 4.
Therefore, the output impedance cannot be lowered below the impedance of the capacitor 5. capacitor 6
Since the purpose of this is to cut commercial frequencies, the impedance at commercial frequencies must be sufficiently large.

Therefore, it is not possible to increase the capacity extremely.

In addition, since commercial power is applied, the withstand voltage must be high. In other words, even if an expensive capacitor with a large capacity and high voltage resistance is used, the output impedance cannot be lowered. As a result, the output voltage changes according to the impedance change of the power line 4, and when the impedance is low, the output voltage becomes small and the transmission distance becomes short.
When the impedance is high, the output voltage becomes large, causing signal leakage outside the specified transmission range.

OBJECTS OF THE INVENTION The present invention solves these drawbacks, and aims to provide a power line carrier transmitter that can reduce the output impedance and downsize the commercial frequency cutting capacitor.

Structure of the Invention The power line carrier transmitter of the present invention has a series resonant circuit connected between the output of a transmitter that superimposes a carrier signal of a predetermined frequency on a power line and transmits the same, and the power line to resonate the predetermined frequency. It is.

DESCRIPTION OF THE EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. The output impedance of the amplifier 7 that amplifies the output signal of the oscillator 6 that generates the carrier signal is much higher than the impedance at the signal frequency of the power line 12.
The output impedance of the power line 12 at the signal frequency
Set the impedance to several ohms, which is approximately the same as the impedance. A series resonant circuit 11 consisting of a series connection of a coil 9 and a capacitor 1o is connected to the output of the transmitter and the pure amount of electric power.
Its resonant frequency should match the signal frequency. Therefore, the impedance of the series resonant circuit 11 is smaller than the output impedance of the output transformer 8. Therefore, the overall output impedance of this transmitter is approximately equal to the line impedance. In other words, the output impedance of the transmitter and the impedance of the power line 12 are matched, and output efficiency is improved. Substitute the actual values below and divide the efficiency.

As an example, it is assumed that the power supply frequency is eoHz, the power supply voltage is 100V, the carrier wave signal frequency is 120 KHz, the power line impedance at the carrier wave signal frequency is 1Ω, and the output impedance of the output transformer 8 is 1Ω.

In the case of the conventional example, if the capacitance of the capacitor 6 is 0.1 μF, the impedance of the capacitor 5 at 120KH2 is 1/2XyrX120X105X0. lX10'4=
13.26 (Ω), and the absolute value of the overall output impedance is 3' = 13.3 (Ω). Therefore, when a signal of 0.1■ is generated on the secondary side of the output transformer 80, the signal injected into the power line is o, 1 x 20, 007 (V) 13.3 +'1 +1, It is very weak.

On the other hand, when the present invention is used, even if the impedance of the series resonant circuit 11 is 1Ω, the overall output impedance is 1+1=2(Ω), and the voltage injected into the power line when the output voltage is 0.1 V is , 1+, +1-0. It can be seen that o3(v) is improved by 4.3 times compared to the conventional example.

With the injection voltage used in the conventional example, it becomes impossible to distinguish noise from noise on the power line, so it is necessary to increase the output voltage on the secondary side of the output transformer.

In such a case, when the impedance of the power line increases, the voltage is injected into the power line without attenuation, and the signal may reach outside the predetermined range, potentially harming other systems.

The impedance of the series resonant circuit 11 during resonance actually decreases as the value of the capacitor 10 increases, but a capacitor with a large capacity as in the conventional example is not necessary, and according to the inventor's experiments, a capacitor of 1° The value is 1 of the value of capacitor 5
It has been confirmed that even a ratio of about /10 can function satisfactorily.

Furthermore, if the signal waveform of the carrier wave is not a perfect sine wave, the impedance of the series resonant circuit 11 with respect to the high and low frequencies of the carrier wave is large, and components other than the fundamental wave cannot pass through the series resonant circuit 11 and are transmitted to the power line 12. The injected voltage becomes smaller. Unfortunately, the linearity of amplifier 7 is also poor.
Not required.

As described in detail, the power line carrier transmitter of the present invention has very high injection efficiency, with the signal injection voltage not changing much even when the impedance of the power line changes, and is suitable for use in small commercial frequency cutting applications. A capacitor may be sufficient, and the entire circuit can be made small and inexpensive.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional example, and FIG. 2 is a circuit diagram of a power line carrier transmitter showing an embodiment of the present invention. 9... Coil, 10... Capacitor, 11
...Series resonant circuit, 12...Power line. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure

Claims (1)

[Claims] A power line carrier transmitter comprising a series resonant circuit that resonates at the predetermined frequency connected between the power line and the output of a transmitter that transmits by superimposing a carrier signal of a predetermined frequency on the power line.