JP2791501B2 - Power line carrier transmitter - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power line carrier transmitting apparatus for transmitting a signal using a power line.

2. Description of the Related Art Conventionally, as a device for transmitting a signal using a power line, apart from a commercial frequency of 60 Hz or 50 Hz, 200 to 500 Hz
In general, an apparatus that uses an AC signal having a frequency in the band as a carrier frequency and transmits a signal by changing the frequency is used.

FIG. 3 shows the configuration of such a conventional power line carrier. In FIG. 3, 1 is an AC power supply, 2 is a rectifier, 3 is a smoothing capacitor, 4 and 5 are transistors, 6
Is a capacitor, 7 is a loosely coupled reactor, and 8 is a capacitor.

The operation of this conventional example is as follows. After the AC power supply 1 is rectified by the rectifier 2, the DC power is smoothed by the capacitor 3 and the transistors 4 and 5 are alternately turned on to obtain a desired AC waveform on the primary side and the secondary side of the reactor 7.

The values of the capacitor 6 and the reactor 7 and of the capacitor 8 and the reactor 7 are set so as to resonate in series with the driving frequency. As shown in FIG. 4, for example, as shown in FIG. 4, when the transmission data is “1”, the carrier frequency is set to the lower side (260 Hz), and when the transmission data is “0”, the carrier frequency is set to the higher side (280 Hz).
Hz), a substantially sinusoidal AC waveform such as B or C is obtained on the primary side and the secondary side of the reactor 7, respectively.

Problems to be Solved by the Invention In the above-described conventional example, the reactor 7 and the capacitors 6 and 8 are selected so as to resonate in series with the carrier frequency. There is an advantage that an AC waveform can be obtained and a commercial frequency component can be cut. On the other hand, as a reactor that resonates at both low and high frequencies, it is loosely coupled, so its size and weight are large.Moreover, it has a large amount of leakage magnetic flux and its current contains low-order harmonics. There is a problem that generation of noise is inevitable.

In addition, since the current value when the carrier signal is injected into the commercial power supply depends on the impedance of the commercial power supply, it is necessary to increase or decrease from the design reference value according to the line conditions at the installation location. However, there is a problem in that the configuration is complicated by changing the taps or increasing or decreasing the DC voltage.

SUMMARY OF THE INVENTION The present invention is to solve such a conventional problem, and to provide an excellent power line carrier transmission device that can be reduced in size and noise and that can easily increase and decrease the power supply injected into a line. With the goal.

Means for Solving the Problems In order to achieve the above object, the present invention rectifies an AC power supply, drives the primary winding of the transformer with a pulse width modulated PWM signal via an inverter after smoothing, and converts the transformer into a transformer. The secondary winding is connected to the AC power supply via a filter.

Operation Since two AC frequencies are pulse width modulated by an inverter and input to the primary winding of the transformer, a sine wave with less low-order harmonic components can be obtained from the secondary winding. In addition to reducing the size of the coupling transformer and reducing noise, the output voltage, which is a feature of the PWM inverter, can be easily varied, so that the signal injection current can be easily increased or decreased according to the line conditions. There is.

Embodiment FIG. 1 shows the configuration of an embodiment of the present invention. First
In the figure, 11 is an AC power supply, 12 is a rectifier for rectifying the AC power supply 11, and 13 is a smoothing capacitor for smoothing the DC output rectified by the rectifier 12. 14, 15,
Reference numerals 16 and 17 denote power transistors, which constitute a bridge inverter 18. Reference numeral 19 denotes a transformer, and the output of the bridge inverter 18 is connected to the primary winding of the transformer 19. Reference numeral 20 denotes a capacitor which is maintained in parallel with the secondary winding of the transformer 19 and further includes another capacitor 21.
And a reactor 22 connected in series to both ends of the AC power supply 11. The capacitor 21 and the reactor 22 constitute a filter 23 for preventing backflow of commercial power to the bridge inverter 18. These bridge inverter 18, transformer
The carrier signal generating means is constituted by 19, the capacitor 20, and the filter 23.

Next, the operation of the above embodiment will be described. First, the AC power supply 11 is rectified by the rectifier 12 and converted to DC by the smoothing capacitor 13, and the transistors 14, 15, 16, 17 are PWM (Pulse Wid
th Modulation), that is, pulse width modulation drive to excite the primary winding of the transformer 19. Although the transistor base drive circuit of the PWM is not shown, for example, the carrier frequency is set to about 15 KHz, and the sine waves of the low band side (260 Hz) and the high band side (280 Hz) are pulse-width modulated, and each transistor is driven. Drive 14, 15, 16, 17

FIG. 2 shows drive waveforms when driving the transistors 14, 15, 16, and 17. FIG. 2A shows the case where the transmission data is "1" and "0", and the corresponding one of the transformers 19 is shown in FIG.
The voltage waveform of the secondary winding is shown in B, and the voltage waveform of the secondary winding is shown in C. The primary winding voltage of the transformer 19 is waveform B
, But the secondary winding voltage waveform C
Is a sine wave of the fundamental frequency component because the capacitor 20 cuts the harmonic component. Then, the sine wave voltage is supplied to the AC power supply 11 via the capacitor 21 and the reactor 22.
Inject into It is desirable that the filter 23 composed of the capacitor 21 and the reactor 22 has a high impedance with respect to the commercial frequency and a sufficiently low impedance with respect to the carrier frequency (260 to 280 Hz). By selecting such a value, only the carrier frequency component can be effectively injected into the power supply, and the influence of the commercial power supply can be reduced.

The feature of this embodiment is that the output current can be easily adjusted. This is a function of the PWM inverter. By setting the conduction width of the pulse of waveform B to X% in FIG. C can be understood from a sine wave having a peak value of X%.

Effect of the Invention As described above, according to the power line carrier transmitting apparatus of the present invention, by using the PWM inverter, it is possible to transmit a sine wave with little distortion on both the high frequency side and the low frequency side of the carrier frequency. Therefore, noise due to harmonics can be reduced. Further, unlike a conventional loosely coupled reactor, a tightly coupled transformer is used, so that there is no noise generation due to resonance of leakage magnetic flux, and the transformer can be downsized. Furthermore, since the output voltage of the inverter can be easily changed by proportionally controlling the conduction time of the PWM, there is an advantage that the signal injection current can be easily increased or decreased according to line conditions.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a power line carrier transmitting apparatus showing an embodiment of the present invention, FIG. 2 is a waveform diagram showing driving waveforms in the apparatus, and FIG. 3 is a schematic diagram showing an example of a conventional power carrier transmitting apparatus. FIG. 4 is a block diagram and FIG. 4 is a waveform diagram showing driving waveforms in the conventional example. 11 ... AC power supply, 12 ... Rectifier 13 ... Capacitor 14, 15, 16, 17 ... Power transistor 18 ... Bridge inverter, 19 ... Transformer 20, 21 ... Capacitor, 22 ... Reactor 23 ... Filter A: Transmission signal waveform B: Transformer primary voltage waveform C: Transformer secondary voltage waveform

Claims (1)

(57) [Claims] A rectifier for rectifying an AC power supply, a smoothing capacitor for smoothing a rectified DC output,
Carrier signal generating means for generating a carrier signal from the smoothed DC output, wherein the carrier signal generating means includes an inverter for pulse width modulation, and a transformer for converting an output voltage waveform from the inverter. , The transformer 2
A power line carrier transmitting device comprising: a filter that prevents a commercial power supply connected between a next winding and the AC power supply from flowing back to the inverter.