JPH039306Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention relates to a transformer that blocks noise in a commercial frequency power supply, and more specifically, it blocks motor noise, switching noise, and high frequency noise from the commercial power supply. This invention relates to a transformer configured to cut off noise input from electronic equipment such as audio equipment, and eliminate noise interference from audio equipment and other electronic equipment.

[Prior Art] Miscellaneous noises such as motor noise, switching noise, high frequency noise, and induction noise from a commercial frequency (50 Hz or 60 Hz) power source invade the electrical equipment connected to it. For this reason, in computer-mounted equipment, these noises cause programs to run out of control, memory to disappear, etc., and in audio equipment, they become a major cause of polluting the sound.

One of the countermeasures against power supply noise is to use a line filter to cut the power supply noise, but the filter's cutoff characteristics change significantly depending on the values of source side impedance and load side impedance, and a stable effect cannot be expected.

In order to eliminate these drawbacks, we first convert energy into another form of energy and cut out the noise.
Energy conversion type noise prevention equipment that restores only the necessary components to the original electrical energy has been put into practical use. However, there is a problem with high AC power transmission.

For this reason, isolation transformers are now mainstream.

There are three types of isolation transformers: isolation transformers, shield transformers, and high-frequency induction countermeasure transformers.

[Problem that the invention attempts to solve] However, in the conventional isolation transformer,
A shielded transformer can prevent relatively low-frequency common mode noise because there is no direct conduction between the primary and secondary, but its effect on preventing normal mode noise is minimal due to core loss, so a shielded transformer is an isolation transformer. In addition to removing low-frequency common mode noise, it also has an electrostatic shielding effect between the primary and secondary windings, which has the effect of removing high-frequency common mode noise. The drawback is that the configuration is complicated and expensive.

[Purpose of the invention] The purpose of this invention is to eliminate the above-mentioned drawbacks.The purpose of this invention is to eliminate the above-mentioned drawbacks. By adding a circuit to the transformer, the unnecessary noise is prevented from being transmitted to the secondary side of the transformer.

[Summary of the invention] The transformer for blocking noise in a commercial frequency power supply of this invention has a primary winding and a secondary winding wound around an iron core, one end of which is connected to the primary winding, and the A compensation winding through which a noise current having a phase opposite to the noise power flowing through the primary winding flows is wound around the iron core, and an inductance of the compensation winding is provided between the other end of the compensation winding and the other end of the primary winding. A capacitive series resonant circuit is constructed by connecting a capacitor with a capacitance sufficiently large compared to that of the transformer. This also eliminates noise depending on high-frequency attenuation characteristics.

[Embodiment of the invention] As shown in Fig. 1, the transformer of this invention for cutting off noise in a commercial frequency power supply has a primary winding 1 of _N1 wound around an iron core 4, and The number of turns is such that one end of the primary winding is wound onto the primary winding.
A compensation winding 2 of Nc is wound between the end of this compensation winding and the other end of the primary winding, and the compensation winding has an inductance obtained by the number of turns Nc and the upper limit of the audio frequency, for example 10KHz. A capacitor 3 having a value that gently resonates in series is connected nearby, and a secondary winding 5 is further wound around the iron core to form a transformer. In addition, the primary winding 1 and the compensation winding 2 are connected to the noise current in and the primary winding as shown in Fig. 3.
Product of N ₁ and noise current inc flowing through capacitor 3
When the product of Nc and the number of turns of the compensation winding is equal, that is,
When in・N ₁ = inc・Nc, the noise will be completely canceled, so in order to reduce the leakage of both magnetomotive forces, the primary winding 1 and the compensation winding 2 should be connected as much as possible as shown in Figure 2. It is preferable to wind the coils in close contact with each other, and to divide the coils so that the compensation winding 2 is wound between the primary windings.

[Operation of the invention] The transformer of this invention is constructed as described above, and the operation of this transformer will be explained below.

Figure 3 is a vector diagram for explaining the principle of the transformer of this invention, where E is the power supply voltage, that is, the commercial power supply voltage (100 or 200V), Ec is the voltage applied to the capacitor 3, and the compensation winding 2 acts as a step-up autotransformer when viewed from the primary winding 1. Therefore, the terminal voltage Ec of the capacitor 3 becomes a voltage slightly higher than the power supply voltage E, and Io is the exciting current of the transformer and the voltage E
The current lags by almost 90 degrees. If the capacitance of the capacitor 3 is set larger than the inductance of the compensation winding 2 so that this series circuit becomes a capacitive circuit, the current Ic flowing to the capacitor 3 will flow through the compensation winding 2, but the voltage against E
It becomes a 90 degree leading current.

Now, considering the relationship between voltage and current from point a to point b in Figure 1, the exciting current Io becomes a 90 degree delayed current as described above, but there is a noise voltage en here. Due to the high inductance of the primary winding 1, the current in is also a 90 degree lagging current regardless of the frequency. Further, a noise current inc also flows through the circuit of the compensation winding 2 through the capacitor 3.

Since this circuit is a capacitive circuit, it naturally leads to a leading current regardless of frequency, similar to the current Ic flowing through capacitor 3. (omitted).

The relationship between the exciting current Io and the current Ic flowing through the capacitor 3 is that the no-load current of the transformer simply becomes a little smaller and there is no other effect, so here the noise current in,
Considering the relationship between inc, primary winding 1 and compensation winding 2, noise current in and magnetomotive force in by primary winding 1
×N ₁ , noise current inc and magnetomotive force due to compensation winding 2
Since inc×Nc has a phase difference of 180 degrees and the windings are wound in the same direction, these two magnetomotive forces cancel each other out. That is, (in×N ₁ )=(inc×Nc)
The noise disappears completely.

In general, noise from a commercial frequency power supply is often a composite noise in which various frequencies are mixed, but if the above-mentioned magnetomotive force canceling effect works for each of the mixed frequencies, the overall composite noise This can be attenuated.

Of course, it is not possible to satisfy the best condition such as (in×N)=(inc×Nc) for all frequencies. However,
Compensating for the best condition near the upper limit of the audible band, 8KHz to 10KHz. By setting the number of turns Nc of winding 2 and the capacitance of capacitor 3, the range is from several hundred Hz at the bottom to 1M at the top.
A high attenuation rate can be obtained over a fairly wide range up to Hz or higher. As described above, the attenuation effect of the present invention only extends to at least about 400Hz.
Therefore, at commercial frequencies such as 50 to 60 Hz, this device does not cause voltage drop or other effects.

However, it is well known that even ordinary transformers have a considerably high noise attenuation rate in high frequency bands (several hundred kilohertz) or higher due to their unique characteristics. characteristics and the attenuation rate due to the broad resonance characteristics of the series circuit of the compensation winding 2 and the capacitor 3 according to this invention.If we consider this as the dynamic characteristic, these two characteristics are completely different, so in the usage state of the transformer, work by adding together.

This complementary and duplicated attenuation rate can provide a high noise attenuation rate over a wide range from the low frequency range to the high frequency range.

In the low frequency range, especially in the audible frequency range of several hundred Hz, which is important for audio equipment, it has been difficult to obtain a high noise attenuation rate even when using a line filter etc. A large noise attenuation rate can be obtained over a wide frequency band.

[Effects of the invention] As described above, the transformer used in the commercial frequency power supply of this invention has a primary winding and a secondary winding wound around an iron core, one end of which is connected to the primary winding, and A compensation winding through which a noise current having a phase opposite to the noise power flowing through the winding flows is wound around the iron core, and an inductance of the compensation winding is connected between the other end of the compensation winding and the other end of the primary winding. By connecting capacitors with sufficiently large capacitance, we constructed a capacitive series resonant circuit that resonates broadly in the noise component region around 10 KHz. The magnetomotive force of normal mode noise is canceled in a fairly wide frequency band centered on the resonant frequency of the dynamic characteristics of the series circuit, that is, the broad resonance characteristics of the series circuit.
In particular, noise can be removed over a wide range above and below the upper limit of the audible frequency band, and this noise removal ability, combined with the noise removal ability due to the static characteristics unique to the transformer, results in a good product with almost no noise. This has the effect of providing power.

[Brief explanation of the drawing]

The figures all show one embodiment of this invention: Figure 1 is a wiring diagram of a transformer, Figure 2 is a configuration diagram showing the relationship between the primary winding and compensation winding, and Figure 3 is the principle of operation. FIG. 1...Primary winding, 2...Compensation winding, 3...Capacitor, 4...Iron core, 5...Secondary winding.

Claims (1)

[Scope of utility model registration request] In a transformer used for a commercial frequency power supply in which a primary winding 1 and a secondary winding 5 are wound around an iron core 4, one end is connected to the primary winding 1, and the noise power flowing through the primary winding 1 is reversely connected. A compensation winding 2 through which phase noise current flows is wound around the iron core 4, and a capacitor with a sufficient capacity compared to the inductance of the compensation winding 2 is connected between the other end of the compensation winding 2 and the other end of the primary winding. A transformer for cutting off noise in a power supply, characterized in that a large capacitor 3 is connected to the capacitor 3 to form a capacitive series resonant circuit that resonates broadly in a noise component region around 10 KHz.