JPS59172822A - Noise filter - Google Patents

Abstract

PURPOSE:To eliminate even a noise having a narrow pulse width and high energy density by using a coil and a capacitor to a circuit connecting a resistor and a coil in parallel. CONSTITUTION:The coil 3 and the capacitor 6 are connected respectively in series and parallel with the parallel circuit comprising the coil 4 and the resistor 5. In selecting values of each coil, the resistor and the capacitor so as to satisfy a prescribed relation, most of the current due to noise having a short pulse width flows to the resistor 5, is attenuated by the circuit constituted with the resistor 5 and the capacitor 6, and since almost no noise current flows to the coil 4, the attenuating oscillation is not produced. Since the amount of timewise change of the noise current flowing to the capacitor 6 is suppressed by the coil 3, the voltage drop caused by a residual inductance of a lead or the like of the capacitor 6 is decreased.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a noise filter that can eliminate noise with a narrow pulse width but high energy density by comprising a resistor with a coil connected in parallel, a coil, and a capacitor. .

[Prior art]

Traditionally, noise filters are low-pass filters composed of a coil and a capacitor, so when noise with a narrow pulse width enters, a damped oscillation with a resonant frequency determined by the values of the capacitor and coil appears in the output, which reduces the energy density of the noise. If the voltage is large, a large voltage damped oscillation will appear in the output, and the function as a noise filter will be exhibited.This device is equipped with a noise filter.

The drawback was that it malfunctioned.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a noise filter that can eliminate even if noise with narrow pulse width but high energy density is included.

[Summary of the invention]

The first principle of the present invention is to narrow the pulse width and eliminate noise using a low-pass filter made of resistors and capacitors.

The noise-free power supply or signal required by the device is passed through the coil, and the second principle is that the coil prevents noise leakage due to residual inductance components due to the lead wires of the capacitors constituting the filter.

[Embodiments of the invention]

Hereinafter, a first embodiment of the present invention will be explained with reference to the first diagram.

In Figure 1, 1 is an input terminal, 2 is an output terminal, 6, 4
5 represents a coil, 5 represents a resistor, and 6 represents a capacitor. coil 3
The value of the coil 4 is L1%, the value of the resistor 5 is R1
The value of capacitor 6 is C1, the residual inductance of the lead wire of capacitor 6 is LI, the maximum Norms width of noise is t, the noise target suppression rate is α, tv L RC< , -) 1o, tv... ...(
1) α R 0°〉1 ・・・・・・(2) L.

If the constants are chosen so that when a noise with a noise width wider than the tv enters, more than 90 current of current due to the noise flows through the resistor 4, is attenuated by the circuit consisting of the resistor 5 and the capacitor 6, and the coil Since almost no noise current flows through 4, damped vibration does not occur. However, because the presence of the coil 3 suppresses the amount of change in the noise flow flowing through the capacitor 6 over time, it is possible to reduce the voltage drop caused by the residual inductance of the Riet wire of the capacitor 6. On the other hand, a signal with a large pulse width or a direct current can pass through the coils 3 and 4 without being attenuated.

As described above, according to this embodiment, even if noise with a narrow noise width is input, a sufficient noise damping effect with less damped vibration can be obtained in the output.

FIG. 2 shows a second embodiment of the invention. In Figure 2, 1 is the input terminal, 2 is the output terminal, 3゜5om 4.4a
is a coil, 5 and 5a are resistors, and 6 and 6a are capacitors. In this embodiment, the first embodiment is connected in series, and the value of the resistor 5 is R1, the value of the resistor 5a is Ra, the value of the capacitor 6 is 01, the value of the capacitor 6a is Ca, and RC<RaCa. It is clear that noise can be greatly attenuated by this. Further, if the amount of noise voltage drop caused by the residual inductance of the lead wire of the capacitor 6 is small, the coil 3a may be removed.

Note that although this embodiment is one in which two of the filters of the first embodiment are connected in series, it is clear that the noise suppression effect increases if six or more stages are connected in series.

[Young fruit of Yuyu]

As described above, according to the present invention, even if a narrow noise enters the filter, almost no damped oscillation is produced in the output.
No more malfunctioning of equipment0

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of one embodiment of the present invention, and FIG. 2 is a circuit diagram of another embodiment of the present invention. 01 input terminal, 2...output terminal, 3, 4. la, 4a・
・Coil, 5.5a...Resistance, 6.6a...Capacitor 0 1st port Fig. 2

Claims (1)

[Claims] A noise filter characterized by using a configuration in which a resistor and a coil are placed in parallel, a coil, and a capacitor.