JPH01318309A - Power circuit - Google Patents

Abstract

PURPOSE:To block the increase in the leakage current when a power supply switch is turned off and to improve the noise elimination effect by providing a switching means interrupting a noise elimination capacitor circuit in interlocking with the power line switch. CONSTITUTION:A switch 1b is an interlocking switch turned on/off in interlocking with a power switch 1a and inserted in series with the noise elimination capacitor 4. With the power switch 1a turned off, the switch 1b is also turned off in interlocking therewith and as soon as the power line is interrupted, the noise elimination capacitor 4 is interrupted from the circuit. The leakage current is zero on one hand (capacitor 5), and the other is a value dividing the power voltage by the impedance of the capacitor 5. The value is equal to a value when the switches 1a/1b is turned on and the leakage current when the power supply switch is turned off is not increased. Thus, the capacitance of the noise elimination capacitor is increased and the noise elimination effect is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a power supply circuit, for example, an input circuit of a household AC power supply to electrical equipment, etc., and particularly relates to an input circuit equipped with a noise removal capacitor between a line and a ground. It is something.

[Conventional technology]

FIG. 4 shows an example of a conventional power supply circuit of this type. In the figure, Ll and L2 are power input lines, Lo, Lo
2 is a power output line. 1 is the power switch, 2 is the
3 is a noise removal capacitor generally called an "X capacitor" inserted between both input terminals L, L2; 3 is a choke coil wound in the same phase, generally called a "common choke coil" for noise removal; 4. Reference numeral 5 denotes a noise removal capacitor generally called a "Y capacitor" inserted between the Ryokawa Kalines Lo, Lo2 and the ground. As is customary, it is assumed that the capacitance of capacitor 2 is sufficiently larger than that of each capacitor 4.5, and that each capacitor 4.5 has the same capacitance.

Further, it is assumed that the impedance of the choke coil 3 at the power supply frequency is set to be sufficiently smaller than that of each capacitor 4.5.

[Problem to be solved by the invention]

In FIG. 4, in general, a noise removal capacitor 4,
By increasing the capacity of No. 5, the effect of removing noise generated by the device and noise mixed into the device can be enhanced. However, safety standards require that the short-circuit current that flows when the ground and one line are short-circuited with low resistance be kept below a certain value. Therefore, the upper limit is automatically determined.

The above short-circuit current is generally called a "leakage current." In the circuit shown in Figure 4, when the power switch 1 is on, the leakage current is equal to the power supply voltage divided by the impedance of the capacitor 4 (or capacitor 5). However, since the capacitance of capacitor 2 is set to be sufficiently larger than the capacitance of capacitor 415, when the power switch 1 is off, the leakage current of one side is 0, but the leakage current of the other side is , 5, or twice the value when the power is switched on. Therefore, in the circuit shown in Fig. 4, the capacitance of each capacitor 4.5 is determined so as to satisfy the leakage current safety standard with the power switch 1 turned off, but the capacitance must be set sufficiently large. Therefore, there was a problem that a sufficient noise removal effect could not be expected. In order to solve this problem, for example, as shown in Fig. 5, a method has been proposed in which the power switch is configured with two circuits 1a and lc and both sides of the power lines L, L2 are turned on. target large current.

Providing a circuit with two switches for turning on and off a high voltage circuit has the disadvantage that it is uneconomical in terms of cost due to the material and structure of the contacts.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the conventional example, and aims to provide a power input circuit of this type that prevents an increase in leakage current when the power is switched off and improves the noise removal effect. .

[Means to solve the problem]

Therefore, the present invention attempts to achieve the above object by providing a switching means that connects and disconnects the noise removal capacitor circuit in conjunction with the power line switch.

(Function) With the above circuit configuration, when the power line is disconnected, part or all of the connection circuit between the power line and the ground is cut off, thereby preventing an increase in leakage current when the power is turned off. This can be achieved at low cost, and the capacitance of the noise removal capacitor can be set to a correspondingly large capacity, resulting in an enhanced noise removal effect.

〔Example〕

The present invention will be explained below based on examples.

FIG. 1 shows an embodiment of the power supply circuit of the present invention.

(Structure) In the figure, 1a is a power switch that turns on and off the power line, and 1b is an interlocking switch that is turned on/off in conjunction with 1a, and is inserted in series with the noise removal capacitor 4. Other components that are the same (equivalent) to those in FIGS. 4 and 5 of the conventional example are denoted by the same reference numerals, 2, 3, 4.
5, redundant explanation will be omitted.

(Operation) Next, the operation in the above configuration will be explained.

When power switch 1a is turned on, switch 1
b is also turned on, and the noise removal capacitor 4 is connected at the same time as the power lines L, L2 are connected. At this time,
The circuit is the same as that in the conventional example shown in FIG. 4, and the leakage current is the value obtained by dividing the power supply voltage by the impedance of the capacitor 4.

Next, when the power switch 1a is turned off, the switch 1b is also turned off, and the power supply line is cut off, and at the same time, the noise removal capacitor 4 is also disconnected from the circuit.

The leakage current at this time is O on one side (on the capacitor 5 side) as in the conventional example shown in FIG. 4, but on the other side, since the circuit of the capacitor 4 is cut off, the power supply voltage is The value divided by This value is equal to the value when the power supply/interlocking switches 1a/1b are turned on, and there is no increase in leakage current when the power supply switch is turned off, as in the conventional example shown in FIG. Therefore, the capacitance of the noise removal capacitor 4.5 is 2 in the conventional example in Fig. 4.
Can be set to double the value.

Here, since the current flowing through the interlocking switch 1b is weak, the material, structure, etc. of its contacts need to be made at a lower cost than the power switch 1a, which is economical.

(Other examples) Other embodiments are shown in FIGS. 2 and 3.

FIG. 2 is an example in which the interlocking switch shown in FIG. 1 is inserted in series from the midpoint of each capacitor 4, 5 to the ground point.
A similar effect can be obtained.

In addition, FIG. 3 shows power supply/interlocking switches 1 in parallel with each other.
a / 1 b are connected in series to the power supply output line Lo and the capacitor 4, respectively. In this case, the same effects as in each of the above embodiments can be obtained, and in particular, the switch 1a and the switch 1b Since there is no regulation on the creepage distance between the two circuits, for example, when these are assembled into the same case, there is no need for insulation between the two circuits, which further simplifies the structure compared to the conventional example (Figure 5). be.

(Effects of the Invention) As explained above, according to the present invention, since the switch circuit is provided to turn on and off the noise removal capacitor circuit in conjunction with the power line switch, it is possible to This method is lower in cost than the method of cutting both power lines at the same time, and prevents an increase in leakage power when the power is switched off, and the capacity of the noise removal capacitor can be increased accordingly, resulting in a higher noise removal effect. I was able to do that.

[Brief explanation of the drawing]

FIG. 1 shows one embodiment of the present invention, FIGS. 2 and 3 show other embodiments of the invention, and FIGS. 4 and 5 show respective conventional power supply circuits. 1 is a power switch, 2 is an X capacitor, 3 is a common choke coil, and 4.5 is a Y capacitor.

Claims (1)

[Claims] The input part of the AC power supply of the electrical equipment is provided with a noise-eliminating capacitor inserted between the power supply line and the ground, and a two-circuit interlocking switch, with one circuit of the switch connected in series with the power supply line. At the same time, the other circuit of the switch is inserted in series with the circuit connecting the power supply line and the ground using the noise elimination capacitor, and when the power supply line is disconnected, the noise elimination capacitor A power supply circuit characterized in that the circuit between the power supply line and the ground is configured so that at least a portion of the circuit is cut off.