JPS631593Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a power conversion device that reduces noise voltage between a power supply line and the ground.

BACKGROUND ART Conventionally, a power conversion circuit configured as shown in FIG. 1, for example, has been considered as a power conversion circuit that receives a commercial AC power supply voltage and generates high-frequency power. This circuit uses a push-pull type inverter circuit as the main power conversion circuit, and this circuit uses a capacitor that is generally installed between input terminals 2a and 2b to which commercial AC power supply 1 is applied to reduce high-frequency noise between power lines. 3 and a rectifier circuit 4 are connected in parallel, a smoothing capacitor 5 similar to the capacitor 3 or a smoothing capacitor 5 is connected between the output terminals of the rectifier circuit 4, and the positive terminal is connected to the primary winding 6 of an output transformer 6, 6, and its negative terminal is connected via an inductance 7 to the emitters of switching elements 8 and 9, which are NPN transistors, for example. The switching element 8 has a collector connected to the other end of the primary winding 6, and a base connected to the common connection point of the primary windings 6 through a bias resistor 10, and the switching element 9 has the collector connected to the other end of the primary winding 6. It is connected to the other end of the primary winding 6, and its base is connected to the common connection point of the primary windings 6, 6 via a bias resistor 11. Above output transformer 6
connects a resonant capacitor 12 between the primary windings 6, 6. Moreover, this transformer 6 has the above-mentioned primary winding 6,
In addition to 6, one end of a secondary winding 6 and a feedback winding 6 are connected to the base of the switching element 8, and the other ends are connected to the base of the switching element 9, respectively. However, for such a circuit, input terminal 2
When an AC input is applied between a and 2b and a base current is applied to the base of each switching element 8, 9 by the rectifier circuit 4 via the bias resistor 10, 11, a slight Due to imbalance, either switching element 8 or 9 turns on first. If the switching element 8 were to be turned on first, a current would flow through the primary winding 6 of the output transformer 6 and an electromotive force would be induced on the secondary winding 6 side. Then, the switching elements 8 and 9 are alternately turned on and off due to the inductance on the secondary winding 6 side and the resonant oscillating voltage generated by the resonant capacitor 12 at this time, resulting in self-oscillation. As a result, high frequency power is applied to the negative end 13 via the output transformer 6. Incidentally, in a circuit configured in this manner, components may be attached to printed wiring, and the wiring may be formed on a printed wiring board. However, in such a circuit, the high-frequency noise potential is particularly high in the lines connected to the switching elements 8 and 9, as shown in the thick line in FIG. May cause significant noise disturbance. The reason for this can be explained from the noise equivalent circuit shown in FIG. That is,
Figure 2 shows the noise system of the circuit in Figure 1 as an equivalent circuit.
A and 9A are high frequency noise voltage sources generated by the switching operation of switching elements 8 and 9;
A and 12B are the capacitors equivalently replacing the resonant capacitor 12 between the primary windings 6 and 6 of the transformer 6, and 14 is the impedance between the power line and the ground (or the noise interference device connected to the commercial AC power supply 1). (ground impedance), 15 and 16 represent the distributed capacitance between the ground that exists through the heat sink of the collectors of the switching elements 8 and 9, and 17 represents the distributed capacitance that occurs between the ground and the ground through the coil and core of the inductance 7. It represents. Although not shown, there are other distributed capacitances between each component and the ground. As is clear from this equivalent circuit, due to the distributed capacitances 15, 16, 17, etc. between the line with particularly high noise potential and the ground, inductance 7 → impedance 14 → earth → each distributed capacitance 15, 1
6, 17→high frequency noise power supplies 8A, 9A→a noise closed loop passing through the inductance 7 is formed, and a large noise voltage is generated in the impedance 14. That is, the noise voltage between the power supply line and the ground increases. Therefore, as shown in FIG. 3, a conductive shield plate 21 sandwiched between insulating plates 20 is placed between the printed wiring board 18 on which the main circuit pattern of FIG. 1 is formed and the installation case 19. It is conceivable to connect the shield plate 21 to the power supply side of the circuit shown in FIG. 1, for example to the positive terminal of the rectifier circuit 4, to reduce the distributed capacitance between the line with high noise potential and the ground, thereby preventing noise interference. ing.
However, in such a configuration, the shield plate 21 must be specially prepared, which increases the number of parts and assembly man-hours, resulting in an expensive product.

As other conventional techniques, for example,
As shown in Japanese Patent No. 31965, there is a printed wiring board in which a ground pattern is formed over a wide range of surfaces.
However, since this device is connected to the earth as described above, if it is applied to a device that generates high-frequency power as in the present application, it will become a source of high-frequency noise, as is clear with reference to Figure 2 of the present application. As the power line and the ground become more short-circuited, the noise between the power line and the ground becomes louder, which has a greater effect on other equipment such as radios.

This invention was devised to eliminate these drawbacks, and the purpose is to provide a power conversion device that is inexpensive and can significantly reduce the noise voltage between one power line and the ground. .

The present invention is to place printed wiring parts for power lines that are connected to the input power supply on the printed wiring board surface and have a relatively low high-frequency noise potential, as described above, in close proximity to wiring parts that have a high high-frequency noise potential, and to reduce the margins of the printed wiring board. It is characterized in that it is formed so as to surround the wiring portion where the noise potential is high.

Note that in the present invention, the wiring portion is something that electrically connects a required connection terminal (or electrical component) to another required connection terminal (or electrical component), and includes printed conductors and jumper wires. Further, the printed wiring portion similarly performs necessary electrical connections and is made of printed conductors.

An embodiment of this invention will be described below with reference to the drawings. For convenience of explanation, FIG. 4 shows only the printed wiring board of the power converter of this invention. In other words, 3 in the figure
2 is a printed wiring board, and the printed wiring part of the power conversion main circuit described in FIG. 1 is formed on the board surface of this printed wiring board 22. In this case, the board surface of the printed wiring board 22 is
The copper foil of the printed wiring portion 23 of the positive side power supply line of the rectifier circuit 4, which is indicated by diagonal lines in FIG. 2), and is formed close to the printed wiring portion 24 having a high noise potential as described above, and so as to surround the printed wiring portion 24 having a high noise potential. Therefore, as shown in FIG. 5, the relatively large distributed capacitance 25 existing between the printed wiring portion 23 and the line with a high noise potential
By, high frequency noise source 8A, 9A - distributed capacitance 2
5 - Printed wiring part 23 - Inductance 7 - Forms a closed circuit of high frequency noise sources 8A and 9A, which can significantly reduce the noise voltage applied to impedance 14, greatly reducing noise interference to other equipment It can be suppressed. That is, it is understood that high frequency noise is contained within the closed circuit of the printed wiring portion 23, distributed capacitance 25, inductance 7, and high frequency noise power supplies 8A and 9A. On the other hand, in the technique disclosed in Japanese Utility Model Publication No. 37-31965, since the printed wiring section 23 is grounded, a closed circuit including the impedance 14 and the high frequency noise sources 8A and 9A is formed, and the noise of the impedance 14 is It is obvious that the voltage should be increased. Note that one pole of the power supply 1 is normally grounded, but this is grounded for low frequencies and is not grounded for high frequencies such as radio noise, which is the problem in this invention. . Therefore,
It should be noted that in the present invention, the power line printed wiring portion 23 and the ground point of the power source 1 are at completely different potentials in terms of high frequency. According to experiments conducted by the present inventors, the power supply 1 is 100 V as shown in Fig. 1.
50Hz, negative terminal 13 is a 40W fluorescent lamp,
When the power conversion circuit outputs 30KHz high frequency power, the configuration shown in Figure 4 is as follows.
525K compared to the one without printed wiring part 23
3 to 5 dB of noise between power line and ground between Hz and 1605 KHz
We were able to reduce this. Note that since the printed wiring portion 23 utilizes the blank space of the printed wiring board 22, the utilization rate of the printed wiring board 22 can be further increased. Here, in the above description, the printed wiring portion 23 that provides a shielding effect is the positive power supply line of the rectifier circuit 4;
The same effect as described above can be expected even if it is formed by the negative side power supply line of the rectifier circuit 4 (the power supply side of the inductance 7) or the AC power supply line. but,
If there are no capacitors 3 and 5 in Figure 1,
The effect of reducing the noise voltage between the power line that is not connected to the printed wiring portion 23 and the ground is small.

Note that this invention is not limited to the above-mentioned embodiments, but can be implemented with appropriate modifications without changing the gist. For example, in order to minimize the number of lines with a relatively high high-frequency noise potential on the printed wiring board and to make the printed wiring part that has a shielding effect wider, the lines with a high noise potential are made jumper wires, and this jumper wire is used as the above-mentioned printed wiring. It may be provided so as to be surrounded by other parts, or may be arranged so that a part thereof passes over the printed wiring part. In this way, the distributed capacitance can be further reduced and the noise voltage can be further reduced.

As described above, according to this invention, the printed wiring part for the power line, which has a relatively low high-frequency noise potential, is placed close to the part with a relatively high high-frequency noise potential on the surface of the printed wiring board, and there is a distributed capacitance between the two parts. By using the blank space of the printed wiring board to surround the part with high noise potential, it is possible to provide an inexpensive power conversion device that can significantly reduce the noise voltage between the power source and the ground. .

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of a power conversion circuit, FIG. 2 is a noise equivalent circuit diagram of a conventional device, and FIG. 3 is a schematic configuration diagram showing a conventional means for reducing noise.
FIG. 4 is a schematic configuration diagram showing an embodiment of this invention.
FIG. 5 is a noise equivalent circuit diagram of FIG. 4. 1...AC power supply, 2a, 2b...input terminal,
8, 9... Switching element, 15-17... Distributed capacitance, 18, 22... Printed wiring board, 23, 24
...Printed wiring part.

Claims (1)

[Claims for Utility Model Registration] (1) In a power conversion device configured using a printed wiring board, including a switching element, and converting an input commercial AC power supply voltage into high-frequency power, A printed wiring section for a power line, which has a relatively low high-frequency noise potential, is disposed close to a wiring section constituting a circuit section where a high-frequency noise potential is relatively high, so that the wiring section with a high high-frequency noise potential and the high-frequency A distributed capacitance is interposed between the printed wiring part for the power supply line having a low noise potential, and the printed wiring part for the power supply line surrounds the wiring part having the high noise potential using the margin of the printed wiring board. A power conversion device characterized in that: (2) The power conversion device according to claim (1), wherein the wiring of the circuit portion having a high noise potential is formed by printed wiring. (3) The power conversion device according to claim (1) of the utility model registration, characterized in that the circuit portion having a high noise potential is wired by a jumper wire.