CN213367740U

CN213367740U - Filter circuit

Info

Publication number: CN213367740U
Application number: CN202022517580.5U
Authority: CN
Inventors: 骆云龙; 亚历克斯·漆; 史歌; 漆一宏; 薛瑞尼; 金荣皓
Original assignee: Zhuhai Haimi Software Technology Co ltd
Current assignee: Zhuhai Haimi Software Technology Co ltd
Priority date: 2020-11-04
Filing date: 2020-11-04
Publication date: 2021-06-04
Anticipated expiration: 2030-11-04

Abstract

The utility model discloses a filter circuit, wherein a first PCB layer consists of a power line, a power interface, a second filter capacitor and a first filter capacitor; the power line comprises a power network and a GND network; the second PCB layer is provided with a conductor plane; the power interface is connected with the GND network and is also connected with the conductor plane; the GND network, the second filter capacitor and the conductor plane are connected in sequence; the power supply network, the first filter capacitor and the conductor plane are connected in sequence. The utility model discloses a circuit structure's circuit design and holistic layout design have fine suppression effect to common mode noise, differential mode noise, radiated noise, conducted noise.

Description

Filter circuit

Technical Field

The utility model relates to a filtering technology, especially a filter circuit.

Background

Conducted noise and radiation noise at a power interface of an electronic product of an external power supply have strict test requirements, and normal operation of other electronic products can be influenced and circuit performance and stability of the electronic products can be influenced if the noise exceeds the standard.

Common filter circuits include two broad categories of passive and active filters, the main forms of passive filtering include capacitive, inductive and duplex (L-type, LC, RC, etc.) filtering. The main form of active filtering is active RC filtering, i.e. electronic filtering.

The noise of the power supply part comprises differential mode noise and common mode noise, and a common filter circuit is only effective to the differential mode noise generally and cannot solve the influence brought by the common mode noise.

Common mode inductor, also called common mode choke, is commonly used to suppress common mode noise, but common mode inductor is bulky and costly. Especially, in electronic devices with high power, the common mode inductor has a large size and high cost for ensuring the current capacity, and is not favorable for circuit design and system integration.

SUMMERY OF THE UTILITY MODEL

The utility model aims to provide a: the filter circuit is provided for solving the problem that the common mode noise is difficult to inhibit in the existing filter circuit.

In order to realize the purpose, the utility model discloses a technical scheme be:

a filter circuit comprises a first PCB layer and a second PCB layer;

the first PCB layer comprises a power line, a power interface, a second filter capacitor and a first filter capacitor; the power line comprises a power network and a GND network;

the second PCB layer includes a conductor plane;

the power interface is connected with the GND network and is also connected with the conductor plane;

the GND network, the second filter capacitor and the conductor plane are connected in sequence;

the power supply network, the first filter capacitor and the conductor plane are connected in sequence.

The utility model discloses a circuit structure's circuit design and holistic layout design have fine suppression effect to common mode noise, differential mode noise, radiated noise, conducted noise.

Preferably, an intermediate layer is further arranged between the first PCB layer and the second PCB layer, and a plurality of via holes are formed in the intermediate layer.

Preferably, the second filter capacitor is connected with the conductor plane through a via hole of the middle layer; the first filter capacitor is connected with the conductor plane through the via hole of the middle layer; the power supply interface 107 is connected to the conductor plane via a via hole in the intermediate layer.

Preferably, the power supply further comprises a third filter capacitor, one end of the third filter capacitor is connected to the power supply network 106, and the other end of the third filter capacitor is connected to the GND network.

Preferably, the device further comprises a first filtering module and a second filtering module, wherein the first filtering module is arranged on the power supply network, and the second filtering module is arranged on the GND network.

Preferably, the first filtering module and the second filtering module are inductors, magnetic beads or common mode chokes.

To sum up, owing to adopted above-mentioned technical scheme, the beneficial effects of the utility model are that:

a filter circuit is characterized in that a first PCB layer consists of a power line, a power interface, a second filter capacitor and a first filter capacitor; the power line comprises a power network and a GND network; the second PCB layer is provided with a conductor plane; the power interface is connected with the GND network and is also connected with the conductor plane; the GND network, the second filter capacitor and the conductor plane are connected in sequence; the power supply network, the first filter capacitor and the conductor plane are connected in sequence. The utility model discloses a circuit structure's circuit design and holistic layout design have fine suppression effect to common mode noise, differential mode noise, radiated noise, conducted noise.

Drawings

Fig. 1 is a schematic view of the Layout structure of the present invention.

Fig. 2 is a schematic circuit diagram of embodiment 1.

Fig. 3 is a schematic circuit diagram of embodiment 2.

Fig. 4 is a schematic circuit diagram of embodiment 3.

Fig. 5 shows the result of a conducted noise test without using the circuit of the present invention.

Fig. 6 is a conducted noise test result using the circuit of the present invention.

Fig. 7 uses the circuit radiation noise test results of the present invention.

Fig. 8 does not use the circuit radiation noise test result of the present invention.

The labels in the figure are: 101A-a first PCB layer, 101B-an intermediate layer, 101C-a second PCB layer, 102-a second filter capacitor, 103-a first filter capacitor, 104-a power line, 105-a GND network, 106-a power network, 107-a power interface, 108-a first metal via, 109-a conductor plane, 110-a clearance area, 111-a third filter capacitor, 112-a first filter module, 113-a second filter module, 114-a second metal via, 115-a third metal via.

Detailed Description

The present invention will be described in detail with reference to the accompanying drawings.

In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the invention.

Example 1

A filter circuit as shown in fig. 1, comprising a first PCB layer 101A, a second PCB layer 101C; the first PCB layer comprises a power line 104, a power interface 107, a second filter capacitor 102 and a first filter capacitor 103; the power line 104 includes a power network 106, a GND network 105; second PCB layer 101C includes conductor plane 109; the power interface 107 is connected with the GND network 105, and the power interface 107 is also connected with the conductor plane 109 through a first metal via hole 108; the GND network 105 is connected with one end of the second filter capacitor 102, and the other end of the second filter capacitor 102 is connected with the conductor plane 109 through a third metal via hole 115; the power supply network 106 is connected to one end of the first filter capacitor 103, and the other end of the first filter capacitor 103 is connected to the conductor plane 109 through the second metal via 114. An intermediate layer is further arranged between the first PCB layer 101A and the second PCB layer 101C, a plurality of through holes are formed in the intermediate layer 101B and used for penetrating through metal through holes, and the intermediate layer can be a dielectric layer or an electric layer plus a dielectric layer. The second filter capacitor 102 is connected with the conductor plane 109 through the via hole of the middle layer 101B; the first filter capacitor 103 is connected with the conductor plane 109 through the via hole of the middle layer 101B; the power interface 107 is connected to the conductor plane 109 via a via of the intermediate layer 101B.

Combine the circuit schematic diagram of fig. 2, the utility model discloses a filtering effect all has apparent effect to falling of making an uproar of differential mode noise and common mode noise, particularly:

for differential mode noise, a path 1 of differential mode noise current on the power supply network is GND network 105- > second filter capacitor 102- > third metal via hole 115- > conductor plane 109- > first metal via hole 108- > power supply interface 107- > GND network 105; the path 2 of the differential mode noise current is a power supply network 106- > a first filter capacitor 103- > a second metal via hole 114- > a conductor plane 109- > a first metal via hole 108- > a power interface 107- > a GND network 105; the differential mode noise enters the PCB from the power line 104 and then returns to the power line 104 after passing through a loop, effectively blocking the noise outside the PCB. The common mode noise exists on both the power supply network and the GND network, and the path of the common mode noise is GND network 105- > second filter capacitor 102- > third metal via hole 115- > conductor plane 109- > first metal via hole 108- > power interface 107- > GND network 105 and power supply network 106- > first filter capacitor 103- > second metal via hole 114- > conductor plane 109- > first metal via hole 108- > power interface 107- > GND network 105. Common mode noise enters the PCB from the power line 104 and also goes back to the power line 104 after a loop, effectively blocking the noise outside the PCB. The common mode noise and the differential mode noise are the same as seen from the path, but the principle of filtering is different.

Example 2

The difference between this embodiment 2 and embodiment 1 is that the present embodiment further includes a third filter capacitor 111, and one end of the third filter capacitor 111 is connected to the power supply network 106, and the other end is connected to the GND network 105, as shown in fig. 3.

The third filter capacitor 111 is added to further optimize the filtering effect of the differential mode noise, because the third filter capacitor 111 provides a noise current path for the differential mode noise, and the specific path is GND network 105- > third filter capacitor 111- > power supply network 106 or power supply network 106- > third filter capacitor 111- >105GND network. The third filter capacitor 111 may be a filter capacitor or a plurality of filter capacitors, and the capacitance value of the capacitor may be selected according to the required filter frequency, such as 1nF or 100 pF.

Fig. 5 is a result of the conducted noise test of the circuit of the present invention, which is only the filter circuit of the third filter capacitor 111, and the result shows that the conducted noise of the low frequency part below 1MHz is too serious. Fig. 6 shows the conducted noise test result using the circuit design of this example 2, and the result shows that no noise within the test range exceeds the standard, and the noise suppression effect is close to 30 dBuV.

Fig. 8 is not using the utility model discloses the circuit, only the radiated noise test result of the filter circuit of S6 structure, and the result shows that 199MHz, 375MHz, 625MHz department exceeds standard seriously. Fig. 7 shows the results of the radiated noise test using the circuit design of this example 2, showing that the radiated noise exceeds the standard at all frequencies within the test range. The noise suppression effect is close to 30 dBuV/m.

Example 3

The difference between this embodiment 3 and embodiment 2 is that the power supply device further includes a first filtering module 112 and a second filtering module 113, the first filtering module 112 is disposed on the power supply network 106, the second filtering module 113 is disposed on the GND network 105, and the first filtering module 112 and the second filtering module 113 are inductors, magnetic beads, or common mode chokes, as shown in fig. 4.

The first filtering module 112 and the second filtering module 113 are added to further optimize the filtering effect of the common mode noise. The first filtering module 112 and the second filtering module 113 may be inductors, beads, or common mode chokes, and the number of the first filtering module 112 and the second filtering module 113 may be plural, and is selected according to the current magnitude of the actual circuit and the frequency of the desired filtering.

The above description is only exemplary of the present invention and should not be taken as limiting the scope of the present invention, as any modifications, equivalents, improvements and the like made within the spirit and principles of the present invention are intended to be included within the scope of the present invention.

Claims

1. The filter circuit is characterized by comprising a first PCB layer and a second PCB layer;

the second PCB layer includes a conductor plane;

2. The filter circuit according to claim 1, wherein an intermediate layer is further disposed between the first PCB layer and the second PCB layer, the intermediate layer is a dielectric layer or a dielectric layer plus an electrical layer, and a plurality of via holes are disposed on the intermediate layer.

3. A filter circuit according to claim 2, wherein the second filter capacitor is connected to the conductor plane by a via in an intermediate layer; the first filter capacitor is connected with the conductor plane through the via hole of the middle layer; the power interface is connected with the conductor plane through the via hole in the middle layer.

4. The filter circuit according to claim 1, further comprising a third filter capacitor, wherein one end of the third filter capacitor is connected to the power supply network, and the other end of the third filter capacitor is connected to the GND network.

5. The filter circuit according to claim 1, further comprising a first filter module and a second filter module, wherein the first filter module is disposed on the power supply network, and the second filter module is disposed on the GND network.

6. The filter circuit according to claim 5, wherein the first filter module and the second filter module are inductors, magnetic beads, or common mode chokes.