CN116405060A

CN116405060A - Frequency band switching circuit and electronic equipment

Info

Publication number: CN116405060A
Application number: CN202310472937.8A
Authority: CN
Inventors: 山峰; 程遥; 陆一凡; 章跃平
Original assignee: Ningbo Sanxing Medical and Electric Co Ltd
Current assignee: Ningbo Sanxing Medical and Electric Co Ltd
Priority date: 2023-04-26
Filing date: 2023-04-26
Publication date: 2023-07-07

Abstract

The embodiment of the application provides a frequency band switching circuit and electronic equipment, and relates to the technical field of carrier communication. The frequency band switching circuit comprises a coupling transformer and a variable inductance module, wherein the coupling transformer comprises an inner side and an outer side. The outer side is used for connecting an outer circuit; the inner side edge comprises a first coil and a second coil, the first end of the first coil and the second end of the second coil are used for being connected with the carrier signal processing module, the second end of the first coil is connected with the first end of the variable inductance module, and the first end of the second coil is connected with the second end of the variable inductance module; the variable inductance module is used for generating different inductance values in different conducting states. The resonance point and the passband can be changed by changing the inductance of the variable inductance module, so that the wider passband can be covered.

Description

Frequency band switching circuit and electronic equipment

Technical Field

The present disclosure relates to the field of carrier communication technologies, and in particular, to a frequency band switching circuit and an electronic device.

Background

The electric meter automation meter reading system uses a power line carrier communication technology to communicate, as shown in fig. 1, the electric meter is electrically isolated from a live wire and a zero wire through a coupling transformer, and a carrier wave is transmitted.

The capacitance in fig. 1 is an X safety capacitor, and there are the following requirements for the X safety capacitor: the lower the carrier frequency is, the higher the capacitance of the required X safety capacitor is, so that the impedance of the X safety capacitor at the carrier frequency can be kept at a lower level, and the signal attenuation caused by the insertion loss of a carrier signal in normal communication is avoided.

It is generally required that the impedance of the compliance capacitance in the passband be no greater than 1 Ω. The impedance calculation formula of the capacitor is as follows:

where f is the carrier frequency, C is the capacitance, and Zc is the impedance of the capacitance.

Because the strong electric interface of the power line carrier is directly connected to the power grid (L in fig. 1 is a live wire, N is a zero wire), and the impedance of the coupling transformer is extremely small under the frequency of the power grid, at this time, the X safety capacitor becomes a capacitive load.

This capacitive load is not negligible if the allowed carrier frequency is low in the country or region in which the product is put. In this case, an inductor L1 may be further connected in series to the X-meter capacitor, so that the X-meter capacitor and the series inductor form LC resonance, and the resonance point of the LC may be located at the geometric center of the passband. This approach can significantly reduce the capacity of the X-lay capacitor. Such an embodiment is shown in fig. 2.

The meaning of geometric center frequency above is:

wherein f _{Several kinds of table} For geometric centre frequency f _{High frequency point} Is the high frequency point frequency of the passband, f _{Low frequency point} Is the low frequency point frequency of the passband.

But the LC resonance is actually a bandpass filter, the smaller C, the narrower the bandwidth of the passband of the LC resonance. When a small X-lay capacitor is applied, the bandwidth of the LC resonator bandpass filter may be too narrow to cover the complete passband.

Therefore, how to cover a wider passband is a technical problem to be solved.

Disclosure of Invention

An object of the present application is to provide a frequency band switching circuit and an electronic device, so as to solve the technical problem of how to cover a wider passband in the prior art.

In order to achieve the above purpose, the following technical solutions are adopted in the embodiments of the present application.

In a first aspect, an embodiment of the present application provides a frequency band switching circuit, including a coupling transformer and a variable inductance module, where the coupling transformer includes an inner side and an outer side.

The outer side edge is used for connecting an outer circuit;

the inner side edge comprises a first coil and a second coil, the first end of the first coil and the second end of the second coil are used for being connected with a carrier signal processing module, the second end of the first coil is connected with the first end of the variable inductance module, and the first end of the second coil is connected with the second end of the variable inductance module; the variable inductance module is used for generating different inductance values in different conducting states.

Optionally, the variable inductance module includes at least two switchable inductors, and each switchable inductor is connected in parallel.

Optionally, each set of the switchable inductors includes: the first switching inductor, the first switch, the second switching inductor and the second switch;

one end of the first switching inductor and one end of the first switch which are connected in series are connected with the first end of the variable inductance module, and the other end of the first switching inductor and the other end of the first switch are grounded;

one end of the second switching inductor and one end of the second switch which are connected in series are connected with the second end of the variable inductance module, and the other end of the second switching inductor and the other end of the second switch are grounded.

Optionally, the frequency band switching circuit further includes at least one dc isolation capacitor;

the first end of the first coil is connected with a direct current isolation capacitor, and the second end of the direct current isolation capacitor is used for being connected with a carrier signal processing module; and/or

The second end of the second coil is connected with a direct current isolation capacitor, and the second end of the direct current isolation capacitor is used for being connected with a carrier signal processing module.

Optionally, the frequency band switching circuit further includes a TX power amplifier, wherein the first end of the first coil and the second end of the second coil are connected to two output ends of the TX power amplifier, and two input ends of the TX power amplifier are used for connecting with a carrier signal modem.

Optionally, the frequency band switching circuit further includes an RX band-pass filter, wherein the first end of the first coil and the second end of the second coil are connected to two input ends of the RX band-pass filter, and two output ends of the RX band-pass filter are used for connecting with a carrier signal modem.

Optionally, the frequency band switching circuit further comprises a TX power amplifier, an RX band-pass filter and a carrier signal modem;

the first end of the first coil and the second end of the second coil are connected to two output ends of the TX power amplifier, and two input ends of the TX power amplifier are used for connecting two transmitting ends of a carrier signal modem;

the first end of the first coil and the second end of the second coil are connected to two input ends of the RX band-pass filter, and two output ends of the RX band-pass filter are used for connecting two receiving ends of a carrier signal modem.

Optionally, the frequency band switching circuit further includes an X-security capacitor, and the outer side is connected in series with the X-security capacitor.

Optionally, the number of turns of the first coil and the second coil is the same.

In a second aspect, an embodiment of the present application provides an electronic device, where the electronic device includes the frequency band switching circuit of the first aspect.

Compared with the prior art, the application has the following beneficial effects:

in the frequency band switching circuit provided by the embodiment of the application, the inner side edge of the coupling transformer is divided into two end inductors, the variable inductance module is arranged between the two inductors on the inner side edge and can replace the outer side edge to be used for resonating with the X safety capacitor, and the inductance of the variable inductance module is variable, so that the inductance of the variable inductance module can be changed to change a resonance point and a passband, and further the wider passband is covered.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered limiting the scope, and that other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic diagram of a prior art electric meter for transmitting a carrier wave by electrically isolating a coupling transformer from a hot line and a neutral line;

FIG. 2 is a schematic diagram of an X-amp capacitor and series inductor forming an LC resonance to reduce capacitive loading;

fig. 3 is a schematic diagram of a frequency band switching circuit according to an embodiment of the present application;

fig. 4 is a schematic diagram of a frequency band switching circuit formed by a carrier signal modem, a TX power amplifier, a dc isolation capacitor, an RX band-pass filter, an X safety capacitor, a coupling transformer and a variable inductance module according to an embodiment of the present application;

fig. 5 is a schematic diagram of a frequency band switching circuit of a variable inductance module according to an embodiment of the present application, where the variable inductance module includes two switchable inductors.

Reference numerals illustrate:

100-frequency band switching circuit

110-carrier signal processing module

111-carrier signal modem

112-TX power amplifier

113-RX band-pass filter

Detailed Description

For the purposes of making the objects, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and the described embodiments are some embodiments of the present application, but not all embodiments. The components of the embodiments of the present application, which are generally described in the figures herein, may be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the present application, as provided in the accompanying drawings, is not intended to limit the scope of the application, as claimed, but is merely representative of selected embodiments of the application. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure. The following embodiments and features of the embodiments may be combined with each other without conflict.

In the description of the present application, it should be noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The term "coupled" is to be interpreted broadly, as being a fixed connection, a removable connection, or an integral connection, for example; can be directly connected or indirectly connected through an intermediate medium.

In the existing power line carrier communication technology, the problem that resonance points are fixed and passband is limited exists.

In order to overcome the above problems, referring to fig. 3, the embodiment of the present application provides a frequency band switching circuit 100, which includes a coupling transformer T1 and a variable inductance module L2, wherein the coupling transformer includes an inner side and an outer side. The inner side corresponds to the left part of T1 in the figure, and is close to the carrier signal processing module 110; the outer side corresponds to the right part of T1 in the figure, and is distant from the carrier signal processing module 110.

Because the carrier signal is composed of a high-frequency alternating current signal, the coupling transformer T1 is utilized to realize electrical isolation, and the specific functions are as follows:

1. the outer side N2 is used for inputting an outer carrier or outputting an inner carrier, the outer carrier is a carrier from an outer circuit, and the inner carrier is a carrier from an inner side;

2. the inner side comprises a first coil N1-1 and a second coil N1-2:

1) The first end of the first coil N1-1 and the second end of the second coil N1-2 are used for inputting an inner carrier or outputting an outer carrier, and are connected with the carrier signal processing module 110;

2) The second end of the first coil N1-1 is connected to the first end of the variable inductance module L2, the first end of the second coil N1-2 is connected to the second end of the variable inductance module L2, and the resonance point is changed and the passband is changed by changing the inductance of the variable inductance module L2, so that the wider passband is covered. The variable inductance module L2 can switch in or out the inductance to generate different inductance values through the on and off states of some switching tubes and other devices.

The present band switching circuit 100 can also be understood as follows:

1. the inductance L1 is removed in fig. 2.

2. The winding N1 in FIG. 2 is divided into two groups of coils, wherein the two groups of coils are N1-1 and N1-2 respectively, and the two groups of coils can be equally divided into the winding N1, namely the N1-1 and the N1-2 are the same in order to facilitate the design of parameters of devices and circuit balance at two sides.

3. Then, a variable inductance module L2 is inserted between the N1-1 and the N1-2, and parameters of the design L2 meet the following formulas, so that the performance of the graph 3 is consistent with that of the graph 2:

in the above formula, N1 is the number of turns of winding N1 in fig. 2, N2 is the number of turns of outer side N2, L1 is the inductance of inductor L1 in fig. 2, and L2 is the inductance of variable inductance module L2.

Therefore, the variable inductance module L2 replaces the L1 inductance in the original circuit, and as the original inductance L1 forms a resonance point of RC resonance, the effect of changing the inductance of the variable inductance module L2 is equivalent to changing the original inductance L1, namely changing the resonance point of RC resonance, and switching of a plurality of LC resonance frequency bands is realized.

Fig. 4 illustrates an embodiment of the carrier signal modem 111, the TX power amplifier 112, the dc isolation capacitors C1 and C3, the RX band-pass filter 113, the X-pass capacitor C2, the coupling transformer T1, and the variable inductance module L2, where the carrier signal modem 111, the TX power amplifier 112, and the RX band-pass filter 113 can be regarded as the carrier signal processing module 110 in fig. 3, and some or all of them can be regarded as the band switching circuit 100.

The functions of the various parts are as follows:

1) Carrier signal modem 111

The digital quantity is modulated and then output to a TX power amplifier; and demodulating the received analog quantity.

2) TX power amplifier 112

And carrying out power amplification on the modulated carrier signal, and improving the capacity of carrying load.

3) DC isolation capacitor C1, C3

DC isolation is realized, and short circuit on the side of the coupling transformer N1 caused by output zero drift of the TX power amplifier is avoided.

4) RX bandpass filter 113

The signal in the passband is passed in a low loss mode, and the signal outside the passband is passed in a high loss mode, thereby improving the signal-to-noise ratio.

5) X safety capacitor C2

The high-frequency carrier signal passes through the coupling transformer in a low-loss mode, and forms high impedance for low-frequency power grid voltage, so that large current is prevented from passing through the coupling transformer.

For the embodiment of the variable inductance module L2, reference may be made to fig. 5, and fig. 5 shows a schematic diagram of an embodiment of the variable inductance module formed by two switchable inductors.

The variable inductance module comprises at least two groupsSwitchable inductanceEach group of switchable inductors are connected in parallel. For example, a variable inductance modeThe block includes a first set of switchable inductances and a second set of switchable inductances, then one of the following states may be selected:

1. the first group of switchable inductors are switched in and the second group of switchable inductors are switched out, and the inductance value of the whole variable inductance module is an inductance value L _x1 。

2. The first group of switchable inductors and the second group of switchable inductors are switched in simultaneously, and the inductance value of the whole variable inductance module is another inductance value L _x2 。

If the inductance values of the first set of switchable inductances and the second set of switchable inductances are different, three states can be realized, in addition to the two states 1, 2 described above, a third type:

3. the second group of switchable inductors are switched in and the first group of switchable inductors are switched out, and the inductance value of the whole variable inductance module is an inductance value L _x3 。

In fig. 5, the first set of switchable inductors includes: inductor L3-1, switching tube Q1, inductor L3-2, switching tube Q2. The individual devices have the following connection relationships:

1. the control terminal of the switching tube Q1 and the control terminal of the switching tube Q2 are used for inputting a control signal CTRL1.

2. One end of the inductor L3-1 and the switching tube Q1 which are connected in series is connected with the first end P1 of the variable inductance module, and the other end is grounded; in the figure, the inductor L3-1 and the switching tube Q1 may be interchanged to form a series relationship.

3. One end of the inductor L3-2 and the switching tube Q2 which are connected in series is connected with the first end P1 of the variable inductance module, and the other end is grounded; in the figure, the inductor L3-2 and the switching tube Q2 may be interchanged to form a series relationship.

It can be understood that the inductance L3-1 and the inductance L3-2 are divided into 2 inductance values of L2 in fig. 4, and are connected to GND through electronic switches respectively. Here, NMOS is used as an electronic switch. Similarly, a relay may be used as a switch.

Similarly, the second set of switchable inductors in fig. 5 includes: inductor L4-1, switching tube Q3, inductor L4-2, switching tube Q4. The individual devices have the following connection relationships:

1. the control terminal of the switching tube Q3 and the control terminal of the switching tube Q4 are used for inputting a control signal CTRL2.

2. One end of the inductor L4-1 and the switching tube Q1 which are connected in series is connected with the first end P1 of the variable inductance module, and the other end is grounded; in the figure, the inductor L4-1 and the switching tube Q1 may be interchanged to form a series relationship.

3. One end of the inductor L4-2 and the switching tube Q2 which are connected in series is connected with the first end P1 of the variable inductance module, and the other end is grounded; in the figure, the inductor L4-2 and the switching tube Q2 may be interchanged to form a series relationship.

As can be summarized from the embodiment of fig. 5, each set of switchable inductors includes:

1. the two inductors are named as a first switching inductor and a second switching inductor respectively;

2. the two switches are named as a first switch and a second switch respectively;

has the following connection relation:

one end of the first switching inductor is connected with the first end of the variable inductance module after being connected in series with the first switch, and the other end of the first switching inductor is grounded;

Similarly, a third set of switchable inductors or more may be provided, and the switch of each set of switchable inductors may be connected to a control signal. The number of the circuits of the switchable inductor can be infinitely extended and connected in parallel, so that the LC resonance band-pass filter with any passband bandwidth is realized.

Based on the above embodiments, the embodiments of the present application further provide an electronic device, for example, an electric energy meter or a communication device of the electric energy meter, which performs power line carrier communication through the above frequency band switching circuit. The LC resonant band-pass filter is used for reducing the capacitance of the X safety capacitor, thereby reducing reactive power brought by the X safety capacitor and further reducing apparent power. Under the condition of using smaller X-meter capacitance, the function of expanding the bandwidth of the LC resonance band-pass filter can still be realized through switching of a plurality of groups of inductors.

The above-described embodiments of the apparatus and system are merely illustrative, and some or all of the modules may be selected according to actual needs to achieve the objectives of the present embodiment. Those of ordinary skill in the art will understand and implement the present invention without undue burden.

The foregoing is merely a preferred embodiment of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions easily contemplated by those skilled in the art within the technical scope of the present application should be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. The frequency band switching circuit is characterized by comprising a coupling transformer and a variable inductance module, wherein the coupling transformer comprises an inner side edge and an outer side edge;

the outer side edge is used for connecting an outer circuit;

2. The band switching circuit of claim 1, wherein the variable inductance module comprises at least two sets of switchable inductances, each set of switchable inductances being connected in parallel.

3. The band switching circuit of claim 2, wherein each set of said switchable inductors comprises: the first switching inductor, the first switch, the second switching inductor and the second switch;

4. The band switching circuit of claim 1, wherein the band switching circuit further comprises at least one dc isolation capacitor;

5. The band switching circuit of claim 1, further comprising a TX power amplifier, the first terminal of the first coil and the second terminal of the second coil being connected to two output terminals of the TX power amplifier, two input terminals of the TX power amplifier being used to connect two transmit terminals of a carrier signal modem.

6. The band switching circuit of claim 1, further comprising an RX band pass filter, wherein the first end of the first coil and the second end of the second coil are connected to two inputs of the RX band pass filter, and wherein two outputs of the RX band pass filter are used to connect two receivers of a carrier signal modem.

7. The band switching circuit of claim 1, wherein the band switching circuit further comprises a TX power amplifier, an RX band pass filter, and a carrier signal modem;

8. The band switching circuit of claim 1, further comprising an X-clamp capacitor, the outer side being in series with the X-clamp capacitor.

9. The band switching circuit of claim 1, wherein the number of turns of the first coil and the second coil are the same.

10. An electronic device comprising the frequency band switching circuit of any one of claims 1-9.