Frequency band switching circuit and electronic equipment

Abstract

The embodiment of the present application provides a frequency band switching circuit and electronic equipment, which relate to the field of carrier communication technology. The frequency band switching circuit includes a coupling transformer and a variable inductance module, and the coupling transformer includes an inner side and an outer side. The outer side is used to connect the outer circuit; the inner side includes a first coil and a second coil, the first end of the first coil and the second end of the second coil are used to connect to the carrier signal processing module, the second end of the first coil is connected to the first end of the variable inductance module, and the first end of the second coil is connected to the second end of the variable inductance module; the variable inductance module is used to generate different inductance values in different conduction states. By changing the inductance of the variable inductance module, the resonance point and the passband can be changed, thereby achieving coverage of a wider passband.

Description

Technical Field

[0001] The present application relates to the field of carrier communication technology, and in particular to a frequency band switching circuit and electronic equipment. Background Art

[0002] The automatic meter reading system uses power line carrier communication technology to communicate, such as Figure 1 , the electric meter is electrically isolated from the live wire and the neutral wire through a coupling transformer, and transmits the carrier.

[0003] Figure 1 The capacitor in the figure is an X safety capacitor. The following requirements apply to X safety capacitors: The lower the carrier frequency, the higher the required capacitance of the X safety capacitor must be. This ensures that the impedance of the X safety capacitor remains low at the carrier frequency, avoiding insertion loss and signal attenuation in the carrier signal during normal communication.

[0004] Generally, the impedance of safety capacitors within the passband is required to be no greater than 1Ω. The impedance calculation formula for capacitors is as follows:

[0005]

[0006] Where f is the carrier frequency, C is the capacitance, and Zc is the impedance of the capacitor.

[0007] Since the strong current interface of the power line carrier is directly connected to the power grid ( Figure 1 L is the live wire and N is the neutral wire), and at the grid frequency, the impedance of the coupling transformer is extremely small. At this time, the X safety capacitor becomes a capacitive load.

[0008] If the carrier frequency allowed in the country or region where the product is launched is very low, this capacitive load cannot be ignored. In this case, an inductor L1 can be connected in series with the X safety capacitor to form an LC resonance between the X safety capacitor and the series inductor, and the LC resonance point is made to fall at the geometric center of the passband. This method can significantly reduce the capacity of the X safety capacitor. This type of implementation plan can be seen in Figure 2 shown.

[0009] The meaning of the geometric center frequency above is:

[0010]

[0011] Where, f 几 is the geometric center frequency, f 高频点 is the high frequency point of the passband, f 低频点 is the low frequency point of the passband.

[0012] However, LC resonance is actually a bandpass filter. The smaller C is, the narrower the bandwidth of the LC resonance passband will be. When using a smaller X safety capacitor, the bandwidth of the LC resonance bandpass filter may be too narrow and unable to cover the entire passband.

[0013] Therefore, how to cover a wider passband is a technical problem that needs to be solved. Summary of the Invention

[0014] The purpose of this application is to provide a frequency band switching circuit and electronic equipment to solve the technical problem of how to cover a wider passband in the prior art.

[0015] To achieve the above objectives, the embodiments of the present application adopt the following technical solutions.

[0016] 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, wherein the coupling transformer includes an inner side and an outer side.

[0017] The outer side is used to connect to the outer circuit;

[0018] The inner side includes a first coil and a second coil, the first end of the first coil and the second end of the second coil are used to connect to the carrier signal processing module, the second end of the first coil is connected to the first end of the variable inductance module, and the first end of the second coil is connected to the second end of the variable inductance module; the variable inductance module is used to generate different inductance values in different conduction states.

[0019] Optionally, the variable inductor module includes at least two groups of switchable inductors, and each group of switchable inductors is connected in parallel.

[0020] Optionally, each group of switchable inductors includes: a first switchable inductor, a first switch, a second switchable inductor, and a second switch;

[0021] One end of the first switching inductor and the first switch connected in series is connected to the first end of the variable inductor module, and the other end is grounded;

[0022] One end of the second switching inductor and the second switch connected in series is connected to the second end of the variable inductor module, and the other end is grounded.

[0023] Optionally, the frequency band switching circuit further includes at least one DC isolation capacitor;

[0024] A first end of the first coil is connected to a DC isolation capacitor, and a second end of the DC isolation capacitor is used to connect to a carrier signal processing module; and / or

[0025] The second end of the second coil is connected to a DC isolation capacitor, and the second end of the DC isolation capacitor is used to connect to a carrier signal processing module.

[0026] Optionally, the frequency band switching circuit further includes a TX power amplifier, 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 the two input ends of the TX power amplifier are used to connect to a carrier signal modem.

[0027] Optionally, the frequency band switching circuit further includes an RX bandpass filter, the first end of the first coil and the second end of the second coil are connected to two input ends of the RX bandpass filter, and the two output ends of the RX bandpass filter are used to connect to a carrier signal modem.

[0028] Optionally, the frequency band switching circuit further includes a TX power amplifier, an RX bandpass filter and a carrier signal modem;

[0029] The first end of the first coil and the second end of the second coil are connected to the two output ends of the TX power amplifier, and the two input ends of the TX power amplifier are used to connect to the two transmitting ends of the carrier signal modem;

[0030] The first end of the first coil and the second end of the second coil are connected to two input ends of the RX bandpass filter, and the two output ends of the RX bandpass filter are used to connect to two receiving ends of a carrier signal modem.

[0031] Optionally, the frequency band switching circuit further includes an X safety capacitor, and the outer side and the X safety capacitor are connected in series.

[0032] Optionally, the first coil and the second coil have the same number of turns.

[0033] In a second aspect, an embodiment of the present application provides an electronic device, comprising the frequency band switching circuit of the first aspect.

[0034] Compared with the prior art, this application has the following beneficial effects:

[0035] In the frequency band switching circuit provided in the embodiment of the present application, the inner side of the coupling transformer is divided into two inductors at both ends. The variable inductor module is located between the two inductors on the inner side and can replace the inductor on the outer side used to resonate with the X safety capacitor. Since the inductance of the variable inductor module is variable, its inductance can be changed to change the resonance point and the passband, thereby achieving wider passband coverage. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0037] Figure 1 This is a schematic diagram of a conventional electric meter that transmits a carrier wave by electrically isolating the electric meter from the live wire and the neutral wire through a coupling transformer;

[0038] Figure 2 This is a schematic diagram of an X-rated capacitor and a series inductor forming an LC resonance to reduce capacitive load;

[0039] Figure 3 A schematic diagram of a frequency band switching circuit provided in an embodiment of the present application;

[0040] Figure 4 A schematic diagram of a frequency band switching circuit provided by an embodiment of the present application, comprising a carrier signal modem, a TX power amplifier, a DC isolation capacitor, an RX bandpass filter, an X safety capacitor, a coupling transformer, and a variable inductor module;

[0041] Figure 5 A variable inductor module provided in an embodiment of the present application includes a frequency band switching circuit schematic diagram of two sets of switchable inductors.

[0042] Description of reference numerals:

[0043] 100-band switching circuit

[0044] 110-Carrier signal processing module

[0045] 111-Carrier Signal Modem

[0046] 112-TX Power Amplifier

[0047] 113-RX Bandpass Filter DETAILED DESCRIPTION

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present application. The described embodiments are part of the embodiments of the present application, but not all of the embodiments. Generally, the components of the embodiments of the present application described in the drawings herein can be arranged and designed in various different configurations.

[0049] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is claimed, but rather merely represents selected embodiments of the present application. All other embodiments derived by persons of ordinary skill in the art based on the embodiments in this application without creative effort are intended to fall within the scope of protection of this application. The following embodiments and features therein may be combined with each other unless there is a conflict.

[0050] In the description of this application, it should be noted that relational terms such as first and second are used solely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. The term "connected" should be understood broadly, for example, it can mean fixed connection, detachable connection, or integral connection; it can be directly connected or indirectly connected through an intermediate medium.

[0051] The existing power line carrier communication technology has the problems of fixed resonance point and limited passband.

[0052] To overcome the above problems, please refer to Figure 3 The present embodiment provides a frequency band switching circuit 100, including a coupling transformer T1 and a variable inductor module L2. The coupling transformer includes an inner side and an outer side. The inner side corresponds to the left side of T1 in the figure and is close to the carrier signal processing module 110. The outer side corresponds to the right side of T1 in the figure and is away from the carrier signal processing module 110.

[0053] Because the carrier signal is composed of a high-frequency AC signal, a coupling transformer T1 is used to achieve electrical isolation. The specific functions are as follows:

[0054] 1. The outer side N2 is used to input the outer carrier or output the inner carrier. The outer carrier refers to the carrier from the outer circuit, and the inner carrier refers to the carrier from the inner side.

[0055] 2. The inner side includes the first coil N1-1 and the second coil N1-2:

[0056] 1) The first end of the first coil N1-1 and the second end of the second coil N1-2 are used to input the inner carrier or output the outer carrier, and are connected to the carrier signal processing module 110;

[0057] 2) The second end of the first coil N1-1 is connected to the first end of the variable inductor module L2, and the first end of the second coil N1-2 is connected to the second end of the variable inductor module L2. The inductance of the variable inductor module L2 itself is changed to change the resonance point and the passband, thereby achieving a wider passband coverage. The variable inductor module L2 can generate different inductance values by switching in and out of the inductance of devices such as switching transistors.

[0058] The frequency band switching circuit 100 can also be understood as follows:

[0059] 1. Figure 2 Remove the inductor L1.

[0060] 2. Then Figure 2 The winding N1 in the circuit is divided into two groups of coils, namely N1-1 and N1-2. In order to facilitate the design of device parameters and the balance of circuits on both sides, the winding N1 can be divided into two groups, that is, N1-1 and N1-2 are the same.

[0061] 3. Then insert the variable inductor module L2 between N1-1 and N1-2, and design the parameters of L2 to meet the following formula, which can make Figure 3 performance and Figure 2 Consistent:

[0062]

[0063] In the above formula, N1 is Figure 2 The number of turns of the middle winding N1, N2 is the number of turns of the outer side N2, L1 is Figure 2 L1 is the inductance of the inductor, and L2 is the inductance of the variable inductor module L2.

[0064] This is equivalent to the variable inductor module L2 replacing the inductor L1 in the original circuit. Since the original inductor L1 forms the resonance point of RC resonance, changing the inductance of the variable inductor module L2 is equivalent to changing the original inductor L1, that is, changing the resonance point of RC resonance, realizing the switching of multiple LC resonance frequency bands.

[0065] Figure 4 An embodiment is shown which comprises a carrier signal modem 111, a TX power amplifier 112, DC isolation capacitors C1 and C3, an RX bandpass filter 113, an X safety capacitor C2, a coupling transformer T1 and a variable inductance module L2. The carrier signal modem 111, the TX power amplifier 112 and the RX bandpass filter 113 can be regarded as Figure 3 The carrier signal processing module 110 in the embodiment may be regarded as part or all of the above as the frequency band switching circuit 100 .

[0066] The functions of each part are as follows:

[0067] 1) Carrier signal modem 111

[0068] It is used to modulate the digital quantity and output it to the TX power amplifier; and to demodulate the received analog quantity.

[0069] 2) TX power amplifier 112

[0070] The modulated carrier signal is power amplified to improve the load carrying capacity.

[0071] 3) DC isolation capacitors C1 and C3

[0072] Achieve DC isolation to prevent the output zero drift of the TX power amplifier from causing a short circuit on the N1 side of the coupling transformer.

[0073] 4) RX bandpass filter 113

[0074] The signal within the passband is passed with low loss, and the signal outside the passband is passed with high loss, thereby improving the signal-to-noise ratio.

[0075] 5) X safety capacitor C2

[0076] It allows high-frequency carrier signals to pass through in a low-loss manner, while forming high impedance to the low-frequency grid voltage, preventing large currents from passing through the coupling transformer.

[0077] For the implementation of the variable inductor module L2, please refer to Figure 5 , Figure 5 A schematic diagram of an implementation method of a variable inductor module composed of two sets of switchable inductors is shown.

[0078] The variable inductor module includes at least two groups Switchable inductor , each group of switchable inductors is connected in parallel. For example, the variable inductor module includes a first group of switchable inductors and a second group of switchable inductors, then one of the following states can be selected:

[0079] 1. The first set of switchable inductors is switched in and the second set of switchable inductors is switched out. The inductance value of the entire variable inductor module is an inductance value L. x1 .

[0080] 2. The first set of switchable inductors and the second set of switchable inductors are switched on at the same time, and the inductance value of the entire variable inductor module is another inductance value L x2 .

[0081] If the inductance values of the first group of switchable inductors are different from those of the second group of switchable inductors, three states can be achieved. In addition to the two states 1 and 2 mentioned above, there is a third state:

[0082] 3. The second set of switchable inductors is switched in and the first set of switchable inductors is switched out. The inductance value of the entire variable inductor module is an inductance value L. x3 .

[0083] Figure 5 In the example, the first group of switchable inductors includes: inductor L3-1, switch tube Q1, inductor L3-2, and switch tube Q2. The connections between the components are as follows:

[0084] 1. The control end of the switch tube Q1 and the control end of the switch tube Q2 are used to input the control signal CTRL1.

[0085] 2. One end of the inductor L3-1 and the switch tube Q1 connected in series is connected to the first terminal P1 of the variable inductor module, and the other end is grounded. The inductor L3-1 and the switch tube Q1 in the figure can be interchanged to form a series relationship.

[0086] 3. One end of the inductor L3-2 and the switch tube Q2 connected in series is connected to the first terminal P1 of the variable inductor module, and the other end is grounded; the inductor L3-2 and the switch tube Q2 in the figure can be interchanged to form a series relationship.

[0087] It can be understood that inductor L3-1 and inductor L3-2 are Figure 4 The inductance of L2 is split into two equal parts, each connected to GND via an electronic switch. An NMOS is used as the electronic switch. Similarly, a relay can also be used as a switch.

[0088] Similarly, Figure 5 The second group of switchable inductors in the circuit includes: inductor L4-1, switch Q3, inductor L4-2, and switch Q4. The connections between the components are as follows:

[0089] 1. The control end of the switch tube Q3 and the control end of the switch tube Q4 are used to input the control signal CTRL2.

[0090] 2. One end of the inductor L4-1 and the switch tube Q1 connected in series is connected to the first terminal P1 of the variable inductor module, and the other end is grounded. The inductor L4-1 and the switch tube Q1 in the figure can be interchanged to form a series relationship.

[0091] 3. One end of the inductor L4-2 and the switch tube Q2 connected in series is connected to the first end P1 of the variable inductor module, and the other end is grounded; the inductor L4-2 and the switch tube Q2 in the figure can be interchanged to form a series relationship.

[0092] Through the above Figure 5 The implementation method can be summarized as follows: each group of switchable inductors includes:

[0093] 1. Two inductors, named as the first switching inductor and the second switching inductor respectively;

[0094] 2. Two switches, named first switch and second switch respectively;

[0095] Has the following connection relationship:

[0096] One end of the first switching inductor and the first switch connected in series is connected to the first end of the variable inductor module, and the other end is grounded;

[0097] One end of the second switching inductor and the second switch connected in series is connected to the second end of the variable inductor module, and the other end is grounded.

[0098] Similarly, a third or more groups of switchable inductors can be provided, with the switches of each group of switchable inductors connected to a control signal. Such circuits of switchable inductors can be infinitely expanded and connected in parallel, thereby realizing an LC resonant bandpass filter with any passband bandwidth.

[0099] Based on the above embodiments, embodiments of the present application also provide an electronic device, such as an electric energy meter or a communication device for an electric energy meter, that performs power line carrier communication via the above-mentioned frequency band switching circuit. An LC resonant bandpass filter is used to reduce the capacitance of the X safety-regulatory capacitor, thereby reducing the reactive power generated by the X safety-regulatory capacitor and, in turn, reducing the apparent power. Even when using a smaller X safety-regulatory capacitance, the bandwidth of the LC resonant bandpass filter can still be expanded by switching multiple inductors.

[0100] The above-described device and system embodiments are merely illustrative, and some or all of the modules may be selected according to actual needs to achieve the purpose of the present embodiment. Those skilled in the art may understand and implement the present invention without inventive effort.

[0101] The above are merely preferred embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A frequency band switching circuit, characterized in that: It includes a coupling transformer and a variable inductance module, wherein the coupling transformer includes an inner side and an outer side; The outer side is used to connect to the outer circuit; The inner side includes a first coil and a second coil, the first end of the first coil and the second end of the second coil are used to connect to the carrier signal processing module, the second end of the first coil is connected to the first end of the variable inductance module, and the first end of the second coil is connected to the second end of the variable inductance module; the variable inductance module is used to generate different inductance values in different conduction states.

2. The frequency band switching circuit according to claim 1, wherein: The variable inductor module includes at least two groups of switchable inductors, and each group of switchable inductors is connected in parallel.

3. The frequency band switching circuit according to claim 2, wherein: Each group of switchable inductors includes: a first switchable inductor, a first switch, a second switchable inductor, and a second switch; One end of the first switching inductor and the first switch connected in series is connected to the first end of the variable inductor module, and the other end is grounded; One end of the second switching inductor and the second switch connected in series is connected to the second end of the variable inductor module, and the other end is grounded.

4. The frequency band switching circuit according to claim 1, wherein: The frequency band switching circuit further includes at least one DC isolation capacitor; A first end of the first coil is connected to a DC isolation capacitor, and a second end of the DC isolation capacitor is used to connect to a carrier signal processing module; and / or The second end of the second coil is connected to a DC isolation capacitor, and the second end of the DC isolation capacitor is used to connect to a carrier signal processing module.

5. The frequency band switching circuit according to claim 1, wherein: The frequency band switching circuit also includes a TX power amplifier, 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 the two input ends of the TX power amplifier are used to connect to two transmitting ends of the carrier signal modem.

6. The frequency band switching circuit according to claim 1, wherein: The frequency band switching circuit also includes an RX bandpass filter, the first end of the first coil and the second end of the second coil are connected to two input ends of the RX bandpass filter, and the two output ends of the RX bandpass filter are used to connect to two receiving ends of the carrier signal modem.

7. The frequency band switching circuit according to claim 1, wherein: The frequency band switching circuit also includes a TX power amplifier, an RX bandpass filter and a carrier signal modem; The first end of the first coil and the second end of the second coil are connected to the two output ends of the TX power amplifier, and the two input ends of the TX power amplifier are used to connect to the two transmitting ends of the 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 bandpass filter, and the two output ends of the RX bandpass filter are used to connect to two receiving ends of a carrier signal modem.

8. The frequency band switching circuit according to claim 1, wherein: The frequency band switching circuit further includes an X safety capacitor, and the outer side and the X safety capacitor are connected in series.

9. The frequency band switching circuit according to claim 1, wherein: The first coil and the second coil have the same number of turns.

10. An electronic device, characterized in that: The electronic device comprises the frequency band switching circuit according to any one of claims 1 to 9.

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