CN112953511A - Signal isolation circuit and signal isolation device - Google Patents

Abstract

The invention discloses a signal isolation circuit and a signal isolation device. The signal isolation circuit includes: a signal access end; a signal output terminal; the isolation driving circuit is used for respectively outputting two paths of amplified signals to the low-frequency isolation circuit and the high-frequency isolation circuit after the amplified signals are subjected to operational amplification; the low-frequency isolation circuit is used for isolating the received amplified signals to obtain two paths of isolated low-frequency signals and respectively outputting the two paths of isolated low-frequency signals to the high-frequency isolation circuit after current-voltage conversion; the high-frequency isolation circuit is used for obtaining a high-frequency signal in the amplified signal according to the amplified signal after the direct current isolation and the low-frequency signal after one path of current-voltage conversion, isolating the high-frequency signal, and obtaining an isolated input signal according to the low-frequency signal after the other path of current-voltage conversion and the isolated high-frequency signal. The technical scheme of the invention can solve the problems of great debugging difficulty and inconvenience for batch production of the signal isolation circuit.

Description

Signal isolation circuit and signal isolation device

Technical Field

The invention relates to the field of electronic measuring equipment, in particular to a signal isolation circuit and a signal isolation device.

Background

In the field of electrical signals, for the reasons of electrical personal safety and the like, some occasions need to isolate the electrical signals. The existing signal isolation scheme is to separate the accessed amplified signal into independent high-frequency component and low-frequency component, and output the separated amplified signal by an addition circuit after the separation of the corresponding signals.

However, in this scheme, feedback loops in two signal isolation circuits of high-frequency and low-frequency components are completely independent, so that after a signal reaches an isolation secondary, the high-frequency and low-frequency components have uncontrollable performance, and the isolated high-frequency and low-frequency components need to be compensated by adjusting parameters of a separation component in the circuit, but the circuit is difficult to adjust, and is not convenient for mass production.

Disclosure of Invention

The invention mainly aims to provide a signal isolation circuit, and aims to solve the problems that the existing signal isolation circuit is difficult to debug and inconvenient to produce in batches.

To achieve the above object, the present invention provides a signal isolation circuit. The signal isolation circuit includes: the device comprises a signal access end, a signal output end, an isolation driving circuit, a low-frequency isolation circuit and a high-frequency isolation circuit;

the signal access end is used for accessing an input signal and outputting the input signal to the isolation driving circuit;

the signal output end is used for outputting the isolated input signal;

the isolation driving circuit comprises a first operational amplifier; the non-inverting input end of the first operational amplifier is connected with the input signal; the first operational amplifier is used for performing operational amplification on the input signals and then respectively outputting two paths of amplified signals; one path of the amplified signal is output to the low-frequency isolation circuit; the other path of the amplified signal is output to the high-frequency isolation circuit;

the low-frequency isolation circuit comprises a low-frequency isolator, a first current-voltage conversion circuit and a second current-voltage conversion circuit; the low-frequency isolator is used for isolating the amplified signals received by the low-frequency isolation circuit and respectively outputting two paths of isolated low-frequency signals; the first current-voltage conversion circuit and the second current-voltage conversion circuit are used for respectively converting the two paths of isolated low-frequency signals through current and voltage and then outputting the two paths of isolated low-frequency signals; and

the high-frequency isolation circuit comprises a transformer; the high-frequency isolation circuit is used for carrying out direct-current isolation on the accessed amplified signals, obtaining high-frequency signals in the amplified signals according to the amplified signals subjected to direct-current isolation and low-frequency signals output by the first current-voltage conversion circuit through operation, and driving a transformer to work according to the high-frequency signals so as to carry out isolation processing on the high-frequency signals; the high-frequency isolation circuit is further configured to add the isolated high-frequency signal to the low-frequency signal output by the second current-voltage conversion circuit to obtain an isolated input signal and output the isolated input signal to the signal output terminal.

Optionally, the high-frequency isolation circuit is further configured to feed back a low-frequency signal output by the first current-voltage conversion circuit and a high-frequency signal in the amplified signal to an inverting input terminal of the first operational amplifier; the first operational amplifier is also used for adjusting two paths of amplified signals output by the first operational amplifier according to signals received by the inverting input end of the first operational amplifier, so that the signals received by the inverting input end of the first operational amplifier are equal to the input signals.

Optionally, the low-frequency isolator is a linear optocoupler; the first end of the linear optocoupler is used for being connected with the input end of the low-frequency isolation circuit; the second end and the third end of the linear optocoupler are used for respectively connecting a preset voltage; the fourth end of the linear optocoupler is connected with the input end of the first current-voltage conversion circuit; and the fifth end of the linear optocoupler is connected with the input end of the second current-voltage conversion circuit. Optionally, the low frequency isolation circuit further comprises a second resistor; the second resistor is connected in series between the input end of the linear optocoupler and the output end of the low-frequency isolation circuit.

Optionally, the high-frequency isolation circuit further includes a first capacitor and a first resistor, and the first capacitor and the first resistor are connected in series to form a dc isolation circuit;

the first input end of the transformer is connected with the output end of the first operational amplifier through the direct current isolation circuit; the first input end of the transformer is also connected with the inverting input end of the first operational amplifier; the second input end of the transformer is connected with the output end of the first current-voltage conversion circuit;

the first current-voltage conversion circuit includes: a third resistor and a second operational amplifier; the non-inverting input end of the second operational amplifier is used for being connected with a reference voltage, the inverting input end of the second operational amplifier is connected with the fourth end of the linear optocoupler, and the output end of the second operational amplifier is connected with the second input end of the transformer; the third resistor is arranged between the inverting input end and the output end of the second operational amplifier.

Optionally, the first output terminal of the transformer is connected to the signal output terminal; the second output end of the transformer is connected with the output end of the second current-voltage conversion circuit;

the second current-voltage conversion circuit includes: a fourth resistor and a third operational amplifier; the non-inverting input end of the third operational amplifier is used for being connected with a reference voltage, the inverting input end of the third operational amplifier is connected with the fifth end of the linear optocoupler, and the output end of the third operational amplifier is connected with the second output end of the transformer; the fourth resistor is arranged between the inverting input end and the output end of the third operational amplifier.

Optionally, the signal isolation circuit further comprises: a fourth operational amplifier disposed between the first output terminal of the transformer and the signal output terminal; the positive phase input end of the transformer is connected with the first output end of the transformer, and the negative phase input end of the transformer is respectively connected with the output end of the transformer and the signal output end.

Optionally, the first input end of the transformer and the first output end of the transformer are homonymous ends.

Optionally, the fourth resistor and the third resistor are fixed-resistance resistors, and the resistance values of the fourth resistor and the third resistor are the same;

or, the third resistor is a fixed resistance resistor, and the fourth resistor is a variable resistance resistor.

The present invention also provides a signal isolation apparatus, comprising:

a housing;

a circuit board; and

the signal isolation circuit is arranged on the circuit board, and the circuit board is accommodated in the shell.

The signal isolation circuit is provided with a signal access end, a signal output end, an isolation driving circuit, a low-frequency isolation circuit and a high-frequency isolation circuit, and after a first operational amplifier in the isolation driving circuit is used for operational amplification of an accessed input signal, two paths of amplified signals are respectively output to the low-frequency isolation circuit and the high-frequency isolation circuit, so that a low-frequency isolator in the low-frequency isolation circuit can be used for isolating the amplified signals and respectively output two paths of isolated low-frequency signals, and the two paths of isolated low-frequency signals are respectively subjected to current-voltage conversion and then output to the high-frequency isolation circuit; the high-frequency isolation circuit can calculate by using the amplified signal after the direct current isolation and the low-frequency signal after the isolation to obtain a high-frequency signal in the amplified signal, and drive the transformer to work according to the high-frequency signal to obtain the high-frequency signal after the isolation; the high-frequency isolation circuit is also used for adding the isolated high-frequency signal and the isolated low-frequency signal to obtain an isolated input signal and outputting the isolated input signal to the signal output end. According to the technical scheme, the low-frequency signal and the high-frequency signal can form closed-loop feedback with the first operational amplifier, so that the first operational amplifier can automatically adjust the isolated input signal, the uncontrollable performance of the isolated low-frequency signal and the isolated high-frequency signal is favorably reduced, compensation operation is not needed to be carried out through board-to-board debugging, the efficiency of batch production is greatly accelerated, and the problems that the existing signal isolation circuit is difficult to debug and inconvenient to produce in batches are solved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.

FIG. 1 is a functional block diagram of a signal isolation circuit according to an embodiment of the present invention;

FIG. 2 is a functional block diagram of another embodiment of a signal isolation circuit according to the present invention;

FIG. 3 is a schematic circuit diagram of a signal isolation circuit according to another embodiment of the present invention;

FIG. 4 is a schematic circuit diagram of a first current-to-voltage conversion circuit according to an embodiment of the present invention;

fig. 5 is a schematic circuit diagram of a first current-voltage conversion circuit in another embodiment of the signal isolation circuit of the present invention.

The reference numbers illustrate:

the implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that all the directional indicators (such as upper, lower, left, right, front and rear … …) in the embodiment of the present invention are only used to explain the relative position relationship between the components, the motion situation, etc. in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indicator is changed accordingly.

In the present invention, unless otherwise expressly stated or limited, the terms "connected," "secured," and the like are to be construed broadly, and for example, "secured" may be a fixed connection, a removable connection, or an integral part; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In addition, the descriptions related to "first", "second", etc. in the present invention are only for descriptive purposes and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.

The invention provides a signal isolation circuit.

Currently in the field of electrical signals, two signal isolation schemes exist. The first one is suitable for stabilizing the frequency band of electric signal, and is to use optical coupler alone to isolate low-frequency signal and transformer alone to isolate high-frequency signal. The second type is suitable for the case where the frequency band of the electric signal is in a fluctuating state, for example: in order to separate high-frequency and low-frequency components from an input signal by arranging a complex signal separation circuit, and after the high-frequency and low-frequency components are respectively isolated by high-frequency and low-frequency signals, the two isolated components are superposed by an addition circuit to obtain a total isolation signal, but in the isolation scheme, the signal isolation circuits of the high-frequency and low-frequency components are completely independent, feedback loops in the signal isolation circuits of the two are completely independent, so that the low-frequency and high-frequency components cannot be closed, and the isolated low-frequency and high-frequency components have uncontrollable property. In the prior art, the isolated high-frequency component and low-frequency component are respectively subjected to signal compensation by adjusting parameters of separated components in the circuit, but the debugging difficulty is high, and the parameter debugging amplitudes of the isolation circuits are different, so that the compensation operation can be carried out only by debugging board by board, and the method is very not beneficial to large-batch production and application.

Referring to fig. 1 to 3, in an embodiment of the present invention, the signal isolation circuit includes: the circuit comprises a signal access end 10, a signal output end 20, an isolation driving circuit 30, a low-frequency isolation circuit 40 and a high-frequency isolation circuit 50; wherein the content of the first and second substances,

the signal access terminal 10 is configured to access an input signal and output the input signal to the isolation driving circuit 30;

the signal output end 20 is configured to output the isolated input signal;

the isolation driving circuit 30 comprises a first operational amplifier A1; the non-inverting input end of the first operational amplifier A1 is connected with the amplified signal; the first operational amplifier A1 is used for performing operational amplification on the amplified signals and then respectively outputting two paths of amplified signals; one path of the amplified signal is output to the low-frequency isolation circuit 40; the other path of the amplified signal is output to the high-frequency isolation circuit 50;

the low-frequency isolation circuit 40 comprises a low-frequency isolator 41, a first current-voltage conversion circuit 42 and a second current-voltage conversion circuit 43; the low-frequency isolator 41 is configured to isolate the amplified signal received by the low-frequency isolation circuit 40, and output two isolated low-frequency signals respectively; the first current-voltage conversion circuit 42 and the second current-voltage conversion circuit 42 are configured to output two paths of isolated low-frequency signals after current-voltage conversion; and

the high-frequency isolation circuit 50 comprises a transformer T1; the high-frequency isolation circuit 50 is configured to perform dc isolation on the accessed amplified signal, obtain a high-frequency signal in the amplified signal through operation according to the amplified signal subjected to dc isolation and the low-frequency signal output by the first current-voltage conversion circuit 42, and drive a transformer T1 to operate according to the high-frequency signal, so as to perform isolation processing on the high-frequency signal; the high frequency isolation circuit 50 is further configured to add the isolated high frequency signal to the low frequency signal output by the second current-voltage conversion circuit 43 to obtain an isolated input signal, and output the isolated input signal to the signal output terminal 20.

In this embodiment, the signal access terminal 10 may be connected to an electrical signal detection component such as a probe, a stylus or a probe, so as to access the electrical signal detection component to detect the output electrical signal. The signal output terminal 20 is used for outputting the isolated input signal to a subsequent stage circuit.

The isolation driving circuit 30 can connect the non-inverting input terminal of the first operational amplifier a1 to the signal input terminal 10, so that the first operational amplifier a1 can receive the input signal and perform the operational amplification processing thereon. The isolation driving circuit 30 may further connect the output terminal of the first operational amplifier a1 to the low frequency isolation circuit 40 and the high frequency isolation circuit 50, respectively, so that the first operational amplifier a1 may output two paths of amplified signals after operational amplification to the low frequency isolation circuit 40 and the high frequency isolation circuit 50, respectively. It should be noted that the first operational amplifier may be a wide-band operational amplifier to ensure high-bandwidth performance of the signal isolation circuit.

The low frequency isolator 41 in the low frequency isolation circuit 40 may be a linear low frequency isolation device, such as a linear optocoupler U1; and the first current-voltage conversion circuit and the second current-voltage conversion circuit can be constructed and realized by adopting discrete electronic devices such as a resistance element, an operational amplifier and the like. In this embodiment, the low frequency isolator 41 is explained by taking a dual-output linear optocoupler U1 as an example, two output ends of the linear optocoupler U1 may be connected to input ends of the first current-voltage conversion circuit and the second current-voltage conversion circuit in a one-to-one correspondence manner. It can be understood that, because the high-frequency signal in the amplified signal cannot drive the linear optocoupler to work, the linear optocoupler can only isolate the low-frequency component, i.e. the low-frequency signal, in the amplified signal, and output two isolated low-frequency signals. It can also be understood that, because the linear optocoupler is adopted, the low-frequency signals after two paths of isolation are the same as the low-frequency signals in the amplified signals, so that the signal isolation of the low-frequency components in the amplified signals is realized. Of course, in other embodiments, the low frequency isolator 41 may also be implemented by using other multi-output linear low frequency isolation devices, which is not limited herein.

The high-frequency isolation circuit 50 can be implemented by a transformer T1 and a dc isolation circuit; the dc isolation circuit 50 may be formed of discrete electronic devices such as a resistive element and a capacitive element. The high frequency isolation circuit 50 can be divided into a high frequency isolation primary side and a high frequency isolation secondary side according to the primary and secondary sides of the transformer, and the high frequency isolation primary side and the high frequency isolation secondary side can be respectively connected to an isolated low frequency signal output by the isolation driving circuit 40. The high-frequency isolation primary side can perform corresponding operations on the amplified signal after the dc isolation and the low-frequency signal after the isolation, for example: the high frequency component in the path of amplified signal, i.e. the high frequency signal, is obtained by subtraction, and the obtained high frequency signal is output to the primary side of the transformer T1, thereby completing the driving of the transformer T1. The transformer T1 can isolate the high frequency signal during operation, and output the isolated high frequency signal at its secondary side, so that the isolated high frequency signal and the isolated low frequency signal can be added at the high frequency isolation secondary side, thereby obtaining the isolated amplified signal. It can be understood that since the primary coil of the transformer T1 corresponds to a wire for a low frequency signal, and when the driving transformer T1 is operated, the signal applied to the primary of the transformer T1 is a high frequency signal. Therefore, when the signal isolation circuit of the present invention operates, the primary side of the transformer T1 is connected to the inverting input terminal of the first operational amplifier a1, so that the high frequency isolation primary side can feed back the isolated low frequency signal and the high frequency signal obtained by operation to the inverting input terminal of the first operational amplifier a1 through the primary side of the transformer T1, so that the first operational amplifier a1 can perform comparison and adjustment by using the signal received from the inverting input terminal, and finally make the amplified signal output by the first operational amplifier a1 equal to the input signal, thereby achieving linear isolation of the input signal.

According to the technical scheme, the transformer T1 is driven by a high-frequency signal obtained by operation of the isolated low-frequency signal and the amplified direct-current signal, and a feedback loop of the low-frequency signal and the high-frequency signal is formed by the transformer T1, so that the first operational amplifier A1 in the isolation driving circuit 30 can work in a negative feedback state. Therefore, the working stability of the first operational amplifier A1 is improved, so that the first operational amplifier A1 can automatically adjust the isolated input signal, the uncontrollable performance of the isolated low-frequency signal and the isolated high-frequency signal can be reduced, signal compensation is not needed by debugging parameters of a separation device plate by plate, and the application of mass production is facilitated.

The signal isolation circuit is provided with a signal access end 10, a signal output end 20, an isolation driving circuit 30, a low-frequency isolation circuit 40 and a high-frequency isolation circuit 50, and after an accessed input signal is subjected to operational amplification through a first operational amplifier A1 in the isolation driving circuit 30, two paths of amplified signals are respectively output to the low-frequency isolation circuit 40 and the high-frequency isolation circuit 50, so that a low-frequency isolator 41 in the low-frequency isolation circuit 40 can perform isolation processing on the amplified signal and respectively output two paths of isolated low-frequency signals, and the two paths of isolated low-frequency signals are respectively subjected to current-voltage conversion and then output to the high-frequency isolation circuit 50; the high-frequency isolation circuit 50 may calculate the amplified signal after the dc isolation and the low-frequency signal after the isolation to obtain a high-frequency signal in the amplified signal, and drive the transformer T1 to operate according to the high-frequency signal to obtain the isolated high-frequency signal; the high frequency isolation circuit 50 is further configured to add the isolated high frequency signal and the isolated low frequency signal to obtain an isolated input signal, and output the isolated input signal to the signal output terminal 20. According to the technical scheme, the low-frequency signal and the high-frequency signal can form closed-loop feedback with the first operational amplifier A1, so that the first operational amplifier A1 can automatically adjust the isolated input signal, the uncontrollable performance of the isolated low-frequency signal and the isolated high-frequency signal is favorably reduced, compensation operation is not needed to be carried out through board-to-board debugging, the efficiency of batch production is greatly accelerated, and the problems that the existing signal isolation circuit is difficult to debug and is inconvenient to produce in batches are solved.

Referring to fig. 1 to fig. 3, in an embodiment of the present invention, the high-frequency isolation circuit 50 is further configured to feed back a low-frequency signal output by the first current-voltage conversion circuit 42 and a high-frequency signal of the amplified signals to an inverting input terminal of the first operational amplifier a 1; the first operational amplifier a1 is further configured to adjust the two-way amplified signal output by the first operational amplifier a1 according to the signal received by the inverting input terminal of the first operational amplifier a, so that the signal received by the inverting input terminal of the first operational amplifier a is equal to the input signal.

In this embodiment, the first operational amplifier a1 may compare the combined signal (the sum of the isolated low-frequency signal and the high-frequency signal obtained by operation) received at the inverting input terminal with the input signal received at the non-inverting input terminal, and may adjust its operational amplifier state according to the comparison result, so as to adjust the two amplified signals output by the first operational amplifier, so that the two amplified signals after adjustment may generate a new combined signal correspondingly, and finally achieve the effect of making the combined signal received at the inverting input terminal equal to the input signal. When the combined signal is equal to the input signal, the high-frequency signal in the combined signal is the same as the high-frequency signal in the input signal, and the low-frequency signal in the combined signal is the same as the low-frequency signal in the input signal; the high-frequency signal in the amplified signal after isolation is the same as the high-frequency signal in the combined signal, and the low-frequency signal in the amplified signal after isolation is the same as the low-frequency signal in the combined signal, so that the amplified signal after isolation is also the same as the input signal, namely, the signal isolation of the input signal is realized.

Referring to fig. 1 to 3, in an embodiment of the present invention, the low frequency isolator 41 is a linear optocoupler U1; a first end of the linear optocoupler U1 is used for being connected with an input end of the low-frequency isolation circuit 40; the second end and the third end of the linear optocoupler U1 are used for respectively connecting a power supply voltage; a fourth end of the linear optocoupler U1 is connected with an input end of the first current-voltage conversion circuit 42; a fifth end of the linear optocoupler U1 is connected to the input end of the second current-voltage conversion circuit 43.

Further, the low frequency isolation circuit 40 further includes a second resistor R2; the second resistor R2 is serially connected between the input end of the linear optocoupler U1 and the output end of the low-frequency isolation circuit 40.

In this embodiment, one light emitter and two photoreceptors may be packaged in the linear optocoupler U1. The light emitter can emit light according to the driving current (i.e. low frequency signal) connected by the low frequency signal isolator 41, so as to drive the two photoreceptors to respectively output the isolated low frequency signal in the form of current to the first current-voltage conversion circuit 42 and the second current-voltage conversion circuit 43. It can be understood that the light emitted by the light emitter is linearly changed with the accessed driving current (low-frequency signal after isolation), and the current output by the two photoreceptors (low-frequency signal before isolation) is linearly changed with the received light, so that the low-frequency signal output by the photoreceptors is equal to the low-frequency signal accessed by the light emitter, and the linear isolation of the low-frequency signal is realized because the two photoreceptors and the light emitter are not in an electrical connection relationship. It should be noted that the resistance of the second resistor R2 needs to be set to match the driving current of the linear optocoupler. According to the technical scheme, the low-frequency signal isolation is carried out on one path of amplified signals output by the isolation driving circuit 30 by adopting the linear optocoupler U1 with double output ends, and two paths of isolated low-frequency signals are output simultaneously, so that the circuit structure is greatly simplified.

Referring to fig. 1 to 3, in an embodiment of the present invention, the high frequency isolation circuit 50 further includes a first capacitor C1 and a first resistor R1, and the first capacitor C1 and the first resistor R1 are connected in series to form a dc isolation circuit;

a first input terminal of the transformer T1 (i.e., the 1 terminal of the transformer T1) is connected to the output terminal of the first operational amplifier a1 via the dc isolation circuit 30; the first input terminal of the transformer T1 is further connected with the inverting input terminal of the first operational amplifier A1; a second input terminal of the transformer T1 (i.e., terminal 2 of transformer T1) is connected to the output terminal of the first current-voltage conversion circuit 42;

the first current-voltage conversion circuit 42 includes: a third resistor R3 and a second operational amplifier a 2; the non-inverting input end of the second operational amplifier A2 is used for connecting a reference voltage, the inverting input end of the second operational amplifier A2 is connected with the fourth end of the linear optocoupler U1, and the output end of the second operational amplifier A2 is connected with the second input end of the transformer; the third resistor R3 is disposed between the inverting input terminal and the output terminal of the second operational amplifier a 2.

In this embodiment, a dc isolation circuit formed by the first capacitor C1 and the first resistor R1 is used to access one path of amplified signal, and output the amplified signal to a first input terminal of the transformer T1 after dc isolation; wherein the first capacitor C1 is used for isolating low frequency and direct current components; the first resistor R1 needs to be matched with the impedance of PCB wiring to prevent signal reflection and oscillation. The third resistor R3 is a negative feedback resistor for feeding back the amplified signal outputted from the second operational amplifier a2 to the inverting input terminal of the second operational amplifier a2, so that the combined circuit formed by the third resistor R3 and the second operational amplifier a2 can convert the low-frequency signal in the form of current outputted from the fourth terminal of the linear optocoupler U1 into a voltage form, and output the voltage form to the second input terminal of the transformer T1 by the second operational amplifier a 2. Since the transformer T1 cannot be driven by the low frequency signal, i.e. the low frequency signal outputted by the second operational amplifier a2 corresponds to the transformer T1, i.e. only the high frequency signal exists between the first input terminal and the second input terminal of the transformer T1, the driving of the transformer T1 is completed.

It should be noted that in the present embodiment, the low-frequency signal output from the second operational amplifier a2 may form a closed-loop negative feedback with the inverting input terminal of the first operational amplifier a1 via the winding coil between the second input terminal and the first input terminal of the transformer T1 (i.e., the primary coil of the transformer T1); the high frequency signal may also be fed back to the inverting input of the first operational amplifier a 1. It should be noted that the reference voltage accessed by the second operational amplifier a2 is a positive reference voltage before isolation, so as to provide a reference point for current-voltage conversion performed by the first current-voltage conversion circuit 42. With the arrangement, the transformer T1 can be driven to work by high-frequency signals obtained through operation, a closed-loop feedback loop is provided for feeding back the high-frequency signals and the low-frequency signals to the first operational amplifier A1, the circuit structure is greatly simplified, and the working stability of the first operational amplifier A1 is improved.

Referring to fig. 1 to 3, in an embodiment of the present invention, a first output terminal of the transformer T1 is connected to the signal output terminal 20; a second output terminal of the transformer T1 is connected to an output terminal of the second current-voltage conversion circuit 43;

the second current-voltage conversion circuit 43 includes: a fourth resistor R4 and a third operational amplifier A3; the non-inverting input end of the third operational amplifier A3 is used for receiving a reference voltage, the inverting input end of the third operational amplifier A3 is connected to the fifth end of the linear optocoupler U1, and the output end of the third operational amplifier A3 is connected to the second output end of the transformer T1; the fourth resistor R4 is disposed between the inverting input terminal of the third operational amplifier A3 and the output terminal thereof.

In the present embodiment, the fourth resistor R4 and the third operational amplifier A3 may form a symmetrical circuit structure with the third resistor R3 and the second operational amplifier a2 in the second current-voltage conversion circuit 42. It should be noted that the reference voltage accessed by the third operational amplifier a3 is an isolated positive reference voltage for providing a reference point for the current-voltage conversion performed by the second current-voltage conversion circuit 43. The fourth resistor R4 is also a negative feedback resistor, and is used for feeding back the amplified signal output by the third operational amplifier A3 to the inverting input terminal of the second operational amplifier A3, so that the combined circuit formed by the fourth resistor R4 and the third operational amplifier A3 can convert the low-frequency signal in the form of current output from the fifth terminal of the linear optocoupler U1 into a voltage form, and output the voltage form to the second output terminal of the transformer T1 by the third operational amplifier A3.

Since the signal potential at the second output terminal of the transformer T1 is the low frequency signal output by the third operational amplifier A3, the signal potential at the first output terminal of the transformer T1 is equivalent to the isolated high frequency potential superimposed on the signal potential at the second output terminal thereof, i.e., the signal at the first output terminal of the transformer T1 is the superimposed sum of the isolated high frequency signal and the isolated low frequency signal. In this way, the low-frequency signal after being isolated and the high-frequency signal after being isolated are automatically added and restored into the input signal at the high-frequency isolation secondary, and an adder or a summation circuit is not required to be arranged. In practical application, the adder or summing circuit of the two signals needs to be designed in an adaptive mode according to the two isolated signals, the circuit structure is quite complex, the design difficulty is high, and the circuit cannot be applied to large-scale production at all.

It should be noted that in practical applications, a person skilled in the art may set up a plurality of current-voltage converting circuits with different circuit structures according to practical needs, but as long as the technical solution is the same as the inventive concept of the present application, and the current-voltage converting circuit in the solution plays the same role as the first/second current-voltage converting circuit in the present application, it falls into the protection scope of the present application. The present application also proposes several circuit implementation methods of the first current-voltage conversion circuit 42:

referring to fig. 4, in this embodiment, the first current-voltage conversion circuit 41 includes a fifth resistor R5 and a fifth operational amplifier a 5; a first end of the fifth resistor R5 is used for accessing a reference voltage, and a second end of the fifth resistor R5 is connected with the linear optocoupler U1 to access one path of isolated low-frequency signals output by the linear optocoupler U1; the linear optical coupler U1 is further connected to the non-inverting input of the fifth operational amplifier a5, the output of the fifth operational amplifier a5 may be connected to the second input of the transformer T1, and the output of the fifth operational amplifier a5 is further connected to its own inverting input to form negative feedback.

Referring to fig. 5, in this embodiment, the first current-voltage conversion circuit 41 includes a sixth resistor R6 and a sixth operational amplifier a 6; a first end of the sixth resistor R6 is used for receiving a reference voltage, and a second end thereof is connected with the linear optocoupler U1 to receive an isolated low-frequency signal output by the linear optocoupler U1; the linear optical coupler U1 is further connected to the non-inverting input terminal of the sixth operational amplifier a6, the output terminal of the sixth operational amplifier a6 may be connected to the second input terminal of the transformer T1, and the output terminal of the sixth operational amplifier a6 is further connected to the inverting input terminal thereof to form negative feedback.

Since the circuit structure and design principle of the second current-voltage conversion circuit 43 can be the same as those of the first current-voltage conversion circuit 42, the description thereof is omitted.

Referring to fig. 1 to 3, in an embodiment of the present invention, the first input terminal of the transformer T1 and the first output terminal of the transformer T1 are homonymous terminals.

In this embodiment, since the transformer T1 is an isolated transformer, the first output terminal needs to be the same name terminal as the first input terminal according to the electromagnetic induction relationship between the primary and secondary terminals. In other embodiments, the first input terminal of the transformer T1 and the first output terminal of the transformer T1 may be different terminals by adopting other circuit structures of the first current-to-voltage converting circuit 41 and the second current-to-voltage converting circuit 42.

Referring to fig. 1 to 3, in an embodiment of the present invention, the signal isolation circuit further includes: a fourth operational amplifier A4, the fourth operational amplifier A4 being disposed between the first output terminal of the transformer T1 and the signal output terminal 20; its non-inverting input terminal is connected to the first output terminal of the transformer T1, and its inverting input terminal is connected to its output terminal and the signal output terminal 20, respectively.

In this embodiment, the fourth operational amplifier a4 is configured to output the isolated input signal after operational amplification, and access the signal output after operational amplification through the inverting input terminal, so as to form negative feedback adjustment again, so as to increase stability of the output signal. And the fourth operational amplifier a4 and the first operational amplifier a1 again form a symmetrical circuit structure in view of the overall circuit structure. The signal isolation circuit provided by the invention further realizes a symmetrical circuit structure while considering the stability of the isolated signal by arranging the fourth operational amplifier A4.

Referring to fig. 1 to 3, in an embodiment of the present invention, the fourth resistor R4 and the third resistor R3 are fixed-resistance resistors, and the resistance values of the fourth resistor R4 and the third resistor R3 are the same;

alternatively, the third resistor R3 is a fixed resistance resistor, and the fourth resistor R4 is a variable resistance resistor.

In this embodiment, according to the principle of a symmetrical circuit, the resistance of the third resistor R3 should be equal to that of the fourth resistor R4. In this way, the low-frequency signals output by the second operational amplifier a2 and the third operational amplifier A3 can be made to be identical, thereby being beneficial to improving the accuracy of the high-frequency signal obtained by the high-frequency isolation primary operation and the accuracy of the isolated input signal obtained by the high-frequency isolation secondary addition.

However, in practical applications, since the electronic device may have a certain parameter error, the third resistor R3 may be a fixed-resistance resistor, and the fourth resistor R4 may be a variable-resistance resistor, so that a tester can conveniently debug the signal isolation circuit of the present invention by debugging the resistance of the fourth resistor R4. Of course, in other embodiments, the third resistor R3 may be a variable resistance resistor, and the fourth resistor R4 may be a fixed resistance resistor; alternatively, the third resistor R3 and the fourth resistor R4 are both variable resistance resistors. Therefore, when the circuit is applied in mass production, the circuit debugging can be flexibly performed on the signal isolation circuit through the fourth resistor R4, and the circuit debugging efficiency in mass production can be improved.

The present invention also provides a signal isolation apparatus, comprising:

a housing;

a circuit board; and

according to the signal isolation circuit, the signal isolation circuit is arranged on the circuit board, and the circuit board is accommodated in the shell.

In this embodiment, the housing may have a receiving cavity with a corresponding size for receiving the circuit board. The detailed structure of the signal isolation circuit can refer to the above embodiments, and is not described herein again; it can be understood that, because the signal isolation circuit is used in the signal isolation device, the embodiment of the signal isolation device includes all technical solutions of all embodiments of the signal isolation circuit, and the achieved technical effects are also completely the same, and are not described herein again.

The above description is only an alternative embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.

Claims (10)

1. A signal isolation circuit, comprising: the device comprises a signal access end, a signal output end, an isolation driving circuit, a low-frequency isolation circuit and a high-frequency isolation circuit;

the signal access end is used for accessing an input signal and outputting the input signal to the isolation driving circuit;

the signal output end is used for outputting the isolated input signal;

the isolation driving circuit comprises a first operational amplifier; the non-inverting input end of the first operational amplifier is connected with the input signal; the first operational amplifier is used for performing operational amplification on the input signals and then respectively outputting two paths of amplified signals; one path of the amplified signal is output to the low-frequency isolation circuit; the other path of the amplified signal is output to the high-frequency isolation circuit;

the low-frequency isolation circuit comprises a low-frequency isolator, a first current-voltage conversion circuit and a second current-voltage conversion circuit; the low-frequency isolator is used for isolating the amplified signals received by the low-frequency isolation circuit and respectively outputting two paths of isolated low-frequency signals; the first current-voltage conversion circuit and the second current-voltage conversion circuit are used for respectively converting the two paths of isolated low-frequency signals through current and voltage and then outputting the two paths of isolated low-frequency signals; and

the high-frequency isolation circuit comprises a transformer; the high-frequency isolation circuit is used for carrying out direct-current isolation on the accessed amplified signals, obtaining high-frequency signals in the amplified signals according to the amplified signals subjected to direct-current isolation and low-frequency signals output by the first current-voltage conversion circuit through operation, and driving a transformer to work according to the high-frequency signals so as to carry out isolation processing on the high-frequency signals; the high-frequency isolation circuit is further configured to add the isolated high-frequency signal to the low-frequency signal output by the second current-voltage conversion circuit to obtain an isolated input signal and output the isolated input signal to the signal output terminal.

2. The signal isolation circuit of claim 1, wherein the high frequency isolation circuit is further configured to feed back a low frequency signal output by the first current-voltage conversion circuit and a high frequency signal of the amplified signals to an inverting input terminal of the first operational amplifier; the first operational amplifier is also used for adjusting two paths of amplified signals output by the first operational amplifier according to signals received by the inverting input end of the first operational amplifier, so that the signals received by the inverting input end of the first operational amplifier are equal to the input signals.

3. The signal isolation circuit of claim 1, wherein the low frequency isolator is a linear optocoupler; the first end of the linear optocoupler is used for being connected with the input end of the low-frequency isolation circuit; the second end and the third end of the linear optocoupler are used for respectively connecting a preset voltage; the fourth end of the linear optocoupler is connected with the input end of the first current-voltage conversion circuit; and the fifth end of the linear optocoupler is connected with the input end of the second current-voltage conversion circuit.

4. The signal isolation circuit of claim 3, wherein the low frequency isolation circuit further comprises a second resistor; the second resistor is connected in series between the input end of the linear optocoupler and the output end of the low-frequency isolation circuit.

5. The signal isolation circuit of claim 3, wherein the high frequency isolation circuit further comprises a first capacitor and a first resistor, the first capacitor and the first resistor being connected in series to form a DC isolation circuit;

the first input end of the transformer is connected with the output end of the first operational amplifier through the direct current isolation circuit; the first input end of the transformer is also connected with the inverting input end of the first operational amplifier; the second input end of the transformer is connected with the output end of the first current-voltage conversion circuit;

the first current-voltage conversion circuit includes: a third resistor and a second operational amplifier; the non-inverting input end of the second operational amplifier is used for being connected with a reference voltage, the inverting input end of the second operational amplifier is connected with the fourth end of the linear optocoupler, and the output end of the second operational amplifier is connected with the second input end of the transformer; the third resistor is arranged between the inverting input end and the output end of the second operational amplifier.

6. The signal isolation circuit of claim 5, wherein the first output terminal of the transformer is connected to the signal output terminal; the second output end of the transformer is connected with the output end of the second current-voltage conversion circuit;

the second current-voltage conversion circuit includes: a fourth resistor and a third operational amplifier; the non-inverting input end of the third operational amplifier is used for being connected with a reference voltage, the inverting input end of the third operational amplifier is connected with the fifth end of the linear optocoupler, and the output end of the third operational amplifier is connected with the second output end of the transformer; the fourth resistor is arranged between the inverting input end and the output end of the third operational amplifier.

7. The signal isolation circuit of claim 5, wherein the signal isolation circuit further comprises: a fourth operational amplifier disposed between the first output terminal of the transformer and the signal output terminal; the positive phase input end of the transformer is connected with the first output end of the transformer, and the negative phase input end of the transformer is respectively connected with the output end of the transformer and the signal output end.

8. The signal isolation circuit of claim 5, wherein the first input terminal of the transformer and the first output terminal of the transformer are homonyms.

9. The signal isolation circuit of claim 7, wherein the fourth resistor and the third resistor are fixed-resistance resistors and have the same resistance;

or, the third resistor is a fixed resistance resistor, and the fourth resistor is a variable resistance resistor.

10. A signal isolation apparatus, comprising:

a housing;

a circuit board; and

the signal isolation circuit of any of claims 1-9, wherein the signal isolation circuit is disposed on the circuit board, and the circuit board is received in the housing.

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