Isolation switching value acquisition circuit

Abstract

The invention belongs to the technical field of rail transit signal control, and particularly relates to an isolation switching value acquisition circuit which comprises a clock source circuit, an excitation source circuit, a first-stage amplification circuit, a second-stage amplification circuit and a third-stage output circuit, the clock source circuit outputs a square wave signal to a field effect transistor in the excitation source circuit to drive a primary excitation signal generated by a first transformer, and the primary excitation signal is coupled and amplified with a corresponding transformer through a first triode, a second triode and a third triode in sequence, and finally, the fourth transformer outputs an isolated differential switching value signal. According to the invention, a complete dynamic excitation signal chain is constructed, so that the output effectiveness completely depends on the continuous transmission of the link, a protection mechanism that the output is automatically guided to the safety side when any key device fails is realized, and meanwhile, the anti-interference capability and the driving capability of the signal are remarkably improved through the coupling and amplification of the multi-stage transformer.

Description

Technical Field

[0001] This application belongs to the field of rail transit signal control technology, specifically relating to an isolated switch quantity acquisition circuit. Background Technology

[0002] In the network control systems of high-speed trains such as maglev trains, the onboard controller needs to collect a large number of switching signals in real time (such as safety interlock status and equipment feedback signals). These signals are often generated in harsh environments with strong electromagnetic interference and have extremely high requirements for the safety integrity level of the system.

[0003] Currently, most commonly used switch signal acquisition solutions are based on opto-isolators. While these solutions achieve electrical isolation, their failure modes are uncontrollable. For example, when the optocoupler or related protection devices fail, the output may be fixed at a high or low level instead of being guided to a safe no-signal state, posing a safety hazard in applications with high safety requirements. Furthermore, these solutions have limited signal driving capability, and their anti-interference ability is easily affected during long-distance transmission.

[0004] Therefore, there is an urgent need for an isolated switch quantity acquisition scheme that can reliably guide the signal to the safe side in the event of failure of any single component, while also having strong anti-interference capabilities. Summary of the Invention

[0005] This invention solves at least to some extent the above-mentioned technical problems and provides an isolated switch quantity acquisition circuit. By constructing a multi-stage transformer-coupled dynamic excitation chain driven by a clock source, the output signal can be automatically and reliably guided to the safe side when any key component fails, while improving the anti-interference capability and driving capability of signal transmission.

[0006] Embodiments of this disclosure provide an isolated switch quantity acquisition circuit, characterized in that it includes: The clock source circuit is configured to output a periodic square wave voltage signal; The excitation source circuit, including a field-effect transistor and a first transformer, is configured to generate a primary high-frequency switching excitation signal based on the periodic square wave voltage signal; The gate of the field-effect transistor is connected to the output terminal of the clock source circuit, and the source of the field-effect transistor is connected to the reference ground power supply; the negative terminal of the primary side of the first transformer is connected to the drain of the field-effect transistor, and the positive terminal of the primary side of the first transformer is connected to the input power supply. A first-stage amplifier circuit, including a first transistor and a second transformer; The base of the first transistor is connected to the positive terminal of the secondary side of the first transformer, and the emitter of the first transistor and the negative terminal of the secondary side of the first transformer are connected together to the negative phase signal of the switching quantity to be acquired; the negative terminal of the primary side of the second transformer is connected to the collector of the first transistor, and the positive terminal of the primary side of the second transformer is connected to the positive phase signal of the switching quantity to be acquired. A two-stage amplifier circuit, including a second transistor and a third transformer; The base of the second transistor is connected to the positive terminal of the secondary side of the second transformer, and the emitter of the second transistor and the negative terminal of the secondary side of the second transformer are both connected to the reference ground power supply; the negative terminal of the primary side of the third transformer is connected to the collector of the second transistor, and the positive terminal of the primary side of the third transformer is connected to the input power supply. The three-stage output circuit includes a third transistor and a fourth transformer. The base of the third transistor is connected to the positive terminal of the secondary side of the third transformer, and the emitter of the third transistor and the negative terminal of the secondary side of the third transformer are connected to the reference ground power supply. The negative terminal of the primary side of the fourth transformer is connected to the collector of the third transistor, and the positive terminal of the primary side of the fourth transformer is connected to the input power supply. The same-name terminal of the secondary side of the fourth transformer outputs the positive phase signal of the switching quantity, and the opposite-name terminal of the secondary side of the fourth transformer outputs the negative phase signal of the switching quantity.

[0007] The technical solution provided in this application offers at least the following benefits: By constructing a complete dynamic excitation signal chain driven by a clock source and coupled through multiple transformer stages, the effectiveness of the output signal depends entirely on the smooth operation of this excitation chain. When any component in the chain fails, the transmission of the excitation signal is interrupted, and the output automatically becomes a state without a valid signal, thereby achieving global fault-oriented safety and greatly improving the system's safety integrity level.

[0008] In other embodiments of this application, the excitation source circuit includes: A first current-limiting resistor, with its first end connected to the input power supply and its second end connected to the positive terminal of the primary side of the first transformer; The second current-limiting resistor has its first end connected to the reference ground power supply and its second end connected to the source of the field-effect transistor.

[0009] The technical solution provided in this application has at least the following beneficial effects: by limiting the current flowing into the primary side of the first transformer and the field-effect transistor by the first current-limiting resistor and the second current-limiting resistor respectively, the components are prevented from being damaged due to excessive current, thereby improving the reliability of the circuit.

[0010] In other embodiments of this application, the first-stage amplifier circuit includes: The third current-limiting resistor has its first end connected to the positive phase signal of the switch quantity to be acquired, and its second end connected to the positive terminal of the primary side of the second transformer. The fourth current-limiting resistor has its first end connected to the negative phase signal of the switch quantity to be acquired, and its second end connected to the emitter of the first transistor and the negative secondary terminal of the first transformer. The resistance value of the third current-limiting resistor is less than the resistance value of the first current-limiting resistor; The resistance value of the fourth current-limiting resistor is less than the resistance value of the second current-limiting resistor.

[0011] The technical solution provided in this application has at least the following beneficial effects: setting a current-limiting resistor with progressively decreasing resistance not only ensures the current-limiting protection function, but also helps the drive current to be smoothly transmitted to the next stage, ensuring that the driving capability of the dynamic excitation chain is progressively enhanced, and optimizing the signal transmission efficiency.

[0012] In other embodiments of this application, the secondary amplifier circuit includes: The fifth current-limiting resistor has its first end connected to the input power supply and its second end connected to the positive terminal of the primary side of the third transformer. The resistance value of the fifth current-limiting resistor is less than the resistance value of the third current-limiting resistor.

[0013] The technical solution provided in this application brings at least the following beneficial effects: continuously optimizing the power transfer path, so that the excitation energy can be more effectively coupled to the subsequent stage, laying the foundation for the final output of a signal with strong driving capability.

[0014] In other embodiments of this application, the first-stage amplifier circuit includes: The first voltage divider protection resistor has its first end connected to the base of the first transistor and its second end connected to the positive secondary terminal of the first transformer.

[0015] The technical solution provided in this application has at least the following beneficial effects: by limiting the base current flowing to the first transistor through the first voltage divider protection resistor, the first transistor is prevented from being damaged due to overdrive, and at the same time, it provides a stable bias in conjunction with the secondary side of the transformer.

[0016] In other embodiments of this application, the secondary amplifier circuit includes: The second voltage divider protection resistor has its first end connected to the base of the second transistor and its second end connected to the positive terminal of the secondary side of the second transformer. The resistance value of the second voltage divider protection resistor is less than the resistance value of the first voltage divider protection resistor.

[0017] The technical solution provided in this application has at least the following beneficial effects: on the one hand, it provides overcurrent protection for the second transistor; on the other hand, the gradual decrease in the resistance value of the voltage divider protection resistor matches the gradual increase in the amplitude of the excitation signal, reducing the attenuation of the drive signal and ensuring amplification efficiency.

[0018] In other embodiments of this application, the three-stage output circuit includes: The third voltage divider protection resistor has its first end connected to the base of the third transistor and its second end connected to the positive secondary terminal of the third transformer. The resistance value of the third voltage divider protection resistor is less than the resistance value of the second voltage divider protection resistor.

[0019] The technical solution provided in this application has at least the following beneficial effects: by using a smaller voltage divider protection resistor in the final output stage, it is ensured that the third transistor can be fully driven to saturation or cutoff state, thereby generating a sufficiently large switching current on the primary side of the fourth transformer, and finally obtaining a powerful output signal.

[0020] In other embodiments of this application, the isolated switch quantity acquisition circuit further includes: The first diode, the negative terminal of which is connected to the second terminal of the first current-limiting resistor; The first Zener diode has its anode connected to the anode of the first diode, and its cathode connected to the cathode of the primary side of the first transformer. The second diode, the negative terminal of which is connected to the second terminal of the third current-limiting resistor; The second Zener diode has its anode connected to the anode of the second diode, and its cathode connected to the cathode of the primary side of the second transformer. The third diode, the negative terminal of which is connected to the second terminal of the fifth current-limiting resistor; The third Zener diode, the positive terminal of which is connected to the positive terminal of the third diode, and the negative terminal of which is connected to the negative terminal of the primary side of the third transformer; A fourth diode, the negative terminal of which is connected to the input power supply; The fourth Zener diode has its positive terminal connected to the positive terminal of the fourth diode, and its negative terminal connected to the negative terminal of the primary side of the fourth transformer.

[0021] The technical solution provided in this application has at least the following beneficial effects: by connecting a branch consisting of diodes and Zener diodes in parallel on the primary side of each transformer, a freewheeling branch is provided for the induced electromotive force generated by the primary coil of the transformer, and the voltage is clamped by the Zener diode, thereby effectively suppressing voltage spikes, protecting transistors and field-effect transistors from breakdown, and greatly enhancing the reliability and lifespan of the circuit.

[0022] In other embodiments of this application, the isolated switch quantity acquisition circuit further includes: The fifth diode, the anode of which is connected to the secondary side terminal of the fourth transformer; The first filter capacitor has its positive terminal connected to the negative terminal of the fifth diode, and its negative terminal connected to the center tap of the fourth transformer.

[0023] The technical solution provided in this application has at least the following beneficial effects: the high-frequency switching signal is rectified and filtered by the positive-phase output filter circuit composed of the fifth diode and the first filter capacitor, thereby outputting a smooth positive-phase DC switching signal and improving the quality of the output signal.

[0024] In other embodiments of this application, the isolated switch quantity acquisition circuit further includes: The sixth diode, the negative terminal of which is connected to the opposite-name terminal of the secondary side of the fourth transformer; The second filter capacitor has its positive terminal connected to the center tap of the fourth transformer and its negative terminal connected to the positive terminal of the sixth diode.

[0025] The technical solution provided in this application offers at least the following advantages: the inverting output filter circuit, composed of the sixth diode and the second filter capacitor, can output a smooth negative-phase DC switching signal. Simultaneously, together with the fifth diode and the first filter capacitor, it forms a differential signal, enhancing the signal's ability to resist common-mode interference.

[0026] Compared with the prior art, the present invention has the following beneficial effects: 1) By constructing a dynamic incentive chain that runs throughout the entire process, a fundamental safety improvement is achieved, ensuring that any single point of failure leads to a safe output.

[0027] 2) Through multi-stage transformer coupling and amplification, the driving capability and anti-interference ability of the output signal are significantly enhanced.

[0028] The above description is merely an overview of the technical solution disclosed herein. In order to better understand the technical means of this disclosure and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this disclosure more apparent and understandable, specific embodiments of this disclosure are described below. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a structural diagram of the isolation switch quantity acquisition circuit in an embodiment of this application. Detailed Implementation

[0031] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0032] The prefixes such as "first" and "second" used in this application embodiment are merely for distinguishing different descriptive objects and do not limit the position, order, priority, quantity, or content of the described objects. The use of ordinal numbers and other prefixes used to distinguish descriptive objects in this application embodiment does not constitute a limitation on the described objects. The description of the described objects is given in the claims or the context of the embodiments, and should not constitute unnecessary restrictions due to the use of such prefixes. Furthermore, in the description of this embodiment, unless otherwise stated, "multiple" means two or more.

[0033] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. In the description of the embodiments of this application, unless otherwise stated, " / " means "or," for example, A / B can mean A or B; the term "and / or" in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone.

[0034] In the embodiments provided in this application, it should be understood that the disclosed systems and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0035] In this application, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0036] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0037] This application provides an isolated switch quantity acquisition circuit. For example... Figure 1 As shown, the circuit mainly includes a clock source circuit Part-1, an excitation source circuit Part-2, a first-stage amplifier circuit Part-3, a second-stage amplifier circuit Part-4, and a third-stage output circuit Part-5. The clock source circuit Part-1, the excitation source circuit Part-2, the first-stage amplifier circuit Part-3, the second-stage amplifier circuit Part-4, and the third-stage output circuit Part-5 together form a dynamic excitation signal chain.

[0038] The clock source circuit Part-1 outputs a periodic square wave voltage signal.

[0039] The excitation source circuit Part-2 includes a field-effect transistor T24 and a first transformer TR25.

[0040] The gate 1 of the field-effect transistor T24 is connected to the output of the clock source circuit Part-1, and the source 2 of the field-effect transistor T24 is connected to the reference ground power supply GND. The negative terminal Ig of the primary side of the first transformer TR25 is connected to the drain 3 of the field-effect transistor T24, and the positive terminal Ia of the primary side of the first transformer TR25 is connected to the input power supply VCC. The field-effect transistor T24 is frequently turned on and off under the drive of a square wave voltage signal, thereby forming a pulsating current on the primary side of the first transformer TR25, which induces an excitation voltage on the secondary side.

[0041] The first-stage amplifier circuit, Part-3, includes the first transistor T25 and the second transformer TR24.

[0042] The base 1 of the first transistor T25 is connected to the positive secondary terminal IIa of the first transformer TR25. The emitter 3 of the first transistor T25 and the negative secondary terminal IIg of the first transformer TR25 are both connected to the negative phase switch signal DIN_N to be acquired. The negative primary terminal Ig of the second transformer TR24 is connected to the collector 2 of the first transistor T25. The positive primary terminal Ia of the second transformer TR24 is connected to the positive phase switch signal DIN_P to be acquired.

[0043] Specifically, the working principle of the first-stage amplifier circuit Part-3 is as follows: The AC excitation voltage induced by the secondary side of the first transformer TR25 is applied between the base 1 and emitter 3 of the first transistor T25, providing the driving basis for the switching action of the first transistor T25. Simultaneously, the external differential switching signals DIN_P and DIN_N to be acquired are respectively connected to the positive terminal Ia of the primary side of the second transformer TR24 and the emitter 3 circuit of the first transistor T25. Only when the positive excitation voltage provided by the first transformer TR25 is sufficient, and an effective loop is formed between the external input signals DIN_P and DIN_N, will the first transistor T25 enter the saturation conduction state. At this time, the operating current flows in from the DIN_P terminal, through the primary coil of the second transformer TR24, the collector 2 of the first transistor T25, the emitter 3 of the first transistor T25, and finally flows out from the DIN_N terminal. The current generates a changing magnetic field on the primary side of the second transformer TR24, thereby inducing a modulated signal on its secondary side that contains both the excitation frequency of the previous stage and external switching status information, and completing the initial power amplification.

[0044] The second-stage amplifier circuit Part-4 includes the second transistor T26 and the third transformer TR26.

[0045] The base 1 of the second transistor T26 is connected to the positive secondary terminal IIa of the second transformer TR24. The emitter 3 of the second transistor T26 and the negative secondary terminal IIg of the second transformer TR24 are both connected to the reference ground power supply GND. The negative primary terminal Ig of the third transformer TR26 is connected to the collector 2 of the second transistor T26, and the positive primary terminal Ia of the third transformer TR26 is connected to the input power supply VCC.

[0046] Specifically, the working principle of the diode amplifier circuit Part-4 is as follows: The signal output from the first-stage amplifier circuit Part-3 is coupled to the base 1 of the second transistor T26 in this stage via the secondary side of the second transformer TR24, forming a driving voltage. When this excitation signal is in the positive half-cycle and has sufficient amplitude, the second transistor T26 conducts, and a current path is established: the current flows from the input power supply VCC through the primary winding of the third transformer TR26, through the collector 2 and emitter 3 of the second transistor T26, and finally into the reference ground power supply GND. This current generates a strong magnetic field change on the primary side of the third transformer TR26, thereby inducing a secondary amplified excitation signal on its secondary side. In this process, the energy source of the circuit is completely converted into the internal power supply (VCC / GND), achieving a significant enhancement in signal driving capability.

[0047] The three-stage output circuit Part-5 includes the third transistor T27 and the fourth transformer TR27.

[0048] The base 1 of the third transistor T27 is connected to the positive secondary terminal IIa of the third transformer TR26. The emitter 3 of the third transistor T27 and the negative secondary terminal IIg of the third transformer TR26 are both connected to the reference ground power supply GND. The negative primary terminal Ig of the fourth transformer TR27 is connected to the collector 2 of the third transistor T27. The positive primary terminal Ia of the fourth transformer TR27 is connected to the input power supply VCC. The same-name terminal 8 of the secondary side of the fourth transformer TR27 outputs a positive switching signal DIN_O_P, and the opposite-name terminal 5 of the secondary side of the fourth transformer TR27 outputs a negative switching signal DIN_O_N.

[0049] Specifically, the working principle of the three-stage output circuit Part-5 is as follows: The excitation signal output from the two-stage amplifier circuit Part-4, after being amplified again, is coupled to the base 1 of the third transistor T27 through the secondary side of the third transformer TR26, controlling its switching state. When the excitation signal is valid, the third transistor T27 is saturated and conducts, forming a strong current path from the input power supply VCC through the primary winding of the fourth transformer TR27, and then through the third transistor T27 to the reference ground GND. This high-power switching current generates a strong magnetic field change on the primary side of the fourth transformer TR27, which in turn generates a fully electrically isolated high-drive-capability differential signal on its secondary winding through electromagnetic induction. Finally, the positive phase signal DIN_O_P and the negative phase signal DIN_O_N are output from the same-name terminal 8 and the opposite-name terminal 5 of the secondary side of the fourth transformer TR27, respectively.

[0050] This application's technical solution introduces a complete dynamic excitation signal chain, consisting of a clock source, excitation source, multi-stage amplification, and output circuitry. This ensures that the validity of the output signal no longer depends on a static comparison of the input voltage, but rather on the continuous and complete transmission of this excitation chain. Since each active device (MOSFET, transistors) and passive coupling device (transformers) in the chain is a necessary link in signal transmission, any open-circuit or short-circuit fault in any single device will immediately interrupt the excitation transmission, causing the final output to automatically and reliably enter a safe state without a valid signal, thus achieving an extremely high level of fail-safe guidance. Furthermore, the cascaded design of multi-stage transformer coupling and transistor amplification provides progressive power enhancement and electrical isolation during signal transmission. This not only significantly enhances the driving capability and load-carrying capacity of the output signal but also, through multi-stage isolation and the final differential output form, greatly suppresses the effects of common-mode interference and electromagnetic noise, ensuring extreme reliability and stability of signal acquisition in environments with strong electromagnetic interference, such as high-speed maglev trains.

[0051] In other embodiments of this application, the excitation source circuit Part-2 includes a first current-limiting resistor R55 and a second current-limiting resistor R58.

[0052] The first terminal of the first current-limiting resistor R55 is connected to the input power supply VCC, and the second terminal is connected to the positive terminal Ia of the primary winding of the first transformer TR25. Its main function is to limit the peak charging current of the primary winding of the first transformer TR25. When the field-effect transistor T24 is turned on by a square wave voltage signal, without the first current-limiting resistor R55, the primary winding of the first transformer TR25 would attempt to draw a very large transient current from the power supply VCC. The presence of the first current-limiting resistor R55 effectively suppresses this current surge.

[0053] The first terminal of the second current-limiting resistor R58 is connected to the reference ground power supply GND, and the second terminal is connected to the source stage 2 of the field-effect transistor T24. The second current-limiting resistor R58 and the on-resistance of the field-effect transistor T24 together form a path from source stage 2 to the reference ground power supply GND. Its voltage drop affects the actual gate-source drive voltage of the field-effect transistor T24 and also helps limit the source current. Working together, they precisely limit the operating current of the excitation source stage within the design range.

[0054] This application's technical solution directly protects the primary winding of the first transformer TR25 and the field-effect transistor T24 from overcurrent stress damage through the first current-limiting resistor R55. The second current-limiting resistor R58 provides additional current sampling and limiting points, enhancing the operational safety of the field-effect transistor T24. Secondly, by suppressing current spikes through the first and second current-limiting resistors R55 and R58, switching noise and potential power supply disturbances are reduced, resulting in a cleaner and more stable primary excitation signal generated by the secondary side of the first transformer TR25, providing a high-quality signal source for subsequent multi-stage amplification chains. More importantly, if the first current-limiting resistor R55 experiences an open-circuit fault, the excitation source stage is completely disabled, and the dynamic excitation chain is interrupted at its source; if the second current-limiting resistor R58 experiences an open circuit, the source circuit of the field-effect transistor T24 is cut off, similarly preventing excitation generation. Both of these fault modes directly cause the system output to be directed to the safe side. Therefore, while fulfilling their basic protection functions, these two current-limiting resistors also become an indispensable part of the high-reliability dynamic excitation chain. Any failure will be identified by the system and trigger a safety response, further consolidating the high safety integrity level of the circuit in this application.

[0055] In other embodiments of this application, the first-stage amplifier circuit Part-3 includes a third current-limiting resistor R54 and a fourth current-limiting resistor R57.

[0056] The first end of the third current-limiting resistor R54 is connected to the positive phase signal DIN_P of the switch quantity to be acquired, and the second end is connected to the positive primary terminal Ia of the second transformer TR24.

[0057] The first end of the fourth current-limiting resistor R57 is connected to the negative phase signal DIN_N of the switch quantity to be acquired, and the second end is connected to the emitter 3 of the first transistor T25 and the negative secondary terminal IIg of the first transformer TR25.

[0058] The resistance of the third current-limiting resistor R54 is less than the resistance of the first current-limiting resistor R55.

[0059] The resistance of the fourth current-limiting resistor R57 is less than the resistance of the second current-limiting resistor R58.

[0060] The third current-limiting resistor R54 is connected in series between the positive phase switch signal DIN_P to be acquired and the positive terminal Ia of the primary side of the second transformer TR24, while the fourth current-limiting resistor R57 is connected in series between the negative phase switch signal DIN_N to be acquired and the emitter 3 of the first transistor T25. Under the combined action of the third and fourth current-limiting resistors R54 and R57, the maximum allowable current in the working circuit formed by the external signal source (DIN_P / N), the primary side of the second transformer TR24, and the first transistor T25 is precisely set when the excitation is effective. Furthermore, in this embodiment, the resistance value of the third current-limiting resistor R54 is less than the first current-limiting resistor R55 in the preceding excitation source, and the resistance value of the fourth current-limiting resistor R57 is less than the second current-limiting resistor R58 in the preceding stage. This decreasing resistance design principle lowers the impedance threshold for the signal to flow from the external input source into this stage's amplification circuit. This allows the external signal circuit to provide operating current with a smoothness no less than the efficiency of the preceding excitation source path when the first transistor T25 should be turned on by the preceding stage excitation.

[0061] The technical solution of this application sets a current-limiting resistor with progressively decreasing resistance value, which not only ensures the current-limiting protection function, but also helps the drive current to be smoothly transmitted to the next stage, ensuring that the driving capability of the dynamic excitation chain is progressively enhanced and optimizing the signal transmission efficiency.

[0062] In some other embodiments of this application, the secondary amplifier circuit Part-4 includes a fifth current-limiting resistor R59.

[0063] The first end of the fifth current-limiting resistor R59 is connected to the input power supply VCC, and the second end is connected to the primary positive terminal Ia of the third transformer TR26.

[0064] The resistance of the fifth current-limiting resistor R59 is less than that of the third current-limiting resistor R54.

[0065] The fifth current-limiting resistor R59, as a key component connected in series in the power loop of Part-4 of the second-stage amplifier circuit, directly sets the upper limit of the operating current drawn by this stage from the input power supply VCC. When the second transistor T26 is turned on by the previous stage, the current flows from the input power supply VCC through the fifth current-limiting resistor R59, the primary winding of the third transformer TR26, and the second transistor T26 to the reference ground power supply GND. The presence of the fifth current-limiting resistor R59 effectively prevents the risk of overcurrent caused by sudden current changes or circuit abnormalities at the moment of turn-on. In addition, the resistance value of the fifth current-limiting resistor R59 is less than the resistance value of the third current-limiting resistor R54 in the previous stage amplifier circuit Part-3. This systematic design of continuously decreasing resistance means that the path impedance from the input power supply VCC to the primary winding of this stage transformer is further reduced, allowing the second-stage amplifier circuit Part-4 to draw a larger operating current from the system power supply more smoothly and efficiently than the previous stage during the effective period of the excitation signal.

[0066] Finally, if the fifth current-limiting resistor R59 experiences an open-circuit fault, Part-4 of the second-stage amplifier circuit will immediately fail, and the dynamic excitation chain will be interrupted. If its resistance value increases abnormally, it will lead to insufficient amplification in this stage, which may also cause the signal chain to fail. Regardless of the failure mode, the consequence is that the system output is forced to the safe side, thus strengthening the robustness and safety of the entire dynamic excitation chain.

[0067] The technical solution of this application continuously optimizes the power transmission path, enabling the excitation energy to be coupled to the subsequent stage more effectively, laying the foundation for the final output of a signal with strong driving capability.

[0068] In other embodiments of this application, the first-stage amplifier circuit Part-3 includes a first voltage divider protection resistor R56. The first end of the first voltage divider protection resistor R56 is connected to the base 1 of the first transistor T25, and the second end is connected to the positive secondary terminal IIa of the first transformer TR25.

[0069] The AC excitation voltage from the secondary side of the first transformer TR25 is not directly applied to the base 1 of the first transistor T25, but must first pass through the first voltage divider protection resistor R56. The first voltage divider protection resistor R56, together with the equivalent input impedance between the base 1 and emitter 3 of the first transistor T25, forms a voltage divider network. Only a sufficiently large positive voltage can drive the first transistor T25 to conduct, thus setting a clear voltage threshold for transistor operation and enhancing anti-interference capability. At the same time, the first voltage divider protection resistor R56 limits the maximum current flowing into the base 1 of the first transistor T25, preventing damage to the transistor's BE junction due to excessive current in the base 1 caused by excessively high excitation voltage or transients.

[0070] The technical solution of this application provides direct and reliable base drive protection for the first transistor T25 through the first voltage divider protection resistor R56, which is the foundation for ensuring the long-term stable operation of the first transistor T25. Secondly, the introduction of the first voltage divider protection resistor R56 means that the activation of the first-stage amplifier circuit Part-3 not only requires the previous stage excitation, but also requires the excitation to reach a certain strength, which improves the ability to distinguish signal quality. More importantly, as a series node in the excitation signal transmission path, if the first voltage divider protection resistor R56 fails to open, it will immediately cut off the drive to the first transistor T25, causing the amplification function of this stage to fail, thereby interrupting the entire dynamic excitation chain and directing the output to the safe side, strengthening the robustness and safety of the entire dynamic excitation chain.

[0071] In other embodiments of this application, the secondary amplifier circuit Part-4 includes a second voltage divider protection resistor R60. The first end of the second voltage divider protection resistor R60 is connected to the base 1 of the second transistor T26, and the second end is connected to the positive terminal IIa of the secondary side of the second transformer TR24.

[0072] The resistance value of the second voltage divider protection resistor R60 is less than the resistance value of the first voltage divider protection resistor R56.

[0073] The AC excitation voltage from the secondary side of the second transformer TR24 first passes through the second voltage divider protection resistor R60 before being applied to the base 1 of the second transistor T26. The second voltage divider protection resistor R60, together with the equivalent input impedance between the base 1 and emitter 3 of the second transistor T26, forms a voltage divider network. Only a sufficiently large positive voltage can drive the second transistor T26 to conduct, thus setting a clear voltage threshold for transistor operation and enhancing its anti-interference capability. At the same time, the second voltage divider protection resistor R60 limits the maximum current flowing into the base 1 of the second transistor T26, preventing damage to the transistor's BE junction due to excessive current caused by excessively high excitation voltage or transients.

[0074] The technical solution of this application provides direct and reliable base drive protection for the second transistor T26 through the second voltage divider protection resistor R60, which is the foundation for ensuring the long-term stable operation of the second transistor T26. Secondly, the introduction of the second voltage divider protection resistor R60 means that the activation of Part-4 of the second-stage amplifier circuit not only requires the excitation from the previous stage, but also requires the excitation to reach a certain strength, which improves the ability to distinguish signal quality. More importantly, as a series node in the excitation signal transmission path, if the second voltage divider protection resistor R60 fails to open, it will immediately cut off the drive to the second transistor T26, causing the amplification function of this stage to fail, thereby interrupting the entire dynamic excitation chain and directing the output to the safe side, strengthening the robustness and safety of the entire dynamic excitation chain.

[0075] In other embodiments of this application, the three-stage output circuit Part-5 includes a third voltage divider protection resistor R61. The first end of the third voltage divider protection resistor R61 is connected to the base 1 of the third transistor T27, and the second end is connected to the positive secondary terminal IIa of the third transformer TR26.

[0076] The resistance value of the third voltage divider protection resistor R61 is less than the resistance value of the second voltage divider protection resistor R60.

[0077] The AC excitation voltage from the secondary side of the third transformer TR26 first passes through the third voltage divider protection resistor R61 before being applied to the base 1 of the third transistor T27. The third voltage divider protection resistor R61, together with the equivalent input impedance between the base 1 and emitter 3 of the third transistor T27, forms a voltage divider network. Only a sufficiently large positive voltage can drive the third transistor T27 to conduct, thus setting a clear voltage threshold for transistor operation and enhancing its anti-interference capability. At the same time, the third voltage divider protection resistor R61 limits the maximum current flowing into the base 1 of the third transistor T27, preventing damage to the transistor's BE junction due to excessive current caused by excessively high excitation voltage or transients.

[0078] The technical solution of this application provides direct and reliable base drive protection for the third transistor T27 through the third voltage divider protection resistor R61, which is the foundation for ensuring the long-term stable operation of the third transistor T27. Secondly, the introduction of the third voltage divider protection resistor R61 means that the activation of the three-stage output circuit Part-5 not only requires the excitation of the previous stage, but also requires the excitation to reach a certain strength, which improves the ability to distinguish signal quality. More importantly, as a series node in the excitation signal transmission path, if the third voltage divider protection resistor R61 fails to open, it will immediately cut off the drive to the third transistor T27, causing the amplification function of this stage to fail, thereby interrupting the entire dynamic excitation chain and directing the output to the safe side, strengthening the robustness and safety of the entire dynamic excitation chain.

[0079] In other embodiments of this application, the isolation switch quantity acquisition circuit further includes: The first diode D27 has its negative terminal 1 connected to the second end of the first current-limiting resistor R55.

[0080] The first Zener diode DZ16 has its positive terminal 2 connected to the positive terminal 2 of the first diode D27, and its negative terminal 1 connected to the negative terminal Ig of the primary side of the first transformer TR25.

[0081] The first clamping freewheeling branch, composed of the first diode D27 and the first Zener diode DZ16, can handle the transient high voltage generated by the inductive load during switching, thereby protecting the critical switching devices. Specifically, during the period when the MOSFET T24 is turned on by the preceding square wave voltage signal, the current flows from the input power supply VCC through the first current-limiting resistor R55, the primary winding of the first transformer TR25 (from the positive terminal Ia to the negative terminal Ig), and the MOSFET T24 to the reference ground power supply GND. At this time, the voltage polarity across the primary winding of the first transformer TR25 is positive at the positive terminal Ia and negative at the negative terminal Ig. This causes the first diode D27 to withstand a reverse voltage (its negative terminal is connected to a high potential, and its positive terminal is connected to a low potential through DZ16). The entire branch is in a reverse cutoff state, which does not affect the normal excitation current path.

[0082] At the instant that MOSFET T24 switches from conducting to turning off, due to the inductive characteristics of the primary winding of the first transformer TR25, its current cannot change abruptly. To maintain the original current direction, the primary winding of the first transformer TR25 generates a reverse induced electromotive force, with its polarity changing to Ia negative and Ig positive. The amplitude of this instantaneous high voltage may far exceed the withstand capability of MOSFET T24. At this moment, the first clamping freewheeling branch responds immediately: the induced electromotive force causes the first diode D27 to become forward biased, and the first Zener diode DZ16 operates in the reverse breakdown regulation region, thus providing a freewheeling release path for the current in the primary winding of the first transformer TR25. The magnetic energy stored in the primary winding of the first transformer TR25 is released through this path. Simultaneously, the first clamping freewheeling branch precisely clamps the reverse voltage across the primary winding of the first transformer TR25 to the sum of the stable voltage Vz of the first Zener diode DZ16 and the forward voltage drop Vf of the first diode D27 (i.e., Vz + Vf). Therefore, the maximum voltage that the drain 3 of T24 can withstand is limited to VCC + Vz + Vf. Within this preset safety value, the risk of high voltage spikes breaking down the field-effect transistor T24 can be effectively avoided.

[0083] The isolated switch quantity acquisition circuit also includes: The second diode D26 has its negative terminal 1 connected to the second end of the third current-limiting resistor R54.

[0084] The second Zener diode DZ15 has its positive terminal 2 connected to the positive terminal 2 of the second diode D26, and its negative terminal 1 connected to the negative terminal Ig of the primary side of the second transformer TR24.

[0085] The second clamping freewheeling branch in Part-3 of the first-stage amplifier circuit is formed by the second diode D26 and the second Zener diode DZ15. Its working principle is similar to that of the corresponding unit in the excitation source stage. Specifically, during the period when the first transistor T25 is turned on by the excitation of the previous stage, the current flows from the positive phase signal DIN_P through the third current-limiting resistor R54, the primary coil of the second transformer TR24 (from the positive terminal Ia to the negative terminal Ig), and the first transistor T25 to the negative phase signal DIN_N. At this time, the voltage polarity across the coil is Ia positive and Ig negative, causing the second diode D26 to withstand reverse voltage and be cut off, and this branch does not work. When the first transistor T25 turns from on to off, the primary coil of the second transformer TR24 generates a reverse induced electromotive force due to the self-inductance effect, and the polarity changes to Ia negative and Ig positive. Its amplitude may endanger the collector 2 of the first transistor T25. At this time, the electromotive force causes the second diode D26 to be forward biased and conduct, and at the same time causes the second Zener diode DZ15 to enter the reverse breakdown voltage regulation state, thereby establishing a freewheeling path for the coil current and clamping the reverse voltage across the coil within the safe range of the sum of the Zener diode DZ15's regulated voltage Vz and the forward voltage drop Vf of the second diode D26 (Vz+Vf).

[0086] The isolated switch quantity acquisition circuit also includes: The third diode D29, with its negative terminal 1 connected to the second terminal of the fifth current-limiting resistor R59.

[0087] The third Zener diode DZ17 has its positive terminal 2 connected to the positive terminal 2 of the third diode D29, and its negative terminal 1 connected to the primary negative terminal Ig of the third transformer TR26.

[0088] The fourth diode D30, with its negative terminal 1 connected to the input power supply VCC.

[0089] The fourth Zener diode DZ18 has its positive terminal 2 connected to the positive terminal 2 of the fourth diode D30, and its negative terminal 1 connected to the primary negative terminal Ig of the fourth transformer TR27.

[0090] The third clamping freewheeling branch, composed of the third diode D29 and the third Zener diode DZ17, and the fourth clamping freewheeling branch, composed of the fourth diode D30 and the fourth Zener diode DZ18, work on a similar principle to the second clamping freewheeling branch, but serve different protected objects. The specific working principle will not be elaborated here.

[0091] The technical solution of this application connects a clamping freewheeling branch consisting of diodes and Zener diodes in parallel on the primary side of each transformer. When the corresponding transistor is turned off, it provides a freewheeling branch for the induced electromotive force generated by the primary coil of the transformer, and the voltage is clamped by the Zener diode, thereby effectively suppressing voltage spikes and protecting the transistors and MOSFETs from breakdown, greatly enhancing the reliability and lifespan of the circuit.

[0092] In other embodiments of this application, the isolated switching quantity acquisition circuit further includes a fifth diode D28 and a first filter capacitor C12. The positive terminal 2 of the fifth diode D28 is connected to the secondary side terminal 8 of the fourth transformer TR27. The positive terminal 2 of the first filter capacitor C12 is connected to the negative terminal 1 of the fifth diode D28, and the negative terminal 1 of the first filter capacitor C12 is connected to the center tap 6 of the fourth transformer TR27.

[0093] The first filtering unit, composed of the fifth diode D28 and the first filter capacitor C12, provides signal interface conversion and shaping for the output signal, converting the AC pulses output by the transformer into a clean DC level that can be directly processed by digital logic circuits. Specifically, the secondary side of the fourth transformer TR27 outputs a set of high-frequency AC differential signals. When the potential of the same-name terminal 8 of the secondary side of the fourth transformer TR27 is positive relative to the center tap 6, i.e., in the positive half-cycle of the signal, the fifth diode D28 is forward biased and conducts. At this time, current flows from the same-name terminal 8 through the fifth diode D28, supplying the subsequent load as output current on the one hand, and charging the first filter capacitor C12 on the other, causing the potential of the positive terminal 2 of the first filter capacitor C12 to rise rapidly to near the pulse peak. When the signal enters the negative half-cycle or zero level, the potential of the same-name terminal 8 of the secondary side of the fourth transformer TR27 is lower than or equal to the potential of the center tap 6, and the fifth diode D28 is reliably cut off due to reverse bias, preventing reverse current. At this time, the charged C12 begins to discharge to the load, maintaining the stability of the output voltage. Through the unidirectional rectification of the fifth diode D28 and the energy storage and smoothing effect of the first filter capacitor C12, a DC output signal with minimal ripple and stable level is finally output at the DIN_O_P terminal.

[0094] The technical solution of this application uses a non-inverting output filter circuit composed of a fifth diode and a first filter capacitor to rectify and filter high-frequency switching signals, thereby outputting a smooth non-inverting DC switching signal and improving the quality of the output signal.

[0095] In other embodiments of this application, the isolated switching quantity acquisition circuit further includes a sixth diode D31 and a second filter capacitor C13. The negative terminal 1 of the sixth diode D31 is connected to the non-representation terminal 5 of the secondary side of the fourth transformer TR27. The positive terminal 2 of the second filter capacitor C13 is connected to the center tap 6 of the fourth transformer TR27, and the negative terminal 1 of the second filter capacitor C13 is connected to the positive terminal 2 of the sixth diode D31.

[0096] The second filter unit, composed of the sixth diode D31 and the second filter capacitor C13, provides signal interface conversion and shaping for the output signal, converting the AC pulses output by the transformer into a clean DC level that can be directly processed by digital logic circuits. Specifically, when the potential of the opposite-name terminal 5 on the secondary side of the fourth transformer TR27 is negative relative to the center tap 6, i.e., it is in the negative half-cycle corresponding to the differential signal, the sixth diode D31 is forward biased and conducts because its negative terminal potential is lower than its positive terminal. At this time, the current flows from the center tap 6 through the second filter capacitor C13 and the sixth diode D31 to the opposite-name terminal 5 to form a loop. This process charges the second filter capacitor C13, establishing a stable voltage difference between its positive terminal 2 and negative terminal 1, thereby causing the DIN_O_N terminal to output a negative DC level. When the signal polarity is reversed, the sixth diode D31 is turned off due to reverse bias, and the second filter capacitor C13 discharges to the load to maintain the stability of the output level. Through unidirectional rectification by the sixth diode D31 and energy storage smoothing by the second filter capacitor C13, a DC differential signal with extremely low ripple and opposite phase to DIN_O_P is finally obtained at the DIN_O_N terminal.

[0097] This application's technical solution achieves a complete differential output interface through the sixth diode, the second filter capacitor, and the fifth diode and the first filter capacitor, greatly facilitating subsequent differential reception and processing. Secondly, any common-mode noise simultaneously coupled to both output lines will be automatically canceled by the differential receiving circuit, thus ensuring extreme reliability of signal transmission in complex electromagnetic environments and significantly improving the system's common-mode rejection capability. More importantly, this branch works in conjunction with the positive-phase branch, deeply integrating into the system's fault-oriented safety mechanism. When the dynamic excitation chain is working normally, the DIN_O_N and DIN_O_P terminals output stable and opposite DC levels, forming effective differential logic. If the excitation chain is interrupted due to a fault, the fourth transformer TR27 has no output, and neither branch has rectified output. After the first filter capacitor C12 and the second filter capacitor C13 discharge, DIN_O_N and DIN_O_P will both tend to the same common reference potential, thus forming a clear and conflict-free safe-side output state.

[0098] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. An isolated switch quantity acquisition circuit, characterized in that, include: The clock source circuit is configured to output a periodic square wave voltage signal; The excitation source circuit, including a field-effect transistor and a first transformer, is configured to generate a primary high-frequency switching excitation signal based on the periodic square wave voltage signal; The gate of the field-effect transistor is connected to the output terminal of the clock source circuit, and the source of the field-effect transistor is connected to the reference ground power supply; the negative terminal of the primary side of the first transformer is connected to the drain of the field-effect transistor, and the positive terminal of the primary side of the first transformer is connected to the input power supply. A first-stage amplifier circuit, including a first transistor and a second transformer; The base of the first transistor is connected to the positive terminal of the secondary side of the first transformer, and the emitter of the first transistor and the negative terminal of the secondary side of the first transformer are connected together to the negative phase signal of the switching quantity to be acquired; the negative terminal of the primary side of the second transformer is connected to the collector of the first transistor, and the positive terminal of the primary side of the second transformer is connected to the positive phase signal of the switching quantity to be acquired. A two-stage amplifier circuit, including a second transistor and a third transformer; The base of the second transistor is connected to the positive terminal of the secondary side of the second transformer, and the emitter of the second transistor and the negative terminal of the secondary side of the second transformer are both connected to the reference ground power supply; the negative terminal of the primary side of the third transformer is connected to the collector of the second transistor, and the positive terminal of the primary side of the third transformer is connected to the input power supply. The three-stage output circuit includes a third transistor and a fourth transformer. The base of the third transistor is connected to the positive terminal of the secondary side of the third transformer, and the emitter of the third transistor and the negative terminal of the secondary side of the third transformer are connected to the reference ground power supply. The negative terminal of the primary side of the fourth transformer is connected to the collector of the third transistor, and the positive terminal of the primary side of the fourth transformer is connected to the input power supply. The same-name terminal of the secondary side of the fourth transformer outputs the positive phase signal of the switching quantity, and the opposite-name terminal of the secondary side of the fourth transformer outputs the negative phase signal of the switching quantity.

2. The isolated switch quantity acquisition circuit according to claim 1, characterized in that, The excitation source circuit includes: A first current-limiting resistor, with its first end connected to the input power supply and its second end connected to the positive terminal of the primary side of the first transformer; The second current-limiting resistor has its first end connected to the reference ground power supply and its second end connected to the source of the field-effect transistor.

3. The isolated switch quantity acquisition circuit according to claim 2, characterized in that, The first-stage amplifier circuit includes: The third current-limiting resistor has its first end connected to the positive phase signal of the switch quantity to be acquired, and its second end connected to the positive terminal of the primary side of the second transformer. The fourth current-limiting resistor has its first end connected to the negative phase signal of the switch quantity to be acquired, and its second end connected to the emitter of the first transistor and the negative secondary terminal of the first transformer. The resistance value of the third current-limiting resistor is less than the resistance value of the first current-limiting resistor; The resistance value of the fourth current-limiting resistor is less than the resistance value of the second current-limiting resistor.

4. The isolated switch quantity acquisition circuit according to claim 3, characterized in that, The secondary amplifier circuit includes: The fifth current-limiting resistor has its first end connected to the input power supply and its second end connected to the positive terminal of the primary side of the third transformer. The resistance value of the fifth current-limiting resistor is less than the resistance value of the third current-limiting resistor.

5. The isolated switch quantity acquisition circuit according to claim 1, characterized in that, The first-stage amplifier circuit includes: The first voltage divider protection resistor has its first end connected to the base of the first transistor and its second end connected to the positive secondary terminal of the first transformer.

6. The isolated switch quantity acquisition circuit according to claim 5, characterized in that, The secondary amplifier circuit includes: The second voltage divider protection resistor has its first end connected to the base of the second transistor and its second end connected to the positive terminal of the secondary side of the second transformer. The resistance value of the second voltage divider protection resistor is less than the resistance value of the first voltage divider protection resistor.

7. The isolated switch quantity acquisition circuit according to claim 6, characterized in that, The three-stage output circuit includes: The third voltage divider protection resistor has its first end connected to the base of the third transistor and its second end connected to the positive secondary terminal of the third transformer. The resistance value of the third voltage divider protection resistor is less than the resistance value of the second voltage divider protection resistor.

8. The isolated switch quantity acquisition circuit according to claim 1, characterized in that, Also includes: The first diode, the negative terminal of which is connected to the second terminal of the first current-limiting resistor; The first Zener diode has its anode connected to the anode of the first diode, and its cathode connected to the cathode of the primary side of the first transformer. The second diode, the negative terminal of which is connected to the second terminal of the third current-limiting resistor; The second Zener diode has its anode connected to the anode of the second diode, and its cathode connected to the cathode of the primary side of the second transformer. The third diode, the negative terminal of which is connected to the second terminal of the fifth current-limiting resistor; The third Zener diode, the positive terminal of which is connected to the positive terminal of the third diode, and the negative terminal of which is connected to the negative terminal of the primary side of the third transformer; A fourth diode, the negative terminal of which is connected to the input power supply; The fourth Zener diode has its positive terminal connected to the positive terminal of the fourth diode, and its negative terminal connected to the negative terminal of the primary side of the fourth transformer.

9. The isolated switch quantity acquisition circuit according to claim 1, characterized in that, Also includes: The fifth diode, the anode of which is connected to the secondary side terminal of the fourth transformer; The first filter capacitor has its positive terminal connected to the negative terminal of the fifth diode, and its negative terminal connected to the center tap of the fourth transformer.

10. The isolated switch quantity acquisition circuit according to claim 1, characterized in that, Also includes: The sixth diode, the negative terminal of which is connected to the opposite-name terminal of the secondary side of the fourth transformer; The second filter capacitor has its positive terminal connected to the center tap of the fourth transformer and its negative terminal connected to the positive terminal of the sixth diode.

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