Bidirectional signal magnetic isolation transmission circuit

Abstract

The application discloses a bidirectional signal magnetic isolation transmission circuit, comprising: a frequency modulation signal processing module, which is used for converting high and low levels of a driving signal into a narrow pulse sequence signal; an amplitude modulation signal demodulation module, which is used for receiving a fault signal or an error signal of an IGBT driver, and performing feedback control on the driving signal according to the fault signal or the error signal; a frequency modulation signal demodulation module, which is used for converting the narrow pulse sequence signal corresponding to the high and low levels into a high and low level pulse signal, and taking the high and low level pulse signal as a gate driving voltage signal of the IGBT driver; and an amplitude modulation signal processing module, which is used for collecting the fault signal and the error signal of the IGBT driver, and transmitting the fault signal and the error signal to a primary coil side of a high-frequency isolation transformer. The application realizes bidirectional information transmission on both sides of the high-frequency isolation transformer, and makes the signal frequency and amplitude information respectively modulated so that the information can be transmitted without interference.

Description

Technical Field

[0001] This invention relates to the field of feedback circuits, and in particular to a bidirectional signal magnetic isolation transmission circuit. Background Technology

[0002] IGBTs are composite, fully controllable, voltage-driven power semiconductor devices composed of BJTs (bipolar junction transistors) and MOSFETs (insulated-gate field-effect transistors). In high-power applications, IGBT drivers often require transformers for electrical isolation between the control circuit and the power circuit. Figure 1 The existing solution uses a high-frequency PWM (Pulse Width Modulation) signal to transmit the drive signal. The PWM_1 signal input to the PWM encoding unit is a square wave signal that drives the IGBT. After being processed by the encoding unit, it becomes a high-frequency PWM signal with a frequency much higher than the original signal. After being transmitted to the secondary side through a high-frequency isolation transformer, the high-frequency PWM signal is converted into a low-frequency signal with the same frequency as the original PWM_1 signal by a signal conversion unit with latching function. After passing through the PWM decoding unit, the drive signal can be transmitted. At the same time, this method can realize the transmission of soft turn-off signal by changing the number of high-frequency PWM signal pulses.

[0003] However, this method cannot achieve signal transmission from the secondary side to the primary side. If the IGBT malfunctions or needs to transmit feedback signals, the circuit cannot perform the corresponding function. Furthermore, this method relies on the recognition of the number of pulses when transmitting soft turn-off information. If pulse loss occurs during the information transmission process, it will lead to incorrect control of the IGBT drive, which may damage the IGBT. Summary of the Invention

[0004] This invention provides a bidirectional signal magnetic isolation transmission circuit to solve the above-mentioned technical problems in the prior art.

[0005] To provide a basic understanding of some aspects of the disclosed embodiments, a brief summary is given below. This summary is not intended as a general commentary, nor is it intended to identify key / important components or to describe the scope of protection of these embodiments. Its sole purpose is to present some concepts in a simple form as a prelude to the detailed description that follows.

[0006] According to an embodiment of the present invention, a bidirectional signal magnetic isolation transmission circuit is provided.

[0007] In one embodiment, the bidirectional signal magnetically isolated transmission circuit includes:

[0008] A high-frequency isolation transformer has a primary winding and a secondary winding, used to couple a narrow pulse sequence signal from the primary winding side to the secondary winding side, and to form a narrow pulse sequence signal with the same frequency as the primary winding side on the secondary winding side;

[0009] A frequency modulation signal processing module is connected to the primary coil side of the high-frequency isolation transformer and is used to convert the high and low levels of the driving signal into narrow pulse sequence signals of different frequencies.

[0010] An amplitude modulation signal demodulation module is connected to the primary winding side of the high-frequency isolation transformer. It is used to receive fault signals or error signals from the IGBT driver and to perform feedback control on the drive signal based on the fault signals or error signals.

[0011] The frequency modulation signal demodulation module is connected to the secondary coil side of the high-frequency isolation transformer. It is used to convert the narrow pulse sequence signal corresponding to the high and low levels into high and low level pulse signals, and use the high and low level pulse signals as the gate drive voltage signal of the IGBT driver.

[0012] An amplitude modulation signal processing module is connected to the secondary coil side of the high-frequency isolation transformer. It is used to collect fault signals and error signals from the IGBT driver and transmit the fault signals and error signals to the primary coil side of the high-frequency isolation transformer.

[0013] In one embodiment, when the frequency modulation signal processing module converts the high and low levels of the driving signal into narrow pulse sequence signals of different frequencies, the frequency of the narrow pulse sequence signal corresponding to the high level is less than the frequency of the narrow pulse sequence signal corresponding to the low level.

[0014] In one embodiment, the frequency of the narrow pulse sequence signal corresponding to the low level is five times the frequency of the narrow pulse sequence signal corresponding to the high level.

[0015] In one embodiment, the amplitude modulation signal demodulation module includes a level comparison module and a signal decoding module. The level comparison module is used to receive fault signals or error signals sent from the secondary coil side of the high-frequency isolation transformer and to distinguish between fault signals and error signals using a window comparator. The signal decoding module is used to decode the distinguished fault signals or error signals according to Manchester coding rules.

[0016] In one embodiment, the level comparison module includes comparator one and comparator two, which are connected in parallel. The positive input terminals of both comparator one and comparator two are connected to the primary winding side of the high-frequency isolation transformer, the inverting input terminals of both comparator one and comparator two are connected to the reference voltage signal input terminal, and the output terminals of both comparator one and comparator two are connected to the signal decoding module.

[0017] In one embodiment, the frequency modulation signal demodulation module includes a transistor 1, a comparator 3, a transistor 2, and a comparator 4. The base of transistor 1 is connected to the secondary winding of the high-frequency isolation transformer, the collector of transistor 1 is connected to a low-level signal, and the emitter of transistor 1 is connected to a parallel capacitor 1 and a controlled current source. The positive input of comparator 3 is connected to the collector of transistor 1, and a capacitor 2 is connected between the positive input of comparator 3 and the collector of transistor 1, with the other end of capacitor 2 grounded. The inverting input terminal of comparator three is connected to the reference voltage signal input terminal, and the output terminal of comparator three is connected to transistor two; the base of transistor two is connected to the output terminal of comparator three, the collector of transistor two is connected to a low-level signal, and the emitter of transistor two is connected to a parallel capacitor one and a controlled current source; the non-inverting input terminal of comparator four is connected to the emitter of transistor two, as well as the parallel capacitor one and the controlled current source, the inverting input terminal of comparator four is connected to the reference voltage signal input terminal, and the output terminal of comparator four is connected to the IGBT driver.

[0018] In one embodiment, the amplitude modulation signal processing module includes a signal encoding module, a level conversion module, and an amplitude modulation signal gating module. The signal encoding module is used to acquire fault signals and error signals from the IGBT driver and encode the fault signals and error signals according to Manchester encoding rules. The level conversion module is used to adjust the high level of the fault signals and error signals respectively. The amplitude modulation signal gating module is used to input the fault signals or error signals to the primary winding side of the high-frequency isolation transformer according to the selection signal sent by the received signal encoding module.

[0019] In one embodiment, the level conversion module includes a diode and a capacitor, wherein one end of the capacitor is connected to the signal encoding module, the other end of the capacitor is connected to the cathode of the diode, and the anode of the diode is connected to a power supply.

[0020] In one embodiment, the amplitude modulation signal gating module includes a first switch, a second switch, and a MOSFET. The connection terminals of the first switch and the second switch are both connected between the power supply and the drain of the MOSFET. The control terminals of the first switch and the second switch are connected in parallel to the signal encoding module. The gate of the MOSFET is connected in parallel with the third capacitor and the cathode of the diode. The source of the MOSFET is connected to the secondary coil side of the high-frequency isolation transformer.

[0021] The technical solutions provided by the embodiments of the present invention may include the following beneficial effects:

[0022] This invention enables bidirectional information transmission between the two sides of a high-frequency isolation transformer. By separately modulating the frequency and amplitude information of the signals, information can be transmitted without interference. The frequency modulation signal demodulation module utilizes the different pulse durations of high-frequency and low-frequency PWM signals to transmit signals using the frequency information of the PWM signals. It also proposes that setting the frequency difference between high-frequency and low-frequency PWM signals can further reduce the delay of this information transmission loop. The amplitude modulation signal processing module uses a three-level amplitude modulation method to realize the reverse transmission of fault information and error information, and sets a window comparator on the primary side to successfully separate fault and error signals.

[0023] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0024] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0025] Figure 1 This is a schematic diagram of an existing IGBT driver structure;

[0026] Figure 2 This is a schematic diagram of a bidirectional signal magnetic isolation transmission circuit according to an exemplary embodiment;

[0027] Figure 3 This is a circuit diagram of a bidirectional signal magnetically isolated transmission circuit according to an exemplary embodiment;

[0028] Figure 4 This is a schematic diagram of the signal waveforms of a bidirectional signal magnetic isolation transmission circuit according to an exemplary embodiment;

[0029] Figure 5 This is a schematic diagram illustrating the encoding principle of a bidirectional signal magnetic isolation transmission circuit according to an exemplary embodiment. Detailed Implementation

[0030] The following description and accompanying drawings fully illustrate specific embodiments described herein to enable those skilled in the art to practice them. Some embodiments may include or substitute parts and features of other embodiments. The scope of the embodiments herein encompasses the entire scope of the claims and all available equivalents thereof. Throughout this document, the terms “first,” “second,” etc., are used only to distinguish one element from another without requiring or implying any actual relationship or order between the elements. Indeed, a first element can also be referred to as a second element, and vice versa. Furthermore, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a structure, apparatus, or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a structure, apparatus, or device. Without further limitation, an element defined by the phrase “comprising one…” does not exclude the presence of other identical elements in the structure, apparatus, or device that includes said element. The various embodiments described herein are presented in a progressive manner, with each embodiment focusing on its differences from other embodiments; similar or identical parts between embodiments can be referred to interchangeably.

[0031] The terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" used in this document to indicate orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings. They are used solely for the convenience of describing the document and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In the description herein, unless otherwise specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two elements; they can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0032] In this document, unless otherwise stated, the term "multiple" means two or more.

[0033] In this article, the character " / " indicates that the objects before and after it are in an "or" relationship. For example, A / B means: A or B.

[0034] In this article, the term "and / or" describes an association between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or A and B.

[0035] It should be understood that although the steps in the flowchart are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order constraint on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the diagram may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the sub-steps or stages of other steps.

[0036] The modules in the apparatus or system of this application can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device in hardware form, or stored in the memory of a computer device in software form, so that the processor can call and execute the operations corresponding to each module.

[0037] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0038] Figure 2-3 An embodiment of a bidirectional signal magnetic isolation transmission circuit according to the present invention is shown.

[0039] In this optional embodiment, the bidirectional signal magnetically isolated transmission circuit includes:

[0040] A high-frequency isolation transformer has a primary winding and a secondary winding, used to couple a narrow pulse sequence signal from the primary winding side to the secondary winding side, and to form a narrow pulse sequence signal with the same frequency as the primary winding side on the secondary winding side;

[0041] A frequency modulation signal processing module is connected to the primary coil side of the high-frequency isolation transformer and is used to convert the high and low levels of the driving signal into narrow pulse sequence signals of different frequencies.

[0042] An amplitude modulation signal demodulation module is connected to the primary winding side of the high-frequency isolation transformer. It is used to receive fault signals or error signals from the IGBT driver and to perform feedback control on the drive signal based on the fault signals or error signals.

[0043] The frequency modulation signal demodulation module is connected to the secondary coil side of the high-frequency isolation transformer. It is used to convert the narrow pulse sequence signal corresponding to the high and low levels into high and low level pulse signals, and use the high and low level pulse signals as the gate drive voltage signal of the IGBT driver.

[0044] The amplitude modulation signal processing module is connected to the secondary coil side of the high-frequency isolation transformer, and is configured to collect a fault signal and an error signal of the IGBT driver, and transmit the fault signal and the error signal to the primary coil side of the high-frequency isolation transformer.

[0045] In this optional embodiment, the frequency modulation signal processing module is configured to convert the high and low levels of the drive signal (denoted as PWM_IN) into narrow pulse sequence signals with different frequencies; wherein the frequency of the narrow pulse sequence signal converted from the high level signal is F1, the frequency of the narrow pulse sequence signal converted from the low level signal is F2, and F1 < F2. For example, F2=5*F1 can be set. The duration of the two groups of narrow pulse sequence signals with different frequencies is the same as the pulse width of the high and low levels. Then the two groups of narrow pulse sequence signals are applied to terminal A (primary coil side) of the high-frequency isolation transformer; terminal B (secondary coil side) of the high-frequency isolation transformer is connected to the amplitude modulation signal processing module and the frequency modulation signal demodulation module.

[0046] Continuing as Figure 3 shown, in use, the signal input to the frequency modulation signal processing module is PWM_IN. When the frequency modulation signal processing module identifies a high level signal of PWM_IN, it will output a PWM_1 signal with a frequency of 20MHz, and when it identifies a low level signal of PWM_IN, it will output a PWM_2 signal with a frequency of 100MHz. The two signals with different frequencies that do not appear simultaneously are applied to terminal A on the primary side of the high-frequency isolation transformer. It should be particularly noted that the frequencies of the two groups of PWM square waves can be adjusted according to the bearable square wave frequency range of the device configured by the user. Theoretically, as the difference between the frequencies of the two groups of PWM square waves increases, the delay between the PWM_OUT signal generated by the subsequent frequency modulation signal demodulation module, that is, the signal driving the IGBT gate, and the original PWM_IN signal decreases.

[0047] In this optional embodiment, for the frequency modulation signal processing module: the signal input to the frequency modulation signal processing module is PWM_IN. The frequency modulation signal processing module is composed of a programmable logic device. When the programmable logic device receives a high level of the PWM_IN signal, the PWM_2 branch continuously outputs a square wave signal with a frequency of 20MHz until the PWM_IN signal turns to a low level; when the programmable logic device receives that the PWM_IN signal turns to a low level, the PWM_1 branch continuously outputs a square wave signal with a frequency of 100MHz until the PWM_IN signal turns to a high level.

[0048] In this optional embodiment, the amplitude modulation signal demodulation module includes a level comparison module and a signal decoding module. The level comparison module receives fault signals or error signals transmitted from the secondary winding side of the high-frequency isolation transformer and distinguishes between the fault signals and error signals using a window comparator. The signal decoding module decodes the distinguished fault signals or error signals according to Manchester encoding rules. The level comparison module includes comparator COM1 and comparator COM2, which are connected in parallel. The positive input terminals of both comparators COM1 and COM2 are connected to the primary winding side of the high-frequency isolation transformer, and the inverting input terminals of both comparators COM1 and COM2 are connected to the reference voltage signal input terminal. The output terminals of both comparators COM1 and COM2 are connected to the signal decoding module.

[0049] In use, the amplitude modulation signal demodulation module receives the voltage signal at point A on the primary side of the high-frequency isolation transformer. This signal is then fed into a level comparison module consisting of two comparators, COM1 and COM2. The comparison threshold range of comparator COM1 corresponds to the state of the VDD1 circuit on the secondary side. This threshold range should be set to ensure accurate identification of the 15V voltage signal at point B on the secondary side. Similarly, the comparison threshold range of comparator COM2 corresponds to the state of the VDD2 circuit on the secondary side. This threshold range should be set to ensure accurate identification of the 12V voltage signal at point B on the secondary side. This level comparison module distinguishes between the two different voltage levels, thus separating fault and error signals. Next, the output signals from comparators COM1 and COM2 are input to a signal decoding module. This module uses Manchester encoding rules to restore the fault and error signals. For specific encoding rules, see [link to relevant documentation]. Figure 5

[0050] In this optional embodiment, the frequency modulation signal demodulation module includes a transistor T1, a comparator COM3, a transistor T2, and a comparator COM4. The base of transistor T1 is connected to the secondary winding of the high-frequency isolation transformer, the collector of transistor T1 is connected to a low-level signal, and the emitter of transistor T1 is connected to a parallel capacitor C1 and a controlled current source CS1. The positive input of comparator COM3 is connected to the collector of transistor T1, and a capacitor C2 is connected between the positive input of comparator COM3 and the collector of transistor T1. The other end of capacitor C2 is grounded. The comparator COM4... The inverting input terminal of M3 is connected to the reference voltage signal input terminal. The output terminal of comparator COM3 is connected to transistor T2. The base of transistor T2 is connected to the output terminal of comparator COM3. The collector of transistor T2 is connected to the low-level signal VDD4. The emitter of transistor T2 is connected to the parallel capacitor C1 and the controlled current source CS1. The non-inverting input terminal of comparator COM4 is connected to the emitter of transistor T2, the parallel capacitor C1, and the controlled current source CS1. The inverting input terminal of comparator COM4 is connected to the reference voltage signal input terminal. The output terminal of comparator COM4 is connected to the IGBT driver.

[0051] In operation, the voltage signal at point B on the secondary side of the high-frequency isolation transformer serves as the input signal for the frequency modulation demodulation module. This signal controls the switching of transistor T1. When the input signal is high, transistor T1 is turned on, while capacitor C2 is effectively short-circuited, with a voltage of 0 across it. Figure 3 At this time, the V_C voltage is 0; however, when the input signal is low, T1 is turned off, and VSS directly charges C1, causing the V_C level to rise. Different frequencies of PWM square waves have different pulse durations. The single high-level pulse duration of a 20MHz PWM square wave signal will be five times that of a 100MHz PWM square wave signal. The charging time of capacitor C2 is directly determined by the low-level duration of the PWM square wave. Therefore, a higher frequency PWM square wave signal will cause capacitor C2 to charge to a lower level, while a lower frequency PWM square wave signal will cause capacitor C2 to charge to a higher level. Figure 3The V_C waveform shows that when the signal V_A at point A on the primary side of the high-frequency transformer is a high-frequency 100MHz PWM square wave, V_C rises to the value Vref4 with each voltage increase. However, when the signal V_A at point A on the primary side of the high-frequency transformer is a low-frequency 20MHz PWM square wave, V_C rises to a level far exceeding Vref4 with each voltage increase. Based on this phenomenon, the comparison threshold of comparator COM3 is set to Vref4. Signals below this threshold will cause the output of comparator COM3 to be low, while signals above this threshold will cause the output of comparator COM3 to be high. For example... Figure 4 Up to this step, there is a delay time Td between the rising edge of the PWM_IN signal and the rising edge of the V_D signal. This delay is directly affected by the threshold Vref4 set by comparator COM3. The purpose of selecting this threshold is to filter out the low voltage signal generated on capacitor C2 by the high-frequency PWM square wave. Therefore, the Vref4 threshold voltage must be greater than the level of the low voltage signal. Otherwise, it is impossible to distinguish between high and low frequency PWM square waves. The smaller the value of the threshold Vref4, the smaller Td is. Therefore, according to the analysis above, the frequency difference between the PWM_1 and PWM_2 signals should be as large as possible under the given conditions.

[0052] Next, the V_D signal will control the switching of transistor T2. When the V_D signal is high, transistor T2 is turned on, and VSS will supply power to the controlled current source CS1. The voltage on capacitor C1 remains the same as VSS. When the V_D signal is low, transistor T2 is turned off, and capacitor C1 supplies power to the controlled current source CS1. The voltage on capacitor C1 gradually decreases. Here, the capacitance value of capacitor C1 can be designed so that when the voltage on capacitor C1 drops to Vref5, the V_D signal turns high. Otherwise, the final output PWM_OUT signal will have a short-term interruption due to the high-level pulse. The specific V_D waveform is as follows: Figure 4 As shown.

[0053] Finally, the voltage V_E on capacitor C1 is sent to comparator COM4 and compared with Vref5. When V_E is greater than Vref5, comparator COM4 outputs a high level, and when V_E is less than Vref5, comparator COM4 outputs a low level. Thus, the frequency modulation signal demodulation module realizes the conversion of the high-frequency PWM square wave signal to the IGBT gate drive signal PWM_OUT.

[0054] In this optional embodiment, the amplitude modulation signal processing module includes a signal encoding module, a level conversion module, and an amplitude modulation signal gating module. The signal encoding module is used to acquire fault signals and error signals from the IGBT driver and encode them according to Manchester encoding rules. The level conversion module is used to adjust the high-level signals of the fault signals and error signals respectively. The amplitude modulation signal gating module is used to receive a selection signal sent by the signal encoding module and input the fault signal or error signal to the primary winding side of the high-frequency isolation transformer according to the selection signal. The level conversion module includes a diode D1 and a capacitor C3. One end of the capacitor C3 is connected to the signal encoding module, and the other end of the capacitor C3 is connected to the cathode of the diode D1. The anode of the diode D1 is connected to the power supply VDD. The amplitude modulation signal gating module includes a first switch S1, a second switch S2, and a MOSFET M1. The connection terminals of the first switch S1 and the second switch S2 are both connected between the power supply VDD and the drain of the MOSFET M1. The control terminals of the first switch S1 and the second switch S2 are connected in parallel to the signal encoding module. The gate of the MOSFET M1 is connected in parallel with the cathode of the third capacitor C3 and the diode D1. The source of the MOSFET M1 is connected to the secondary coil side of the high-frequency isolation transformer.

[0055] In practical use, the signal encoding module receives fault signals and error signals from the equipment and encodes them into PWM square waves conforming to Manchester encoding rules. The PWM square wave signals from the signal encoding module are then sent to the level shifting module, which adjusts the high levels of the corresponding PWM square waves for the two signals to VDD1 and VDD2 respectively, while the low levels of both signals are the same, VSS. The amplitude modulation signal processing module sends the signals, after passing through the signal encoding module and the level shifting module, to the amplitude modulation signal gating module. The working logic of this module is as follows: when a fault signal is input to the amplitude modulation signal processing module, the fault signal is selected first; when the fault signal is not sent to the amplitude modulation signal processing module, the error signal is selected. After passing through the amplitude modulation signal gating module, the fault signal or error signal is loaded onto both ends of the high-frequency isolation transformer and coupled to the primary side, causing an amplitude change at point A on the primary side of the high-frequency isolation transformer. The amplitude modulation signal demodulation module samples the amplitude fluctuation signal at point A.

[0056] During operation, IGBT drivers may experience faults such as short circuits and overcurrents. Furthermore, in specific applications such as DC-DC converters, it is necessary to transmit the error value between the output voltage and the reference voltage back to the drive signal side for feedback control. The input signals to the amplitude modulation signal processing module are the fault signal and the error signal; by default, these two signals are as follows: Figure 4The PWM_C signal is a square wave signal that transmits binary information. The signal encoding module re-encodes the input fault signal and error signal according to the Manchester encoding rule. The encoding principle is as follows: Figure 5 This can be simply understood as encoding a low-to-high level transition as a 1 signal and a high-to-low level transition as a 0 signal. Using the Manchester encoding rule ensures that the winding voltage integral of the high-frequency isolation transformer is always zero, meaning the magnetic flux integral of the high-frequency isolation transformer is always zero, preventing saturation. The fault and error signals encoded by the signal encoding module are sent to a level transfer module composed of diode D1 and capacitor C3. Assuming VDD3 is 4V and VSS is 6V, when MOSFET M1 is off, VDD3 charges capacitor C3 through diode D1, maintaining its voltage at 4V. When the PWM_3 signal, i.e., the output signal of the signal processing module, is high, the voltage across capacitor C3 rises above VSS, turning on MOSFET M1 and thus changing the high-frequency isolation transformer... The voltage at terminal B of the secondary side of the transformer rises from VSS to either VDD1 or VDD2. VDD1 can be set to 15V and VDD2 to 12V. The selection of VDD1 or VDD2 is achieved by the V_crtl signal generated by the signal processing module. When a fault signal is present, this signal controls switch S1 on the VDD1 branch to turn off, while switch S2 on the VDD2 branch to turn on. When no fault signal is present, it controls switch S1 on the VDD1 branch to turn on, while switch S2 on the VDD2 branch to turn off. This V_crtl signal, together with switches S1 and S2, forms an amplitude modulation signal selection module. This module controls the voltage change at terminal B of the secondary side of the high-frequency isolation transformer, thereby controlling the level change at terminal A of the primary side. The amplitude modulation signal demodulation module on the primary side can achieve signal transmission from the secondary side to the primary side by acquiring the voltage change at point A.

[0057] This invention enables bidirectional information transmission between the two sides of a high-frequency isolation transformer. By separately modulating the frequency and amplitude information of the signals, information can be transmitted without interference. The frequency modulation signal demodulation module utilizes the different pulse durations of high-frequency and low-frequency PWM signals to transmit signals using the frequency information of the PWM signals. It also proposes that setting the frequency difference between high-frequency and low-frequency PWM signals can further reduce the delay of this information transmission loop. The amplitude modulation signal processing module uses a three-level amplitude modulation method to realize the reverse transmission of fault information and error information. Furthermore, a window comparator is set on the primary side to successfully separate fault and error signals.

[0058] This invention is not limited to the structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this invention is limited only by the appended claims.

Claims

1. A bidirectional signal magnetically isolated transmission circuit, characterized in that, include: A high-frequency isolation transformer has a primary winding and a secondary winding, used to couple a narrow pulse sequence signal from the primary winding side to the secondary winding side, and to form a narrow pulse sequence signal with the same frequency as the primary winding side on the secondary winding side; A frequency modulation signal processing module is connected to the primary coil side of the high-frequency isolation transformer and is used to convert the high and low levels of the driving signal into narrow pulse sequence signals of different frequencies. An amplitude modulation signal demodulation module is connected to the primary winding side of the high-frequency isolation transformer. It is used to receive fault signals or error signals from the IGBT driver and to perform feedback control on the drive signal based on the fault signals or error signals. The frequency modulation signal demodulation module is connected to the secondary coil side of the high-frequency isolation transformer. It is used to convert the narrow pulse sequence signal corresponding to the high and low levels into high and low level pulse signals, and use the high and low level pulse signals as the gate drive voltage signal of the IGBT driver. An amplitude modulation signal processing module is connected to the secondary coil side of the high-frequency isolation transformer. It is used to collect fault signals and error signals from the IGBT driver and transmit the fault signals and error signals to the primary coil side of the high-frequency isolation transformer. The amplitude modulation signal demodulation module includes a level comparison module and a signal decoding module, wherein, The level comparison module is used to receive fault signals or error signals sent from the secondary coil side of the high-frequency isolation transformer, and to distinguish between fault signals and error signals using a window comparator. The signal decoding module is used to decode the distinguished fault signals or error signals according to the Manchester encoding rules. The level comparison module includes comparator one and comparator two, which are connected in parallel. The positive input terminals of both comparator one and comparator two are connected to the primary winding side of the high-frequency isolation transformer. The inverting input terminals of both comparator one and comparator two are connected to the reference voltage signal input terminal. The output terminals of both comparator one and comparator two are connected to the signal decoding module.

2. The bidirectional signal magnetic isolation transmission circuit according to claim 1, characterized in that, When the frequency modulation signal processing module converts the high and low levels of the driving signal into narrow pulse sequence signals of different frequencies, the frequency of the narrow pulse sequence signal corresponding to the high level is less than the frequency of the narrow pulse sequence signal corresponding to the low level.

3. The bidirectional signal magnetic isolation transmission circuit according to claim 2, characterized in that, The frequency of the narrow pulse sequence signal corresponding to the low level is five times that of the narrow pulse sequence signal corresponding to the high level.

4. The bidirectional signal magnetic isolation transmission circuit according to claim 1, characterized in that, The frequency modulation signal demodulation module includes transistor one, comparator three, transistor two, and comparator four, wherein... The base of transistor one is connected to the secondary coil side of the high-frequency isolation transformer, the collector of transistor one is connected to a low-level signal, and the emitter of transistor one is connected to a parallel capacitor one and a controlled current source. The positive input terminal of comparator three is connected to the collector of transistor one, and capacitor two is connected between the positive input terminal of comparator three and the collector of transistor one, with the other end of capacitor two grounded; the inverting input terminal of comparator three is connected to the reference voltage signal input terminal, and the output terminal of comparator three is connected to transistor two. The base of transistor two is connected to the output of comparator three, the collector of transistor two is connected to a low-level signal, and the emitter of transistor two is connected to a parallel capacitor one and a controlled current source. The positive input terminal of comparator four is connected to the emitter of transistor two, the parallel capacitor one, and the controlled current source. The inverting input terminal of comparator four is connected to the reference voltage signal input terminal. The output terminal of comparator four is connected to the IGBT driver.

5. The bidirectional signal magnetic isolation transmission circuit according to claim 1, characterized in that, The amplitude modulation signal processing module includes a signal encoding module, a level conversion module, and an amplitude modulation signal gating module, wherein... The signal encoding module is used to acquire fault signals and error signals from the IGBT driver and encode them according to the Manchester encoding rules. The level conversion module is used to adjust the high level of fault signals and error signals respectively. An amplitude modulation signal gating module is used to input a fault signal or error signal to the primary coil side of the high-frequency isolation transformer based on the selection signal sent by the received signal encoding module.

6. The bidirectional signal magnetic isolation transmission circuit according to claim 5, characterized in that, The level conversion module includes a diode and a capacitor. One end of the capacitor is connected to the signal encoding module, and the other end of the capacitor is connected to the cathode of the diode. The anode of the diode is connected to the power supply.

7. The bidirectional signal magnetic isolation transmission circuit according to claim 6, characterized in that, The amplitude modulation signal gating module includes a switch, a switch, and a MOSFET. The connection terminals of the switches are connected between the power supply and the drain of the MOSFET. The control terminals of the switches are connected in parallel to the signal encoding module. The gate of the MOSFET is connected in parallel with the capacitor and the cathode of the diode. The source of the MOSFET is connected to the secondary coil side of the high-frequency isolation transformer.

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