Isolated power converter based on fsk magnetic coupling feedback

Abstract

This disclosure provides an isolated power converter based on FSK magnetic coupling feedback. The output voltage is obtained by rectifying and filtering the alternating current transmitted through the primary side circuit of the rectifier. The FSK signal, processed by a voltage sampling circuit and a voltage-controlled oscillator (VCO), is coupled to an isolation transformer via a frequency coupler. A frequency-to-voltage conversion circuit converts the FSK signal extracted by the frequency detection circuit into a feedback voltage, which is then processed by an error amplifier to obtain an error signal. A PWM generator generates a duty cycle control signal based on the error signal to control the alternating current transmitted through the isolation transformer. This disclosure converts the voltage divider voltage into an FSK signal using a VCO, and the FSK signal is fed back from the secondary side circuit to the primary side circuit only through the magnetic coupling path of the isolation transformer. This eliminates the need for additional isolation capacitors or digital isolators, significantly reducing cost and process requirements, and improving isolation withstand voltage and anti-interference capabilities.

Description

Technical Field

[0001] This disclosure relates to the field of isolated power converter technology, and in particular to an isolated power converter based on FSK magnetic coupling feedback. Background Technology

[0002] Isolated DC-DC converters are key components in industrial, automotive, and medical fields. Their core function is to achieve electrical isolation, suppress common-mode interference, and safely transmit energy and signals between different potential domains, providing a stable and reliable power supply for downstream circuits. Currently, most mainstream isolated power feedback solutions rely on optocouplers or isolation capacitors to achieve signal feedback across isolation barriers. These solutions not only require additional isolation devices, increasing system cost and chip area, but also have limitations in the voltage withstand capability and common-mode transient immunity (CMTI) performance of isolation capacitors, making it difficult to meet the requirements of high isolation levels such as 5kVrms. Digital isolators, on the other hand, have high process requirements, limiting the application of ordinary CMOS processes. At the same time, they are prone to introducing signal distortion and parasitic losses under high-frequency operation. Overall, these solutions have significant limitations in applications requiring high isolation, low cost, and high interference immunity. Summary of the Invention

[0003] The technical problem to be solved by this disclosure is to overcome the shortcomings of existing technologies, which rely on optocouplers or isolation capacitors to achieve signal feedback across isolation barriers, resulting in high cost and poor isolation withstand voltage and anti-interference capabilities. This disclosure provides an isolated power converter based on FSK magnetic coupling feedback.

[0004] This disclosure solves the above-mentioned technical problems through the following technical solution:

[0005] This disclosure provides an isolated power converter based on FSK magnetic coupling feedback. The isolated power converter includes a primary-side circuit, a secondary-side circuit, and an isolation transformer. The primary-side circuit is electrically connected to the secondary-side circuit through the isolation transformer. The primary-side circuit includes a full-bridge drive circuit, a resonant circuit, a frequency detection circuit, a frequency-to-voltage conversion circuit, an error amplifier, and a PWM generator. The resonant circuit includes a resonant capacitor. The secondary-side circuit includes a rectifier, a voltage sampling circuit, a voltage-controlled oscillator, and a frequency coupler.

[0006] The rectifier is used to receive the alternating current transmitted by the primary side circuit through the isolation transformer, rectify and filter the alternating current to obtain the output voltage, and transmit the output voltage to the voltage sampling circuit.

[0007] The voltage sampling circuit is used to perform voltage division sampling on the output voltage to obtain a divided voltage, and transmit the divided voltage to the voltage-controlled oscillator;

[0008] The voltage-controlled oscillator is used to convert the divided voltage into an FSK signal corresponding to the output voltage, and to transmit the FSK signal to the frequency coupler;

[0009] The frequency coupler is used to couple the FSK signal to the isolation transformer, so that the FSK signal is magnetically reflected to the resonant circuit through the isolation transformer;

[0010] The frequency detection circuit is used to sample the frequency across the resonant capacitor to obtain a sampled signal carrying the FSK signal, extract the FSK signal from the sampled signal, and transmit the FSK signal to the frequency-to-voltage conversion circuit.

[0011] The frequency-to-voltage conversion circuit is used to convert the FSK signal into a feedback voltage and transmit the feedback voltage to the error amplifier;

[0012] The error amplifier is used to compare and amplify the feedback voltage and the reference voltage to obtain an error signal, and then transmit the error signal to the PWM generator.

[0013] The PWM generator is used to generate a duty cycle control signal based on the error signal; the duty cycle control signal is used to control the duty cycle of the full-bridge drive circuit, so as to control the alternating current transmitted by the isolation transformer based on the duty cycle, thereby adjusting the output voltage of the secondary side circuit.

[0014] Preferably, the primary-side circuit further includes a ring oscillator;

[0015] The full-bridge drive circuit is used to drive the resonant circuit to generate alternating current under the control of the ring oscillator.

[0016] Preferably, the resonant circuit further includes a resonant inductor;

[0017] The resonant circuit is used to transmit the alternating current to the rectifier through the isolation transformer.

[0018] Preferably, the frequency coupler is used to inject the FSK signal into the secondary winding of the isolation transformer in an impedance modulation manner, and to couple the FSK signal to the resonant circuit of the primary side circuit using the backscattering effect.

[0019] Preferably, the frequency detection circuit is used to filter the sampled signal carrying the FSK signal to obtain the FSK signal, identify the frequency of the FSK signal, and transmit the frequency of the FSK signal to the frequency-to-voltage conversion circuit;

[0020] The frequency-to-voltage conversion circuit is used to convert the frequency of the FSK signal into a feedback voltage and transmit the feedback voltage to the error amplifier.

[0021] Preferably, the voltage sampling circuit includes a first resistor and a second resistor, wherein the first resistor and the second resistor are connected in series.

[0022] Preferably, the first input terminal of the error amplifier is connected to the feedback voltage, and the second input terminal of the error amplifier is connected to the reference voltage.

[0023] Preferably, the secondary side circuit further includes an output capacitor, which is connected in parallel with the first resistor and the second resistor.

[0024] Preferably, the output voltage is positively correlated with the frequency of the FSK signal.

[0025] Preferably, the feedback voltage is positively correlated with the frequency of the FSK signal.

[0026] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of this disclosure.

[0027] The positive and progressive effects of this disclosure are as follows:

[0028] This disclosure converts the voltage divider obtained from the output voltage into an FSK signal using a voltage-controlled oscillator, and transmits the FSK signal from the secondary side circuit to the primary side circuit only through the magnetic coupling path of the isolation transformer. This eliminates the need for additional isolation capacitors or digital isolators, significantly reducing costs and process requirements, and improving isolation withstand voltage and anti-interference capabilities. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of a traditional isolated power converter.

[0030] Figure 2 This is a schematic diagram of the structure of the isolated power converter based on FSK magnetic coupling feedback provided in Embodiment 1 of this disclosure.

[0031] Figure 3 This is a schematic diagram of the output regulation waveform of the isolated power converter provided in Embodiment 1 of this disclosure. Detailed Implementation

[0032] The present disclosure is further illustrated below by way of embodiments, but the present disclosure is not limited to the scope of the embodiments described herein.

[0033] The prefixes such as "first" and "second" used in this disclosure 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 disclosure 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 be construed as an unnecessary limitation. Furthermore, in the description of this embodiment, unless otherwise stated, "multiple" means two or more.

[0034] In this embodiment of the disclosure, the collection, storage, use, processing, transmission, provision, and disclosure of user personal information comply with relevant laws and regulations and do not violate public order and good morals.

[0035] Example 1

[0036] Figure 1 This is a schematic diagram of a traditional isolated power converter. The traditional isolated power converter includes a primary side 11, a secondary side 12, a transformer, and an isolation capacitor C1. The primary side 11 includes a full-bridge drive circuit 111, an oscillator 112, an envelope detector 113, a front-end amplifier 114, and a resonant network composed of a resonant inductor Lr and a resonant capacitor Cr. The secondary side 12 includes a rectifier 121, a third resistor R3, a fourth resistor R4, a first capacitor C2, an error amplifier 122, and a PWM generator 123.

[0037] Its working principle is as follows: The resonant network on the primary side generates a high-frequency alternating current and transmits it to the secondary side through a transformer; the secondary side is rectified and filtered by a rectifier to obtain the output voltage Vo. The output voltage Vo is sampled by voltage divider of the third resistor R3 and the fourth resistor R4 and then sent to the error amplifier. It is compared and amplified with the reference voltage to obtain the error signal. The error signal is modulated by the PWM generator into a PWM signal with a duty cycle that varies with the output error. It is then coupled back to the primary side through the isolation capacitor. After being amplified by the front-end amplifier and demodulated by envelope detection, it is sent to the oscillator to adjust the duty cycle of the primary side switching frequency, thereby controlling the energy transmission of the transformer and realizing closed-loop voltage regulation of the output voltage. Its disadvantages are that the presence of the isolation capacitor limits the isolation withstand voltage level of the converter, making it difficult to meet the requirements of high isolation applications such as 5kVrms. In addition, the common-mode transient immunity (CMTI) performance of the capacitor coupling method is poor. At the same time, the feedback link increases the cost of additional components and parasitic losses. At high frequency operation, it also introduces signal distortion and efficiency loss. The overall solution has obvious limitations in high isolation, high immunity, and low cost scenarios.

[0038] To address the shortcomings of traditional isolated power converters, which rely on optocouplers or isolation capacitors for signal feedback across isolation barriers, resulting in high cost and poor isolation withstand voltage and anti-interference capabilities, Embodiment 1 of this disclosure provides an isolated power converter based on FSK magnetic coupling feedback. Figure 2 As shown, the isolated power converter includes a primary side circuit 21, a secondary side circuit 22, and an isolation transformer. The primary side circuit 21 is electrically connected to the secondary side circuit 22 through the isolation transformer. The primary side circuit 21 includes a full-bridge drive circuit 211, a resonant circuit 212, a frequency detection circuit 213, a frequency-to-voltage conversion circuit 214, an error amplifier 215, and a PWM generator 216. The resonant circuit 212 includes a resonant capacitor C3. The secondary side circuit 22 includes a rectifier 221, a voltage sampling circuit, a voltage-controlled oscillator 223, and a frequency coupler 224.

[0039] Rectifier 221 is used to receive the alternating current transmitted through the isolation transformer from the primary side circuit, rectify and filter the alternating current to obtain the output voltage, and transmit the output voltage to the voltage sampling circuit.

[0040] In an alternative implementation, such as Figure 2 As shown, the voltage sampling circuit includes a first resistor R1 and a second resistor R2, with the first resistor R1 and the second resistor R2 connected in series.

[0041] In this embodiment, the alternating current is rectified and filtered by a rectifier to obtain the output voltage Vo, and the output voltage Vo is transmitted to the first resistor R1 and the second resistor R2.

[0042] The voltage sampling circuit is used to perform voltage division sampling on the output voltage Vo to obtain the divided voltage, and then transmits the divided voltage to the voltage-controlled oscillator 223.

[0043] In this embodiment, the output voltage Vo is sampled by a voltage divider between the first resistor R1 and the second resistor R2 and then sent to the voltage-controlled oscillator 223.

[0044] The voltage-controlled oscillator 223 is used to convert the voltage divider into an FSK signal corresponding to the output voltage and transmit the FSK signal to the frequency coupler 224.

[0045] In this embodiment, a voltage-controlled oscillator (VCO) converts the divided voltage into a high-frequency FSK signal of 100MHz to 230MHz that corresponds linearly to the output voltage. That is, the voltage-controlled oscillator (VCO) linearly converts the divided voltage into a high-frequency FSK signal with a frequency range of 100MHz to 230MHz.

[0046] It should be noted that the frequency of the FSK signal increases with increasing voltage divider voltage and decreases with decreasing voltage divider voltage.

[0047] Frequency coupler 224 is used to couple the FSK signal to the isolation transformer so that the FSK signal is magnetically reflected to the resonant circuit 212 through the isolation transformer;

[0048] In an alternative implementation, a frequency coupler is used to inject the FSK signal into the secondary winding of the isolation transformer in an impedance-modulated manner and to couple the FSK signal to the resonant circuit of the primary side circuit using the backscattering effect.

[0049] In this embodiment, the 100MHz~230MHz high-frequency FSK signal is injected into the secondary winding of the isolation transformer through the frequency coupler 224 in an impedance modulation manner, and the 100MHz~230MHz high-frequency FSK signal is coupled to the resonant circuit 212 in the primary side circuit by utilizing the backscattering effect.

[0050] It should be noted that the frequency coupler is selected to present high impedance (e.g., capacitive reactance much greater than the inductive reactance of the secondary winding Ls) at the power transmission frequency of 15MHz, so as not to affect the transmission of the main power signal; and to present low impedance (e.g., capacitive reactance much less than the inductive reactance of the secondary winding Ls) in the FSK signal frequency range of 100MHz to 230MHz, so as to achieve effective injection of the FSK signal.

[0051] Furthermore, the frequency change of the FSK signal causes a corresponding change in the equivalent impedance of the secondary winding Ls. This impedance change is reflected to the primary circuit through the magnetic coupling of the isolation transformer. In other words, the FSK signal is transmitted to the primary circuit across the isolation barrier by means of reflected impedance modulation, without the need for any dedicated isolation feedback components.

[0052] The frequency detection circuit 213 is used to sample the frequency across the resonant capacitor to obtain a sampled signal carrying the FSK signal, extract the FSK signal from the sampled signal, and transmit the FSK signal to the frequency-to-voltage conversion circuit 214.

[0053] Frequency-to-voltage conversion circuit 214 is used to convert the FSK signal into a feedback voltage and transmit the feedback voltage to error amplifier 215;

[0054] In this embodiment, the 100MHz~230MHz high-frequency FSK signal is demodulated into a DC feedback voltage Vfb proportional to the 100MHz~230MHz high-frequency FSK signal by a frequency-to-voltage conversion circuit (FVC), and the DC feedback voltage Vfb is transmitted to the error amplifier (EA).

[0055] Error amplifier 215 is used to compare and amplify the feedback voltage and the reference voltage to obtain an error signal, and then transmit the error signal to PWM generator 216;

[0056] In an optional implementation, the first input terminal of the error amplifier is connected to the feedback voltage Vfb, and the second input terminal of the error amplifier is connected to the reference voltage Vref.

[0057] In this embodiment, the feedback voltage Vfb and the reference voltage Vref are fed together into the error amplifier (EA) for comparison and amplification, and the error signal is output and input into the PWM generator.

[0058] The PWM generator 216 is used to generate a duty cycle control signal based on the error signal. The duty cycle control signal is used to control the duty cycle of the full-bridge drive circuit, so as to control the alternating current transmitted by the isolation transformer based on the duty cycle, thereby adjusting the output voltage of the secondary side circuit.

[0059] In this embodiment, the duty cycle of the full-bridge drive circuit is controlled by a duty cycle control signal generated by the PWM generator, which in turn controls the alternating current transmitted by the isolation transformer based on the duty cycle, thereby adjusting the output voltage of the secondary side circuit. Thus, the primary side circuit realizes the complete function of extracting the FSK signal from the composite voltage signal and converting it into the adjustment amount required for closed-loop control.

[0060] This implementation converts the voltage divider obtained from the output voltage into an FSK signal using a voltage-controlled oscillator, and transmits the FSK signal from the secondary side circuit to the primary side circuit only through the magnetic coupling path of the isolation transformer. No additional isolation capacitors or digital isolators are required, which greatly reduces costs and process requirements, and improves isolation withstand voltage and anti-interference capabilities.

[0061] In an alternative implementation, such as Figure 2 As shown, the primary side circuit 21 also includes a ring oscillator 217;

[0062] The full-bridge drive circuit 211 is used to drive the resonant circuit 212 to generate alternating current under the control of the ring oscillator.

[0063] In an alternative implementation, such as Figure 2 As shown, the resonant circuit 212 also includes a resonant inductor L1;

[0064] The resonant circuit 212 is used to transmit alternating current to the rectifier 221 through the isolation transformer.

[0065] In the specific implementation process, Figure 2The isolated power converter based on FSK magnetic coupling feedback disclosed herein operates as follows: The full-bridge drive circuit in the primary side circuit, under the control of a ring oscillator, drives an LLC resonant network (i.e., a resonant circuit) composed of resonant inductor L1 and resonant capacitor C3, generating a 15MHz high-frequency alternating current, which is then transmitted to the secondary side circuit via an isolation transformer. The secondary side circuit, after rectification and filtering by a rectifier, obtains the output voltage Vo. This output voltage Vo is then sampled by a voltage-controlled oscillator after being divided by a first resistor R1 and a second resistor R2 (i.e., a voltage sampling circuit), and converted into a 100MHz~230MHz voltage range linearly corresponding to the output voltage Vo. A high-frequency FSK signal (MHz) is injected into the secondary winding of the isolation transformer via a frequency coupler using impedance modulation. The backscattering effect couples the FSK signal to the resonant circuit in the primary side circuit. The primary side circuit samples the frequency across the resonant capacitor C3, demodulates it into a DC feedback voltage Vfb proportional to the FSK signal, and compares and amplifies the feedback voltage Vfb with the reference voltage Vref using an error amplifier. This amplified voltage is then fed into a PWM generator to adjust the switching frequency or duty cycle of the primary side circuit, thereby controlling the energy transfer of the isolation transformer and regulating the output voltage Vo to stabilize it at a set value, achieving closed-loop voltage regulation of the output voltage. The entire closed-loop backscattering... The feeder link achieves both energy transfer and FSK feedback signal transmission simultaneously through an isolation transformer, eliminating the need for any digital isolators or isolation capacitors, thus forming a complete isolator-free closed-loop voltage regulation control system. This disclosed solution eliminates the isolation capacitors or digital isolators found in traditional architectures, and can be implemented using ordinary CMOS technology, significantly reducing costs. It also avoids the limitations of isolation capacitor withstand voltage and common-mode transient immunity (CMTI). Furthermore, since the FSK signal is much higher than the power transmission frequency, it can be easily separated through filtering and will not be submerged by the power waveform. While ensuring closed-loop control accuracy, it significantly improves the isolation level and anti-interference capability, making it more suitable for high-isolation, high-reliability industrial and automotive applications.

[0066] Furthermore, such as Figure 2As shown, the secondary circuit includes a first resistor R1 and a second resistor R2, a voltage-controlled oscillator (VCO) 223, a frequency coupler 224, and the secondary winding Ls of the transformer. The primary circuit operates as follows: the output voltage Vo is divided by the first resistor R1 and the second resistor R2 to obtain a voltage divider proportional to the output voltage Vo. This voltage divider is input to the voltage control terminal of the VCO. The VCO linearly converts this voltage divider into a high-frequency FSK signal with a frequency range of 100MHz to 230MHz; that is, the frequency of the FSK signal increases with increasing voltage divider and decreases with decreasing voltage divider. This FSK signal is coupled to both ends of the secondary winding Ls of the isolation transformer via the frequency coupler. The frequency coupler is selected to exhibit high impedance (e.g., capacitive reactance much greater than the inductive reactance of the secondary winding Ls) at the power transmission frequency of 15MHz, thus not affecting the transmission of the main power signal; and low impedance (e.g., capacitive reactance much less than the inductive reactance of the secondary winding Ls) in the FSK signal frequency range of 100MHz to 230MHz, thereby achieving effective injection of the FSK signal. Frequency variations in the FSK signal cause corresponding changes in the equivalent impedance of the secondary winding Ls. This impedance change is reflected to the primary circuit via the magnetic coupling of the isolation transformer. In other words, the FSK signal is transmitted across the isolation barrier to the primary circuit using reflected impedance modulation, without the need for any dedicated isolation feedback components.

[0067] Furthermore, such as Figure 2As shown, the working principle of the primary-side circuit is as follows: In the primary-side circuit, the frequency across the resonant capacitor C3 simultaneously contains a 15MHz power transmission fundamental frequency and its harmonic components, as well as an FSK feedback signal of 100MHz to 230MHz. The voltage sampling circuit acquires the sampled signal across the resonant capacitor C3 and sends it to the high-pass filter circuit. The cutoff frequency of the high-pass filter circuit is designed to be around 80MHz to effectively filter out the 15MHz power component and its low-order harmonics, retaining only the 100MHz-230MHz FSK signal. This FSK signal is amplified by the signal amplification circuit to an amplitude sufficient for subsequent circuits to recognize, and then sent to the frequency detection circuit. The frequency detection circuit identifies the instantaneous frequency of the current FSK signal and outputs an analog voltage or current signal (which can also be a digital code, but analog output is preferred in this embodiment) representing that frequency. This output signal (i.e., the FSK signal) is sent to the frequency-to-voltage converter (FVC), which converts it into a DC feedback voltage Vfb proportional to the FSK signal. The DC feedback voltage Vfb and the reference voltage Vref are fed together into the error amplifier EA for comparison and amplification, outputting an error signal. This error signal is then input to the PWM generator, which generates a corresponding duty cycle control signal based on the error signal. This signal is used to control the output frequency of the oscillator or the duty cycle of the full-bridge drive circuit. Thus, the primary-side circuit achieves the complete function of extracting the FSK feedback signal from the composite voltage signal and converting it into the adjustment value required for closed-loop control.

[0068] In an optional implementation, a frequency detection circuit is used to filter out the sampled signal carrying the FSK signal to obtain the FSK signal, identify the frequency of the FSK signal, and transmit the frequency of the FSK signal to a frequency-to-voltage conversion circuit.

[0069] A frequency-to-voltage conversion circuit is used to convert the frequency of the FSK signal into a feedback voltage and transmit the feedback voltage to the error amplifier.

[0070] In this embodiment, the voltage sampling circuit acquires the sampling signal across the resonant capacitor C3 and sends it to the high-pass filter circuit. The cutoff frequency of the high-pass filter circuit is designed to be around 80MHz to effectively filter out the 15MHz power component and its low-order harmonics, retaining only the 100MHz-230MHz FSK signal. This FSK signal is amplified by the signal amplification circuit to an amplitude sufficient for subsequent circuits to recognize, and then sent to the frequency detection circuit. The frequency detection circuit identifies the instantaneous frequency of the current FSK signal and outputs an analog voltage or current signal (which can also be a digital code, but analog output is preferred in this embodiment) representing that frequency. This output signal (i.e., the FSK signal) is then sent to the frequency-to-voltage converter (FVC).

[0071] In an alternative implementation, such as Figure 2As shown, the secondary side circuit also includes an output capacitor C4, which is connected in parallel with the first resistor R1 and the second resistor R2.

[0072] In one alternative implementation, the output voltage is positively correlated with the frequency of the FSK signal.

[0073] In an alternative implementation, the feedback voltage is positively correlated with the frequency of the FSK signal.

[0074] In this embodiment, Figure 3 This is a schematic diagram of the output regulation waveform of the isolated power converter disclosed herein. The waveform illustrates the timing relationship between the secondary-side circuit FSK feedback signal frequency, the primary-side circuit restored FSK signal frequency, the error amplifier output voltage VEA, and the PWM control signal duty cycle during the transition from light load to heavy load (and vice versa). Figure 3 As shown, when the load transitions from heavy to light, the output voltage Vo shows an increasing trend. The voltage-controlled oscillator (VCO) in the secondary circuit detects this increase in output voltage (through voltage divider sampling) and subsequently increases the frequency of its output FSK signal (labeled as "lower frequency" in the figure corresponding to heavy load). This FSK signal is injected into the secondary winding of the isolation transformer through a frequency coupler and transmitted to the primary circuit via reflective impedance modulation. The frequency detection and frequency-to-voltage conversion circuit (FVC) in the primary circuit reconstructs a DC feedback voltage proportional to the FSK signal frequency; that is, the frequency of the reconstructed FSK signal also increases (labeled as "higher frequency" in the figure). This increase in FSK signal frequency leads to an increase in the DC feedback voltage Vfb output by the frequency-to-voltage conversion circuit. After comparing Vfb with the reference voltage Vref, the error amplifier EA reduces the output error voltage VEA (labeled as "higher frequency" in the figure corresponding to a decrease in VEA). When the error voltage VEA decreases, the PWM generator correspondingly reduces its output duty cycle (marked "low duty cycle" in the diagram for light load). The full-bridge drive circuit and LLC resonant circuit reduce energy transfer, thereby reducing the output voltage Vo to the set value. Conversely, when the load transitions from light to heavy load, the output voltage Vo decreases, the frequency of the voltage-controlled oscillator (VCO) output FSK signal decreases (marked "lower frequency" in the diagram), the primary-side circuit restores the FSK signal frequency to a lower frequency, the error voltage VEA increases, the PWM generator increases its duty cycle (marked "high duty cycle" in the diagram for heavy load), increasing energy transfer and causing the output voltage to rise back to the set value. The entire adjustment process requires no digital isolator or isolation capacitor; the cross-barrier transmission and closed-loop control of the FSK signal frequency are achieved solely through the isolation transformer.

[0075] Figure 3The complete transient response relationship of output voltage change → FSK signal frequency change → PWM duty cycle adjustment → output voltage recovery in this disclosure is intuitively shown in waveform form, which verifies the feasibility and effectiveness of the isolator-free closed-loop voltage regulation scheme based on FSK magnetic coupling feedback.

[0076] The FSK magnetically coupled feedback-based isolated power converter architecture proposed in this embodiment eliminates the need for isolation capacitors or digital isolators in traditional solutions. It converts the output voltage into a high-frequency FSK signal via a voltage-controlled oscillator and injects it into the isolation transformer via backscattering. Closed-loop voltage regulation is achieved by detecting the frequency components in the resonant circuit on the primary side. This eliminates the need for additional isolation capacitors or digital isolators, significantly reducing cost and process requirements while improving isolation withstand voltage and anti-interference capabilities. Specifically, the FSK magnetically coupled feedback-based isolated power converter of this embodiment has significant advantages in terms of technology, economy, and social benefits compared to existing isolated power supply solutions that rely on digital isolators or isolation capacitors. The specific effects are as follows: 1. Achieving an isolation withstand voltage of up to 5kVrms: Due to the elimination of dedicated feedback components across the isolation barrier, the converter's isolation withstand voltage is determined solely by the insulation structure of the planar air-core transformer. 2. Improved common-mode transient immunity (CMTI): The FSK feedback signal is transmitted entirely through magnetic coupling, without relying on capacitive voltage division or optocoupler current transmission, thus making it insensitive to transient changes in common-mode voltage. 3. Reduced power consumption and chip area: By eliminating the digital isolator and its associated modulation / demodulation circuitry, both the primary and secondary circuits can be fully integrated using a standard 0.18μm CMOS process. Simultaneously, the feedback link does not consume additional quiescent current (no isolation capacitor drive losses). 4. Promotes domestic production and cost reduction of isolated power supplies: This disclosure does not rely on high-barrier digital isolator processes, supporting mature 0.18μm CMOS processes in domestic wafer fabs. This helps break the monopoly of foreign manufacturers in the high-end isolation chip field, reducing reliance on imported isolation devices in industrial automation, new energy vehicles, and medical devices. 5. Improved safety of high-isolation power supplies in medical and automotive fields: With a 5kVrms isolation withstand voltage and no risk of isolation capacitor breakdown, it significantly improves the electrical safety redundancy of in vivo medical devices such as pacemakers and defibrillators, as well as the battery management system (BMS) of electric vehicles, reducing electric shock or equipment damage accidents caused by isolation failure.

[0077] While specific embodiments of this disclosure have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of this disclosure is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of this disclosure, but all such changes and modifications fall within the scope of protection of this disclosure.

Claims

1. An isolated power converter based on FSK magnetic coupling feedback, characterized in that, The isolated power converter includes a primary side circuit, a secondary side circuit, and an isolation transformer. The primary side circuit is electrically connected to the secondary side circuit through the isolation transformer. The primary side circuit includes a full-bridge drive circuit, a resonant circuit, a frequency detection circuit, a frequency-to-voltage conversion circuit, an error amplifier, and a PWM generator. The resonant circuit includes a resonant capacitor. The secondary side circuit includes a rectifier, a voltage sampling circuit, a voltage-controlled oscillator, and a frequency coupler. The rectifier is used to receive the alternating current transmitted by the primary side circuit through the isolation transformer, rectify and filter the alternating current to obtain the output voltage, and transmit the output voltage to the voltage sampling circuit. The voltage sampling circuit is used to perform voltage division sampling on the output voltage to obtain a divided voltage, and transmit the divided voltage to the voltage-controlled oscillator; The voltage-controlled oscillator is used to convert the divided voltage into an FSK signal corresponding to the output voltage, and to transmit the FSK signal to the frequency coupler; The frequency coupler is used to couple the FSK signal to the isolation transformer, so that the FSK signal is magnetically reflected to the resonant circuit through the isolation transformer; The frequency detection circuit is used to sample the frequency across the resonant capacitor to obtain a sampled signal carrying the FSK signal, extract the FSK signal from the sampled signal, and transmit the FSK signal to the frequency-to-voltage conversion circuit. The frequency-to-voltage conversion circuit is used to convert the FSK signal into a feedback voltage and transmit the feedback voltage to the error amplifier; The error amplifier is used to compare and amplify the feedback voltage and the reference voltage to obtain an error signal, and then transmit the error signal to the PWM generator. The PWM generator is used to generate a duty cycle control signal based on the error signal; The duty cycle control signal is used to control the duty cycle of the full-bridge drive circuit, so as to control the alternating current transmitted by the isolation transformer based on the duty cycle, thereby adjusting the output voltage of the secondary side circuit.

2. The isolated power converter based on FSK magnetic coupling feedback as described in claim 1, characterized in that, The primary-side circuit also includes a ring oscillator; The full-bridge drive circuit is used to drive the resonant circuit to generate alternating current under the control of the ring oscillator.

3. The isolated power converter based on FSK magnetic coupling feedback as described in claim 1, characterized in that, The resonant circuit also includes a resonant inductor; The resonant circuit is used to transmit the alternating current to the rectifier through the isolation transformer.

4. The isolated power converter based on FSK magnetic coupling feedback as described in claim 1, characterized in that, The frequency coupler is used to inject the FSK signal into the secondary winding of the isolation transformer in an impedance modulation manner, and to couple the FSK signal to the resonant circuit of the primary side circuit using the backscattering effect.

5. The isolated power converter based on FSK magnetic coupling feedback as described in claim 1, characterized in that, The frequency detection circuit is used to filter the sampled signal carrying the FSK signal to obtain the FSK signal, identify the frequency of the FSK signal, and transmit the frequency of the FSK signal to the frequency-to-voltage conversion circuit. The frequency-to-voltage conversion circuit is used to convert the frequency of the FSK signal into a feedback voltage and transmit the feedback voltage to the error amplifier.

6. The isolated power converter based on FSK magnetic coupling feedback as described in claim 1, characterized in that, The voltage sampling circuit includes a first resistor and a second resistor, with the first resistor connected in series with the second resistor.

7. The isolated power converter based on FSK magnetic coupling feedback as described in claim 1, characterized in that, The first input terminal of the error amplifier is connected to the feedback voltage, and the second input terminal of the error amplifier is connected to the reference voltage.

8. The isolated power converter based on FSK magnetic coupling feedback as described in claim 6, characterized in that, The secondary side circuit also includes an output capacitor, which is connected in parallel with the first resistor and the second resistor.

9. The isolated power converter based on FSK magnetic coupling feedback as described in claim 5, characterized in that, The output voltage is positively correlated with the frequency of the FSK signal.

10. The isolated power converter based on FSK magnetic coupling feedback as described in claim 5, characterized in that, The feedback voltage is positively correlated with the frequency of the FSK signal.

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