An isolated power supply system and a wireless modulation device and method facing PFM control

Abstract

This application provides an isolated power supply system and a wireless modulation device and method for PFM control, applicable to the fields of PFM modulation and isolated power supply technology. In the PFM-modulated isolated power supply system, based on the power transformer's ability to transmit power signals, a low-frequency PFM signal used for power modulation is used as a switching signal. A portion of the secondary-side power inductor is used to form a resonance, generating a high-frequency signal to achieve PFM modulation and transmission through an isolation barrier. Finally, the corresponding decoding circuit on the primary side can restore the signal to complete the PFM signal modulation and transmission. Power and signal transmission are achieved through the same power transformer, eliminating the need for additional digital transformers / isolation capacitors, bias modules, oscillators, etc., simplifying the circuit structure and effectively reducing cost and chip area.

Description

Technical Field

[0001] This application relates to the fields of PFM modulation and isolated power supply technology, specifically to an isolated power supply system and a wireless modulation device and method for PFM control. Background Technology

[0002] In isolated power supply / wireless charging systems, power is transmitted through transformers. PFM (Pulse Frequency Modulation) control is a common load modulation scheme, which regulates power by changing the driving frequency of the power stage. The principle is that a low-frequency PFM signal with a fixed duty cycle but varying frequency is transmitted on the secondary side, and the primary side decodes it and multiplies the frequency to drive the power stage. However, voltage isolation exists between the primary and secondary sides, so the modulated signal often requires an additional feedback channel, such as a digital transformer or isolation capacitor. Furthermore, lower-frequency PFM signals (approximately 500kHz) cannot be directly transmitted to the transmitting chip through the digital transformer / capacitor. An additional module is responsible for encoding and decoding the feedback signal at both ends of the on-chip transformer / capacitor to achieve different frequency PFM signal transmissions to adjust the average input power and ensure stable output voltage. Therefore, PFM signal transmission not only requires complex encoding and decoding circuits to ensure signal channel reliability but also necessitates the use of additional on-chip digital transformers or isolation capacitors as isolation channels, significantly increasing chip cost and design complexity. Summary of the Invention

[0003] In view of this, this application provides an isolated power supply system and a wireless modulation device and method for PFM control, which can complete signal transmission based on power inductors, eliminating the need for additional isolation channels, simplifying the design and reducing costs.

[0004] This application provides the following technical solution:

[0005] This application provides a wireless modulation device for PFM control, comprising:

[0006] Power transformer: A transformer composed of a primary coil and a secondary coil, serving as an isolation medium for power and signal transmission. The primary coil includes a primary power transmission port and a primary signal transmission port, while the secondary coil includes a secondary power transmission port and a secondary signal transmission port. The primary signal transmission port is formed by taking a portion of the inductance from the primary coil and extending it to the outside. The secondary signal transmission port is also formed by taking a portion of the inductance from the secondary coil and extending it to the outside. Power signals are transmitted from the primary coil to the secondary coil through the primary power transmission port, and PFM signals are transmitted from the secondary coil to the primary coil through the secondary signal transmission port.

[0007] The resonant circuit includes a PFM control signal input port, two resonant ports, and a resonant circuit. The two resonant ports are connected to the secondary signal transmission port. The PFM control signal input port is used to input a PFM signal. The resonant circuit, together with a portion of the inductance taken from the secondary coil in the secondary signal transmission port, forms a new resonant unit to resonate a preset high-frequency signal under the control of the PFM signal, thereby realizing the wireless modulation transmission of the PFM signal from the secondary coil side to the primary coil side. The connection between the two resonant ports of the resonant circuit and the secondary signal transmission port is controlled by the PFM signal: when the PFM signal is valid, the connection between the two resonant ports of the resonant circuit and the secondary signal transmission port is connected; when the PFM signal is invalid, the connection between the two resonant ports of the resonant circuit and the secondary signal transmission port is disconnected.

[0008] Preferably, the resonant circuit includes a capacitor and a switch; wherein, the control terminal of the switch serves as the control signal input port, one end of the capacitor and one end of the switch serve as the two resonant ports respectively, and the other end of the capacitor and the other end of the switch are connected. When the PFM signal is valid, the capacitor and a portion of the inductance taken from the secondary coil in the secondary signal transmission port form a new resonant unit in parallel resonance.

[0009] Preferably, the capacitor is an on-chip capacitor.

[0010] Preferably, the switch is a transistor switch.

[0011] Preferably, the transistor switch is a MOS transistor.

[0012] Preferably, the capacitor and the switch are integrated on the same chip.

[0013] Preferably, the frequency of the high-frequency signal obtained by the new resonant unit is different from the frequency of the power signal and the frequency of the ringing signal generated by the power signal, wherein the frequency of the high-frequency signal is:

[0014]

[0015] Where L is the inductance value of a portion of the inductance taken from the secondary coil in the secondary signal transmission port, and C is the capacitance value of the capacitor.

[0016] Preferably, the PFM-controlled wireless modulation device described in any one of the present application is used to replace the isolation barrier in a PFM-controlled isolated power supply system.

[0017] This application also provides a wireless modulation method for PFM control, including:

[0018] The PFM signal is input to the PFM control signal input port, which is the PFM control signal input port provided in any of the wireless modulation devices for PFM control described in this application.

[0019] The power transmission of the power signal from the primary coil to the secondary coil is achieved based on a power transformer, and the PFM signal is resonated to a preset high-frequency signal by a portion of the inductance taken from the secondary coil in the secondary signal transmission port based on a resonant circuit, and the high-frequency signal is transmitted from the secondary coil to the primary coil as a feedback signal; wherein, the power transformer and the resonant circuit are the power transformer and resonant circuit provided in the wireless modulation for PFM control as described in any one of the claims of this application.

[0020] Preferably, the frequency of the high-frequency signal obtained by resonance is determined as follows: based on the inductance value of a portion of the inductance in the secondary coil and / or the capacitance value in the resonant circuit at the secondary signal transmission port, wherein the frequency of the high-frequency signal is:

[0021]

[0022] Where L is the inductance value of a portion of the inductance taken from the secondary coil in the secondary signal transmission port, and C is the capacitance value of the capacitor.

[0023] This application also provides an isolated power supply system based on PFM control, including an inverter circuit, a rectifier circuit, an isolation barrier, a PFM encoding circuit, and a PFM decoding circuit. The isolation barrier includes a power transformer provided by a wireless modulation device for PFM control as described in any one of the claims of this application. The PFM encoding circuit includes a feedback circuit and a resonant circuit, wherein the resonant circuit includes a resonant circuit provided by a wireless modulation device for PFM control as described in any one of the claims of this application.

[0024] Among them, the primary power transmission port of the power transformer is electrically connected to the inverter circuit, the secondary power transmission port is connected to the rectifier circuit, the primary signal transmission port is electrically connected to the PFM decoding circuit, the secondary signal transmission port is connected to the resonant circuit, and the PFM control signal input port of the resonant circuit is electrically connected to the feedback circuit.

[0025] The feedback circuit is used to sample the output voltage of the rectifier circuit and generate a low-frequency PFM control signal of the corresponding frequency; the PFM decoding circuit is used to recover the low-frequency PFM signal from the high-frequency signal output from the primary side signal transmission port; the inverter circuit is used to convert the input DC voltage into an AC power signal according to the PFM signal output by the PFM decoding circuit; the power transformer is used for power signal and high-frequency signal transmission; and the rectifier circuit is used to convert the power signal from the power transformer into a DC output voltage.

[0026] Compared with the prior art, the beneficial effects that at least one of the above-mentioned technical solutions adopted in this application can achieve include at least:

[0027] Compared to traditional digital signal transmission methods, this invention uses a power transformer and resonant circuit to construct PFM signal modulation and isolation transmission, which has the following advantages:

[0028] (1) Signal transmission is achieved through a power transformer, eliminating the need for additional digital isolation barriers and greatly reducing cost and area.

[0029] (2) The encoding circuit is simple, requiring only one switching transistor and a resonant capacitor, without the need for bias circuits, oscillator circuits, etc. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a functional block diagram of a traditional isolated power supply system;

[0032] Figure 2 This is a schematic diagram of a PFM-controlled isolated power supply system for wireless transmission according to this application.

[0033] Figure 3 This is a waveform diagram of a key node in the wireless signal transmission in this application;

[0034] Figure 4 This is a schematic diagram of a capacitor and switch forming a resonant structure for wireless transmission in an isolated power supply system based on PFM control, as described in this application. Detailed Implementation

[0035] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0036] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0037] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0038] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The drawings only show the components related to this application and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0039] Additionally, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that practice can be carried out without these specific details.

[0040] like Figure 1 As shown, existing isolated power supply systems typically include key components such as a transmitter chip, an isolation chip, and a receiver chip. The transmitter chip usually includes an inverter and a controller, which, under the control of the controller, transmits the input DC power V... DDThe AC power signal is inverted and used to drive an isolation chip, thereby transferring power to the receiving chip. The isolation chip mainly consists of a power transformer and a digital isolation capacitor, which serve as the system's isolation barrier to achieve AC power transmission and control signal feedback transmission, respectively. The receiving chip typically includes an inverter and a feedback circuit, used to rectify the received AC power signal into a stable DC output voltage V. ISO The actual output generates a feedback signal, which is then transmitted to the transmitter chip via the digital isolation capacitor of the isolation chip.

[0041] It should be noted that in the feedback signal transmission channel, the high-voltage digital isolation capacitor composed of SiO2 provides an insulation barrier between different voltage domains and provides a high-frequency signal transmission path. Currently, the commonly used feedback digital channel scheme is the OOK on-off keying modulation scheme. Its principle is that the transmitter (TX) modulates the input signal onto the carrier frequency. That is, in one input state, TX transmits a high-frequency signal through the isolation capacitor, while in another input state, no signal passes through the isolation capacitor, thereby realizing coded (i.e., modulated) transmission. Then, the receiver (RX) reconstructs the TX transmitted signal based on the detected in-band data.

[0042] Therefore, the signal transmission in the solution relies heavily on additional isolation capacitors. In other words, in an isolated power supply system, an additional isolation channel is required for load modulation, which not only increases the cost but also hinders the miniaturization and integration of the chip.

[0043] In view of this, through in-depth research and improvement exploration of isolated power supply systems and their modulation methods, it was found that:

[0044] On the one hand, transformers can achieve isolated energy transfer between the primary and secondary sides, making power transformers a common component in isolated power supply systems. Therefore, if a power transformer can be used to transmit the feedback signal from the secondary side to the primary side, then the isolated transmission of the feedback signal should no longer require digital isolation capacitors.

[0045] Secondly, in an isolated power supply system based on PFM (Pulse Frequency Modulation) control, during the power transmission process, the secondary power inductance L... S Energy is always present. Therefore, if a small amount of power energy can be used to transmit the feedback signal from the secondary side to the primary side based on the power transformer, then the isolated transmission of the feedback signal should no longer require additional bias circuitry.

[0046] like Figure 2 As shown, this invention proposes an isolated power supply system and a wireless modulation transmission scheme for PFM control:

[0047] On the one hand, the isolation chip (also called isolator, isolation circuit, isolation barrier, etc., without distinction) in the isolated power supply system is improved into an isolation barrier form containing only a power transformer 200 for power transmission, and the power transformer 200 is improved into the following new structural form, namely, the power transformer 200 includes: a primary-side power transmission port V PP V PN Inverter circuit 100 for connecting to the transmitter chip side; secondary power transmission port V SP V SN , for connecting the rectifier circuit 300 on the receiving chip side; and, the primary-side signal transmission port V PA V PB and secondary signal transmission port V SA V SB They are used to connect the decoding circuit 600 and the encoding circuit, respectively (see the improvement in the example below).

[0048] After the power transformer 200 is improved to a new isolation structure, since the power transformer 200 can realize the transmission of power energy from the primary side to the secondary side and the transmission of PFM feedback signal from the secondary side to the primary side, the digital isolation capacitor required for feedback signal transmission no longer needs to be set in the isolation chip, which simplifies the design of the isolation barrier and saves circuit area.

[0049] Secondly, to meet the needs of PFM signal transmission, the PFM encoding circuit is improved to obtain a new encoding circuit, which may include: a resonant circuit 500 and a feedback circuit 400. The resonant circuit 500 and the power transformer 200 form a new resonant unit. That is, in the PFM-controlled isolated power supply system, a portion of the inductance is taken from the secondary power inductor Ls and combined with the newly added resonant circuit 500 to form a new resonant frequency that can resonate higher than the PFM frequency, thereby realizing the transmission of the PFM feedback signal (i.e., the low-frequency PFM signal generated by the feedback circuit 400 according to the output voltage) from the secondary side to the primary side.

[0050] The low-frequency PFM signal used for power feedback modulation is used to connect or disconnect the resonant circuit 500 to the secondary signal transmission port V of the secondary power inductor Ls. SA V SB Therefore, when the resonant circuit 500 is connected, the resonant circuit 500 and a portion of the inductance taken from the secondary power inductor Ls form a new resonant unit, generating a high-frequency signal with a higher frequency than the PFM signal. Thus, the PFM feedback signal in the form of this high-frequency signal can reach the primary side from the secondary side through the isolation barrier, and be transmitted to the primary side signal transmission port V. PA V PB The decoding circuit 600 restores the feedback signal.

[0051] In summary, the improved technical solution does not require additional digital transformers / isolation capacitors, additional bias modules, oscillators, etc. It only requires forming corresponding signal transmission ports on the primary and secondary sides of the power transformer, and using a small portion of the inductance in the secondary inductor Ls to reconstruct a new resonant unit with the newly added resonant circuit. The principle and operation are simple, and the circuit structure is simplified.

[0052] It should be noted that although the example of the wireless modulation scheme for PFM signals in this application is based on PFM signals in an isolated power supply system, other systems that are oriented towards PFM control and require isolated transmission of PFM signals can also be implemented using the device of this application. That is, the isolated power supply system is an application example of the wireless modulation scheme for PFM signals in this application, and other similar application scenarios can refer to the application method of PFM signals in the isolated power supply system.

[0053] The technical solutions provided by the various embodiments of this application are described below with reference to the accompanying drawings.

[0054] The core idea of ​​this invention is to use the power transformer in the isolated power supply system as the signal transmission path, without the need to add an additional digital isolation transformer / capacitor, which greatly reduces the chip area and packaging cost.

[0055] refer to Figure 2 As shown, the present invention proposes an isolated power supply system, which mainly includes: an inverter circuit 100, a power transformer 200, a rectifier circuit 300, a feedback circuit 400, a resonant circuit 500, and a decoding circuit 600. It should be noted that the inverter circuit 100 and the rectifier circuit 300 can be related circuits in the original scheme or newly designed circuits, and are not limited here.

[0056] The following is combined Figure 3 The schematic waveforms illustrate the composition and function of each circuit:

[0057] Inverter circuit 100: used to convert the input DC voltage V DD Inverted into a differential high-frequency oscillating power signal V PP and V PN And from V PP and V PN The port output is connected to the primary coil L of the miniature transformer 200. P ;

[0058] Power transformer 200: consisting of primary coil L P and secondary coil L S It consists of an isolation medium and enables the transmission of power from the primary to the secondary and the transmission of signals from the secondary to the primary.

[0059] Rectifier circuit 300: Used to convert the voltage at the secondary terminal V of transformer 200. SPand V SN The received high-frequency oscillation signal is rectified into a DC signal and provided to the output load;

[0060] Feedback circuit 400: Used to sample the output voltage and generate low-frequency PFM signals of different frequencies to achieve a constant output voltage;

[0061] Resonant circuit 500: Used to convert low-frequency PFM signals into high-frequency oscillation signals V. SA V SB ;

[0062] Decoding circuit 600: used to decode the high-frequency oscillation signal V PA V PB Decode and restore it to a low-frequency PFM signal, which is then fed back to inverter circuit 100.

[0063] The transformer 200 includes: a primary power transmission port V PP V PN Used to connect to the secondary power transmission port V of inverter circuit 100. SP V SN For connecting to rectifier circuit 300, it also includes primary-side signal transmission port V. PA V PB Used to connect the decoding circuit 600 and the secondary signal transmission port V SA V SB This circuit is used to connect to an encoding circuit, which can be a circuit consisting of the aforementioned resonant circuit 500 and feedback circuit 400 to achieve PFM signal modulation (i.e., encoding).

[0064] Where V PA V PB The port formed by taking a portion of the inductance from the primary coil, V SP V SN The port is formed by taking a portion of the inductance from the secondary coil, and the two portions of inductance are coupled to each other.

[0065] Combination Figure 2 and Figure 3 The schematic diagram shows the overall circuit operation as follows: The power signal is transmitted through the primary-side power transmission port V. PP V PN and secondary power transmission port V SP V SN Power transfer is achieved; after the PFM signal resonates to a higher frequency signal, it is transmitted through the secondary signal transmission port V. SA V SB and primary side signal transmission port V PA V PB Signal transmission is achieved, and then the primary-side decoding circuit transmits the signal through V.PA V PB The feedback transmission of the PFM signal can be completed by decoding the high-frequency oscillation signal.

[0066] Additionally, due to V SA V SB The inductance between the two sides is only a portion of the secondary inductance, and the resonant frequency needs to be distinguished from the power stage drive frequency and the chip ringing frequency. The capacitance of the on-chip resonant capacitor is very limited, therefore its oscillation amplitude is relatively small compared to the power inductor V. SP V SN The voltage between them is negligible, does not affect the power transmission of the power stage, and does not increase the output ripple.

[0067] from Figure 3 The waveform diagrams of key nodes in the signal transmission shown indicate that: PFM_S is the low-frequency signal output by the secondary feedback control module. When PFM_S is high, the resonant circuit operates, and V... SP -V SN When transmitting high-frequency signals to the primary side, the output PFM_P of the decoding circuit is translated as high, and the primary power stage alternately operates to transmit power; when PFM_S is low, the resonant circuit is turned off, the output PFM_P of the decoding circuit is translated as low, and the primary power stage is turned off.

[0068] In some examples, preferred embodiments of the resonant circuit 500 may be referred to Figure 4 The schematic circuit shown, i.e., the resonant circuit 500, can be simplified to the following circuit structure: it includes only a resonant capacitor C1 and a switch S1.

[0069] refer to Figure 4 As shown, the PFM signal serves as the control signal for S1, connecting / disconnecting the LC circuit via an on / off switch to achieve signal encoding. Its main principle is that during power transmission, the secondary power inductor L... S Energy exists on it. When the PFM signal is high (i.e., the switch is closed), the resonant capacitor C1 will interact with V. SA V SB The inductance between them forms an LC resonance, requiring no additional power supply or oscillation circuit, and its resonant frequency is:

[0070]

[0071] The frequency of this signal depends on V. SA V SB The inductance and resonant capacitance C1 between them.

[0072] In summary, in a PFM-modulated isolated power supply system, the low-frequency PFM signal used for power modulation is used as a switching signal. A portion of the secondary-side power inductor is used to form an LC series resonance, and the resulting high-frequency signal can pass through the isolation barrier. The corresponding decoding circuit on the primary side can then restore the signal to complete signal transmission. This solution requires no additional digital transformer / isolation capacitor, no additional bias module, oscillator, etc., only a resonant capacitor and a switching transistor, and its principle is simple.

[0073] In some preferred examples, the capacitor in the resonant circuit is set as an on-chip capacitor.

[0074] In some preferred examples, the switch is preferably an electronic switch composed of transistors, such as a MOS transistor, and specifically a PMOS transistor or an NMOS transistor can be preferred depending on the circuit design.

[0075] In some preferred examples, the capacitor and switch can be integrated on the same chip to form a resonant circuit chip. When different resonant frequencies are required, the corresponding chip can be selected to resonate with the inductance of the power transformer.

[0076] In some preferred examples, to meet the requirements of setting the resonant frequency, the power transformer is equipped with secondary signal transmission ports with different inductance values ​​on the secondary side, or different power transformers are equipped with secondary signal transmission ports with corresponding inductance values, so as to flexibly adapt to the selection of different resonant frequencies.

[0077] Based on the same inventive concept, this application also provides a wireless modulation method for PFM control.

[0078] Referring to the foregoing device examples, a wireless modulation method for PFM control may include:

[0079] Step 1: Input the PFM signal to the PFM control signal input port, wherein the PFM control signal input port is the PFM control signal input port provided in the wireless modulation device for PFM control as described in any one of the claims of this application.

[0080] It should be noted that PFM signals can be low-frequency signals that require isolated transmission, such as the PFM signals used for feedback control in isolated power supply systems, which have a frequency of approximately 500kHz. In isolated transmission, these signals often need to be modulated to a higher frequency and then transmitted in isolation through an isolation capacitor. Using the wireless modulation scheme of this application, the low-frequency PFM signal can be used as a switching signal for the resonant circuit, thereby causing part of the inductance of the power transformer to resonate with the resonant circuit under switching control.

[0081] Step 2: Power transmission of the power signal from the primary coil to the secondary coil is realized based on the power transformer, and the PFM signal is resonated to a preset high-frequency signal based on the resonant circuit and a portion of the inductance taken from the secondary coil in the secondary signal transmission port, and the high-frequency signal is transmitted from the secondary coil to the primary coil as a feedback signal; wherein, the power transformer and resonant circuit are the power transformer and resonant circuit provided in the wireless modulation for PFM control as described in any one of the claims of this application.

[0082] It should be noted that the power transformer achieves both power transmission and PFM signal modulation and transmission. For the specific working principle, please refer to the examples mentioned above, which will not be elaborated further here.

[0083] In some implementations, modulation is achieved through resonance. Resonance can be achieved by forming an LC resonant circuit using a resonant capacitor in a resonant circuit and a portion of the inductance in the secondary winding of a power transformer. Therefore, in wireless modulation of PFM signals, the frequency of the modulated signal can be determined by the values ​​of the capacitor and / or inductor. Thus, the frequency of the high-frequency signal obtained through resonance can be determined by setting the inductance value of a portion of the inductance taken from the secondary coil in the secondary signal transmission port and / or the capacitance value in the resonant circuit. In other words, in practical applications, different inductance and capacitance values ​​can be used to meet the modulation frequency requirements in different situations. Regarding the resonant frequency, please refer to the aforementioned example; it will not be elaborated upon here.

[0084] In this specification, the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the descriptions of the embodiments described later are relatively simple, and relevant parts can be referred to the descriptions of the foregoing embodiments.

[0085] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A wireless modulation device oriented to PFM control, characterized in that, include: Power transformer: A transformer composed of a primary coil and a secondary coil, serving as an isolation medium for power and signal transmission. The primary coil includes a primary power transmission port and a primary signal transmission port, while the secondary coil includes a secondary power transmission port and a secondary signal transmission port. The primary signal transmission port is formed by taking a portion of the inductance from the primary coil and extending it to the outside. The secondary signal transmission port is also formed by taking a portion of the inductance from the secondary coil and extending it to the outside. Power signals are transmitted from the primary coil to the secondary coil through the primary power transmission port, and PFM signals are transmitted from the secondary coil to the primary coil through the secondary signal transmission port. The resonant circuit includes a PFM control signal input port, two resonant ports, and a resonant circuit. The two resonant ports are connected to the secondary signal transmission port. The PFM control signal input port is used to input a PFM signal. The resonant circuit, together with a portion of the inductance taken from the secondary coil in the secondary signal transmission port, forms a new resonant unit to resonate a preset high-frequency signal under the control of the PFM signal, thereby achieving wireless modulation transmission of the PFM signal from the secondary coil side to the primary coil side. The connection between the two resonant ports of the resonant circuit and the secondary signal transmission port is controlled by the PFM signal: when the PFM signal is valid, the connection between the two resonant ports of the resonant circuit and the secondary signal transmission port is connected; when the PFM signal is invalid, the connection between the two resonant ports of the resonant circuit and the secondary signal transmission port is disconnected. The resonant circuit includes a capacitor and a switch; wherein, the control terminal of the switch serves as the input port of the PFM control signal, one end of the capacitor and one end of the switch serve as the two resonant ports respectively, and the other end of the capacitor and the other end of the switch are connected; the switch is used to close when the PFM signal is high, and the capacitor and a portion of the inductance taken from the secondary coil in the secondary signal transmission port form a new resonant unit in parallel resonance, using the energy present on the portion of the inductance during the power transmission process of the power transformer to generate a high-frequency signal higher than the frequency of the PFM signal; the switch is also used to open when the PFM signal is low, so as to turn off the resonant circuit; the power transformer is used to transmit the power signal through the primary power transmission port and the secondary power transmission port, and simultaneously transmit the high-frequency signal through the secondary signal transmission port and the primary signal transmission port, so as to realize the modulation and transmission of the PFM signal.

2. The PFM control-oriented wireless modulation apparatus according to claim 1, wherein, The capacitor is an on-chip capacitor; And / or, the switch is a transistor switch.

3. The PFM control-oriented wireless modulation apparatus according to claim 2, wherein, The transistor switch is a MOS transistor.

4. The PFM control-oriented wireless modulation apparatus according to claim 1, wherein, The capacitor and the switch are integrated on the same chip.

5. The PFM control oriented wireless modulation apparatus according to claim 1, wherein, The frequency of the high-frequency signal obtained by the resonance of the new resonant unit is different from the frequency of the power signal and the frequency of the ringing signal generated by the power signal, wherein the frequency of the high-frequency signal is: Where L is the inductance value of a portion of the inductance taken from the secondary coil in the secondary signal transmission port, and C is the capacitance value of the capacitor.

6. The wireless modulation apparatus for PFM control according to any one of claims 1-5, characterized in that, The PFM-controlled wireless modulation device is used to replace the isolation barrier in a PFM-controlled isolated power supply system.

7. A wireless modulation method for PFM control, characterized in that, include: The PFM signal is input to the PFM control signal input port, wherein the PFM control signal input port is the PFM control signal input port provided in the wireless modulation device for PFM control as described in any one of claims 1-6; The power transmission of the power signal from the primary coil to the secondary coil is achieved based on a power transformer, and the PFM signal is resonated to a preset high-frequency signal by a portion of the inductance taken from the secondary coil in the secondary signal transmission port based on a resonant circuit, and the high-frequency signal is transmitted from the secondary coil to the primary coil as a feedback signal; wherein, the power transformer and resonant circuit are the power transformer and resonant circuit provided in the wireless modulation device for PFM control as described in any one of claims 1-6.

8. The wireless modulation method for PFM control according to claim 7, characterized in that, The frequency of the high-frequency signal obtained by resonance is determined as follows: based on the inductance value of a portion of the inductance in the secondary coil taken from the secondary signal transmission port and / or the capacitance value in the resonant circuit, wherein the frequency of the high-frequency signal is: Where L is the inductance value of a portion of the inductance taken from the secondary coil in the secondary signal transmission port, and C is the capacitance value of the capacitor.

9. An isolated power supply system based on PFM control, comprising an inverter circuit, a rectifier circuit, an isolation barrier, a PFM encoding circuit, and a PFM decoding circuit, characterized in that, The isolation barrier includes a power transformer provided by the PFM-controlled wireless modulation device as described in any one of claims 1-6; the PFM encoding circuit includes a feedback circuit and a resonant circuit, wherein the resonant circuit includes a resonant circuit provided by the PFM-controlled wireless modulation device as described in any one of claims 1-6. Among them, the primary power transmission port of the power transformer is electrically connected to the inverter circuit, the secondary power transmission port is electrically connected to the rectifier circuit, the primary signal transmission port is electrically connected to the PFM decoding circuit, the secondary signal transmission port is connected to the resonant circuit, and the PFM control signal input port of the resonant circuit is electrically connected to the feedback circuit. The feedback circuit is used to sample the output voltage of the rectifier circuit and generate a low-frequency PFM control signal of the corresponding frequency; the PFM decoding circuit is used to recover the low-frequency PFM signal from the high-frequency signal output from the primary side signal transmission port; the inverter circuit is used to convert the input DC voltage into an AC power signal according to the PFM signal output by the PFM decoding circuit; the power transformer is used for power signal and high-frequency signal transmission; and the rectifier circuit is used to convert the power signal from the power transformer into a DC output voltage.

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