Demodulation circuit, wireless charging transmitting module and wireless charging equipment

Abstract

The utility model provides a demodulation circuit, a wireless charging transmitting module and wireless charging equipment, and relates to the technical field of wireless charging. The demodulation circuit comprises a detection module, a subtraction module and a demodulation module, the input end of the detection module serves as the first input end of the demodulation circuit and is connected with a transmitting coil of the wireless charging transmitting module so as to detect carrier signals of the transmitting coil, and the output end of the detection module is connected with the first input end of the subtraction module. A second input end of the subtraction module serves as a second input end of the demodulation circuit and is connected with a midpoint of a second bridge arm of a full-bridge switching circuit in the wireless charging transmitting module, so that subtraction processing is carried out on the carrier signal and a switching state signal of the second bridge arm, and a half-sine-wave carrier signal is obtained; and the output end of the subtraction module is connected with the demodulation module so as to demodulate the carrier signal of the half sine wave. According to the invention, demodulation precision and reliability can be improved.

Description

Technical Field

[0001] The present application relates to the field of wireless charging technology, and more specifically, to a demodulation circuit, a wireless charging transmitter module, and a wireless charging device. Background Art

[0002] Currently, the basic method for demodulating amplitude shift keying (ASK) signals for wireless charging is to collect the voltage or loop current on the transmitting coil, then filter and remove the carrier signal to obtain a 2K ASK signal on the carrier. How to better obtain this 2K ASK signal is crucial for subsequent signal processing.

[0003] Existing wireless charging decompresses voltage signals by using a detection module and then RC filtering to obtain a 2K ASK signal. This circuit has a simple structure, but the quality of the output 2K ASK signal is greatly affected by the input carrier signal strength and frequency, resulting in low demodulation accuracy. Utility Model Content

[0004] The purpose of this application is to provide a demodulation circuit, a wireless charging transmitter module and a wireless charging device to improve the demodulation accuracy in order to address the deficiencies in the above-mentioned prior art.

[0005] To achieve the above objectives, the technical solutions adopted in the embodiments of the present application are as follows:

[0006] In a first aspect, an embodiment of the present application provides a demodulation circuit applied to a wireless charging transmitter module, wherein the demodulation circuit includes: a detection module, a subtraction module, and a demodulation module;

[0007] The input end of the detection module serves as the first input end of the demodulation circuit and is connected to the transmitting coil of the wireless charging transmitting module to detect the carrier signal of the transmitting coil. The output end of the detection module is connected to the first input end of the subtraction module.

[0008] The second input end of the subtraction module serves as the second input end of the demodulation circuit and is connected to the midpoint of the second bridge arm of the full-bridge switch circuit in the wireless charging transmitter module to perform subtraction processing on the carrier signal and the switch state signal of the second bridge arm to obtain a modulated signal;

[0009] The output end of the subtraction module is connected to the demodulation module to demodulate the modulated signal.

[0010] Optionally, the demodulation circuit further includes: an amplification module;

[0011] The amplification module is connected between the output end of the subtraction module and the demodulation module.

[0012] Optionally, the detection module includes a detection diode; the anode of the detection diode serves as the input end of the detection module, and the cathode of the detection diode serves as the output end of the detection module.

[0013] Optionally, the subtraction module includes: a first operational amplifier, a first resistor, a second resistor, a third resistor and a fourth resistor;

[0014] The positive input terminal of the first operational amplifier is connected to the first resistor as the first input terminal of the subtraction module, the positive input terminal of the first operational amplifier is also grounded through the second resistor, the negative input terminal of the first operational amplifier is connected to the third resistor as the second input terminal of the subtraction module, the negative input terminal of the first operational amplifier is connected to the output terminal of the first operational amplifier through the fourth resistor, and the output terminal of the first operational amplifier serves as the output terminal of the subtraction module.

[0015] Optionally, the demodulation circuit further includes: a first filtering module, wherein the output end of the first operational amplifier is connected to one end of a capacitor of the first filtering module through a resistor of the first filtering module, and the other end of the capacitor of the first filtering module is grounded.

[0016] Optionally, the subtraction module includes: a transistor and a fifth resistor;

[0017] The emitter of the transistor serves as the first input terminal of the subtraction module, the base of the transistor is connected to the fifth resistor as the second input terminal of the subtraction module, and the collector of the transistor serves as the output terminal of the subtraction module.

[0018] Optionally, the demodulation circuit further includes: a second filtering module, the collector of the transistor is connected to one end of the resistor and capacitor of the second filtering module respectively, and the other end of the capacitor of the second filtering module is grounded.

[0019] Optionally, the amplification module includes: a second operational amplifier, a seventh resistor, an eighth resistor, a first capacitor and a third filtering module;

[0020] The positive input terminal of the second operational amplifier serves as the input terminal of the amplification module, the negative input terminal of the second operational amplifier is grounded through the seventh resistor and the first capacitor, the negative input terminal of the second operational amplifier is also connected to the output terminal of the second operational amplifier through the eighth resistor, the output terminal of the second operational amplifier is connected to one end of the capacitor of the third filtering module through the resistor of the third filtering module as the output terminal of the amplification module, and the other end of the capacitor of the third filtering module is grounded.

[0021] In a second aspect, an embodiment of the present application further provides a wireless charging transmitter module, the wireless charging transmitter module comprising: a full-bridge switching circuit, a resonant circuit, a control unit, and a demodulation circuit as described in any one of the first aspects;

[0022] The resonant circuit is connected between the midpoint of the first bridge arm and the midpoint of the second bridge arm of the full-bridge switching circuit. The resonant circuit includes a transmitting coil and a resonant capacitor connected in series. The detection module of the demodulation circuit is connected to the transmitting coil. The subtraction module of the demodulation circuit is connected to the midpoint of the second bridge arm. The output end of the demodulation circuit is connected to the control unit, and the control unit is also connected to the control end of the full-bridge switching circuit.

[0023] In a third aspect, an embodiment of the present application further provides a wireless charging device, which includes at least the wireless charging transmitting module as described in the second aspect.

[0024] The beneficial effects of this application are:

[0025] The demodulation circuit, wireless charging transmitter module and wireless charging device provided in the present application detect the carrier signal through the detection module, subtract the switch state signal of the second bridge arm from the carrier signal through the subtraction module, obtain the sinusoidal half-wave carrier signal as the modulation signal based on the subtraction module, reduce the interference of the carrier signal, and can demodulate a high-precision ASK signal from the sinusoidal half-wave carrier signal, thereby improving the demodulation accuracy and reliability of the demodulation circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 is a schematic diagram of an existing demodulation circuit;

[0028] Figure 2 The principle block diagram of the demodulation circuit provided in the embodiment of the present application Figure 1 ;

[0029] Figure 3 The principle block diagram of the demodulation circuit provided in the embodiment of the present application Figure 2 ;

[0030] Figure 4 The circuit principle of the demodulation circuit provided in the embodiment of the present application Figure 1 ;

[0031] Figure 5The circuit principle of the demodulation circuit provided in the embodiment of the present application Figure 2 ;

[0032] Figure 6 Signal waveform diagram provided for the embodiment of the present application;

[0033] Figure 7 A schematic diagram of a wireless charging transmitter module provided in an embodiment of the present application. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0035] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application without creative work are within the scope of protection of the present application.

[0036] In addition, the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0037] It should be noted that, in the absence of conflict, the features in the embodiments of this application can be combined with each other.

[0038] Figure 1 A schematic diagram of an existing demodulation circuit is shown in FIG. Figure 1 As shown, the existing demodulation circuit includes: a detection module, at least one level of RC filter module and a capacitor C3, Figure 1 Taking the two-stage RC filter module as an example, the carrier signal of the transmitting coil is obtained, the 2K modulated waveform is extracted through the detection module, the higher frequency part of the carrier signal is filtered out through the first-stage filter module, and then the 2K modulated waveform is filtered through the second-stage filter module. After that, the DC component in the modulated waveform is removed through capacitor C3 so that it can be decoded by the demodulation module.

[0039] Existing wireless charging decompresses voltage signals by using a detection module and then RC filtering to obtain a 2K ASK signal. This circuit has a simple structure, but the quality of the output 2K ASK signal is greatly affected by the input carrier signal strength and frequency, resulting in low demodulation accuracy.

[0040] Figure 2 The principle block diagram of the demodulation circuit provided in the embodiment of the present application Figure 1 ,like Figure 2 As shown, the demodulation circuit is applied to a wireless charging transmitter module. The demodulation circuit 100 may include: a detection module 11 , a subtraction module 12 and a demodulation module 13 .

[0041] The input end of the detection module 11 serves as the first input end of the demodulation circuit 100 and is connected to the transmitting coil of the wireless charging transmitting module to detect the carrier signal of the transmitting coil. The output end of the detection module 11 is connected to the first input end of the subtraction module 12.

[0042] The second input end of the subtraction module 12 serves as the second input end of the demodulation circuit 100 and is connected to the midpoint of the second bridge arm of the full-bridge switch circuit in the wireless charging transmitter module to perform subtraction processing on the carrier signal and the switch state signal of the second bridge arm to obtain a modulated signal.

[0043] An output end of the subtraction module 12 is connected to the demodulation module 13 to demodulate the modulated signal.

[0044] In this embodiment, when the wireless charging receiving module needs to send a signal to the wireless charging transmitting module, the ASK signal transmitted by the wireless charging receiving module is modulated onto a carrier and then transmitted to the wireless charging transmitting module. A carrier signal containing the ASK signal is generated on the transmitting coil of the wireless charging transmitting module.

[0045] like Figure 2 As shown, the full-bridge switching circuit includes a first bridge arm and a second bridge arm. The first bridge arm includes a first upper tube HS1 and a first lower tube LS1, and the second bridge arm includes a second upper tube HS2 and a second lower tube LS2. A transmitting coil L and a resonant capacitor C are connected between the endpoint of the first bridge arm and the midpoint of the second bridge arm. The transmitting coil L and the resonant capacitor C form a resonant circuit. When the first upper tube HS1 and the second lower tube LS2 are turned on, the resonant capacitor C is charged. When the second upper tube HS2 and the first lower tube LS1 are turned on, the resonant capacitor C resonates with the transmitting coil L, discharging the resonant capacitor C.

[0046] The input end of the detection module 11 is connected to the connection point of the transmitting coil L and the resonant capacitor C, and is used to detect the carrier signal on the transmitting coil L, and detect the upper half of the detection signal, that is, the half-wave carrier signal. The first input end of the subtraction module 12 receives the upper half signal of the carrier signal.

[0047] The second input end of the subtraction module 12 is connected to the midpoint of the second bridge arm of the full-bridge switching circuit. The voltage signal at the midpoint of the second bridge arm is the voltage signal of the lower plate of the resonant capacitor C, which represents the charging and discharging state of the resonant capacitor C, that is, represents the conduction state of the lower tube of the second bridge arm. Therefore, the signal received by the second input end of the subtraction module 12 is the switching state signal SW2 of the lower tube of the second bridge arm, and the switching state signal SW2 is a PWM signal.

[0048] The subtraction module 12 subtracts the switch state signal SW from the half-wave carrier signal output by the detection to subtract the PWM signal from the carrier signal, retaining the waveform signal of the part of the carrier signal greater than 0 to obtain a modulated signal. The modulated signal is a half-wave signal close to a sine wave, and a 2K ASK signal can be extracted from the sine half-wave signal. The envelope quality of the 2K ASK signal is better. The demodulation module 13 demodulates the instruction sent by the wireless charging receiving module according to the ASK signal to control the wireless charging transmitting module through the control chip in the wireless charging receiving module.

[0049] The demodulation circuit provided in the above embodiment detects the carrier signal through the detection module, subtracts the switch state signal of the second bridge arm from the carrier signal through the subtraction module, obtains the sinusoidal half-wave carrier signal as the modulation signal based on the subtraction module, reduces the interference of the carrier signal, and can demodulate a high-precision ASK signal from the sinusoidal half-wave carrier signal, thereby improving the demodulation accuracy and reliability of the demodulation circuit.

[0050] In one possible implementation, Figure 3 The principle block diagram of the demodulation circuit provided in the embodiment of the present application Figure 2 ,like Figure 3 As shown, the demodulation circuit 100 may further include: an amplification module 14 .

[0051] The amplification module 14 is connected between the output end of the subtraction module 12 and the demodulation module 13 .

[0052] In this embodiment, the amplification module 14 amplifies the modulated signal output by the subtraction module 12 to improve the signal quality of the modulated signal, thereby ensuring that the demodulation module demodulates the modulated signal more accurately.

[0053] In one possible implementation, Figure 4 The circuit principle of the demodulation circuit provided in the embodiment of the present application Figure 1 ,like Figure 4 As shown, the detection module 11 may include a detection diode D1 ; the anode of the detection diode D1 serves as the input end of the detection module 11 , and the cathode of the detection diode D1 serves as the output end of the detection module 11 .

[0054] In this embodiment, the anode of the detection diode D1 is connected to the transmitting coil, and the cathode of the detection diode D1 is connected to the first input terminal of the subtraction module 12. The detection diode D1 performs envelope detection on the carrier signal on the transmitting coil, removes the lower half of the carrier signal transmitted by the wireless charging receiving circuit, and leaves the high-frequency carrier signal in the upper half of the envelope signal.

[0055] In one possible implementation, Figure 4 As shown, the subtraction module 12 may include: a first operational amplifier U1 , a first resistor R1 , a second resistor R2 , a third resistor R3 , and a fourth resistor R4 .

[0056] The positive input terminal of the first operational amplifier U1 is connected to the first resistor R1 as the first input terminal of the subtraction module 12. The positive input terminal of the first operational amplifier U1 is also grounded through the second resistor R2. The negative input terminal of the first operational amplifier U1 is connected to the third resistor R3 as the second input terminal of the subtraction module 12. The negative input terminal of the first operational amplifier U1 is connected to the output terminal of the first operational amplifier U1 through the fourth resistor R4. The output terminal of the first operational amplifier U1 serves as the output terminal of the subtraction module 12.

[0057] In this embodiment, if Figure 4 As shown, the positive input terminal of the first operational amplifier U1 is connected to the cathode of the detection diode D4 through the first resistor R1, and the negative input terminal of the first operational amplifier U1 is connected to the midpoint of the second bridge arm of the full-bridge switch circuit through the third resistor R3.

[0058] The fourth resistor R4 is connected between the negative input terminal and the output terminal of the first operational amplifier U1 as a feedback resistor, so that the first operational amplifier U1 implements a subtraction function to subtract the switch state signal SW from the carrier signal coil.

[0059] Furthermore, if Figure 4 As shown, the demodulation circuit 100 may further include: a first filtering module 15, the output end of the first operational amplifier U1 is connected to one end of the capacitor C2 of the first filtering module 15 through the resistor R9 of the first filtering module 15, and the other end of the capacitor C2 of the first filtering module 15 is grounded.

[0060] In this embodiment, the first filtering module 15 is connected between the output end of the subtraction module 12 and the demodulation module 13 or the amplification module 14, and is used to filter the frequency of the modulated signal output by the subtraction module 12 and retain the frequency that meets the requirements.

[0061] The first filter module 15 is composed of a resistor R9 and a capacitor C2, and the specific connection relationship is as follows: Figure 4 As shown, the filtering frequency of the first filtering module 15 can be determined according to the values ​​of the resistor R9 and the capacitor C2.

[0062] In another possible implementation, Figure 5 The circuit principle of the demodulation circuit provided in the embodiment of the present application Figure 2 ,like Figure 5 As shown, the subtraction module 12 may include: a transistor Q1 , a fifth resistor R5 , and a sixth resistor R6 .

[0063] The emitter of the transistor Q1 is connected to the fifth resistor R5 as the first input terminal of the subtraction module 12 , the base of the transistor Q1 is connected to the sixth resistor R6 as the second input terminal of the subtraction module 12 , and the collector of the transistor Q1 is the output terminal of the subtraction module 12 .

[0064] In this embodiment, the emitter of the transistor Q1 is connected to the cathode of the detection diode D1 through the fifth resistor R5, the base of the transistor Q1 is connected to the midpoint of the second bridge arm of the full-bridge switch unit through the sixth resistor R6, and the collector of the transistor Q1 is used to output the modulation signal.

[0065] Furthermore, if Figure 5 As shown, the demodulation circuit may further include: a second filtering module 16, wherein the collector of the transistor is respectively connected to the resistor R10 of the second filtering module 16 and one end of the capacitor C3, and the other end of the capacitor C3 of the second filtering module 16 is grounded.

[0066] In this embodiment, the second filtering module 16 is connected between the output end of the subtraction module 12 and the demodulation module 13 or the amplification module 14, and is used to filter the frequency of the modulated signal output by the subtraction module 12 and retain the frequency that meets the requirements.

[0067] The second filter module 16 is composed of a resistor R10 and a capacitor C3, and the specific connection relationship is as follows: Figure 5 As shown, the filtering frequency of the second filtering module 16 can be determined according to the values ​​of the resistor R10 and the capacitor C2.

[0068] The working principle of using transistors to implement subtraction is as follows: when the carrier signal coil and the switch state signal SW2 are both valid, and the carrier signal after detection by the detection diode is greater than the switch state signal SW2, the transistor Q1 is in a saturated state, so that the collector current IC of the transistor Q1 follows the voltage of the portion where the carrier signal is greater than the switch state signal SW2, generating a voltage on the load. When the carrier signal after detection is equal to or lower than the voltage of the switch state signal SW2, the transistor Q1 works in a cut-off state, thereby realizing the function of subtracting the carrier signal coil and the switch state signal SW2.

[0069] When the carrier signal coil on the transmitting coil is detected by the detection diode D1, the switch state signal SW2 of the base of the transistor is subtracted, and the sinusoidal half-cycle signal of the carrier signal is obtained on the output load resistor R11. The sinusoidal half-cycle signal is then filtered by the resistor R10 and the capacitor C3, and then demodulated by the demodulation module to obtain a 2K ASK signal.

[0070] For example, Figure 6 The signal waveform diagram provided in the embodiment of the present application is as follows: Figure 6 As shown, the blue signal waveform is the carrier signal coil, the yellow signal waveform is the switch state signal SW2, and the green signal waveform is the sinusoidal half-cycle signal on the output load resistor R11.

[0071] In order to make the transistor work in a deep saturation state, the Ib current value that initially enters the saturation state can be calculated according to Ib*β=V / R.

[0072] According to the transistor's datasheet, when the carrier signal coil is at point a, the saturation current Ic ≈ {[(15V-0.7V-0.3V-11V) / (1K+3K)]*3K} / 100 = 2.25mA, and Ib = Ic / β = 22.5uA. At this point, the actual Ib current is (Ic*R11+0.3V-0.95V) / R6 = 610uA, where R6 is 10kohm and R11 is 3kohm.

[0073] It can be seen that the actual current Ib is much larger than the current value of Ib in the saturation state, so the transistor works in a deep saturation state. Figure 6 The voltage at point a in the diagram is 15V, β is 100, the voltage drop of the detector diode is 0.7V, the voltage drop of the transistor Q1 is 0.3V, and the base-emitter voltage of the transistor Q1 is Vbe = 0.95V.

[0074] It should be noted that the parameter values ​​of each component in the demodulation circuit mentioned above are only examples. In actual applications, the parameter values ​​of each component can be set according to actual needs. It is only necessary to ensure that the transistor Q1 operates in a saturated state. This embodiment does not impose any restrictions on this.

[0075] In one possible implementation, Figure 4 or Figure 5 As shown, the amplifying module 14 may include: a second operational amplifier U2 , a seventh resistor R7 , an eighth resistor R8 , a first capacitor C1 and a third filtering module 141 .

[0076] The positive input terminal of the second operational amplifier U2 serves as the input terminal of the amplification module 14, the negative input terminal of the second operational amplifier U2 is grounded through the seventh resistor R7 and the first capacitor C1, the negative input terminal of the second operational amplifier U2 is also connected to the output terminal of the second operational amplifier U2 through the eighth resistor R8, the output terminal of the second operational amplifier U2 is connected to one end of the capacitor C4 of the third filtering module 141 through the resistor R12 of the third filtering module as the output terminal of the amplification module 47, and the other end of the capacitor C4 of the third filtering module 141 is grounded.

[0077] In this embodiment, the positive input terminal of the second operational amplifier U2 is connected to the resistor R9 of the first filtering module 15, or the resistor R10 of the second filtering module 16, the negative input terminal of the second operational amplifier U2 is connected to the seventh resistor R7 and the eighth resistor R8, the eighth resistor R8 is arranged between the negative input terminal and the output terminal of the second operational amplifier U2, and the seventh resistor R7 is also grounded through the first capacitor C1.

[0078] In this embodiment, the second operational amplifier U2, the seventh resistor R7 and the eighth resistor R8 constitute an amplification unit, which amplifies the signal output by the subtraction module 12, thereby improving the quality of the output modulated signal. A first capacitor C1 is also connected between the seventh resistor R7 and the ground. The first capacitor C1 is used to isolate the DC signal to further improve the quality of the amplification of the output signal by the amplification unit.

[0079] The decoding circuit provided in the above embodiment uses a detection diode to detect the carrier signal, and then uses a subtractor composed of an operational amplifier or a transistor to further subtract the carrier signal to obtain only the upper half waveform signal of the carrier. After passing through the low-pass filtering and amplification module, the frequency interference of the signal can be reduced, and a higher quality 2K ASK signal can be obtained, thereby improving the accuracy of the ASK signal.

[0080] Based on the above demodulation circuit, the embodiment of the present application further provides a wireless charging transmitter module. Figure 7 A schematic diagram of a wireless charging transmitter module provided in an embodiment of the present application is shown in FIG. Figure 7 As shown, the wireless charging transmitter module may include: a full-bridge switch circuit 200 , a resonant circuit 300 , a control unit 400 and a demodulation circuit 100 .

[0081] A resonant circuit 300 is connected between the midpoint of the first bridge arm and the midpoint of the second bridge arm of the full-bridge switching circuit 200. The resonant circuit 300 includes a transmitting coil L and a resonant capacitor C connected in series. The detection module of the demodulation circuit 100 is connected to the transmitting coil L. The subtraction module 20 of the demodulation circuit 100 is connected to the midpoint of the second bridge arm. The output end of the demodulation circuit 100 is connected to the control unit 400. The control unit 400 is also connected to the control end of the full-bridge switching circuit 200.

[0082] In this embodiment, the wireless charging transmitting module receives a carrier signal including a modulated signal sent by the wireless charging receiving module. The demodulation circuit 100 performs subtraction processing on the carrier signal according to the switch control signal of the second bridge arm to obtain a modulated signal, and demodulates the modulated signal through the demodulation module in the demodulation circuit 100, and sends the demodulated instruction to the control unit 400. The control unit 400 is connected to the gates of each switching tube of the full-bridge switching circuit 200 to control the full-bridge switching circuit 200 according to the demodulation instruction.

[0083] In a possible implementation, an embodiment of the present application further provides a wireless charging device, which may at least include the above-mentioned wireless charging transmitting module.

[0084] The wireless charging transmitter module can be encapsulated inside the housing to form a wireless charging device.

[0085] The above are only specific embodiments of the present application, but the scope of protection of this application is not limited to them. Any changes or substitutions that can be easily conceived by any person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A demodulation circuit, characterized in that: Applied to the wireless charging transmitter module, the demodulation circuit includes: a detection module, a subtraction module and a demodulation module; The input end of the detection module serves as the first input end of the demodulation circuit and is connected to the transmitting coil of the wireless charging transmitting module to detect the carrier signal of the transmitting coil. The output end of the detection module is connected to the first input end of the subtraction module. The second input end of the subtraction module serves as the second input end of the demodulation circuit and is connected to the midpoint of the second bridge arm of the full-bridge switch circuit in the wireless charging transmitter module to perform subtraction processing on the carrier signal and the switch state signal of the second bridge arm to obtain a modulated signal; The output end of the subtraction module is connected to the demodulation module to demodulate the modulated signal.

2. The demodulation circuit according to claim 1, wherein: The demodulation circuit further includes: an amplification module; The amplification module is connected between the output end of the subtraction module and the demodulation module.

3. The demodulation circuit according to claim 1, wherein: The detection module includes a detection diode; the anode of the detection diode serves as the input end of the detection module, and the cathode of the detection diode serves as the output end of the detection module.

4. The demodulation circuit according to claim 1, wherein: The subtraction module includes: a first operational amplifier, a first resistor, a second resistor, a third resistor and a fourth resistor; The positive input terminal of the first operational amplifier is connected to the first resistor as the first input terminal of the subtraction module, the positive input terminal of the first operational amplifier is also grounded through the second resistor, the negative input terminal of the first operational amplifier is connected to the third resistor as the second input terminal of the subtraction module, the negative input terminal of the first operational amplifier is connected to the output terminal of the first operational amplifier through the fourth resistor, and the output terminal of the first operational amplifier serves as the output terminal of the subtraction module.

5. The demodulation circuit according to claim 4, wherein: The demodulation circuit further includes: a first filtering module, wherein the output end of the first operational amplifier is connected to one end of the capacitor of the first filtering module through the resistor of the first filtering module, and the other end of the capacitor of the first filtering module is grounded.

6. The demodulation circuit according to claim 1, wherein: The subtraction module includes: a transistor, a fifth resistor and a sixth resistor; The emitter of the transistor is connected to the fifth resistor as the first input end of the subtraction module, the base of the transistor is connected to the sixth resistor as the second input end of the subtraction module, and the collector of the transistor serves as the output end of the subtraction module.

7. The demodulation circuit according to claim 6, wherein: The demodulation circuit further includes: a second filtering module, wherein the collector of the transistor is connected to one end of the resistor and the capacitor of the second filtering module respectively, and the other end of the capacitor of the second filtering module is grounded.

8. The demodulation circuit according to claim 2, wherein: The amplification module includes: a second operational amplifier, a seventh resistor, an eighth resistor, a first capacitor and a third filtering module; The positive input terminal of the second operational amplifier serves as the input terminal of the amplification module, the negative input terminal of the second operational amplifier is grounded through the seventh resistor and the first capacitor, the negative input terminal of the second operational amplifier is also connected to the output terminal of the second operational amplifier through the eighth resistor, the output terminal of the second operational amplifier is connected to one end of the capacitor of the third filtering module through the resistor of the third filtering module as the output terminal of the amplification module, and the other end of the capacitor of the third filtering module is grounded.

9. A wireless charging transmitter module, characterized in that: The wireless charging transmitter module comprises: a full-bridge switching circuit, a resonant circuit, a control unit and a demodulation circuit according to any one of claims 1 to 8; The resonant circuit is connected between the midpoint of the first bridge arm and the midpoint of the second bridge arm of the full-bridge switching circuit. The resonant circuit includes a transmitting coil and a resonant capacitor connected in series. The detection module of the demodulation circuit is connected to the transmitting coil. The subtraction module of the demodulation circuit is connected to the midpoint of the second bridge arm. The output end of the demodulation circuit is connected to the control unit, and the control unit is also connected to the control end of the full-bridge switching circuit.

10. A wireless charging device, characterized in that: The wireless charging device at least includes the wireless charging transmitting module according to claim 9.

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