Amplitude-modulated signal demodulation circuit, control method thereof and wireless charging transmission system

Abstract

The invention discloses an amplitude modulation signal demodulation circuit, a control method thereof and a wireless charging transmission system, and belongs to the technical field of signal processing. The amplitude-modulated signal demodulation circuit comprises: an envelope detector, the input end of which is used for accessing an amplitude-modulated signal, converting the amplitude-modulated signal into an envelope signal and filtering the envelope signal to generate a first signal; the signal amplification circuit is electrically connected with the output end of the filter circuit, amplifies the first signal and generates a second signal, and the gain of the signal amplification circuit is adjustable; the hysteresis comparator is electrically connected with the output end of the signal amplification circuit; the input end of the amplitude detection circuit is electrically connected with the output end of the signal amplification circuit, and the amplitude detection circuit detects the amplitude of the second signal; and the main control circuit is electrically connected with the signal amplification circuit and the hysteresis comparator, and is used for adjusting the gain of the signal amplification circuit and / or the hysteresis voltage of the hysteresis comparator according to the amplitude of the second signal so as to improve the demodulation success rate of the transmitting end amplitude modulation signal demodulation circuit.

Description

Technical Field

[0001] The present application belongs to the field of signal processing technology, and in particular relates to an amplitude modulation signal demodulation circuit and a control method thereof, and a wireless charging transmission system. Background Art

[0002] The wireless charging system mainly consists of two parts: the transmitter and the receiver. The transmitter and the receiver need to communicate bidirectionally. The receiver can use capacitance modulation, resistance modulation, load current modulation and other methods to send information to the transmitter. During the operation, due to changes in coil coupling, load power, modulation mode, frequency and voltage, the ASK (Amplitude Shift Keying) modulation signal will be significantly affected, resulting in a low demodulation success rate of the ASK at the transmitter. Summary of the invention

[0003] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, the present application proposes an AM signal demodulation circuit, an AM signal demodulation method and a wireless charging transmission system to improve the demodulation success rate of the AM signal demodulation circuit at the transmitting end.

[0004] In a first aspect, the present application provides an amplitude modulated signal demodulation circuit, comprising:

[0005] An envelope detector, wherein an input end of the envelope detector is used to receive an amplitude modulated signal, and the envelope detector is configured to convert the amplitude modulated signal into an envelope signal, and filter the envelope signal to generate a first signal;

[0006] A signal amplifying circuit, wherein an input end of the signal amplifying circuit is electrically connected to an output end of the filtering circuit and is configured to amplify the first signal and generate a second signal, and the gain of the signal amplifying circuit is adjustable;

[0007] A hysteresis comparator, wherein an input terminal of the hysteresis comparator is electrically connected to an output terminal of the signal amplifying circuit;

[0008] an amplitude detection circuit, wherein an input end of the amplitude detection circuit is electrically connected to an output end of the signal amplification circuit, and the amplitude detection circuit is configured to detect the amplitude of the second signal;

[0009] A main control circuit, wherein an input end of the main control circuit is electrically connected to an output end of the amplitude detection circuit, and an output end of the main control circuit is electrically connected to a gain adjustment end of the signal amplification circuit and a hysteresis voltage input end of the hysteresis comparator, respectively, and the main control circuit is configured to reduce the gain of the signal amplification circuit and / or increase the hysteresis voltage when the amplitude of the second signal is greater than a first threshold value, and to increase the gain of the signal amplification circuit and / or reduce the hysteresis voltage when the amplitude of the second signal is less than a second threshold value;

[0010] The first threshold is greater than the second threshold.

[0011] According to one embodiment of the present application, the amplitude detection circuit includes:

[0012] a peak holding circuit, wherein an input end of the peak holding circuit is electrically connected to an output end of the signal amplifying circuit, and the peak holding circuit is configured to obtain an amplitude of the second signal and maintain the amplitude within a delay time;

[0013] A first comparator, wherein a non-inverting input terminal of the first comparator is electrically connected to an output terminal of the peak holding circuit, an inverting input terminal of the first comparator is used to access a first reference voltage, and an output terminal of the first comparator is electrically connected to a main control circuit;

[0014] The second comparator has a non-inverting input terminal electrically connected to the output terminal of the peak holding circuit, an inverting input terminal of the second comparator for accessing a second reference voltage, and an output terminal of the second comparator electrically connected to the main control circuit.

[0015] According to one embodiment of the present application, the envelope detector includes:

[0016] An envelope detection circuit, wherein the input end of the envelope detection circuit is used to receive an amplitude modulated signal, and the envelope detection circuit is configured to convert the amplitude modulated signal into an envelope signal;

[0017] A low-pass filter, wherein an input end of the low-pass filter is electrically connected to an output end of the envelope detection circuit, and the low-pass filter is configured to filter out a carrier signal from the envelope signal;

[0018] A high-pass filter, the input end of the high-pass filter is electrically connected to the output end of the low-pass filter, the output end of the high-pass filter is electrically connected to the input end of the signal amplification circuit, and the high-pass filter is configured to isolate the DC signal in the output signal of the low-pass filter.

[0019] According to one embodiment of the present application, the input end of the main control circuit is electrically connected to the output end of the hysteresis comparator, and the main control circuit is also configured to reduce the hysteresis voltage when the pulse width of the output signal of the hysteresis comparator is greater than the first pulse width threshold when the amplitude of the second signal is greater than or equal to the second threshold and less than or equal to the first threshold and the demodulation fails, and to increase the hysteresis voltage when the pulse width is less than the second pulse width threshold.

[0020] According to one embodiment of the present application, the signal amplification circuit includes:

[0021] A first resistor, a first end of the first resistor is electrically connected to an output end of the filter circuit;

[0022] an operational amplifier, wherein an inverting input terminal of the operational amplifier is electrically connected to the second end of the first resistor, and a non-inverting input terminal of the operational amplifier is used to access a third reference voltage;

[0023] a second resistor, wherein a first end of the second resistor is electrically connected to an inverting input terminal of the operational amplifier and a second end of the first resistor respectively, and a second end of the second resistor is electrically connected to an output terminal of the operational amplifier;

[0024] At least one of the first resistor and the second resistor is an adjustable resistor, and the output end of the main control circuit is electrically connected to the adjustment end of the adjustable resistor.

[0025] In a second aspect, the present application provides a control method for an AM signal demodulation circuit, which is applied to the aforementioned AM signal demodulation circuit. The AM signal demodulation method includes:

[0026] obtaining the amplitude of the second signal;

[0027] When the amplitude of the second signal is greater than the first threshold, reducing the gain of the signal amplification circuit and / or increasing the hysteresis voltage;

[0028] When the amplitude of the second signal is less than the second threshold, the gain of the signal amplification circuit is increased and / or the hysteresis voltage is reduced.

[0029] According to an embodiment of the present application, when the amplitude of the second signal is greater than the first threshold, reducing the gain of the signal amplification circuit and / or increasing the hysteresis voltage includes:

[0030] When the amplitude of the second signal is greater than the first threshold, reducing the gain of the signal amplification circuit;

[0031] When the gain of the signal amplifying circuit decreases to a minimum value and the amplitude of the second signal is greater than the first threshold, the hysteresis voltage is increased.

[0032] According to an embodiment of the present application, when the amplitude of the second signal is less than the second threshold, increasing the gain of the signal amplification circuit and / or reducing the hysteresis voltage includes:

[0033] When the amplitude of the second signal is less than the second threshold, increasing the gain of the signal amplification circuit;

[0034] When the gain of the signal amplifying circuit increases to a maximum value and the amplitude of the second signal is less than the first threshold, the hysteresis voltage is reduced.

[0035] According to an embodiment of the present application, the input end of the main control circuit is electrically connected to the output end of the hysteresis comparator, and the amplitude modulation signal demodulation method further includes:

[0036] When the amplitude of the second signal is greater than or equal to the second threshold and less than or equal to the first threshold, and demodulation fails, obtaining a pulse width of an output signal of the hysteresis comparator;

[0037] When the pulse width is greater than a first pulse width threshold, reducing the hysteresis voltage;

[0038] When the pulse width is less than the second pulse width threshold, the hysteresis voltage is increased.

[0039] In a third aspect, the present application provides a wireless charging transmission system, including a signal transmitting module and a signal receiving module, wherein the signal transmitting module includes the aforementioned amplitude modulation signal demodulation circuit.

[0040] According to the AM signal demodulation circuit and its control method, and the wireless charging transmission system of multiple embodiments of the present application, the gain and hysteresis voltage of the signal amplification circuit can be adjusted according to the amplitude of the second signal, that is, when the AM signal is weak, the gain of the signal amplification circuit can be increased and the hysteresis voltage can be reduced to ensure reliable signal demodulation; when the AM signal is strong, the gain of the signal amplification circuit can be reduced and the hysteresis voltage can be increased to avoid excessive amplification of noise, thereby improving the demodulation success rate of the AM signal demodulation circuit at the transmitting end.

[0041] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0043] Figure 1 is a structural block diagram of a wireless charging transmission system provided in an embodiment of the present application;

[0044] Figure 2 is a structural block diagram of an AM signal demodulation circuit provided in an embodiment of the present application;

[0045] Figure 3 is a circuit diagram of an amplitude detection circuit provided in an embodiment of the present application;

[0046] Figure 4 is a circuit diagram of an AM signal demodulation circuit provided in an embodiment of the present application;

[0047] Figure 5 It is one of the waveform diagrams of the signal conversion performed by the hysteresis comparator provided in the embodiment of the present application;

[0048] Figure 6 This is the second waveform diagram of the signal conversion performed by the hysteresis comparator provided in the embodiment of the present application;

[0049] Figure 7 It is one of the flow charts of the control method of the amplitude modulation signal demodulation circuit provided in the embodiment of the present application;

[0050] Figure 8 This is the second flowchart of the control method of the amplitude modulation signal demodulation circuit provided in the embodiment of the present application.

[0051] Reference numerals:

[0052] Signal transmitting module 10, signal receiving module 20, DC source 100, inverter circuit 200, FM signal modulation circuit 300, AM signal demodulation circuit 400, envelope detector 410, envelope detection circuit 411, filter circuit 420, low-pass filter 421, high-pass filter 422, signal amplification circuit 430, hysteresis comparator 440, main control circuit 450, amplitude detection circuit 460, peak holding circuit 461, transmitting controller 500, rectifier circuit 600, DC conversion circuit 700, load 800, FM signal demodulation circuit 900, AM signal modulation circuit 1000, receiving controller 1100, transmitting coil Lp, receiving coil Ls, first resonant capacitor Cp, second resonant capacitor Cs, first to second comparators A1~A2, operational amplifier A3, diode D, first to sixth resistors R1~R6, first to third capacitors C1~C3. DETAILED DESCRIPTION

[0053] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0054] In the following description, "circuit" refers to a conductive loop composed of at least one element or subcircuit through electrical connection or electromagnetic connection. When an element or circuit is said to be "coupled to" or "connected to" another element or an element / circuit is said to be "coupled to" or "connected to" two nodes, it can be directly coupled or connected to another element or there can be an intermediate element, and the connection between the elements can be physical, logical, or a combination thereof. On the contrary, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there is no intermediate element between the two.

[0055] In the description, the terms "first", "second", etc. are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the numerical descriptors used in this way are interchangeable where appropriate, so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are generally of the same type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0056] In addition, descriptions with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0057] With the increasing use of mobile electronic devices, people's demand for chargers is increasing day by day. Compared with traditional wired charging methods, wireless charging has the advantages of high safety, strong flexibility and good versatility, so it has developed rapidly. With more and more devices supporting wireless charging on the market, the compatibility between devices has become more and more intense. Data communication is the bridge between the wireless charging transmitter and the receiver. Stable data communication is the prerequisite for achieving compatibility of charging devices. As an important data communication circuit at the wireless charging transmitter, the performance of the ASK demodulation circuit has become a concern of technicians in this field.

[0058] In related technologies, voltage demodulation technology usually uses detection, filtering, amplification and hysteresis comparison to demodulate. During operation, the ASK modulated signal will be significantly affected by changes in coil coupling, load power, modulation mode, frequency and voltage. The amplifier's amplification factor and hysteresis voltage are fixed, and this method is difficult to cover significantly changing ASK modulated signals.

[0059] Reference Figure 1 , Figure 1 The structure of a wireless charging transmission system is shown. In order to more clearly illustrate the working principle of the AM signal demodulation circuit 400 in the present application, an embodiment of the present application proposes a wireless charging transmission system. In this embodiment, the wireless charging transmission system includes a signal transmitting module 10 and a signal receiving module 20. The signal transmitting module 10 includes a DC source 100, an inverter circuit 200, a FM signal modulation circuit 300, an AM signal demodulation circuit 400, a transmitting controller 500, a transmitting coil Lp and a first resonant capacitor Cp; the signal transmitting and receiving module includes a rectifier circuit 600, a DC conversion circuit 700, a load 800, a FM signal demodulation circuit 900, an AM signal modulation circuit 1000, a receiving controller 1100, a receiving coil Ls and a second resonant capacitor Cs.

[0060] The receiving coil Ls is coupled to the transmitting coil Lp. In the signal transmitting module 10, the DC source 100 is electrically connected to the DC side of the inverter circuit 200, the AC side of the inverter circuit 200 is electrically connected to the transmitting coil Lp and the first resonant capacitor Cp respectively, the transmitting coil Lp and the first resonant capacitor Cp are connected in series, the FM signal modulation circuit 300 is electrically connected to the inverter circuit 200, and the transmitting controller 500 is electrically connected to the inverter circuit 200, the FM signal modulation circuit 300 and the AM signal demodulation circuit 400 respectively. The AM signal demodulation circuit 400 is electrically connected to the connection node of the transmitting coil Lp and the first resonant capacitor Cp, and is mainly used to demodulate the AM signal received by the transmitting end.

[0061] In the signal receiving module 20, the receiving coil Ls and the second resonant capacitor Cs are connected in series and electrically connected to the AC side of the rectifier circuit 600, the DC side of the rectifier circuit 600 is electrically connected to the input side of the DC conversion circuit 700, and the output side of the DC conversion circuit 700 is electrically connected to the load 800. The receiving controller 1100 is electrically connected to the rectifier circuit 600, the FM signal demodulation circuit 900 and the AM signal modulation circuit 1000, respectively, and the FM signal demodulation circuit 900 and the AM signal modulation circuit 1000 are both electrically connected to the rectifier circuit 600.

[0062] Reference Figure 2 , Figure 2 The structure of an AM signal demodulation circuit 400 is shown. An embodiment of the present application provides an AM signal demodulation circuit 400, including: an envelope detector 410, a signal amplification circuit 430, a hysteresis comparator 440, an amplitude detection circuit 460 and a main control circuit 450. The input end of the envelope detector 410 is used to receive the amplitude modulated signal. The envelope detector 410 is configured to convert the amplitude modulated signal into an envelope signal, and filter the envelope signal to generate a first signal; the input end of the signal amplifying circuit 430 is electrically connected to the output end of the envelope detector 410, and is configured to amplify the first signal and generate a second signal. The gain of the signal amplifying circuit 430 is adjustable; the input end of the hysteresis comparator 440 is electrically connected to the output end of the signal amplifying circuit 430; the input end of the main control circuit 450 is electrically connected to the output end of the amplitude detection circuit 460, and the output end of the main control circuit 450 is electrically connected to the gain adjustment end and the hysteresis voltage input end of the signal amplifying circuit 430 respectively. The main control circuit 450 is configured to reduce the gain of the signal amplifying circuit 430 and / or increase the hysteresis voltage when the amplitude of the second signal is greater than the first threshold, and to increase the gain of the signal amplifying circuit 430 and / or reduce the hysteresis voltage when the amplitude of the second signal is less than the second threshold; wherein the first threshold is greater than the second threshold.

[0063] The input end of the envelope detector 410 is used to access the amplitude modulated signal. The main function of the envelope detector 410 is to convert the received amplitude modulated signal into its envelope signal and filter the envelope signal. The amplitude modulated signal is usually composed of a carrier signal and a modulation signal. The envelope detector 410 extracts the amplitude change of the amplitude modulated signal to obtain an envelope signal reflecting the change of the modulation signal. The amplitude change of the envelope signal is closely related to the change of the modulation signal. The envelope detector 410 can also remove high-frequency noise and unnecessary components in the envelope signal to make the signal smoother, and output a relatively pure signal (i.e., the first signal) after filtering. This signal reflects the low-frequency part of the amplitude modulated signal, that is, the original information of the amplitude modulated signal. The specific structure of the envelope detector 410 has a relatively mature solution in the relevant technology and is not limited here.

[0064] The input end of the signal amplifier circuit 430 is electrically connected to the output end of the envelope detector 410, and is mainly used to amplify the first signal and generate a second signal. Through the signal amplifier circuit 430, the envelope signal can be amplified to an amplitude range suitable for subsequent processing, thereby enhancing the strength and reliability of the signal. The gain adjustment end of the signal amplifier circuit 430 is electrically connected to the output end of the main control circuit 450, and the gain of the signal amplifier circuit 430 can be adjusted by the main control circuit 450 so that the amplified signal is in an appropriate level range.

[0065] The input end of the hysteresis comparator 440 is electrically connected to the output end of the signal amplification circuit 430. The hysteresis comparator 440 is mainly used to digitally process the second signal, that is, to convert the analog signal into a discrete digital signal, and output high and low level signals to facilitate subsequent logical judgment and demodulation operations. The hysteresis comparator 440 has a hysteresis characteristic, which can effectively avoid false triggering due to noise and provide a more stable output. The specific structure of the hysteresis comparator 440 has a relatively mature solution in the relevant technology and is not limited here.

[0066] The amplitude detection circuit 460 can obtain the current amplitude of the second signal in real time by monitoring the strength or amplitude change of the signal and transmit it to the main control circuit 450. The amplitude detection circuit 460 can be a circuit including a multi-stage amplification and detection module, which can effectively obtain the dynamic amplitude change of the second signal.

[0067] The input end of the main control circuit 450 is electrically connected to the output end of the amplitude detection circuit 460, and the amplitude of the second signal can be monitored in real time. The output end of the main control circuit 450 is electrically connected to the gain adjustment end and the hysteresis voltage input end respectively. The gain adjustment end is used to adjust the gain of the signal amplification circuit 430, and the hysteresis voltage input end is used to adjust the hysteresis voltage, that is, the main control circuit 450 can adjust the gain and / or hysteresis voltage of the signal amplification circuit 430 according to the change of the amplitude.

[0068] Specifically, the main control circuit 450 can adjust the gain of the signal amplifier circuit 430 according to the amplitude of the actual input amplitude modulation signal. When the amplitude modulation signal is less than the second threshold, the main control circuit 450 can increase the gain of the signal amplifier circuit 430 so that the amplified signal is in an appropriate level range, and can also reduce the hysteresis voltage to reduce the situation where the output changes due to a small amplitude change of the input signal cannot be caused; when the amplitude modulation signal is greater than the first threshold, the main control circuit 450 can reduce the gain of the signal amplifier circuit 430 so that the amplified signal is in an appropriate level range, and can also increase the hysteresis voltage to prevent the hysteresis comparator 440 from responding incorrectly when the noise amplitude is large, resulting in demodulation failure.

[0069] The values ​​of the first threshold voltage and the second threshold voltage can be determined according to actual application scenarios and are not limited here. For example, the first threshold voltage can be 1V, 1.1V or 1.2V, and the second threshold voltage can be 0.7V, 0.8V or 0.9V.

[0070] It should be noted that when the amplitude of the second signal is greater than the first threshold or less than the second threshold, the main control circuit 450 can only adjust the gain of the signal amplification circuit 430, or only adjust the hysteresis voltage, or adjust both the gain and the hysteresis voltage of the signal amplification circuit 430 to achieve a higher demodulation success rate.

[0071] According to the AM signal demodulation circuit 400 of the present application, the gain and hysteresis voltage of the signal amplification circuit 430 can be adjusted according to the amplitude of the second signal, that is, when the AM signal is weak, the gain of the signal amplification circuit 430 can be increased and the hysteresis voltage can be reduced to ensure reliable signal demodulation; when the AM signal is strong, the gain of the signal amplification circuit 430 can be reduced and the hysteresis voltage can be increased to avoid excessive amplification of noise, thereby improving the demodulation success rate of the AM signal demodulation circuit 400 at the transmitting end.

[0072] Reference Figure 3 , Figure 3The amplitude detection circuit 460 provided by the embodiment of the present application is shown. In some embodiments, the amplitude detection circuit 460 includes: a peak holding circuit 461, a first comparator A1, and a second comparator A2. The input end of the peak holding circuit 461 is electrically connected to the output end of the signal amplification circuit 430, and the peak holding circuit 461 is configured to obtain the amplitude of the second signal and maintain the amplitude during the delay time; the non-inverting input end of the first comparator A1 is electrically connected to the output end of the peak holding circuit 461, the inverting input end of the first comparator A1 is used to access the first reference voltage, and the output end of the first comparator A1 is electrically connected to the main control circuit 450; the non-inverting input end of the second comparator A2 is electrically connected to the output end of the peak holding circuit 461, the inverting input end of the second comparator A2 is used to access the second reference voltage, and the output end of the second comparator A2 is electrically connected to the main control circuit 450.

[0073] The peak holding circuit 461 is mainly used to receive the second signal output by the signal amplification circuit 430, obtain the amplitude of the second signal, and maintain the amplitude within a certain delay time to prevent misjudgment caused by instantaneous fluctuations of the signal. The specific structure of the peak holding circuit 461 has a relatively mature solution in the relevant technology and is not limited here.

[0074] The first comparator A1 is used to compare the amplitude of the second signal with the first reference voltage. If the first comparator A1 outputs a high level signal, it indicates that the amplitude of the second signal is greater than the first reference voltage; if the first comparator A1 outputs a low level signal, it indicates that the amplitude of the second signal is less than the first reference voltage.

[0075] Similarly, the second comparator A2 is used to compare the amplitude of the second signal with the second reference voltage. If the second comparator A2 outputs a high level signal, it indicates that the amplitude of the second signal is greater than the second reference voltage; if the second comparator A2 outputs a low level signal, it indicates that the amplitude of the second signal is less than the second reference voltage.

[0076] The first reference voltage may be the aforementioned first threshold voltage, and the second reference voltage may be the aforementioned second threshold voltage.

[0077] As an example, the first reference voltage is 1V, and the second reference voltage is 0.5V. If the amplitude of the second signal is greater than 1V, the output signal flag_H of the first comparator A1 is 1 (that is, the output signal of the first comparator A1 is a high level signal), if the amplitude of the second signal is less than 0.5V, the output signal flag_L of the second comparator A2 is 0 (that is, the output signal of the second comparator A2 is a low level signal), if the amplitude of the second signal is less than or equal to 1V and greater than or equal to 0.5V, the output signal flag_H of the first comparator A1 is 0, and the output signal flag_L of the second comparator A2 is 1 (that is, the output signal of the first comparator A1 is a low level signal, and the output signal of the second comparator A2 is a low level signal).

[0078] The input end of the main control circuit 450 is electrically connected to the output end of the first comparator A1 and the output end of the second comparator A2. The main control circuit 450 can adjust the gain and hysteresis voltage of the amplifier circuit according to the signals output by the first comparator A1 and the second comparator A2.

[0079] Reference Figure 4 , Figure 4 The AM signal demodulation circuit 400 provided in an embodiment of the present application is shown. In some embodiments, the envelope detector 410 includes: an envelope detection circuit 411 and a filter circuit 420. The input end of the envelope detection circuit 411 is used to access the AM signal, and the envelope detection circuit 411 is configured to convert the AM signal into an envelope signal; the input end of the filter circuit 420 is electrically connected to the output end of the envelope detection circuit 411, and the output end of the filter circuit 420 is electrically connected to the input end of the signal amplification circuit, and the filter circuit 420 is configured to filter the envelope signal to generate a first signal.

[0080] The envelope detection circuit 411 is mainly used to extract the envelope signal from the amplitude modulated signal, thereby restoring the information of the original signal. The envelope signal contains a high-frequency carrier component, and the signal changes rapidly. The filter circuit 420 is mainly used to smooth the signal, remove the high-frequency carrier part, and leave the envelope of the signal.

[0081] The specific structure of the envelope detection circuit 411 has a relatively mature solution in the relevant technology. As an example, the envelope detection circuit 411 includes a diode D, a third resistor R3 and a first capacitor C1. The anode of the diode D is used to access the amplitude modulation signal, the cathode of the diode D is electrically connected to the first end of the third resistor R3 and the first end of the first capacitor C1, respectively, and the second end of the third resistor R3 and the second end of the first capacitor C1 are both electrically connected to the ground node.

[0082] In some embodiments, the filter circuit 420 includes a low-pass filter 421 and a high-pass filter 422. The input end of the low-pass filter 421 is electrically connected to the output end of the envelope detection circuit 411, and the low-pass filter 421 is configured to filter out the carrier signal in the envelope signal; the input end of the high-pass filter 422 is electrically connected to the output end of the low-pass filter 421, and the output end of the high-pass filter 422 is electrically connected to the input end of the signal amplification circuit 430, and the high-pass filter 422 is configured to isolate the DC signal in the output signal of the low-pass filter 421.

[0083] The input end of the low-pass filter 421 is electrically connected to the output end of the envelope detection circuit 411. The low-pass filter 421 is mainly used to filter out the carrier signal in the envelope signal, thereby retaining only the low-frequency part in the amplitude modulation signal, ensuring that the envelope signal only contains the envelope component and does not include the high-speed carrier frequency part. The design of the low-pass filter 421 can effectively suppress high-frequency noise and carrier components and only transmit low-frequency envelope information.

[0084] The signal processed by the low-pass filter 421 enters the high-pass filter 422. The high-pass filter 422 is configured to further process the signal output from the low-pass filter 421, especially to isolate the DC component in the signal to ensure the purity of the signal in the subsequent processing process and provide a suitable input voltage for the subsequent signal amplification circuit 430.

[0085] The specific structures of the low-pass filter 421 and the high-pass filter 422 have relatively mature solutions in the relevant technology. As an example, the low-pass filter 421 includes a fourth resistor R4 and a second capacitor C2, the first end of the fourth resistor R4 is electrically connected to the first end of the first capacitor C1, the first end of the second capacitor C2 is electrically connected to the second end of the fourth resistor R4, and the second end of the second capacitor C2 is electrically connected to the ground node. The high-pass filter 422 includes a third capacitor C3, a fifth resistor R5 and a sixth resistor R6, the first end of the fifth resistor R5 is used to access the power supply voltage, the second end of the fifth resistor R5 is electrically connected to the first end of the sixth resistor R6, the second end of the sixth resistor R6 is electrically connected to the ground node, the first end of the third capacitor C3 is electrically connected to the second end of the fourth resistor R4, and the second end of the third capacitor C3 is electrically connected to the connection node of the fifth resistor R5 and the sixth resistor R6.

[0086] It should be noted that the above embodiment is only an illustrative example, and other equivalent specific structures of the low-pass filter 421 and the high-pass filter 422 are also included in the protection scope of the present application.

[0087] In some embodiments, the input end of the main control circuit 450 is electrically connected to the output end of the hysteresis comparator 440, and the main control circuit 450 is also configured to reduce the hysteresis voltage when the pulse width of the output signal of the hysteresis comparator 440 is greater than the first pulse width threshold when the amplitude of the second signal is greater than or equal to the second threshold and less than or equal to the first threshold and the demodulation fails, and to increase the hysteresis voltage when the pulse width is less than the second pulse width threshold.

[0088] The amplitude of the second signal is greater than or equal to the second threshold and less than or equal to the first threshold, indicating that the amplitude modulated signal is in an appropriate level range after being amplified by the signal amplification circuit 430. If the demodulation is unsuccessful at this time, it may be that the hysteresis voltage is too large or too small.

[0089] Reference Figure 5 , Figure 5 The waveform diagram of the signal conversion performed by the hysteresis comparator 440 provided in the embodiment of the present application is shown. If the pulse width of the output signal of the hysteresis comparator 440 is greater than the first pulse width threshold (such as the curve VDM1), it indicates that the hysteresis voltage (such as the rising threshold and the falling threshold of the hysteresis voltage are vhyp1 and vhyn1 respectively) is too large, resulting in the inability to demodulate the second signal with a smaller amplitude. At this time, the hysteresis voltage can be reduced to vhyp2 and vhyn2, so that the pulse of the output signal of the hysteresis comparator 440 is reduced (such as the curve VDM2).

[0090] Reference Figure 6 , Figure 6 The waveform diagram of the signal conversion performed by the hysteresis comparator 440 provided in the embodiment of the present application is shown. If the pulse width of the output signal of the hysteresis comparator 440 is less than the second pulse width threshold (such as the curve VDM3), it indicates that the hysteresis voltage (such as the rising threshold and the falling threshold of the hysteresis voltage are vhyp3 and vhyn4 respectively) is too small, resulting in misjudgment of the noise signal with a smaller amplitude. At this time, the hysteresis voltage can be increased to vhyp3 and vhyn4, so that the pulse of the output signal of the hysteresis comparator 440 increases (such as the curve VDM4).

[0091] It should be noted that the specific values ​​of the first pulse width threshold and the second pulse width threshold can be selected according to the actual application scenario and are not limited here. For example, for a 2KHz amplitude modulation signal, one cycle is 500us. When judging the pulse width within one cycle, the first pulse width threshold can be 620us or 625us, etc., and the second pulse width threshold can be 375us or 380us, etc.

[0092] In some embodiments, the signal amplification circuit 430 includes: a first resistor R1, an operational amplifier A3, and a second resistor R2. The first end of the first resistor R1 is electrically connected to the output end of the filter circuit 420; the inverting input end of the operational amplifier A3 is electrically connected to the second end of the first resistor R1, and the non-inverting input end of the operational amplifier A3 is used to access the third reference voltage; the first end of the second resistor R2 is electrically connected to the inverting input end of the operational amplifier A3 and the second end of the first resistor R1, respectively, and the second end of the second resistor R2 is electrically connected to the output end of the operational amplifier A3; at least one of the first resistor R1 and the second resistor R2 is an adjustable resistor, and the output end of the main control circuit 450 is electrically connected to the adjustment end of the adjustable resistor.

[0093] It should be noted that the operational amplifier A3 can be a non-inverting amplifier or an inverting amplifier. The following description will be made by taking the operational amplifier A3 as an inverting amplifier as an example.

[0094] The non-inverting input terminal of the operational amplifier A3 is used to access the third reference voltage, and the specific value of the third reference voltage can be selected according to the actual application scenario and is not limited here. For example, the third reference voltage can be 2.5V.

[0095] The first end of the first resistor R1 is electrically connected to the output end of the filter circuit 420 for receiving the first signal. As an example, the voltage of the first signal is V1, and the voltage of the second signal output by the operational amplifier A3 is V2, then V2 / V1=-R2 / R1. Wherein R1 is the resistance value of the first resistor R1, and R2 is the resistance value of the second resistor R2.

[0096] In this embodiment, the first resistor R1 can be an adjustable resistor and the second resistor R2 can be a fixed resistor; or the first resistor R1 can be a fixed resistor and the second resistor R2 can be an adjustable resistor; or both the first resistor R1 and the second resistor R2 can be adjustable resistors. The main control circuit 450 sends an adjustment signal to the adjustment end of the adjustable resistor, that is, the gain of the signal amplification circuit 430 can be adjusted.

[0097] Reference Figure 7 , Figure 7 The flow of the control method of the AM signal demodulation circuit 400 provided in the embodiment of the present application is shown. An embodiment of the present application provides a control method of the AM signal demodulation circuit 400, which is applied to the aforementioned AM signal demodulation circuit 400. The AM signal demodulation method includes: step 10, step 20 and step 30.

[0098] Step 10: obtaining the amplitude of the second signal;

[0099] Step 20: when the amplitude of the second signal is greater than the first threshold, reduce the gain of the signal amplifying circuit 430 and / or increase the hysteresis voltage;

[0100] Step 30: When the amplitude of the second signal is less than the second threshold, increase the gain of the signal amplification circuit 430 and / or reduce the hysteresis voltage.

[0101] The execution subject of the control method provided in the embodiment of the present application may be the main control circuit 450 or a functional module or functional entity in the main control circuit 450 that can implement the control method. The control method provided in the embodiment of the present application is described below using the main control circuit 450 as an example of the execution subject.

[0102] The main control circuit 450 can monitor the amplitude of the second signal in real time. The amplitude of the second signal represents the envelope information in the AM signal and is usually related to the strength or amplitude of the AM signal.

[0103] When the amplitude of the second signal is less than the second threshold, the main control circuit 450 can increase the signal strength by increasing the gain of the signal amplifying circuit 430, ensuring that the subsequent circuit can normally receive and process the signal. Conversely, when the amplitude of the second signal is greater than the first threshold, the main control circuit 450 can reduce the gain of the signal amplifying circuit 430 to avoid signal overload or distortion, thereby maintaining the quality of the signal and ensuring the stability and linear response of the demodulation circuit.

[0104] The function of the hysteresis comparator 440 is to compare the threshold of the second signal and determine the high and low levels of the signal according to the set hysteresis voltage. By adjusting the hysteresis voltage, it is possible to effectively avoid misjudgment or jitter caused by signal fluctuations and improve the stability and accuracy of the signal. When the amplitude of the second signal is small, reducing the hysteresis voltage can reduce the situation where the output changes due to small changes in the input signal are not caused; when the amplitude of the second signal is large, increasing the hysteresis voltage can prevent the hysteresis comparator 440 from responding incorrectly when the noise amplitude is large, resulting in demodulation failure.

[0105] According to the control method of the AM signal demodulation circuit 400 of the present application, the gain and hysteresis voltage of the signal amplification circuit 430 can be adjusted according to the amplitude of the second signal, that is, when the AM signal is weak, the gain of the signal amplification circuit 430 can be increased and the hysteresis voltage can be reduced to ensure reliable signal demodulation; when the AM signal is strong, the gain of the signal amplification circuit 430 can be reduced and the hysteresis voltage can be increased to avoid excessive amplification of noise, thereby improving the demodulation success rate of the AM signal demodulation circuit 400 at the transmitting end.

[0106] In some embodiments, when the amplitude of the second signal is greater than the first threshold, the gain of the signal amplification circuit 430 is reduced and / or the hysteresis voltage is increased, including: when the amplitude of the second signal is greater than the first threshold, the gain of the signal amplification circuit 430 is reduced; when the gain of the signal amplification circuit 430 is reduced to a minimum value and the amplitude of the second signal is greater than the first threshold, the hysteresis voltage is increased.

[0107] It should be noted that, under normal circumstances, when the amplitude of the second signal is greater than or equal to the second threshold and less than or equal to the first threshold, the demodulation success rate is higher. When the amplitude of the second signal is greater than the first threshold, the gain of the signal amplification circuit 430 is reduced so that the amplitude of the second signal is reduced to a range greater than or equal to the second threshold and less than or equal to the first threshold, thereby improving the demodulation success rate. If the amplitude of the second signal is still greater than the first threshold after the gain of the amplifier circuit is reduced to the minimum value, the main control circuit 450 increases the hysteresis voltage to prevent the hysteresis comparator 440 from being falsely triggered by noise or signal jitter, resulting in demodulation failure.

[0108] In some embodiments, when the amplitude of the second signal is less than the second threshold, the gain of the signal amplification circuit 430 is increased and / or the hysteresis voltage is reduced, including: when the amplitude of the second signal is less than the second threshold, the gain of the signal amplification circuit 430 is increased; when the gain of the signal amplification circuit 430 is increased to a maximum value and the amplitude of the second signal is less than the first threshold, the hysteresis voltage is reduced.

[0109] When the amplitude of the second signal is less than the second threshold, the gain of the signal amplification circuit 430 is increased so that the amplitude of the second signal is increased to a range greater than or equal to the second threshold and less than or equal to the first threshold, thereby improving the demodulation success rate. If the amplitude of the second signal is still less than the second threshold after the gain of the amplifier circuit is increased to the maximum value, the main control circuit 450 reduces the hysteresis voltage to prevent the hysteresis comparator 440 from being insensitive to smaller amplitude changes, thereby missing some minor signal changes and causing demodulation failure.

[0110] Reference Figure 8 , Figure 8 The flow of the control method of the AM signal demodulation circuit 400 provided in the embodiment of the present application is shown. In some embodiments, the input end of the main control circuit 450 is electrically connected to the output end of the hysteresis comparator 440, and the AM signal demodulation method further includes: when the amplitude of the second signal is greater than or equal to the second threshold and less than or equal to the first threshold, and the demodulation fails, obtaining the pulse width of the second signal; when the pulse width is greater than the first pulse width threshold, reducing the hysteresis voltage; when the pulse width is less than the second pulse width threshold, increasing the hysteresis voltage.

[0111] When the amplitude of the second signal is greater than or equal to the second threshold and less than or equal to the first threshold, it indicates that the amplitude modulated signal is in an appropriate level range after being amplified by the signal amplifying circuit 430 .

[0112] The main control circuit 450 obtains the pulse width of the square wave signal output from the output end of the hysteresis comparator 440, and compares the pulse width of the square wave signal with the pulse width threshold. When the pulse width is greater than the first pulse width threshold, it indicates that the hysteresis comparator 440 missed the second signal with a smaller amplitude. At this time, reducing the hysteresis voltage can enable the hysteresis comparator 440 to detect the second signal with a lower amplitude, thereby improving the demodulation success rate; when the pulse width is less than the second pulse width threshold, it indicates that the hysteresis comparator 440 is too sensitive and has generated a false trigger to the noise signal. At this time, increasing the hysteresis voltage can reduce the situation of responding to the noise signal and improve the demodulation success rate.

[0113] An embodiment of the present application provides a wireless charging transmission system, including a signal transmitting module 10 and a signal receiving module 20 . The signal transmitting module 10 includes the aforementioned amplitude modulation signal demodulation circuit 400 .

[0114] The specific structure and working principle of the AM signal demodulation circuit 400 may refer to the aforementioned embodiments and will not be described in detail here.

[0115] According to the wireless charging transmission system of the present application, the gain and hysteresis voltage of the signal amplifying circuit 430 can be adjusted according to the amplitude of the second signal, that is, when the amplitude modulated signal is weak, the gain of the signal amplifying circuit 430 can be increased and the hysteresis voltage can be reduced to ensure reliable signal demodulation; when the amplitude modulated signal is strong, the gain of the signal amplifying circuit 430 can be reduced and the hysteresis voltage can be increased to avoid excessive amplification of noise, thereby improving the demodulation success rate of the amplitude modulated signal demodulation circuit 400 at the transmitting end.

[0116] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. An amplitude modulated signal demodulation circuit, characterized in that: include: An envelope detector, wherein an input end of the envelope detector is used to receive the amplitude modulated signal, and the envelope detector is configured to convert the amplitude modulated signal into an envelope signal, and filter the envelope signal to generate a first signal; a signal amplifying circuit, wherein an input end of the signal amplifying circuit is electrically connected to an output end of the envelope detector and is configured to amplify the first signal and generate a second signal, and a gain of the signal amplifying circuit is adjustable; A hysteresis comparator, wherein an input end of the hysteresis comparator is electrically connected to an output end of the signal amplifying circuit; an amplitude detection circuit, wherein an input end of the amplitude detection circuit is electrically connected to an output end of the signal amplification circuit, and the amplitude detection circuit is configured to detect the amplitude of the second signal; a main control circuit, wherein an input end of the main control circuit is electrically connected to an output end of the amplitude detection circuit, and an output end of the main control circuit is electrically connected to a gain adjustment end of the signal amplification circuit and a hysteresis voltage input end of the hysteresis comparator, respectively, and the main control circuit is configured to reduce the gain of the signal amplification circuit and / or increase the hysteresis voltage when the amplitude of the second signal is greater than a first threshold value, and to increase the gain of the signal amplification circuit and / or reduce the hysteresis voltage when the amplitude of the second signal is less than a second threshold value; The first threshold is greater than the second threshold.

2. The AM signal demodulation circuit according to claim 1, characterized in that: The amplitude detection circuit comprises: a peak holding circuit, wherein an input end of the peak holding circuit is electrically connected to an output end of the signal amplifying circuit, and the peak holding circuit is configured to obtain an amplitude of the second signal and maintain the amplitude within a delay time; a first comparator, wherein a non-inverting input terminal of the first comparator is electrically connected to an output terminal of the peak holding circuit, an inverting input terminal of the first comparator is used to access a first reference voltage, and an output terminal of the first comparator is electrically connected to the main control circuit; A second comparator, wherein the non-inverting input terminal of the second comparator is electrically connected to the output terminal of the peak holding circuit, the inverting input terminal of the second comparator is used to access a second reference voltage, and the output terminal of the second comparator is electrically connected to the main control circuit.

3. The AM signal demodulation circuit according to claim 1, characterized in that: The envelope detector comprises: An envelope detection circuit, wherein an input end of the envelope detection circuit is used to receive the amplitude modulated signal, and the envelope detection circuit is configured to convert the amplitude modulated signal into the envelope signal; A low-pass filter, wherein an input end of the low-pass filter is electrically connected to an output end of the envelope detection circuit, and the low-pass filter is configured to filter out a carrier signal in the envelope signal; A high-pass filter, wherein the input end of the high-pass filter is electrically connected to the output end of the low-pass filter, the output end of the high-pass filter is electrically connected to the input end of the signal amplification circuit, and the high-pass filter is configured to isolate the DC signal in the output signal of the low-pass filter.

4. The AM signal demodulation circuit according to any one of claims 1 to 3, characterized in that: The input end of the main control circuit is electrically connected to the output end of the hysteresis comparator. The main control circuit is also configured to reduce the hysteresis voltage when the pulse width of the output signal of the hysteresis comparator is greater than the first pulse width threshold when the amplitude of the second signal is greater than or equal to the second threshold and less than or equal to the first threshold and the demodulation fails, and to increase the hysteresis voltage when the pulse width is less than the second pulse width threshold.

5. The AM signal demodulation circuit according to any one of claims 1 to 3, characterized in that: The signal amplification circuit comprises: a first resistor, wherein a first end of the first resistor is electrically connected to an output end of the filter circuit; an operational amplifier, wherein an inverting input terminal of the operational amplifier is electrically connected to the second end of the first resistor, and a non-inverting input terminal of the operational amplifier is used to access a third reference voltage; a second resistor, wherein a first end of the second resistor is electrically connected to an inverting input end of the operational amplifier and a second end of the first resistor respectively, and a second end of the second resistor is electrically connected to an output end of the operational amplifier; At least one of the first resistor and the second resistor is an adjustable resistor, and the output end of the main control circuit is electrically connected to the adjustment end of the adjustable resistor.

6. A control method for an amplitude modulated signal demodulation circuit, characterized in that: Applied to the AM signal demodulation circuit according to any one of claims 1 to 5, the AM signal demodulation method comprises: acquiring the amplitude of the second signal; When the amplitude of the second signal is greater than a first threshold, reducing the gain of the signal amplification circuit and / or increasing the hysteresis voltage; When the amplitude of the second signal is less than a second threshold, the gain of the signal amplification circuit is increased and / or the hysteresis voltage is reduced.

7. The control method of the AM signal demodulation circuit according to claim 6, characterized in that: When the amplitude of the second signal is greater than a first threshold, reducing the gain of the signal amplification circuit and / or increasing the hysteresis voltage comprises: When the amplitude of the second signal is greater than a first threshold, reducing the gain of the signal amplifying circuit; When the gain of the signal amplifying circuit decreases to a minimum value and the amplitude of the second signal is greater than a first threshold, the hysteresis voltage is increased.

8. The control method of the AM signal demodulation circuit according to claim 6, characterized in that: When the amplitude of the second signal is less than a second threshold, increasing the gain of the signal amplification circuit and / or reducing the hysteresis voltage comprises: When the amplitude of the second signal is less than a second threshold, increasing the gain of the signal amplifying circuit; When the gain of the signal amplifying circuit increases to a maximum value and the amplitude of the second signal is less than a first threshold, the hysteresis voltage is reduced.

9. The control method of the AM signal demodulation circuit according to claim 6, characterized in that: The input end of the main control circuit is electrically connected to the output end of the hysteresis comparator, and the amplitude modulation signal demodulation method further includes: When the amplitude of the second signal is greater than or equal to the second threshold and less than or equal to the first threshold, and demodulation fails, acquiring a pulse width of the output signal of the hysteresis comparator; When the pulse width is greater than a first pulse width threshold, reducing the hysteresis voltage; When the pulse width is less than a second pulse width threshold, the hysteresis voltage is increased.

10. A wireless charging transmission system, characterized in that: It comprises a signal transmitting module and a signal receiving module, wherein the signal transmitting module comprises an amplitude modulated signal demodulation circuit according to any one of claims 1 to 5.

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