Dual-load coil wireless electric energy transmission system

Abstract

The invention discloses a dual-load coil wireless electric energy transmission system, and relates to the technical field of wireless electric energy transmission, the system comprises a full-bridge inverter, a transmitting end, a first receiving end and a second receiving end, the output of the full-bridge inverter is connected with the input of the transmitting end, the transmitting end comprises a switch control capacitor C, a coil inductor L and a resistor R, and the switch control capacitor C is connected with the coil inductor L; the switch control capacitor C, the coil inductor L and the resistor R form a first resonance circuit, and the first receiving end and the second receiving end are both magnetically coupled with the coil inductor L; the first receiving end comprises a first load, and the second receiving end comprises a second load; the full-bridge inverter is used for converting direct current into alternating current and then transmitting the alternating current to the transmitting end; by controlling the capacitance value of the switch control capacitor C, different resonant frequencies are controlled to carry out time-sharing charging on the first load and the second load, and double loads are charged at different frequencies.

Description

Technical Field

[0001] The present application relates to the technical field of wireless power transmission, and in particular to a dual-load coil wireless power transmission system. Background Art

[0002] Wireless Power Transfer (WPT) technology can provide a safe, convenient and free way to obtain electric energy. Currently, wireless power transfer technology has been widely used in production and life. With the continuous updating and iteration of WPT technology, the structure of wireless power transmission system has been improved while the transmission performance has also been improved. Therefore, it has been widely used in many fields, such as charging needs in electric vehicles, medical equipment, underwater vehicles, kitchen omnidirectional charging and other occasions.

[0003] For the existing magnetically coupled wireless power transmission, the transmission efficiency of the wireless power transmission system will decrease as the distance between the transmitting coil and the receiving coil changes. The wireless power transmission system based on the Parity-Time (PT) symmetry principle can effectively solve the problem of reduced transmission efficiency due to distance changes. When the wireless power transmission system operates in the precise area of ​​PT symmetry, the output power and transmission efficiency of the system can remain constant. At present, the research on the PT-WPT system for a single load is relatively mature. According to research, the wireless power transmission system based on PT symmetry has a more stable transmission in terms of power distribution and adjustment between different loads, and can simultaneously meet the power supply of dual-load devices. However, there are still the following shortcomings for the dual-load PT symmetric system: when the dual load ends receive power, they can only receive power transmission at the same frequency, which cannot meet the charging needs of different electrical devices. Summary of the invention

[0004] The purpose of the present application is to provide a dual-load coil wireless power transmission system, which realizes charging of dual loads at different frequencies.

[0005] To achieve the above objectives, this application provides the following solutions:

[0006] The present application provides a dual-load coil wireless power transmission system, the dual-load coil wireless power transmission system comprising: a full-bridge inverter, a transmitter, a first receiving end and a second receiving end, the output of the full-bridge inverter is connected to the input of the transmitter, the transmitting end comprises a switch-controlled capacitor C, a coil inductor L and a resistor R, the switch-controlled capacitor C, the coil inductor L and the resistor R constitute a first resonant circuit, the first receiving end and the second receiving end are both magnetically coupled with the coil inductor L; the first receiving end comprises a first load, and the second receiving end comprises a second load; the full-bridge inverter is used to convert direct current into alternating current and then transmit it to the transmitting end;

[0007] By controlling the capacitance value of the switch control capacitor C, different resonant frequencies are controlled to perform time-sharing charging on the first load and the second load.

[0008] Optionally, the dual-load coil wireless power transmission system further includes a drive signal generation module; the drive signal generation module is used to control the fundamental component of the output voltage of the full-bridge inverter to be in phase with the current of the transmitting end.

[0009] Optionally, the drive signal generating module includes a current sampling circuit, an advance compensation circuit, a differential amplifier circuit, a zero-crossing comparison circuit and a dead zone generating circuit connected in sequence, the current sampling circuit is used to sample the circuit of the transmitting end, the advance compensation circuit is used to convert the current output by the current sampling circuit into a voltage signal, the differential amplifier circuit is used to increase the voltage signal to a set voltage signal, the zero-crossing comparison circuit is used to convert the set voltage signal into a pulse width modulation signal, and the dead zone generating circuit is used to generate a first drive signal and a second drive signal from the pulse width modulation signal, the first drive signal and the second drive signal are drive signals of the two bridge arms in the full-bridge inverter.

[0010] Optionally, the switch control capacitor C includes a capacitor C x , capacitor C a 、Diode D a And MOS tube Q a , the capacitor C a , the diode D a And the MOS tube Q a Connected in parallel, the capacitor C x With the capacitor C a Series connection;

[0011] When the MOS tube Q a When conducting, C'=C x ';

[0012] When the MOS tube Q a When not conducting,

[0013] Wherein, C' is the capacitance value of the switch control capacitor C, C x ' is the capacitance C x Capacitance value, C y For the MOS tube Q a When the conduction angle is α, the capacitance C a The capacitance value across the two terminals, C a ' is the capacitance C a Capacitance value.

[0014] Optionally, the first receiving end further includes a coil inductance L r1 , capacitor C r1 , resistor R r1 , the first rectifier, parallel compensation capacitor C r1S , load resistance R r1S and a first switch relay; the capacitor C r1 , the coil inductance L r1 and the resistor R r1 are connected in series to form a second resonant circuit, the load resistor R r1S and the first switch relay in series with the parallel compensation capacitor C r1S The first rectifier is connected in parallel with the second resonant circuit and the parallel compensation capacitor C r1S The load resistance R r1S is the resistance of the first load;

[0015] The second receiving end also includes a coil inductor L r2 , capacitor C r2 , resistor R r2 , the second rectifier, parallel compensation capacitor C r2S , load resistance R r2S and a second switch relay; the capacitor C r2 , the coil inductance L r2 and the resistor R r2 are connected in series to form a third resonant circuit, the resistor R r2 The second switch relay is connected in series with the parallel compensation capacitor C r2S The second rectifier is connected in parallel with the third resonant circuit and the parallel compensation capacitor C r2S The load resistance R r2S is the resistance of the second load.

[0016] Optionally, the symmetry condition satisfied by the dual-load coil wireless power transmission system when it is working is:

[0017]

[0018] Among them, ω t is the resonant angular frequency of the first resonant circuit, ω r1 is the resonant angular frequency of the second resonant circuit, ω r2 is the resonant angular frequency of the third resonant circuit, ω0 is the set resonant angular frequency, R r1S ' is the load resistance R r1S The resistance value, R r2S ' is the load resistance R r2S The resistance value, Rr1 ' is the resistance R r1 The resistance value, R r2 ' is the resistance R r2 The resistance value, L r1 ' is the coil inductance L r1 The inductance value, L r2 ' is the coil inductance L r2 Inductance value, -R N is the resistance value of the equivalent resistor, and the equivalent resistor is used to be equivalent to the output of the full-bridge inverter, R' is the resistance value of the resistor R, and L' is the inductance value of the coil inductance L.

[0019] Optionally, the first rectifier includes a MOS tube Q r11 、MOS tube Q r12 、Diode D r11 、Diode D r12 、Diode D r13 and diode D r14 ; The MOS tube Q r11 The drain of the diode D r11 The positive electrode of the MOS tube Q is connected to one end of the second resonant circuit. r11 The source of the MOS tube Q r12 The source of the MOS tube Q r12 The drain of the diode D r12 The anode of the diode D is connected to the other end of the second resonant circuit. r13 The positive electrode of the MOS tube Q r11 The source of the diode D r13 The negative electrode of the MOS tube Q r11 The drain connection of the diode D r14 The positive electrode of the MOS tube Q r12 The source of the diode D r14 The negative electrode of the MOS tube Q r12 The drain connection of

[0020] The second rectifier includes a MOS tube Q r21 、MOS tube Q r22 、Diode D r21 、Diode D r22 、Diode D r23 and diode D r24 ; The MOS tube Q r21 The drain of the diode D r21 The positive electrode of the MOS tube Q is connected to one end of the third resonant circuit. r21 The source of the MOS tube Qr22 The source of the MOS tube Q r22 The drain of the diode D r22 The anode of the diode D is connected to the other end of the third resonant circuit. r23 The positive electrode of the MOS tube Q r21 The source of the diode D r23 The negative electrode of the MOS tube Q r21 The drain connection of the diode D r24 The positive electrode of the MOS tube Q r22 The source of the diode D r24 The negative electrode of the MOS tube Q r22 The drain connection of

[0021] The first switch relay, the MOS tube Q r11 And the MOS tube Q r12 The duty cycle of the second switch relay and the MOS tube Q r21 And the MOS tube Q r22 The duty cycle is the same.

[0022] Optionally, the first pulse width modulation waveform is the same as the second pulse width modulation waveform, and the first pulse width modulation waveform is opposite to the third pulse width modulation waveform;

[0023] The first pulse width modulation waveform is applied to the MOS tube Q a The gate pulse width modulation waveform;

[0024] The second pulse width modulation waveform is applied to the MOS tube Q r11 The gate and the MOS tube Q r12 The gate pulse width modulation waveform;

[0025] The third pulse width modulation waveform is applied to the MOS tube Q r21 The gate and the MOS tube Q r22 The gate pulse width modulation waveform.

[0026] Optionally, the dual-load coil wireless power transmission system further includes a drive signal feedback control module, and the drive signal feedback control module is used to:

[0027] The load resistor R r1S and the load resistance R r2S The current is sampled;

[0028] If the load resistance R r1S The sampling current and the load resistance Rr1S If the difference between the sampling currents is greater than the set reference value, the first switch relay and the MOS tube Q are adjusted. r11 And the MOS tube Q r12 Duty cycle;

[0029] If the load resistance R r2S The sampling current and the load resistance R r2S If the difference between the sampling currents is greater than the set reference value, the second switch relay and the MOS tube Q are adjusted. r21 And the MOS tube Q r22 duty cycle.

[0030] Optionally, the dual-load coil wireless power transmission system further includes a DC power supply and a boost converter, wherein the boost converter is connected between the DC power supply and the full-bridge inverter.

[0031] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0032] The present application provides a dual-load coil wireless power transmission system. By changing the capacitance value of the transmitter switch to control the capacitor C, the transmitter generates different resonant frequencies corresponding to the capacitance value, thereby controlling the different resonant frequencies to charge the first load and the second load in a time-sharing manner, thereby realizing the function of the wireless power transmission system to charge the dual loads at different frequencies. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 A schematic structural diagram of a dual-load coil wireless power transmission system provided in one embodiment of the present application;

[0035] Figure 2 A full-bridge inverter control circuit diagram for realizing negative resistance provided by an embodiment of the present application;

[0036] Figure 3 A negative resistance control circuit and a full-bridge inverter output waveform provided in an embodiment of the present application;

[0037] Figure 4 A system operating frequency characteristic diagram provided in an embodiment of the present application;

[0038] Figure 5A system power characteristic diagram provided for an embodiment of the present application;

[0039] Figure 6 A schematic diagram of a switch-controlled capacitor structure provided in an embodiment of the present application;

[0040] Figure 7 An effective circuit diagram of a dual-load coil wireless power transmission system provided in one embodiment of the present application;

[0041] Figure 8 A schematic diagram of the change in capacitance of a switch-controlled capacitor when the driving signal and the current have the same positive and negative change cycles provided by an embodiment of the present application;

[0042] Fig. 9 A schematic diagram of the change in capacitance of a switch-controlled capacitor when the positive and negative change periods of a driving signal and a current provided in an embodiment of the present application are different;

[0043] Fig.10 Schematic diagram of a switch controlling a capacitor to control a load end switch provided in an embodiment of the present application

[0044] Fig.11 A schematic diagram of the working process of a switch relay regulating a sudden change in output current provided in one embodiment of the present application. DETAILED DESCRIPTION

[0045] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions 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. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0046] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0047] The present application provides a dual-load coil wireless power transmission system, such as Figure 1 As shown, Figure 1 (a) includes a boost converter and a full-bridge inverter. Figure 1(b) is a first receiving end and a second receiving end, and the dual-load coil wireless power transmission system includes: a full-bridge inverter, a transmitting end, a first receiving end and a second receiving end, the output of the full-bridge inverter is connected to the input of the transmitting end, the transmitting end includes a switch-controlled capacitor C, a coil inductance L and a resistor R, the switch-controlled capacitor C, the coil inductance L and the resistor R constitute a first resonant circuit, the first receiving end and the second receiving end are both magnetically coupled with the coil inductance L; the first receiving end includes a first load, and the second receiving end includes a second load; the full-bridge inverter is used to convert direct current into alternating current and then transmit it to the transmitting end.

[0048] By controlling the capacitance value of the switch control capacitor C, different resonant frequencies are controlled to perform time-sharing charging on the first load and the second load.

[0049] The present application changes the capacitance value of the capacitor C controlled by the transmitter switch, and the transmitter generates different resonant frequencies corresponding to the capacitance values, thereby controlling the different resonant frequencies to charge the first load and the second load in a time-sharing manner, thereby realizing the function of the wireless power transmission system to charge the dual loads at different frequencies.

[0050] Due to the internal loss of actual components and other reasons, the input voltage of the transmitter is reduced during the transmission process of the entire WPT system, resulting in a decrease in the actual voltage and current received by the dual load end, which will affect the problem that the actual output cannot meet the power supply requirements of electrical appliances. Therefore, the dual-load coil wireless power transmission system also includes a DC power supply and a boost converter, and the boost converter is connected to the DC power supply U DC Between the full-bridge inverter, the transmission performance of the entire WPT is improved.

[0051] The boost converter includes a MOS tube Q S 、Diode D S1 、Diode D S2 and capacitor C S Capacitor C S As a parallel compensation capacitor, the voltage U d is the capacitance C S The voltage across the two ends, DC power supply U DC Connected in series with an inductor and then in parallel to the MOS tube Q S Between the drain and source, the diode D S1 The positive electrode and MOS tube Q S The source connection of diode D S1 The negative electrode and MOS tube Q S The drain connection of diode D S2 The positive electrode and MOS tube Q S The drain connection of diode DS2 The negative electrode and capacitor C S One end of the capacitor C S The other end is connected to the MOS tube Q S Source connection.

[0052] The full-bridge inverter includes MOS tube Q1, MOS tube Q2, MOS tube Q3, MOS tube Q4, diode D1, diode D2, diode D3 and diode D4. Diode D1, diode D2, diode D3 and diode D4 play a protective role; the drain of MOS tube Q1 is connected to the drain of MOS tube Q2, the source of MOS tube Q1 is connected to the drain of MOS tube Q3, the source of MOS tube Q2 is connected to the drain of MOS tube Q4, the source of MOS tube Q4 is connected to the drain of MOS tube Q S The diode D1 is connected in parallel between the source and drain of the MOS tube Q1, the diode D2 is connected in parallel between the source and drain of the MOS tube Q2, the diode D3 is connected in parallel between the source and drain of the MOS tube Q3, the diode D4 is connected in parallel between the source and drain of the MOS tube Q4, one end of the switch control capacitor C is connected to the source of the MOS tube Q1, the other end of the switch control capacitor C is connected to one end of the resistor R through the coil inductance L, and the other end of the resistor R is connected to the source of the MOS tube Q2.

[0053] In order to achieve parity-time symmetry, the dual-load coil wireless power transmission system also includes a drive signal generation module; the drive signal generation module is used to control the fundamental component of the output voltage of the full-bridge inverter to be in phase with the current of the transmitting end.

[0054] The drive signal generating module comprises a current sampling circuit, an advance compensation circuit, a differential amplifier circuit, a zero-crossing comparison circuit and a dead zone generating circuit connected in sequence, wherein the current sampling circuit is used to sample the circuit of the transmitting end, the advance compensation circuit is used to convert the current output by the current sampling circuit into a voltage signal, the differential amplifier circuit is used to increase the voltage signal to a set voltage signal, the zero-crossing comparison circuit is used to convert the set voltage signal into a pulse width modulation (PWM) signal, and the dead zone generating circuit is used to generate a first drive signal and a second drive signal from the pulse width modulation signal, wherein the first drive signal and the second drive signal are drive signals of two bridge arms in the full-bridge inverter.

[0055] Function of the lead compensation circuit: Since the amplifier and digital chip in the actual circuit have different degrees of delay when working, the trigger signal actually sent to the full-bridge inverter driver integrated circuit (IC) can no longer meet the current zero point switching bridge arm conduction requirement. Therefore, the lead compensation circuit is used to adjust the phase of the input signal.

[0056] The function of the differential amplifier circuit is to increase the reference voltage and adjust the output voltage to a DC signal suitable for the adapter chip in the actual circuit, so that the output voltage is within the appropriate peak-to-peak value range, which facilitates the subsequent zero-crossing comparison to achieve more accurate comparison.

[0057] like Figure 6 As shown, the switch control capacitor C includes a capacitor C x , capacitor C a 、Diode D a And MOS tube Q a , the capacitor C a , the diode D a And the MOS tube Q a Connected in parallel, the capacitor C x With the capacitor C a Series connection.

[0058] When the MOS tube Q a When conducting, C'=C x ';

[0059] When the MOS tube Q a When not conducting,

[0060] Wherein, C' is the capacitance value of the switch control capacitor C, C x ' is the capacitance C x Capacitance value, C y For the MOS tube Q a When the conduction angle is α, the capacitance C a The capacitance value across the two terminals, C a ' is the capacitance C a Capacitance value.

[0061] When AC current passes through, the MOS tube Q a The conduction angle α is used to output different capacitance values, respectively achieving the conditions of resonance with the load end, thereby charging the dual loads.

[0062] According to the frequency formula Different operating frequencies are obtained to meet the charging requirements of dual loads at different frequencies.

[0063] Among them, f iis the resonant frequency of the circuit, let L1=L2=L', C1=C x ',

[0064] The first receiving end also includes a coil inductor L r1 , capacitor C r1 , resistor R r1 , the first rectifier, parallel compensation capacitor C r1S , load resistance R r1S and a first switch relay; the capacitor C r1 , the coil inductance L r1 and the resistor R r1 are connected in series to form a second resonant circuit, the load resistor R r1S and the first switch relay in series with the parallel compensation capacitor C r1S The first rectifier is connected in parallel with the second resonant circuit and the parallel compensation capacitor C r1S The load resistance R r1S is the resistance of the first load;

[0065] The second receiving end also includes a coil inductor L r2 , capacitor C r2 , resistor R r2 , the second rectifier, parallel compensation capacitor C r2S , load resistance R r2S and a second switch relay; the capacitor C r2 , the coil inductance L r2 and the resistor R r2 are connected in series to form a third resonant circuit, the resistor R r2 The second switch relay is connected in series with the parallel compensation capacitor C r2S The second rectifier is connected in parallel with the third resonant circuit and the parallel compensation capacitor C r2S The load resistance R r2S is the resistance of the second load.

[0066] The first switch relay controls the on and off of the first receiving end, and the second switch relay controls the on and off of the second receiving end. The first switch relay and the second switch relay are arranged to prevent the two loads from interfering with each other.

[0067] The first rectifier includes a MOS tube Q r11 、MOS tube Q r12 、Diode D r11 、Diode D r12 、Diode D r13 and diode D r14 ; The MOS tube Qr11 The drain of the diode D r11 The positive electrode of the MOS tube Q is connected to one end of the second resonant circuit. r11 The source of the MOS tube Q r12 The source of the MOS tube Q r12 The drain of the diode D r12 The anode of the diode D is connected to the other end of the second resonant circuit. r13 The positive electrode of the MOS tube Q r11 The source of the diode D r13 The negative electrode of the MOS tube Q r11 The drain connection of the diode D r14 The positive electrode of the MOS tube Q r12 The source of the diode D r14 The negative electrode of the MOS tube Q r12 Drain connection.

[0068] The second rectifier includes a MOS tube Q r21 、MOS tube Q r22 、Diode D r21 、Diode D r22 、Diode D r23 and diode D r24 ; The MOS tube Q r21 The drain of the diode D r21 The positive electrode of the MOS tube Q is connected to one end of the third resonant circuit. r21 The source of the MOS tube Q r22 The source of the MOS tube Q r22 The drain of the diode D r22 The anode of the diode D is connected to the other end of the third resonant circuit. r23 The positive electrode of the MOS tube Q r21 The source of the diode D r23 The negative electrode of the MOS tube Q r21 The drain connection of the diode D r24 The positive electrode of the MOS tube Q r22 The source of the diode D r24 The negative electrode of the MOS tube Q r22 Drain connection.

[0069] MOS tube Q r11 And MOS tube Q r12 The on and off of the MOS tube Q is controlled by the duty cycle of the signal applied to the gate, which is used to prevent the instantaneous mutation of the voltage and current at the first receiving end.r21 And MOS tube Q r22 The on and off of are controlled by the duty cycle of the signal applied to the gate, which prevents the instantaneous mutation of the voltage and current at the second receiving end, thereby improving the stability of the system power transmission.

[0070] The first switch relay, the MOS tube Q r11 And the MOS tube Q r12 The duty cycle of the second switch relay and the MOS tube Q r21 And the MOS tube Q r22 The duty cycle is the same.

[0071] The dual-load coil wireless power transmission system also includes a controller, which is used to automatically switch the conduction direction of the metal-oxide-semiconductor field-effect transistor (MOSFET) in the full-bridge inverter when the resonant cavity current passes through zero, so that the output of the full-bridge inverter can be equivalent to a nonlinear resistance element with a negative value -R n and provide energy for the subsequent circuit. n Not only does the resonant cavity satisfy PT symmetry, but its nonlinear characteristics also keep the overall gain rate and loss rate of the system in dynamic balance, thereby achieving stable energy transmission. MOS is the abbreviation of MOSFET, and the system is the dual-load coil wireless power transmission system of this application.

[0072] By sampling the loop current i in the resonant tank at the transmitting end, the negative resistance can be obtained. Figure 2 The negative resistance control circuit and its implementation strategy are given. The transmitter current i is sampled, and the current is sampled, captured and converted into a voltage signal through the current detection transformer CU8965. Then it is directed to the zero-crossing comparator AD8611 and the dead zone generation circuit to convert it into a rectangular PWM signal. Ideally, without considering the MOSFET switching dead time, the duty cycle width of the PWM signal of switches Q1-Q4 is 50%. The isolated driver chip Silicon Labs SI8271 is used as the driver of the full-bridge inverter circuit to amplify the PWM signal from the zero-crossing comparator. Figure 3 The full-bridge inverter output waveform and the PWM signal controlled by the self-oscillation control are shown in Figure 1. Figure 3 (a) is the output waveform of the full-bridge inverter when MOS tube Q1 and MOS tube Q4 are turned on. Figure 3 (b) is the output waveform of the full-bridge inverter when MOS tube Q2 and MOS tube Q3 are turned on. Figure 3 (c) is the voltage U across the transmitting coil inductance L in And the full-bridge inverter output voltage fundamental component Ufha The waveform of Figure 3 (d) is the waveform of the loop current i in the resonant tank of the first resonant circuit. The first resonant circuit is the resonant circuit at the transmitting end.

[0073] According to the PT symmetry condition, the symmetry condition satisfied by the dual-load coil wireless power transmission system when working is:

[0074]

[0075] Among them, ω t is the resonant angular frequency of the first resonant circuit, ω r1 is the resonant angular frequency of the second resonant circuit, ω r2 is the resonant angular frequency of the third resonant circuit, ω0 is the set resonant angular frequency, R r1S ' is the load resistance R r1S The resistance value, R r2S ' is the load resistance R r2S The resistance value, R r1 ' is the resistance R r1 The resistance value, R r2 ' is the resistance R r2 The resistance value, L r1 ' is the coil inductance L r1 The inductance value, L r2 ' is the coil inductance L r2 Inductance value, -R N is the resistance value of the equivalent resistor, and the equivalent resistor is used to be equivalent to the output of the full-bridge inverter, R' is the resistance value of the resistor R, and L' is the inductance value of the coil inductance L.

[0076] Depend on Figure 1 According to Kirchhoff voltage and current power, we know that:

[0077]

[0078] When the distance between load 1 circuit (second resonant circuit) and load 2 circuit (third resonant circuit) is far, M can be ignored. 23 , that is, M 23 =0, where k i is the coupling coefficient between the coils, When i=1, M is M 12 , when i=2, M is M 13 , k1 is the coil inductance L and coil inductance L r1 The coupling coefficient between them, k2 is the coil inductance L and the coil inductance L r2 The coupling coefficient between 12 is the coil inductance L and the coil inductance L r1The mutual inductance between 13 is the coil inductance L and the coil inductance L r2 The mutual inductance between 23 is the coil inductance L r1 and coil inductance L r2 The mutual inductance coefficient between them, I represents the current flowing through the inductor in the first resonant circuit, I r1 represents the current flowing through the inductor at the first receiving end, I r2 represents the current flowing through the inductor in the second receiving end, and ω represents the natural angular frequency.

[0079] The condition for a matrix to have a non-zero solution is that the determinant of the matrix is ​​0, and when the angular frequency value is a real number, we can get:

[0080]

[0081] Among them, R e is the real part, I m Is the imaginary part.

[0082] Define the quality factor of the coil load as Q, then:

[0083]

[0084] Define the system's natural resonant frequency as f0 and the critical coupling coefficient as k c ,but:

[0085]

[0086] Among them, the weak coupling range is The strong coupling range is

[0087] Therefore, it can be deduced that the frequency of the dual-load coil wireless power transmission system is:

[0088]

[0089] Among them, f H is the high frequency, f L For low frequencies, such as Figure 4 shown.

[0090] The power characteristics of this application system are as follows: Figure 5 As shown, the total power P of the dual-load coil wireless power transmission system is:

[0091]

[0092] The total efficiency of the dual-load coil wireless power transfer system is:

[0093]

[0094] In this application, the voltage and current at the transmitting end form a non-correlated structure, and the phase difference Then the transmitter loop can be equivalent to a negative resistance -R N Structure, the overall equivalent structure of the circuit is as follows Figure 7 As shown. And because the driving signal of the full-bridge inverter is generated according to the current sampling circuit and the zero-crossing comparison circuit, it is possible to realize the negative resistance -R N Adaptive control of Figure 1 In, C 1x =C', C 1y =C', R1 = R', L1 = L'.

[0095] The switch control capacitor C is composed of different PWM drive signals. By setting different duty cycles of the PWM drive signals, the switch control capacitor C can be controlled by the drive signal to switch at different values, such as Figure 8 and Fig. 9 As shown. Among them, MOS tube Q a It is driven by PWM drive signal, such as Figure 8 As shown, when a given value is applied to the MOS tube Q a The driving signal on the same cycle as the current, and because the current is alternating current, the time for the direction change is half of the cycle, so the driving signal is set to a 50% duty cycle, and the output capacitance value can be changed in the corresponding cycle. 0-T2 is a cycle, and the current direction changes. When the current value is positive, the MOS tube Q is driven in the 0-T1 stage. a Working, the current flows from the MOS tube Q a flows through, that is, the capacitor C a short circuit, so the output capacitance is C x During the time T1-T2, the current value is negative, and the drive signal is set to 0, that is, the MOS tube Q a No conduction, capacitance value is C x and C y The series value. T2-T4 is the next cycle. When the current is positive, the T2-T3 stage resumes driving, and the conduction is the same as the 0-T1 stage; the conduction in the T3-T4 stage is the same as the T1-T2 stage. This cycle is cycled to achieve different output capacitance values, thereby achieving power supply to dual loads at different frequencies. Fig. 9 As shown, when the period and duty cycle of the driving signal are different from the period of the current, the percentage of the two capacitance values ​​occupied in the entire period can also be adjusted, so that the charging time of each load in one cycle is adjusted to be the same as the time occupied by its corresponding capacitance value in the cycle.

[0096] The current of the present application is converted into AC power through the full-bridge inverter structure, and the current is transmitted to the receiving end through the coupling of the coil at the transmitting end and the coil at the receiving end, that is, the coil inductance L of the transmitting end and the coil inductance L of the first receiving end r1 and the coil inductance L of the first receiving end r2 Phase coupling, the current is transmitted to the first receiving end and the second receiving end. The current is converted into direct current by the rectifier at the receiving end. Since the system needs to meet the above-mentioned PT symmetry conditions, the compensation capacitor is set as a switch-controlled capacitor, so that its duty cycle can be adjusted according to the given drive signal, combined with the positive and negative directions of the current to adjust the resonant state to meet the charging of the dual loads. Feedback regulation is set. When the switch-controlled capacitor changes, the change in capacitance is fed back to the control switch of the dual load end through the feedback regulation module, so that when the capacitance value changes, the switch is turned off, thereby avoiding the situation where one load is in a resonant state and affects the other load end.

[0097] In the present application, the first pulse width modulation waveform is the same as the second pulse width modulation waveform, and the first pulse width modulation waveform is opposite to the third pulse width modulation waveform, so as to realize time-sharing charging of the first load and the second load.

[0098] The first pulse width modulation waveform is applied to the MOS tube Q a The gate pulse width modulation waveform.

[0099] The second pulse width modulation waveform is applied to the MOS tube Q r11 The gate and the MOS tube Q r12 The gate pulse width modulation waveform.

[0100] The third pulse width modulation waveform is applied to the MOS tube Q r21 The gate and the MOS tube Q r22 The gate pulse width modulation waveform.

[0101] Since each component has internal losses and instantaneous on-off in actual situations, setting and adjusting the switch relay can alleviate the impact of internal losses, such as Fig.10 As shown, α1 and α2 are MOS tube Q a Different conduction angles.

[0102] like Fig.11As shown, when current passes through, the current size is detected, and the current at the next moment forms a difference. According to the current situation of each load end when the current is in the passage, the duty cycle of the MOS tube drive signal of each load end is adjusted to make the transmitted current more stable, so that the power supply effect of the load is more stable, and the electrical equipment is effectively protected. More specifically, the dual-load coil wireless power transmission system also includes a drive signal feedback control module, which is used to: respectively control the load resistor R at a set time interval r1S and the load resistance R r2S The current is sampled.

[0103] If the load resistance R r1S The sampling current The load resistance R r1S The sampling current The difference △ is greater than the set reference value, then the first switch relay and the MOS tube Q are adjusted. r11 And the MOS tube Q r12 duty cycle.

[0104] If the load resistance R r2S The sampling current and the load resistance R r2S If the difference between the sampling currents is greater than the set reference value, the second switch relay and the MOS tube Q are adjusted. r21 And the MOS tube Q r22 duty cycle.

[0105] Since the dual-load coil wireless power transmission system of the present application has a negative resistance structure and satisfies the conditions of PT symmetry, the dual-load system can be analyzed as a whole during analysis, which maintains the same constant output characteristics as the single-load system. According to the formulas of the above system frequency, total power and total efficiency, it can be clearly seen that the total output power and total efficiency of the system within the strong coupling region are only related to the circuit element parameters inside the system, and have nothing to do with the coupling coefficient of the dual load. In the weak coupling region, the total output power and total efficiency of the system change with the change of the coupling coefficient and cannot remain constant. Therefore, when the system region is in the strong coupling region, the system can always maintain a constant output power and output efficiency. At the same time, the corresponding resonant capacitor parameters and the time of the cycle occupied can be adjusted according to the setting of the switch control capacitor duty cycle, thereby realizing the adjustment of the dual load charging time.

[0106] The working process of the dual-load coil wireless power transmission system of this application is as follows:

[0107] Step 1: Connect the circuit and turn on the DC power supply to make the system start working.

[0108] Step 2: Detect the current at the transmitting end, and convert the current signal into a voltage signal through the current sampling circuit and the advance compensation circuit. The signal passes through the zero-crossing comparison circuit and the dead zone generation circuit to form a full-bridge inverter control that realizes negative resistance. The output controls the PWM waveform of the MOS tube in the full-bridge inverter, and the duty cycle is 50%.

[0109] Step 3: For the first receiving end or the second receiving end, set the PWM waveform of the switch relay and the MOS tube in the receiving end so that the duty cycle is consistent, which can effectively control the timely on and off of the voltage and current of the receiving end and prevent the voltage and current stored in the components from affecting the load.

[0110] Step 4: Set the PWM waveform and duty cycle of the two loads to be the same, and observe the energy transfer when the two loads work simultaneously. By setting the PWM waveform and duty cycle of the two loads to be the same, the transfer of each part can be compared with that during time-sharing control.

[0111] Step 5: Apply a PWM waveform to the switch-controlled capacitor, and adjust the switch-controlled capacitor to output different capacitance values ​​by changing the setting of the PWM wave duty cycle.

[0112] Step 6: Change the duty cycle of the MOS tube at the receiving end so that the duty cycle of the PWM wave applied by the MOS tube in one of the receiving ends is the same as the duty cycle of the PWM wave applied to the switch control capacitor, and the PWM wave applied by the MOS tube at the other receiving end is opposite.

[0113] Step 7: Observe and measure the voltage and current output from the two receiving ends respectively.

[0114] Step 8: Sample the current at the receiving end at the current moment and the next moment, and compare the difference with the set reference value. If the difference is large, adjust the duty cycle of the relay and the MOS tube at the receiving end. If the difference is small, output the current.

[0115] Step 9: Change the duty cycle of the PWM wave applied to the switch control capacitor, synchronously adjust the duty cycle of the PWM wave at the two receiving ends, and re-observe and measure the energy transfer.

[0116] Step 10: By adjusting the duty cycle of the PWM wave applied to the switch control capacitor, the output of different capacitance values ​​can be achieved. According to the above resonance conditions, time-sharing control of different frequencies of the dual loads can be achieved.

[0117] The present application can realize separate power supply to dual loads at different frequencies. By requiring the capacitor at the transmitting end to meet the resonance condition, a switch-controlled capacitor is designed. When the switch-controlled capacitor changes, the switch closure at the load end is controlled, thereby realizing separate control of different loads. At the same time, the current at the dual load ends is detected, and the conduction angle of the drive signal of the MOS tube in the receiving end is adjusted to prevent damage to the electrical equipment due to sudden changes in current and voltage, thereby laying the foundation for stable power supply to different electrical equipment with power requirements. At the same time, the dual-load coil wireless power transmission system of the PT symmetrical system realizes robustness to distance, and according to the conditions and characteristics of PT symmetry, high transmission efficiency and high stability of power transmission can be achieved within a certain area.

[0118] The technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0119] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A dual-load coil wireless power transmission system, characterized in that: The dual-load coil wireless power transmission system includes: a full-bridge inverter, a transmitter, a first receiving end and a second receiving end, the output of the full-bridge inverter is connected to the input of the transmitter, the transmitter includes a switch-controlled capacitor C, a coil inductor L and a resistor R, the switch-controlled capacitor C, the coil inductor L and the resistor R form a first resonant circuit, the first receiving end and the second receiving end are both magnetically coupled with the coil inductor L; the first receiving end includes a first load, and the second receiving end includes a second load; the full-bridge inverter is used to convert direct current into alternating current and then transmit it to the transmitter; By controlling the capacitance value of the switch control capacitor C, different resonant frequencies are controlled to perform time-sharing charging on the first load and the second load.

2. The dual-load coil wireless power transmission system according to claim 1, characterized in that: The dual-load coil wireless power transmission system also includes a drive signal generation module; the drive signal generation module is used to control the fundamental component of the output voltage of the full-bridge inverter to be in phase with the current of the transmitting end.

3. The dual-load coil wireless power transmission system according to claim 2, characterized in that: The drive signal generating module comprises a current sampling circuit, an advance compensation circuit, a differential amplifier circuit, a zero-crossing comparison circuit and a dead zone generating circuit connected in sequence, wherein the current sampling circuit is used to sample the circuit of the transmitting end, the advance compensation circuit is used to convert the current output by the current sampling circuit into a voltage signal, the differential amplifier circuit is used to increase the voltage signal to a set voltage signal, the zero-crossing comparison circuit is used to convert the set voltage signal into a pulse width modulation signal, and the dead zone generating circuit is used to generate a first drive signal and a second drive signal from the pulse width modulation signal, wherein the first drive signal and the second drive signal are drive signals of two bridge arms in the full-bridge inverter.

4. The dual-load coil wireless power transmission system according to claim 1, characterized in that: The switch control capacitor C includes a capacitor C x , capacitor C a 、Diode D a And MOS tube Q a , the capacitor C a , the diode D a And the MOS tube Q a Connected in parallel, the capacitor C x With the capacitor C a Series connection; When the MOS tube Q a When conducting, C′=C x ′; When the MOS tube Q a When not conducting, Wherein, C' is the capacitance value of the switch control capacitor C, C x ' is the capacitance C x Capacitance value, C y For the MOS tube Q a When the conduction angle is α, the capacitance C a The capacitance value across the two terminals, C a ' is the capacitance C a Capacitance value.

5. The dual-load coil wireless power transmission system according to claim 4, characterized in that: The first receiving end also includes a coil inductor L r1 , capacitor C r1 , resistor R r1 , the first rectifier, parallel compensation capacitor C r1S , load resistance R r1S and a first switch relay; the capacitor C r1 , the coil inductance L r1 and the resistor R r1 are connected in series to form a second resonant circuit, the load resistor R r1S and the first switch relay in series with the parallel compensation capacitor C r1S The first rectifier is connected in parallel with the second resonant circuit and the parallel compensation capacitor C r1S The load resistance R r1S is the resistance of the first load; The second receiving end also includes a coil inductor L r2 , capacitor C r2 , resistor R r2 , the second rectifier, parallel compensation capacitor C r2S , load resistance R r2S and a second switch relay; the capacitor C r2 , the coil inductance L r2 and the resistor R r2 are connected in series to form a third resonant circuit, the resistor R r2 The second switch relay is connected in series with the parallel compensation capacitor C r2S The second rectifier is connected in parallel with the third resonant circuit and the parallel compensation capacitor C r2S The load resistance R r2S is the resistance of the second load.

6. The dual-load coil wireless power transmission system according to claim 5, characterized in that: The symmetry conditions satisfied by the dual-load coil wireless power transmission system when it is working are: Among them, ω t is the resonant angular frequency of the first resonant circuit, ω r1 is the resonant angular frequency of the second resonant circuit, ω r2 is the resonant angular frequency of the third resonant circuit, ω0 is the set resonant angular frequency, R r1S ' is the load resistance R r1S The resistance value, R r2S ' is the load resistance R r2S The resistance value, R r1 ' is the resistance R r1 The resistance value, R r2 ' is the resistance R r2 The resistance value, L r1 ' is the coil inductance L r1 The inductance value, L r2 ' is the coil inductance L r2 Inductance value, -R N is the resistance value of the equivalent resistor, and the equivalent resistor is used to be equivalent to the output of the full-bridge inverter, R′ is the resistance value of the resistor R, and L′ is the inductance value of the coil inductance L.

7. The dual-load coil wireless power transmission system according to claim 5, characterized in that: The first rectifier includes a MOS tube Q r11 、MOS tube Q r12 、Diode D r11 、Diode D r12 、Diode D r13 and diode D r14 ; The MOS tube Q r11 The drain of the diode D r11 The positive electrode of the MOS tube Q is connected to one end of the second resonant circuit. r11 The source of the MOS tube Q r12 The source of the MOS tube Q r12 The drain of the diode D r12 The anode of the diode D is connected to the other end of the second resonant circuit. r13 The positive electrode of the MOS tube Q r11 The source of the diode D r13 The negative electrode of the MOS tube Q r11 The drain connection of the diode D r14 The positive electrode of the MOS tube Q r12 The source of the diode D r14 The negative electrode of the MOS tube Q r12 The drain connection of The second rectifier includes a MOS tube Q r21 、MOS tube Q r22 、Diode D r21 、Diode D r22 、Diode D r23 and diode D r24 ; The MOS tube Q r21 The drain of the diode D r21 The positive electrode of the MOS tube Q is connected to one end of the third resonant circuit. r21 The source of the MOS tube Q r22 The source of the MOS tube Q r22 The drain of the diode D r22 The anode of the diode D is connected to the other end of the third resonant circuit. r23 The positive electrode of the MOS tube Q r21 The source of the diode D r23 The negative electrode of the MOS tube Q r21 The drain connection of the diode D r24 The positive electrode of the MOS tube Q r22 The source of the diode D r24 The negative electrode of the MOS tube Q r22 The drain connection of The first switch relay, the MOS tube Q r11 And the MOS tube Q r12 The duty cycle of the second switch relay and the MOS tube Q r21 And the MOS tube Q r22 The duty cycle is the same.

8. The dual-load coil wireless power transmission system according to claim 7, characterized in that: The first pulse width modulation waveform is the same as the second pulse width modulation waveform, and the first pulse width modulation waveform is opposite to the third pulse width modulation waveform; The first pulse width modulation waveform is applied to the MOS tube Q a The gate pulse width modulation waveform; The second pulse width modulation waveform is applied to the MOS tube Q r11 The gate and the MOS tube Q r12 The gate pulse width modulation waveform; The third pulse width modulation waveform is applied to the MOS tube Q r21 The gate and the MOS tube Q r22 The gate pulse width modulation waveform.

9. The dual-load coil wireless power transmission system according to claim 7, characterized in that: The dual-load coil wireless power transmission system further includes a drive signal feedback control module, and the drive signal feedback control module is used to: The load resistor R r1S and the load resistance R r2S The current is sampled; If the load resistance R r1S The sampling current and the load resistance R r1S If the difference between the sampling currents is greater than the set reference value, the first switch relay and the MOS tube Q are adjusted. r11 And the MOS tube Q r12 Duty cycle; If the load resistance R r2S The sampling current and the load resistance R r2S If the difference between the sampling currents is greater than the set reference value, the second switch relay and the MOS tube Q are adjusted. r21 And the MOS tube Q r22 duty cycle.

10. The dual-load coil wireless power transmission system according to claim 1, characterized in that: The dual-load coil wireless power transmission system further includes a DC power supply and a boost converter, wherein the boost converter is connected between the DC power supply and the full-bridge inverter.

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