A wireless charging device without communication and cascaded DC-DC converters

Abstract

The present invention discloses a wireless charging device that does not require communication and cascaded DC-DC converters, which is characterized by comprising a DC source, a square wave generator, a primary side LCC compensation network, a transmitting coil, a receiving coil, a secondary side variable parameter LCC compensation network, a rectifier filter circuit and a load; the output end of the DC source is connected to the input end of the square wave generator; the output end of the square wave generator is connected to the input end of the primary side compensation network; the output end of the primary side compensation network is connected to the transmitting coil; the receiving coil is connected to the input end of the secondary side variable parameter compensation network, and the output end of the secondary side variable parameter compensation network is connected to the input end of the rectifier filter circuit; the output end of the rectifier filter circuit is connected to the load. The present invention avoids the need for communication between the primary and secondary sides, while reducing the cost and volume increase caused by the cascaded DC-DC converter, and can achieve constant current and constant voltage output.

Description

Technical Field

[0001] The present invention relates to the field of wireless power transmission, and in particular to a wireless charging device without communication and cascade DC-DC converters. Background Art

[0002] In recent years, wireless power transmission technology has attracted more and more attention in fields such as electric vehicles, underwater equipment, implantable medical products and consumer electronics, and has become a current research hotspot because it does not require much manual operation, can realize intelligent and automated charging, and has the characteristics of flexibility, safety, and strong adaptability to the environment.

[0003] For wireless power transmission technology, realizing constant current and constant voltage charging is of great significance for extending the service life of the battery and improving the charging efficiency. However, due to the characteristics of wireless power transmission technology, the transmitting coil and the receiving coil are coupled through the magnetic field, and there is no direct electrical connection. It is impossible to directly feed back the voltage and current information of the load to the primary side of the system like a traditional converter. Moreover, this structural feature easily causes the transmitting coil and the receiving coil to be offset and misaligned, causing the mutual inductance of the coil to change, causing the output voltage and output current of the system to deviate from the normal value, which not only affects the service life of the battery, but also reduces the safety and stability of the system, and is prone to safety accidents.

[0004] In this regard, some researchers have proposed using wireless communication to transmit the voltage and current information of the load to the primary side, and adjust the system output through frequency conversion control or phase shift control to achieve constant current and constant voltage output of the system. However, the use of wireless communication not only increases the cost of the system, but also affects the rapidity and reliability of control. Some researchers have also proposed a method of cascading DC-DC converters on the secondary side of the system, which can avoid the requirement for communication between the primary and secondary sides, but it will increase the size and cost of the system and reduce efficiency. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a wireless charging device that does not require communication and cascaded DC-DC converters, while ensuring the rapidity and reliability of system control and reducing the volume increase caused by the cascaded DC-DC converters.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a wireless charging device without communication and cascade DC-DC converter, including a DC source, a square wave generator, a primary side LCC compensation network, a transmitting coil, a receiving coil, a secondary side variable parameter LCC compensation network, a rectifier filter circuit and a load; the output end of the DC source is connected to the input end of the square wave generator; the output end of the square wave generator is connected to the input end of the primary side compensation network; the output end of the primary side compensation network is connected to the transmitting coil; the receiving coil is connected to the input end of the secondary side variable parameter compensation network, and the secondary side variable parameter compensation network includes a variable inductor and a conventional compensation network; the output end of the secondary side variable parameter compensation network is connected to the input end of the rectifier filter circuit; the output end of the rectifier filter circuit is connected to the load.

[0007] A further improvement of the technical solution of the present invention is that the square wave generator adopts a full-bridge inverter circuit, the duty cycle of the full-bridge inverter circuit is a fixed value of 50%, and includes a first switch tube S1, a second switch tube S2, a third switch tube S3, and a fourth switch tube S4, the drain of the first switch tube S1 is connected to the drain of the third switch tube S3, the source of the first switch tube S1 is connected to the drain of the second switch tube S2, the source of the third switch tube S3 is connected to the drain of the fourth switch tube S4, and the source of the second switch tube S2 is connected to the source of the fourth switch tube S4.

[0008] A further improvement of the technical solution of the present invention is that the primary LCC compensation network includes a primary compensation inductor L1, a primary parallel compensation capacitor C1, and a primary series compensation capacitor C P One end of the primary compensation inductor L1 is connected to the source of the first switch tube S1 and the drain of the second switch tube S2; the other end of the primary compensation inductor L1 is connected to one end of the primary parallel compensation capacitor C1 and the primary series compensation capacitor C P The other end of the primary parallel compensation capacitor C1 is connected to the source of the third switch tube S3, the drain of the fourth switch tube S4 and the transmitting coil L P One end of the primary side series compensation capacitor C P The other end is connected to the transmitting coil L P The other end of the transmitting coil L P With receiving coil L S Energy is transferred between the coils through magnetic field coupling, and the magnitude of the magnetic field coupling between the coils is represented by mutual inductance M.

[0009] A further improvement of the technical solution of the present invention is that: the secondary variable parameter LCC compensation network includes a variable inductor L x and a secondary side LCC compensation network; the secondary side LCC compensation network includes a secondary side series compensation capacitor CS , secondary side parallel compensation capacitor C2, secondary side compensation inductor L2; the variable inductor L x One end is connected to the receiving coil L S One end of the variable inductor L x The other end is connected to the secondary side series compensation capacitor C S The secondary side is connected in series with a compensation capacitor C S The other end of the secondary side parallel compensation capacitor C2 is connected to one end of the secondary side compensation inductor L2; the other end of the secondary side parallel compensation capacitor C2 is connected to the receiving coil L S the other end.

[0010] A further improvement of the technical solution of the present invention is that: the variable inductor L x It includes two E-type magnetic cores, the main power inductor winding N ac , DC bias control winding N dc , DC bias power supply; the two E-type core openings are placed opposite to each other, the middle column has a certain size of air gap, and the two side columns have no air gap; the main power inductor winding N ac It is wound on a central column with an air gap, one end of which is connected to the receiving coil L S One end of the secondary side is connected to the series compensation capacitor C S One end of the DC bias control winding N dc Wound on the side column, one group on each side column, two groups of DC bias control winding N dc The winding direction and number of turns are exactly the same; the two sets of DC bias control windings N dc One end of each is connected to each other, and the other end is connected to the two ends of the DC bias power supply; the DC bias power supply is implemented by a buck circuit or an operational amplifier circuit. When the current I dc gradually increases, the variable inductance L x The inductance value gradually decreases.

[0011] The further improvement of the technical solution of the present invention is that: the rectifier filter circuit includes a rectifier circuit and an output filter capacitor C o The rectifier circuit includes a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4; the anode of the first diode D1 and the cathode of the second diode D2 are connected to the other end of the secondary compensation inductor L2; the cathode of the first diode D1 is connected to the cathode of the third diode D3, the output filter capacitor C o One end and load R o The anode of the third diode D3 and the cathode of the fourth diode D4 are connected to the other end of the secondary parallel compensation capacitor C2; the anode of the fourth diode D4 is connected to the anode of the second diode D2, the output filter capacitor Co The other end and the load R o the other end.

[0012] A further improvement of the technical solution of the present invention is that: the switching frequencies of the first switch tube S1, the second switch tube S2, the third switch tube S3, and the fourth switch tube S4 are equal, the switching signals of the first switch tube S1 and the third switch tube S3 are complementary to the switching signals of the second switch tube S2 and the fourth switch tube S4, respectively, and the duty ratios are both 0.5, the first switch tube S1 and the fourth switch tube S4 are turned on and turned off at the same time, and the second switch tube S2 and the third switch tube S3 are turned on and turned off at the same time; the switching frequencies of the first switch tube S1, the second switch tube S2, the third switch tube S3, and the fourth switch tube S4 are fixed values ​​during operation, and are equal to the inherent resonant frequencies of the primary side LCC compensation network and the secondary side LCC compensation network, and satisfy the following formula:

[0013]

[0014] Wherein, f is the switching frequency of the first switch tube S1, the second switch tube S2, the third switch tube S3, and the fourth switch tube S4.

[0015] A further improvement of the technical solution of the present invention is that the variable inductor has two working modes, namely, a constant current mode and a constant voltage mode. In the constant current mode, the DC transconductance gain expression is:

[0016]

[0017] According to the DC transconductance gain expression, the variable inductance L in the constant current stage is obtained: x The matching formula is:

[0018]

[0019] In constant voltage mode, the DC voltage gain expression is:

[0020]

[0021] According to the DC voltage gain expression, the variable inductance L in the constant voltage stage can be obtained: x The matching formula is:

[0022]

[0023] A further improvement of the technical solution of the present invention is that: in the constant current mode, when the load resistance R o When the mutual inductance M of the coil changes, the variable inductance L in the constant current stage x The matching formula adjusts the variable inductance L x , realize constant current output; in the constant voltage mode, when the load resistance Ro When the mutual inductance M of the coil changes, the variable inductance L in the constant voltage stage x The matching formula adjusts the variable inductance L x , to achieve constant voltage output; in the constant current mode and constant voltage mode, the variable inductor L x The regulation adopts closed-loop control, directly applying the load R o The voltage U o 、Current I o The variable inductor L is adjusted in each mode through the current loop and the voltage loop. x The inductance value is adjusted so that it changes according to the matching formula of the constant current stage and the constant voltage stage to achieve constant current and constant voltage output.

[0024] A further improvement of the technical solution of the present invention is that the system input impedance expression of the wireless charging device is:

[0025]

[0026] In the entire working range, the input impedance of the system is inductive, and the first switch tube S1, the second switch tube S2, the third switch tube S3, and the fourth switch tube S4 are all turned on at zero voltage.

[0027] Due to the adoption of the above technical solution, the technical progress achieved by the present invention is:

[0028] 1. Compared with traditional frequency conversion control and phase shift control, the present invention avoids the requirement of wireless communication between the primary and secondary sides, can directly use the voltage and current information of the load, improves the rapidity and reliability of system control, and reduces system cost;

[0029] 2. Compared with the traditional cascade DC-DC converter, the present invention avoids the requirement of multi-stage conversion and only relies on single-stage conversion. By adjusting the size of the variable inductor, constant current and constant voltage output can be achieved, which reduces the volume and cost of the system and has a simple structure.

[0030] 3. The switch tube of the primary full-bridge inverter circuit of the present invention can realize zero voltage switching in the entire working range, thereby reducing switching loss and making the system have higher efficiency;

[0031] 4. In the constant voltage mode of the present invention, the variable inductance only needs to change within a relatively small range to meet the requirement of a wide load variation range. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the circuit structure of the present invention;

[0033] Figure 2 It is a circuit schematic diagram of the present invention;

[0034] Figure 3 is a schematic diagram of the variable inductor structure of the present invention;

[0035] Figure 4 It is the fundamental wave equivalent circuit diagram of the present invention;

[0036] Figure 5 It is a relationship curve between the variable inductor matching load resistance and the change of coil mutual inductance in the present invention;

[0037] Figure 6 It is the variable inductance curve of the present invention under different load resistance values ​​when the coil mutual inductance is 32μH;

[0038] Figure 7 The output voltage and output current curves of the present invention under different load resistance values ​​when the coil mutual inductance is 32μH;

[0039] Figure 8 It is the variable inductance curve of the present invention under different coil mutual inductances when the load resistance is 43Ω.

[0040] The symbols in the above figures are as follows: A, B, a, b are the midpoints of the bridge arms; U in is a DC source; S1, S2, S3, S4 are the first, second, third, and fourth switch tubes respectively; L1 is the primary compensation inductor; C1 and C P They are the primary parallel compensation capacitor and the primary series compensation capacitor respectively; L P is the primary transmitting coil; L S is the receiving coil; M is the mutual inductance between coils; L x is the variable inductor; C S and C2 are the secondary side series compensation capacitor and the secondary side parallel compensation capacitor; L2 is the secondary side compensation inductor; D1, D2, D3, and D4 are the first, second, third, and fourth diodes respectively; C o is the output filter capacitor; R o is the load; u AB and u ab is the AC input voltage and AC output voltage of the system; i L1 、i LP 、i LS 、i L2 They are AC input current, transmitting coil current, receiving coil current, and AC output current respectively; I o and U o are DC output current and DC output voltage respectively; and They are the fundamental components of the AC input voltage and the AC output voltage respectively; are the fundamental components of AC input current, transmitting coil current, receiving coil current, and AC output current respectively; R acN is the equivalent AC load converted to the AC side; ac and N dc They are the main power inductor winding and the DC bias control winding respectively; Φ ac and Φ dc are the main power AC flux and DC bias flux respectively; I dc is the DC bias current. DETAILED DESCRIPTION

[0041] The present invention is further described in detail below in conjunction with embodiments:

[0042] Example 1

[0043] The following describes the first embodiment of the present invention in detail with reference to the accompanying drawings.

[0044] like Figure 1 As shown, a wireless charging device without communication and cascade DC-DC converter includes a DC source, a square wave generator, a primary side LCC compensation network, a transmitting coil, a receiving coil, a secondary side variable parameter LCC compensation network, a rectifier filter circuit and a load; the output end of the DC source is connected to the input end of the square wave generator; the output end of the square wave generator is connected to the input end of the primary side compensation network; the output end of the primary side compensation network is connected to the transmitting coil; the receiving coil is connected to the input end of the secondary side variable parameter compensation network, and the secondary side variable parameter compensation network includes a variable inductor and a conventional compensation network; the output end of the secondary side variable parameter compensation network is connected to the input end of the rectifier filter circuit; the output end of the rectifier filter circuit is connected to the load.

[0045] like Figure 2 As shown, the square wave generator adopts a full-bridge inverter circuit, the duty cycle of the full-bridge inverter circuit is a fixed value of 50%, including a first switch tube S1, a second switch tube S2, a third switch tube S3, and a fourth switch tube S4, the drain of the first switch tube S1 is connected to the drain of the third switch tube S3, the source of the first switch tube S1 is connected to the drain of the second switch tube S2, the source of the third switch tube S3 is connected to the drain of the fourth switch tube S4, and the source of the second switch tube S2 is connected to the source of the fourth switch tube S4.

[0046] The primary LCC compensation network includes a primary compensation inductor L1, a primary parallel compensation capacitor C1, and a primary series compensation capacitor C P One end of the primary compensation inductor L1 is connected to the source of the first switch tube S1 and the drain of the second switch tube S2; the other end of the primary compensation inductor L1 is connected to one end of the primary parallel compensation capacitor C1 and the primary series compensation capacitor C PThe other end of the primary parallel compensation capacitor C1 is connected to the source of the third switch tube S3, the drain of the fourth switch tube S4 and the transmitting coil L P One end of the primary side series compensation capacitor C P The other end is connected to the transmitting coil L P the other end.

[0047] The transmitting coil L P and the receiving coil L S There is no direct electrical connection between the two coils. Energy is transferred through magnetic field coupling. The magnitude of the magnetic field coupling between the coils is represented by the mutual inductance M.

[0048] The secondary side variable parameter LCC compensation network includes a variable inductor L x and a secondary side LCC compensation network; the secondary side LCC compensation network includes a secondary side series compensation capacitor C S , secondary side parallel compensation capacitor C2, secondary side compensation inductor L2; the variable inductor L x One end is connected to the receiving coil L S One end of the variable inductor L x The other end is connected to the secondary side series compensation capacitor C S The secondary side is connected in series with a compensation capacitor C S The other end of the secondary side parallel compensation capacitor C2 is connected to one end of the secondary side compensation inductor L2; the other end of the secondary side parallel compensation capacitor C2 is connected to the receiving coil L S the other end.

[0049] The rectifier and filter circuit includes a rectifier circuit and an output filter capacitor C o The rectifier circuit includes a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4; the anode of the first diode D1 and the cathode of the second diode D2 are connected to the other end of the secondary compensation inductor L2; the cathode of the first diode D1 is connected to the cathode of the third diode D3, the output filter capacitor C o One end and load R o The anode of the third diode D3 and the cathode of the fourth diode D4 are connected to the other end of the secondary parallel compensation capacitor C2; the anode of the fourth diode D4 is connected to the anode of the second diode D2, the output filter capacitor C o The other end and the load R o the other end.

[0050] The inductance values ​​of the primary compensation inductor L1 and the secondary compensation inductor L2 are equal; the capacitance values ​​of the primary parallel compensation capacitor C1 and the secondary parallel compensation capacitor C2 are equal; the primary series compensation capacitor C P And the secondary side series compensation capacitor CS The capacitance values ​​of the transmitting coil L are equal; P and the receiving coil L S The self-inductance values ​​are equal.

[0051] like Figure 3 As shown, the magnetically controlled variable inductor includes two E-type magnetic cores, a main power inductor winding N ac , DC bias control winding N dc , DC bias power supply; the two E-type core openings are placed opposite to each other, the middle column has a certain size of air gap, and the two side columns have no air gap; the main power inductor winding N ac It is wound on a central column with an air gap, one end of which is connected to the receiving coil L S One end of the secondary side is connected to the series compensation capacitor C S One end of the DC bias control winding N dc Wound on the side column, one group on each side column, two groups of DC bias control winding N dc The winding direction and number of turns are exactly the same; the two sets of DC bias control windings N dc One end of each is connected to each other, and the other end is connected to the two ends of the DC bias power supply; the DC bias power supply can be implemented by a buck circuit or an operational amplifier circuit. When the current I dc gradually increases, the variable inductance L x The inductance value will gradually decrease.

[0052] The switching frequencies of the first, second, third and fourth switch tubes S1, S2, S3 and S4 are equal, the switching signals of the first switch tube S1 and the third switch tube S3 are complementary to the switching signals of the second switch tube S2 and the fourth switch tube S4, respectively, and the duty ratios are all 0.5, the first switch tube S1 and the fourth switch tube S4 are turned on and turned off at the same time, and the second switch tube S2 and the third switch tube S3 are turned on and turned off at the same time; in specific implementation, a reasonable dead time must be set between the switching signals of the first switch tube S1 and the second switch tube S2 to avoid the occurrence of bridge arm direct conduction, and a reasonable dead time must be set between the switching signals of the third switch tube S3 and the fourth switch tube S4 to avoid the occurrence of bridge arm direct conduction; the switching frequencies of the first, second, third and fourth switch tubes S1, S2, S3 and S4 are fixed values ​​during operation, and are equal to the inherent resonant frequencies of the primary and secondary LCC compensation networks, satisfying:

[0053]

[0054] Wherein, f is the switching frequency of the first, second, third and fourth switch tubes S1, S2, S3 and S4.

[0055] Figure 4This is the fundamental wave equivalent circuit diagram of the embodiment 1 of the wireless charging device without communication and cascaded DC-DC converter of the present invention. The following assumptions are made before analysis: (1) the system is in a stable operating state; (2) all components in the system are ideal components, and the influence of parasitic impedance is ignored; (3) only the AC fundamental wave component in the circuit is considered, and the influence of higher harmonics is ignored.

[0056] according to Figure 2 and Figure 4 The fundamental wave analysis method can be used to obtain the DC transconductance gain and DC voltage gain as follows:

[0057]

[0058]

[0059] From the DC transconductance gain and DC voltage gain of Example 1, we can see that there are only three independent variables in the formula, namely, the coil mutual inductance M, the load resistance R o , variable inductance L x , when the coil mutual inductance M or the load resistance R o When the variable inductance L changes, it is necessary to adjust x The value is used to match the coil mutual inductance M or load resistance R o The change of can ensure the stability of DC transconductance gain and DC voltage gain.

[0060] According to the DC transconductance gain expression, the variable inductance L in the constant current stage can be obtained: x The matching formula is:

[0061]

[0062] According to the DC voltage gain expression, the variable inductance L in the constant voltage stage can be obtained: x The matching formula is:

[0063]

[0064] Preferably, the wireless charging device embodiment 1 without communication and cascaded DC-DC converters proposed in the present invention has two working modes, namely, constant current mode and constant voltage mode; in the constant current mode, when the load resistance R o When the mutual inductance M of the coil changes, the variable inductance L only needs to be adjusted according to the constant current stage. x The matching formula adjusts the variable inductance L x , constant current output can be achieved; in the constant voltage mode, when the load resistance R o When the mutual inductance M of the coil changes, the variable inductance L in the constant voltage stage x The matching formula adjusts the variable inductance L x, constant voltage output can be achieved; in the constant current mode and constant voltage mode, the variable inductor L x The regulation adopts closed-loop control, which can directly apply the load R o The voltage U o 、Current I o The variable inductor L is adjusted in each mode through the current loop and the voltage loop. x The inductance value is adjusted so that it changes according to the matching formula of the constant current stage and the constant voltage stage to achieve constant current and constant voltage output.

[0065] according to Figure 4 , the system input impedance expression of this embodiment can be obtained as:

[0066]

[0067] It can be seen from the system input impedance expression that in the entire working range, the input impedance of the system is inductive, so in the entire working range, all switching devices can achieve zero voltage turn-on.

[0068] In this embodiment, the relevant circuit parameters are: DC source U in =400V; the switching frequency of the first, second, third and fourth switch tubes S1, S2, S3 and S4 is f=85kHz; the inductance of the primary compensation inductor L1 and the secondary compensation inductor L2 are equal, which is 38μH; the capacitance of the primary parallel compensation capacitor C1 and the secondary parallel compensation capacitor C2 are equal, which is 92nF; the primary series compensation capacitor C P And the secondary side series compensation capacitor C S The capacitance value of the transmitting coil L is equal to 24nF; P and receiving coil L S The self-inductance value is equal to 183μH; the mutual inductance M between the coils is 23μH~32μH; in the constant current stage, the output current I o =7.5A, output voltage U o 250V~400V, load resistance R o The range of change is: 33.3Ω~53.3Ω; in the constant voltage stage, the output voltage U o =400V, output current I o 0.75A~7.5A, load resistance R o The range of variation is 53.3Ω~533Ω.

[0069] Figure 5 : is a curve showing the relationship between the load resistance value of the variable inductor and the change of the mutual inductance of the coil in the embodiment 1 of the wireless charging device without communication and cascade DC-DC converter of the present invention; it can be seen from the figure that in the constant current stage, the variable inductor L x With the load resistance R oThe variable inductance L decreases monotonically with the increase of x With the load resistance R o It increases monotonically with the increase of. At the same time, it can be seen that in the constant voltage mode, the variable inductance L x Only a small change range is needed to meet the requirements of a wide load change range; for variable inductance L x In terms of the relationship between the coil mutual inductance M, it can be seen that as the coil mutual inductance M increases, the variable inductance L x The larger the value that needs to be matched.

[0070] According to the simulation, the variable inductance L can be obtained x Matching different load resistance R o Inductance value when the mutual inductance M of the coil is Figure 6 The variable inductance curves of Example 1 of the wireless charging device without communication and cascaded DC-DC converters of the present invention under different load resistance values ​​when the coil mutual inductance is 32 μH are given; Figure 7 The output voltage and output current curves of Example 1 of the wireless charging device without communication and cascaded DC-DC converters of the present invention under different load resistance values ​​when the coil mutual inductance is 32 μH are given; Figure 6 and Figure 7 In the figure, the load resistance values ​​are 33.3Ω, 43Ω, 53.3Ω, 64Ω, 80Ω, 120Ω, and 160Ω. As can be seen from the figure, by adjusting the variable inductor L x The value of constant current stage output current I o Maintain 7.5A unchanged, the output voltage U in the constant voltage stage o Maintaining 400V unchanged, the system achieves constant current and constant voltage output.

[0071] Figure 8 The variable inductance curves of Example 1 of the wireless charging device without communication and cascaded DC-DC converter of the present invention under different coil mutual inductances when the load resistance is 43Ω; Figure 8 In the figure, the mutual inductance M of the coil is 32μH, 29μH, 26μH, and 23μH. As can be seen from the figure, when the load resistance R o When the inductance M of the coils is constant, the variable inductance value required to be matched becomes smaller as the mutual inductance M of the coils gradually decreases.

Claims

1. A wireless charging device without communication and cascaded DC-DC converters, characterized in that: It includes a DC source, a square wave generator, a primary side LCC compensation network, a transmitting coil, a receiving coil, a secondary side variable parameter LCC compensation network, a rectifier filter circuit and a load; the output end of the DC source is connected to the input end of the square wave generator; the output end of the square wave generator is connected to the input end of the primary side LCC compensation network; the output end of the primary side LCC compensation network is connected to the transmitting coil; the receiving coil is connected to the input end of the secondary side variable parameter compensation network, and the secondary side variable parameter compensation network includes a variable inductor and a conventional compensation network; the output end of the secondary side variable parameter compensation network is connected to the input end of the rectifier filter circuit; the output end of the rectifier filter circuit is connected to the load; The primary LCC compensation network includes a primary compensation inductor L1, a primary parallel compensation capacitor C1, and a primary series compensation capacitor C P One end of the primary compensation inductor L1 is connected to the source of the first switch tube S1 and the drain of the second switch tube S2; the other end of the primary compensation inductor L1 is connected to one end of the primary parallel compensation capacitor C1 and the primary series compensation capacitor C P The other end of the primary parallel compensation capacitor C1 is connected to the source of the third switch tube S3, the drain of the fourth switch tube S4 and the transmitting coil L P One end of the primary side series compensation capacitor C P The other end is connected to the transmitting coil L P The other end of the transmitting coil L P With receiving coil L S Energy is transferred between them through magnetic field coupling, and the magnitude of magnetic field coupling between coils is represented by mutual inductance M. The secondary side variable parameter LCC compensation network includes a variable inductor L x and a secondary side LCC compensation network; the secondary side LCC compensation network includes a secondary side series compensation capacitor C S , secondary side parallel compensation capacitor C2, secondary side compensation inductor L2; the variable inductor L x One end is connected to the receiving coil L S One end of the variable inductor L x The other end is connected to the secondary side series compensation capacitor C S The secondary side is connected in series with a compensation capacitor C S The other end of the secondary side parallel compensation capacitor C2 is connected to one end of the secondary side compensation inductor L2; the other end of the secondary side parallel compensation capacitor C2 is connected to the receiving coil L S The other end of The variable inductor has two working modes, namely constant current mode and constant voltage mode. In the constant current mode, the DC transconductance gain expression is: According to the DC transconductance gain expression, the variable inductance L in the constant current stage is obtained: x The matching formula is: In constant voltage mode, the DC voltage gain expression is: According to the DC voltage gain expression, the variable inductance L in the constant voltage stage can be obtained: x The matching formula is: Among them, R o is the load, M is the mutual inductance of the coil, I o is the current, R ac is the equivalent AC load converted to the AC side, U in is a DC source, U o For load R o The DC output voltage.

2. A wireless charging device without communication and cascaded DC-DC converters according to claim 1, characterized in that: The square wave generator adopts a full-bridge inverter circuit, the duty cycle of the full-bridge inverter circuit is a fixed value of 50%, and includes a first switch tube S1, a second switch tube S2, a third switch tube S3, and a fourth switch tube S4. The drain of the first switch tube S1 is connected to the drain of the third switch tube S3, the source of the first switch tube S1 is connected to the drain of the second switch tube S2, the source of the third switch tube S3 is connected to the drain of the fourth switch tube S4, and the source of the second switch tube S2 is connected to the source of the fourth switch tube S4.

3. A wireless charging device without communication and cascaded DC-DC converters according to claim 1, characterized in that: The variable inductor L x It includes two E-type magnetic cores, the main power inductor winding N ac , DC bias control winding N dc , DC bias power supply; the two E-type core openings are placed opposite to each other, the middle column has a certain size of air gap, and the two side columns have no air gap; the main power inductor winding N ac It is wound on a central column with an air gap, one end of which is connected to the receiving coil L S One end of the secondary side is connected to the series compensation capacitor C S One end of the DC bias control winding N dc Wound on the side column, one group on each side column, two groups of DC bias control winding N dc The winding direction and number of turns are exactly the same; the two sets of DC bias control windings N dc One end of each is connected to each other, and the other end is connected to the two ends of the DC bias power supply; the DC bias power supply is implemented by a buck circuit or an operational amplifier circuit. When the current I dc gradually increases, the variable inductance L x The inductance value gradually decreases.

4. A wireless charging device without communication and cascaded DC-DC converters according to claim 2, characterized in that: The rectifier and filter circuit includes a rectifier circuit and an output filter capacitor C o The rectifier circuit includes a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4; the anode of the first diode D1 and the cathode of the second diode D2 are connected to the other end of the secondary compensation inductor L2; the cathode of the first diode D1 is connected to the cathode of the third diode D3, the output filter capacitor C o One end and load R o The anode of the third diode D3 and the cathode of the fourth diode D4 are connected to the other end of the secondary parallel compensation capacitor C2; the anode of the fourth diode D4 is connected to the anode of the second diode D2, the output filter capacitor C o The other end and the load R o the other end.

5. A wireless charging device without communication and cascaded DC-DC converters according to claim 4, characterized in that: The switching frequencies of the first switch tube S1, the second switch tube S2, the third switch tube S3, and the fourth switch tube S4 are equal, the switching signals of the first switch tube S1 and the third switch tube S3 are complementary to the switching signals of the second switch tube S2 and the fourth switch tube S4, respectively, and the duty ratios are both 0.5, the first switch tube S1 and the fourth switch tube S4 are turned on and turned off at the same time, and the second switch tube S2 and the third switch tube S3 are turned on and turned off at the same time; the switching frequencies of the first switch tube S1, the second switch tube S2, the third switch tube S3, and the fourth switch tube S4 are fixed values ​​during operation, and are equal to the inherent resonant frequencies of the primary side LCC compensation network and the secondary side LCC compensation network, and satisfy the following formula: Wherein, f is the switching frequency of the first switch tube S1, the second switch tube S2, the third switch tube S3, and the fourth switch tube S4.

6. A wireless charging device without communication and cascaded DC-DC converters according to claim 1, characterized in that: In the constant current mode, when the load R o When the mutual inductance M of the coil changes, the variable inductance L in the constant current stage x The matching formula adjusts the variable inductance L x , realize constant current output; in the constant voltage mode, when the load resistance R o When the mutual inductance M of the coil changes, the variable inductance L in the constant voltage stage x The matching formula adjusts the variable inductance L x , to achieve constant voltage output; in the constant current mode and constant voltage mode, the variable inductor L x The regulation adopts closed-loop control, directly applying the load R o The voltage U o 、Current I o The variable inductor L is adjusted in each mode through the current loop and the voltage loop. x The inductance value is adjusted so that it changes according to the matching formula of the constant current stage and the constant voltage stage to achieve constant current and constant voltage output.

7. A wireless charging device without communication and cascaded DC-DC converters according to claim 6, characterized in that: The system input impedance expression of the wireless charging device is: In the entire working range, the input impedance of the system is inductive, and the first switch tube S1, the second switch tube S2, the third switch tube S3, and the fourth switch tube S4 are all turned on at zero voltage.

Images