A wireless power transmission system with ZCS operation and charging blocking oscillation

Abstract

The present invention belongs to the technical field of wireless power transmission, and specifically relates to a wireless power transmission system operating in a ZCS with charging and blocking oscillation, including a power supply, a transmitting end and a receiving end, wherein the transmitting end has a resonant capacitor and a transmitting coil, and the receiving end has a receiving coil; the transmitting end also includes: an equivalent resistor, which is connected in series with the transmitting coil and in parallel with the resonant capacitor to form an energizing and blocking oscillation circuit; and a control switch, which is connected in series with the energizing and blocking oscillation circuit and connected to both ends of the power supply. The present invention realizes self-oscillation by adopting energizing and blocking, and blocks the resonant cavity after energization, so that the energy is enclosed in a closed-loop resonant circuit, and the energy will oscillate. Compared with the traditional self-oscillating WPT based on negative resistance, the present invention has fewer switching devices and does not require any additional circuit design, so it has better cost and robustness.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless power transmission, and in particular relates to a wireless power transmission system operating in a ZCS mode with charging and blocking oscillation. Background Art

[0002] As a safe, convenient and efficient way of energy transmission, wireless power transfer (WPT) technology has achieved long-term development and has been valued by industry personnel and widely used in medical, automotive, drone, mobile phone and other fields.

[0003] The precise matching of the WPT operating frequency with the natural resonant frequency of the circuit is a prerequisite for efficient energy transmission of the system. However, affected by factors such as temperature, device tolerance, and charging distance, the resonant frequency will shift, which will deteriorate the system operation status. Therefore, how to make the WPT operating frequency track the resonant frequency is the focus of research in WPT.

[0004] The operating frequency of traditional WPT is determined by the external driving signal of the inverter. Since the resonant state is changeable and difficult to detect, the traditional method requires a large number of auxiliary circuits and measurement controls to achieve resonant tracking operation, which creates bottlenecks in control accuracy, real-time performance and robustness.

[0005] As a physical phenomenon, resonance can occur not only through external AC energy drive, but also through self-oscillation. As a way of energy transmission for WPT, resonance can also transmit energy through self-oscillation. The operating frequency of self-oscillating WPT is only determined by the resonance parameters, and is approximately equal to the natural resonance frequency, which greatly improves the bottleneck of traditional WPT in resonance tracking operation.

[0006] There are many ways to achieve self-oscillating WPT. As shown in Figure 1(a), Tesla used a transformer to generate high voltage to break through the air gap to create a resonant loop, which is actually a primitive self-oscillating WPT. Due to the limitations of device manufacturing and power electronics technology at the time, and the huge loss caused by breaking through the air gap, this self-oscillation method is no longer of application value today. As shown in Figure 1(b), constructing a resonant loop by converting an AC source into a negative resistance is another way to achieve self-oscillating WPT. Using the nonlinear parity model constructed by negative resistance, WPT achieves stable power transmission with high and constant transmission efficiency under the condition of dynamic changes in coupling. Although negative resistance can achieve self-oscillating WPT, the design of negative resistance circuits is very complicated, which not only increases the cost but also reduces the robustness of the system. Summary of the invention

[0007] The present invention aims to solve the technical problem that the traditional method in the prior art requires a large number of auxiliary circuits and measurement controls to achieve resonance tracking, which not only increases the cost but also reduces the real-time performance and robustness. The present invention aims to provide a wireless power transmission system with ZCS operation for charging and blocking oscillation.

[0008] In order to solve the aforementioned technical problems, one aspect of the present invention provides a wireless power transmission system for ZCS operation with charging blocking oscillation, including a power supply, a transmitting end and a receiving end, wherein the transmitting end has a resonant capacitor and a transmitting coil, and the receiving end has a receiving coil, wherein the receiving coil generates a magnetic field coupling with the transmitting coil;

[0009] The transmitting end also includes:

[0010] an equivalent resistor, which is connected in series with the transmitting coil and then in parallel with the resonant capacitor to form an energy-charging and blocking oscillation circuit;

[0011] A control switch is connected in series with the charging blocking oscillation circuit and then connected to two ends of the power supply.

[0012] Optionally, in the wireless power transmission system operating in a ZCS with charging blocking oscillation as described above, when the control switch is controlled to be turned on, the transmitting end is in a charging stage, and the transmitting end is connected to the power supply and charged;

[0013] When the control switch is controlled to be disconnected, the transmitting end is in the self-oscillation stage, the transmitting end forms a blockage, there is energy oscillation between the transmitting coil and the resonant capacitor, and the receiving coil of the receiving end obtains energy to realize wireless power transmission.

[0014] Optionally, in the wireless power transmission system operating in a ZCS mode with charging and blocking oscillation as described above, the control switch is arranged between the positive electrode of the power supply and the charging and blocking oscillation circuit.

[0015] Optionally, in the wireless power transmission system operating in a ZCS with charging and blocking oscillation as described above, the transmitting end further includes:

[0016] A buffer filter inductor is connected in series with the energy-charging blocking oscillator circuit, and the buffer filter inductor is arranged between the negative electrode of the power supply and the energy-charging blocking oscillator circuit.

[0017] Optionally, in the wireless power transmission system operating in ZCS with charging and blocking oscillation as described above, the buffer filter inductor is selected to be 15nH to 15uH, preferably 1.5uH.

[0018] Optionally, in the wireless power transmission system operating in a ZCS mode with charging and blocking oscillation as described above, it is assumed that the transmitting coil has a first voltage detection terminal near the control switch, and a second voltage detection terminal is provided between the control switch and the power supply;

[0019] If the voltage at the first voltage detection terminal reaches a preset maximum value, turning on the control switch;

[0020] If the energy of the second voltage detection terminal reaches a preset minimum value, the control switch is disconnected.

[0021] Optionally, in the wireless power transmission system operating in a ZCS with charging and blocking oscillation as described above, the wireless power transmission system operating in a ZCS with charging and blocking oscillation further includes a control circuit, and the control circuit includes:

[0022] a controller connected to a driving end of the control switch;

[0023] a first detection circuit, wherein an input end of the first detection circuit is connected to the first voltage detection end, the first detection circuit is used to detect the voltage of the first voltage detection end, and an output end of the first detection circuit is connected to the signal input end of the controller;

[0024] a second detection circuit, wherein an input end of the second detection circuit is connected to the second voltage detection end, the second detection circuit is used to detect energy at the second voltage detection end, and an output end of the second detection circuit is connected to a signal input end of the controller;

[0025] Initially, the controller outputs an initial control signal to the control switch to start oscillation, the controller obtains the voltage of the first voltage detection end through the first detection circuit and determines whether to turn on the control switch, and the controller obtains the energy of the second voltage detection end through the second detection circuit and determines whether to turn off the control switch.

[0026] Optionally, in the wireless power transmission system operating in a ZCS manner with charging and blocking oscillation as described above, the first detection circuit uses a bandpass filter circuit to perform voltage detection.

[0027] Optionally, in the wireless power transmission system operating in a ZCS manner with charging and blocking oscillation as described above, the second detection circuit uses a diode energy storage circuit to perform pulse energy detection.

[0028] Optionally, in the wireless power transmission system operating in a ZCS with charging and blocking oscillation as described above, the first detection circuit includes:

[0029] a first operational amplifier, wherein an inverting input terminal of the first operational amplifier is connected to an input terminal of the first detection circuit via a first capacitor and a first resistor in sequence, a non-inverting input terminal of the first operational amplifier is connected to an output terminal of the first operational amplifier via a second resistor, the non-inverting input terminal of the first operational amplifier is also grounded via a third resistor, and an output terminal of the first operational amplifier is an output terminal of the first detection circuit;

[0030] A common end of the first capacitor and the first resistor is connected to the output end of the first operational amplifier via a fourth resistor, a common end of the first capacitor and the first resistor is grounded via a second capacitor, and a common end of the first capacitor and the inverting input end of the first operational amplifier is grounded via a fifth resistor.

[0031] Optionally, in the wireless power transmission system operating in a ZCS mode with charging and blocking oscillation as described above, the second detection circuit includes:

[0032] a second operational amplifier, wherein the inverting input terminal of the second operational amplifier is grounded via a sixth resistor, the inverting input terminal of the second operational amplifier is also connected to the output terminal of the second operational amplifier via a seventh resistor, the inverting input terminal of the second operational amplifier is also connected to the output terminal of the second operational amplifier via a third capacitor, the non-inverting input terminal of the second operational amplifier is grounded via a bidirectional voltage regulator, an eighth resistor, and a fourth capacitor respectively, the non-inverting input terminal of the second operational amplifier is also connected to the cathode of a diode, and the output terminal of the second operational amplifier is connected to the output terminal of the second detection circuit via a ninth resistor;

[0033] The anode of the diode is connected to the input end of the second detection circuit via the fifth capacitor, and the output end of the second detection circuit is grounded via the sixth capacitor.

[0034] Optionally, in the wireless power transmission system operating in ZCS with charging and blocking oscillation as described above, the control switch uses a pair of MOS tubes connected in reverse series to perform charging and energy blocking functions.

[0035] Optionally, in the wireless power transmission system operating in a ZCS mode with charging and blocking oscillation as described above, the control switch includes:

[0036] a first MOS transistor, wherein a gate of the first MOS transistor is connected to the controller as a driving end, and a drain of the first MOS transistor is connected to the positive electrode of the power supply;

[0037] A second MOS tube, wherein the gate of the second MOS tube is connected to the controller as a driving end, the drain of the second MOS tube is connected to one end of the charging blocking oscillation circuit, and the source of the second MOS tube is connected to the source of the first MOS tube.

[0038] The positive and progressive effects of the present invention are:

[0039] 1. The wireless power transmission system of the present invention realizes self-oscillation by adopting charging blocking. By blocking the charged resonant cavity, the energy is confined inside the closed-loop resonant circuit, and the energy will oscillate. Compared with the traditional self-oscillating WPT based on negative resistance, the present invention has fewer switching devices and does not require any additional circuit design, so it has better cost and robustness.

[0040] 2. By adding buffer filter inductance to the system, the impact current when the control switch is turned on can be resolved, and the control switch can be turned on with zero current.

[0041] 3. The present invention realizes effective control of the control switch by detecting the voltage of the first voltage detection terminal and the voltage of the second voltage detection terminal, thereby obtaining an optimal charging cycle and optimizing the operating efficiency of ZCS (zero-current switching). BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The disclosure of the present invention will become more apparent with reference to the accompanying drawings. It should be understood that these drawings are only for illustrative purposes and are not intended to limit the scope of protection of the present invention. In the drawings:

[0043] Figure 1(a) is a circuit diagram proposed by Tesla to achieve self-oscillation WPT by breaking down the spark gap with high voltage;

[0044] FIG1( b ) is a circuit diagram of a prior art method for realizing a self-oscillating WPT by using a negative resistance equivalent;

[0045] FIG2( a ) is a circuit diagram of the present invention when the control switch is turned on;

[0046] FIG2( b ) is a circuit diagram of the present invention when the control switch is disconnected;

[0047] FIG3( a ) is a diagram showing an ideal current waveform of a WPT transmitting coil during charging blocking oscillation of the present invention;

[0048] FIG3( b ) is an equivalent circuit of the oscillating energy transfer process based on energy blocking of the present invention;

[0049] FIG3( c ) is an equivalent circuit of the transmitting end based on energy blocking of the present invention;

[0050] FIG3( d ) is a schematic diagram of the splitting frequency and the true value of wo under different k during simulation of the present invention;

[0051] FIG3( e ) is a tracking error diagram of the present invention under different Q conditions;

[0052] FIG. 4( a) is another circuit diagram of the present invention;

[0053] FIG4(b) is a diagram showing the change of IC when three different buffer filter inductance parameters are selected in the circuit diagram of FIG4(a);

[0054] FIG4(c) is a schematic diagram of the circuit diagram of FIG4(a) with a high turn-off voltage on the control switch;

[0055] FIG5( a) is another circuit diagram of the present invention;

[0056] FIG5( b ) is a control block diagram of the circuit of FIG5( a );

[0057] FIG5(c) is a control waveform diagram of the circuit of FIG5(a);

[0058] Figure 6 A circuit diagram of a first detection circuit of the present invention;

[0059] Figure 7 is a circuit diagram of a second detection circuit of the present invention;

[0060] FIG8(a) is a waveform diagram of the experiment using the circuit of FIG5(a) with fixed parameter control;

[0061] FIG8(b) is a waveform diagram of ZCS control when the circuit of FIG5(a) is used for the experiment;

[0062] FIG9(a) is a diagram of the oscillation frequency of the transmitting coil under different couplings when the circuit of FIG5(a) is used for the experiment;

[0063] FIG9( b ) is a diagram showing the system efficiency at different spacings when the circuit of FIG5( a ) is used for the experiment. DETAILED DESCRIPTION

[0064] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0065] It should be noted that the following embodiments and features therein may be combined with each other if there is no conflict.

[0066] In the description of the present invention, it should be noted that directional words such as the terms "outside", "middle", "inside", "outside", etc., which indicate directions and positional relationships, are based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and cannot be understood as limiting the specific protection scope of the present invention.

[0067] In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features. Therefore, the definition of "first" and "second" features can explicitly or implicitly include one or more of the features. In the description of the present invention, "several" and "a number" mean two or more, unless otherwise clearly and specifically defined.

[0068] The embodiment of the present invention provides a wireless power transmission system for ZCS operation with charging and blocking oscillation, including a power source U IN , the transmitting end and the receiving end, the transmitting end has a resonant capacitor C P and the transmitting coil L P , the receiving end has a receiving coil L S , receiving coil L S With the transmitting coil L P Generate magnetic field coupling to achieve wireless power transmission.

[0069] Referring to Figure 2(a) and Figure 2(b), the transmitter also includes an equivalent resistor r P And control switch K. Equivalent resistance r P With the transmitting coil L P After connecting in series with the resonant capacitor C P The control switch K is connected in series with the charging blocking oscillator circuit and then connected to the power supply U. IN both ends of .

[0070] In some embodiments, referring to FIG. 2( a ), when the control switch K is turned on, the transmitter is in the charging stage (also called the charging stage), and the transmitter is connected to the power source U IN Connect and recharge.

[0071] Referring to Figure 2(b), when the control switch K is disconnected, the transmitter is in the self-oscillation stage, the transmitter forms a blockage, and the transmitting coil L P and resonant capacitor C P There is energy oscillation between the receiving coil L at the receiving end. S Harvest energy and realize wireless power transmission.

[0072] In some embodiments, the control switch K is disposed at the power source U INBetween the positive pole and the charging blocking oscillation circuit.

[0073] The present invention realizes a passive self-resonant WPT energy transmission method through the design shown in Figure 2 (a) and Figure 2 (b). The mutual relationship between the driving frequency and the operating frequency is isolated through the process of charging and blocking the oscillation, so that the operating frequency of the system is only related to the resonance parameters. Compared with the traditional design, the present invention does not require any additional circuits and measurement controls to achieve resonant operation, thereby having better cost advantages and system characteristics.

[0074] The working principle of the present invention is as follows:

[0075] 1. Charging stage:

[0076] Different from the undamped self-oscillation based on negative resistance shown in FIG1( b ), the present invention proposes a damped self-oscillation, which completes the continuous oscillation and energy transfer of the resonant cavity through frequency energy injection and blocking. The present invention includes two processes of charging and oscillating and one action of blocking.

[0077] As shown in Figure 2(a), when the control switch K is turned on, the transmitter and the power supply U IN Connected and charged, the input energy of the system is the resonant capacitor energy W C and the transmitting coil energy W L Composition, of which W C Stored in the resonant capacitor in the form of voltage W L Stored in the transmitting coil in the form of current WPT transfers energy through electromagnetic induction between coils, which means that L P The absolute value (uH level) is much larger than C P (nF level), so only W can be considered during the charging phase L .W L By the charging cut-off current I P,M Decision, I P,M It is also the transmitting coil L during system operation. P The maximum instantaneous current on

[0078] The following equation is the loop voltage equation during the charging phase: (All symbols in the equation correspond to those in Figure 2(a))

[0079]

[0080] Solving the above equation, we can get the charging time t on I P,M for:

[0081]

[0082] In order to reduce the equivalent resistance r P The loss on It can be converted into t on < <L P / r P . Then, Taylor expansion of equation (2) yields P for:

[0083]

[0084] W L Represents the input energy of each charging process system, which is related to the charging frequency f c Multiplying them together gives the system input power P IN As shown below:

[0085]

[0086] The above analysis ignores the influence of the receiving end, because when charging, i P The high-frequency current component is relatively small, which leads to L S The induced voltage generated on the circuit can be ignored. By using equations (3) and (4), we can establish t on 、f c with I P,M , P IN However, it is only valid when the initial state is zero, that is, the energy is consumed in each oscillation cycle. The actual full response analysis needs to add the zero input response of the oscillation process, and the conversion time between charging and oscillation has a great influence on the energy input and output and switching loss. In the application, mathematical simulation and waveform analysis can be used to further design f c With t on At the same time, the above analysis also ignores the equivalent resistance r of the transmitting coil P This is because in order to ensure efficiency, the charging time is very short. P It will not be very large, and it is loaded on the equivalent resistance r P The voltage on it is so small that it can be ignored.

[0087] 2. Self-oscillation stage:

[0088] As shown in Figure 2(b), after the circuit is charged, the control switch K is disconnected. At this time, the charging blocking oscillation circuit will block the energy in the resonant cavity. P It cannot be mutated, so the blocked i P Will continue to supply the resonant capacitor C P When the resonant capacitor C P When the voltage on the circuit reaches its maximum value, it will charge in the reverse direction, thus causing energy oscillation. PThe waveform is shown in Figure 3(a), where the current peak point I P,M That is the blocking moment.

[0089] The current in the oscillation is high frequency, and the receiving end cannot be ignored and will obtain energy. As in the traditional WPT analysis, as shown in Figure 3(b), the receiving end can be equivalent to the series reflection impedance Z on the transmitting coil. r , where Z s is the receiving end loop reactance (Z s =jwL S +1 / jwC S ). When analyzing a self-oscillating circuit, the following equations show the equations for a conventional symmetrical circuit constructed using negative resistance:

[0090]

[0091] Formula (5) shows the difference between the negative resistance and the present invention in terms of formula. -R The complex nonlinear characteristics make it difficult to use traditional circuit analysis methods, so the coupled mode theory model is usually used to analyze it.

[0092] Different from the existing methods, there is no negative resistance in the fourth-order equations constructed in this invention, so the characteristics can be analyzed directly by solving the circuit equations. Figure 3(c) shows the equivalent second-order LCR circuit of the transmitter during the oscillation process, where the equivalent inductance L O For L P With Z r The sum of the equivalent inductance and equivalent capacitance C O C P , equivalent resistance R O For r P With Z r The equivalent damping of . Their specific formula is as follows, then L O With C O The angular frequency w r The resonant angular frequency of the system

[0093]

[0094] Oscillation frequency w O Is it equal to the resonant frequency w r This is the key to whether the present invention can achieve self-oscillation resonance tracking. If we only study w O With w r The relationship can be first L O With R O As a quantitative analysis, this will simplify the calculation process. OThe actual value of and its relationship with the splitting frequency need to be O With R O Considered as a variable, this will be further studied in equations (16) and (17).

[0095] The loop current in Figure 3(c) Resistor voltage Inductor voltage Substituting them into the transmitter loop voltage equation in equation (5) yields the following linear constant coefficient second-order homogeneous differential equation:

[0096]

[0097] To solve the above differential equation, we can set u C =Ae pt Substituting into the characteristic equation, we can get:

[0098] L O C O p 2 +R O C O p+1=0(8)

[0099] Solving the above equation, we can get the characteristic root p:

[0100]

[0101] at this time,

[0102]

[0103] Since p has both positive and negative signs, u C It can be written as:

[0104]

[0105] The constants A1 and A2 in the above equation can be solved by substituting the initial oscillation conditions, as shown in the following equation:

[0106]

[0107] Assume that the initial oscillation voltage U int is zero, the initial oscillation current I int For I PM , solving the above formula yields:

[0108]

[0109] From the analysis of equations (9) and (10), we can see that when Q<0.5, u CIt has two unequal negative real roots. At this time, the circuit does not have high-frequency oscillation characteristics. When Q>0.5, the equation has a pair of conjugate complex roots with negative real parts. By combining these two conjugate complex roots, we can get u C for:

[0110]

[0111] Among them U PM is the initial oscillation voltage, which is also the maximum instantaneous voltage when the circuit is running. P,M The value of I P,M Charging the capacitor determines U P，M =I P，M / (wC O ).

[0112] Bundle Substituting into equation (13) we can get the oscillation stage i P :

[0113]

[0114] Through equations (8) and (9), we can get w O With w r The relationship is as follows:

[0115]

[0116] In WPT, since |L|>>|C|, Q>>0.5. Formula (15) shows that the oscillation frequency of the coil current is approximately equal to the resonant frequency. So far, the feasibility of the proposed system in resonant tracking has been theoretically verified. At the same time, since w O It is only related to the resonance parameters, so compared with the traditional method, the present invention does not require any additional circuits and controls.

[0117] The above is based on L O With R O For quantitative analysis, in order to further study w O , Substituting formula (5) into formula (15) we can get w O The actual value is:

[0118]

[0119] By simulating the above formula, we can get w under different k as shown in Figure 3(d). O The actual value of . At the same time, Figure 3(d) also shows the splitting frequency of the system, which uses the following simulation formula:

[0120]

[0121] at this time,

[0122] Compare w O With w ± It can be seen that their error is 0.96%, which is mainly caused by Q. The error can be further reduced by increasing the Q value, which is shown and confirmed in Figure 3(e). It can also be seen from Figure 3(e) that the error increases with the increase of coupling, because the increase of the reflected impedance equivalent resistance is greater than the equivalent reactance.

[0123] Table 1 below shows the difference between the method for realizing self-oscillation WPT by negative resistance equivalent (referred to as negative resistance method) shown in FIG. 1( b ) and the method of the present invention (referred to as charging blocking oscillation method):

[0124] Table 1

[0125]

[0126]

[0127] In some embodiments, referring to FIG. 4( a ), the transmitter further includes a buffer filter inductor L f , buffer filter inductor L f Connected in series with the charging blocking oscillation circuit, buffer filter inductor L f Set on power supply U IN Between the negative pole and the charging blocking oscillation circuit.

[0128] In actual operation, the circuits of FIG. 2(a) and FIG. 2(b) are operated by the power supply U IN With the resonant capacitor C P It is directly connected. When the control switch K is turned on to start charging, there will be a large impact current, which will cause loss and device damage. In order to alleviate the impact current when the switch tube is turned on, a buffer filter inductor L needs to be connected in series on the power bus. f , achieving the purpose of zero current start-up control switch, so that the present invention forms a ZCS control self-oscillation system.

[0129] In some embodiments, the buffer filter inductor L f Select 15nH to 15uH, preferably 1.5uH.

[0130] Buffer filter inductor L f The design can start with simulation and add buffer filter inductor L f The equivalent circuit equations are:

[0131]

[0132] Simulate the above formula, when simulating, L P =23μH; C P =47nf;rP =0.5Ω; L S =23μH; C S =47nf;r S =0.5Ω; R L =12.5Ω; k=0.3.

[0133] Simulating the above formula, we can get different L f Next C The changes are shown in Figure 4(b). f When it is relatively large (L f =15uH), L f With C P The resonant period is relatively long, because t on It's relatively small, so I C The oscillation cannot be completed in one charging cycle, so i C It is impossible to control it to zero. f When the voltage is relatively low (Lf = 15nH), i C Will oscillate at high frequency, although i C It will cross zero many times, but the rapid change speed makes it difficult to detect and control. f The selection principle should ensure that 1 to 2 oscillations are best within a charging time. The circuit experimental parameters of the present invention are designed based on L f Preferably 1.5uH.

[0134] As shown in Figure 4(c), although the buffer filter inductor L f It can solve the impact current when the control switch K is turned on, but when it is turned off, since the inductor current cannot change suddenly, this will load an extremely high turn-off pulse voltage u on the control switch K. off , which will also cause loss and device damage. off Mainly composed of buffer filter inductor L f With charging current i C Determine that it can be written as:

[0135]

[0136] Through the buffer filter inductor L f Design and charging time on Control Order C Zero is an effective way to solve the high turn-off voltage problem. f The actual WPT circuit in the charging stage C P Not only with L P Form a resonant circuit, also with L f Therefore, i under the resonance relationship C It is not monotonically increasing. fFlexible design and t on Accurate control can make the closing time i C is zero, thus solving the high turn-off voltage problem and achieving ZCS.

[0137] The present invention does not require any feedback control in realizing self-oscillation WPT through energy blocking. f The addition and charging time t on The control can achieve ZCS operation and optimize efficiency. However, the charging time t on Effective control requires accurate acquisition of i C The moment when is zero. Obtaining by real-time calculation of formula (18) is a feasible solution, but this will consume a lot of system computing resources. Therefore, the present invention also makes the following improvements:

[0138] In some embodiments, referring to FIG. 5( a ), the transmitting coil L P The side close to the control switch K has a first voltage detection terminal u p , suppose the control switch K and the power supply U IN There is a second voltage detection terminal u between off If the first voltage detection terminal u p When the voltage at the second voltage detection terminal u reaches the preset maximum value, the control switch K is turned on. off When the energy reaches the preset minimum value, the control switch K is disconnected.

[0139] For the start time of circuit charging, it is mainly related to the first voltage detection terminal u p When the first voltage detection terminal u p When the first voltage detection terminal u p When the current is at the highest value, the opposite is true. For the system, when the output power is constant, the smaller the current, the lower the main line loss and the higher the efficiency. Therefore, the system designed in this embodiment selects the first voltage detection terminal u p The highest value turns on charging.

[0140] In this embodiment, the second voltage detection terminal u is directly detected off The energy of C The zero-crossing moment. Since the second voltage detection terminal u off The value of is difficult to measure accurately. The system determines the value of the second voltage detection terminal u off energy to adjust. off When the energy is minimum, i C Crossing zero, the system outputs the optimal charging cycle.

[0141] In some embodiments, referring to FIG. 5( a ), the system of the present invention further includes a control circuit, which includes a controller (Control module), a first detection circuit and a second detection circuit (collectively referred to as Detection module).

[0142] The controller is connected to the driving end of the control switch K, and the controller is used to control the on or off of the control switch K. The input end of the first detection circuit is connected to the first voltage detection end u p The first detection circuit is used to detect the first voltage detection terminal u p The output end of the first detection circuit is connected to the signal input end of the controller. The input end of the second detection circuit is connected to the second voltage detection end u off The second detection circuit is used to detect the second voltage detection terminal u off The output end of the second detection circuit is connected to the signal input end of the controller.

[0143] 5(b) and 5(c), at the initial stage, the controller outputs an initial control signal to the control switch K to start oscillation, and the controller obtains the first voltage detection terminal u through the first detection circuit. p The voltage at the first voltage detection terminal u p When the voltage at the second voltage detection terminal u reaches the preset maximum value, the control switch K is turned on. The controller obtains the voltage at the second voltage detection terminal u through the second detection circuit. off energy and judge whether to disconnect the control switch K. off When the energy reaches the preset minimum value, the control switch K is disconnected.

[0144] In this embodiment, by detecting u p with u off Used to adjust the start time and charging cycle until u p The maximum instantaneous value and u off The energy is minimum. p The frequency and waveform are determined only by the resonance parameters and are not affected by energy blocking, so the start time control precedes the charging cycle control.

[0145] In some embodiments, the first detection circuit uses a bandpass filter circuit to perform voltage detection.

[0146] In some embodiments, reference Figure 6 The first detection circuit includes a first operational amplifier U1, a first capacitor C1, a second capacitor C2, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4 and a fifth resistor R5.

[0147] The inverting input terminal of the first operational amplifier U1 is connected to the input terminal of the first detection circuit via the first capacitor C1 and the first resistor R1 in sequence, the non-inverting input terminal of the first operational amplifier U1 is connected to the output terminal of the first operational amplifier U1 via the second resistor R2, the non-inverting input terminal of the first operational amplifier U1 is also grounded via the third resistor R3, and the output terminal of the first operational amplifier U1 is the output terminal of the first detection circuit. The common terminal of the first capacitor C1 and the first resistor R1 is connected to the output terminal of the first operational amplifier U1 via the fourth resistor R4, the common terminal of the first capacitor C1 and the first resistor R1 is grounded via the second capacitor C2, and the common terminal of the first capacitor C1 and the inverting input terminal of the first operational amplifier U1 is grounded via the fifth resistor R5.

[0148] In some embodiments, the second detection circuit uses a diode energy storage circuit to perform pulse energy detection.

[0149] In some embodiments, reference Figure 7 The second detection circuit includes a second operational amplifier U2, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a sixth capacitor C6, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a bidirectional voltage regulator D1 and a diode D2.

[0150] The inverting input terminal of the second operational amplifier U2 is grounded via the sixth resistor R6, the inverting input terminal of the second operational amplifier U2 is also connected to the output terminal of the second operational amplifier U2 via the seventh resistor R7, the inverting input terminal of the second operational amplifier U2 is also connected to the output terminal of the second operational amplifier U2 via the third capacitor C3, the non-inverting input terminal of the second operational amplifier U2 is grounded via the bidirectional voltage regulator D1, the non-inverting input terminal of the second operational amplifier U2 is grounded via the eighth resistor R8, the non-inverting input terminal of the second operational amplifier U2 is grounded via the fourth capacitor C4, the non-inverting input terminal of the second operational amplifier U2 is also connected to the cathode of the diode D2, and the output terminal of the second operational amplifier U2 is connected to the output terminal of the second detection circuit via the ninth resistor R9. The anode of the diode D2 is connected to the input terminal of the second detection circuit via the fifth capacitor C5, and the output terminal of the second detection circuit is grounded via the sixth capacitor C6.

[0151] In some embodiments, the first operational amplifier U1 and the second operational amplifier U2 are both NE5532 operational amplifiers.

[0152] In some embodiments, the control switch K uses a pair of MOS tubes connected in reverse series to perform charging and energy blocking functions.

[0153] In some embodiments, referring to FIG. 5( a ), the control switch K includes a first MOS transistor U3 and a second MOS transistor U4 .

[0154] The gate of the first MOS tube U3 is connected to the controller as a driving end, the drain of the first MOS tube U3 is connected to the positive electrode of the power supply UIN, and a second voltage detection terminal u is provided between the drain of the first MOS tube U3 and the positive electrode of the power supply UIN. off The gate of the second MOS tube U4 is connected to the controller as a driving end, the drain of the second MOS tube U4 is connected to one end of the charging blocking oscillation circuit, and the source of the second MOS tube U4 is connected to the source of the first MOS tube U3.

[0155] In some embodiments, the controller is of prior art, and the controller model is TMS320F28335 DSP, which has a main frequency of 150 MHz.

[0156] In some embodiments, the first MOS transistor U3 and the second MOS transistor U4 are configured according to the initial pulse voltage U during circuit oscillation. P,M The SIC with a withstand voltage of 1200V, model C2M0080120D, was selected.

[0157] In some embodiments, the first MOS transistor U3 and the second MOS transistor U4 are N-channel enhancement MOSFETs.

[0158] In some embodiments, referring to FIG. 5( a ), the rectifier at the receiving end adopts TI's UCC24624 half-bridge rectifier solution, which helps to reduce system losses.

[0159] Embodiment 1:

[0160] System circuit and control method adopt Figure 5(a) to Figure 7 , the system parameters are shown in Table 2 below:

[0161] Table 2

[0162] <![CDATA[L P ]]> <![CDATA[C P ]]> <![CDATA[r P ]]> <![CDATA[L f ]]> <![CDATA[R L ]]> 23uH 47nF 0.5Ω 1.5uH 12.5Ω <![CDATA[L S ]]> <![CDATA[C S ]]> <![CDATA[r S ]]> Uout MOSFET 23uH 47nF 0.5Ω 10v C2M0080120D

[0163] In Table 2, r P and r S FIG5(a) is not shown, and the setting is consistent with FIG2(a) and FIG2(b). Uout is the output voltage of the receiving end. MOSFET is the first MOS tube U3 and the second MOS tube U4.

[0164] The first operational amplifier U1 and the second operational amplifier U2 are both NE5532 operational amplifiers. The controller is a TMS320F28335 DSP with a main frequency of 150 MHz. The rectifier at the receiving end uses TI's UCC24624 half-bridge rectifier solution.

[0165] The control parameter can be defined as the start charging time t on The oscillation off time t offThe control parameters determine the state of the switch tube at the moment of switching, which greatly affects the switching loss. In order to verify the influence of the control parameters on the efficiency, the present invention also experiments with two sets of control parameter systems, namely fixed control parameters (t on =2.44us, t off =21.95us) and feedback control parameters under ZCS operation.

[0166] Figure 8(a) and Figure 8(b) are the experimental waveforms under the two control systems at a charging distance of 15 mm, showing the switch control signal and the transmitting coil voltage u respectively. P and the receiving coil voltage u S From the figure, we can find the frequency f under different parameters o are the same, both are 146KHz, which verifies the strong robustness of the present invention in achieving resonant operation. For fixed parameters, the initial oscillation voltage is not high, which is due to the filter capacitor at the output end. on Period buffer filter inductor L f With the resonant capacitor C P The resonance will cause high frequency oscillation and be transmitted to the receiving coil L S As for the waveform under ZCS control, the voltage at the switch switching point is very smooth, which also indicates its efficient working state.

[0167] Figure 9(a) shows the experimental oscillation frequency and simulation frequency of the coil at different distances. The experimental frequency uses the receiving coil L S The test data of the voltage on the upper side. Due to the change in inductance, the experimental frequency is lower than the simulation, so the figure also shows the simulation data after adding inductance correction. It can be seen from the figure that the oscillation frequency decreases as the coupling increases, which is in line with the law of SS topology resonant frequency operation. At the same time, it is found through calculation that under strong coupling, the frequency f o There are some deviations. After calculation, it is known that the error with the experimental frequency is about 0.5%. At this time, because Ro becomes larger under strong coupling, Q is reduced. The error can be further improved by increasing the Q value.

[0168] Figure 9(b) shows the experimental efficiency of the system at different spacings, and the fixed control parameter self-oscillation system, the traditional fixed frequency system and the ZCS controlled self-oscillation system are tested respectively. For the efficiency test, compared with the traditional fixed frequency system, the ZCS controlled self-oscillation system of the present invention maintains high efficiency under strong coupling, and the specific ZCS controlled self-oscillation system is shown in Table 3. The maximum efficiency of the WPT that realizes self-oscillation by charging and blocking oscillation of the present invention exceeds 90%, which shows that the proposed present invention has good prospects in application implementation.

[0169] Table 3

[0170]

[0171]

[0172] The present invention is described in detail above in conjunction with the embodiments of the accompanying drawings. A person skilled in the art can make various variations of the present invention according to the above description. Therefore, some details in the embodiments should not be construed as limiting the present invention, and the present invention shall be protected by the scope defined by the attached claims.

Claims

1. A wireless power transmission system with ZCS operation of charging blocking oscillation, comprising a power supply, a transmitting end and a receiving end, wherein the transmitting end has a resonant capacitor and a transmitting coil, and the receiving end has a receiving coil, wherein the receiving coil generates a magnetic field coupling with the transmitting coil; It is characterized in that The transmitting end also includes: an equivalent resistor, which is connected in series with the transmitting coil and then in parallel with the resonant capacitor to form an energy-charging and blocking oscillation circuit; a control switch, wherein the control switch is connected in series with the charging blocking oscillation circuit and then connected to both ends of the power supply, and the control switch is arranged between the positive electrode of the power supply and the charging blocking oscillation circuit; Assume that the transmitting coil has a first voltage detection terminal near the control switch, and assume that a second voltage detection terminal is provided between the control switch and the power supply; If the voltage at the first voltage detection terminal reaches a preset maximum value, turning on the control switch; If the energy of the second voltage detection terminal reaches a preset minimum value, the control switch is disconnected.

2. A wireless power transmission system with ZCS operation and charging blocking oscillation as claimed in claim 1, characterized in that: When the control switch is turned on, the transmitter is in a charging stage, and the transmitter is connected to the power supply and charged; When the control switch is controlled to be disconnected, the transmitting end is in the self-oscillation stage, the transmitting end forms a blockage, there is energy oscillation between the transmitting coil and the resonant capacitor, and the receiving coil of the receiving end obtains energy to realize wireless power transmission.

3. A wireless power transmission system with ZCS operation and charging blocking oscillation as claimed in claim 1 or 2, characterized in that: The transmitting end also includes: A buffer filter inductor is connected in series with the energy-charging blocking oscillator circuit, and the buffer filter inductor is arranged between the negative electrode of the power supply and the energy-charging blocking oscillator circuit.

4. A wireless power transmission system with ZCS operation and charging blocking oscillation as claimed in claim 3, characterized in that: The buffer filter inductor is selected from 15nH to 15uH.

5. A wireless power transmission system with ZCS operation and charging blocking oscillation as claimed in claim 4, characterized in that: The buffer filter inductor is selected to be 1.5uH.

6. A wireless power transmission system with ZCS operation and charging blocking oscillation as claimed in claim 1, characterized in that: The wireless power transmission system for ZCS operation with charging and blocking oscillation further includes a control circuit, wherein the control circuit includes: a controller connected to a driving end of the control switch; a first detection circuit, wherein an input end of the first detection circuit is connected to the first voltage detection end, the first detection circuit is used to detect the voltage of the first voltage detection end, and an output end of the first detection circuit is connected to the signal input end of the controller; a second detection circuit, wherein an input end of the second detection circuit is connected to the second voltage detection end, the second detection circuit is used to detect energy at the second voltage detection end, and an output end of the second detection circuit is connected to a signal input end of the controller; Initially, the controller outputs an initial control signal to the control switch to start oscillation, the controller obtains the voltage of the first voltage detection end through the first detection circuit and determines whether to turn on the control switch, and the controller obtains the energy of the second voltage detection end through the second detection circuit and determines whether to turn off the control switch.

7. A wireless power transmission system with ZCS operation and charging blocking oscillation as claimed in claim 6, characterized in that: The first detection circuit uses a bandpass filter circuit to perform voltage detection; And / or, the second detection circuit uses a diode energy storage circuit to perform pulse energy detection; And / or, the control switch uses a pair of MOS tubes connected in reverse series to perform charging and energy blocking functions.

8. A wireless power transmission system with ZCS operation and charging blocking oscillation as claimed in claim 6, characterized in that: The first detection circuit comprises: a first operational amplifier, wherein an inverting input terminal of the first operational amplifier is connected to an input terminal of the first detection circuit via a first capacitor and a first resistor in sequence, a non-inverting input terminal of the first operational amplifier is connected to an output terminal of the first operational amplifier via a second resistor, the non-inverting input terminal of the first operational amplifier is also grounded via a third resistor, and an output terminal of the first operational amplifier is an output terminal of the first detection circuit; A common end of the first capacitor and the first resistor is connected to the output end of the first operational amplifier via a fourth resistor, a common end of the first capacitor and the first resistor is grounded via a second capacitor, and a common end of the first capacitor and the inverting input end of the first operational amplifier is grounded via a fifth resistor.

9. A wireless power transmission system with ZCS operation and charging blocking oscillation as claimed in claim 6, characterized in that: The second detection circuit comprises: a second operational amplifier, wherein the inverting input terminal of the second operational amplifier is grounded via a sixth resistor, the inverting input terminal of the second operational amplifier is also connected to the output terminal of the second operational amplifier via a seventh resistor, the inverting input terminal of the second operational amplifier is also connected to the output terminal of the second operational amplifier via a third capacitor, the non-inverting input terminal of the second operational amplifier is grounded via a bidirectional voltage regulator, an eighth resistor, and a fourth capacitor respectively, the non-inverting input terminal of the second operational amplifier is also connected to the cathode of a diode, and the output terminal of the second operational amplifier is connected to the output terminal of the second detection circuit via a ninth resistor; The anode of the diode is connected to the input end of the second detection circuit via the fifth capacitor, and the output end of the second detection circuit is grounded via the sixth capacitor.

10. A wireless power transmission system with ZCS operation and charging blocking oscillation as claimed in claim 6, characterized in that: The control switch comprises: a first MOS transistor, wherein a gate of the first MOS transistor is connected to the controller as a driving end, and a drain of the first MOS transistor is connected to the positive electrode of the power supply; A second MOS tube, wherein the gate of the second MOS tube is connected to the controller as a driving end, the drain of the second MOS tube is connected to one end of the charging blocking oscillation circuit, and the source of the second MOS tube is connected to the source of the first MOS tube.

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