EC-WPT system for realizing constant-current and constant-voltage output switching

Abstract

The invention discloses an EC-WPT system for realizing constant-current and constant-voltage output switching. The EC-WPT system comprises a direct-current voltage power supply, a full-bridge inverter circuit, a primary side LC resonance network, a coupling mechanism, a secondary side resonance network, a full-bridge rectifier circuit, a filter capacitor and a load. According to the system, the secondary side resonance network is switched through the switch to realize constant current / constant voltage output under load change; when the secondary side resonance network is in an LC structure topology, the system works in a constant current mode, and when the secondary side resonance network is in an LCLCL structure topology, the system works in a constant voltage mode. According to the system provided by the invention, the working modes can be switched according to load requirements; the system does not need a complicated control circuit and algorithm, so that the complexity of the system is reduced; the system can work in a zero phase angle state in a constant current mode and a constant voltage mode, and the system efficiency is high. The method can be widely applied to the field of wireless power transmission.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wireless power transfer, in particular to an EC-WPT system for realizing constant current and constant voltage output switching. BACKGROUND

[0002] Wireless power transfer (WPT) technology realizes wireless transmission of electric energy through magnetic field, electric field, microwave, laser, ultrasonic wave and other carriers in a non-electric contact manner. Compared with magnetic coupling wireless power transfer technology, electric-field coupled wireless power transfer (EC-WPT) technology has the advantages of thin structure, low cost, small electromagnetic interference and small eddy current loss. In recent years, domestic scholars have carried out research on EC-WPT in the fields of electric vehicles, unmanned aerial vehicles, underwater power equipment and implantable medical devices, and have achieved certain results.

[0003] In practical applications, some power equipment needs a constant current source for power supply, such as the driving of LED; some power equipment needs a constant voltage source for power supply, such as the operation of a router; and some power equipment needs to switch between constant current mode and constant voltage mode in different operation stages, such as the charging process of a lithium battery which needs to be charged in constant current mode first and then in constant voltage mode. Therefore, realizing stable and controllable output characteristics is one of the important requirements of an EC-WPT system.

[0004] At present, the main method for realizing constant current or constant voltage output of an electric-field coupled wireless power transfer system is to adjust the working frequency of the system to realize the switching between constant current mode and constant voltage mode, but the system will generate large oscillation when the frequency is adjusted. SUMMARY

[0005] Therefore, in order to solve the technical problem that the switching between constant current mode and constant voltage mode in the existing electric-field coupled wireless power transfer system is mainly realized by changing the frequency, thereby generating large oscillation, the present application provides an EC-WPT system for realizing constant current and constant voltage output switching, which comprises a direct current voltage power supply, a full-bridge inverter circuit, a primary side LC resonance network, a coupling mechanism, a secondary side resonance network, a full-bridge rectifier circuit, a filter capacitor and a load. The system realizes constant current / constant voltage output under load change by switching the secondary side resonance network; when the secondary side resonance network is an LC structure topology, the system works in constant current mode; and when the secondary side resonance network is an LCLCL structure topology, the system works in constant voltage mode.

[0006] The primary-side LC resonant network includes a first inductor and a first capacitor, which are connected in series between the two output terminals of the full-bridge inverter circuit. The two ends of the first capacitor are connected to the first emitter plate and the second emitter plate of the coupling mechanism, respectively.

[0007] The secondary-side resonant network includes a second inductor, a third inductor, a fourth inductor, a second capacitor, a third capacitor, a first switch, and a second switch. The two ends of the second capacitor are respectively connected to the third receiving plate and the fourth receiving plate of the coupling mechanism. One end of the second inductor is connected to the third receiving plate, and the other end of the second inductor is connected to one end of the third inductor. The other end of the third inductor is connected to one end of the fourth inductor. The other end of the fourth inductor is connected to the positive output terminal of the secondary-side resonant network. The third capacitor is connected in series between the third inductor and the fourth inductor.

[0008] The first switch is connected in parallel across the three terminals of the third capacitor. One end of the second switch is connected to the common terminal of the third and fourth inductors, and the other end of the second switch is connected to the negative output terminal of the secondary resonant network.

[0009] When the first switch is closed and the second switch is open, the system operates in constant current mode; When the first switch is open and the second switch is closed, the system operates in constant voltage mode.

[0010] Based on the above solution, this invention provides an EC-WPT system for switching between constant current and constant voltage output, switching the operating mode according to load requirements. The system does not require complex control circuits and algorithms, reducing system complexity. The system can operate in zero phase angle (ZPA) mode in both constant current and constant voltage modes, resulting in high system efficiency. When the load requires constant current power, the first switch is closed and the second switch is open, suitable for applications such as LED driving. When the load requires constant voltage power, the first switch is open and the second switch is closed, suitable for applications such as router operation. Attached Figure Description

[0011] Figure 1 A topology diagram of an EC-WPT system with constant current / constant voltage output characteristics provided by the present invention; Figure 2 The equivalent circuit model diagram of the coupling mechanism provided by this invention; Figure 2 (a) is the equivalent model of a six-capacitor circuit. Figure 2 (b) is the equivalent Π model; Figure 3 Simplified circuit analysis diagram provided for this invention; Figure 3 (a) is the Π-type equivalent circuit diagram of the system. Figure 3 (b) is the T-type equivalent circuit diagram of the system; Figure 4The equivalent circuit diagram provided by the present invention when the first switch is closed and the second switch is open; Figure 5 The equivalent circuit diagram provided by the present invention when the first switch is open and the second switch is closed; Figure 6 The simulation waveforms of the inverter output voltage and current in constant current mode when the load resistance is 24Ω are provided for the present invention. Figure 7 The simulation waveforms of the inverter output voltage and current in constant voltage mode with a load resistance of 24Ω provided by the present invention; Figure 8 The simulation waveform of the system output current under load variation provided by this invention; Figure 9 The simulation waveform diagram of the system output voltage under load variation provided by this invention; Figure label: U dc 1. Input DC voltage source; Q1, first transistor; Q2, second transistor; Q3, third transistor; Q4, fourth transistor; L1, first inductor; C1, first capacitor; P1, first emitter plate; P2, second emitter plate; P3, third receiver plate; P4, fourth receiver plate; C2, second capacitor; L2, second inductor; L3, third inductor; C3, third capacitor; L4, fourth inductor; S1, first switch; S2, second switch; D1, first diode; D2, second diode; D3, third diode; D4, fourth diode; C f Filter capacitor; R L ,load. Detailed Implementation

[0012] The core of this invention is to propose an EC-WPT system with constant current / constant voltage output characteristics. According to the power supply requirements of the load, the operating mode is switched by switching the secondary resonant network to achieve constant current / constant voltage output under load changes.

[0013] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0014] It should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings. Unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0015] It should be understood that the term "system" as used in this application is used to distinguish a method of different components, elements, parts, sections, or assemblies at different levels. However, if other terms can achieve the same purpose, they can be replaced by other expressions.

[0016] As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "a," and / or "the" are not specifically singular and may include the plural. Generally, the terms "comprising" and "including" only indicate the inclusion of expressly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements. An element defined by the phrase "comprising an..." does not exclude the presence of other identical elements in the process, method, product, or apparatus that includes the element.

[0017] In the description of the embodiments of this application, "a plurality of" refers to two or more. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0018] Reference Figure 1 Here is a topology diagram of the invention system, which includes an input DC voltage source U. dc Full-bridge inverter circuit, primary-side LC resonant network, coupling mechanism, secondary-side resonant network, full-bridge rectifier circuit, filter capacitor C f Load R L .

[0019] Specifically, Q1-Q4 are four MOSFETs forming a full-bridge inverter circuit; the first inductor L1 and the first capacitor C1 form a primary-side LC resonant network; the first emitter plate P1, the second emitter plate P2, the third receiver plate P3, and the fourth receiver plate P4 form a coupling mechanism; the second capacitor C2, the second inductor L2, the third inductor L3, the third capacitor C3, and the fourth inductor L4 form a secondary-side resonant network; and D1-D4 are four diodes forming a full-bridge rectifier circuit.

[0020] The coupling mechanism consists of parallel four plates, with a coupling capacitor between every two plates, forming a total of six coupling capacitors. The equivalent model of these six capacitors is as follows: Figure 2 As shown in (a).

[0021] Specifically, C 13 and C 24 For the main coupling capacitance formed on the board, C 12 C 34 C 14 C 23The cross-coupling capacitance is formed by the edge effect.

[0022] To simplify the analysis of the coupling mechanism, the six-capacitor equivalent model is represented as a Π model, such as... Figure 2 As shown in (b).

[0023] Specifically, C m For mutual capacitance, C a and C b These are the primary self-capacitance and the secondary self-capacitance, respectively, and due to the symmetry of the parallel quadrupole, C a =C b And they satisfy the following relationship: Based on the fundamental frequency analysis method, the inverter output voltage can be expressed as U. in U in The effective value satisfies: The reflection resistance before rectification satisfies: Figure 3 (a) shows the Π-type equivalent circuit diagram of the system.

[0024] Specifically, C p1 and C p2 The following relationship must be satisfied: Figure 3 (b) shows the T-type equivalent circuit diagram of the system.

[0025] Specifically, C t1 C t2 and C n The following relationship must be satisfied: Figure 4 The diagram shown is the equivalent circuit diagram when the first switch S1 is closed and the second switch S2 is open.

[0026] Specifically, the system is operating in constant current mode at this time, and the inductor L1 = L 11 +L 12 L2=L 21 +L 22 Each component satisfies the following relationship: right Figure 4 By writing out the equations and solving them, the output current I in constant current mode can be obtained. cc and equivalent input impedance Z cc for: Analysis of the above equation shows that, in constant current mode, when the system input is a constant voltage source, the output current magnitude depends only on the inverter's operating angular frequency ω and the capacitor C. n It is related to the load resistance. At this time, the equivalent input impedance is a pure resistance, and the system operates in ZPA state.

[0027] Figure 5 The diagram shown is the equivalent circuit diagram when the first switch S1 is open and the second switch S2 is closed.

[0028] Specifically, the system is currently operating in constant voltage mode, with inductor L1 = L 11 +L 12 L2=L 21 +L 22 Each component satisfies the following relationship: right Figure 5 By writing out the equations and solving them, we can obtain the output voltage U in constant voltage mode. cv and equivalent input impedance Z cv for: Analysis of the above formula shows that, in constant voltage mode, when the system input is a constant voltage source, the output voltage magnitude is only related to the capacitor C. n It is related to C3, but not to the load resistance. At this time, the equivalent input impedance is a pure resistance, and the system can operate in ZPA state.

[0029] Figure 6 The figure shows the simulated waveforms of the inverter output voltage and current when the load resistance is 24Ω in constant current mode.

[0030] Specifically, in constant current mode, the inverter output voltage and current are basically in phase, and the system is basically in ZPA state.

[0031] Figure 7 The figure shows the simulated waveforms of the inverter output voltage and current when the load resistance is 24Ω in constant voltage mode.

[0032] Specifically, in constant voltage mode, the inverter output voltage and current are basically in phase, and the system is basically in ZPA state.

[0033] Figure 8 The figure shown is a simulated waveform of the system output current.

[0034] Specifically, during the time period 0-t3, the first switch S1 is closed and the second switch S2 is open, and the system operates in constant current mode. The initial load resistance in constant current mode is 18Ω. At time t1, the load resistance increases from 18Ω to 30Ω; at time t2, the load resistance decreases from 30Ω to 24Ω.Figure 8 It can be seen that in constant current mode, the system output current remains basically constant when the system load changes.

[0035] Figure 9 The figure shown is a simulated waveform of the system output voltage.

[0036] Specifically, at time t3, the first switch S1 opens and the second switch S2 closes, switching the system to constant voltage mode. At time t4, the load resistance increases from 24Ω to 40Ω; at time t5, the load resistance decreases from 40Ω to 30Ω. Figure 9 It can be seen that in constant voltage mode, the system output voltage remains basically constant when the system load changes.

[0037] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. An EC-WPT system for achieving constant current and constant voltage output switching, characterized in that, The circuit includes, in sequence, a DC voltage power supply, a full-bridge inverter circuit, a primary-side LC resonant network, a coupling mechanism, a secondary-side resonant network, a full-bridge rectifier circuit, a filter capacitor, and a load, wherein: The secondary-side resonant network is provided with a first switch and a second switch, and the secondary-side resonant network is switched by controlling the states of the first switch and the second switch. When the secondary-side resonant network is an LC structure topology, the EC-WPT system operates in constant current mode; When the secondary resonant network is an LCLCL structure topology, the EC-WPT system operates in constant voltage mode.

2. The EC-WPT system for achieving constant current and constant voltage output switching according to claim 1, characterized in that, The primary-side LC resonant network includes a first inductor and a first capacitor, wherein: The first end of the first inductor is connected to the full-bridge inverter circuit, and the second end of the first inductor, the first end of the first capacitor, and the first emitter plate of the coupling mechanism are connected. The second terminal of the first capacitor is connected to the second emitter plate of the full-bridge inverter circuit and the coupling mechanism.

3. The EC-WPT system for achieving constant current and constant voltage output switching according to claim 2, characterized in that, The secondary-side resonant network includes a second inductor, a third inductor, a fourth inductor, a second capacitor, a first switch, and a second switch, wherein: The first end of the second inductor, the first end of the second capacitor, and the third receiving plate of the coupling mechanism are connected; The second terminal of the second inductor, the first terminal of the third inductor, the first terminal of the first switch, and the first terminal of the third capacitor are connected together. The second terminal of the third inductor, the first terminal of the second switch, and the first terminal of the fourth inductor are connected. The second terminal of the first switch, the second terminal of the third capacitor, the second terminal of the fourth inductor, and the full-bridge rectifier circuit are connected. The second terminal of the second capacitor, the second terminal of the second switch, the fourth receiving plate of the coupling mechanism, and the full-bridge rectifier circuit are connected.

4. The EC-WPT system for achieving constant current and constant voltage output switching according to claim 2, characterized in that: When the first switch is closed and the second switch is open, the EC-WPT system operates in constant current mode; When the first switch is open and the second switch is closed, the EC-WPT system operates in constant voltage mode.

5. The EC-WPT system for achieving constant current and constant voltage output switching according to claim 4, characterized in that, The full-bridge inverter circuit includes four transistors.

6. The EC-WPT system for achieving constant current and constant voltage output switching according to claim 5, characterized in that, The full-bridge rectifier circuit includes four diodes.

7. The EC-WPT system for achieving constant current and constant voltage output switching according to claim 6, characterized in that, The coupling mechanism is composed of parallel quadrilateral plates, and its coupling capacitance satisfies the following relationship: Among them, C m For mutual capacitance, C a For primary self-capacitance, C b For secondary self-capacitance, C 13 and C 24 For the main coupling capacitance formed by different pairs of plates, C 12 C 34 C 14 C 23 This refers to the cross-coupling capacitance formed by edge effects between different plates.

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