LCLCCL structure for wireless charging transmitter

Abstract

The invention relates to the technical field of wireless charging, and provides an LCLCCL structure for a wireless charging transmitter, which comprises a power supply, a wireless power transmitting end and an LCLCCL circuit which are connected in sequence. According to the LCLCCL circuit, electromagnetic interference can be effectively reduced, and different load requirements can be met in parameter design.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless charging, and in particular to a LCLCCL structure for a wireless charging transmitter. Background Art

[0002] In recent years, wireless charging technology has been more and more widely used in consumer electronics, industrial products, automobiles and other fields. There are more and more wireless charging devices such as smart phones, wireless headphones, wearable devices, etc. However, the traditional wireless charging method has high requirements for coil alignment, and users will be subject to certain restrictions. The emergence of magnetic wireless charging has solved this problem very well. With the introduction of the MPP protocol (Magnetic Power Protocol) in Qi 2.0, magnetic wireless charging has attracted more and more attention, and there are more and more magnetic wireless charging products. Electromagnetic safety issues are becoming more and more important. The main problems faced by current magnetic wireless charging products are:

[0003] 1. Due to the large high-order harmonic components of the system operating frequency, the electromagnetic interference problem is serious, especially in the automotive field, where the requirements for electromagnetic safety are more stringent than those for consumer electronics, making it difficult for many products to pass EMI testing.

[0004] 2. Common primary side matching method: With the increase of frequency and coupling coefficient, it is difficult for the matching capacitor to take into account the different matching requirements from full load to light load in design. Summary of the invention

[0005] The present invention aims to provide a LCLCCL structure for a wireless charging transmitter to effectively reduce electromagnetic interference, and the parameter design takes into account different load requirements, thereby promoting the application of magnetic wireless charging products in various fields.

[0006] The present invention provides a LCLCCL structure for a wireless charging transmitter, comprising a power supply, a wireless power transmitting end and a LCLCCL circuit which are connected in sequence.

[0007] In some embodiments, the LCLCCL circuit includes a first LC circuit, a second LC circuit, and a CL circuit connected in sequence.

[0008] In some embodiments, the first LC circuit includes an inductor L3 and a capacitor C2.

[0009] In some embodiments, the second LC circuit includes an inductor L1, an inductor L2, and a capacitor C1.

[0010] In some embodiments, the inductor L1 and the inductor L2 are combined into an inductor L12.

[0011] In some embodiments, the CL circuit includes a capacitor Cp and an inductor Lp'.

[0012] In some embodiments, the inductor L3, the inductor L1, the inductor L2, the capacitor Cp and the inductor Lp' are connected in series; the capacitor C2 is connected to the bypass between the inductor L3 and the inductor L1, and the capacitor C1 is connected to the bypass between the inductor L2 and the capacitor Cp.

[0013] In some embodiments, the capacitive reactance of the capacitor C1 is smaller than the reactance of the Lp'+Cp+Zr branch.

[0014] In some embodiments, the inductor L1 and the capacitor C1 form a series resonance.

[0015] In some embodiments, the inductor L2, the capacitor C2, and the inductor L3 are perfectly matched.

[0016] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0017] 1. The present invention can effectively reduce the high-order harmonic components in the wireless charging system, reduce electromagnetic interference, improve the electromagnetic safety performance of the product, and significantly help EMI testing.

[0018] 2. In the present invention, capacitor C1 plays a bypass function (see formula (7)), which can reduce the impact of Zr on the system due to load changes.

[0019] 3. In the present invention, since L2 / C2 / L3 are perfectly matched, the effective value of the current of the inductor L3 is smaller than the effective value of the current of the inductor L2, which can reduce the loss in the front-stage driving circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the traditional wireless charging system model.

[0021] Figure 2 Schematic diagram of the original side equivalent model.

[0022] Figure 3 Schematic diagram of common primary edge matching methods.

[0023] Figure 4 Schematic diagram of the LCLCCL structure used for the wireless charging transmitter in an embodiment of the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0025] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] First, some traditional solutions:

[0027] 1. Traditional wireless charging system

[0028] Conventional wireless charging systems can be used Figure 1 The model represents that L′ p and L′ s represents the primary coil and the secondary coil, k is the coupling coefficient, expressed as:

[0029]

[0030] Among them, M is the mutual inductance between the primary coil and the secondary coil, Cs is the resonant capacitance of the secondary coil, which can reduce the reactive power of the secondary side; Cp is the primary resonant capacitance, which can also reduce the reactive power of the primary side and improve the system efficiency; Zload is the equivalent load impedance.

[0031] 2. Primary side equivalent model

[0032] generally Figure 1 The model can be transformed into Figure 2 The primary side equivalent model shown in the figure, Zr represents the equivalent reduced impedance of the secondary side at the primary side, which is expressed as:

[0033]

[0034] Where f is the system operating frequency, Z2 is the secondary impedance, expressed as:

[0035]

[0036] 3. Common original edge matching methods

[0037] Common primary edge matching methods include: Figure 3As shown, C1 and L1 are the added capacitance and inductance. This structure is usually called LCCL structure and has the following advantages:

[0038] 1. Capacitor C1 can compensate for the primary side L′ p +Reactive power in Cp branch, improving system efficiency;

[0039] 2. Through reasonable design, the current of L1 can be made smaller than L' p Since the current of L1 comes from the primary drive circuit (such as inverter), a smaller L1 current can reduce the loss in the drive circuit;

[0040] 3. Inductor L1 and capacitor C1 form a first-level filter, which can reduce L' p Harmonics and interference in the

[0041] The following methods are usually used in the design process:

[0042] Assuming Zr is purely resistive, L′ p The equivalent inductance in series with Cp is L″ p ,Right now

[0043] Calculate the capacitance C1 so that

[0044] Calculate the inductance L1 so that L1 = L" p ;

[0045] When the above conditions are met, it is called perfect matching. At this time, the inductance L' p The current in the circuit has nothing to do with the load and is equivalent to a constant current source, which can achieve the most stable system.

[0046] It should be noted that in the above calculation, it is assumed that Zr is purely resistive or the imaginary part of Zr is small, which is not applicable to L′. p The reactance of the +Cp branch has little effect. However, in actual systems, it can be seen from formulas (2) and (3) that the imaginary part of Zr is not zero and is usually capacitive (the imaginary part is negative). The greater the load power, that is, the smaller the equivalent resistance of Zload, the more obvious the negative imaginary part of Zr.

[0047] The existence of the negative imaginary part of Zr makes the design of capacitor C1 difficult. If the negative imaginary part (absolute value) of Zr is large, the capacitor C1 calculated according to the above calculation steps (the influence of Zr needs to be included) will be too large, which will cause "overcompensation", adding additional capacitive reactive power to the system, which will reduce system efficiency.

[0048] In the usual Qi system, the negative imaginary part of Zr is related to the inductance L′ pFor example, assuming the operating frequency is 128kHz, the coupling coefficient k = 0.65, when the load resistance Zload = 10Ω (approximately corresponding to 12V / 15W), the negative imaginary part of Zr (the absolute value of L') only accounts for p 24% of the inductive reactance. Through proper design, the "perfect match" condition mentioned above can still be met or approximately met. To prevent "overcompensation", the capacitive reactance of capacitor C1 usually meets the following conditions:

[0049] Condition A:

[0050]

[0051] Condition B:

[0052]

[0053] Formulas (4) and (5) take into account both full load and no-load conditions. Usually, C1 takes an intermediate value that takes into account both full load and no-load conditions, that is,

[0054]

[0055] From formula (2), it can be seen that the size of Zr is proportional to ω and the square of M. As the frequency and coupling coefficient increase, Zr, especially the negative imaginary part, will become larger and larger. For example, assuming the operating frequency is 360kHz, the coupling coefficient is increased to 0.9, when the load resistance is still maintained at Zload = 10Ω, the negative imaginary part of Zr (the absolute value) will reach L' p Such a large negative imaginary part of Zr will make it difficult to design C1 to take into account the different matching requirements from full load (formula (4)) to light load (formula (5)).

[0056] Therefore, in order to effectively reduce electromagnetic interference, different load requirements must be taken into account in parameter design, such as Figure 4 As shown, this embodiment proposes a LCLCCL structure for a wireless charging transmitter, including a power supply, a wireless power transmitting end and a LCLCCL circuit connected in sequence;

[0057] The LCLCCL circuit includes a first LC circuit, a second LC circuit and a CL circuit connected in sequence. In this embodiment, the first LC circuit includes an inductor L3 and a capacitor C2, the second LC circuit includes an inductor L1, an inductor L2 and a capacitor C1, and the CL circuit includes a capacitor Cp and an inductor Lp'.

[0058] The inductor L3, the inductor L1, the inductor L2, the capacitor Cp and the inductor Lp′ are connected in series; the capacitor C2 is connected to the bypass between the inductor L3 and the inductor L1, and the capacitor C1 is connected to the bypass between the inductor L2 and the capacitor Cp.

[0059] The LCLCCL structure adds L2 / C2 / L3 on the basis of the original L1 / C1 matching. The design idea is:

[0060] 1. The capacitive reactance of capacitor C1 is less than the reactance of Lp'+Cp+Zr branch, that is:

[0061]

[0062] Among them, Zr is the equivalent reduced impedance at full load. It should be noted that its imaginary part is usually a negative number, and imag represents the imaginary part of the complex number.

[0063] Since the capacitance of capacitor C1 is small, it acts as a bypass for the Lp'+Cp+Zr branch. Even if Zr has a huge range of variation due to load changes, the presence of the bypass capacitor C1 will greatly reduce the impact on the previous stage circuit.

[0064] 2. Inductor L1 and capacitor C1 form a series resonance, that is:

[0065]

[0066] This makes the L2 / C2 / L3 equivalent load close to zero.

[0067] 3. Design L2 / C2 / L3 to be perfectly matched, that is:

[0068]

[0069] 4. Inductor L1 and inductor L2 can be combined into an inductor L12, that is, L 12 =L1+L2.

[0070] In summary, the LCLCCL structure has the following technical effects:

[0071] 1. The present invention can effectively reduce the high-order harmonic components in the wireless charging system, reduce electromagnetic interference, improve the electromagnetic safety performance of the product, and significantly help EMI testing.

[0072] 2. In the present invention, capacitor C1 plays a bypass function (see formula (7)), which can reduce the impact of Zr on the system due to load changes.

[0073] 3. In the present invention, since L2 / C2 / L3 are perfectly matched, the effective value of the current of the inductor L3 is smaller than the effective value of the current of the inductor L2, which can reduce the loss in the front-stage driving circuit.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A LCLCCL structure for a wireless charging transmitter, characterized in that: It includes a power supply, a wireless power transmitter and an LCLCCL circuit which are connected in sequence.

2. The LCLCCL structure for a wireless charging transmitter according to claim 1, characterized in that: The LCLCCL circuit includes a first LC circuit, a second LC circuit and a CL circuit connected in sequence.

3. The LCLCCL structure for a wireless charging transmitter according to claim 2, characterized in that: The first LC circuit includes an inductor L3 and a capacitor C2.

4. The LCLCCL structure for a wireless charging transmitter according to claim 3, characterized in that: The second LC circuit includes an inductor L1, an inductor L2 and a capacitor C1.

5. The LCLCCL structure for a wireless charging transmitter according to claim 4, characterized in that: The inductor L1 and the inductor L2 are combined into an inductor L12.

6. The LCLCCL structure for a wireless charging transmitter according to claim 4, characterized in that: The CL circuit includes a capacitor Cp and an inductor Lp'.

7. The LCLCCL structure for a wireless charging transmitter according to claim 6, characterized in that: The inductor L3, the inductor L1, the inductor L2, the capacitor Cp and the inductor Lp' are connected in series; the capacitor C2 is connected to the bypass between the inductor L3 and the inductor L1, and the capacitor C1 is connected to the bypass between the inductor L2 and the capacitor Cp.

8. The LCLCCL structure for a wireless charging transmitter according to claim 7, characterized in that: The capacitive reactance of the capacitor C1 is smaller than the reactance of the Lp'+Cp+Zr branch.

9. The LCLCCL structure for a wireless charging transmitter according to claim 7, characterized in that: The inductor L1 and the capacitor C1 form a series resonance.

10. The LCLCCL structure for a wireless charging transmitter according to claim 7, characterized in that: The inductor L2, the capacitor C2 and the inductor L3 are perfectly matched.

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