CN106961165A - Wireless power transmission circuit, radio energy transmitting terminal and radio energy receiving terminal - Google Patents

Abstract

Disclose a kind of wireless power transmission circuit, radio energy transmitting terminal and radio energy receiving terminal, by the way that the electric capacity in resonance circuit is divided into two, and it is arranged at the two ends of coil in a series arrangement respectively, so that common mode current flows to ground to a part by coil over the ground, simultaneously, common mode current flows to coil to another part by ground over the ground, so as to cancel out each other, suppresses total common mode current over the ground.

Description

Wireless power transmission circuit, wireless power transmitter and wireless power receiver

technical field

The present invention relates to power electronics technology, in particular to wireless charging technology, and more specifically, to a wireless power transmission circuit, a wireless power transmitter and a wireless power receiver.

Background technique

Wireless power supply technology can transmit power between electronic devices in a wireless manner, so it is widely used in consumer electronic products and other types of electronic products. The wireless power supply technology usually realizes the wireless transmission of electric energy through the mutual electromagnetic coupling of the coil on the transmitting side and the coil on the receiving side. Among them, the magnetic resonance type wireless power supply method can efficiently provide electric energy to receiving ends separated by a certain distance in a wireless manner. In this method, both the power transmitting end and the power receiving end are equipped with a resonant circuit consisting of a coil and a capacitor, which allows electric and magnetic fields to resonate between the two circuits to transmit power wirelessly.

As shown in Figure 1, the existing wireless power transmission circuit usually uses a coil Ls and a capacitor Cs in series to form an LC resonant circuit, and the LC resonant circuit resonates at a predetermined operating angular frequency ω0, so that the impedance of the wireless power transmission circuit is zero (also which is, ), so that electric energy can be transmitted with high transmission efficiency.

However, in order to supply power based on greater positional freedom of the wireless power receiving end or to couple multiple wireless power receiving ends at the same time, the size and inductance of the transmitting coil Ls or receiving coil Ld are usually increased to improve the transmission and reception. coil coupling. This will lead to an increase in the number of turns and the area of the coil, thereby increasing the parasitic capacitance of the coil to the ground Cp=εS/D, where ε is the dielectric constant, S is the area of the coil, and D is the distance between the coil and the ground. At the same time, as shown in Figure 2, due to the existence of parasitic capacitance C1-Cn, the jump voltage on the coil is easy to form a common mode current Icm to the ground through the parasitic capacitance, I _CM =Cp dV/dt, causing conducted electromagnetic interference (EMI) .

Contents of the invention

In view of this, the present disclosure provides a wireless power transmission circuit, a wireless power transmitting end and a wireless power receiving end, so as to effectively suppress the common mode current to the ground while increasing the coil size or the number of turns.

In the first aspect, a wireless power transmission circuit is provided, including:

Coil;

a first capacitor connected in series at the first end of the coil; and

a second capacitor connected in series to the second end of the coil;

Wherein, the first capacitor, the second capacitor and the coil resonate at a predetermined operating frequency.

Further, the capacitance ratio of the first capacitor to the second capacitor is set to minimize the common mode current of the coil to the ground.

Further, the capacitance values of the first capacitor and the second capacitor are equal.

Further, the capacitance ratio of the first capacitor and the second capacitor matches the winding shape of the coil.

Further, the capacitance values of the first capacitor and the second capacitor are configured such that the equivalent capacitance value connected in series resonates with the inductance value of the coil at the operating frequency.

Further, the wireless power transmission circuit is a wireless power transmitting circuit or a wireless power receiving circuit.

In a second aspect, there is provided a wireless power transmitting end adapted to transmit electric energy in a wireless manner, wherein the wireless power transmitting end includes the wireless power transmission circuit as described above.

In a third aspect, there is provided a wireless power receiving end adapted to receive electric energy in a wireless manner, wherein the wireless power receiving end includes the wireless power transmission circuit as described above.

By dividing the capacitance in the resonant circuit into two, and setting them in series at both ends of the coil, the voltage on the coil is basically symmetrically distributed, a part of the common mode current to the ground flows from the coil to the ground, and the other part to the ground The common-mode currents flow from ground to the coil, thereby canceling each other out and suppressing the total common-mode current to ground.

Description of drawings

Fig. 1 is the circuit diagram of the wireless power transmitting circuit of prior art;

Fig. 2 is the equivalent circuit diagram of the wireless power transmitting circuit of prior art;

Fig. 3 is the equivalent circuit diagram of the wireless energy transmission circuit of prior art;

FIG. 4 is a circuit diagram of a wireless power transmission circuit according to an embodiment of the present disclosure;

5 is an equivalent circuit diagram of a wireless power transmission circuit according to an embodiment of the disclosure;

FIG. 6 is a schematic diagram of a wireless power transmitting circuit according to an embodiment of the present disclosure;

FIG. 7 is a schematic diagram of a wireless power transmission system involved in an embodiment of the present disclosure.

detailed description

Several preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings, but the present disclosure is not limited to these embodiments. The present disclosure covers any alternatives, modifications, equivalent methods and schemes made within the spirit and scope of the present disclosure. In order to provide the public with a thorough understanding of the present disclosure, specific details are set forth in the following preferred embodiments of the present disclosure, and those skilled in the art can fully understand the present disclosure without the description of these details.

The term "comprising", used in the claims, should not be interpreted as limiting to the means listed thereafter. It does not exclude other elements or steps. Therefore, the scope of the expression "a device including means A and B" should not be limited to a device including parts A and B only. It means that for this disclosure, the relevant parts of the device are A and B.

Furthermore, the terms first, second, third, etc. in the present specification and claims are used to distinguish between similar elements and not necessarily to describe order or timing. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the disclosure described herein are capable of operation in sequences other than described or illustrated herein.

It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be construed in the same fashion (i.e., "between" and "directly between", "adjacent" with "directly adjacent", etc.).

Fig. 3 is an equivalent circuit diagram of a wireless power transmitting circuit in the prior art. As shown in Figure 3, in the prior art wireless power transmission circuit, since the capacitor Cs and the transmitting coil Ls resonate at frequency f0, when the current Is=I1·Sin(ω0) flowing in the coil, the electric current on the capacitor Cs The voltage Vc satisfies:

At the same time, the voltage Vl on the coil Ls satisfies:

That is, Vc and Vl have the same amplitude and opposite phases, which makes the total voltage at both ends of the wireless power transmitting circuit zero. The high-frequency alternating voltage on the coil Ls can generate n common-mode currents Icm0 to Icmn to the ground through equivalent ground parasitic capacitances C0, C1, . . . Because at the same moment, the voltage distribution on the coil Ls is not symmetrical. Therefore, the total common-mode current Icm satisfies:

Icm=Icm0+Icm1+...+Icmn

A non-zero common-mode current Icm can cause conducted EMI.

FIG. 4 is a circuit diagram of a wireless power transmission circuit according to an embodiment of the present disclosure. As shown in FIG. 4 , the wireless power transmitting circuit 1 of this embodiment includes a coil Ls, a first capacitor Cs1 and a second capacitor Cs2. Wherein, the first capacitor Cs1 is connected in series to the first end of the coil Ls, and the second capacitor Cs is connected in series to the second end of the coil Ls. The first capacitor Cs1, the second capacitor Cs2 and the coil Ls together form a CLC resonant circuit, which resonates at a predetermined operating frequency f0. That is, the first capacitor Cs1, the second capacitor Cs2 and the coil Ls satisfy:

Among them, ω0 is the angular frequency corresponding to the working frequency f0. As a result, the impedance of the wireless power transmitting circuit 1 is zero at the working frequency f0, so that electric power can be transmitted with higher efficiency.

FIG. 5 is an equivalent circuit diagram of a wireless power transmitting circuit according to an embodiment of the present disclosure. As shown in FIG. 5 , in this embodiment, the capacitance values of the first capacitor Cs1 and the second capacitor Cs2 are equal as an example for description. In FIG. 5, the equivalent circuit of the coil Ls is symmetrical about its center. Since the impedance of the wireless power transmitting circuit 1 is zero, the voltage at both ends of the circuit is zero. Therefore, the voltage distribution on the coil Ls is also completely symmetrical. That is, the voltage at point 0 is symmetrical to the voltage at point n, Vn=-V0, Vn-1=-V1, . . . , and so on. Thus, the common-mode current to ground at point 0 satisfies:

At the same time, the common-mode current to ground at the corresponding point n satisfies:

When C0 is equal to Cn, Icm0=-Icmn.

Thus, the currents Icm0 and Icmn can form a closed loop, and no common mode current will flow into the ground. Similarly, the currents Icm1 and Icmn-1 have the same amplitude and opposite directions, forming a closed loop by themselves, and will not form a common-mode current to flow into the ground. As a result, part of the common-mode current to the ground flows from the coil to the ground, and at the same time, another part of the common-mode current to the ground flows from the ground to the coil, and the overall common-mode current satisfies:

Icm=Icm0+Icm1+...+Icmn=0

As a result, multiple closed loops are formed to reduce the common-mode current flowing into the ground, thereby achieving the purpose of suppressing the common-mode current to the ground.

FIG. 6 is a schematic diagram of a wireless power transmission circuit according to an embodiment of the present disclosure. As shown in FIG. 6 , in practical application scenarios, the coil is usually formed in a planar helical manner to make the coil as flat as possible. The first capacitor Cs1 and the second capacitor Cs2 are respectively arranged in series at two lead ends of the coil to form a resonant circuit. The flattening of the coil Ls can make the wireless power transmission circuit applicable to various portable electronic devices. As shown in FIG. 6 , since the coil is wound from the outside to the inside, the sections of the coil are not symmetrical about the center. Therefore, the overall distribution of the coils is not symmetrical, so that the distribution of parasitic capacitances at different positions is not completely symmetrical. At this time, the capacitance values of the first capacitor Cs1 and the second capacitor Cs2 can be configured, and by adjusting the ratio of the two, the voltage distribution on the coil Ls can be matched as much as possible with the distribution of the parasitic capacitance (that is, with the shape of the coil match), adjust the common-mode current to ground of different segments to minimize the common-mode current to ground.

Certainly, if the coil is symmetrical, then by setting the capacitance values of the first capacitor Cs1 and the second capacitor Cs2 to be equal, theoretically the common mode current to the ground can be made zero.

Therefore, in this embodiment, by dividing the capacitance in the resonant circuit into two, and setting them in series at both ends of the coil, a part of the common-mode current to the ground flows from the coil to the ground, and at the same time, the other part of the common-mode current to the ground The currents flow from ground to the coil, thereby canceling each other out and suppressing the total common-mode current to ground.

Further, the circuit structure of the wireless power transmitting circuit 1 shown in FIG. 4 can also be applied to the wireless power receiving circuit 2. Based on the same principle, while increasing the receiving area of the wireless power receiving circuit, suppressing the interference in the wireless power receiving circuit ground common-mode current.

FIG. 7 is a schematic diagram of a wireless power transmission system involved in an embodiment of the present disclosure. As shown in FIG. 7 , the system includes a wireless power transmitting terminal A and a wireless power receiving terminal B. Wherein, the wireless power transmitting end A includes a wireless power transmitting circuit 1 . The wireless power receiving end B includes a wireless power receiving circuit 2 . Specifically, the wireless power receiving circuit 2 includes a first capacitor Cd1, a second capacitor Cd2 and a coil Ld. Similar to FIG. 4, the first capacitor Cd1 and the second capacitor Cd2 are respectively connected in series at both ends of the coil Ld to form a substantially symmetrical circuit structure, so that when the wireless power receiving circuit 2 resonates at the frequency f0, the voltage on the coil Ld is basically Symmetrical distribution, parasitic capacitances at different positions form a current loop, and the common-mode currents flowing through the parasitic capacitances cancel each other out, minimizing the total common-mode current to ground. In FIG. 7 , the wireless power transmitting circuit 1 and the wireless power receiving circuit 2 of the wireless power transmission system both adopt the circuit structure of the embodiment of the present disclosure. It should be understood that in other application scenarios, only the wireless power transmitting circuit 1 may adopt the circuit structure of the embodiment of the present disclosure or only the wireless power receiving circuit 2 may adopt the circuit structure of the embodiment of the present disclosure. The wireless power transmitter A may also include an inverter circuit 3 and a control circuit 4 . The inverter circuit 3 is used to convert the input direct current into a high frequency alternating current of working frequency, and the control circuit 4 is used to control the inverter circuit 3 . The wireless power receiving end B may also include a rectification circuit 5 and a control circuit 6 . The rectifying circuit 5 is used to convert the high-frequency alternating current received by the wireless power receiving circuit into direct current for output. The control circuit 6 is used to control the rectification circuit.

The above description is a description of the embodiments of the present disclosure. Various alterations and changes can be made without departing from the scope of the present disclosure. This disclosure is presented for illustrative purposes and should not be construed as an exclusive description of all embodiments of the disclosure or to limit the scope of the disclosure to the specific elements illustrated and described in connection with these embodiments. Without limitation, any one or more individual elements of the described invention may be replaced by alternative elements serving substantially similar function or otherwise providing sufficient operation. This includes currently known replacement elements, such as those currently known to those skilled in the art, as well as replacement elements that may be developed in the future, such as those skilled in the art may recognize as replacements at the time of development.

Claims (8)

1. A wireless power transmission circuit, comprising: Coil; a first capacitor connected in series at the first end of the coil; and a second capacitor connected in series to the second end of the coil; Wherein, the first capacitor, the second capacitor and the coil resonate at a predetermined operating frequency. 2. The wireless power transmission circuit according to claim 1, wherein the ratio of the capacitance values of the first capacitor to the second capacitor is set to minimize the common mode current of the coil to the ground. 3. The wireless power transmission circuit according to claim 2, wherein the capacitance values of the first capacitor and the second capacitor are equal. 4. The wireless power transmission circuit according to claim 2, wherein the capacitance ratio of the first capacitor and the second capacitor matches the winding shape of the coil. 5. The wireless power transmission circuit according to claim 2, wherein the capacitance values of the first capacitor and the second capacitor are configured such that the equivalent capacitance after series connection and the inductance value of the coil are within the specified range. resonant at the operating frequency. 6. The wireless power transmission circuit according to claim 1, wherein the wireless power transmission circuit is a wireless power transmission circuit or a wireless power reception circuit. 7. A wireless power transmitting end, adapted to transmit electric energy wirelessly, wherein the wireless power transmitting end comprises the wireless power transmission circuit according to any one of claims 1-5. 8. A wireless power receiving end, adapted to receive electric power wirelessly, wherein the wireless power receiving end comprises the wireless power transmission circuit according to any one of claims 1-5.