KR102179796B1 - High frequency wireless charger for constant current/constant voltage charge and control method thereof - Google Patents

Abstract

Disclosed are a super-high frequency wireless charger for constant current (CC)/constant voltage (CV) charging and a control method thereof. The super-high frequency wireless charger for constant current (CC)/constant voltage (CV) charging comprises: a transmission end connected to an input power source; and a reception end including an S-LCC topology connected to a receiving coil, and a T-LCL topology connected to a rear end of the S-LCC topology to configure a resonance tank in the S-LCC topology or configure the resonance tank in the S-LCC topology and the T-LCL topology so as to output constant voltage or constant current.

Description

Ultra high frequency wireless charger for constant current (CC)/constant voltage (CV) charging and its control method {HIGH FREQUENCY WIRELESS CHARGER FOR CONSTANT CURRENT/CONSTANT VOLTAGE CHARGE AND CONTROL METHOD THEREOF}

The present invention relates to an ultra-high frequency wireless charger for constant current (CC)/constant voltage (CV) charging and a control method thereof, and more particularly, to a constant current (CC) through inductive power transfer (IPT) between a transmitting end and a receiving end. It relates to an ultra-high frequency wireless charger for charging a constant current (CC)/constant voltage (CV) charging a battery according to a /constant voltage (CV) charging process, and a control method thereof.

A wireless power transfer (WPT) system, which has recently been in the spotlight, does not require a connection between a charger and an electronic device, so that inconvenience of a conventional plug-in charger can be solved.

The switching frequency of the inductive power transfer (IPT) of such a wireless power transfer (WPT) system is in the MHz band (typically 6.78Hz or 13.56Hz), which can achieve a high quality factor of the coil. And reduce the influence of the low coupling coefficient caused by long distances or imbalances, and consequently can have better efficiency.

Meanwhile, lithium batteries are widely used in mobile electronic devices such as laptops and mobile phones. The charging process of the lithium battery may generally include constant current (CC) charging and constant voltage (CV) charging to charge the lithium battery.

Specifically, the lithium battery is first charged with a constant current (CC), and at this time, the voltage may gradually increase. When the voltage of the lithium battery reaches the maximum charging voltage, the lithium battery may be charged with a constant voltage (CV). In addition, when the battery current decreases at a rate of a specific value (for example, 0.1C), the charging process of the lithium battery may be terminated.

In such a constant current (CC)/constant voltage (CV) charging process, in order to ensure the life of the battery, a charger must stably provide an accurate current and voltage.

For example, in order to implement a constant current (CC)/constant voltage (CV) charging process in a high frequency wireless power transfer (WPT) system, a single-phase converter or an additional back-end DC-DC converter is employed at the receiving end to control closed-loop control for frequency modulation. Has to be implemented, which has the problem of increasing the cost, complexity and power loss of the entire system.

In order to solve the above problems, a method of implementing a constant current (CC)/constant voltage (CV) charging process by executing open loop control in a wireless power transmission (WPT) system has been proposed. This can implement a constant current (CC)/constant voltage (CV) charging process by using two different frequencies using the inherent characteristics of the resonance compensation network. That is, the wireless power transfer (WPT) system may operate at one of two resonance frequencies to achieve constant current (CC) charging or constant voltage (CV) charging.

However, since the wireless power transfer (WPT) system operates in the MHz band, the use of multiple frequencies is limited due to circuit complexity and difficulty in digital implementation. Also, for wireless power transfer (WPT) systems, frequency modulation is not recommended to avoid electromagnetic interference to wireless communications.

Accordingly, in order to implement constant current (CC)/constant voltage (CV) charging in a wireless power transmission (WPT) system operating in the MHz band, it is desirable to convert the resonance network.

The basic topology of the proposed resonance compensation circuit for implementing constant current (CC)/constant voltage (CV) charging in wireless power transfer (WPT) systems is series-series (SS), series-parallel (SP), and parallel-series (PS). ) And parallel-parallel (PP). When these resonance compensation circuits are used in wireless power transfer (WPT) systems, the zero phase angle (ZPA) condition can be automatically achieved through load-independent constant voltage (CV) and constant current (CC) output characteristics. have. However, the basic topologies of the resonance compensation circuit as described above have a problem in that the resonance compensation network and coil design are limited because the output value largely depends on the coil parameter.

Meanwhile, a high-order resonance network has been proposed as a resonance network for implementing constant current (CC)/constant voltage (CV) charging in a wireless power transmission (WPT) system.

For example, as the topology of a high-order resonance compensation circuit, S-LCC (Series-Inductor-Capacitor-Capacitor) and LCC-S (Inductor-Capacitor-Capacitor-Series) are constant voltage (CV) output and zero phase angle (ZPA). It is in the spotlight for its characteristics. In addition, the double-sided LCC has the advantage of being able to achieve constant current (CC) output and zero phase angle (ZPA) conditions. In addition, the T-LCL, Π-CLC, T-CLC, and Π-LCL types of the immittance converter can convert the constant voltage CV to the constant current CC or vice versa.

However, since the wireless power transfer (WPT) system employing the above-described high-order resonance network is designed to operate in the kHz band, there is a problem that the power density of the system is not sufficient for portable devices.

One aspect of the present invention is a constant current (CC) / constant voltage (CC) / constant voltage (constant current (CC) / constant voltage (CV) charging under one operating frequency by changing the resonant network between the constant current (CC) charging mode and the constant voltage (CV) charging mode) CV) Ultra-high frequency wireless charger for charging and its control method are provided.

The technical problem of the present invention is not limited to the technical problem mentioned above, and other technical problems that are not mentioned will be clearly understood by those skilled in the art from the following description.

The ultra-high frequency wireless charger for constant current (CC)/constant voltage (CV) charging according to an aspect of the present invention for solving the above problem is the receiving coil through inductive power transfer (IPT) between the transmitting coil and the receiving coil. In the ultra-high frequency wireless charger for charging a constant current (CC)/constant voltage (CV) charging a battery connected to the transmission coil, the input voltage supplied from the input power is transmitted by a switching operation of a plurality of switches connected to the input power. Transmitting end transmitting to and including an S-LCC topology connected to the receiving coil and a T-LCL topology connected to a rear end of the S-LCC topology, and a transmitting coil by a resonance tank configured in the S-LCC topology and the A constant voltage is output through induction power transfer between receiving coils, or a constant current is output through induction power transfer between the transmitting coil and the receiving coil by a resonance tank composed of the S-LCC topology and the T-LCL topology to save the battery. It includes a receiving end for charging.

Meanwhile, the receiving end includes a first resonance switch connecting the S-LCC topology and a rectifier circuit connected to the battery, and a second resonance having both ends connected to an output voltage line connected to the T-LCL topology and the receiving coil, respectively. A switch and a voltage at both ends of the battery are sensed, and a switching operation of the first resonance switch and the second resonance switch is performed to switch between a constant current (CC) charging mode and a constant voltage (CV) charging mode according to the voltage at both ends of the battery. It may include a resonance switch control unit for changing the structure of the resonance tank by controlling.

In addition, the receiving end is provided between the S-LCC topology and the rectifier circuit connected to the battery, and between the second and third resonant inductors connected in series, and between the second and third resonant inductors. It may include the T-LCL topology including a third resonant capacitor connected to a contact point.

In addition, the receiving end, a first resonant switch connected to both ends of the second resonant inductor and the third resonant inductor connected in series, and both ends are respectively connected to an output voltage line connected to the third resonant capacitor and the receiving coil. It may include a second resonance switch.

In addition, the receiving end may include the S-LCC topology including a second resonant capacitor and a first resonant inductor connected to the first resonant capacitor in parallel with the first resonant capacitor connected to the receiving coil. have.

In addition, the transmitting end is provided on a bridge connected to both ends of the input power, and controls a first switch and a second switch implemented as a GaN MOSFET switch, and a turn-on or turn-off operation of the first switch and the second switch. Class D amplifier, which is connected to a contact point between the first switch and the second switch, and includes a ZVS inductor and a ZVS capacitor, and a negative current for discharging the parasitic capacitor added to the first switch and the second switch. It may include a ZVS tank for generating a ZVS tank and a transmission capacitor provided between the ZVS tank and the transmission coil, and constituting the S-LCC topology or the T-LCL topology and the resonance tank.

In addition, the first switch and the second switch may be controlled to be switched under a zero voltage switching condition by the ZVS tank.

On the other hand, the control method of the ultra-high frequency wireless charger for constant current (CC)/constant voltage (CV) charging of the present invention is to charge the battery provided at the receiving end through inductive power transfer (IPT) between a transmitting end and a receiving end. In the control method of an ultra-high frequency wireless charger for constant current (CC)/constant voltage (CV) charging, the resonant tank formed at the receiving end is configured in a series-connected S-LCC topology and a T-LCL topology to enter a constant current (CC) charging mode. Controlling, sensing the voltage across the battery, and when the voltage across the battery reaches the maximum charging voltage, the resonance tank formed at the receiving end is configured in an S-LCC topology to enter a constant voltage (CV) charging mode. And controlling.

On the other hand, the step of configuring the resonance tank formed at the receiving end in a series-connected S-LCC topology and a T-LCL topology to control the constant current (CC) charging mode, the S-LCC topology and the rectifying circuit connected to the battery Turn-off control of the first resonant switch to be connected, and the steps of turning-on-controlling the second resonant switch connected to the output voltage line connected to the T-LCL topology and the receiving coil that receives the induced power from the transmitting end, respectively. Can include.

In addition, when the voltage at both ends of the battery reaches the maximum charging voltage, the step of configuring a resonance tank formed at the receiving end in an S-LCC topology to control the constant voltage (CV) charging mode includes turning on the first resonance switch. It may include controlling and turning off the second resonance switch.

According to the present invention, it is configured to change the resonant network according to the charging mode, and constant current (CC)/constant voltage (CV) charging can be implemented at one operating frequency (eg, 6.78 MHz).

In addition, since it does not require a back-end DC-DC converter for implementing a constant current (CC)/constant voltage (CV) charging mode, it has the advantage of reducing the loss and cost of the entire system.

In addition, since the zero voltage switching condition of the power switch of the transmitter can be achieved within the entire load range including the ZVS tank at the transmitter, the overall efficiency of the system can be improved.

Further, in switching from the constant current (CC) charging mode to the constant voltage (CV) charging mode, a feedback circuit between the transmitting end and the receiving end is not required.

1 is a schematic circuit diagram of an ultra-high frequency wireless charger for charging a constant current (CC) / constant voltage (CV) according to an embodiment of the present invention.
2 to 4 are diagrams for explaining a constant voltage (CV) charging operation characteristic of the charger illustrated in FIG. 1.
5 to 8 are views for explaining the constant current (CC) charging operation characteristics of the charger illustrated in FIG. 1.
9 is a diagram illustrating an example of a voltage and an equivalent impedance of a battery during a charging mode by an ultra-high frequency wireless charger for charging a constant current (CC)/constant voltage (CV) according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION The detailed description of the present invention to be described below refers to the accompanying drawings, which illustrate specific embodiments in which the present invention may be practiced. These embodiments are described in detail sufficient to enable a person skilled in the art to practice the present invention. It is to be understood that the various embodiments of the present invention are different from each other but need not be mutually exclusive. For example, certain shapes, structures, and characteristics described herein may be implemented in other embodiments without departing from the spirit and scope of the present invention in relation to one embodiment. In addition, it should be understood that the location or arrangement of individual components within each disclosed embodiment may be changed without departing from the spirit and scope of the present invention. Accordingly, the detailed description to be described below is not intended to be taken in a limiting sense, and the scope of the present invention, if appropriately described, is limited only by the appended claims, along with all scopes equivalent to those claimed by the claims. In the drawings, like reference numerals refer to the same or similar functions over several aspects.

1 is a schematic circuit diagram of an ultra-high frequency wireless charger for charging a constant current (CC) / constant voltage (CV) according to an embodiment of the present invention.

Referring to Figure 1, the ultra-high frequency wireless charger 1 for constant current (CC) / constant voltage (CV) charging according to an embodiment of the present invention is a wireless power transfer (WPT) charger, a transmitter 10 The battery of the receiver 20 may be charged through an inductive power transfer (IPT) from the receiver to the receiver 20.

The ultra-high frequency wireless charger 1 for charging a constant current (CC)/constant voltage (CV) according to an embodiment of the present invention can achieve constant current (CC)/constant voltage (CV) charging of a battery.

The ultra-high frequency wireless charger 1 for constant current (CC)/constant voltage (CV) charging according to an embodiment of the present invention is a constant current (CC)/constant voltage of a battery under a switching frequency condition of an ultra high frequency (eg, 6.78 MHz). It can be implemented to change the resonant network to achieve (CV) charging.

Specifically, the ultra-high frequency wireless charger 1 for constant current (CC)/constant voltage (CV) charging according to an embodiment of the present invention is a resonant network for achieving constant voltage (CV) charging, and the S-LCC topology 21 And a T-LCL topology 23 connected with the S-LCC topology 21 and the S-LCC topology 21 as a resonant network for achieving constant current (CC) charging.

To this end, the receiving end 20 includes a receiving coil (L _rx ), an S-LCC topology (21), a T-LCL topology (23), a first resonance switch (S _a ), a second resonance switch (S _b ), and a rectifier circuit. (Rectifier) may be included.

The receiving coil L _rx may receive induced power generated from the transmitting coil L _tx provided in the transmitting terminal 10.

The S-LCC topology 21 may include a first resonance capacitor (S _1s ), a second resonance capacitor (S _2s ), and a first resonance inductor (L _1s ). The first resonance capacitor S _1s may be connected to a second resonance capacitor S _2s and a first resonance inductor L _1s having one end connected to the receiving coil L _rx and the other end connected in parallel.

The T-LCL topology 23 is connected to the rear end of the S-LCC topology 21, and includes a second resonant inductor (L _sc1 ), a third resonant capacitor (C _sc ), and a third resonant inductor (L _sc2 ). I can. The second resonance inductor L _sc1 and the third resonance inductor L _sc2 are connected in series, and a third resonance capacitor C _sc may be connected to a contact point therebetween.

First resonance switch (S _a) it can be coupled to both ends of the series-connected second resonant inductor (L _sc1) and a third resonance inductor (L _sc2).

The second resonance switch S _b may be connected to the third resonance capacitor C _sc . Specifically, both ends of the second resonant switch S _b may be connected to the third resonant capacitor C _sc and the output voltage line connected to the receiving coil L _rx , respectively.

The rectifier circuit is a full bridge circuit in which four diodes D ₁ , D ₂ , D ₃ and D ₄ are provided, and may be connected to the rear end of the T-LCL topology 23. Specifically, the T-LCL topology 23 is connected to the contact between the first diode D ₁ and the third diode D ₃ provided in the first leg of the rectifier circuit, and the rectifier circuit An output voltage line connected to the receiving coil L _rx may be connected to a contact point between the second diode D ₂ and the fourth diode D ₄ provided in the second leg of ). The rear end of the rectifier circuit (Rectifier) may be connected to the parallel-connected output capacitor (C _o) and the battery (Battery).

In such a receiving end 20, the S-LCC topology 21 and the T-LCL topology 23 may operate as resonance tanks for inductive power transfer (IPT) from the transmitting end 10. Here, the receiving end 20 may change the structure of the resonance tank according to the operation of the first resonance switch (S _a ) and the second resonance switch (S _b ). To this end, the receiving end 20 may further include a resonance switch controller (Driver IC).

The method for controlling the charging mode of the ultra-high frequency wireless charger 1 for charging constant current (CC)/constant voltage (CV) according to an embodiment of the present invention by a resonance switch controller (Driver IC) is a resonance tank formed at the receiving end 20 S-LCC topology (21) and T-LCL topology (23) connected in series to control the constant current (CC) charging mode, sensing the voltage at both ends of the battery, and the voltage at both ends of the battery to the maximum charging voltage. When reaching, it may include the step of configuring the resonance tank formed in the receiving end 20 in the S-LCC topology 21 to control the constant voltage (CV) charging mode.

Specifically, the resonance switch controller (Driver IC) may first perform the constant current (CC) charging mode control according to the constant current (CC)/constant voltage (CV) charging process. To this end, the resonance switch controller (Driver IC) may turn off the first resonance switch (S _a ) and control the turn on the second resonance switch (S _b ). Accordingly, all elements constituting the S-LCC topology 21 and the T-LCL topology 23 may participate in the resonance operation as a resonance tank. In this case, the ultra-high frequency wireless charger 1 for constant current (CC)/constant voltage (CV) charging according to an embodiment of the present invention may achieve constant current (CC) charging. In this regard, a detailed description will be provided later.

In addition, the resonance switch controller (Driver IC) can sense the voltage across the battery (Battery). When the voltage of the battery reaches the maximum charging voltage according to the constant current (CC)/constant voltage (CV) charging process, the resonance switch driver IC may perform constant voltage (CV) charging mode control. To this end, the resonance switch controller (Driver IC) may control the turn-on of the first resonance switch (S _a ) and control the turn-off of the second resonance switch (S _b ). Accordingly, the second resonant inductor (L _sc1 ), the third resonant capacitor (C _sc ), and the third resonant inductor (L _sc2 ) constituting the T-LCL topology 23 cannot participate in the resonance operation as a resonance tank, Only elements constituting the S-LCC topology 21 can participate in the resonance operation. In this case, the ultra-high frequency wireless charger 1 for constant current (CC)/constant voltage (CV) charging according to an embodiment of the present invention may achieve constant voltage (CV) charging. In this regard, a detailed description will be provided later.

On the other hand, the transmission terminal 10 may be connected to the input power (V _IN ), the first switch (S ₁ ), the second switch (S ₂ ), the ZVS tank, the transmission capacitor (C _p ) and the transmission coil It may include (L _tx ).

The first switch S ₁ and the second switch S ₂ may be implemented as GaN MOSFET switches.

The first switch (S ₁ ) and the second switch (S ₂ ) may be provided on the same bridge, and both ends of the input power (V _IN ) are connected to the upper and lower ends of the bridge, and the input power (V _IN ) can be transmitted to the transmitting coil (L _tx ).

The turn-on or turn-off operation of the first switch S ₁ and the second switch S ₂ may be controlled by a power amp, for example, a Class D amplifier, which will be described later in detail. .

ZVS tank (ZVS tank) has a first switch (S ₁₎ and second switch (S ₂₎ is connected to the contact point between the first switch (S ₁₎ and second switches to achieve the zero voltage switching conditions of the (S ₂₎ can do. ZVS tank (ZVS TANK) the first switch (S ₁₎ and the second switch the first switch prior to turn-on operation of the (S ₂₎ (S ₁₎ and including a ZVS inductor (L _ZVS) and ZVS capacitor (C _ZVS) A negative current for discharging the parasitic capacitor added to the second switch S ₂ may be generated.

The transmission capacitor C _p may be provided between the ZVS tank and the transmission coil L _tx .

The transmission capacitor C _p configures the S-LCC topology 21 and a resonance tank to enable the transfer of induced power from the transmission coil L _tx to the reception coil L _rx .

Hereinafter, characteristics of a constant voltage (CV)/constant current (CC) charging operation of the ultra-high frequency wireless charger 1 for charging a constant current (CC)/constant voltage (CV) according to an embodiment of the present invention will be described.

As described above, the ultra-high frequency wireless charger 1 for constant current (CC) / constant voltage (CV) charging according to an embodiment of the present invention resonates the S-LCC topology 21 to implement a constant voltage (CV) charging operation. Both the S-LCC topology 21 and the T-LCL topology 23 may be adopted as a resonance tank in order to adopt a tank and implement a constant current (CC) charging operation.

First, constant voltage (CV) charging operation characteristics of the ultra-high frequency wireless charger 1 for constant current (CC)/constant voltage (CV) charging according to an embodiment of the present invention will be described.

2 to 4 are diagrams for explaining a constant voltage (CV) charging operation characteristic of the charger illustrated in FIG. 1.

Referring to FIG. 2, an equivalent circuit when the ultra-high frequency wireless charger 1 for charging a constant current (CC)/constant voltage (CV) shown in FIG. 1 adopts the S-LCC topology 21 as a resonance tank can be confirmed. .

In FIG. 2, L _tx and L _rx denote the self inductance of the transmitting coil and the receiving coil, respectively, and M denotes the mutual inductance between the transmitting coil and the receiving coil. C _p , C _1s , C _2s , and L _1s represent resonant capacitances and resonant inductances, respectively. In addition, V _{in_AC} represents the voltage source and R _AC represents the equivalent resistance of the load, which can be applied to each variable of the following equations.

In FIG. 2, the first resonant inductor L _1s , the second resonant capacitor C _{2 s} , and the load R _AC may be expressed by merging them into an equivalent impedance Z _{S_cv} as shown in Equation 1 below.

Equation 1 may be expressed as Equation 3 below at a resonance frequency (ω ₀ ) that satisfies Equation 2 below.

Referring to Equation 3, the equivalent impedance Z _{s_cv} may be composed of resistance and capacitance. Accordingly, the equivalent circuit of FIG. 2 can be converted as shown in FIG. 3.

In FIG. 3, the reflected impedance Z _ref from the transmitting end 10 to the receiving end 20 can be expressed as Equation 4 below.

In order to remove the imaginary part in Equation 4, the condition as in Equation 5 below must be satisfied. As a result, the reflection impedance Z _ref at the resonance frequency ω ₀ is a pure resistance component and can be expressed as Equation 6 below.

The equivalent circuit of FIG. 3 can be converted as shown in FIG. 4 by applying the reflection impedance Z _ref (Z _ref (ω ₀ )).

In FIG. 4, the equivalent input impedance Z _in and the transmission current I ₁ can be expressed as Equations 7 and 8 below.

The phase of the equivalent input impedance (Z _in ) can be determined as arg[im{Z _in }/Re{Z _in }], the zero phase of the equivalent input impedance (Z _in ) at the resonance frequency (ω ₀ ). In order to achieve the angle (ZPA: Zero Phase Angle), the imaginary component of the equivalent input impedance Z _in needs to be removed by satisfying the condition as in Equation 9 below.

If the imaginary component of the equivalent input impedance (Z _in) is to satisfy the conditions such as the equation (9) at the resonance frequency (ω _0), the equivalent input impedance at the resonance frequency _{(ω 0) (Z in)} (ω 0) is the following It can be expressed as a real component as shown in Equation 10.

In addition, the resonance frequency transfer current (I ₁₎ (ω ₀₎ of the (ω ₀₎ is expressed as Equation (11) below.

According to Equation 11, since the transmission current (I ₁ ) (ω ₀ ) at the resonance frequency (ω ₀ ) has the same phase as the input voltage, constant current (CC) / constant voltage (CV) charging according to an embodiment of the present invention The ultra-high frequency wireless charger 1 has the advantage of being able to greatly suppress the circulating current of the transmission loop.

On the other hand, when applying a voltage law (Kirchhoff's voltage law) of Kirchhoff in Figure 3, the received current of the receiving electric current (I ₂₎ and a resonant frequency (ω ₀₎ of the receiving coil (I ₂₎ (ω ₀₎ is It can be expressed as Equations 12 and 13 below, respectively.

From Equation 13, the voltage gain during the constant voltage (CV) charging operation of the ultra-high frequency wireless charger 1 for charging a constant current (CC)/constant voltage (CV) according to an embodiment of the present invention can be expressed as Equation 14 below. have.

According to Equation 14, the ultra-high frequency wireless charger 1 for charging a constant current (CC)/constant voltage (CV) according to an embodiment of the present invention is, when the charging operation at the resonance frequency (ω ₀ ), the output voltage is a load condition It can be confirmed that it is constant regardless of.

According to Equation 14, the ultra-high frequency wireless charger 1 for charging a constant current (CC)/constant voltage (CV) according to an embodiment of the present invention is an input voltage when charging operation at a resonance frequency (ω ₀ ). It can be seen that it varies according to (V _{in_AC} ), resonance inductance (L _1s ), and mutual inductance (M) between the transmitting coil and the receiving coil. Here, when the mutual inductance (M) is fixed, the output voltage may be adjusted by the resonance inductance (L _1s ).

Accordingly, when the ultra-high frequency wireless charger 1 for constant current (CC)/constant voltage (CV) charging according to an embodiment of the present invention is designed so that each parameter of the resonant elements satisfies Equations 2, 5 and 9, It will be possible to implement constant voltage (CV) charging.

Hereinafter, characteristics of a constant current (CC) charging operation of the ultra-high frequency wireless charger 1 for charging a constant current (CC)/constant voltage (CV) according to an embodiment of the present invention will be described.

5 to 8 are views for explaining the constant current (CC) charging operation characteristics of the charger illustrated in FIG. 1.

Referring to FIG. 5, an S-LCC topology 21 and a T-LCL topology 23 in which an ultra-high frequency wireless charger 1 for charging a constant current (CC)/constant voltage (CV) shown in FIG. 1 is connected in series with a resonance tank. The equivalent circuit in the case of adopting can be checked. The T-LCL topology 23 may receive a constant voltage V _{in_T} from the S-LCC topology 21.

In FIG. 5, each parameter is replaced with the one described with reference to FIG. 2, but L _sc1 , L _sc2, and C _sc denote resonance inductances and resonance capacitances included in the T-LCL topology 23, respectively.

Referring to FIG. 6, the T-LCL topology 23 may include two inductors L _sc1 and L _sc2 and one capacitor C _sc , and R _AC represents the equivalent resistance of the load.

In FIG. 6, the third resonant inductor L _sc2 , the third resonant capacitor C _sc , and the load R _AC may be expressed by merging them into an equivalent impedance Z _eq as shown in Equation 15 below.

Equation 15 can be expressed as Equation 17 below at a resonance frequency (ω ₀ ) that satisfies Equation 16 below.

Referring to Equation 17, the equivalent impedance Z _eq at a resonance frequency ω ₀ that satisfies the conditions as in Equation 16 may be composed of resistance and capacitance. Therefore, the equivalent circuit of FIG. 6 can be converted as shown in FIG. 7.

In FIG. 7, the equivalent input impedance Z _{in_T} can be expressed as Equation 18 below.

When the second resonant inductor L _sc1 is designed to satisfy Equation 19 below, the reactive components in FIG. 7 may be canceled from each other, and the equivalent circuit of FIG. 7 can be converted as shown in FIG. I can.

When the second resonant inductor L _sc1 satisfies Equation 19, the equivalent input inductance Z _{in_T} may have a pure resistance component as shown in Equation 20 below.

Accordingly, in FIG. 8, the input current I _{in_T} and the output current I _{o_T} can be calculated as shown in Equations 21 and 22 below, respectively.

According to Equation 22, the ultra-high frequency wireless charger 1 for charging a constant current (CC)/constant voltage (CV) according to an embodiment of the present invention is an S-LCC topology 21 and a T-LCL topology connected in series by a resonance tank. When (23) is adopted and the charging operation at the resonance frequency (ω ₀ ), it can be confirmed that the output current (I _{o_T} (ω ₀ )) is constant regardless of the load condition.

According to Equation 22, the ultra-high frequency wireless charger 1 for charging a constant current (CC)/constant voltage (CV) according to an embodiment of the present invention is an S-LCC topology 21 and a T-LCL topology connected in series by a resonance tank. (23), and when charging operation at the resonance frequency (ω ₀ ), the output current (I _{o_T} (ω ₀ )) is the input voltage (V _{in_T} ), the operating frequency (ω ₀ ), and the T-LCL topology (23 It can be seen that the fluctuation only depends on the resonance components (L _sc2 and C _sc ) included in ).

Here, the input voltage (V _{in_T} ) is the output voltage of the S-LCC topology 21, and as described above, the S-LCC topology 21 generates a constant output voltage when the resonance parameters are designed to satisfy a predetermined condition. can do.

Accordingly, the ultra-high frequency wireless charger 1 for constant current (CC)/constant voltage (CV) charging according to an embodiment of the present invention may operate as a load-independent current source to implement constant current (CC) charging.

Hereinafter, the present invention for achieving constant current (CC)/constant voltage (CV) charging of a battery under the conditions of the constant current (CC)/constant voltage (CV) charging parameters and the resonance frequency (switching frequency) of the battery as shown in Table 1 below. A method of designing an ultra-high frequency wireless charger 1 for charging a constant current (CC)/constant voltage (CV) according to an embodiment will be described.

9 is a diagram illustrating an example of a voltage and an equivalent impedance of a battery during a charging mode by an ultra-high frequency wireless charger for charging a constant current (CC)/constant voltage (CV) according to an embodiment of the present invention.

When the ultra-high frequency wireless charger 1 for constant current (CC) / constant voltage (CV) charging according to an embodiment of the present invention is designed under the conditions shown in Table 1, the battery is constant current (CC) / constant voltage ( CV) mode will be charged and fully charged.

First, the design of the transmitter 10 of the ultra-high frequency wireless charger 1 for charging a constant current (CC)/constant voltage (CV) according to an embodiment of the present invention will be described.

The ultra-high frequency wireless charger (1) for constant current (CC) / constant voltage (CV) charging according to an embodiment of the present invention connects the transmitter 10 to a first switch (S ₁ ), a second switch (S ₂ ), and a ZVS tank. It can be configured as, and may include a Class D amplifier for controlling the first switch (S ₁ ) and the second switch (S ₂ ) (see FIG. 1).

For example, the output of the Class D amplifier may be the gate voltage of the first switch (S ₁ ) and the second switch (S ₂ ).

In general, Class D amplifiers or Class E amplifiers are widely used in ultra-high frequency wireless power transfer (WPT) systems. Class E amplifiers have high conversion efficiency as the number of parasitic components is small compared to Class D amplifiers. However, when compared to Class D amplifiers, Class E amplifiers are sensitive to load changes, making it difficult to achieve ZVS (Zero Voltage Switching) conditions for the entire load range. Accordingly, in recent years, Class D amplifiers can implement zero voltage switching operation and are evaluated as being able to achieve higher efficiency compared to Class E amplifiers in that they do not require a choke inductor.

In addition, GaN MOSFETs switches have lower gate charge and output capacitance than silicon switches, and thus show excellent performance in wireless power transfer (WPT) systems. In a low-power converter, since the charge required for switch operation is relatively large, low gate charge and output capacitance are important factors.

Therefore, GaN MOSFETs switches and Class D amplifiers with zero voltage switching characteristics are suitable to be applied as power amplifiers for wireless power transfer (WPT) chargers.

Accordingly, the ultra-high frequency wireless charger 1 for charging a constant current (CC)/constant voltage (CV) according to an embodiment of the present invention includes a first switch (S ₁ ) and a second switch (S ₂ ) provided at the transmitting end 10. ) Can be implemented as a GaN MOSFET switch, and the transmitter 10 can be configured including a Class D amplifier that controls it and a ZVS tank to achieve its zero voltage switching condition.

In order to achieve the maximum efficiency of the transmitting end 10, the ZVS tank must be designed to accurately perform the resonance operation in the resonance condition.

The ultra-high frequency wireless charger 1 for constant current (CC)/constant voltage (CV) charging according to an embodiment of the present invention is a zero voltage of the first switch (S ₁ ) and the second switch (S ₂ ) by a Class D amplifier. Switching conditions can be achieved. However, the Class D amplifier may generate high switching losses due to parasitic capacitances of the first switch S ₁ and the second switch S ₂ within a specific load range.

Accordingly, the ultra-high frequency wireless charger 1 for charging a constant current (CC)/constant voltage (CV) according to an embodiment of the present invention may include a ZVS tank. The ZVS tank may contain a series connected ZVS inductor (L _ZVS ) and a ZVS capacitor (C _ZVS ) (see FIG. 1 ). The ZVS tank may generate a sufficient negative current to discharge the parasitic capacitor before the turn-on operation of the first switch S ₁ and the second switch S ₂ . For this, the value of the ZVS tank inductor L _ZVS of the ZVS tank may be calculated as in Equation 23 below.

△ t _vt in equation (23) is of the first switch (S ₁₎ or the second switch (S _2), and a voltage transition represents the time C _oss the first switch (S ₁₎ or the second switch (S ₂₎ Means parasitic capacitance.

Hereinafter, a design of a resonance tank included in the receiving end 20 of the ultra-high frequency wireless charger 1 for charging a constant current (CC)/constant voltage (CV) according to an embodiment of the present invention will be described.

The relationship between the DC input and the AC output of the ultra-high frequency wireless charger 1 for constant current (CC) / constant voltage (CV) charging according to an embodiment of the present invention is based on the Fundamental Harmonic Analysis (FHA) as shown in Equation 24 below. Can be indicated.

_Substituting V _{in_AC} and V _{o_AC} of Equation 24 into Equation 14, the DC voltage gain (G _v ) of the ultra-high frequency wireless charger 1 for charging a constant current (CC) / constant voltage (CV) according to an embodiment of the present invention (ω ₀ )) can be calculated as in Equation 25 below.

Using Equation 22, the mutual inductance gain G _{i_T} (ω ₀ ) of the T-LCL topology 23 can be calculated as in Equation 26 below.

Meanwhile, since the T-LCL topology 23 is connected to the S-LCC topology 21 in a cascade structure, the mutual inductance gain (G _i (ω ₀ )) of the receiving end 20 is calculated according to Equations 24, 25, and 26. It can be calculated as in Equation 27 below.

The resonance tank of the ultra-high frequency wireless charger 1 for charging a constant current (CC)/constant voltage (CV) according to an embodiment of the present invention may be designed in the following order.

If the input DC voltage (V _i ), rated power (P _o ), required constant current (CC)/constant voltage (CV) values (I _O , V _O ) and coil distance and dimensions are determined as shown in Table 1, the transmitter Inductance and mutual inductance (M) of the transmitting coil (L _tx ) and the receiving coil (L _rx ) of each of (10) and the receiving end 20 may be calculated.

And setting the inductance of the first resonance inductor (L _1s) of the resonant capacitor (C _p) S-LCC topology 21 by setting the capacitance, and using the equation (25) of the transmitting terminal 10 by using the equation (9) And, using Equation 2, the capacitance of the second resonant capacitor C _2s of the S-LCC topology 21 is set, and the first resonant capacitor C of the S-LCC topology 21 is set using Equation 5 _1s ) of capacitance can be set.

In addition, the inductance of the second and third resonant inductors L _sc1 and L _sc2 of the T-LCL topology 23 is set using Equation 27, and the T-LCL topology 23 is The capacitance of the third resonant capacitor C _sc may be set.

The ultra-high frequency wireless charger 1 for constant current (CC)/constant voltage (CV) charging according to an embodiment of the present invention can design a resonance tank with the parameters set as above, and Table 2 below is in the same order as above. It shows an example of the parameters of the resonance tank set accordingly.

The ultra-high frequency wireless charger 1 for constant current (CC)/constant voltage (CV) charging according to an embodiment of the present invention is configured to change the resonance network according to the charging mode, so that one operating frequency (for example, 6.78 MHz) can implement constant current (CC)/constant voltage (CV) charging.

As such, the ultra-high frequency wireless charger 1 for constant current (CC)/constant voltage (CV) charging according to an embodiment of the present invention is a back-end DC-DC converter for implementing a constant current (CC)/constant voltage (CV) charging mode. It has the advantage of reducing the loss and cost of the entire system because it does not require.

In addition, the ultra-high frequency wireless charger 1 for charging a constant current (CC)/constant voltage (CV) according to an embodiment of the present invention includes a ZVS tank in the transmission terminal 10 and a power switch of the transmission terminal 10 within the entire load range. Since the zero voltage switching condition of (S ₁ , S ₂ ) can be achieved, the overall efficiency of the system can be improved.

In addition, the ultra-high frequency wireless charger 1 for constant current (CC)/constant voltage (CV) charging according to an embodiment of the present invention is the transmitting end 10 in the conversion from the constant current (CC) charging mode to the constant voltage (CV) charging mode. ) And a feedback circuit between the receiving end 20 are not required, and thus can be applied to a wireless power transmission (WPT) system.

Although the above has been described with reference to embodiments, those skilled in the art will understand that various modifications and changes can be made to the present invention without departing from the spirit and scope of the present invention described in the following claims I will be able to.

1: Ultra-high frequency wireless charger for constant current (CC)/constant voltage (CV) charging
10: transmitting end
20: receiving end
21: S-LCC topology
23: T-LCL topology

Claims (10)

In the ultra-high frequency wireless charger for charging a constant current (CC) / constant voltage (CV) charging a battery connected to the receiving coil through inductive power transfer (IPT) between a transmitting coil and a receiving coil,
A transmission terminal for transferring an input voltage supplied from the input power to the transmission coil by a switching operation of a plurality of switches connected to the input power; And
An S-LCC topology connected to the receiving coil and a T-LCL topology connected to a rear end of the S-LCC topology, and induced power between the transmitting coil and the receiving coil by a resonance tank composed of the S-LCC topology Includes a receiving end for charging the battery by outputting a constant voltage through transmission, or outputting a constant current through induction power transfer between the transmitting coil and the receiving coil by a resonance tank composed of the S-LCC topology and the T-LCL topology. and,
The receiving end,
A first resonant switch connecting the S-LCC topology and a rectifier circuit connected to the battery;
A second resonance switch having both ends connected to an output voltage line connected to the T-LCL topology and the receiving coil, respectively; And
By sensing the voltage at both ends of the battery and controlling the switching operation of the first resonance switch and the second resonance switch to switch between the constant current (CC) charging mode and the constant voltage (CV) charging mode according to the voltage of both ends of the battery Ultra-high frequency wireless charger for charging constant current (CC) / constant voltage (CV) including a resonance switch control unit that changes the structure of the resonance tank. delete The method of claim 1,
The receiving end,
A third provided between the S-LCC topology and the rectifier circuit connected to the battery and connected to a contact point between the second and third resonant inductors connected in series, and the second and third resonant inductors. Ultra-high frequency wireless charger for charging constant current (CC)/constant voltage (CV) including the T-LCL topology including a resonant capacitor. The method of claim 3,
The receiving end,
A first resonant switch connected to both ends of the second resonant inductor and the third resonant inductor connected in series; And
An ultra-high frequency wireless charger for charging a constant current (CC)/constant voltage (CV) including a second resonance switch having both ends connected to the third resonance capacitor and an output voltage line connected to the receiving coil. The method of claim 1,
The receiving end,
Constant current (CC)/constant voltage including the S-LCC topology including a second resonant capacitor and a first resonant inductor connected to the first resonant capacitor in parallel with the first resonant capacitor connected to the receiving coil ( CV) Ultra-high frequency wireless charger for charging. The method of claim 1,
The transmitting end,
A first switch and a second switch provided on a bridge connected to both ends of the input power and implemented as GaN MOSFET switches;
A Class D amplifier controlling a turn-on or turn-off operation of the first switch and the second switch;
A ZVS tank connected to a contact point between the first switch and the second switch and generating a negative current for discharging the parasitic capacitor added to the first switch and the second switch including a ZVS inductor and a ZVS capacitor ; And
An ultra-high frequency wireless charger for charging a constant current (CC)/constant voltage (CV) provided between the ZVS tank and the transmission coil and comprising a transmission capacitor constituting the S-LCC topology or the T-LCL topology and the resonance tank. The method of claim 6,
The first switch and the second switch,
An ultra-high frequency wireless charger for charging a constant current (CC)/constant voltage (CV) controlled by switching under a zero voltage switching condition by the ZVS tank. In the method of controlling an ultra-high frequency wireless charger for charging a constant current (CC)/constant voltage (CV) charging a battery provided in the receiving end through inductive power transfer (IPT) between a transmitting end and a receiving end,
Configuring a resonant tank formed at the receiving end in a series-connected S-LCC topology and a T-LCL topology to control in a constant current (CC) charging mode;
Sensing a voltage across the battery; And
When the voltage at both ends of the battery reaches the maximum charging voltage, a constant current (CC)/constant voltage (CV) comprising the step of controlling a resonant tank formed at the receiving end in an S-LCC topology to a constant voltage (CV) charging mode. ) How to control ultra-high frequency wireless charger for charging. The method of claim 8,
The step of configuring a resonance tank formed at the receiving end in a series-connected S-LCC topology and a T-LCL topology to control in a constant current (CC) charging mode,
Turning-off control of a first resonant switch connecting the S-LCC topology and a rectifier circuit connected to the battery; And
Constant current (CC)/constant voltage (CV) charging comprising the step of turning on a second resonant switch connected to an output voltage line connected to a receiving coil and a receiving coil that receives induction power from the T-LCL topology and the transmitting end, respectively. How to control ultra-high frequency wireless charger for use. The method of claim 9,
When the voltage at both ends of the battery reaches the maximum charging voltage, the step of configuring a resonance tank formed at the receiving end in an S-LCC topology to control the constant voltage (CV) charging mode,
Turning on the first resonance switch; And
Control method of an ultra-high frequency wireless charger for charging a constant current (CC)/constant voltage (CV) comprising the step of controlling the turn-off of the second resonance switch.

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