KR20120100666A - Overvoltage protection circuit, power transfer apparatus comprising it and control method of power transfer apparatus - Google Patents

Abstract

PURPOSE: An overvoltage protecting circuit, a power transmitting device including the same, and a control method of the device are provided to improve performance for dealing with overvoltage by consistently maintaining receiving-end impedance. CONSTITUTION: A sensing unit(242a) generates a control signal by sensing an input voltage and a first current. The first current flows from an input terminal to an output terminal. A current control unit(242b) controls a second current flowing from the input terminal to a ground connection. An input current is generated by combing the first current with the second current. The current control unit is placed between the input terminal and the ground connection. [Reference numerals] (242a) Sensing unit; (242b) Current control unit; (AA) Input current; (BB,CC) First current; (DD) Input terminal; (EE) Output terminal; (FF) Second current; (GG) Equivalent resistance; (HH) Sensing signal; (II) Control signal; (JJ) Input voltage

Description

OVERVOLTAGE PROTECTION CIRCUIT, POWER TRANSFER APPARATUS COMPRISING IT AND CONTROL METHOD OF POWER TRANSFER APPARATUS}

The present invention relates to an overvoltage protection circuit, a power transmission device including the same, and a control method of the power transmission device.

Recently, with the development of wireless communication technology, electronic products for transmitting various information and signals wirelessly are increasing. In addition, studies on a method of wirelessly transmitting power required for driving electronic products are also in progress. Examples of methods of transmitting power wirelessly include electromagnetic induction and magnetic resonance.

The power transmission device generally includes a resonant circuit. At times, a very large overvoltage may be applied to the inside of the power transmission device due to the resonance effect and external influence of the resonant circuit. Such overvoltages can damage internal circuits and their associated electronics. Therefore, an overvoltage protection circuit is needed to protect the circuit from overvoltage. However, the overvoltage protection circuit consumes power on its own. In addition, an impedance mismatch may occur between the transmitter and the receiver due to the overvoltage protection circuit. As a result, the transmission efficiency of the wireless power transmission device is lowered.

An object of the present invention is to provide an overvoltage protection circuit having a low power consumption, a power transmission device including the same, and a control method of the power transmission device.

Another object of the present invention is to provide an overvoltage protection circuit having improved impedance matching characteristics, a power transmission device including the same, and a control method of the power transmission device.

Still another object of the present invention is to provide an overvoltage protection circuit for protecting an internal circuit from overvoltage, a power transmission device including the same, and a control method of the power transmission device.

An overvoltage protection circuit according to an embodiment of the present invention includes a sensing unit and a current control unit. The sensing unit generates a control signal by sensing a first current flowing from an input terminal to an output terminal and an input voltage transmitted to the input terminal. The current controller controls the second current flowing from the input terminal to the ground to maintain a constant ratio of the input voltage to the input current flowing from the input terminal in response to the control signal.

In an embodiment, the input current may be a sum current of the first current and the second current.

In an embodiment, the current controller may include a variable resistor connecting the input terminal and the ground.

The power transmission apparatus according to the embodiment of the present invention includes a receiver and a transmitter. The receiver includes an overvoltage protection circuit and provides a feedback signal to the transmitter. The transmitter supplies the transmission power to the receiver. The transmitter controls the magnitude of the transmission power with reference to the feedback signal to control the power consumption of the overvoltage protection circuit.

In example embodiments, the overvoltage protection circuit may include a detector and a current controller. The sensing unit generates a control signal by sensing a first current flowing from an input terminal to an output terminal and an input voltage transmitted to the input terminal. The current controller controls the second current flowing from the input terminal to the ground to maintain a constant ratio of the input voltage to the input current flowing from the input terminal in response to the control signal.

In an embodiment, the input current may be a sum current of the first current and the second current.

In an embodiment, the receiver may include a DC converter that converts the power output from the overvoltage protection circuit and provides the load to the load.

According to an embodiment, the apparatus may include a feedback controller which receives the sensing signal and provides the feedback signal as a feedback signal.

In example embodiments, the detection signal may include a signal representing the value of the second current.

In example embodiments, the overvoltage protection circuit may further include a switch configured to electrically disconnect the DC converter from the overvoltage protection circuit.

In an embodiment, the switch unit may include a switch located between the sensing unit and the DC converter and a switch controller that controls opening and closing of the switch.

In example embodiments, the receiver may further include a rectifier positioned at a front end of the overvoltage protection circuit to rectify AC power into DC power.

In example embodiments, the receiver may further include a matching circuit positioned in front of the rectifier to match an impedance between the transmitter and the receiver.

According to an embodiment of the present invention, a method of controlling a power transmission device including an overvoltage protection circuit may include: detecting a first current flowing from an input terminal of the overvoltage protection circuit to an output terminal of the overvoltage protection circuit; Sensing an input voltage delivered to the input terminal; And controlling a second current flowing from the input terminal to the ground such that the ratio of the input voltage to the current flowing from the input terminal is constant with reference to the first current and the input voltage.

As an example. Providing a value of the input voltage or the value of the second current to a transmitter as a feedback signal; And controlling the magnitude of power transmitted from the transmitter to the receiver with reference to the feedback signal.

In an embodiment, the controlling of the magnitude of power may include reducing the magnitude of the transmitted power when the second current value exceeds the reference current value, and increasing the magnitude of the transmitted power when the second current value exceeds the reference current value. have.

According to the embodiment of the present invention as described above, a power transmission device with low power consumption is provided.

In addition, the internal circuit of the power transmission device is protected from overvoltage.

In addition, the impedance matching characteristic of the power transmission device is improved.

1 is a block diagram illustrating a power transmission apparatus 1000 according to an exemplary embodiment of the present invention.
FIG. 2 is a block diagram illustrating the overvoltage protection circuit 240 shown in FIG. 1.
FIG. 3 is a circuit diagram assuming that the current divider 242 shown in FIG. 2 is a fixed resistor.
4 is a block diagram illustrating an example of a current distributor 242 according to the present invention.
FIG. 5 is a block diagram illustrating the switch unit 241 illustrated in FIG. 2.
FIG. 6 is a diagram illustrating the DC / DC converter 250 illustrated in FIG. 1.
FIG. 7 is a diagram illustrating an embodiment of a power transmission device having reduced power consumed by an overvoltage protection circuit.
FIG. 8 is a diagram for describing the matching circuit 220 of FIG. 1.
FIG. 9 is a block diagram illustrating the rectifying unit 230 illustrated in FIG. 1.
10A is a circuit diagram exemplarily illustrating the rectifier circuit 231 of FIG. 9.
FIG. 10B is a waveform diagram comparing the input voltage V _A and the output voltage V _B shown in FIG. 10A.
FIG. 11 is an exemplary view illustrating the noise filter 232 illustrated in FIG. 9.
12A is a circuit diagram exemplarily illustrating the smoothing circuit 233 shown in FIG. 9.
FIG. 12B is a waveform diagram comparing the input voltage (dotted line, V _I ) and the output voltage (solid line, V _O ) shown in FIG. 12A.
13 is a flowchart illustrating a control method of a power transmission apparatus according to an embodiment of the present invention.

Both the foregoing general description and the following detailed description are exemplary in order to provide further explanation of the claimed invention. Therefore, the present invention is not limited to the embodiments described herein and may be embodied in other forms. The embodiments introduced herein are provided to ensure that the disclosed contents are thorough and complete, and that the spirit of the present invention can be sufficiently delivered to those skilled in the art.

In the present specification, when a part is mentioned to include a certain component, it means that it may further include other components. In addition, each embodiment described and illustrated herein also includes a complementary embodiment thereof. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As a method of transmitting power wirelessly, an electromagnetic induction method is generally used. Specifically, wireless power transmission using electromagnetic induction is used in electric toothbrushes and the like. However, in the electromagnetic induction method, the rate of decrease in transmission efficiency with increasing distance is too large. In addition, there is a problem that heat generation may occur due to the eddy current.

 Recently, the magnetic resonance wireless power transmission method can obtain high transmission efficiency even from a long distance compared with the electromagnetic induction method. Magnetic resonance wireless power transfer is based on attenuation wave coupling. Attenuation wave coupling refers to a phenomenon in which electromagnetic waves move from one medium to another through a near field when two mediums resonate at the same frequency. Therefore, the magnetic resonance wireless power transfer method transfers energy only when the resonant frequencies between the two media are the same, and the untransmitted energy is reabsorbed by the electromagnetic field.

On the other hand, although the magnetic resonance type is capable of wireless power transmission to a far distance than the conventional electromagnetic induction method, there is still a problem that the transmission efficiency decreases depending on the distance. In addition, the optimum impedance matching point cannot be determined when the electronic device receiving the power is not fixed.

1 is a block diagram illustrating a power transmission apparatus according to an embodiment of the present invention. Referring to FIG. 1, the power transmission apparatus 1000 includes a transmitter 100 and a receiver 200.

The transmitter 100 includes a power generator 110 and a transmission coil 120 that generate power. The receiver 200 includes a receiver coil 210, a matching circuit 220, a rectifier 230, an overvoltage protection circuit 240, a DC / DC converter 250 (hereinafter referred to as a DC converter), and a feedback controller 260. do. Power transmission between the transmitter 100 and the receiver 200 is achieved by exchanging electromagnetic waves.

The transmission coil 120 transmits the power generated by the power generator 110 in the form of electromagnetic waves. The receiving coil 210 receives the electromagnetic wave transmitted from the transmitting coil 120 and converts it into electric power. Mutual conversion between electromagnetic waves and power is caused by electromagnetic induction or magnetic resonance.

The transmitting coil 120 and the receiving coil 210 may have different configurations depending on the wireless power transmission method. For example, in the electromagnetic induction method, the transmitting coil 120 and the receiving coil 210 may each be composed of one coil. On the other hand, in the magnetic resonance method, the transmitting coil 120 and the receiving coil 210 may be respectively composed of two or three coils.

Since the contents of the transmitting coil 120 and the receiving coil 210 are well known in the art, detailed description thereof will be omitted.

The transmitter 100 and the receiver 200 of the power transmission apparatus 1000 generally include a resonant circuit. Therefore, a very large overvoltage may occur due to the resonance phenomenon. Overvoltage can also be caused by external interference. Since the internal circuit and the connected load 300 may be damaged from the overvoltage, the receiver 200 includes the overvoltage protection circuit 240.

Another problem caused by overvoltage is that the transmitter 100 may change an equivalent impedance (hereinafter referred to as a receiver impedance) viewed by the receiver 200. For example, when overvoltage occurs, the switch 241b connecting the load 300 and the receiver 200 may be turned off to protect the load 300. This increases the receiver impedance. In general, the power transmitter matches the impedance between the transmitter 100 and the receiver 200 in order to increase transmission efficiency. However, when the receiving terminal impedance changes, the impedance matching point changes, and thus impedance matching is not performed. This generates reflected power, which cannot deliver maximum power and degrades power transfer efficiency.

In addition, a change in the load 300 can itself cause a greater overvoltage. Equation 1 shows how the voltage across the load changes when the load changes.

Where V is the voltage across the load and R is the resistance of the load. Referring to Equation 1, the voltage across the load increases with the ratio of the square root of the load change rate.

In particular, when an overvoltage is generated at an input terminal and a current path connecting the receiver 200 and the load 300 is cut off, the receiver impedance increases. When the power supplied is constant, the voltage is proportional to the square root of the resistance (see Equation 1), so the voltage increases as the resistance increases. Thus, the result is that the receiver impedance increased by the overvoltage generates a larger overvoltage.

The present invention proposes an overvoltage protection circuit that not only protects an internal circuit and a load from overvoltage, but also maintains a constant impedance of a receiver to increase power transmission efficiency and improve overvoltage response performance.

2 is a block diagram illustrating the overvoltage protection circuit 240 illustrated in FIG. 1. Referring to FIG. 2, the overvoltage protection circuit 240 includes a switch unit 241 and a current distributor 242. The switch unit 241 protects the load and the internal circuits by blocking a current path connected to the load when an overvoltage is applied. The current distributor 242 allows the equivalent resistance seen from the input terminal to be kept constant. This is done by adjusting the magnitude of the current flowing from the input terminal to ground. The configuration and operation principle of the switch unit 241 and the current distribution unit 242 will be described in detail below.

FIG. 3 is a circuit diagram assuming that the current divider 242 shown in FIG. 2 is a fixed resistor. Referring to FIG. 3, the current distributor 242 includes a ground resistor R _M connected between the input terminal and the ground. Ground resistance (R _M ) flows a constant current to ground depending on the input voltage (V _IN ).

This is a simple example in which the current distributor 242 is composed of only one fixed resistor, but this alone can reduce the change in the load impedance and the change in the receiver impedance due to the overvoltage. In detail, when the load 300 is directly connected to the current distributor 242, the equivalent resistance R _IN may be the same as the load 300 when there is no ground resistance R _M. At that time, the rate of change of the equivalent resistance R _IN according to the change of the load 300 becomes 1. On the other hand, the equivalent resistance R _IN of the circuit including the ground resistance R _M is expressed by Equation 2 below.

At this time, the change rate of the equivalent resistance (R _IN ) according to the change of the load 300 is shown in Equation 3.

In Equations 2 and 3, R _L denotes a resistance value of the load 300.

Referring to Equation 3, it can be seen that the change rate e of the equivalent resistance RIN according to the change of the load 300 is smaller than one. That is, only the configuration as shown in FIG. 3 has the effect of reducing the change in the receiver impedance.

As shown in Equation 3, when the fixed resistor is used, the smaller the ground resistance R _M , the smaller the rate of change e of the equivalent resistance R _IN . In addition, even in the event of an overvoltage, the ground resistance R _M must be small in order to quickly flow a large amount of current to the ground. Therefore, the smaller the ground resistance R _M value is, the better the performance.

However, selecting a small ground resistance (R _M ) value causes some problems. The first is that the ground resistance (R _M ) continues to consume power even when it is not in an overvoltage condition, thus reducing power transmission efficiency. In particular, since the power consumption is inversely proportional to the size of the resistor (P = V ² / R), the smaller the ground resistance R _M , the greater the power consumed.

The second is to use a fixed ground resistor (R _M ), so that the equivalent resistance (R _IN ) cannot be completely prevented from changing with the load. That is, in Equation 3, the use of the ground resistor R _M can reduce the change in the equivalent resistance R _IN , but cannot be changed at all. In addition, since it has a fixed resistance value, it is impossible to proactively respond to various situations. Therefore, the current distribution unit 242 in which the above problem is solved should be considered.

4 is a block diagram illustrating an example of a current distributor 242 according to the present invention. Referring to FIG. 4, the current distributor 242 includes a detector 242a and a current controller 242b. The current distributor 242 distributes the input current I _IN flowing from the input terminal into current paths. By way of example, the current path may be from the input to the output and from the input to ground.

The sensing unit 242a refers to a current flowing from the input terminal to the output terminal (I ₁ , hereinafter referred to as a first current) and a voltage applied to the input terminal (V _IN , hereinafter referred to as an input voltage), and outputs a corresponding control signal to the current controller. To 242b.

The current controller 242b controls the magnitude of the current I ₂ (hereinafter referred to as a second current) flowing from the input terminal to the ground with reference to the control signal. In an embodiment, the input voltage V _IN may be detected by the current controller 242b. In this case, the detector 242a generates a control signal with reference to only the first current, and the current controller 242b controls the second current I ₂ with reference to the control signal and the input voltage V _IN .

Current control section (242b) controls the input voltage (V _IN), the first and second currents (I _1, I ₂₎ and a second current so as to satisfy the relation such as Equation 4 (I _2).

Referring to FIG. 4, the current I _IN coming from the input terminal of the current distributor 242 is equal to the sum of the first current I ₁ and the second current I ₂ . In this case, the equivalent resistance R _IN viewed from the input terminal is a value obtained by dividing the input voltage V _IN by the input current I _IN .

Therefore, if Equation 4 is satisfied, the equivalent resistance R _IN may be expressed as Equation 5.

When the second current I ₂ is controlled to satisfy Equation 4, the equivalent resistance R _IN may be kept constant despite the change in the input voltage V _IN and the first current. This fixes the impedance viewed toward the load 300 from the input terminal of the overvoltage protection circuit 240. Therefore, even if the load 300 and the first current change due to the overvoltage, the receiver impedance is kept constant.

More specifically, the detector 242a outputs a control signal to the current controller 242b with reference to the input voltage V _IN and the first current I ₁ . The control signal is provided as a reference signal necessary for controlling the second current I ₂ in the current controller 242b. The current controller 242b flows a current required to maintain the equivalent resistance R _IN to the ground with reference to the control signal.

Referring to Equation 5, the second current I ₂ should be controlled in a direction proportional to the input voltage V _IN and inversely proportional to the first current I ₁ . That is, the current controller 242b controls the second current I ₂ , which is the remaining factor, to cancel the change of the input voltage V _IN and the first current I ₁ , which are two factors shown in Equation 5. When the overvoltage is applied and the input voltage V _IN becomes high, the second current is increased. The current path to the load is interrupted, increasing the second current as the first current decreases. As a result, the equivalent resistance R _IN can be maintained at a constant value.

In an embodiment, the current controller 242b may include a variable resistor. The variable resistor can be connected in parallel between the input terminal and ground. The current controller 242b adjusts the resistance value of the variable resistor with reference to the control signal shown in FIG. 4. When the resistance of the variable resistor changes, the magnitude of the second current I ₂ also changes. Therefore, if the resistance value of the variable resistor is properly adjusted according to the control signal, the magnitude of the second current I ₂ can be controlled.

According to this configuration, the current controller 242b can variably adjust the magnitude of the second current I ₂ . By precisely controlling the variable resistor, the equivalent resistance R _IN can be kept constant.

According to the configuration of the present invention as described above, since the second current is controlled so that the equivalent resistance (R _IN ) seen from the input terminal of the overvoltage protection circuit 240 is constant, the receiving terminal impedance is kept constant. As a result, the impedance matching characteristic of the power transmission apparatus 1000 is improved.

Meanwhile, the current controller 242b provides the input voltage V _IN value and the second current I ₂ value to the feedback controller 260 (see FIG. 1) as a detection signal. In addition, according to the configuration of the present invention, the power consumed by the overvoltage protection circuit 240 can be minimized. Details thereof will be described in detail later with reference to the DC converter 250 and the feedback controller 260.

FIG. 5 is a block diagram illustrating the switch unit 241 illustrated in FIG. 2. Referring to FIG. 5, the switch unit 241 includes a switch 241b and a switch controller 241a. The switch 241b electrically connects or blocks the receiver 200 and the load 300. The switch controller 241a controls the opening and closing of the switch 241b.

The voltage (hereinafter referred to as node voltage) applied at the input terminal of the switch unit 241 is sensed by the switch controller 241a. In an embodiment, the switch controller 241a may store a reference voltage (hereinafter, referred to as a reference voltage) for determining whether an overvoltage exists. When the node voltage exceeds the reference voltage, the switch controller 241a turns off the switch 241b. When the switch 241b is off, the load 300 is electrically disconnected from the receiver 200. As a result, the load 300 is protected from overvoltage. When the node voltage is below the reference voltage (hereinafter, referred to as a normal voltage state), the switch controller 241a turns on the switch 241b. When the switch 241b is turned on, the load 300 is electrically connected to the receiver 200. Therefore, power is supplied from the receiver 200 to the load 300 in the normal voltage state.

In an embodiment, the switch 241b may be formed of a MOSFET. At this time, the switch controller 421a may turn the switch 241b on and off by controlling the gate voltage of the MOSFET.

According to the configuration of the switch unit 241 as described above, the current path to the load is interrupted by turning off the switch when an overvoltage occurs. As a result, the load is protected from overvoltage.

FIG. 6 is a diagram illustrating an example of the DC converter illustrated in FIG. 1. Referring to FIG. 6, an output terminal of the DC converter 250 is connected to a load R _L.

The applied voltage Va and the applied current Ia are input to the input terminal of the DC converter 250. The output voltage Vo and the output current Io are output from the output terminal of the DC converter 250. The DC converter 250 is a device for supplying rated power necessary for driving a load. Therefore, the DC converter 250 serves to convert the applied voltage into the rated voltage of the load to provide. At this time, the DC converter 250 will supply a constant voltage as the output voltage Vo.

On the other hand, the supply power Pa input from the input terminal and the load power Po output from the output terminal are expressed as in Equation 6.

However, assuming that Vo = Io × R _L and the DC converter 250 has 100% conversion efficiency, Pa = Po.

For example, suppose the load is an electrical device with a rated specification of 5V, 10W. In this case, the power supplied to the DC converter 250 should also be 10W. For example, when the applied voltage is 10V, the current applied to the DC converter 250 becomes 1A. On the other hand, when the applied voltage is 4V, the current applied to the DC converter 250 becomes 2.5A. The magnitude of the applied voltage and the applied current of the DC converter 250 may vary according to the amount of power required by the load.

7 is a view for explaining an embodiment of the power transmission apparatus of the present invention to reduce the power consumed in the overvoltage protection circuit. Referring to FIG. 7, the power transmission apparatus according to the present embodiment includes a detector 242a, a current controller 242b, a switch unit 241, and a DC converter 250. The output terminal of the DC converter 250 is connected to the load 300.

Specific functions of the detector 242a, the current controller 242b, the switch unit 241, and the DC converter 250 are as described above. In the following description, the power consumption of the current controller 242b is reduced according to the above configuration.

In FIG. 7, it is assumed that there is little voltage drop in the sensing unit 242a and the switch unit 241. According to the above assumption, it is the input voltage V _IN ≒ applied voltage Va and becomes the first current I ₁ ≒ applied current Ia.

In this case, the input power P _IN may be expressed as shown in Equation 7.

At this time, the first term Pa is transferred to the load as supply power and used to drive the load. The second term V _IN × I ₂ is power consumed by the current controller 242b and corresponds to unnecessary power consumption generated during operation of the power transmission device.

The present invention controls the amount of power transmitted from the transmitter 100 to the receiver 200 in order to reduce unnecessary power consumption (V _IN × I ₂ ). To this end, the input voltage V _IN or the second current I ₂ value is output from the current controller 242b as a detection signal (see FIG. 3). The feedback controller 260 provides the output detection signal to the transmitter 100 as a feedback signal (see FIG. 1). The transmitter 100 controls the amount of power transmitted to the receiver with reference to the feedback signal.

The transmitter 100 reduces the magnitude of power to be transmitted in order to reduce the magnitude of the second term (V _IN × I ₂ ) of Equation 7. As a result, the magnitude of the input power P _IN is reduced. As described above, since the DC converter 250 supplies a constant voltage as the output voltage Vo, if the load 300 is constant, the magnitude of the load power Po is constant. Referring to Equation 6, the size of the supply power (Pa) by the DC converter 250 is also constant.

Therefore, in order to satisfy the equation (7), the second term (V _IN × I ₂ ) of the equation (7) is reduced by the decrease of the left side (P _IN , input power).

More specifically, as the input power P _IN decreases, the magnitude of the input voltage V _IN and the input current I _IN decreases. Since the magnitude of the load power Po is constant, referring to Equation 6, the magnitude of the first current I ₁ increases (∵Va ≒ V _IN , Ia ≒ I ₁ ).

On the other hand, as described above, the current controller 242b controls the second current I ₂ so that the magnitude of the equivalent resistance R _IN is constant. Referring to Equation 5, the current controller 242b reduces the magnitude of the second current I ₂ to offset the influence of the decrease in the input voltage V _IN and the increase in the first current I ₁ . Since the magnitude of the input voltage (V _IN) and a second current (I2) both reduced, reducing the size of the power consumption (V _IN × I ₂₎ of the current control unit (242b).

The transmitter 100 may reduce the transmitted power until the magnitude of the second current I ₂ approaches zero with reference to the feedback signal. When the magnitude of the second current I ₂ approaches zero, the unnecessary power consumption V _IN × I ₂ will also approach zero. That is, in Equation 7, the second term on the right side is removed (P _IN ≒ Pa = Po).

In an embodiment, a power transmission apparatus that assumes a case in which the load 300 is changed may be considered.

First, when the load 300 increases, the load power Po decreases (Po = Vo ² / R _L ). Referring to Equation 7, the decrease of the load power Po is represented by the increase of the second term (V _IN × I ₂ ), and I ₂ is increased. Increased I ₂ to reduce unnecessary power consumption With reference to the value, the transmitter 100 reduces the transmission power. Through the same process as described with reference to FIG. 7, unnecessary power consumption may be reduced.

Next, when the load 300 decreases, the load power Po increases. In this case, if I ₂ is 0, then Po> P _IN, so the power required by the load is not sufficiently supplied. Therefore, in the power transmission apparatus according to the present embodiment, the magnitude of the second current I ₂ is controlled to maintain a reference current value (eg, 100 mA).

As the load power Po increases in such a power transmission device, the magnitude of the first current I ₁ is increased to increase the supply power Pa, and as a result, the magnitude of the second current I ₂ is reduced. (See Equations 5 and 7). The reduced second current I ₂ is transmitted to the transmitter 100 as a feedback signal, and the transmitter 100 increases the transmission power with reference to the feedback signal. Therefore, when the input power P _IN increases, the magnitude of the second current I ₂ also increases. The transmitter 100 continuously controls the transmission power so that the magnitude of the second current I ₂ maintains a constant reference current value (for example, 100 mA).

As a result, when the load power Po increases due to the change in the load, the required power is taken from the power consumed by the current controller 242b. On the other hand, if the load power Po decreases due to the change in load, the surplus power will be consumed by the current controller 242b. The increase or decrease of power consumed by the current controller 242b may function as a kind of reserve power. However, the power consumed by the current controller 242b in the normal operation is unnecessary power consumption. Therefore, it is necessary to limit the magnitude of the second current I ₂ to a small value so that the magnitude thereof is not large.

According to the configuration of the present invention as described above, unnecessary power (V _IN × I ₂ ) consumed when the power transmission apparatus 1000 is operated is minimized. In addition, the power Pa may be actively controlled according to the change of the load 300.

In an embodiment, the receiver 200 of the power transmission apparatus 1000 may further include a matching circuit 220 and a rectifier 230 in front of the overvoltage protection circuit 240.

8 is an exemplary diagram for describing the matching circuit 220 of FIG. 1. The matching circuit 220 is a circuit for matching the impedance between the transmitter 100 and the receiver 200. The matching circuit 220 may be configured in various forms. In an embodiment, the matching circuit 220 may include one coil and one capacitor. If the impedance is not matched, the reflected power is generated in the receiver 200, and thus the maximum power transfer is not performed.

In general, impedance matching requires that both impedances Z _A and Z _B viewed from a contact point be in a complex conjugate relationship with each other. The impedance can be matched by knowing the power supply impedance Z _S and the load impedance Z _L and selecting the corresponding Lm and Cm values (hereinafter referred to as impedance matching points). Since the specific configuration and design method of the matching circuit 220 is well known in the art, a description thereof will be omitted.

FIG. 9 is a block diagram illustrating the rectifying unit 230 illustrated in FIG. 1. Referring to FIG. 9, the rectifier 230 includes a rectifier circuit 231, a noise filter 232, and a smoothing circuit 233. The rectifier circuit 231 rectifies the AC power output from the matching circuit 220 into DC power. The noise filter 232 removes noise included in the rectified DC power. The smoothing circuit 233 removes an AC component included in the rectified DC power.

10A is a circuit diagram exemplarily illustrating the rectifying circuit 231 shown in FIG. 9. 10A shows a full-wave rectifier circuit, which is one type of rectifier circuit 231. Referring to FIG. 8A, the rectifier circuit 231 receives an alternating voltage V _A as an input and provides a DC voltage V _B as an output.

When the input AC voltage V _A is a positive value, diodes D2 and D4 are turned on and diodes D1 and D3 are turned off. At this time, the output DC voltage (V _B ) has a positive value. When the input AC voltage V _A is negative, diodes D1 and D3 are turned on and diodes D2 and D4 are turned off. At this time, the output DC voltage V _B has a positive value.

FIG. 10B is a waveform diagram comparing the input AC voltage V _A and the output DC voltage V _B shown in FIG. 10A. Referring to FIG. 10B, despite the change in the sign of the AC voltage V _A , the DC voltage V _B always has a positive value.

Meanwhile, the rectifier circuit 231 illustrated in FIG. 10A is exemplary, and the rectifier circuit 231 may be configured in various other forms. More specific design methods of the rectifier circuit 231 are well known in the art, and a description thereof is omitted.

11 is a schematic diagram illustrating the noise filter 232. The noise filter 232 removes noise included in voltage or current. In an embodiment, in the noise filter, two coils respectively connected to two terminals of the input V _C may be wound in opposite directions on one core. According to such a configuration, the magnetic force lines of the respective terminals are reversed, so that the noises present in the respective terminals cancel each other out. Therefore, the noise-free voltage is provided as the output V _d of the noise filter 232. Depending on the type of the noise filter 232 may include a capacitor connected in parallel with the input terminal or the output terminal.

The noise filter 232 illustrated in FIG. 11 is exemplary, and the noise filter 232 may be configured in various other forms. The noise filter 232 may be implemented in various forms. Since the specific configuration and design method of the noise filter 232 is well known in the art, a description thereof will be omitted.

12A is a circuit diagram exemplarily illustrating the smoothing circuit 233 shown in FIG. 9. 12A, the smoothing circuit 233 removes an AC component included in the voltage after rectification.

In exemplary embodiments, the smoothing circuit 233 may be configured as one coil and one capacitor. In general, a capacitor has a property of blocking a direct current component and passing an alternating current component. In contrast, the coil passes a direct current component and blocks an alternating current component. Referring to FIG. 12A, the coil L connected between the input V _I and the output V _O blocks AC components from being delivered to the output. At this time, a coil having a large inductance value is used. Capacitor C connected in parallel between the output and ground further removes the remaining alternating current component by inducing alternating current to ground.

12B is a waveform diagram comparing the input (dashed line, V _I ) and the output (solid line, V _O ) of the smoothing circuit 233. It can be seen that the ripple of the output (solid line, V _O ) is smaller than the ripple of the input (dashed line, V _I ).

Meanwhile, the smoothing circuit 233 shown in FIG. 12A is exemplary, and the smoothing circuit 233 may be configured in various other forms. More specific design methods of the smoothing circuit 233 are well known in the art, and a description thereof is omitted.

13 is a flowchart illustrating a control method of the power transmission apparatus 1000 according to an embodiment of the present invention. Referring to FIG. 13, when a voltage is applied to the overvoltage protection circuit 240, an overvoltage protection process is started.

In step S100, the switch unit 241 detects the node voltage. Specifically, the node voltage is sensed by the switch controller 241a included in the switch unit 241. The switch controller 241a controls the opening and closing of the switch 241b, and controls the switch 241b to close in the normal voltage state.

In step S200, the switch controller 241a determines whether the node voltage exceeds a pre-programmed reference voltage.

In step S300, when the node voltage exceeds the reference voltage, the switch controller 241a opens the switch 241b. When the switch 241b is opened, the load 300 is electrically disconnected from the receiver 200. If the transferred voltage does not exceed the reference voltage, the switch 241b remains closed.

In operation S400, the detector 242a detects the first current and the input voltage and provides a control signal to the current controller 242b. In this case, the input voltage is a voltage applied to the input terminal of the current distributor 242. The first current is a current flowing from the input terminal to the output terminal of the current distributor 242. In an embodiment, the detector 242a may not detect the input voltage. In this case, the input voltage is sensed by the current controller 242b.

In operation S500, the current controller 242b controls the magnitude of the second current with reference to the control signal. The second current is a current flowing from the input terminal of the current distributor 242 to the ground. The second current is controlled so that the ratio of the input voltage to the input current is constant. In this case, the input current refers to the total current coming from the input terminal of the current distributor 242. In an embodiment, the input current is equal to the sum of the second current and the first current. In this case, the second current is controlled in a direction proportional to the magnitude of the input voltage and inversely proportional to the magnitude of the first current (see Equation 5). This operation has been described in detail in the embodiment of the overvoltage protection circuit 240.

In operation S600, the current controller 242b provides the input voltage and the second current value as a detection signal to the feedback controller 260. The feedback controller 260 provides the detection signal to the transmitter 100 as a feedback signal.

In steps S700 and S800, the transmitter 100 compares the magnitude of the second current with a reference current value with reference to a feedback signal.

In steps S900 and S910, when the second current is less than the reference current value, the transmitter 100 increases the transmit power. If the magnitude of the second current is greater than the reference current value, the transmitter 100 reduces the transmission power. If the transmit power is increased or decreased, the magnitude of the second current will also increase or decrease. The transmitter 100 controls the magnitude of the transmission power until the magnitude of the second current is equal to the reference current value.

According to the overvoltage protection method as described above, the load 300 can be protected from overvoltage. In addition, the power consumed by the overvoltage protection circuit 240 may be reduced. In addition, even if overvoltage occurs or load changes, the receiver impedance is kept constant, thereby increasing transmission efficiency.

In the detailed description of the present invention, a specific embodiment has been described. However, each embodiment may be modified in various forms without departing from the scope of the present invention. In addition, although specific terms have been used herein, they are used only for the purpose of describing the present invention and are not used to limit the scope of the present invention as defined in the meaning or claims. Therefore, the scope of the present invention should not be limited to the above-described embodiments, but should be defined by the equivalents of the claims of the present invention as well as the following claims.

Claims (18)

In the overvoltage protection circuit of the power transmission device,
A detector configured to generate a control signal by sensing a first current flowing from an input terminal to an output terminal and an input voltage transmitted to the input terminal; And
And a current controller configured to control a second current flowing from the input terminal to the ground to maintain a constant ratio of the input voltage to the input current flowing from the input terminal in response to the control signal. The method of claim 1,
And the input current is a sum current of the first current and the second current. The method of claim 2,
And the current controller is located between the input terminal and the ground. The method of claim 3, wherein
And the current controller includes a variable resistor connecting the input terminal and the ground.
A receiver including an overvoltage protection circuit; And
Includes a transmitter for wirelessly transmitting power to the receiver,
And the transmitter controls power consumption of the overvoltage protection circuit by controlling the magnitude of the transmit power with reference to a feedback signal provided from the receiver. The method of claim 5, wherein
The overvoltage protection circuit,
A detector configured to generate a control signal by sensing a first current flowing from an input terminal to an output terminal and an input voltage transmitted to the input terminal; And
And a current controller configured to control a second current flowing from the input terminal to the ground to maintain a constant ratio of the input voltage to the input current flowing from the input terminal in response to the control signal. The method according to claim 6,
And the input current is a sum current of the first current and the second current. The method of claim 7, wherein
The receiver may further comprise:
A DC converter converting power output from the overvoltage protection circuit and providing the load to a load; And
And a feedback controller configured to receive a sensing signal from the overvoltage protection circuit and provide the sensing signal as the feedback signal. The method of claim 8,
And the sense signal comprises a signal indicative of the value of the second current. The method of claim 9,
The transmitting unit,
And controlling the power consumption of the overvoltage protection circuit by reducing the magnitude of the transmission power if the value of the second current exceeds the reference current value and increasing the magnitude of the transmission power if less than the value of the second current. 11. The method of claim 10,
The overvoltage protection circuit,
And a switch unit capable of electrically disconnecting the DC converter from the overvoltage protection circuit. The method of claim 11,
The switch unit,
A switch located between the sensing unit and the DC converter; And
And a switch controller for controlling opening and closing of the switch. The method of claim 12,
The switch controller,
And sensing a node voltage between the sensing unit and the switch to turn off the switch when the node voltage exceeds a reference voltage, and to turn on the switch below. The method of claim 13,
The receiver may further comprise:
And a rectifier positioned at a front end of the overvoltage protection circuit to rectify AC power into DC power. The method of claim 14,
The receiving unit
And a matching circuit located in front of the rectifier and matching an impedance between the transmitter and the receiver. In the control method of a power transmission device comprising an overvoltage protection circuit in a receiver,
Sensing a first current flowing from an input terminal of the overvoltage protection circuit to an output terminal of the overvoltage protection circuit;
Sensing an input voltage delivered to the input terminal; And
And controlling the second current flowing from the input terminal to the ground such that the ratio of the input voltage to the current flowing from the input terminal is constant with reference to the first current and the input voltage. 17. The method of claim 16,
Providing a value of the input voltage or the value of the second current to a transmitter as a feedback signal; And
And controlling the amount of power wirelessly transmitted from the transmitter to the receiver with reference to the feedback signal. The method of claim 17,
Controlling the magnitude of the power,
And if the second current value exceeds a reference current value, decreases the magnitude of the transmitted power and decreases the magnitude of the transmitted power.

Images