KR20150125354A - Wireless Charging System for Electric Vehicle - Google Patents

Abstract

The present invention relates to a wireless charging system for an electric vehicle which wirelessly transfers power to an electric vehicle and provides a system for transferring wireless power to an electric vehicle in connection with power line communication based on a magnetic field communication control protocol. According to the present invention, power is wirelessly provided to an electric vehicle through magnetic field communication between a wireless power transmitter and the electric vehicle while stably supplying power through power line communication.

Description

Technical Field [0001] The present invention relates to a wireless charging system for an electric vehicle,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for charging a battery of an electric vehicle, and more particularly, to an electric vehicle wireless charging system for charging a battery of an electric vehicle in connection with a power line communication based on a magnetic field communication control protocol.

Demand for automobiles is increasing exponentially as the economic environment is getting better. As automobile demand grows, exhaust gas emitted from automobiles is the main cause of environmental pollution. Therefore, in order to solve environmental pollution problem, automobile exhaust gas is required to be reduced, and automobile manufacturers are focusing on development of automobile which can reduce exhaust gas.

As a result, interest in electric vehicles that do not generate exhaust gas ultimately increases, and they are now being put to practical use. Since environmental pollution is a global problem, demand for electric vehicles have.

Such an electric vehicle is composed of an electric motor that is driven by electricity and runs an electric vehicle and a battery that supplies electricity to the electric motor. That is, the electric motor and the battery replace the engine and the fuel of the ordinary automobile.

However, the electric motor that drives the electric vehicle consumes the electric energy excessively, so that the distance that can be operated by a single charge is considerably shorter than the running distance of the general car. Therefore, the battery provided in the electric vehicle must be charged periodically. Further, the time for charging the battery is considerably longer than the time for refueling the general fuel, so that the electric vehicle can not be operated for at least several hours in order to charge the battery.

As a charging method of a conventional electric vehicle, a data transmission method using power line communication, and an electric vehicle and a charging device for an electric vehicle are disclosed in Patent Registration No. 10-1225077. In the case of the charging device for an electric vehicle disclosed in the Japanese Patent Registration No. 10-1225077, since electric power can be supplied and the data can be transmitted using the power line, it can greatly help the utilization of the electric vehicle which is expected to be commercialized in the near future.

Conventionally, an electric vehicle charging apparatus transmits a data signal received through a power line to a data processing apparatus using power line communication (hereinafter, referred to as 'PLC') technology. However, PLC technology has a problem that it is difficult to transmit data effectively and reliably due to noise, high load interference, and signal distortion in the power line.

In addition, PLC technology is not only poor in communication quality due to latent noise on a power line, but also has difficulty in developing a core chip technology for solving the transmission speed and distance limitation, so there is a restriction on the communication distance. Therefore, it is necessary to install a high-power PLC amplifying device in the middle, so there is a disadvantage that it is a large initial cost for constructing an infrastructure.

As described above, the charging device for an electric vehicle using the conventional PLC technology has a problem that it is not easy for the user to reliably and effectively transmit data to the vehicle from a remote place, and it takes a lot of cost to solve such a problem.

In order to solve the above-described problems, it is an object of the present invention to provide a wireless charging system for an electric vehicle, which wirelessly charges an electric vehicle by linking magnetic field communication and power line communication.

According to an aspect of the invention, there is provided a wireless power transmitter for transmitting wireless power to an electric vehicle and for transmitting data in accordance with a magnetic field communication protocol; A power supply for supplying power to the wireless power transmitter through power line communication; And a power line connecting the wireless power transmitter and the power supply unit.

The wireless power transmitter comprising: a power line communication modem for performing power line communication with the power supply; A magnetic field communication modem for performing magnetic field communication with the electric vehicle; And a controller for controlling operation of the power line communication modem and the magnetic field communication modem.

Wherein the wireless power transmitter requests power supply to the power supply unit when the charging state of the electric vehicle is confirmed or when the electric vehicle is requested to supply electric power and the power supply unit is requested to supply power from the wireless power transmitter, Lt; / RTI > to the wireless power transmitter.

According to another aspect of the present invention, there is provided a battery comprising: a battery; A receiving coil for receiving wireless power transmitted from a wireless power transmitter; A matching circuit coupled to the receive coil and matching the resonant frequency with the wireless power transmitter; A switch coupled to the matching circuit; A rectifying circuit connected to the switch and rectifying the radio power received through the receiving coil; And a DC-DC converter having one end connected to the rectifying circuit and the other end connected to the battery.

The matching circuit comprising: a power control capacitor coupled in parallel with the matching circuit; And a matching switch having one end connected to the matching circuit and the other end connected to the power control capacitor.

The present invention enables electric power to be supplied to a wireless power transmitter by allowing an electric vehicle to be charged wirelessly by linking magnetic field communication and power line communication so that an electric vehicle can be supplied with power wirelessly in a parked state.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a wireless charging system for an electric vehicle according to an embodiment of the present invention. Fig.
2 illustrates a structure of a wireless charging system for an electric vehicle according to an embodiment of the present invention.
3 is a block diagram illustrating a structure of a wireless power transmitter of an electric vehicle wireless charging system according to an embodiment of the present invention;
4 is a block diagram illustrating a structure of a wireless power receiver of an electric vehicle wireless charging system according to an embodiment of the present invention;
5 illustrates a structure of a wireless power transmission superframe based on magnetic field communication;
6 is a diagram illustrating an envelope form of a magnetic field communication protocol;
7 shows an FSK modulated signal of a magnetic field communication protocol;
8 is a diagram showing a frame structure of a physical layer of a magnetic field communication protocol;
9 is a diagram showing a preamble structure of a magnetic field communication protocol;
10 is a diagram showing a header structure of a magnetic field communication protocol;
11 is a diagram showing a coding circuit of a header check cyclic redundancy code of a magnetic field communication protocol.
12 shows a payload structure of a magnetic field communication protocol;
13 is a diagram showing a modulation method of a magnetic field communication protocol;
14 shows a definition of Manchester coding of a magnetic field communication protocol;
15 illustrates the definition of NRZ-L coding of a magnetic field communication protocol;
16 shows an interleaving matrix of a magnetic field communication protocol;
17 shows a scrambler structure of a magnetic field communication protocol;
18 shows a process of modulating and coding a preamble of a magnetic field communication protocol;
19 shows a process of modulating and coding a header of a magnetic field communication protocol;
20 shows a modulation and coding process of a payload of a magnetic field communication protocol;

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. And is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined by the claims.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. &Quot; comprises " and / or "comprising" when used in this specification is taken to specify the presence or absence of one or more other components, steps, operations and / Or add-ons. Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 and 2 show a structure of a wireless charging system for an electric vehicle according to an embodiment of the present invention.

As shown in FIG. 1, an electric vehicle wireless charging system according to an embodiment of the present invention includes a power supply 100, a power line 200, and a wireless power transmitter 300.

The power supply unit 100 stores electric power to be supplied to the electric vehicle and supplies electric power to the electric vehicle through the wireless power transmitter 300. The power supply unit 100 is connected to the power line 200 and transmits power to the wireless power transmitter 300 through power line communication.

When the power supply unit 100 receives a power supply request from the wireless power transmitter 300, the power supply unit 100 supplies electric power to the wireless power transmitter 300 through the power line communication and is connected to the plurality of wireless power transmitters 300 through the power line, It is possible to supply electricity to electric vehicles.

The power line 200 connects the power supply unit 100 and the wireless power transmitter 300 and transmits a power supply request from the wireless power transmitter 300 to the power supply unit 100 and requests power supply from the power supply unit 100 And transfers power to the wireless power transmitter 300.

The wireless power transmitter 300 requests the wireless power supply 100 to the power supply unit 100 through the power line communication when the wireless power receiver 400 of the electric vehicle is detected and the electric vehicle is confirmed to be in chargeable state. Alternatively, upon receiving the wireless power supply request signal from the electric vehicle, the power supply unit 100 may be requested to supply electric power.

The wireless power transmitter 300 wirelessly transmits power to the wireless power receiver 400 of an electric vehicle using a self resonance method and transmits and receives data between the wireless power transmitter 300 and the electric vehicle through magnetic field communication have.

The wireless power transmitter 300 may be installed at a position away from the power supply unit 100 by being connected to the power supply unit 100 by the power line 200 and may be installed at a position where the electric vehicle is parked such as a parking lot. Therefore, according to the present invention, electric power can be wirelessly transmitted to the electric vehicle through the wireless power transmitter 300 installed in the parking position of the electric vehicle during the time when the electric vehicle is parked in a space such as a parking lot.

3 shows a specific structure of the wireless power transmitter 300. As shown in FIG.

3, the wireless power transmitter 300 includes a power line communication modem 301, a controller 302, a magnetic field communication modem 303, an inverter 304, a matching circuit 305, .

The power line communication modem 301 allows the wireless power transmitter 300 to perform power line communication with the power supply 100 and the magnetic field communication modem 303 allows the wireless power transmitter 300 to perform magnetic field communication with the electric vehicle .

The controller 302 controls the wireless power transmitter 300 to perform power transmission / reception or data transmission / reception with the power supply unit 100 or the electric vehicle. The controller 302 requests power supply to the power supply unit 100 when the rechargeable state of the electric vehicle is sensed or a power supply request is received from the electric vehicle. When the electric power is received from the power supply unit 100, .

The transmitting coil 306 transmits wireless power to the electric vehicle and the matching circuit 305 coupled to the transmitting coil 306 performs resonant frequency matching between the wireless power transmitter 300 and the wireless power receiver 400 of the electric vehicle do.

4 shows a structure of a wireless power receiver 400 mounted on an electric vehicle.

4, the wireless power receiver 400 includes a battery 401, a DC-DC converter 402, a rectifying circuit 403, a switch 404, a matching circuit 405, a receiving coil 406, A controller 407, a magnetic field communication modem 408, and an analog circuit 409.

The battery 401 stores the wireless power received from the wireless power transmitter 300, and the rectifying circuit 403 rectifies the received wireless power. The switch 404 is turned ON / OFF to control the reception of the radio power, and ON / OFF of the switch 404 can be controlled by the controller 407.

The receiving coil 406 receives the wireless power transmitted by the wireless power transmitter 300 and the matching circuit 405 performs the resonant frequency matching for the wireless power reception from the wireless power transmitter 300.

The controller 407 controls reception of wireless power, request for supply of wireless power, and data transmission / reception with the wireless power transmitter 300 via the magnetic field communication modem 408. [

5 shows a structure of a super frame for transmitting wireless power based on magnetic field communication.

5, one super frame is composed of a request period, a response period, and a spontaneous period, and the lengths of the request period and the response period are variable to be.

The superframe is initiated by the wireless power transmitter 300 transmitting a response request packet in the request interval. The response request packet has information on the wireless power receiver 400 that can transmit a response packet during the response period and the wireless power receiver 400 transmits the response packet during the response period using the information in the response request packet .

In the autonomous period, the wireless power receiver 400 may transmit data to the wireless power transmitter 300 without the request of the wireless power transmitter 300.

Hereinafter, a mobile magnetic field communication protocol will be described with reference to FIGS.

1. Overview

The mobile magnetic field communication protocol is a wireless communication technology for transmitting and receiving data using a magnetic field signal in a low frequency band (30 KHz to 300 KHz) on the move. The lower operating frequency of the wireless communication is 128 KHz, and the modulation method uses a frequency shift keying (FSK) method. Manchester coding and non-return-to-zero level (NRZ-L) coding, interleaving coding, Hamming coding, and scrambling to vary the data rate. Thereby providing a data rate of several Kbps at a distance of several meters.

The mobile magnetic field communication protocol affects the data transmission rate because the transmission channel state changes flexibly. The data transmission speed can be flexibly selected according to the transmission channel state. Also, by selecting an interleaving coding method and a Hamming coding method having an error correction function, the data transmission rate can be increased. This can be applied to sensor networks, home networks, and application services such as construction, agriculture, and transportation.

2. Composition and scope of standards

This standard defines the physical layer of a wireless network that transmits data using magnetic field signals during movement in the low frequency band. In particular, it defines the mobile field communication physical layer frame structure, data rate, coding and modulation. This standard specifies a method of communicating in a low frequency band (30 KHz ~ 300 KHz) by constructing a few Kbps wireless network within a few meters of distance. This can be applied to sensor networks, home networks, and application services such as construction, agriculture, and transportation. This standard is to comply with the emission limit regulations that are allowed for non-licensed devices in each country.

3. Reference standards (Recommendations)

- None

4. Definitions

4.1. Terms

Magnetic Field Communication (Magnetic Field Communication): Wireless communication technology that transmits and receives data using magnetic field signals in low frequency band

Mobile Magnetic Field Communication: Wireless communication technology that transmits and receives data by using a magnetic field signal while moving in a low frequency band

4.2. Abbreviation

CRC cyclic redundancy check

HCS header check sequence

FCS frame check sequence

FSK frequency shift keying

5. Wireless Interface

5.1 Frequency

In mobile magnetic field communication, a minimum frequency-shift keying scheme is used for efficient wireless communication during movement. In the minimum frequency shift keying scheme, the difference between the low operating frequency (f ₀ ) and the high operating frequency (f ₁ ) is equal to half the bit rate. Therefore, the difference between the waveform representing 0 and 1 bit exactly matches half of the cycle. The maximum frequency deviation (δ) is 0.25 f _1. At this time, the center frequency f _c of the low operating frequency f ₀ and the high operating frequency f ₁ is 128 KHz, and the maximum tolerance of the frequency is ± 20 ppm.

5.2 Signal waveform

The converted bit signal according to the definitions in Chapters 6 and 7 is made up of the envelope defined in Fig. 6 and Table 1.

Figure 6 shows the envelope shape, and Table 1 shows the envelope parameter. In Table 1, A is the size of the envelope. The magnitude of the envelope size can be divided into the positive change magnitude (M _h ) and the negative change magnitude (M _I ). The maximum value of M _h and M _I is within 10% of A

parameter symbol maximum Amount of Change M _h 0.1A Change of sound M _I 0.1A

The signal transmitted to the antenna is an FSK modulated signal according to the envelope defined in this section as shown in FIG.

6. Physical layer frame structure

This section defines the frame structure of the physical layer. As shown in FIG. 8, the physical layer frame includes a preamble, a header, and a payload. The frame is transmitted from the least significant bit (LSB).

6.1 Preamble

Preamble (Preamble) is composed of a 16-bit sequence, a 12-bit '0 (s)' and 16-bit and 4-bit 0101 8888 _{h 2} as shown in FIG. The first 12 bits of the preamble are used for packet synchronization and symbol time adjustment at the receiving end. 12 bits The following 16 bits are used for characterizing the magnetic field channel and are used for normal recovery of the received signal in the equalizer. The preamble is coded using the TYPE 0 scheme defined in Section 6.2.

6.2 Header

As shown in FIG. 10 and Table 2, the header includes a 4-bit data rate and coding field, an 8-bit payload data length field, a 4-bit reserved field, and an 8-bit header check sequence field. Since the header is transmitted from the LSB, the data rate and the LSB of the coding field are transmitted first, and the most significant bit (MSB) of the header check sequence is transmitted last. Headers are coded using the TYPE 0 scheme defined in this section.

beat Contents Remarks b3-b0 Data rate and coding The value of b3-b0 (4 bits) specifies the data rate and coding scheme. b11-b4 Payload data length The value of b11-b4 (8 bits) indicates the data length of the payload in bytes. The MSB is b11 and the LSB is b4. b15-b12 Reserved Reserved b23-b16 Header check sequence b23-b16 (8 bits) circulant residue code.

6.2.1 Data rate and coding field

The data rate and coding field specifies the data rate and coding scheme applied to the payload of a frame to be transmitted, and is represented by 4 bits as shown in Table 3. [

The bits (b3 b2 b1 b0) Data rate and coding 0000 TYPE 0 0001 TYPE 1 0010 TYPE 2 0011 TYPE 3 0100 TYPE 4 0101 TYPE 5 0110 TYPE 6 0111 TYPE 7 1000 TYPE 8 1001 TYPE 9 1010 TYPE 10 1011 TYPE 11 1100 TYPE 12 1101 TYPE 13 1110 TYPE 14 1111 TYPE 15

The data rate and coding method according to the data rate and the coding field value are defined as shown in Table 4. TYPE 0, TYPE 1, TYPE 2 use Manchester coding and the data rates are 1kbps, 2kbps and 4kbps, respectively. TYPE 3, TYPE 4, and TYPE 5 are scrambled after NRZ-L coding and the data rates are 2kbps, 4kbps and 8kbps, respectively. TYPE 6, TYPE 7 and TYPE 8 are scrambled after interleaving and Hamming coding, and data rates are 1kbps, 2kbps and 4kbps, respectively.

Data rate and coding Data rate Coding method Remarks TYPE 0 1 kbps Manchester - TYPE 1 2 kbps Manchester - TYPE 2 4 kbps Manchester - TYPE 3 2 kbps NRZ-L + scrambling - TYPE 4 4 kbps NRZ-L + scrambling - TYPE 5 8 kbps NRZ-L + scrambling - TYPE 6 1 kbps Interleaving + Hamming + Scrambling - TYPE 7 2 kbps Interleaving + Hamming + Scrambling - TYPE 8 4 kbps Interleaving + Hamming + Scrambling - TYPE 9-15 Reserved Reserved -

6.2.2 Payload Data Length field

The payload data length field consists of a total of 8 bits. The payload data length indicates the number of payload data of the transmitted frame in units of bytes. The payload data length is from 0 bytes to a maximum of 255 bytes.

6.2.3 Header Check Sequence Field

The header checks for errors using a header check sequence (HCS). The header check sequence is generated using an 8-bit cyclic redundancy code (CRC), and a primitive polynomial for this is given by Equation 1 below.

11 is an example of a coding circuit of a header check cyclic redundancy code. Data is input in the state where the switch S shown in FIG. 11 is set to '1', and when the last bit is input, the state of S is changed to '2' to set the initial value of the register of the encoding circuit to [0000 0000] Transmits the sequence from the register. At this time, the value stored in D ⁷ is transmitted.

6.3 Payload

The payload is composed of a data field to be transmitted and a frame check sequence (FCS) field for checking an error therebetween as shown in FIG. When the length of the data is 0, the frame check sequence is not included. Therefore, the length of the payload is 0 to 257 bytes. The payload can select and transmit the data rate and coding scheme defined in Section 6.2 depending on the transmission channel state.

6.3.1 Frame Check Sequence Field

The frame check sequence field is generated using a 16-bit cyclic redundancy code. The frame check sequence is calculated for the payload data, and if the length of the payload data is 0, the frame check sequence is not generated. The frame check sequence is computed according to the definition in Table 5, and then it is replaced with 1's complement and sent after the data.

CRC type Length Polynomial Initial value Surplus value ISO / IEC 13239 16bits X ¹⁶ + X ¹² + X ⁵ + 1 0xFFFF 0x1D0F

7. Physical layer modulation and coding scheme

7.1 Modulation method

In mobile magnetic field communication, a minimum frequency-shift keying scheme is used for efficient wireless communication during movement. As shown in FIG. 13, a signal converted into each TYPE i (i = 0 to 8) is modulated to a low operating frequency ( f _c -x ) and a high frequency ( f _c + x ) to be transmitted.

7.2 Coding scheme

7.2.1 Manchester

The Manchester coding changes the signal level in the middle of each bit interval (T _bit ) as shown in FIG. At this time, when the data bit is '0', the level changes from level '1' to level '0'. Conversely, when the data bit is '1', the level changes from level '0' to level '1'.

7.2.2 NRZ-L

The Nonreturn-to-Zero Level (NRZ-L) is matched to level '0' when the data bit is '0' and to level '1' when the data bit is '1', as shown in FIG.

7.2.3 Interleaving

As shown in FIG. 16, the interleaving is defined as a depth of 6 and a codeword length of 8, as shown in FIG. The position i of the output data is determined by the following equation (2). k means a value of 0 (codeword-1).

7.2.4 Hamming

The Hamming code is composed of a data bit and a parity bit for error detection / correction. The number of parity bits according to the number of data bits to be transmitted is obtained by the following equation (3).

d is the number of data bits, p is the number of parity bits, and the number of parity bits is the minimum value satisfying the formula. The parity bits are placed in the 2 ⁿ positions from the lowest 1. The parity check bits for each parity bit are read by the number of positions of each bit including itself and skipped by the number of positions. However, when calculating the parity, it excludes itself and applies even parity.

7.2.5 Scrambling

The payload of a frame using NRZ-L coding and interleaving coding is scrambled through a scrambler. However, the preamble and header are not scrambled. The primitive polynomial g (D) of the scrambler is given by the following equation (4).

Where D is a bit delay element. 17 shows the structure of a scrambler. Here, d _k is made according to the following equation (5).

는 GF(2) 덧셈(Exclusive OR)이다. 다항식의 초기값은 모두 1로 둔다. 데이터 입력 s_k를 스크램블링 되기 전의 비트라 두면 스크램블된 데이터 출력 b_k는 다음의 수학식 6과 같다.At this time

Is a GF (2) addition (Exclusive OR). The initial value of the polynomial is set to 1. If the data input s _k is a bit before being scrambled, the scrambled data output b _k is given by Equation 6 below.

7.3 Modulation and coding process

In this section, a frame is formed for each of the preamble, the header, and the payload, and a series of processes for modulating and coding are defined.

7.3.1 Preamble

As shown in FIG. 18, the preamble transforms the preamble sequence defined in section 6.1 into the TYPE 0 scheme defined in section 6.2, and then transmits using the FSK modulation.

7.3.2 Headers

The header carries a total of 24 bits as defined in Section 6.2. As shown in FIG. 19, first, 8 bits of the header check sequence are added to 16 bits of the pure header information, and conversion is performed using the TYPE 0 scheme defined in Section 6.2, and then the FSK modulation is used.

7.3.3. Payload

As shown in FIG. 20, the payload adds 16 bits of the payload check sequence to the data to be transmitted as described in Section 6.3, and selects one of the nine conversion methods TYPE i (i = 0 to 8) are selected and converted and then transmitted using FSK modulation.

The foregoing description is merely illustrative of the technical idea of the present invention and various changes and modifications may be made without departing from the essential characteristics of the present invention. Therefore, the embodiments described in the present invention are not intended to limit the scope of the present invention, but are intended to be illustrative, and the scope of the present invention is not limited by these embodiments. It is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents, which fall within the scope of the present invention as claimed.

Claims (7)

A wireless power transmitter for transmitting wireless power to an electric vehicle and for transmitting data according to a magnetic field communication protocol;
A power supply for supplying power to the wireless power transmitter through power line communication; And
And a power line connecting the wireless power transmitter and the power supply unit
The electric vehicle charging system comprising:
2. The wireless power transmitter of claim 1,
A power line communication modem for performing power line communication with the power supply unit;
A magnetic field communication modem for performing magnetic field communication with the electric vehicle; And
And a controller for controlling operation of the power line communication modem and the magnetic field communication modem
Electric car wireless charging system.
2. The wireless power transmitter of claim 1,
And requesting power supply to the power supply unit when the charging state of the electric vehicle is confirmed
Electric car wireless charging system.
The plasma display apparatus of claim 1, wherein the power supply unit
And supplying power to the wireless power transmitter via the power line upon receipt of a request for power supply from the wireless power transmitter
Electric car wireless charging system.
battery;
A receiving coil for receiving wireless power transmitted from a wireless power transmitter;
A matching circuit coupled to the receive coil and matching the resonant frequency with the wireless power transmitter;
A switch coupled to the matching circuit;
A rectifying circuit connected to the switch and rectifying the radio power received through the receiving coil;
A DC-DC converter having one end connected to the rectifying circuit and the other end connected to the battery
Wherein the electric charging system comprises:
6. The method of claim 5,
And a magnetic field communication modem coupled between the switch and the DC-DC converter.
6. The method of claim 5,
A power control capacitor coupled in parallel with the matching circuit; And
Further comprising a matching switch, one end of which is connected to the matching circuit and the other end of which is connected to the power control capacitor.

Images