CN106160105B - A kind of charging method and mobile terminal of mobile terminal - Google Patents

Abstract

The invention provides a charging method for a mobile terminal and the mobile terminal, which relate to the field of communication technology and are used to solve the problem of large interference to other signals caused by wide wiring width in the existing low-voltage high-current charging method. The method includes: obtaining charging mode information and charging mode priority information supported by the charger; judging according to the charging mode information and charging mode priority information to obtain a judgment result; if the judgment result indicates that the first charging mode and the second charging mode are supported at the same time charging method and the priority of the first charging method is higher than that of the second charging method, use the first charging circuit to charge the mobile terminal; if the judgment result indicates that both the first charging method and the second charging method are supported and the priority of the first charging method is The level is lower than the second charging mode, and the mobile terminal is charged by the second charging circuit; wherein both the first charging circuit and the second charging circuit include independent charging paths. The invention is mainly used in the charging technology of the mobile terminal.

Description

A charging method for a mobile terminal and the mobile terminal

technical field

Embodiments of the present invention relate to the field of communication technologies, and in particular, to a charging method for a mobile terminal and the mobile terminal.

Background technique

With the rapid development of mobile communication technology, the hardware of mobile terminals is continuously upgraded. However, since the capacity of the battery is limited by the technical development, and the current mobile terminals are all developing in a thinner direction, the volume of the battery is limited.

The increase of new functions of the mobile terminal accelerates the power consumption of the mobile terminal, so there is a new demand for the charging speed of the mobile terminal. The fast charging technology currently applied to mobile terminals is mainly a high-voltage and high-current charging method. However, in this charging method, a high-voltage and high-current charging IC (Integrated Circuit, integrated circuit) is placed on a PCB (Printed Circuit Board, printed circuit board) of the mobile terminal. In this case, the greater the charging current, the greater the heat generated by the PCB board, and the greater the temperature rise of the mobile terminal. In order to reduce the heat generation of mobile terminals, fast charging technology is developing towards low-voltage and high-current direct charging. In this way, the output voltage and current of the charger are directly charged into the mobile terminal without passing through the charging IC located on the PCB board of the mobile terminal.

In the low-voltage high-current charging mode, two charging circuits are provided: a first charging circuit and a second charging circuit. Wherein, the first charging circuit is a common 5V charging circuit; the second charging circuit is a low voltage and high current charging circuit. As shown in Figure 1, in the section of the charging circuit from the USB port to the OVP (Over Voltage Protection, overvoltage protection) of the first charging circuit, and from the USB port to the switch 1 of the second charging circuit, the two charging circuits A part of the shared charging path is called a shared charging path. However, since the charging current values of the first charging circuit and the second charging circuit differ greatly (the charging current of the second charging circuit is greater than the charging current of the first charging circuit), the requirements for the wiring width when designing the charging circuit Higher, that is, the line width of the line must meet the requirement of the charging current of the second charging circuit, while a wide line width of the line is unnecessary for the first charging circuit. As the line width increases, the heating rate of the charging circuit increases, which increases the interference to other signals.

Contents of the invention

Embodiments of the present invention provide a charging method for a mobile terminal and the mobile terminal, so as to solve the problem of relatively large interference to other signals caused by wide wiring width in the existing low-voltage high-current charging method.

In a first aspect, a method for charging a mobile terminal is provided, including:

When using the charger to charge the mobile terminal, obtain the charging mode information and charging mode priority information supported by the charger;

making a judgment according to the charging mode information and the charging mode priority information, and obtaining a judgment result;

If the judgment result indicates that the charger supports both the first charging method and the second charging method and the priority of the first charging method is higher than that of the second charging method, use the first charging method corresponding to the first charging method A charging circuit charges the mobile terminal;

If the judgment result indicates that the charger supports both the first charging method and the second charging method and the priority of the first charging method is lower than that of the second charging method, use the first charging method corresponding to the second charging method A charging circuit charges the mobile terminal;

Wherein the first charging circuit and the second charging circuit both include independent charging paths.

In a second aspect, a mobile terminal is provided, including:

An acquisition module, configured to acquire charging mode information and charging mode priority information supported by the charger when using the charger to charge the mobile terminal;

A judging module, configured to judge according to the charging mode information acquired by the acquiring module and the charging mode priority information, and obtain a judging result;

The first charging module is configured to if the judgment result of the judging module indicates that the charger supports both the first charging mode and the second charging mode and the priority of the first charging mode is higher than that of the second charging mode, charging the mobile terminal by using a first charging circuit corresponding to the first charging method;

The second charging module is configured to if the judging result of the judging module indicates that the charger supports both the first charging mode and the second charging mode and the priority of the first charging mode is lower than the second charging mode, charging the mobile terminal by using a second charging circuit corresponding to the second charging method;

Wherein the first charging circuit and the second charging circuit both include independent charging paths.

In this way, in the embodiment of the present invention, judgment is made based on the obtained charging mode information and charging mode priority information supported by the charger, and the corresponding first or second charging circuit is selected to charge the mobile terminal according to the judgment result, and the first Both the charging circuit and the second charging circuit include independent charging paths. Since the first charging circuit and the second charging circuit both include independent charging paths, different charging circuits can be designed with different wiring widths, that is, charging methods with smaller currents do not need to use corresponding charging methods with larger currents. The line width of the line. Therefore, the temperature rise rate of the charging circuit can be reduced by using the embodiments of the present invention, thereby reducing interference to other signals.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings that need to be used in the description of the embodiments of the present invention. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those skilled in the art, other drawings can also be obtained based on these drawings without any creative effort.

Fig. 1 is a schematic diagram of a charging circuit in the prior art;

2 is a flowchart of a charging method for a mobile terminal according to a first embodiment of the present invention;

Fig. 3 is the schematic diagram of two charging circuits in the first embodiment of the present invention;

FIG. 4 is a schematic diagram of a mobile terminal according to a second embodiment of the present invention;

Fig. 5 is a schematic diagram of a mobile terminal according to a third embodiment of the present invention.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

first embodiment

As shown in FIG. 2, the charging method of the mobile terminal according to the first embodiment of the present invention includes:

Step 101 , when using the charger to charge the mobile terminal, acquire charging mode information and charging mode priority information supported by the charger.

In the embodiment of the present invention, when using the charger to charge the mobile terminal, the CPU (Central Processing Unit, central processing unit) of the mobile terminal can be used to communicate with the charger to obtain the charging mode information and information supported by the charger. Charging method priority information.

In the embodiment of the present invention, the charging modes supported by the charger include: a first charging mode and a second charging mode. Wherein, the first charging method refers to a normal 5V charging method, and the second charging method refers to a low-voltage high-current charging method. Since the charging power is fixed, when the charging voltage decreases, the charging current must increase. Wherein, the so-called low voltage refers to a charging voltage lower than 5V.

Step 102 , making a judgment according to the charging mode information and the charging mode priority information, and obtaining a judgment result.

Here, the determination result is obtained by analyzing the charging mode information and the charging mode priority information.

Step 103: If the judgment result indicates that the charger supports both the first charging method and the second charging method and the priority of the first charging method is higher than that of the second charging method, use the first charging circuit corresponding to the first charging method to charge the mobile terminal. Charge.

Step 104. If the judgment result indicates that the charger supports both the first charging method and the second charging method and the priority of the first charging method is lower than that of the second charging method, use the second charging circuit corresponding to the second charging method to charge the mobile terminal. Charge.

Wherein the first charging circuit and the second charging circuit both include independent charging paths.

As shown in FIG. 1 , the first charging circuit and the second charging circuit have a part of the shared charging path. However, in the embodiment of the present invention, the first charging circuit and the second charging circuit do not have this part of the shared charging path, that is, the first charging circuit and the second charging circuit are completely independent charging circuits.

It can be seen from the above that since the first charging circuit and the second charging circuit both include independent charging paths, different charging circuits can be designed with different wiring widths, that is, for charging with a small current, there is no need to use a larger charging path. The line width corresponding to the high current charging method. Therefore, the temperature rise rate of the charging circuit can be reduced by using the embodiments of the present invention, thereby reducing interference to other signals.

The composition of the two charging circuits in the embodiment of the present invention will be described below with reference to FIG. 3 .

Mobile terminals generally adopt a three-stage design. The upper part is the main PCB board, the middle part is the battery unit (including the battery protection board and the battery), and the lower part is the secondary PCB board connected to the USB (Universal Serial Bus, Universal Serial Bus) port. The main PCB board and the auxiliary PCB board are connected through FPCB (Flexible Printed Circuit Board, flexible printed circuit board).

In the embodiment of the present invention, as shown in FIG. 3, the first charging circuit includes: a charging port 311, a connection mechanism 312 between the secondary PCB board and the main PCB board, a 5V charging unit 313, and a connection mechanism 314 between the main PCB board and the battery unit . The battery unit 315 ; the second charging circuit includes: a charging port 311 , a low-voltage high-current charging unit 321 , a connection mechanism 322 between the secondary PCB board and the battery unit, and the battery unit 315 .

Wherein, the charging port 311 may be a USB port, and is shared by two charging circuits.

Referring again to FIG. 3 , in the first charging circuit, the connecting mechanism 312 between the secondary PCB board and the main PCB board includes: a first connecting piece 3121 , a second connecting piece 3122 , and a third connecting piece 3123 . Wherein, the first connecting piece 3121 is used to connect the auxiliary PCB board with one end of the second connecting piece 3122 ; the other end of the second connecting piece 3122 is connected with the main PCB board through the third connecting piece 3123 . Wherein, the second connecting member may adopt a flexible printed circuit board. The battery unit 315 includes a battery protection board 3151 and a battery; the connection mechanism 314 between the main PCB board and the battery unit is: a connector for connecting the main PCB board and the battery board.

Referring again to FIG. 3 , in the second charging circuit, the connecting mechanism 322 between the sub-PCB and the battery unit includes: a fourth connecting piece 3221 , a fifth connecting piece 3222 , and a sixth connecting piece 3223 . Wherein, the fourth connecting piece 3221 is used to connect the auxiliary PCB board with one end of the fifth connecting piece 3222 ; the other end of the fifth connecting piece 3222 is connected with the battery protection board 3151 through the sixth connecting piece 3223 . The fifth connecting member 3222 can use a flexible printed circuit board.

When it is determined to use the first charging circuit for charging according to the judgment result, the charging path is: the charging port, the first connector, the second connector, the third connector, the 5V charging unit, the connection mechanism between the main PCB board and the battery unit, battery unit. When it is determined to use the second charging circuit for charging according to the judgment result, the charging path is: the charging port, the low-voltage high-current charging unit, the fourth connector, the fifth connector, the sixth connector, and the battery unit.

In this way, the ordinary 5V charging path is separated from the low-voltage and high-current charging path, which can reduce the wiring requirements of the ordinary 5V charging circuit, thereby reducing impedance and reducing interference to other sensitive signals.

second embodiment

As shown in FIG. 4, the mobile terminal 400 of the second embodiment of the present invention includes:

The obtaining module 401 is used to obtain the charging method information and charging method priority information supported by the charger when the mobile terminal is charged by the charger; the judging module 402 is used to obtain the charging method information and charging method according to the obtaining module 401 The priority information is judged to obtain a judgment result; the first charging module 403 is used for if the judgment result of the judging module 402 indicates that the charger supports both the first charging method and the second charging method and the priority of the first charging method is higher than that of the charging method. The second charging method uses the first charging circuit corresponding to the first charging method to charge the mobile terminal; the second charging module 404 is used for if the judgment result of the judging module 402 indicates that the charger supports the first charging method and the second charging at the same time and the priority of the first charging method is lower than that of the second charging method, and the mobile terminal is charged by using the second charging circuit corresponding to the second charging method; wherein both the first charging circuit and the second charging circuit include independent charging paths.

Wherein, the compositions of the first charging circuit and the second charging circuit can be referred to as shown in FIG. 3 .

The mobile terminal 400 can implement various processes implemented by the mobile terminal in the method embodiment in FIG. 1 , and details are not repeated here to avoid repetition.

It can be seen from the above that since the first charging circuit and the second charging circuit both include independent charging paths, different charging circuits can be designed with different wiring widths, that is, for charging with a small current, there is no need to use a larger charging path. The line width corresponding to the high current charging method. Therefore, the temperature rise rate of the charging circuit can be reduced by using the embodiments of the present invention, thereby reducing interference to other signals.

third embodiment

Fig. 5 is a schematic structural diagram of a mobile terminal according to another embodiment of the present invention. Specifically, the mobile terminal in FIG. 5 may be a mobile phone, a tablet computer, a personal digital assistant (Personal Digital Assistant, PDA), or a vehicle-mounted computer.

The mobile terminal in FIG. 5 includes a radio frequency (Radio Frequency, RF) circuit 510, a memory 520, an input unit 530, a display unit 540, a processor 560, an audio circuit 570, a WiFi (Wireless Fidelity) module 550 and a power supply 590.

Wherein, the input unit 530 can be used for receiving number or character information input by the user, and generating signal input related to user setting and function control of the mobile terminal. Specifically, in the embodiment of the present invention, the input unit 530 may include a touch panel 531 . The touch panel 531, also referred to as a touch screen, can collect user's touch operations on or near it (such as the user's operation on the touch panel 531 using any suitable object or accessory such as a finger and a stylus), and The specified program drives the corresponding connected device. Optionally, the touch panel 531 may include two parts, a touch detection device and a touch controller. Among them, the touch detection device detects the user's touch orientation, and detects the signal brought by the touch operation, and transmits the signal to the touch controller; the touch controller receives the touch information from the touch detection device, converts it into contact coordinates, and sends it to the to the processor 560, and can receive and execute commands sent by the processor 560. In addition, the touch panel 531 can be implemented in various types such as resistive, capacitive, infrared, and surface acoustic wave. In addition to the touch panel 531, the input unit 530 may also include other input devices 532, which may include but not limited to physical keyboards, function keys (such as volume control buttons, switch buttons, etc.), trackballs, mice, joysticks, etc. one or more of.

Wherein, the display unit 540 can be used to display information input by the user or information provided to the user and various menu interfaces of the mobile terminal. The display unit 540 may include a display panel 541, and optionally, the display panel 541 may be configured in the form of an LCD or an organic light-emitting diode (Organic Light-Emitting Diode, OLED).

It should be noted that the touch panel 531 can cover the display panel 541 to form a touch display screen. When the touch display screen detects a touch operation on or near it, it is sent to the processor 560 to determine the type of the touch event, and then the processor The 560 provides corresponding visual output on the touch display screen according to the type of the touch event.

The touch display screen includes an application program interface display area and a common control display area. The arrangement of the display area of the application program interface and the display area of the commonly used controls is not limited, and may be an arrangement in which the two display areas can be distinguished, such as vertical arrangement, left-right arrangement, and the like. The application program interface display area can be used to display the interface of the application program. Each interface may include at least one interface element such as an icon of an application program and/or a widget desktop control. The application program interface display area can also be an empty interface without any content. The commonly used control display area is used to display controls with a high usage rate, for example, application icons such as setting buttons, interface numbers, scroll bars, and phonebook icons.

Wherein the processor 560 is the control center of the mobile terminal, utilizes various interfaces and lines to connect the various parts of the whole mobile phone, runs or executes the software programs and/or modules stored in the first memory 521, and calls the software programs and/or modules stored in the second memory The data in 522 executes various functions of the mobile terminal and processes data, so as to monitor the mobile terminal as a whole. Optionally, the processor 560 may include one or more processing units.

In the embodiment of the present invention, by calling the software programs and/or modules stored in the first memory 521 and/or the data in the second memory 522, the processor 560 is used to:

When using the charger to charge the mobile terminal, obtain the charging mode information and charging mode priority information supported by the charger; judge according to the charging mode information and charging mode priority information, and obtain a judgment result; if the judgment result indicates that the charger Both the first charging method and the second charging method are supported and the priority of the first charging method is higher than that of the second charging method, and the first charging circuit corresponding to the first charging method is used to charge the mobile terminal; if the judgment result indicates that the charger is simultaneously Support the first charging method and the second charging method and the priority of the first charging method is lower than the second charging method, and use the second charging circuit corresponding to the second charging method to charge the mobile terminal; wherein the first charging circuit and the second The charging circuits all include independent charging paths.

Optionally, the first charging circuit in the power supply 590 includes: a charging port, a connecting mechanism between the secondary PCB board and the main PCB board, a 5V charging unit, a connecting mechanism between the main PCB board and the battery unit, and the battery unit; the second charging circuit includes : Charging port, low-voltage high-current charging unit, connection mechanism between sub-PCB and battery unit, battery unit.

Optionally, the connecting mechanism of the secondary PCB board and the main PCB board includes: a first connecting piece, a second connecting piece, and a third connecting piece; wherein, the first connecting piece is used to connect one end of the secondary PCB board and the second connecting piece ; The other end of the second connector is connected to the main PCB board through the third connector.

Optionally, the battery unit includes a battery protection board and a battery; the connection mechanism between the main PCB board and the battery unit is: a connector for connecting the main PCB board and the battery board.

Optionally, the battery unit includes a battery protection board and a battery; the connection mechanism between the sub-PCB board and the battery unit includes: a fourth connector, a fifth connector, and a sixth connector; wherein, the fourth connector is used to connect the sub-PCB One end of the plate and the fifth connecting piece; the other end of the fifth connecting piece is connected with the battery protection plate through the sixth connecting piece.

Optionally, the second connecting part is: a flexible printed circuit board.

Optionally, the fifth connecting member is: a flexible printed circuit board.

It can be seen from the above that since the first charging circuit and the second charging circuit both include independent charging paths, different charging circuits can be designed with different wiring widths, that is, for charging with a small current, there is no need to use a larger charging path. The line width corresponding to the high current charging method. Therefore, the temperature rise rate of the charging circuit can be reduced by using the embodiments of the present invention, thereby reducing interference to other signals.

Those skilled in the art can appreciate that the units and algorithm steps of the examples described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are executed by hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art may use different methods to implement the described functions for each specific application, but such implementation should not be regarded as exceeding the scope of the present invention.

Those skilled in the art can clearly understand that for the convenience and brevity of the description, the specific working process of the above-described system, device and unit can refer to the corresponding process in the foregoing method embodiment, which will not be repeated here.

In the embodiments provided in this application, it should be understood that the disclosed devices and methods may be implemented in other ways. For example, the device embodiments described above are only illustrative. For example, the division of units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated. to another system, or some features may be ignored, or not implemented. In another point, the mutual coupling or direct coupling or communication connection shown or discussed may be through some interfaces, and the indirect coupling or communication connection of devices or units may be in electrical, mechanical or other forms.

A unit described as a separate component may or may not be physically separated, and a component displayed as a unit may or may not be a physical unit, that is, it may be located in one place, or may be distributed to multiple network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, each unit may exist separately physically, or two or more units may be integrated into one unit.

If the functions are realized in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the essence of the technical solution of the present invention or the part that contributes to the prior art or the part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including Several instructions are used to make a computer device (which may be a personal computer, a server, or a network device, etc.) execute all or part of the steps of the methods in various embodiments of the present invention. The aforementioned storage medium includes: various media capable of storing program codes such as U disk, mobile hard disk, ROM, RAM, magnetic disk or optical disk.

The above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Anyone familiar with the technical field can easily think of changes or replacements within the technical scope disclosed in the present invention, and should cover all Within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (10)

1. A charging method for a mobile terminal, comprising: When using the charger to charge the mobile terminal, obtain the charging mode information and charging mode priority information supported by the charger; making a judgment according to the charging mode information and the charging mode priority information, and obtaining a judgment result; If the judgment result indicates that the charger supports both the first charging method and the second charging method and the priority of the first charging method is higher than that of the second charging method, use the first charging method corresponding to the first charging method A charging circuit charges the mobile terminal; If the judgment result indicates that the charger supports both the first charging method and the second charging method and the priority of the first charging method is lower than that of the second charging method, use the first charging method corresponding to the second charging method A charging circuit charges the mobile terminal; Wherein the first charging circuit and the second charging circuit both include independent charging paths; Wherein, the first charging circuit includes: a connection mechanism between the secondary PCB board and the main PCB board; The connecting mechanism of the secondary PCB board and the main PCB board includes: a first connecting piece, a second connecting piece, and a third connecting piece; Wherein, the first connecting piece is used to connect the secondary PCB board and one end of the second connecting piece; the other end of the second connecting piece is connected to the main PCB board through the third connecting piece. 2. The method of claim 1, wherein, The first charging circuit also includes: a charging port, a 5V charging unit, a connection mechanism between the main PCB board and the battery unit, and the battery unit; The second charging circuit includes: the charging port, a low-voltage high-current charging unit, a connection mechanism between the sub-PCB board and the battery unit, and the battery unit. 3. The method according to claim 2, wherein the battery unit includes a battery protection board and a battery; the connection mechanism between the main PCB board and the battery unit is: used to connect the main PCB board and the battery unit Connectors for battery panels. 4. The method according to claim 2, wherein the battery unit includes a battery protection board and a battery; the connection mechanism between the secondary PCB board and the battery unit includes: a fourth connector, a fifth connector , the sixth connector; Wherein, the fourth connecting piece is used to connect the auxiliary PCB board and one end of the fifth connecting piece; the other end of the fifth connecting piece is connected to the battery protection board through the sixth connecting piece. 5. A mobile terminal, characterized in that, comprising: An acquisition module, configured to acquire charging mode information and charging mode priority information supported by the charger when using the charger to charge the mobile terminal; A judging module, configured to judge according to the charging mode information acquired by the acquiring module and the charging mode priority information, and obtain a judging result; The first charging module is configured to if the judgment result of the judging module indicates that the charger supports both the first charging mode and the second charging mode and the priority of the first charging mode is higher than that of the second charging mode, charging the mobile terminal by using a first charging circuit corresponding to the first charging method; The second charging module is configured to if the judging result of the judging module indicates that the charger supports both the first charging mode and the second charging mode and the priority of the first charging mode is lower than the second charging mode, charging the mobile terminal by using a second charging circuit corresponding to the second charging method; Wherein the first charging circuit and the second charging circuit both include independent charging paths; Wherein, the first charging circuit includes: a connection mechanism between the secondary PCB board and the main PCB board; The connecting mechanism of the secondary PCB board and the main PCB board includes: a first connecting piece, a second connecting piece, and a third connecting piece; Wherein, the first connecting piece is used to connect the secondary PCB board and one end of the second connecting piece; the other end of the second connecting piece is connected to the main PCB board through the third connecting piece. 6. The mobile terminal according to claim 5, characterized in that, The first charging circuit also includes: a charging port, a 5V charging unit, a connection mechanism between the main PCB board and the battery unit, and the battery unit; The second charging circuit includes: the charging port, a low-voltage high-current charging unit, a connection mechanism between the sub-PCB board and the battery unit, and the battery unit. 7. The mobile terminal according to claim 6, wherein the battery unit comprises a battery protection board and a battery; The connection mechanism between the main PCB board and the battery unit is: a connector for connecting the main PCB board and the battery board. 8. The mobile terminal according to claim 6, wherein the battery unit includes a battery protection board and a battery; the connection mechanism between the secondary PCB board and the battery unit includes: a fourth connecting piece, a fifth connecting piece piece, the sixth connecting piece; Wherein, the fourth connecting piece is used to connect the auxiliary PCB board and one end of the fifth connecting piece; the other end of the fifth connecting piece is connected to the battery protection board through the sixth connecting piece. 9. The mobile terminal according to claim 5 or 7, wherein the second connecting member is a flexible printed circuit board. 10. The mobile terminal according to claim 8, wherein the fifth connecting member is a flexible printed circuit board.