Bluetooth car charger control board development

The bluetooth car charger can be plugged into the cigarette lighter port of the car, and takes power from the power supply of the cigarette lighter port of the car, and provides 2 USB charging ports externally, which can charge 2 mobile devices at the same time, and can automatically identify Apple, Samsung Android devices, others The Android device outputs the corresponding current to realize safe and fast charging; it also has the function of Bluetooth to FM, and the mobile phone can be connected to it through Bluetooth, and it will convert the received Bluetooth signal into an FM signal and then transmit it to the car stereo. In this way, the mobile phone can send music or voice to the car stereo for playback; it also has a built-in microphone, which can be used as a Bluetooth hands-free device to answer calls directly, solving the unsafe problem of using the mobile phone while driving; with the help of the mobile phone APP, it can also have Other purposes, such as navigation broadcast, listening to Internet radio and so on.

1. Function overview of Bluetooth car charger

(1) On-board charging function: Compatible with all 12V and 24V models. The output is 5V, and the maximum continuous charging current is 3.1A. Can automatically identify Apple, Samsung, and other Android devices to achieve optimal charging.

(2) Achieve the best RF performance of Bluetooth and pass Bluetooth certification.

(3) Achieve the best FM RF index and pass SRRC certification.

(4) Realize the best overall audio indicators (including distortion, signal-to-noise ratio, frequency response). (5) Pass the ESD and EMC tests to solve the interference problem and not affect the use of the car's own FM radio and navigation system.

2. The overall architecture design of the hardware circuit of the Bluetooth car charger

2.1 Description of the overall hardware architecture

(1) Power supply part: Convert the 12VDC or 24VDC of the car cigarette lighter port to 5VDC for use by other parts of the circuit. (2) USB part: output 5VDC to the USB port, and control the charging current according to the level of D+ and D- signal lines. (3) Bluetooth part: responsible for receiving the Bluetooth signal of the user's mobile phone or tablet and converting it into a differential audio signal, and outputting it to the audio PA. (4) Audio PA part: responsible for converting the differential audio signal output by the Bluetooth chip into a single-ended audio signal, and then outputting it to the FM chip (4) FM part: responsible for converting the input single-ended audio signal into an FM radio frequency signal, and then transmitting FM radio for the car.

The Bluetooth and FM of this product are combined through analog audio and audio, and the fast charging function is relatively independent, and the three are powered by the vehicle power supply.

2.2 Bluetooth hardware circuit design

The bluetooth part uses CSR's CSR8635 bluetooth SoC chip, which supports bluetooth protocol V4.0, supports bluetooth application protocols (profiles) such as AVRCP, A2DP and Handset, the maximum transmission power is 8dBm, and the receiving sensitivity is -89dBm. The core of the chip is an 80MHz MCU plus a 80MIPS DSP, built-in ROM memory, and supports external expansion of serial Flash or EEPROM. Built-in stereo audio codec (CODEC), multi-channel analog and digital audio input and output, support 5-segment EQ adjustment, unique CVC call sound quality optimization patented technology. Support USB, UART, I2C, SPI and other interfaces, 3 dedicated LED drive IOs. 68-pin QFN package with an area of 8mmX8mm.

2.3 Main control CPU hardware circuit design

The main control part can use STC15 series 51-core single-chip microcomputer, which is responsible for the power supply of the Bluetooth part, the control of buttons and LEDs, and the control of the FM chip through the I2C bus.

2.4 Power supply and charging hardware circuit design

The power supply part uses ANT's ACT4523 vehicle power supply chip. It is a single-chip step-down switching power supply chip with a wide input range (10V~38V), strong output current capability (3A@5V), and a maximum conversion efficiency of 94%. The frequency is optional, and the output current limit can be set. Complete protection functions, such as input and output overvoltage protection, overheat protection. 8-pin SOP package, area 6mmX5mm.

The power supply of the car cigarette lighter is divided into 12V (car) and 24V (truck) according to different models, and the input voltage range of this chip can be adapted to all models.

The USB charging part uses the CX2901 chip, which is a single-chip USB charging protocol identification chip, which can support the Apple mobile phone and tablet charging protocol, Samsung mobile phone and tablet charging protocol, and the general Android phone and tablet charging protocol.

2.5 PCB design

Lamination design of each sub-board (1) BT-FM board: 4-layer board (2) MCU board: 2-layer board (3) Charger board: 2-layer board

3. The overall architecture design of the car charger software

The software design can be divided into two parts: (1) Bluetooth part: no programming is required, only the parameters need to be set using CSR's software. (2) Main control part: need to use C51 language to program STC15 microcontroller.

The Bluetooth software adopts ConfigTool-CSR8600 ROM series parameter setting software. ConfigTool-CSR8600 ROM series is a setting software integrating setting, saving, calling and downloading. It provides a convenient and fast development interface for the software development and design of the application system .

The main control software adopts Keil C51 integrated development environment. Keil C51 is an integrated development environment integrating writing, compiling, debugging and downloading. It provides a convenient and fast development interface for the software development and design of the application system.

The above is the development example of Bluetooth car wireless charging introduced by Shenzhen Zuchuang Microelectronics Co., Ltd. for you. If you have a need for car wireless charger solution development, you can trust us. We represent a variety of single-chip microcomputers, voice chips, dual-mode Bluetooth ICs, and wifi chips. Brands include Songhan MCU, Yingguang MCU, Jerry Bluetooth, Ankai Bluetooth, Allwinner, and Realtek. Our technical services include: PCB design, microcontroller development, Bluetooth solutions, software and hardware custom development, APP development, small program development, WeChat official account development, etc. It can also undertake the design of intelligent electronic products, the development of living appliances, the research and development of beauty equipment, the application of Internet of things platform, the smart home control system, the development of TWS earphones, Bluetooth earphone speakers, the development of children's educational toys, the design of electronic education products, etc.