First, power supply circuit and CPU input detection circuit

CPU input power supply circuit and detection circuit diagram as shown below.

The power supply circuit of the machine is provided by IC701 and IC702. IC701 provides all kinds of operating voltage required by the main board circuit, and its various functions are shown in the table below.

After the output of the +5v voltage regulator IC901, output +3.3V voltage, power supply for small signal processing circuit.

The input circuit is divided into reverse detection control, detection and control, GPS brake mute detection control and detection circuit. R706, Q701, R707 reverse detection control circuit, reversing lamp voltage control through R706 Q701 conduction, low level output into the IC601 (3) feet, make the IC601 control AV signal selection circuit outputs the video signal reversing camera is displayed on the LCD screen, Q702, R709; GPS mute detection control circuit, when the host in GPS display mode, the external module in the sound output, GPS module output voltage through R708 Q702 mute, conducting high output, sent to the IC601 by the divider (5 feet), after the IC601 electronic volume control IC attenuation current radio or DVD / audio signal to audio signal, GPS, superposition; Q703, R711 hand brake detection control circuit, only when the brake line grounding, the host can view the image when the car is running, R712, D703; D706, Q705, Q704, BATT detection circuit, the +12V voltage by D706 isolation, after the breakdown D703 control Q704 conduction, high level output to IC601 (8 feet).

Two, GPS and DVD/CD interface circuit changer

GPS and DVD/CD changer interface circuit diagram as shown below. GPS module to output the R, G, B signal after Q501 to Q503 electronic switch, into the display driving circuit, electronic switch control signal is controlled by the IC601 (36) foot, high level; GPS module and the output of the composite sync signal into the AV signal selection circuit switching; GPS module output block Navi - sens system (GPS connection signal detection) and show activity detection signal) are respectively sent to the, (35 feet). Due to a liquid crystal display of the machine does not support the touch and remote control receiver with only one, so GPS module user instruction only with remote control operation to complete. IC601 isolated belongs to the GPS module of the remote control instruction from 25 feet in the output, by, D01, r511 consisting of constant pressure data put circuit processing, into the GPS module.

The interface circuit of DVD/CD changer by IC501. IC501 in the industry known as changer bus interface IC, and its essence is a Schmitt trigger integrated circuit, its role is constant voltage, prevent due to noise caused by multiple triggers.

Three, radio module and digital PLL circuit tuning

Radio component is also called electronic AM / FM tuner, mainly to complete the reception of radio signals and mixing output analog audio radio signal, the pin functions.

Pin function

2, 1 AM, FM signal input terminal

4, 19, 23, 26, 3

7, 8, 10, 15, 5, 18 GND

6 FM tuning voltage output terminal

9 radio components within the AM circuit power supply input terminal

11 AM / FM of the output end of the vibration frequency;

12 radio components within the FM circuit power supply input terminal

25, 13 AM / FM shared circuit power supply input side

14 AM tuning voltage input

16, 17 left and right channel analog audio signal output

20 frequency signal output terminal

21 S wave signal output terminal

22 stop the search for radio control signal output terminal

24 FM detection output

IC601 through radio bus enable digital tuning PLL circuit IC51 frequency stability, frequency modulation decoding, Kam to complete, and the reception component VT voltage tuning, signal intensity and the wavelength selection control.

Four, AV signal selection and collection / playback sharing circuit

AV signal selection and admission / playback common circuit diagram see figure below shows, the circuit including: AV signal selection circuit IC201, circuit IC203 source and electronic volume control, operational amplifier circuit and its IC204 IC202 IC206, power amplification circuit IC207.

The audio / video signals of various AV signals are sent to the IC201 via the AV input port. IC601 through the IIC bus (SDA, SCL) control IC201, the current selection of the effective signal sent to IC203. IC202 after the audio / video signal amplification, to the RCA port, as the head of the head of the screen and power amplifier signal source. GPS module of the composite sync signal in the IC201 and the current effective video signal switch, sharing an output, from (40) pin output, into the display driver circuit.

IC601 through the IIC bus control IC203, high, bass, right and left, front and back channel balance to regulate and overweight bass processing output 4 road (front left, front right, rear left and right) of the audio signal and a subwoofer audio signal of the input audio signal. The subwoofer audio signal after amplification IC204 into the RCA port; rear left and right of the audio signal sent directly IC207; GPS module output (SP, SP) audio signal into processing with IC205 electronic gain control, and the left front, right front audio signal together to send into the IC206 to zoom in, finally sent to IC207 power amplification of the.

Five, liquid crystal display board DC - DC power supply circuit

DC - DC power supply circuit diagram shown below.

And L914 C960 to (D1 (negative, positive, the electric potential drop L910, cut-off, holds the pulse PWM in storage L910, (1Q904 Q904 pulse PWM in (IC903 (46 feet output PWM pulse is sent through the Q904 1 foot asked rest period within 5 feet, L910, flowing through the current increases, L910; during Q1 through current zero L910 inductance current C960 > C960 Q904 3 feet - > > Q904 4 feet, L910 - > the C960 charge in the form of negative voltage, the capacitor filter, the output voltage is 10V for liquid crystal display panel power supply. IC903 (41) pin output PWM pulse into the Q905 (1) feet, in Q2, + 5V voltage, L911, Q2, and increase the current flowing through the L911, energy storage L911; in Q2 off period, the current flowing through the L911 decreased to zero. L911 generate self induced electromotive force, the rectification of D2 and + 5V voltage superimposed together to C965 charge, formed the + 15V voltage for the liquid crystal display panel power supply. LCD panels are required for +5V to be supplied directly by IC702.